Resistivity Of Metals Research Articles

Tribocorrosion studies on DLC films with silver nanoparticles for prosthesis applications

Metals and their alloys are very important for orthopedic applications, and the basic requirements for a successful implant are chemical stability, mechanical behavior, and biocompatibility in body fluids and tissues. For prosthesis applications, the corrosion resistance of metals is one of the major prerequisites to avoid impairment of the material properties due to degradation. The combined action of corrosion and wear on the material is called tribocorrosion and DLC (Diamond-Like Carbon) films have been extensively studied to increase prosthesis biocompatibility and to protect from corrosion. Additionally, DLC coatings can prevent the prosthesis to release toxic elements due to plastic deformation and corrosion. This paper is about tribocorrosion studies on DLC and DLC-Ag (DLC containing silver nanoparticles) on Ti-6Al-4V substrates. These films were obtained by PECVD (Plasma Enhanced Chemical Vapor Deposition) using hexane as a precursor. The tribocorrosion behavior of uncoated and coated samples was investigated in the reciprocating mode in Ringer’s lactate solution. From the polarization test results, the protective efficiency of the film was calculated. Silver nanoparticles improved the corrosion resistance of the films. The protective efficiency was 15 and 19% for DLC and DLC-Ag films, respectively.

Multifunctional coatings fabricated from Chinese hemp–derived superhydrophobic micro–nanocellulose

Ecologically feasible strategies for constructing superhydrophobic surfaces offer versatile applications in waterproofing, self–cleaning, selective absorption, and corrosion protection. Herein, we prepared low–surface–energy branched–chain–enriched micronanorod (F@SiO2@MNC) by hydrolyzing silane coupling agent and modifying fluoropolymer using micro–nanocellulose extracted from waste straw (Chinese hemp). These rods were sprayed and adhered to various substrates precoated with a binder, resulting in superhydrophobic surfaces. F@SiO2@MNC addition allowed for the formation of stable spherical liquid droplets when in contact with different types of aqueous liquids. Furthermore, these surfaces demonstrated excellent self–cleaning, robustness, abrasion resistance, UV resistance, cycling stability, and other multifunctionalities. They significantly enhanced the mechanical properties of filter paper, effectively separated oil water mixtures, and improved the corrosion resistance of metals. Our proposed strategy represents a novel approach for developing multifunctional coatings assembled from micronanocellulose.

Sustainable engineered geopolymer composites: A study on the potential of fly ash, BOF slag, and iron ore tailings

Industrial residues like Basic Oxygen Furnace (BOF) slag and Iron Ore Tailings (IOT) in the construction sector conserves natural resources by reducing carbon emissions and enhancing sustainability. However, it is crucial to establish significant research findings to build confidence among end users and stakeholders to facilitate the adoption of the same for practical applications. This study aims to investigate the feasibility of using BOF slag and Fly ash (FA) as primary precursors in the development of steel fibre (SF) reinforced Engineered Geopolymer Composites (EGC) with IOT replacing M-Sand as fine aggregate. Trial mixes (600 No.s) were conducted to synthesize EGC with BOF slag, FA, IOT, and SF. Compressive strength was measured and IOT was found to significantly improve the strength of EGC, following SF and BOF levels. Six optimized mixes were identified and subjected for water absorption, flexure, impact resistance and leaching toxicity of heavy metals. The mix comprising 40% BOF, 1.5% SF and 45% IOT showed the highest strength characteristics viz., 41.8 MPa, 5.78 MPa and 313.92 Nm correspondingly for compression, flexure and impact. The obtained results have implications for sustainable construction involving BOF slag and FA as viable precursors, alongside IOT as a partial substitute for fine aggregate.

