Energy Barrier For Nucleation Research Articles

Role of graphitized mesoporous carbon on solidification and melting characteristics of water for cool thermal storage

Cool thermal energy storage systems (CTES) using phase change materials (PCM) are paramount in the energy management of buildings. This work aims to investigate the role of graphitized mesoporous carbon (GMC) on the thermal storage behavior of water based nanofluid PCM (NFPCM) in a spherical capsule. The NFPCMs exhibit a lower contact angle, indicating a reduction in the nucleation energy barrier. Thermal conductivity of NFPCM shows an enhancement of 36% with the presence of graphitized walls and isotropic nature of GMC. Temperature–time history method is used to evaluate the latent heat of fusion for the NFPCMs and the results are compared with differential scanning calorimetry measurements. Addition of GMC shortens the solidification duration by 6% and reduces the subcooling of NFPCM compared to base PCM. The charging results of NFPCMs demonstrate a cool energy storage of 96% in accelerated mode. The melting rate of NFPCM is expedited at a minimal GMC concentration and melting duration prolongs with further GMC addition. In conclusion, the proposed NFPCMs exhibiting a lower subcooling, improved nucleation behavior and accelerated mode of charging shows great potential for CTES applications.

Nitrogen-doped carbonaceous scaffold anchored with cobalt nanoparticles as sulfur host for efficient adsorption and catalytic conversion of polysulfides in lithium-sulfur batteries

The effective inhibition of lithium polysulfides (LiPSs) and promotion of their conversion in the redox processes is indispensable to achieve the long cycle stability and excellent rate performance of lithium-sulfur (Li-S) batteries. Especially, the generally slow electrocatalytic sulfur redox kinetics and large interfacial Li2S nucleation energy barriers have hindered the widespread application of Li-S batteries. Herein, a robust three-dimensional sulfur carrier (denoted as Co-NCNT) is well-constructed using the potassium citrate derived porous carbon sheets as substrate and the catalytic growth nitrogen-doped porous carbon nanotubes as vertical scaffolds. Such a rationally designed structure guarantees efficient electron transfer pathways and ions diffusion channels. More importantly, it is conducive to the adsorption/catalytic conversion of intermediate lithium polysulfides and the nucleation of Li2S. Due to these merits, the S@Co-NCNT cathode achieves an initial discharge capacity up to 1072.7 mAh g−1 at 1.0 C, and it can retain a high capacity of 482.9 mAh g−1 with a capacity attenuation rate of only 0.045% per cycle after 1000 cycles. Upon a high sulfur loading of 5.87 mg cm−2, the S@Co-NCNT electrode can still reach an initial capacity of 739.5 mAh g−1 at 0.3 C. Particular emphasis is that our work broadens the way to prepare well-designed carbonaceous materials sulfur host for long-life Li-S batteries.

Fouling propensity in reverse electrodialysis operated with hypersaline brine

The impact of fouling on the performance of Reverse Electrodialysis operated with highly concentrated brine is a poorly investigated area. In this work, the fouling propensity and stability of Ion Exchange Membranes (IEMs), developed by Fujifilm Manufacturing Europe BV (The Netherlands), is investigated under the condition of seawater and brine. The fouling propensity of the IEMs was depicted by the determination of the Gibbs energy barrier of based-on the Classical Nucleation along with the Theoretical modeling of heterogeneous nucleation as a function of electrochemical (contact angle, permittivity, charge density) and morphological (roughness) membrane properties validated by CaCO3 precipitation. Results indicate that Cation Exchange Membranes (CEM) are more susceptible to the scaling due to the reduced energy barrier of heterogeneous nucleation. FTIR-ATR analysis on six months-aged membranes samples indicated a partial modification in the chemical structure of Anion Exchange Membranes (AEM) induced by the organic fouling associated with humic substances. The tensile tests demonstrated substantial mechanical stability of IEMs. Lab-scale RED tests operated with artificial brine over 30 days showed a significant increase in pressure drop through feed channels due to significant colloidal fouling along with a 23% reduction of maximum gross power density with consequent decrease of net power density.

