• Journal of the Korean Ceramic Society
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• v.32 no.9
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• pp.1076-1084
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• 1995

A mixture of aluminum isopropoxide (Al(OC3H7i)3) solution and sodium hydroxide (NaOH) solution was hydrolyzed in the range between pH 1~14. the powder obtained from sol-gel process was calcined at several temperatures and crystallization behaviors of various samples were investigated. The hydrolyzed sols of pH 1~6 wre clear, or near clear. On the other hand, powder precipitated from sols of pH 7~14. The sample obtained from pH 3 solution crystallized via complicated route, and $\beta$-Al2O3 and $\beta$"-Al2O3 phases appeared at lower temperature than samples from other pH conditions. And the quantity of remained $\beta$"-Al2O3 phase after heat treatment at 150$0^{\circ}C$ was more than samples from other pH conditions. After sintering, ionic conductivities were 1.3$\times$10-4S.cm-1 to 0.76$\times$10-4S.cm-1.0-4S.cm-1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.234-234
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• 2008

Chemically homogeneous $Ba_{0.6}Sr_{0.4}TiO_3$ (BST) sols were synthesized using barium acetate, strontium acetate, and titanium isoproxide as starting materials. BST thin films of thickness 340 nm were deposited on Pt/$TiO_2/SiO_2$/Si and alumina substrates using spin coating method. The technique used for the processing of these films was Ultraviolet (UV) sol-gel photoannealing, using phto-sensitivity precursor solutions and UV-assisted rapid thermal processing(UV-RTP). The crystallization behaviour of the BST sols and thin films was studied by differential thermal analysis (DTA) and X-ray diffraction (XRD). Variation of permittivity and dielectric loss were measured in LCR-meter, model HP 4394A.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.634-641
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• 2004

The photocatalytic performance of $TiO_2$ thin films coated on porous alumina balls using various aqueous $TiOCl_2$ solutions as starting precursors, to which 1.0 $mol\%$ transition metal ($Ni^{2+},\;Cr^{3+},\;Fe^{3+},\;Nb^{3+},\;and\;V^{5+}$) chlorides had been already added, has been investigated, together with characterizations for $TiO_2$ sols synthesized simultaneously in the same autoclave through hydrothermal method. The synthesized $TiO_2$ sols were all formed with an anatase phase, and their particle size was between several nm and 30 nm showing ${\zeta}-potential$ of $-25{\sim}-35$ mV, being maintained stable for over 6 months. However, the $TiO_2$ sol added with Cr had a much lower value of -potential and larger particle sizes. The coated $TiO_2$ thin films had almost the same shape and size as those of the sol. The pure $TiO_2$ sol showed the highest optical absorption in the ultraviolet light region, and other $TiO_2$ sols containing $Cr^{3+},\;Fe^{3+}\;and\;Ni^{2+}$ showed higher optical absorption than pure sol in the visible light region. According to the experiments for removal of a gas-phase benzene, the pure $TiO_2$ film showed the highest photo dissociation rate in the ultraviolet light region, but in artificial sunlight the photo dissociation rate of $TiO_2$ coated films containing $Cr^{3+},\;Fe^{3+}\;and\;Ni^{2+}$ was measured higher together with the increase of optical absorption by doping.

• Journal of the Korean Ceramic Society
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• v.38 no.7
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• pp.621-627
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• 2001

알루미나 졸에 평균 25nm의 TiO$_2$(Degussa P25) 광 촉매 분말을 분산하여 광촉매 코팅제를 제조하였다. 점도 약 24 cps를 가지 4.4 wt%의 알루미나 졸로부터 약 300nm 두께의 코팅막이 제조되었으며, 졸 점도의 증가에 비례하여 코팅막의 두께도 증가하였다. TiO$_2$광 촉매의 코팅용 바인더로 이용한 알루미나 졸의 결정형은 25~30$0^{\circ}C$에서 pseudo boehmite (AlOOH)이었으며, 50$0^{\circ}C$ 이상에서는 ${\gamma}$-Al$_2$O$_3$으로 전환되었다. AlOOH/TiO$_2$코팅막은 oleic acid와 humic acid에 대한 기상 및 수상 조건에서의 광 촉매 실험에서 우수한 유기물의 광분해 효능을 나타내었다. 아울러 EGI(Electro-Galvanized Iron)에 코팅된 AlOOH/TiO$_2$코팅막은 내식성 및 내지문성의 효과도 부수적으로 나타내었다.

