Fabrication of graphitic carbon spheres and their application in Al2O3-SiC-C refractory castables

Graphitic carbon spheres (GCS) with an average diameter of about 0.8m were prepared via hydrothermal carbonization combined with catalytic graphitization using glucose and insitu formed Fe nanoparticles (NPs) as, respectively, a carbon precursor and catalyst. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and thermogravimetric analysis/differential scanning calorimetry (TG/DSC). The optimal content of Fe catalyst for graphitization of amorphous CS was found to be 1.0wt%, and the optimal temperature and soaking time were, respectively, 1473K and 3hours. The transformation from CS to GCS was considered to be dominated by the dissolution-precipitation mechanism. Using as-prepared GCS instead of flake graphite (FG) as a carbon source, not only reduced water demand for casting Al2O3-SiC-C samples and decreased their final apparent porosity, but also enhanced their modulus of rupture and cold crushing strength. In addition, castable samples using GCS showed better oxidation resistance than those using FG.