Double-walled carbon nanotube/zirconia composites: Preparation by spark plasma sintering, electrical conductivity and mechanical properties

摘要

Double-walled carbon nanotube/yttria-stabilized zirconia composite powders with carbon contents up to 6.3 wt% are prepared by soft covalent functionalization of carbon nanotubes (CNTs) followed by mixing with a nanometric yttria-stabilized zirconia (YSZ) powder. Composites are densified by spark plasma sintering (SPS). The composites present an electrical conductivity (0.09–0.88 S cm−1) which is among the highest values reported in the literature. Both the fracture strength (σf) and the single-edged notched beam fracture toughness (KIc) are measured for the first time on CNT/YSZ composites. The best mechanical properties (σf=694 MPa; KIc=7 MPa m1/2), obtained for low carbon contents (up to 1.2 wt%), are among the highest reported up to now. However, the fracture toughness is lower than that of the YSZ ceramic (KIc=10.3 MPa m1/2) whose mechanical properties are outstanding, taking into account its very fine microstructure.