An ultra-high temperature ceramic, tantalum carbide, has received much attention for its favorable characteristics: a superior melting point and chemical compatibility with carbon and other carbides. One drawback is the high temperature erosion of carbon/carbon (C/C) composites. To address this drawback, we deposited TaC on C/C with silicon carbide as an intermediate layer. Prior to the TaC deposition, the TaCl5-C3H6-H2 system was thermodynamically analyzed with FactSage 6.2 and compared with the TaCl5-CH4-H2 system. The results confirmed that the TaCl5-C3H6-H2 system had a more realistic cost and deposition efficiency than TaCl5-CH4-H2. A dense and uniform TaC layer was successfully deposited under conditions of Ta/C = 0.5, 1200 oC and 100 torr. This study verified that the thermodynamic analysis is appropriate as a guide and prerequisite for carbide deposition.

To prepare Mn4+-activated K2TiF6 phosphor, a precipitation method without using hydrofluoric acid (HF) was designed. In the synthetic reaction, to prevent the decomposition of K2MnF6, which is used as a source of Mn4+ activator, NH5F2 solution was adopted in place of the HF solution. Single phase K2TiF6:Mn4+ phosphors were successfully synthesized through the designed reaction at room temperature. To acquire high luminance of the phosphor, the reaction conditions such as the type and concentration of the reactants were optimized. Also, the optimum content of Mn4+ activator was evaluator based on the emission intensity. Photoluminescence properties such as excitation and emission spectrum, decay curve, and temperature dependence of PL intensity were investigated. In order to examine the applicability of this material to a white LED, the electroluminescence property of a pc-WLED fabricated by combining the K2TiF6:Mn4+ phosphor with a 450 nm blue-LED chip was measured.

This study is subway tunnel field application about repair materials with crack self-healing capability. It was found that it showed good durability compared to the existing repair materials through lab test. Utilization of these mortars may have high potential for a new repair material.