Pure Copper Surface Research Articles

Effect of surface corrosion on the zeta potential of copper in acidic solutions

The comprehensive investigation was conducted to analyze the corrosion behavior and surface potential of pure copper surfaces in various acidic solutions. We carried out Zeta potential measurement, electrochemical measurement and in situ Raman spectroscopy to investigate the corrosion process and surface potential of copper in acidic solutions with different pH. It was found that the variation in zeta potential with pH corresponds to the corrosion behavior of copper during this process. In 1mmol / L aqueous chloride media, when the pH is greater than 3.5, unalloyed copper is oxidized to monovalent copper. At this stage, as the pH decreases, the zeta potential gradually increases. When the pH reaches 3.5, the Zeta potential reaches the highest, and the rate of cuprous oxide formation reaches the maximum. When the pH continues decrease, unalloyed copper begins to be oxidized to divalent copper, and the zeta potential will also decrease, the surface charge state shifts to the positive direction. Furthermore, our experimental findings are complemented by Density Functional Theory (DFT) calculations.

Study on micro-arc oxidation coating of copper pretreated at high temperature

Micro-arc oxidation (MAO), also known as plasma electrolytic oxidation (PEO), is a surface treatment technology widely used in valve metals. As a widely used non-valve metal, copper is generally not easy to prepare MAO coating on its surface. In this paper, from the principle of MAO, the black coating was successfully prepared on the surface of pure copper by using high temperature pretreatment method and MAO technology, and the surface morphology and composition of the coating are characterised in detail. Friction experiments show that the MAO coatings formed by copper after high-temperature pretreatment at 300 °C have better wear resistance. The water contact angle test and electrochemical experiments show that the 300 °C sample has a higher water contact angle and excellent corrosion resistance. This study expands the surface treatment method of copper and provides a new idea for MAO technology in the surface treatment of other non-valve metals.

Enhancement of Flow Boiling Heat Transfer Characteristics on Diamond/Cu Heterogeneous Surface

Surface treatment is an effective method of enhancing the heat transfer performance of flow boiling. Diamond/Cu, as a particle‐reinforced composite, exhibits heterogeneous surface properties and surface microstructures that play distinct roles in heat transfer. To elucidate the synergistic effect of heterogeneous material surfaces and microstructures, pure copper surface (PC), untreated diamond/Cu surface (DC), and surface‐treated diamond/Cu surface (SDC) are prepared for this experiment. These surfaces demonstrate various combinations of diamond, copper, and their corresponding surface microstructures. DC, characterized by heterogeneous wetting properties, demonstrates a heat transfer coefficient (HTC) that is 9%–24% higher than that of PC. The surface treatment of SDC results in the formation of a superhydrophilic CuO nanosheet structure, significantly enhancing both surface roughness and energy. SDC develops microcracks on the surface of diamond. The increased roughness provides numerous nucleation areas for the hydrophobic diamond, enhancing the overall wettability of the surface when combined with the superhydrophilic CuO region. SDC demonstrates the advantage of enhanced flow boiling on the surface of heterogeneous materials. At the identical heat flux, SDC exhibits a reduction of 5–10 °C in wall superheat and an increase of 38%–47% in HTC.

Potential-dependent insights into the origin of high ammonia yield rate on copper surface via nitrate reduction: A computational and experimental study

Focusing on revealing the origin of high ammonia yield rate on Cu via nitrate reduction (NO3RR), we herein applied constant potential method via grand-canonical density functional theory (GC-DFT) with implicit continuum solvation model to predict the reaction energetics of NO3RR on pure copper surface in alkaline media. The potential-dependent mechanism on the most prevailing Cu (111) and the minor (100) and (110) facets were established, in consideration of NO2−, NO, NH3, NH2OH, N2, and N2O as the main products. The computational results show that the major Cu (111) is the ideal surface to produce ammonia with the highest onset potential at 0.06 V (until −0.37 V) and the highest optimal potential at −0.31 V for ammonia production without kinetic obstacles in activation energies at critical steps. For other minor facets, the secondary Cu (100) shows activity to ammonia from −0.03 to −0.54 V with the ideal potential at −0.50 V, which requires larger overpotential to overcome kinetic activation energy barriers. The least Cu (110) possesses the longest potential range for ammonia yield from −0.27 to −1.12 V due to the higher adsorption coverage of nitrate, but also with higher tendency to generate di-nitrogen species. Experimental evaluations on commercial Cu/C electrocatalyst validated the accuracy of our proposed mechanism. The most influential (111) surface with highest percentage in electrocatalyst determined the trend of ammonia production. In specific, the onset potential of ammonia production at 0.1 V and emergence of yield rate peak at −0.3 V in experiments precisely located in the predicted potentials on Cu (111). Four critical factors for the high ammonia yield and selectivity on Cu surface via NO3RR are summarized, including high NO3RR activity towards ammonia on the dominant Cu (111) facet, more possibilities to produce ammonia along different pathways on each facet, excellent ability for HER inhibition and suitable surface size to suppress di-nitrogen species formation at high nitrate coverage. Overall, our work provides comprehensive potential-dependent insights into the reaction details of NO3RR to ammonia, which can serve as references for the future development of NO3RR electrocatalysts, achieving higher activity and selectivity by maximizing these characteristics of copper-based materials.

