• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.275-276
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• 2008

통신기기가 고주파수화 함에 따라서 저유전 저손실 재료의 필요성이 증대되고 있으며, 세라믹/폴리머 복합재료를 고주파 회로 기판 소재로 이용하려는 관심이 증폭되고 있다. 본 연구에서는 저손실, 저유전율 특성을 구현하기 위해 $SiO_2$를 세라믹 필러로 복합물을 제작하였다. 평균 입자 크기가 16nm, $2.3{\mu}m$의 fumed 실리카와 평균 입자 크기 $1{\mu}m$, $4{\mu}m$의 fused 실리카를 사용하였다. 이 4종류 실리카를 사용하여 slurry를 제작하고 이를 활용하여 tape을 제작하였다. 제작된 복합체 tape을 적층하여 기판을 제작해 기판의 유전특성을 측정하였다. fumed 실리카의 경우 $SiO_2$ 10vol%이상에서는 균일한 tape성형이 어려워졌으며, 유전 손실이 fused 실리카와 비교하였을 때 큰 폭으로 증가하였다. fumed silica, fused silica 두 종류 모두 입도가 증가하면 유전손실이 증가하였다.

• Analytical Science and Technology
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• v.29 no.3
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• pp.105-113
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• 2016

The present study investigated the immobilization of lipases on silica nanoparticles and silica-coated magnetite nanoparticles as supports with a functional group to enhance the stability of lipase. The influence of functional groups, such as the epoxy group and the amine group, on the activity and stability of immobilized lipase was also studied. The epoxy group and the amino group were introduced onto the surface of nanoparticles by glycidyl methacrylate and aminopropyl triethoxysilane, respectively. Immobilized Candida rugosa lipase on silica nanoparticles and silica-coated magnetite nanoparticles with a functional group showed slightly lower initial enzyme activities than free enzyme; however, the immobilized Candida rugosa lipase retained over 92 % of the initial activity, even after 3 times reuse. Lipase was also immobilized on the silica-coated magnetite nanoparticles by cross-linked enzyme aggregate (CLEA) using glutaraldehyde and covalent binding, respectively, were also studied. Immobilized Candida rugosa lipase on silica nanoparticles and silica-coated magnetite nanoparticles by CLEA and covalent binding showed higher enzyme activities than free enzyme, while immobilized Candida rugosa lipase retained over 73 % of the initial activity after 5 times reuse.

• Polymer(Korea)
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• v.37 no.3
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• pp.308-315
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• 2013

In this study, we performed surface modification of silica nanoparticles with bis[3-(triethoxysilylpropyl)]tetrasulfide (TESPT) silane coupling agent to study the effects of treatment temperature, treatment time, and amount of TESPT used on the silanization degree with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis (EA) and solid state $^{13}C$ and $^{29}Si$ cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance spectroscopy (NMR). We found peak area of isolated silanol groups at $3747cm^{-1}$ decreased, but peak area of $-CH_2$ asymmetric stretching of TESPT at $2938cm^{-1}$ increased with the amount of TESPT from FTIR measurements. We also used universal testing machine (UTM) to study mechanical properties of styrene butadiene rubber (SBR) nanocomposites with 20 phr (parts per hundred of rubber) of pristine and TESPT modified silicas, respectively. The tensile strength and 100% modulus of modified silica/SBR nanocomposite were enhanced from 5.65 to 9.38MPa, from 1.62 to 2.73 MPa, respectively, compared to those of pristine silica/SBR nanocomposite.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.514-521
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• 2010

A new one-shot process was employed to fabricate proton exchange membranes (PEMs) over conventional solvent-casting process. Here, PEMs containing nano-dispersed silica nanoparticles were fabricated using one-shot process similar to the bulk-molding compounds (BMC). Different components such as reactive dispersant, urethane acrylate nonionmer (UAN), styrene, styrene sulfuric acid and silica nano particles were dissolved in a single solvent dimethyl sulfoxide (DMSO) followed by copolymerization within a mold in the presence of radical initiator. We have successfully studied the water-swelling and proton conductivity of obtained nanocomposite membranes which are strongly depended on the surface property of dispersed silica nano particles. In case of dispersion of hydrophilic silica nanoparticles, the nanocomposite membranes exhibited an increase in water-swelling and a decrease in methanol permeability with almost unchanged proton conductivity compared to neat polymeric membrane. The reverse observations were achieved for hydrophobic silica nanoparticles. Hence, hydrophilic and hydrophobic silica nanoparticles were effectively dispersed in hydrophilic and hydrophobic medium respectively. Hydrophobic silica nanoparticles dispersed in hydrophobic domains of PEMs largely suppressed swelling of hydrophilic domains by absorbing water without interrupting proton conduction occurred in hydrophilic membrane. Consequently, proton conductivity and water-swelling could be freely controlled by simply dispersing silica nanopartilces within the membrane.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.1-6
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• 2019

