Metal Surface Research Articles

Microstructure and mechanical properties of wire and arc additive manufactured 2319 aluminum alloy treated by laser shock peening

The components manufactured by Wire and Arc Additive Manufacturing (WAAM) have some problems to be solved urgently, such as uneven microstructure, numerous pore defects, and residual tensile stress. Laser Shock Peening (LSP) is an innovative and advanced surface modification technology that improves mechanical characteristics by inducing significant plastic deformation and high compressive residual stress on metal surfaces. Therefore, combining LSP with WAAM is expected to solve its existing problems. In this work, LSP with different energy parameters was used to post-process the WAAM 2319 aluminum alloy. The results indicated that LSP could improve the microstructure, eliminate near-surface pores, harden the surface layer, and induce a residual compressive stress layer, and the effect was more effective with the increase of laser energy applied. The yield strength of the peened specimens significantly increased by 60.73 %, and the ultimate tensile strength also increased by 16.03 %. The hole fatigue life of the peened specimens was significantly improved, increasing by 179.8 % and 261.7 %, respectively, applying laser energies of 5 J and 10 J. Therefore, the engineering industry may benefit from a combination of LSP and WAAM technology.

Mechanism of the hydrazine hydrate electrooxidation reaction on metallic Ni electrodes in alkaline media as revealed by electrochemical methods, online DEMS and ex situ XPS

Metallic Ni surface was examined as a catalyst for the hydrazine hydrate oxidation reaction (HHOR) by cyclic voltammetry, chronoamperometry, and online differential electrochemical mass-spectrometry (DEMS). It was found that N2 is the sole gaseous product formed during the HHOR on Ni and 4 electrons are transferred in the process, which corresponds to a complete oxidation of the hydrazine molecule. The mechanism of the HHOR on the Ni surface involves OH− and adsorbed OHads intermediate, the latter improving the rate of the HHOR. Ni catalysts were found to be poisoned during the HHOR, the extent of poisoning depending on the number of surface sites, hydrazine concentration, and the α-Ni(OH)2 coverage. Ex situ X-ray photoelectron spectroscopy (XPS) measurements were performed to characterize the species poisoning Ni surface.

Hybrid Quantum Mechanical, Molecular Mechanical, and Machine Learning Potential for Computing Aqueous-Phase Adsorption Free Energies on Metal Surfaces.

Performing reliable computer simulations of elementary processes occurring at metal-water interfaces is pivotal for novel catalyst design in sustainable energy applications. Computational catalyst design hinges on the ability to reliably and efficiently compute the potential energy surface (PES) of the system. Due to the large system sizes needed for studying processes at liquid water-metal interfaces, these systems can currently not be described using density functional theory (DFT). In this work, we used a hybrid quantum mechanical, molecular mechanical, and machine learning potential for studying the adsorption behavior of phenol, atomic hydrogen, 2-butanol, and 2-butanone on the (0001) facet of Ru under reducing conditions when Ru is not oxidized. Specifically, we describe the adsorbate and the surrounding metal atoms at the DFT level of theory. Here, we also considered the electrostatic field effect of the water molecules on adsorbate-metal interactions. Next, for the water-water and water-adsorbate interactions, we used established classical force fields. Finally, for the water-Ru surface interaction, for which no reliable force fields have been published, we used Behler-Parrinello high-dimensional neural network potentials (HDNNPs). Employing this setup, we used our explicit solvation for metal surface (eSMS) approach to compute the aqueous-phase effect on the low-coverage adsorption of selected molecules and atoms on the (0001) facet of Ru. In agreement with previous experimental and computational studies of oxygenated molecules over transition metal facets, we found that liquid water destabilizes the tested adsorbates on Ru(0001). Interestingly, our findings indicate that adsorbates on Ru are less affected by the presence of an aqueous phase than on other transition metals (e.g., Pt), highlighting the necessity of experimental investigations of Ru-based catalytic systems in liquid water.

