Enhanced mechanical properties of Al2O3-C refractories with silicon hybridized expanded graphite

Expanded graphite (EG) is a promising reinforcement for fabricating Al2O3-C refractories. However, the smooth surface of EG layers results in weak interfacial bonding strength between EG and matrix. Meanwhile, the EG is prone to react with antioxidants or reactive vapors (Al (g), Si (g) and SiO (g)) at high temperature. To overcome these problems, two kinds of silicon hybridized EG were introduced into Al2O3-C refractories. They are β-SiC whiskers hybridized EG (labeled as EG/SiC) and SiOx spheres hybridized EG (labeled as EG/SiOx), respectively. Afterward, the microstructure and mechanical properties of Al2O3-C refractories coked at the temperatures ranging from 800 °C to 1400 °C were investigated in this work. The results showed that the interfacial characterization of EG/SiC and EG/SiOx hybrids were remarkably improved compared with original EG. Moreover, the EG/SiC and EG/SiOx hybrid remained relative intact structure at high temperature. In addition, the mechanical properties such as cold modulus of rupture (CMOR), force and displacement of Al2O3-C specimens containing hybrids were improved in comparison with the specimen containing original EG. Furthermore, with the addition of EG/SiC or EG/SiOx hybrid, the thermal shock resistance of Al2O3-C refractories was considerably promoted. The above enhanced mechanical properties could attribute to the hybridized β-SiC whiskers and SiOx spheres on EG, which were pulled out to consume the fracture energy when the Al2O3-C specimens were bearing loading.