Electrolytic Copper Powder Research Articles

Investigation of electrophysical and mechanical characteristics of porous copper-carbon composite materials prepared by spark plasma sintering

Copper-carbon composites are attractive materials for electrical applications, such as contact strips for pantographs and collector shoes in electric railways and brushes for motor technology. Because the copper-carbon composites combine the positive characteristics of both components, i.e. thermal and electrical conductivity from the copper and low thermal expansion coefficient and resistivity properties from the carbon. In this report the porous copper-carbon composite material with optimal ratio was prepared and electrophysical, mechanical characteristics were investigated. The specimens were sintered by spark plasma sintering technique which allowed preparing the specimens for short time. The copper-carbon composites samples were prepared with using additional sodium oleate and sodium chloride admixtures for making porous structure. The sintering pressure and temperature are one of the important parameter which influences the properties of the specimens. After sintering for making porous structure the prepared composite samples were treated in boiled deionized water where remained organic materials dissolved in liquid solution. It was shown that the physical, mechanical, electrical properties and porosity degree are directly depends from the initial size of the powders, and material composition. In particular, at different pressure, and applying the optimal copper-carbon ratio (Cu-C) was fabricated porous samples from copper-derived composites where used carbon source and electrolytic grade copper powder. The structural and composition parameters and the obtained composite samples fabricated by spark plasma sintering technique have been investigated by micro-hardness tester, hall system, density tester, optical microscope, XRD and FE-SEM

Effects of particle size and type of conductive additive on the electrode performances of gas atomized AB5-type hydrogen storage alloy

The phase composition, morphology, structure, and state of the surface of gas atomized LaNi4.5Al0.5 alloy powders constituting a fine (≤50 μm), a medium (160–316 μm), and a coarse (630–1000 μm) fraction have been investigated. The electrochemical and storage characteristics of electrodes made from these powders with addition of electrolytic copper powder or a carbon composite (1 wt.% carbon nanotubes + 7 wt.% nanosized carbon black) as a conductive additive have been studied. In the work, X-ray diffraction, scanning electron microscopy, electron-probe microanalysis, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and several electrochemical methods have been used. It has been established that, in the initial state, the coarse-fraction gas atomized powders show a better kinetics of the hydrogen exchange reactions and higher discharge capacity (∼300 mA h/g). It is shown that electrodes made from the powders of all the fractions have a good high-rate discharge capability. Hydrogen diffusion coefficients during discharge of the electrodes made from the alloy powders of all the fractions and conductive additives have been calculated. It is shown that, for LaNi4.5Al0.5 alloy electrodes with the composite carbon additive, the hydrogen diffusion coefficients during discharge computed from data obtained by the electrochemical impedance spectroscopy method agree well with those calculated from cyclic current–voltage curves (2–4 × 10−9 cm2/s).

Effect of Different Concentrations of Sodium Silicate Impregnated on the Performance of Carbon/Copper Composites

Sodium silicate solution-impregnated carbon/copper composites were prepared from electrolytic copper powder, graphite particulate and pitch coke powder through compression molding, carbonization and impregnation. The effect of different concentrations of sodium silicate solution on their mechanical and tribological properties was studied. The results showed that the density of the composites increased monotonically with increasing the concentration of the sodium silicate solution. As did the bending strength and compressive strength, and they reached maxima of 47.78 MPa and 170.06 MPa at 30 wt. % of sodium silicate, respectively. The friction coefficient and wear rate of composite decreased monotonically with increasing the concentration of sodium silicate due to the formation of a lubricating film. The wear mechanism of the impregnated composites was abrasive wear accompanied by slight adhesive wear. The netlike silicon dioxide skeleton reduced the probability of abrasive wear, forming an integrated lubricating film.