Hydrogen adsorption on fcc metal surfaces towards the rational design of electrode materials

The successful large-scale implementation of hydrogen as an energy vector requires high performance electrodes and catalysts made of abundant materials. Rational materials design strategies are the most efficient means of reaching this goal. Here we present a study on the adsorption of H-atoms onto fcc transition metal surfaces and propose descriptors for the rational design of electrodes and catalysts by means of correlations between fundamental properties of the materials and among other properties, their experimentally measured performance as hydrogen evolution electrodes (HEE). A large set of quantum mechanical modelling data at the DFT level was produced, covering the adsorption of H-atoms onto the most stable surfaces (100), (110) and (111) of: Ag, Au, Co, Cu, Ir, Ni, Pd, Pt and Rh. For each material and surface, a coverage dependent set of minimum energy structures was produced and chemical potentials for adsorption of H-atoms were obtained. Averaging procedures are here proposed to approach modelling to the experiments. Several correlations between the computed data and experimentally measured quantities are done to validate our methodology: surface plane dependent adsorption energies, chemical potentials and experimentally determined surface energies and work functions. We search for descriptors of catalytic activity by testing correlations between the DFT data obtained from our averaging procedures and experimental data on HEE performance. Our methodology allows us to obtain linear correlations between the adsorption energy of H-atoms and the exchange current density (i0) in a HEE, avoiding the volcano-like plots. We show that the chemical potential has limitations as a descriptor of i0 because it reaches an early plateau in terms of i0. Simple quantities obtained from database data such as the first stage electronegativity (χ) as devised by Mulliken has a strong linear correlation i0. With a quantity we denominate modified second-stage electronegativity (χ2m) we can reproduce the typical volcano plot in a correlation with i0. A theoretical and conceptual framework is presented. It shows that both χ and χ2m, that depend on the first ionization potential, second ionization potential and electron affinity of the elements can be used as descriptors in rational design of electrodes or of catalysts for hydrogen systems.

Friction Mechanism of Sulfur-Containing Lubricant Additives Confined between Fe(100) Substrates.

Sulfur-containing lubricant additives can chemically react with metal surfaces under extreme conditions, such as high temperature and high pressure, forming protective films on the surfaces. However, the formation mechanisms and the friction-reducing and antiwear properties of these films remain unclear. In this study, we investigated the friction process of sulfur-containing additives confined between two iron surfaces using reactive molecular dynamics simulations. Our research revealed that in systems with a higher S/C ratio, an iron sulfide layer formed on the iron surfaces with Fe-S-Fe bridging bonds at the interface, resulting in relatively smaller friction and wear even under higher loads. However, in systems with lower S/C ratios, the presence of numerous interfacial Fe-Cn-Fe bridging bonds, caused by the hydrocarbon radicals released from the additives, led to the formation of thick amorphous shearing bands at the interface between the two substrates. In this case, the distributed sulfur atoms also exhibited some effect in reducing the shear resistance of the amorphous shearing bands due to the weak strength of S-Fe bonds compared to the strength of C-Fe bonds. These atomic-level insights help understand the antiwear characteristics of sulfur-containing lubricant additives confined between iron substrates.

Assessment of Warionia saharea Essential Oil as a Green Corrosion Inhibitor for Mild Steel in HCl: Experimental and Computational Studies

The objective of this research work is the study of the inhibitory effect of Warionia saharea essential oil (WSEO) on the corrosion of mild steel (MS) in molar HCl solution, employing both experimental and theoretical methods. This inhibitory effect (IE) has been evaluated by using a combination of weight loss measurements (LW) and various electrochemical methods, such as open circuit potential (OCP), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) experiments. The LW results indicated that IE increased with inhibitor concentration, reaching 83.34% at 3.00 g/L. The PDP analysis suggested that WSEO functions as a mixed inhibitor, while in the EIS results the Rct values increased with inhibitor concentration to reach 165.8 Ω cm2 at 2.00 g/L, suggesting a defensive film formation by WSEO molecules over the metallic surface. The thermodynamic study demonstrated that the WSEO molecules adsorption on the MS surface followed a Langmuir isotherm, involving mixed physical and chemical (physicochemical) adsorption on the MS surface. Theoretical methods, including density functional theory (DFT) and molecular dynamics (MD) simulations, were employed to elucidate the inhibition mechanisms of the three main components of WSEO. The quantum chemical analysis, using density functional theory (DFT) and molecular dynamics (MD) simulations, showed a low ΔEgap value of 6.30 eV and a low adsorption energy (Eads) value on an Fe (110) substrate of −258 Kcal/mol for (E)-Nerolidol, indicating the significant contribution of this molecule to the overall corrosion inhibition effect of WSEO. The scanning electron microscope (SEM) analysis verified the presence of a protective film formed by the inhibitor on the MS surface. This study highlights the potential of WSEO as a sustainable and green corrosion inhibitor in acidic environments.

