Effect of the addition of carbon nanotubes on the properties of low carbon Al₂O₃ refractory materials

A new type of low carbon Al₂O₃ refractory material was prepared using coarse-grain white fused alumina , tabular alumina (≤0.043mm), graphite flake (≤0.147mm), silicon powder (≤0.074mm) and carbon nanotubes (CNTs) as fillers, and thermosetting phenolic resol as binder. The CNTs were added directly to the fillers or coated onto tabular alumina by catalytic chemical vapor deposition (CVD). Properties of the samples were tested, such as apparent porosity, bulk density, mechanical strength, modulus of rupture at 1100℃, thermal shock resistance and oxidation resistance. The morphologies of the CNTs and fractured samples were examined by scanning and transmission electron microscopy. Results indicate that bulk density, mechanical strength, modulus of rupture at 1100℃, thermal shock resistance and oxidation resistance of the sample obtained by the CVD method are higher while apparent porosity is lower than for the sample obtained by the direct addition method. The addition of CNTs improves the oxidation resistance of the refractory materials. The direct addition method not only has no influence on thermal shock resistance, but also decreases the modulus of rupture at 1100℃.