• 마이크로전자및패키징학회지
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• 제18권4호
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• pp.39-42
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• 2011

복합전기도금은 도금 중 반응성이 없는 물질을 첨가하여 도금층 내부에 함께 존재하도록 함으로써 이루어진다. 퍼멀로이는 철과 니켈의 합금을 말하는 것으로써 마모 특성과 내부식성이 우수하고 복합도금을 함으로써 도금층의 잔류응력 완화와 경도증가, 높은 투자율를 나타내기 때문에 산업 여러 분야에 응용된다. 복합도금을 통해 제품의 미세경도를 향상시킬 수 있으며 이는 제품의 수명과 연관된다. 하지만 실리카 나노분말 표면의 수산화기는 표면을 수분에 취약하게 만들고 이는 나노분말의 응집을 발생시켜 균일한 도금층의 형성을 어렵게 하는 요인이 된다. 본 연구에서는 실리카 나노분말의 zeta potential의 측정과 실리카 나노분말의 응집을 줄이기 위하여 전류밀도의 변화, 첨가제의 변화를 살펴보았다. 표면은 전류밀도 20 $mA/cm^2$에서 가장 효과적이었으며 이 때 실리카의 함량은 $50^{\circ}C$에서 9%로 확인되었다. 첨가제에 따라 표면 형상과 공석되는 실리카 나노입자의 함량 차이가 나타났다. 염기성 도금용액에서 sodium lauryl sulfate를 사용하였을 경우 표면이 매끄럽고 공석되는 실리카 나노분말의 양도 높았다.

• 한국주조공학회지
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• 제14권6호
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• pp.499-507
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• 1994

The effect of sodium gluconic acid on the collapsability of the sodium silicate type $CO_2$ mold was studied. The bending strength was saturated with gassing $CO_2$ for 60 sec. under $1kg/cm^2$ and with the flow rate of $10\;{\ell}\;/min$. It was decreased with aging after having been fully hardened. The retained strength was reduced in the heating temperature range of $100{\sim}1,100^{\circ}C$ and the retained strength peak near the heating temperature of $100^{\circ}C$ was removed by the effect of the sodium gluconic acid. Silica gel, $Na_2CO_3$ and dehydrated sodium silicates were formed from the binder of sodium silicate with the addition of sodium gluconic acid at the heating temperature of $100^{\circ}C$. $Na_4SiO_4$ was formed by the reaction of $Na_2O$, from decomposed $Na_2CO_3$, with the dehydrated sodium silicate at $500^{\circ}C$. The crystobalite type of $SiO_2$ was formed at $900^{\circ}C$. The sodium gluconic acid had no effect on the bending strength at around $1,100^{\circ}C$ due to the combustion loss of it.

• 한국세라믹학회지
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• 제45권7호
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• pp.395-400
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• 2008

This paper indicates the investigation about the development of ET (Environmental Technology) industrial geopolymeric materials from mixture silica mine waste, coal fly ash and alkali activator solution (sodium silicate) by the geopolymer technique at ambient temperature. The results showed that higher compressive strength of geopolymeric mortar increased with a reduce of L/S ratio and increased along with an increase of coal fly ash content. The compressive strengths of geopolymer mortar on low silica of C Silica Mine and K Silica Mine are 18.7 MPa, 20.4 MPa, respectively. Compressive strength of geopolymeric mortar depends on L/S ratio and coal fly ash content added.. Additionally, scanning electron microscope (SEM) techniques are used to characterize the microstructure of the geopolymeric mortars. SEM observation shows that it is possible to have amorphous aluminosilicate gel within mortar. XRD patterns indicate the fact that geopolymeric mortar is composed of amorphous aluminosilicate phase, calcite and quartz.

• 한국재료학회지
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• 제15권11호
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• pp.717-721
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• 2005

Silica powders were synthesized using emulsion solution containing water, nonionic surfactant of Triton N-57, and cyclohexane. Silica powders were prepared at low cost using inexpensive starting material of sodium silicate and ammonium sulfate. Morphology, size and size distribution were observed and determined using SEM. The powder was identified as silica by FT-IR and XRD analysis. Particle size and size distributions were affected by concentration of reactants, reaction time, and concentration of surfactant. Particle size were increased with increasing concentration of reactants and particles became dense with increasing reaction time. As R value increased, tile particle size was increased, reached a certain value and then decreased again. The silica powders synthesized under optimum condition were spherical in shape, $0.8{\mu}m$ in average particle size, narrow in particles size distribution, and well dispersed.