Regularities of Structure Formation, Morphology and Properties of Pure Copper Surface Layers Under Intensive Thermal Impact During Plasma Cutting

Regularities of Structure Formation, Morphology and Properties of Pure Copper Surface Layers Under Intensive Thermal Impact During Plasma Cutting

Novel blue diode laser cladding for high-performance nickel-based coatings on copper substrates

The high reflectivity and excellent thermal conductivity exhibited by copper substrates pose considerable challenges for conventional laser cladding techniques aiming to achieve high-performance coatings on their surfaces. In this study, a novel blue diode laser cladding approach was proposed to prepare nickel-based coatings on copper substrates. Under the conditions of a preheating temperature of 200 °C and laser power of 1500 W, a Ni60A coating was successfully fabricated on the surface of pure copper, with metallurgical bonding achieved and no crack defects observed. The average microhardness of the coating ranges from 468 HV0.1 to 775 HV0.1, which is approximately 8.8–14.6 times greater than that of the copper substrate. Furthermore, the wear resistance of the coating is approximately 3.6–4.7 times higher than that of copper at 25 °C, and approximately 3.8–5.4 times higher at 300 °C. The performance of the coating exhibit gradient variations in the cladding direction. Consequently, the challenges posed by the high laser reflectivity and the need for a high preheating temperature of copper substrate have been effectively overcome through the utilization of a blue laser cladding, facilitating the industrial-scale preparation of large-area coatings on copper components.

Infrared spectroscopy reveals the reactivity of fatty acids on copper surfaces and its implications for cultural heritage objects

The reactivities of various fatty monoacids and diacids on copper metal-containing surfaces were investigated through reflection–absorption infrared spectroscopy. The formation of copper carboxylates is detected on pure copper surfaces, while copper and zinc carboxylates are simultaneously formed on brass surfaces. Following the decrease of acid carbonyl and the formation of carboxylate infrared bands, it is shown that fatty monoacids C8 and C10 react with clean/polished copper and its zinc alloy within 2–4 h, while those with chains > C12 react within days. At the end of the processes, only the corresponding metal carboxylates are detected in all cases. An explanation for the above is offered on a molecular mobility and acidity basis, where the lower monoacids (liquids in room temperature), also having lower pKa values, favor higher reaction rates. Furthermore, it is argued that longer-chain fatty monoacids, when deposited from their solutions, allow for favorable orientation resulting in self-assembled monolayer-type molecular packing on the copper surface, which may additionally rationalize the slower reaction. Interestingly, fatty diacids do not form any carboxylate products under the same conditions, as it is argued that their molecules may efficiently pack as self-assembled multilayers on copper and ultimately protect it. The possible implications of the fatty monoacid and diacid behavior on the archaeological organic residues level and regarding the stability of copper alloys are discussed.

Detailed characterisation of batch-manufactured flexible micro-grinding tools for electrochemical assisted grinding of copper surfaces