Features of The Electrolytic Copper Powder Deposition in the Presence of Polyols

Features of The Electrolytic Copper Powder Deposition in the Presence of Polyols

고압비틀림 공정을 이용한 구리 분말의 치밀화

In this study, electrolytic copper powders were consolidated by high-pressure torsion process (HPT) which is the most effective process to produce bulk ultrafine grained and nanocrystalline metallic materials among various severe plastic deformation processes. The bulk samples were manufactured by the HPT process at 2.5 GPa and 1/2, 1 and 10 turns. After 10 turns, full densification was achieved by high pressure with shear deformation and ultrafine grained structure (average grain size of 677 nm) was observed by electron backscatter diffraction and a scanning transmission electron microscope.

Effect of electrolysis parameters on the morphologies of copper powder obtained at high current densities

The effects of copper ion concentrations and electrolyte temperature on the morphologies and on the apparent densities of electrolytic copper powders at high current densities under galvanostatic regime were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy was used for analyzing the morphology of the copper powders. It was found that the morphology was dependent over the copper ion concentration and electrolyte temperature under same current density (CD) conditions. At 150 mA cm-2 and the potential of 1000?20 mV (vs. SCE), porous and disperse copper powders were obtained at low concentrations of Cu ions (0.120 M Cu2+ in 0.50 M H2SO4). Under this condition, high rate of hydrogen evolution reaction took place parallel to copper electrodeposition. The morphology was changed from porous, disperse and cauliflower-like to coral-like, shrub-like and stalk-stock like morphology with the increasing of Cu ion concentrations towards 0.120 M, 0.155 M, 0.315 M, 0.475 M and 0.630 M Cu2+ in 0.5 M H2SO4 respectively at the same CD. Similarly, as the temperature was increased, powder morphology and apparent density were observed to be changed. The apparent density values of copper powders were found to be suitable for many of the powder metallurgy applications.

Friction and Wear Behavior of SiC<sub>P</sub>/Cu Composite Prepared by Powder Injection Molding

Take electrolytic copper powder and SiC powder as the raw materials, apply powder injection moulding to prepare SiCp/Cu composite, while the test result shows that only Cu and SiC exist in the sintered composite, the SiC particles evenly distribute within the Cu substrate. The friction coefficient and the morphology and elemental composition of the worn composite surface are measured in the fiction and wear test. The result shows that the friction coefficient of composite increase in a more gentle pace with the prolonging of the sliding time; the adhesion and plastic deformation of the worn surface of the composite containing 10 vol.% SiCp is light, and there exists certain abrasive wear; while the worn surface of the composite containing 15 vol.% SiCp show obvious abrasive wear, and there exist dense mechanically mixed layer; in addition to the inherent elements of the composite of Cu, Si and C, the worn surface also contains the elements of Fe and O.

Preparation of electrolytic copper powders with high current efficiency enhanced by super gravity field and its mechanism

Super gravity field was employed to enhance electrolytic reaction for the preparation of copper powders. The morphology, microstructure and size of copper powders were characterized by scanning electron microscopy, X-ray diffractometry and laser particle analysis. The results indicated that current efficiencies of electrolytic copper powders under super gravity field increased by more than 20% compared with that under normal gravity condition. Cell voltage under super gravity field was also much lower. The size of copper powders decreased with the increase of gravity coefficient ( G). The increase of current efficiency can be contributed to the disturbance of electrode/electrolyte interface and enhanced mass transfer of Cu 2+ in super gravity field. Meanwhile, the huge gravity acceleration would promote the detachment of copper powders from electrode surface during electrolytic process, which can prevent the growth of copper powders.

