Optimized synthesis for improved TiO2 NT array surface

Different thicknesses of photoresist layers were deposited on the Ti foil in order to decrease the initial current during the anodization process, avoiding or diminishing in this way the formation of the initial compact TiO2 layer. The studies of the initial synthesis stages were performed in both cases, for the conventional synthesis and for that with photoresist layer on top of the Ti foil. TiO2 nanotube pH electrodes were fabricated to study the effect of this change in the anodization process. The nanostructure morphology was analyzed through scanning electron microscopy technique. Total removal of the undesirable layer and a complete release of the nanotube mouth were obtained. The pH electrodes were characterized utilizing a buffer solution and improved pH sensitivity and absence of hysteresis effects were observed for the devices fabricated with TiO2 nanotubes obtained with the optimized process.

Raman spectroscopy of nanograins, nanosheets and nanorods of copper oxides obtained by anodization technique.

Different nanostructures such as: CuOH nanorods, CuO nanosheets and Cu2O nanograins were obtained by anodization approach at room temperature during times from 10 to 40 minutes. By scanning electron microscopy technique, it was found that Cu2O nanograins were formed at 10 minutes, CuO nanosheets vertically oriented on nanograins were observed at 20 and 30 minutes, and from 20 minutes CuOH nanorods with low vertical orientation on nanosheets were formed, coexisting the three types of nanostructures at the same system. In samples without thermal treatment were observed that Raman spectra of nanograins have a typical signal at 218 cm-1 associated to Cu2O, Raman spectra of nanosheets have signals at 287 and 630 cm-1 associated to CuO and Raman spectra of nanorods, it was observed that Raman spectrum is dominated by an intense signal associated to CuOH located around 488cm-1. In addition, after 3 hours of thermal treatment at 300 °C, the morphology was conserved, and the hydrogen-related compound decreased. Raman spectra of nanorods only presented a signal at 287 cm-1 associated to CuO whereas in nanosheets three peaks at 150, 218, 304 cm-1 associated to the Cu2O were observed.

SÍNTESE E CARACTERIZAÇÃO DE NANOCOMPÓSITOS POLIMÉRICOS REFORÇADOS COM VERMICULITAS

<p><em>As propriedades de proteção de um material por um revestimento polimérico são enfraquecidas por mecanismos térmicos e químicos, onde a reação de corrosão é favorecida na interface entre o material protegido e o material protetor. Para isso, faz-se necessário o estudo de sínteses menos complexas e eficientes de materiais que atuem com essa finalidade. </em><em>Este trabalho busca analisar o efeito das propriedades térmicas, mecânicas e morfológicas na resina epóxi, a partir da adição de argila vermiculita paraibana nos teores de 1 e 3% em massa numa matriz à base de resina epóxi, após o processo de organofilização das argilas, que se apresentam naturalmente hidrofílicas e sem afinidade à compostos orgânicos. Os resultados mostraram uma estabilidade na temperatura de degradação do nanocompósito e um impressionante aumento na temperatura de transição vítrea. Houve também uma melhora na resistência à tração em relação a resina não modificada, sugerindo a intercalação polímero/argila, estrutura essa, comprovada a partir da técnica de Microscopia Eletrônica de Varredura (MEV).</em></p><p><em> </em></p><p><em>ABSTRACT</em></p><p><em></em><em>The protective properties of a material by a polymer coating are weakened by thermal and chemical mechanisms, where the corrosion reaction is favored at the interface between the protected material and the protective material. For this, it is necessary to study less complex and efficient syntheses of materials that act for this purpose. This work aims at analyzing the effect of thermal, mechanical and morphological properties on the epoxy resin, from the addition of vermiculite paraibaan clay at 1 and 3% by mass in a matrix based on epoxy resin, after the organophilization process of the clays, which are naturally hydrophilic and have no affinity for organic compounds. The results showed a stability in the degradation temperature of the nanocomposite and an impressive increase in the glass transition temperature. There was also an improvement in the tensile strength in relation to the unmodified resin, suggesting the polymer / clay intercalation, a structure that was proven using the Scanning Electron Microscopy technique (SEM).</em></p>

Preparation of optimal feedstock for low-pressure injection molding of Al/SiC nanocomposite

This study aims to prepare optimal feedstock for fabrication of Al/SiC nanocomposites by the low-pressure injection molding technique. For this purpose, micron-sized aluminum and nanosized SiC powders were mixed with different amounts of the binder consisting of 89 wt% paraffin wax, 9 wt% bees wax, and 2 wt% stearic acid. Rheometry analyses as well as the Weir model were utilized to determine the optimal feedstock with the desired rheological properties and high homogeneity. Considering powder to binder ratios, shear sensitivity, flow activation energy, and homogeneity within the rheometry analyses, the feedstock of 78 wt% powder loading is selected as the optimal sample for injection molding. Investigation of optimal feedstock by the scanning electron microscopy technique also verified the high homogeneity of this feedstock. In addition, it was observed that all of the feedstocks had thixotrop behavior.