• 한국세라믹학회지
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• 제33권12호
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• pp.1353-1364
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• 1996

Recently semiconductor doped glasses have attracted attention as nonlinear optical materials because of their large third order nonlinear optical properties. The transparent and homogeneous CdS-doped SiO2 glass thin films were obtained by the dip=coating process of the sol-gel method. Thin films were consisted of glasses containing CdS microcrystallites which were formed by dissolved Cd2+ and S2- ions in a SiO2 matrix solutions. A subsequent thermal treatment of this samples led the formation of colloidal agglomerates and finally of microcrystallites. The size of CdS microcrystallites was about 4 to 15 nm after thermal treatments at various heating conditions. From the optical absorption spectra of the CdS-doped SiO2 glass films it was found that the absorption edge was blue-shifted compared with that of the bulk CdS crystal(~2, 4 eV) and that the amount of energy shift was inversely proportional to the crystal size. And the band gap energy increased with the decrease in crystallite size indicating that the quantum size effects occured.

• 한국재료학회지
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• 제14권8호
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• pp.600-606
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• 2004

$Zn_{2}SiO_{4}:Mn$ phosphor particles were prepared by a flame spray pyrolysis method. It has been generally known that the high-temperature flame enables fast drying and decomposition of droplets. In the present investigation, the morphology and luminescent property of $Zn_{2}SiO_{4}:Mn$ phosphor were controlled in a severe flame preparation condition. The particle formation in the flame spray pyrolysis process was achieved by the droplet-to-particle conversion without any evaporation of precursors, which made it possible to obtain spherical $Zn_{2}SiO_{4}:Mn$ particles of a pure phase from a droplet. Using colloidal solutions wherein dispersed nano-sized silica particles were adopted as a silicon precursor. $Zn_{2}SiO_{4}:Mn$ particles with spherical shape and filled morphology were prepared and the spherical morphology was maintained even after the high-temperature heat treatment, which is necessary to increase the photoluminescence intensity. The $Zn_{2}SiO_{4}:Mn$ particles with spherical shape, which were prepared by the flame spray pyrolysis and posttreated at $1150^{\circ}C$, showed good luminescent characteristics under vacuum ultraviolet (VUV) excitation.

• Journal of Advanced Marine Engineering and Technology
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• 제29권1호
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• pp.98-106
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• 2005

The chemical conversion film formed on magnesium alloy was investigated by using the colloidal silica with some parameters such as solution pH. temperature, solution conditions, and treatment time. Moreover. the solutions consisted of colloidal silica titanium sulfate, and cobalt ions were used for the colloidal silica film to having a good corrosion resistance and adhesion properties. It was thought that the film at 298K was made with combination of Si-O. The quantity of film formed at high temperature such as 333K and 353K is smaller than dissolved quantity during chemical conversion treatment. Adding $CoSO_4$ to the colloidal silica solution enhanced the adhesion force between the silica film and magnesium substrate, The optimum conditions for the chemical conversion treatment solution were PH 2.90 s treatment, and 298K.

• 한국재료학회지
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• 제11권5호
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• pp.413-418
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• 2001

황산구리 전해욕에 분산제인 콜리이달 실리카($SiO_2$현탁액)를 첨가시키는 분산도금의 방법을 이용하여 음극에 석출하는 전해 석출물의 결정구조, 표면형상, 결정방향 등의 변화를 검토하였고 내식성, 물리적 특성 또한 조사하였다. 콜로이달 실리카를 분산시킨 구리 전해욕의 석출피막의 특성에 대해서 조사한 결과, 다음과 같은 결론을 얻었다. 전해 석출피막의 결정입자가 미세화 되고, 균일하게 성장됨은 물론, 결정 수가 증가하였으며, 콜로이달 실리카의 분산 효과에 의해서 전해 석출피막의 경도가 대략 16%까지 상승하였다. 또한 콜로이달 실리카를 분산시킨 극리 전착층의 X-선 회절패턴이 (111)면, (200)면과 (311)면이 거의 소멸되어 우선 방위가 (111)에서 (110)면으로 변화되었다. 부식전위의 측면에서도 콜로이달 실리카의 흡착 효과에 의해서 구리 전착층의 전위가 귀하게 이동하는 효과를 얻을 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.553-554
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• 2007

By sol-gel method, we have fabricated silica-titania hybrid film using silane treated colloidal $TiO_2$ and characterized the film through FT-IR, TGA, UV-VIS and AFM. The silica-titania hybrid film showed Ti-O-Si chemical bond at FT-IR peak of $910{\sim}940cm^{-1}$. The fabricated hybrid film showed thermal stability of around $350^{\circ}C$(5wt% loss temperature) and transparency more than 90%. In addition, the good surface smoothness was confirmed by AFM. Therefore, the silica-titania hybrid film with outstanding properties can be potential for application in electronics and displays.

