Copper Agglomeration Research Articles

Exploring the multiferroic and water sensing behavior of Cu/Er co-substituted ferrites as key enablers for next-gen hydroelectric cells

Currently, the consumption of energy has enormously risen which in turn causes environmental degradation and this associated degraded environment prompts the research around the devices that produce green energy. Here, we have reported a cost-effective way to produce copper and erbium co-substituted cobalt ferrite nanoparticles [Co1-xCuxFe1.85Er0.15O4, 0.00 ≤ x ≤ 0.09] via sol-gel auto combustion synthesis route. The structural analysis from X-ray diffraction (XRD) measurements confirms the cubic structure of nanoparticles with an average crystallite size of 22 nm. The FT-IR (Fourier transform infrared spectroscopy) studies have revealed the expansion in the octahedral (431-434.85 cm−1) and tetrahedral bands (523-538.82 cm−1) with the increase in the copper content. FESEM-EDX (Field emission scanning electron microscopy) morphology unveils the porous nanostructures with an average particle size around 82.38 nm using ImageJ software. Electrical studies display a net increment in the dielectric constant (ε´) value from 66.908 to 147.97 with an increase in copper concentration from 0 % to 9 % because of the agglomeration of copper and erbium ions at the grain boundaries. It has been also noted that the addition of Cu2+ ions above 6 % into erbium-substituted cobalt ferrite caused a tremendous decrease in the Ms value from 93.75 emu/g to 57.25 emu/g due to weak superexchange interaction upon the co-substitution of copper and erbium ions in cobalt ferrites. The overall value of saturation polarization (Ps) has been improved from 1.009 μC/cm2 to 12.79 μC/cm2 upon increasing the copper concentration in the spinel ferrite. The improvement in ferroelectricity and ferromagnetism in co-substituted cobalt ferrite confirms the presence of multiferroicity in them. The I–V measurements yield prepared hydroelectric cells can deliver a maximum current of 14.772 mA with a power of 11.300 mW for 9 % copper doping in the erbium substituted spinel ferrite while the lowest is reported around 4.08 mA and power of 3.18 mW for only erbium substituted cobalt ferrite. Therefore, the prepared material can be suggested for its useful application in hydroelectric cells.

Copper nanoparticles encapsulated in zeolite 13X for highly selective hydrogenation of CO2 to methanol

High dispersion of active metal is always approved for better catalytic performance in CO2 hydrogenation to methanol. Herein, a strategy was proposed to encapsulate copper nanoparticles in supercages of zeolite 13X, and hence the growth of copper nanoparticles can be controlled. In the present work, catalysts were prepared using ion-exchange and hydrogen reduction at a tiny positive pressure. The results show that as-synthesized catalyst consists of metallic copper and FAU-type zeolite. Excessive amount of copper will destroy zeolite frameworks, and the amount of 5.9 at% is appropriate for considerable BET surface area and ideal copper dispersion. Meanwhile, copper nanoparticles may grow outside from zeolite at high reduction temperatures (≥220 °C), resulting in serious surface area decline and metallic copper agglomeration. Afterwards catalytic tests reveal good stability of the optimal CX-220 catalyst in continuous reactions. The CX-220 achieves remarkably high methanol selectivity of ≥ 95% within wide ranges of reaction temperatures and reaction pressures. Further analyses reveal that the encapsulation of copper nanoparticles reduces micropores and enriches mesopores in zeolite. The apparent activation energy for methanol synthesis over CX-220 catalyst has been lowered to a very low level because of the unique microstructure, and thus the methanol synthesis reaction is dominant in CO2 hydrogenation for dramatic methanol selectivity. Therefore, this work gives important insights and applicable routes for catalysts analyses of CO2 hydrogenation to methanol.