Precision machining is becoming more and more important with the increasing demands on surface quality for various components. This applies, for example, to mirror components in micro-optics or cooling components in microelectronics. Copper is a frequently used material for this purpose, but its mechanical properties make it difficult to machine. In this study, a process strategy for finishing copper surfaces with batch-manufactured micro-grinding tools in an electrochemically assisted grinding process is demonstrated. The tool heads are manufactured from a polyimide-abrasive-suspension and silicon as a carrier substrate using microsystems technology. The matching shafts are milled from aluminium. The tools are then used on pure copper and oxidised copper surfaces. By using finer abrasives grains (1.6–2.4 µm instead of 4–6 µm) than previously, similar surface roughness values could be achieved (Ra = 0.09 ± 0.02 µm, Rz = 1.94 ± 0.73 µm) with the same grinding process. An optimised grinding process that combines the use of rough and fine tools, on the other hand, achieves significantly better surface finishes in just four grinding iterations (Ra = 0.02 ± 0.01 µm, Rz = 0.83 ± 0.21 µm). In order to achieve a further increase in surface quality, this optimised grinding process is combined with the anodic oxidation of the copper workpieces. The surface modification is done to increase the machinability of the surface by creating an oxide layer. This is confirmed by the results of scratch tests carried out, which showed less force acting on the tool during machining with the oxide layer than with a pure copper surface. To realise this within the machine tool, an electrochemical cell is shown that can be integrated into the machine so that the oxidation can be carried out immediately before the grinding process. The copper layers produced inside the electrochemical cell in the machine tool show similar characteristics to the samples produced outside. Processing the oxidised samples with the optimised grinding process led to a further reduction of about 17% in the Rz values (Ra = 0.03 ± 0.01 µm, Rz = 0.69 ± 0.20 µm). The combination of the shown grinding process and the integration of anodic oxidation within the machine tool for the surface modification of copper workpieces seems to be promising to achieve high surface finishes.

Cu2S Nanoparticle-Modified Copper Hydroxide Nanowire Arrays for Optimized Electrochemical CO2 Reduction Selectivity

A copper-based catalyst exhibits a wide distribution of catalytic products in electrochemical CO2 reduction. However, it faces a grand challenge in reaction selectivity. A deeper understanding is needed regarding the mechanism of its diversified product selectivity. Herein, we design a cuprous sulfide nanoparticle-modified copper hydroxide nanowire array precatalyst by a simple solvothermal method for revealing the catalytic mechanism of copper-based catalysts in electrochemical CO2 reduction. The role of cuprous sulfide nanoparticle modification in copper hydroxide nanowires on formate formation during CO2 reduction is investigated. The intermediate during CO2 reduction is altered by sulfur modification, resulting in improvement in formate selectivity. Density functional theory is used to investigate the effect of trace sulfur modification in copper on activity and selectivity toward formate formation. Compared with a pure copper surface, sulfur modification in copper can promote the formation of *OCHO, a key intermediate along the formate pathway.

Study on magnetic performance and corrosion resistance of CoPtWP coating prepared by electrodeposition

Electrodeposition is used to prepare the Co, CoPt, CoPtW, and CoPtWP coatings on the surface of pure copper. The association between magnetic performance, corrosion resistance, surface morphology, roughness, thickness, and electrodeposition process is investigated by contrasting the four electrodeposited coatings. The deposition of cobalt and tungsten is discovered to be a type of induced codeposition. The chloroplatinate and hypophosphate ions receive electrons to reduce to the CoPtWP alloy at the surface of the CoPt coating. The adding of WO42- and H2PO2- ions in the plating solution is beneficial to promote the electrochemical reaction near cathode surface. The surface of Co coating shows leaf-like and loose morphology with largest surface roughness leading to poor magnetic performance and corrosion resistance. However, the surface morphology of the CoPt coating, CoPtW coating, and CoPtWP coating is all compact with nodular structures. With the least surface roughness and greatest thickness, the CoPtWP electrodeposited coating exhibits superior magnetic performance and enhanced corrosion resistance.

Freezing processes for a vertically copper, superhydrophobic, and hybrid patterned surface – A visualization study

The purpose of this study is to investigate the frost and condensation heat transfer in vertical plate surface with different surface conditions. The test surfaces include a copper surface, a superhydrophobic surface and a novel tree-shaped surface containing hydrophilic and hydrophobic surfaces. Tests was carried out in an environmental chamber subject to various frontal velocity, and relative humidity. The ratio of cold frost area and the heat transfer coefficient (HTC) of are reported and visualization of the condensate/frost formation was analyzed by visual images. The copper surface exhibits obvious filmwise condensation due to its high wettability. Upon frosting, the condensate droplets slide to form thin frost layer which attracts more droplet to yield a thicker frost layer. The superhydrophobic surface offers condensate jumping that can effectively delay the frosting time, thereby showing a better HTC. At a relative humidity of 85 % and a velocity is 2.5 m s−1, the HTC of the superhydrophobic sample is increased by 42.1 % and the area ratio is decreased by 76.9 % when compared to pure copper surface. Yet, the frosting time of the superhydrophobic surface is 2.6 times longer than that of copper surface. The delay is reduced to 1.85 times when the relative humidity is reduced to 45 %. Upon defrosting also at a relative humidity of 85 %, the surface area of residual water is higher than that of the superhydrophobic surface by 447 % while the surface area of residual water of the pattered surface is lower than that of superhydrophobic surface by 173 %.

