Revealing the Impact of Catalyst Phase Transition on Carbon Nanotube Growth byin SituRaman Spectroscopy

Abstract

The physical state of the catalyst and its impact on the growth of single-walled carbon nanotubes (SWNTs) is the subject of a long-standing debate. We addressed it here using in situ Raman spectroscopy to measure Fe and Ni catalyst lifetimes during the growth of individual SWNTs across a wide range of temperatures (500-1400 °C). The temperature dependence of the Fe catalyst lifetimes underwent a sharp increase around 1100 °C due to a solid-to-liquid phase transition. By comparing experimental results with the metal-carbon phase diagrams, we prove that SWNTs can grow from solid and liquid phase-catalysts, depending on the temperature.

Gold Nanoparticles as the Catalyst of Single-Walled Carbon Nanotube Synthesis

“…SWCNT growth from solid catalysts has been confirmed as well as nanowire growth [22,23]. The active forms of Fe catalyst have been reported to be liquid phase, solid Fe metal or Fe carbide depending on the growth temperature and the carbon contamination level [22,24,25]. The Ni catalyst is reported to be in the solid state up to 1200 °C [24].…”

“…The active forms of Fe catalyst have been reported to be liquid phase, solid Fe metal or Fe carbide depending on the growth temperature and the carbon contamination level [22,24,25]. The Ni catalyst is reported to be in the solid state up to 1200 °C [24]. The point is that carbon uptake into the metal particles and carbon precipitation from the carbon-metal eutectic alloy, i.e., continuous carbon supply from the bulk of the nanoparticle.…”

Temperature-dependent chemical state of the nickel catalyst for the growth of carbon nanofibers

“…[8] The recent in-situ Raman analyses also revealed that CNTs could grow from both solid and liquid catalyst Fe, depending on the growth temperature. [9] The debate on the chemical state of catalysts was originated from the argument in 1980s that the deviation of C equilibrium during the growth process of CNFs could be attributed to the formation of the metastable carbides, Ni 3 C or Ni 3 C 1-x . [7,[10][11][12] However, the validity of such a carbide-assisted mechanism has been strongly questioned in the past.…”

Nanoscale Silicon as a Catalyst for Graphene Growth: Mechanistic Insight from in Situ Raman Spectroscopy

“…Raman 4 modes provide fingerprints of carbon to track the thermodynamics and kinetics of in-situ carbon growth processes, such as for single-walled carbon nanotubes and graphene. [25][26][27] In-situ monitoring enables the capability to finely distinguish between mechanistic processes occurring in the growth of carbon nanostructures.…”