• 한국세라믹학회지
• /
• 제42권6호
• /
• pp.399-404
• /
• 2005

Anti-reflection film was coated by using spherical silica nano colloidal particles and fumed silica particles. Silica colloid sol was reserved between two inclined slide glasses by capillary force, and particles were stacked to form a film onto the substrate as the upper glass was sliding. The deposition processes were studied to enhance the wavelength dependency of the light transmittance and to control the effective refractive index of the film. Both of the spherical and fumed silica particles showed an enhancement of $4.0-4.4\%$ in light transmittance by one step coating. The dependence of the transmittance on wavelength was largely improved at the longer wavelength by partial coating of fumed particles on the film of spherical particles. The effective refractive index of the film was controlled by removing latex particles that were co-deposited with silica particles. Using this process the light reflectance from one side of the glass substrate could be reduced from $4.2\%$ to $0.6\%$ although zero reflectance was not achieved due to the agglomeration of the latex particles.

• 한국재료학회지
• /
• 제15권5호
• /
• pp.285-292
• /
• 2005

Anti-reflection film was coated by using spherical silica nano colloids. Silica colloid sol was reserved between two inclined slide glasses by capillary force, and particles were convectively stacked to form a film onto the substrate as the water evaporates. As the sliding speed increased, the thickness of the film decreased and the wavelength at the maximum transmittance decreased. The microstructure observed by SEM showed that silica particles were nearly close packed, which enabled the calculation of the effective refractive index of the film. The film thickness was measured by proffer and calculated from the wavelength of maximum transmittance and the effective refractive index. The effective refractive index of the film could be controlled by a subtle controlling of the coating speed and by mixing two different sized silica particles. When the 100 nm and 50 m particles were mixed at 4:1-5:1 volume ratio, the maximum transmittance of $95.2\%$ for one-sided coating was obtained. This is the one that has increased by $3.8\%$ compared to bare glass substrate, and shows that $99.0\%$ of transmittance or $1.0\%$ of reflectance can be achieved by the simple process if both sides of the substrate are coated.

• 대한기계학회논문집A
• /
• 제31권9호
• /
• pp.910-914
• /
• 2007

We present a simple and an inexpensive method for the fabrication of a nano-fluidic filter and a nano-pore micromixer using self-assembly of nano-spheres and surface tension. Colloid-plug was formed by surface tension of liquid in a microchannel to fabricate nanofluidic filter. When colloid is evaporated, nano-spheres in a colloid are orderly stacked by a capillary force. Orderly stacked nano-spheres form 3-D nano-mesh which can be used as a mesh structure of a fluidic filter. We used silica nano-sphere whose diameter is $567{\pm}85nm$, and silicon micro-channel of $50{\mu}m$-diameter. Fabricated nano-fluidic filter in a micro-channel has median pore diameter of 158nm which was in agreement with expected diameter of the nano-pore of $128{\pm}19nm$. A nano-pore micromixer consists of $200\;{\mu}m-wide,\;100\;{\mu}m-deep$ micro-channel and self-assembled nano-spheres. In the nano-pore micromixer, two different fluids had no sooner met together than two fluids begin to mix at wide region. From the experimental study, we completely apply self-assembly of nano-spheres to nano-fluidic devices.

