Liquid-phase shear exfoliation combined with hydrothermal processing for the preparation of graphene nanosheet/AlOOH nanofiber composite powder to enhance high-temperature performance of MgO-carbon castable

Flake graphite (FG) is difficult to be added into castables due to its hydrophobic nature. In this paper, a liquid-phase shear exfoliation (LPSE) combined with hydrothermal synthesis strategy was proposed to produce hydrophilic graphene nanosheet/AlOOH nanofiber (GN/ANF) composite powders to address the issue. Under optimal shear exfoliation conditions, the yield of graphene nanosheets (GNs) can reach up to 57%. After a simple hydrothermal treatment, the water contact angle of as-prepared GN/ANF composite powders reduced to 53.1° compared with 103.6° of the original FG. Benefiting from the hydrophilic performance of the composite powders and the homogeneous dispersion of GNs in the MgO castables, the sample with 0.5 wt% GNs exhibits better high-temperature performance than its counterparts. Compared with the control specimen, the slag corrosion index of the sample with 0.5 wt% GNs decreased from 0.60 to 0.13, and the thermal shock resistance increased by approximately 2.8 times.