In this study, the influence of catalyst microstructure on carbon nanotube (CNT) growth by thermal chemical vapor deposition (Thermal CVD) was investigated.Particular emphasis was placed on clarifying the role of aluminum as a promoter in iron/aluminum (Fe/Al) bilayer catalysts.For comparison, Fe films deposited on silicon (Si) substrates and Fe films deposited on alumina (AlO) substrates were also prepared.The density and particle size distribution of catalyst nanoparticles during both catalyst activation and CNT growth in Thermal CVD, as well as the microstructure of the synthesized CNTs, were systematically examined.The results revealed that the Fe/Al bilayer catalyst exhibited the highest catalyst particle density and the smallest average particle size during both stages.These findings indicate that the Al promoter effectively suppresses agglomeration and grain growth of Fe catalyst particles during CNT synthesis, resulting in enhanced CNT growth and the formation of high-density CNT films.
IKEYA et al. (Thu,) studied this question.