Microstructure and physicomechanical properties of pressureless sintered multiwalled carbon nanotube/alumina nanocomposites

Multiwalled carbon nanotube (MWCNT)/alumina (Al2O3) nanocomposites containing CNT from 0.15 vol.% to 2.4 vol.% have been successfully fabricated by simple wet mixing of as-received commercial precursors followed by pressureless sintering. Extent of densification of nanocomposites sintered at low temperature (e.g. 1500 °C) was <90%, but increased up to ∼99% when sintered at 1700 °C and offered superior performance compared to pure Al2O3. Nanocomposites containing 0.3 vol.% MWCNT and sintered at 1700 °C for 2 h in Argon led to ∼23% and ∼34% improvement in hardness and fracture toughness, respectively, than monolithic Al2O3. In addition, the highest improvement (∼20%) in bending strength was obtained for 0.15 vol.% MWCNT/Al2O3 nanocomposite compared to pure Al2O3. Weibull analysis indicated reliability of nanocomposites increased up to 0.3 vol.% MWCNT, whereas, beyond that loading consistency was the same as obtained for pure Al2O3. Detailed microstructure and fractographic analysis were performed to assess structure-property relationship of present nanocomposites.