• Journal of Powder Materials
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• v.17 no.4
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• pp.342-346
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• 2010

In the present work, water-based gold nanofluids were synthesized by the solution plasma processing (SPP). The size distribution and the shape of gold nanoparticles in the nanofluids were investigated using high resolution transmission electron microscopy (HR-TEM). The dispersion stability of gold nanofluids was characterized using zeta potential, as well. The thermal properties of gold nanofluids were measured by utilizing lambda measurement device. Nanofluids containing nanoparticles with $64.0{\pm}42.1\;nm{\sim}18.10{\pm}5.0\;nm$ in diameter were successfully synthesized. As diameter of nanoparticles decreased, dispersion stability of nanofluids increased and the enhanced ratio of thermal conductivity increased. The nanofluid with nanoparticles of $18.10\;{\pm}\;5.0\;nm$ in diameter showed approximately 3% improvement in thermal conductivity measurement and this could be due to the enhanced Brownian movement.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.8
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• pp.833-837
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• 2015

Li-air batteries have a promising future for because of their high energy density, which could theoretically be equal to that of gasoline. However, substantial Li-air cell performance limitations exist, which are related to the air cathode. The cell discharge products are deposited on the surfaces of the porous carbon materials in the air electrode, which blocks oxygen from diffusing to the reaction sites. Hence, the real capacity of a Li-air battery is determined by the carbon air electrode, especially by the pore volume available for the deposition of the discharged products. In this study, a simple and fast method is reported for the large-scale synthesis of carbon nanoballs (CNBs) consisting of a highly mesoporous structure for Li-air battery cathodes. The CNBs were synthesized by the solution plasma process from benzene solution, without the need for a graphite electrode for carbon growth. The CNBs so formed were then annealed to improve their electrical conductivity. Structural characterization revealed that the CNBs exhibited both an pore structure and high conductivity.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.17-18
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• 2011

Plasma in liquid phase has attracted great attention in the last few years by the wide domain of applications in material processing, decomposition of organic and inorganic chemical compounds and sterilization of water. The plasma in liquid is characterized by three main regions which interact each - other during the plasma operation: the liquid phase, which supply the plasma gas phase with various chemical compounds and ions, the plasma in the gas phase at atmospheric pressure and the interface between these two regions. The most complex region, but extremely interesting from the fundamental, chemical and physical processes which occur here, is the boundary between the liquid phase and the plasma gas phase. In our laboratory, plasma in liquid which behaves as a glow discharge type, is generated by using a bipolar pulsed power supply, with variable pulse width, in the range of 0.5~10 ${\mu}s$ and 10 to 30 kHz repetition rate. Plasma in water and other different solutions was characterized by electrical and optical measurements. Strong emissions of OH and H radicals dominate the optical spectra. Generally water with 500 ${\mu}S/cm$ conductivity has a breakdown voltage around 2 kV, depending on the pulse width and the repetition rate of the power supply. The characteristics of the plasma initiated in ultrapure water between pairs of different materials used for electrodes (W and Ta) were investigated by the time-resolved optical emission and the broad-band absorption spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depend on the electrode material, but have been independent on the polarity of the applied voltage pulses. Recently, Coherent anti-Stokes Raman Spectroscopy method was employed to investigate the chemistry in the liquid phase and at the interface between the gas and the liquid phases of the solution plasma system. The use of the solution plasma allows rapid fabrication of the metal nanoparticles without being necessary the addition of different reducing agents, because plasma in the liquid phase provides a reaction field with a highly excited energy radicals. We successfully synthesized gold nanoparticles using a glow discharge in aqueous solution. Nanoparticles with an average size of less than 10 nm were obtained using chlorauric acid solutions as the metal source. Carbon/Pt hybrid nanostructures have been obtained by treating carbon balls, synthesized in a CVD chamber, with hexachloro- platinum acid in a solution plasma system. The solution plasma was successfully used to remove the template remained after the mesoporous silica synthesis. Surface functionalization of the carbon structures and the silica surface with different chemical groups and nanoparticles, was also performed by processing these materials in the liquid plasma.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.137-137
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• 2008

This paper presents the ability of plasma electrolytic polishing technology to polish surface of stainless steel materials. The results show that the surface of its can be polished clearly using potentiostatic regimes in various concentration of $(NH_4)_2SO_4$ solution that had been warmed to a certain initial temperature. The equipment and deposition produces for polishing process are described and the effect of processing parameters on the characterizations polishedsamples has been has been investigated.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.280-280
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• 2014

