Abstract
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.
Highlights
Of dry-pressed compacts were determined in order to investigate the reinforcing effect of graphene oxide-coated coarse aggregates and the effect of including the graphite fraction in a calculated aggregate size distribution (ASD)
Analyses of variances (ANOVA) were used on all results to investigate the influence of individual factors and of their interactions
Coarse tabular alumina grains can be coated using a highly viscous graphene oxide suspension by means of dip coating followed by drying in air
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Carbon-bonded alumina refractories (Al2 O3 –C) are key ceramic materials in the steel industry for their extraordinary chemical, mechanical and thermal properties. Due to the nature of the steelmaking process, materials in contact with the molten metal often require a high thermal shock resistance, a high corrosion and erosion resistance, a low wettability and a sufficient mechanical strength at high temperatures [1,2,3,4,5]. Compared to pure oxide refractories, the implementation of a carbon bond and the addition of graphite may improve all these properties [1,6]
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