Development of high strength and high electrical conductive Cu and Cu–W composite by friction stir processing: Effect of traverse speed

In this work, pure copper and copper-tungsten (Cu-W) surface composite is produced using a single pass friction stir processing (FSP) with an intention to enhance the hardness and wear resistance without impairing electrical conductivity. FSP is performed by changing the traverse speed from 50 to 200 mm/min and at a constant tool rotational speed of 600 rpm. The samples extracted from the stir zone are characterized for their microstructure, hardness, wear behaviour and electrical conductivity. The average grain size, at the stir zones, was significantly reduced (from 40 to 3 µm) after FSP. In the case of pure copper, the grain size decreased from 9 to 3 µm with an increase in traverse speed, however, grain size increased from 4 to 6 µm in the case of Cu-W composite. The hardness of FSP’ed Cu and FSP’ed Cu-W surface composite was increased in the order of 52% and 130% compared to the unprocessed copper. The wear rate significantly reduced after FSP also with an addition of W particles. A negligible reduction (1.83% IACS) in electrical conductivity was noticed for both Cu and Cu-W after FSP. This study demonstrates that the FSP is an effective approach to improve the surface mechanical properties of Cu without much impairing the electrical conductivity.

Impact of pre-treatments on the surface composition, the optical and flow properties of a CuCrZr powder dedicated to laser powder bed fusion use

Laser Powder Bed Fusion is not power efficient at processing copper‑chromium‑zirconium alloy due to the high reflectivity of the powder at the laser standard wavelength (1070 nm). A way to reduce the optical reflectivity is to modify the powder surface. This work aims to study the impact of reduction and oxidation pre-treatments on the surface chemistry of the particles, and to understand their consequences on the powder properties. X-ray photoelectron spectroscopy analyses show that, starting from a 2–3 nm thick native Cu 2 O layer, a wet atmosphere leads to the formation of a 54 nm thick Cu 2 O layer, whereas a reduction under hydrogen leads to pure copper. Under argon, the Cu 2 O thickness slightly increases up to 3–4 nm. The oxidation and the reduction treatments improve the flowability, respectively, by 46% and 26%. The reduction increases the reflectivity by 2%, whereas the oxidation reduces it by 26%. • Humid atmosphere leads to a strong increase of Cu 2 O layer thickness (2–3 to 54 nm) • Reduction under H 2 leads to a pure copper surface decorated with Cr and Zr oxides • Argon atmosphere gives a slight increase of Cu 2 O layer thickness (2–3 to 3–4 nm) • Positive impact of the oxidation and the reduction treatments on powder flowability • Correlation observed between oxide layer thickness and optical reflectivity of powder

Fabricating micro-dent on the surface of ultrafine-grained pure copper by laser-induced shock wave and its deformation behavior

Fabricating micro-dent on the surface of ultrafine-grained pure copper by laser-induced shock wave and its deformation behavior

Real-time contact angle’s measurement of molten solder balls in laboratory conditions

PurposeThe purpose of this paper is to show a possibility to measure a change of a contact angle during the melting in real-time and to reveal significant factors of a wettability. Influence of the flux with combination of plasma on copper surface was investigated in experiment as well.Design/methodology/approachLaboratory equipment consists of heating and optical part that was developed and tested for real-time contact angle’s measurements. Solder balls based on Sn96.5/Ag3/Cu0.5 and Sn63Pb37 spread out on a copper substrate during a melting process. The wettability of pure copper surface was compared with copper surface treated with flux or combination plasma–flux. The contact angle and spreading rate of a melted solder balls observed by the charged-coupled device camera were analyzed in real-time and measured using the JavaScript.FindingsLaboratory equipment allows for analysis of contact angle and spreading rate in real-time during the melting process. The contact angle decreases more noticeable after applying the plasma-flux treatment in contrast to no flux or flux treatment only. Using the plasma treatment before application of the flux improves the wettability and the effectivity of the flux activity on the copper surface during the melting process.Originality/valueThe interpretation of the results of such a comprehensive measurement leads to a better understanding of the mutual relation between flux and combination plasma–flux of the wetting during the melting process. The simple, cheap, fast and accurate laboratory equipment, which consists of the heating and the optical part, allows for the wettability evaluation of the melting process in real-time.

