Abstract
Magnesia tuned alumina ceramic nanocomposites, reinforced with multi-walled carbon nanotubes, were condensed using pressureless and hot-press sintering processes. Densification, microstructure and mechanical properties of the produced nanocomposites were meticulously investigated. Electron microscopy studies revealed the homogenous carbon nanotube dispersion within the alumina matrix and confirmed the retention of carbon nanotubes' distinctive tubular morphology and nanoscale features during the extreme mixing/sintering processes. Pressureless sintered nanocomposites showed meagre mechanical responses due to the poorly-integrated microstructures with a slight improvement upon magnesia addition. Conversely, both the magnesia addition and application of hot-press sintering technique resulted in the nanocomposite formation with near-theoretical densities (~99%), well-integrated microstructures and superior mechanical properties. Hot-press sintered nanocomposites incorporating 300 and 600ppm magnesia exhibited an increase in hardness (10 and 11%), flexural strength (5 and 10%) and fracture toughness (15 and 20%) with respect to similar magnesia-free samples. Compared to monolithic alumina, a decent rise in fracture toughness (37%), flexural strength (22%) and hardness (20%) was observed in the hot-press sintered nanocomposites tuned with merely 600ppm magnesia. Mechanically superior hot-press sintered magnesia tailored nanocomposites are attractive for several load-bearing structural applications.
•MgO tailored Al2O3–2wt.% CNT nanocomposites are presented.•The role of MgO and sintering on nanocomposite structures and properties was studied.•Well-dispersed CNTs maintained their morphology/structure after harsh sintering.•Hot-pressing and MgO led nanocomposites to higher properties/unified structures.•MgO tuned composites showed higher toughness (37%) and strength (22%) than Al2O3.