Microstructural and mechanical investigation of high alumina refractory castables containing nano-titania

• Published in: Ceramics international 2019-01, Vol.45 (1), p.287-298
• Main Authors: Abbasian, Ahmad Reza, Omidvar-Askary, Najmeh
• Format: Article
• Language: English
• Subjects: Al2O3-CaO-TiO2; Alumina refractory; Castable; Hibonite; Nano-titania; Sintering
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2018.09.165

In this study, mechanical and structural properties of two high alumina refractory castables, i.e. without nano-titania and with 0.4 wt% TiO2, are investigated. Bulk density, apparent porosity, cold compressive strength, cold modulus of rupture, permanent linear changes, hot modulus of rupture and shock resistance tests were performed on the samples. The microstructure and phase analyses were conducted by field emission scanning electron microscope equipped with EDX analyzer and X-ray diffraction, respectively. Results showed that hibonite phase formation in refractory is dependent on the temperature which could be decreased by addition of nano-titania, leading to the improvement of refractory strength. On the other hand, the decrease of hot modulus of rupture and shock resistance was observed for the refractory castable containing nano-titania. Also, Ca3Ti8Al12O37 phase was produced after firing at 1000 °C in the presence of nano-titania. Probable mechanisms are proposed for phase and microstructural changes in high alumina refractory castable containing nano-titania. •Ca3Ti8Al12O37 phase formed in castable containing nano-titania after firing at 1000 °C.•The Ca3Ti8Al12O37 is responsible for the formation of planar hibonite phase.•Hibonite formation at lower temperatures during sintering act as pressure assistance for alumina sintering.•The deposited CaTiO3 phase in grain boundaries is responsible for decreasing HMOR and thermal shock resistance.