• 대한금속재료학회지
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• 제47권11호
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• pp.716-721
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• 2009

The major drive for the application of low-temperature plasma treatment in nitrocarburizing of austenitic stainless steels lies in improved surface hardness without degraded corrosion resistance. The low-temperature plasma nitrocarburizing was performed in a gas mixture of $N_{2}$, $H_{2}$, and carbon-containing gas such as $CH_{4}$ at $450^{\circ}C$. The influence of the processing time (5~30 h) and $N_{2}$ gas composition (15~35%) on the surface properties of the nitrocarburized layer was investigated. The resultant nitrocarburized layer was a dual-layer structure, which was comprised of a N-enriched layer (${\gamma}_N$) with a high nitrogen content on top of a C-enriched layer (${\gamma}_C$) with a high carbon content, leading to a significant increase in surface hardness. The surface hardness reached up to about $1050HV_{0.01}$, which is about 4 times higher than that of the untreated sample ($250HV_{0.01}$). The thickness of the hardened layer increased with increasing treatment time and $N_{2}$ gas level in the atmosphere and reached up to about $25{\mu}m$. In addition, the corrosion resistance of the treated samples without containing $Cr_{2}N$ precipitates was enhanced than that of the untreated samples due to a high concentration of N on the surface. However, longer treatment time (25% $N_{2}$, 30 h) and higher $N_{2}$ gas composition (35% $N_{2}$, 20 h) resulted in the formation of $Cr_{2}N$ precipitates in the N-enriched layer, which caused the degradation of corrosion resistance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 반도체재료
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• pp.12-16
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• 2001

We investigated the etching characteristics of $YMnO_3$ thin films in high-density plasma etching system. In this study. $YMnO_3$ thin films were etched with $CF_{4}/Ar$ gas chemistries in inductively coupled plasma (ICP). Etch rates of $YMnO_3$ were measured according to gas mixing ratios. The maximum etch rate of $YMnO_3$ is 18 nm/min at $CF_{4}/(CF_{4}+Ar)$ of 20%. In optical emission spectroscopy (OES) analysis, F radical and Ar* ions in plasma at various gas chemistries decreased with increasing $CF_4$ content. Chemical states of $YMnO_3$ films exposed in plasma were investigated with x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). There is a chemical reaction between metal (Y, Mn) and F and metal-fluorides were removed effectively by Ar ion sputtering. $YF_x$, $MnF_x$ such as YF, $YF_2$, $YF_3$ and $MnF_3$ Were detected using SIMS analysis. The etch slope is about $65^{\circ}C$ and free of residues.

• 마이크로전자및패키징학회지
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• 제11권4호
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• pp.29-35
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• 2004

암모니아 펄스플라즈마를 이용하여 $WF_6$ 가스와 $NH_3$ 가스를 교대로 흘려줌으로써 Si 기판위에 질화텅스텐 확산방지막을 증착하였다. $WF_6$ 가스는 Si과 반응하여 표면침식이 과도히 발생하였으나 암모니아 ($NH_3$)가스를 펄스 플라즈마를 인가하여 $WF_6$와 같이 사용하면 Si 표면을 질화처리 함으로써 표면침식을 막아주며 질화텅스텐 박막을 쉽게 증착할 수 있었다. 그 이유는 암모니아 가스의 분해를 통한 Si 기판의 흡착을 용이하게 하여 질화텅스텐 박막 증착이 가능하기 때문이다. 이러한 증착 미케니즘과 암모니아 펄스 플라즈마 효과에 대하여 조사하였다.

• 대한기계학회논문집B
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• 제31권10호
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• pp.832-839
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• 2007

The geometry and dimensions of an expansion chamber are decisive factors in thermal puffer plasma chamber designs. Because they together dominate the temperature and speed at which the cooling gas from the chamber flows back through a flow channel to the arcing zone for the successful interruption of fault currents. In this study, we calculated the flow and mass transfer driven by arc plasma, and investigated the effects of a flow guide installed inside a thermal puffer plasma chamber. It is found that the existing cold gas of the chamber mixes with hot gases entrained from the arcing zone and is subjected to compression due to pressure build-up in the chamber. The pressure build-up with the flow guide is larger than that without due to a vortex which rotates clockwise around the chamber center. By the reverse pressure gradient, the mixing gas of the chamber flows back out for cooling down the residual plasma near current zero. In the case with the flow guide, the temperature just before current zero is lower than that without, and the Cu concentration with high electrical conductivity is also less than that without the flow guide.

• 대한화학회지
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• 제40권4호
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• pp.235-242
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• 1996

기체 크로마토그래피와 쉽게 연결할 수 있는 Surfatron형의 MIP(Microwave Induced Plasma)용 cavity를 제작하고 헬륨, 아르곤, 질소 등을 플라스마 가스로 사용하여 플라스마를 생성시키고 스펙트럼을 비교하였다. 또한 헬륨과 아르곤, 질소에 미량의 CO2를 혼합하여 각 기체의 스펙트럼을 비교 분석하였으며, 제작한 MIP cavity가 질량분석기와 연결되었을 때 분자이온을 생성시킬 수 있는 이온원으로서의 가능성을 연구하였다. 헬륨과 아르곤 MIP는 높은 준안정 준위의 에너지를 가지기 때문에 분자들이 거의 다 깨어지므로 분자상태로 시료기체의 검출은 거의 불가능하였다. 그러나 질소는 다른 비활성기체에 비하여 낮은 준안정 준위의 어네지를 가지므로 검출하려는 기체성분이 상당부분 분자상태로 존재함을 알 수 있었다.

