Abstract
The effect of α-Al2O3 nanoparticles (up to 5 wt.%) on the physical, mechanical, and thermal properties, as well as on the microstructural evolution of a dense magnesia refractory is studied. Sintering temperatures at 1300, 1500, and 1600 °C are used. The physical properties of interest were bulk density and apparent porosity, which were evaluated by the Archimedes method. Thermal properties were examined by differential scanning calorimetry. The mechanical behavior was studied by cold crushing strength and microhardness tests. Finally, the microstructure and mineralogical qualitative characteristics were studied by scanning electron microscopy and X-ray diffraction, respectively. Increasing the sintering temperature resulted in improved density and reduced apparent porosity. However, as the α-Al2O3 nanoparticle content increased, the density and microhardness decreased. Microstructural observations showed that the presence of α-Al2O3 nanoparticles in the magnesia matrix induced the magnesium-aluminate spinel formation (MgAl2O4), which improved the mechanical resistance most significantly at 1500 °C.
Highlights
Since the introduction of magnesia (MgO), its use as a basic refractory has tremendously increased due to its reasonable cost, excellent chemical resistance to basic slags and fluxes at high temperatures, as well as a high melting point (2800 ◦ C)
The results showed that as the particle size of Cr2 O3 was reduced (≈20 nm), the density of the MgO refractories was enhanced at relatively low temperatures (≈850 ◦ C)
Industrial-grade magnesia (MgO) with high purity and high-grade nano-alumina oxide (α-Al2 O3 ) in α polymorphic phase were used as raw materials in this investigation
Summary
Since the introduction of magnesia (MgO), its use as a basic refractory has tremendously increased due to its reasonable cost, excellent chemical resistance to basic slags and fluxes at high temperatures, as well as a high melting point (2800 ◦ C). These properties have made MgO-based refractories preferred by the iron, non-ferrous, and cement industries [1,2,3,4]. The mechanical and chemical properties exhibited by carbon-containing refractories have allowed them to be widely used to form specific compounds for certain applications in the steel industry
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