Mechanical properties and interfaces of zirconia/nickel in micro - and nanocomposites

The effect of processing parameters on the hardness and toughness of yttria-doped zirconia/nickel nanocomposites is reported. The experimental procedure consists in the deposition of nickel nanoparticles––previously obtained from nickel nitrate salts––on the surface of the zirconia powders. Slight changes in the proposed processing route (i.e. drying temperature of powders) gave rise to a noticeable decrease in the hardness (15–20%). However, no effect was observed on the toughness values in the studied composition range (0–30 vol% Ni). These results have been explained in terms of the nickel particle size distribution and agglomeration due to differences in the melting temperature of nickel nanoparticles, and because of epitaxial growth of nickel on the zirconia surface. For comparison purposes, samples obtained following a conventional wet-processing route starting from micrometric nickel and yttria-doped zirconia powders were prepared. In this case, the toughness is strongly dependent on the nickel fraction. This fact has been related to the weak bonding between metal and ceramic particles.