Abstract
The effect of chlorine on the morphology of carbon nanotubes (CNTs) prepared from a Fe-Co/CaCO 3 catalyst was investigated using chlorobenzene (CB), dichlorobenzene (DCB), trichlorobenzene (TCB), dichloroethane (DCE), trichloroethane (TCE) and tetrachloroethane (TTCE) as chlorine sources using a catalytic chemical vapour deposition (CCVD) method. Toluene was used as a chlorine-free carbon source for comparison. Multi-walled carbon nanotubes (MWCNTs) were successfully synthesized. The physicochemical properties of the CNTs were studied using transmission electron microscopy (TEM), Raman spectroscopy, thermal gravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), powder X-ray diffraction (PXRD) spectroscopy, and X-ray photoelectron spectroscopy (XPS) techniques. The inner and outer diameters of the MWCNTs increased with an increase in the number of chlorine atoms contained in the reactant. Chlorine incorporation into the MWCNTs was observed by EDS analysis for all reactants. Formation of ‘bamboo-like’ structures for the MWCNTs generated from TCE and TTCE was also observed, facilitated by the presence of the high percentage of chlorine in these reactants. Numerous MWCNTs revealed the presence of small carbon nanostructures that grew on top of the dominant CNTs, suggesting an unexpected secondary carbon growth mechanism. KEYWORDS Multi-walled carbon nanotubes, CVD, synthesis, chlorine, benzenes, ethanes.
Highlights
Nanotechnology is a topic that is attracting the interest of scientists in academia, research institutions and industry as well as government officials and journalists
To further explore the role of this catalyst we have investigated the role of chlorine on the morphology of carbon nanotubes (CNTs) produced by pyrolysis of various chlorinesubstituted benzene and ethane feeds using a chemical vapour deposition (CCVD) method
All the products made in the study were black in colour; those obtained with CB, DCB, DCE, and TCE as chlorine sources appeared spongy, while those obtained with TCB, TTCE and toluene were powdery
Summary
Nanotechnology is a topic that is attracting the interest of scientists in academia, research institutions and industry as well as government officials and journalists. In previous studies by our group it was found that a Fe-Co/CaCO3 catalyst can be used to make good quality CNTs56,57 and nitrogen doped CNTs.[58] To further explore the role of this catalyst we have investigated the role of chlorine on the morphology of CNTs produced by pyrolysis of various chlorinesubstituted benzene and ethane feeds using a CCVD method. Calculated amounts of the Fe and Co nitrates were mixed, ground to a fine powder and dissolved in distilled water to make a 0.3 mol L–1 Fe-Co (50:50 m/m) precursor solution This solution (30 mL) was added to the CaCO3 support (20 g) and the mixture was stirred for 30 min. The samples were sputtered with a 2 kV 2 μA 1 ×1 mm raster – Ar ion gun at a sputter rate of about 18 nm min–1 for 60 seconds
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