• Membrane Journal
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• v.25 no.1
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• pp.15-26
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• 2015

In this study, porous metal (O.D. = 10 mm, length = 10 mm, 316 L SUS, Mott Corp.) and ${\alpha}$-alumina tube (O.D. = 10 mm, length = 50 mm, Pall, German) support was modified with suspension sols, which were consisted of $3{\sim}4{\mu}m$ and 150 nm size of ${\alpha}$-alumina particle in the water or silica-zirconia colloidal sol. The porous support was fabricated by dip coating method for 5 seconds with suspension of alumina particles. After drying at $100^{\circ}C$ for 1 h, it was calcined at $550^{\circ}C$ for 30 min. It was repeated several times in order to decrease big pore on support. The surface roughness and largest pore size on the porous support was decreased by increasing coating times with $3{\sim}4{\mu}m$ size of ${\alpha}$-alumina particle and alumina coating with 150 nm size of ${\alpha}$-alumina particle served as further smoothening the surface and decreasing the pore size of the substrate. And the silica-zirconia membranes were successfully prepared on the modified porous metal and ${\alpha}$-alumina supports, and showed hydrogen permeance in the range of $1.8-8.4{\times}10^{-4}mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$ and $3.3-5.0{\times}10^{-5}mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.772-775
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• 2003

The development of new improved type of dielectric materials on the conception of multiphase structure has been carried out in this paper. Metal alkoxides solutions were used for application of thin film by electrophoretic deposition technique. We succeeded in preparation of amorphous and composite dielectric films from Al alkoxides. Specific features of the preparation technique were considered. Microstructure of the films was examined as well as their dielectric properties. TEM analyses reveals that films deposited from aging sols and heat-treated at temperatures as low as $400^{\circ}C$ contain small whiskers of ${\delta}-Al_2O_3$.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.243-243
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• 2003

무기 나노 입자와 유기물간의 균일한 화학적 결합으로 제조된 나노 구조형 재료는 수많은 용도에 부응할 수 있는 기계적, 전기적 및 광학적 특성을 설계, 제조하는데 유용한 방법으로 사용되고 있다. 이중 화학적 습식 졸-겔 공정은 나노 구조형 유/무기 하이브리드 재료 제조에 매우 효과적인 방법으로 알려져 있으며 내부식성 금속 코팅막, 내 스크래치 코팅막 제조에 활용되고 있다. 그러나 무기 나노 졸 입자와 유기물과의 매개로 작용하는 커플링제와의 하이브리드 과정에 대한 정보는 극히 조금 알려져 있다. 본 연구에서는 알루미나 나노 졸과 GPS((3-glycidoxypropyl-triethoxysilane)와의 하이브리드 생성 과정을 이온 전도도 측정으로 관찰한 결과를 보고하고자 한다. 알루미나 나노 졸은 Al(NO$_3$)$_3$.9$H_2O$ 수용액에 NH$_4$OH를 가하여 침전물을 얻고 여과 및 수세하여 졸 입자의 함량이 약 5 wt%가 되게 이온교환수와 해교제인 초산을 소량 가하여 10$0^{\circ}C$에서 약 50시간 열처리하는 방법으로 제조하였다. 알루미나 졸 입자와 GPS와의 결합 과정을 reactor FT-IR로 시간에 파라 연속적으로 분석하여 그 반응 경로를 이온 전기전도와 비교하여 논의 될 것이다. 아래 그림 1은 알루미나 나노 졸에 GPS를 첨가한 후 시간에 따라 얻어진 이온 전기전도도를 나타낸 그림이다.

• The Journal of Natural Sciences
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• v.6 no.1
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• pp.103-108
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• 1993

Zeolites were discovered as a natural mineral more than two hundred ago. In the beginning, the mineral was used as ion-exchange material and adsorbent. After the end of World War II , however, a variety of zeolites have become available in large amounts because of the establishment of low temperature synthesis and the discobery of natural zeolite deposits of sedimentary origin. Various uses of xeolite were developed utilizing the unique crystal strucrure and function of these minerals. In connection with this development remakable progress has also been made in basic stuides on the related geology and mineralogy, crystallization from sols and gels, structure, ion exchange, adsorption and cataiysis. As a result, zeolites, which had been known only as mineral specimens displayed in museums. established a firm position among the high-technology masterials with excellent functional capabilities.