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In this study, films of graphene oxide and chemically or thermally reduced graphene oxide were produced by a simple vacuum filtration method and submitted to a thorough characterization by X-ray diffraction (XRD), Raman and infrared spectroscopies, field-emission scanning electron microscopy, transmission electron microscopy, atomic force microscopy, confocal microscopy, and contact angle measurements. Graphene oxide (GO) was produced from graphite by the modified Hummers method and thereafter reduced with NaBH4 or by heating under argon in a tubular furnace. The films were produced from aqueous solutions by vacuum filtration on a cellulose membrane. Graphite presents two characteristic XRD peaks corresponding to d=0.34 nm and d=0.17 nm. After oxidation, only a peak at d=0.84 nm is found for powder GO, confirming the insertion of oxygen groups with an increase in the interplanar distance of graphene nanoplatelets. However, for GO films, other unexpected peaks are observed at d=0.63 nm, d=0.52 nm, and d=0.48 nm. After reduction, both chemical and thermal, the peak at 0.84 nm disappears, while those corresponding to interplanar distances of 0.63 nm, 0.52 nm, and 0.48 nm are still present. The other characterizations confirm the production and chemical composition of GO and reduced GO films. The results indicate the combination of crystalline regions with different interplanar distances, suggesting the ordering of graphene/graphene oxide intercalated sheets.

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DC Triode Reactive Magnetron Sputtered TiN and TiC films were deposited on quenched and tempered AISI H13 AISI D2 tool steels, and silicon (111) substrates, under nitrogen and argon or methane and argon reactive plasma. Hybrid duplex treatments were carried out in a home-built hybrid reactor, where pulsed plasma nitriding and unbalanced DC Reactive Magnetron Sputtering were performed in the same cycle, without exposing the surface of the sample to atmospheric pressure. The ceramic thin films were characterized by X-ray diffraction, WDS spectrometry, scanning electron microscopy, atomic force microscopy, depth sensing techniques (nanoscale), nanoscratch tests, Rockwell C and linear sclerometry adhesion tests.Nanoscale depth sensing was used for measuring hardness (H), Young modulus (E*), the H/E * ratio (elastic strain to failure), resistance to plastic deformation, H 3 /E *2 and elastic recovery. The pulsed plasma nitriding was performed in conditions which avoided the formation of a white layer obtaining only a diffusion zone. When TiN and TiC films were deposited on the quenched and tempered tool steels the adhesion of the ceramic films to the substrate was poor. When the steels were plasma nitrided before deposition the adhesion of the TiN layer to the substrate was improved.However, the adhesion of the TiC film deposited on the nitrided tool steels was also very poor. Therefore, plasma nitriding does not guarantee a better adhesion of the TiC film to the substrate. The abrupt transition of mechanical properties (hardness, Young Modulus and elastic recovery) between the TiC film and the substrate were responsible for the lower adhesion observed. To improve the adhesion of the ceramic film to the substrate, TiN-TiC multilayers were deposited on the surface of the nitrided tool steels, so as to obtain functionally graded films, in which the values of H/E* ratio and elastic recovery, increased in a less abrupt way from the substrate to the film. In the nanoscratch test high it was observed that high values of the H/E* and the H 3 /E *2 ratios and of the elastic recovery presented lower residual scratch depth. As soluções adotadas para o problema da formação da camada preta foram:• Redução da temperatura de deposição;• Utilização de condições de nitretação que inibem a formação da camada branca;• Posterior remoção da camada branca por um processo mecânico. Este trabalho se desenvolveu durante o desenvolvimento do projeto temático e seus objetivos são:• Obter filmes TiN e TiC por deposição reativa magnetron sputtering com diferentes propriedades mecânicas, determinadas por técnicas de nanoindentação instrumentada.• Verificar a influência das propriedades mecânicas na adesão do conjunto filme substrato. 12• Realizar tratamento duplex em reator híbrido: nitretação seguida de recobrimentos monocoberturas e multicoberturas de TiN e TiC sobre aços ferramenta AISI H13 e AISI D2.• Obter um aumento gradual de propriedades mecânicas de modo a obter um gradiente funcional de propriedades elastoplásticas, utilizand...

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In this work, a series of depositions of titanium nitride (TiN) films on M2 and D2 steel substrates were conducted in a Triode Magnetron Sputtering chamber. The temperature; gas flow and pressure were kept constant during each run. The substrate bias was either decreased or increased in a sequence of steps. Residual stress measurements were later conducted through the grazing X-ray diffraction method. Different incident angles were used in order to change the penetration depth and to obtain values of residual stress at different film depths. A model described by Dolle was adapted as an attempt to calculate the values of residual stress at each incident angle as a function of the value from each individual layer. Stress results indicated that the decrease in bias voltage during the deposition has produced compressive residual stress gradients through the film thickness. On the other hand, much less pronounced gradients were found in one of the films deposited with increasing bias voltage.