Abstract
In this research, the effects of MWCNT addition on mechanical properties and microstructures of pressureless sintered MWCNT/alumina composites were investigated by using four types of MWCNTs having different fracture characteristics and dispersibility. It was demonstrated that it is possible to fabricate MWCNT/alumina composites by pressureless sintering at a temperature of 1400℃. Fracture tests showed that the MWCNTs annealed at 2200℃ was the most effective in improving the mechanical properties of the MWCNT/alumina composites, and 0.9 vol.% MWCNT addition resulted in 25% and 45% simultaneous increase in bending strength (742.6 ± 13.1 MPa) and fracture toughness (5.83 ± 0.19 MPa m^<1/2>), respectively, compared with MWCNT-free sintered bodies. An improvement in the fracture properties may be attributed to the use of the MWCNT having a higher load carrying capacity. For the larger amount of the MWCNTs, strong correlation between mechanical properties of the composites and dispersibility of the MWCNTs was observed, and the degradation of mechanical properties was shown to be primarily attributed to the severe phase segregation. Our finding suggests that the important factor for the preparation of ceramics composites with MWCNT for higher strength and toughness will thus be the use of MWCNT having a much higher load carrying capacity as well as a good dispersion in the matrix.
