Al2O3(w)–Al2O3(n)–ZrO2 (TZ-3Y)n multi-scale nanocomposite: An alternative for different dental applications?

The influence of the addition of Al2O3 whiskers (2.5 wt.% up to 30 wt.%) on Vickers hardness and fracture toughness in an Al2O3(n)+ZrO2 (TZ-3Y)n (90, 80 and 70 wt.%) composite was investigated. Green compacts were obtained by uniaxial pressing at 50 MPa and pressureless sintering at 1500 °C in air for 2 h. After sintering, relative densities ranging from 75% to 97% were reached. The whiskers resisted particle rearrangement owing to the extensive sliding distances along the whisker boundaries during sintering and the high length/diameter ratios. Sintering becomes more difficult with increasing whisker content, because whiskers come into contact with each other, forming a rigid network which hinders densification. The 2.5 wt.% Al2O3 whiskers + 27.5 wt.% Al2O3 nanoparticles + 70 wt.% TZ-3Y composite showed a hardness > 13 GPa and a maximum fracture toughness of 6.9 MPa m−1/2, with an average grain size of 0.4 ± 0.17 μm. The observed crack deflection was an important mechanism in the improved fracture toughness of the composite. In addition, the grain size and residual porosity also seem to be factors in obtaining a wide range of hardness as well as fracture toughness by varying the Al2O3 whiskers and ZrO2 (TZ-3Y) content. The use of alumina-whisker-reinforced composites in dental applications could be promising for increasing hardness and fracture toughness compared with other materials. The reported values for these composites can compete with those of commercially available materials in different dental applications.