Smooth Metal Research Articles

Wear properties of textured lubricant films filled with graphite and polytetrafluoroethylene (PTFE) via laser surface texturing (LST)

One of major issues to laser processing lies in unavoidably existing high points at the edge of affected zones. However, these high points can act as anchorage points to tackle the problem that some functional materials are difficult to manufacture completely lubrication films on smooth metal surfaces. In this study, two kinds of textured lubricant films, namely graphite filled textured lubricant film and polytetrafluoroethylene (PTFE) filled textured lubricant film, were investigated by means of laser surface texturing. Such PTFE/graphite lubrication films and reverse use of the capture function of surface texture microconcaves were employed to enhance the tribology properties. The friction coefficient of these two films sliding against PTFE/Kevlar fabric composites was decreased by 10–45%, and the time to reach a stable state was shortened 100 times. The wear mechanism of these films is adhesive and fatigue wear and the transfer films are complete and continuous.

DEVELOPMENT AND ANALYSIS OF THE ACCURACY OF ENGINEERING METHODS FOR DETERMINATION OF INTERACTION VOLUME FOR CALCULATION OF THE TIGHTNESS OF NON-LUBRICATING CYLINDER-PISTON SEALS

Based on the theory of stochastic processes, methods of engineering calculation of the contact volume for the calculation of the tightness of non-lubricating cylinder-piston seals of compressors have been developed. The result is the creation of methods for calculating the tightness (duration of gas flow) in non-lubricating cylinder-piston metal-polymer seals, as well as assessing the accuracy of the created methods for piston seals. The article considers the elastic contact of a strongly anisotropic rough surface (polymer surface) with a smooth (metal) surface. The dependence of the intercontact gas volume on the complex of contact conditions based on the theory of stochastic fields is investigated. An estimate of the error that occurs when replacing the exact formula for calculating the contact volume with an approximate formula is performed. The values ​​calculated according to the exact and calculated formula of the consolidated inflow differ by no more than 0.17 percent. Accurate methods for calculating the tightness of non-lubricating cylinder-piston seals for molecular and viscous modes of gas flow, which is the basis for practical calculations of the tightness of the seals of non-lubricating pneumatic compressors, are theoretically substantiated and developed. The dependence of the contact volume, the effective level of deformation and the average height of the gap on the set of contact conditions has been studied. It is established that at low loads the deformation level, the effective deformation level, the reduced contact volume and the reduced average gap height are numerically equal. The values ​​calculated by the exact and calculated formula of the contact volume differ by no more than 0.17 percent at K 1 and no more than 0.00029 percent at K> 1.

Electrodynamic solution for polarized reflectivity and wide-field orientation imaging of uniaxial metals

The polarized reflectivity of an ideally smooth metal with a uniaxial anisotropic complex refractive index, for instance, metals with hexagonally close-packed (HCP) symmetry, is derived from the electromagnetic wave equation for normal incidence and arbitrary crystal orientation. The resulting orientation-dependent Mueller matrices of the surface are applicable to c axis orientation imaging of metals including beryllium, magnesium, titanium, cobalt, zinc, zirconium, tin, and most of their alloys, as well as other uniaxial compounds. Comparing orientation images recorded with a generalized polarized-light microscope (PLM), in this case an original coherent laser PLM, with orientation images obtained by electron backscatter diffraction (EBSD) enables imaging ellipsometry (IE) at near-normal incidence and increases confidence in ellipsometric refractive-index measurements. In this initial study, without modeling oxides, the resulting c axis orientation images of several titanium alloys are still verified to better than 11% against EBSD maps of the same samples over instantaneous fields of view (FOVs) exceeding 1 c m 2 and FOVs approaching 1 i n 2 obtained by stitching several such images together.

Synergistic Effect of Iodide Ion and N‐methyl‐N,N,N‐trioctylammonium Chloride on Corrosion Inhibition of Carbon Steel in 0.5 M H2SO4: Experimental and Computational Approach

AbstractAn ionic liquid Aliquat 336 was for the first time analyzed for its adsorption and corrosion inhibition behavior for carbon steel surface in 0.5 M H2SO4. The inhibition performance was studied using gravimetric and electrochemical techniques supported by surface analytical measurements. The inhibitor exerted an efficiency of 96.53 % at 12×10−6 M. Significant improvement was achieved with iodide ions, which at 3.01×10−4 M, produced a remarkable rise in the efficiency to 99.03 %. The adsorption of the inhibitor on the metallic surface followed the Langmuir isotherm at 298 K in the concentration range of 2.47 to 12.37×10−6 M. Polarization studies indicated a mixed‐mode of inhibitor action with the cathodic predominance. The SEM studies showed a smooth metal surface in contact with the inhibitor, and a representative decrease in surface roughness was observed by AFM studies. Monte Carlo simulations showed inhibitor adsorption in a flat orientation on the metal surface with high adsorption energy.

