In-situ synthesis of magnesium aluminate spinel – Zirconium diboride composite powder in magnesium chloride melt

Phase pure MgAl 2 O 4 –ZrB 2 composite powder was successfully synthesized at 1200 °C for 4 h from ZrO 2 , B 2 O 3 , and Al, in molten MgCl 2 which acted as not only an Mg-bearing reactant but also a liquid reaction medium. Mediated by such a liquid medium, Al initially reduced B 2 O 3 , forming B and Al 2 O 3 which further reacted with ZrO 2 and MgCl 2 , forming ZrB 2 and MgAl 2 O 4 , respectively. As prepared powder comprised angular MgAl 2 O 4 grains with sizes from ∼100 nm to ∼2 μm, and ZrB 2 particles of ∼100 nm in average. The molten salt synthesis strategy demonstrated here is believed to be universally applicable to preparations of a range of MgAl 2 O 4 -boride composite powders for future in-depth exploration.