A multicomponent porous MAX phase (Ti0.25Zr0.25Nb0.25Ta0.25)2AlC: Reaction process, microstructure and pore formation mechanism

A multicomponent porous MAX phase (Ti0.25Zr0.25Nb0.25Ta0.25)2AlC has been successfully synthesized by using pressureless sintering of mixed elemental powders. The microstructure and phase composition of the samples sintered at various temperatures have been characterized by using SEM, XRD, EDS and other analyses, from which conclusions regarding the reaction and pore forming processes could be drawn. During the whole sintering process, the pores did mainly arise from the diffusion related reactions between Al and other elements at low temperatures (below 1200 °C), and the formation reaction of the MAX phase took place at higher temperatures (above 1200 °C). An exception is the clearance holes that were left from the pressing. The optimum sintering temperature for the final MAX phase (Ti0.25Zr0.25Nb0.25Ta0.25)2AlC was 1600 °C. A too high sintering temperature (1700 °C) caused a serious loss of Al atoms and a decomposition of the synthesized MAX phase.