• 한국세라믹학회지
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• 제45권12호
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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.

• 한국세라믹학회지
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• 제40권6호
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• pp.572-576
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• 2003

$UO_2$-20 wt% CeO$_2$ 소결 펠렛의 밀도에 따른 개/폐 기공도, 기공의 크기 및 그 분포 그리고 기공의 형태를 조사하였다. 이론 소결밀도 약 96% 이상에서는 기공도는 개기공이 거의 없는 폐기공으로 나타났다. 반면에 기공크기 분포는 소결밀도에 관계없이 bimodal 형태를 보이나, 소결밀도가 증가할수록 기공 개수만 적게 나타났다. 기공의 형태는 소결밀도가 증가할수록 불규칙한 형태에서 둥근 형태로 바뀌었다.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.2979-2984
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• 2015

본 연구에서는 발포제를 이용하여 형성된 기공을 확대하는 방식의 공정으로써, 선택적 하이브리드 구조의 폴리머 필름의 제작을 위한 새로운 발포기술을 제시하였다. 기존의 발포제만을 이용한 폐쇄형 기공보다 큰 기공을 형성하기 위해서 PP에 발포제와 구리분말(Copper powder)을 혼합하여 만든 필름 내부에 355nm파장의 UV 펄스레이저를 이용하여 LAMO(Laser Aided Micro pore Opening) 공정 방식을 통한 기공의 크기를 확장하는 실험을 진행하였다. 그 결과 발포공정만 수행된 기공의 크기보다 추가적인 LAMO 공정을 통해 형성된 기공의 크기가 훨씬 더 크게 관찰되었다. 본 실험의 결과를 통해 LAMO 공정에 의한 기공의 특성과의 상관관계를 파악할 수 있었으며, 기존의 UV laser를 이용하여 원하는 부위에 선택적으로 폐쇄형 기공을 형성하는 것 이상으로 기공의 크기를 제어하는 방안을 제시하고자 한다.

• Journal of the Korean Wood Science and Technology
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• 제47권1호
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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.

• 한국세라믹학회지
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• 제45권1호
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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.

• Journal of the Korean Wood Science and Technology
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• 제46권6호
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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.

• 마이크로전자및패키징학회지
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• 제22권2호
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• pp.21-26
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• 2015

낮은 열전도도 및 높은 비표면적 특성으로 흡착제 및 가스센서 등 여러 응용 분야로 연구되고 있는 규칙적 메조기공 세라믹 소재는 폐기공 메조기공 구조와 개기공 메조기공 구조로 나뉜다. 이중 폐기공 메조기공 세라믹 소재는 개기공 메조기공 세라믹 소재보다 높은 기계적 특성을 가짐에도 내부에 존재하는 기공을 이용한 비표면적 증가에 한계가 있어 응용에 제약을 가지고 있다. 본 연구팀은 규칙적 폐기공 메조기공 타이타니아($TiO_2$)의 열처리 시간 변화에 따른 입자성장으로부터 폐기공 연결의 도입을 통하여 비표면적을 변화시키는 연구를 수행하고자 하였다. 열처리 시간 증가시 타이타니아 결정상의 변화는 없었으며 입자성장이 일어나게 되면서 기공구조의 무너짐 및 기공의 연결성 증가를 확인할 수 있었다. 24시간 열처리 시료의 경우, 기공률은 36.3%에 34.1%로 감소하였으나 기공의 연결도 증가로 인해 비표면적은 $48m^2/g$에서 $156m^2/g$으로 증가하였다. 이러한 비표면적의 증가는 CO 가스의 감응도 측정을 통하여 감응도가 약 7.4배 증가하는 것으로부터 확인될 수 있었다.

• 한국세라믹학회지
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• 제36권11호
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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.

• 한국세라믹학회지
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• 제42권10호
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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$.

• 한국결정성장학회지
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• 제15권2호
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• pp.61-67
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• 2005

본 연구에서는 질화규소의 소결 과정에서 인위적으로 형성시킨 기공내부에 질화규소의 휘스커를 성장시키는 새로운 방법을 시도하였다. 실험변수로는 기공의 크기, 기공률 및 질소압력을 사용하였다. 기공률이 14vol%와 27vol%로 낮은 경우에는 질화규소 휘스커가 기공내부에 잘 성장되었으나 39vol%와 50vol%로 기공률이 증가된 경우에는 휘스커가 거의 성장하지 않았다. 한편 기공의 크기와 질소압력은 기공내부에 질화규소 휘스커의 성장에 거의 영향을 주지 않았고, 소결과정에 기공 내에 휘스커를 성장시키는 중요한 조건은 고립된 형태의 닫힌 기공을 유지하는 것임을 알았다.