A Salt‐in‐Metal Anode: Stabilizing the Solid Electrolyte Interphase to Enable Prolonged Battery Cycling

AbstractMetallic lithium (Li) is the ultimate anode candidate for high‐energy‐density rechargeable batteries. However, its practical application is hindered by serious problems, including uncontrolled dendritic Li growth and undesired side reactions. In this study a concept of “salt‐in‐metal” is proposed, and a Li/LiNO3 composite foil is constructed such that a classic electrolyte additive, LiNO3, is embedded successfully into the bulk structure of metallic Li by a facile mechanical kneading approach. The LiNO3 reacts with metallic Li to generate Li+ conductive species (e.g., Li3N and LiNxOy) over the entire electrode. These derivatives afford a stable solid electrolyte interphase (SEI) and effectively regulate the uniformity of the nucleation/growth of Li on initial plating, featuring a low nucleation energy barrier and large crystalline size without mossy morphology. Importantly, these derivatives combined with LiNO3 can in‐situ repair the damaged SEI from the large volume change during Li plating/stripping, enabling a stable electrode‐electrolyte interface and suppressing side reactions between metallic Li and electrolyte. Stable cycling with a high capacity retention of 93.1% after 100 cycles is obtained for full cells consisting of high‐loading LiCoO2 cathode (≈20 mg cm−2) and composite metallic Li anode with 25 wt% LiNO3 under a lean electrolyte condition (≈12 µL) at 0.5 C.

Dislocation nucleation in Al single crystal at shear parallel to (111) plane: Molecular dynamics simulations and nucleation theory with artificial neural networks

We develop the theory of homogeneous nucleation of dislocations, which predicts plasticity incipience in FCC single crystal using material properties at elastic stage. In contrast to previous nucleation theories, we show that the work of shear stress is compensated by variation of the generalized stacking fault (GSF) energy during the loop formation. As a result, the energy barrier of nucleation includes only the line defect energy of the critical loop, which radius is defined by balance between all three contributions including the work of shear stress, the surface defect energy of the GSF and the line defect energy. This distinction is consequence of the difference between the mechanisms of the initial loop formation consisting in gradual shear along the proto-loop area and the following growth by slip of bordering dislocation line. Calculation of the energy barrier requires material properties at elastic stage such as stress-strain relationship, the GSF and shear modulus. These data are determined from molecular dynamics (MD) simulations and approximated in the form of artificial neural networks (ANNs). We perform direct MD simulations of the dislocation nucleation for simple shear in different directions parallel to (111) plane in Al single crystal at initial pressures from −3 to +3 GPa. MD simulations show complex and nonlinear evolution of stresses at simple shear deformation even at elastic stage before the dislocation nucleation. Predictions of ANN-informed theory are in accordance with our MD simulations and with the literature data. The calculated nucleation threshold for shear along the Burgers vector of partial Shockley dislocation in [112¯] direction at zero initial pressure varies from 2.03 to 2.16 GPa at the strain rate increase from 1 to 109 s−1. The conditions for homogeneous nucleation are close to the states of matter in thin metal films under powerful sub-picosecond laser irradiation. It is shown that twins are nucleated at angles less or equal to 7.5° between the shear direction and [112¯] direction. Perfect dislocation loops formed by leading and trailing partial dislocations arise at larger angles. In spite of change in the final form of nucleated defect, the energy barrier of nucleation is well-described by the same theoretical expression. It is explained by the fact that the initial defect in both cases is the loop of leading partial dislocation with the stacking fault over the entire loop area. The formation of twin or perfect dislocation occurs after the nucleation and does not influence the nucleation threshold. The ANNs reveal themselves as an efficient tool for approximation of the complex and non-obvious dependencies, while one should be careful with using them for data extrapolation. The paper is supplemented by files with the parameters of the trained ANNs and description of their structure so that one can use them within the nucleation model or separately.

