• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1331-1335
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• 2010

A novel spherical carbon composite material, in which nanosized disordered carbons are dispersed in a soft carbon matrix, has been prepared and investigated for use as a potential anode material for lithium ion batteries. Disordered carbons were synthesized by ball milling natural graphite in air. The composite was prepared by mixing the ball-milled graphite with petroleum pitch powder, pelletizing the mixture, and pyrolyzing the pellets at $1200^{\circ}C$ in an argon flow. The ballmilled graphite consists of distorted nanocrystallites and amorphous phases. In the composite particle, nanosized flakes are uniformly distributed in a soft carbon matrix, as revealed by X-ray diffractometer (XRD) and transmission electron microscopy (TEM) experiments. The composite is compatible with a pure propylene carbonate (PC) electrolyte and shows high rate capability and excellent cycling performance. The electrochemical properties are comparable to those of hard carbon.

• Journal of Sericultural and Entomological Science
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• v.42 no.1
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• pp.42-47
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• 2000

Structural and thermal characteristics of silk fibroin/poly(2-hydroxyethyl methacrylate)(PHEMA) blend films were investigated using FTIR, X-ray diffractometer, differential scanning calorimeter, thermogravimeter and scanning electron microscope. FTIR spectra showed that the conformation of silk fibroin prepared by dissolving in formic acid was $\beta$-sheet, which did not affected by blending with PHEMA. The X-ray diffraction patterns also showed that individual crystalline structure of silk fibroin and PHEMA was not affected for the blend films. The initial thermal decomposition temperature of silk fibroin/PHEMA blend film tends to be higher than either of silk fkbroin or PHEMA. Thermal stability of both polymers, more notably PHEMA, can be improved by blending two components. As a result of SEM observation, the phases separation for silk fibroin/PHEMA blend films occured regardless of blend ratio ; continuous and dispersed phase were silk fibroin and PHEMA component, respectively.

• Structural Engineering and Mechanics
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• v.38 no.4
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• pp.503-516
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• 2011

Uncertainty in concrete properties, including concrete modulus of elasticity and modulus of rupture, are predicted by developing a microstructural homogenization model. The homogenization model is developed by analyzing a concrete representative volume element (RVE) using the finite element (FE) method. The concrete RVE considers concrete as a three phase composite material including: cement paste, aggregate and interfacial transition zone (ITZ). The homogenization model allows for considering two sources of variability in concrete, randomly dispersed aggregates in the concrete matrix and uncertain mechanical properties of composite phases of concrete. Using the proposed homogenization technique, the uncertainty in concrete modulus of elasticity and modulus of rupture (described by numerical cumulative probability density function) are determined. Deflection uncertainty of reinforced concrete (RC) beams, propagated from uncertainties in concrete properties, is quantified using Monte Carlo (MC) simulation. Cracked plane frame analysis is used to account for tension stiffening in concrete. Concrete homogenization enables a unique opportunity to bridge the gap between concrete materials and structural modeling, which is necessary for realistic serviceability prediction.

• The Korean Journal of Ceramics
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• v.1 no.2
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• pp.69-74
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• 1995

The optimal condition for minimal agglomeration of barium titanyl oxalate tetrahydrate, the precipitate on preparing barium titanate by oxalate process, was investigated. Burette-dropping and dual-nozzle-spraying were used as adding methods. pH of washing water for precipitates was changed, and sodium pyrophosphate solution, methanol, ethoanol, and acetone were used as washing agents for precipitates, as well as distilled water. Drying temperature was changed from $50^{\circ}C$ to $120^{\circ}C$. Spraying, methanol-washing, and drying at $60^{\circ}C$ showed the most dispersed distribution, Below $70^{\circ}C$, the crystalline phases were observed.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.362-364
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• 2010

Shock wave interaction with droplet-gas medium is investigated in this paper. In the present computation, the shock wave is initially started in a pure gas and reflected from the wedge to interact with the droplet-ridden gas flows. We used the compressible two-fluid two-phase model that is solved by the two-fluid version of the HLL scheme. The interfacial drag force and heat transfer were included to model the interaction between continuous and dispersed phases. The parametric effect of void fraction on the shock wave reflection in the two-phase media was investigated.

