Near-Armchair-Enriched Growth of Single-Walled Carbon Nanotubes via W-Containing Fe-Based Catalyst Systems in Mist FC-CVD.

Chiral-angle-controlled synthesis of carbon nanotubes (CNTs) remains a central challenge, particularly in continuous growth processes such as floating catalyst chemical vapor deposition (FC-CVD), where high productivity is attractive but tight structural control is difficult to achieve. In this study, a mist-based FC-CVD platform is established for continuous single-walled CNT (SWCNT) growth, enabling systematic modulation of the chiral-angle distribution through expanded catalyst-precursor design. By introducing ultrasonic aerosol-mist delivery, volatility constraints in precursor feeding are relaxed, allowing co-delivery of a non-volatile W precursor (ammonium metatungstate) with ferrocene to create a W-containing Fe-based catalyst system under atmospheric-pressure FC-CVD conditions. This catalyst system promotes pronounced near-armchair enrichment, shifting the CNT chiral-angle distribution away from achiral limits while narrowing the distribution compared with W-free synthesis. Analysis based on a theoretical abundance expression for CNT growth on solid catalysts is consistent with a stabilization-based interpretation, in which W-containing species may increase the effective thermal/structural stability of Fe-based catalyst nanoparticles and the catalyst-CNT interface, thereby strengthening chiral-angle selectivity. Furthermore, tuning the carbon supply reveals an optimal regime for maximizing near-armchair enrichment, whereas supply-limited and overfed conditions broaden the distribution through distinct kinetic pathways. These results provide a practical route toward scalable chiral-angle-controlled CNT synthesis in continuous FC-CVD.