Mechanochemistry can be used to produce corundum nanoparticles https://www.mpg.de/14078015/korund-nanoparticles-mechanochemistry
Chemists led by F. Schüth at the Max-Planck-Institut für Kohlenforschung mechanochemically produce corundum nanoparticles in a ball mill.
They used a soft alumina (gamma-alumina) mixed with gold particles as a catalyst