• Title/Summary/Keyword: DC glow discharge

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Ion Nitriding Using Pulsed D.C Glow Discharge Combined with Inductively Coupled Plasma (펄스직류방전과 유도결합방전의 복합에 의한 SCM440강의 이온질화)

  • Kim, Yoon-Kee
    • Journal of the Korean institute of surface engineering
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    • v.43 no.2
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    • pp.91-96
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    • 2010
  • SCM440 steels were nitrided using pulsed dc plasma combined with inductively coupled plasma (ICP) generated by 13.56 MHz rf power in order to enhance case hardening depth. The case hardening depth was increased with rf power. The effective case-depth with ICP at 900 watt was as 1.6 times as that nitrided without ICP. The hardening depth was also increased up to 1.45 times. The compound layers formed on top surface were dense and thin when pulsed dc plasma was combined with ICP.

The Effect of Activated Nitrogen Species for Diffusion Rate during a Plasma Nitriding Process (플라즈마질화에서 발생기 질소와 질화 속도에 관한 연구)

  • Kim, Sang-Gweon;Kim, Sung-Wan;Brand, P.J.
    • Journal of the Korean Society for Heat Treatment
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    • v.23 no.3
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    • pp.150-155
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    • 2010
  • Generally, plasma nitriding process has composed with a nitriding layer within glow discharge region occurred by energy exchange. The dissociations of nitrogen molecules are very difficult to make neutral atoms or ionic nitrogen species via glow discharge area. However, the captured electrons in which a double-folded screen with same potential cathode can stimulate and come out some single atoms or activated ionic species. It was showed an important thing that is called "hat is a dominant component in this nitriding process?" in plasma nitriding process and it can take an effective species for without compound layer. During a plasma nitriding process, it was able to estimate with analyzing and identification by optical emission spectroscopy (OES) study. And then we can make comparative studies on the nitrogen transfer with plasma nitriding and ATONA process using plasma diagnosis and metallurgical observation. From these observations, we can understand role of active species of nitrogen, like N, $N^+$, ${N_2}^+$, ${N_2}^*$ and $NH_x$-radical, in bulk plasma of each process. And the same time, during DC plasma nitriding and other processes, the species of FeN atom or any ionic nitride species were not detected by OES analyzing.

Trace impurity analysis of Cu films using GDMS: concentration change of impurities by applying negative substrate bias voltage (글로우방전 질량분석법을 이용한 구리 박막내의 미량불순물 분석: 음의 기판 바이어스에 의한 불순물원소의 농도변화)

  • Lim Jae-Won;Isshiki Minoru
    • Journal of the Korean Vacuum Society
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    • v.14 no.1
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    • pp.17-23
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    • 2005
  • Glow discharge mass spectrometry(GDMS) was used to determine the impurity concentrations of the deposited Cu films and the 6N Cu target. Cu films were deposited on Si (100) substrates at zero substrate bias voltage and a substrate bias voltage of -50 V using a non-mass separated ion beam deposition method. Since do GDMS has a little difficulty to apply to thin films because of the accompanying non-conducting substrate, we have used an aluminum foil to cover the edge of the Cu film in order to make an electrical contact of the Cu film deposited on the non-conducting substrate. As a result, the Cu film deposited at the substrate bias voltage of -50 V showed lower impurity contents than the Cu film deposited without the substrate bias voltage although both the Cu films were contaminated during the deposition. It was found that the concentration change of each impurity in the Cu films by applying the negative substrate bias voltage is related to the difference in their ionization potentials. The purification effect by applying the negative substrate bias voltage might result from the following reasons: 1) Penning ionization and an ionization mechanism proposed in the present study, 2) difference in the kinetic energy of accelerated Cu+ ions toward the substrate with/without the negative substrate bias voltage.

