Suppression Of Nucleation Research Articles

Assessment of Ammoniacal Leaching Agents for Metal Cation Extraction from Construction Wastes in Mineral Carbonation.

The use of carbon mineralization to produce carbonates from alkaline industrial wastes is gaining traction as a method to decarbonize the built environment. One of the environmental concerns during this process is the use of acids, which are required to extract Ca2+ or Mg2+ from the alkaline waste to produce carbonates. Conventionally, acids such as hydrochloric, nitric, or sulfuric are used which allow for the highest material recovery but are corrosive and difficult to regenerate as they are utilized in a linear fashion and generate additional process waste. An alternative is to use regenerable protonatable salts of ammonia, such as ammonium chloride (AC) or ammonium sulfate, the former of which is used globally during the Solvay process as a reversible proton shuttle. In this study, we show that regenerable ammonium salts, such as AC (NH4Cl) and ammonium bisulfate (NH4HSO4), can be effectively used for material recovery and the production of calcium carbonate during the leaching of waste cement paste as an alternative to conventional acids such as HCl. Leaching kinetics, postreaction residue, and carbonate characterization were performed to assess the productivity of this system and potential uses of these materials downstream. The stabilization of vaterite was observed in the case of AC leaching, suggesting its importance in the kinetic stability of vaterite and suppression of calcite nucleation. Overall, this study motivates the use of alternative leaching agents, such as salts of ammonia, to facilitate material recovery and carbon capture from alkaline industrial wastes.

Elucidating the influence of electrolyte additives on iron electroplating performance

Iron electroplating is great interest for multiple large-scale industrial and emerging energy applications, such as all-iron redox flow batteries. However, the process efficiency and material lifetime are limited by the poorly understood plating process and the presence of competitive reactions. In this work, we propose a methodology to deconvolute the nucleation parameters of iron plating via a suite of electrochemical techniques, spectroscopy, and analytical models, coupled with microscopic and crystallographic techniques. We perform a systematic analysis with iron-based electrolytes to deconvolute the simultaneous plating and hydrogen evolution reactions, and investigate an array of additives to tune electroplating descriptors. We find that all additives studied are able to regulate the plating process and that highly stable iron-complexes based on buffers, such as iron-borates or -citrates deliver greater overall electroplating performance. These additives show superior selectivity, with improvements in faradaic efficiencies from 60 % to ∼90 % due to the balanced effects of enhanced nucleation and side reaction suppression. Herewith, the aim of this study is to bridge the knowledge gap between the role of additives, kinetics and efficiency of the electrodeposition reaction, and their interplay defining the quality of the resulting plated layers.

Grain size-dependent delay of avalanches during void evolution in a nanocrystalline Ni

The effect of grain size on the underlying dynamics of void evolution in a nanocrystalline (NC) Ni was dissected. Multiscale characterizations reveal that, unlike the suppression of void nucleation by the compressive stress in coarse-grained Ni, dispersive nano- and micro-voids formed readily in NC Ni during compression. Acoustic emission measurements and molecular dynamic simulations demonstrate that the unique structural features and deformation mechanics implicitly occurring in NC metals play multifaceted roles during void evolution. Although the presence of excessive nucleation sites, such as grain boundaries and triple junctions, together with the activation of intergranular plasticity facilitate void nucleation, high interface population retards dislocation-driven void expansion, resulting in sluggish void growth and a corresponding delay of coalescence avalanches.

Suppression of Nucleation in a Turbulent Gas Flow

Suppression of Nucleation in a Turbulent Gas Flow

Theory of Chiral Electrodeposition by Micro-Nano-Vortexes under a Vertical Magnetic Field-2: Chiral Three-Dimensional (3D) Nucleation by Nano-Vortexes

The contributions of magnetohydrodynamic (MHD) vortexes to chiral electrodeposition in a vertical magnetic field were theoretically examined based on the three-generation model of the 2D nucleus, 3D nucleus, and screw dislocation; for the vortexes to rotate in the second and third-generation, the kinematic viscosity must be at least 10−18 and 10−30 times lower than the ordinary value in the first generation, i.e., almost equal to zero. This implies that the ionic vacancy created on the electrode surface works as an atomic-scale lubricant. At the same time, the vortexes played three roles: promotion and suppression of nucleation, and transport of the chirality from the upper generation to the lower generation through precessional motion. Then, the rule of the chirality transfer was established, and finally, the relationship between the chiral activity and magnetic field was clarified in the presence and absence of chloride ions.

