ABSTRACT: Carbon fibers (CFs) have been widely applied in the manufacture of polymeric composites. The mechanical properties of these composites depend on the adhesion in the matrix/CF interface. Since the CFs have poor adhesion properties, a surface treatment of the CFs becomes necessary. The plasma process used in this work was the dielectric barrier discharge (DBD). The DBD treatment of twill weave carbon fibers (2×2) was performed during 2.0; 5.0; 7.5 and 10.0 minutes. CF/polypropylene (PP) composites were produced by hot pressing method. The surface morphology, structure and mechanical properties of CFs were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, interlaminar shear test (ILSS) and dynamical mechanical analysis (DMA), respectively. SEM images show great changes on the CF surface after the treatment, AFM results show that the fiber treated for 2.0 min exhibited the highest roughness and Raman spectra revealed that the carbon fiber crystalline structure did not change after the treatment. The ILSS and DMA results show an increase of the mechanical strength and no major change in the glass temperature of the composites after the DBD treatment, respectively. Some results were compared to those obtained in our previous study, in which the plain weave fiber (1×1) was evaluated.

Boron-doped polycrystalline diamond films have been deposited over silicon substrate by hot-filament chemical-vapor-deposition process. A gas mixture of 0,5 vol. % methane and 1 vol. % methanol on hydrogen at a pressure of 50 Torr, have been used. Boric oxide dissolved in methanol have been used as the boron doping source during the diamond growth process. Raman spectroscopy and Scanning Electron Microscopy (SEM) have been performed on the samples. A change of Raman spectra with film doping was observed. The diamond characteristic line at 1333 cm-1 down shifted and its intensity decreased as the film resistivity decreased. On the other hand, a broad peak around 1220 cm-1 appeared and its intensity increased with decreasing film resistivity. No modifications on films morphology have been observed with different boron doping level. The grains were well-faceted with 2 <FONT FACE="Symbol">m</font>m average size