Effect of nanopowder deagglomeration on the densities of nanocrystalline ceramic green bodies and their sintering behaviour

The agglomeration of nanoscaled powders in general decreases the density of green bodies pressed from those nanopowders. Depending on the strength and morphology of the agglomerates different densities can be achieved. It is shown that in the case of ceramic nanopowders as alumina and yttria-stabilised zirconia which are produced by laser ablation technique or in the case of alumina also by physical vapour synthesis process the stronger agglomerates can easily be cracked by a short milling procedure. Green bodies pressed from the conditioned nanopowders exhibit up to 15% larger densities than bodies made from unmodified nanopowders. Due to the decreased porosity in those specimens the sintering activity is significantly increased and therefore ceramics of up to 99% of the theoretical density having median grain diameters less than 500 nm can be manufactured under simplified processing conditions. (C)1999 Acta Metallurgica Inc.