• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.35-36
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• 2006

The influence of the concentration of precursor solution and the number of solution coatings on the densification of the Pb($Zr_xTi_{1-x}$)$O_3$(PZT) thick films was studied. PZT powder and PZT precursor solution were prepared by sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The powder and solution of composition were PZT(70/30) and PZT(30/70), respectively. The coating and drying procedure was repeated 4 times. And then the PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 to 2.0 mol/L[M] and the number of coating was repeated from 0 to 6. The relative dielectric constant of the PZT thick film was increased with increasing the number of solution coatings and the thick films with 15M, 6-time coated showed the 698. The remanent polarization of the 1.5M, 6-time coated PZT thick films was 38.3 ${\mu}C/cm^2$.

• 한국연소학회지
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• 제11권2호
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• pp.7-14
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• 2006

Catalytic combustion is one of the suitable methods for micro power source due to high energy density and it can be applied to micro structured chamber without consideration of quenching since it is flameless combustion. Catalyst loading in the micro structured combustion chamber is one of the most important issues in the development of micro catalytic combustors. In this research, to coat catalyst on the chamber wall, two methods were investigated. First, $Al_2O_3$ was selected as a support of Pt and $Pt/Al_2O_3$ was synthesized through the alumina sol-gel procedure. To improve the coating thickness and adhesion between catalyst and substrate, heat resistant and water solvable organic-inorganic hybrid binder was used. Porous silicon was also investigated as a catalyst support for platinum. Through the parametric studies of current density and etching time, fabrication process of $1{\sim}2{\mu}m$ of diameter and about $25{\mu}m$ depth pores was confirmed. Coated substrates were test in the micro channel combustor which was fabricated by the wet etching and machining of SUS 304. Using $Pt/Al_2O_3$ coated substrate and Pt coated porous silicon substrate, conversion rate of fuel was over 95 % for $H_2/Air$ premixed gas.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 추계학술발표강연 및 논문개요집
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• pp.136-136
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• 2003

In fiber optic networks, system size and cost can be significantly reduced by development of optical components through planar optical waveguides. One important step to realize the compact optical devices is to develop planar optical amplifier to compensate the losses in splitter or other components. Planar amplifier provides optical gain in devices less than tens of centimeters long, as opposed to fiber amplifiers with lengths of typically tens of meters. To achieve the same amount of gain between the planar and fiber optical amplifier, much higher Er doping levels responsible for the gain than in the fiber amplifier are required due to the reduced path length. These doping must be done without the loss of homogeniety to minimize Er ion-ion interactions which reduce gain by co-operative upconversion. Sol-gel process has become a feasible method to allow the incorporation of Er ion concentrations higher than conventional glass melting methods. In this work, Er-doped $SiO_2$-A1$_2$ $O_3$ films were prepared by two different method via sol -Eel process. Tetraethylorthosilicate(TEOS)/aluminum secondary butoxide [Al (OC$_4$ $H_{9}$)$_3$], methacryloxypropylcnethoxysaane(MPTS)/aluminum secondary butofde [Al(OC$_4$ $H_{9}$)$_3$] systems were used as starting materials for hosting Er ions. Er-doped $SiO_2$-A1$_2$ $O_3$ films obtahed after heat-treating, coatings on Si substrate were characterized by X-ray din action, FT-IR, and N-IR fluorescence spectroscopy. The luminescence properties for two different processing procedure will be compared and discussed from peak intensity and life time.

• 센서학회지
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• 제16권6호
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• pp.395-400
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• 2007

Ambient drying sol-gel processing was used for monolithic silica ambigels in the temperature range of $130-250^{\circ}C$. A new method of mesopore ambigels, which mean the aerogels prepared by ambient pressure drying process synthesis, is suggested at first. This method includes two important approaches. The first point is that $SiO_{2}$ surface modification of wet gel was performed by trimethylchlorosilane in n-butanol solution. This procedure is provided the silica gel mesopore structure formation. The second point is a creation of the ternary azeotropic mixture water/n-butanol/octane as porous liquid, which is effectively provided removing of water such a low temperature by 2 step drying condition under ambient pressure. The silica aerogels, which were prepared by ambient pressure drying from azeotropic mixture of water/n-butanol/octane, are transparent, crack-free and mesoporous (pore size ${\sim}$ 5.6 nm) with surface area of ${\sim}$ $923{\;}m^2/g$, bulk density of $0.4{\;}g/cm^3$ and porosity of 85 %.