FLOW BOILING HEAT TRANSFER IN MICROCHANNEL HEAT EXCHANGERS WITH MICRO POROUS COATING SURFACE

This study experimentally investigated the heat transfer and pressure drop performance of refrigerant HFC-245fa flow boiling in microchannel heat exchangers with and without microporous coating. The flow boiling heat transfer performance at various mass fluxes, heating rate, exit vapor qualities, and surface coating thickness was compared. The test results showed that the 52 μm coating thickness porous surface exhibited 65-148% higher heat transfer performance than the smooth surface, while the 98 μm microporous coating surface showed a lower improvement of 41-90% at various mass fluxes. Partial dry out was observed at high and moderate mass fluxes on both smooth and porous coating channels. It happened at lower exit vapor qualities in microporous coating channels than that in smooth channels. The partial dry-out exit vapor qualities increased with decreasing mass fluxes. For the lowest mass flux, because of the low heat flux and low nucleation suppression, no significant partial dry out was investigated. The pressure drops in microporous coating channels were around 25-47% higher than those in smooth channels. There was no significant influence of microporous coating layer thickness on flow boiling pressures drops.

Suppression of polycrystal nucleation by methane addition at moderate timing to maintain GaN crystal growth on point seeds in the Na-flux method

We have grown low-dislocation, large-diameter GaN substrates using small seed crystals, called as point seeds (PSs) in the Na-flux method. To further reduce dislocation density and improve wafer bowing, reducing the PS diameter is effective. However, it was found that crystals did not start to grow on a small diameter PS. In this study, we also found that a growth on a small diameter PS can be carried out in the condition without graphite addition. However, graphite is conventionally added to suppress polycrystals, so those could not be avoided at the latter process to planarize crystal surface by raising and lowering the crystal, called the flux film coated (FFC) process, in which polycrystals are likely generated. Thus, in this study, we newly proposed to suppress polycrystals by adding methane gas before the FFC process, instead of graphite which cannot be added during the middle of growth.

Categorization of iso-pentane flashing spray based on morphology, thermodynamical and mechanical effects

Accidental release of superheated liquids is typically accompanied with hazardous flashing jets. Indeed, flashing jets undergo fragmentation into massive fine droplets, thus forming ideal circumstances for fires and explosion. To gain a deeper understanding of depressurized release, we studied the dynamics of iso-pentane at superheats of 40–80 °C and injection pressures of 0.6–3.0 MPa. The internal flow pattern and external spray morphology are visualized at quasi-steady stage using a high-speed camera. Results show that the flashing patterns can be classified into non-flashing, transitional flashing, and flare flashing arising from the interaction between thermodynamic and mechanical effects. The contribution of thermodynamic effect decreases as mechanical effect intensifies, due to the suppression of bubble nucleation and burst. We propose the index k, based on JaRp = k(WevOh)−1/7, to identify different flashing regions, i.e., k below 211 for non-flashing, k between 212 and 425 for transitional flashing, and k above 425 for flare flashing. Besides, the microscopic characteristics involving droplet velocity and diameter distribution are investigated and a new correlation for drop size is proposed, which is dependent on factors such as nozzle aspect ratio, mechanical force, and thermodynamic force. These findings should help to define policies to decrease the risk associate with flashing jets.

Impact of n-butanol addition to hydrogenated catalytic biodiesel fueled a constant volume combustion chamber; a computational study

ABSTRACT The continuous quest for renewable, efficient, and clean energy sources has led to significant advances in the field of biodiesel production. Hydrogenated catalytic biodiesel (HCB) seems to be a promising option among various renewable biodiesel fuels which can be obtained from waste cooking oil. However, its extreme ignitability limits its application in existing engines. Therefore, a blend of n-butanol and HCB has been proposed in the present study, aiming to explore the spray combustion and soot formation behavior of these blends as a step toward the best possible utilization of this blend in engine. The objective was to examine the impact of adding n-butanol to HCB fuel on spray combustion and soot particles. A new skeletal chemical kinetic model of HCB/n-butanol blend was introduced and validated through measured data reported in the literature. Numerical studies have been performed in a constant volume combustion chamber under reactive spray environments. The simulation results concluded that, blending 20%, 40%, and 60% n-butanol with HCB fuel increased the heat release rates by 31.6%, 47.8%, and 87%, respectively. Furthermore, introducing a 20% of n-butanol into HCB fuel resulted in a 35.7% increase in ignition delay time and a 35.3% increase in flame liftoff length. These results demonstrated the reactivity of n-butanol/HCB mixture experienced a decrease when increasing the n-butanol fraction in the blend, while the fuel atomization was improved. The simulation results also demonstrated a notable reduction in the equivalence ratio when the n-butanol addition ratio was increased, which was a result of the entrainment effect that enhanced the mixing of fuel spray and surrounding fresh air. The simulation results also demonstrated that, adding 20%, 40%, and 60% n-butanol to HCB fuel resulted in a 25%, 43%, and 50% reduction in soot mass of HCB, respectively. This was mainly attributed to the less amount of C2H2, A1, and A4 species with n-butanol addition. Consequently, this sequential reduction leads to suppression of PAHs growth, nucleation, surface growth, and soot coagulation. Besides, a longer flame length resulting from the increased blending ratio of n-butanol could also have an additional soot suppression effect by improving air-fuel mixing and thus suppressing the overall soot mass.