Crystalline to Amorphous: Unveiling the Potential of Transition Metal Oxide‐based Electrocatalysts for Facile Oxygen Evolution Reaction in Alkaline Media

AbstractTransition metal oxides/hydroxides exhibit reasonable oxygen activity in alkaline electrolytes and have been identified as potential electrocatalysts. Some highly active transition metal oxides or hydroxides can alter their surface chemistry in response to the electrolyte environment. This review presents the performance of some of the recently developed transition metal‐based oxides in electrocatalytic oxygen evolution reaction (OER). Despite the promising catalytic activity of many transition metals and their alloys due to their incompletely filled d orbitals, their low corrosion resistance in alkaline media barriers their use as electrocatalysts. Metallic glasses (MGs), with their disordered atomic structure, have many unique and exciting properties that cannot be found in crystalline metals. Metallic glasses′ unique chemical activity and corrosion resistance stem from their metastable and defective nature, as well as their structural and chemical homogeneity. In the case of Zr‐based MGs, the presence of MG−OHads and MG−Ox species on the surface for oxygen evolution enables rapid electron transfer to chemisorbed OH− with an “activated” MG surface leading to the generation of an amorphous Zr‐rich layer. Zr‐rich oxide layer formation favors the OER understood by decreased Tafel slope and highly stable nature during open circuit potential measurements in the alkaline solution. Unlike the as‐spun counterpart, the relatively small impedance magnitude and characteristic frequency for the post‐OER electrode corroborate the enhancement of oxygen evolution kinetics after electrochemistry. Compared with the early discovered electrodes, the MG‐oxide assembly outperforms many transition and precision metal‐based oxides and their composite forms regarding oxygen electroactivity and stability.

Laser Shock Peening: Fundamentals and Mechanisms of Metallic Material Wear Resistance Improvement.

With the rapid development of the advanced manufacturing industry, equipment requirements are becoming increasingly stringent. Since metallic materials often present failure problems resulting from wear due to extreme service conditions, researchers have developed various methods to improve their properties. Laser shock peening (LSP) is a highly efficacious mechanical surface modification technique utilized to enhance the microstructure of the near-surface layer of metallic materials, which improves mechanical properties such as wear resistance and solves failure problems. In this work, we summarize the fundamental principles of LSP and laser-induced plasma shock waves, along with the development of this technique. In addition, exemplary cases of LSP treatment used for wear resistance improvement in metallic materials of various nature, including conventional metallic materials, laser additively manufactured parts, and laser cladding coatings, are outlined in detail. We further discuss the mechanism by which the microhardness enhancement, grain refinement, and beneficial residual stress are imparted to metallic materials by using LSP treatment, resulting in a significant improvement in wear resistance. This work serves as an important reference for researchers to further explore the fundamentals and the metallic material wear resistance enhancement mechanism of LSP.

Utilizing a Metagenome Assembled Genome Approach Revealed Further Insights into Microbially Mediated Heavy-Metal Resistance in Soils from a Former Nuclear Materials Production Facility

Soils and sediments from the Savannah River Site (SRS), located in the USA are known to have a long history of co-contamination with radionuclides (mainly uranium) and heavy metals. To better understand the bacterial taxonomic and genomic characteristic of the SRS soil habitat, shotgun metagenomes were obtained from three different levels of contaminated soil—high, medium, and low. Sequences were then assembled and annotated to generate metagenome-assembled genomes (MAGs) using toolkits within the nf-core/mag. The initial analysis resulted in a total of 254 MAGs. After bin refinement and de-replication, 55 MAGs which met the quality standard with a completeness > 75% and contamination < 25%, accounting for 21.67% of all the MAGs, were reconstructed. Further refinement with completeness > 90% and contamination < 10% yielded 24 MAGs (18 from the winter season and 6 from the summer season) spanning 6 bacterial phyla, predominantly Actinomycetota, Proteobacteriota, Bacteroidota, and Cyanobacteria. Overall, the Arthrobacter MAG was found to be robust for further analysis, with over 1749 genes putatively involved in the crucial metabolism of elements viz. nitrogen, phosphorous, and sulfur, and 598 genes encoding enzymes for the resistance of metals including cadmium, zinc, chromium, arsenic, and copper. In summary, this project enhances our understanding of genes conferring resistance to heavy metals in uranium-contaminated soils.

