Alumina-MWCNT composites: microstructural characterization and mechanical properties

In the present work, Al2O3-multiwalled carbon nanotube (MWCNT) composites have been developed by both conventional sintering and spark plasma sintering (SPS) and their microstructures, mechanical properties and wear behavior have been investigated. Further, the influence of various other parameters such as the sintering time, sintering temperature, MWCNT loading level and processing technique adopted for development of the composites has also been analyzed. The powder metallurgy route was selected for development of Al2O3-0.2, 0.5, 0.8, 3, 5 vol% MWCNT composites using both conventional sintering and SPS. For conventionally sintered Al2O3-MWCNT composites, it has been found that both the hardness and relative density of the composites decreased up to a loading level of 0.2 vol% of MWCNTs, followed by a continuous increase with the addition of MWCNTs to the Al2O3 matrix, attaining a maximum value in the case of Al2O3-3 vol% MWCNT composite. The wear behavior of conventionally sintered composites also exhibits significant improvement with increase in sintering time. The SPSed Al2O3-MWCNT composites show a much higher relative density and better mechanical and tribological properties as compared to conventionally sintered Al2O3-MWCNT composites.