Effect of Iron Concentration on the Growth of Carbon Nanotubes on Clay Surface
2012
Huakang, Fu | Miao, Du | Qiang, Zheng
The successful growth of carbon nanotubes (CNTs) on montmorillonite (MMT) precursors treated with different concentrations of ferric nitrate at 50 °C (MMT(Fe)-50) and 100 °C (MMT(Fe)-100) was achieved via the in situ chemical vapor deposition (CVD) of acetylene. The as-obtained MMT-CNTs composites were characterized using X-ray diffraction, inductively coupled plasma emission spectrometry, scanning electron microscopy, and transmission electron microscopy. All Fe³⁺ ions were intercalated into the MMT interlayers at either 50 or 100 °C in the case of [Fe³⁺]/[clay] = 1. However, the iron content in MMT(Fe)-100 increased rapidly with the amount of ferric nitrate added, whereas the iron content in MMT(Fe)-50 did not exhibit significant changes. On the other hand, the physical and chemical adsorption of Fe³⁺ onto the MMT surface was believed to be responsible for the great diversity of iron contents in MMT(Fe)-50 and MMT(Fe)-100 at the same [Fe³⁺]/[clay] ratios. Moreover, the CNT yield showed variation similar to the iron content because the CNTs yield depends primarily on the amount of catalyst available. The CNTs embedded onto MMT(Fe)-100 exhibited narrower diameter distributions than those on the MMT(Fe)-50 precursors, with more CNTs with diameters less than 50 nm on the former. It is suggested that a porous structure with many pores formed by iron species and MMT laminas is related to the morphology and structure of CNTs embedded on the surface of MMT.
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