Synthesis and characterization of pressureless sintered carbon nanotube reinforced alumina nanocomposites

This paper presents sintering and characterization of multiwalled carbon nanotube reinforced alumina nanocomposites and their comparison with the sintering behavior of pure alumina. Two types of composites were prepared by different techniques and both contained 1, 2 and 3 wt% of as-received and functionalized carbon nanotubes which were synthesized by pressureless sintering. The mixing and dispersion of carbon nanotubes in alumina were done by a novel technique of gas purging sonication. Varying percentages of carbon nanotubes in the composites were compacted using a uniaxial press followed by sintering at 1600 °C in flowing argon. Nanocomposites with 1 wt% carbon nanotubes gave 98.5% relative density with no degradation of carbon nanotubes. Moreover, it also resulted in an increase in fracture toughness from 8.1% and 9.4% and Young's modulus by 5% and 7% when compared to as-received and functionalized carbon nanotube nanocomposites respectively with respect to pure alumina. This investigation has shown that the densification can be achieved without degradation of carbon nanotubes at elevated temperatures in the carbon nanotube–alumina nanocomposites sintered by the conventional route.