Zirconia-based nanocomposite toughened by functionalized multi-wall carbon nanotubes

• We reported a novel approach to fabricate 3Y-TZP/CNTs nanocomposites.
• Functionalized multi-walled CNTs were used to improve the distribution of CNTs.
• Homogeneous distribution of CNTs in ceramic matrix has been achieved.
• A clear improvement in the fracture toughness was achieved after adding CNTs.

In the present work, we have reported a novel approach to fabricate 3Y-TZP/carbon nanotube (CNTs) nanocomposites with improved fracture toughness using spark plasma sintering technology through the incorporation of functionalized multi-walled carbon nanotubes. For this approach, homogeneous distribution of CNTs in ceramic matrix has been achieved up to 4 wt% CNTs content, revealed by SEM observations of both composite powders and fracture surfaces of sintered specimens. In addition, Raman spectroscopic indicates that CNTs can be retained at high sintering temperatures from 1250 to 1400 °C. A clear improvement in the fracture toughness was achieved after adding CNTs, and the specimen with 4 wt% CNTs sintered at 1300 °C exhibited the best indentation toughness of 6.24 MPa m1/2, increasing 31% over monolithic ZrO2 sintered at the same temperature. Furthermore, the fracture mode transition and the activated toughening mechanisms during crack propagation were taken into account to explain the improvement in fracture toughness.