• Journal of the Korean Recycled Construction Resources Institute
• /
• v.12 no.1
• /
• pp.33-39
• /
• 2024

In this study, the basic properties of cement paste with varying replacement ratio of micro-silica and fumed silica were analyzed to determine the suitability of nanomaterials for use as concrete admixtures. Referring to the ultra-high strength mix, the fluidity of cement paste was evaluated according to the nanomaterial replacement rate and the compressive strength characteristics were compared and analyzed. The related properties of the reactive nanomaterials to the cement hydrate were analyzed using SEM and EDS to observe the microstructure and identify the components of the hydration product. The reactive nanomaterials used in this study had tap densities between 0.061 and 0.264 g/cm³, which were lower than SF. Micro silica exhibited excellent compressive strength properties with increasing replacement ratio, but fumed silica, unlike micro white, obtained excellent compressive strength at replacement ratio of 0.01~0.1 %. The same trend was observed in the hydration characterization.

• Proceedings of the Optical Society of Korea Conference
• /
• 2001.02a
• /
• pp.44-45
• /
• 2001

실리카 마이크로 스피어는 손실이 대단히 적은 초고품위 공진기로 알려져 있다. 최근의 실험들에 의하면 실리카 마이크로 스피어는 공진기 Q 값이 $10^{9-10}$ 정도인데, 이는 현재까지 만들어진 마이크로 공진기들 중에서 가장 높은 값이다. 최근 마이크로 스피어는 저손실의 공진기로서 문턱조건이 없는 레이저 연구에 활용되고 있으며, 레이저와 좁은 공명 모드 선폭을 이용하여 레이저 주파수 안정화 및 광섬유 결합기 등에 활용되고 있다. 또한 Cavity-QED 연구와 Cavity-QED 효과를 이용한 소수의 양자점 레어저 연구에도 활용도고 있다. (중략)략)

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2012.05a
• /
• pp.89.2-89.2
• /
• 2012

$150^{\circ}$ 이상의 접촉각을 가지는 초소수성 표면은 self-cleaning, anti-fingerprint, anti-contamination 등의 특성을 가지므로 전자, 도료, 자동차 등 다양한 산업에서 활용될 수 있다. 재료 표면의 친/소수성은 물리적 요인과 화학적 요인 두 가지 요인을 조절함으로써 제어할 수 있다. 즉, 표면의 거칠기를 크게 하거나 표면에너지를 낮춰줌으로써 초소수성 표면을 구현할 수 있다. 실리카는 자연계에 매우 풍부하게 존재하고 있으며, 생체무해하며 내구성과 내마모성, 화학적 안정성, 고온 안정성 등을 지니고 있어 박막소재로 이용하기에 우수한 특징을 지니고 있다. 이러한 실리카 초소수성 코팅층을 형성하는 방법으로 본 연구에서는 전기분무법으로 마이크로 크기의 실리카 입자로 형성된 코팅층을 형성하였다. 이러한 마이크로 구조의 표면거칠기를 더욱 높이기 위하여 금 나노입자를 부가적으로 형성시켜 마이크로-나노구조 혼성의 계층구조를 만들고자 하였다. 금 나노입자는 자외선 조사 광환원법을 사용하였고, 이러한 계층구조에 플루오린 처리를 하여 계층구조 초소수성 코팅층을 형성하였다. 계층구조를 가지는 실리카 코팅층은 물 이외에 표면장력이 낮은 용액에서도 높은 접촉각을 보였고, 이러한 코팅층의 고온 안정성과 내구성, UV 저항성 등을 조사하여 실제 응용 가능성을 검토하였다.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.3
• /
• pp.269-275
• /
• 2022

In this study, the setting time and compressive strength of cement paste composites applied with nano-micro pozzolanic binders were experimental analyzed. The pozzolanic binder was reduced initial and final setting time and the compressive strength was increased. Micro silica was effective in decrease the initial setting and final setting time and impressing the compressive strength. When two or more cement binders were used, the using of silica fume and a small amount of nano silica at reduced the setting time to 62-64 % to OPC cement and the compressive strength was increased to 117 %. A small amount of mixing the nano silica was effect to pore filling and pozzolanic activation. However, the addition of a chemical admixture should be considered when mixing table design because pozzolanic binders high specific surface area causes a decrease in cement composites flow.

• Polymer(Korea)
• /
• v.27 no.5
• /
• pp.464-469
• /
• 2003

In this work, the fragrant oil release behavior of poly($\varepsilon$-caprolactone) (PCL) microcapsules containing SiO$_2$ was investigated. The SiO$_2$ was chemically treated in 10, 20, and 30 wt% hydrochloric acid and sodium hydroxide. The acid and base values were determined by Boehm's titration technique and $N_2$/77 K adsorption isotherm characteristics, the specific surface area and total pore volume were studied by BET. The PCL microcapsules containing SiO$_2$ and fragrant oil were prepared by oil-in-water (o/w) emulsion solvent evaporation method. The shape and surface of PCL microcapsules were observed using image analyzer and scanning electron microscope (SEM). The fragrant oil release behavior of PCL microcapsules was characterized using UV/vis. spectra. The average diameters of PCL microcapsules were decreased from 35 to 21 $\mu$m with increasing stirring rate. It was found that in the case of acidic treatment the fragrant oil adsorption capacity and release rate were increased due to the increase of specific surface area and acid value. In the case of basic treatment, the fragrant oil adsorption capacity and release rate were decreased due to the decrease of sp ecific surface area and the increase of acid-base interactions between SiO$_2$-NaOH and fragrant oil with increasing base value of SiO$_2$.

