• Carbon letters
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• v.1 no.2
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• pp.53-59
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• 2000

The synthetic methods for high yield of multiwalled carbon nanotube (MWNT) and singlewalled carbon nanotube (SWNT) with high purity by arc discharge have been investigated. MWNTs were synthesized under different pressures of helium and the gas mixture of argon and hydrogen. Relatively high pressure of 300-400 torr was required for high yield MWNTs synthesis at low bias voltage of about 20 V and 55 A, whereas low pressure of about 100 torr was required for SWNTs. The introduction of hydrogen gases during the synthesis of MWNTs improved the yield and purity of the samples. The SWNTs were synthesized by the assistance of a small amount of mixture of transition metals, which played as a catalyst during the formation process. The purity and yield of SWNTs were higher at a lower pressure and enhanced by mixing more components of the transition metals.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.487-492
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• 1998

Ultrafine particles of $SnO_2$ or $(Sn,Ti)O_2$ and thin films of $SnO_2$ were synthesized by introducing aqueous tin chloride solution into a high temperature argon inductively coupled plasma (ICP) generated under ambient pressure (the spray-ICP technique). As-deposited $SnO_2$ particles from each concentration of solution were all tetragonal $SnO_2$ crystallline phase and their mean size decreased in proportion to the increase of solution concentration. The mean size of $SnO_2$ particles was in the 10~40 nm range.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.511-515
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• 2004

Fe nano powders were synthesized by plasma arc discharge (PAD) process and studied by means of X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). Pure Fe rod($99.9\%$) was used as a source of metallic vapor under argon and hydrogen mixed atmosphere. The synthesized Fe nano powders had nearly spherical shapes and core-shell type structures. The influence of process parameters on the structure and size was investigated. The powder size increased with increasing of the chamber pressure and input current. High hydrogen gas ratio in chamber atmosphere affected the particle size and amount of Fe nanopowder.

• Analytical Science and Technology
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• v.7 no.2
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• pp.155-164
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• 1994

A conventional Grimm-type glow discharge source was constructed and applied to radio-frequency(13.56MHz) discharge for metal and ceramic analysis. We investigated the emission spectrum for aluminium and aluminium oxide and the influence of discharge operating paramaters including argon pressure, rf-power and DC-bias voltages at the sample-side electrode. Scanning Electron Microscope(SEM) also was used to investigate the effect of rf-sputtering on the microstructure formation of the aluminium oxide. Linear analytical calibration curves were constructed for Manganese and zinc element in samples of low alloy steel(BAS 401-405) and brass(NIST 1108-1117).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.611-615
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• 2004

In recent, there have been several developments in lamp technology that promise savings in electrical power consumption and improved quality of the lighting space. Above all, Electrodeless fluorescent lamp is the removal of internal electrodes and heating filaments that are a light-limiting factor of conventional fluorescent lamps. The electrodeless fluorescent lamp is intended as a high efficacy replacement for the incandescent reflector lamp in many applications. Therefore, the electrodeless fluorescent lamps is substantially higher than that of conventional fluorescent lamps and last up to 60,000 hours. In this paper, electron temperature and electron density were measured in a radio-frequency inductively coupled plasma using a Langmuir probe method for emission characteristics. Measurement was conducted in an argon discharge for pressure from 10 [mTorr] and input RF power 100 [W] to 150 [W]. As for the electron density, a electron temperature was more distinguished for a emission characteristic. The results of ideal may contribute to systematic understanding of a electrodeless fluorescent lamps of emission characteristics.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.1066-1068
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• 1999

Magnetic field is commonly used in low temperature processing plasmas in order to obtain high density. E $\times$ B magnetron or surface multipole configuration were most popular. However, the properties of capacitively coupled rf plasma confined by axially applied static magnetic fields have rarely been studied. In this paper, the effects of magnetic field on the characteristics of 13.56MHz/40KHz argon plasma will be reported. Ion saturation current, electron temperature and plasma potential were measured by Langmuir probe and omissive probe. At low pressure region ($\sim$10mTorr), ion current was increased by a factor of 3 - 4 due to reduction of diffusion loss of charged particles to the wall. It was observed that magnetic field induces large time variation of the plasma potential. The experimental result was compared with particle-in-cell simulation. It was also observed that electron temperature tend to decrease with increasing magnetic induction level for 40KHz discharge.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.567-572
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• 2015

Discharge characteristics of linear microwave plasma were investigated by using fluid simulation of 2D axis-symmetry based on finite elements method. The microwave power was 2.45 GHz TEM mode and transmitted through linear antenna. Resistive power and pressure were considered simulation variables and argon was used for working gas. A decrease of electron density along the quartz tube was observed in low power condition but relatively uniform plasmas were generated in chamber by increasing the resistive power. The electron temperature was highly detected near the surface of quartz tube because the electron was heated only dielectric surface. The power transmission efficiency decreased and characteristics of surface plasma were observed in high electron density condition.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.49-51
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• 2002

In this thesis, Josephson junction using high-Tc superconducting multi-layer thin film has been fabricated by on-axis RF magnetron sputtering method. And, the characterizations were performed by X-ray diffraction, SEM and the measuring system of critical current density. The physical properties of multi-layer superconducting thin films were also analyzed with the measured results. To fabricate the multi-layer superconducting thin films, the optimum partial pressure of Argon and Oxgen and the temperature of substrate were measured. Also, YBaCuO thin film was grown on MgO and $SrTiO_3$ substrates by rf-sputtering and LGO thin film of 30 A was epitaxially grown on the YBaCuO thin film as a josephson junction with the same condition. The schottky barrier at the contact surface between YBaCuO/LGO and YBaCuO/Au and the energy gap of 0.5 ${\sim}$ 0.6 mV in Nb were observed from the dI/dV-V of YBaCuO/LGO/Au/Nb and YBaCuO/Au/Nb.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.184-185
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• 2007

We investigated the growth behaviors of ZnO epilayers on sapphire substrates fabricated sing RF magnetron puttering and RTA. The effects of deposition temperature and oxygen partial pressure in plasma on the structural and electrical properties were measured by XRD, AFM, SEM, and Hall effect measurement. It was found that ZnO thin films became denser and smoother with increasing deposition temperature and $O_2$ content in the puttering gas. ZnO thin film of oxygen and argon with a ratio of 5:5 had an electron concentration of $8.048{\times}10^{18}cm^{-3}$, resistivity of $0.0141{\Omega}{\cdot}Cm$, and mobility of $55.07cm^2/V{\cdot}s$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.866-870
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• 2008

In this study, we designed cold gas propulsion system with minimum 0.25 mm nozzle and micro-thrust measurement system to analyze flow characteristic of micro propulsion system in ambient and vacuum condition. Argon and Nitrogen are used for propellant and the result of experiments is compared with CFD analysis and theory. But there is a point where reduced scale versions of conventional propulsion systems will no longer be practical. Therefore, a fundamentally different approach to propulsion systems was taken. That is thermal transpiration based micro propulsion system. It has no moving parts such as lubricants, pressurizing system and can pump the gaseous propellant by temperature gradient only(cold to hot). We are advancing basic research of propulsion system based on thermal transpiration in vacuum conditions and had tried experiment process and theoretical access in advance. To characterize membrane of Knudsen pump, we select Polyimide material that has low thermal conductivity(0.29 W/mK) and can stand high temperature($300^{\circ}C$) for long time. And we fabricated hole diameter 1, 0.5, 0.2, 0.1 mm using precision manufacturing. Experimental results show that pressure gradient efficiency of Knudsen pump is increased to maximum 82% according to Knudsen number and thick membranes are more effective than thin membranes in transition flow regime.