Energy Barrier For Nucleation Research Articles

π-d Interaction to promote Zn ion de-solvation and transference toward high-performance Zn-MnO2 battery

Aqueous zinc ion batteries (AZIBs) are one class of high-safety and low-cost electrochemical energy storage devices supplementary to the current lithium ion technologies. However, their cycling performance has been severely tethered by the high de-solvation barrier of hydrated Zn ions and uncontrolled dendrite growth and side reactions on the Zn anodes. Herein, an artificial zincophilic passivation layer is constructed on the Zn anode surface by impregnating the porous Zn-based zeolitic imidazole frameworks (ZIF-8) with polypyrrole of rich π-electron donation. This not only lowers the de-solvation and nucleation barriers through π-d interaction, but also offers spatial room for accommodating 3D matrix Zn storage, lending smooth Zn plating/stripping with greatly improved kinetics in addition to inhibited dendrite formation and side reactions. Consequently, at 5 mA cm−2 the as-modified Zn anodes demonstrate a high CE of 99.6 % for more than 1500 cycles in half-cells and a stable operation for more than 2500 h in symmetrical cells. The aqueous Zn-MnO2 full cells further present a superb cycling performance with a capacity retention of 86.3 % after 1200 cycles at 1 A g−1. This work underscores the application of zincophilic and porous passivation layer to mediate smooth Zn plating/stripping by modulating the de-solvation and nucleation energy barriers.

In situ constructing a porous organic component-zincophilic Cu clusters layer on zinc anode for high performance aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) with Zn metal anodes stand out as a promising candidate for large-scale energy storage systems, owing to their high safety, low cost, and environmental friendliness. However, the commercialization of AZIBs is plagued by issues such as Zn dendrite growth and side reactions. Herein, an organic component-Cu metal composite layer is constructed on Zn anode (Org-Cu@Zn) by a novel, one-step and in situ spontaneous displacement reaction. The outer porous organic layer with functional groups may serve as migration sites and transport channels for Zn2+ ions, promoting transfer kinetics. The inner zincophilic Cu clusters layer diminishes the interfacial resistance, facilitating Zn2+ ions diffusion and even Zn deposition. Compared to the bare Zn, the unique dual-layer structure exhibits stronger zincophilicity, smaller interface resistance, lower nucleation energy barrier, and stronger anti-corrosion capability, thus effectively suppressing the Zn dendrite growth and side reactions. Remarkably, the Org-Cu@Zn electrode shows an ultra-long lifespan of 3600 h (1800 cycles) with an average Coulombic efficiency of 99.7 %, realizes long cycling stability over 4300 h (1 mA cm−2) and 1350 h (5 mA cm−2), and assures the stable operation of Org-Cu@Zn||ZVO full cells with coin-type configurations.

A numerical study on the effect of particle surface wettability on homogeneous and heterogeneous condensation processes in supersonic flows

Supersonic separators are an emerging device for processing natural gas impurities. Natural gas contains solid particulate impurities in addition to gaseous impurities, which can trigger heterogeneous condensation within the supersonic separator. There is a lack of research on the effect of particle wettability on supersonic condensation flow, although there have been studies on the effect of particle surface wettability on heterogeneous condensation in this area. Therefore, in this paper, the supersonic condensation flow is modeled considering the contact angle, and the effects of particle contact angle on heterogeneous condensation and homogeneous condensation are investigated separately. The results show that homogeneous condensation is inhibited and heterogeneous condensation is promoted by decreasing the particle contact angle. The reason is the smaller contact angle leads to the reduction of the free energy barrier for heterogeneous nucleation, which makes the conditions for heterogeneous nucleation lower and condensation more likely to occur.

