LAUSR

Abstract In spite of the advantages of CaO-MgO refractory composites, such as high refractoriness, potential to produce pure steel molten, high alkaline corrosion resistance and economical advantage for consumers, their application has been limited in different industries due to the fast and easy reaction of the existing free CaO and MgO in the composites. These constituents react with atmosphere humidity and form calcium hydroxide [Ca (OH) 2] and magnesium hydroxide [Mg (OH) 2] phases in the microstructure as a destructive phase. In this study, the effects of Iron (III) oxide nanoparticles addition on the properties and microstructure of CaO-MgO composite is investigated. After formulation, cylindrical samples (50*50 mm2 dimensions) were prepared at 90 MPa pressure and then tempered at 110 °C for 24 h and finally fired at 1650 °C for 3 h in an electrical furnace. Physical and mechanical properties of the samples, such as bulk density, apparent porosity, hydration resistance and cold crushing strength were evaluated. XRD and SEM/EDX analyses were also used to analyze of the formed phases and microstructure evolution. The results showed that hydration resistance, bulk density and cold crushing strength properties were increased, while apparent porosity was decreased by the addition of Iron (III) oxide nanoparticles. These variation trends might be due to the i) nature alternation of free calcia and magnesia and formation of low melting point phases, such as C2F and CF phases, ii) filling up porosities and voids in the microstructure and iii) enhancement firing process of the specimen via liquid phase sintering mechanism.