Flexible fabrication of core/shell nanoparticles for tailored infrared emissivity on aluminum via femtosecond laser self-deposition.

A metal surface with controllable infrared emissivity has a wide range of applications. However, a flexible and simple fabrication method is needed. Here, a controllable femtosecond laser self-deposition technology was developed to fabricate Al@AlOx core/shell micropillars (MPs) with diverse size distribution on the aluminum surface in a single-step operation under ambient conditions. By establishing a deterministic relationship between pulse-repetition frequency (PRF) and particle size distribution (PSD), we achieved continuous control of the infrared emissivity of the surface by lower PRF, ranging from low (0.31) to high (0.93). Additionally, by using higher PRF, we attained dual-band emissivity control, featuring high emissivity in the range of 10-14 µm and near-continuous change in the range of 2.5-10 µm.

Growth Mediated Disassembly of Cucurbit[8]uril Cross‐linked Static Cubic Self‐assembly of Silver Nanoparticles

AbstractStatic self‐assembly resides in thermodynamically stable global minima of the energy landscape, whereas dynamic self‐assembly occupies local minima of the energy profile and remains in the ordered state for a limited time via dissipation of energy to surroundings. This makes the spatiotemporal control over the assembly and disassembly mechanism easily controllable in the case of dynamic self‐assembly. However, due to the higher thermal stability of static self‐assembly, it is very challenging to perform reverse engineering on these types of systems. Herein we report growth reaction‐based reversal of static silver cubes obtained via cucurbit[8]uril (CB[8]) crosslinked self‐assembly of silver nanoparticles (AgNP). The AgNP building units with variable CB[8] surface coverage have been used as seeds onto which deposition of gold via growth reaction has been performed. The disassembly of supracube structure has been controlled by the formation of [AuCl4]−–CB[8] complex and successive reduction of [AuCl4]− to Au0 on the surface of the seed. The resulting monodispersed isotropic nanoparticles, formed from the CB[8] based cubic self‐assembly after growth, exhibit Au−Ag bimetallic nature. Quenching of the fluorogenic response from the hydrophobic dye coumarin‐7, added after growth, suggests direct interaction with the metallic nanoparticle surface after disassembly and thereby confirms successful growth reaction mediated reversal of self‐assembly.

A facile preparation of durable superhydrophobic PFA coatings with superior anti-icing, anti-corrosion and self-cleaning performance

The potential of superhydrophobic coatings for various applications has been widely recognized. However, preparing durable superhydrophobic coatings on metal surfaces remains a significant challenge. Perfluoroalkoxy Alkane (PFA), a fluorine-rich material, has recently emerged as a promising candidate for constructing superhydrophobic coatings. In this study, a mechanically stable superhydrophobic PFA coating was prepared using a simple combination of electrodeposition and annealing. The prepared PFA coating displays excellent water repellency, as evidenced by a water contact angle of 171 ± 0.3° and a sliding angle of 1.0 ± 0.4° The water contact angle of the coating only decreases by 0.6°after undergoing 400 tape stripping tests, indicating the remarkable stability. The PFA coating significantly prolongs the freezing time of water droplets on a cool surface at temperatures of -6 °C, -8 °C, and -10 °C, with improvements of 19.4, 72.5, and 47.8 times respectively. The corrosion current density on the coated surface is reduced by four orders of magnitude compared to bare aluminum alloy, and the PFA coating exhibits a high inhibition corrosion efficiency of 99.995 %. Furthermore, the coating possesses exceptional self-cleaning performance by repelling dirt particles and maintaining a clean surface. Consequently, the developed superhydrophobic PFA coating holds significant promise for long-lasting anti-icing, anti-corrosion and self-cleaning applications.

