Ultrafine Copper Powders Research Articles

The Preparation of an Ultrafine Copper Powder by the Hydrogen Reduction of an Ultrafine Copper Oxide Powder and Reduction Kinetics.

Ultrafine copper powders were prepared by the air-jet milling of copper oxide (CuO) powders and a subsequent hydrogen (H2) reduction. After milling, the particle size and grain size of CuO powders decreased, while the specific surface area and structural microstrain increased, thereby improving the reaction activity. In a pure H2 atmosphere, the process of CuO reduction was conducted in one step, and followed a pseudo-first-order kinetics model. The smaller CuO powders after milling exhibited higher reduction rates and lower activation energies compared with those without milling. Based on the unreacted shrinking core model, the reduction of CuO powders via H2 was controlled by the interface reaction at the early stage, whereas the latter was limited by the diffusion of H2 through the solid product layer. Additionally, the scanning electron microscopy (SEM) indicated that copper powders after H2 reduction presented a spherical-like shape, and the sintering and agglomeration between particles occurred after 300 °C, which led to a moderate increase in particle size. The preparing parameters (at 400 °C for 180 min) were preferred to obtain ultrafine copper powders with an average particle size in the range of 5.43-6.72 μm and an oxygen content of less than 0.2 wt.%.

Study on the preparation of ascorbic acid reduced ultrafine copper powders in the presence of different protectants and the properties of copper powders based on methionine protection.

High-purity, monodisperse, and low-oxygen submicron copper powder particles with particle sizes in the range of 100-600 nm were synthesized under alkaline conditions using ascorbic acid (C6H8O6) as a reductant and copper chloride (CuCl2·2H2O) as a copper source. The redox potential of the Cu-Cl-H2O system was obtained by calculations and plotted on pH-E diagrams, and a one-step secondary reduction process (Cu(ii) → CuCl(i) → Cu2O(i) → Cu(0)) was proposed to slow down the reaction rate. The commonalities and differences in the nucleation and growth process of copper powders under methionine (Met), hexadecyl trimethyl ammonium bromide (CTAB), and sodium citrate dihydrate (SSC) as protectants and without the addition of protectants are compared, and the reaction mechanism is discussed. Among them, methionine (Met) showed excellent properties and the Cu2O(i) → Cu(0) process was further observed by in situ XRD. The synthesized copper powder particles have higher particle size controllability, dispersibility, antioxidant properties, and stability, and can be decomposed at lower temperatures (<280 °C). The resistivity can reach 21.4 μΩ cm when sintered at a temperature of 325 °C for 30 min. This green and simple synthesis process facilitates industrialization and storage, and the performance meets the requirements of electronic pastes.

Analysis of the Impact of Electrochemical Properties of Copper-Doped Electrode Membranes on the Output Force of Biomimetic Artificial Muscles.

In this study, a biomimetic artificial muscle electroactive actuator was fabricated using environmentally friendly sodium alginate extract. Ultrasonic agitation was employed to embed ultrafine copper powder within a mesh-like structure formed by multi-walled carbon nanotubes (MWCNTs), aimed at reducing the internal resistance of the composite electrode membrane and enhancing its output force performance. Focused gallium ion beam-scanning electron microscopy observations, energy-dispersive X-ray spectroscopy (EDS) analysis, and surface morphology imaging confirmed the successful incorporation of the ultrafine copper powder into the MWCNT network. Additionally, we designed and constructed an output force measurement apparatus to assess the output performance of biomimetic artificial muscles (BMAMs) doped with varying quantities of ultrafine copper powder. Electrochemical testing results demonstrated that the artificial muscles exhibited optimal performance when doped with a mass of 1.5 g, yielding a maximum output force of 6.96 mN, an output force density of 30.64 mN/g, and a peak average rate of 0.059 mN/s. These values represented improvements of 224%, 189%, and 222% compared to the electrode membrane without the addition of ultrafine copper powder, respectively.

