Penetration Of Atoms Research Articles

Study on Mechanical Behaviours and Microstructure Features of Q690 Steel Weldments with Various Electrochemical Hydrogen Charging Conditions.

Regarding the application of high-strength steel welded components to large marine equipment, prolonged exposure to marine environments results in the infiltration of hydrogen, leading to a significant decline in mechanical performance. In this study, the electrochemical hydrogenation characteristics of Q690 high-strength steel welded components at room temperature are examined under various conditions to investigate their mechanical properties. The welded specimens initially undergo electrochemical hydrogenation and, subsequently, uniaxial tensile testing to explore the influences of hydrogenation methods on their mechanical properties such as tensile strength, yield strength, and elongation after fracture. X-ray diffraction (XRD) and scanning electron microscopy (SEM) are utilized to observe changes in the microstructure features in heat-affected zones (HAZs) and highlight the mechanisms affecting material mechanical properties. The results indicate that the tensile strength, yield strength, and elongation after fracture of the material decrease with increasing hydrogenation time, solution concentration, and current density. Moreover, the fracture modes of Q690 high-strength steel welded components shift from ductile fracture to brittle fracture with increasing hydrogen atom penetration.

A Multipole-Based Reactive Force Field for Hydrocarbons.

The computational complexity of quantum chemistry methods has prompted the development of reactive force fields, facilitating practical applications of molecular dynamics simulations for large-scale reactive systems. Current reactive force fields typically employ intricate corrections based on prior chemical knowledge, which severely impedes their further advancement. This study presents a new atomic multipole-based reactive model with bond free (OPERATOR). The force field is constructed on a simple, physically motivated model within the AMOEBA framework that closely resembles the physical representation of the chemical reaction processes. In the force field, the atomic multipoles are generated dynamically according to the atomic environments, aiming to effectively capture significant changes in the electrostatic environments during chemical reactions. Subsequently, atomic multipole-based charge penetration, polarization, and charge transfer effects are incorporated into the force field to describe the complex electrostatic interactions in the system. The force field also includes van der Waals interactions and three-body potentials. In addition, to extend these nonreactive interactions to chemical reactions, the atom distribution multipole moments are used to characterize different chemical environments. The force field has been optimized using the dataset of potential energy surfaces (PESs) of hydrocarbons derived from DFT results of millions of conformations with six degrees of freedom (DOFs). The results demonstrate that the new force field effectively replicates both the monopoles and the energies. In comparison to ReaxFF, the new force field exhibits comparable or superior performance. Furthermore, molecular dynamics simulations of n-heptane decomposition effectively reproduce the primary products and reactions observed in the experiments. Given the simplicity and physically motivated nature of the model, it is expected that the new force field will be utilized in future studies to investigate chemical reaction mechanisms involving more elements.

Hydrogen resistance of reduced graphene oxide coatings prepared by electrophoretic deposition on duplex stainless steel

In this study, reduced graphene oxide (rGO) coatings were fabricated on duplex stainless steel (DSS) substrates using the electrophoretic deposition (EPD) method to evaluate their hydrogen resistance performance. The successful fabrication of rGO coatings was confirmed using Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). The structural characteristics were characterized using Raman spectroscopy and X-ray Diffraction (XRD). The results indicate that the EPD voltage is a crucial factor affecting the surface quality of and hydrogen resistance performance of rGO. Lower voltages resulted in lower degrees of rGO reduction and higher surface wrinkle density, while higher voltages caused bubble formation, significantly degrading the coating quality and hydrogen resistance performance. The optimal hydrogen resistance was achieved at an EPD voltage of 7.5V and a deposition time of 6 min. Electrochemical hydrogen charging tests and thermal desorption analysis (TDA) demonstrated that rGO coatings prepared under optimal conditions exhibited excellent hydrogen resistance efficiency, significantly reducing hydrogen atom penetration in hydrogen environments. The study further revealed that bubble formation significantly reduces the hydrogen resistance of rGO, which is attributed to increased interlayer spacing and the loss of the “labyrinth effect”.