Effect of electrolysis parameters on the morphologies of copper powder obtained in a rotating cylinder electrode cell

Abstract In this paper, electrolysis method was used to produce copper powder particulates. The effects of parametric values, such as current density, concentration of copper ions, electrolyte temperature and rotation speed of cathode, on the morphologies and on the apparent densities of copper powders were examined. These parameters were evaluated by the current efficiency of hydrogen evolution. In addition, scanning electron microscopy (SEM) was used for analyzing the morphology of the copper powders. It was found that the increasing of the current density or the electrolyte temperature decreased the size of the powder particles promoting their morphology into dendritic structure. In contrast, the increase of copper ion concentration or rotation speed of cathode also increased the size of the particles resulting in a cauliflower-like morphology. All powder particles obtained were consisted of agglomerated copper grains. The most important difference was the size and the shape of the copper grains which were notably influenced by the electrolysis parameters. The apparent density values of copper powders were found to be suitable for many powder metallurgical applications. Attempts were also made in the later part of the paper to determine optimum process parameters for the production of electrolytic copper powders.

Development of pitch-based carbon–copper composites

Carbon–copper composites with varying copper to carbon ratio of 0.66–1.5 (by weight) were developed from coal-tar-pitch-derived green coke (as such or modified with natural graphite) as carbon source and electrolytic grade copper powder at different heat treatment temperatures (HTTs) of 1000–1400 °C. The physical, mechanical, and electrical properties differ depending upon the HTT and also on copper to carbon ratio (Cu/C). The composites prepared at HTT of 1100 °C having Cu/C ratio of 0.66 and 0.9 exhibited a high bending strength of 150 and 140 MPa, bulk density of 2.63 and 2.81 gm/cm3, electrical resistivity of 1.6 and 0.96 m Ω cm and shore hardness of 88 and 84, respectively, in spite of well-known inadequate wettability between copper and carbon. Increasing the temperature from 1100 °C for processing of the composites deteriorated the properties mainly due to the loss of copper through melting above 1100 °C as revealed by X-ray, scanning electron microscopy, thermal analysis and EDAX studies.

Effects of copper and Al 2O 3 particles on characteristics of Cu–Al 2O 3 composites

High-energy milling was used for production of Cu–Al 2O 3 composites. The inert gas-atomized prealloyed copper powder containing 2 wt.%Al and the mixture of the different sized electrolytic copper powders with 4 wt.% commercial Al 2O 3 powders served as starting materials. Milling of prealloyed copper powders promotes formation of nano-sized Al 2O 3 particles by internal oxidation with oxygen from air. Hot-pressed compacts of composites obtained from 5 and 20 h milled powders were additionally subjected to the high-temperature exposure in argon at 800 °C for 1 and 5 h. Characterization of processed material was performed by optical and scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), microhardness, as well as density and electrical conductivity measurements. Due to nano-sized Al 2O 3 particles microhardness and thermal stability of composite processed from milled prealloyed powders are higher than corresponding properties of composites processed from the milled powder mixtures. The results were discussed in terms of the effects of different size of starting copper powders and Al 2O 3 particles on the structure, strengthening of copper matrix, thermal stability and electrical conductivity of Cu–Al 2O 3 composites.

Comparative research on high-velocity compaction and conventional rigid die compaction

Experiments were carried out with different apparatus to compact electrolytic copper powders at distinct loading speeds. It appears that green densities of compacts prepared by HVC out-number that by conventional compaction by one percent. Compacts by quasi-static compaction are almost as dense as those by HVC under comparable peak pressure. The relationship between green compact density and peak pressure accords with Hang Pei-yun formula well. Spring-backs of HVC compacts are far smaller than those of conventional compaction and quasi-static compaction. HVC compacts are harder than compacts by conventional compaction and quasi-static compaction when they have the same density.

Effect of electrolyte characteristics on electrowinning of copper powder

This paper is concerned with studying the effect of electrolyte characteristics on the production process of electrolytic copper powder from partially depleted Cu containing synthetic electrolytes by electrowinning technique. The main electrolyte characteristics are temperature, circulation rate, Cu and H2SO4 concentrations, residence time in the cell, and utilization of organic bath additives. The process is positively affected by increasing the values of all of the studied parameters except for the addition of organic bath additives, which causes a negative effect. However addition of organic bath additives remarkably increases the degree of refinement of the produced powders. In most cases pure and fine copper powders were obtained with a dendritic shape, as indicated by scanning electron microscope (SEM) analysis.