Modulation of zinc deposition behaviour by electrostatically spun PAN-ZnTFSI fibre layer on separator for aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) are well-suited for current energy storage technologies due to their high safety and low cost. However, battery failures resulting from dendrites and side reactions restrict their widespread application. Here, we designed a polyacrylonitrile (PAN)-zinc trifluoromethanesulfonate (ZnTFSI) nanofibre synergistic glass fibre (PZ-GF) to modulate the interfacial deposition kinetics. The effective coordination of numerous CN functional groups within PZ, in conjunction with Zn2+, results in the homogeneous dispersion of the electric field across the electrode, which promotes the uniform deposition of Zn2+ on the zinc anode and thus significantly inhibits the rapid growth of zinc dendrites. ZnTFSI is hydrophilic and has strong hydrogen bonding interactions with the H2O molecule so that the separator can be used as a molecular sieve to regulate the flux of H2O, promote the desolvation of hydrated zinc ions, and inhibit side reactions.Tests of the initial nucleation overpotential of the symmetric battery and calculation of the activation energy reflect that PZ-GF has a smaller nucleation energy barrier and enhanced kinetic effect. And the zinc symmetric battery with PZ-GF film shows an ultra-long cycle stability of 1200 cycles with a capacity retention of 75 % even at 0.5 A g−1 for the Zn//VO2 full cells.

Microstructure and mechanical properties of Al-Cu alloy during wire and arc additive manufacturing by adding micron TiB2 particles

ABSTRACT Micron TiB2 particles were added to the 2319 aluminum alloy using a surface coating method during the additive process. The study focused on the formation, microstructure, and properties in order to achieve deposited components with a uniform microstructure and enhancing strength and plasticity. The critical migration velocity (Vcr = 335 μm/s) of with micron-sized TiB2 particles addition was larger than the solidification rate, which caused particles to be pushed by the solid-liquid interface and ultimately reside at the grain boundary position. The micron-sized TiB2 particles reduced the activation energy for nucleation of the precipitation of the θ’ phase, lowered the energy barrier for nucleation, and introduced dislocations to create lattice distortion channels. This enabled rapid diffusion of solute atoms and facilitated the precipitation and growth of the θ’ phase. Finally, the transverse strength and elongation were higher, reaching 339.07 MPa and 21.3%, which increased by 45% and 60% respectively.

The role of Mg content in regulating microstructures and mechanical properties of Al–Mg–ZnO composites fabricated via in-situ reaction sintering

Al–Mg-oxides composite system exhibits great potential for achieving aluminum matrix composites (AMCs) with exceptional mechanical properties. However, the effects of Mg element on in-situ reaction mechanism and precipitation behavior remains largely unknown. In this work, Al–Mg–ZnO composite was successfully fabricated by using segmented ball milling, reaction sintering and heat treatment, resulting in an ultimate tensile strength of ∼760 MPa and fracture elongation of ∼3.5 %. The Mg content-dependent reaction pathway and precipitation evolution were systematically investigated through thermodynamic analysis and microstructural characterization. The results revealed that the relatively high Mg content promotes the in-situ generation of the hybrid reinforcements composed of MgAl2O4 and MgO. Additionally, the semi-coherent reinforcement-matrix interface facilitates interfacial precipitation by reducing the energy barrier for nucleation. Consequently, solute-rich/vacancy-rich Guinier-Preston (GP) zones are activated to form η′ and T′ precipitates. These high-density nano-sized secondary phases contribute to the considerable strengthening effect of the composite. The present work provides valuable theoretical insight into the effect of Mg content on the microstructure evolution of Al–Mg–ZnO composite system, which offers promising avenues for achieving AMCs with superior mechanical properties.

Na3P interphase reduces Na nucleation energy enabling stable anode-less sodium metal batteries

Sodium metal batteries (SMBs) are rising as viable alternatives to lithium-ion systems due to their superior energy density and sodium's relative abundance. However, SMBs face significant impediments, particularly the exceedingly high negative-to-positive capacity ratios (N/P ratios) which severely encumber energy density and hinder their practical application. Herein, a novel nucleophilic Na3P interphase on aluminum foil has been designed to significantly lower the nucleation energy barrier for sodium atom deposition, resulting in a remarkable reduction of nucleation overpotential and efficient mitigation of dendritic growth at high sodium deposition of 5 mA h cm−2. The interphase promotes stable cycling in anode-less SMB configurations with a low N/P ratio of 1.4 and high cathode mass loading of 11.5 mg cm−2, and demonstrates a substantial increase in high capacity retention of 92.4% after 500 cycles even under 1 C rate condition. This innovation signifies a promising leap forward in the development of high-energy-density, anode-less SMBs, offering a potential solution to the longstanding issues of cycle stability and energy efficiency.