Effect of deposition rate and annealing on Nb thin film growth on Cu substrate: Molecular dynamics simulation

Molecular dynamics (MD) simulations are performed to study the growth mechanisms of Nb thin film on Cu substrate. In this investigation, we provide insights and information about the quality of the deposited Nb thin film by analyzing the growth mode, stress, and evolution of its microstructural and morphological properties by considering different deposition rates and thermal annealing processes. The results show that the growth of Nb atoms on the Cu substrate follows the island mode. The interface analysis reveals the presence of a nucleation phenomenon, moreover, the results indicate that the first layer of Nb film remains incomplete until approximately the amount of 4 monolayers of Nb is deposited. The analysis of interdiffusion indicates that Nb penetration is initially limited to the first Cu layer. However, after annealing, there is a significant increase in Nb atom penetration and a clear rearrangement of Nb within each layer of the film. The film adopts a BCC structure, with crystallinity rates varying based on the deposition rate. The highest crystallinity rate is observed at 5 atoms/ps, and annealing further increases these percentages. Deposition at different rates leads to different levels of compressive normal and biaxial stress.

Engineering of LiTaO3 Nanoparticles by Flame Spray Pyrolysis: Understanding In Situ Li-Incorporation into the Ta2O5 Lattice.

Lithium tantalate (LiTaO3) perovskite finds wide use in pyroelectric detectors, optical waveguides and piezoelectric transducers, stemming from its good mechanical and chemical stability and optical transparency. Herein, we present a method for synthesis of LiTaO3 nanoparticles using a scalable Flame Spray Pyrolysis (FSP) technology, that allows the formation of LiTaO3 nanomaterials in a single step. Raman, XRD and TEM studies allow for comprehension of the formation mechanism of the LiTaO3 nanophases, with particular emphasis on the penetration of Li atoms into the Ta-oxide lattice. We show that, control of the High-Temperature Particle Residence Time (HTPRT) in the FSP flame, is the key-parameter that allows successful penetration of the -otherwise amorphous- Li phase into the Ta2O5 nanophase. In this way, via control of the HTPRT in the FSP process, we synthesized a series of nanostructured LiTaO3 particles of varying phase composition from {amorphous Li/Ta2O5/LiTaO3} to {pure LiTaO3, 15-25 nm}. Finally, the photophysical activity of the FSP-made LiTaO3 was validated for photocatalytic H2 production from H2O. These data are discussed in conjunction with the role of the phase composition of the LiTaO3 nanoparticles. More generally, the present work allows a better understanding of the mechanism of ABO3 perovskite formation that requires the incorporation of two cations, A and B, into the nanolattice.

Metal Penetration and Grain Boundary in MoS2 Memristors

Abstract2D semiconductors have demonstrated outstanding switching performance in resistive random‐access memory (RRAM). Despite the proposed resistive switching (RS) mechanism involving the penetration of electrode metal atoms, direct observation of metal penetration in these van‐der‐Waals stacked 2D semiconductors remains absent. This study utilizes 2D molybdenum disulfide (MoS2) as the switching material, employing gold and multilayer graphene as electrodes. Through analysis of the switching characteristics of these RRAM devices, the pivotal role of grain boundaries and metal atoms is identify in achieving RS. High‐resolution transmission electron microscopy and energy‐dispersive X‐ray spectroscopy provide direct evidence of metal penetration into multilayer MoS2. This study offers valuable insights into the RS mechanism in memristors based on multilayer MoS2, providing guidance for designing and optimizing 2D material memristive devices.

Nanotransfer Printing for Synthesis of Vertically Aligned Carbon Nanotubes with Enhanced Atomic Penetration

AbstractVertically aligned carbon nanotubes (VACNTs) exhibit outstanding mechanical strength, chemical stability, and electrical characteristics; however, their constrained mechanical elasticity and chemical responsiveness spurred research on atomic decoration techniques for enhancing their mechanochemical attributes. Nevertheless, achieving uniform atomic decoration on the VACNT surface is difficult because of the high density and large aspect ratio of VACNT. Herein, a strategy to design and apply nanopatterned VACNTs (nVACNTs) based on a nanotransfer printing process is proposed to improve atomic penetrability. Nanopatterns inherent to nVACNTs facilitate atomic penetration, allowing for the more consistent and higher quality deposition of functional materials such as zinc oxide and alumina by atomic layer deposition. Furthermore, physical vapor deposition provides an improved coating of metal catalysts such as gold. The uniform deposition of ceramic layers on the entire surface of nVACNTs strengthens its mechanical resilience, owing to the diminished van der Waals forces of CNTs. Surface‐decorated nVACNTs display an increased sensitivity to NO2 gas, which is attributed to the enhanced quality of the reactive catalyst deposition and augmented permeability. This strategy achieves a larger decorated area while increasing a catalytically active reaction area. The obtained results promise that the enhanced nVACNTs will expand the industrial applications of carbon nanotubes.