Precise Droplet Manipulation Based on Surface Heterogeneity

ConspectusThe control of droplet behavior has been investigated for several centuries due to its universality and significance in nature, daily life, and industrial applications. Diverse strategies have been developed and employed to regulate droplet behavior, and great progress has been achieved such as accelerated droplet bouncing, controlled droplet dispensing, and enhanced droplet adhesion. Compared with the strategies utilizing external fields including magnets, heat, light, and electricity as well as various topological structures, the heterogeneous wettability surface provides a facile and efficient way to manipulate droplet behavior and thus has aroused increasing research interest in many fields.The heterogeneous wettability substrate integrates wettable and less wettable regions onto an individual surface, with rational design and a geometrical arrangement. Therefore, it shows more precise, diverse, and controllable interactions with droplets than homogeneous surfaces. In addition to confining the droplet position and morphology and regulating the droplet dynamics, the nonuniformity in wettability can induce a difference in electrical conductivity, nucleation energy barriers, and so forth, which greatly extends its application in the fields of functional materials deposition and device fabrication. In this Account, recent progress in the precise droplet manipulation based on heterogeneous wettability is summarized. First, the principle of droplet control by a heterogeneous surface and the development of the green printing technique based on this principle are introduced. Then the droplet manipulation, categorized as droplet patterning, droplet isolation, and droplet dynamics, is described. Meanwhile, related applications, such as high-capacity information coding, highly sensitive detection, and high-performance optic/electric device fabrication, are demonstrated. In addition, the general principle for controlling the droplet impact using heterogeneous wettability substrates is highlighted. Finally, a brief summary of this Account, with challenges and opportunities in this field, is proposed.

Probing Kinetics and Mechanism of Formation of Mixed Metallic Nanoparticles in a Polymer Membrane by Galvanic Replacement between Two Immiscible Metals: Case Study of Nickel/Silver Nanoparticle Synthesis.

Galvanic replacement between metals has received notable research interest for the synthesis of heterometallic nanostructures. The growth pattern of the nanostructures depends on several factors such as extent of lattice mismatch, adhesive interaction between the metals, cohesive forces of the individual metals, etc. Due to the difficulties in probing ultrafast kinetics of the galvanic replacement reaction and particle growth in solution, real-time mechanistic investigations are often limited. As a result, the growth mechanism of one metal on the surface of another metal at the nanoscale is poorly understood so far. In the present work, we could successfully probe the galvanic replacement of silver ions with nickel nanoparticles, stabilized in a polymer membrane, using two complementary methods, namely, small-angle X-ray scattering (SAXS) and radiolabeling, and the results are supported by density functional theory (DFT) computations. The silver-nickel system has been chosen for the present investigation because of the high degree of bulk immiscibility caused by the large lattice mismatch (15.9%) and the weak adhesive interaction, which makes it a perfect model system for immiscible metal pairs. Membrane, as a host medium, plays a crucial role in retarding the kinetics of atomic and particle rearrangements (nucleation and growth) due to slower mobility of the atoms (monomers) and particles within the polymer network. This allowed us to examine the real-time concentration of silver monomers during galvanic replacement of silver ions with nickel nanoparticles and evolution of Ni/Ag nanoparticles. From combined experiment and DFT computations, it has been demonstrated, for the first time to the best of our knowledge, that the majority of silver atoms, which are produced on the nickel nanoparticle surface by galvanic reactions, do not form traditional core-shell nanostructures with nickel and undergo a self-governing sequential nucleation and growth of silver nanoparticles via formation of intermediate prenucleation silver clusters, leading to the formation of mixed metallic nanoparticles in the membrane. The surface of NiNPs has a heterogeneous effect on the silver nucleation pathway, which is evident from the reduced critical free energy barrier of nucleation (ΔGcrit). The present work establishes an original mechanistic pathway based on a sequential nucleation model for formation of mixed metallic nanoparticles by the galvanic replacement route, which opens up future possibilities for size-controlled synthesis in mixed systems.

