Sintering, mechanical, electrical and oxidation properties of ceramic intermetallic TiC–Ti3Al composites obtained from nano-TiC particles

The paper discusses the development of a new material system for interconnect application in Solid Oxide Fuel Cells (SOFC) based on TiC–Ti3Al. Nano-sized TiC powders utilized in this research were synthesized using carbon coated TiO2 precursors from a patented process. The pressureless sintering of TiC–Ti3Al in a vacuum was applied at temperatures between 1100°C and 1500°C and content of Ti3Al was varied in the range of 10–40wt%. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used for phase evaluation and sintering behavior. Relative density increased markedly with increasing sintering temperature because of grain growth and formation of the Ti3AlC2 secondary phase. Dense products (>95% TD) were prepared from nanosized TiC powders with 10 and 20wt% Ti3Al, but with about 8 to 10% porosity for 30 and 40wt% Ti3Al. The mechanical properties were determined from Vickers hardness and fracture toughness calculations. Vickers hardness decreased and fracture toughness increased with increasing Ti3Al content. The electrical conductivity and oxidation behavior of TiC–Ti3Al composites were investigated to evaluate the feasibility for SOFC interconnect application. The electrical conductivity measurements in the air at 800°C for 100h were made using the Kelvin 4-wire method.