The combined effects of uniaxial pressure and defects on the mechanism of martensitic transformation in pure iron: A molecular dynamics study

The as-produced martensitic steel fabricated by selective laser melting (SLM) is generally softer and weaker than the wrought specimen due to the residual austenite in the microstructure. To avoid additional post-heat treatment, this study proposes a strategy to reduce the residual austenite by applying additional pressure after each laser scanning. Therefore, the combined effects of uniaxial pressure and stacking faults (SFs) on martensitic transformation (MT) in the parent face-centered cubic (FCC) phase of pure Fe are investigated via molecular dynamics (MD) simulation. The simulation results show that the supercooling, uniaxial pressure, and pre-existing SF defects in the parent FCC phase provide chemical driving force, and mechanical driving force and reduce the energy barrier of MT, respectively. The Ms temperatures increase gradually with the pressure from 0 to 200 MPa. The MT process consists of nucleation and growth. The heterogeneous nucleation occurs in the parent FCC phase with pre-existing defects and favoring intersecting-SF, SF, and defect-free FCC phase region in order. The homogeneous nucleation occurs in the parent FCC phase without pre-existing defect and the MT process is achieved by the growth and coalescence of the scattered crystal nucleus. The stress field generated by the dislocation lines at the intersecting region of SFs results in the lattice distortion of the atoms nearby, reducing the energy barrier of MT nucleation. The study verifies the feasibility of reducing residual austenite in SLM-ed martensitic steel by applying pressure during the cooling process of each layer.

Unraveling the Role of 2D Ti3C2Tx MXene Nanosheets in Cu-Based Double Perovskite Active Layer for Enhanced Photovoltaic Performance.

Although the atmospheric stability of lead-free inorganic double perovskite (DP) solar cells (PSCs) looks promising, their further development is hampered by inadequate film quality and non-radiative carrier recombination at the interfaces. Herein, the incorporation of a newly developed intriguing class of 2D material Ti3C2Tx MXene nanosheets with the photo-absorbing Cu2AgBiI6 (CABI) active layer of a fully inorganic solar cell is reported. The highly conductive Ti3C2Tx nanosheets work as a multi-functional additive by tuning the band gap, reducing the non-radiative carrier recombination, and inhibiting carrier accumulation. In addition, the presence of Ti3C2Tx MXene increases the surface free energy of the perovskite film, which elevates the energy barrier for nucleation and realizes a highly crystalline CABI perovskite film. Primarily, the MXene modification accelerates the charge extraction and transport at the interfaces of the active layer, utilizing energy level alignment with the charge transport layers. Consequently, the photo-conversion efficiency (PCE) of the device with MXene is substantially enhanced to 1.50%. Moreover, the 2D Ti3C2Tx nanosheets increased the long-term stability of the devices by retaining 70% of the initial PCE after 1680 h. With regard to relieving the severe carrier recombination at the interfaces, this work sets a new paradigm toward imminent solar energy conversion.

Melt-crystallization and self-nucleation of UHMWPE/bi-HDPE blends: The combined role of composition and molecular weight