• 한국주조공학회지
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• 제23권5호
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• pp.235-243
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• 2003

The collapsibility of sodium silicate-bonded sands mixed with the L.D converter slag powder to form a hardener were investigated. Five to six percent sodium silicate on the basis of silica sand and 30-40% L.D converter slag powder on the basis of sodium silicate, were mixed and the compressive strength, surface stability index(SSI), bench time, retained strength of the standard sand specimens were measured. The properties were similar to those of general inorganic bonded self-setting molds. The compressive strength and surface stability index were increased and the retained strength and bench time were decreased with increased amount of the L.D converter slag powder. The retained strength of sodium silicate-bonded self-setting molds with the L.D converter slag powder were decreased than $CO_2$ sand molds. The collapsibility of sodium silicate-bonded self-setting molds with the L.D converter slag powder were superior in comparison with $CO_2$ sand molds. The L.D converter slag powder could be used as hardener and collapse agent for the sodium silicate-bonded self-setting molds.

• 한국세라믹학회지
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• 제54권5호
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• pp.429-437
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• 2017

Micro hollow plate type silica with low refraction properties was synthesized and its hollow structure was applied as an optical structure to develop a light diffusion material that simultaneously satisfies the requirements of good light diffusibility, high transmissibility, and high luminance. The developed light diffusion material was applied to a light diffusion film and the film's optical properties were assessed. Hollow silica was synthesized by precipitation method using $Mg(OH)_2$ core particles, sodium silicate, and ammonium sulfate as the silica precursors. The concentration of the silica precursor was adjusted to control hollow silica shell thickness. The total light transmittance of the light diffusion film composed of the hollow silica was 94.55%, which was 4.57% higher than that of the PC film; new film's haze was 71.20%, which was 70.9% higher. Furthermore, the luminance increased by 5.34% compared to that of the light source. The reason for the results is not only that the micro plate type hollow silica, which has a low refractive property, played a role in reducing the difference in refractive index between the medium boundaries, but also that there was a light-concentrating effect due to the changing of light paths to the front direction inside the hollow structure. Optical simulation verified the enhanced optical properties when hollow silica was applied to the light diffusion film.

• 한국전기전자재료학회논문지
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• 제26권3호
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• pp.221-226
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• 2013

The water soluble quantum dots (QDs) are synthesized by the phase transfer and silica coating reaction. The photoluminescence intensity of silica-coated QDs are mainly affected by the amount of phase transfer agent, SDS (sodium dodecyl sulfate), and the maximum value is obtained at the cmc (critical micell concentration) concentration of SDS in the phase transfer reaction. Based on fluorescence spectra and field emission transmission electron microscope (FETEM), the energy transfer rate by forster resonance energy transfer (FRET) is increasing with the thickness of the silica shell coated on CdSe/ZnS QDs.

• Journal of Pharmaceutical Investigation
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• 제31권2호
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• pp.81-87
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• 2001

