• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.160-160
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• 2011

In the present work, $TiO_2$ fiilms supported by porous silica gel with high surface area synthesized by atomic layer deposition(ALD). Porous structure of silica substrate could be maintained even after deposit large amount of $TiO_2$ (500 cycles of ALD process), suggesting the differential growth mode of $TiO_2$ on top surface and inside the pore. All the $TiO_2$-covered silica samples showed improved MB adsorption abilities, comparing to bare one. In addition, when silica surface was covered with $TiO_2$ films, MB adsorption capacity was almost fully recovered by re-annealing process (500$^{\circ}C$, for 1 hr, in ambient pressure), whereas MB adsorption capacity of bare silica was decreased after re-heaing process. FT-IR study demonstrated that $TiO_2$ film could prevent deposition of surface-bound intermediate species during thermal decomposition of adsorbed MB molecules. Photocatalytic activity of $TiO_2$/silica sample was also investigated.

• 한국세라믹학회지
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• 제45권2호
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• pp.87-89
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• 2008

A nano structured silica aerogel thin film was manufactured from inexpensive sodium silicate (water glass) using an ambient pressure drying method. High purity silicic sol was prepared by passing a water glass solution through an ion exchange resin, and the gel films were prepared on a modified glass substrate via dip coating. The dip coating conditions, such as coating time and solvent, were optimized. The optical and physical properties of the obtained silica aerogel thin film were characterized using a UV-visable spectrometer and a scanning electron microscope.

• 대한화학회지
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• 제55권6호
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• pp.1024-1029
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• 2011

PVA/silica hybrid xerogels were synthesized by sonohydrolysis of a mixture of 2-way catalyzed TEOS and water solution of PVA. PVA was successfully removed from the xerogels through calcination and its removal was confirmed through TGA analysis of the calcined gel. Microstructure of the gels was studied through SEM, XRD and FTIR. Nitrogen sorption studies were conducted to find out surface area of different samples. It was found out that the samples having PVA removed through calcinations have higher surface area (411.64 $m^2$/g) than the samples (353.544 $m^2$/g) synthesized without any PVA. Adsorption properties of these xerogels synthesized by using different ratios of components were studied by taking Rhodamine G6 as a model adsorbate. The experiments were conducted at room temperature ($25^{\circ}C$). UV visible spectroscopy was used to measure the concentration of the dye before and after adsorption. The adsorption data of Rhodamine G6 on PVA modified silica is described by the Freundlich's adsorption model.

• 한국세라믹학회지
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• 제54권1호
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• pp.49-54
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• 2017

In this study, based on hydrolysis and condensation via $St{\ddot{o}}ber$ process of sol-gel method, synthesis of mono-dispersed silica nanoparticles was carried out with hydrophilic solvent. This operation was expected to be a more simplified process than that with organic solvent. Based on the sol-gel method, which involves simply controlling the particle size, the particle size of the synthesized silica specimens were ranged from 30 to 300 nm by controlling the composition of tetraethylorthosilicate (TEOS), DI water and ammonia solution, and by varying the stirring speeds while maintaining a fixed amount of ethanol. Increasing the content of DI water and decreasing the content of ammonia caused the particle size to decrease, while controlling the stirring speed at a high level of RPMs enabled a decrease of the particle size. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were utilized to investigate the success factors for synthesizing process; Field emission scanning electron microscopy (FE-SEM) was used to study the effects of the size and morphology of the synthesized particles. To analyze the dispersion properties, zeta potential and particle size distribution (PSD) analyses were utilized.

• 한국지반환경공학회 논문집
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• 제11권9호
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• pp.47-53
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• 2010

본 연구는 최근 개발된 실리카졸 그라우트재의 압축강도 특성을 규명한 것으로써 연구에 사용된 그라우트재는 3차원 겔형성재인 실리카졸 그라우트재와 규산나트륨 그라우트재에 대한 공학적 특성을 비교하기 위하여 일축압축강도시험(호모겔, 샌드겔), 투수시험, 휨강도시험등을 통해 강도 특성과 친환경성을 규명하고자 하였다. 실리카졸 그라우트재가 규산나트륨 그라우트재보다 초기(72시간 이내)에 일축압축강도가 3~5배 이상의 고강도로 증진되고 있음을 확인하였다. 샌드겔과 호모겔의 재령 28일의 일축압축강도로 비교 시 실리카졸 그라우팅제의 경우 샌드겔이 호모겔에 비해 약 1.3배 정도 강도가 높게 측정되었고, 이는 실리카졸의 경우 실제로 지반에 주입되어 사용되었을 경우 고강도를 발휘하는 특성이 있기 때문으로 추정된다. 투수시험 결과 실리카졸이 차수성면에서 현장에 적용하는데 무리가 없다고 판단되어 차수성을 요구하는 현장에 적용이 가능하다고 판단된다. 휨강도시험결과 그라우팅제용 실리카졸은 최종 28일 강도의 경우 규산나트륨 그라우팅제에 비해 3배 이상의 차이를 보이고 있다.