Effect of ion-specific water structures at metal surfaces on hydrogen production

Water structures at electrolyte/electrode interfaces play a crucial role in determining the selectivity and kinetics of electrochemical reactions. Despite extensive experimental and theoretical efforts, atomic-level details of ion-specific water structures on metal surfaces remain unclear. Here we show, using scanning tunneling microscopy and noncontact atomic force microscopy, that we can visualize water layers containing alkali metal cations on a charged Au(111) surface with atomic resolution. Our results reveal that Li+ cations are elevated from the surface, facilitating the formation of an ice-like water layer between the Li+ cations and the surface. In contrast, K+ and Cs+ cations are in direct contact with the surface. We observe that the water network structure transitions from a hexagonal arrangement with Li+ to a distorted hydrogen-bonding configuration with Cs+. These observations are consistent with surface-enhanced infrared absorption spectroscopy data and suggest that alkali metal cations significantly impact hydrogen evolution reaction kinetics and efficiency. Our findings provide insights into ion-specific water structures on metal surfaces and underscore the critical role of spectator ions in electrochemical processes.

High performance ultra-thin lithium metal anode enabled by vacuum thermal evaporation

The passivation layer that naturally forms on the lithium metal surface contributes to dendrite formation in lithium metal batteries by affecting lithium nucleation uniformity during charging. Herein, we propose using vacuum thermal evaporation to produce a high-performance ultra-thin lithium metal anode (≤25 µm) with a native layer much thinner than that of extruded lithium. The evaporated lithium metal shows significantly reduced charge-transfer resistance, resulting in uniform and dense lithium plating in both carbonate and ether electrolytes. This study reveals that the evaporated lithium metal outperforms the extruded version in ether electrolyte and with LiFePO4 cathodes, showing a 30% increase in cycle life. Additionally, when paired with LiNi0.6Mn0.2Co0.2O2 cathodes in carbonate electrolyte, the evaporated anode’s cycle life is tripled compared to the extruded lithium metal. This demonstrates that vacuum thermal evaporation is a viable method for producing ultra-thin lithium metal anodes that prevent dendrite growth due to their excellent surface condition.

Molecule-Supported Magnetic-Atom Dimers on Au(111): Multiple Structures and Kondo Resonances

Magnetic-atom dimers on surface provide a powerful platform to study single spin interactions and qubit controls. They have been experimented on bare and thin-insulator-covered metallic surfaces, with strong and weak couplings between atoms and surfaces, respectively. If they are embedded in single molecules on surfaces, they may allow new geometric and electronic configurations as well as different coupling levels. But such system has rarely been studied. Here we report our scanning tunneling microscopy studies for molecule-supported magnetic-atom dimers on Au(111). Through on-surface reactions, Fe-Co dimers were embedded to porphyrin molecules in three different types. We observed zero-bias resonance in our scanning tunneling spectroscopy from one type with the Kondo temperature lower than Co-porphyrin molecules. Based on our density functional theory calculation results, atomic structures of three dimer structures were reproduced, and the observed Kondo behaviors were explained. Our study shows that the molecule supported magnetic-atom dimers can be a useful platform for studying spin physics and quantum information science.

Development and performance evaluation of green superhydrophobic coating for fouling and corrosion protection