Reflection interference removal for infrared thermography images based on GAN

Reflection in images is common and the removal of complex noise such as image reflection is still being explored. The problem is difficult and ill-posed, not only because there is no mixing function but also because there are no constraints in the output space (the processed image). When it comes to detecting defects on metal surfaces using infrared thermography, reflection from smooth metal surfaces can easily affect the final detection results. Therefore, it is essential to remove the reflection interference in infrared images. With the continuous application and expansion of neural networks in the field of image processing, researchers have tried to apply neural networks to remove image reflection. However, they have mainly focused on reflection interference removal in visible images and it is believed that no researchers have applied neural networks to remove reflection interference in infrared images. In this paper, the authors introduce the concept of a conditional generative adversarial network (cGAN) and propose an end-to-end trained network based on this with two types of loss: perceptual loss and adversarial loss. A self-built infrared reflection image dataset from an infrared camera is used. The experimental results demonstrate the effectiveness of this GAN for removing infrared image reflection.

EXPERIMENTAL SETTING FOR TESTING THE BOND STRENGTH BETWEEN METAL ALLOY AND PEEK

Purpose: The aim of the article is to present an experimental setting for bending strength testing of metal specimens covered with PEEK. Materials and methods: Three groups of metal specimens made of cobalt chromium alloy are produced using the lost wax technique: group 1 – specimens with a smooth metal surface; group 2 – sand blasted metal surface; group 3 - sand blasted metal surface with retention crystals. The shape and size of the specimens are designed to correspond to the retentive elements of the apparatus for micro tension and micro pressure LMT 100. PEEK is pressed over the specimens, and after thermal cycling, the bond between metal alloy and PEEK is studied using bending strength three-point micro testing. Results and discussion: The experimental setting is focused on the type of specific contact surface between the two materials. The design corresponds to the requirements of apparatus LMT 100 and allows the production of a big number of specimens. Because of the thermal regime of BioHPP pressing, it is impossible to add groups of specimens using contemporary adhesives on the metal surface. Conclusion: Created specimens allow strength investigation by three-point bending micro testing. The experimental setting provides the production of a big number of specimens with the same shape and size.

An operando ORP-EIS study of the copper reduction reaction supported by thiourea and chlorides as electrorefining additives

Additives are used in metal electroreduction processes to obtain a smooth and optimal metal deposit. However, the mechanism with which these additives influence the metal deposition is poorly understood. Operando odd random phase electrochemical impedance spectroscopy (ORP-EIS) experiments have been performed to study the effect of a chloride-thiourea additive mixture on the reduction of copper ions in a sulfuric acid solution. This additive mixture is crucial in the copper electrorefining process. An optimal experimental design and a well-founded methodology is applied to study this complex additive mixture. The ORP-EIS data is studied to analyze non-stationarities and non-linearities and the time-varying impedance is resolved when necessary. Two equivalent circuits are proposed to model the impedance data and the model parameters are linked to physical processes in the system. The use of the time-varying impedance when studying thiourea in a plating process and the use of distributed circuit elements in the EIS model is discussed.

Robust method for broadband efficiency enhancement of electron photocathodes using optical interferences

We demonstrate the key features of an interference cathode using both simulations and experiments. We deposit Cs3Sb photocathodes on Ag to produce an interference enhanced photocathode with 2–5× quantum efficiency (QE) enhancement using a robust procedure that requires only a smooth metal substrate and QE monitoring during growth. We grow both an interference cathode (Ag substrate) and a typical photocathode (Si reference substrate) simultaneously to confirm that the effects are due to optical interactions with the substrate rather than photocathode composition or surface electron affinity differences. Growing the cathodes until the QE converges shows both the characteristic interference peaks during growth and the identical limiting case where the cathode is “infinitely thick,” in agreement with simulations. We also grow a cathode until the QE on Ag peaks and then stop the growth, demonstrating broadband QE enhancement.

Realizing high-power and high-capacity zinc/sodium metal anodes through interfacial chemistry regulation

Stable plating/stripping of metal electrodes under high power and high capacity remains a great challenge. Tailoring the deposition behavior on the substrate could partly resolve dendrites’ formation, but it usually works only under low current densities and limited capacities. Here we turn to regulate the separator’s interfacial chemistry through tin coating with decent conductivity and excellent zincophilicity. The former homogenizes the electric field distribution for smooth zinc metal on the substrate, while the latter enables the concurrent zinc deposition on the separator with a face-to-face growth. Consequently, dendrite-free zinc morphologies and superior cycling stability are achieved at simultaneous high current densities and large cycling capacities (1000 h at 5 mA/cm2 for 5 mAh/cm2 and 500 h at 10 mA/cm2 for 10 mAh/cm2). Furthermore, the concept could be readily extended to sodium metal anodes, demonstrating the interfacial chemistry regulation of separator is a promising route to circumvent the metal anode challenges.

