• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.422-422
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• 2009

Photocurable inorganic-organic hybrid materials were prepared from colloidal-silica nanoparticles synthesized through the solgel process and using acryl resin. The synthesized colloidal-silica nanoparticles had uniform diameters of around 20 nm, and they were organically modified, using methyl and methacryl functional silanes, for efficient hybridization with acryl resin. The organically modified and stabilized colloidal-silica nanoparticles could be homogeneously hybridized with aeryl resin without phase separation. The successfully fabricated hybrid materials exhibit efficient photocurability and simple film formation due to the photopolymerization of the organically modified colloidal-silica nanoparticles and acryl resin upon UV exposure. The fabricated hybrid films exhibit an excellent optical transmission of above 90% in the visible region as well as an enhanced surface smoothness of around 1 nm RMS roughness. In addition, the hybrid films exhibit improved thermal and mechanical characteristics, much better than those of acryl resin. More importantly, these photocurable hybrid materials fabricated through the synergistic combination of colloidal-silica nanoparticles with acryl resin are candidates for optical and electrical applications.

• Carbon letters
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• v.4 no.1
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• pp.36-39
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• 2003

Carbon and carbon-based materials are used in nuclear reactors and there has recently been growing interest to develop graphite and carbon based materials for high temperature nuclear and fusion reactors. Efforts are underway to develop high density carbon materials as well as amorphous isotropic carbon for the application in thermal reactors. There has been research on coated nuclear fuel for high temperature reactor and research and development on coated fuels are now focused on fuel particles with high endurance during normal lifetime of the reactor. Since graphite as a moderator as well as structural material in high temperature reactors is one of the most favored choices, it is now felt to develop high density isotropic graphite with suitable coating for safe application of carbon based materials even in oxidizing or water vapor environment. Carboncarbon composite materials compared to conventional graphite materials are now being looked into as the promising materials for the fusion reactor due their ability to have high thermal conductivity and high thermal shock resistance. This paper deals with the application of carbon materials on various nuclear reactors related issues and addresses the current need for focused research on novel carbon materials for future new generation nuclear reactors.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.648-652
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• 2009

Ceramic fiber separator is the promising material for thermal battery system because it reduces the production cost and offers the potential to a new application compared to a pellet type electrolyte. The electrolyte separator for thermal battery should be easily handled and loaded a large amount of the molten lithium salt. Ceramic fibers were used as an electrolyte separator and the lithium based molten salts were infiltrated into the ceramic filters. Leakage of molten salt (several lithium salts) leads to short-circuit during the thermal battery operation. In this study, a uniform and fine SiOC mat with fibers ranging from 1 to 3 ${\mu}m$ was obtained by electrospinning of polycarbosilane and pyrolysis. The optimum spinning conditions for obtaining fine diameters of SiOC fiber were controlled by the solution composition and concentration, applied voltage and spinning rate, release rate by porosity. The pore structures of the ceramic filter and the melting properties of the lithium salts affected to the electrolyte loading and leakage. The importance of the fiber size and porosity and their control was discussed and the mechanical properties were also discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.181-181
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• 2010

Few-walled carbon nanotubes (FWNTs)-based field emitters with long term stability are fabricated by using a spray method. Tetraethylorthosilicate (TEOS) sol as a binder was mixed with dispersed solution of FWNTs to enhance the adhesion of FWNTs on the cathode substrate. Due to the strong intermolecular interaction of TEOS to the functional groups attached on CNTs and substrate, CNTs are tightly adhered to the cathode electrode when heat treatment is performed at $150^{\circ}C$ for 1 hour, resulting in a stable electron emission of CNT emitters for long time. Excellent field emission characteristics were exhibited, with a large field enhancement factor and low turn-on voltage, comparable to those of CNT emitters fabricated by a screen printing of CNT paste. Therefore, FWNTs / TEOS hybrid films could be utilized as an alternative for the efficient and reliable field emitters.

• Journal of the Korean Ceramic Society
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• v.45 no.7
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• pp.423-429
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• 2008

Ceramic Fiber separator is the promising material for thermal battery system because it reduces the production cost and offers the potential to a new application compared to a pellet type electrolyte. The molten salt electrolytes for thermal battery were prepared by the impregnation of the commercial glass filters such as GF-A, C and F (Whatman, USA) with two types of molten-lithium salts, LiCl-KCl and LiK-LiBr-LiF. The wetting properties were evaluated by wetting balance test and wetting angle measurement. The wetting behaviors were strongly affected by the composition of the molten salts and the pore structure of the glass separators. The optimum wetting conditions for maximum loading and effective retention of the molten electrolyte were also studied.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.27-32
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• 1997

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.183-188
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• 1999

Due to many advantages of advanced composite materials, research on the application of composites to the construction industry is initiated. In this paper, fabrication methods efficient for infrastructures and application examples of each method are discussed. It also presents the structural characteristics of concrete filled glass fiber reinforced composite tubular member. Experimental results shows that strength and ductility of composite compression member is considerably increased due to concrete confinement action of composite surface.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.5-8
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• 2004

About 175 vehicular bridges and 160 pedestrian bridges in service now, worldwide, are made of composites, completely of partially. In this paper, the status of this application is briefly explained.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.1
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• pp.23-29
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• 2003

Stencil is used normally as a mask for solder pasting on pad of a printed circuit board (PCB). The objective of this study is to develop a stencil cutting system and determine the optimal conditions to make good-quality stencil by using a Nd:YAG laser. The effects of process parameters such as laser power, type of mask, gas pressure, cutting speed and pulse duration on the cut edge quality were investigated. In order to analyze the cut surface characteristics (roughness, kerfwidth, dross) optical microscopy, SEM microscopy and roughness measurements were used. As a result, the optimal conditions of cutting process parameters were determined, and the practical feasibility of the proposed system was also examined by using a commercial Gerber file for PCB stencil manufacturing.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.178.1-178
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• 2002