Toughening effect of multiwall carbon nanotubes on 3Y-TZP zirconia ceramics at cryogenic temperatures

Multiwalled carbon nanotubes (MWCNTs) could effectively improve the fracture toughness of 3 mol% Y₂O₃ stabilized zirconia (3Y-TZP) because of their excellent mechanical properties. Fully dense 3Y-TZP toughened by MWCNTs was fabricated by spark plasma sintering (SPS), and their mechanical properties at cryogenic temperatures were investigated. The hardness of 1.5 wt% MWCNTs toughened 3Y-TZP increased from 12.4970.19 GPa to 15.10±0.45 GPa as the decrease of temperature from 293 K to 77 K, while the fracture toughness increased from 5.36±0.12 MPa m^1/2 to 6.6970.21 MPa m^1/2. The enhancement mechanical properties at cryogenic temperature over room temperature were due to the unique high mechanical properties of ZrO₂ matrix, elastic modulus, fracture surface energy and residual stress at cryogenic temperature. The above results suggested that the prepared MWNT toughened 3Y-TZP could be a candidate material for cryogenic application.