Novel water-based processing of graphene oxide and sub-micrometric alumina towards tougher and electrically-conductive structural ceramics

Balancing the mechanical and functional properties of graphene-reinforced ceramics can be a challenge because agglomeration of the reinforcement must be avoided to minimise microstructural defects and it is difficult to organise the constituents into meaningful structures. The water-based processing strategy that is demonstrated here illustrates the potential to fabricate layered alumina composites using a combination of freeze-casting, vacuum infiltration, and spark plasma sintering. Layers of alumina between 0.5 and 7 μm thick and consist of an average grain size of 0.7 ± 0.4 μm were separated by highly-oriented reduced graphene oxide. Mechanical and functional properties were investigated alongside a monolithic counterpart sintered at 1300 °C. The flexural strength and fracture toughness increased from 262 to 314 MPa and 3.5–5.4 MPa m 1/2 respectively, whilst electrical conductivity rose by nine orders of magnitude to 10 −1 S cm −1 . • Alumina-based composites with highly-oriented graphene were produced by freeze-casting, vacuum infiltration, and spark plasma sintering. • The microstructure consisted of layers of alumina between 0.5 – 7 μm thick that are separated by well-distributed reduced graphene oxide. • The composite´s flexural strength, K IC and electrical conductivity increased 20 %, 54 %, and nine orders of magnitude compared to alumina.