The Effects of Edge Dislocations on The Corrosion Behavior of Pure Iron in Liquid Lead-Bismuth Eutectic: A Molecular Dynamics Study

The effect of liquid lead–bismuth eutectic (LBE) on the corrosion evolution of iron-based materials with varying densities of edge dislocation defects was studied. Molecular dynamics simulations were conducted at temperatures ranging from 823 K to 1173 K, and the process of penetration of Pb and Bi atoms at the dislocation core was analyzed. The results indicated that Fe atoms near the dislocation core have the lowest substitution energy (−4.79 eV/atom), making them more likely to be replaced by Pb and Bi atoms. Moreover, it was found that the increase in dislocation density did not result in a high penetration depth of LBE atoms, attributed to the interaction of dislocations. These findings provide crucial insights into the LBE corrosion mechanism in iron-based materials with dislocation defects.

Hot extrusion-induced Mg-Ni-Y alloy with enhanced hydrogen storage kinetics

In this work, the influence of the hot-extrusion method on the hydrogen storage kinetics of Mg-Ni-Y alloy was investigated. It was shown that the extruded Mg91.47Ni6.97Y1.56 alloy exhibits improved hydriding and dehydriding (H/D) kinetics, with a capacity of 3.5 wt.% H2 absorption within 60 s and 5.4 wt.% H2 desorption within 5 min at 573 K. The dehydrogenation activation energy of extruded alloy is 71.4 kJ mol−1, smaller than that of as-cast alloy (140.5 kJ mol−1). The enhancement of H/D kinetics is attributed to the microstructural refinement and increased grain/phase boundaries introduced by hot extrusion, as well as the catalytic effects from the in-situ generated and grain-refined Mg2Ni and YH2 particles during the H/D process. Furthermore, the dehydrogenated rate-determining step transforms from hydrogen diffusion in the hydride (as-cast alloy) to the surface penetration of hydrogen atoms (extruded alloy). These findings provide crucial insights for the design of Mg-based hydrogen storage alloys in the future.

Atomistic mechanism of AlCu thin film alloy growth on trenched Si substrate

Molecular dynamics simulation was employed to study the growth mechanisms of an AlCu thin film on a trenched Si(001) substrate. The atomic interactions between Al, Cu, and Si atoms were described by using the Modified Embedded Atom Method (MEAM). This investigation focused on examining the effect of both incident energy and trench heights on the structure, and the morphology of deposited AlCu thin film. The results reveal that the growth mode follows an island mode, and the AlCu film surface exhibits both non-flat and non-uniform texture. The increase in the trench height leads to a more pronounced change in surface morphology and roughness. However, a higher incident energy can significantly reduce the surface roughness due to the mobility of deposited atoms. In addition, a mixing region was observed at the interface between the film and substrate. It is revealed that increasing the incident energy leads to deeper penetration of Al and Cu atoms into the substrate. More importantly, Al atoms penetrate deeper than the Cu atoms. On the other hand, deposition on a trench with 15 monoatomic layers leads to the formation of voids in the film. However, these voids disappear with higher incident energy. The microstructural evolution during deposition film was also analyzed based on the radial distribution function. The results of this function indicate that changes in trench height and the energy of incident adatoms do not significantly influence the structure of the film.

