Tailoring intergranular binding phase by Pr6O11 in Mg2SiO4-MgO refractories prepared from magnesite flotation tailings

In order to improve the comprehensive utilization rate of magnesite flotation tailings and solve its accumulation pollution problem. In this work, Mg 2 SiO 4 -MgO refractories were prepared by solid-phase method using magnesite flotation tailings as raw material and Pr 6 O 11 as additive. The adjustment mechanism of Pr 6 O 11 on the intergranular binding phase of Mg 2 SiO 4 -MgO refractories was investigated and the optimal addition amount of Pr 6 O 11 was determined through thermodynamic calculations, DSC test, phase composition test, microstructure observations and physical property tests. The results show that when Pr 6 O 11 is not added, the intergranular binding phase of Mg 2 SiO 4 -MgO refractories is CaO·MgO·SiO 2 . After Pr 6 O 11 is added, Pr 6 O 11 takes advantage of its high reactivity to extract SiO 2 and CaO from the MgO-SiO 2 -CaO system, which is supposed to synthesize CaO·MgO·SiO 2 , and reacts to produce Ca 2 Pr 8 (SiO 4 ) 6 O 2 , which consumes the reactants for synthesizing CaO·MgO·SiO 2 , thus inhibiting the production of CaO·MgO·SiO 2 . Thereby adjust the refractories intergranular binding phase from low melting point CaO·MgO·SiO 2 (melting point:1498°C) to high melting point Ca 2 Pr 8 (SiO 4 ) 6 O 2 (melting point:1780°C), which resulted in the improvement of the refractories's high temperature resistance and thermal shock resistance. At the same time, Pr 6 O 11 can form solid solution with Mg 2 SiO 4 and MgO to promote the sintering densification of the refractories, and the overall performance of the refractories is optimal when the addition amount of Pr 6 O 11 is 2wt%.