• Korean Journal of Materials Research
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• v.21 no.3
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• pp.156-160
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• 2011

FePt nanoparticles suspension was synthesized by reduction of platinum acetylacetonate and decomposition of iron pentacarbonyl in the presence of oleic acid and oleyl amine. FePt nanoparticles were coated on a substrate by convective assembly from the suspension. To prevent the coalescence during the annealing of FePt nanoparticles double convective coatings were tried. First convective coating was for silica particle assembly on a silicon substrate and second one was for FePt nanoparticles on the previously coated silica layers. It was observed by scanning electron microscopy (SEM) that FePt nanoparticles were dispersed on the silica particle surface. After annealing at $700^{\circ}C$ for 30 minutes under nitrogen atmosphere, FePt nanoparticles on silica particles were maintained in a dispersed state with slight increase of particle size. On the contrary, FePt nanoparticles that were directly coated on silicon substrate showed severe particle growth after annealing due to the close-packing of nanoparticles during assembly. The size variation during annealing was also verified by X-ray diffractometer (XRD). It was suggested that pre-coating, which offered solvent flux oppose to the capillary force between FePt nanoparticles, was an effective method to prevent coalescence of nano-sized particles under high temperature annealing.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.83-88
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• 2010

The wear behavior of epoxy matrix composites filled with nano sized silica particles is discussed in this paper. Especially, the variation of the coefficient of friction and the wear resistance according to the change of apply load and sliding velocity were investigated for these materials. Wear tests of pin-on-disc mode were carried out and the wear test results exhibited as following ; The epoxy matrix composites showed lower coefficient of friction compared to the neat epoxy through the whole sliding distance. As increasing the sliding velocity the epoxy matrix composites indicated lower coefficient of friction, whereas the neat epoxy showed higher coefficient of friction as increasing the sliding velocity. The specific friction work of both materials were increased with apply load. In case of the epoxy matrix composites, the running in periods of friction were reduced as increase in apply load. The epoxy matrix composites were improved the wear resistance by adding the nano silica particles remarkably. It is expected that the load carrying capacity of the epoxy matrix composites will be improved by increase of Pv factor.

• Advances in nano research
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• v.3 no.4
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• pp.243-255
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• 2015

In this investigation, ecotoxicity of nano and micro metal oxides, namely silica ($SiO_2$) and alumina ($Al_2O_3$), on the growth of green algae (Porphyridium aerugineum Geitler) is discussed. Effects of nano and micro particles on the growth, chlorophyll content and protein content of algae are analysed using standard protocols. Results indicate that $SiO_2$ nano and micro $SiO_2$ particles are non-toxic to P. aerugineum Geitler up to a concentration of 1000 mg/L. In addition, $Al_2O_3$ microparticles are less toxic to P. aerugineum Geitler, whereas $Al_2O_3$ nanoparticles are found to be highly toxic at 1000 mg/L. Moreover, $Al_2O_3$ nanoparticles decrease the growth, chlorophyll content, and protein content of tested algae. In addition, zeta potential and contact angle are also important in enhancing the toxicity of metal oxide nanoparticles in aquatic environment. This study highlights a new insight into toxicity evaluation of nanoparticles on beneficial aquatic organisms such as algae.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.142-142
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• 2010

This research proposed an advanced Electronic bead (EB) using MMA (Methy methacrylate) and CCA (Charge Control Agent). In the first, this paper presents about measurement method and characterization analysis of EB and nano-silica with pulse waveform in aging. Furthermore; this work presents the positive and negative EB fabrication procedure. As the experimental results, the proposed EB with square waveform is very attractive to Electronic paper driving characterization.

• Journal of the Korean Geosynthetics Society
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• v.22 no.4
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• pp.51-61
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• 2023

In this study, in order to improve the fire resistance performance of structures in case of fire in buildings and structures, PVA fibers and the ZnO particles combined with mesoporous nano silica (MSNs) were mixed with cement mortar, and the specimen was exposed to a temperature range of 20~1100℃. Then the residual compressive strength and weight change rate were measured to determine whether the fire resistance performance changed. As a result of the study, it was found that mixing mesoporous nano silica and PVA fiber together did not contribute to improving the fire resistance performance of cement mortar. On the other hand, mixing 0.5% of mesoporous nano silica and 0.1 vol% of PVA fiber showed the best improvement test results, showing that it was advantageous for fire resistance performance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.86-92
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• 2009