Effects of Powder Shape and Processing Parameters on Heat Dissipation of Heat Pipes with Sintered Porous Wicks

The thermal performance of sintered-type heat pipes can be determined from their permeability, capillary pressure, and capillary speed. These characteristics are closely related to the pore structure, which is influenced by the powder used. To investigate the effects of powder shape on the heat dissipation of a heat pipe, gas atomized, water atomized, and electrolytic copper powders were used in this study. The results showed that the gas atomized spherical powder, despite having the lowest porosity, provided the highest permeability and capillary speed and thus the best heat dissipation. The water atomized irregular powder had a smaller permeability, slightly higher capillary speed, and better thermal performance compared to dendritic electrolytic powder. These results suggest that capillary speed is favorable over the permeability for evaluating whether a copper powder is suitable for heat pipe applications or not. The geometrical factor in the Kozeny-Carman permeability equation, which takes into account the effective pore length, pore surface roughness, and tortuosity, could vary from the 250 of the spherical powder to the 3108 of the dendritic powder for compacts with similar permeabilities, showing the effect of powder shape. The processing parameters, compacting pressure and sintering temperature, were also important. Compacts that were loose-powder-sintered at high temperatures showed higher permeability than those using compaction and low temperature sintering due to the differences in the pore surface roughness. These results demonstrate that the thermal performance of heat pipes is closely related to the powder shape and the process used, in addition to the effects of particle size and particle size distribution. [doi:10.2320/matertrans.M2009152]

High-temperature interaction of carbon ferromanganese and copper powders

The thermal synthesis of a master alloy produced from a mixture of carbon ferromanganese and electrolytic copper powders and interaction of the mixture components in various heating conditions are examined. It is shown that the interaction mainly involves the extraction of manganese dissolved in γ-Fe with copper melt followed by the formation (in cooling) of viscous Cu−Mn phases.

Particle shape modification and related property improvements

The increasing sophistication of powder metallurgy processing, together with the greater demands on final product quality have led to an increased demand for metal powders of high quality. In this paper we report the successful preparation of two spheroidized metal powders, —electrolytic copper powder mixed with Al 2O 3 particles and hydrogenation–dehydrogenation (HDH) titanium powder — produced by high speed impact using a particle composite system (PCS). Experimental results show that irregularly shaped metal particles can be processed into spherical particles by use of this process. The spheroidizing process increases bulk density of Ti powder from 1.15 g/cm 3 to 1.73 g/cm 3 and its fluidity index from 46 to 71, improves surface morphology of either single Ti particles or composite Al 2O 3/Cu particles and molding properties of bulk powders. The characteristics of sintered parts made from spheroidized powders are superior to those of products made from the untreated irregular powders.

Properties of copper matrix reinforced with various size and amount of Al2O3 particles

Abstract Copper matrix was reinforced with Al2O3 particles of different size and amount by internal oxidation and mechanical alloying accomplished using high-energy ball milling in air. The inert gas-atomised prealloyed copper powder containing 1 wt.% Al as well as a mixture of electrolytic copper powder and 3 wt.% commercial Al2O3 powder served as starting materials. Milling of Cu-1 wt.% Al prealloyed powder promoted formation of fine dispersed particles (1.9 wt.% Al2O3, approximately 100 nm in size) by internal oxidation. During milling of Cu-3 wt.% Al2O3 powder mixture the uniform distribution of commercial Al2O3 particles has been obtained. Following milling, powders were treated in hydrogen at 400 °C for 1 h in order to eliminate copper oxides formed at the surface during milling. Compaction was executed by hot-pressing. Compacts processed from 5 to 20 h-milled powders were additionally subjected to high-temperature exposure at 800 °C in order to examine their thermal stability and electrical conductivity. Compacts of Cu-1 wt.% Al prealloyed powders with finer Al2O3 particles and smaller grain size exhibited higher microhardness than compacts of Cu-3 wt.% Al2O3 powder mixture. This indicates that nano-sized Al2O3 particles act as a stronger reinforcing parameter of the copper matrix than micro-sized commercial Al2O3 particles. Improved thermal stability of Cu-1 wt.% Al compacts compared to Cu-3 wt.% Al2O3 compacts implies that nano-sized Al2O3 particles act more efficiently as barriers obstructing grain growth than micro-sized particles. Contrary, the lower electrical conductivity of Cu-1 wt.% Al compacts is the result of higher electron scatter caused by nano-sized Al2O3 particles.

