SINTERING, MECHANICAL, ELECTRICAL AND OXIDATION PROPERTIES OF CERAMIC INTERMETALLIC TiC-Ti_3Al COMPOSITES FROM NANO-TiC PARTICLES

摘要

The paper discusses the development of a new material system for interconnect application in Solid Oxide Fuel Cells (SOFC) based on TiC-Ti_3Al. Nano-size TiC powders utilized in this research were synthesized using carbon coated TiO_2 precursors from a patented process. The pressureless sintering of TiC-Ti_3Al in vacuum was applied at temperatures between 1300-1500°C and content of Ti_3 Al was varied in the range of 10-40 wt. %. XRD and SEM were used for phase evaluation and sintering behavior. Relative density increased markedly with increasing sintering temperature because of grain growth and formation of Ti_3AlC2 secondary phase. Dense products (＞95% TD) were synthesized from nanosized TiC powders with 10 and 20 wt. % Ti_3Al, but with about 8 to 10% porosity for 30 and 40 wt. % Ti_3Al. The mechanical properties were determined from Vickers hardness and fracture toughness calculations. Vickers hardness decreased and fracture toughness increased with increasing Ti_3Al content. The electrical conductivity and oxidation behavior of TiC-Ti_3Al composites were investigated to evaluate the feasibility for SOFC interconnect application. The electrical conductivity measurements in air at 800 °C for 100 hours were made using Kelvin Method 4 wire 2 point method.