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Since the discovery of carbon nanotubes, they have been intensely studied as filler materials into different matrices, including polymers to obtaining composites with enhancing properties. Carbon spheres are other type of nanostructures that have not been enough studied as reinforcement material. Polymeric composites with enhanced properties have gradually replaced many of the conventional materials in several areas. In this research, a comparative study of composites based in MWCNTs and CSs incorporated in poly(methyl methacrylate) matrices by mixing solution method was carried out. Composites with 2 wt%, 3 wt%, and 4 wt% of MWCNTs and CSs were obtained through solution mixing and were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Carbon sphere composites were observed with better dispersion than carbon nanotube composites through SEM. D, G, and G' characteristic bands of carbon nanostructures and typical bands of PMMA were observed by Raman spectroscopy in all composites. C–H, C=O, and CH2 vibrations were depicted in composites spectra by FTIR. Vickers microhardness and electrical conductivity of composites were measured. A significant increasing in electrical conductivity was obtained in MWCNTs/PMMA composites, reaching values up to 8.45 × 10–5 S/cm. Nevertheless, the highest electrical conductivity values were observed in CSs composites (7.98 × 10–4 S/cm). Vickers microhardness also was enhanced in all composites; however, CSs/PMMA composites showed the highest values in contrast with MWCNTs/PMMA composites. The major Vickers and electrical conductivity properties of CSs/PMMA composites are attributed to better carbon spheres dispersion into polymer matrix. [ABSTRACT FROM AUTHOR]

A functionalization process has to occur in order to employ carbon nanotubes, generally by using certain types of acids. Multiwalled carbon nanotubes synthetized from benzene and ferrocene were oxidized at different temperatures between 270-600 °C through thermal treatment at atmospheric conditions. Samples were characterized by SEM, EDS, XRD, FTIR and Raman. The weight loss is shown with fluctuations from 0-78% according to different temperature conditions. FTIR analysis demonstrated presence of carbonyl groups and decrease of CHx. [ABSTRACT FROM AUTHOR]

Carbon nanotubes were produced via chemical vapor deposition using ferrocene as catalyst, benzene as carbon source and argon as carrier gas. Samples were synthesized at 800, 850 and 900 °C, carrier gas flow of 50, 80 and 110 ml/min and reaction time of 1 h. The morphology and average microstructure were analyzed by scanning electron microscopy and X-ray powder diffraction. The Scherrer’s equations were used to estimate the average number of walls in the carbon nanotubes. It was observed that the flow of carrier gas modifies the number of the tube walls as follows: for 50 ml/min (40–42 walls), for 80 ml/min (33–39 walls) and for 110 ml/min (30–34 walls). Additionally, was analyzed the effect on the micro-hardness as a result of the incorporation of carbon nanotubes into an epoxy resin. Mechanical tests showed an increase up to 30% in the microhardness with the incorporation of 3 wt% of nanotubes. [ABSTRACT FROM AUTHOR]