Cellulose is a polymer widely available in nature, however its applications may be restrict due to its hydrophilic character. The creation of hierarchical structures on the surface is one of the required factors to obtain the hydrophobicity of this material. In order to compare the morphological and chemical effects caused by the action of different gases in the creation of nanostructures on the cellulose surface, samples were exposed to oxygen (O 2 ) and sulfur hexafluoride (SF 6 ) plasma treatments. The changes in morphology after treatment prove that both the gases were able to create similar nanostructures in the material. The analysis of elemental composition and identification of functional groups on the sample surface showed that chemical modifications occurred differently for each treatment. Contact angle measurements revealed that samples treated by O 2 plasma remained hydrophilic, whereas low receptivity to polar (θ > 120º) and non-polar (θ > 100º) liquids was observed for samples exposed to SF 6 plasma.

Porous anodic alumina (PAA) films with periodically arranged horizontal and vertical nanopores have been applied as templates or platforms upon which optical sensors can be based.While the porosity and the refractive index of these 3D PAA can be tuned by varying the anodization parameters, estimating them from reflectance data has not been explored. In this study, we estimated the porosity and refractive index of thin anodized Al-0.5 wt% Cu from the alumina film thickness and the interference pattern composed of the incident and reflected light beam in the alumina film. The 3D PAA films were prepared by anodization of Al-0.5 wt% Cu thin film deposited on TiN/Si substrate. Anodization was performed in three electrolytes at different concentrations (1 M sulfuric acid, 0.3 M oxalic acid and 0.75 M phosphoric acid) within the voltage range of 10-90 V. The structural characteristics showed that both pore size and inter-pore distance increased with increased anodization voltage and time while the pore density decreases exponentially. The results from reflectance spectra clearly showed that the effective refractive index of the samples decreased with voltage and anodization time, while porosity (total, vertical and horizontal) increased. Also, the density of PAA samples is estimated and shows an inverse proportionality with the porosity.

Resumo Este trabalho apresenta a elaboração e aplicação de um jogo de tabuleiro didático, como uma atividade de revisão, envolvendo conceitos de física relacionados ao cotidiano dos alunos. A pesquisa foi aplicada para 51 estudantes do terceiro ano do ensino médio, no final do primeiro semestre. A metodologia destaca a importância de se empregar o lúdico na exploração das habilidades de argumentação e na relação social dos estudantes que, normalmente, não são contempladas em uma aula tradicional. Observou-se um progresso nas relações entre os próprios alunos e também entre alunos-professor, durante a elaboração conjunta das respostas às perguntas contidas nas cartas do jogo. Cabe destacar a importância destas interações nas discussões teóricas dos conteúdos de física e na construção das relações entre esses conceitos e o seu dia-a-dia. Após a aplicação da atividade, o professor descreveu que houve um maior interesse dos estudantes pela disciplina de física, além de uma postura mais crítica, observada pelos diálogos em sala de aula, durante a finalização da disciplina.

Plasma Electrolytic Oxidation (PEO) is promising for the processing of biomaterials because it enables the production of surfaces with adjustable composition and structure. In this work, aimed at the improvement of the bioactivity of titanium, PEO has been used to grow calcium phosphide coatings on titanium substrates. The effects of the addition of magnesium acetate to the electrolytes on the composition of the coatings produced during 120 s on Ti disks using bipolar voltage pulses and solutions of calcium and magnesium acetates and sodium glycerophosphate as electrolytes have been studied. Scanning electron microscopy, X-ray energy dispersive spectroscopy, Rutherford backscattering spectroscopy, X-ray diffractometry with Rietveld refinement and profilometry were used to characterize the modified samples. Coatings composed of nearly 50 % of Mg-doped hydroxyapatite have been produced. In certain conditions up to 4% Mg can be incorporated into the coating without any observable significant structural modifications of the hydroxyapatite.