Enhanced thermal shock resistance of low-carbon Al2O3-C refractories with direct CVD synthesis of nano carbon decorated oxides

Novel low carbon Al2O3-C refractories were prepared through adopting chemical vapour deposition (CVD) synthesized nano carbon decorated Al2O3 powder. The phase compositions, microstructures, mechanical properties and thermal shock resistance of Al2O3-C refractories were characterized and evaluated. The results show that the morphologies of nano carbon composites are mainly dominated by the concentration of catalyst. Specifically, the growth of MWCNTs is preferred with a Ni2+ concentration at 0.1 mol/L, while higher concentrations e.g. 0.3 mol/L would stimulate the formation of nano-onion like carbon. With the introduction of nano carbon decorated Al2O3 additives, the residual strength after thermal shock can reach 12.4 MPa, which is much higher than the 2 wt% nano carbon black containing specimens (6.4 MPa). The enhanced thermal shock resistance should be attributed to that the nano onion-like carbon reduces the cohesion between the matrix and the Al2O3 particles and decreases the thermal expansion coefficient.