The Hydrolysis of AlN Powder - A Powerful Tool in Advanced Materials Engineering.

The tendency for aluminium nitride (AlN) powder to undergo hydrolysis, which can lead to a complete degradation of the material, is unique in metal nitrides. Although this form of hydrolysis has been known for a long time, it is generally considered as a nuisance, because it prevents the aqueous powder processing of AlN-based ceramics. However, careful investigations of the course of hydrolysis, the reaction kinetics and the evolution of aluminium hydroxides have uncovered exceptional possibilities for the exploitation of this naturally driven process in the area of advanced materials engineering. It can be employed as superior synthesis path for hierarchically-assembled, mesoporous alumina powders or coatings consisting of 2D nanocrystalline lamellas. The beneficial surface characteristics of the powder serve as an ideal template for further modifications useful in catalysis, while the powder's flowability enables facile preparation of high-performance hierarchically porous structures. The coatings, on the other hand, are suitable as templates for superhydrophobic surfaces or as adhesive coatings for cementing zirconia dental ceramics. Finally, the hydrolysis-assisted solidification (HAS) process has proved to be an important asset in the processing science and technology for fabrication of porous and dense ceramics and nanocomposites.