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The novel carbon coating process for interlayer of fiber reinforced ceramic composites between fiber and matrix was performed by carbonizing phenolic resin solution that coated on fiber surface in N 2 atmosphere at 600 o C to improve the strength and fracture toughness of CMC(ceramic matrix composite). 160 nm carbon layer was coated on fiber surface with 5 vol% of phenolic resin solution. Since the process temperature (600 o C) is lower than chemical vapor deposition(900~1000 o C), the strength and toughness could be preserved. Furthermore the coating thickness uniformity was improved to 8% of deviation along the stacking sequence. Therefore, prevention from fiber degradation during coating process and controlling coating thickness uniformity along the preform depth were achieved by coating with phenolic resin carbonizing method.

In this study, we investigated the mechanical behavior of carbon fiber reinforced silicon carbide composites by indentation stress. Relatively porous and dense fiber reinforced ceramic composites were fabricated by liquid silicon infiltration (LSI) process. Densification of fiber composite was controlled by hardening temperature of preform and consecutive LSI process. Load-displacement curves were obtained during indentation of WC sphere on the carbon fiber reinforced silicon carbide composites. The indentation damages at various loads were observed, and the elastic modulus were predicted from unloading curve of load-displacement curve.

Porous YSZ ceramics are fabricated using 3 mol% yittria-stabilized zirconia (3YSZ) and NiO with different particlesizes (0.6 and 7 µm). Nickel oxide (NiO) is added to the YSZ powder as a pore former with different amounts(40, 50, and 60 vol%) and at different sintering temperatures (1350 and 1400 o C) are applied in order to evaluate the temperature effects on the pore and mechanical properties. Heat treatment is conducted after sintering at 700 o C in H 2 for the NiO reduction process; then, Ni is removed using a HNO 3 etchant solution. According to the NiO contentand sintering temperatures, 41-67% porous YSZ ceramic is obtained and the flexural strength increases, while the porosity decreases with an increasing sintering temperature. The optimum flexural strength (136.5 ± 13.4MPa) and porosity (47%) for oxygen transport porous YSZ membrane can be obtained with 40 vol% of 7 µm NiO particle at a sintering temperature of 1350 o C.