Preparation and Application of Ultrafine Copper Powder

Ultrafine copper powder has the excellent characteristics of both copper and ultrafine particles and has been widely used in industry. Different fields have different requirements for ultrafine copper powder, so various preparation methods have been derived. In this paper, the characteristics of electrolysis, liquid phase reduction, hydrothermal method and polyol method are analyzed. Some new preparation methods with novel ideas are also enumerated. Also, the applications of ultrafine copper powder are described. In electronic industry, ultrafine copper powder can be used in preparing conductive paste of multilayer ceramic capacitor (MLCC) and conductive ink. In catalysts, copper powder can catalyze the reaction alone, can be loaded on other substances and form alloys with other metals for catalysis. In antibacterial materials, copper nanoparticles can distort the DNA of bacteria and interrupt its biochemical process. Finally, the application trend of ultrafine copper powder is prospected, which is helpful to develop new synthesizing methods and applications of ultrafine copper powder.

Synthesis of Multiscale Ultrafine Copper Powder via Radio Frequency Induction Coupled Plasma Treatment

Nano-sized spherical copper powder has important applications in the fields of microelectronic devices, highly efficient catalysts and lubricant additives. In this study, nano-sized and micron-sized spherical copper powders were simultaneously prepared by radio frequency (RF) induction coupled plasma technology. The effects of processing parameters on the powder properties were studied. The results show that by inputting copper powder with D50 = 34.6 μm, nano-sized spherical powder with a particle size of 10–220 nm and micron-sized spherical powder with a particle size of 4.0–144.0 μm were obtained. The ratio of the nano-sized powder reached 86.4 wt.%. The optimal processing parameters are as follows: powder feed rate is 5.5 g/min, carrier gas flow rate is 5–6 L/min and reaction chamber pressure is 15 Psia. When the carrier gas flow rate is 6 L/min, in the plasma zone (&gt;10,000 K), the powder with particle size &lt;42.0 μm is completely vaporized, which forms nano-sized powder during cooling, while the powder with particle size &gt;42.0 μm is melted and partially vaporized, forming a micron-sized powder. The research results provide a new way for engineering the production of copper nano-powder and some other nano-powders with low melting points, such as silver powder, tin powder and so on.

ULTRAFINECOPPER AND NICKEL POWDERS IN THE ELECTRO-CATALYTIC HYDROGENATION OF ORGANIC COMPOUNDS

Ultrafine copper and nickel powders are synthesized by a chemical reduction of the metal cations from their salts in an aqueous ethanol solution without and with the addition of a polymer stabilizer (polyvinylpyrrolidone and polyvinyl alcohol). The structure and morphological features of the prepared metal powders were investigated by X-ray phase analysis and electron microscopy. The electrocatalytic properties of the Cu and Ni powders have been studied in the electrohydrogenation of acetophenone, nitrobenzene, p-nitroaniline, and cyclohexanone. A higher electrocatalytic activity of Cu powders, as well as skeletal copper, was established in the electrohydrogenation of the first three of the listed compounds in comparison with nickel powders, which is explained by the ability of copper cations to be reduced from its oxides in the electrochemical system under investigation. It is shown that the use of polymer stabilizers in the synthesis of Cu and Ni powders contributes to reducing metal particle sizes, but does not increase the electrocatalytic activity of the corresponding metal powders.

Obtaining ultrafine copper electrolytic dendritic powders

In recent years, ultrafine copper powder has become one of the most promising industrial materials due to its unique physical and chemical properties. For example, the high electrical conductivity of the powder allows to use it as a conductive paste or screen for protection against electromagnetic waves. JSC Uralelectromed is a unique enterprise in Russia with multi-tonnage production of copper electrolytic powder. The particle size of the powders varies depending on the brand in a wide range &mdash; from 5 to 250 microns. It is necessary to obtain ultrafine copper powder with an average particle size of 3 to 6 &mu;m. The literature review showed the possibility to obtain ultrapowders by chemical methods and electrolysis from various media. However, the above examples of obtaining ultrafine copper powder differ significantly from the JSC Uralelectromed technology. Therefore, laboratory experiments were performed to optimize the existing electrolysis mode and determine the effect of the electrolyte components concentration and cathode current density on the process of obtaining a powder with a high content of fractions up to 5 &mu;m. Regression equations were compiled, which showed the predominant effect of chloride ions and sulfuric acid, whose growth results in increase in the content of the required fraction. Industrial tests, in addition to the modified electrolysis step, included experiments on the separation of the powder on an air-centrifugal classifier. The range of the optimal specific surface and the average particle size of the initial (before classification) powder was determined. The modes of operation of the air classifier to obtain the required fractional composition of the powder were also determined. The specific surface area of the obtained ultrapowders ranged from 4400 to 5600 cm2/g.

