• Title, Summary, Keyword: Closed pore

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Expansion Characteristics of the Hydrated Sodium Silicate which Synthesized by Hydrothermal Reaction (열수반응으로 합성된 수화규산소다의 팽창 특성)

  • Cho, Ho-Yeon;Kong, Yang-Pyo;Suhr, Dong-Soo
    • Journal of the Korean Ceramic Society
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    • v.45 no.12
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    • pp.845-850
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    • 2008
  • Hydrated sodium silicate was synthesized by hydrothermal reaction using anhydrous sodium silicate. The optimum additions of water was 25wt% to make hydrated sodium silicate with homogeneous and purposed water contents. Porous ceramics with homogeneous microstructure and spherical closed pore can be fabricated by elimination of the large pores(a few mm in size) which was formed during first heat treatment through the decomposition of water. Spherical closed pore was formed above $600^{\circ}C$ and the pore size was increased with increasing second heat treatment temperature due to growth of pores. The size of spherical closed pore was varied from 35 to $233\;{\mu}m$ and specific gravity was varied from 0.2 to 1.02 depending on the combinations of the first and second heat treatment temperature.

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.

A study on selective hybrid-structure film fabricated by 355nm UV-pulsed laser processing (355nm UV 레이저를 이용한 선택적 하이브리드 구조 필름의 제작에 관한 연구)

  • Kim, Myung-Ju;Lee, Sang-Jun;Shin, Bo-Sung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.5
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    • pp.2979-2984
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    • 2015
  • This paper has presented a new foaming technology of selective hybrid-structured polymer film with expanded pores. The porous structure of closed pore was firstly fabricated by applying the 355nm UV-pulsed laser to 0.1mm thick film that was uniformly mixed with PP pellets, copper powder, and CBA (Chemical Blowing Agent). In order to expand pore size of closed-cell shape, LAMO(Laser Aided Micro pore Opening) processing was conducted to heat the copper powder, and then the bigger pore size of closed-cell more than existing pore size was successfully formed because of rapid conduction of heated metal powder. From the experimental results, various process parameters such as laser fluence, intensity, scan rate, spot size and density of powder and CBA were considerably considered to reveal the correlation among the pore characteristics. In the future, a function experiment will be carried out to use the hybrid film of industrial applications.

Pore Characterization in Cross Section of Yellow Poplar (Liriodendron tulipifera) Wood

  • Jang, Eun-Suk;Kang, Chun-Won;Jang, Sang-Sik
    • Journal of the Korean Wood Science and Technology
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    • v.47 no.1
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    • pp.8-20
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    • 2019
  • This study was conducted to analyze the pore structure of Yellow poplar. Cross-sectional surfaces of heartwood and sapwood of Yellow poplar (Liriodendron tulipifera) were observed by SEM, and the true density of the heartwood, intermediate wood and sapwood were measured by gas pycnometery, while gas permeability and pore size of heartwood, intermediate wood and sapwood were measured by capillary flow porometery. The pores were classified as through pore, blind pore and closed pore. It was determined that the permeability was increased due to the content and size of through pore being increased although the total porosity of specimen showed slight difference from pith to bark. The content of through pore porosity was 33.754 % of heartwood and 47.810 % of sapwood, showed an increasing trend from pith to bark, however, those for the blind pore porosity and closed pore porosity were 27.890 % and 19.492 % for heartwood and 19.447 % and 4.660 % for sapwood, showed a decreasing trend from pith to bark. The max pore size of specimens was increased by about 5 times from $5.927{\mu}m$ to $31.334{\mu}m$, and mean flow pore size was increased by about 315 times from $0.397{\mu}m$ to $12.437{\mu}m$ from pith to bark.

Expansion Characteristics of the Hydrated Sodium Silicate (수화된 규산소다의 팽창 특성)

  • Kong, Yang-Pyo;Cho, Ho-Yeon;Suhr, Dong-Soo
    • Journal of the Korean Ceramic Society
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    • v.45 no.1
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    • pp.54-59
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    • 2008
  • Hydrated sodium silicate with 25 wt% water contents was synthesized by hydrothermal reaction using anhydrous sodium silicate. The hydrated sodium silicate was expanded at $370^{\circ}C$ for 30 min. and then pulverized, classified (- 200 mesh) and press-formed. The samples were heat treated at $400{\sim}900^{\circ}C$ for 30 min. in order to study the expansion characteristics depending on heat treatment temperature. A porous body with closed pore was formed above $600^{\circ}C$. The volume expansion ratio and the pore size were increased and the specific gravity was decreased with increasing heat treatment temperature. However, the volume expansion ratio was decreased and the specific gravity was increased above $850^{\circ}C$ due to the softening of the sodium silicate.