Tailoring microbial response to stainless steel surfaces via electrolyte jet machining and electrodeposition

Electrolyte jet machining (EJM) and electrodeposition present unexploited opportunities for the manufacturing of multiscale structured surfaces. The present work assesses the morphology and antibacterial properties of textured and multiscale stainless steel surfaces produced by EJM with a new 50 mm × 0.3 mm slit nozzle, as well as multiscale surfaces subject to electrodeposition with copper. Characterisation of the surface morphology obtained via EJM with various combinations of current density, machining time and groove spacing is performed to facilitate the selection of representative surfaces for bacterial retention tests. Higher current density with constant applied charge leads to lower surface roughness at constant scanning speed and greater groove depth and width under static conditions. Groove depth is proportional to machining time at constant current density, while a groove pitch of 1.05 mm is found to provide the optimum compromise between maximum groove depth and complete surface coverage. Microscale surface features are found to reduce Escherichia coli and Pseudomonas aeruginosa retention by up to 97% compared to untextured control surfaces, while larger grooves play a role in inhibiting bacterial attachment by inducing turbulence. The presence of copper agglomerates completely eliminates bacterial retention under the tested conditions. The developed process provides a flexible approach to tailoring surface properties for specific applications requiring antimicrobial properties.

Thermal transformation of copper incorporated hydrotalcite-derived oxides and their catalytic activity for ethanol dehydrogenation

Thermal transformation of copper incorporated hydrotalcite-derived oxides is investigated in ethanol dehydrogenation. Among the copper supported catalyst c-10Cu/HT600 prepared by impregnation of thermally treated hydrotalcite at 600 °C with Cu(NO3)2 solution followed by a calcination provides a high catalytic activity, selectivity and stability. XRD, DR-UV, TGA, H2-TPR, CO2-TPD, TEM and XPS techniques reveal that the nature of the copper species depended on the thermal treatment process and support. Such treatment at high temperatures yields a homogeneous dispersion mixed metal oxide. After copper incorporation generated CuAl2O4 spinel structure linked to the copper oxide species can suppress copper agglomeration leading to the catalytic stability. Moreover, the c-10Cu/HT600 catalyst can provide a high activity and high selectivity to acetaldehyde even at low reaction temperatures (200 °C). However, the copper species may agglomerate to form relatively larger clusters upon increasing metal loading leading to the deactivation.

An ammonia-free denitration method: Direct reduction of NOx over activated carbon promoted by Cu-K bimetals

As ammonia slip becomes more serious with the traditional deNOx application, ammonia-free technologies have received more and more attention recently. Cu-K bimetal loaded activated carbon catalysts were prepared by equivalent-volume impregnation method for the direct reduction of NO and showed good NO reduction performance in a wide temperature range under temperature-programmed surface reactions (TPSRs) conditions in aerobic and anaerobic environments. The catalysts were characterized by BET, SEM, XRD, XPS, H2-TPR, Raman and FT-IR techniques and the NO reduction mechanism was analyzed. Experimental results show that the active functional groups formed on the surface of activated carbon are the important intermediate products and play a key role in the reduction reaction. The presence of O2 greatly promotes the formation of the intermediate, C(O) (Oxygen-containing functional groups on the carbon surface), leading to the increase reduction rate of NO. The bimetallic oxides catalysts are obviously effective to directly reduce NO. When the ratio of copper: potassium is 2:1, the NO reduction efficiency is about 90% at 300 °C. The catalytic activity mainly depends on the redox cycle of CuO/Cu2O, and the potassium inhibits the agglomeration of copper on the surface of carbon materials and enhances the catalytic reactivity of Cu.

Fluorine tin oxide-supported copper nanofilms as effective and selective de-nitration electrocatalysts

