Metal Slab Research Articles

Molecular Dynamics Simulation Model of Alkali Metal Reduction of Gaseous Halides and Reaction Mechanism Analysis.

The reaction of gaseous hydrogen halides with alkali metals provides a new pathway for producing hydrogen. The structure and reactivity of alkali metals are crucial for the reduction of gaseous halides. However, traditional gas-phase reaction models fail to provide insights into the dynamic processes occurring during alkali metal reactions. In this paper, based on the reaction between Hydrogen fluoride (HF) and alkali metal sodium (Na), we have established a metallic Na slab. HF molecules were randomly inserted above the surface of the Na slab, creating a reaction model for the reduction of HF by metallic Na. The reaction of HF on the Na surface was calculated using first-principles molecular dynamics. The configuration and reaction of the Na surface and HF molecules at different times were judged by analyzing the radial distribution function and mean squared displacement. Na atoms reacted with HF to produce intermediate NaFH, and then the F-H bond broke to form NaF and H. The F-H bond breaking of intermediate NaFH was the key step, and the kinetic parameters of this key step were calculated.

Improving the precision of work-function calculations within plane-wave density functional theory

Abstract Work function is a fundamental property of metals and is related to many surface-related phenomena of metals. Theoretically, it can be calculated with a metal slab supercell in density functional theory (DFT) calculations. In this paper, we discuss how the commensurability of atomic structure with the underlying fast Fourier transform (FFT) grid affects the accuracy of work function obtained from plane-wave pseudopotential DFT calculations. We show that the macroscopic average potential, which is an important property in work function calculations under the ‘bulk reference’ method, is more numerically stable when it is calculated with commensurate FFT grids than with incommensurate FFT grids. Due to the stability of the macroscopic average potential, work function calculated with commensurate FFT grids shows better convergence with respect to basis set size, vacuum length and slab thickness of a slab supercell. After we control the FFT grid commensurability issue in our work function calculations, we obtain well-converged work functions for Al, Pd, Au and Pt of (100), (110) and (111) surface orientations. For all the metals considered, the ordering of our calculated work functions of the three surface orientations agrees with experiment. Our findings reveal the importance of the FFT grid commensurability issue, which is usually neglected in practice, in obtaining accurate metal work functions, and are also meaningful to other DFT calculations which can be affected by the FFT grid commensurability issue.

Investigating the Existence of a Pseudo-Initial State in Proton Transfer during the Volmer Reaction in a Grand Canonical Environment

Protons play a significant role in electrochemical reactions. In a simulated Volmer reaction, we can imagine the initial state as a situation where protons are in a bulk state with an empty metal slab. To study the reaction barrier, we need to move the protons from the reservoir to the surface of the electrode. We term the state where the proton has reached the near-surface layer the pseudo-initial state. This prompts the question of how protons from the bulk migrate to the near-surface and whether this pseudo-initial state truly exists. If protons don't become localized at the near-surface layer but follow a concerted mechanism, the existence of the pseudo-initial state becomes uncertain. In our research, we examined the pathways of protons in the grand canonical system using the solvated jellium method and determined the localization of protons in the near-surface layer, thus confirming the existence of pseudo-initial states.

Lithium Orbital Hybridization Chemistry to Stimulate Oxygen Redox with Reversible Phase Evolution in Sodium-Layered Oxide Cathodes.

Searching for high energy-density electrode materials for sodium ion batteries has revealed Na-deficient intercalation compounds with lattice oxygen redox as promising high-capacity cathodes. However, anionic redox reactions commonly encountered poor electrochemical reversibility and unfavorable structural transformations during dynamic (de)sodiation processes. To address this issue, we employed lithium orbital hybridization chemistry to create Na-O-Li configuration in a prototype P2-layered Na43/60Li1/20Mg7/60Cu1/6Mn2/3O2 (P2-NaLMCM') cathode material. That Li+ ions, having low electronegativity, reside in the transition metal slabs serves to stimulate unhybridized O 2p orbitals to facilitate the stable capacity contribution of oxygen redox at high state of charge. The prismatic-type structure evolving to an intergrowth structure of the Z phase at high charging state could be simultaneously alleviated by reducing the electrostatic repulsion of O-O layers. As a consequence, P2-NaLMCM' delivers a high specific capacity of 183.8 mAh g-1 at 0.05 C and good cycling stability with a capacity retention of 80.2% over 200 cycles within the voltage range of 2.0-4.5 V. Our findings provide new insights into both tailoring oxygen redox chemistry and stabilizing dynamic structural evolution for high-energy battery cathode materials.