Deep Insights into the Twinning Mechanism in High-Performance Al Alloys: A Comprehensive First-Principles Study

The twinning mechanism of Al solid solutions is comprehensively investigated via the first-principles method. The relative stability of C and H atoms at tetrahedral and octahedral centers is discussed. Moreover, the interaction energies between solute atoms at different atomic layers and generalized stacking-fault structures are calculated. Results indicate that the stable occupation of C atom exists at the octahedral center rather than at the tetrahedral center. By contrast, the H atom stably exists at the tetrahedral center rather than at the octahedral center. Both atoms can effectively reduce the minimum energy barrier of dislocation nucleation, thereby promoting dislocation nucleation. The C atom more easily promotes dislocation nucleation than the H atom. Furthermore, both atoms are repelled by the stacking-fault plane. However, they are more likely to be segregated in the second neighboring layer of unstable stacking fault, intrinsic stacking fault (ISF), and unstable twinning fault (UTF) structures. Charge density measurements reveal that the twinning process is likely inhibited because of the strong local chemical bonding around the UTF layer from the ISF structure to the UTF structure. High concentrations of both atoms inhibit the twinning deformation at crack tips and grain boundaries, but they have almost no effect on the twinning deformation inside the grains. This study provides deep insights into the twinning deformation mechanism of face-centered-cubic alloy systems.

Initiation of nanosecond-pulsed discharge in water: Electrostriction effect

Underwater nanosecond-pulsed discharges have been widely utilized in numerous industrial applications. The initial stage of nanosecond-pulsed discharge in water contains extremely abundant physical processes, however, it is still difficult to reveal the details of charge transportation and multiplicative process in liquid within several nanoseconds by currently existing experimental diagnostic techniques. Up to now, the initiation mechanism of underwater nanosecond discharge has been still a puzzle. In this paper, we develop a two-dimensional axially symmetric underwater discharge model of pin-to-plane, and numerically investigate the electrostriction process, cavitation process, and ionization process in water, induced by nanosecond-pulsed voltage. The negative pressure in water caused by tensile ponderomotive force is calculated. The creation of nanoscale cavities (so-called nanopores) in liquid due to negative pressure is modeled by classical nucleation theory with modified nucleation energy barrier. When estimating the temporal development of nanopore radius, a varying hydrostatic pressure is considered to restrain the unlimited expansion of nanopores. We estimate the electron generation rate by the product of the generation rate of incident electrons and the number density of nanopores. The simulation results show that cavitation occurs in liquid within several microns from pin electrode due to the electrostriction, which results in the formation of a large number of nanopores. The expansion of nanopore, caused by electrostrictive pressure on nanopore surface, provides a sufficient acceleration distance for electrons. The impact ionization of water molecules can be triggered by energetic electrons, leading the local liquid to be ionized rapidly. The effects of nanopores on rapid electron generation in water are discussed. Once nanopores are formed, the electrons can be generated in the following ways: 1) Field ionization of water molecules on the nanopore wall continuously provides seed electrons; 2) the seed electrons accelerated in nanopores enter into the liquid and collide with water molecules, resulting in the rapid increase of electrons. It can be inferred that the randomly scattered nanopores act as micro-sources of charges that contribute to the continuing ionization of liquid water in cavitation region near pin electrode. Electrostriction mechanism provides a new perspective for understanding the initiation of nanosecond-pulsed discharge in water.

Suppression of ice nucleation in supercooled water under temperature gradients

Understanding the behaviours of ice nucleation in non-isothermal conditions is of great importance for the preparation and retention of supercooled water. Here ice nucleation in supercooled water under temperature gradients is analyzed thermodynamically based on classical nucleation theory (CNT). Given that the free energy barrier for nucleation is dependent on temperature, different from a uniform temperature usually used in CNT, an assumption of linear temperature distribution in the ice nucleus was made and taken into consideration in analysis. The critical radius of the ice nucleus for nucleation and the corresponding nucleation model in the presence of a temperature gradient were obtained. It is observed that the critical radius is determined not only by the degree of supercooling, the only dependence in CNT, but also by the temperature gradient and even the Young’s contact angle. Effects of temperature gradient on the change in free energy, critical radius, nucleation barrier and nucleation rate with different contact angles and degrees of supercooling are illustrated successively. The results show that a temperature gradient will increase the nucleation barrier and decrease the nucleation rate, particularly in the cases of large contact angle and low degree of supercooling. In addition, there is a critical temperature gradient for a given degree of supercooling and contact angle, at the higher of which the nucleation can be suppressed completely.

