• Title/Summary/Keyword: Nitrogen atmosphere

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Behavior of Nitrogen in the Variation of Heat Treatment Conditions of Super Duplex Stainless Steel (수퍼 2상 스테인리스강의 열처리 조건변화에 따른 첨가원소 질소의 거동)

  • Joo, Dong Won;Sung, Jang Hyun
    • Journal of the Korean Society for Heat Treatment
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    • v.10 no.1
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    • pp.30-39
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    • 1997
  • After changing the heat treating atmosphere of nitrogen gas, argon gas and vacuum, the nitrogen contents, microstructural changes, hardness and corrosion resistance of 0.25wt.%N alloyed super duplex stainless steel have been investigated in the temperature range from $1050^{\circ}C$ to $1350^{\circ}C$. The nitrogen content showed to be increased up to 0.36wt.% after heat treating the specimen in nitrogen gas at $1200^{\circ}C$, while the decrement of nitrogen content in vacuum atmosphere was shown down to 0.03wt.% at $1350^{\circ}C$. After heat treating in the mixed gas atmosphere of argon and nitrogen at $1250^{\circ}C$, the surface ${\gamma}$ phase existed as ${\alpha}+{\gamma}$ phase increased with increasing nitrogen gas content. The ${\gamma}$ single phase appeared at the surface above $80%N_2$ gas, while the surface ${\alpha}$ single phase was shown below $20%N_2$ gas. When heat treating the specimen in nitrogen gas at $1050^{\circ}C$, the hardness of austenite phases increased above Hv 40 at the surface layer compared to the hardness of the core parts, while decrement of denitriding effect caused to the hardness nearly unchanged between surface and the core parts after heat treating in vacuum atmosphere. The surface ${\gamma}$ single phase specimen showed superior corrosion resistance than the surface ${\alpha}$ single phase specimen. The surface ${\alpha}$ phase existed in the ${\alpha}+{\gamma}$ microstructure showed higher corrosion resistance after heat treating in the nitrogen gas atmosphere than the ${\alpha}$ phase heat treated in the argon gas and vacuum atmosphere.

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Nitrogen Doping in Polycrystalline Anatase TiO2 Ceramics by Atmosphere Controlled Firing

  • Chang, Myung Chul
    • Journal of the Korean Ceramic Society
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    • v.56 no.4
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    • pp.374-386
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    • 2019
  • A process for nitrogen doping of TiO2 ceramics was developed, whereby polycrystalline titania particles were prepared at 450-1000℃ with variation of the firing schedule under N2 atmosphere. The effect of nitrogen doping on the polycrystallites was investigated by X-ray diffraction (XRD) and Raman analysis. The microstructure of the TiO2 ceramics changed with variation of the firing temperature and the firing atmosphere (N2 or O2). The microstructural changes in the nitrogen-doped TiO2 ceramics were closely related to changes in the Raman spectra. Within the evaluated temperature range, the nitrogen-doped titania ceramics comprised anatase and/or rutile phases, similar to those of titania ceramics fired in air. Infiltration of nitrogen gas into the titania ceramics was analyzed by Raman spectroscopy and XRD analysis, showing a considerable change in the profiles of the N2-doped TiO2 ceramics compared with those of the TiO2 ceramics fired under O2 atmosphere. The nitrogen doping in the anatase phase may produce active sites for photocatalysis in the visible and ultraviolet regions.

Tribological Behaviour of $WS_2$Solid Lubricant ($WS_2$ 고체윤활제의 마찰.마모 거동)

  • 신동우;김인섭;윤대현;김경도;김성진;정진수
    • Tribology and Lubricants
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    • v.14 no.2
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    • pp.35-41
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    • 1998
  • The $WS_2$ solid lubricant synthesized through the vapour phase transport method was coated on the commercial bearing steel (SUJ 2) substrate, and the tribological behaviour of the lubricant was investigated using a ball-on-disk type tester. The $WS_2$ powder was spray-coated at room temperature using compressed air, and the change of friction coefficient was examined in various conditions, i.e., specimen configuration, atmosphere (air and nitrogen), applied load and rotating speed. $WS_2$ coated ball and disk showed the optimum friction coefficient of 0.07 and wear life of 45,000 cycles in the nitrogen atmosphere under 0.3 kgf and 100 rpm, whereas relatively high coefficient of 0.13 and reduced wear life of 4,000 cycles were observed in air atmosphere. The effect of rotating speed on the friction coefficient was not observed both in nitrogen and in air atmospheres. This confirmed that the spray-coated $WS_2$ solid lubricant was effective in reducing the friction coefficient and improving wear life in nitrogen atmosphere, and the oxygen and moisture existing in air could seriously deteriorate the lubrication effect of $WS_2$ coating layer.