• 한국세라믹학회지
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• 제47권6호
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• pp.590-597
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• 2010

HTGR using a TRISO coated particles as nuclear raw fuel material can be used to produce clean hydrogen gas and process heat for a next-generation energy source. For these purposes, a TRISO coated particle was prepared with 3 pyro-carbon (buffer, IPyC, and OPyC) layers and 1 silicone carbide (SiC) layer using a CVD technique on a spherical $UO_2$ kernel surface as a fissile material. In this study, a spherical $UO_2$ particle was prepared using a modified sol-gel method with a vibrating nozzle system, and TRISO coating fabrication was carried out using a fluidized bed reactor with coating gases, such as acetylene, propylene, and methyltrichlorosilane (MTS). As the results of this study, a spherical $UO_2$ kernel with a sphericity of 1+0.06 was obtained, and the main process parameters in the $UO_2$ kernel preparation were the well-formed nature of the spherical ADU liquid droplets and the suitable temperature control in the thermal treatment of intermediate compounds in the ADU, $UO_3$, and $UO_2$ conversions. Also, the important parameters for the TRISO coating procedure were the coating temperature and feed rate of the feeding gas in the PyC layer coating, the coating temperature, and the volume fraction of the reactant and inert gases in the SiC deposition.

• 멤브레인
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• 제16권4호
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• pp.303-312
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• 2006

상변환과 졸-겔 반응을 동시에 행하는 새로운 제막법으로 나노크기의 $ZrO_2$ 입자가 함유된 비대칭형 PES-$ZrO_2$ 복합 막을 제조하였다. PES-$ZrO_2$ 복합 막 제조의 최적 제막 조건을 복합 막에의 인 흡착실험을 수행하여 인 흡착량이 최대가 되는 조건으로서 결정하였는바, 최적 제막 조건은 캐스팅 용액에 1 mL의 PES 당 0.15 mL의 $Zr(PrO)_4$ 첨가 및 비용매 1 L에 1 mL $Zr(PrO)_4$ 당 30 mL의 $HNO_3$ 촉매를 첨가했을 때 이었다. 복합 막의 단면 구조, 막성능 및 $ZrO_2$ 입자 함유량 변화를 SEM, 순수투과량, TGA, ICP, XRD 및 접촉각 측정을 통해 결정하였는바, 캐스팅 용액에의 $Zr(PrO)_4$ 첨가량이 증가할수록 순수 투과량이 증가하며, $ZrO_2$ 입자 함유량은 1 mL의 PES 당 0.15 mL의 $Zr(PrO)_4$ 첨가했을 때 최대가 되었다. 복합 막의 표면 특성을 친수성으로 개선하기 위하여 인산처리를 하였으며, 인산처리 전후(前後)의 두 종류 PES-$ZrO_2$ 복합 막을 대상으로 한 BSA 용액의 dead-end 한외여과 실험을 수행하여 막오염 형성의 억제 정도를 평가한 결과 인산처리 시킨 복합 막의 경우 투과량과 BSA 배제도 모두 약 40% 정도 증가하였는데 이는 복합 막을 인산처리 시킴으로서 막특성이 친수화 되었기 때문이다.

• 한국콘텐츠학회논문지
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• 제9권10호
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• pp.451-463
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• 2009

본 연구의 목적은 태양전지의 변환효율을 높이기 위한 박막형 소재 물질 개발과 전지의 조립과정을 개선 발달시키기 위한 것이다. 이 연구에 사용된 이산화티타니움은 물과 알콕사이드 몰비, 용액 pH의 변화, 분말의 묵힘조건 등 반응조건을 조절한 솔-겔 방법에 의하여 조제되었다. 준비된 이산화티타니움은 $300{\sim}750^{\circ}C$의 열처리조건 범위에서 소결하였다. $600^{\circ}C$의 열조건에서 만들어진 이산화티타니움은 XRD 패턴에서 강한 세기의 아나타제형이 나타났고, $750^{\circ}C$에서 소결되었을 때에는 아나타제형와 루틸형의 혼합물이 나타났다. 또한 소결온도와 묵힘시간 등에 따라 합성된 이산화티타니움의 특성은 묵힘시간이 증가함에 따라 아나타제형 결정으로 변환되는 것을 확인할 수 있었다. 한편 전류밀도는 묵힘시간과 온도에 따라 증가하였고, 변환효율은 전류밀도의 증가로 역시 증가함을 알 수 있었다. 산소분위기하에서 산소와 카드뮴텔루라이드의 화학결합이 생성됨을 관찰할 수 있었고, 카드뮴텔루라이드의 박막위의 산소가 크롬메이트와 하이드라진 처리에 의하여 감소되는 것을 알수 있었다. 결론적으로 공기분위기하에서 $550^{\circ}C$의 급속 소결조건에서 만들어진 카드뮴텔루라이드의 에너지변환효율은 $0.07cm^2$, $1.0cm^2$의 면적에 대해 각각 12.0%, 6.0%로 나타내었다.

