Synthesis, properties and thermal decomposition of the Ta4AlC3 MAX phase

The present work describes a synthesis route for bulk Ta4AlC3 MAX phase ceramics with high phase purity. Pressure-assisted densification was achieved by both hot pressing and spark plasma sintering of Ta2H, Al and C powder mixtures in the 1200-1650 degrees C range. The phases present and microstructures were characterized as a function of the sintering temperature by X-ray diffraction and scanning electron microscopy. High-purity alpha-Ta4AlC3 was obtained by hot pressing at 1500 degrees C for 30 min at 30 MPa. The beta-Ta4AlC3 allotrope was observed in the samples produced by SPS. The Young's modulus, Vickers hardness, flexural strength and single-edge V-notch beam fracture toughness of the high-purity bulk sample were determined. The thermal decomposition of Ta4AlC3 into TaC and Al vapour in high ((similar to)10(-5) mbar) vacuum at 1200 degrees C and 1250 degrees C was also investigated, as a possible processing route to produce porous TaCx components.