• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.337-343
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• 2014

A single layer ultrafiltration(UF) ceramic membrane was prepared using boehmite sol. Boehmite was synthesized using a typical sol-gel process with optimization of the viscosity, pH, molar ratio of aluminum isopropoxide(AIP) and $HNO_3$. Boehmite sol was coated on a microfiltration(MF) support using the dip-coating method. MF support was dipped into the boehmite sol with a withdrawal speed of 5 mm/s and was maintained for 10 s in the boehmite sol, resulting in a uniform UF membrane layer of $10{\mu}m$ thickness. The porosity of the obtained membrane was measured and found to be 41.2%; the pore size was found to range from 80~100 nm, corresponding to the pore size of the UF membrane. The flux of the obtained membrane was initially 540 $L/m^2h$ and approximately 85% of the initial flux was recovered using a periodic back-flushing process.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.876-880
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• 2001

The supported and unsupported boehmite ($\gamma$-AlOOH) membranes were prepared using a boehmite sol. The supported membrane was consisted of a porcelain support, two intermediate $\alpha-{Al_2}{O_3}$ layers, and a top boehmite membrane. XRD patterns showed that the supported top membrane had a higher $\theta-$ to $\alpha-{Al_2}{O_3}$ transformation temperature compared to the unsupported membrane. This result was also confirmed from microstructural study of the membrane. The shift in the phase transformation temperature should be explained by difference of a stress generated in the supported top membrane due to interaction between the support layers and the top membrane.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.451-456
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• 2010

A promising candidate material for a $H_2$ permeable membrane is SiC due to its many unique properties. A hydrogen-selective SiC membrane was successfully fabricated on the outer surface of an intermediate multilayer $\gamma-Al_2O_3$ with a graded structure. The $\gamma-Al_2O_3$ multilayer was formed on top of a macroporous $\alpha-Al_2O_3$ support by consecutively dipping into a set of successive solutions containing boehmite sols of different particle sizes and then calcining. The boehmite sols were prepared from an aluminum isopropoxide precursor and heated to $80^{\circ}C$ with high speed stirring for 24 hrs to hydrolyze the precursor. Then the solutions were refluxed at $92^{\circ}C$ for 20 hrs to form a boehmite precipitate. The particle size of the boehmite sols was controlled according to various experimental parameters, such as acid types and acid concentrations. The topmost SiC layer was formed on top of the intermediate $\gamma-Al_2O_3$ by pyrolysis of a SiC precursor, polycarbosilane, in an Ar atmosphere. The resulting amorphous SiC-on-$Al_2O_3$ composite membrane pyrolyzed at $900^{\circ}C$ possessed a high $H_2$ permeability of $3.61\times10^{-7}$ $mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$ and the $H_2/CO_2$ selectivity was much higher than the theoretical value of 4.69 in all permeation temperature ranges. Gas permeabilities through a SiC membrane are affected by Knudsen diffusion and a surface diffusion mechanism, which are based on the molecular weight of gas species and movement of adsorbed gas molecules on the surface of the pores.

• Proceedings of the Membrane Society of Korea Conference
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• 1992.10a
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• pp.7-7
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• 1992

Slip-casting 법으로 제조한 튜브형 다공성 $Al_2O_3$ 담체에 boehmite 입자를 단층 및 다층 졸-겔 침지코팅법과 본 실험실에서 개발한 새로운 가압 졸-겔 코팅법을 이용하여 알루미나 복합막을 제조하였다. 종래의 Yoldas법을 보완한 새로운 졸 제조방법에 의하여 입자크기가 작고 안정한 boehmite 졸을 제조 하였으며 졸의 제조조건에 따른 입자크기 변화와 열처리에 따른 겔의 상전이 및 비표면적 변화, 그리고 pH와 aging에 따른 안정성등을 규명하였다. 졸의 농도와 코팅시간 및 코팅 방법에 따른 코팅특성 등을 비교, 분석하여 복합막 제조에 최적인 코팅용 졸을 이용함으로써 담체 튜브내에 균열이 없고 재현성 있는 복합분리막을 제조할 수 있었다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.35.1-35.1
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• 2008