Blends of bi-modal high-density polyethylene (bi-HDPE) and ultra-high molecular weight polyethylene (UHMWPE) with varying content (0–30 wt%.) and different molecular weights (MWs) (2.2, 3.5, and 4.5 M g/mol) of UHMWPE were prepared. The effect of UHMWPE content, MW, and their interplay on the microstructure, nucleation, and crystallization behavior of bi-HDPE was examined through rheology, scanning electron microscopy, and differential scanning calorimetry. The results revealed that UHMWPE serves as a partially miscible nucleating agent, effectively dispersing in the bi-HDPE matrix up to 5 wt%, thereby promoting the transition from randomly dispersed lamellae to a spherulitic morphology. The nucleating effect saturated when the UHMWPE content reached 10 wt%, leading to a diminished spherulitic structure. Beyond 10 wt% of UHMWPE, an anti-nucleation effect with segregated crystalline regions emerged. Isothermal kinetics analysis also revealed the highest crystallization rate at the optimum UHMWPE content of 5 wt%, where the critical nucleation energy barrier and fold-surface free energy were minimized. Apart from the UHMWPE content, signs of nucleation enhancement were slightly more pronounced in the bi-HDPE blend with the lowest molecular weight of UHMWPE. This phenomenon results from increased concentration fluctuations due to the larger interfacial area, as postulated from entanglement density measurements. For the first time, self-nucleation (SN) analysis revealed that the incorporation of 5 wt% of UHMWPE into bi-HDPE resulted in a wider Domain II width, indicating an increased memory effect. Notably, the crystalline memory was more pronounced in the blend containing UHMWPE with the MW of 2.2 M g/mol, exhibiting the super-nucleating effect with the highest nucleation efficiency of 218 %.

Molecular Simulations Reveal the Free Energy Landscape and Transition State of Membrane Electroporation.

The formation of pores over lipid membranes by the application of electric fields, termed membrane electroporation, is widely used in biotechnology and medicine to deliver drugs, vaccines, or genes into living cells. Continuum models for describing the free energy landscape of membrane electroporation were proposed decades ago, but they have never been tested against spatially detailed atomistic models. Using molecular dynamics (MD) simulations with a recently proposed reaction coordinate, we computed potentials of mean force of pore nucleation and pore expansion in lipid membranes at various transmembrane potentials. Whereas the free energies of pore expansion are compatible with previous continuum models, the experimentally important free energy barrier of pore nucleation is at variance with established models. The discrepancy originates from different geometries of the transition state; previous continuum models assumed the presence of a membrane-spanning defect throughout the process, whereas, according to the MD simulations, the transition state of pore nucleation is typically passed before a transmembrane defect has formed. A modified continuum model is presented that qualitatively agrees with the MD simulations. Using kinetics of pore opening together with transition state theory, our free energies of pore nucleation are in excellent agreement with previous experimental data.

Effects of process conditions and nano-fillers on the cell structure and mechanical properties of co-injection molded polypropylene-polyethylene composites

Compared with traditional injection foaming, co-injection foaming serves as a method to prepare products with high-quality surfaces and enhanced mechanical properties, demonstrating excellent technical advantages and economic benefits. The effects of high-density polyethylene (HDPE) content, foaming agent content, melting temperature of core material, and nano-organic montmorillonite (OMMT) content on the cell structure, mechanical properties, and crystallization behavior of isotactic polypropylene (iPP)/HDPE composite foam prepared by co-injection foaming were systematically studied. At a foaming agent content of 2 wt.%, HDPE content of 30 wt.%, OMMT content of 3 wt.%, and the melting temperature of core material of 190 °C, the composite foam exhibited a cell size measuring 85 μm, a cell density of 2.5 × 105 cells/cm3, a tensile strength of 25.8 MPa, and an impact strength of 12.5 kJ/m2. The addition of HDPE reduced the crystallinity of iPP matrix, while enhancing the solubility of carbon dioxide within the matrix. The non-miscible interface between HDPE and iPP helped reduce the energy barrier for cell nucleation. Furthermore, the introduction of OMMT as a nucleating agent in iPP/HDPE composite material dramatically decreased the energy barrier for cell nucleation. These synergistic effects result in foam with the smaller cell size and the higher cell density, exhibiting excellent comprehensive mechanical properties. This work provides a feasible method for preparing composite foam with excellent comprehensive performance.

