Fabrication of bulk nanocrystalline alumina–zirconia materials

Eutectic mixtures of alumina and zirconia have been successfully transformed to thick amorphous coatings and free-standing parts by plasma spraying. The as-sprayed material has very low open porosity and crystallizes when heated above 950 °C. Short annealing times at the crystallization temperature result in the formation of a very fine microstructure throughout the sample volume with average grain size below 15 nm. The fine nanocomposite structure was confirmed by transmission electron microscopy. High hardness and abrasion resistance of the as-sprayed materials are significantly improved upon annealing due to the nanocomposite structure, which makes the bulk nanocrystalline ceramic material attractive.