Flame-synthesis limits and self-catalytic behavior of carbon nanotubes using a double-faced wall stagnation flow burner

摘要

Flame-synthesis limits of carbon nanotubes (CNTs) are measured using a double-faced wall stagnation flow (DWSF) burner that shows potential in mass production of CNTs. With nitrogen-diluted premixed ethylene-air flames established on the nickel-coated stainless steel double-faced plate wall, the limits of CNT formation are determined using field-emission scanning and transmission electron microscopies and Raman spectroscopy. Also, self-catalytic behavior of the synthesized CNTs is evaluated using the DWSF burner with a CNT-deposited stainless steel double-faced plate wall. Results show narrow CNT-synthesis limits (in terms of fuel-equivalence ratio) at high flame stretch rates but substantially extended limits at low flame stretch rates. This implies that the synthesis limits are very sensitive to the fuel-equivalence ratio variation for high stretch rate condition, yielding a lot of impurities and soot rather than CNTs. A self-catalytic behavior of multi-walled CNTs (MWCNTs) shows the enhanced ratio of channel diameter to tube wall thickness, implying that the quality of metal-catalytic, flame-synthesized MWCNTs can be much improved via a CNT self-catalytic flame-synthesis process. Thus, using a DWSF burner through the self-catalytic process has potential in mass production of CNTs having much improved quality.