Growth of Nanotubes inside eDIPS Carbon Nanotubes ^†

The growth of carbon nanotubes is a very important process. It is controlled by the synthesis parameters, such as the catalysts, the catalyst support, the carbon source, temperature, and pressure. There are the different experimental setups for this method. The results of the conducted work are the following. Here, pristine outer single-walled carbon nanotubes (SWCNTs) are obtained by means of enhanced direct injection pyrolytic synthesis (eDIPS), and they have a diameter of 1.7 nm [1]. The filling of the SWCNTs with ferrocene is performed using the gas phase method at 350 °C in a quartz ampoule sealed under an ultrahigh vacuum. The annealing of the ferrocene-filled SWCNTs leads to the growth of the inner SWCNTs with different diameters. Therefore, double-walled carbon nanotubes (DWCNTs) are formed. I analyze all DWCNTs using the Raman spectroscopy method with different laser wavelengths between 458 and 647 nm. The growth process is traced at different annealing temperatures between 500 and 1000 °C. The temperature difference of about 70 °C is found for the diameter difference of about 0.16 nm.