Shuffling pathway of anti-twinning in body-centered-cubic metals

In this study, anti-twinning and deformation twinning of body-centered-cubic (BCC) metals under nanoindentation were examined. Molecular dynamics (MD) simulations of BCC tantalum (Ta) showed both the existence of anti-twinning and a novel two-layer-by-two-layer anti-twinning pathway consisting of a staggered shuffle sliding of {112} atomic planes in the [111¯] and [1¯1¯1] directions, generating finite shear displacement along the anti-twin direction. The density functional theory (DFT) multi-dimensional interlayer slipping energy landscape of the newly observed shuffling anti-twinning process has a lower energy barrier for both twin nucleation and growth than the recently proposed layer-by-layer anti-twinning process.

Dendrite‐free Zn deposition initiated by nanoscale inorganic–organic coating‐modified 3D host for stable Zn‐ion battery

AbstractA 3D nanostructured scaffold as the host for zinc enables effective inhibition of anodic dendrite growth. However, the increased electrode/electrolyte interface area provided by using 3D matrices exacerbates the passivation and localized corrosion of the Zn anode, ultimately bringing about the degradation of the electrochemical performance. Herein, a nanoscale coating of inorganic–organic hybrid (α‐In2Se3‐Nafion) onto a flexible carbon nanotubes (CNTs) framework (ISNF@CNTs) is designed as a Zn plating/stripping scaffold to ensure uniform Zn nucleation, thus achieving a dendrite‐free and durable Zn anode. The introduced inorganic–organic interfacial layer is dense and sturdy, which hinders the direct exposure of deposited Zn to electrolytes and mitigates the side reactions. Meanwhile, the zincophilic nature of ISNF can largely reduce the nucleation energy barrier and promote the ion‐diffusion transportation. Consequently, the ISNF@CNTs@Zn electrode exhibits a low‐voltage hysteresis and a superior cycling life (over 1500 h), with dendrite‐free Zn‐plating behaviors in a typical symmetrical cell test. Additionally, the superior feature of ISNF@CNTs@Zn anode is further demonstrated by Zn‐MnO2 cells in both coin and flexible quasi‐solid‐state configurations. This work puts forward an inspired remedy for advanced Zn‐ion batteries.

Isotope Effect-Enabled Crystal Enlargement in Metal-Organic Frameworks.

Synthesizing large metal-organic framework (MOF) single crystals has garnered significant research interest, although it is hindered by the fast nucleation kinetics that gives rise to numerous small nuclei. Given the different chemical origins inherent in various types of MOFs, the development of a general approach to enhancing their crystal sizes presents a formidable challenge. Here, we propose a simple isotopic substitution strategy to promote size growth in MOFs by inhibiting nucleation, resulting in a substantial increase in the crystal volume ranging from 1.7- to 165-fold. Impressively, the crystals prepared under optimized conditions by normal approaches can be further enlarged by the isotope effect, yielding the largest MOF single crystal (2.9 cm × 0.48 cm × 0.23 cm) among the one-pot synthesis method. Detailed in situ characterizations reveal that the isotope effect can retard crystallization kinetics, establish a higher nucleation energy barrier, and consequently generate fewer nuclei that eventually grow larger. Compared with the smaller crystals, the isotope effect-enlarged crystal shows 33% improvement in the X-ray dose rate detection limit. This work enriches the understanding of the isotope effect on regulating the crystallization process and provides inspiration for exploring potential applications of large MOF single crystals.

Spatial Confinement of Sn/TiO2 Nanoparticles in Hollow Mesoporous Carbon Spheres Opal for Stable Zn Metal Anodes

AbstractThe sluggish Zn2+ diffusion and high nucleation energy barrier induce uncontrolled growth of Zn dendrites and detrimental parasitic reactions, severely hampering the commercialization of Zn metal anodes (ZMAs). Herein, hollow mesoporous carbon sphere opal with confined Sn/TiO2 clusters (HMCSST) is designed as the host to spatially regulate the Zn deposition. Owing to the capillary effect of the ordered hierarchical porous structure, the mass diffusion can be dramatically accelerated to promote a fast deposition kinetics at the interface between ZMA and electrolyte. Besides, the encapsulated ultrafine Sn/TiO2 clusters serve as zincophilic sites to achieve both the uniform Zn deposition on the hierarchical porous opal host and the high thermodynamic stability of ZMAs. Benefiting from the structural and componential merits, the HMCSST host effectively reduces the activation energy to enable a temporal‐spatial ordering of Zn nucleation and growth. As expected, the stable HMCSST‐Zn electrode guarantees steady Zn platting/stripping with long‐term stability over 1300 h in a symmetrical cell at a depth of discharge of 37.5%. As a proof‐of‐concept demonstration, an HMCSST‐Zn||ammonium vanadate full cell shows a long lifespan over 5000 cycles at 10.0 A g−1 with low polarization.

