• Journal of the Korean Electrochemical Society
• /
• v.13 no.4
• /
• pp.270-276
• /
• 2010

Nickel-copper foam electrodes with pore gradient micro framework and nano-ramified wall have been prepared by using an electrochemical deposition process. Growth habit of nickel-copper co-deposits was quite different from that of pure nickel deposit. In particular, the ramified structure of the individual particles was getting clear with chloride ion content in the electrolyte. The ratio of nickel to copper in the deposits decreased with the distance away from the substrate and the more chloride ions in the electrolyte led to the more nickel content throughout the deposits. Compositional analysis for the cross section of a ramified branch, together with tactical selective copper etching, proved that the copper content increased with approaching central region of the cross section. Such a composition gradient actually disappeared after heat treatment. It is anticipated that the pore gradient nickel-copper nanostructured foams presented in this work might be a promising option for the high-performance electrode in functional electrochemical devices.

• Applied Microscopy
• /
• v.36 no.2
• /
• pp.47-55
• /
• 2006

In this paper a transmission electron microscope (TEM) observation of fine Cu precipitates distributed randomly in Al-2.5Cu-1.5Mg wt.% alloy is first reported. This new observation happened to occur when an ion milling was peformed to remove oxides on the specimen, particularly, aged 100 hours at $150^{\circ}C$. Meanwhile the oxides were identified to be $Cu_2O$ particles. For this work involved with analysis of diffraction rings, the formulation of the electron diffraction rings pattern for powder particles was made. Finally the significance of this unexpected ion milling effort on the alloy was discussed

• Transactions of Materials Processing
• /
• v.7 no.1
• /
• pp.66-71
• /
• 1998

The present study is concerned with the hydrostatic extrusion process of copper-clad aluminium bar to investigate the bonding conditions as well as the basic flow characteristics. Considering the bonding mechanism of bi-metal contact surface as cold pressure welding the normal pressure and the contact surface expansion are selected as process parameters governing the bonding conditions, in this study the critical normal pressure required for the local extrusion-the protrusion of virgin surfaces by the surface expansion at the interface-is obtained using a slip line method and is then used as a criteron for the bonding. A rigid plastic finite element method is used to analyze the steady state extrusion process. The interface profile of bi-metal rod is predicted by tracking the paths of two particles adja-process. The interface profile of bi-metal rod is predicted by tracking the paths of two particles adja-cent to interface surface. The contact surface area ration and the normal pressure along the interface are calculated and compared to the critical normal pressure to check bonding. It is found that the model predictions are generally in good agreement with the experimental observations. The compar-isons of the extrusion pressure and interface profile by the finite element with those by experi-ments are also given.

• Journal of Advanced Marine Engineering and Technology
• /
• v.36 no.7
• /
• pp.869-875
• /
• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9 ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.12 no.4
• /
• pp.825-832
• /
• 1988

An experiment was performed to study the heat pipe phenomenon of porous media heated above at one-dimensional steady state for the range of heat flux, 300 W/ $m^{2}$ ~ 2000w/ $m^{2}$. Glass beads, sand, and copper particles were used as porous media and distilled water was used as a working fluid. Result of experiment shows that the length of the two-phase zone increases with the decreasing particle size for the same heat flux. At relatively lower heat flux the length of the two-phase zone increases with the increasing heat flux, which contradicts the result of earlier work. However, its length remains nearly constant when the heat flux increases above a certain value. The length of the two-phase zone is proportional to the product of the heat flux by the hydrostatic capillary height under the limited value on heat flux, that is, $l_{t}$ = A(q. $l_{cap}$)+B, q.leg.1/A(C+B/ $l_{cap}$) where A is 1.7*10$^{-4}$ $m^{2}$/w, B is 1.9*10$^{-2}$ m, and C is 0.43 for copper particles and 0.31 for glass beads and sand.d.d.d.

• Journal of the Korean Society of Visualization
• /
• v.10 no.3
• /
• pp.16-20
• /
• 2012

In the past decades, extensive studies on convection heat transfer on internal flow have been conducted by using high specific surface area, by increasing heat transfer coefficient and swirl flow, and by improving the transport properties. In this study, we applied a tangential slot swirl generator to improve heat transfer in a horizontal circular copper tube. The Al-Mg particles (approximately $100{\mu}m$ to $130{\mu}m$) were employed for this experimental work. The copper tube was heated uniformly by winding a heating coil with a resistance of 9ohm per meter for heat transfer. Using Al-Mg particles, experiments were performed in the Reynolds number range of 5,000 to 13,130, with and without swirl. Experimental data transfers or comparisons between Nusselt numbers with and without swirl along the test tube and Reynolds numbers are presented. The Nusselt number is improved by increasing Reynolds numbers or swirl intensities along the test tube.

