Fabrication and properties of in situ intergranular CaZrO3 modified microporous magnesia aggregates.

Lightweight microporous magnesia aggregates with closed porosity of 6.2%, apparent porosity of 2.1% and median pore size of 2.36 μm were fabricated by introducing nano-sized ZrO 2 combined with magnesite decomposition and sintered at 1780 °C. The sintering properties and microstructure revealed that nano-sized ZrO 2 promoted the sintering and formation of closed intragranular pores by increasing abundant crystal defects and producing cation vacancies (V M g ' ' ) raising the migration rate of grain boundaries, which induced a change in porosity type from large open pores to small closed pores. The nano-sized ZrO 2 changed the bonding of magnesia grains from single CaO–SiO 2 –MgO phases bonding to composited CaO–SiO 2 –MgO phases-CaZrO 3 phases bonding, significantly enhancing the slag penetration resistance. The closed porosity played a more important role in reducing the thermal conductivity compared with total porosities. The microporous magnesia aggregates and thermal conductivity of 8.994 W (m K)−1 at 800 °C exhibit potential for application in wear lining refractories. [ABSTRACT FROM AUTHOR]