Irradiation temperature and dose rate dependence of void swelling in RAFM steel during irradiation: Reaction rate theory analysis

Reaction rate theory analysis has performed to investigate the irradiation temperature and dose rate dependence of void swelling of RAFM steel under a wide range of irradiation temperatures and dose rates (250 to 620 °C and 10−7 to 10−3 dpa/s) with focusing on nucleation behavior of voids. In the rate theory analysis, an improved nucleation model is employed where the stable nucleus size of voids is estimated by the vacancy flux into/from voids which depends on irradiation condition and void size. The calculation says that the void swelling strongly depends on irradiation temperature and dose rate, and there is one unique peak temperature for each dose rate. As dose rate increases, the peak temperature shifts to higher temperatures and the peak swelling decreases; this results from the enhancement and suppression of void nucleation. The calculated stable nucleus size of voids remarkably depends on irradiation conditions and varies widely from 5 to about 50: the nucleus size drastically increases at higher temperatures, while it decreases at higher dose rates. For the dose rate dependence of the peak temperature of void swelling, the calculation provides a good agreement with the experiment more than a conventional model.

Molecular Mechanisms of Amyloid-β Self-Assembly Seeded by In Vivo-Derived Fibrils and Inhibitory Effects of the BRICHOS Chaperone.

Self-replication of amyloid-β-peptide (Aβ) fibril formation is a hallmark in Alzheimer's disease (AD). Detailed insights have been obtained in Aβ self-assembly in vitro, yet whether similar mechanisms are relevant in vivo has remained elusive. Here, we investigated the ability of in vivo-derived Aβ fibrils from two different amyloid precursor protein knock-in AD mouse models to seed Aβ42 aggregation, where we quantified the microscopic rate constants. We found that the nucleation mechanism of in vivo-derived fibril-seeded Aβ42 aggregation can be described with the same kinetic model as that in vitro. Further, we identified the inhibitory mechanism of the anti-amyloid BRICHOS chaperone on seeded Aβ42 fibrillization, revealing a suppression of secondary nucleation and fibril elongation, which is strikingly similar as observed in vitro. These findings hence provide a molecular understanding of the Aβ42 nucleation process triggered by in vivo-derived Aβ42 propagons, providing a framework for the search for new AD therapeutics.

Effect of pre-existing crystals and melt homogeneity on the decompression-induced crystallization of hydrous rhyodacite magma

Abstract Decompression-induced crystallization is an important process that controls the behavior of volcanic eruptions because it strongly affects magma rheology and degassing behavior in the shallow parts of volcanic conduits. Several decompression experiments have been performed to understand and model the crystallization processes; however, the effect of superheating (i.e., heating above the liquidus temperature for a definite period of time) before decompression has not been elucidated, despite the proposal of its importance in previous cooling experiments. As the superheating influences the number of pre-existing crystals and melt homogeneity, it is expected to control decompression-induced crystallization. In this study, we investigated the effects of pre-existing crystals and melt homogeneity on crystallization during the decompression of rhyodacitic magma at a temperature of 900 °C. The magma studied herein has a liquidus temperature of ~920 °C. Five starting materials were prepared via heating at different super-liquidus temperatures (940, 970, 1050, and 1300 °C) and a sub-liquidus temperature (900 °C) using an internally heated pressure vessel and a cold-seal pressure vessel, respectively. Decompression experiments using these starting materials were conducted from 130 to 30 MPa at decompression rates of 5, 20, and 100 MPa h–1. When the melt was completely homogenized (at 1050 and 1300 °C), no crystals were formed at 100 MPa h–1 and the small amounts of crystals heterogeneously formed along the capsule wall were found at 5 and 20 MPa h–1. At the same decompression rate, the number density of plagioclase formed during decompression increased as the superheating temperature decreased from 970 to 900 °C, despite the higher number densities of pre-existing crystals before decompression in the samples with lower superheating. Such finding indicates that nucleation occurs easily when the number density is initially high. This result is inconsistent with the idea that nucleation occurs when supersaturation is sufficient to overcome the energy barrier for nucleation, and the growth of pre-existing crystals decreases supersaturation. In contrast, the results of our experiments can be explained by considering that higher superheating results in a more homogeneous melt structure with few pre-crystal clusters, which are growth sites, and ultimately the suppression of nucleation. Based on these results, we conclude that pre-existing crystals and melt homogeneity strongly affect the crystal texture formed by decompression. For application to natural systems, the high number density of microlites found in natural samples may be due to heterogeneous nucleation caused by the presence of pre-crystal clusters and other mechanisms. Furthermore, the superheating of magma in a reservoir caused by the injection of high-temperature mafic magma may influence the crystal texture during magma ascent and, hence, control the explosivity of the eruption.

