Thin Copper Layer Research Articles

Hydrothermal Treatment of Arsenopyrite Particles with CuSO4 Solution.

The nature of the hydrothermal reaction between arsenopyrite particles (FeAsS) and copper sulfate solution (CuSO4) was investigated in this study. The effects of temperature (443–523 K), CuSO4 (0.08–0.96 mol/L) and H2SO4 (0.05–0.6 mol/L) concentrations, reaction time (1–120 min), stirring speed (40–100 rpm) and particle size (10–100 μm) on the FeAsS conversion were studied. The FeAsS conversion was significant at >503 K, and it is suggested that the reaction is characterized by the formation of a thin layer of metallic copper (Cu0) and elemental sulfur (S0) around the unreacted FeAsS core. The shrinking core model (SCM) was applied for describing the process kinetics, and the rate of the overall reaction was found to be controlled by product layer diffusion, while the overall process was divided into two stages: (Stage 1: mixed chemical reaction/product layer diffusion-controlled) interaction of FeAsS with CuSO4 on the mineral’s surface with the formation of Cu1+ and Fe2+ sulfates, arsenous acid, S0, and subsequent diffusion of the reagent (Cu2+) and products (As3+ and Fe2+) through the gradually forming layer of Cu0 and molten S0; (Stage 2: product layer diffusion-controlled) the subsequent interaction of CuSO4 with FeAsS resulted in the formation of a denser and less porous Cu0 and S0 layer, which complicates the countercurrent diffusion of Cu2+, Cu1+, and Fe2+ across the layer to the unreacted FeAsS core. The reaction orders with respect to CuSO4 and H2SO4 were calculated as 0.41 and −0.45 for Stage 1 and 0.35 and −0.5 for Stage 2. The apparent activation energies of 91.67 and 56.69 kJ/mol were obtained for Stages 1 and 2, respectively.

Transparent and Sprayable Surface Coatings that Kill Drug-Resistant Bacteria Within Minutes and Inactivate SARS-CoV-2 Virus.

Antimicrobial coatings are one method to reduce the spread of microbial diseases. Transparent coatings preserve the visual properties of surfaces and are strictly necessary for applications such as antimicrobial cell phone screens. This work describes transparent coatings that inactivate microbes within minutes. The coatings are based on a polydopamine (PDA) adhesive, which has the useful property that the monomer can be sprayed, and then the monomer polymerizes in a conformal film at room temperature. Two coatings are described (1) a coating where PDA is deposited first and then a thin layer of copper is grown on the PDA by electroless deposition (PDA/Cu) and (2) a coating where a suspension of Cu2O particles in a PDA solution is deposited in a single step (PDA/Cu2O). In the second coating, PDA menisci bind Cu2O particles to the solid surface. Both coatings are transparent and are highly efficient in inactivating microbes. PDA/Cu kills >99.99% of Pseudomonas aeruginosa and 99.18% of methicillin-resistant Staphylococcus aureus (MRSA) in only 10 min and inactivates 99.98% of SARS-CoV-2 virus in 1 h. PDA/Cu2O kills 99.94% of P. aeruginosa and 96.82% of MRSA within 10 min and inactivates 99.88% of SARS-CoV-2 in 1 h.

Quantification of the Nano-Voids in Electroless Deposited Copper Layers Using SiNx TEM Grids

A plan-view analytical method to detect nano-voids of deposited copper layers, especially for the fabrication of printed circuit boards, was investigated using transmission electron microscopy (TEM). Through electroless plating, thin copper layers were directly deposited on small silicon nitride window grids, and the presence of nano-voids within the deposited copper layers were confirmed with various TEM analytical techniques. The amount and size of the nano-voids were further quantified from the plan-view TEM images, making it possible to compare quickly multiple samples prepared under various plating conditions. This analytical method is practical as it is faster in detecting and measuring nano-scale defects when compared to typical cross-sectional analytical methods.

Sacrificial Cu Layer Mediated the Formation of an Active and Stable Supported Iridium Oxygen Evolution Reaction Electrocatalyst.

