Copper Particles Research Articles

Copper oxide‐ and copper‐modified antibacterial ceramic surfaces

AbstractIn the present study, copper oxide (CuO) and copper (Cu) particles were characterized and investigated to observe the effects of antimicrobial activity on ceramic tile surfaces. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) techniques were used for particle characterization. A new formulation of antimicrobial glaze was achieved by the combination of two glaze compositions with different Cu and CuO content to obtain micro–nano hybrid surface morphology to provide the antibacterial property. Surface morphology of coated ceramic surfaces was examined by SEM in detail and water contact angles were measured with goniometer. The relationships between antibacterial effect, phase evolution, surface topography, and wettability of surfaces were determined. The tenorite phase of CuO was observed on both Cu‐ and CuO‐modified surfaces. Both Cu and CuO particles in glazed ceramic surfaces showed the similar antibacterial activity against Staphylococcus aureus and Escherichia coli. The antibacterial activity was dependent on mainly tenorite phase crystallization. The amount of the tenorite phase that was slightly higher in the case of Cu‐incorporated surfaces instead of CuO and hence the bactericidal effect was slightly more pronounced. Although the developed surfaces are not hydrophobic, they show antibacterial properties.

Theoretical Insights into Synergistic Effects at Cu/TiC Interfaces for Promoting CO2 Activation.

The adsorption behaviors of CO2 at the Cun/TiC(001) interfaces (n = 1–8) have been investigated using the density functional theory method. Our results reveal that the introduction of copper clusters on a TiC surface can significantly improve the thermodynamic stability of CO2 chemisorption. However, the most stable adsorption site is sensitive to the size and morphology of Cun particles. The interfacial configuration is the most stable structure for copper clusters with small (n ≤ 2) and large (n ≥ 8) sizes, in which both Cu particles and TiC support are involved in CO2 activation. In such a case, the synergistic behavior is associated with the ligand effect introduced by directly forming adsorption bonds with CO2. For those Cun clusters with a medium size (n = 3–7), the configuration where CO2 adsorbs solely on the exposed hollow site constructed by Cu atoms at the interface shows the best stability, and the charger transfer becomes the primary origin of the synergistic effect in promoting CO2 activation. Since the most obvious deformation of CO2 is observed for the TiC(001)-surface-supported Cu4 and Cu7 particles, copper clusters with specific sizes of n = 4 and 7 exhibit the best ability for CO2 activation. Furthermore, the kinetic barriers for CO2 dissociation on Cu4- and Cu7-supported TiC surfaces are determined. The findings obtained in this work provide useful insights into optimizing the Cu/TiC interface with high catalytic activation of CO2 by precisely controlling the size and dispersion of copper particles.

Functionalization of polylactic acid thin films via polydopamine-assisted chelation of copper (II) ions for antibacterial applications

Polylactic acid (PLA) is a biodegradable polymer, which has been widely investigated for use in biomedical and packaging applications due to its excellent biodegradability, biocompatibility, non-toxicity, low cost, good stability, and thermal processability. In this work, PLA was functionalized to improve the membrane’s hydrophilicity and impart antimicrobial activity by simultaneously depositing polydopamine (PDA) and chelating Cu2+ metal ions on the membrane surface. Pristine PLA films were modified via one-pot dip coating method using dopamine-copper (II) solution at different coating times (6, 12, 24 h). FTIR analysis confirmed the deposition of PDA on the modified membranes (PLA/PDA/Cu) as indicated by the presence of catechol and amine moieties on the samples. TGA results revealed the degradation of the same functional groups on PLA/PDA/Cu. The hydropilicity of PLA was significantly reduced upon coating with PDA as indicated by the decrease in the membrane’s contact angle from 96.5 ± 5.3° to 56.2 ± 4.7°. SEM images and EDS results clearly showed that copper particles were deposited on the PLA/PDA/Cu membranes (atomic % ~ up to 0.88) and coating with PDA did not alter the porous structure of the pristine PLA film. Results also demonstrated that the concentration of copper immobilized on the modified membranes increased with longer coating; thus, offering a way of tailoring the metal concentration on the membrane for its specific use. PLA/PDA/Cu membranes showed antibacterial property against the B. subtilis, which could be attributed to the chelation of Cu2+ ions with the catechol moiety of the PDA coating.