• Copper nanofilms are electrodeposited directly on FTO/Glass. • Catalyst can re-designed and scaled-up for continuous-flow rate water de-nitration. • Cu@FTO is more efficient and nitrogen-selective than Cu or FTO. • Cu@FTO lowers nitrate to acceptable levels. Due to widespread water pollution with nitrate ion, methods to remove or lower the nitrate concentrations in water are needed. A novel route to reproducibly electro-deposit copper nano-films, with no need for additional treatments or additives, from acidic media onto fluorine-doped tin oxide/glass (Cu@FTO) is described. The films involve elemental copper nanoparticles inside copper agglomerates of larger sizes. Within 2 h, at ambient potential (−1.8 V), the Cu@FTO electrode reduces aqueous nitrate ions (∼40%) more effectively than the benchmark bare Cu metal sheet (∼11%). The Cu@FTO is also more selective to N 2 production (∼30%) compared to bare Cu sheet with only (∼1.1%). Furthermore, the Cu@FTO effectively functions for 7 h and continues to bring down the nitrate ion concentration from 200 ppm to acceptable levels (less than 60 ppm), reproducibly in 5 attempts. The results are promising for future water de-nitration processes using easy-to-prepare Cu@FTO electrodes, aiming at producing electrodes for continuous flow reactors at larger scale.

Calcium and copper substitution in stoichiometric and La-deficient LaFeO3 compositions: A starting point in next generation of Three-Way-Catalysts for gasoline engines

Calcium and copper substitutions, in A-site and B-site respectively, of parent stoichiometric LaFeO3 and La-deficient La0.7FeO3 perovskites led to significant improvements in the kinetics of CO and propene oxidation in typical three-way operating conditions. La-deficient La0.7Fe1-yCuyO3 perovskites were found more prone to surface copper oxide segregation leading to more active extra-framework copper oxide species in CO oxidation. Optimal performances were obtained on La0.7Fe0.8Cu0.2O3 composition. At higher Cu content, strong copper agglomeration leads to deactivation. More stable systems were obtained on dual substituted samples thanks to calcium substitution stabilizing copper inside the perovskite lattice and slowing down subsequent surface agglomeration. Rate enhancements in propene oxidation is observed on A-site deficient La0.6CaxFe0.8Cu0.2O3 with x ≤ 0.2 but a sharp loss in rate is observed on stoichiometric La0.6Ca0.4Fe0.8Cu0.2O3 perovskite explained by a progressive shift from suprafacial to intrafacial mechanism involving in this latter case the redox Fe4+/Fe3+ couple and lattice oxygen species.

The Effect of a Small Copper Addition on the Electrical Conductivity of Aluminum

Aluminum powder blended with 10, 20, and 30 wt% of copper powder is compacted at 400 °C by four reciprocal extrusion passes. Simultaneous compaction and strengthening result in more than double increase in mechanical strength characteristics for 20 and 30 wt% of copper and a significant increase in electrical conductivity for 30 wt% of copper. This phenomenon is investigated here by the expansion of the “effective media” model for a random binary mixture so that it includes the presence of intermetallic phases and considers the distribution of large copper agglomerates.

Impact of temperature on the physicochemical, structural and biological features of copper-silica nanocomposites.

Classical wet chemical synthesis was used to fabricate a hybrid composite that contained copper nanoparticles (average size ∼1 nm), which were embedded into a silicon oxide carrier. The structural and chemical alternations in the copper-functionalized silica were investigated in systems that were sintered at 573 K, 873 K, 1173 K, and 1473 K. A general trend, which was associated with the transformation of metallic copper with a cubic structure into copper(II) oxide with a monoclinic structure in the heat-treated systems, was found. XPS and FTIR spectroscopies also revealed the presence of copper(I) oxide, which formed a shell around the CuO. SEM and TEM showed gradual densification of the hybrid system at ever higher sintering temperatures, which corresponded with the gradual copper agglomeration. A temperature of 873 K was determined to be the temperature at which amorphous silica was transformed into cristoballite and tridymite, as well as the formation of a bulk-like copper structure. In relation to the physicochemical and structural data, high antimicrobial features that had a relatively low toxicity effect on the normal human fibroblasts (NHDF) below 250 mg/L was found for the initial copper-silica composite and the samples that were sintered at 573 K. In turn, a significant decrease in the biological impact was observed in the samples that were sintered at temperatures above 573 K. As a result, the paper discusses the model of structural modifications in copper-silica nanocomposite concerning their biological impact that was developed.

