• Title/Summary/Keyword: atmospheres

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Effects of Additives and Atmospheres on the Grain Growth of TiO2 Ceramics (분위기와 첨가제가 TiO2 세라믹스의 입자성장에 미치는 영향)

  • 박정현;최헌진;박한수
    • Journal of the Korean Ceramic Society
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    • v.25 no.4
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    • pp.390-398
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    • 1988
  • Effects of atmospheres and adidtives on the grain growth of TiO2 ceramics were investigated. In the range of 1300~140$0^{\circ}C$, grain growth was increased in CO2 as compared with O2 atmosphere and the grain boundary migration activation energy was lower than the diffusion activation energy of oxygen ion in TiO2. Also, in the case of addition of oxides, the grain growth was increased by oxides acting as a acceptor andinhibited by oxides acting as a donor. From the above results, when the oxygen vacancy concentration was increased, the intrinsic grain boundary mobility was increased and the pore drag force was decreased due to the rapid densification. Also it seems that the pore was migrated by the surface diffusion rather than lattice diffusion.

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A Study on the Influence of Atmospheres in Frictional Machining(Part II) (摩찰加工 에 있어서의 零圍氣 영향 에 관한 硏究 제2보)

  • 손명환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.6 no.2
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    • pp.113-120
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    • 1982
  • In the previously reported Part I, the experimental results in frictional machining that finished medium carbon steel SM 50 C under 6 kinds of liquid atmospheres by using ceramic tip as a frictional tool was described. The present study reports the experimental results that all the machining conditions are same in the Part I except tool material changed ceramics into tungsten carbide. The ceramic tool material is a stable oxide and a non-metallic material, but the tungsten carbide has the metallic characteristics that adhere to carbon steel at about 750.deg.C. The present study shows th comparison of the experimental results for the above 2 kinds of frictional tool material.

On Atmospheres for Firing the Thick Film Coper Conductors (Thick Film Copper Conductor 의 소결과 소성 분위기)

  • Lee, Joon
    • Applied Chemistry for Engineering
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    • v.2 no.3
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    • pp.193-198
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    • 1991
  • Thick film copper conductors are of considerable interest in thick film industries because of both the potential cost saving compared to the noble metal conductors and the favorable properties in electrical conductivity, solderability, solder leach resistance and wire bondability, However, formation of the excellent copper thick film is a lot complicated due to easily oxidizing property of copper at high temperature. In order to get favorable thick film copper conductor, hybrid microcircuit industry utilizes majorly three kinds of firing atmosphere, such as nitrogen atmosphere, reactive atmosphere and air atmosphere. The processes and the three atmospheres for firing thick film copper conductor were extensively reviewed in this article.

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Chemical composition of Am stars: RR Lyn and $\rho$ Pup

  • Yushchenko, A.V.;Lee, J.J.;Kang, Y.W.;Doikov, D.N.
    • Bulletin of the Korean Space Science Society
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    • 2008.10a
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    • pp.22.3-22.3
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    • 2008
  • We present the results of the investigations of high dispersion spectra of two stars. These are the eclipsing binary RR Lyn, and $\rho$ Pup - the prototype of the group of pulsating variables. The spectra were obtained at 1.8 m Bohyuunsan observatory telescope, and 8.2 m VLT. We found the chemical composition. The both components of RR Lyn are Am stars (metallic line stars), but the abundance patterns of the components are not similar - the iron abundance and the abundances of other elements are surely different. For few elements the differences exceeds 1 dex. We found the abundances of 56 chemical elements in the atmosphere of $\rho$ Pup. This is one of the best stellar abundance patterns. It permits to investigate the role of the charge-exchange reactions in stellar atmospheres. These reactions can produce the abundance anomalies in the atmospheres of B-F type stars. These reactions can be one of the sources of galactic cosmic rays, and the reason of the braked rotation of A-F type chemically peculiar stars.

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Effects of Heat Treatment on the Properties of ITO Films Deposited with Powder Target (분말 타겟을 이용하여 증착된 ITO 박막의 열처리 특성)

  • Lee Jae-Hyeong
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.2
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    • pp.109-115
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    • 2006
  • Indium tin oxide (ITO) films have been prepared by DC magnetron sputtering. In order to improve the utilization efficiency of the target and reduce the cost of the film deposition processes, the powder target was used instead of the conventional ceramic target. As-deposited films were annealed at temperatures between $200^{\circ}C$ and $500^{\circ}C$ for 30 min in air. Also, the film was annealed in various atmospheres such as air, $O_2,\;H_2,\;N_2$, and vacuum at $400^{\circ}C$C for 30 min. Effects of the heat treatment conditions on structural, electrical, and optical properties of ITO films were investigated. The annealing temperature of $400^{\circ}C$ and atmospheres of $H_2$ and $N_2$ seem to be the most suitable conditions for post processing.