Single–crystalline LiNi0.8Co0.1Mn0.1O2 stabilized by F–doping–induced superlattice for 4.8 V lithium–ion batteries

Single–crystalline Ni–rich ternary layered oxides represent the cutting–edge cathode materials for lithium–ion batteries, offering enhanced cycling stability compared to the polycrystalline counterparts by eliminating grain boundaries. However, their structural stability encounters a significant challenge when operated under high voltages (cut–off charging potential ≥ 4.6 V). Excessive extraction of Li+ ions can lead to the localized collapse of transition metal (TM) slabs and accumulation of lattice dislocations, which hinders Li+ diffusion and eventually cause capacity decay. This study demonstrate that the introduction of F dopants triggers an ordered mixing of Li+ and Ni2+ ions to form a superlattice in single–crystalline LiNi0.8Co0.1Mn0.1O2. This unique F–doping–induced superlattice stabilizes the deintercalated structure through Ni2+ (Li layer)–O2––Ni2+ (TM layer) interlayer super–exchange strong interactions, thereby facilitating the reversible H2–H3 phase transformation during cycling. Consequently, when cycled between 2.8–4.8 V at 1C, the F doped single–crystalline LiNi0.8Co0.1Mn0.1O2 exhibits unprecedented cycling stability, retaining 90.3 % of its initial capacity after 200 cycles, while achieving a high discharge capacity of 186.8 mAh/g and an impressive energy density of 706.5 Wh/kg. This work sheds light on the microstructural engineering for Ni–rich layered cathode materials.

Constructing a Cr-Substituted Co-Free Li-Rich Ternary Cathode with a Spinel-Layered Biphase Interface.

Lithium-rich manganese-based layered oxides (LRMOs) have recently attracted enormous attention on account of their remarkably big capacity and high working voltage. However, some inevitable inherent drawbacks impede their wide-scale commercial application. Herein, a kind of Cr-containing Co-free LRMO with a topical spinel phase (Li1.2Mn0.54Ni0.13Cr0.13O2) has been put forward. It has been found that the high valence of Cr6+ can reduce the Li+ ion content and induce the formation of a local spinel phase by combining more Li+ ions, which is beneficial to eliminate the phase boundary between the spinel phase and the bulk phase of the LRMO material, thus dramatically avoiding phase separation during the cycling process. In addition, the introduction of Cr can also expand the layer spacing and construct a stronger Cr-O bond compared with Mn-O, which enables to combine the transition metal (TM) slab to prevent the migration of TM ions and the transformation of the bulk phase to the spinel phase. Simultaneously, the synergistic effect of the successfully constructed spinel-layered biphase interface and the strong Cr-O bond can effectively impede the escape of lattice oxygen during the initial activation process of Li2MnO3 and provide the fast diffusion path for Li+ ion transmission, thus further reinforcing the configurable stability. Besides, Cr-LRMO presents an ultrahigh first discharge specific capacity of 310 mAh g-1, an initial Coulombic efficiency of as high as 92.09%, a good cycling stability (a capacity retention of 94.70% after 100 cycles at 1C), and a small voltage decay (3.655 mV per cycle), as well as a good rate capacity (up to 165.88 mAh g-1 at 5C).

Effect of Casting Temperature Control on Microstructure and Properties of Continuously Cast Zr-Based Bulk Metallic Glass Slabs

Effect of Casting Temperature Control on Microstructure and Properties of Continuously Cast Zr-Based Bulk Metallic Glass Slabs

Fast Na+ Kinetics and Suppressed Voltage Hysteresis Enabled by a High-Entropy Strategy for Sodium Oxide Cathodes.

O3-type layered transition metal cathodes are promising energy storage materials due to their sufficient sodium reservoir. However, sluggish sodium ions kinetics and large voltage hysteresis, which are generally associated with Na+ diffusion properties and electrochemical phase transition reversibility, drastically minimize energy density, reduce energy efficiency, and hinder further commercialization of sodium-ion batteries (SIBs). Here, this work proposes a high-entropy tailoring strategy through manipulating the electronic local environment within transition metal slabs to circumvent these issues. Experimental analysis combined with theoretical calculations verify that high-entropy metal ion mixing contributes to the improved reversibility of redox reaction and O3-P3-O3 phase transition behaviors as well as the enhanced Na+ diffusivity. Consequently, the designed O3-Na0.9Ni0.2Fe0.2Co0.2Mn0.2Ti0.15Cu0.05O2 material with high-entropy characteristic could display a negligible voltage hysteresis (<0.09 V), impressive rate capability (98.6 mAh g-1 at 10 C) and long-term cycling stability (79.4% capacity retention over 2000 cycles at 5 C). This work provides insightful guidance in mitigating the voltage hysteresis and facilitating Na+ diffusion of layered oxide cathode materials to realize high-rate and high-energy SIBs.