The production of hydrogen via a proton-exchange membrane water electrolyzer (PEM-WE) is directly dependent on the rational design of electrocatalysts for the anodic oxygen evolution reaction (OER), which is the bottleneck of the process. Here, we present a smart design strategy for enhancing Ir utilization and stabilization. We showcase it on a catalyst, where Ir nanoparticles are efficiently anchored on a conductive support titanium oxynitride (TiONx) dispersed over carbon-based Ketjen Black and covered by a thin layer of copper (Ir/CuTiONx/C), which gets removed in the preconditioning step. Electrochemical OER activity, stability, and structural changes were compared to the Ir-based catalyst, where Ir nanoparticles without Cu are deposited on the same support (Ir/TiONx/C). To study the effect of the sacrificial less-noble metal layer on the catalytic performance of the synthesized material, characterization methods, namely X-ray powder diffraction, X-ray photoemission spectroscopy, and identical location transmission electron microscopy were employed and complemented with scanning flow cell coupled to an inductively coupled plasma mass spectrometer, which allowed studying the online dissolution during the catalytic reaction. Utilization of these advanced methods revealed that the sacrificial Cu layer positively affects both Ir OER mass activity and its durability, which was assessed via S-number, a recently reported stability metric. Improved activity of Cu analogue was ascribed to the higher surface area of smaller Ir nanoparticles, which are better stabilized through a strong metal–support interaction (SMSI) effect.

Modification of polymer thin film-coated metallic layer inside acid solutions

Modification of polystyrene (PS) thin film-coated copper (Cu) layer is studied by varying the PS layer thickness inside different acidic environments. PS-coated Cu films are exposed to acetic and hydrochloric acid environments and are investigated using UV–visible spectroscopy, atomic force microscopy, water contact angle and electrical measurements. Polymeric and metallic layer thicknesses are obtained from the X-ray reflectivity analysis. It is found that the metallic layer corrosion nearly follows an exponential decay with time and the decay time constant takes the higher values for the thicker PS films. The contact angle values, surface morphologies and in-plane current–voltage curves obtained from the films confirm that with increase in the acid concentration, corrosion of the metallic layer is much higher than the polymeric layer, as the in-plane current is reduced by a relatively higher value than the water contact angle. Penetration of the acid solution through intermolecular spacing or microscopic pores of the polymeric layer is the most probable reason for such corrosion of the metallic layer, but the removal of the polymeric layer is not favourable due to the hydrophobic effect.

Vacuum infiltration molding and mechanical property of short carbon fiber reinforced Ti-based metallic glass matrix composite

• New vacuum infiltration method using Cu-mold-prepared CF preform is developed. • Electroless-Cu-plated layer dissolves to improve the wettability during infiltration. • Interface microstructure control is achieved by Cu-layer and short-term infiltration. • Ti-based CFRMGMC has obviously improved plasticity together with high-strength. • Randomly and uniformly distributed short CF leads to brittle-ductile transition. The molding process is the key technology for the development of carbon fiber reinforced metallic glass matrix composites (CFRMGMCs), which not only needs to tackle the challenge of the mixing uniformity of carbon fibers, but also should take into account the rapid cooling technology to obtain a fully glassy matrix. Herein, a new vacuum pressure infiltration molding method is developed to fabricate a Ti-based CFRMGMC, in which a copper mold is performed as the container for carbon fiber preforms in addition to being used as a rapid cooling device. In order to prevent the interface reaction between carbon fiber and metal liquid, an electroless copper layer is plated on the surface of carbon fiber. It is found that the thin copper layer is dissolved in the glassy matrix and no crystalline phase is formed on the interface between the fiber and the matrix, showing a good effect on the control of interface microstructure. Meanwhile, electroless copper layer also effectively improves the wettability between the carbon fiber and the titanium alloy melt, thereby improving the infiltration forming ability of the composite material and reducing the tendency to form macroscopic defects. The as-prepared Ti-based CFRMGMC shows a significantly improved plasticity of ∼5 % and a high yield strength of 1880 MPa. The toughening mechanism can be attributed to the random distribution of short carbon fibers in different directions, which originates from the preparing process of carbon fiber preforms. This multi-directional posture is frozen in the glassy matrix and stimulates the multiple shear band behavior of the CFRMGMC. This work sheds lights on the use of carbon fiber in bulk metallic glasses, and is of great significance to the lightweight development and the interface reaction control of CFRMGMCs.

