• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1463-1465
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• 2003

In this paper, we studied on the growing characteristics of dendrite structure of melted wire deteriorated by over current. Electric wire was melted by Jolue's heat. By using HSIS(High Speed Imaging System), we found out a lot of melted parts of wire were dispersed and radiated. Electric wire had narrow melted areas in case of short fusing time. A lot of very small dots generated around the grain of copper cross-section and they were changed into dendrite structure. Dendrite structure appeared at the values lower than 2.5[A/sec]. In case of very short fusing time, fusing current was calculated by empirical formula. The Preece equation was not enough to analyze a variety of characteristics of melted wire because it did not consider melting time, atmosphere, etc.

• KSBB Journal
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• v.22 no.4
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• pp.239-243
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• 2007

A method of forming agar microcapsule with fibroin coating was developed in this report. The capsules were prepared from a W/O emulsion of hot agar in mineral oil and were subsequently coated by fibroin. The capsules were harvested as precipitated aggregates, which can be dispersed in an aqueous media. The diameter of the microcapsule was less than $10{\mu}m$ by microscopic observation and 90% of them were between $1.32{\mu}m\;and\;6.0{\mu}m$. The structure of the aggregates and their dispersed microspheres were investigated by scanning electron microscope. Confocal microscopy was applied to visualize the core-shell structure of the agar microcapsule with fibroin coating. Thermogravimetric analysis (TGA) measured their composition to be agar 51.2%, fibroin 13.8%, Span 80 1.4% by weight.

• Fibers and Polymers
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• v.6 no.4
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• pp.289-296
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• 2005

Biodegradable nanocomposites were prepared by mixing a polymer resin and layered silicates by the melt intercalation method. Internal structure of the nanocomposite was characterized by using the small angle X-ray scattering (SAXS) and transmission electron microscope (TEM). Nanocomposites having exfoliated and intercalated structures were obtained by employing two different organically modified nanoclays. Rheological properties in shear and extensional flows and biodegradability of nanocomposites were measured. In shear flow, shear thinning behavior and increased storage modulus were observed as the clay loading increased. In extensional flow, strain hardening behavior was observed in well dispersed system. Nanocomposites with the exfoliated structure had better biodegradability than nanocomposites with the intercalated structure or pure polymer.

• Proceedings of the Korean Fiber Society Conference
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• 1998.04a
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• pp.5-8
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• 1998

Polyurethane elastomers are segmented cocoplymer with an [HS]n-type structure. Typically, these materials are two-phase systems, prepared from relatively polar and stiff component called the hard segment(H) and relatively flexible component known as the soft segment(S). Diisocyanate and chain extender together form the hard segment, which is dispersed within a matrix of the soft segment, composed of the macrodiolos.(omitted)

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.467-470
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• 2007

Ultrafine Indium tin oxide (ITO) nanoparticle was successfully fabricated by low temperature synthetic method (LTSM). Mean size of ITO nanoparticle is 5 nm, and uniformly dispersed with (222) orientated cubic structure. Using the nanoparticle, ITO thin film with good optical and electrical properties was fabricated by inkjet printing.

• Korean Journal of Materials Research
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• v.3 no.6
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• pp.668-677
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• 1993

The microstructural and shear tests of STS304/, STS430/ and low-C steel/Cu joints brazed using Cu-P, Cu-P-Sn(four type) and Cu-P-Sn-Ag(three type) filler metals at 1003 and 1033K for 1.2ks in Ar atomsphere were performed. Interfacial microstructures were divided into three type ; first, reaction layer contained cracks second, dispersed layer without cracks third, dispersed layer and reaction layer contained cracks. The joints composed only of dispersed layer without cracks have the high shear strength of above 40-60 MPa and result in failure in copper base metal. Low shear strength and joint failure result from the formation of reaction layer which induced cracks. The reaction layer is a Fe-P compound. This tendency of microstructure and shear strength depends on the existence and/or nonexistence of Sn in filler metals as well as Ni (and Cr) in base metals.

