Properties of nanocrystalline ceramic powders prepared by laser evaporation and recondensation

Nanocrystalline ceramic powders (ZrO 2, Al 2O 3, Si 3N 4, AlN) are prepared by evaporation of solid materials (sintered rods or coarse powder) in thefoeus of a CO 2 laser and the following recondensation in a carrier gas stream. The production rates are in the range of 40–100 g h −1 (cw mode, oxides) or more than 200 g h −1 (cw mode, nitrides), respectively. The particle size distribution can be influenced by different parameters of the formation process like laser power, area of the laserfocus, pulse length in case of pw mode, streaming velocity and type of the carrier gas. The powders consist of nearly spherical particles with diameters in the range of 10–100 nanometers. Features of the produced alumina and zirconia powders are reported concerning phase transformation, behaviour in suspensions and processing properties.