Factors Controlling Friction Coefficient of WS$_2$ Solid Lubricant (각종 응용환경에서 WS$_2$ 고체윤활제의 마찰 계수)

  • 신동우;윤대현;최인혁;김인섭
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1997.10a
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    • pp.110-116
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    • 1997
  • The tribological behaviour of WS$_2$ solid lubricant was investigated using a ball-on-disk type tester. The WS$_2$ powder was spray-coated at room temperature and the effects of specimen configuration, atmosphere, applied load and rotating spccd on the friction coefficient was examined. WS$_2$ coated ball and disk showed the lowest friction coefficient of 0.05 in the nitrogen atmosphere under 0.3 kgf and 100 rpm, whereas relatively high coefficient of 0.1 - 0.15 was observed in air atmosphere. This confirmed that the spray-coated WS$_2$ solid lubricant was effective in reducing the friction coefficient and improving wear life in nitrogen atmosphere.

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Nitrogen-Oxygen Separation Characteristics by Polyimide Membrane System for Controlled Atmosphere Storage (CA저장을 위한 폴리이미드 막 시스템의 질소-산소 분리특성)

  • 이호원;현명택;고정삼
    • Food Science and Preservation
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    • v.5 no.3
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    • pp.239-246
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    • 1998
  • Polyimide membrane system was designed for manufacturing nitrogen-enriched gas, and basic technical data was suggested for appling this system to controlled atmosphere storage. The permeability characteristics of pure oxygen and nitrogen could be explained by dual-mode sorption model. There was substantial decrease in the permeation rates of oxygen, which is the more permeable gas, through the polyimide membrane due to the presence of nitrogen in comparison with pure oxygen. However, the permeation rates of nitrogen was increased by the presence of oxygen. The ideal separation factor was in the range of 5 to 6 in the range of temperature and pressure difference studied, and the separation factor of air was lower than the ideal separation factor. The increase of ideal separation factor with increasing temperature is due to the fact that the activation energy for oxygen is larger than that for nitrogen. Nitrogen concentration decreased rapidly with increasing product recovery, and it was found that this is a major operating factor to obtain nitrogen concentration required for controlled atmosphere storage. A relation equation, by which nitrogen concentration in storehouse can be predicted, was suggested under the establishment of a hypothetical model for controlled atmosphere storage process using polyimide membrane system.

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Nitrogen-incorporated (Ba, Sr)$TiO_3$ thin films fabricated by r.f.- magnetron sputtering

  • Lim, Won-Taeg;Jeong, Yong-Kuk;Lee, Chang-Hyo
    • Journal of Korean Vacuum Science & Technology
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    • v.4 no.4
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    • pp.97-101
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    • 2000
  • In this study, two kinds of barium strontium titanate (BST) samples were prepared. One is a conventional BST film that is sputtered in a mixture of argon and oxygen. The other is a nitrogen-incorporated BST film that is sputtered in a mixture of oxygen and intentionally added nitrogen instead of argon gas. The structural properties of both of the BST films had not changed significantly with the species of sputtering gas. However, the leakage current of BST films sputtered at ($N_2$+O$_2$) atmosphere was lower than those sputtered at (Ar +O$_2$) atmosphere: 1.9$\times$10$^{-8}$ A/cm$^2$ at 2V for the films prepared at (Ar +O$_2$) atmosphere and 8.6$\times$10$^{-9}$ A/cm$^2$ for the films at ($N_2$+O$_2$) atmosphere. From an XPS analysis, it has been found that nitrogen atoms are incorporated in BST films with a concentration of 1.92 at% and form a certain oxynitride phase. It is proposed that nitrogen atoms are able to fill the oxygen vacancies of BST films during sputtering process, and then the leakage current reduces due to a decrease in the vacancies. The BST films sputtered at ($N_2$+O$_2$) atmosphere have superior electrical properties to the films sputtered at (Ar +O$_2$), without any significant structural changes.

