• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.181-186
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• 2011

In this study, we used 3-(trimethoxysilyl)propylmethacrylate(MPS) silane coupling agent for surface modification of silica nanoparticles. We studied effects of reaction conditions such as solvent pH, MPS hydrolysis time, reaction time, and molar ratio of MPS to Si-OH groups on silica nanoparticle surfaces, on the surface modification reactions of silica nanoparticles. Fourier Transform Infrared Spectroscopy(FTIR), Elemental Analysis(EA) and solid state crosspolarization magic angle spinning(CP/MAS) Nuclear Magnetic Resonance Spectroscopy(NMR) techniques were used to determine the type and the degree of surface modification. We found MPS reacts preferentially with Si-OH groups of the silica nanoparticles as monomeric form at solvent pH = 4.5. But increasing hydrolysis time of MPS from 30 mins to 90 mins, and molar ratio of MPS to Si-OH groups on silica nanoparticle surfaces, we found that MPS reacts preferentially with Si-OH groups of the silica nanoparticles as oligomeric form.

• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.205-210
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• 2005

Nanoscale silica powder was synthesized from $SiO_2$ precursor solution using Tetraethyl Orthosilicate (TEOS) by polyacrylamide gel method. This process was of simplicity and provided ultrafine powders at relatively low calcination temperatures because polymer network could inhibit aggregation of $SiO_2$ powder. The particle size of Si02 powder was affected by the concentration of ammonium persulphate and N, N'-methylene-bis-acrylamide(BIS) in the gel precursor. The particle size decreased with increasing ammonium persulphate and was mininum size of 10 nm at 0.01 M. Also, the size decreased with increasing BIS concentration and was 5 nm at its concentration of 0.05 M.

• Resources Recycling
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• v.16 no.5
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• pp.41-45
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• 2007

Tetramethylorthosilicate (TMOS) and silica nanopowder were synthesized from the waste silicon sludge containing 15% weight of silicon powder. TMOS, a precursor of silica nanopowder, was firstly prepared from the waste silicon sludge by catalytic chemical reaction. The maximum recovery of the TMOS was 100% after 5 hrs regardless of reaction temperature above $130^{\circ}C$. But the initial reaction rate became faster while the reaction temperature was higher than $150^{\circ}C$. As the methanol feedrate Increased from 0.8 ml/min to 1.4 ml/min, the yield of reaction was not varied after 3 hrs. Then, silica nanopowder was synthesized from the synthesized TMOS by flame spray pyrolysis. The morphology of as-prepared silica nanopowder was spherical and non-aggregated. The average particle diameters ranged from 9 nm to 30 nm and were in proportional to the precursor feed rate, and precursor concentration.

• 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.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.198-199
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• 2009

티타늄과 스테인리스 기판위에 졸-겔 코팅법으로 무기질 보호막을 형성하였고 기계적 특성을 테스트 하였다. 무기질 보호막은 금속 표면위에 졸-겔 코팅용액을 스프레이 코팅하여 제작하였다. 티타늄과 스테인리스 기판위에 적용한 무기질 보호막은 현저한 내스크래치성 향상을 보였다. 또한 실리카 나노입자의 첨가에 따른 무기질 보호막의 경도 향상을 보였다. 그러나 실리카 나노입자가 2 wt% 이상 첨가됨에 따라 보호막의 경도가 감소함을 알 수 있었다.

• Journal of Adhesion and Interface
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• v.13 no.4
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• pp.151-155
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• 2012

In the present study, we synthesized mesoporous silica hollow spheres with different wall thickness using polystyrene (PS) spheres as a structure template, tetraethoxysilane (TEOS) as a silica source, cetyltrimethylammonium bromide (CTAB) as a template. Particle size and dispersion of PS spheres were strongly depended on the concentration of surfactant in the aqueous solutions. The size of PS spheres was increased with decreasing concentration of surfactants. Dispersion of PS particle was improved when the surfactant concentration was lower than 0.5 g of surfactant.

• Korean Chemical Engineering Research
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• v.53 no.1
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• pp.78-82
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• 2015

Hollow silica particles were prepared using sodium silicate and organic templates. Polystyrene latex (PSL) particles produced by dispersion polymerization were used as organic templates. PSL particles ranged from $1{\mu}m$ to $3{\mu}m$ in diameter were synthesized by adjusting the amount of 2,2'-azobisisobutyronitrile (AIBN). The PSL/$SiO_2$ core-shell particles were prepared by coating of silica nanoparticles originated from sodium silicate using sol-gel method. The organic templates were removed by the organic solvent, tetrahydrofuran (THF). Morphology of hollow silica particles was investigated with respect to types of the reaction medium and pH during the process. By changing the solvent from ethanol to water, hollow silica particles were successfully formed. Hollow silica particles with the uniform shell thickness were produced at low pH as well. The reflectivity of the as-prepared silica particles was measured in the range of the wavelength of UV and visible light. Hollow silica particles showed much better reflective properties than the commercial light reflector, Insuladd.

• Analytical Science and Technology
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• v.20 no.5
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• pp.413-418
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• 2007

Poly(vinylpyrrolidone) stabilized cadmium sulfide (CdS) nanoparticles were loaded onto the surface of silica ($SiO_2$) nanoparticles by using ${\gamma}$-irradiation. TEM micrograph reveals the presence of ~20nm sized CdS nanoparticles on the surface of $SiO_2$ nanoparticles. XRD patterns confirm the crystalline. PL spectra of the simple PVP-stabilized CdS nanoparticle and $SiO_2$@CdS composite confirm the differences in the emission characteristics between them. Two prominent emission peaks were noted around 550 nm and 600 nm for PVP-stabilized CdS nanoparticles). The emission peaks noted for the PVP-stabilized CdS nanoparticles were found to be blue shifted for $SiO_2$@CdS composites. Besides, an additional emission peak around 450 nm was noticed for the $SiO_2$@CdS composite. The presence of CdS nanoparticles influence the emission characteristics and induce quantum confinement effect.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.12
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• pp.945-952
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• 2020

In this study, the effects of Low Earth Orbit(LEO) environments on the degradation behavior of epoxy nano silica composite materials were investigated. The nanocomposite materials containing silica particles in different weight ratios of 10% and 18% were prepared and degraded in a LEO simulator to compare with the neat epoxy cases. Thermogravimetric analysis (TGA) was performed on the degraded nanocomposites and the activation energies were calculated by Friedman method, Flynn-Wall-Ozawa (FWO) method, Kissinger method, and DAEM (Distributed Activation Energy Method) based on the iso-conversional method. As the results, for the neat epoxy sample cases, it was found that the average activation energy was increased as the degradation was progressed. When the nano particles were mixed, however, the energy increased to the 15 environmental test cycles, and decreased afterwards, meaning that the particle mixture contributed adversely to the thermal degradation. Discussions on the results of the different calculation methods were also given.

• 한국전자현미경학회:학술대회논문집
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• 2003.05a
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• pp.73-77
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• 2003