Organic dye-doped silica nanoparticles are used as a promising nanomaterials for bio-labeling, bio-imaging and bio-sensing. Fluorescent silica nanoparticles(NPs) have been synthesized by the modified $St{\ddot{o}}ber$ method. In this study, dye-free fluorescent silica NPs of various sized were synthesized by Sol-Gel process as the modified $St{\ddot{o}}ber$ method. The functional material of APTES((3-aminopropyl)triethoxysilane) was added as an additive during the Sol-Gel process. The as-synthesized silica NPs were calcined at $400^{\circ}C$ for 2 hours. The surface morphology and particle size of the as-synthesized silica NPs were characterized by field-emission scanning electron microscopy. The fluorescent characteristics of the as-synthesized silica NPs was confirmed by UV lamp irradiation of 365 nm wavelength. The photoluminescence (PL) of the as-synthesized silica NPs with different size was analyzed by fluorometry. As the results, the as-synthesized silica NPs exhibits same blue fluorescent characteristics for different NPs size. Especially, as increased of the silica NPs size, the intensity of PL was decreased. The blue fluorescence of dye-free silica NPs was attributed to linkage of $NH_2$ groups of the APTES layer and oxygen-related defects in the silica matrix skeleton.

• Electrical & Electronic Materials
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• v.4 no.1
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• pp.19-30
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• 1991

W/Si의 조성비가 2.6인 CVD텅스텐 실리사이드를 어닐링처리후 dry 또는 wet oxidation하여 폴리사이드 구조에서 다결정 Si내의 농도가 실리사이드의 산화반응속도에 미치는 영향을 조사하였다. 인의 농도에 관계없이 항상 실리사이드의 산화속도가 (100)Si의 그것보다 더 높았다. 저온에서 dry oxidation한 경우 인의 농도가 증가함에 따라 산화속도는 감소하였으나 고온에서 dry oxidation한 경우에는 P농도와 산화속도간에 상관관계가 별로 없었다. 한편, wet oxidation의 경우에는 모든 산화온도에서 인의 농도가 높을수록 실리사인의 산화속도가 더 낮은 것으로 나타났다.

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.514-515
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• 2014

실리신의 single vacancy에 Sc부터 Zn까지 전이금속을 넣고 이에 따른 실리신의 자기 모멘트와 구조 변화를 density funtional theory(DFT) 계산을 통해 알아보았다. 실리신은 그래핀(Graphene)과는 다소 다른 경향을 보였으며, 이는 실리신의 buckled 구조와 결합 길이의 차이로 인한 것으로 생각된다. 자기 모멘트는 전이금속 impurity에 큰 영향을 받았다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.67-67
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• 2011

퍼멀로이의 내식성, 기계적 성질 등을 증가시키기 위해 복합도금을 실시하였다. 실리카 나노분말의 분산특성을 Zeta potential을 이용하여 측정하였으며 알칼리 도금액에서 퍼멀로이-실리카 복합도금을 실시하였다. 실리카 나노분말의 응집을 최소로 하기 위하여 전극의 RPM 변화, 첨가제와 초음파의 복합처리에 따른 변화, 전류 밀도 변화를 살펴보았다.

• Polymer(Korea)
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• v.34 no.1
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• pp.1-7
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• 2010

To enhance the transport properties of gas separation membrane, we prepared 6FDA-6FpDA based polyimide membrane with PMMA-graft-silica nanoparticles. The silica was grafted PMMA which is miscible with 6FDA-based polyimide after surface treatment by 3-methacryloxypropyltrimethoxysilane ($\gamma$-MPS). The untreated silica/6FDA-6FpDA membrane showed greater permeability and less selectivity than PMMA-g-silica/6FDA-6FpDA due to its low dispersion. The transport properties of PMMA-g-silica/6FDA-GFpDA membrane were measured as a function of filler concentration. These membranes were evaluated using pure gases (He, $O_2$, $N_2$, $CO_2$). The increase in permeation was attributed to changes in the free volume distribution until 1 wt%. After 1 wt%, the permeability was decreased by excess silica which decreased effective area in polymer matrix. The selectivity was decreased with increasing permeability on the whole. However, the selectivity of $CO_2$ showed more enhance value.

• Membrane Journal
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• v.24 no.4
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• pp.301-310
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• 2014

In this study, the silica nanoparticles were considerably chosen to improve a dimensional stability, proton transport and electrochemical performance of the resulting inorganic-organic nanocomposite membranes. For this purpose, hydrophobic silica (Aerosil$^{(R)}$ 812, Degussa) and hydrophilic silica (Aerosil$^{(R)}$ 380, Degussa) nanoparticles were, respectively, introduced into a Sulfonated poly(arylene ether sulfone) (SPAES) polymer matrix. The $SiO_2$ particles are evenly dispersed in a SPAES matrix by the aid of a non-ionic surfactant (Pluronics$^{(R)}$ L64). A $SiO_2$ content plays an important role in membrane microstructures and membrane properties such as proton conductivity and water uptake. Therefore, to study nanocomposite membranes with excessive amount of silica, the content of silica nanoparticles were increased up to 5 wt%. Interestingly, a hydrophobic $SiO_2$ containing nanocomposite membrane showed better electrochemical performance (29% higher than pristine SPAES) despite of low proton conductivity due to its adhesive properties with a catalyst layer in a single cell test. All the silica-SPAES membranes exhibited better performance than a pristine SPAES membrane.