Study on the thermal load of the laser impulse metal bonding process to the metallized thermal sensitive substrate

The laser impulse metal bonding (LIMBO) process opens a new possibility to join a thick interconnector on a thin metal layer which lays on a sensitive substrate such as epoxy resin (FR4) material. Since the FR4 tolerates only limited amount of the thermal load during the joining process, the LIMBO process applies a novel approach to separate the melting and joining phase. Hence, the thermal load on the underlying substrate during the joining phase is minimized and therefore allows a welding approach even for electric as well as electronic components. However, the substrate is thermally affected due to the heat conduction which is induced during the joining phase. In this paper, the thermal cycle induced to the sensitive substrate during the LIMBO process and the overlap welding process for enlarging the weld joint area will be investigated. To evaluate the maximal amount of thermal load on the sensitive substrate below a thin copper layer by given setting, the thermal destruction threshold of substrate is exceeded on purpose. For the understanding of the heat distribution during the joining stage, the experimental results are validated with simulation results.

Response of electroless copper coated CFRP laminates to emulated lightning strikes

Lightning strike emulatorwas employed for evaluating the response of copper electroless coatings on epoxy-CFRP laminates under these high demanding electrical events. Samples were coated for 15 and 30 min producing0.6 and 1.2 µm thick layers, respectively, and their performances were compared with commercially protected and naked laminates. Data show that a thin copper layer can improve the performance of CFRP under 40 kA discharges by absorbing part of the electrical energy, as a sacrificial protection. The surface of delaminated composite was lower whereas the coating area affected was larger for samples treated at longer times. An interesting relationship was found between the charge transfer and the damaged area, for all samples. In addition, sustained 30 A injection tests were performed and both electrical data and thermal imaging showed a better tolerance to continuous currents and a better heat dissipation of 30 min versus 15 min coated samples.

Copper Oxide Passivation Effect on Electromigration Lifetime of Plasma Etched Copper Lines

The degradation of the copper oxide passivated copper line prepared from a room temperature plasma-based etch process under the electromigration condition has been studied. The copper line surface was oxidized into the copper oxide layer in a parallel-plate plasma reactor operated under the plasma etching or reactive ion etching mode. The surface roughness of the oxide is contributed by the high ion bombardment energy. The lifetime of the sample was shortened by the addition of the oxide passivation layer. It was also decreased with the increase of the stress current density. The sample with the thin bulk copper layer is more resistant to the thermal stress than that with the thick bulk copper layer, which delayed the voids formation in the line breakage process.

Ultralong Electrospun Copper–Carbon Nanotube Composite Fibers for Transparent Conductive Electrodes with High Operational Stability

Recent advances in nanotechnology have provided new materials which have the potential to surpass copper and aluminum alloys in electrical conductivity, weight and ampacity [2-6]. Among these carbon nanotubes (CNTs) stand out due to their remarkable thermal and electrical conductivity and ampacity (103 times of copper), low density, abundance of precursor materials and supreme mechanical properties. However, making these materials into a continuous fiber or macrostructures has remained the main obstacle. A promising approach to tackle this issue is employing CNTs as nanofillers in copper matrixes. Subramaniam et al. [5] combined several simple fabrication to produce high density CNT (45 vol%)-Cu composite films with specific conductivity 26% greater than copper. These results show that by improving the interfacial interactions between the CNTs and the copper matrix strong and highly conductive nanocomposites can be made. In this research continuous CNT-Cu nanocomposite is produced using electrospinning method. For improving the interfacial interaction the surface of the CNTs were first coated with a thin layer of copper using electroless deposition methods (the process is explained in details in [7]).

Development of a RFID sensitive tag dedicated to the monitoring of the environmental corrosiveness for indoor applications

The environmental corrosiveness is governed for indoor applications by the presence of gaseous pollutants in air and levels of temperature and relative humidity. Its determination is a challenging task and requires the monitoring of thickness reduction of selected metals in the range of few tens of nanometers. The present work aims at developing an UHF RFID (Ultra High Frequency Radio Frequency Identification) sensor dedicated to such measurements. The sensor is based on the coupling between the antenna of a commercial RFID tag and a thin layer of copper exposed to the environment. The ability of the proposed sensor to be sensitive to a variation of the metal thickness in the range of tens of nanometers is demonstrated experimentally through exposure tests in a climatic chamber. The results are supported by electromagnetic simulations performed in the case of a coupling between a dipolar antenna and a thin metallic layer.

