• Title/Summary/Keyword: Pure gas

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Effect of Nitrogen Volume in Ar-N2 Shielding Gas on Microstructure and Hardness of GTA Welded Pure Ti (순 Ti GTA 용접부의 미세조직과 경도에 미치는 Ar-N2 보호가스 중 질소량의 영향)

  • An, Hyun-Jun;Jeon, Ae-Jeong;Hong, Jae-Keun;Jeong, Bo-Young;Lee, Jong-Sub;Kang, Chung-Yun
    • Journal of Welding and Joining
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    • v.30 no.2
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    • pp.70-75
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    • 2012
  • In this study, effect of nitrogen volume in the shielding gas of Ar-$N_2$ mixing gas on the bead shape, hardness and microstructure of GTA welds of 3mm thick Commercial Pure Ti was investigated. As the nitrogen volume increased, the welding current for full penetration was reduced and hardness in the fusion zone significantly increased compared with that of the base metal, but there is no difference in the hardness of HAZ. Microstructure in the fusion zone with pure Ar gas changed from equiaxed alpha of the base metal to serrated alpha. On the other hand, microstructure using Ar-$N_2$ mixing gas changed to acicular alpha. With the increasing of nitrogen content, the amount of acicular alpha increased and the size of that was fine.

Ultra fast Marx Generator of N2, SF6, N2-SF6 Mixture Gas based on Research Output Characteristics (초고속 Marx Generator의 N2, SF6, N2-SF6 혼합가스에 따른 출력 특성 연구)

  • Doo, Jin-Suk;Han, Seung-Moon;Huh, Chang-Su;Choi, Jin-Soo
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.10
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    • pp.1850-1855
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    • 2010
  • The application field of the pulse power is very wide. Recently, Pulse power technologies take a large place in several applications. Then, many civil and military applications proceed. Marx generator is widely used in high voltage applications. Marx generator is widely used in high voltage applications, such as eletromagnetic wave and power lasers. This paper, we described about the high voltage pulse generator. A compact size high voltage pulse generator with nanosecnd rise time has been fabricated and investigated experimentally. The marx generator has 2 stages. Each stage was constructed one charging capacitor, two electrodes and one charging resistor. A inductance structure is used in order to improve the switching performances fo the whole generator. The experiments of rise time in pure gas and mixtures of gases were described. We tested the Marx generator at different insulation gas. the results show that the dielectric strength of the $N_2-SF_6$ mixture was significantly increased compared with pure nitrogen gas. The experimental results show that the rise time characteristics of the Marx generator can be controlled through varying insulation gas.

Methane hydrate formation Using Carbon Nano Tubes (탄소나노튜브를 이용한 메탄 하이드레이트 형성)

  • Park, Sung-Seek;Seo, Hyang-Min;Kim, Nam-Jin
    • 한국신재생에너지학회:학술대회논문집
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    • 2009.11a
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    • pp.549-552
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    • 2009
  • Methane hydrate is crystalline ice-like compounds which formed methane gas enters within water molecules composed cavity at specially temperature and pressure condition, and water molecule and each other from physically-bond. $1m^3$ hydrate of pure methane can be decomposed to the maximum of $172m^3$ at standard condition. If these characteristics of hydrate are reversely utilized, natural gas is fixed into water in the form of hydrate solid. Therefore the hydrate is considered to be a great way to transport and store natural gas in large quantity. Especially the transportation cost is known to be 18~24% less than the liquefied transportation. However, when methane hydrate is formed artificially, the amount of consumed gas is relatively low due to a slow reaction rate between water and methane gas. In this study, for the better hydrate reaction rate, there is make nano fluid using ultrasonic dispersion of carbon nano tube. and then, Experiment with hydrate formation by nano fluid and methane gas reaction. The results show that when the carbon nano tubes of 0.004 wt% was added to pure water, the amount of consumed gas was about 300% higher than that in pure water and the hydrate formation time decreased.

