Properties Of Copper Powders Research Articles

Effect of Flow Pattern on Energy Consumption and Properties of Copper Powder in the Electrolytic Process

Because of distinctive properties, such as dendritic structure, high green strength, and low oxygen content, electrolytic copper powder has been widely used in aviation, aerospace, national defense industry and other domains. But at present, energy consumption of the electrolysis process in copper powder production is high, and the current efficiency is only about 90%. Therefore,the decrease in energy consumption of the electrolysis process has become the major bottlenecks in the development of the enterprises. In this paper, a new electrolysis cell with different electrolyte inlet arranged on the cell was manufactured. Then, the effect of flow pattern of electrolyte on the current efficiency, energy consumption and properties of copper powder was investigated. The experimental results showed that the electrolytic process had the higher current efficiency, lower energy consumption and smaller copper powders when the flow rate is 0.5l/min in the paralleled inlet and 1.5 l/min in the traditional inlet. Under the optimal conditions, the current efficiency, energy consumption and copper powder size were 99.10%, 712.90kw∙h/t and 47.80um respectively. This means an obvious rise in current efficiency and decrease in energy consumption compared to traditional feeding method.

Effect of Nanocrystalline TiB2 Addition on Properties of Copper Powder Reinforced Epoxy Composites

The present investigation aims at understanding the influence of nanocrystalline TiB2 powder on thermal and mechanical properties of Epoxy–Cu microcomposites. The nanocrystalline TiB2 powder has been synthesized by SHS and the particle size is in the range of 60–70 nm as revealed from TEM studies. The Epoxy–Cu microcomposites are casted using hand-layout technique and cured under vacuum at room temperature. The nanocomposites have been prepared by addition of 0.2, 0.4, 0.6, 0.8, and 1.0 vol% TiB2 to Epoxy–4 vol% Cu microcomposite. Ductility has increased by 3–4 times in comparison to neat epoxy, and it has increased by 2–3 times in comparison to microcomposites. The Vickers hardness of composites shows an increasing trend with increasing particulate content. XRD studies show the intensity of amorphous epoxy phase decreasing with increasing filler content. The SEM micrographs show a uniform and dispersed distribution of Cu particles in the epoxy matrix. DSC studies reveal the glass transition temperature, Tg, of the epoxy composites to be higher than the neat epoxy and a decreasing trend is observed with increasing filler content.

Comparison of effective parameters for copper powder production via electrorefining and electrowinning cells and improvement using DOE methods

The influences of cupric ion concentration (5–35 g/L), current density (500–2000 A/m2), circulation rate of the electrolyte solution (15–120 mL/min), and temperature (25–60°C) on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated. Two industrial processes, electrorefining (ER) cells with a synthetic electrolyte and electrowinning (EW) cells with an original solution of copper mineral leaching, were utilized to produce copper powders. Finally, the statistical full factorial method of design of experiments (DOE) was employed to investigate the interaction or the main effects of processes. The results show that increasing the copper concentration and temperature can increase the grain size, apparent density, and electrical energy consumption. On the other hand, increasing the current density and circulation rate of the electrolyte can decrease them. This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.

Numerical Simulation on Fluid Field of Different Structure Supersonic Atomizing Nozzle

A supersonic atomizing nozzle is the quite vital component in manufacturing superfine copper powders. The performances of the nozzle have a extremely major influence on the properties of copper powders. Base on the manufacturing technological conditions and the structural features of supersonic nozzle, the mathematical models of fluid field in the supersonic nozzle can be established. According to the method of computational fluid dynamics, the control equation is dispersed. The gridding is created by the means of free division. The finite element equations are set up by Galerkin. Then the impact of nozzle structures on airflow is showed. In the same situation of fluid parameters, the out velocity becomes higher by changing the nozzle structure. The result proves that quadric accelerating nozzle is better.