High-sensitivity and temperature-controlled switching methanol sensor prepared based on the dual catalysis of copper particles

In this work, based on the dual catalytic properties of copper (Cu) particles for methanol oxidation and persulfate initiated radical polymerization, a temperature-controlled catalytic electrode, defined the PNIPAM-Cu@CP, was constructed by electrodepositing Cu particles on a carbon paper electrode and triggering the polymerization of the temperature-sensitive polymer N-isopropylacrylamide (PNIPAM) on the surface of the electrode, which is expected to be applicated in the micro-direct methanol fuel cell (DMAC) for detection of methanol crossover and also has temperature recognition and high-temperature self-protection functions. Cu particles and PNIPAM were characterized by X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) for their specific structure and morphology. The cyclic voltammetry (CV) results showed the proposed electrode as a temperature-controlled switch-like methanol sensor, has a wide linear range (1–300 mM and 300–1200 mM), excellent sensitivity (72.8 μA cm−2 mM−1 and 11.5 μA cm−2 mM−1) and a low detection limit of 0.3 mM for methanol. In addition, the sensor also has excellent selectivity and temperature-triggered switchable electrocatalytic activity. The efficient and simple preparation method of the electrode is expected to be used in the development of a methanol sensor for real-time methanol detection in micro-DMAC.

Copper recovery from waste printed circuit boards by the flotation-leaching process optimized using response surface methodology

ABSTRACT Recycling of waste printed circuit boards (PCBs) receives increasing attention due to abundant metallic resources and significant environmental threats. This work proposes a process for copper recovery from PCBs by froth flotation and oxidation leaching. Copper grade is improved from 38.70% to 68.34% with the recovery of 88.76% by froth flotation, and froth flotation is significantly influenced by copper liberation and particles dispersion of PCB powders. Process variables of oxidation leaching are examined by response surface methodology (RSM). A reliable mathematical model is obtained to predict the response as a function of independent variables and their interactions. Oxidation leaching is remarkably influenced by experimental variables, and the interactions between sulfuric acid and hydrogen peroxide are significant. Optimum conditions are achieved as sulfuric acid 1.0 mol/L, hydrogen peroxide 17%, temperature 50°C, and time 234 minutes, and the maximum leaching ratio of Cu is up to 99.94%, indicating that oxidation leaching is an effective method for Cu recovery from PCBs. Implications: Recycling of waste printed circuit boards (PCBs) receives increasing attention due to abundant metallic resources and significant environmental threats. This work proposes a novel process for copper recovery from PCBs by froth flotation and oxidation leaching. Froth flotation is efficient to enrich copper in metal fractions. Process variables of oxidation leaching are examined by response surface methodology (RSM). A reliable mathematical model is obtained to predict the response as a function of independent variables and their interactions. The froth flotation-oxidation leaching process is practicable and effective for copper recovery from waste printed circuit boards. This study significantly contributes to recycling metal resources from waste PCBs. We believe that this work will attract a broad readership and lead others to follow our approach.

Laser heating conditions for copper sphere implantation into borosilicate glass

Implanting metals in glass can serve many different purposes, ranging from enhancing the electro-optical properties to modifying the mechanical properties of the substrate. One approach involves the use of continuous laser illumination to implant metal spheres by transferring particles from a metal foil in direct contact with one side of the glass substrate. The process, which occurs in a very short period time (in tens of milliseconds), is unidentified: due to the bright thermal emissions, it cannot be directly observed. In this study, the continuous laser heating conditions required for implanting copper spheres in borosilicate glass were investigated via spectroscopy and numerical calculations to estimate the temperature of the copper foil. Emission spectroscopy revealed that the temperature during implantation reached 5100 K, which largely exceeded the temperature threshold for laser absorption (∼2000 K). Under such conditions, the plasma forms and enables the migration of copper particles into the glass host. The plasma propagation speed increased with increasing laser power density. The copper sphere was implanted when the plasma propagation speed was 20–50 mm/s. The copper sphere could not be implanted, and fiber fuse occurred when the plasma propagation speed was higher than 50 mm/s.