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$High-J_c\;NdBa_2Cu_3O_{7-{\delta}}$ thin films on $SrTiO_3$(100) substrates prepared by the PLD process

  • Wee, Sung-Hun;Moon, Seung-Hyun;Yoo, Sang-Im
    • Progress in Superconductivity and Cryogenics
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    • v.11 no.2
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    • pp.1-6
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    • 2009
  • We report a successful fabrication of $high-J_c\;NdBa_2Cu_3O_{7-{\delta}}$ (NdBCO) films on $SrTiO_3$(STO) (100) substrates by pulsed laser deposition (PLD) in a relatively wide processing window. Under various oxygen pressures controlled by either 1%$O_2$/Ar mixture gas or pure $O_2$ gas, strongly c-axis oriented NdBCO films were grown at the substrate temperature $(T_s)\;of\;800^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas and also in 400 and 800 mTorr with pure $O_2$ gas. These samples exhibited $T_c$ values over 90K and $J_c$ values of $2.8-3.5MA/cm^2$ at 77K in self-field (77K, sf). On the other hand, $J_c$ values over $1A/cm^2$ were obtained at the temperature regions of $700-830^{\circ}C$ in 800 mTorr with 1%$O_2$/Ar gas at those of $750-830^{\circ}C$ in 800 mTorr with pure $O_2$ gas. Unlike previous reports, resent results support that the PLD processing window for high-Jc NdBCO films is not narrow.

Observation of Gas Hydrate Formation by View Cell (View cell에 의한 가스 하이드레이트 생성 관찰)

  • Cho Byoung-Hak;Lee Young-Chul;Mo Yung-Gi;Baek Young-Soon
    • Journal of the Korean Institute of Gas
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    • v.8 no.3 s.24
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    • pp.24-30
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    • 2004
  • Gas hydrate formation process is studied in this paper. Natural gas was introduced into both pure water and water added anionic surfactant(promotor) at 276.65 K and 6 MPa. Gas hydrate nuclei was easily generated by instantaneous agitation. Gas hydrate film was formed on the interface of water and gas. The very thin film which was instantly covered the surface of the water, followed by generation of the clear film layer. Whiskery crystal of gas hydrate was created more actively in the water added naionic surfactant than in the pure water. Whiskery hydrate formed in the pure water looks like short and thick thread colony while the one shoes long and thin thread colony in the water added promoter.

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Discharge Properties of an AC-Plasma Display Panel

  • Sungkyoo Lim
    • Journal of the Microelectronics and Packaging Society
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    • v.5 no.1
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    • pp.1-6
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    • 1998
  • Two kinds of the ac-plasma display panel (PDP) with the comb type and the matrix type electrodes were fabricated. The discharge properties were studied as a function of as species (Ne and Ne+He+Xe) and its pressure. The firing voltages (Vf) of the PDP with comb type electrodes were 159 V and 195 V under pure Ne and ne+He+Xe(68:30:2) gas mixture respectively. In case of PDP cell with the matrix type electrodes the Vf was increased to 200 V for pure Ne and 240 V for Ne+He+Xe gas mixture under the same gas pressure(300 mbar).

Effects of metal catalysts on the characteristics of NO sensor using ZnO thin film as sensing material (금속 촉매가 ZnO 박막을 감지물질로 이용한 NO 센서의 특성에 미치는 영향)

  • Chung, Gwiy-Sang;Jeong, Jae-Min
    • Journal of Sensor Science and Technology
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    • v.19 no.1
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    • pp.58-61
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    • 2010
  • This paper describes the fabrication and characteristics of NO sensor using ZnO thin film by RF magnetron sputter system. The sensitivity, working temperature, and response time of sputtered pure ZnO thin film and added catalysts such as Pt, Pd, Al, Ti on those films were measured and analyzed. The sensitivity of pure ZnO thin film at working temperature of $300^{\circ}C$ is 0.875 in NO gas concentration of 0.046 ppm. At same volume of the gas in chamber, measuring sensitivity of 1.87 at $250^{\circ}C$ was the case of Pt/ZnO thin film. The ZnO thin films added with catalyst materials were showed higher sensitivity, lower working temperature and faster adsorption characteristics to NO gas than pure ZnO thin film.