Fine-tuning of the size of supramolecular nanotoroids suppresses the subsequent catenation of nano-[2]catenane.

A judicious combination of ring-closing supramolecular polymerization and secondary nucleation can hierarchically organize a diphenylnaphthalene barbiturate monomer bearing a 3,4,5-tri(dodecyloxy)benzyloxy unit into self-assembled nano-polycatenanes composed of nanotoroids. In our previous study, nano-polycatenanes of variable length have been formed uncontrollably from the monomer that provides nanotoroids with sufficiently wide inner void space wherein secondary nucleation is driven by non-specific solvophobic interaction. In this study, we found that the elongation of the alkyl chain length of the barbiturate monomer decreases the inner void space of nanotoroids while increasing the frequency of secondary nucleation. These two effects resulted in an increase in the yield of nano-[2]catenane. This unique property observed in our self-assembled nanocatenanes might be extended to a controlled synthesis of covalent polycatenanes using non-specific interactions.

Tuning Interfacial Concentration Enhancement through Dispersion Interactions to Facilitate Heterogeneous Nucleation.

Classical molecular dynamics simulations were used to investigate how dispersion (van der Waals) interactions between non-polar, hydrophobic surfaces and aqueous glycine solutions affect the solution composition, molecular orientation, and dynamics at the interface. Simulations revealed that dispersion interactions lead to a major increase in the concentration of glycine at the interface in comparison with the bulk solution, resulting from a competition between solute and solvent molecules to be or not to be near the interface. This can then lead to kinetic and/or structural effects facilitating heterogeneous nucleation of glycine at non-polar surfaces, in agreement with recent observations for tridecane, graphene, and polytetrafluoroethylene. A novel parameterization process was developed to map a model surface with tunable dispersion interactions to heptane, tridecane, and graphite materials. The model surface was capable of reproducing the solution structure observed in fully atomistic simulations with excellent agreement and also provided good agreement for dynamic properties, at a significantly reduced computational cost. This approach can be used as an effective tool for screening materials for heterogeneous nucleation enhancement or suppression, based on non-specific dispersion interactions based on bulk material molecular properties, rather than interfacial functional groups, templating or confinement effects.

Shear-induced amorphization in nanocrystalline NiTi micropillars under large plastic deformation

Shear-induced amorphization is a phenomenon observed in polycrystalline NiTi shape memory alloys under severe plastic deformation, but the underlying mechanism of such a microstructural change remains elusive. To study the isothermal large-strain plastic deformation behavior and the associated mechanisms, uniaxial compression is performed on nanocrystalline NiTi cuboidal micropillars with initial grain sizes of 35 and 110 nm. It is found that the micropillars demonstrate high deformability with plastic strains up to 110% via shear-induced amorphization. It is shown that plastic strain localization in shear bands of the 35 nm-grain-size sample prompts notable amorphization up to an area fraction of 90% and crystal refinement down to 5 nm. High-resolution transmission electron microscope and molecular dynamics simulations reveal that the shear-induced amorphization starts from the local martensite phase near grain boundaries through accumulation of crystalline defects. The amorphization can lead to a reduction in the crystal size and an increase in the plastic flow stress. The large plastic deformation of the nanocrystalline NiTi micropillars via shear-induced amorphization is enabled by the suppression of crack nucleation through dynamic recovery of nanovoids. Our work provides new perspectives for producing crystalline-amorphous nanostructures in shape memory alloys at small scale.