Measurements of the charging-up effect in Gas Electron Multipliers

Gas Electron Multipliers (GEM) are widely used as amplification stages in gaseous detectors exposed to high rates. The GEM consists of a polyimide foil which is coated by two thin copper layers. Charges collected into the holes or created during the amplification process may adhere to the polyimide part inside the holes. This is often accompanied by a change of the effective gain. The effect is commonly known as the “charging-up effect”.This work presents a systematic investigation of the effect under well-controlled and monitored conditions for a single standard GEM foil in Ar/CO2 (90/10) gas for varying rates of X-ray interactions in the detector and for different gains of the foil. In order to cover a wide range of different rates, we apply two different methods. The first one is based on a current measurement while the second one relies on the analysis of 55Fe spectra over time. Both methods give consistent results, showing an initial increase of the effective gain with time and an asymptotic saturation, which can be well described by a single-exponential function. We find that the characteristic time constants extracted from our measurements scale inversely proportional to the rate of incoming electrons for a given GEM voltage. Introducing characteristic quantities, which describe either the number of incoming electrons per hole or the total number of electrons in a hole per characteristic time, we find consistent numbers for measurements taken at the same GEM voltages. For measurements taken at different GEM voltages, however, also the characteristic total number of electrons inside the hole, which is supposed to take into account the different effective gains, is found to be higher by a factor of about 3.5 for UGEM=350V (ntot=8.8×108) compared to 400V (ntot=2.4×108). This hints at a residual dependence of the charging-up characteristics on the GEM voltage.

Laser induced formation of copper species over TiO2 nanotubes towards enhanced water splitting performance

We proposed fast and scalable route where the ordered TiO2 nanotubes coated with thin copper layers were annealed by the laser beam of 355 nm wavelength at different fluencies in the range of 15–120 mJ/cm2. As a result, copper species are integrated with the titania substrate and the formed material exhibits unique optical absorption bands in the visible range. Moreover, X-ray photoelectron spectroscopy analysis reveals the formation of Cu2O while the 4+ oxidation state of titanium is preserved. According to the electrochemical results, the material treated by laser exhibits outstanding photoelectrochemical activity comparing to the pristine titania or the one only covered by the thin copper film. In particular, when the fluence of 60 mJ/cm2 was used for the modification of the titania decorated with Cu film, the current density recorded in KOH electrolyte reaches nearly 4.5 mA/cm2 at +2.0 V vs. Ag/AgCl/0.1 M KCl upon visible light.

Electrochemical Copper Deposition on Nanoscale-Sculptured Aluminum for Mechanically Stable Joints with Optimal Electrical and Heat Transport Properties

Copper is a material with a very high conductivity per volume; therefore it is widely used in the industry for nearly every electric application. However, with respect to weight aluminum (due to its low density of 2.7 g/cm3) shows a significantly higher electrical conductivity than copper. For many lightweight applications, aluminum would be the preferred material, but it lacks for good technical solutions for forming easy to apply, corrosion resistant, highly conductive contacts to (other) metals, especially to copper. Many of these problems are related to the native aluminum oxide coating on all aluminum surfaces in contact to air. State of the art solutions for electrical contacting aluminum surfaces require high temperatures and/or high pressure, thus making them expensive and typically damage the surface near microstructure of the aluminum.In this abstract, we will discuss details of a room temperature technique, which allows for a mechanically stable, corrosion resistant, galvanic copper deposition on aluminum surfaces with extremely high interface conductivity for heat as well as for electrical current. This allows the application of standard bonding technologies for copper (e.g. soldering or using conductive glues) onto aluminum as a conducting material.The copper deposition technique contains three steps: 1. A special surface preparation, i.e. nanoscale-sculpturing (cf. [1]) which creates a low corrosive aluminum surface structure full of mechanical hooks, composed of 100 crystallographic facets.2. A preconditioning step before galvanostatic copper deposition.3. Galvanic copper deposition controlling the nucleation of copper islands within the hooking structure and the morphology of the growing copper layer.Due to the nanoscale-sculpturing, the deposited copper is mechanically stable bonded to the aluminum surface. Dependent on the demands for subsequent bonding applications, the galvanic copper deposition must be adjusted; e.g. for gluing, large parts of the hook like structure from the underlying aluminum surface should still exist after a thin layer of copper is deposited.In contrast, for soldering application, a robust and thick layer of copper is needed.How the nanoscale-sculpturing and the galvanic copper deposition can be adjusted to various application will be discussed in detail.[1] Baytekin-Gerngross, M., Gerngross, M., Carstensen, J. and Adelung, R. (2016). Making metal surfaces strong, resistant, and multifunctional by nanoscale-sculpturing. Nanoscale Horizons, 1(6), pp.467-472.

