Carbon nanofiber-reinforced alumina nanocomposites: Fabrication and mechanical properties

This work reports for the first time the fabrication and mechanical properties of hot-pressed alumina reinforced with 1, 2.5 and 5 vol.% carbon nanofiber (CNF). An improvement in fracture toughness of ∼13% over pure alumina was observed in the alumina reinforced with 2.5 vol.% CNF, whereas hardness and bending strength of the nanocomposites were reduced with increasing the volume fraction of CNF. Annealing at 1300 °C in air for 2 h led to the enhancement in the bending strength as high as 33% in the 5 vol.% CNF-reinforced alumina. This improvement is attributed to crack healing in parallel with an oxidation reaction of the CNF, leading to a reduction in the surface flaw density and critical flaw size.