• Title/Summary/Keyword: 기공(氣功)

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Study on the Enhanced Specific Surface Area of Mesoporous Titania by Annealing Time Control: Gas Sensing Property (열처리 시간에 따른 메조기공 타이타니아의 비표면적 향상 연구: 가스센싱 특성 변화)

  • Hong, M.-H.;Park, Ch.-S.;Park, H.-H.
    • Journal of the Microelectronics and Packaging Society
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    • v.22 no.2
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    • pp.21-26
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    • 2015

  • Mesoporous ceramic materials were applied in various fields such as adsorbent and gas sensor because of low thermal conductivity and high specific surface area properties. This structure could be divided into open-pore structure and closed-pore structure. Although closed-pore structure mesoporous ceramic materials have higher mechanical property than open-pore structure, it has a restriction on the application because the increase of specific surface area is limited. So, in this work, specific surface area of closed-pore structure $TiO_2$ was increased by anneal time. As increased annealing time, crystallization and grain growth of $TiO_2$ skeleton structured material in mesoporous structure induced a collapse and agglomeration of pores. Through this pore structural change, pore connectivity and specific surface area could be enhanced. After anneal for 24 hrs, porosity was decreased from 36.3% to 34.1%, but specific surface area was increased from $48m^2/g$ to $156m^2/g$. CO gas sensitivity was also increased by about 7.4 times due to an increase of specific surface area.

  • https://doi.org/10.6117/kmeps.2015.22.2.021 인용 PDF KSCI

Stomatal Movement and Related Environmental Factors to Stomate in the Wheat II. Effect of Nitrogen Application on the Stomatal Aperture of Wheat (소맥 엽신의 기공운동과 기공의 환경변이 II. 질소의 퇴비가 소맥엽신의 기공개도에 미치는 영향)

  • 남윤일;하용웅;김기준
    • KOREAN JOURNAL OF CROP SCIENCE
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    • v.29 no.3
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    • pp.267-274
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    • 1984

  • This experiment was carried out to investigate the stomatal aperture of wheat variety 'Chokwang' grown in the two different nitrogen level. Stomatal aperture was measured at the maximal tillering, shooting, booting, flowering and grain filling stages. Stomatal aperture in leaf blades gradually increased in accordance with the successive leaf growth. The maximal opening of stomata was observed at flowering stage and around noon in a day, but stomata closed around six o'clock in the afternoon. Stomata opened wider in the high nitrogen application than in the low nitrogen and their effects were the highest at the booting and flowering stage. Diurnal course at stomatal aperture of upper leaves was wider than that of lower leaves regardless of growth stages. Positive correlation (r=0.66$^{**}$) appeared between nitrogen content in leaf blades and stomatal aperture. The leaves of low position and the developing leaves showed smaller stomatal aperture than the full expanded top leaves irrespective of leaf stages. Water content of leaf, root weight and root activity were increased by the nitrogen application and thus considered as factors increase the stomatal aperture.ication and thus considered as factors increase the stomatal aperture.

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Pore Size and its Distribution as a Function of Sintered Density of UO2-20 wt%CeO2Pellets (UO2-20 wt%CeO2소결체의 밀도에 따른 기공크기 및 분포)

  • 나상호;김기홍;김시형;이영우;유명준
    • Journal of the Korean Ceramic Society
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    • v.40 no.6
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    • pp.572-576
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    • 2003

  • Open/closed porosity, pore size and its distribution and pore type as a funtion of sintered density of UO$_2$-20 wt％CeO$_2$ pellets were investigated. Pore appeared almost closed-type with the density above 96％ of the theoretical density. Bimodal pore size distribution was observed regardless of the sintered density, but the number of pore decreased with increasing the sintered density. The shape of pore was changed from irregular shape to round type with increasing the sintered density.

  • https://doi.org/10.4191/KCERS.2003.40.6.572 인용 PDF KSCI