Reinforcing capability of multiwall carbon nanotubes in alumina ceramic hybrid nanocomposites containing zirconium oxide nanoparticles

Abstract In this study, we investigate the reinforcing capability of multiwall carbon nanotubes (mwCNT) in alumina (Al 2 O 3 ) ceramic hybrid nanocomposites containing zirconium oxide nanoparticles (ZrO 2 np). For this purpose, highly dense hybrid nanocomposites containing well-dispersed ZrO 2 np (8 vol%) and mwCNT (4 vol%) were fabricated by the hot-pressing method. The resulting hybrid nanocomposite exhibited a ten-fold finer microstructure and 116% enhanced fracture toughness as well as 12% greater hardness over the benchmarked monolithic Al 2 O 3 . The superior mechanical performance of the hybrid nanocomposite was attributed to the synergistic role of ZrO 2 np and mwCNT in refining the matrix microstructure and inducing unique toughening mechanisms of micro-cracking by ZrO 2 np and pull-out as well as crack-bridging by mwCNT. Qualitative and quantitative approaches were utilized to assess the individual and collective role of the reinforcing constituents in enhancing the performance of hybrid nanocomposite. The qualitative analysis by electron microscopes demonstrated strong interfacial adhesion of both reinforcing constituents with the based Al 2 O 3 matrix. Furthermore, the quantitative analysis verified that the enhanced mwCNT/Al 2 O 3 interfacial shear strength is caused by the intricate physical arrangement of the mwCNT within the matrix grains besides their chemical bonding at the interface. The role of fine-grained microstructure in establishing idiosyncratic mwCNT interlocking with the Al 2 O 3 matrix grains was meticulously investigated. Moreover, the influence of mwCNT/matrix interlocking on the mwCNT reinforcing ability and toughening mechanisms efficiency in the hybrid nanocomposite is discussed.