• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.12 s.243
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• pp.1329-1334
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• 2005

Synthesis of silver nanoparticles by the supersonic nozzle expansion method with corona discharge ions was investigated. Corona discharge ions functioned as seeds for heterogeneous nucleation in the silver nanoparticles formation process and provided silver nanoparticles with electronic repulsive force that prevents aggregation of the particles. For ion ejecting, we used sonic-jet corona discharger. Upon application of the corona discharge ions, the mean diameter of the produced particles was decreased from 12.54 to 6.22nm and the standard deviation was decreased from 5.02 to 3.34nm. In addition, the agglomeration of silver nanoparticles was reduced.

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2575-2580
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• 2010

We present a method for chemically reducing silver alkylcarbamate complex with hydrazine to synthesize silver nanocolloids in an organic solvent using polyvinylpyrrolidone (PVP) as the stabilizer. To determine the optimal conditions for preparing stable silver colloids of controlled size and shape, the silver 2-ethylhexylcarbamate (Ag-EHCB) complex, PVP, hydrazine, and 2-propanol solvent concentrations in the reaction mixture were varied. The initial colloid has a mean particle diameter of 5-80 nm, and it exhibits an absorption band with various shapes in the UV region with a maximum near 420 nm. UV-vis spectroscopy, TEM, and X-ray diffraction techniques were used to investigate the formation and growth process of the metallic silver nanocolloids.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1591-1593
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• 1996

The experimental study was carried out to investigate the effects of metallic particulate filler on the mechanical properties and the thermal properties of epoxy resin system filled with Cu powder. As Cu contents increased, the tensile strength, surface hardness and $T_d$ decreased. $T_g$ increased and decreased at 300 phr. $E_d$ decreased and increased at 200 phr, because the thermal conducting path of filler was formed and dissipated thermal stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.179-186
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• 2006

Dielectrophoresis has received considerable attention for separating nanotubes according to electronic types. Here we examine the effects of surface conductivity of semiconducting single-walled carbon nanotubes (SWNT), induced by ionic surfactants, on the sign of dielectrophoretic force. The crossover frequency of semiconducting SWNT increases rapidly as the conductivity ratio between the particle and medium increases, leading to an incomplete separation of ionic surfactant suspended SWNT at an electric field frequency of 10 MHz. The surface charge of SWNT is neutralized by an equimolar mixture of anionic surfactant sodium dodecyl sulfate (SDS) and cationic surfactant cetyltrimenthylammonium bromide (CTAB), resulting in negative dielectrophoresis of semiconducting species at 10 MHz. A comparative Raman spectroscopy study shows a nearly complete separation of metallic SWNT.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1887-1889
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• 2002

One of the most frequent sources of the accident is metal contaminant in GIS. This paper deals with the characteristics of breakdown voltage of metallic particles using electrodes of various epoxy coating thickness. As experimental results, breakdown voltage of the thickly coated electrode is higher than that of thinly coated electrode. It is considered that resistance of the epoxy coating impedes the development of pre-discharges in the gas.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.5
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• pp.80-86
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• 2005

High velocity oxy-fuel thermally sprayed coating of the WC-Co cermet material is a well-established process for modifying the surface properties of the structural components exposed to the corrosive and wear attacks. The hard WC phase in the coating resists to the wear while the soft metallic Co increases the adhesive and cohesive bonding properties. The coating properties deposited by the HVOF process are greatly dependent on the feedstock materials and processing parameters. The effects of the feedstock material and process coating parameters including the in-flight particle parameters and resultant coating microstructures were observed in this paper.

• KSTLE International Journal
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• v.1 no.1
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• pp.34-42
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• 2000

A method and results of classification of four different metallic wear debris were presented by using their color features. The color image of wear debris was used far the initial data, and the color properties of the debris were specified by HSI color model. Particles were characterized by a set of statistical features derived from the distribution of HSI color model components. The initial feature set was optimized by a principal component analysis, and multidimensional scaling procedure was used fer the definition of a classification plane. It was found that five features, which include mean values of H and S, median S, skewness of distribution of S and I, allow to distinguish copper based alloys, red and dark iron oxides and steel particles. In this work, a method of probabilistic decision-making of class label assignment was proposed, which was based on the analysis of debris-coordinates distribution in the classification plane. The obtained results demonstrated a good availability for the automated wear particle analysis.

• Journal of Welding and Joining
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• v.29 no.5
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• pp.90-94
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• 2011

Ag metallic particles from nano-scale to submicron-scale are combined with organic solvent to provide fine circuits and interconnection. Ink-jet printing with Ag nano particle inks demonstrated the potentials of the new printed electronics technology. The bonding at the interface between the Ag wiring layer and the various substrates is very important. In this study, the details of interfaces in Ag wiring are investigated primarily by microstructure observation. By adjusting the materials and sintering conditions, nicely formed interfaces between Ag wiring and Cu, Au or organic substrates are achieved. In contrast, transmission electron microscope (TEM) image clearly shows interface debonding between Ag wiring and Sn substrate. Sn oxides are formed on the surface of the Sn plating. The formation of these is a root cause of the interface debonding.

• Journal of Powder Materials
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• v.10 no.3
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• pp.181-185
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• 2003

Resistance sintering under ultra-high pressure if developed to fabricate W-Cu composite containing 5 to 80v/o copper. The consolidation was carried out under pressure of 6 to 8 GPa and input power of 18 to 23 kW for 50 seconds. The densification effect and microstructure of these W-Cu composites are investigated. The effect of W particle size on ,sintering density was also studied. The micro hardness was measured to evaluate the sintering effect.

• Journal of Korea Foundry Society
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• v.14 no.1
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• pp.62-74
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• 1994

The concentration and particle size distribution of non-metallic inclusions which suspended in the molten aluminum at $700^{\circ}C$ were measured by using LiMCA apparatus. The result revealed that the number of inclusions increased with increasing the applied current or decreasing the orifice diameter, while decreased with increasing the purity of aluminum. And also, it was found that the number of inclusions increased with increasing the amount of boron added to molten aluminum. This was found to be attributed to the formation of the inclusions of TiB and $V_3B_2$. It was investigated that the average concentration of inclusions in a constant volume of 20ml of molten aluminum was increased in the order of pure molten aluminum, molten aluminum containing 20ppm of boron and molten aluminum used repeatly in the experimental casting in this study.