Synthesis of MAX Phases in the Ti2AlC–V2AlC System as Precursors of Heterometallic MXenes Ti2 – xVxC

Abstract

Abstract A relatively low-temperature molten salt assisted synthesis is developed to prepare MAX phase solid solutions in the Ti2AlC–V2AlC system, to be used as precursors for the preparation of heterometallic MXenes Ti2 –xVxC. When the synthesis temperature is 1000°С, Ti1V1AlC, Ti0.5V1.5AlC, and Ti0.2V1.8AlC samples (despite the formation of a MAX phase and a systematic shift of reflection (002) in response to progressing vanadium-for-titanium substitution) typically feature appreciable amounts of impurity phases, namely Al2O3 and vanadium (their reflections are partially overlapping). An increase in synthetic temperature to 1100°С appreciably reduces the amount of impurities and, in a Ti1V1AlC sample, decreases the unit cell parameter a, which yet far exceeds the calculated and published values (while the parameter c corresponds with those values). Thermal analysis of Ti2AlC, Ti1V1AlC, and V2AlC samples in the range 20–1000°С shows that the oxidation resistance decreases in the progress of vanadium-for-titanium substitution in a MAX phase. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to study the microstructure of the prepared Ti2AlC and V2AlC phases.