Structural properties and mechanical behavior of SWCNTs and MWCNTs reinforced Al2O3 fabricated by spark plasma sintering

Abstract Carbon nanotubes due to their structural and mechanical properties are good candidates as the second phase to improve the mechanical properties of alumina-based ceramics. In the present study, the effects of single wall and multi-wall carbon nanotubes on structural and mechanical properties of alumina were investigated. SWCNTs and MWCNTs were dispersed in alumina powder via a conventional method using 1 wt % PVA water solution as media. Sintering process for two different composite powders, alumina-2 wt. % SWCNTs and alumina 2 wt % MWCNTs was performed by spark plasma sintering technique at 1500 °C and 20 MPa for 10 min. Results showed that the presence of CNTs in alumina caused a considerable amount of porosity in final bodies. SEM images of fracture surfaces revealed the agglomeration of SWCNTs which played a dominant role in the deterioration of mechanical properties. MWCNTs reinforced alumina obtained higher Vickers hardness and bending strength values (12.91 GPa and 291 MPa, respectively) compared to that of SWCNTs (9.18 GPa and 276 MPa, respectively), due to sever agglomerate of SWCNTs throughout sintered composites. Typical load-displacement ( P / h ) curves were obtained from bending strength test and discussed. It was concluded that the addition of MWCNTs to alumina represented better densification and mechanical properties compared to SWCNTs.