Oxide-Free Copper Pastes for the Attachment of Large-Area Power Devices

Pastes based on copper (Cu) nanoparticles (NPs) are promising electronic-packaging materials for the attachment of high-power devices. However, the rapid oxidation of nanostructured Cu requires the use of reducing agents during processing, which makes it less suitable for attaching large-area dies (> 4 mm2). Recently, the functionalization of Cu-NP surfaces with a mixture of amines prevented oxidation, allowing for sintering without the need for reducing agents. Here we investigate the sintering mechanisms involved during die attachment using pastes of passivated Cu NPs, with particular focus on the critical role of the carrier solvents. Using 1-nonanol or 1-decanol as solvents, we first demonstrate the absence of Cu-oxide phases in the pastes after fabrication and the stability of the resulting nanostructured copper for as much as 30 min in air. By measuring the evolution of the electrical characteristics of the paste during drying and sintering, we show that electrically conductive agglomerates form among the NPs between 141°C and 144°C, independent of the carrier solvent used. The carrier solvent was found to affect mainly the densification temperature of the copper agglomerates. Because they lead to uniform sintering of the material, Cu pastes based on solvents with a low boiling point and high vapor pressure are preferable for attaching dies with area greater than 25 mm2. We show that dies with an area as large as 100 mm2 can be attached using a Cu paste based on 1-nonanol. These pastes enables the formation of temperature-resistant bonding for high-power devices using a simple and cost-effective approach.

Electroless Cu plating on the microstructure and hardness of Al–Cu powder metallurgy alloy

Oxide film and agglomeration are two obstacles against the property improvement of the Al-based powder metallurgy (P/M) alloy. In the work, the aluminum powders treated by the electroless Cu plating were processed by powder metallurgy technology. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS) were used to investigate the phase, microstructure and composition of the Cu-plated aluminium powder and the sintered bulks. For comparison, the P/M Al–Cu alloy were also prepared from the premixed powders by the traditional mixing processing. The results show that the electroless Cu plating can eliminate the agglomeration of copper in the sintered compact. The removal of the oxide film via the electroless plating provides more effective surface contact than could be obtained by the conventional process. A CuAl2 phase with a network structure formed in the sintering process. This phase contributed to the uniform microstructure and hardness improvement.

Latent Fingerprint Visualization and Subsequent DNA Extraction Using Electron Beam Evaporation of Metallic Ultra-Thin Films

Background: Proper detection and subsequent extraction of biological evidence are crucial for crime scene reconstruction. Vacuum metal deposition is currently an effective technique used in latent fingerprint development. However, the established procedures commonly undergo a direct plasma bombardment, a high ablation fluence and/or a high temperature process in vacuum metal deposition system. Method: In this work, electron beam evaporation (EBE) was used to investigate the development of latent fingerprints and subsequent DNA extraction of biological evidence. Gold or copper is preferentially nucleated on the background surfaces rather than the fingerprint residues due to the difference of the nature of the surface, which indicates that the gold / copper and copper agglomerates are binding to the fingerprint valleys not the ridges of the fingerprint, revealing bright patterns with excellent ridge detail clarity on black surfaces. Result: It is demonstrated that the co-extraction of the latent fingerprints and DNA is attributed to electron beam evaporated one-step process with relatively low energy bombarding energetic species and neutral particles, less possibility of contamination and without toxic and fluorine-based gases. Conclusion: Our results demonstrate that EBE is a promising technique for the latent fingerprints and DNA co-extraction.

Influence of humic acid and dihydroxy benzoic acid on the agglomeration, adsorption, sedimentation and dissolution of copper, manganese, aluminum and silica nanoparticles - A tentative exposure scenario.