Горячее деформирование сварных заготовок листов алюминиевого сплава 1565чМ

The details of forming in cold or heated position for welded blanks of alloy 1565chM with a thickness of 8,0 mm, performed by friction stir welding, are viewed. It is found that welded joints of alloy 1565chM with a thickness of 8,0 mm, obtained by friction stir welding have high strength properties together with sufficient toughness. Thus, bending angle of the joints is 165…170 °. The strength factor of the welded joint is 0.96 of the strength of the base metal. At the same time, the temporary resistance of the weld metal exceeds temporary resistance of both: base metal and the welded joint in its value. The 1565chM alloy joints, made by friction stir welding have good formability under cold deformation. This special feature of welded blanks made of 1565chM alloy sheets is explained by the presence of a fine-grained recrystallized structure in a stir zone, which is formed as a result of heat impact and force action of the working tool on the material to be welded. Welding modes providing specified mechanical properties of the joints were used for welding shells (blanks) of gas cylinders (liners). Manufacturing technique for such cylinders includes the following operations: welding of the shell, calibration of the shell, quality control of the weld on the shell, jumping into a hot mold for forming bottoms, welding of fittings and general tightness control. Experiments on forming liners bottoms due to the shell jumping into a heated to 450...500 °C mold have shown that there is an intensive weld metal runout due to differences in the strain capacity of the weld metal and the base metal. This behavior of the weld metal during hot forming can be explained by superductility of the weld metal owing to the presence of a recrystallized ultrafine-grained structure. It was found that starting from a temperature of 400 °C, the relative elongation of the weld metal significantly exceeds the elongation value of the base metal. In case of 450 °C, this difference reaches 
 72 %. For the weld of the 1565chM alloy, starting from the heating temperature of 540 °C, an abnormal grain growth occurs along the entire weld.

Multiple Metal-Nitrogen Bonds Synergistically Boosting the Activity and Durability of High-Entropy Alloy Electrocatalysts.

The development of Pt-based catalysts for use in fuel cells that meet performance targets of high activity, maximized stability, and low cost remains a huge challenge. Herein, we report a nitrogen (N)-doped high-entropy alloy (HEA) electrocatalyst that consists of a Pt-rich shell and a N-doped PtCoFeNiCu core on a carbon support (denoted as N-Pt/HEA/C). The N-Pt/HEA/C catalyst showed a high mass activity of 1.34 A mgPt-1 at 0.9 V for the oxygen reduction reaction (ORR) in rotating disk electrode (RDE) testing, which substantially outperformed commercial Pt/C and most of the other binary/ternary Pt-based catalysts. The N-Pt/HEA/C catalyst also demonstrated excellent stability in both RDE and membrane electrode assembly (MEA) testing. Using operando X-ray absorption spectroscopy (XAS) measurements and theoretical calculations, we revealed that the enhanced ORR activity of N-Pt/HEA/C originated from the optimized adsorption energy of intermediates, resulting in the tailored electronic structure formed upon N-doping. Furthermore, we showed that the multiple metal-nitrogen bonds formed synergistically improved the corrosion resistance of the 3d transition metals and enhanced the ORR durability.

Preparation of highly dewetted porous steel for shallow water AUV based on laser ablation method

Over the past two decades, autonomous underwater vehicles (AUVs) have been developed for various marine, commercial, and military applications. Porous metals, known for their lightweight high performance, suit AUV hulls, especially in shallow waters. However, because of their inherent hydrophilicity and porous structure, high humidity causes corrosion. In this study, a novel solution involving laser ablation and subsequent heat treatment of porous steel is proposed to improve the waterproofing performance both above and below water. By analyzing the surface structures, wetting attributes, and droplet behavior, the optimal laser and heat treatment parameters for superior performance are revealed. The porous nested structures created by laser ablation effectively reduce fog accumulation and, enhance the anti-fogging capabilities. Furthermore, the underwater stability ofsuperhydrophobic porous steels at different depths is systematically investigated. A method involving air injection into porous steel is proposed to address the limited air-pocket lifespan and instability of dehumidified surfaces. Experimental results confirm rapid and complete restoration of superhydrophobicity at a 0.9-meter depth. Thus, this study presents a practical corrosion-resistant surface material for AUVs in shallow-water environments and a new approach for achieving corrosion resistance in porous metals exposed to long-term aquatic conditions.

