The Application of Gas Dwell Time Control for Rapid Single Wall Carbon Nanotube Forest Synthesis to Acetylene Feedstock

Abstract

One aspect of carbon nanotube (CNT) synthesis that remains an obstacle to realize industrial mass production is the growth efficiency. Many approaches have been reported to improve the efficiency, either by lengthening the catalyst lifetime or by increasing the growth rate. We investigated the applicability of dwell time and carbon flux control to optimize yield, growth rate, and catalyst lifetime of water-assisted chemical vapor deposition of single-walled carbon nanotube (SWCNT) forests using acetylene as a carbon feedstock. Our results show that although acetylene is a precursor to CNT synthesis and possesses a high reactivity, the SWCNT forest growth efficiency is highly sensitive to dwell time and carbon flux similar to ethylene. Through a systematic study spanning a wide range of dwell time and carbon flux levels, the relationship of the height, growth rate, and catalyst lifetime is found. Further, for the optimum conditions for 10 min growth, SWCNT forests with ~2500 μm height, ~350 μm/min initial growth rates and extended lifetimes could be achieved by increasing the dwell time to ~5 s, demonstrating the generality of dwell time control to highly reactive gases.

One millimeter per minute growth rates for single wall carbon nanotube forests enabled by porous metal substrates

“…3b. 10,11,19 It should be noted that the resolution of the CNT forest height monitoring system has been reported previously to be $10 mm. From these observations, we conclude that an additional critical parameter in achieving optimum SWCNT growth yield per height was maintaining the porous structure to sustain the uniform gas ow.…”

“…As a result, the deactivation of catalysts due to carbon coating is reduced, hence increased lifetime and reduced growth rates. 10,11,19 2.4 High SWCNT growth speed on mesh substrates Finally, to demonstrate the potential of this approach, we selected the mesh which demonstrated the highest yield and then optimized the growth conditions. The ow of gases through a porous substrate represents a complex system and in addition to depending on the substrate structure (porosity), it also depends on the impinging gas ow rate.…”

“…This value is comparable to the highest values reported for single wall synthesis reported the literature for at substrates grown by ethylene, acetylene, and alcohol CVD methods. 6,7,11,12,19,28,29 3…”

“…"dwell time") of the carbon feedstock gas was demonstrated as a vital parameter for very rapid SWCNT forest growth with long (catalyst) lifetime. 11,19 Therefore, a high surface area substrate system where gas can be delivered uniformly to all surfaces and held at a xed growth condition is ideal.…”

The Effect of Catalyst Sublimation Temperature on the Purity of Multi-Walled Carbon Nanotube Vertically Aligned Arrays

“…The growth rate of ethylene and acetylene can be comparable depending on experimental parameters selected. Acetylene had a carbon efficiency 32% higher than ethylene in a SWCNT experiment [84]. An excessive decomposition rate of acetylene can lead to amorphous carbon growth on the catalyst layer [82].…”