Graphene-reinforced ceramics obtained by slip casting and pressureless sintering: Interactions and stability of particles in aqueous environment

Ceramic-graphene composites had been considered very promising for both their conductivity and superior fracture toughness compared to nonreinforced materials. However, agglomeration of graphene flakes occurring during the shaping process causes the properties of obtained composites to differ from theoretical values. Authors investigate slip casting as the alternative to the granulation and powder metallurgy route. Slip casting as a near-net-shape technique results in fewer steps compared to the standard routes of ceramic-graphene composites preparation. To enable slip casting of such materials stable ceramic-graphene suspensions of low viscosity are required. The influence of dispersing agents on zeta potential and viscosity of obtained suspensions had been investigated. Authors define possible interactions between graphene and alumina powder within suspension and their influence on the properties of suspensions. The composite materials have been well densified by pressureless sintering in a reductive atmosphere. The composites exhibited much higher fracture toughness in comparison to pure alumina samples. [Display omitted] •Colloidal processing is favourable in preparation of graphene reinforced ceramics.•Stable Al2O3-graphene oxide slurries are achievable by adjustment of zeta potential.•Well densified Al2O3-graphene composites can be obtained by pressureless sintering.•Significant improvement in fracture toughness of reinforced materials was achieved.