Mechanical properties of carbon nanotube–alumina nanocomposites synthesized by chemical vapor deposition and spark plasma sintering

Carbon nanotubes–alumina (CNT–Al2O3) nanocomposites with variable CNT content were directly synthesized by chemical vapor deposition (CVD). The as-grown CNT–Al2O3 mixture was densified by spark plasma sintering (SPS) at 1150 and 1450 °C. Vickers hardness of 9.98 GPa and fracture toughness of 4.7 MPam1/2 were obtained for 7.39 wt.% CNT–Al2O3 nanocomposite. The addition of CNTs gives rise to 8.4% increase in hardness and 21.1% increase in toughness over that of the pure Al2O3. The optimum amount of CNTs is considered to be able to significantly enhance the mechanical property of ceramics in composites.