Preparation and Characteristics of SiO_x Coated Carbon Nanotubes with High Surface Area

An easy method to synthesize SiO_x coated carbon nanotubes (SiO_x-CNT) through thermal decomposition of polycarbomethylsilane adsorbed on the surface of CNTs is reported. Physical properties of SiO_x-CNT samples depending on various Si contents and synthesis conditions are examined by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen isotherm, scanning electron microscope (SEM), and transmission electron microscope (TEM). Morphology of the SiO_x-CNT appears to be perfectly identical to that of the pristine CNT. It is confirmed that SiO_x is formed in a thin layer of approximately 1 nm thickness over the surface of CNTs. The specific surface area is significantly increased by the coating, because thin layer of SiO_x is highly porous. The surface properties such as porosity and thickness of SiO_x layers are found to be controlled by SiO_x contents and heat treatment conditions. The preparation method in this study is to provide useful nano-hybrid composite materials with multi-functional surface properties.