• Advances in nano research
• /
• 제1권3호
• /
• pp.159-169
• /
• 2013

A preparation method for gadolinium compound (GdC) nanoparticles coated with silica ($GdC/SiO_2$) is proposed. GdC nanoparticles were prepared with a homogeneous precipitation method at $80^{\circ}C$ using $1.0{\times}10^{-3}$ M $Gd(NO_3)_3$, 0.5 M urea and $0-3.0{\times}10^{-4}$ M ethylenediarinnetetraacetic acid disodium salt dihydrate (ETDA) in water. As a result of preparation at various EDTA concentrations, GdC nanoparticles with a size as small as $40.5{\pm}6.2$ nm, which were colloidally stable, were prepared at an EDTA concentration of $2.0{\times}10^{-4}$ M. Silica-coating of the GdC nanoparticles was performed by a St$\ddot{o}$ber method at $35^{\circ}C$ using $1.0-10.0{\times}10^{-3}$ M tetraethylorthosilicate (TEOS), 11 M $H_2O$ and $1.5{\times}10^{-3}$ M NaOH in ethanol in the presence of $1.0{\times}10^{-3}$ M GdC nanoparticles. Performance of preparation at various TEOS concentrations resulted in production of $GdC/SiO_2$ particles with an average size of $106.1{\pm}11.2$ nm at a TEOS concentration of $5.0{\times}10^{-3}$ M. The gadolinium (Gd) concentration of $1.0{\times}10^{-3}$ M in the as-prepared $GdC/SiO_2$ particle colloid solution was increased up to a Gd concentration of 0.2 M by concentrating with centrifugation. The core-shell structure of $GdC/SiO_2$ particles was undamaged, and the colloid solution was still colloidally stable, even after the concentrating process. The concentrated $GdC/SiO_2$ colloid solution showed images of X-ray and magnetic resonance with contrast as high as commercial Gd complex contrast agents.

• 한국분무공학회지
• /
• 제8권1호
• /
• pp.16-22
• /
• 2003

Zeta potential measurements of colloid particles suspended in a liquid are performed by a Zeta Meter developed. There are many applications of colloid stability in spray technology, paints, wastewater treatment, and pharmaceuticalse. Zeta potentials of charged particles are obtained by measuring the electrophoretic velocities of the particles using video enhanced microscopy and image analysis program. The values of zeta potential of polystyrene latex(PSL), $silica(SiO_2)$M, polyvinylidence difluoride(PVDF), silicon nitride, and alumina particles in deionized (DI) water were measured to be -40.5, -31.9, -25.2, -15.1 and -10.1mV, respectively. The particles having high zeta potential less than -20 mV are stable in DI water, because the double layers of them have strong repulsive forces mutually, and the particles having low zeta potential over -20mV are unstable due to Van Der Waals forces. Silica(>20nm), PSL, aluminum and PVDF particles were found to be stable that would remain separate and well disperse, while silicon nitride and alumina particles were found to be unstable that would gradually agglomerate in DI water.

• 한국세라믹학회지
• /
• 제41권10호
• /
• pp.766-770
• /
• 2004

구형 실리카 나노 콜로이드 입자를 이용하여 반사방지막을 제조하였다. 실리카 콜로이드 현탁액을 모세관 힘을 이용하여 기울어진 두 장의 유리판 사이에 저장한 후 위의 유리를 이동시켜 반사 방지막을 코팅하였다. 상판 유리의 이동속도가 빨라질수록 막의 두께는 감소하였고, 막의 두께 변화에 따라 광 투과율이 변하였다. SEM으로 관찰된 실리카 나노 입자는 최밀충진에 가깝게 유리 기판에 부착되어 있었으며, 이로부터 고체 입자와 기공을 포함하는 막의 유효 굴절율을 구하였다. 최대의 광투과율을 나타내는 파장과 유효 굴절율로 부터 계산한 막의 두께는 SEM 사진 및 profiler로 구한 값과 잘 일치하였다. $94.7\%$의 최대 광투과율을 얻었으며, 양면으로 코팅한다면 $97.4\%$의 투과율 즉 $1.3\%$의 반사율을 얻을 수 있는 것으로 나타났다.

• 한국재료학회지
• /
• 제22권7호
• /
• pp.362-367
• /
• 2012

Magnetite nanoparticles(NPs) have been the subject of much interest by researchers owing to their potential use as magnetic carriers in drug targeting and as a tumor treatment in cases of hyperthermia. However, magnetite nanoparticles with 10 nm in diameter easily aggregate and thus create large secondary particles. To disperse magnetite nanoparticles, this study proposes the infiltration of magnetite nanoparticles into hybrid silica aerogels. The feasible dispersion of magnetite is necessary to target tumor cells and to treat hyperthermia. Magnetite NPs have been synthesized by coprecipitation, hydrothermal and thermal decomposition methods. In particular, monodisperse magnetite NPs are known to be produced by the thermal decomposition of iron oleate. In this study, we thermally decomposed iron acetylacetonate in the presence of oleic acid, oleylamine and 1,2 hexadecanediol. We also attempted to disperse magnetite NPs within a mesoporous aerogels. Methyltriethoxysilicate(MTEOS)-based hybrid silica aerogels were synthesized by a supercritical drying method. To incorporate the magnetite nanoparticles into the hybrid aerogels, we devised two methods: adding the synthesized aerogel into a magnetite precursor solution followed by nucleation and crystal growth within the pores of the aerogels, and the infiltration of magnetite nanoparticles synthesized beforehand into aerogel matrices by immersing the aerogels in a magnetite nanoparticle colloid solution. An analysis using a vibrating sample magnetometer showed that approximately 20% of the magnetite nanoparticles were well dispersed in the aerogels. The composite samples showed that heating under an inductive magnetic field to a temperature of $45^{\circ}C$ is possible.