First-principles calculations on the intrinsic resistivity of realistic metals: a case study of monolayer V2N.

The Ziman resistivity formula is extensively employed to calculate the intrinsic resistivity of realistic metals using recent works of first-principles calculations. Owing to the approximation, Allen's generalization, which relates the solution of the Boltzmann transport equation (BTE) for metals to the transport electron-phonon (e-ph) spectral function, the applicability of the Ziman resistivity formula still needs to be discussed. In this work, we perform first-principles calculations of the intrinsic resistivity of the V2N monolayer, a kind of MXene material, by employing the Ziman resistivity formula and the iterative solution of BTE. We find that in the wide temperature range of 50-1400 K, the intrinsic resistivity of the V2N monolayer obtained by means of the two approaches, has the same order of magnitude. However the Ziman resistivity formula fails to correctly describe the Fermi level dependence of the intrinsic resistivity of the V2N monolayer. The underlying reason is that the band edge of the V2N and hence Van Hove singularity (VHS), is near the shifted Fermi level. We suggest a modified Ziman resistivity formula which is valid even if there is a band edge at the Fermi level.

Influence of MC Carbides on Pitting Corrosion Resistance of Weld Metal in Austenitic Stainless Steels

Influence of MC Carbides on Pitting Corrosion Resistance of Weld Metal in Austenitic Stainless Steels

Technological features of fusion welding of Al – Mg system alloys rationally alloyed with scandium

The results of the formation of macro- and microstructure of welded joints of aluminum alloy sheets of the Al– Mg–Sc system obtained by automatic argon-arc and electron-beam welding are presented. The mechanical characteristics of welded joints and weld metal under the types of welding used are given. Satisfactory weldability of the studied alloy by fusion welding methods is established with the provision of strength properties of welded joints at the level of 0.8...0.85 of temporary resistance of the base metal. The effect of the welding direction in relation to the rolling direction of the sheets on the mechanical properties of welded joints is studied. The destruction of welded joints during the tests occurred in the metal and fusion zone. The fractures are of a macro viscous nature with a viscous pit micro mechanism of destruction. The strength factor of welded joints of aluminum V-1579 alloy is at the level of 0.89 for automatic argon arc welding and 0.79 for electron beam welding.

Semimetallic electrical properties of rock salt-type LaBi thin films grown by solid-phase reaction of La/Bi multilayer precursors

Highly crystalline LaBi thin films, grown by solid-phase reaction of La/Bi multilayer precursors, showed metallic conduction and nonlinear Hall resistance, indicating the semimetallic nature with electron and hole carriers.

Optimization of Wire-bonding Process Parameters for Gold Wire and Aluminium Substrate using Response Surface Method

Wire bonding is a connecting technique that uses a combination of temperature, force, ultrasonic power, and time to attach two metallic materials, a wire, and a bond pad. In electronics, gold-aluminium (Au-Al) contact wire bonds are widespread due to corrosion resistance and great conductivity of both metals. However, due to the large contact-potential difference, the intermetallic compound growth at the metal’s interaction boundary has considerably worsened the advantageous properties of Au-Al intermetallic system. This intermetallic exhibit low toughness, and possibly low corrosion resistance, which would result in poor bonding quality. In this work, the materials used are 4x8 aluminium substrates and a 100-meter-long gold wire spool. This study aims to investigate the most optimised set of parameters to be used in Au-Al wire bond system, due to how problematic this system could have towards bonding quality. The experimental array was created using a response surface methodology (RSM)-based design of experiments. The effect of parameters and their significance to bonding quality in the Au-Al bond system were studied using analysis of variance (ANOVA). A correlation model was created for the wire bond strength data. The findings suggest that, within the range of parameters examined, the proposed correlation model can be utilized to predict performance measures. The optimum value of Au-Al wire bond system parameters was established at the time of bond at the first bonding site selected for 300 milliseconds (ms), wire looping height selected for 1200 micrometre (μm), wire bond Y-axis length selected for 996 micrometre (μm), and ultrasonic force at second bonding site selected for 300 milli Newton (mN). The outcomes of this research add to our understanding of the Au-Al wire bonding contact, in addition, to enhancing the wire bond's quality.