• Korean Journal of Materials Research
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• v.21 no.1
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• pp.28-33
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• 2011

This paper describes the fabrication of AlN thin films containing iron and iron nitride particles, and the magnetic and electrical properties of such films. Fe-N-Al alloy films were deposited in Ar and $N_2$ mixtures at ambient temperature using Fe/Al composite targets in a two-facing-target DC sputtering system. X-ray diffraction results showed that the Fe-N-Al films were amorphous, and after annealing for 5 h both AlN and bcc-Fe/bct-$FeN_x$ phases appeared. Structure changes in the $FeN_x$ phases were explained in terms of occupied nitrogen atoms. Electron diffraction and transmission electron microscopy observations revealed that iron and iron nitride particles were randomly dispersed in annealed AlN films. The grain size of magnetic particles ranged from 5 to 20 nm in diameter depending on annealing conditions. The saturation magnetization as a function of the annealing time for the $Fe_{55}N_{20}Al_{25}$ films when annealed at 573, 773 and 873 K. At these temperatures, the amount of iron/iron nitride particles increased with increasing annealing time. An increase in the saturation magnetization is explained qualitatively in terms of the amount of such magnetic particles in the film. The resistivity increased monotonously with decreasing Fe content, being consistent with randomly dispersed iron/iron nitride particles in the AlN film. The coercive force was evaluated to be larger than $6.4{\times}10^3Am^{-1}$ (80 Oe). This large value is ascribed to a residual stress restrained in the ferromagnetic particles, which is considered to be related to the present preparation process.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3218-3224
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• 2012

Uniform and well dispersed metal sulfide semiconductor nanoparticles incorporated into matrices of alginate biopolymer are prepared by using a facile in situ method. The reaction was accomplished by impregnation of alginate with divalent metal ions followed by reaction with thioacetamide. XRD analysis showed that the nanoparticles incorporated in the polymer matrix were of cubic structure with the average particle diameter of 1.8 to 4.8 nm. Field emission scanning electron microscopy and high resolution transmission electron microscopy images indicated that the particles were well dispersed and distributed uniformly in the matrices of alginate polymer. FT-IR spectra confirmed the presence of alginate in the nanocomposite. The crystalline nature and thermal stability of the alginate polymer was found to be influenced by the nature of the divalent metal ions used for the synthesis. The proposed method is considered to be a simple and greener approach for large scale synthesis of uniform sized nanoparticles.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.6
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• pp.714-724
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• 1985

Two-phase(air-solid, air-liquid droplet) turbulent round jet has been analyzed numerically using two equation turbulence model. The mean motion of suspending particles in air has been treated as the secondary fluid with virtual density and eddy viscosity. In this paper, the local mean velocity of secondary fluid is not assumed to be the same as that of the primary one. Dissipation rate of turbulent kinetic energy which arises because the particles can not catch up with the turbulent fluctuations of the primary fluid has been modelled by using the concept of Kolmogorov's spectral energy transfer. Numerical computations were performed for flows with different volume fraction of the dispersed phase and the diameter of particle. Results show that the total rate of turbulent energy dissipation, turbulent intensities and spreading rate of jets are reduced by the increase of volume fraction of dispersed phase. However it does not show consistent tendency with increasing the particle diameter. This investigation also shows that presence of particles in the fluid modifies the structure of the primary fluid flow significantly. Predicted velocity profiles and turbulence properties qualitatively agree with available data.

• Journal of Korea Foundry Society
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• v.13 no.3
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• pp.238-247
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• 1993

Microstructure, hardness and wear characteristics of $SiC_p/Al-6.5wt%Si-1.7wt%Mg$ alloy composites fabricated by the method of rheo-compocasting and hot pressing are investigated in this study. The dispersion of SiC particles in the composites is homogeneous and the hardness improves as additional amount increases. The wear amount of the matrix metal increases highly as wear rates increase, for the wear mechanism changes from adhesive wear to melt wear, and the matrix metal was coated on the surface of revolving disc and its weight increases. In the 5vol% composites, Fe is adhered on the surface of specimen by the projection of the dispersed hard SiC particles which have net-work structure and the coating layer is about $300{\mu}m$. But in the composite more than 20vol%, the wear amount of composite decreases because the SiC particles which have superior hardness, wear resistance and heat resistance properties resist wear, the abrasive wear turn out predominant wear mechanism and so the wear amount of revolving disc increases.