Thermal stability and dielectric properties of 2D Ti2C MXenes via annealing under a gas mixture of Ar and H2 atmosphere

Abstract

The thermal stability and dielectric properties of 2D Ti2C nanosheets, prepared by exfoliation of Ti2AlC powders in LiF and HCl solution and annealed in a gas mixture of Ar and H2 atmosphere from 500 °C to 800 °C, were first investigated in the frequency range of 8.2-12.4 GHz. The anatase TiO2 emerges after annealing at 500 °C and then transferred into thermal stabile rutile TiO2 after annealing at higher temperature without sacrificing the 2D multilayered structure of Ti2C nanosheets for all the annealing process. The minimum reflection coefficient (RCmin) reaches −27.1 dB at 9.0 GHz with a sample thickness of 2.7 mm after annealing at 600 °C, the effective absorption bandwidth reaches 1.8 GHz with a sample thickness of 2.5 mm after annealing at 800 °C. The Debye relaxation process originated from dipolar polarization contribute mainly to the dielectric loss and microwave absorbing performance. This work shows that the annealing of Ti2C nanosheets in Ar and H2 atmosphere is a sufficient method to tune the dielectric properties and to prepare microwave absorbing materials.