Synthesis and characterization of a remarkable ceramic: Ti3SiC2

Polycrystalline bulk samples of Ti3SiC2 were fabricated by reactively hot-pressing Ti, graphite, and SiC powders at 40 MPa and 1600 degrees C for 4 h. This compound has remarkable properties. Its compressive strength, measured at room temperature, was 600 MPa, and dropped to 260 MPa at 1300 degrees C in air. Although the room-temperature failure was brittle, the high-temperature load-displacement curve shows significant plastic behavior. The oxidation is parabolic and at 1000 degrees and 1400 degrees C the parabolic rate constants mere, respectively, 2 x 10(-8) and 2 x 10(-5) kg(2) . m(-4). s(-1). The activation energy for oxidation is thus approximate to 300 kJ/mol. The room-temperature electrical conductivity is 4.5 x 10(6) Omega(-1). m(-1), roughly twice that of pure Ti. The thermal expansion coefficient in the temperature range 25 degrees to 1000 degrees C, the room-temperature thermal conductivity, and the heat capacity are respectively, 10 x 10(-6) degrees C-1, 43 W/(m . K), and 588 J/(kg . K). With a hardness of 4 GPa and a Young's modulus of 320 GPa, it is relatively soft, but reasonably stiff. Furthermore, Ti3SiC2 does not appear to be susceptible to thermal shock; quenching from 1400 degrees C into mater does not affect the postquench bend strength. As significantly, this compound is as readily machinable as graphite, Scanning electron microscopy of polished and fractured surfaces leaves little doubt as to its layered nature.