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Selective Laser Sintering of WC-Co Mixture (텅스텐 카바이드와 코발트 혼합물의 선택적 레이저 소결)

  • 김광희;조셉비만
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2001.10a
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    • pp.269-274
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    • 2001
  • This paper describes the experimental results on direct selective laser sintering of WC-Co mixture. The experiments were carried out within an air, argon and nitrogen atmosphere. The main problem occurred during sintering within an air atmosphere was oxidation of WC-Co mixture. As the power of laser is increased and scanning speed is decreased, more severe oxidation takes place. Within an argon and nitrogen atmosphere the oxidation is reduced significantly. As the energy density is increased the thickness of the sintered layer is increased.

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Comparison of Nitrogen and Oxygen Annealing Effects on the Structural, Optical and Electrical Properties of ALD-ZnO Thin Films (ALD법으로 증착한 ZnO 박막의 열처리 분위기에 따른 구조적, 전기적 특성 비교)

  • Park Y. K.;Park A. N.;Lee C. M.
    • Korean Journal of Materials Research
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    • v.15 no.8
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    • pp.514-517
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    • 2005
  • Effects of nitrogen and oxygen annealing on the carrier concentration, carrier mobility, electrical resistivity and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD). X-ray diffraction (XRD), Scanning electron microscope (SEM), photoluminescence (PL) analyses, and Hall measurement were performed to investigate the crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. According to the XRD analysis results the crystallinity of the ZnO film annealed in an oxygen atmosphere is better than that of the ZnO film annealed in a nitrogen atmosphere. Annealing undoped ZnO films grown by ALD at a high temperature above $600^{\circ}C$ improves the crystallinity and enhances W emission but deteriorates the electrical conductivity of the flms. The resistivity of the ZnO film annealed particularly at $800^[\circ}C$ in a nitrogen atmosphere is much higher than that annealed at the same temperature in an oxygen atmosphere.

Luminescence Properties of $Eu^{2+}$-doped $Ca_2Si_5N_8$ Thin Films ($Eu^{2+}$-doped $Ca_2Si_5N_8$ 박막의 광학특성)

  • Jang, Bo-Yun;Pakr, Joo-Seok
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.11a
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    • pp.25-27
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    • 2007
  • $Eu^{2+}$-doped $Ca_2Si_5N_8$ was grown on Si(100) substrate using metal-organic deposition (MOD) method and post-annealed at $900^{\circ}C$ in various atmosphere. Luminescence properties of these thin films were investigated with variations of $Eu^{2+}$-doped concentrations and annealing atmosphere. Thin film was formed with clean surface and uniform thickness of about 72 nm. From the measurements of luminescence properties of thin films, film must be post-annealed in nitrogen or mixture of nitrogen and hydrogen atmosphere to emit a sufficient light. For $Ca_{1.5}Eu_{0.5}Si_5N_8$ thin film annealed at $900^{\circ}C$ in nitrogen atmosphere, excitation band from 380 to 420 nm was detected with the maximum intensity at 404 nm and two broad emission bands from 530 to 630 nm were observed. These broad excitation and emission bands must be attributed to the nitrogen incorporations into the films. From the results, $Ca_{2-x}Eu_xSi_5N_8$ thin film has probability for next generation thin film lighting applications such as light emitting diode (LED) or electro-luminescence (EL).

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Effect of Post-deposition Annealing in a Nitrogen Atmosphere on the Properties of SnO2 Thin Films (질소분위기 열처리에 따른 SnO2 박막의 구조적, 전기광학적 특성 변화)

  • Song, Young-Hwan;Eom, Tae-Young;Heo, Sung-Bo;Kim, Jun-Ho;Kim, Daeil
    • Journal of the Korean Society for Heat Treatment
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    • v.30 no.1
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    • pp.1-5
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    • 2017
  • A 100 nm thick $SnO_2$ thin films were prepared by radio frequency magnetron sputtering on glass substrates and then annealed in nitrogen atmosphere for 30 minutes at 100, 200, and $300^{\circ}C$, respectively. While the visible light transmittance and electrical resistivity of as deposited $SnO_2$ films were 81.8% and $1.5{\times}10^{-2}{\Omega}cm$, respectively, the films annealed at $200^{\circ}C$ show the increased optical transmittance of 82.8% and the electrical resistivity also decreased as low as $4.3{\times}10^{-3}{\Omega}cm$. From the observed results, it is concluded that post-deposition annealing in nitrogen atmosphere at $200^{\circ}C$ is an attractive condition to optimize the optical and electrical properties of $SnO_2$ thin films for the various display device applications.