Fracture and wear mechanisms of FeMnCrNiCo + x(TiC) composite high-entropy alloy cladding layers

FeMnCrNiCo + x(TiC) composite high-entropy alloy (HEA) coatings were manufactured by laser cladding. Then the small punch and wear experiments at room temperature were conducted. The phases and microstructures of the composite HEA coatings were characterized using XRD, SEM/EDS, EBSD and TEM, and the strengthening, fracture and wear mechanisms of coatings were systematically analyzed and discussed. The results showed that small-sized particles and large-sized particles in coatings reduced the nucleation energy barrier of grain, and particles precipitated at grain boundaries hindered the movement of grain boundary. And the refined grain and increased dislocation density enhanced the capability of coatings to resist potential plastic deformation. As for the properties, the strength of the coating with 5 wt% TiC was increased, but cracks easily initiated and propagated around the precipitated particles at grain boundaries, which lowered the toughness. The excess TiC made the brittle and large-sized particles become cracking sources in coatings, thus the strength and toughness of coatings were deteriorated. Obvious fatigue wear tendency in these two coatings (5 wt% & 10 wt%) influenced their service life in the wear environment, although the coating with 10 wt% TiC had better surface wear performance.

Crystallization Kinetics Modulation of FASnI3 Films with Pre-nucleation Clusters for Efficient Lead-Free Perovskite Solar Cells.

Tin halide perovskites are rising as promising materials for lead-free perovskite solar cells (PSCs). However, the crystallization rate of tin halide perovskites is much faster than the lead-based analogs, leading to more rampant trap states and lower efficiency. Here, we disclose a key finding to modulate the crystallization kinetics of FASnI3 through a non-classical nucleation mechanism based on pre-nucleation clusters (PNCs). By introducing piperazine dihydriodide to tune the colloidal chemistry of the FASnI3 perovskite precursor solution, stable clusters could be readily formed in the solution before nucleation. These pre-nucleation clusters act as intermediate phase and thus can reduce the energy barrier for the perovskite nucleation, resulting in a high-quality perovskite film with lower defect density. This PNCs-based method has led to a conspicuous photovoltaic performance improvement for FASnI3 -based PSCs, delivering an impressive efficiency of 11.39 % plus improved stability.

Crystallization Kinetics Modulation of FASnI3 Films with Pre‐nucleation Clusters for Efficient Lead‐Free Perovskite Solar Cells

AbstractTin halide perovskites are rising as promising materials for lead‐free perovskite solar cells (PSCs). However, the crystallization rate of tin halide perovskites is much faster than the lead‐based analogs, leading to more rampant trap states and lower efficiency. Here, we disclose a key finding to modulate the crystallization kinetics of FASnI3 through a non‐classical nucleation mechanism based on pre‐nucleation clusters (PNCs). By introducing piperazine dihydriodide to tune the colloidal chemistry of the FASnI3 perovskite precursor solution, stable clusters could be readily formed in the solution before nucleation. These pre‐nucleation clusters act as intermediate phase and thus can reduce the energy barrier for the perovskite nucleation, resulting in a high‐quality perovskite film with lower defect density. This PNCs‐based method has led to a conspicuous photovoltaic performance improvement for FASnI3‐based PSCs, delivering an impressive efficiency of 11.39 % plus improved stability.

Direct Self‐Assembly of MXene on Zn Anodes for Dendrite‐Free Aqueous Zinc‐Ion Batteries

Metallic zinc is a promising anode candidate of aqueous zinc-ion batteries owing to its high theoretical capacity and low redox potential. However, Zn anodes usually suffer from dendrite and side reactions, which will degrade their cycle stability and reversibility. Herein, we developed an in situ spontaneously reducing/assembling strategy to assemble a ultrathin and uniform MXene layer on the surface of Zn anodes. The MXene layer endows the Zn anode with a lower Zn nucleation energy barrier and a more uniformly distributed electric field through the favorable charge redistribution effect in comparison with pure Zn. Therefore, MXene-integrated Zn anode exhibits obviously low voltage hysteresis and excellent cycling stability with dendrite-free behaviors, ensuring the high capacity retention and low polarization potential in zinc-ion batteries.