Development of Volume Modified Sorption Model and Prediction for Volumetric Strain of Coal Matrix (흡착에 의한 석탄암체의 부피변화가 고려된 흡착모델 개선 및 부피변형률 예측)

  • Kim, Sang-Jin;Sung, Won-Mo
    • Journal of the Korean Institute of Gas
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    • v.19 no.2
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    • pp.37-44
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    • 2015
  • We proposed the improved Langmuir adsorption relations considering volume change effect of coal matrix during primary production of CBM and Enhanced-CBM with injection of carbon dioxide or CCS in coalseam but also volumetric strain. To verify this model, experimental data of pure gas adsorption such as $CO_2$, $CH_4$, and $N_2$ on coals were used to compare conventional Langmuir model with this model. From the results, we obtained that the larger adsorption capacity of coal and the higher adsorption affinity of gas, the larger error occur with Langmuir model. Using this model, however, we found not only substantially better fit in all condition but also reasonable volumetric strain of the coal matrix. We also applied this volume modified pure gas adsorption model to the IAS model to describe gas adsorption and volumetric strain for mixed gas. This modified-IAS model fitting experimental data by Hall et al(1994) improved accuracy of mixed gas adsorption calculation compared with conventional model.

Use of High-Temperature Gas-Tight Electrochemical

  • Park, Jong-Hee;Beihai Ma;Park, Eun-Tae
    • The Korean Journal of Ceramics
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    • v.4 no.2
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    • pp.103-113
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    • 1998
  • By using a gas-tight electrochemical cell, we can perform high-temperature coulometric titration and measure electronic transport properties to determine the elecronic defect structure of metal oxides. This technique reduces the time and expense required for conventional thermogravimetric measurements. The components of the gas-tight coulometric titration cell are an oxygen sensor, Pt/yttria stabilitized zirconia(YSZ)/Pt, and an encapsulated metal oxide sample. Based on cell design, both transport and thermodynamic measurements can be performed over a wide range of oxygen partial pressure ($pO_2=10^{-35}$ to 1 atm). This paper describes the high-temperature gas-tight electrochemical cells used to determine electronic defect structures and transport properties for pure and doped-oxide systems, such as YSZ, doped and pure ceria $(Ca-CeO_2 \;and\; CeO_2)$, copper oxides and copper-oxide-based ceramic superconductors, transition metal oxides, $SrFeCo_{0.5}O_x,\; and \;BaTiO_2$.

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Phase Changes of Pure Ti During High Temperature Gas Nitriding (순 Ti의 고온 가스질화에 따른 미세조직 변화)

  • Lee, H.J.;Kong, J.H.;Bae, J.B.;Seo, J.H.;Kim, Y.H.;Sung, J.H.
    • Journal of the Korean Society for Heat Treatment
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    • v.22 no.2
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    • pp.88-94
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    • 2009
  • The effect of high temperature gas nitrding (HTGN) on the surface microstructure in pure Ti was investigated. Two phases of TiN and $Ti_2N$ appeared at the outmost surface, and the wide ${\alpha}$-Ti layer was formed at the next layer. On the other hand, the interior region, where the nitrogen was not permeated, exhibited ${\alpha}$'phase. The outmost surface of TiN and $Ti_2N$ showed the maximum hardness of 1000Hv, while the interior ${\alpha}$'phase was ${\sim}350$ Hv. The permeation depth of nitrogen increased with increasing the gas nitriding temperature and time. The nitrogen concentration of the surface layer seems to be over 12.7% at $1100^{\circ}C$.