Facilitating the high voltage stability of NFM via transition metal slabs high-entropy configuration strategy

Sodium ion batteries, which is viewed as the potential candidate of Li-ion batteries, are now at the edge of wildly application. The layered oxide cathode materials, represented by NaNi1/3Fe1/3Mn1/3O2 (NFM), inherits the experience of success from LIBs are now promising of commercialization. Yet, the relative low operation voltage of NFM causing by the existence of Fe migration above 4.2 V hinder its further application nowadays. Herein, high-entropy O3-type NaMg0.08Cu0.12Ni0.2Fe0.2Mn0.2Ti0.2O2(HNFM) was proposed addressing working voltage at 4.3 V with the inhibition of large amount of Fe migration. Electrochemical test showed a specific capacity of 131 mAh g−1 was achieved within the voltage range from 2.0 to 4.3 V at current density of 0.2 C which boosted an energy density of up to 425 Wh kg−1. After 200 cycles at a 1 C current density, the capacity retention remains at 84 %. In-situ XRD analysis revealed that HNFM alleviated phase transition at high voltage compared to NFM thus it can withstand a wide operating voltage range of 2–4.3 V. DFT calculations demonstrated that transition metal slabs with high-entropy configurations could effectively suppress the migration of Fe ions from the transition metal slabs to the Na layer, thereby further enhancing the material's stability during cycling. These research findings shed light on the high-voltage operating for the layered oxide materials which provide the novel insight of the material design and inspire the commercialization of sodium ion batteries.

Sustainable Anionic Redox by Inhibiting Li Cross-Layer Migration in Na-Based Layered Oxide Cathodes.

The irrational utilization of an anionic electron often accompanies structural degradation with an irreversible cation migration process upon cycling in sodium-layered oxide cathodes. Moreover, the insufficient understanding of the anionic redox involved cation migration makes the design strategies of high energy density electrodes even less effective. Herein, a P3-Na0.67Li0.2Fe0.2Mn0.6O2 (P3-NLFM) cathode is proposed with the in-plane disordered Li distribution after an in-depth remolding of the Li ribbon-ordered P3-Na0.6Li0.2Mn0.8O2 (P3-NLM) layered oxide. The disordered Li sublattice in the transition metal slab of P3-NLFM leads to the dispersed |O2p orbitals, the lowered charge transfer gap, and the suppressed phase transition at high voltages. Then the enhanced Mn-O interaction and electronic stability are disclosed by the crystal orbital Hamilton population (COHP) analysis at high voltage in P3-NLFM. Furthermore, ab initio molecular dynamics (AIMD) simulation suggests the order/disorder of the transition metal layer is highly correlated with the stability of the Li sublattice. The cross-layer migration and loss of Li in P3-NLM are suppressed in P3-NLFM to enable the high reversibility upon cycling. As a result, the P3-NLFM delivers a high capacity of 163 mAh g-1 without oxygen release and an enhanced capacity retention of 81.9% (vs 42.9% in P3-NLM) after 200 cycles, which constitutes a promising approach for sustainable oxygen redox in rechargeable batteries.

Theoretical Estimates of the Thermoelectric Power Factor of Graphene Encapsulated between 3D and 2D Semiconductor and Metal Slabs

Theoretical Estimates of the Thermoelectric Power Factor of Graphene Encapsulated between 3D and 2D Semiconductor and Metal Slabs

Ultrahigh efficiency plasmonic mode conversion between symmetric and antisymmetric modes in metal slab waveguides by introducing a gyration-managed waveguide link

Ultrahigh efficiency plasmonic mode conversion between symmetric and antisymmetric modes in metal slab waveguides by introducing a gyration-managed waveguide link

Eliminating the Mn 3d Orbital Degeneracy to Suppress the Jahn–Teller Distortion for Stable MnO2 Cathode

