Effect of Multiwalled Carbon Nanotubes on the Thermal Conductivity and Porosity Characteristics of Blast Furnace Carbon Refractories

Different amounts of carbon nanotubes (CNTs) (0–5 mass pct) containing carbon refractory specimens for a blast furnace were prepared and coked for 3 hours at 1473 K (1200 °C) and 1673 K (1400 °C). The thermal conductivity and porosity characteristics of the coked specimens were evaluated using the flash diffusivity technique and mercury porosimetry, respectively. It was found that CNTs acted as carbon source, and most of them were consumed during coking. With the increase of CNT content, the aggregation of CNTs became more severe, the amount of SiC whiskers formed increased and their aspect ratio became larger, and the SiC whiskers tended to be distributed nonhomogeneously. The thermal conductivity of a 4 mass pct CNT containing a carbon specimen was highest because of the contributions of SiC and residual CNTs. The porosity characteristics of a 0.5 mass pct CNT containing a carbon specimen was best because of the uniform filling of SiC whiskers. The excessive addition of CNTs degraded the porosity characteristics because of the severe aggregation of CNTs.