• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.181-181
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• 2016

Hydrogenated microcrystalline silicon (${\mu}c-Si:H$) films have attracted much attention as materials of the bottom-cells in Si thin film tandem photovoltaics due to their low bandgap and excellent stability against light soaking. However, in PECVD, the source gas $SiH_4$ must be highly diluted by $H_2$, which eventually results in low deposition rate. Moreover, it is known that high-rate ${\mu}c-Si:H$ growth is usually accompanied by a large number of dangling-bond (DB) defects in the resulting films, which act as recombination centers for photoexcited carriers, leading to a deterioration in the device performance. During film deposition, Si nanoparticles generated in $SiH_4$ discharges can be incorporated into films, and such incorporation may have effects on film properties depending on the size, structure, and volume fraction of nanoparticles incorporated into films. Here we report experimental results on the effects of nonoparticles incorporation at the different substrate temperature studied using a multi-hollow discharge plasma CVD method in which such incorporation can be significantly suppressed in upstream region by setting the gas flow velocity high enough to drive nanoparticles toward the downstream region. All experiments were performed with the multi-hollow discharge plasma CVD reactor at RT, 100, and $250^{\circ}C$, respectively. The gas flow rate ratio of $SiH_4$ to $H_2$ was 0.997. The total gas pressure P was kept at 2 Torr. The discharge frequency and power were 60 MHz, 180 W, respectively. Crystallinity Xc of resulting films was evaluated using Raman spectra. The defect densities of the films were measured with electron spin resonance (ESR). The defect density of fims deposited in the downstream region (with nonoparticles) is higher defect density than that in the upstream region (without nanoparticles) at low substrate temperature of RT and $100^{\circ}C$. This result indicates that nanoparticle incorporation can change considerably their film properties depending on the substrate temperature.

• Journal of the Korean Ceramic Society
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• v.55 no.6
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• pp.562-569
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• 2018

We propose an economic and facile method for the preparation of silica nanoparticles through a two-step process utilizing chlorosilane residues. Mixed chlorosilane residue was alcoholized with absolute ethanol as a first step to form tetraethoxysilane (TEOS). The TEOS was then utilized as a silicon source to synthesize silica nanoparticles in a sol-gel method. The alcoholysis process was designed and optimized utilizing the Taguchi experimental design method and the yield of TEOS was as high as 82.2% under optimal synthetic conditions. Similarly, the Taguchi method was also utilized to study the effects of synthesis factors on the particle size of silica nanoparticles. The results of statistical analysis indicate that the concentration of ammonia has a greater influence on particle size compared to the mass fractions of TEOS and polyethylene glycol (4.6% and 9.7%). The purity of the silica particles synthesized in our experiments is high, but the specific surface area and pore volume are small.

• Transactions on Electrical and Electronic Materials
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• v.10 no.3
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• pp.85-88
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• 2009

This report demonstrates the immobilization of uniformly sized gold nanoparticles (AuNPs) on UV cross-linked poly(4-vinylpyridine) (P4VP) polymer thin films and the preparation of micropatterned structures of AuNPs on these films. The polymer thin films were prepared by a spin-coating of P4VP onto a cleaned silicon wafer surface. Upon UV irradiation, these films were then photo cross-linked. Gold nanoparticles were immobilized by immersing the polymer surface in a colloidal solution of gold nanoparticles stabilized by citric acid. The morphology of the films and the immobilization of AuNPs were studied by atomic force microscopy (AFM) and UV-visible spectroscopic techniques. The micropatterned gold structures that were produced on the polymer surface are delineated by combining with the photolithographic method. While untreated and simply spin coated films were physisorbed and unstable that could be easily removed by rinsing with a solvent, the cross-linked and AuNPs immobilized P4VP films were found to be highly stable even after repeated solvent extractions.

• Computers and Concrete
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• v.20 no.6
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• pp.711-718
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• 2017

Nanotechnology is a new filed in concrete structures which can improve the mechanical properties of them in confronting to impact and blast. However, in this paper, a mathematical model is introduced for the concrete models subjected to impact load for wave propagation analysis. The structure is simulated by the sinusoidal shear deformation theory (SSDT) and the governing equations of the concrete model are derived by energy method and Hamilton's principle. The silicon dioxide ($SiO_2$) nanoparticles are used as reinforcement for the concrete model where the characteristics of the equivalent composite are determined using Mori-Tanaka approach. An exact solution is applied for obtaining the maximum velocity of the model. In order to validate the theoretical results, three square models with different impact point and Geophone situations are tested experimentally. The effect of different parameters such as $SiO_2$ nanoparticles volume percent, situation of the impact, length, width and thickness of the model as well as velocity, diameter and height of impactor are shown on the maximum velocity of the model. Results indicate that the theoretical and experimental dates are in a close agreement with each other. In addition, using from $SiO_2$ nanoparticles leads to increase in the stiffness and consequently maximum velocity of the model.

