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

Abstract

Graphitic carbon spheres (GCS) with an average diameter of about 0.8 μm were prepared via hydrothermal carbonization combined with catalytic graphitization using glucose and in situ 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 1.0 wt%, and the optimal temperature and soaking time were, respectively, 1473 K and 3 hours. 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.

Preparation of Hierarchically Porous Graphitic Carbon Spheres and Their Applications in Supercapacitors and Dye Adsorption

“…The HGCS showed sharply increased specific surface area (from 12 to 564 m 2 /g), which could be explained as follows. (1) After catalytic graphitization, the average size of the HGCS was decreased (from 0.48 to 0.35 μm) ( Figure 7 and Figure S1 ), and correspondingly about 50% weight was lost with respect to the presynthesized carbon spheres, indicating that a significant number of original oxygen containing groups were lost during the graphitization process, creating lots of new pores in the HGCS [ 20 , 28 ]; (2) the Fe(NO 3 ) 3 9H 2 O precursor not only acted as a catalyst, but also as an oxidizing agent during the graphitization process. It reacted with carbon spheres, releasing some gaseous phases such as NO x , CO, and CO 2 , which was beneficial to the physical activation of micro/meso pores formation [ 10 ]; and (3) comparison of Figure S4 and Figure 9 a revealed that, after catalyzed graphitization, the disordered carbon atoms in the original presynthesized amorphous carbon spheres were rearranged into regular graphite layers, which believed to have left some tiny gaps between the amorphous carbon layer and the regular graphite layer, and thus increased the specific surface area of the HGCS.…”

Preparation of Hierarchically Porous Graphitic Carbon Spheres and Their Applications in Supercapacitors and Dye Adsorption

“…7 and Fig. S1)), and correspondingly about 50% weight was lost with respect to the pre-synthesized carbon spheres, indicating that lots of the original oxygen containing groups were lost during the graphitization process, creating lots of new pores in the HGCS [20,22]; 2) the Fe(NO3)3• 9H2O…”

Effect of in-situ carbon containing calcium aluminate cement on properties of Al2O3-SiC-C based trough castables

“…Presently, several technologies, including micropellets [6,7], coatings [8][9][10][11][12][13][14], and graphitic carbon spheres [15,16], have been employed to overcome the above issues. However, in practical applications, these technologies suffer from such drawbacks as discontinuous coating, aggregation and uneven distribution of carbon materials in the castables.…”