Interrogating the Effect of Assay Media on the Rate of Virus Inactivation of High‐Touch Copper Surfaces: A Materials Science Approach

AbstractContamination of high‐touch surfaces with infected droplets of bodily secretions is a known route of virus transmission. Copper surfaces have been reported to inactivate human coronaviruses after several minutes, via the release of Cu cations. Utilization of copper alloys for high‐touch surfaces can be a pivotal preemptive strategy for preventing the next pandemic. Understanding the true efficacy by which copper, and copper alloys, inactivate the virus under realistic conditions is essential for tuning intrinsic alloy features such as composition, grain orientation, and surface attributes, to optimize for antiviral function. However, virus inactivation measurements depend on the presence of an assay media (AM) solution as a carrier for the virus, and its effects on the surface properties of pure copper that regulate oxidative copper release are previously unknown. Herein, these properties and the influence of AM on the efficacy of virus inactivation occurring on the surface of pure copper are investigated. The process is uncovered by which a five‐fold decrease in virus half‐life is observed in simulated real‐life conditions, relative to exposure to traditional AM. The investigation highlights the notion that virus inactivation on copper surfaces may be significantly more effective than previously thought.

Pool boiling experiment characteristics on the pure copper surface

Pool boiling experiment characteristics on the pure copper surface

Study on the Preparation and Characteristics of Copper-Chromium Alloy Cladding Layer

Copper is widely used in the power industry due to its good electrical conductivity. However, owing to its low hardness and resistance to abrasion, copper is prone to damage when working under harsh environmental conditions. In order to protect the power equipment and improve the surface strength of the material, this study explores the feasibility of using laser cladding technology to prepare a protective layer on the copper substrate. The phase, microstructure and element distribution of the cladding layer were analyzed, and the changes in the microhardness of the cross-section were measured. The wear resistance of the two cladding layers was tested and compared with the wear resistance of pure copper. The experimental results show that the cladding layer has uniform structure distribution, fine grains, and no element segregation; the hardness of the cladding layer is greatly increased, and the average hardness of the CuCr20 cladding layer is 155.8 HV, which can reach 2.2 times that of the substrate. The average hardness of the CuCr40 cladding layer is 254.4HV, which can reach 3.6 times that of the matrix. The wear resistance of the CuCr40 cladding layer is higher than that of the CuCr20 cladding layer, which can reach three times that of pure copper. Experiments have proved that the protective effect can be achieved by preparing a laser cladding layer on the surface of pure copper.

Catalytic Cooperation between a Copper Oxide Electrocatalyst and a Microbial Community for Microbial Electrosynthesis.

Electrocatalytic metals and microorganisms can be combined for CO2 conversion in microbial electrosynthesis (MES). However, a systematic investigation on the nature of interactions between metals and MES is still lacking. To investigate this nature, we integrated a copper electrocatalyst, converting CO2 to formate, with microorganisms, converting CO2 to acetate. A co-catalytic (i. e. metabolic) relationship was evident, as up to 140 mg L-1 of formate was produced solely by copper oxide, while formate was also evidently produced by copper and consumed by microorganisms producing acetate. Due to non-metabolic interactions, current density decreased by over 4 times, though acetate yield increased by 3.3 times. Despite the antimicrobial role of copper, biofilm formation was possible on a pure copper surface. Overall, we show for the first time that a CO2 -reducing copper electrocatalyst can be combined with MES under biological conditions, resulting in metabolic and non-metabolic interactions.

On the interpretation of X-ray photoelectron spectra of Pt-Cu bimetallic alloys

The progress in the design of a perspective alloy catalyst relies on correct interpretation of its photoelectron spectra. Particularly, X-ray photoelectron spectroscopic (XPS) analysis of platinum-copper alloys represents a serious challenge for both qualitative and quantitative analyses due to the complexity of the Pt 4f spectra arising from its overlapping with the Cu 3p region. Studies regarding XPS investigation of Pt-Cu alloys often ignore the Cu 3p contribution while fitting Pt 4f spectra, which leads to partially incorrect interpretation of measured XPS data. This is most noticeable for alloys containing more than 50 % of platinum where the low-intensity Cu 3p core levels can be hidden under a more intense contribution of Pt 4f. In this work, we present the correct way of processing photoemission spectra of such systems. First, we thoroughly examine the XPS Cu 3p spectra of pure copper surfaces of different oxidation states, namely Cu°, Cu+, and Cu2+. Then, the obtained results are applied for the fitting of Pt 4f spectra of both metallic and oxidized Pt-Cu systems. The precise curve-fitting and data analysis procedure showcased in this study can be utilized to eliminate uncertainties in the analysis of Pt-Cu photoemission spectra.