Structure-property correlation of alumina/nickel composites for their mechanical and electrical properties

Al2O3/nickel (Ni) composites were fabricated via hot-press sintering at 1400 °C to investigate the effects of microstructure on their mechanical and electrical properties. For this purpose, various amounts of Ni metal particles (5–20 vol%) were dispersed in Al2O3 ceramics. All the composites were highly densified, with a theoretical density of over 97%, and microstructural observations revealed elongated Ni phases and strong Al2O3/Ni interfaces. The Young’s moduli of the composites with 5–15 vol% Ni content were higher than that of the pure Al2O3 matrix. Additionally, all the composites showed higher fracture toughness than the pure Al2O3 ceramic matrix, owing to toughening mechanisms such as crack deflection and bridging between Al2O3 grains. This microstructural evolution also affected the formation of continuous conductive pathways connecting the elongated Ni particles. As a result, the electrical resistivity of the composite dramatically decreased to 3.6 × 103 Ωcm at 15 vol% Ni and was further reduced to 1.1 × 102 Ωcm when the volume fraction of Ni was increased to 20 vol%. These results suggest that controlling the amount of Ni, which greatly affects the microstructural evolution, can simultaneously enhance the mechanical and electrical properties of Al2O3/Ni composites.