This work describes the microstructure, indentation toughness and electrical conductivity of alumina-carbon black and alumina-carbon nanotubes nanocomposites prepared by spark plasma sintering. Materials have been studied by SEM, Vickers indentation technique and two-point electrical conductivity measurement. The addition of 5 % CNTs increased the indentation toughness from 3.24 MPa m(1/2) to 4.14 MPa m(1/2). The electrical conductivity of alumina-CNT nanocomposites is approximately ten times higher in comparison to the alumina-carbon black nanocomposites due to the fibrous nature and high aspect ratio of CNTs