Surface modification on copper particles toward graphene reinforced copper matrix composites for electrical engineering application

Graphene has been demonstrated as an effective reinforcement for metal matrix composites, due to its excellent mechanical properties, robust chemical inertness, thermal stability, and self-lubricating. Nevertheless, the limiting factor for its further use in metal matrix composites, is to realize the homogeneous dispersion of graphene for taking advantage of its exceptional and fascinating properties, because of the poor wettability and density contrast between metal matrix and graphene. Herein, we design a gel-assisted route to synthesize high-quality graphene nanoplatelets modified monodispersed copper particles, followed by hot pressing to fabricate graphene reinforced copper matrix composites bulk. This simple route with high efficiency and low cost, offers a new solution for the mass-production of graphene reinforced copper matrix composites and other graphene-based composites on an industrial scale. Significantly enhanced tensile strength of 253 MPa, and yield strength of 145 MPa, accompanied by the low friction coefficient and improved wear resistance, can be simultaneously achieved in the composites. For the real electrical contact performance test, the service life of electrical contacts made of graphene reinforced copper matrix composites, is 10 times longer as that of the commercial pure copper electrical contacts and almost comparable to CuAg20 contacts, demonstrating its superior ability to solve the electrical contact issues in electrical engineering systems.

Effect of ionic liquid on graphene decorated with copper nanostructure dispersion towards silicon/graphene/copper composites with enhanced thermal, electrical and antimicrobial properties

Graphene decorated with cooper nanostructures were prepared with and without ionic liquid (IL) using different milling times. The obtained samples were characterized by Raman, X-ray diffraction (XRD) and transmission electron microscopy (TEM), to analyze the effect of the grinding time on the copper particles adhesion to the graphene sheets. Composites of silicon with two contents of G/Cu, at two weight ratios, nanostructures were prepared and the crosslinking characteristics were analyzed by a rubber process analyzer. The thermal conductivity, electrical resistivity and antimicrobial characteristics against E. coli and S. aureus for these silicon/G/Cu composites were determined. It was found that the use of IL enhances the G/Cu nanostructures dispersion into the silicon polymer matrix with a noticeable improvement in thermal conductivity of 1.12 W/mK for a 7 wt% of G/Cu, a volume electrical resistivity of 4.1 × 1010 Ω cm with 7 wt% of G/Cu nanoparticles and antimicrobial response of 4.21 ± 0.11 to E. coli and 5.33 ± 0.11 to S. aureus with 7% of G/Cu nanoparticles. It was determined that π–π interactions between graphene and aromatic molecule of IL may be influencing the observed improvement in G/Cu dispersion and final composite performance. The novelty of this work is the use of IL to improve the G/Cu NPs dispersion into the silicon polymer matrix. This silicon/G/Cu composite could be an option to prepare medical devices for electrotherapy or face protection against COVID-19 or other silicon-based devices for medical applications.Graphic abstract

Effect of Cu content on properties of Cu/Zn+15%SAC0307+xCu/Al joint by ultrasonic excitation at low temperature

The ultrasonic-assisted soldering joint of Cu/Al with different contents of copper particles added to solder powder at low temperature was studied. In this study, 15%SAC0307 solder powder with a diameter of 500 nm, different amounts copper particles with a diameter of 500 nm were mixed with zinc particles of a diameter of 45 μm to fill the Cu/Al joint, and the soldered was heated to 240 °C for ultrasonic-assisted under the environmental atmosphere. Successfully achieved micro-joining of Cu/Al under ultrasonic-assisted at low-temperature. The results have shown that, when the copper content was 0%-15%, two layers of complete and continuous CuxZny compounds were formed at the copper side interface. When the copper content was more than 15%, the IMC layer of the copper side interface was not obvious, and a large amount of CuxZny compounds were formed near the copper side. The base metals on the aluminum side formed a solid solution combination with zinc. When the addition amount of copper powder was 15%, the soldering seam was smooth and flat, the defect between balls was not obvious, and the IMC was uniformly distributed, so the average shear strength reached the maximum value of 47.37 MPa.