• Advances in nano research
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• 제6권1호
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• pp.1-19
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• 2018

Iron oxide nanoparticles excite researcher interest in biomedical applications due to their low cost, biocompatibility and superparamagnetism properties. Magnetic iron oxide especially magnetite ($Fe_3O_4$) possessed a superparamagnetic behaviour at certain nanosize which beneficial for drug and gene delivery, diagnosis and imaging. The properties of nanoparticles mainly depend on their synthesis procedure. There has been a massive effort in developing the best synthetic strategies to yield appropriate physico-chemical properties namely co-precipitation, thermal decomposition, microemulsions, hydrothermal and sol-gel. In this review, it is discovered that magnetite nanoparticles are best yielded by co-precipitation method owing to their simplicity and large production. However, its magnetic saturation is within range of 70-80 emu/g which is lower than thermal decomposition and hydrothermal methods (80-90 emu/g) at 100 nm. Dimension wise, less than 100 nm is produced by co-precipitation method at $70^{\circ}C-80^{\circ}C$ while thermal decomposition and hydrothermal methods could produce less than 50 nm but at very high temperature ranging between $200^{\circ}C$ and $300^{\circ}C$. Thus, co-precipitation is the optimum method for pre-compliance magnetite nanoparticles preparation (e.g., 100 nm is fit enough for biomedical applications) since thermal decomposition and hydrothermal required more sophisticated facilities.

• 한국분말재료학회지
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• 제18권4호
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• pp.347-358
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• 2011

Two different schemes were adopted to fabricate ordered macroporous structures with face centered cubic lattice of air spheres. Monodisperse polymeric latex suspension, which was synthesized by emulsifier-free emulsion polymerization, was mixed with metal oxide ceramic nanoparticles, followed by evaporation-induced self-assembly of the mixed hetero-colloidal particles. After calcination, inverse opal was generated during burning out the organic nanospheres. Inverse opals made of silica or iron oxide were fabricated according to this procedure. Other approach, which utilizes ceramic precursors instead of nanoparticles was adopted successfully to prepare ordered macroporous structure of titania with skeleton structures as well as lithium niobate inverted structures. Similarly, two different schemes were utilized to obtain disordered macroporous structures with random arrays of macropores. Disordered macroporous structure made of indium tin oxide (ITO) was obtained by fabricating colloidal glass of polystyrene microspheres with low monodispersity and subsequent infiltration of the ITO nanoparticles followed by heat treatment at high temperature for burning out the organic microspheres. Similar random structure of titania was also fabricated by mixing polystyrene building block particles with titania nanoparticles having large particle size followed by the calcinations of the samples.

• 한국분말재료학회지
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• 제12권4호
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• pp.249-254
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• 2005

Titanium dioxide was prepared by Polymer Complex Solution Method(PCSM) according to the mole ratio of Titanium (IV) isopropoxide(TTIP)/solvent and polymer(Poly Ethylene Glycol). Polymer electrolytes were usually made by dispersing preproduced ceramic nanoparticles in a polymer matrix. Using this method, pure and nano-sized $TiO_2$ powder was synthesized through a simple procedure and polymer entrapment route. At the optimum amount of the polymer, the titanium ions are dispersed in solution and a homogeneous polymeric network is formed. The maximum intensity of anatase phase of $TiO_2$ was achieved by calcining at $500^{\circ}C$ for 2h. The synthesized $TiO_2$ powders were nano-sized and the average size was about 50nm. Anatase/Rutile ratio of the synthesized $TiO_2$ was 70%/30%.