• 한국세라믹학회지
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• 제25권1호
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• pp.59-65
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• 1988

To develop porous glass membranes used for a effective membrane-separation process, porous glasses and glass membranes were prepared from the sodium borosilicate parent glass by the phaseseparation technique and effects of heat-treatment and leaching conditions on their characteristics were investigated. The crack-free glass membranes could be fabricated from the 9.4 Na2-O-30.7 B2O3-59.2 SiO2-0.7 Al2O3(wt%) parent glass by heat-treatment at the lower temperature(550-570$^{\circ}C$) and for longer than 45 hrs for the phase separation, followed by leaching with 3N-HCl＋60% ethylene glycol solution at 90$^{\circ}C$ over 25 hrs. Porous glasses prepared in this work showed large specific surface areas(400㎡/g) and narrow pore size distribution with the mean pore radius of 14${\AA}$ enough for the application as reverse osmosis membranes. The salt-rejection efficiency and product-flux of the glass membranes heat-treated at 570$^{\circ}C$ for 80 hrs were found to be 51.8% and 270cc/㎡. hr, respectively. This result suggests that the porous glass membranes fabricated in this study could be applied for the reverse osmosis process.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.325-326
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• 2006

Using $6wt%Y_2O_3-2wt%Al_2O_3$ as sintering additives and Si as a raw powder, the continuously porous in-situ $Si_2N_2O-Si_3N_4$ bodies were fabricated by multi-pass extrusion process and their microstructures were investigated depending on the addition of carbon (0-9wt%) in the mixture powder. The introduction of $Si_2N_2O$ fibers observed in the unidirectional continuous pores as well as in the pore-frame regions of the nitrided bodies can be an effective method in increasing the filtration efficiency. In the case of no carbon addition, the network type $Si_2N_2O$ fibers with high aspect ratio appeared in the continuous pores with diameters of 150-200 nm. However, in the case of 9wt% C addition, the fibers were found without any network type and had diameters of 200-250 nm.

• 한국세라믹학회지
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• 제44권7호
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• pp.354-357
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• 2007

The nitriding and post-sintering behavior of silicon powder compact containing sintering additives of 2.3 wt% and 7 wt% were investigated in this study. Regardless of the liquid phase content, elongated large grains of a typical morphology evolved in the post-sintered specimens. Phase analysis revealed a complete phase transformation into ${\beta}-Si_3N_4$ in both porous systems. Oxynitride second phases (mellilite) precipitated in the latter, while those were free in the former containing less amount of liquid phase. The post-sintering condition that yielded a favorable microstructure for a filter application was achieved when the specimens were soaked at $1800^{\circ}C$ for 2 h. It was found that the thermal conductivity of porous $Si_3N_4$ ceramics is dominated by the porosity more than this factor is influenced by the addition of $Al_2O_3$.

• 한국세라믹학회지
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• 제46권5호
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• pp.467-471
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• 2009

Effects of boron and carbon on the densification and thermal decomposition of an AlN-SiC-$TiB_2$ system were investigated. $SiO_2$ was mostly removed by the addition of carbon, while $Al_2O_3$ formed $Al_4O_4C$ and promoted the densification of the systems above $1850^{\circ}C$. Rather porous specimens were obtained without the additives after hot pressing at $2100^{\circ}C$, while densification was mostly completed at $2000^{\circ}C$ by using the additives. The sintering temperature decreased further to $1950^{\circ}C$ by applying spark plasma sintering. The additives promoted the shrinkage of AlN by forming a liquid phase which was originated from the carbo- and boro-thermal reduction of $Al_2O_3$ and AlN.

• 한국세라믹학회지
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• 제41권7호
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• pp.528-533
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• 2004

입자크기가 20∼700nm인 구형 실리카입자의 자연침강 혹은 원심분리법으로 제조한 주형체에 탄화규소 전구체 polymethyl-silane (PMS) 혹은 polycarbosilane (PCS) 고분자 용액을 함침한다음, 가교 및 1000∼140$0^{\circ}C$ 열분해하고 마지막으로 불산 (HF)으로 실리카를 식각하여 84∼658nm 기공이 3차원으로 정렬된 메크로다공성(macroporous) 탄화규소 세라믹과 불규칙적인 15∼65nm 기공을 가진 메조다공성(mesoporous) 탄화규소 세라믹을 제조하였다. 전자는 112nm 실리카 입자 주형체를 사용하여 140$0^{\circ}C$로 처리했을 때, 표면적 584.64$m^2$g$^{-1}$을 나타낸 반면, 후자는 20-30nm 실리카 주형체를 사용하여 100$0^{\circ}C$로 처리하였을때, 최대의 표면적 619.4$m^2$g$^{-1}$를 나타내었다, 이와 같이 사용된 실리카 입자, 고분자 전구체, 그리고 열처리 조건에 따른 기공특성을 SEM. TEM 및 BET으로 분석 설명하였다.

• 한국세라믹학회지
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• 제43권5호
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• pp.265-269
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• 2006

We have deposited NiO films by RF sputtering on $Al_2O_3/SiO_2/Si$ and 100 nm-thick Gd doped $CeO_2$ covered $Al_2O_3/SiO_2/Si$ substrates at various $Ar/O_2$ ratios. The deposited films were reduced to form porous Ni thin fllms in 4% $H_2\;at\;400^{\circ}C$. For the films deposited in pure Ar, the reduction was retarded due to the thickness and the orientation of the NiO films. On the other hand, the films deposited in oxygen mixed ambient were reduced and formed porous Ni films after 20 min of reduction. We also investigated the possibility of using the films for the single chamber operation by studying the electrical property of the films in the fuel/air mixed environment. It is shown that the resistance of the Ni film increases quickly in the mixed gas environment and thus further improvements of Ni-base anodes are required for using them in the single chamber operation.