In this paper, a simple and environmentally friendly superhydrophobic stearic acid-modified zinc-nickel-cobalt composite coating (SA@ZNC) is presented. The zinc-nickel-cobalt (ZNC) coating with petal-like micro/nano-rough structure was constructed on the metal surface by combining electrodeposition and chemical substitution techniques. Subsequently, the coating was modified with low surface energy by adding stearic acid, and the SA@ZNC coating with excellent superhydrophobicity (water contact angle of 161.08 ± 0.31° and rolling angle of 3.50 ± 0.54°) was prepared. The coating is self-cleaning against a wide range of simulated contaminants and can remain superhydrophobic in air for over a year. Changes in pH do not significantly affect the superhydrophobicity and at low temperatures, the freezing time of water droplets on the coating was extended by 2.1 times compared to a blank steel sheet. Furthermore, the SA@ZNC coating demonstrated remarkable robustness, withstanding 30 minutes of water impact, a wear mass of 0.2 % after rubbing with weights over 2400 mm and retaining its superhydrophobicity after 80 tape stripping cycles. The results of the corrosion protection tests demonstrated that the SA@ZNC coating provided excellent corrosion protection for N80 steel, exhibiting a current density two orders of magnitude lower than that of the blank sample. Furthermore, the coating exhibited a corrosion inhibition rate of 95.75 ± 0.33 % and excellent charge transfer resistance. The multiple protection mechanisms and homogeneous micro/nanostructure of the coatings resulted in significantly better corrosion resistance than most of the reported zinc-nickel based coatings. The use of low-energy consumption methods and environmentally friendly modifiers positions this coating for large-scale production and potential applications in sectors like food and medicine, with promising implications for corrosion protection in various industries.

Improvement of tribological and anti-corrosive performance of MXene nanosheets by grafting polymer brush

Herein, the anti-corrosive polymer brush functionalized MXene (P-MBTS2MA@MXene) was successfully prepared via surface-initiated polymerization. First, the dopamine initiator (DA-Br) can self-assemble onto MXene nanosheets formation of initiator modified MXene (PDA-Br@MXene) via spontaneous oxidative polymerization, then the corrosion inhibitor MBT derivative MBTS2MA monomer was grafted onto MXene nanosheets through surface-initiated atom transfer radical polymerization (SI-ATRP) to obtain polymer brush P-MBTS2MA functionalized MXene (P-MBTS2MA@MXene). The prepared P-MBTS2MA@MXene served as lubricant additive, manifesting good tribological properties with a low COF of 0.098 % and 94.8 % wear-reduction, which is attributed to the shielding effect and protective film formed by P-MBTS2MA@MXene. Additionally, the grafting P-MBTS2MA endows MXene nanosheets with improved anti-corrosion property, which prevents further corrosion of the metal surface via releasing corrosion resistance molecule MBT.

Eco-friendly corrosion inhibition and scale control in seawater using Foeniculum vulgare and Pimpinella anisum extracts with chemical compounds

This study investigated the corrosion inhibition and scale control properties of both natural extracts and chemical inhibitors for C25 galvanized steel sheets with an 85-μm thick zinc coating steel exposed to seawater. The inhibitors, including Foeniculum vulgare (AF-Sha), Pimpinella anisum (AF-Sim), M640, and Veo, underwent rigorous evaluation through techniques such as Tafel extrapolation, potentiodynamic polarization analysis, concentration factor scale, seawater analysis, X-ray diffraction (XRD), infrared spectroscopy (IR), and conductivity-temperature analysis. Notably, AF-Sha and AF-Sim exhibited outstanding corrosion prevention capabilities, achieving inhibitory efficiencies of 87% and 85%, respectively. Comparative analyses with chemical inhibitors, M640 and Veo, demonstrated promising performance, positioning natural inhibitors as environmentally friendly alternatives. Corrosion rates, inhibition efficiency, and concentration factor scale results provided insights into the inhibitory effectiveness of each compound, with Veo showing superior performance. The study also explored the antiscalant behavior of inhibitors, revealing their ability to prevent corrosion and scale formation. XRD analysis indicated the impact of inhibitors on the crystal structure of scales, while IR spectra provided insights into vibration properties. Conductivity and temperature analyses illustrated the inhibitors' role in reducing ion exchange and gypsum concentration in seawater. These findings suggest that the inhibitors offered robust protection for ferrous metal surfaces and hold significant potential for practical applications. Additionally, our weight loss investigation extends this understanding, demonstrating the practical applicability of corrosion inhibitors like AF-Sha and AF-Sim in real-world scenarios. The presented results contribute significantly to the understanding of galvanized steel corrosion behavior in seawater, offering valuable insights for corrosion engineering applications.