Corrosion Characteristics of Cast Stainless Steel under Plasma Ion Nitriding Process Temperature in Marine Environment (주조 스테인리스강의 해양환경 하에서 플라즈마 이온질화 공정온도에 따른 부식특성 연구)

  • Chong, Sang-Ok;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
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    • v.50 no.6
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    • pp.504-509
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    • 2017
  • In order to improve corrosion resistance for cast stainless steel in seawater, the characteristics of corrosion resistance after plasma ion nitriding was investigated. Plasma ion nitriding process was conducted in a mixture of nitrogen of 25% and hydrogen of 75% at substrate temperature ranging from 350 to $500^{\circ}C$ for 10 hours using pulsed-DC glow discharge plasma with working pressure of 250 Pa in vacuum condition. Corrosion tests were carried out for as-received and plasma ion nitrided specimens. The corrosion characteristics were investigated by measurement of weight loss and observation of surface morphology. In anodic polarization experiment, relatively less damage depth and weight loss were presented at a nitrided temperature of $400^{\circ}C$, attributing to the formation of S-phase.

Magnetic Properties and Microstructure of Co Thin Films by RF-diode Sputtering Method (RF-diode Sputtering법으로 제작한 Co박막의 자기특성과 미세구조)

  • Han, Chang-Suk;Kim, Sang-Wook
    • Korean Journal of Materials Research
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    • v.28 no.3
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    • pp.159-165
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    • 2018
  • In order to increase the efficiency of the sputtering method widely used in thin film fabrication, a dc sputtering apparatus which supplies both high frequency and magnetic field from the outside was fabricated, and cobalt thin film was fabricated using this apparatus. The apparatus can independently control the applied voltage, the target-substrate distance, and the target current, which are important parameters in the sputtering method, so that a stable glow discharge is obtained even at a low gas pressure of $10^{-3}$ Torr. The fabrication conditions using the sputtering method were mainly performed in $Ar+O_2$ mixed gas containing about 0.6 % oxygen gas under various Ar gas pressures of 1 to 30 mTorr. The microstructure of Co thin films deposited using this apparatus was examined by electron diffraction pattern and X-ray techniques. The magnetic properties were investigated by measuring the magnetization curves. The microstructure and magnetic properties of Co thin films depend on the discharge gas pressure. The thin film fabricated at high gas pressure showed a columnar structure containing a large amount of the third phase in the boundary region and the thin film formed at low gas pressure showed little or no columnar structure. The coercivity in the plane was slightly larger than that in the latter case.

Development of a Microplasma Source under Atmospheric Pressure using an External Ballast Capacitor (방전에너지 제어용 외부 커패시터를 이용한 대기압 마이크로 플라즈마 소스 개발)

  • Ha, Chang-Seung;Lee, Je-Hyun;Son, Eui-Jeong;Park, Cha-Soo;Lee, Ho-Jun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.6
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    • pp.31-38
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    • 2013
  • A pulse driven atmospheric plasma jet controlled by external ballast capacitor is developed. Unlike the most commonly use DBD sources, the proposed device utilizes bare metal electrode. The discharge energy per pulse can precisely be determined by changing voltage and capacitance of the ballast capacitor. It is shown that the device can provide wide range of plasma, from stable glow mode to near arc state. Current-voltage waveforms, optical emission spectra and discharge images are investigated as a function of an injection energy. The OES shows that He and oxygen lines are increased as a function of the external ballast capacitor. Ozone and rotational temperature have similar tendency with a power consumption. The feeding gas is He and the applied DC voltage is from 400V to 800V when the gap distance is $500{\mu}m$.

Effects of plasma ion nitriding temperature using DC glow discharge on improvement of corrosion resistance of 304 stainless steel in seawater (천연 해수에서 304 스테인리스강의 내식성에 미치는 DC glow 방전 플라즈마 이온질화처리 온도의 영향)

  • Chong, Sang-Ok;Park, Il-Cho;Kim, Seong-Jong
    • Journal of Advanced Marine Engineering and Technology
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    • v.41 no.3
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    • pp.238-244
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    • 2017
  • Plasma ion nitriding has been widely used in various industries to improve the mechanical properties of materials, especially stainless steels by increasing the surface hardness. It has the particular advantages of less distortion compared to that in the case of hardening of steel, gas nitriding, and carburizing; in addition, it allows treatment at low-temperatures, and results in a high surface hardness and improved corrosion resistance. Many researchers have demonstrated that the plasma ion nitriding process should be carried out at temperatures of below $450^{\circ}C$ to improve corrosion resistance via the formation of the expanded austenite phase(S-phase). Most experimentals studied to date have been carried out in chloride solutions like HCl or NaCl. However, the electrochemical characteristics for the chloride solutions and natural seawater differ. Hence, in this work, plasma ion nitriding of 304 stainless steels was performed at various temperatures, and the electrochemical characteristics corresponding to the different process temperatures were analyzed for the samples in natural seawater. Finally the optimum plasma ion nitriding temperature that resulted in the highest corrosion resistance was determined.