Direct Self‐Assembly of MXene on Zn Anodes for Dendrite‐Free Aqueous Zinc‐Ion Batteries

AbstractMetallic zinc is a promising anode candidate of aqueous zinc‐ion batteries owing to its high theoretical capacity and low redox potential. However, Zn anodes usually suffer from dendrite and side reactions, which will degrade their cycle stability and reversibility. Herein, we developed an in situ spontaneously reducing/assembling strategy to assemble a ultrathin and uniform MXene layer on the surface of Zn anodes. The MXene layer endows the Zn anode with a lower Zn nucleation energy barrier and a more uniformly distributed electric field through the favorable charge redistribution effect in comparison with pure Zn. Therefore, MXene‐integrated Zn anode exhibits obviously low voltage hysteresis and excellent cycling stability with dendrite‐free behaviors, ensuring the high capacity retention and low polarization potential in zinc‐ion batteries.

The role of water in the primary nucleation of protein amyloid aggregation

The understanding of the complex conformational landscape of amyloid aggregation and its modulation by relevant physicochemical and cellular factors is a prerequisite for elucidating some of the molecular basis of pathology in amyloid related diseases, and for developing and evaluating effective disease-specific therapeutics to reduce or eliminate the underlying sources of toxicity in these diseases. Interactions of proteins with solvating water have been long considered to be fundamental in mediating their function and folding; however, the relevance of water in the process of protein amyloid aggregation has been largely overlooked. Here, we provide a perspective on the role water plays in triggering primary amyloid nucleation of intrinsically disordered proteins (IDPs) based on recent experimental evidences. The initiation of amyloid aggregation likely results from the synergistic effect between both protein intermolecular interactions and the properties of the water hydration layer of the protein surface. While the self-assembly of both hydrophobic and hydrophilic IDPs would be thermodynamically favoured due to large water entropy contributions, large desolvation energy barriers are expected, particularly for the nucleation of hydrophilic IDPs. Under highly hydrating conditions, primary nucleation is slow, being facilitated by the presence of nucleation-active surfaces (heterogeneous nucleation). Under conditions of poor water activity, such as those found in the interior of protein droplets generated by liquid-liquid phase separation, however, the desolvation energy barrier is significantly reduced, and nucleation can occur very rapidly in the bulk of the solution (homogeneous nucleation), giving rise to structurally distinct amyloid polymorphs. Water, therefore, plays a key role in modulating the transition free energy of amyloid nucleation, thus governing the initiation of the process, and dictating the type of preferred primary nucleation and the type of amyloid polymorph generated, which could vary depending on the particular microenvironment that the protein molecules encounter in the cell.

Promoting Lithium Electrodeposition Towards the Bottom of 3-D Copper Meshes in Lithium-Based Batteries

Lithium (Li) has been considered as the promising negative electrode in rechargeable batteries, owing to the negative redox potential (-3.04 V vs. SHE), low density (0.534 g/cm3), and high theoretical specific capacity (3,860 mAh/g). However, the non-uniform stripping/plating process of the metallic Li is still challenging.[1] As one of the solutions, three-dimensional (3-D) metallic scaffolds were introduced to the negative electrode. The uniform electric field applied in the porous scaffolds could suppress the dendritic growth of the Li during the plating process. In addition, a decrease in the effective current density prolonged Sand’s time.[2] However, such a Li deposition mainly proceeded on the top surface and led to rapid surface clogging due to the strong surface electric field. In this presentation, we show the preferred Li deposition inside the 3-D copper (Cu) scaffold using gold nanoparticles (Au NPs). The lower Li nucleation energy barrier on the Au surface than that on the typical Cu current collector was investigated intensively.[3] However, the role of Au for spatially promoting Li deposition was not studied in depth. We added the Au NPs with an average particle size of ~7.5 nm to the bottom of 3-D Cu. The Au NPs with a total ~28 nmol reduced the charge-transfer resistance, which suggested the fast Li nucleation on the Au. In addition, we coated aluminum oxide (Al2O3) layer with ~ 26 nm of thickness on the top surface of 3-D Cu scaffold through the atomic layer deposition (ALD) process. This insulating layer further suppressed the Li deposition on the surface. As a result, apparent Li deposition towards the bottom of 3-D Cu was clearly demonstrated. During Li plating/stripping cycles, the surface clogging of the 3-D Cu/Au by an accumulation of solid electrolyte interphase (SEI) was also dramatically alleviated even in the absence of Al2O3 layer. It demonstrated the continuous Li deposition towards the bottom of the 3-D Cu/Au scaffold. Besides, symmetric 3-D Cu/Au cells exhibited over 95 % of Coulombic efficiency (CE) for ~120 cycles. The full cells comprised of the 3-D Cu/Au and LiFePO4 (LFP) electrodes delivered stable 300 cycles with a capacity of ~140 mAh/g at 1 C-rate. I will discuss the detailed role of the Au NPs and the Al2O3 layer, and comparative cell performances in the presentation.