AbstractThe cycle stability of manganese‐based oxides cathode for sodium‐ion supercapacitor is impeded by severe structural collapse due to the Jahn–Teller (J–T) distortion of [MnO6] octahedra as Mn4+ is reduced to Mn3+. Herein, MnO2 cathode is stabilized by Mg2+ ions confinement between transition metal slabs. The Mg2+ confinement induces the transformation from original cubic [MnO6] octahedra to compressed configuration (com‐MnO2), resulting in the elimination of Mn 3d orbital degeneracy, thereby alleviating the structural deformation of [Mn3+O6] octahedra by suppressing J–T distortion during the reduction of Mn4+. As a result, the prepared com‐MnO2 exhibits greatly improved cycling stability with 99.1% retention of its initial capacity after 20 000 cycles due to inhibited J–T distortion. Additionally, an enhanced capacity of 434 F g−1 at 1 A g−1, a rate capacity of 275 F g−1 at 20 A g−1 can be achieved by com‐MnO2. The in situ XRD, Raman spectra reveal the reversible structural transformation during a cycle. It is concluded that the elimination of Mn 3d orbital degeneracy plays a crucial role in suppressing J–T distortion, which is conducive to in‐depth understanding of electron structure of transition metal oxides toward cycling performance.

Design and Development of Iot Based Apparatus For Measuring Thermal Conductivity of Insulating Slabs

Thermal conductivity is the amount of heat that can be passed through or conducted by any material. Evaluating the thermal conductivity of insulators is critical for many applications. The available thermal conductivity apparatuses are expensive, time-consuming, and tedious to operate. With the advent of nanotechnology, there is a tremendous increase in the research and development of new insulating materials to be used for various applications. So, there is an urgent need to develop a portable, simple, and cost-effective apparatus that can be used in research laboratories to measure the thermal conductivity of newly developed insulating materials. In this regard, a portable and cost-effective thermal conductivity apparatus has been indigenously developed in the laboratory. The apparatus has been used to measure the thermal conductivity of insulating slabs. The values obtained from the apparatus have been verified with known material and found to be in broad agreement with the value available in the literature. The results obtained have been deployed onto the cloud in real-time using the Internet of Things platform. A plot of the thermal conductivity of the insulating slab at different temperatures has been displayed in the cloud. It can be concluded that the developed apparatus can be used to measure the thermal conductivity of any insulating slab with reasonable accuracy. Furthermore, this apparatus gives the same accuracy for measuring the thermal conductivity of metals as long as their dimensions are known, such as metallic bars or slabs. The thermal conductivity of the metals is compared to the standard values and this can determine their purity and if composites such as nanomaterials have been added. It is very useful for the mining industry as well, to measure the thermal conductivity of metals and assess their purity.

Correction to: Plasmonic Modes of Metallic Slab in Anisotropic Plasma Environment

Correction to: Plasmonic Modes of Metallic Slab in Anisotropic Plasma Environment

Harnessing Short-Range Surface Plasmons in Planar Silver Films via Disorder-Engineered Metasurfaces.

Short-range surface plasmon polaritons (SR-SPPs) can arise due to the hybridization of surface plasmon polaritons propagating along the two interfaces of a thin metal slab. In optics, they have gained particular interest for imaging and sensing applications because of their short wavelengths at optical frequencies along with strong field enhancement. However, mediating the interaction of SR-SPPs with photons in planar films is difficult because of the large momentum mismatch. For efficient coupling, nanostructuring such thin films (∼20 nm thickness), or placing metallic nanostructures in close proximity to the planar film, is technologically challenging and can strongly influence the SR-SPP properties. In this article, harnessing SR-SPPs in planar silver films is demonstrated using disorder-engineered metasurfaces. Disorder-engineering is realized by the light-controlled growth of silver nanoparticles. The dispersion of the hybrid modes with the silver thickness is measured and compared with simulations. We anticipate these results to introduce a facile method for harnessing SR-SPPs in planar optical systems and make use of their promising properties for imaging, sensing, and nonlinear optics.

