Influence of zirconia addition on the properties of magnesia refractories

Abstract This paper concerns basic refractories used, among others, in the cement industry. Zirconium oxide was added to modify the properties of an MgO refractory. These MgO–ZrO2 materials can replace magnesia-chromite refractory ceramics in accordance with current environmental policy guidelines and can improve the properties, such as thermal shock resistance, of a typical magnesia refractory. In the experiments, commercially available magnesia clinker and monoclinic zirconia were used. The effect of particle size and amount of zirconium oxide content were determined in the prepared ceramic masses. The addition of zirconia was at a level of from 0 to 8 wt% in green compacts. After the firing cycle at 1660 °C the ceramic properties were measured, such as linear shrinkage, open porosity, apparent density, cold crushing strength, gas permeability and thermal shock resistance (water cycles). For selected materials, resistance to corrosion by two different corrosive agents was determined. The research results show that the addition of zirconia improved the refractories' properties. The cold crushing strength of samples with 2 wt% of added ZrO2 reached maximum values. The obtained ceramics were also characterised by good dimensional stability (firing shrinkage less than 1%), high cold crushing strength (50–75 MPa) and uncommonly high values of thermal shock resistance (8–10 water cycles). The addition of ZrO2 also clearly increased the materials’ corrosion resistance against a cement-like and glass-like agent.