• Journal of Powder Materials
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• v.21 no.3
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• pp.191-195
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• 2014

This study reports a simple way of fabricating the porous Cu with unidirectional pore channels by freeze drying camphene slurry with Cu oxide coated Cu powders. The coated powders were prepared by calcination of ball-milled powder mixture of Cu and Cu-nitrate. Improved dispersion stability of camphene slurry could be achieved using the Cu oxide coated Cu powders instead of pure Cu powders. Pores in the frozen specimen at $-25^{\circ}C$ were generated by sublimation of the camphene during drying in air, and the green bodies were sintered at $750^{\circ}C$ for 1 h in $H_2$ atmosphere. XRD analysis revealed that the coated layer of Cu oxide was completely converted to Cu phase without any reaction phases by hydrogen heat treatment. The porous Cu specimen prepared from pure Cu powders showed partly large pores with unidirectional pore channels, but most of pores were randomly distributed. In contrast, large and aligned parallel pores to the camphene growth direction were clearly observed in the sample using Cu oxide coated Cu powders. Pore formation behavior depending on the initial powders was discussed based on the degree of powder rearrangement and dispersion stability in slurry.

• Economic and Environmental Geology
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• v.27 no.6
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• pp.549-556
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• 1994

Geochemical studies on gold-bearing quartz veins and wallrocks from the Okgye mine were carried out in order to investigate the primary dispersion patterns of gold and associated elements and to quantify the dispersion width of elements with distance from the gold-bearing quartz veins. Gold-bearing quartz veins occur in basaltic trachyandesite of unknown age. Enrichment of $k_2O$, MnO, Au, As, Rb, Sb, Pb, Zn, Cu, Ag and Cd, and depletion of $Na_2O$ and Sr are found in altered wallrocks. The ratio of $k_2O(k_2O+Na_2O)$, alteration index for trace elements, and Rb/Sr in altered wallrocks are increased, whereas Sr/CaO ratio is decreased with approach to the gold-bearing quartz veins. The widths of primary dispersion range from 17 cm to 155 cm. The relative dispersion width increases in order Au=Cu=Zn=Ag=Cd$k_2O$=Rb and Ba< $Na_2O$ $Na_2O$, As, Sb, Sr, Pb, Au, Cu, Zn, Ag and Cd, and a quadratic function for $k_2O$, MnO, Rb and Ba.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.123-126
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• 2007

In this work, the dispersion behavior of $Y_2O_3$ particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and ${\theta}$ phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of $Y_2O_3$ particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of $Y_2O_3$ particles is probably due to the difference in the val- ues of specific gravity between $Y_2O_3$ particles and primary phases. At eutectic composition, $Y_2O_3$ particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that $Y_2O_3$ particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

• Particle and aerosol research
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• v.6 no.1
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• pp.37-46
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• 2010

Cu nano-colloid was prepared by wire electric explosion process under de-mineralized water and anhydrous ethanol. To control the properties of Cu nano-colloid, experimental conditions such as diameter of Cu wire and applied voltage were changed. The optimal Cu nano-colloid was prepared when the 0.1mm diameter of Cu wire with the applied voltage of 2000 V was used. The shape of Cu particles in colloid was spherical and the XRD result revealed that the phase of Cu particles was cubic phase. About 20nm Cu nanoparticles with high crystallinity were successfully prepared using wire explosion process under anhydrous ethanol and they showed more than 100 hours dispersion stability.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.11a
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• pp.20-20
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• 2000

• Journal of the Korean institute of surface engineering
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• v.50 no.4
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• pp.244-250
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• 2017

Effects of plating conditions (dispersant concentration, plating time, and ultrasonication) on electroless Cu plating on SiC fabric woven by crossing of SiC continuous fibers vertically were studied. The ultrasonic dispersion treatment not only did not improve the dispersion of the SiC fibers, but also did not change the plating thickness. The ultrasonication in the pretreatment step of electroless plating did not improve the dispersion of the fibers, while the ultrasonication in the plating step enhanced the dispersion of the fibers and decreased the thickness of the Cu films. It was possible to control the thickness of the Cu coating layer as well as the dispersion of the fibers in the fabric by changing the plating conditions such as dispersant concentration, plating time, and ultrasonication, but it was very difficult to coat copper on the intersection of vertical fibers in the fabric.

• Economic and Environmental Geology
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• v.30 no.2
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• pp.117-122
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• 1997

Soils collected from pusan metropolitan city were analysed for Cu, Pb, Zn, Cd, Mn to determine their dispersion patterns, mode of occurrences and to investigate the pollution level of heavy metals by urbanization. Element couples of Zn-Cu and Pb-Cd showed good correlation respectively and pollution sources of Zn-Cu, and Pb-Cd were similar. Pb was highly enhanced in dense traffic areas. Soil chemistry around mineralized areas originating from basic host rocks are characterized by high content of Pb, Zn, Cu, Cd, Mn and As.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.05a
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• pp.38-46
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• 1999

Dispersion strengthened Cu alloys have been manufactured by spray forming and also by reactive spray forming, followed by hot extrusion of the spray deposited billets. The size of dispersed particles in the reactive spray formed alloy was much finer than that in the spray formed alloy. That was because the dominant chemical reaction between Ti and B had occurred in Cu-Ti-B alloy melt in spray forming while it had occurred after deposition of droplets in reactive spray forming. The yield strength of the reactive spray formed alloy was greater than that of the spray formed alloy. To understand the mechanism responsible for this observed strengthening, the yield strength of two Cu alloys were analyzed using the dislocation pile-up model and Orowan mechanism, which were fairly consistent with the experimental results. Increase in yield strength of reactive spray formed alloy relative to spray formed alloy was largely attributed to nano-scale TiB dispersoids.

• Polymer(Korea)
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• v.38 no.5
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• pp.671-675
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• 2014

Well-defined star shaped and linear block copolymers were synthesized to study the dispersion stability of copper phthalocyanine (CuPc). We synthesized dispersants using (2-dimethylamino) ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methyl ether methacrylate) (PEGMA) by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP). pDMAEMA-b-pPEGMA copolymers were characterized by GPC and NMR. Furthermore, we studied the effect of the dispersion stability of copper phthalocyanine by controlling the degree of polymerization of PEGMA as a stabilizing group. The 4-arm star shaped polymeric dispersant showed better dispersion stability of CuPc at $25^{\circ}C$ for 7 days.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.656-660
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• 2002

It was investigated that $Al_2$$O_3$/Cu nanocomposite powder could be optimally prepared by dispersion and reduction of Cu oxide, and suitably consolidated by employing pulse electric current sintering (PECS) process. $\alpha$-$Al_2$$O_3$ and CuO powders were used as elemental powders. In order to obtain $Al_2$O$_3$ embedded by finely and homogeneously dispersed CuO particles, the elemental powders were high energy ball milled at the rotating speed of 900 rpm, with the milling time varying up to 10 h. The milled powders were heat treated at $350^{\circ}C$ in H$_2$ atmosphere for 30 min to reduce CuO into Cu. The reduced powders were subsequently sintered by employing PECS process. The composites sintered at $1250^{\circ}C$ for 5 min showed the relative density of above 98%. The fracture toughness of the $Al_2$$O_3$/Cu nanocomposite was as high as 4.9MPa.$m^{1}$2//, being 1.3 times the value of pure $Al_2$$O_3$ sintered under the same condition.