Development of Nano-ZrO2 Reinforced Self-Flowing Low and Ultra Low Cement Refractory Castables

Abstract

The main goal of this research is to develop high strength high toughness nano-ZrO2 reinforced self flow low cement (5%) and ultra low cement (3 and 1%) castables based on tabular alumina. In processing these castables, the Andreassen model was used to obtain optimum self flow properties in both, low and ultra low castables. The castables thus produced were fired at 110 and 1000, 1300 and 1500oC and the phases obtained were investigated by X-ray diffraction (XRD) including energy dispersive X-ray (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In addition, the other castable properties were measured such as cold crushing strength (CCS), apparent porosity (AP), bulk density (BD), water absorption (WA), weight loss (WL), zeta potential (ZP), flexural strength (MOR), fracture toughness (KIC), indentation toughness and self-leveling flowability. It was found that 5% cement castables exhibit the highest densification and strength after firing at 1500oC for 3 hours. In addition, castables with various amounts of of nano-ZrO2 and YSZ (yttria stabilized zirconia) (5%, 3%, 1%, 0.1% and 0.01%) were fired at 1300oC in order to improve the flexural strength and fracture toughness. The results indicate that the addition of nano-ZrO2 improves the flexural strength by 20% but it does not have an important effect on the KIC. Apparently, the presence of a relatively high density of pores and cracks overrides the potential benefits associated with the nano-ZrO2 and YSZ reinforcement additions.