Carbon nanotubes synthesis using carbonization of pretreated rice straw through chemical vapor deposition of camphor
There is a pressing demand to prepare low-cost carbon nanotubes (CNTs) from renewable biomass resources as cheap carbon precursors and catalyst supports during chemical vapor deposition (CVD). Camphor and rice straw are quite an eco-friendly, renewable and low-cost carbon sources to prepare CNTs. Here, successful attempts for preparing CNTs through carbonization of hydrothermally treated rice straw using either mono-catalyst of ferrocene (RS-H/Fe) or mixed catalysts of ferrocene and nickel nitrate (RS-H/Fe–Ni) in presence of gaseous carbon source emitted from heating camphor under flowing N2 gas were achieved. Scanning electron microscope (SEM) combined with energy-dispersive spectroscopy (EDS), transmission electron microscope (TEM), Raman spectroscopy and thermal gravimetric analysis (TGA) techniques were used to determine the morphology, surface, electronic structures and thermal stability of the produced CNTs. Different structures of CNTs were grown with outer diameters ranging from 22 nm to 66 nm. Few amounts with small outer diameters of coiled CNTs–Fe bundles were produced over carbonized rice straw with ferrocene (RS-H/Fe) through a bottom growth mechanism. Whereas considerable amounts of straight and large outer diameter of CNTs-bundles (CNTs–Fe–Ni) were formed over RS-H/Fe–Ni substrate via a bottom growth mechanism also. Raman spectra showed two main bands of CNTs; G-band at ∼1580 cm−1 and D-band at 1356 cm−1 or 1335 cm−1 which obtained on RS-H/Fe and RS-H/Fe–Ni samples, respectively. Conclusively, the presence of Ni with ferrocene can enhance the yield, thickness and graphitization extent of the as-prepared CNTs. Therefore, conversion of available-cheap biomasses into high added-value materials such as CNTs becomes a realistic, feasible and thus reduces the cost production of CNTs.