Molybdenum trioxide (MoO3) thin films are generally deposit on metallic surfaces to increase their tribological performance. In this manuscript, MoOx coatings were for the first time deposited on plasma nitrided surfaces. Vickers microhardness tests, X-ray diffractometry, and micro abrasive wear tests characterized the samples. It was investigated the effect of temperature in hardness and tribological properties of austenitic stainless steel surfaces. When the temperature of plasma nitriding increases, the coating thickness and the nitrogen diffusion on the treated surface also increases, favoring the hardness of the coatings. After MoOx deposition, the predominant MoO3 phase with monoclinic and orthorhombic unit cells was observed. MoOx coatings after plasma nitriding demonstrated the highest wear resistance.

RESUMO Neste trabalho, filmes finos de carbono tipo diamante DLC (Diamond-like carbon) foram depositados em substratos de aço ferramenta AISI D6 por meio da técnica de deposição a plasma com gaiola catódica de grafite, com o objetivo de avaliar a influência dos parâmetros de tratamento, tais como a duração do tratamento e a polarização das amostras. As amostras tratadas foram avaliadas em termos de morfologia e estrutura por Difração de Raios X (DRX), Espectroscopia Raman e Microscopia Eletrônica de Varredura (MEV). Os resultados dos difratogramas indicaram a presença das estruturas de ferrita, grafite e diamante para as amostras tratadas com alumina e a formação de grafite com estrutura hexagonal para amostras tratadas sem alumina. Os espectros Raman identificaram a banda D e G característicos de materiais grafíticos e os melhores resultados foram obtidos para as amostras que não utilizaram alumina. As micrografias dos filmes utilizando alumina indicaram estruturas na forma de minúsculas partículas, com contornos mais claros e definidos. Já para as amostras sem alumina, os filmes DLC apresentaram um aspecto mais uniforme e de coalescência dos grãos. As camadas das amostras tratadas com alumina apresentaram as maiores espessuras de camadas, principalmente para a amostra tratada durante 6 horas. Em relação aos tratamentos sem alumina, as amostras tratadas por 5 e 6 horas apresentaram em média a maior espessura de camada. Assim, foi possível afirmar que a alumina e, também, o tempo de tratamento influenciam de forma significativa nas características de microestrutura e espessura final do filme.

ABSTRACT In this work, thin films of diamond-like carbon DLC (Diamond-like carbon) were deposited on substrates of AISI D6 tool steel by means of the plasma deposition technique with cathodic cage of graphite, with the objective of evaluating the influence of the treatment parameters, such as the duration of the treatment and the polarization of the samples. The treated samples were evaluated in terms of morphology and structure by X-ray Diffraction (XRD), Raman Spectroscopy and Scanning Electron Microscopy (SEM). The results of the diffractograms indicated the presence of the ferrite, graphite and diamond structures for the samples treated with alumina and the formation of graphite with hexagonal structure for treated samples without alumina. The Raman spectra identified the D and G bands characteristic of graphite materials and the best results were obtained for samples that did not use alumina. Micrographs of the films using alumina indicated structures in the form of tiny particles, with clearer and defined contours. As for the non-alumina samples, the DLC films presented a more uniform appearance and coalescence of the grains. The layers of the alumina treated samples had the highest layer thicknesses, especially for the treated sample for 6 hours. Regarding the treatments without alumina, the samples treated for 5 and 6 hours presented on average the highest layer thickness. Thus, it was possible to affirm that the alumina and, also, the time of treatment influence in a significant way the characteristics of microstructure and final thickness of the film.

Nanobiomaterials based on superhydrophilic vertically-aligned multi-walled carbon nanotubes (VAMWCNT-O2) are promising for their properties and bone tissue biocompatibility. VAMWCNT-O2 films with nanohydroxyapatite (nHAp) aim to improve mechanical properties and biocompatibility of this new nanocomposite due to its resemblance to bone matrix structure. This study aimed to produce in vitro biomineralized nHAp/VAMWCNT-O2 nanocomposites using simulated body fluid (SBF) with two different pHs (6.10 and 7.40) during 7 days to obtain a new surface design with higher crystalinity and better morphology of nHAp/VAMWCANT-O2 nanocomposites. The objective is to obtain biomineralized nanobiomaterials to enable its applicability as "scaffold" to cellular support and consequent bone tissue formation, accelerating the osseointegration. Layer densification has been achieved due to polycrystalline nanoapatites deposition on surface and between the biomineralized nHAp/VAMWCNT-O2 nanocomposites, without any heat treatment. Therefore, through its characteristics and properties these nanocomposite applications can be considered extremely viable for acceleration of in vivo regenerative processes.

Nanocomposites based on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O2) and nanohydroxyapatite (nHAp) are of great interest in bone regenerative medicine. The biomineralization using simulated body fluid (SBF) has been extensively studied to evaluate the bioactivity of biomaterials. Thus, the combination of nHAp and VAMWCNT-O2 is attractive and promising. The aim of this study was to evaluate the in vitro calcification of nHAp/VAMWCNT-O2 nanocomposites before and after the period of biomineralization in SBF. In vitro calcification of the extracellular matrix (ECM) of HOB cells in culture after 24 hours was investigated through the assay of alkaline phosphatase. These promising in vitro results validate biomineralized nHAp/VAMWCNT-O2 as possible scaffolds for bone tissue regeneration.

For the first time, the growth mechanism of biominerals formed on plate-like nanohydroxyapatite (nHAp) electrodeposited on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O2) is presented and a model for the specific growth preference is discussed. VAMWCNT-O2 films were obtained by microwave-assisted chemical vapor deposition method and funcionalized by oxygen plasma. nHAp/VAMWCNT-O2 nanocomposites were fabricated with a direct electrodeposition of the thin nHAp films onto the VAMWCNT-O2 films. The biomineralized "scaffolds" were obtained by soaking nHAp/VAMWCNT-O2 in simulated body fluid for 7, 14 and 21 days. Results show that the carboxyl functional groups directly attached onto VAMWCNT tips after oxygen plasma treatment were essential for the acceleration of the OH- formation and the deposition of plate-like nHAp crystals.