Influence of the synthesis temperature and silicon concentration on the properties of Si doped MWCNT

Silicon doped multiwalled carbon nanotubes (Si-CNT) were synthesized by a modified chemical vapor deposition method, using toluene as carbon source, ferrocene as metal catalyst and triphenylsilane to provide the dopant atoms. The effect of synthesis temperature and concentration of Si-containing precursor on the microstructural properties were studied by high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Thermogravimetric analysis. The microscopy results showed that the Si-CNT were structurally modified with various forms of roughness, distortions and defects not only in the inner walls but also on outer walls. The elevated synthesis temperature had the most significant effect in the graphitic carbon network. XPS elemental surface composition analysis showed that the maximum silicon content was 1.3 +/- 0.2 at.%. It was found that the increment in the silicon content, inhibited the growth of Si-CNT. According to Raman results, the Si-CNT presented greater structural disorder due to the integration of silicon atoms in the carbon, which increased the disorder in the hexagonal network due to the higher ionic radius of Si. TGA confirmed that silicon was introduced into the Si-CNT and that they are also thermally stable. Based on the results, the nanotube growth mechanism was proposed, which showed that silicon has high mobility and diffusion on the carbon network as the temperature rises. Prime novelty statement: The originality reported in the manuscript is the novel and facile method to obtain carbon nanotubes doped with silicon and the effect of synthesis temperature on the physical-chemical properties. Also the growth mechanism of the Si-CNT is proposed.