Research on multi-stage deep drawing with electro-permanent magnet technology

Nowadays, the application of highly efficient forming techniques has been paid great attention to multi-stage sheet metal forming. In this work, the deep drawing of a circular sheet with stainless steel 304 into a cylindrical contour is performed via electro-permanent magnetic (EPM) multi-stage forming (EPMIF). Applying Lorenz force generated by directional moving electric charges, EPMIF is a hybrid forming process that combines a quasi-static stamping technique and EPM actuators to form a workpiece. During the process of EPMIF, the optimal feed increment value is designed theoretically and confirmed experimentally, which is unequal spacing and gradually decreasing for better forming performance. Excellent formability of the sheet can be observed without significant rapture and wrinkling defects, in detail, the relative forming height of the metal slab could reach 0.65. Furthermore, under different feed increments, the evolution law of metal sheet deformation is investigated by common evaluation indices including forming height, strain distribution, and thinning ratio. Meanwhile, the microscopic structure of the workpiece is compared with the simulated profile. The result shows that the deep drawing with EPMIF is conducive to improving the forming performance of metal sheets and avoiding the fracture induced by uneven deformation at the same time.

Orbital-free density-functional theory for metal slabs.

Orbital-Free Density-Functional Theory (OF-DFT) is known to represent a promising alternative to the standard Kohn-Sham (KS) DFT, as it relies on the electron density alone, without the need to calculate all KS single-particle orbitals and energies. Here, we investigate the behavior of the main ingredients of this theory, which are the non-interacting kinetic-energy density (KED) and the Pauli potential, for metal slabs. We derive explicit density functionals for these quantities in the quantum limit where all electrons are in the same slab discrete level of energy, and we present numerical calculations beyond this quantum limit for slabs of various widths. We have found the first explicit KED functional for a realistic many-particle fermionic system, which we prove to be generally valid with no assumption about the KS potential. We also discuss the total non-interacting kinetic energy and the corresponding enhancement factor, which represent basic quantities for the practical implementation of OF-DFT.

Aluminum and Indium Co‐Modified Ni‐Rich Layered Cathode with Enhanced Microstructure and Surface Stability for Lithium‐Ion Batteries

AbstractNi‐rich layered oxides are considered as promising cathodes for next‐generation lithium‐ion batteries. However, they still suffer microstructure and surface instability particularly under high operating voltage, leading to rapid capacity fading and battery failure. In this context, Ni‐rich layered cathodes (LiNixCoyMn1−x−yO2; LNCM) with aluminum and indium co‐modified crystal and surface structures are developed by a simple one‐pot calcination approach. Battery tests show that the Al and In co‐modified LNCM electrodes demonstrate remarkably enhanced rate capability and cycling stability compared with the pristine LNCM, Al‐doped LNCM, and In‐modified LNCM counterparts. Further characterizations reveal a simultaneous suppression of cracking and resistive film growth. The improved microstructural and surface stability originate from the synergistic functions of Al and In co‐modification. The incorporation of Al3+ into transition metal slab significantly reduces the Li+/Ni2+ antisite, which noticeably mitigates the undesired layer to rock‐salt phase transformation. The In3+ dopant dispersed in Li interslab can dissipate the anisotropic lattice strain, enabling greatly improved reversibility of H2↔H3 phase transition occurred in delithiation‐lithiation processes. Meanwhile, the synchronously formed LiInO2 adherent coatings deplete lithium residues, facilitate lithium‐ion transfer, and resist electrolyte corrosion. Microstructure and surface engineering through Al and In co‐modification offer a promising design strategy for Ni‐rich layered cathodes.

Total Focusing (TFM) for the Ultrasonic Testing (UT) of drawn arc stud welding

This article describes the results obtained applying ultrasonic testing (UT) with phased arrays (PAUT) using full matrix capture (FMC) and total focusing method (TFM) for the inspection of drawn arc stud welding. Weld studs are usually directly applied on the top of a metal slab using a dedicated welding gun. This procedure involves heating the end tip of the stud using a strong electric arc created by a positive electric current. This welding procedure shall comply to various normative requirements, but on the other side there is not a clear reference to any applicable non-destructive method (NDT) to control the quality of the weld seam. Shear connectors are normally used in concrete/steel composite structures to allow the combined action of the concrete slab and the steel profile thereby increasing both the stiffness and strength of the structure. Flaws in this connection would result in severe bending and cracking of the entire structure. This article proposes an advanced UT method to inspect the weld between shear connections and metal slab using FMC. Data acquired with FMC are processed by TFM algorithms improving image resolution, signal to noise performances and allowing 3D data imaging. The combined use of PAUT searching units and signal processing with high resolution measurement shows a great potential in industrial NDT applied to civil engineering, resulting in a more effective, reliable, and faster inspection methodology than many other methods, such as radiographic testing (RT).