Characterizations of Plating Structures and Electromagnetic Shielding Properties of the Micron-Sized Flaky Silver-Coated Copper Powder

A new kind of the micron-sized flaky silver-coated copper powder was prepared by electroless silver plating in this paper. Its plating structures were characterized by XRD, SEM and EDS. And a new kind of the electromagnetic shielding composite coatings containing 60 wt% the micron-sized flaky silver-coated copper powders and 40 wt% epoxy resin was prepared. Its electromagnetic shielding properties were analyzed by coaxial transmission line equipment. The study results show the micron-sized flaky silver-coated copper powders are composed of 91.35 wt% Cu and 8.65 wt% Ag and have high width-thickness ratio and crystal structure characteristics. In the frequency range of 0.3-1000 MHz, the shielding effectiveness of the coatings is up to 70.15-77.46 dB and increased an average of 22.18 dB compared with the coatings containing 60 wt% micron-sized flaky copper powders when the coating layer thickness is 300 μm. It is seen that the electroless silver plating method effectively improves the inoxidizability, conductivity and electromagnetic shielding properties of copper powders.

AN OVERVIEW OF PROCESS OPTIONS AND BEHAVIORAL ASPECTS OF THE COPPER VALUES RECOVERED FROM THE COPPER BLEED STREAM OF A COPPER SMELTER DEVELOPED AT THE NATIONAL METALLURGICAL LABORATORY

In the present research, an effort has been made to prepare copper salt/powder from the copper bleed stream generated during the electrowinning of pure copper from the copper anode in a copper smelter. Various approaches have been opted for the complete recovery of copper values such as: evaporation–crystallization, electrolytic process, and direct hydrogen reduction. Physical and chemical properties of copper powder/salt produced from the large-scale experiments from actual plant and model solutions have been evaluated for P/M applications and compared with the standard properties. Thus, mixed crystal suitable for recycling back to the system as a makeup salt containing nickel in a tolerable range could be recovered by evaporation and crystallization of the bleed stream up, to 50%. Copper powder recovery by the electrolysis process at a current density of 700 A/m2 was about 95%. Scanning electron microscope examination showed that the powder was dendritic in nature. On annealing, the purity of the copper powder was found to be 99.95%. The annealed powder had apparent density of 3.04 g/cc, hydrogen loss 0.72%, and acid insoluble as 0.27%. On compaction of <104-µm sized powder, the green density was found to be 8.7 g/cc. Similarly, the recovery of the copper powder obtained from the model copper solution by the hydrogen reduction process was found to be >99% and the annealed powder had an apparent density of 3.50 g/cc, flow rate 35.6 g/min, hydrogen loss 0.195%, purity 99.8%, and green density of 8.57 g/cc while the powder from the actual plant solution was found to have an apparent density of 3.49 g/cc, flow rate 46.0 g/min, hydrogen loss 0.598%, purity 99.4%, and green density 8.57 g/cc for the powder < 100 µm in size. Thus, the properties of copper powder produced by hydrogen reduction and electrolytic route were compared and were found to be suitable for the P/M applications.

A Study on the Pressure Distribution along the Powder-Die Interfaces in Powdered Metal Compaction Process

This paper is concerned with the pressure distribution along the die-powder interface in long parts. The pressure exerted on the interface at various points on the moving and stationary punch, and also on the sidewall of container was investigated by the finite element method. A plasticity theory describing asymmetric behavior of powdered metals in tension and compression was briefly summarized. The yield criterion applied to the sintered powdered metals had been modified for describing this asymmetric behavior. The material properties of copper powders under compaction were also briefly described for the completeness of the paper. The copper powders were selected as a model material in the present study. The main purpose of this study is to investigate the pressure distribution along the interface of tooling quantitatively by the finite element method so that the results could be applied usefully to the design of tooling, especially container design for powdered metal compaction. Geometrical condition for analysis was confined to the Class II components which is very long parts without steps. It was concluded from the simulation results that the pressure exerted on the moving punch increases sharply near the outer circumference of punch and the pressure on the sidewall decreases at a distance from moving punch to fixed punch. It was also seen from the simulation that the pressure on the stationary punch is not significantly built up and decreases toward outer periphery. These trends were seen amplified with severe frictional conditions imposed on the tooling and powder interface.

Effect of surface-active agents on the properties of a copper powder produced by the autoclave method

Carboxyl-containing water-soluble polymers have the strongest influence on the properties of copper powders and are the most effective in reducing their deposits on the inside reactor surface. The optimum SAA consumption rate is 0.003–0.007 g per 1 g of copper. Higher consumption rates intensify the flocculatton of powder particles and increase the carbon content of the powder, which is undesirable, since it makes the latter's subsequent processing more difficult. The carboxyl-containing substances currently produced by industry can be used as SAAs, but, because of their low carboxyl-group content (not more than 45–60%), powders produced in their presence become fairly severely contaminated with carbon owing to destruction of inert radicals. By suitable choice of type of carboxyl-containing SAA it is possible to vary the properties of powders in the following ranges: specific surface 0.02–0.18 m2/g, apparent density 0.9–2.9 g/cm3, mean particle size 20–42μm, and flowability 0–2.6 g/sec.

