LAUSR

Abstract At this study the effect of Cr 2 O 3 nanoparticles (up to 3 wt.%) on the physical and mechanical properties of MgO–CaO refractory composition with emphasis on the hydration resistance improvement have been investigated. Specimens pressed at 90 MPa then were sintered at 1650 °C for 5 h in an electric furnace. Properties such as bulk density, apparent porosity, cold crushing strength and hydration resistance were examined. The crystalline phases and microstructure characteristics of sintered specimens were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS), respectively. Results shown that add of the 1.5 wt.% Cr 2 O 3 nanoparticles have the best results i.e. increased the bulk density (3.41 g/cm 3 ), cold crushing strength (848 kg/cm 2 ), hydration resistance (1.5%) and decreased apparent porosity (5.58%), respectively. The mechanism of specimens hydration resistance improvement are: (i) decreasing the amount of free CaO and MgO with converted to high hydration resistance phases such as CaCr 2 O 4 and MgCr 2 O 4 phases, (ii) promotion of the densification as well as (iii) modification of the microstructure.