A multifunctional constrained host towards dendrite-free lithium anode

Uncontrolled growth of Li dendrites, the huge volume change of anode as well as unstable solid-electrolyte interphase (SEI) hinder the safety application of high specific energy Li metal batteries (LMBs). Herein, a synergistic strategy is introduced to address the above issues via building a multifunctional constrained host of Ag2S/Ti3C2 film. Anchor the Ti3C2 nanosheets layers with Ag2S nanowires (Ag2S NWs) network to build a solid skeleton structure, which can provide sufficient void space, alleviate the collapse of the host structural during repeated Li plating/stripping. Furthermore, with the Li plating, Ag2S can be reduced to lithiophilic Ag, inducing the uniform Li nucleation and dendritic growth suppression, and the by-product Li2S in situ generation along the Ag2S NWs could strengthen the SEI. Consequently, the electrode of Li-Ag2S/Ti3C2 can operate stably for more than 1200 h at a current density of 0.5 mA cm–2 in the symmetric cell cycling test. The Li-Ag2S/Ti3C2||NCM811 coin cell exhibits high Coulombic efficiencies (CE) (97.94%) after 300 cycles at 1 C.

Thermal suppression of bubble nucleation at first-order phase transitions in the early Universe

One of the key observables in a gravitational wave power spectrum from a first order phase transition in the early Universe is the mean bubble spacing, which depends on the rate of nucleation of bubbles of the stable phase, as well as the bubble wall speed. When the bubbles expand as deflagrations, it is expected that the heating of the fluid in front of the phase boundary suppresses the nucleation rate. We quantify the effect, showing that it increases the mean bubble separation, and acts to enhance the gravitational wave signal by a factor of up to order 10. The effect is largest for small wall speeds and strong transitions.

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Tuning Ice Nucleation by Mussel-Adhesive Inspired Polyelectrolytes: The Role of Hydrogen Bonding

Gas-Phase Alkali Metal-Assisted MOCVD Growth of 2D Transition Metal Dichalcogenides for Large-Scale Precise Nucleation Control.

Advances in large-area and high-quality 2D transition metal dichalcogenides (TMDCs) growth are essential for semiconductor applications. Here, the gas-phase alkali metal-assisted metal-organic chemical vapor deposition (GAA-MOCVD) of 2D TMDCs is reported. It is determined that sodium propionate (SP) is an ideal gas-phase alkali-metal additive for nucleation control in the MOCVD of 2D TMDCs. The grain size of MoS2 in the GAA-MOCVD process is larger than that in the conventional MOCVD process. This method can be applied to the growth of various TMDCs (MoS2 , MoSe2 , WSe2 , and WSe2 ) and the generation of large-scale continuous films. Furthermore, the growth behaviors of MoS2 under different SP and oxygen injection time conditions are systematically investigated to determine the effects of SP and oxygen on nucleation control in the GAA-MOCVD process. It is found that the combination of SP and oxygen increases the grain size and nucleation suppression of MoS2 . Thus, the GAA-MOCVD with a precise and controllable supply of a gas-phase alkali metal and oxygen allows achievement of optimum growth conditions that maximizes the grain size of MoS2 . It is expected that GAA-MOCVD can provide a way for batch fabrication of large-scale atomically thin electronic devices based on 2D semiconductors.

Efficient and Controlled Seeded Growth of Poly(3-hexylthiophene) Block Copolymer Nanofibers through Suppression of Homogeneous Nucleation

Low-dispersity, length-tunable block copolymer nanofibers with spatially controlled functionalization and a crystalline core have recently become accessible using the ambient temperature, living crystallization-driven self-assembly (CDSA) seeded-growth method. The crystallizable π-conjugated polymer, poly(3-hexylthiophene) (P3HT), is of particular interest as a core-forming block as a result of its useful optoelectronic properties. However, attempts to apply the living CDSA method to P3HT diblock copolymers have had limited success as, in addition to seeded growth, homogeneous nucleation events result in the spontaneous formation of new fibers, which leads to a loss of length control. Herein, we demonstrate that by performing detailed variable temperature ultraviolet–visible (UV–vis) spectroscopic studies of the homogeneous nucleation of rrP3HT106-b-rsP3HT47 block copolymer (rr = regioregular and rs = regiosymmetric, respectively) we were able to identify conditions (40 °C) under which spontaneous (homogeneous) nucleation is suppressed. Addition of preformed seeds under these conditions allowed for highly efficient living CDSA to yield nanofibers with a rrP3HT106 core and controllable lengths up to ca. 4 μm with low length dispersity. Analogous use of this technique also allowed the efficient preparation of B-A-B triblock comicelles through the growth of P3HT70-b-PS197 from the termini of rrP3HT106-b-rsP3HT47 nanofibers that function as seed micelles, and also multiarm starlike arrays of fiberlike micelles with variable arm lengths, which were formed when seed micelles derived from rrP3HT150 homopolymer were used.