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

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 (RC_min) 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.