X-ray Fluorescence Spectroscopy Features of Micro- and Nanoscale Copper and Nickel Particle Compositions.

The study is devoted to X-ray fluorescence spectroscopy (XRF) features of micro- and nanosized powder mixtures of copper and nickel. XRF is a high accuracy method that allows for both qualitative and quantitative analysis. However, the XRF measurement error due to the size of the studied particles is not usually taken into account, which limits the use of the method in some cases, such as analysis of Ni-Cu mixtures and coatings. In this paper, a method for obtaining copper and nickel nanoparticles was investigated, and the XRF of powder compositions was considered in detail. The initial micro- and nanoparticles of copper and nickel were studied in detail using SEM, TEM, XRD, and EDX. Based on experimental data, calibration curves for copper-nickel powder compositions of various sizes were developed. According to the results, it was experimentally established that the calibration curves constructed for nanoscale and microscale powders differ significantly. The presented approach can be expanded for other metals and particle sizes.

Liquid Metal Composites with Enhanced Thermal Conductivity and Stability Using Molecular Thermal Linker.

Gallium-based liquid metal (LM) composite with metallic fillers is an emerging class of thermal interface materials (TIMs), which are widely applied in electronics and power systems to improve their performance. In situ alloying between gallium and many metallic fillers like copper and silver, however, leads to a deteriorated composite stability. This paper presents an interfacial engineering approach using 3-chloropropyltriethoxysilane (CPTES) to serve as effective thermal linkers and diffusion barriers at the copper-gallium oxide interfaces in the LM matrix, achieving an enhancement in both thermal conductivity and stability of the composite. By mixing LM with copper particles modified by CPTES, a thermal conductivity (κ) as high as 65.9 W m-1 K-1 is achieved. In addition, κcan be tuned by altering the terminal groups of silane molecules, demonstrating the flexibility of this approach. The potential use of such composite as a TIM is also shown in the heat dissipation of a computer central processing unit. While most studies on LM-based composites enhance the material performance via direct mixing of various fillers, this work provides a different approach to fabricate high-performance LM-based composites and may further advance their applications in various areas including thermal management systems, flexible electronics, consumer electronics, and biomedical systems.

A semi-empirical model for thermal resistance and dryout during boiling in thin porous evaporators fed by capillary action

Two-phase passive heat transport devices such as vapor chambers, loop heat pipes, and capillary pumped loops utilize porous evaporators for phase change and to drive fluid transport. Nucleate boiling can occur within such capillary-fed porous evaporators, especially under high-heat-flux operation, as has been visually observed in various experimental studies in the literature. However, prior modeling efforts have typically only considered single-phase flow of liquid through a completely saturated porous medium for characterizing the dryout limit and thermal performance. The present work offers a new semi-empirical model for prediction of thermal resistance and dryout during boiling in capillary-fed evaporators. Thermal conduction across the solid and volumetric evaporation within the pores are solved to obtain the temperature distribution in the porous structure. Capillary-driven lateral liquid flow from the outer periphery of the evaporator to its center, with vapor flow across the thickness, is considered to obtain the local liquid and vapor pressures. The capillary pressure and the relative permeabilities (fraction of single-phase permeabilities) for two-phase flow in the porous medium are modeled as a function of the local liquid saturation. The heat flux at which the liquid saturation at the center of the evaporator becomes zero is defined as the dryout limit of the evaporator. Experiments are conducted on sintered copper particle evaporators of different particle sizes and heater areas to collect data for model calibration. To demonstrate the wider applicability of the model for other types of porous evaporators, the model is further calibrated against a variety of dryout limit and thermal resistance data collected from the literature. The model is shown to predict the experimentally observed trends in the dryout limit with mean particle/pore size, heater size, and evaporator thicknesses.

Oscillating Motion of Oil Droplets in the Emulsion Near the Air-Water Interface.

