Alumina-carbon-based refractories, due to their unique physical and mechanical properties, are widely used as sliding gates, shroud nozzles, monoblock stoppers, and sub-entry nozzles in the steelmaking industry. In this study, the effect of modified surface of nano alumina additives and their composites with multi-walled carbon nanotubes with silane group in alumina-carbon refractories was investigated.
In this regard, nano alumina was added to functionalized carbon nanotubes to prepare the nanocomposite. To achieve better distribution of the nano additives, the particles were first functionalized with APTES silane groups. Then, 1% by weight of the additive was added to the fine grain part and subsequently mixed with the coarse particles of the alumina-carbon body. For the physical and mechanical property assessments, the samples were shaped under uniaxial pressing at a pressure of 150 MPa, tempered at 200°C for 6 hours, and fired at 1450°C for 2 hours in a reducing atmosphere under a coke bed.
Apparent density, apparent porosity, and cold crushing strength (CCS) were determined according to the standards. For microstructural phenomena and phase analysis, SEM and XRD were used. The results showed that the sample containing 1% by weight of the alumina-MWCNT nanocomposite exhibited the highest cold crushing strength of approximately 156 MPa. Additionally, the Weibull modulus results confirmed this finding. According to the SEM results, the improvement in mechanical properties can be associated with the increased formation of SiC in the presence of Al2O3-MWCNT by the vapor-solid mechanism.