Synthesis Of Carbon Nanotubes On Quartz And Porous α-Al₂O₃ Substrates

Sholl and coworkers found that the transport rates in nanotubes were magnitude of orders faster than in zeolites with comparable pore size calculated by atomic simulation method. One-dimensional pore of carbon nanotubes can improve the Selective separation of gas mixtures. Thus, we predict that carbon nanotubes film with a uniform pore size will have a high selectivity and high permeation flux. In this paper, films of carbon nanotubes were prepared on quartz and porousα-Al₂O₃ substrates, and carbon nanotube films obtained were characterized and studied.A floating catalytic pyrolysis method, with ferrocene as the precursor of catalyst and acetylene as a carbon source, was employed in the growth of CNTs on the porousα-Al₂O₃ substrate. The CNT growth is affected by many factors. In view of this, this paper examined the process conditions on the growth of carbon nanotube films. The parameters in the CNT growth process, including the amount of catalyst, temperature, were examined in details. It was found that the catalyst particles become larger with the amount of catalyst increase, leading to the substantially reduction of the catalytic activity. The amount of iron particles drastically reduced and the size become smaller with the amount of ferrocene reduction. Consequently, the space between the iron catalyst particles increases and the density of iron catalyst particles decrease. As the reaction temperature increasing, the carbon nanotube growth is accelerated. Less carbon deposited due to the quick deactivation of the catalyst. An optimum condition for the growth of the aligned carbon nanotube arrays is given as follows: the amount of catalyst is 0.25 g; reaction temperature is 750 o C; reaction time is 10 min; the flow rate of acetylene is 100 sccm. The outer diameter of carbon nanotubes prepared are smaller than 40 nm.Nano-scale Co/Mo bimetallic catalyst particles were prepared and deposited on the quartz substrate with smaller sizes and uniform distribution by dip-coating method. Hydroxylation treatment of quartz surfaces and addition of viscous agent ethylene glycol in the acetate ethanol solution is preferred to small, evenly distributed catalyst particles preparation. Then by using CVD method we prepare carbon nanotubes with smaller size on quartz. The optimum conditions are as follows: the catalysts are reduced in 300 sccm N₂/H₂ (3 vol% H₂); the reaction temperature is 750o C; acetylene gas flow rate is 30 sccm; and reaction time is...