Selective electrochemical extraction of copper from multi-metal e-waste leaching solution and its enhanced recovery mechanism

Recycling activity for waste electrical and electronic equipment is always accompanied with leaching solution containing copper. Its selective extraction is of environmental and economic significance, and is beneficial for subsequent resource purification procedure. Compared with techniques such as chemical precipitation and solvent extraction, potentiostatic electrodeposition is outstanding with the advantage of high selectivity, electron as clean reagent, and minimal chemical usage. However, key factors affecting copper electrodeposition behavior as well as its kinetic process remain unclear, which blocks its further application. In this study, selective copper electrochemical extraction from multi-metal leaching solution of waste liquid crystal display panels is explored. Copper electrodeposition is analyzed from electrochemical and mass transport point of view, and the main results are summarized: (i) copper can be first electrodeposited due to its higher reduction potential compared with indium; (ii) applied potential and agitation are the most influential factors towards space-time yield and current efficiency; (iii) a semi-empirical kinetic model could quantitatively describe the influence of agitation and the time-current-concentration relationship. The model-predicted extraction rate agreed well with experimental data throughout electrodeposition; (iv) electrodeposition experiments show over 95% of copper can be selectively extracted as ultrafine copper powder (~150 nm) at 0.05 V (vs. SHE).

Influence of Polyelectrolytes on the Processes of Structure Formation of Copper Powders

The results of the studies on the synthesis of ultrafine copper powders are described in the article. The mechanisms of formation of ultrafine powders, using water-soluble polyacrylamide and polyvinyl-pyrrolidone polymers, as particle growth inhibitors, are presented. The processes occurring in the presence of water-soluble polymers and their influence on the structure of the obtained ultrafine copper powders are described. The interaction of the matrix of polymer composite materials with filler particles is analyzed. The kinetics of crystallization and transformation of crystalline phases of the powder, due to the process in the presence of water-soluble polymers, as stabilizers of particle growth, are investigated.

Preparation and Properties of Thermally Conductive Copper Paper

A new thermally conductive copper paper was prepared with cellulose pulp and ultrafine copper powder in a traditional paper making process. The thermal conductivity of the copper paper was studied in different weight ratios, and the surface morphology was observed by scanning electron microscopy (SEM). The results showed that the addition of copper powder enhanced the thermal conductivity of copper paper distinctly, with a maximum of up to 0.560 w•m-1•K-1 in the weight ratio of pulp/copper of 1:12, which was an increase of 143% compared with the paper without copper. Scanning electron microscopy images showed that copper papers consisted of copper powder particles distributing compactly on the fiber surface. The tensile index of copper paper decreased compared with the paper without filler. A calendaring process was used to improve the combination between copper particles and fibers and to enhance the thermal conductivity of copper paper.

Preparation of High-Purity Ultrafine Copper Powder in Mass-Production by Chemical Reduction Method: Taguchi Robust Design Optimization

The Taguchi robust design method is implemented for the optimization of experimental conditions in the synthesis of high-purity ultrafine copper powder (HUCP) in mass-production by the chemical reduction method. A reducing agent, reaction temperature, reducing agent weight, and a stirring rate are chosen as the major optimization factors and the conversion rate, particle size, and reaction time are chosen as the desired targets. It is established that the reducing agent and the reaction temperature are the most significant factors that affect the desired targets. Among the selected or designed factors, the optimal conditions for producing the HUCP are: NaH2PO2 · H2O as the reducing agent (level 2), temperature 70°C (level 3), a reducing agent weight of 8.14 kg (level 3), and a stirring rate 300 rpm (level 2). The study results for the three desired targets are in agreement with the prediction made by the Taguchi method. Furthermore, the pure (impurity <0.06%) facecentered cubic structure of the HUCP with 1.51 μm average particle size is extensively characterized and determined by inductively coupled plasma–optical emission spectrometer (ICP–OES), laser particle-size analyzer (DLS), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. This surfactant-free facility method is suitable for the synthesis of highpurity ultrafine copper powder by mass-production method.