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.

Comparison of the Mercury Intrusion Porosimerty, Capillary Flow Porometry and Gas Permeability of Eleven Species of Korean Wood

  • Jang, Eun-Suk;Kang, Chun-Won;Jang, Sang-Sik
    • Journal of the Korean Wood Science and Technology
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    • v.46 no.6
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    • pp.681-691
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    • 2018
  • The typical methods of mercury intrusion porosimetry (MIP) and capillary flow porometry (CFP) were used to evaluate the pore size of cross-section of wood and the effect of the pore structure on the permeability of wood was analyzed in this study. The results of this study were as followings: The pore size of wood measured by CFP was larger than that measured by MIP except for Lime tree, Korean red pine and Paulownia. Among the three pore types of porous materials defined by IUPAC (through pores, blind pores, and closed pores), only through pores are related to permit fluid flow. MIP measures the pore size of both through pores and blind pores, while CFP measures the pore size of only constricted through pores. Therefore, pore size measured by MIP was not related to gas permeability, however pore size measured by CFP had a proportional relationship with gas permeability.

Characteristics of Porous Ceramics Depending on Water Content of the Water Glass and Heat Treatment Temperature (물유리의 수분 함량 및 열처리 온도에 따른 다공체의 특성)

  • Kong, Yang-Pyo;Seo, Sang-Hun;Kim, Jong-Ho;Suhr, Dong-Soo
    • Journal of the Korean Ceramic Society
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    • v.42 no.10
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    • pp.691-697
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    • 2005
  • Porous ceramics which have closes pore were fabricated by heat treatment at 100$\∼$ 600$^{\circ}C$ for 30 min using dried water glasses with 25, 35, and 45 wt$\%$ water contents. Size and distribution of the closed pore were varied depending on the water contents and heat treatment temperature. The expansion procedure could be distinguished by two stages. The frist stage occurred around loo$\%$ due to the evaporation of water and the second stage occurred at 200$\∼$400$^{\circ}C$ due to the decomposition of Si-OH compounds. The specimen was not expanded successfully because of the softening of the dried water glass at 500$\∼$600$^{\circ}C$.

Effect of SiC Particles Size on the Densification of $Al_2O_3-SiC$ Composite During Pressureless Sintering ($Al_2O_3-SiC$ 복합재료의 상압소결시 치밀화에 미치는 SiC 원료분말의 크기영향)

  • 채기웅
    • Journal of the Korean Ceramic Society
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    • v.36 no.11
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    • pp.1261-1265
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    • 1999
  • Effect of SiC particle size of the densification of Al2O3-SiC composite during pressureless sintering was investigated. Two types of SiC powders having average particle size of 0.15${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$ were used. Densification rate of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was slower than that of the specimen containg 3${\mu}{\textrm}{m}$ SiC particles. Although the relative density of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was below 90% of theoretical density after sintering at 155$0^{\circ}C$ the complete closure of open pores occurred. Therefore full densification could be obtained by subsequent HIP. On the other hand in the specimen containing 3${\mu}{\textrm}{m}$ SiC particles the complete closed pore was observed at 95% of theoretical density. Such a fast pore closure in the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles is likely to occur as a result of dense reaction layer formation on the specimen surface which is attributed to the high reactivity of small size particles with sintering atmosphere.

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Growth of silicon nitride whiskers using tailored pores (제어된 기공을 이용한 질화규소 휘스커의 성장)

  • Kim, Chang-Sam;Han, Kyong-Sop;Kim, Shin-Woo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.15 no.2
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    • pp.61-67
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    • 2005
  • In this study a new growing method of silicon nitride whiskers in the inside of large pores made intentionally during the sintering was conducted. Pore size, pore vol%, and nitrogen pressure were used as experimental variables. Silicon nitride whiskers were well grown in the inside of pores with low pore vol% range from 14 to 27 but not grown with high pore vol% such as 39 and 50. On the other hand, pore size and nitrogen pressure did not have any influence on the whisker growth. Therefore the most important factor to grow silicon nitride whisker in the inside of large pores during sintering was to make pores isolated or closed.