Effect of stepped Si (001) substrate on Cu thin film growth

The growth processes of Cu thin film on stepped Si(001) substrate were investigated using molecular dynamics simulation. The modified embedded atom method was used to describe the atomic interaction between Cu-Cu, Si-Si, and Si-Cu. In this study, four different Si(001) substrate configurations were examined: (i) flat Si(001) substrate; (ii) stepped Si surface with 3-monoatomic layers step; (iii) Stepped Si surface with 5-monoatomic layers step; (iiii) stepped surface with 7-monoatomic layers. Our aim here is to investigate the effect of stepped substrate on the structure, the surface roughness, and the morphology of deposited Cu thin film. The results show that the Cu film obtained has a crystalline structure based on the radial distribution function. In addition, the morphology of Cu film is not smooth for the different stepped substrates. More precisely, the surface roughness increases when the substrate presents a step and rises with the augmentation of the step height. On the other hand, our results reveal that the penetration of Cu atoms in the simplest case of the flat configuration is limited to the top layer of the substrate. While for the stepped substrate, our findings show that the penetration in the stepped substrate is more important and deeper within the upper terrace compared to the lower terrace. Furthermore, the numerical calculations demonstrate that the step height has no significant effect on the penetration of Cu atoms on the Si(001) stepped substrate. These results are appropriate for the deposition of copper atoms into the stepped substrate of silicon.

H2 -free Semi-hydrogenation of Butadiene by the Atomic Sieving Effect of Pd Membrane with Tree-like Pd Dendrites Array.

H2 -free semi-hydrogenation at room temperature shows great advantage for replacing the thermocatalytic process in industry owing to the high energy and resource saving, however, remains great challenges. Herein, a tree-like Pd dendrites array decorated Pd membrane was constructed as the core device in an electrochemistry assisted gas-fed membrane reactor for butadiene semi-hydrogenation. It reveals that hydrogen atomic sieving effect of this Pd-based membrane under electrochemical condition was the key for semi-hydrogenation. The configuration study of Pd nanostructured membrane demonstrates that the penetration of hydrogen atoms through Pd membrane from electrochemical side to chemical side is affected by the consumption of hydrogen atom in semi-hydrogenation step. Such atomic sieving property of nanostructured Pd membrane with 5.1 times increase in catalytic active surface area brings above 14 times higher in butadiene conversion than that of bare Pd foil, with ≈90 % of butenes selectivity at butadiene conversion ≈98 % over 300 h of H2 -free reaction under 15 mA cm-2 .

H2‐free Semi‐hydrogenation of Butadiene by the Atomic Sieving Effect of Pd Membrane with Tree‐like Pd Dendrites Array

AbstractH2‐free semi‐hydrogenation at room temperature shows great advantage for replacing the thermocatalytic process in industry owing to the high energy and resource saving, however, remains great challenges. Herein, a tree‐like Pd dendrites array decorated Pd membrane was constructed as the core device in an electrochemistry assisted gas‐fed membrane reactor for butadiene semi‐hydrogenation. It reveals that hydrogen atomic sieving effect of this Pd‐based membrane under electrochemical condition was the key for semi‐hydrogenation. The configuration study of Pd nanostructured membrane demonstrates that the penetration of hydrogen atoms through Pd membrane from electrochemical side to chemical side is affected by the consumption of hydrogen atom in semi‐hydrogenation step. Such atomic sieving property of nanostructured Pd membrane with 5.1 times increase in catalytic active surface area brings above 14 times higher in butadiene conversion than that of bare Pd foil, with ≈90 % of butenes selectivity at butadiene conversion ≈98 % over 300 h of H2‐free reaction under 15 mA cm−2.

Corrosion behavior of Zn in electrolyte during the charge and discharge process and its influence on the electrochemical performance of zinc doped Mg2Ni1-xZnx rapidly quenched alloys

In the electrochemical process, a continuous passivation layer of Mg(OH)2 is formed on the surface of Mg2Ni alloy particles and prevents the penetration of hydrogen atoms, which have a negative impact on the discharge capacity. In this work, Mg2Ni1-xZnx (x = 0, 0.17, or 0.33) rapid quenching alloys were prepared by partially replacing Ni with Zn in order to modify the surface of the alloy with the corrosiveness of Zn in alkaline solution. The microstructure results indicate that Zn doping promotes the corrosion of Mg2Ni alloy in the electrolyte, and many corrosion holes are formed on the surface after the electrochemical process. With the increase of Zn, the charge-transfer reaction resistance (Rct) and polarization resistance (Rp) of the alloy electrode increase from 306.24 and 366.41 mΩ to 508.76 and 526.57 mΩ, respectively, and the corrosion current density (Io) decreases from 70.08 to 48.77 mA/g. The appropriate amount of Zn atoms increases the discharge capacity, and the highest value can reach 92.94 mAh/g at x = 0.33. This reveals that corrosion holes are formed on the surface of Zn-doped alloys during the electrochemical process and destroy the continuity of the passivation layer on the Mg2Ni surface, which facilitate the penetration of hydrogen atoms.

