Superficial treatment by anodization in order to obtain titanium oxide nanotubes applicable in implantology

Titanium and its alloys are the most popular metals applied on end osseous implants manufacturing. Commercially pure titanium (Ti c.p.) has been successfully used as a biomaterial because of its mechanical and chemical properties, excellent corrosion resistance and biocompatibility. In order to improve and accelerate the osseointegration process after implantation, superficial treatments are performed aiming properties that stimulate the growth of the newly-formed bone. In this work, self organized titanium dioxide (TiO2) nanotubes were obtained by anodic oxidation on Ti c.p. (grade 2). Also, it has been shown that the process is industrially reproducible for this purpose. As parameters for the anodizing process, it was concluded that the optimal electrolyte was H3PO4 solution + 0.15% HF under potentiostatic mode for 30 minutes. Potentials of 1, 5, 10, 15 and 20 V were tested in order to verify the best conditions to obtain nanotubes. In this case, potential was set at 10V. The morphology of the samples was characterized by Scanning Electron Microscopy (SEM), Scanning Electron Microscopy with Field Emission (SEM-FEG) and Atomic Force Microscopy (AFM). The results showed the nanotubes formation throughout the titanium samples surface. In accordance to the obtained roughness, it was observed that the formed nanotubes film is thin, however, the literature indicates that the film thickness is not relevant on the performance of nanostructures as optimizers of the osseointegration process, unlike the nanotubes morphology and diameter. In the wettability analysis, the nanotubes behaved as hydrophilic. Therefore, it is possible to obtain TiO2 nanotubes for using in implants by a superficial treatment, allowing a better osseointegration quality.Keywords: Titanium, Nanotubes, Anodization, Implants, Osseointegration.

MODIFICAÇÃO SUPERFICIAL EM ÓXIDO DE NIÓBIO PARA A PRODUÇÃO DE HIDROGÊNIO

RESUMONa separação fotocatalítica da água podem ser utilizados semicondutores como catalisadores da reação de desprendimento de hidrogênio, sendo que a atividade fotocatalítica do semicondutor depende da área superficial e de sua cristalinidade. Nesse contexto, o Nb2O5 diferencia-se como catalisador, uma vez que seu intervalo de band gap situa-se entre os intervalos das reações de oxirredução da água e pode ser obtido na forma porosa e cristalina. Com isso, o objetivo deste trabalho é verificar a influência da modificação superficial de Nb2O5, obtido por anodização, para a produção de hidrogênio por meio de fotocatálise. Para tanto, amostras de nióbio foram anodizadas em 0,3 M ácido oxálico + HF, com densidade de corrente de 12,73 mA/cm2 por 300 s, e analisadas morfologicamente, quanto à condutividade elétrica e por meio de curvas de polarização catódicas. Os resultados mostraram que a melhor condição de modificação superficial para catalisar a reação de desprendimento de hidrogênio por fotocatálise foi da amostra anodizada até ocorrência de sparking, a qual apresentou características de óxido cristalino.Palavras-chave: Anodização. Nióbio. Fotocatálise. ABSTRACTIn photocatalytic separation of water semiconductors can be used as catalysts of the hydrogen release reaction, and the photocatalytic activity of the semiconductor depends on its surface area and its crystallinity. In this context, Nb2O5 differs as a catalyst, since its band gap is between the ranges of water redox reactions and can be obtained in porous and crystalline form. Thus, the objective of this work is to verify the influence of surface modification of Nb2O5, obtained by anodization, for hydrogen production through photocatalysis. For this purpose, niobium samples were anodized in 0.3 M oxalic acid + HF, with current density of 12.73 mA / cm2 for 300 s, and analyzed morphologically for electrical conductivity and cathodic polarization curves. The results showed that the best surface modification condition to catalyze the hydrogen detachment reaction by photocatalysis was from the anodized sample until sparking, which presented crystalline oxide characteristics.Keywords: Anodizing. Niobium. Photocatalysis

Analysis of the effects of alumina (Al2 O3) addition in micrastructure and hardness in Zamac 5 by gravity

O objetivo deste trabalho foi verificar se é possível a incorporação Al2 O3 à liga de Zamac por meio do processo de fundição por gravidade. Para isto amostras de Zamac foram fundidas em triplicata, sem e com adições de 0,1%, 0,5% e 7% em massa de óxido de alumínio. Análises ao Microscópio Eletrônico de Varredura (MEV), medição dos tamanhos de grão e ensaio de dureza das amostras fundidas foram realizados para validação da incorporação da alumina à liga. Após analisar os resultados, verificou-se que a alumina foi satisfatoriamente incorporada à liga. No entanto, a incorporação de Al2 O3 foi baixa e em forma de clusters. Ainda foi verificado que a adição de alumina não causou alterações na microestrutura da nova liga, entretanto, quando comparada com a amostra sem adição de alumina, foi constatado um aumento de 4% na dureza da amostra fundida com 7% de Al2 O3.The objective of this work was to verify if it is possible to incorporate aluminum oxide into the Zamak alloy through the die casting process. For this purpose Zamak samples were melted in triplicates, without and with additions of 0.1%, 0.5% and 7% by mass of aluminum oxide. Scanning Electronic Microscopy (SEM) analysis, grain size measurements as well as hardness tests were performed in order to validate the incorporation of the alumina to the Zamak alloy. After analyzing the results, it was verified that the alumina was satisfactorily incorporated into the alloy. Besides that, there was a low oxide incorporation, and in the form of clusters. It was also verified that the alumina added did not cause changes in the new alloy’s microstructure, however, when compared with the pure sample, an increase of 4% in the hardness of sample casted with 7% of Al2 O3 was found