• Journal of Powder Materials
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• v.22 no.6
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• pp.403-407
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• 2015

Poly-methylmetacrylate (PMMA) is mainly applied in the plastic manufacturing industry, but PMMA is weak and gradually got discolor. The strength of PMMA can be improved through organic-inorganic hybrid nano composites with inorganic nano particles such as, $SiO_2$ or ZrO. However, inorganic nano particles are mostly agglomerated spontaneously. In this study, the zeta potential is controlled using different types of organic solvent with different concentrations, dispersibillity of $SiO_2$ nano particles on the PMMA particle are analyzed. When 3 M acetic acid is used, absolute value of the zeta potential is higher, $SiO_2$ nano particle is well attached, and dispersed on the PMMA particle surface. Results indicate that the absolute value of the zeta potential affects the stability of $SiO_2$ dispersion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.120-121
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• 2007

Nano-floating gate memory (NFGM) devices were fabricated by using the low temperature poly-Si thin films crystallized by ELA and the $In_2O_3$ nano-particles embedded in polyimide layers as charge storage. Memory effect due to the charging effects of $In_2O_3$ nano-particles in polyimide layer was observed from the TFT NFGM. The post-annealing in 3% diluted hydrogen $(H_2/N_2)$ ambient improved the retention characteristics of $In_2O_3$ nano-particles embedded poly-Si TFT NFGM by reducing the interfacial states as well as grain boundary trapping states.

• 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 Ceramic Society
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• v.34 no.4
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• pp.406-412
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• 1997

Al2O3/SiC hybrid-composite has been fabricated by the conventional powder process. The addition of $\alpha$-Al2O3 as seed particles in the transformation of ${\gamma}$-Al2O3 to $\alpha$-Al2O3 provided a homogeneity of the microstructure. The grain growth of Al2O3 are significantly surpressed by the addition of nano-size SiC particles. Dislocation were produced due to the difference of thermal expansion coefficient between Al2O3 and SiC and piled up on SiC particles in Al2O3 matrix, resulting in transgranular fracture. The high fracture strength of the composite was contributed to the grain refinement and the transgranular fracture mode. The addition of SiC platelets to Al2O3/SiC nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC platelets with nitrides such as BN and Si3N4 enhanced fracture toughness much more than non-coated SiC platelets by enhancing crack deflection.

• 연구논문집
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• s.26
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• pp.103-112
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• 1996

$Al_2O_3/SiC$ Hybrid-Composite has been fabricated by conventional powder process. The addition of $\alpha-Al_2O_3$ as seed particles in the transformation of $\gamma-Al_2O_3 to $\alpha-Al_2O_3$ provided a homogeneity of the microstructure, resulting in increase of mechanical properties. The grain growth of $Al_2O_3$ are significantly surpressed by the addition of nano-sized. SiC particles, increasing in fracture strength. The addition of SiC plates to $Al_2O_3$ nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC plates with nitrides such as BN and /SiC$Si_3N_4$ enhanced fracture toughness much more than uncoated SiC plates by inducing crack deflection.

• Computers and Concrete
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• v.20 no.2
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• pp.119-127
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• 2017

Time-dependent buckling of embedded straight concrete columns armed with Silicon dioxide($SiO_2$) nano-particles exposed to fire is investigated in the present study for the fire time. The column is simulated mathematically with Timoshenko beam model. The governing mass conservation equations to describe heat and moisture transport in concrete containing free water, water vapor, and dry air in conjunction with the conversion of energy are considered. The characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the critical buckling load and critical buckling time of structure. The influences of volume percent of $SiO_2nano-particles$, geometrical parameters, elastic foundation and concrete porosity are investigated on the time-dependent buckling behaviours of structure. Numerical results indicate that reinforcing the concrete column with $SiO_2nano-particles$, the structure becomes stiffer and the critical buckling load and time increase.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.439-440
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• 2002

Nano-Crystalline $CeO_2$ particles were dispersed in deionized water with controlled slurry chemicals for CMP test. According to the CMP test, the removal rate of $SiO_2$ layer was mainly controlled by the size and crystallinity of $CeO_2$ particles which can be controlled by the heat-treatment condition during $CeO_2$ synthesis. In contrast, the removal rate of $Si_3N_4$ layer was significantly influenced by the passivation reagent which protects the $Si_3N_4$ surface layer from excessive dissolution during CMP.

• Journal of the Korean Ceramic Society
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• v.56 no.3
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• pp.256-268
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• 2019

In this research, some mechanical properties of Al₂O₃-based composites containing nanoSiC and nanoMgO additives, including elasticity modulus, hardness, and fracture toughness, have been evaluated. Micron-sized Al₂O₃ powders containing 0.08 wt.% nanoMgO particles have been mixed with different volume fractions of nanoSiC particles (2.5 to 15 vol.%). Untreated samples have been sintered by using hot-press technique at temperatures of 1600 to 1750℃. The results show significant increases in the mechanical characteristics with increases in the sintering temperature and amount of nanoSiC particles, with the result that the elasticity modulus, hardness, and fracture toughness were obtained as 426 GPa, 21 GPa, and 4.5 MPa.m^1/2, respectively.

• 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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• 2009.11a
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• pp.225-225
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• 2009

In this study, Nano and micro-filler mixture composites were fabricated by fixed value of $SiO_2$ nano-filler 0.4 [wt%] according to increase of $SiO_2$ micro-filler [wt%] from 1 to 10. Composites with a good dispersion of mixed $SiO_2$ Nano and micro-particles in the epoxy resins were prepared and experiments were performed to measure the dielectric breakdown strength properties with various temperature and thickness. The dielectric strength properties are compared and analyzed with respect to nano/micro-composites filled with $SiO_2$ fillers less than properties obtained for nanocomposites.