This work focuses on kinetic aspects of stability, mobility, and dissolution of bare Cu, Al and Mn, and SiO2 NPs in synthetic freshwater (FW) with and without the presence of natural organic matter (NOM). This includes elucidation of particle and surface interactions, metal dissolution kinetics, and speciation predictions of released metals in solution. Dihydroxy benzoic acid (DHBA) and humic acid adsorbed rapidly on all metal NPs (<1 min) via multiple surface coordinations, followed in general by rapid agglomeration and concomitant sedimentation for a large fraction of the particles. In contrast, NOM did not induce agglomeration of the SiO2 NPs during the test duration (21 days). DHBA in concentrations of 0.1 and 1 mM was unable to stabilize the metal NPs for time periods longer than 6 h, whereas humic acid, at certain concentrations (20 mg/L) was more efficient (>24 h). The presence of NOM increased the amount of released metals into solution, in particular for Al and Cu, whereas the effect for Mn was minor. At least 10% of the particle mass was dissolved within 24 h and remained in solution for the metal NPs in the presence of NOM. Speciation modeling revealed that released Al and Cu predominantly formed complexes with NOM, whereas less complexation was seen for Mn. The results imply that potentially dispersed NPs of Cu, Al and Mn readily dissolve or sediment close to the source in freshwater of low salinity, whereas SiO2 NPs are more stable and therefore more mobile in solution.

Copper Chloride Catalysis: Do μ4-Oxido Copper Clusters Play a Significant Role?

Copper chloride catalysis is a well-established field in organic and inorganic chemistry. However, in most cases a detailed mechanistic understanding of the individual reaction steps and identification of reactive intermediates are still missing. The present study reports the results of spectroscopic and spectrometric measurements that support formation of copper agglomerates during catalytic processes. The composition of CuCl2·2H2O in several coordinating solvents and the influence of basic coreagents such as NaO(t)Bu and K2CO3 on the structure in the solid state as well as in solution were investigated. Several experiments involving crystal structure determination, IR spectroscopy, and ultra-high-resolution cryospray-ionization mass spectrometry were performed. The crystal structures of [CuCl2(H2O)]·0.5(CH3)2CO (1), [Cu2(CH3CN)2Cl4] (2), [Cu3(CH3CN)3Cl6] (3), [Cu3Cl6(THF)4] (4), [Cu(DMSO)2Cl2] (5), (H2N(CH3)2)2[CuCl3] (6), and [Cu4OCl6(THF)(urea)3]·3THF·urea (8) are reported herein. It can be clearly demonstrated that μ4-oxido copper clusters of the formula [Cu4OCl6(solvent)4] are the main product from the reactions of CuCl2·2H2O and basic coreagents. As a final result of these experiments, it can be stated that μ4-oxido copper clusters most likely play an important role in the mechanism of copper chloride-catalyzed reactions.

Effect of Aging in Acidic Condition on Mechanical Properties of Copper (II) Oxide Added LDPE Composites

In this work, the effect of aging duration time and copper (II) oxide loading level on the physico-mechanical properties of copper (II) oxide added LDPE composites have been investigated. The addition of copper (II) oxide particles in LDPE matrix has significantly decreased the tensile strength of LDPE composites. The occurrence of copper (II) oxide particles in LDPE matrix could reduce the matrix continuities of copper (II) oxide added LDPE composites by the agglomeration of copper (II) oxide particles. This could further cause the applied straining stress unable to be effectively transferred throughout the whole polymer matrix. The increasing of aging time duration up to 8 days has slightly reduced the tensile strength of all copper (II) oxide added LDPE composites. The increasing of copper (II) oxide loading level has significantly decreased the elongation at break of LDPE composites. This is due to poor interfacial adhesion between copper (II) oxide particles and LDPE matrix could further restrict the mobility of LDPE chains under straining stress and thus decrease the elongation at break.

Experimental study on bounce of submicron agglomerates upon inertial impaction

This paper evaluated the break-up and bounce of iron oxides and copper agglomerates during inertial impaction. The results were compared with data acquired earlier with TiO2 agglomerates. It was found that the total mass-based bounce fraction of the iron oxide agglomerates did not increase monotonically with the impaction velocity. The reason behind this appeared to be the transition from non-fragmentation to fragmentation as the impaction velocity increased. The copper agglomerates were found to de-agglomerate but not bounce in these experiments. Different impaction surface materials were also examined to determine their effect on the impaction process, but only small variations were found in the bounce fractions or the size of the particles after bounce and deagglomeration.