Numerous living organisms as well as artificially created self-propelled objects can form dissipative structures due to the nonlinear effects and nonequilibrium of the system. Here we present an active oil-in-water emulsion in which the oil droplets take part in the reciprocating motion under the action of Marangoni flow near the air-water interface. The droplet dynamics in the emulsion is governed by the chemical reaction proceeding between quiescent copper particles and ammonia and by the convective mixing of a surfactant. We established that the reciprocating motion of droplets in the emulsion arises as a result of a periodic change in the Marangoni flow direction at the air-water interface. The feature of the considered system is that the reciprocating motion of droplets is realized only when the surface area fraction of droplets in the emulsion is close to the density of a two-dimensional colloid crystal. Oscillations degenerate under the reduction in surface area fraction to the critical value of ∼50% since the existence of oscillations in the emulsion requires a suppression of the surfactant convective mixing between the inner layers of liquid film and the air-water interface.

CHF enhancement of downward-facing saturated pool boiling on the SCGS-modified surfaces with multi-scale conical pin fin structures

Enhancing the critical heat flux (CHF) of external reactor vessel cooling (ERVC) to achieve the strategy of in-vessel retention (IVR) has been deemed as an essential requirement for the security of modern commercial PWR nuclear power plants. A new type of multi-scale conical pin fin structures had been designed to meet this need. These conical structures of four different axial heights (1.0, 1.5, 2.0 & 2.5mm) and similar radial geometric parameters were fabricated on four heating surfaces of copper substrates by supersonic cold gas spray technique (SCGS), and the conical pin fin structures were combined with a thin layer of micro porous structures. Transient-state (quenching) and steady-state (heating) pool boiling experiments had been respectively conducted on 6 different downward-facing surfaces under different inclination angles including 5°, 30°, 45°, 60°, 75° & 90° (in vertical), which included above-mentioned four pin fin surfaces, a plain surface and a coated surface covered with a 1mm-thick layer of uniform porous coating fabricated by SCGS with copper particles. The experimental results showed that the CHF increased with the inclination angles. The CHF of all the SCGS-modified surfaces were significantly enhanced compared with those of the plain surface. The maximum CHF value and the maximum CHF enhancement belonged to the 2.0mm-height pin fin surface whose CHF values were more than 1.7 times of those of the plain surface, and up to 2.1 times in 90°. The 1.0mm pin fin surface had the greatest performance in boiling heat transfer coefficient (HTC) and its CHF-enhancing performance also greatly exceeded that of 1.0mm uniform porous coating surface. Remarkable performances of multi-scale conical pin fin structures had been experimentally confirmed, hence the safety margin of IVR-ERVC will be greatly enhanced after adopting them. In addition, the CHF enhancement mechanism of the multi-scale conical pin fin structures was analyzed.

Microstructures and Properties of Cu-rGO Composites Prepared by Microwave Sintering.

This study investigated the effects of microwave sintering on the microstructures and properties of copper-rGO composites. Graphene oxide was coated onto copper particles by wet ball milling, and copper-rGO composites were formed upon microwave sintering in an argon atmosphere. Scanning electron microscopy was then used to observe the mixing in the ball-milled composite powder, and the morphology of the bulk composite after microwave sintering. Raman spectra revealed how graphene oxide changed with ball milling and with microwave sintering. The microhardness, electrical conductivity, and thermal conductivity of the composite were also measured. The results showed that graphene oxide and copper particles were well combined and uniformly distributed after wet ball milling. The overall microhardness of microwave-sintered samples was 81.1 HV, which was 14.2% greater than that of pure copper (71 HV). After microwave sintering, the microhardness of the samples in areas showing copper oxide precipitates with eutectic structures was 89.5 HV, whereas the microhardness of the precipitate-free areas was 70.6 HV. The electrical conductivity of the samples was 87.10 IACS%, and their thermal conductivity was 391.62 W·m−1·K−1.

Anchoring strategy for highly active copper nanoclusters in hydrogenation of renewable biomass-derived compounds

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is a common reaction that is critical to biomass transformation. However, it is a great challenge to employ non-noble metal catalysts in realizing highly effective conversion from LA to GVL. Herein, we report an efficient strategy for anchoring highly active copper nanocluster catalysts on the defect sites of graphitic carbon nitride (g-C3N4) and dispersing in mesoporous silica (SBA-15). The combination of g-C3N4 and SBA-15 stabilized the copper clusters, leading to a high GVL yield of 92 % and excellent stability in 100 h. This result is comparable to that of the Ru/AC catalyst but much more economically favorable. Density functional theory calculations revealed that the reaction barrier of the new catalyst was reduced from 1.93 to 1.12 eV compared with those of unconfined copper particles. This research provides a simple anchoring strategy for constructing highly active and inexpensive copper nanocluster catalysts.

