Characteristics of mesocarbon microbeads generated from a coal tar pitch with addition of micro-alumina powder

In the present experiments, mesocarbon microbeads (MCMBs) were prepared from a coal tar pitch with or without micro-Al2O3 powder under 410 °C for 7 h to study the influence of alumina on the MCMBs. OM, SEM, XRD and EDS were used to analyze the as-received MCMBs, among which SEM was used firstly to observe the microtextures of MCMBs systemically. The results show that the irregular alumina particles, which have been enwrapped in the MCMBs, impede the growth of the mesophase spheres and consequently decrease the yield of them. The textural layers of the formed MCMBs were disturbed by the aluminum oxide particles. Although the alumina in the spheres could escape and seems to maintain the sphericity of MCMBs during the graphitization, the bad influence would remain. In addition, ash analysis of MCMBs was carried out, which further confirmed the existence of alumina particles in the as-received spheres and the absence of them in the graphitized spheres. In conclusion, alumina in raw pitches is disadvantageous for the growth and the final structure of MCMBs and should be removed in advance if high yield and regular structure are expected.