Single crystal Cu (110) inducing lateral growth of electrodeposition Li for dendrite-free Li metal-based batteries

Inducing uniform nucleation and unidirectional growth of lithium (Li) electrodeposition is of vital significance to achieve dendrite-free lithium metal batteries. Herein, a lateral growth model of Li electrodeposition on the single crystal Cu with (110) crystallographic plane is realized. The influence of grain boundaries and crystal grains on the electrodeposition of Li metal and related mechanisms are further explained from the perspective of thermodynamics. The combined simulation and experiment results reveal that the electrodeposited Li grows along (110) crystallographic plane of single crystal Cu foil due to the homogeneous physical and chemical properties surfaces, indicating a typical lateral growth model. With the achieved smooth and flat Li metal electrodeposition layer on the single crystal Cu substrate, the Li|Cu half cell exhibits a high initial Coulombic efficiency of ~98% under different current densities of 0.5 and 1.0 mA cm−2, and Li|NCM523 full cell displays remarkable cycle stability with a high cycle retention of 76.71% even after 300 cycles at the current density of 1 C. This work not only proposes the electrocrystalline growth model of Li metal, but also provides guidance for the commercialization of safe and stable LMBs.

Directional Raman scattering spectra of metal–sulfur bonds at smooth gold and silver substrates

AbstractThe gold–sulfur (Au–S) and silver–sulfur (Ag–S) bonds are integral to the surface modification of metal films with alkanethiol monolayers. Although the metal–sulfur bond can be characterized with surface‐enhanced Raman spectroscopy (SERS) at roughened metal films, some applications require or perform better when using a smooth metal surface, which is not suitable for SERS signal enhancement. Directional‐surface‐plasmon‐coupled Raman scattering (directional Raman scattering) is an approach to measure metal–sulfur bonds on smooth metal films with sub‐monolayer sensitivity. The metal–sulfur bonds formed from a benzenethiol monolayer on smooth planar gold or silver films are observed in the directional Raman scattering spectra between 240 and 270 cm−1; the signal‐to‐noise ratio of the Au–S Raman peak is 60. Importantly, the directional Raman scattering signal measured with smooth metal surfaces can be simply modeled and easily compared across many samples. Directional Raman scattering can also be measured at roughened metal films, which makes it applicable for many analyses.

An enhancement on corrosion resistance of low carbon steel by a novel bio-inhibitor (leech extract) in the H2SO4 solution

In this research, to enhance the corrosion resistance of low carbon steel in the H2SO4 solution, the leech extract as a novel bio-inhibitor was utilized. Electrochemical tests were applied to investigate corrosion characteristics of steel in the corrosive acid solution. Moreover, the atomic force microscopy (AFM) and the field emission scanning electron microscopy (FE-SEM) techniques were performed for studying the morphology of corroded steel surfaces. Based on the polarization data, the inhibition efficiency raised from 75 to 91% in the presence of the inhibitor with concentrations of 1–3 g/L. However, electrochemical impedance spectroscopy test results showed that such an increase was about 66–84%. When the test temperature increased to 40°C, the inhibition efficiency reduced from 91 to 44%. Polarization test results explained that the adsorption of leech extract molecules on metallic surfaces operated as a mixed inhibitor. In this situation, the measured activation energy increased from 65.28 to 152.93 kJ/mol.K. In addition, based on the obtained electrochemical data, leech extract molecules were adsorbed on steel surfaces through the Langmuir adsorption mechanism. Both FE-SEM and AFM micrographs from corroded metallic surfaces depicted that when the utilized bio-inhibitor was added to the H2SO4 solution a much smoother metal surface would be observed.

