Papers by Author: Jin Chun Kim

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Authors: Yun Hae Kim, Soo Hyun Eum, Byung Kyu Choi, Jin Chun Kim, S.C. Kwon, P.K. Dutta
Abstract: Recently, composites are widely used for interior panel of the transportation facilities such as railway vehicle, ships and aircraft, etc. These interior composites panels are often made by vacuum bagging, hand lay-up method and autoclave, etc. In this study, we carried out tests for the evaluation of material properties of the panels under more severe conditions than real environment to evaluate the dimension stability of the interior composite panels. Two sets of panels, one made by hand lay-up method with glass mat/polyester resin (Type 1), and the other, by vacuum bagging method with epoxy prepreg/NOMEX (Type 2) are exposed to the low temperature, high temperature and room temperature. And then we measured the dimensions of the strained panels. To monitor the characteristics of cured resin, we used DSC (Differential Scanning Calorimeter). It was observed that Type 2 has higher mechanical properties and dimensional stability than Type 1.
Authors: Chul Jin Choi, Jin Chun Kim, Ji Hun Yu, Byoung Kee Kim
Abstract: Nanosized Fe based powders have been synthesized by both chemical vapor condensation (CVC) and plasma arc discharge (PAD) processes. Fe, Fe-C and Fe-N nanopowders were successfully synthesized. The influence of experimental parameters on microstructures and phase composition of nanopowders was investigated. The prepared powders were nearly spherical in shape and core-shell type in structure. Various kinds of Fe-C and Fe-N composite nanopowders could be synthesized by controlling the carrier gas and precursor decomposition temperature, etc.
Authors: Dae Gun Kim, Gil Su Kim, Jin Chun Kim, Sung Tag Oh, Young Do Kim
Abstract: The sintered microstructure homogeneity of W-15wt%Cu nanocomposite powders prepared from W-CuO mixture was investigated. The increment of heating rate considerably affected the homogeneity of sintered microstructure. In case of the higher heating rate, the microstructure was more homogeneous than that of the lower heating rate by reason of Cu- exudation during heating-up process.
Authors: Yong Jin Kim, L.F. Wang, In Sang Chung, Jin Chun Kim, Tae Suk Jang
Abstract: The hypereutectic prealloyed Al-Si powders were prepared by gas atomization process. The microstructure and compacting ability of the atomized Al-Si powders were investigated. With increasing the gas pressure of the atomization, the average powder size and oxygen content were decreased. The size of primary eutectic Si particles in the as-atomized powders was about 8~10. As-atomized powders were hot-pressed into a cylindrical shape. Relative density of the hot-pressed samples was achieved about 96~99 % of theoretical density. Some properties of the samples were evaluated in this paper.
Authors: Zhi Wang, Chul Jin Choi, Byoung Kee Kim, Jin Chun Kim, Z.D. Zhang
Authors: Si Young Chang, Jin Chun Kim, Seung Kyun Ryu, Sung Tag Oh, Kae Myung Kang
Authors: Myoung Seok Sung, Yoon Bok Lee, Young Seok Kim, Young Mok Rhyim, Jin Chun Kim, In Bae Kim, Yang Do Kim
Abstract: CdSe nanoparticles with average particles size of ~ 3.4 nm were successfully prepared by the sonochemical reduction of a mixed solution of CdCl2, Na2SeSO3 and CH2CH2OH)2NH at room temperature. CdSe nanoparticles characterized by TEM, XPS and XRD analysis revealed the formation of high purity cubic phase CdSe nanoparticles with lattice constant of a=6.415Å. CdSe nanoparticles showed relatively large range of particle size distribution from 20 to 50 nm as the sonication time increased. UV-Vis absorption spectra showed a red-shift in the wavelength region of 545-590 nm as increasing sonication time due to the gradual growth of CdSe nanoparticles in the solution. This paper will mainly present the effects of ultrasonic irradiation on the formation and properties of CdSe nanoparticles.
Authors: Shin Ho Kim, Yoon Bok Lee, Seung Chan Cho, Young Mok Rhyim, Jin Chun Kim, Young Seok Kim, In Bae Kim, Yang Do Kim
Abstract: Cadmium selenide (CdSe) have been prepared by the reduction of mixed solution of cadmium chloride (CdCl2), sodium selenosulfate (Na2SeSO3) and diethanolamine ((CH2CH2OH)2NH) at temperatures of 80-200°C under Ar atmosphere. Characteristics of CdSe nanoparticles were analyzed using transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) and UV-Vis absorption spectra. CdSe samples prepared at relatively low temperature of below 100°C showed cubic structure while samples synthesized at temperature above 100°C showed hexagonal phase. The increased reaction temperature caused the particle size increase as well as the agglomeration of particles to form a hollow sphere. UV-Vis absorption spectra also showed a red-shift as increasing reaction temperatures due to the gradual growth of CdSe nanoparticles in the solution. The relatively sharp absorption band from samples synthesized at 80 and 100°C can be attributed to homogeneous particle size distribution compared with those of prepared at elevated temperatures. This paper will mainly discuss the phase stability of CdSe nanoparticles as well as the hollow sphere formation.
Authors: Ai Bin Ma, Yoshinori Nishida, Masakazu Nagase, Jing Hua Jiang, Jin Chun Kim, Naobumi Saito, Ichinori Shigematsu
Abstract: Squeeze-cast 20vol%SiCw/2024 composite was processed by rotary-die equal-channel angular pressing (RD-ECAP) and tensile-tested at elevated temperatures. RD-ECAP does not require billet removal and reinsertion between ECAP passes and can produce large cumulative deformation of type A in the billet at a controlled extrusion temperature. Tensile specimens were machined from the RD-ECAP processed billets along the longitudinal direction. 16 RD-ECAP passes at 623 K produced an average matrix grain size of about 0.8 μm in the composite. The ECAP processed 20vol%SiCw/2024 composite exhibited 330% elongation to failure when tested at 783 K and the high strain rate of 1.17×10-1 s-1. The values of strain rate sensitivity exponent of the SiCw/2024 composite determined over the strain rates between 10-2 and 1.0 s-1, was 0.39, 0.47 and 0.53 at 763, 773 and 783 K, respectively. The grain sizes of the aluminum alloy matrix in the composite after superplastic deformation increased from 0.8 μm to be about 1.5 μm. There was no cavity found within the uniformly deformed area. The apparent activation energy for the superplastic deformation of the 20vol%SiCw/2024 composite was determined to be 284 kJ·mol-1.
Authors: Jin Chun Kim, Jae Wook Lee, Byung Yeon Park, Chul Jin Choi
Abstract: Fe/SiO2 nanocomposite powders were synthesized by the chemical vapor condensation(CVC) process. Phase and microstructures of the as-prepared powders were investigated with CVC experimental parameters by XRD, TEM and VSM. The analysis of XRD patterns revealed that the Fe/SiO2 powders could be produced above 700. With increasing reaction temperature, the XRD peaks became clearer. The size of powders was about 50nm at 1100oC. The Fe/SiO2 powders showed an intricate long-stand structure attributed to their magnetic characteristics. TEM results revealed that the Fe powders were covered by SiO2 layer fully or partially depending on the experimental condition. The saturation magnetization and the coercive force of the as-sytheised powders were investigated with the decomposition temperature.
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