Experiment Research On Pyrolysis Flame Synthesis Of Carbon Nanotubes Via Catalytic Decomposition Of Ethylene

Carbon nanotubes, as an emerging material, have caused worldwide concern since their discovery by NEC Corporation of Japanese basic research laboratory electron microscopy expert Iijima in 1991. The structure and properties of carbon nanotubes is unique. It has a wide future prospect. Because of this, how to prepare carbon nanotubes with high quality, low power and high yield have become scientists’focus, primarily. In this paper, carbon nanotubes (CNTs) were synthesized by catalytic pyrolysis of ethylene(C2H4) using flame method with carrier catalyst of Fe/Mo/Al2O3. The sampling time, the gas flow rate of ethylene (C2H4), catalyst calcination temperature and acetylene flame temperature were all studied. After determining the better experimental conditions, the synthetic product of different carbon sources carbon monoxide(CO) and methane(CH4), ethylene(C2H4) and acetylene(C2H2) are compared respectively.The experimental results showed that:(1) The yield is increased with the sampling time increasing between 3～11min. The amount of carbon nanotubes has been basically stable, when the sampling time is at 7 min. The product rate gradually reduces with the increase of experimental time. (2) The yield of carbon nanotubes increased first, but it gradually decreased after it reach max value with the gas flow rate of ethylene increasing from 0.05L/min to 0.4L/min progressively. The carbon nanotubes achieve better both in quality and quantity, when the gas flow rate of ethylene is 0.2L/min. It was not favorable for carbon nanotubes growth when the gas flow rate was too high or too low. (3) When the catalyst is in air calcined at 900℃, the yield of carbon nanotubes is high, mostly as with 3-5 layers of wall. The walls are smooth and crisp. The yield will be reduced if the catalyst calcination temperature is too low or too high. But the product is the most straight when the catalyst calcination temperature is at 700℃. And double-walled carbon nanotubes are synthesized when the catalyst calcination temperature is at 700℃ and 800℃. (4) Large quantities of carbon nanotubes can be synthesized when the acetylene flame temperature is 1050℃. And the distribution is uniform, but with a certain degree of bend. There is a small amount of more straight carbon nanotubes when the acetylene flame temperature is at 980℃ and 1100℃. (5) Respectively, carbon monoxide and methane, or ethylene and acetylene as carbon source, types and forms of the synthesized product are different.