Evaluation of N80 Carbon Steel Corrosion in 15 wt.% HCl Using Isatin-hydrazones: A Comprehensive Approach with Chemical, Electrochemical Techniques, and DFTB Calculations

The adverse effects of corrosion on industrial metals, particularly N80 carbon steel under acidic conditions, call for developing effective corrosion inhibitors. Due to their structural and electrical properties, isatine-hydrazones have emerged as possible corrosion inhibitors. This study investigates the corrosion inhibition capabilities of two specific Isatin-hydrazones, (E)-1-octyl-3-(2-(5-oxo-4,4-diphenyl)-4,5-dihydro-1H-imidazol-2-yl)hydrazono)indolin-2-one (OPHIHI) and (E)-3-(2-(5-oxo-4,4-diphenyl)-4,5-dihydro-1H-imidazol-2-yl)hydrazono)indolin-2-one (OIHIHI), on N80 carbon steel in a highly acidic medium. The study assessed the corrosion inhibition efficacy of OIHIHI and OPHIHI using both computational and experimental approaches. Weight loss measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy were used in the experiments. In contrast, density functional theory (DFT), molecular dynamics (MD), and tight-binding density functional theory (DFTB) were used in the computational analyses to elucidate the interaction mechanisms between the inhibitors and metal surfaces. The experiment demonstrated that both OPHIHI and OIHIHI effectively reduce corrosion rates in a 15 wt.% HCl solution at 303 K, achieving an inhibition efficiency of 96 % and 92 %, respectively, at an optimal 5 × 10−3 mol/L concentration. These inhibitors were discovered to form protective layers on the N80 carbon steel surface, offering mixed protective qualities (cathodic and anodic protection) with a preponderance of cathodic protection against carbon steel corrosion in 15 wt.% HCl. Computational studies supported the experiment's findings by demonstrating that isatin-hydrazones' superior electronic properties enabled them to form robust covalent bonds with the Fe (110) surface. Based on these results, OPHIHI and OIHIHI could be used as corrosion inhibitors in the oil and gas industry, particularly under highly acidic conditions.

INNOVATIVE INSULATING MATERIAL IN THE ASPECT OF ENSURING THE SAFETY OF HYDROCARBON TRANSPORTATION

Ensuring continuous and safe operation of the main oil and gas pipelines is a critical aspect for preserving the environment and efficient use of hydrocarbon resources. More than half of accidents on trunk gas pipelines occur due to corrosion wear of the metal caused by insufficient protection of the insulation coating. The consequences of such incidents have a devastating impact on the environment and human lives: spilled oil and oil products pollute the soil, and leaking gas can lead to explosions and forest fires.Corrosion processes hiding under the coating due to poor adhesion and due to non-fulfillment of their functions by the coating lead to increased peeling of insulation and the formation of new corrosion foci, including stress-corrosion processes. Consequently, imperfect insulation coating and insufficient adhesion to metal are one of the main causes of accidents on main pipelines.The purpose of this work was to study and prove the chemical interaction of the functional groups of asmol insulation compositions with the metal surface. In the course of work, the following tasks were solved:- assessment of the ratio of initial adhesion parameters obtained in laboratory and route conditions and their values after 1.5 and 6 years of operation;- study of the IR spectrum in order to prove the presence of functional groups in the asmol material;- study of the protective capacity of the asmol coating structure in an aggressive corrosive environment at different temperatures.Methods were used to measure the quantitative adhesion of the anti-corrosion coating and the peel area during cathode polarization, in accordance with State Standard R 51164-98. The composition of the asmol material was studied by IR spectroscopy.It has been shown that functional groups, the presence of which has been confirmed by spectral analysis, of asmol material in the insulation coating make it possible to chemically adhere to steel. Indirect proof of this is the stability of the adhesion strength over time, the cohesive separation of the asmol coating in determining adhesion indicators under trace conditions and the relatively small area of coating detachment during cathode polarization.