Flexible Anode Catalysts for Direct Hydrazine Fuel Cells

In this study we report a facile approach for fabrication of flexible anode catalysts consisting of a fiber-shaped cobalt deposited on the polyimide (PI) surface for direct hydrazine fuel cells (DHFCs). At first, a thin copper layer has been deposited on the PI surface using electroless metal plating method. Then, the fiber-shaped cobalt coating has been plated by the electrochemical deposition method from the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. For comparison, the cobalt layer that has the smooth structure has been deposited on the flexible PI surface via electroless deposition using morpholine borane as a reducing agent.The morphology and composition of the prepared flexible catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The activity of catalysts has been investigated with respect to the oxidation of hydrazine in an alkaline medium.The results of electrochemical measurements showed that the deposited cobalt layer that has a fiber-shaped structure on the flexible PI surface exhibits an enhanced electrocatalytic activity towards the oxidation of hydrazine as compared with that for cobalt catalyst that has a smooth structure. Moreover, the prepared flexible catalysts seem to be a promising anode material for DHFCs.

Powder mixed-electrical discharge machining (EDM) with the electrode is made by fused deposition modeling (FDM) at Ti-6Al-4V machining procedure

Rapid prototyping (RP) is a collection of techniques, and it is used in many industries to make a robust model of a mechanical sample instantly. RP is usually implemented by employing 3D printing or additive manufacturing (AM) technology with three-dimensional modeling. In the context of RP, rapid tooling (RT) is the result of applying the RP with non-conventional tooling. RT causes many discharge channels between the electrode in electro-discharge machining (EDM). In our study, acrylonitrile butadiene styrene is coated with a thin layer of copper and is used as an electrode tool in powder mixed electro-discharge machining (PM-EDM). We have employed the fused deposition modeling (FDM) method of rapid prototyping to improve the conductivity of the electrode tools for the PM-EDM. Cost, machining-time, and the quality of the surface are the significant outputs of the PM-EDM process for the fabrication of tools in sensitive industries. In our present research, a new kind of electrode is compared with a solid electrode with powder and without powder. Material removal rate (MRR), tool wear rate (TWR), and surface roughness (SR) have been measured for both scenarios. In this method, peak current, pulse-on time, and concentration of aluminium powder are the input parameters. We have also added a surfactant on kerosene for separating and distributing the powders. Our study demonstrates that the RP electrodes have the potential for utilizing the PM-EDM tools with complex shapes. The conventional processes do not make these complex shapes. Indeed, comparing the results of the output parameters in our proposed method with the PM-EDM existing methods indicates an improvement for MRR, TWR, and SR, by 33%, 31%, and 77%, respectively. Hence, the average surface quality, which is created by the PM-EDM, has been substantially improved. Thus, our proposed method is cost-effective, and it can be used to create various complex topologies, potentially in the medical and aerospace industries.

Direct observation of spin accumulation in Cu induced by spin pumping

This paper shows how X-ray transmission microscopy can provide spatial mapping of spin accumulations in a thin layer of copper, which are generated without any directly applied charge currents through spin pumping from ferromagnetic magnetization dynamics in adjacent permalloy.