Heterogeneous nucleation of CO2 hydrate: A thermodynamics analysis considering effects of wall characteristics and solution activity

The massive emission of greenhouse gas CO2 has significant effects on global climate and environment, causing worldwide concern. It has been proposed to store CO2 in clathrate hydrates as a possible strategy for reducing atmospheric CO2 emission. Nevertheless, the CO2 hydrate formation rate is slow and its associated heterogeneous nucleation mechanisms are not well understood, which limit commercial applications of this technology. This study developed a thermodynamic model based on the change in availability function approach, considering effects of surface characteristics (including surface topography, roughness, curvature radius, and wettability), and CO2 dissolution on the solution's activity. The critical nucleation radius and energy barrier of CO2 hydrate nucleation are determined. Effects of pressure, temperature, wall characteristics and solution activity on the nucleation radius of CO2 hydrate are discussed. The results of this paper contribute to advancing carbon capture and storage technology based on hydrate methods.

Prompt Molten Na Infusion and Fluidic Transport by Virtue of Versatile Nano Canal Defects on Tin Oxide Sodiophilic Hosts

AbstractIntrinsically weak metal affinity and sluggish sodium (Na) nucleation/molten fluidic transport of conventional hosts impede the fabrication of high‐capacity Na anodes. Mediating surface free energies (SFEs) of hosts and reinforcing their intermolecular attraction to viscous Na fluids can radically solve these problems. Herein, “canaled” tin oxide nanorod arrays grown on a 3D carbon cloth (CC) matrix exhibit distinct polar/nonpolar SFE components that markedly elevate the solid–liquid wettability for molten Na is reported. Such nanocanal defects render strong capillary forces for spontaneous molten Na imbibition and help to instantly activate Na─Sn alloying and Na nucleation reactions. Furthermore, sodiophilic Na15Sn4 interlayers evolved in former alloying procedures also aid in reducing Na nucleation energy barriers and guide the planar electro‐deposition/dispersion, alleviating the uncontrolled Na dendrite growth. The derived Na/Na15Sn4/CC anodes can thus keep stable after 2000 h of galvanostatic cycling at 1 mA cm−2 or high‐rate testing, without notable dendritic formation. The packed full cells also show superior rate capability and cyclability (capacity retention over 91.5% after all cycling at 1 C). This work provides a smart nano‐engineering way to trigger a fast infusion of molten metals into hosts and synergistically facilitate Na fluidic transport, which may push forward the scalable application of Na metal batteries.

Revealing the Heterogeneous Bubble Nucleation at Individual Silica Nanoparticles.

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

Electrochemical Signatures of Potassium Plating and Stripping

Alkali metal anodes can enable unmatched energy densities in next generation batteries but suffer from insufficient coulombic efficiencies. To deduce details about processes taking place during galvanostatic cycling, voltage profiles are commonly analyzed, however the interpretation is not straightforward as multiple processes can occur simultaneously. Here we provide a route to disentangle and interpret features of the voltage profile in order to build a mechanistic understanding on alkali metal stripping and deposition, by investigating potassium metal deposition as a model case where processes and reactions are exaggerated due to the high reactivity of potassium. In particular, the importance of separating SEI formation and nucleation to correctly estimate the energy barrier for nucleation is demonstrated. Further, we show how the native layer formed on alkali metal foils gives rise to strong features in the voltage profile and propose forming alkali metal electrode through electrodeposition to mitigate these effects.