Plastic deformation and microstructural evolution during the shock consolidation of ultrafine copper powders

Shock consolidation of ultrafine copper powders at room temperature for bulk nano/ultrafine structured materials is achieved in a gas gun system. The stress states in the powders during the shock consolidation process are analyzed using the finite element method associated with the dynamic densification model (P-α model). The mechanical properties of the shock-consolidated copper are evaluated in terms of hardness, static tensile and compressive strengths, and dynamic compressive strength. The microstructures are characterized using an optical microscope, a scanning electron microscope, and X-ray diffraction (XRD). The XRD patterns are quantitatively analyzed in order to estimate the crystallite sizes and dislocation densities using the Convolution Multiple Whole Profile method. The shock-consolidated specimens were highly densified over 98% of relative density with uniform spatial distributions of high hardness. However, insufficient consolidation due to the tensile stress wave induced by the interactions between shock waves in the powders and due to the ultrafine particles requiring high pressure for good bonding has resulted in several defects in the consolidated specimens. These defects cause tension–compression asymmetry in the shock-consolidated materials. Compared with the tensile results, where fractures occurred at low stresses without plastic deformation due to weak interparticle bonding, the high compressive yield stresses of 600 and 900MPa with large plastic strains are achieved in the static and dynamic compression results, respectively. These high compressive flow stresses are attributed to the extremely high dislocation density and the refinement of the crystallite size via the shock deformations. A microstructure model is proposed for the extremely high dislocation density, where dislocations are generated not only by shock waves but also by plastic flow during the void collapses. The strengths of the shock-consolidated specimen are slightly decreased during the post-shock deformations due to decreases in the excess dislocations despite further refinement of the crystallite size.

Using design of experiments in synthesis of ultra-fine copper particles by electrolysis

Abstract Electrolysis is a method of producing fine and ultra-fine copper powders with high purity. In this paper the effects of current density (i), sulfuric acid concentration [H2SO4], copper (II) ion concentration [Cu2 +] and chloride ion concentration [Cl−] on this process were studied. The considered parameters were varied as follows: current density, 0.25–0.35 A/cm2; [H2SO4], 140–180 g/L; [Cu2 +], 2–8 g/L; and [Cl−], 0–60 ppm. To optimize these parameters, nonregular fractional factorial design of experiments was used. Produced powders were characterized by X-ray diffraction (XRD), a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and a Laser Particle Size Analyzer (LPSA). After surveying the results and analysis of variance, optimized parameters were determined and a mathematical model was presented. The optimum condition was: current density, 0.35 A/cm2; [H2SO4], 140 g/L; [Cu2 +], 2 g/L; and [Cl−] 0 ppm. The predicted particle size at the optimum condition was found to be 0.71 μm which was very close to the experimental value of 0.68 μm.

Preparation of spherical ultrafine copper powder via hydrogen reduction-densification of Mg(OH)2-coated Cu2O powder

A novel process was developed to produce spherical copper powder for multilayer ceramic capacitors (MLCC). Spherical ultrafine cuprous oxide (Cu2O) powder was prepared by glucose reduction of Cu(OH)2. The Cu2O particles were coated by Mg(OH)2 and reduced to metallic copper particles. At last, the copper particles were densified by high-temperature heat treatment. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tap density, and thermogravimetry (TG). It is found that the shape and size distribution of the copper powder are determined by the Cu2O powder and the copper particles do not agglomerate during high-temperature heat treatment because of the existence of Mg(OH)2 coating. After densification at high temperature, the particle tap density increases from 3.30 to 4.18 g/cm3 and the initial oxidation temperature rises from 125 to 150°C.

Preparation of Ultrafine Copper Powders with Controllable Size via Polyol Process with Sodium Hydroxide Addition

A facile polyol process for producing copper powders with controllable size is described here. The copper powders have been readily synthesized by the reduction of copper (II) nitrate trihydrate with the solution of glycerol and sodium hydroxide. The X-ray diffraction, SEM and FESEM were used to characterize the obtained copper powders. The effect of the concentration of NaOH and the reaction temperature were investigated. The sizes and the complete reaction time of the copper powders were decreased at the condition of increasing the concentration of NaOH and the reaction temperature. For example, at the constant reaction temperature of 140°C, the sizes of the obtained powders of the molar ratio of NaOH:Cu(NO 3 ) 2 range from 2:1 to 5:1 were decreased from 1.40 to 0.10 µm as well as the complete reaction times which were reduced from 240 to 17 minutes, respectively. By controlling the process parameters the uniform nano-sized copper powders could be achieved at the optimal condition.

