Papers by Author: Min Sung Kang

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Authors: Hun Sik Kim, Byung Hyun Park, Min Sung Kang, Jin San Yoon, Hyoung Joon Jin
Abstract: Polycarbonate/multiwalled carbon nanotubes (PC/MWNT) nanocomposites with different contents of MWNT were successfully prepared by melt compounding. The mechanical properties of the PC/MWNT nanocomposites were effectively increased due to the incorporation of MWNTs. The composites were characterized using scanning electron microscopy in order to obtain the information on the dispersion of MWNT in the polymeric matrix. In case of 0.3 wt% of MWNT in the matrix, strength and modulus of the composite increased by 30% and 20%, respectively. In addition, the dispersion of MWNTs in the PC matrix resulted in substantial decrease in the electrical resistivity of the composites as the MWNTs loading was increased from 1.0 wt% to 1.5 wt%.
Authors: Jine Sung Jung, S.Y. Chang, Keun Bong Yoo, Gee Wook Song, Min Sung Kang, M.T. Kim
Abstract: Degradation of the gas turbine hot-gas-path components, the 1st stage blades and vanes, serviced for a period was evaluated by measuring the mechanical properties. For this, tensile and impact tests on these gas turbine parts were performed. Microstructure of the substrate and coating layers were also observed. The mechanical properties of the serviced blades were degraded by about 30% comparing with those of unused ones. In terms of the microstructure, the dissolution of the secondary g’ phase and subsequent coarsening of precipitates were observed in the substrate. And the interdiffusion zone near the coating layer was disappeared.
Authors: Seok Ho Yoon, Min Sung Kang, Hun Sik Kim, Hyoung Joon Jin
Abstract: Electrorheological (ER) particles were obtained by the adsorption of multiwalled carbon nanotubes (MWCNT) on the surface of silk fibroin microspheres. The resulting spherical polymeric microspheres consist of a silk fibroin core and an MWCNT shell, which is electrically conducting. The silk fibroin microspheres were prepared by the phase separation of the silk fibroin and poly(ethylene oxide) (PEO) blend solution, and the MWCNT dispersion was prepared by ultrasonication with cetyltrimethylammonium bromide (CTAB) surfactant. The ER particles were prepared using a simple process involving the blending of the silk fibroin microsphere suspension and aqueous MWCNT dispersion. The morphology of the ER particles was examined by field emission scanning electron microscopy (FESEM) and their electrical conductivity measured by the four-probe method was 4.8×10-4 S/cm. The prepared composite microspheres suspended in silicone oil showed typical ER characteristics, including the formation of a chain-like structure under an applied electric field (1.9 kV/mm). This phenomenon can be explained by the interfacial polarizability of the MWCNTs adsorbed on the surface of the polymeric microspheres.
Authors: Min Sung Kang, Hyoung Joon Jin
Abstract: Multi-walled carbon nanotubes (MWNTs) were incorporated in electrospun Nylon 610 fibers. The MWNTs used were synthesized by a thermal CVD method. To eliminate metallic catalyst residues in as synthesized MWNTs, they were treated in HNO3 and HCl. The potential adhesion between the MWNTs and Nylon 610 was expected by the interaction between the amide group of Nylon 610 and the oxygen-containing species on the MWNTs such as carboxylic acid group introduced during the purification step. Contrary to the previous works on electrospinning using a simple blend of carbon nanotubes with polymeric materials, we incorporated MWNTs as nanoscale fillers by in-situ interfacial polymerization. We also investigated morphology of the electrospun Nylon 610 fibers with MWNTs.
Authors: Min Sung Kang, Seok Ho Yoon, Hyoung Joon Jin
Abstract: A simple and mass producible method was developed to incorporate multiwalled carbon nanotubes (MWCNTs) into electrospun silk fibroin (Bombyx mori) nanofibers. The process consists of dispersing the acid-treated MWCNTs in an aqueous silk fibroin solution, and blending this solution with a water-soluble polymer, poly(ethylene oxide) (PEO), followed by electrospinning of the composite solution. The morphology and microstructure of the electrospun nanofibers were characterized using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The FESEM and TEM images show that the MWCNTs are embedded along the nanofibers. Aqueous-based electrospinning of silk/PEO/MWCNTs composites provides potentially useful options for the fabrication of biomaterial scaffolds, e.g. wound dressings, based on this unique fibrous protein.
Authors: Min Sung Kang, Won Il Park, Rira Jung, Hyoung Joon Jin
Abstract: A highly concentrated solution of polystyrene (PS) in N,N-dimethyl formamide (DMF) was electrospun and the surface morphology of the electrospun PS fibers was investigated. Unlike the porous morphology observed on the surface of the fibers electrospun from the PS solution in a volatile solvent, e.g. tetrahydrofuran, a regular protuberance morphology was found on the surface of the fibers electrospun from the PS solution in the non-volatile solvent, DMF. This unique surface morphology was formed due to the presence of residual DMF solvent inside the electrospun PS fiber. Due to the large diameter of the PS fibers (~5 to ~10 μm) formed from the highly viscous PS solution, the DMF could not evaporate completely from inside them during the electrospinning process. Therefore, the extrusive force of the residual solvent inside the fiber induced the formation of a unique surface morphology. We believe that this unique surface morphology increases the surface area of the electrospun fibers, thus making it possible to control their wetting or adsorption behavior.
Authors: Hun Sik Kim, Byung Hyun Park, Min Sung Kang, Hyoung Joon Jin, Jin San Yoon
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