Control of the properties of copper powders produced by atomization

The properties of an atomized powder subjected to dissolution in sulfuric acid differ from those of the starting powder; chemical pickling can therefore be regarded as a method by which the characteristics of a powder can be modified. Residual salts, in particular sulfates, have a deleterious effect on the quality of resultant parts, and thorough washing is therefore necessary to rid powders of them. There is also a need to develop improved annealing and sintering techniques.

Treatment and properties of copper powders produced by the autoclave method

Treatment and properties of copper powders produced by the autoclave method

Effects of Atmosphere during Water Atomization on Properties of Copper Powders

Molten copper was atomized by using a conical water jet in air and nitrogen to examine effects of atmosphere on properties of powders. With increasing water pressure of more than 100 kg/cm2, geometrical standard deviation σg for particle size distribution increases in nitrogen, but does not change in air. Oxygen contents of powders atomized in nitrogen and air are 0.04 and 0.12 wt%, respectively. Particles are composed of lots of fine spheres which may come to a critical size in the breakup of droplets. The relationship between critical size d and surface tension γ is given by dair/dN2=γair/γN2=0.89. Atomizing at the temperature range of 1200-1270°C under a water pressure of 135 kg/cm2 with a flow-rate of 320 1/min in nitrogen atmosphere, the apparent density attains a minimum, as low as 2.0 g/cm3 for 145/200 mesh powder, and σg a maximum. Compactibility of this kind of powder is improved by annealing at 500-600°C for 1 hr. in hydrogen. Compacts pressed at 1 t/cm2 show a density ratio of 65% and a rattler's value of 1.5%.

Effects of a pulsating electric current on the physicomechanical properties of copper powder

1. It is shown that copper powder can be produced by electrolysis with a periodic current and that such a process has distinct advantages compared with dc deposition. Changing the parameters of the periodic current enables, other things being equal, the apparent density and particle size distribution of the powder to be regulated within wide limits. 2. It was established that raising the value of pulse spacing factor markedly increases the apparent density of copper powder, reduces its particle size, and increases the fine fraction content of the powder and its uniformity compared with powder produced by dc electrolysis. 3. A fine copper powder suitable for direct use without additional milling can be produced by deposition with a periodic current at pulse spacing factor values ranging from three to 10. To obtain maximum current efficiency, the electrodeposition of fine copper powders with a periodic current should be performed at low pulse spacing factor values (q≤4) and high frequencies (f≥4) or at large pulse spacing factors (q≥4) and low frequencies (f≤1).

Effect of surface-active substances on the physicotechnological properties of copper powders produced by autoclave deposition

1. In the autoclave deposition of copper, it is possible to employ various polyacrylamide derivatives and acrylic acid as well as AMF grade polyacrylamide. 2. The particle size and shape of the powder produced can be controlled by varying the type of SAS. 3. Use of various SAS and of repeated consolidation cycles enables the physicotechnological properties of copper powders to be varied between wide limits. Thus, a two-cycle deposition process can yield powders with apparent densities of 0.96–1.82 g/cm3, specific surfaces of 425–1800 cm2/g, and flowabilities of up to 2.27 g/sec; by varying the number of consolidation cycles, it is possible to produce powders with apparent densities of 0.49–2.49 g/cm3, specific surfaces of 340–2260 cm2/g, and flowabilities of up to 4.17 g/sec. 4. The properties of deposited powder can be altered slightly and its carbon and sulfur contents reduced substantially by subjecting it to an annealing operation.

Conditions of preparation and pressing behavior of copper powder

1. The optimum conditions have been established for the preparation of pressing-quality copper powder of increased ductility from a sulfamate electrolyte. 2. A study was made of the effect of heat treatment on the structure and properties of copper powders. It is shown that a powder subjected to heat treatment becomes more ductile. Heat treatment is particularly effective in the case of copper powder prepared from the sulfamate electrolyte.