Characterization of ultrafine copper powder prepared by novel electrodeposition method

The auto-evolved ultrafine copper powders were synthesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray powder diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and laser size distribution analyzer (SL) respectively. The formation mechanisms of the powders and the efficiency of the elctrodeposition were discussed. The results show that the as-prepared powders are high-purity copper nanoparticles with the fcc structure taking a mixture of fishbone-like and irregular shapes. When the concentration of Cu2+ increases from 0.03 to 0.09 mol/L, the average size of copper particles increases from 0.92 to 1.80 µm, and current efficiency of electrodeposition linearly changes from 66.5% to 91.3%.

Preparation of ultra-fine copper powder and its lead-free conductive thick film

In this paper, non-agglomerated monodispersed ultra-fine copper metallic powders have been synthesized with chemical reduction method. Fine lead-free glass powders were also prepared by solid synthesis process. Thick film paste prepared by above-mentioned copper metallic powders and lead-free glass powders was applied as conductive paste of MLCC. Mixture of glass and zinc oxide give the thick film a high adhesion strength which is attributed to the rough interface from interfacial reaction between glass and chip, and a good densification. Diffusion of metal between copper thick film and nickel thick film is clear. Ni–Cu solid solution appears under high temperature firing.

Preparation of fine copper powder using ascorbic acid as reducing agent and its application in MLCC

The preparation of ultrafine copper powder with chemical reduction method was investigated. Ascorbic acid was employed as reducing agent. Reaction of CuSO 4·5H 2O with ascorbic acid at 70 °C gives polyhedron monodispersed ultrafine copper powder. The copper powder having excellent dispersibility was prepared when the pH value was controlled at 6 with aqueous ammonia. Influences of reaction temperature on the efficiency of copper powders were also studied. TG/DTG/DTA of copper powder was discussed with thermal analyzer. As-prepared copper powder was applied in BME-MLCC. The micro-structures of end termination and interface were discussed with SEM and polarized light microscope. The copper end termination has high adhesion force, excellent solderibility behavior and resistance behavior to soldering.

Formation Characterization of Ultra-Fine Cu Powder from Cu(OH)&lt;sub&gt;2&lt;/sub&gt; Slurry by Wet Reduction Method

Ultra-fine copper powders with an average size of 150 nm were synthesized from Cu(OH)2 .H2O slurry with hydrazine monohydrate as a reduction agent by using the wet reduction method. Parameters such as temperature, reduction agent feeding rate, stirring rate, stirring speed, Cu(OH)2 concentration, and surfactants were investigated. It was found that the feeding rate of hydrazine monohydrate and the use of surfactants mainly affect the morphology and size of the copper powders along with their dispersion. XRD, PSA, and SEM were used to characterize the prepared particles.

Cementation-induced recovery of self-assembled ultrafine copper powders from spent etching solutions of printed circuit boards

Ultrafine copper powders have been recovered from spent etching solutions of printed circuit boards by cementation on helical-form iron scrap chips. The tested solution is an ammoniacal copper solution containing 135 g/l copper with minor impurities. The influences of contact time, temperature, pH, initial copper concentration and Fe stoichiometry on the yield, purity and grain size and shape of the precipitated copper powders were studied. Ultrafine self-assembled copper nanocubes with high purity of about > 99% was obtained at temperature 25 °C, time 20 min, pH 2, Fe stoichiometry 1 X and initial copper concentration 20 g/l Cu. It was proposed that the precipitation of copper from the solution involved two main processes: (1) adsorption of copper ions on the surface of the iron chips due to the iron oxides present on it and (2) cementation of copper ions onto the metallic iron contained in the chips. Scrap iron chips is seen to be an effective material for copper powder recovery from spent etching solutions in a pure and fine form.