Fabrication of energy-saving MgO with large grain size and low thermal conductivity: Towards a new type of magnesia for high-temperature furnaces

Abstract

The development of advanced refractories with low thermal conductivity and long service life is of great significance for optimizing the energy consumption structure of high-temperature industries. For this purpose, a series of magnesia refractories with large grain size, low thermal conductivity, and high slag resistance had been successfully prepared at 1600 °C, in which Al2O3 and La2O3 were chosen as the additives. The results show that with the introduction of additives, MgAl2O4 and LaAlO3 as the second phase are formed inside and at the grain boundaries of the MgO matrix grains, and further promote the growth of grains and improved certain properties. Meanwhile, the grown grains (from 4.92 to 29.51 μm, increased ∼5 times), the increased density, and the enhanced strength can be attributed to the activated sintering triggered by Al2O3; the lower thermal conductivity (from 18.49 to 15.73 W·m−1·K−1 at 500 °C, decreased ∼15%) and the better slag resistance can be ascribed to the formation of LaAlO3 and MgAl2O4. However, due to the Nener effect, the maximum grain size is obtained at additives of 4 wt%, but the thermal conductivity is not limited by this.