Computational modeling of the curing of a frame of an inflatable satellite antenna in near-earth orbit

Temperature analysis of a new technological process, curing of prepregs in near-earth orbit, is performed via computational modeling. The problem arose in connection with the currently discussed possibility of using inflatable antennas for small space satellites. Inflatable antennas have a number of advantages over classic extendable metal antennas. However, in order to ensure the continuous operation of inflatable antennas, it is necessary that they acquire rigidity over time and cease to depend on the pressure of air in them. This can be achieved using a frame made of an orbital-curable prepreg. This idea requires experimental justification and analysis by means of computational modeling. In this work, only one of the aspects (temperature effect) of the in-orbit curing technological process is considered. The creation of special equipment for heating prepregs in the satellite body is undesirable because it will increase weight and sizes of a satellite. However, the natural heating of structural elements in space can be due to the radiation emitted from the Sun and the Earth. Numerical experiments demonstrate that the required curing temperature can be achieved in the case when, instead of a simple prepreg frame, use is made of the frame on which a thin layer of copper is deposited. Temperature distributions in the structure during its rotation are examined. Analysis of the results yields time intervals at which the antenna orientation with respect to the solar flux direction should be changed in order to obtain the required temperatures, striving to achieve curing of all elements of the frame in a small number of revolutions around the Earth, that is, as long as a high gas pressure remains in the inflatable antenna.

High volume fraction of copper coated graphite flake∖Nitrogen doped carbon fiber reinforced aluminum matrix composites

High volume fraction of carbon material reinforced aluminum matrix composites were developed by optimized vacuum gas pressure infiltration method, among which the reinforced materials are graphite flake and carbon fiber. To enhance the wettability between the reinforments and aluminum matrix, graphite flake was coated with a thin layer of copper by electroless plating and CF was doped with nitrogen, which proves to be effective and efficient. With the increase of reinforcements from 50 to 80 vol%, the flexural strength of the composites remains at practical level; the coefficients of thermal expansion decrease under the same temperature in direction parallel to basal planes of graphite flake; the thermal conductivity of the composites increase from 327 to 402 W/m K, adding up to relatively high comprehensive performances.

Measuring Local Electric Fields and Local Charge Densities at Electrode Surfaces Using Graphene-Enhanced Raman Spectroscopy (GERS)-Based Stark-Shifts.

We report spectroscopic measurements of the local electric fields and local charge densities at electrode surfaces using graphene-enhanced Raman spectroscopy (GERS) based on the Stark-shifts of surface-bound molecules and the G band frequency shift in graphene. Here, monolayer graphene is used as the working electrode in a three-terminal potentiostat while Raman spectra are collected in situ under applied electrochemical potentials using a water immersion lens. First, a thin layer (1 Å) of copper(II) phthalocyanine (CuPc) molecules are deposited on monolayer graphene by thermal evaporation. GERS spectra are then taken in an aqueous solution as a function of the applied electrochemical potential. The shifts in vibrational frequencies of the graphene G band and CuPc are obtained simultaneously and correlated. The upshifts in the G band Raman mode are used to determine the free carrier density in the graphene sheet under these applied potentials. Of the three dominant peaks in the Raman spectra of CuPc (i.e., 1531, 1450, and 1340 cm-1), only the 1531 cm-1 peak exhibits Stark-shifts and can, thus, be used to report the local electric field strength at the electrode surface under electrochemical working conditions. Between applied electrochemical potentials from -0.8 V to 0.8 V vs NHE, the free carrier density in the graphene electrode spans a range from -4 × 1012 cm-2 to 2 × 1012 cm-2. Corresponding Stark-shifts in the CuPc peak around 1531 cm-1 are observed up to 1.0 cm-1 over a range of electric field strengths between -3.78 × 106 and 1.85 × 106 V/cm. Slightly larger Stark-shifts are observed in a 1 M KCl solution, compared to those observed in DI water, as expected based on the higher ion concentration of the electrolyte. Based on our data, we determine the Stark shift tuning rate to be 0.178 cm-1/ (106 V/cm), which is relatively small due to the planar nature of the CuPc molecule, which largely lies perpendicular to the electric field at this electrode surface. Computational simulations using density functional theory (DFT) predict similar Stark shifts and provide a detailed atomistic picture of the electric field-induced perturbations to the surface-bound CuPc molecules.