Electrochemical Characteristics of Cast Stainless Steel using DC Glow Discharge Surface Treatment in Seawater (DC 글로우 방전 표면처리를 적용한 주조 스테인리스강의 해수 내 전기화학적 특성)

  • Jeong, Sang-Ok;Park, Il-Cho;Kim, Seong-Jong
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2018.06a
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    • pp.105-105
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    • 2018
  • 스테인리스강은 내식성과 내구성이 우수하여 파이프 및 일반 구조용 고온재료에 널리 사용된다. 그러나 선박 및 해양플랜트 등의 고부가가치 산업에 사용될 경우 내피로성, 내구성 및 내식성이 더욱 요구되고 있다. 특히 해수 환경 하에서 스테인리스강은 재료 표면의 부동태 피막 파괴로 공식 또는 틈부식에 의한 국부부식을 초래하여 해양환경용 재료로 사용하는데 제한적이다. 플라즈마 이온질화는 저온에서 열처리가 가능하며 재료의 변형이 없어 스테인리스강에 널리 적용되는 열화학적 표면처리 기술이다. 플라즈마 이온질화는 일반적으로 고온에서 실시하여 스테인리스강의 기계적 특성을 향상시키는 목적으로 주로 적용하였으나, 저온-플라즈마 이온질화 처리 시 질소의 확산계수 증가로 표면에 S-phase 생성에 기인하여 부식 저항성이 향상된다고 알려져 있다[1-2]. 그러나 해수 펌프, 밸브, 스트레이너(Strainer) 등의 해양 환경용 기자재로 널리 사용되고 있는 주조 스테인리스강에 대한 플라즈마 이온질화 적용과 그 연구는 미비하다. 따라서 본 연구에서는 주조용 스테인리스강에 대하여 플라즈마 이온질화 기술을 적용하여 공정온도에 따른 해수 내 전기화학적 부식 특성을 규명하였다. 플라즈마 이온질화 공정은 $25%N_2$$75%H_2$ 비율로 $350^{\circ}C{\sim}500^{\circ}C$의 공정온도에서 10시간 동안 실시하였다. X-선 회절분석을 통해 공정온도 변수에 따른 표면에 형성된 질화층의 상변화를 분석하였다. 또한 비커스 경도계를 이용하여 표면경도를 측정하여 기계적 특성 향상을 확인하였다. 전기화학적 부식 실험 후 표면 손상 형상 관찰, 무게 감소량 및 손상 깊이 계측을 통해 공정 온도와 부식 저항 특성을 규명하였다. 또한 타펠 분석을 통해 모재와 플라즈마 이온질화 온도 변수에 따른 부식 속도를 비교 분석하였다.

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Observation of Light-Propagation along the Tube of Cold Cathode Fluorescent Lamp (냉음극 형광램프의 광 전파)

  • Cho, Y.H.;Jin, D.J.;Kim, J.H.;Han, S.H.;Cho, G.S.
    • Journal of the Korean Vacuum Society
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    • v.20 no.2
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    • pp.114-126
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    • 2011
  • The light propagation along a long positive column has been observed in a cold cathode fluorescent lamp. The optical signals are observed with the DC and AC voltage power during lamp operation. The light propagating is observed in the operation with the DC-rippled voltage as well as the AC-voltage. The optical signals propagate from the high voltage side to the ground. These signals show two kinds of features according to the before and after Townsend breakdown. At the dark current before Townsend breakdown, the optical intensity is damped and the propagation velocity is $10^4{\sim}10^5m/s$. At the high current of normal glow after Townsend breakdown, the propagation velocity is 1$10^5{\sim}10^6m/s$ without damping.