• Journal of Integrative Natural Science
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• v.3 no.4
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• pp.210-214
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• 2010

Relationship between etch current and morphology and porosity of porous silicon (PS) has been investigated. The gravimetric method is applied to measured the porosity of PS. As the current density increase, the silicon dissolution rate increases, resulting in a higher porosity and etching rate. The result shows that linear dependence of PS porosity and etching rate as a function of current density. The morphology of porous silicon was investigated by using cold field emission scanning electron micrograph (FE-SEM). The size of pores formed during anodization is predominantly controlled by the current density, with an increase in the pore size corresponding to an increase in the current density.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.411-417
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• 2013

To use as an anode material of lithium secondary battery, graphite-silicon composite powders are prepared by ball-milling with silicon nanoparticles (average diameter 100 nm, 0~50 wt%) and graphite powder (average diameter $15{\mu}m$) and their electrochemical properties are examined. As the silicon content increases, the graphite becomes smaller by the ball-milling and amorphous phase appears whereas the silicon do not suffer the change of nanocrystalline phases and embeds within the amorphous phase of graphite. Cyclic voltammetry at low scan rate reveals that typical oxidation peaks of graphite and silicon appear at 0.2~0.35 and 0.55~0.6 V, respectively, with higher reversibility for repeated cycles. In contrast, the high-scan-rate redox behavior is very irreversible for repeated cycles. High irreversible capacity is exhibited in the initial charging-discharging cycles, but it diminishes as the cycle number increases. The saturated discharge capacity achieves about 485 mAh $g^{-1}$ at 50th cycle for the composite of Si 20 wt%. This is due to the formation of amorphous graphite morphology by the adequate composition (C:Si=8:2 w/w), which efficiently buffers the volume change during alloying/dealloying between silicon and lithium.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.210-214
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• 2007

Silicon nanoparticles are widely studied as a material with great potential for wide applications. For application to present industry, it should be easy to control the characteristics of nanoparticle including the size and structure. In this paper, we investigated the formation of Si nanoparticle using pulse plasma technology. Plasma technology is already quite common in device industry and the size of nanoparticle can be easily controlled according to plasma pulse duration. An inductively-coupled plasma chamber with RF power (13.56 MHz) was used with DC-biased grid $(-200\sim+200\;V)$ installed above the substrate. In order to measure the shape and size of nanoparticle, TEM was used. It was found that the size of nanoparticles can be controlled well with the plasma pulse duration and the collection efficiency is increased with the use of either negative or positive DC-bias.

• Macromolecular Research
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• v.17 no.12
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• pp.987-994
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• 2009

Palladium nanoparticles having cubic silsesquioxanes (POSS) (Pd-POSS) were produced by the reaction of palladium (II) acetate and octa(3-aminopropyl)octasilsesquioxane octahydrochloride (POSS-${NH_3}^+$ in methanol at room temperature. Functionalized multiwalled carbon nanotubes (MWNT-COOH) were prepared by acid treatment of pristine MWNTs. The hybrid nanocomposites of Pd-POSS and MWNT-COOH (Pd-MWNT nanocomposites) were synthesized by self-assembly method via ionic interaction between positively charged Pd-POSS and negatively charged MWNT-$COO^-$. The spherical aggregates of Pd-POSS with a diameter of 40-60 urn were well attached to the surfaces of MWNT-COOH on Silicon wafer. The composition, structure, and surface morphology of Pd-MWNT nanocomposites were studied by UV-vis spectrophotometer, energy dispersive spectrum (EDX), scanning electron microscopy (SEM), and atomic force microscope (AFM).

• Wind and Structures
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• v.24 no.1
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• pp.43-57
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• 2017

The use of nanotechnology materials and applications in the construction industry should be considered for enhancing material properties. However, the nonlinear buckling of an embedded straight concrete columns reinforced with silicon dioxide ($SiO_2$) nanoparticles is investigated in the present study. The column is simulated mathematically with Euler-Bernoulli and Timoshenko beam models. Agglomeration effects and the characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. The governing equations are derived using energy method and Hamilton's principal. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of $SiO_2$ nanoparticles, geometrical parameters and agglomeration on the buckling of column are investigated. Numerical results indicate that considering agglomeration effects leads to decrease in buckling load of structure.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1723-1726
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• 2008

In recent years, there has been a remarkable progress in the development of the fiber optic sensors for the detection of various chemicals. Fiber optic sensors have the advantages of very small size, flexibility and low cost. The fiber optic sensors employing different optical or spectroscopic phenomena have been reported such as bulk absorption, optical reflectance, fluoresces and energy transfer. In this study, the effect of nanoparticle concentration in liquid upon light absorption and scattering was studied using extrinsic fiber optic method. For the evaluation, we used Red (650 nm) and Blue (430 nm) light sources which are coupled through the standard cuvette using optical fiber to detector. The experiments are carried out with Polystyrene latex (400 - 800 nm), and Silicon (35 - 110 nm) nanoparticles suspended in Isopropanol. Differences in light absorption and scattering depending on nanoparticle concentration and type are discussed. This method may be useful to study nanoparticles properties for various application and research.