NANOCOATED PARTICLES - A SPECIAL TYPE OF CERAMIC POWDER

Ceramic particles with sizes below 10 nm consisting of two different o xides in the core and the coating have been prepared by using a two-st ep microwave plasma process. Precursors for the synthesis are the chlo rides. The structures occurring in such particles are demonstrated in the system alumina (Al2O3)-zirconia (ZrO2). When the alumina kernels c overed with zirconia are small, or alternatively when the alumina coat ing on the zirconia kernels are thin, no special structure features al e observed. In this case, the alumina is glassy and the zirconia is cr ystallized. In contrast, particles consisting of a crystallized zircon ia core and a crystallized gamma-alumina coating exhibit structural de fects similar to dislocations that adjust to the different structures. These could be sessile dislocations in the {211} plane of the gamma-a lumina. Additionally, maghemite (gamma-Fe2O3) particles coated with cu bic zirconia were studied. The coating of this material is free of dis locations.