본 연구에서는 유체 플라즈마 공정 (Solution plasma process; SPP)이라고 불리우는 새로운 공정법을 이용하여 ZnO 나노입자를 합성하였고 그 입도와 분산성을 평가하였다. 이 방법으로 인해 합성된 ZnO 나노입자는 10~60 nm 범위의 입도를 가지며, 플라즈마 처리시간이 길어질수록 유체 내 ZnO 나노입자의 분산성이 향상되었다.

• Journal of the Semiconductor & Display Technology
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• v.22 no.1
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• pp.118-123
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• 2023

Partially magnetized capacitively coupled plasma (CCP) sources are investigated using a two-dimensional kinetic simulation code named EDIPIC-2D. A converging numerical solution was obtained for CCP with a 60 MHz power source, while properly capturing the dynamics of electrons and power absorption over a single RF period. The effects of magnetic fields with different orientations were evaluated. Axial magnetic fields caused changes in the spatial distribution of plasma density, affecting the loss channel. Transverse magnetic fields enhanced stochastic heating near the powered electrode, leading to an increase in plasma density while the significant E×B drift loss compensated for this rise.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.4
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• pp.223-227
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• 2009

The feasibility of plasma electrolytic polishing technology of stainless steel was examined. The results show that austenitic stainless steel can be polished clearly using potentiostatic regimes with various concentration of ammonium sulfate ($(NH_4)_2SO_4$) solution above certain initial temperature. The equipment and deposition produces for polishing process are described and the effect of processing parameters on the characterizations polished-samples has been investigated.

• Journal of Powder Materials
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• v.30 no.5
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• pp.424-430
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• 2023

YAG phosphor powders were fabricated by the atmospheric plasma spraying method with the spray-dried spherical YAG precursor. The YAG precursor slurry for the spray drying process was prepared by the PVA solution chemical processing utilizing a domestic easy-sintered aluminum oxide (Al₂O₃) powder as a seed. The homogenous and viscous slurry resulted in dense granules, not hollow or porous particles. The synthesized phosphor powders demonstrated a stable YAG phase, and excellent fluorescence properties of approximately 115% compared with commercial YAG:Ce³⁺ powder. The microstructure of the phosphor powder had a perfect spherical shape and an average particle size of approx imately 30 ㎛. As a result of the PKG test of the YAG phosphor powder, the synthesized phosphor powders exhibited an outstanding luminous intensity, and a peak wavelength was observed at 531 nm.

• Journal of the Korean Society for Heat Treatment
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• v.33 no.4
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• pp.185-192
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• 2020

In this study, materials characterization of pure copper and copper based carbon nano-tube composite prepared by powder metallurgy method were investigated. Prior to evaluate materials characterization, spark plasma sintering processing variables such as sintering temperature, pressure, thickness and diameter of compacts was optimized to ensure the microstructure and materials property of pure Cu and Cu-CNT composite. In addition, corrosion behavior of Cu-based CNT composite produced by powder sintering method was investigated. It was confirmed from this study that the corroded surfaces of the composite shows less dissolution compared with pure copper in 3.5 wt% NaCl solution. The measured corrosion current density (I_corr) indicates improved corrosion property of Cu based composite containing small additions of CNTs in chloride containing media. Micro-galvanic activity between Cu and CNT was not observed in given sintering condition.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.179-184
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• 2018

In this study, Ni and tungsten carbide (WC) nanoparticles are simultaneously synthesized with the mesoporous carbon nanoparticles (CNP) using a solution plasma processing (SPP) in the benzene. The Ni and WC nanoparticles were formed through the sputtering effect of electrodes during discharge, and mean time CNP were formed through reduction reaction. TEM observation showed that loaded Ni and WC nanoparticles were evenly dispersed on the CNP. The results of electrochemical analysis demonstrated that an introduction of Ni nanoparticles promoted to improve catalytic activity for oxygen reduction reaction (ORR). Moreover, Ni-WC/CNP lead to fast electron transfer process compared to that of WC/CNP. Therefore, the inexpensive Ni-WC/CNP might be a promising as catalytic material for cathodes in fuel cell applications.