Mechanical and dielectric properties of reduced graphene oxide nanosheets/alumina composite ceramics

Reduced graphene oxide (rGO) nanosheets/alumina (Al2O3) composite ceramics were fabricated by hot-pressing sintering. The density, porosity, microhardness, flexural strength and complex permittivity were investigated to study their mechanical and dielectric properties. The results revealed that the rGO nanosheets were uniformly distributed in the Al2O3 matrix and that the composite ceramics were highly dense at 3.67-3.99 g/cm(3). Due to low rGO hardness and elevated porosity, the microhardness exhibits a decreasing trend as the rGO content increases. The flexural strength first increased and then decreased with the escalation of rGO content, and the highest strength of 313.75 MPa was obtained at 3 wt%, increasing by 37.61% relative to that of the hot-pressing sintered Al2O3 ceramic. Owing to the enhanced interfacial polarization, dipole polarization, polarization relaxation loss and conductance loss, the real part and imaginary part of complex permittivity increase from 10.40 to 52.73 and from 0.08 to 28.86 as the rGO content rose from 0 wt% to 4 wt%, respectively.