NANOSTRUCTURED ALUMINA COATINGS FORMED BY A DISSOLUTION/PRECIPITATION PROCESS USING AlN POWDER HYDROLYSIS

The hydrolysis of aluminum nitride (AlN) powder was exploited in the preparation of nanostructured coatings on a sintered yttria-stabilized tetragonal zirconia (Y-TZP) ceramic substrate, with the aim to enhance the adhesion of dental cements to the ceramic core structure. The nanocrystalline coating formed using this method consists of gamma-AlOOH (boehmite) in the form of 6-nm-thick and 240-nm-long interconnected lamellas. During a subsequent heat treatment in the temperature range from 600 degrees C to 1200 degrees C this coating was transformed to various transient aluminas without any noticeable change in the morphology, but its bonding to the substrate was significantly improved. By varying the precipitating conditions, such as the temperature and the time, it was also possible to synthesize coatings differing in composition and morphology, resulting in nano- or micron-sized particles. This nanosized alumina coating has the potential to improve the adhesion of composite dental cements to the sintered Y-TZP ceramic.