The thesis addresses the incorporation of phosphorus atoms into the structure of multi-walled carbon nanotubes (MWCNTs) grown by the Spray Pyrolysis method. To this end, the concentration of ferrocene in the precursor was fixed in 2,0 wt %, while the concentration of triphenylphosphine (Ph3P) was varied from 0,15 to 0,65 wt %. Scanning and transmission electron microscopy images showed as first evidence of doped tubes, the presence of corrugated tubes, constituted of a special bamboo type morphology, like a carbon necklace growth being approximately ten times shorter when compared to the undopes tubes. The analysis of the Raman spectra shows that the D to G band ratios increase as the Ph3P concentration was increased from 0,15 to 0,65 wt % as an indication of the defects introduced into the nanotubes. On the other hand, the frequency of the G band, highly sensitive to changes in the sp2 carbon structures induced by doping or defects, downshifts as the phosphorus concentration increases, possibly related to a renormalization of the energies of the phonons and the electrons of the nanotubes at the defect or doping sites of the carbon lattice. The XPS spectra obtained from doped tubes were compared with the spectra obtained from Ph3P and metallic phosphorus. The most important results was obtained by X-ray photoelectron spectroscopy (XPS) because without unprecedented detail, the studies on the P 2p peak shows it’s constitute of two components located at 133,3 and 129,5 eV, attributed to P-Fe and C-P bonding, confirming the phosphorus doping MWCNTs. The X-ray diffraction analysis showed a high degree of crystallinity and the formation of iron oxides and iron-phosphorus compounds once the Ph3P was introduced as the starting material in the nanotubes growth. Finally, thermogravimetric analysis in oxidative and inert atmospheres shows the doped tubes has higher chemical reactivity and more defects in their structure.