• 한국정밀공학회지
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• 제19권8호
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• pp.134-140
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• 2002

Chemical mechanical polishing of aluminum and photoresist using colloidal silica-based slurry was experimented. The effects of slurry pH, silica concentration, and oxidizer ($H_2O_2$) concentration on surface roughness and removal rate were studied. The optimum slurry conditions for reduction of micro-scratch were investigated. The optimum chemical mechanical polishing with the colloidal silica-based slurry was compared with conventional chemical mechanical polishing with alumina-based slurry. Chemical mechanical polishing of the aluminum with the colloidal silica-based slurry showed improved result but chemical mechanical polishing of the photoresist did not. The improved result was comparative with that of chemical mechanical polishing with filtered alumina-based slurry which one of desirable methods to reduce the micro-scratch.

• Journal of Magnetics
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• 제20권3호
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• pp.221-228
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• 2015

Colloidal particles consisted of individual nanosized magnetite grains on the surface of the silica cores were obtained by two-stage sol-gel technique. Size distribution and microstructure of the particles were analyzed using atomic force microscopy, X-ray diffraction and Nitrogen thermal desorption. Magnetic properties of the particles were studied by the method of the longitudinal nonlinear response. It has been shown that nanoparticles of magnetite have a size corresponding to a superparamagnetic state but exhibit hysteresis properties. The phenomenon was explained using the magnetostatic interaction model based on the hypothesis of iron oxide particles cluster aggregation on the silica surface.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.278-278
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• 2010

Electrically tunable photonic band gap (PBG) materials based on crystalline structures have been developed for active components of display. Despite considerable advances, the intrinsic drawbacks of the crystalline PBG materials such as the strong angle dependent hue and difficulty of fabricating defect-free structures in large area have yet to be addressed for their practical applications. Here we report quasi-amorphous colloidal structures exhibiting angle-independent photonic colors in response to the electric stimuli. Moderately polydisperse colloidal Fe3O4@SiO2 nanoparticles dispersed in organic solvents exclusively form quasi-amorphous photonic materials at sufficiently high concentrations (> 30 wt%), and which reversibly reflect incident light in visible region ($\lambda$ peak = 490~655 nm) in response to the relatively low bias voltage (0~4 V). We show the angle-independent tunable photonic colors with the fast response time (50~170 ms) due to the isotropic nature of quasi-amorphous structures. Conventional vacuum injection technique is applicable for fabricating flexible full color photonic display pixels with various pre-defined shapes.

• 한국해양공학회지
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• 제23권5호
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• pp.85-91
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• 2009

A stainless steel that contains aggressive negative ion was known to decrease the corrosion resistance. Stainless steel with super corrosion resistance was developed for improvement of corrosion resistance. Super duplex stainless steel is widely used under sever environment because of good mechanical properties and corrosion resistance. Also, Super duplex stainless steel has long life in severe environments by showing the enough strength and corrosion resistance. But duplex stainless steel is not stabilized compared to austenite stainless steel in corrosion resistance. In this study, corrosion characteristic were investigated to super duplex stainless steel with additive 0.2% nitrogen with $SiO_2$ thin films coated or no coated by sol-gel method in 3.5% NaCl. From test results, corrosion current density in the heat-treated specimen for ${\sigma}$ phase precipitation was higher than that of different heat-treated specimen. Also, $SiO_2$ colloidal-coated specimen had not occurred almost corrosion.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.204-206
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• 2009

Luminescent films were prepared by infiltration of tris(dibenzoylmethane) mono(1, 10-phenanthroline) europium incorporated ormosil into colloidal $SiO_2$ photonic crystal templates. The PL intensity of the infiltrated film into the template was about 13 times higher than that of the plane film prepared without the template.