Preparation of Al2O3–ZrO2–Ni nanocomposite by pulse electric current and pressureless sintering

In the present study, dense Al2O3/(ZrO2 + Ni) nanocomposites are prepared by pulse electric current sintering (PECS) at 1350 °C for 5 min or by pressureless sintering (PLS) at 1600 °C for 1 h. The nanometer-sized Ni particles (∼10 nm) were first introduced into the (Al2O3 + ZrO2) powder mixtures by using a coating technique. The presence of the Ni particles prohibits the coarsening of the composite prepared by PLS; nevertheless, enhances the grain growth of the composites prepared by PECS. The sub-micrometer-sized ZrO2 particle acts as microstructural stabilizer that slows down the coarsening of matrix grains in the composites prepared by both processes. Due to microstructural refinement, the strength of the Al2O3/(5%ZrO2 + 1%Ni) nanocomposite is ∼40% higher than that of Al2O3 alone.