The purpose of this study was to investigate the effect of additives on the powder characteristics of peonja dry elixir. Peonja dry elixirs were prepared with various amounts of dextrin using a spray-dryer, and their powder characteristics such as flow, cohesion and compressibility were evaluated as an angle of repose, cohesion index and compressibility index, respectively. Their powder characteristics were not significantly different from one another, indicating that the hydrophilic dextrin, a base of dry elixir hardly affected their powder characteristics. Peonja dry elixirs were prepared with 10% dextrin and various amounts of additives such as mannitol (hydrophilic excipient), sodium lauryl sulfate (surfactant), colloidal silica (hydrophobic excipient) and HPMC (polymer), respectively, and their angle of repose, cohesion index and compressibility index were measured. The powder characteristics of peonja dry elixirs prepared with mannitol were not significantly different from one another, indicating that the mannitol scarcely improved the powder characteristics of peonja dry elixirs. The angle of repose and cohesion index of peonja dry elixirs significantly decreased with increasing amount of sodium lauryl sulfate to 0.3% followed by no significant changes in them. The cohesion index of peonja dry elixir significantly decreased with increasing amount of colloidal silica. The angle of repose and cohesion index of peonja dry elixir significantly decreased with increasing amount of HPMC to 0.3% followed by an abrupt increase in them. However, the compressibility index of peonja dry elixir significantly increased with increasing amount of HPMC to 0.3% followed by an abrupt decrease in them. Our results suggested that a small amount of sodium lauryl sulfate, colloidal silica and HPMC improved markedly the powder characteristics of peonja dry elixirs due to forming stronger and less hygroscopic shell of peonja dry elixirs. Among the peonja dry elixirs studied, the peonja dry elixir prepared with 0.3% sodium lauryl sulfate and 0.3% HPMC had the lowest angle of repose of $27^{\circ}$ and cohesion index of 37.8%, and the highest compressibility index of 38.7%, respectively. Thus, sodium lauryl sulfate and HPMC appear to be promising additives for peonja dry elixir, if used in adequate amounts.

• 자연과학논문집
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• 제8권2호
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• pp.119-127
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• 1996

Zeolite인 mordenite 광물을 수산화나트륨용액으로 화학처리한 효과에 대해서 화학분석, X-선 분말회절, 열분석, 이산화탄소의 흡착측정 및 GC를 통하여 조사하였다. 출발원료로 mordenite 광물을 3시간동안 water bath 중 약 $95^{\circ}C$에서 NaOH 0.1-5N의 농도범위로 화학 처리한 결과, 시료중 함유된 모든 화학성분은 NaOH 0.5N 이하의 농도에서는 불용이고 mordenite 구조는 변화하지 않았으며 1N 이상의 농도에서는 실리카, 알루미나 등과 같이 성분들이 용해되었고 시료중 실리카의 용해비율이 알루미나의 용해보다 높으며 실리카와 알루미나의 비가 2-3N 농도 범위에서는 급격히 감소하였다.Mordenite 의 (202)면의 X-선 회절피크 강도와 $CO_2$ 흡착량은 1N 이상의 NaOH 농도가 증가함에 따라 감소하며 이로 인하여 mordenite 구조의 붕괴가 나타났다.산소, 질소 및 일산화탄소의 GC분리공정에서는 NaOH 용액 처리에 의한 영향을 받지 않으나 메탄과 크립톤의 용출피크가 넓어지는 경향이 나타나며 retention time 은 단축되었고 이 두 기체모두 용리피크는 산소 또는 질소와 중복되기 쉬운 경향을 보여주었다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권6호
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• pp.465-470
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• 2004

Optimal conditions for the in situ immobilization of lipase in aldehyde-silica packed columns, via reductive amination, were investigated. A reactant mixture, containing lipase and sodium borohydride (NaCBH), was recirculated through an aldehyde-silica packed column, such that the covalent bonding of the lipase, via amination between the amine group of the enzyme and the aldehyde terminal of the silica, and the reduction of the resulting imine group by NaCBH, could occur inside the bed, in situ. Mobile phase conditions in the ranges of pH $7.0{\~}7.8$, temperatures between $22{\~}28^{circ}C$ and flow rates from $0.8{\~}1.5\;BV/min$ were found to be optimal for the in situ immobilization, which routinely resulted in an immobilization of more than 70 mg­lipase/g-silica. Also, the optimal ratio and concentration for feed reactants in the in situ immobilization: mass ratio [NaCBH]/[lipase] of 0.3, at NaCBH and lipase concentrations of 0.75 and 2.5 g/L, respectively, were found to display the best immobilization characteristics for concentrations of up to 80 mg-lipase/g-silica, which was more than a 2-fold increase in immobilization compared to that obtained by batch immobilization. For tributyrin hydrolysis, the in situ immobilized lipase displayed lower activity per unit mass of enzyme than the batch-immobilized or free lipase, while allowing more than a $45\%$ increase in lipase activity per unit mass of silica compared to batch immobilization, because the quantity of the immobilization on silica was aug­mented by the in situ immobilization methodology used in this study.