Strong Catalyst-Support Interaction in WOx Nanowires Supported Iridium Nanocatalysts: A Pathway to Efficient Water Electrolysis

This paper investigates the use of sub-stoichiometric tungsten oxide nanowires (WOxNW) as a support material for Ir nanocatalysts in the oxygen evolution reaction (OER) for proton exchange membrane water electrolysis (PEMWE). The results demonstrate that Ir@WOxNW has exceptional activity and durability, which paves the way for large-scale PEMWE deployment. The catalyst-support interaction plays a crucial role in explaining this performance boost.The preparation and characterization of Ir@WOxNW involved loading ultra-fine Ir nanoparticles onto WOxNW through hydrothermal treatment. High-resolution transmission electron microscopy (HR-TEM) and energy-dispersive X-ray spectroscopy (EDS) mapping analysis revealed that the iridium nanoparticles were uniformly loaded on the WOxNW support material, indicating efficient loading and dispersion. X-ray photoelectron spectroscopy (XPS) analysis showed that the supported Ir catalysts had a mixed valence state of Ir0 and Ir4+. Ir@WOxNW was compared with three other Ir-based OER catalysts, outperforming them in terms of activity and durability.The Ir@WOxNW catalyst demonstrated superior OER activity compared to the other three catalysts, with a mass activity of 812 A/gIr at 1.55 V vs reversible hydrogen electrode (RHE). The Tafel slopes of the OER catalysts were grouped into two categories: Ir Black and Ir@WOxNW showed smaller values (about 40 mV/dec), and larger values for Ir@ATO and Ir Oxide (about 120 mV/dec), respectively. Electrochemical impedance spectroscopy (EIS) measurements indicated that the high mass activity of Ir@WOxNW was due to a high population of catalytic sites with fast intrinsic kinetics from the dispersed ultra-fine Ir catalyst on WOxNW. The durability of all catalysts was investigated using an accelerated durability test (ADT), and the Ir@WOxNW catalyst demonstrated unexpectedly high durability compared to the other catalysts.The postmortem XPS analysis showed that the Ir@WOxNW catalyst exhibited a subtle change in Ir0/Ir4+ ratio after the ADT, indicating suppressed Ir oxidation and greater stability compared to the other catalysts. Additionally, non-destructive depth profile analysis by synchrotron based XPS was conducted on the supported ultrafine Ir catalysts before and after the ADT test. The difference in oxidation state increased as the supported Ir catalysts were probed deeper into the core. The results showed that after oxidation potential cycles ADT, the WOxNW-supported Iridium exhibited strong resistance to oxidation. The core location remained a high percentage of metal peak, in contrast to the other three control catalysts.Density functional theory calculations suggested that the oxygen-deficient WOxNW support helps to maintain the OER-active metal@metal oxide core@shell-like form of the Ir catalyst particles by enhancing electron transfer from the WOxNW to the Ir surface, thereby weakening the binding of oxygen to the Ir surface and enhancing the oxidation resistance of the Ir metal to oxides.In conclusion, ultrafine Ir nanoparticles supported on WOxNW have significant potential for practical applications in electrochemical water splitting. The high activity and durability of Ir@WOxNW make it a promising candidate for large-scale PEMWE deployment.

