Synthesis of a new nanocrystalline titanium aluminum fluoride phase by reaction of Ti2AlC with hydrofluoric acid

Abstract

A new nanocrystalline phase of titanium aluminum fluoride, with a stoichiometry of Ti₂AlF₉—exact stoichiometry measured herein is Ti_2.1Al_0.9F₉,—was synthesized by the fluorination of Ti₂AlC in anhydrous hydrofluoric acid at 55 °C for 2 h. The results from X-ray diffraction, scanning and high-resolution transmission electron microscopy and selected area diffraction, together with crystal structure solution via simulated annealing, confirmed the formation of a nanocrystalline material with a trigonal structure belonging to the R3 space group. The structure can also be viewed as being comprised of corner-sharing octahedra that are arranged in a distorted simple cubic arrangement. Thermogravimetric analysis, in argon, indicates that this phase is stable up to ≈ 850 °C. Density functional theory calculations estimate the band gap to be ≈ 5 eV and the bulk modulus to be ≈ 109 GPa.