• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.333-336
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• 2010

Fe/$Al_2O_3$ granules with various compositions were prepared by combining sol-gel with oil drop method for Fishcer-Tropsh reaction to produce light olefin from synthesis gas. The granules was characterized and employed as a catalyst in the reaction. The surface area of granules was decreased with increasing Fe concentration. Especially, granule with 1.5 of Al/Fe ratios showed the highest CO conversion. However, the olefin selectivity was hardly affected by Al/Fe ratio. K concentration of granule gave a significant effect on catalytic performance. Initial CO conversion and olefin selectivity were increased with K concentration. However, the catalyst with higher K concentration was deactivated rapidly.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.592-597
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• 2014

The graphite/$SiO_2$ composites as anode materials for lithium-ion batteries were prepared by sol-gel method to improve the graphite's electrochemical characteristics. The prepared graphite/$SiO_2$ composites were analysed by XRD, FE-SEM and EDX. The graphite surface modified by silicon dioxide showed several advantages to stabilize SEI layer. The electrochemical characteristics were investigated for lithium ion battery using graphite/$SiO_2$ as the working electrode and Li metal as the counter electrode. Electrochemical behaviors using organic electrolytes ($LiPF_6$, EC/DMC) were characterized by charge/discharge, cycle, cyclic voltammetry and impedance tests. The lithium ion battery using graphite/$SiO_2$ electrodes had better capacity than that of using graphite electrodes and was able to deliver a discharge capacity with 475 mAh/g at a rate of 0.1 C. Also, the capacity retention ratio of the modified graphite reaches 99% at a rate of 0.8 C.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3031-3038
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• 2009

Cobalt-loaded activated carbon fibers (ACFs) supported titanium dioxide ($TiO_2$) photocatalyst was developed by sol-gel method. The Co-ACFs/$TiO_2$ photocatalyst were characterized by scanning electron microscope (SEM), X.ray diffraction patterns (XRD), energy dispersive X.ray analysis (EDX) and UV-vis absorption spectroscopy. Decomposition efficiency of methylene blue (MB) solution by Co-ACFs/$TiO_2$ photocatalyst reached almost 100% under 300 min reaction. The MB molecules in the bulk solutions were supposed to be condensed around $TiO_2$ particles by adsorption of ACFs. Therefore, the photocatalyst possesses the combined effect of adsorption by activated carbon fibers and photocatalytic reactivity of $TiO_2$ on MB degradation. Due to the cobalt has electron transition effece, thus improved the photodegradation of MB solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1760-1767
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• 2010

FAT compounds photocatalysts were prepared with $TiOSO_4{\cdot}xH_2O$ (TOS) by a sol-gel method. The samples were characterized by scanning electron microscopy (SEM), BET specific surface area, X-ray diffraction analysis (XRD) and energy dispersive X-ray spectroscopy (EDX). The SEM results showed that ferric compounds and titanium dioxide were fixed onto the AC surfaces. The XRD results showed that Fe-AC/$TiO_2$ composites mostly contained anatase phase. EDX showed the presence of C, O, and Ti with Fe peaks in all samples. The photocatalytic activities were evaluated by the photocatalytic oxidation of methylene blue (MB) solution, via compare photodegradation of MB solution under visible light and UV light separately. Fe-AC/$TiO_2$ composites had an excellent photocatalytic under strong visible light irradiation. A small amount of Fe ions in AC/$TiO_2$ particles could obviously enhance their photocatalytic activity.

• Korean Chemical Engineering Research
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• v.50 no.1
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• pp.182-185
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• 2012

N-doped $TiO_2$nanotubes have been newly prepared by two stage sol-gel and strong-alkali hydrothermal process using $TiCl_4$ and hydrazine/ammonia aqueous solution as raw materials. These nanotubes revealed a well developed anatase crystalline phase and perfect nanotube morphology with the diameter around 10nm and the wall thickness below 3 nm. Also, they showed a superior visible light activity and yellowish color due to the light absorption redshifted by ~35 nm and ~25 nm compared to undoped $TiO_2$ nanotubes and anatase nanoparticles, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05b
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• pp.102-105
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• 2005

가스센서는 응용 분야와 기능 및 종류가 다양하고 최첨단 분야로서 학문적으로는 물리, 화학, 전기, 전자 및 기계 등의 배경을 필요로 하며 산업적으로는 공업 전 분야와 농림, 축산, 사무기기에서 뿐만 아니라 공해 방진용(자동차 연소제어 및 배출가스 제어, 대기오염 감시등), 민생용(조리, 환기, 공조 등), 교통 보안용(음주운전측정 및 음주운전 방지장치 등), 방재용(가스 누설 탐지기, 불완전 연소 방지, 산소 결핍, 화재 등), 의료용(호기, 마취가스의 분석 등) 매우 광범위하며 점점 더 확대되어 가고 있다. 본 연구에서는 검출 가스 종류에 따라 졸-겔법으로 감응막을 최적 설계하고, 최적으로 설계된 감응막을 디핑법으로 코팅처리한 후 최적으로 열처리하여 센서를 제작하였다. 또한, 자체 제작한 가스검출 시스템에 제작된 센서를 장착하여 센서의 가스 검출 특성을 측정하고, 측정 데이터를 이용하여 휴대용 가스 검출 시스템을 설계 제작하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.8
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• pp.680-684
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• 2007