Crystallization of FCC and BCC Liquid Metals Studied by Molecular Dynamics Simulation

The atomic structure variations on cooling, vitrification and crystallization processes in liquid metals face centered cubic (FCC) Cu are simulated in the present work in comparison with body centered cubic (BCC) Fe. The process is done on continuous cooling and isothermal annealing using a classical molecular-dynamics computer simulation procedure with an embedded-atom method potential at constant pressure. The structural changes are monitored with direct structure observation in the simulation cells containing from about 100 k to 1 M atoms. The crystallization process is analyzed under isothermal conditions by monitoring density and energy variation as a function of time. A common-neighbor cluster analysis is performed. The results of thermodynamic calculations on estimating the energy barrier for crystal nucleation and a critical nucleus size are compared with those obtained from simulation. The differences in crystallization of an FCC and a BCC metal are discussed.

Covalent Organic Frameworks Construct Precise Lithiophilic Sites for Uniform Lithium Deposition

<h2>Summary</h2> Lithium (Li) metal represents one of the most promising anode materials for constructing high-energy-density rechargeable batteries. However, uncontrolled Li dendrite growth induces limited lifespan and safety hazards, impeding the development of Li metal batteries severely. Introducing a Li host has been shown to effectively relieve dendrite growth, while further construction of lithiophilic sites will significantly facilitate uniform Li deposition for stably cycling Li metal batteries. Herein, a boroxine covalent organic framework (COF-1) is employed to construct a lithiophilic host for dendrite inhibition in working Li metal batteries. The well-defined boroxine sites demonstrate ideal lithiophilicity to reduce the Li nucleation energy barrier, and the ordered framework structure of COF-1 affords a uniform distribution of the lithiophilic sites. As a result, the COF-1-based Li host affords a more than doubled lifespan of routine anodes in both half- and full cells. This work demonstrates the promising potential of applying advanced framework materials to essential energy-related processes.

Predominant Effect of Material Surface Hydrophobicity on Gypsum Scale Formation.

Scale formation is an important challenge in water and wastewater treatment systems. However, due to the complex nature of membrane surfaces, the effects of specific membrane surface characteristics on scale formation are poorly understood. In this study, the independent effect of surface hydrophobicity on gypsum (CaSO4·2H2O) scale formation via surface-induced nucleation and bulk homogeneous nucleation was investigated using quartz crystal microbalance with dissipation (QCM-D) on self-assembled monolayers (SAMs) terminated with -OH, -CH3, and -CF3 functional groups. Results show that higher surface hydrophobicity enhances both surface-induced nucleation of gypsum and attachment of gypsum crystals formed from homogeneous nucleation in the bulk solution. The enhanced surface-induced nucleation is attributed to the lower nucleation energy barrier on a hydrophobic surface, while the increased gypsum crystal attachment results from the favorable hydrophobic interactions between gypsum and more hydrophobic surfaces. Contrary to previous findings, the role of Ca2+ adsorption in surface-induced nucleation was found to be relatively small and similar on the different SAMs. Therefore, increasing material hydrophilicity is a potential approach to reduce gypsum scaling.