Nonuniformity of magnetization processes of a cobalt-based amorphous alloys in the as-quenched state

The magnetization processes nonuniformity of an amorphous cobalt-based soft-magnetic alloy AMAG-172 (Co-Ni-Fe-Cr-Mn-Si-B) in the as-quenched state were studied. Studies have shown that the main reason of the magnetic characteristics and magnetization processes nonuniformity is the nonuniformity of internal stresses due to the alloy manufacture method. An indirect characteristic of internal stresses is the domains volume with orthogonal magnetization. The observed bimodal field dependence of the magnetic permeability and the field shift of the hysteresis loops in the region of 180-degree domain walls displacement are a consequence of the nonuniformity of the alloy over its thickness. The field shift and the asymmetry of hysteresis loops are explained in terms of the formation of a unidirectional exchange anisotropy at the interface between the ferromagnetic and antiferromagnetic phases of the planar magnetization components oriented along the ribbon axis. The field shift disappearance and the asymmetry of the hysteresis loops along the width of the tape can be interpreted as a decrease in the thickness of the CoO oxide antiferromagnetic layer due to the difference in the concentrations and depth of oxygen and hydrogen atoms penetration induced into the surface of the tape during the manufacture of the tape as a result of interaction with atmospheric vapor.

Hydrogen permeability of 48Cu52Pd cold-rolled alloy foil and different methods of its surface pretreatment

The process of atomic hydrogen penetration into the metal phase is complicated by the phase-boundary transition from the liquid and/or gas phase. That is why the cleanliness of metal and alloy surfaces is of particular importance. The purpose of this work was to determine the effect of surface pretreatment using photon pulses, ultrasound, and potential cycling on the parameters of hydrogen permeability for 48Cu52Pd metal cold-rolled membranes. The study was focused on a foil of copper-palladium homogeneous alloy with 48 at. % Cu and 52 at. % Pd composition. The studied samples were obtained by cold rolling and their thickness were 10 and 16 μm. Surface pretreatment included rinsing in acetone, using ultrasound, pulsed photon treatment, and quadruple potential cycling over a wide range of potentials. Electrochemical studies included cyclic voltammetry and cathode-anodic chronoamperometry in a deaerated 0.1 M H2SO4 solution. Hydrogen permeability was calculated using mathematical models for samples of finite and semi-infinite thickness. It was found that the surface treatment of a 48Cu52Pd foil with photon pulses leads to both an increase in the ionisation rate of atomic hydrogen and an increase in the roughness of the foil surface. The diffusion coefficient of atomic hydrogen does not depend on the method of surface pretreatment with ultrasound and photon pulses. The extraction rate constant for the extraction of the atomic hydrogen after photon treatment increases, which facilitates the processes of both H introduction and ionisation due to the release of active centres of the surface. Electrochemical cleaning of the surface during the quadruple potential cycling contributes to the growth of the extraction rate constant for the extraction of atomic hydrogen

RESEARCH OF THE STRUCTURAL-PHASE STATE OF TUNGSTEN SURFACE LAYER CROSS-SECTION AFTER CARBIDIZATION IN A BEAM-PLASMA DISCHARGE USAGE ELECTRON MICROSCOPY METHODS

This paper presents research results on the structural-phase state of a tungsten surface layer cross-section after carbidization in a beam-plasma discharge. Tungsten surface carbidization in a beam-plasma discharge was conducted in a plasma-beam installation (PBI). Research on the cross-section structure of the surface layer of tungsten samples after carbidization at temperatures of 1000 °C, 1200 °C, and 1400 °C was conducted using transmission and scanning electron microscopy. Based on the results of SEM studies, a multilayer EMF map and local elemental analysis were obtained, based on which the depth of penetration of carbon atoms into tungsten was evaluated. It is established that the penetration depth is ~20 µm. The surface layer fine structure was researched using TEM. For TEM analysis of the tungsten sample cross-section with a carbidized layer, sections were prepared by ion thinning using an Ion Slicer EM-09100 IS unit. According to the research results, it was revealed that after carbidization, tungsten is available in the surface layer mainly in the composition of carbides WC and W2C. On bright-field TEM images of the cross-section of the surface layer of tungsten samples after carbidization at a temperature of 1200 °C and 1400 °C, bending extinction contours are revealed, which indicate the elastically stressed state of the sample surface layer, which leads to bending-torsion of the foil.