• Particle and aerosol research
• /
• v.8 no.1
• /
• pp.37-43
• /
• 2012

In this study, we designed a 'spark in liquid' system. The spark discharge between two electrodes were used to generate particles by using sufficient temperature to evaporate a part of electrodes. The power supply system provides a continuous spark discharge by discharging of the capacitor to ionize the electrodes in liquid. The DC spark discharge system operates with 1-10 kV voltage. Processed copper and graphite rods were used to both electrodes with 1-3 mm diameter. There are several variables which can control the particle size and concentration such as gap distance between electrodes, applied voltage, operating liquid temperature, electrode type and liquid type. So we controlled these variables to confirm the change of particle size distribution and concentration of particles contained in liquid as wt%. 'spark in liquid' system is expected to apply nanoink by control of concentration with analysis of characteristics.

• Korean Journal of Veterinary Research
• /
• v.30 no.1
• /
• pp.85-91
• /
• 1990

This study was designed in order to investigate the effect of copper sulfate to the ultrastructural changes of the hepatocytes in Sprague Dawley rats. The animals were administered with copper sulfate (10mg/kg B.W.), which was dissolved in normal saline. The solution was injected into abdominal cavity every day. The animals were sacrificed at the 6th, 12th, and 24th day from the beginning of administration. The specimens obtained from the liver were observed with electron microscope and significant changes were as follows. 1. A prominent dilatation and disruption of the cisternae of rough endoplasmic reticulum were recognized. Also, the detachment of membrane bound ribosomes was shown. 2. The proliferation of smooth endoplasmic reticulum and the depletion of glycogen particles were noted. 3. The increase of primary lysosomes and autophagic vacuoles was obserbed. 4. The dilatation of mitochondrial cristae was obserbed. And it was irregulary scattered in the stroma of mitochondria. 5. The atrophy of microvilli in the bile canaliculi and space of Disse was prominent. 6. Membrane of hepatocytes was damaged and significant hydrophic degeneration was obserbed in the perisinusoidal regions. 7. The damage of Fat-storing cells was more significant than that of hepatocytes.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.3
• /
• pp.472-479
• /
• 2013

The conductive polymer composites recently became increasingly to many fields of industry due to their electrical properties. To understand these properties of composites, electrical properties were measured and were studied relatively. Electrical conductivity measurements showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in composites made of a conductive filler and an insulating matrix. It has been showed both experimentally and theoretically that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. This paper was to study epoxy resin filled with copper. The experiment was made with vehicle such as epoxy resin replenished with copper powder and the study about their practical use was performed in order to apply to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 3.065~13.325 in using copper powder. The weight loss of conductive composites happened from $350^{\circ}C{\sim}470^{\circ}C$.

• Corrosion Science and Technology
• /
• v.16 no.5
• /
• pp.247-256
• /
• 2017

The feasibility of using hydrazine for inhibiting pitting corrosion in copper sprinkler tubes was investigated by examining microscopical and structural evolution of corrosion by-products with SEM, EDS, and XRD. Hydrazine removed dissolved oxygen and reduced CuO and $Cu_2O$ as well. The stable phase was changed from CuO to $Cu_2O$ or Cu depending on hydrazine concentration. Hydrazine concentration of 500 ppm could convert all CuO corrosion by-products to $Cu_2O$. In a tightly sealed acryl tube filled with aqueous solution of 500 ppm hydrazine, octahedral $Cu_2O$ particles were formed while plate-like structures with high concentration of Cu, O, N and C were formed near a corrosion pit. The inside structure of a corrosion pit was not altered by hydrazine aqueous solution. Uniform corrosion of copper was almost completely stopped in aqueous solution of 500 ppm hydrazine. Corrosion potential of a copper plate was linearly dependent on log (hydrazine concentration). The concept of stopping pitting corrosion reaction by suppressing oxygen reduction reaction could be verified by applying this method to a reasonable number of real sprinkler systems before full-scale application.