Effects of copper fillers on mechanical and electrical properties of selective laser sintered PA 12-Cu composites

ABSTRACT Selective Laser Sintering (SLS) is a widely used additive manufacturing (AM) technique for creating 3D geometries by adding materials in layers. Although neat polymer is mainly used in powder forms for production, organic or inorganic fillers can be added to produce polymer composites by SLS method. In this study, Polyamide 12 (PA 12) matrix composite parts filled with two different copper particles, dendritic and spherical shaped, were produced, and their mechanical, structural and electrical properties were investigated. The present study outlined that by increasing incident energy densities during sample fabrication, changes in mechanical and electrical characteristics were examined. The findings were analysed in terms of filler type and energy input, which were discovered to have a slight change in the bending behaviour of SLS components. Furthermore, the impact strength was shown to increase constantly with increasing energy density. Furthermore, whereas the electrical conductivity of spherical Cu-filled parts rose considerably, no significant change was seen in dendritic-shaped Cu-filled parts.

Application of Parallel Difference Tests to Resolve the Axial Activation\u2013Deactivation Profile of Copper\u2013Zinc Oxide Catalyst During Hydrogenation of Methyl Acetate

The deactivation of a copper–zinc oxide catalyst has been studied in a set of parallel tests which covered a range of space-times with equal flow and variable catalyst quantity, from 1/8th bed to full bed. The activation–deactivation trends over time in different segments of the full catalyst bed have been determined by two alternative parallel difference methods. The relative trends in segmental activity over time were followed by (a) using a pre-determined reaction model, and (b) by referencing the axial conversion profile against the initial profile. The trends estimated by both methods were in broad agreement. The results show that the front segment of the catalyst bed experienced a more rapid process of deactivation than the rest of the catalyst bed. This process is consistent with the known susceptibility of this type of catalyst to deactivation by chlorine and sulfur impurities in the feedstock. The main part of the catalyst bed appeared to undergo a process of activation during the first 150 h, followed by a slow process of deactivation which was more rapid during periods at increased temperature. The slow deactivation is most likely associated with sintering of copper particles. The conversion parallel difference method provides a convenient and rapid tool for segmental analysis of parallel life tests, and is well-suited to resolving the impact of a poison front within a catalyst bed.

Mechanical properties and fatigue life detection of copper particle filled polyester composite material under rotating bending load

Mechanical properties and fatigue life detection of copper particle filled polyester composite material under rotating bending load

Highly Active CuOx/SiO2 Dot Core/Rod Shell Catalysts with Enhanced Stability for the Reverse Water Gas Shift Reaction.

Cu-based catalysts are highly active and selective for several CO2 conversion reactions; however, traditional monometallic Cu-based catalysts suffer poor thermal stability due to the aggregation of copper particles at high temperatures. In this work, we demonstrate a crystal engineering strategy to controllably prepare copper/silica (CuOx/SiO2) catalysts for the reverse water gas shift reaction (RWGS) at high temperatures. We show that CuOx/SiO2 catalysts derived from the in situ reduction of pure copper silicate nanotubes in a CO2 and H2 atmosphere exhibit superior catalytic activity with enhanced stability compared to traditional monometallic Cu-based catalysts for the RWGS at high temperatures. Detailed structural characterization reveals that there is a strong interaction between Cu and SiO2 in CuOx/SiO2 catalysts, which produces more Cu+ sites and smaller CuOx nanoparticles. Moreover, CuOx/SiO2 catalysts possess a unique dot core/rod shell structure, which could prevent the aggregation of Cu particles. This structural confinement effect, enhanced CO2 adsorption by Cu+, and small CuOx nanoparticles presumably caused the catalyst's extraordinary activity with enhanced stability at high temperatures.