• 한국세라믹학회지
• /
• 제41권4호
• /
• pp.297-301
• /
• 2004

분무연소합성법을 이용하여 나노크기의 물라이트(3Al$_2$O$_3$$.$2SiO$_2$) 콜로이드를 제조하였다. 연소반응을 위한 산화제로서 Al(NO$_3$)$_3$$.$9$H_2O$와 환원제(연료)로서 CH$_{6}$N$_4$O를 사용하였으며, 실리카 소스로서 콜로이드 실리카를 첨가하였다. 분무된 액적들의 착화를 위해 연소반응기의 온도를 80$0^{\circ}C$로 유지하였다. 액적의 응고에 의한 액적크기 성장을 억제하기 위하여 금속 스크린 필터를 사용함으로써 액적의 개수 농도를 감소시켰으며, 에어로졸 입자의 체류시간을 2.5초로 유지하여 열 유체의 흐름을 층류로 유도하였다. 제조된 입자들의 모양은 모두 구형이었으며, 평균입자크기는 130nm이었다 XRD와 TEM 분석 결과 각각의 초미립자들은 정량화합물의 물라이트 결정성을 나타내었다.

• Tribology and Lubricants
• /
• 제25권6호
• /
• pp.404-408
• /
• 2009

본 연구에서는 마이크로/나노입자를 이용한 연마가공 공정에서의 입자-표면간 접촉상황에서 접촉계면의 기계적 성질과 재료제거율간의 관계를 실험적으로 고찰하였다. 연마가공 공정에서의 입자-평면간 접촉을 모사하기 위하여 팁 대신 실리카 입자를 부착한 콜로이드 프로브를 이용한 원자현미경 실험을 통하여 마찰력과 강성을 실험적으로 측정하였다. 실험결과와 이론적 접촉해석으로부터, 마찰계수는 횡방향 접촉강성에 따라 대체적으로 증가하고 재료제거율은 실리카 입자와 Cu, PolySi, Ni과 같은 다양한 재료표면간 접촉에서의 마찰계수들과 지수함수적인 비례관계를 가지고 있음을 규명하였다.

• 유기물자원화
• /
• 제30권3호
• /
• pp.5-12
• /
• 2022

본 연구에서는 반도체를 포함한 다양한 산업 분야에서 발생하는 슬러지 폐기물을 활용하여 고부가 가치의 균일한 콜로이달 실리카 나노입자를 제조하고자 하였다. 상세히는 슬러지 폐기물에서 고분자를 용해하여 추출한 실리카(s-SiO₂)를 분리하였고, 암모니아와 소니케이터를 활용한 에칭을 통해 실라놀 전구체를 추출하였다. 실라놀 전구체를 활용하여 졸-겔법으로 균일한 약 50nm 크기의 실리카 나노입자(n-SiO₂)를 성공적으로 합성되었음을 확인할 수 있었다. 또한, s-SiO₂의 에칭 시간에 따른 n-SiO₂의 수득량을 확인하였으며, 8시간의 에칭 시간에서 가장 많은 n-SiO₂가 제조되는 것을 확인할 수 있었다. 최종적으로 n-SiO₂를 기반으로 한 CMP용 슬러리를 제조하여, 반도체 칩의 연마에 활용하였다. 그 결과, 반도체 칩의 표면에 존재하던 빗살 무늬의 데미지들이 성공적으로 제거되었으며, 이를 통해 슬러지 폐기물에서 고부가 가치의 반도체 급 n-SiO₂ 소재가 성공적으로 제조되었음을 확인할 수 있었다.