The chemistry of premixed flame synthesis of carbon nanotubes using supported catalysts

A premixed flame is used to create the reactive environment for carbon nanotube (CNT) synthesis using stainless steel mesh supporting Co as catalyst. The CNT relative growth density morphology, and internal structure are interpreted in terms of the chemical composition of the flame gases. Different flame gas compositions are produced by varying the fuel/air equivalence ratio, φ. For φ > 1.62, carbon deposition occurs too rapidly relative to reactive etching of surface carbon by species such as H₂, CO₂, and H₂O. For φ < 1.62, the reverse trend of insufficient carbon supply relative to the rate of carbon removal again stunts CNT growth. A value of φ = 1.62 produces CNTs with the best yield, uniformity, and graphitic structure as gauged by scanning and transmission electron microscopies. Yields of up to 1% mass increase of catalyzed CNTs grown upon this catalyst-support system are measured. Initial scalability is demonstrated where CNTs can be uniformly synthesized upon catalyst-coated meshes greater than 2 cm² in area.