• The Science & Technology
• /
• v.32 no.3 s.358
• /
• pp.78-79
• /
• 1999

반월공단의 한복판에 자리잡고 있는 신흥규산(주)은 기능성 미분말 실리카의 제조기술 개발에 성공, 상용화작업을 진행하고 있다. 미분말 실리카는 규산소다를 원료로 하여 생산한 2차 제품으로 석유화학과 도료 잉크산업, 제지산업 등에서 특정한 기능을 살리기 위해 첨가되는 소재이다. 62년 설립된 신흥규산(주)은 65명의 가족을 거느린 중소기업으로 올해는 미분말 실리카와 크로마토그래피용 무기소재를, 내년엔 제지보류 향상용 마이크로실리카겔을 일본을 비롯한 아시아 전역에 수출할 계획을 세우고 있다.

• Applied Chemistry for Engineering
• /
• v.16 no.4
• /
• pp.588-593
• /
• 2005

In this study, biodegradable poly(${\varepsilon}$-caprolactone) (PCL) microcapsules containing chemically treated $SiO_2$ and nifedipine were prepared by oil-in-water (O/W) emulsion solvent evaporation method. The microcapsules containing drugs were confirmed using FT-IR spectra. The morphologies of the microcapsules were observed with scanning electron microscope (SEM). The nifedipine's release behaviors from the microcapsules were also examined with UV/vis spectroscopy. As a result, the inclusion of nifedipine into the microcapsules was determined by the presence of nifedipine's specific peak, i.e., C=O stretch vibration at $1682cm^{-1}$. The average particle size of the microcapsules decreased with increasing stirring rate. The nifedipine adsorption capacity and release rate of treated $SiO_2$ that was treated with basic solution decreased because with the increased basicity it lowered the specific surface area of $SiO_2$ and promoted stronger acid-base interactions between $SiO_2$ and nifedipine.

• Applied Chemistry for Engineering
• /
• v.22 no.3
• /
• pp.328-331
• /
• 2011

ZnSe quantum dots (QDs) were prepared by employing water-containing Dioctyl sodium sulfosuccinate (AOT) reversed micelles (microemulsions) and the silica-encapsulated ZnSe QDs were obtained by a direct injection of tetraethyl orthosilicate (TEOS) into the microemulsion system. When the QDs were coated by silica, well-defined spherical shapes were formed and the average size of the QDs was near 7 nm. In addition, the photoluminescence (PL) efficiency of the QDs was reduced from 8.0 to 1.1% as they were encapsulated by silica. However, the solid layers of the silica-encapsulated ZnSe QDs on gold surfaces showed the excellent photostability. In particular, they are cadmium free and thus, less toxic. Moreover, the present method does not require a hot reaction temperature or extremely toxic H2Se gas as a Se precursor. Accordingly, the method can be a safer and more economical process for producing silica-encapsulated ZnSe QDs, which may be a potential media for biosensors.

• Journal of the Korea Concrete Institute
• /
• v.27 no.1
• /
• pp.29-35
• /
• 2015

Recent studies to develop Very Large Floating Structure(VLFS) has shown that the construction procedure of the structure needs to acquire precast concrete module connection system using prestressing. However, the loads occurring on water are complex combinations of various condition, so the safe and stable performance of the module joints and bonding materials are key to the success of the construction. Therefore, micro-silica mixed aqua-epoxy development was introduced in Part 1 using a bonding material developed in this study. The performance of the micro-silica mixed aqua-epoxy(MSAE) applied joint of concrete module specimens connected by prestressing tendon was evaluated to verify the usability and safety of the material. RC beam, spliced beam connected by prestressing tendon and MSAE, and continuous prestressed concrete beam were tested for their initial cracking and maximum loads as well as cracking procedure and pattern. The results showed that the MSAE can control the stress concentration effect of the shear key and the crack propagation, and the maximum load capacity of MSAE joint specimens are only 5% less than that of continuous RC specimen. The details of the study are discussed in detail in the paper.

• Applied Chemistry for Engineering
• /
• v.31 no.6
• /
• pp.635-638
• /
• 2020

We prepared spherical silica by minimizing the amount of oil through water/oil (W/O) emulsion. The spherical silica was successfully synthesized by using 20 to 60 mL of hexane as an oil for 283 g of water glass. The size of silica was dependent on the amount of oil where the size of silica particles increased as the amount of oil increased. The specific surface areas of samples measured using the BET method were 186 to 230 ㎡/g. X-ray fluorescence (XRF) analysis results showed that the SiO2 content was more than 90% while sodium was 3.27~4.5 wt. %. The spherical silica prepared in this study could be optimized for mass synthesis and commercialization because the industrial sodium silicate solution was used as a precursor of Si as well as the minimum amounts of hexane and nonionic surfactant were employed.