Layered structure of alumina/graphene-augmented-inorganic-nanofibers with directional electrical conductivity

Implementation of layered structures with strong nanoscale optimized interfaces, enables engineering of materials with functional properties. In this work, anisotropic functional multi-layered structures are produced by integration of a thin hybrid inter-layer of graphene-augmented-nanofibers/alumina into α-alumina through an ex-situ strategy of precipitating the tailored hybrid from a solution. Spark plasma sintering was used to consolidate the layered structures at 1150 and 1450 °C under 75 and 50 MPa pressure. Raman spectroscopy suggests presence of C–H bonds and sp3 hybridization for the samples sintered at 1150 °C, while graphene structure is purified at the sintering temperature of 1450 °C. The multilayer structures demonstrate a high in-plane electrical conductivity which can be modulated, ranging from 300 to 1800 S m−1 as a function of the interlayer thickness and the carbon content. A p-type conduction at room temperature and n-type down to 4 K in graphene-augmented nano-fillers was observed in Hall measurement. However, the multilayered systems display a p-type conduction in the entire temperature range. Hardness was preserved despite the high concentration of the graphene-augmented nano-fillers in the hybrid interlayer leaving a highest value of ∼22 GPa. The results have the potential to fuel the development of functional electronic enclosures with additional functionalities such as electromagnetic interference shielding.