• Korean Membrane Journal
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• 제3권1호
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• pp.69-74
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• 2001

Films of TiO$_2$/SiO$_2$ were deposited on the inner surface of the porous glass support tubes by decomposition of tetraisopropyl titanate (TIPT) and tetraethyl orthosilicate (TEOS) at atmospheric pressure. Dense and hydrogen -permselective membranes were formed at 400-600$\^{C}$. The permeation rates of H$_2$ through the membrane at 600$\^{C}$ were 0.2-0.4 ㎤(STP)/min-㎠ atm and H$_2$:N$_2$permeation ratios were above 1000. The permeation properties of the membranes were investigated at various deposition temperatures and TIPT/TEOS concentrations. Decomposition of TIPT alone at temperatures above 400$\^{C}$ produced porous crystalline TiO$_2$ films and they were not H7-selective. Decomposition of TEOS produced H$_2$-permeable SiO$_2$ films at 400-600$\^{C}$ but film deposition rate was very low. Addition of TIFT to the TEOS stream significantly accelerated the deposition rate and produced highly H$_2$-selective films. Increasing the TIPT/TEOS concentration ratio increased the deposition rate. The TiO$_2$/SiO$_2$ membranes formed at 600 $\^{C}$ have the permeation properties comparable to those of SiO$_2$ membranes produced from TEOS.

• 자연과학논문집
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• 제8권1호
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• pp.53-59
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• 1995

Alumina 세라믹스의 기계적 물성 증진을 위하여 SiC whisker로 강화시키고 소결 조제 및 소결 온도의 영향을 고찰하였다. Whiker의 소결억제 효과로 인하여 고상소결을 촉진하는 MgO나 $TiO_2$를 소결조제로 사용한 경우에서는 치밀한 소결체를 얻을 수 없었으나, 액상을 형성하는 $Y_2O_3$를 2wt% 첨가한 경우에 양호한 소결밀도를 얻을 수 있었다. whisker 첨가에 의한 기지의 기계적 물성의 증진 효과도 함께 얻을 수 있었다. 강화 효과는 보강재인 whiker 자체의 보강 효과와 함께 입성장 억제 효과가 복합적으로 작용한 것으로 판단되었다. 소결체를 HIP 처리한 경우에는 거의 이론 밀도까지 이르는 아주 치밀한 소결체의 제조가 가능하였으며, 기계적 물성은 상압소결 후의 결과에 비하여 향상됨을 확인할 수 있었다.

• 한국수소및신에너지학회논문집
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• 제23권4호
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• pp.353-363
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• 2012

The relationship between the diffusivity and electrochemical characteristics of lithium secondary battery with the modified Si anode material prepared in HF/$AgNO_3$ solution was investigated. The crystallographic structure and images of the modified porous Si and modified Si/Cu was examined using the X-ray diffraction, BET and SEM. To examine the effect of metal composite and pore size distribution according to chemical etching on the electrochemical characterization, the electrodes for half cells were prepared with the modified Si, modified Si/Cu, and modified Si/Cu annealed with $600^{\circ}C$. Our results showed that the chemical diffusivity of lithium ions was related to structure and resistance of Si/Cu composite anode material. The lithium diffusivity in modified silicon compound calculated from the CV was at the range of $1{\times}10^{-12}$ to $9{\times}10^{-16}cm^2/s$. The effects of modified silicon structure and resistance on the cycling efficiency were significant.

• 한국세라믹학회지
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• 제41권7호
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• pp.518-527
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• 2004

본 연구에서는 다공성 알루미나 기판의 기공 형상 개질을 통해서 필터의 집진 효율, 성능 및 내구성 향상을 위한 공정에 대해서 다루었다. 탄화규소 휘스커를 통한 기공 개질을 위해서 모재의 표면뿐만 아니라 기공 내부에까지 균일한 탄화규소 휘스커를 얻고자 화학 기상 침착법(Chemical Vapor Infiltration： CVI)을 사용하여 실험을 진행하였다. 실험결과 증착 온도와 증착 위치 및 입력 기체비와 같은 공정 조건의 변화에 따라 증착 경향에 확연한 차이를 나타내는 것을 알 수 있다. 다시 말해 첫째, 시편의 관찰 위치가 표면에서 내부로 들어갈수록 “반응 기체의 고갈 효과”로 인해 휘스커가 점점 세선화 되는 것을 볼 수 있으며 두 번째로 증착 온도에 따라서 debris, whisker, film등과 같이 증착물의 형상이 변화하게 된다. 이러한 형상의 변화는 여러 가지 물성의 변화를 가져오게 되는데 그 중에서, film이 증착 되는 경우에는 기판의 강도가 박 115.7% 가량 현저하게 증가하는 반면에 비표면적과 기체 투과율은 감소하게 되지만, 휘스커의 경우에는 강도가 95%, 비표면적은 33.5% 정도가 증가하며 기체 투과율 감소를 최소화 할 수 있다. 따라서 다공성 알루미나 기판 내부 기공에 휘스커를 증착 하면 필터로 인한 압력 저하를 최소화하면서 기공의 크기보다 작은 미세 분진들을 걸러 낼 수 있게 되므로 차세대 필터 재료로 기대된다.