Al2O3/BN nanocomposites were fabricated through a novel chemical route involving hot-pressing of α–Al2O3 powders covered partly with turbostratic BN (t-BN). The nano-sized hexagonal BN (h-BN) particles were found to be homogeneously dispersed within the Al2O3 grains as well as at grain boundaries, which is indicative of nanocomposite structures. Thus, the present nanocomposites exhibited the unique properties of high strength and low Young’s modulus associated with nanocomposites. This paper discusses in detail the synthesis process and microstructural features of these materials.

Multi Wall Carbon Nanotubes (MWCNTs) with a diameter of 20-30 nm were used as a conductive phase to add electric conductivity to yttria stabilized tetragonal zirconia (3Y-TZP). Almost fully dense 3Y-TZP/MWCNTs nanocomposite was obtained by pressureless sintering under inert atmosphere and Hot Isostatic Pressing (HIP) treatment. The conductivity of the nanocomposites increased with increasing content of MWCNTs. Moreover, the fracture toughness increment of the composite was confirmed at 0.5 wt% addition. Scanning electron microscopy and transmission electron microscopy observation of the microstructures showed that MWCNTs were fairly homogeneously dispersed in the 3Y-TZP matrix.

Dense ceramic/metal nanocomposite has been fabricated by internal reduction method, which includes a two‐step process: sintering of ceramic–metal oxide solid solution and subsequent heat treatment in a reducing atmosphere to precipitate metal nanoparticles. This novel technique has been applied to yttria‐stabilized tetragonal zirconia (Y‐TZP) and nickel oxide (NiO) system to fabricate Y‐TZP/Ni nanocomposite. Dense Y‐TZP and 0.3 mol% NiO solid solution ceramic was successively prepared by the pressureless sintering, and Y‐TZP/Ni was fabricated by the internal reduction treatment. The obtained Y‐TZP/Ni nanocomposite possessed characteristic intragranular nanostructure with nano‐sized metallic Ni particles of around 20 nm. Fracture toughness of both the solid solution and nanocomposite was remarkably improved because of the solid solution of NiO into Y‐TZP and resultant destabilization of the tetragonal phase, and the Y‐TZP/Ni nanocomposite was still destabilized by the remaining nickel solution after the reduction. The nanocomposite exhibited ferromagnetism, while the Y‐TZP–NiO solid solution had diamagnetic nature. Comparison of saturation magnetization values revealed that 39.5 at.% of introduced nickel was reduced to metallic nanoparticle, proving the existence of residual NiO solute in zirconia that contributed to higher toughness value than the monolithic Y‐TZP. It is concluded that the introduced internal reduction method is a suitable process to achieve multifunctional ZrO2/Ni nanocomposite with high toughness and coexistent magnetic characteristic.