In recent years, efforts in developing high strength-low density materials are increasing significantly. One of the promising materials to attend this demand is the carbon nanotube (CNT), to be used mainly as a reinforcing phase in lightweight metal matrix composites (MMC). In the present work, the sol-gel technique has been employed to obtain TiO 2 coating on the surface of commercial multiwall carbon nanotubes (MWCNT). The aim of such coating is to improve the thermal stability of MWCNT in oxidize environment, which is necessary in most of MMC processing routes. Calcination in inert atmosphere was performed in order to crystallize a stable coating phase. The hybrid CNT/TiO 2 nanocomposite was characterized by X-Ray Diffractometry (XRD), Raman spectroscopy, Thermogravimetry (TGA) and Field Emission Gun -Scanning Electron Microscopy (FEG-SEM). The coating structure was observed to change from anatase to rutile, as the calcination temperature increases from 500 to 1000ºC. Results from thermogravimetric analysis showed that the samples calcined at 1000 ºC were more resistant to oxidation at high temperatures.

e production of metal matrix composites with elevated mechanical properties depends largely on the reinforcing phase properties. Due to the poor oxidation resistance of multiwalled carbon nanotubes (MWCNTs) as well as their high reactivity with molten metal, the processing conditions for the production of MWCNT-reinforced metal matrix composites may be an obstacle to their successful use as reinforcement. Coating MWCNTs with a ceramic material that acts as a thermal protection would be an alternative to improve oxidation stability. In this work, MWCNTs previously functionalized were coated with titanium dioxide (TiO 2 ) layers of different thicknesses, producing a core-shell structure. Heat treatments at three different temperatures (500°C, 750°C, and 1000°C) were performed on coated nanotubes in order to form a stable metal oxide structure. e MWCNT/TiO 2 hybrids produced were evaluated in terms of thermal stability. ermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (RS), and X-ray photoelectron spectroscopy (XPS) were performed in order to investigate TiO 2 -coated MWCNT structure and thermal stability under oxidative atmosphere. It was found that the thermal stability of the TiO 2 -coated MWCNTs was dependent of the TiO 2 layer morphology that in turn depends on the heat treatment temperature.

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