Properties of copper matrix reinforced with nano- and micro-sized Al 2O 3 particles

The mixture of electrolytic copper powder with 5 wt.% of commercial Al 2O 3 powder (average particle size: 15 and 0.75 μm, respectively) and the inert gas atomized prealloyed copper powder (average particle size: 30 μm) containing 2.5 wt.% aluminum were separately milled in air up to 20 h in the planetary ball mill. During milling aluminum in the prealloyed copper powders was oxidized in situ by internal oxidation with oxygen from the air forming very fine nano-sized Al 2O 3 particles. The internal oxidation of 2.5 wt.% aluminum generated 4.7 wt.% of Al 2O 3 in the copper matrix. Powders and compacts were characterized by light and scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction analysis. Microhardness and electrical conductivity were also included in measurements. The microhardness of Cu–2.5 wt.% Al compacts was 3.6 times higher than that of compacts processed from electrolytic copper powder. This increase in microhardness is a consequence of a fine dispersion of Al 2O 3 particles and refined grain structure. The average values of electrical conductivity of compacts processed from Cu–5 wt.% Al 2O 3 and Cu–2.5 wt.% Al powders previously milled for 20 h and were 88% and 70% IACS, respectively, which is a rather significant increase if compared with values of 60% and 23% IACS of compacts processed from as-received and non-milled powders. The microhardness of 20-h milled compacts decreases with the heat treatment at 800 °C. Due to the effect of nano-sized Al 2O 3 particles Cu–2.5 wt.% Al compacts show lower decrease in microhardness. The results are discussed in terms of the effect of Al 2O 3 particle size and fine grain structure on the reinforcing of the copper matrix.

Recovery of copper powder from copper bleed electrolyte of an Indian copper smelter by electrolysis

Copper bleed solution generated from an Indian Copper smelter contains high amount of copper and nickel along with several impurities. Attempts have been made to develop a new process for the production of pure copper powder from such streams. The purity of the electrolytic copper powder produced from such bleed streams was found to be 99.93%. Properties such as compact density of the annealed copper powder, flow-ability, particle size, etc. were evaluated and were found to be suitable for the powder metallurgical applications.

Characterization of prealloyed copper powders treated in high energy ball mill

The inert gas atomised prealloyed copper powders containing 3.5 wt.% Al were milled up to 20 h in the planetary ball mill in order to oxidize aluminium in situ with oxygen from the air. In the next procedure compacts from milled powder were synthesized by hot-pressing in argon atmosphere. Compacts from as-received Cu-3.5 wt.% Al powder and electrolytic copper powder were also prepared under the same conditions. Microstructural and morphological changes of high energy milled powder as well as changes of thermal stability and electrical conductivity of compacts were studied as a function of milling time and high temperature exposure at 800 °C. Optical, scanning electron microscopy (SEM) and X-ray diffraction analysis were performed for microstructural characterization, whereas thermal stability and electrical conductivity were evaluated by microhardness measurements and conductometer Sigmatest, respectively. The prealloyed 5 h-milled and compacted powder showed a significant increase in microhardness reaching the value of 2600 MPa, about 4 times greater than that of compacts synthesized from as-received electrolytic copper powder (670 MPa). The electrical conductivity of compacts from 5 h-milled powder was 52% IACS. The results were discussed in terms of the effect of small grain size and finely distributed alumina dispersoids on hardening and thermal stability of compacts.