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Abstract Hybrid alumina (Al 2 O 3) ceramic nanocomposites containing 3 wt% silicon carbide nanoparticles (SiCnp) and 0.5 wt% multilayer graphene (MLG) were consolidated to near theoretical density (99%) by an inductive hot-pressing (IHP) technology. The enhanced fracture toughness and hardness by 97% and 15% respectively, for the hybrid nanocomposites over the reference Al 2 O 3 were attributed to the higher densification, uniformly dispersed reinforcing constituents within the base matrix, toughening mechanisms of crack-deflection by the 0D-SiCnp and grain-anchoring as well as crack-bridging induced by the 2D-MLG. Thermal investigations of the hybrid nanocomposite verified the occurrence of a chemical reaction at the MLG/Al 2 O 3 interface and thermal diffusion at SiCnp/Al 2 O 3 interface during inductive hot-pressing. The bonding characteristics and interfacial microstructure were appraised by infra-red spectroscopy and high-resolution TEM microscope. Furthermore, the thermal stability in different gaseous environments and the ballistic performance of the hybrid nanocomposites were characterized and discussed. The produced hybrid nanocomposites may be suitable for high-temperature aerospace structural parts and may have applications in high-velocity impact technology. Highlights • Dense hybrid nanocomposites were prepared by inductive hot pressing method. • The hybrid nanocomposites demonstrated 97% higher fracture toughness over Al 2 O 3. • Hybrid nanocomposites manifested high thermal stability and ballistic performance. • Reinforcing phases (SiC and MLG) formed sturdy interface with Al 2 O 3 matrix. [ABSTRACT FROM AUTHOR]

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. • Al 2 O 3 /CNT/ZrO 2 hybrid nanocomposites were prepared by hot-pressing technique. • A 10 fold fine-grained microstructure was obtained for hybrid nanocomposites. • The hybrid nanocomposites showed 116% better fracture toughness over Al 2 O 3. • Reinforcing capability of the CNT in hybrid nanocomposite was gauged. [ABSTRACT FROM AUTHOR]