Structural and vibrational spectroscopy characterizations of carbon nanostructures synthesized using mineral oxides

Carbon nanostructures have attracted increasing interest in the past two decades due to their singular properties and their potential applications in the field of nanotechnology. Current processes with the active metals for the hydrocarbon decomposition are not meeting the present demand and supply of carbon nanomaterials on large scale level. However, metals or metal oxides, in small or even trace amounts, can be easily found in almost all natural materials and they are in the ideal form to be used as catalysts for carbon nanomaterials synthesis via CVD route. In this thesis work, we have focused on synthesis of carbon nanostructures using natural materials such as low Ni content iron laterite ores, siliceous breccia, as a catalyst and organic matter rich black carbon powder and hydrocarbon gases as a precursor and the growth process behind it. The 1st chapter gives a brief and general background on carbon nanomaterials, on related synthesis methods and underlying growth mechanisms. In 2nd chapter, synthesis process and characterization techniques have been explained in details with their working and characterization process. The 3rd chapter deals with the synthesis of carbon nanostructures on dehydrated limonite laterite as catalyst carried out via CVD route under methane flux he phase transformation from FeOOH to Fe2O3 was carried out successfully in the reducing Ar atmosphere, which was used as a catalyst source. The diameter of the carbon nanotubes was found to vary between 10 and 100 nm, and to increase with the CVD chamber temperatures. Furthermore, the 4th chapter, reports a detailed study on the synthesis of growth of carbon nanostructures on natural limonite laterite iron ore with low-Ni content under ethylene flux, and a comparative study as a function of the temperature as well as of the H2/C2H4/Ar/O2 flux ratio supplied on the catalyst. Before the catalytic tests, iron existed as Fe2O3 (limonite laterite after dehydration). During the catalytic tests, Fe2O3 has been reduced to Fe3O4, FeO, or Fe as the deposition temperature increase from 700 to 800 and 900 ºC. Another interesting behaviour of the as synthesized carbon nanostructures is that it starts forming a carbon nanospheres when the deposition temperature increases.. The 5th chapter concerns the synthesis of carbon nanotubes on the natural drill core siliceous breccia powder v containing mainly quartz and some traces of hematite and goethite. Furthermore, comparative studies by varying the H2/C2H4 flux ratio supplied on the catalyst. The 6rd chapter deals with two cases of drilled core organic matter rich black shale samples. In the first case, the results of combined spectroscopic analyses, performed on an organic matter rich black carbon sample, are considered. The aim of the work was to detect the major mineral component phases. Further, in the second case, black shale carbon powders, mainly containing quartz and dolomite, were exploited to obtain coating layers, on Cu substrates. Finally, in the 7th chapter, the results of the investigation of vibrational properties of silicon oxycarbide powders, doped with different amounts of boron, produced from solgel- derived poly(boro)siloxanes are reported and discussed. The evolution of Raman spectra of the different samples, annealed at 1200 °C and 1400 °C, has been investigated in order to get insights about the effects of Boron-doping on the nanostructure of the studied materials.