Study on the effect of the catalyst thickness and the flow rate of ethanol vapor entering the reacto r chamber, on the synthesis of vertically aligned carbon nanotubes by chemical vapor deposition method

Vertically aligned carbon nanotubes (VA-CNTs) were synthesized by chemical vapor deposition (CVD) method using Cobalt (Co) catalyst supported by Aluminum oxide (Al2O3) layer. Specified mixture of Argon carrier gas and ethanol vapor was used for growth process. The effect of entrance flow rate of hydrocarbon gas (ethanol), on the length and density of carbon nanotubes was studied. In our experiments at constant pressure of 10 mmHg, by increasing the rate of ethanol vapor, the density and also the length of nanotubes increases up to approximate rate of 2 ml/min, and then decreases for higher rates of ethanol. Also, it was found that the diameter, length and density of carbon nanotubes were controllable by varying the catalyst layer thickness. Scanning electron microscopy (SEM) was utilized to provide information of the length, density and diameter of CNTs under various conditions, and Raman spectroscopy was used to measure impurities in carbon nanotubes