Упругое последействие в процессе уплотнения асфальтобетонной смеси

Asphalt concrete of various brands is mainly used as a road surface. The quality and durability of the coating depends on its density. To achieve the required density of the asphalt concrete pavement, road rollers are used. The working body of the roller is a metal drum or a set of pneumatic tires. The article discusses the process of the asphalt concrete mixture compaction with a smooth metal drum. A rheological model of the force interaction of a smooth drum with a material is adopted, which includes elastic, viscous and plastic elements. The adopted model was corrected taking into account the investigated process of elastic aftereffect that occurs in the asphalt concrete mixture during compaction. The law of behavior of asphalt-concrete mixture with elastic aftereffect is established. A simulation model has been developed to study the behavior of a material in the process of elastic aftereffect. In the course of dynamic modeling, the relationship between the physical and mechanical characteristics of the compacted material with the design and technological parameters of the road roller was established. A statistical analysis of the design parameters of existing models of road rollers has been carried out. The results of the analysis, as well as the obtained dependencies, can be used to designate the technological modes of operation of a set of road rollers when compacting the asphalt concrete pavement of a motor road. Taking into account the elastic aftereffect when assigning the operating modes of the compaction equipment will improve the compaction efficiency, as well as the quality of the resulting coating.

Compact Corrugated Plate for Double-Sided Contactless Waveguide Flange

A compact double-sided contactless electromagnetic bandgap (DCEBG) structure is introduced in this letter. It consists of three metal plates placed in parallel, including two smooth metal plates and a corrugated metal plate in the middle. The middle plate is double-sided corrugated alternatively with a displacement of half period. The depth of the corrugations is about quarter wavelength of center frequency of its stopband. The thickness of the proposed DCEBG is slightly thicker than the depth of the corrugations. A double-sided contactless waveguide flange (CWF) based on the DCEBG is proposed. Compared with the back-to-back CWF in the form of bed of nails, the thickness is effectively reduced. A prototype of the double-sided CWF (DCWF) suited for standard WR75 waveguide is designed, manufactured, and tested. The measured insertion loss is less than 0.048 dB and the return loss is lower than 25 dB over the entire WR75 waveguide frequency band.

Gravimetrical, theoretical, and surface morphological investigations of corrosion inhibition effect of 4-(benzoimidazole-2-yl) pyridine on mild steel in hydrochloric acid

Abstract The corrosion inhibition efficiency of the novel pyridine namely, 4-(Benzoimidazole-2-yl)pyridine has been studied for mild steel in a 1 M hydrochloric acid environment by utilizing gravimetrical techniques. The synthesized inhibitor exhibits a significant inhibitive efficiency of 93.8% at 0.005 M. The adsorption isotherm of the investigated inhibitor on mild steel surface obeys the Langmuir isotherm. Surface morphology investigated by utilizing scanning electron microscopy (SEM) demonstrates a smooth metal surface with the addition of 4-(Benzoimidazole-2-yl)pyridine in a hydrochloric acid environment. Quantum chemical calculations using density functional theory (DFT) have been used to investigate the molecular structure and behavior of 4-(Benzoimidazole-2-yl) pyridine as a corrosion inhibitor. Different parameters have been calculated using DFT, such as energies of highest occupied molecular orbital and lowest occupied molecular orbital (EHOMO and ELUMO), energy gap (∆E), and dipole moment (μ). These parameters were important to elucidate the behavior of the investigated molecule as a corrosion inhibitor in acidic solution and also suggest the mechanism of inhibition.

High Performance Sodium Secondary Batteries Using Ionic Liquid Electrolytes

Sodium secondary batteries are attracting more and more attention as large-scale energy storage devices owing to high abundance and low cost of sodium resources.[1-3] Ionic liquid electrolytes have unique properties such as low volatility, low flammability, and thermal stability and enable construction of safe electrochemical devices, including sodium secondary batteries.[4,5] In particular, intermediate temperature operation of sodium secondary batteries using ionic liquid electrolytes is attractive by considering the improvement of battery performance. Such environments are ubiquitous in our daily life or industries and can be achieved with minimal extra energy. Self-heating of batteries can also contribute to operation at elevated temperatures.Highly improved performance is observed for some electrode materials by intermediate-temperature operation of sodium secondary batteries with bis(fluorosulfonyl)amide-based ionic liquid electrolytes. As for the sodium metal negative electrode, morphology of sodium metal electrodeposit is significantly dependent on operation temperature; smooth sodium metal deposition with a high deposition/dissolution efficiency is observed at 90 deg C. High rate performance is observed for a number of positive electrode materials. The NASICON-type Na3V2(PO4)3 especially provides a long cycle life, exhibiting more than 5000 cycles at 90 deg C in a half cell configuration at a rate of 2C, which is also due to the high cycleability of sodium metal electrode.[6] Metal phosphide negative electrodes also show improved rate and cycle performance by intermediate-temperature operation. The copper phophide-carbon composite, CuP2/C, electrode prepared by high-energy ball-milling shows a stable cycling based on a conversion mechanism at 90 deg C over 300 cycles.[7]Na metal is used as a counter electrode in a half-cell configuration to test electrode performance for Na secondary batteries, but its unstability and large interfacial resistance causes unreliable results, especially at high rates. The Na3V2(PO4)3 and NaV2(PO4)3 electrode prepared by mixing them in a target ratio exhibits a flat plateau at 3.4 V vs. Na+/Na and lower polarization than the Na metal. This new electrode enables trustable electrochemical evaluation of a target electrode even at a temperature above the melting point of Na metal.[8]