FORMATION OF CRYSTALLINE SiC IN NEAR-SURFACE SILICON LAYERS BY METHOD OF COORDINATED SUBSTITUTION OF ATOMS

In this work, monocrystalline films of silicon carbide were synthesized on the surface of a Si(100) silicon wafer using the method of coordinated substitution of atoms. The films were synthesized at temperatures of 1200 °C and 1300 °C for 20 minutes in a CO gas flow at a pressure of 0.8 Pa. The effect of 1200–1300 °C temperatures on the formation of single- and polycrystalline layers, as well as nanostructured SiC phases in the near-surface region of silicon by the method of atom substitution, is analyzed. The formation of a high-quality crystalline silicon carbide film and the influence of synthesis conditions on the total volume of SiC structural phases, microstructure and nanostructure of the surface are shown. It was found that an increase in temperature from 1200 °C to 1300 °C led to a more intensive formation of silicon carbide and an increase in the number of Si–C bonds by 1.9 times due to an increase in the thickness of the synthesized silicon carbide layer. There is an increase in the proportion of the crystalline phase due to a more intense transformation of the nuclei of nanocrystals into micro- and nanocrystals. Intense processes of penetration of carbon atoms deep into silicon at a temperature of 1300 °C with amorphization of its structure and the formation of Si-C, which can transform into crystalline phases at temperatures above 1300 °C, are assumed. The proportion of the SiC crystalline phase increases to 50.2% of the film volume due to the intensive transformation of nanocrystal nuclei into micro- and nanocrystals. It has been experimentally shown that the formation of various SiC structures on Si (100) occurs in full accordance with the main principles of the method of coordinated substitution of atoms.

Molecular dynamics simulation on the dissolution and diffusion characteristics of FeCrAl alloy in liquid LBE

Lead-bismuth eutectic (LBE) corrosion-resistant materials are crucial for the development of future fourth-generation nuclear reactors, and the dissolution and diffusion of material components are important processes in LBE corrosion-resistant materials. FeCrAl alloy is an important structural material for fourth-generation reactors, and it is essential to study its dissolution and diffusion processes in liquid LBE. Molecular dynamics simulations (MD) were used to investigate the mutual diffusion process between the FeCrAl alloy and liquid LBE. The dissolution and diffusion abilities of Fe, Cr, and Al atoms in liquid LBE were evaluated using mean-square displacement (MSD) and diffusion activation energy (DAE). Fe atoms exhibited the highest degree of diffusion, while Al atoms showed the lowest degree of diffusion, resulting in a distinct difference in the elemental distribution at the solid–liquid interface (SLI). There was a significant difference in the depth of penetration of Pb and Bi atoms into the FeCrAl alloy matrix, with Bi atoms penetrating deeper. Furthermore, there is a thermal vibration process during the invasion of Pb and Bi atoms into the FeCrAl alloy matrix, which promotes the invasion process of Pb and Bi atoms. In addition, an increase in temperature exacerbates the diffusion of Fe, Cr, and Al atoms in liquid LBE and the process of Pb and Bi atom invasion into the FeCrAl alloy matrix. Our research may contribute to the design of future nuclear-grade FeCrAl alloy and the development of next-generation reactors.

Swelling effect of 2D BC[formula omitted] anode material in Li-, Na- and Mg-ion energy storage systems

The development of high-performance metal-ion batteries mainly focuses on searching for high-capacity anodes but neglects the volume expansion effect of the materials during the charge/discharge process. Using the first-principles calculation method, we examine the efficacy of bilayer BC7 as an anode material for Li/Na/Mg-ion batteries. Our results illustrate a strong swelling effect caused by the penetration of Na and Mg atoms into the interlayer space of BC7, which is responsible for a large volume expansion and renders the BC7 anodes unsuitable for Na- and Mg-ion batteries. On the other hand, intercalation of Li into the BC7 structure could deliver an acceptable volume expansion of the 2D anode and a theoretical capacity of 423.69 mAh/g, which is higher than that of commonly used anodes for Li-ion batteries.