BaMxAl12-xO19-delta (M = Mn, Fe, Co, x = 1, 2) hexaaluminate nanomaterials were successfully prepared using the ARS (Activated Reactive Synthesis) process, a top-down and solvent free original synthesis route. The crystal sizes of the nanomaterials range at 24 +/- 2 nm, which allows them to display high surface area (from 60 to 100 m(2) g(-1)). The role of Mn+ cations in the redox and oxygen transfer properties of the nanomaterials was studied by H-2-TPR and O-18/O-16 isotopic exchange, respectively. The nature of the transition metal as well as its content is observed to play a key role in the oxygen transfer properties. The catalytic properties of the nano-hexaaluminates, evaluated for methane oxidation, a reaction involving severe conditions (high temperature), resulted from multiple factors including oxygen transfer properties and transition metal valence and concentration on the surface