Interfacial electronic insulation strategy for high-performance Zinc-ion batteries

Aqueous rechargeable zinc metal batteries have garnered widespread attention due to their inherent high safety, high volumetric capacity, and low cost. However, the uncontrollable growth of zinc dendrites and severe hydrogen evolution reaction (HER) side reactions lead to low Coulombic efficiency and short lifespan of zinc metal anodes, hindering their practical application. We employed a plasma fluorination strategy to in-situ react on the surface of zinc metal to generate an electron-insulating ZnF2 coating, which reduces HER, suppresses dendrite growth, and enhances the wettability of the electrode with the electrolyte. Through density functional theory (DFT) and molecular dynamics (MD) simulations, we systematically studied the mechanism by which ZnF2 improves interfacial properties, suppresses the hydrogen evolution reaction (HER), and inhibits dendrite formation. Ultimately, symmetric batteries and Zn@ZnF2||Cu batteries assembled with Zn@ZnF2 electrodes exhibited significantly extended cycle life and high Coulombic efficiency. Full cells of Zn@ZnF2||MnO2@CNT achieved a cycle life of over 5000 cycles at a current density of 1 A g−1. This study provides a practical method for industrial treatment of the Zn surface and offers an in-depth analysis and discussion of the role of ZnF2 in inhibiting dendrite growth, HER, and improving interfacial wettability in zinc-ion batteries.

Coupled model for liquid lithium plasma facing components

Numerical analysis provides the design choice and operating window of liquid metal Plasma Facing Components (PFC) concepts. Coupled analysis of boundary plasma together with the surrounding boundary structures is required. To achieve this goal, PPPL is developing a comprehensive multi-physics model for modeling of PFCs in fusion devices. The model includes the fluid-kinetic code SOLPS-ITER and the flow and heat transfer code CFX from ANSYS. SOLPS-ITER was augmented with a liquid metal boundary condition algorithm, allowing direct two-way coupling of the plasma analysis with the two-dimensional analytical slab flow model which includes heat convection in the liquid metal PFC. The target heat flux resulting from this coupled analysis is used as a boundary condition for detailed 3D Computational Fluid Dynamics (CFD) Magneto Hydro Dynamics (MHD) and heat transfer analysis. A new formulation of MHD equations is introduced in the numerical procedure ensuring current conservation of the discretized equations. Results of the 3D analysis are used for final validation of the coupled model. A PFC design where a porous wall is used to stabilize the liquid metal surface, while MHD drive is used to push the liquid metal flow inside the PFC, will be investigated in the regimes where vapor shielding is created for enhanced volumetric plasma heat dissipation.

Framework Integrated with Flow Cell Experiments and Simulations for Understanding Etching in Chemical Conversion Treatments

In this study, a new framework integrates simulations and flow cell experimentation to quantitatively understand the mechanism of chemical treatment reactions. Using this framework, the mechanisms of etching reactions induced by weak and strong acids were specifically investigated. A flow cell system experiment was developed for the etching experiment. Two acids (HNO3 and HF) were used, along with HNO3 without electrolytes. Average flow velocities were measured, and the molar flux of Fe2+ ions was determined by sampling the solution passing through the flow cell and measuring the iron content by using inductively coupled plasma. A concentration field simulation of the etching reaction in the flow cell was conducted. The concentration field within the boundary layer was visualized to understand the mechanism of H+ ion supply to the metal surface. In the case of weak acid solutions, H+ ions are primarily supplied by dissociation. In contrast, they were supplied by diffusion in strong acid solutions. A boundary layer formed within 100 μm from the metal surface. The experimental and simulated molar flux of Fe2+ ions were compared. The molar flux attributed to weak acid etching was more than 10 times that attributed to strong acids. The reaction rate constant of the H+ reduction reaction was evaluated through a parameter study. The influence of spectator ions on the etching process was investigated. An experiment was conducted to compare the etching of iron plates using HNO3 solutions with different concentrations of spectator ion. The results confirmed that the higher the concentration of the spectator ion, the greater the etching amount. Numerical analysis revealed that the electric field in the electric migration term acts in a direction that impedes the movement of H+ ions to the metal surface. While it is already known that electric migration inhibits electrode reactions, this study enabled its quantitative visualization and evaluation.