• Journal of the Korean Ceramic Society
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• v.45 no.12
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• pp.782-787
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• 2008

Ni-ceria cermets have been extensively investigated as candidates for the anode in intermediate-temperature solid oxide fuel cells. We have used the citric method to synthesize nanocomposite powders consisting of NiO (Ni metal content: $40{\sim}60%$ by volume) highly dispersed in $Ce_{0.9}Gd_{0.1}O_{1.95}$ (CGO). The microstructure characteristics and sintering behaviors of the nanocomposites were investigated. No impurity phases were observed and the shrinkage of these substrates matched well with that of a CGO electrolyte with a specific surface area of $11\;m^2/g$. Densification of the CGO electrolyte layer to $<5\;{\mu}m$ thickness was achieved by co-firing the laminated electrolyte with the porous NiO-CGO substrate at $1400^{\circ}C$ for 6 h.

• Journal of Mechanical Science and Technology
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• v.14 no.12
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• pp.1365-1375
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• 2000

Two phase flows have been numerically calculated to analyze plume characteristics and liquid circulation in gas injection through a porous plug. The Eulerian approach has been for formulation of both the continuous and dispersed phases. The turbulence in the liquid phase has been modeled using the standard $textsc{k}$-$\varepsilon$ turbulence model. The interphase friction coefficient has been calculated using correlations available in the literature. The turbulent dispersion of the phase has been modeled by the "dispersion Prand시 number". The predicted mean flows is compared well with the experimental data. The plume region area and the axial velocities are increased with the gas flow rate and with the decrease in the inlet area. The turbulent intensity also shows the same trend. Also, the space-averaged turbulent kinetic energy for various gas flow rates and inlet areas has been obtained. The results are of interest in the design and operation of a wide variety of materials and chemical processing operations.

• Laser Solutions
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• v.2 no.2
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• pp.34-41
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• 1999

A RS840 $CO_2$laser and a powder auto-feeding apparatus have been used to deposit single tracks of Ni-base superalloy on low carbon steel. In this paper, the effects of laser cladding parameters on clad geometry, dilution and microhardness are studied. As a results, the w/h ratio of the clad layer increases with decreasing powder feed rate and increasing laser scan speed. Increase of powder density and decrease of specific energy have little effect on dilution. It was found that the clad layer of the highest hardness has a structure in which fine and leaf like phases are dispersed in ${\gamma}$Ni matrix.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.130-134
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• 2017

Organic aerosols dispersed in the atmosphere likely undergo phase separation. Such internally mixed particles are often described as comprising an organic phase and an aqueous phase separately. We studied the morphology of two liquid separated aerosols in the sub-microscale by using a simple thermodynamic model with Russian doll geometry. The morphology of particles can be easily predicted from the simple criteria on the surface tension and two algebraic equations (the volume constraint and Young equation). This result may give the potential explanation about the complex morphology of the organic airborne particles.

• Proceedings of the Membrane Society of Korea Conference
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• 1993.04a
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• pp.52-53
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• 1993

The pervaporation behavior of EtOH/Water mixture through IPN membranes was predicted in this study. The pervaporation characteristics of single polymer membrane were modeled according to the "six-coefficients model" proposed by Brun. In the case of the IPN membrane, two models were proposed according to the phase structure of the IPN. For a uniphase membrane with no phase separation, the compositional average of the single polymer membrane was used. in the case of the phase separated IPN's two cases existed. The first was the island and sea model: in which one phase was continuous and the other was dispersed. The second was the co-continuous model where two continuous phases existed. For these cases, the permeation rate and the separation factor of the IPN membrane were calculated using the experimental sorption data and the cornponent polymer properties. Comparison with the experimental data indicated that these models could be used to predict the performances of IPN membranes depending on the morphology of the IPN.