Implication of low temperature and sonication on electrocrystallization mechanism of Cu thin films: a kinetics and structural correlation

The effect of an ultrasonic environment during electrodeposition of copper on graphite at various electrolyte temperatures of 25, 20, 15, 10 and 5 °C is reported in this investigation. Resulting Cu deposits formed by potentiostatic deposition were characterized by electrochemical methods, scanning electron microscopy and atomic force microscopy. It was found that in presence of ultrasound the deposition kinetics was mainly dominated by the charge transfer. Copper nucleated according to 3D instantaneous mechanisms for all temperature ranges. The extent of nucleation was found to be increased at low temperatures. Diffusion coefficients and nuclei population density were calculated for each temperature range. Sonicated deposits with good surface coverage were found to consist of spherical copper agglomerates of nanosized particles.

Catalytic cleavage of lignin β-O-4 link mimics using copper on alumina and magnesia–alumina

Copper on γ-alumina and on mixed magnesia–alumina, Cu/MgO–Al2O3, catalyse the hydrodeoxygenation (HDO) of β-O-4 lignin-type dimers, giving valuable aromatics. The typical selectivity to phenol is as high as 20%. By changing the support's acidity we can modify the dispersion of copper. Interestingly, more HDO occurs with larger copper agglomerates than with finely dispersed particles. The presence of copper also increases the selectivity of the HDO cleavage. Three different pathways are hypothesized for the reaction on the catalyst surface. Thus, copper activates ketones more and especially more selective towards cleavage than their corresponding alcohols. DFT calculations of bond dissociation energies correlate well with this experimental observation. Excitingly, ethylbenzene is formed in proportional amounts to phenol, showing that these catalysts can reduce the oxygen content of lignin-type product streams. Considering its low price and ready availability, we conclude that copper on alumina is a promising alternative catalyst for lignin depolymerization.

The mechanism of electroreduction of nitrate ions on a hybrid electrode nanodispersed copper-MK-40 membrane

Based on a MK-40 sulfocation-exchange membrane, a hybride electrode material containing nanodispersed copper is prepared. The methods of scanning electron microscopy and X-ray diffraction (XRD) analysis reveal the formation of copper agglomerates measuring 250–470 nm and consisting of individual particles of 20–30 nm. The procedure of multistage chemical deposition of copper into the ion-exchange carrier makes it possible to obtain a continuous cluster of metal particles which determines the electron conducting properties of the resulting hybrid material. The electrochemical activity of the nanocomposite electrode is studied in the reaction of nitrate ion electroreduction. Nanodispersed copper deposited into the membrane is shown to intensify the electroreduction of nitrate ions by a factor of 1.5–2 as compared with a compact copper electrode. The electroreduction of nitrate ions on compact copper is shown to involve 6 electrons, whereas the electroreduction on the nanocomposite involves 8 electrons. The electroreduction products of nitrate ions are identified by the IR spectroscopy method.

Use of delaminated hectorites as supports of copper catalysts for the hydrogenolysis of glycerol to 1,2-propanediol

Delaminated hectorites were used as supports of copper catalysts for the hydrogenolysis of glycerol. Catalytic results were compared with those obtained for copper catalysts prepared with other supports: hectorites, synthesized by conventional heating and with microwaves, and silicate-bearing hectorite. Copper was introduced by impregnation, solids blend with ultrasounds, and ion-exchange methods. Catalytic tests were carried out in liquid phase at 40 bar, 473 K and stirring of 400 rpm. The selectivity to 1,2-propanediol was very high for all catalysts (>90%). The highest conversion (61% after 8 h of reaction) was obtained for a delaminated hectorite impregnated with 40 wt.% of copper. This was related to the highest surface area of this delaminated hectorite together with its lower hydrophilic character (lower C.E.C.), which made possible to best control copper agglomeration. In fact, copper dispersion increased during reaction for this catalyst.