Microstructure and mechanical properties of single wall carbon nanotube reinforced yttria stabilized zircona ceramics

Fully dense yttria-stabilized zirconia (YSZ) ceramics reinforced with single wall carbon nanotubes (SWCNTs) were fabricated by spark plasma sintering (SPS), and their electrical and mechanical properties were investigated. Dimethylformamide (DMF) was used as a solvent and tip-sonicator was employed to disperse SWCNTs homogeneously throughout the matrix and reduce the damage on the SWCNTs during mixing. The microstructure of the composite ceramics indicated that undamaged SWCNT bundles were well distributed throughout the matrix with intimate contact with ZrO2 grains without interlayer or amorphous carbon layer. The electrical resistivity of ZrO2 ceramics drastically decreased with SWCNT addition and it reached 0.3 Ω cm at 1.0 wt%. The SWCNT addition to ZrO2 ceramics increased the fracture toughness from 4.4 to 5.2 MPa m1/2 at 1.0 wt%. The nanotube pull-out and crack bridging contributed to the improved fracture toughness. The frictional behavior was not affected, but the wear resistance of ZrO2 ceramics was significantly improved by SWCNT addition.