We fabricated the charged particle type display using opposite-charged two toner particles. The particles were composed of polymer, colorant($TiO_2$, carbon black) and external additives(nano-sized silica and so on). In fabrication process we controlled the putting layers of this toner particles on the inner panel. To get the effect of number of layers ($1{\sim}3$), we measured the threshold, driving and breakdown voltages, reflectivity, viewing angle, and color characteristics using RT-300 anisotropic scattering system. We ascertained that these voltages are increased with increasing of layers of particles. Cell gap between electrodes must be enlarged with increment of layers and the size of particles. The lumping phenomena of particles at near of the rib observed by optical system with same CIE values.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.619-624
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• 2003

The $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ (x=0.02, 0.05, 0.08, and 0.12) powders (${\thickapprox}1{\mu}m$) synthesized by sol-gel method, whose surfaces are modified in a colloidal silica suspension (size of $SiO_2$ particles: ${\sim}30$ nm), have been fabricated to highly stable and effective luminescent films on the glass substrates. Thanks to the fused $SiO_2$ nano particles in the vicinity of the glass softening temperature (at around $700^{\circ}C$), $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ powders are strongly attached onto the surface of glass substrate (>9H, pencil hardness tester). This simple and low-cost method to get $Gd_{1.9-x}Li_{0.1}Eu_xO_3$ phosphor films without any loss of luminescence brightness would promise for applications to display devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.352-358
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• 2019

In recent years, printing paper with a function of information delivery and aesthetic value has attracted a great attention with increasing market demand for coated paper that is capable of high quality printing. The coated paper for inkjet printing with high-quality of photorealistic grades requires the coating layer with a good wettability and porous surface structure in order to improve the printability of ink. In this study, the coated paper was prepared using polyvinyl alcohol (PVA) and surface treated nano silica sol with silane coupling agent. It was confirmed that the coating layer with surface treated nano silica sol showed a uniform pore distribution and flat surface roughness. Glossiness of the prepared printing paper was similar to that of commercial high quality photo paper. Especially, the coated paper with surface treated nano silica sol showed improved printability with excellent roundness of the printed dot of ink. These results indicates that the coating layer with excellent wettability and uniform pore distribution can be formed by using the nano-silica particles with improved dispersibility through the surface treatment of the silane coupling agent.

• Applied Chemistry for Engineering
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• v.30 no.1
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• pp.68-73
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• 2019

We prepared hydrophobic silica particles by a sol-gel process from tetraethyl orthosilicate (TEOS), followed by coupling the reaction with octyltrimethoxysilane (OTMS) or hexadecyltrimethoxysilane (HDTMS) under various reaction conditions. We confirmed the extent of silica surface modification with organic compounds by SEM-EDS, thermogravimetry and elemental analysis. The silica particles obtained after the hydrolysis reaction of TEOS in ethanol at $50^{\circ}C$ for 24 h and the coupling reaction with OTMS for 2 h at the same temperature displayed the optimum performance in terms of the dispersity in an organic solvent and the surface roughness of films composited with epoxy resins. The oxygen permeability of the composite film with modified-silica was 12% lower than that of using the film without modified-silica.

• Journal of the Korean Chemical Society
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• v.60 no.5
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• pp.317-320
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• 2016

Efficient copper removal from water was achieved by using surface modified silica spheres with 3-mercaptopropyltrimethoxysilane (MPTMS) using base catalyst. The surface modification of silica spheres was performed by hydrolysis and condensation reactions of the MPTMS. The characteristic infrared absorption peaks at 2929, 1454, and 1343 cm⁻¹ represent the −CH₂ stretching vibration, asymmetric deformation, and deformation, respectively. The absorption peaks at 2580 and 693 cm⁻¹ corresponding the −SH stretching vibration and the C-S stretching vibration indicate the incorporation of MPTMS to the surface of silica spheres. Field emission scanning electron microscope (FESEM) image of the surface modified silica sphere (SMSS) shows nano-particles of MPTMS on the surface of silica spheres. High concentration of copper solution (1000 ppm) was used to test the copper removal efficiency and uptake capacity. The FESEM image of SMSS treated with the copper solution shows large number of copper lumps on the surface of SMSS. The copper concentration drastically decreased with increasing the amount of SMSS. The residual copper concentrations were analyzed using inductively coupled plasma mass spectrometer. The copper removal efficiency and uptake capacity with 1000 ppm of copper solution were 99.99 % and 125 mg/g, respectively.