In this study, we investigated the effects of structural and electrical properties of $(Ba_{0.6},\;Sr_{0.3},\;Ca_{0.1})TiO_3$ thick films with variation $Dy_2O_3$ contents. $(Ba_{0.6},\;Sr_{0.3},\;Ca_{0.1})TiO_3$ powders, prepared by the sol-gel method, were mixed organic vehicle. The BSCT thick films doped with 0.1, 0.3, 0.5, 0.7 mol% $Dy_2O_3$ were fabricated by the screen-printing techniques on the alumina substrates and the structural and dielectric properties were investigated with variation of $Dy_2O_3$ doping contents. All BSCT thick films were sintered at $1420^{\circ}C$, for 2hr. In the TG-DTA analysis, the formation of the polycrystalline perovskite phase was observed at around $670 ^{\circ}C$. In the XRD analysis, all BSCT thick films showed the cubic perovskite structure. The average thickness of BSCT thick films was approximately $65{\mu}m$. The Curie temperature decreased with increasing $Dy_2O_3$ amount. The relative dielectric constant and dielectric loss of BSCT thick films doped with $Dy_2O_3$ 0.1 mol% were 6267 and 2.6 %, respectively.

• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.96-99
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• 2005

Phase transition from normal- to inverse-spinel structure has been observed for $Fe_xCo_{3-x}O_4$ thin films as the Fe composition (x) increases from 0 to 2. The samples were fabricated as thin films by sol-gel method on Si(100) substrates. X-ray diffraction measurements revealed a coexistence of two phases, normal and inverse spinel, for $0.76{\le}x{\le}0.93$. The normal-spinel phase is dominant for $x{\le}0.55$ while the inverse-spinel phase for $x{\ge}l.22$. The cubic lattice constant of the inverse-spinel phase is larger than that of the normal-spinel phase. For both phases the lattice constant increases with increasing x. X-ray photoelectron spectroscopy measurements revealed that both $Fe^{2+}$ and $Fe^{3+}$ ions exist with similar strength in the x=0.93 sample. Conversion electron $M\ddot{o}ssbauer$ spectra measured on the same sample showed that $Fe^{2+}$ ions prefer the octahedral $Co^{3+}$ sites, indicating the formation of the inverse-spinel phase. Analysis on the measured optical absorption spectra for the samples by spectroscopic ellipsometry indicates the dominance of the normal spinel phase for low x in which $Fe^{3+}$ ions tend to substitute the octahedral sites.

• Macromolecular Research
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• v.17 no.9
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• pp.688-696
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• 2009

In this study, a new class of polyurethane (PU) nanofibers containing silver (Ag) nanoparticles (NPs) was synthesized by electrospinning. A simple method that did not depending on additional foreign chemicals was used to self synthesize the silver NPs in/on PU nanofibers. The synthesis of silver NPs was carried out by exploiting the reduction ability of N,N-dimethylformamide (DMF), which is used mainly to decompose silver nitrate to silver NPs. Typically, a sol-gel consisting of $AgNO_3$/PU was electrospun and aged for one week. Silver NPs were created in/on PU nanofibers. SEM confirmed the well oriented nanofibers and good dispersion of pure silver NPs. TEM indicated that the Ag NPs were 5 to 20 nm in diameter. XRD demonstrated the good crystalline features of silver metal. The mechanical properties of the nanofiber mats showed improvement with increasing silver NPs content. The fixedness of the silver NPs obtained on PU nanofibers was examined by harsh successive washing of the as-prepared mats using a large amount of water. The results confirmed the good stability of the synthesized nanofiber mats. Two model organisms, E. coli and S. typhimurium, were used to check the antimicrobial influence of these nanofiber mats. Subsequently, antimicrobial tests indicated that the prepared nanofibers have a high bactericidal effect. Accordingly, these results highlight the potential use of these nanofiber mats as antimicrobial agents.

• Korean Journal of Materials Research
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• v.16 no.8
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• pp.524-528
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• 2006

On the synthesis of Au/$TiO_2$ core-shell structure nanoparticle, the effect of concentration of $Ti^{4+}$ and reaction temperature on the morphology and optical property of Au/$TiO_2$ core-shell nanoparticles is examined. A gold colloid was prepared by $HAuCl_4{\cdot}4H_2O\;and\;C_6H_5Na_3{\cdot}2H_2O$. Titanium stock solution was prepared by mixing solution of titanium(IV) isopropoxide (TTIP) and triethanolamine (TEOA). The concentrations of $Ti^{4+}$ stock solution were adjusted to $10.01{\sim}0.3$ mM, and then the gold colloid is added to the $Ti^{4+}$ stock solution. Au/$TiO_2$ core-shell structure nanoparticles could be prepared by the hydrolysis of the $Ti^{4+}$ stock solution at $80^{\circ}C$. The size of synthesized Au nanoparticles was 15 nm. The thickness of $TiO_2$ shell on the surface of gold particles was about 10 nm. The absorption peak of synthesized Au/$TiO_2$ core-shell nanoparticles shifted towards the red end of the spectrum by about 3 nm because of the formation of $TiO_2$ shell on the surface of gold particles. The good $TiO_2$ shell is produced when $Ti^{4+}$ concentration is varied between 0.01 and 0.05 mM, and reaction temperature is maintained at $80^{\circ}C$. The crystal structure of $TiO_2$ shell was amorphous.