Effects of NiO addition on the microstructural evolution and performance of sintered magnesia aggregates

This study introduces a novel approach to enhance the properties of sintered magnesium oxide (MgO) aggregates by incorporating nickel oxide (NiO) powder as a solid-solution modification additive. The addition of NiO improves the densification of the specimens and promotes grain growth through the activation of sintering via the solid-solution reaction of MgO–NiO at high temperatures. The formation of the (Mg, Ni)O solid-solution structure enhances the strength of the specimens, while gradually reducing thermal conductivity. However, excessive addition of NiO (>6 mol%) adversely affects the sintering properties of the specimens due to limited diffusive mass transfer rate during sintering and the Zener effect, resulting in diminished grain size and strength. Although thermal conductivity is not significantly affected, at 1000 °C, one specimen (MN-6) demonstrates a 61.03 % decrease in thermal conductivity compared to a specimen without NiO addition. These findings suggest that the incorporation of a moderate amount of NiO enhances the corrosion resistance of the cement clinker of the specimens primarily by increasing densification, grain size, and high-temperature contact angle. •Proposed a sintered MgO enhancement method via solid-solution NiO addition.•(Mg, Ni)O structure formation improves strength and reduces thermal conductivity.•Excess NiO addition (>6 mol%) adversely affects grain size and strength.•Optimized NiO addition improves grain size, density, and corrosion resistance.