Charge Transfer between STM Tip and Au(100) in Dry, H2O, and D2O Atmospheres

  • Utami, Anggi;Chung, Yonghwa;Lee, Chi-Woo
    • Journal of Electrochemical Science and Technology
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    • v.4 no.4
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    • pp.153-156
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    • 2013
  • Charge transfer between STM tip and Au(100) has been investigated by using a Scanning Tunneling Microscopy (STM) technique in dry, $H_2O$, and $D_2O$ atmospheres. Dry atmosphere was indicated by humidity as low as 5 % and high humidity as high as 98% was managed by injecting $H_2O$ and $D_2O$ to the chamber. The current decayed more slowly in high humidity than in dry atmosphere. The plateau currents were found to appear at separations larger than ca. $5{\AA}$ where the current decay stopped depending on applied bias voltages. The polarity dependence was observed at the STM junction between Pt-Ir tip and the gold. On the contrary, little dependence was seen at the one between Au tip and the substrate electrode.

Sintering Atmosphere Effect on the Grain Size and Phase Distribution of a Zirconia ($ZrO_2$ 의 입자크기과 상분포에 미치는 소결분위기 영향)

  • 백용균;안중호
    • Journal of the Korean Ceramic Society
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    • v.36 no.11
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    • pp.1198-1204
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    • 1999
  • The effect of sintering atmosphere on the grain sizes and phase distributions in 3Y-ZrO2 and 8Y-ZrO2 was investigated O2 and N2 were used as sintering atmospheres. In the case of 3Y-ZrO2 the sintered density was higher in N2 than in O2 while in the case of 8Y-ZrO2 contrary results were obtained. The observation can be explained by the nitrogen solubility into the zirconia lattice. That is nitrogen gas can behave as a diffusive gas contrary to the behavior in other oxides depending on the amount of Y2O3. In 3Y-ZrO2 tetragonal phase was retained at room temperature irrespective of sintering atmospheres. Grain sizes of two specimens were below 2㎛ and larger in O2 thin in N2 Under a given stress the transformability of tetragonal phase into monoclinic phase was higher in O2 than N2. The results are discussed on the basis of an effect of the grain size and non-transformable ttragonal(t') phase.

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Electrical Machines and Drives for Potentially Explosive Atmospheres

  • Grantham, Colin
    • Journal of international Conference on Electrical Machines and Systems
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    • v.1 no.1
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    • pp.128-134
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    • 2012
  • This paper gives an overview of the requirements for electrical equipment in potentially explosive atmospheres and describes how these are applied to electrical machines and drives in hazardous areas. The method by which equipment can be shown to be safe in a whole range of gases, by testing in a single test gas, is covered. It is shown how the more recently introduced methods of protection for hazardous areas, increased safety and nonsparking, are ideally suited to AC machines and drives. A novel method of measuring the fullload temperature rise of electrical machines for hazardous, and other areas, without the need to connect a mechanical load to the machine's drive shaft is explained.

ACTIVE GALACTIC NUCLEUS INTERACTION WITH THE HOT GAS ENVIRONMENT: UNDERSTANDING FROM THE RADIO AND X-RAY DATA

  • LAL, DHARAM V.
    • Publications of The Korean Astronomical Society
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    • v.30 no.2
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    • pp.423-427
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    • 2015
  • Recognition of the role of radio galaxies in the universe has been increasing in recent years. Their colossal energy output over huge volumes is now widely believed to play a key role not only in the formation of galaxies and their supermassive black holes, but also in the evolution of clusters of galaxies and, possibly, the cosmic web itself. In this regard, we need to understand the inflation of radio bubbles in the hot gas atmospheres of clusters and the importance of the role that radio galaxies play in the overall energy budget of the intracluster medium. Here, we present results from X-ray and radio band observations of the hot gas atmospheres of powerful, nearby radio galaxies in poor clusters.

A study on the Creep Behavieo of Rene 80 Superalloy (Rene 80초내열 합금의 크리프 거동에 관한 연구)

  • Han, Seong-Ho;Lee, Gi-Ryong;Jo, Chang-Yong;Kim, In-Bae;Kim, Hak-Min
    • Korean Journal of Materials Research
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    • v.3 no.6
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    • pp.575-584
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    • 1993
  • The effects of atmosphere on the creep rupture properties of Ni-base superalloy Ren6 80 were investigated. Creep rupture tests were performed at $760^{\circ}C$, 657MPa and 982%, 157MPa under Ar gas atmospheres. Creep rupture mode and rupture properties (rupture life and elongation) were similar in two different atmospheres under the condition of $760^{\circ}C$, 657MPa. However, the results at $982^{\circ}C$, 157MPa showed different creep rupture mode and life between air and Ar gas atmospheres. In air, it was shown that creep cracks were initiated at surface-exposed grain boundaries and propagated along grain boundaries. In Ar gas atmosphere, the cracks were initiated at inner grain boundaries and coalesced to surface cracks which cause cup-and-cone type fracture. Due to protective oxide layer formation, air test showed longer rupture life than Ar test.

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