In situ bend testing of niobium-reinforced alumina nanocomposites with and without single-walled carbon nanotubes

Alumina-based nanocomposites were fabricated and consolidated via spark plasma sintering. The effect of single-walled carbon nanotube (SWCNT) and niobium additions to nanocrystalline alumina was examined by in situ bend testing. The addition of 10 vol.% niobium to nanocrystalline alumina provided substantial improvement of fracture toughness (6.1 MPa m1/2)—almost three times that of nanocrystalline alumina. Observation of cracks emanating from Vickers indents, as well as bend specimen fracture surfaces, reveal the operation of ductile phase toughening in the Nb–Al2O3 nanocomposites. Further addition of 5 vol.% SWCNTs to the 10 vol.%Nb–Al2O3 revealed a more porous structure and less impressive fracture toughness—having an indentation and bend fracture toughness of 2.9 MPa m1/2 and 3.3 MPa m1/2, respectively.