• 한국염색가공학회지
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• 제27권2호
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• pp.126-131
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• 2015

Silica-polyurethane hybrid breathable films were prepared and their breathabilities were assessed. Appropriately aggregated silica was prepared through sol-gel reaction of water glass and its particle size ranged 360~500nm. The polyurethane dispersion was prepared by the reaction of isophorone diisocyanate(IPDI) as diisocyanate and polytetramethylene glycol(PTMG) and dimethylol propionic acid(DMPA) as polyol, particle size ranging 30~120nm. The reaction between isocyanate and hydroxyl group to form urethane bonding was checked by the intensity of the stretch peak of isocyanate at $2270cm^{-1}$ in the FT-IR. The silica was incorporated into polyurethane dispersion and casted into film. It was shown that the incorporated silica(1~5wt.%) increased water vapour permeability of the films by 30~100%, and decreased the hydrostatic pressure by 10~40%. From the results, it could be concluded that the appropriate hybridization of silica can increase the breathability of polyurethane dispersion film, while minimizing the loss of hydrostatic pressure.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2012년도 춘계학술발표대회 논문집
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• pp.364-369
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• 2012

The development of solar thermal energy used adsorption desalination technology have been examined as a viable option for supplying clean energy. In this study, the modelling of the main devices for solar thermal energy used and adsorption desalination system was introduced. Silica gel type adsorption desalination system is considered to be a promising low-temperature heat utilization system. The design is divided into three parts. First, the evaporator for the vaporization of the tap water is designed, and then the reactor for the adsorption and release of the steam is designed, followed by the condenser for the condensation of the fresh water is designed. In addition, new features based on the energy balance are also included to design absorption desalination system. In this basic research, One-bed(reactor) adsorption desalination plant that employ a low-temperature solar thermal energy was proposed and experimentally studied. The specific water yield is measured experimentally with respect to the time controlling parameters such as heat source temperatures, coolant temperatures, system switching and half-cycle operational times. Desalination is processes that permeate our daily lives, but It requires substantial energy input, powered either from electricity or from thermal input. From the environmental and sustainability perspecives, innovative thermodynamic cycles are needed to produce the above-mentioned useful effects at a lower specific energy input. This article describes the development of adsorption cycles for the production of desalting effects. We want that this adsorption system can be driven by low temperature heat sources at 60 to $80^{\circ}C$, such as renewable, solar thermal energy.

• 한국재료학회지
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• 제13권3호
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• pp.144-149
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• 2003

This study shows an experimental investigation of a reversible nano colloidal damper, which is statically loaded. The porous matrix is composed from silica gel (labyrinth or central-cavity architecture), coated by organo-silicones substances, in order to achieve a hydrophobic surface. Water is considered as associated lyophobic liquid. Reversible colloidal damper static test rig and the measuring technique of the static hysteresis are described. Influence of the pore and particle diameters, particle architecture and length of the grafted molecule upon the reversible colloidal damper hysteresis is investigated, for distinctive types and mixtures of porous matrices. Variation of the reversible colloidal damper dissipated energy and efficiency with temperature, pressure, is illustrated. As a result, he proposed nano damper is effective one, which can be replaced the conventional damper.

• 에너지공학
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• 제21권1호
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• pp.43-46
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• 2012

A fluidized bed drying approach was utilized to the synthesis of water glass based silica aerogel powders. The effects of the fluidized bed drying conditions such as the superficial velocity and temperature of hot air and bead size as well as bead/wet-gel ratio, on the physical properties such as tapping density and productivity of the aerogel powders were systematically investigated. The experimental results showed that the amount of beads mixed with wet-gels in the fluidized bed column has the most profound impact on the fluidization efficiency, greatly enhancing the yield of the aerogel powders up to 98% with a proper bead/wet-gel weight ratio as compared to 72% without using beads. No significant change was observed in the tapping density over a wide range of the fluidized drying condition. Consequently the fluidized bed drying approach shows a good promise as an alternative route for the large-scale production of the aerogel powders.

• 약학회지
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• 제40권4호
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• pp.462-467
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• 1996

Forsythiae Fructus was studied on cytotoxic activities for the purpose of finding out active consituents against L1210 and HL60 cells. To isolate the active ones, the methanolic extract was partitioned into water insoluble and water soluble fractions. Furthermore, the water soluble fraction was fractionated into four parts, n-hexane, benzene, ethylacetate and water fractions. Among these, the water insoluble fraction showed the most potent cytotoxic activities on L1210 and HL60 cells in vitro. The water insoluble fraction was applied to silica gel column chromatography and divided into 5 fractions(fr. 1-5). The active constituents I and II were isolated from fr.2 and 3, respectively, by repeated silica gel column chromatography and recrystallization. The constituents were identified as 3${\beta}$-acetylbetulinic acid and betulinic acid by means of physicochemical data. The $ED_{50}$ values of 3${\beta}$-acetylbetulinic acid and betulinic acid were 9.10 and 16.43${\mu}g$/ml against L1210 cells and 2.72 and 2.41${\mu}g$/ml against HL60 cells, respectively.