Fabrication and mechanical properties of in situ prepared mesocarbon microbead/carbon nanotube composites

Carbon nanotubes (CNTs)-doped mesophase spherules were prepared from coal tar pitch blended with CNTs by in situ method after heat-treated at 420 °C for 120–150 min. Mesocarbon microbead/carbon nanotube (MCMB/CNT) composite blocks were successfully obtained after compaction and calcination. The morphology and microstructure of the composites indicate that the added CNTs enhance the nucleation and restrict the growth and coalescence of the mesophase spherules. The relatively higher flexural strength of 146 MPa and compressive strength of 439 MPa were obtained with CNTs content of about 2–5 wt.%, while excess amount of CNTs over 10% led to mechanical property deterioration because of CNTs agglomeration. The strengthening effect of proper CNTs addition is attributed to voids reduction and reinforced interstitial substance between the microbeads. It is also indicated that better dispersion of more CNTs with large lengths in the matrix would offer more space to enhance mechanical properties of MCMB/CNT composites.