Carbon-bonded alumina refractories offer excellent thermal shock performance but are lacking in terms of mechanical strength. In the present contribution, the influence of the particle packing and the addition of graphene oxide (GO) to carbon-bonded alumina refractories on the physical and mechanical properties before and after thermal shock was investigated. Coarse tabular alumina grains were coated by a GO suspension and used to prepare dry-pressed compacts. The included graphite fraction (15 wt%) was either regarded as a lubricating matrix component or as a quasi-spherical component of a calculated density-optimized aggregate size distribution. During coking, the GO was reduced to thermally reduced graphene. The porosity, true density and thermal shock behavior in terms of the cold modulus of rupture (CMOR) and Young's modulus were compared. Samples with a higher density were obtained when the irregularly shaped graphite was considered as the matrix component (lubricant). The results showed that the use of GO had a positive impact on the mechanical properties of the graphene-reinforced Al2O3-C refractories, especially in the case of a less optimized packing, due to the bridging of delamination gaps. In addition, the thermal shock only had a minor impact on the Young's modulus and CMOR values of the samples. SEM investigation revealed very similar microstructures in coked as well as thermally shocked samples.
Keywords: composites; graphene oxide; packing density; refractories; thermal shock resistance.