Towards an Understanding of the SEI Formation and Lithium Preferential Plating on Copper

‘Anode-free’ batteries present a significant advantage due to their substantially higher energy density and ease of assembly in a dry air atmosphere. However, potential safety issues due to lithium (Li) dendrite growth rather than smooth Li metal plating on the Cu current collector, and low cycling coulombic efficiency during their operation are delaying their practical implementation. To understand the interplay between Cu surface chemistry and the morphology of the plated Li, we studied the SEI formation on Cu and the preferential plating of Li using ssNMR, insitu NMR, XPS, ToF-SIMS, SEM and EIS.A native interphase layer (N-SEI) is formed instantaneously on copper current collectors upon their immersion in LiPF6-based electrolyte. The nature of the N-SEI is affected by the copper interface composition, homogeneity and formation time. In addition to the typical SEI components, it contains CuxO and its reaction products. Parasitic semi-reversible electrochemical reactions were observed with in-situ NMR measurements of Li plating efficiency during the first five cycles. The morphology of the plated lithium is affected by the SEI homogeneity, current density and rest time in the electrolyte before the plating. The preferential plating of Li is governed by the distribution of ionic conducting compounds rather than electronic conducting compounds.[i] [i] Menkin, Svetlana; O'Keefe, Christopher A.; Gunnarsdottir, Anna B.; Dey, Sunita; Pesci, Federico; Shen, Zonghao; et al. (2020): Towards an Understanding of the SEI Formation and Lithium Preferential Plating on Copper. ChemRxiv. Preprint. https://doi.org/10.26434/chemrxiv.12839792.v1

Thermal analysis of TIG-WAAM based metal deposition process using finite element method

The Tungsten Inert gas welding-based wire and arc additive manufacturing (TIG-WAAM) process is one of the most energy-efficient processes among the direct energy deposition processes. The TIG-WAAM process involves layer by layer deposition of a material using wire and arc. The path planning in the metal deposition process affects the temperature distribution during the layer by layer deposition in wire arc additive manufacturing (WAAM) process. The distribution of the temperature affects the quality of the metal deposition and its dimensional accuracy. In this paper, a Finite element analysis (FEA) based model for TIG-WAAM process was developed for analyzing the effect of the temperature distribution on the metal deposition process. The developed model has been used for simulating metal deposition using TIG-WAAM process for a single layer of low carbon steel. The distribution of temperature across the deposited material has been recorded. The results showed that the concentration of the temperature takes place at all turning points in the deposition path which may lead to deteriorating the quality of deposition. The developed model can be used further for the development of the feedback-based temperature management system to provide smooth metal deposition with better quality.

Stabilizing Lithium-Sulfur Cells with Practical Loading and Cycling Conditions Using Li2S8-Containing Ethereal Electrolyte Solution

We report on stabilization of Li–S cells cycled with an areal charge/discharge capacity of 2 mAh cm−2 at current densities of 1–2 mA cm−2 using ethereal LiTFSI/LiNO3/DOL/DME electrolyte solution containing 0.1M Li2S8. This electrolyte solution enables stable lithium metal stripping−plating both in symmetric Li∣Li and full Li–S cells with composite binder free sulfur impregnated activated carbon fibers cathodes. The addition of Li2S8 substantially extends cycling life of these cells due to the formation of smooth non-dendritic Li metal surface protected with an effective SEI enriched with Li sulfides, sulfites and sulfates species. Symmetric Li∣Li could be cycled stably for more than 1000 h at 1–2 mA cm−2 with Li2S8-containing electrolyte solutions. Full Li–S cells demonstrate more than 500 stable cycles (at least 3 times more than with Li2S8 free electrolyte solution) at a current density of 1 mA cm−2 and an areal capacity of 2 mAh cm−2. The most stable cycling results were achieved for the cells cycled with discharge cut off voltage of 1.9 V preventing the depletion of LiNO3. The use of electrolyte solutions containing liquid lithium poly-sulfides makes possible considerable decrease in the amount of the electrolyte solution and increases the energy density of the cells.

Three-step deposition process for improved nucleation of noble metal thin films

A three-step atomic layer deposition process tested with ruthenium could hold the key to creating continuous and smooth noble metal thin films.