Rapid Sintering and Synthesis of Nanocrystalline Ta-ZrO<sub>2</sub> Composite

Abstract

ZrO<sub>2</sub> is a promising candidate for knee and hip joint replacements due to its excellent combination of low density, corrosion resistance and biocompatibility. Nevertheless, a low fracture toughness of pure ZrO<sub>2</sub> at room temperature limits its wider application in the industry. One of the most obvious ways to solve the problem is to add a reinforcing phase, to produce a nanocrystalline composite material. Nanomaterials have been widely studied in recent years because they can improve hardness and fracture toughness. To produce nanocrystalline materials, the pulsed current activated sintering method has the advantage of simultaneously applying mechanical pressure and pulsed current during sintering. As a result, nanocrystalline materials can be produced within a very short time. Ta and ZrO<sub>2</sub> nanopowders were mechanically synthesized from Ta<sub>2</sub>O<sub>5</sub> and 2.5Zr powders according to the reaction (Ta<sub>2</sub>O<sub>5</sub> + 5/2Zr → 2Ta + 5/2ZrO<sub>2</sub>). The synthesized powders were then sintered using pulsed current activated heating under 80 MPa uniaxial pressure within two minutes. Hardness and fracture toughness were measured using a Vickers hardness tester. The average hardness and fracture toughness of the nanocrystalline 2Ta-5/2ZrO<sub>2</sub> composite sintered at 1350 <sup>o</sup>C were 1008 kg/mm<sup>2</sup> and 10 MPa·m<sup>1/2</sup>, respectively. Both the hardness and fracture toughness of the composite were higher than monolithic ZrO<sub>2</sub>. The microstructure and phase of the composite was also investigated by FE-SEM and XRD.