Papers by Author: Jin Seok Lee

Abstract: Cordierite-bonded silicon carbide porous ceramics were prepared by a reactive process, in which kaolin, talc, and alumina powders were mixed with silicon carbide powders and graphite powder was used as a pore former. The mixture was heated in air so that graphite was burned out and silicon carbide particles were bonded by reaction-derived cordierite. Open porosity and strength of porous ceramics were strongly dependent on the volume fraction of graphite and cordierite. A three-point bending strength of 13.9 MPa was achieved at a open porosity of 38.5 %, exhibiting coefficient of thermal expansion of 7.28 × 10-6/oC at the range of 25 – 800oC. Increase of cordierite volume in SiC matrix indicated mechanical improvement of the porous ceramics due to the increase of neck area among the SiC particles. Porous ceramics sintered at 1450oC possessed higher open porosity and median pore diameter than those of samples sintered at 1250 and 1350oC, since pore generated by the transport of dissolved talc materials as increasing temperature.

Abstract: Bi-based glass pastes were prepared in the mixed organic solvents (α-terpineol and texanol) with different kinds and concentrations of organic dispersant such as fish oil , phosphate ester and poly methyl methacrylate (PMMA). The rheological stability of glass pastes was characterized by using a rheometer and adsorption behavior of organic additives for the glass powders was carried out by using a thermal gravimetric analyzer (TGA).The Bi-based glass pastes exhibited the most stable rheological behavior at an addition of phosphate ester of 0.5 in mass %, due to the steric repulsive force acting on the surface of glass powers with adsorbing the organic additives. This study allowed significant delay of the sedimentation time and suppressed generation of micropores during practical forming process by a screen printing method.

Abstract: Well-crystallized and nano-sized indium tin oxide (ITO) powders were prepared by a solvothermal process from a mixed solution consisting of indium nitrate and tin chloride. The characteristics of the solvothermally synthesized ITO powders were studied to investigate the contribution of the processing variables on the physico-chemical properties of powders. The results of this study show that the nano-sized blue ITO powders with a single phase could be directly obtained by changing the medium from water to organic solvent.