ACCELERATED TESTING OF MECHANICAL AND CHEMICAL EFFECT OF THE ENVIRONMENT ON WEAR RESISTANCE OF PARTS OF TRIBOCOUPLES UNDER COMPLEX DYNAMIC LOADING

The wear of tribocouplings parts under complex dynamic loading conditions is considered. A methodology for accelerated testing of friction pairs under multi-component dynamic loading is offered. The designs stand for modeling the processes of contact interaction, and studies of the wear resistance of tribocouplings, which operate under complexdynamic loading conditions with various lubricating and cooling media, are presented. The results of the impact assessment of mechanic and chemical transformations in the contact zone of tribological interfaces for wear resistance according to the developed method are presented. The variable effectiveness evaluation of the degradation influence products of macromolecular compounds in the composition of cutting fluid on wear resistance of metals in the contact zone of tribocouplings are analysed. The use ofthe presented materials allows rationally selecting friction pair materials for given operating conditions, developing new wear-resistant materials and coatings, lubricant composition and cooling mediums.

Heat Resistance of Transition Metals with an Aluminized Coating

Heat Resistance of Transition Metals with an Aluminized Coating

Effect of Anisotropy of Elastic Energy and Shear Waves on Electron–Phonon Relaxation and Electrical Resistivity of Noble Metals. Review 4

Effect of Anisotropy of Elastic Energy and Shear Waves on Electron–Phonon Relaxation and Electrical Resistivity of Noble Metals. Review 4

ANTI-CORROSION PROTECTION OF PIPELINES

Currently, in our country, the issue of protecting metals from corrosion has achieved high results, so there is a big gap between the achievements of scientific research in this direction and their use in industry. It is necessary to develop and implement highly effective methods of increasing the strength, corrosion resistance, heat and cold resistance of metals and alloys. Popularization, dissemination and implementation of effective methods of protection against corrosion and corrosive-mechanical destruction of machines, devices, equipment and metal structures are of great importance.
 During surface-plastic deformation, a chip is not formed, but a fine plastic deformation of the surface layer takes place. As a result, the surface layer is strengthened, wear resistance and resistance to corrosive environment increases. In many cases, the use of surface-plastic deformation makes it possible to increase the safety margin of parts working under variable loads by 1.5 to 3 times, and to increase the service life of parts. The paper examines directions for increasing the stability of parts of oil industry equipment by the method of surface plastic deformation, for resistance against various types of corrosion and corrosive-mechanical destruction.
 Fatigue is the phenomenon of gradual accumulation of material damage under the action of variable loads, which leads to changes in the properties of crack formation, their development and destruction. The processes of metal fatigue have been studied by many researchers, many hypotheses have been put forward, but the nature of fatigue remains largely unexplained.

Enhanced wear and corrosion resistance of the laser direct metal deposited AISI 316L stainless steel by in-situ interstitial N alloying

To meet the applicability in aggressive environments, the wear and corrosion resistance of additively manufactured 316L stainless steel can be improved by alloying with N. In this work, the in-situ interstitial N alloying of 316L with varying amount of CrxN is first manufactured at ambient environment utilizing the rapid cooling character of laser direct metal deposition (DMD). Combined effects of CrxN addition and DMD processing parameters on the relative density, dissolved N content, microstructure, microhardness, wear performance and corrosion behavior are systematically investigated. The results show that the relative density of the DMD 316L decreases with increasing additive amount of CrxN. A full density 316L sample with a high N content of 0.5 wt% is obtained. The N alloying transforms the solidification mode of DMD 316L from “AF” to “A”, resulting in a fully austenitic phase. The interstitial N promotes the formation of planar dislocations, nano-stacking faults and nano-twins during DMD. As the CrxN addition increases, both the microhardness (278–312 HV) and wear resistance are significantly enhanced owing to the dislocation strengthening and interstitial N solid solution strengthening. Compared with CrxN-free DMD 316L, the DMD 316L with CrxN addition presents superior pitting corrosion resistance. The increasing CrxN addition progressively improves the pitting corrosion resistance due to the positively synergistic effect Cr-N on the stability and repassivation ability of the passive film. This work provides a practical and cost-effective approach for manufacturing advanced 316L with exceptional properties.