Synthesis of MAX Phases in the Ti2AlC–V2AlC System as Precursors of Heterometallic MXenes Ti2 – xVxC
Е. П. Симоненко, Н. П. Симоненко, Ilya A. Nagornov, T. L. Simonenko, Artem S. Mokrushin, V. G. Sevastyanov, Н. Т. Кузнецов
Abstract
Abstract A relatively low-temperature molten salt assisted synthesis is developed to prepare MAX phase solid solutions in the Ti 2 AlC–V 2 AlC system, to be used as precursors for the preparation of heterometallic MXenes Ti 2 – x V x C. When the synthesis temperature is 1000°С, Ti 1 V 1 AlC, Ti 0.5 V 1.5 AlC, and Ti 0.2 V 1.8 AlC 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 Al 2 O 3 and vanadium (their reflections are partially overlapping). An increase in synthetic temperature to 1100°С appreciably reduces the amount of impurities and, in a Ti 1 V 1 AlC 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 Ti 2 AlC, Ti 1 V 1 AlC, and V 2 AlC 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 Ti 2 AlC and V 2 AlC phases.