• Proceedings of the Membrane Society of Korea Conference
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• 1993.04a
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• pp.35-35
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• 1993

튜브형 $\alpha-Al_2O_3$ 담체에 졸-겔 침지코팅법과 가압코팅(pressurized coating) 법으로 boehmite 졸과 극미세 입자 SiO$_2$ 및 TiO$_2$ 졸을 코팅한 후 200$\circ$C~500$\circ$C 에서 열처리하여 복합분리막을 제조하였다.

• Korean Journal of Materials Research
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• v.10 no.9
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• pp.619-623
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• 2000

Alumina membrane was prepared by sol-gel coating method using boehmite powder(${\Upsilon}-AlOOH$). The supported and the unsupported alumina membrane were fabricated to investigate the phase transformation and change of microstructure. It is important to control the homogeneous pore size and distribution in application of filtering process. The ${\theta}-to\;{\alpha}-AL_2O_3$ phase transformation (XRD) and the change of microstructure was investigated using scanning electron microscopy(SEM). XRD patterns showed that the supported membrane had $100^{\circ}C$ higher ${\theta}-to\;{\alpha}-AL_2O_3$ transformation temperature compared to the unsupported membrane. The similar effect was also observed for microstructural change of the membrane.

• Membrane Journal
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• v.28 no.1
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• pp.21-30
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• 2018

In this study, homogeneous and defect-free ceramic ultrafiltration membranes were fabricated by using the sol-gel method. A boehmite sol was synthesized and coated onto the surface of alumina hollow fiber microfiltration membranes. The effect of sol viscosity and surface tension on the coating layer homogeneity and thickness was investigated. The optimum coating repetition using pristine sol was determined to be 3 times, as the samples coated more than 4 times showed delamination. Fixing the coating repetition to 3 times, the effect of sintering temperature was also studied in this work. The samples sintered at $1000^{\circ}C$ exhibited the highest pure water permeability with the molecular weight cut-off (MWCO) of approximately 51 kDa (10 nm dextran), and the samples sintered at 600, $800^{\circ}C$ displayed the MWCO of 12 kDa (5 nm dextran). The ultrafiltration membranes prepared in this work showed competitive performance compared to the reported ceramic ultrafiltration membranes.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.622-624
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• 2001

The CVD film of methoxysilane derived from diphenyldimethoxysilane(DPDMS) was formed on the outer surface of a porous ${\alpha}-alumina$ support tube coated(via dipping-drying-calcining) with a boehmite sol(0.3 mol-Al/L). The resulting silica membrane($500^{\circ}C,\;P_{fe}\;=\;130\;Pa$) showed a permeance of $5.18{\times}10^{-8}\;mol\;{\cdot}\;m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}\;for\;CO_2$ and a permselectivity of 13.35 for $CO_2/N_2\;at\;30^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.32 no.1
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• pp.63-70
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• 1995

A crack-free ceramic composite membrane with micropores has been synthesized by the pressurized sol-gel coating technique using the mixed Al2O3-SiO2 sols. The mixed sols were prepared by mixing nanoparticulate SiO2 and boehmite sols. These sols were more stable at lower pH, but very unstable when their copositions were in the range of 50~75mol% of SiO2 at the same pH. The mixed Al2O3-SiO2 membrane prepared from the mixed sol (0.2mol/$\ell$ of solid content and pH=2) containing 40mol% of SiO2 had the mean pore radius of 0.80nm and the specific surface area of 280$m^2$/g. The nitrogen permeability through the coated Al2O3-SiO2 layer was 42$\times$107mol/$m^2$.s.Pa. It was found that the thermal stability of aluminosilicate membranes, even through similar to that of SiO2 membranes, was much improved in comparison with ${\gamma}$-alumina membranes.