Properties of Multiwalled Carbon Nanotube-Reinforced Alumina Composites Produced Following the Sol-Spray Technique

Multi-wall carbon nanotube (MWNT)-reinforced alumina composites were prepared by a sol-spray process combined with a vacuum hot press process. The relative densities of all the samples were higher than 97%. Scanning electron microscopy (SEM) results showed that the MWNTs were well-dispersed in the alumina matrix; specifically, most of them were distributed along the grain boundaries in the form of networks, whereas the others were located in the grains. For 0.5 wt.% MWNTs, the Vicker hardness and fracture toughness were 32.1% and 75.6% higher than those of pure alumina, and the average increment of the thermal diffusivity under different test temperatures is ~ 26.2%. When the content of MWNTs is higher than 0.5 wt.%, the composites showed conductor properties. Moreover, the percolation threshold of the prepared composites was 0.37 wt.% with the nonlinear fitting of conductivity data, which indicates that the MWNTs were well dispersed in the alumina matrix.