Effect of phase evolution and microstructure on thermal shock resistance and hydration resistance of low-carbon MgO-C refractories: Al-TiB2 hybrid addition

The thermal shock resistance (TRS) is essential to the service life of low-carbon MgO-C refractories. In the experiment, the low-carbon MgO-C refractories with the excellent TRS and the hydration resistance (HR) were obtained by using an Al-TiB2 additive instead of the traditional Al additive. The results showed that the TiB2 improved the binding affinity between Al and O, causing the formation of the non-hydratable Al4O4C and suppressing the formation of the hydratable Al4C3. Meanwhile, the formation of the in-situ synthesized ceramic phases such as Mg3B2O6, MgAl2O4, TiO2, and TiC enhanced the densification and strength of the refractories. Additionally, the liquid B2O3 provided the liquid-phase condition in the V-L-S growth mechanism to various carbon structures. The TSR was improved by the combined effects of these in-situ ceramic phases and carbon structures, including carbon nanospheres, carbon nanotubes, carbon films, rod-shaped and baseball-bat-shaped carbon structures. Compared with the Al additive, the TRS and HR of the refractories with the 2 wt% Al-1wt % TiB2 additive increased by 18.8 % and 42.9 %, respectively.