Sintering of a Nanostructured CoZr-ZrO₂ Composite from Mechanochemically Synthesized Powders

Since their development in the 1970s ZrO2 ceramics have been shown to be promising alternative materials for total hip arthroplasty (THA) and total knee arthroplasty (TKA). However, ZrO2 is so brittle that in vivo failure can result from fracture of the ceramic femoral head and fracture of the ceramic acetabular liner due to the low toughness of the ceramics. To improve its fracture toughness, the approach commonly utilized has been the addition of a second phase to form a composite and produce nanostructured materials. The purpose of this study was to produce a mechanical synthesis of CoZr and ZrO2 nanopowders from CoO and Zr powders, and fabricate dense nanocrystalline 2CoZr-ZrO2 composites within two minutes using this pulsed current activated sintering method. Their mechanical properties, biocompatibility and microstructure were then evaluated. Nanopowders of CoZr and ZrO2 were synthesized mechanochemically according to the reaction (2 CoO + 3 Zr → 2CoZr + ZrO2) from CoO and Zr powders by high-energy ball milling. The synthesized powders were consolidated by the pulsed current activated sintering method within two minutes under 80Mpa pressure. CoZr and ZrO2 composite was sintered by the rapid heating of the nanophase. The hardness and fracture toughness of the 2 CoZr-ZrO2 composite in this study were better than the hardness of monolithic CoZr and the fracture toughness of a monolithic ZrO2. Additionally, the 2 CoZr-ZrO2 composite exhibited good biocompatibility.