Alumina-Based Nanocomposites Using Graphite Nanoplatelets as Reinforcement

Abstract

Graphene has outstanding mechanical properties and unique electrical and thermal properties which makes it an attractive filler and a good reinforcement for producing multifunctional ceramics for a wide range of applications. Here, alumina (Al2O3) based nanocomposites have been developed using exfoliated graphite nanoplatelets (xGnP) as reinforcement. The xGnP were synthesized by subjecting a graphite intercalation compound (GIC) to a thermal shock. The Al2O3 and xGnP powders were mixed by milling them for a short period of time in a planetary ball mill using zironica vials and balls in order to ensure homogeneous distribution of xGnP in the Al2O3 matrix. Al2O3-0.2, 0.5, 0.8, 3 and 5 vol. % xGnP nanocomposites were developed by powder metallurgy route. Sintering was done by the conventional sintering process at 1650oC for different periods of holding time (2, 3 and 4 h). The hardness, fracture toughness and tribological properties of the composites having different vol. % xGnP loading were investigated. Results show a significant improvement in the wear resistance of the Al2O3-xGnP composites having more than 0.8 vol. % xGnP loading. The improvement in mechanical properties is attributed to the uniform dispersion of the xGnP and toughening mechanisms such as xGnP bridging, crack deflection and strong interaction between xGnP and Al2O3 at the interfaces. Results of the dry sliding wear tests of the composites with different vol. % xGnP loading suggest a significant improvement in the wear resistance of the composites upto the addition of 3 vol. % xGnP. The hardness of the composites also show a gradual increase upto the addition of 3 vol. % xGnP beyond which there is a deterioration in both the hardness and the wear properties.