• 한국진공학회지
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• 제9권1호
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• pp.7-15
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• 2000

An ECR-PECVD system with the characteristics of high ionization rat다 ability of plasma processing in a wide pressure range and deposition at low temperature was manufactured and characterized for the deposition of thin films. The system consists of a vacuum chamber, sample stage, vacuum gauge, vacuum pump, gas injection part, vacuum sealing valve, ECR source and a control part. The control of system is carried out by the microprocessor and the ROM program. We have investigated the vacuum characteristics of ECR-PECVD system, and also have diagnosed the characteristics of ECR microwave plasma by using the Langmuir probe. From the data of system and plasma characterization, we could confirmed the stability of pressure in the vacuum chamber according to the variation of gas flow rate and the effect of ion bombardment by the negative DC self bias voltage. The plasma density was increased with the increase of gas flow rate and ECR power. On the other hand, it was decreased with the increase of horizontal radius and distance between ECR source and probe. The calculated plasma densities were in the range of 49.7\times10^{11}\sim3.7\times10^{12}\textrm{cm}^{-3}$. It is also expected that we can estimate the thickness uniformity of film fabricated by the ECR-PECVD system from the distribution of the plasma density.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.177-178
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• 2012

In this experiment, post-nitriding treatment has been performed at $400^{\circ}C$ on AISI 316 stainless steel which is plasma carburized previously at $430^{\circ}C$ for 15 hours. Plasma nitriding was implemented on AISI 316 stainless steel at various gas compositions (25% N2, 50% N2 and 75% N2) for 4 hours. Additionally, during post nitriding Ar gas was used with H2 and N2 to observe the improvement of treatment. After treatment, the behavior of the hybrid layer was investigated by optical microscopy, X-ray diffraction, and micro-hardness testing. Potentiodynamic polarization test was also used to evaluate the corrosion resistance of the samples. Meanwhile, it was found that the surface hardness increased with increasing the nitrogen gas content. Also small percentage of Ar gas was introduced in the post nitriding process which improved the hardness of the hardened layer but reduces the corrosion resistance compared with the carburized sample. The experiment revealed that AISI 316L stainless steel showed better hardness and excellent corrosion resistance compared with the carburized sample, when 75% N2 gas was used during the post nitriding treatment. Also addition of Ar gas during post nitriding treatment were degraded the corrosion resistance of the sample compared with the carburized sample.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.264-269
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• 2010

This paper presents the analysis of the dielectric characteristics of a hot $SF_6$ gas in a gas circuit breaker. Hot gas flow is analyzed using the FVFLIC method considering the moving boundary, material properties of real $SF_6$ gas, and arc plasma. In the arc model, the re-absorption of the emitted radiation is approximated with the boundary source layer where the re-absorbed radiation energy is input as an energy source term in the energy conservation equation. The breakdown criterion of a hot gas is predicted using the critical electric field as a function of temperature and pressure. To validate the simulation method, breakdown voltage for a 145kV 40kA circuit breaker was measured for various conditions. Consistent results between the simulation and experiment were confirmed.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.784-785
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• 2010

전북대학교 고온플라즈마 응용연구센터 구축사업단에서는 MW급 초음속 플라즈마 풍동을 구축하고 있다. 구축되는 장비는 0.4MW/2.4MW급 Huels형 DC 플라즈마 장치 및 60kW/200kW급 RF 플라즈마 장치 등으로 구성되며 이러한 장비를 지원하는 공통지원설비가 별도로 구축되게 된다. 공통지원설비는 플라즈마 풍동을 구동하기 위한 수변전설비 및 가스공급설비, 냉각수공급설비, NOx 제거용 후처리 설비, 예비전원설비 등으로 구성되어 있다.

• 전기학회논문지P
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• 제58권1호
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• pp.44-47
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• 2009

This paper describes the information for quantitative simulation of weakly ionized plasma. We must grasp the meaning of the plasma state condition to utilize engineering application and to understand materials of plasma state. $SF_6$ gas is widely used in industrial of insulation field. In this paper, $N_2$ is mixed to improve pure $SF_6$ gas characteristics. Electron transport coefficients in $SF_6-N_2$ mixture gases are simulated in range of E/N values from 70 to 400 [Td] at 300K and 1 Torr by using Boltzmann equation method. The results of this method. which are ionization coefficient, attachment coefficient, effective ionization coefficient, and critical E/N, can be important data to present characteristic of gas for insulation. Specially critical E/N is a data to evaluate insulation strength of a gas and is presented in this paper for various mixture ratios of $SF_6-N_2$ mixture gases.