Papers by Author: J.O. Carneiro

Abstract: Highly ordered Anodic Aluminum Oxide (AAO) structures produced from aluminum by using an electrochemical anodizing method were developed towards its application for the next generation of micro/nanomedical and energy devices. In addition of analyzing the anodizing current profile, the surface morphology was characterized by using Scanning Electron Microscopy (SEM), the crystalline structure by X-Ray Diffraction (XRD) and the mechanical properties by nanoindentation experiments. The anodizing time and applied potential determines the nanopores regularity and their size, although the effect of the potential is more pronounced than the effect of temperature in the transformation from crystalline alumina to amorphous alumina. Optimum pore growth was achieved with an applied potential of 17 V which led to a pore fraction - P(f) - of about 17.5%. The experimental Berkovich nanoindentation method was used to determine the AAO hardness as a function of the indenter depth, during the loading stage, using mechanical response and deformation behaviour of the nanopores structure. From the experimental data of the load-displacement curves, this method allows the calculation of the indenter contact depth at each reloading point, thus leading to the estimation of the materials hardness. The results reveal that the hardness depends on the processing conditions used for the production of the AAO samples that also strongly influences the organization and pore size uniformity.

Abstract: Urbanism and communities centralization enlarges atmospheric pollution that affects both human beings as well as their constructed buildings. Different scientific and technological studies are being conducted, both in academic and construction industry, aiming the development of new construction materials with properties that can decrease visual pollution of cities, reducing also the number of cleanings required. The present research work aims the study and the production of self-cleaning ceramic surfaces in an economical and viable way without changing aesthetical aspect of material substrates used. The use of TiO₂ nanoparticles (TiO₂-NNPs) represents an attractive way to generate self-cleaning surfaces, therefore promoting the degradation of pollutant agents and reducing cleaning maintenance costs. In order to impart self-cleaning properties to ceramic surfaces, TiO₂-NNPs based layers were deposited on different ceramic material substrates using the dip-coating method. The Photocatalytic activity (degradation of pollutants adsorbed on the surface) of the TiO₂-NNPs based layers was characterized via the decomposition rate of an aqueous solution of Methylene blue (MB) under UV light irradiation. Colourless layers were successfully produced onto gray and white ceramic substrates using this sol-gel technique, without changing their aesthetical appearance. It was observed that the best photocatalytic activity was exhibited by the most porous ceramic substrate (gray); nevertheless, all the TiO₂-NNPs coated ceramic surfaces showed good photocatalytic efficiency.

Abstract: Biosensors’ research filed has clearly been changing towards the production of multifunctional and innovative design concepts to address the needs related with sensitivity and selectivity of the devices. More recently, waveguide biosensors, that do not require any label procedure to detect biomolecules adsorbed on its surface, have been pointed out as one of the most promising technologies for the production of biosensing devices with enhanced performance. Moreover the combination of optical and electrochemical measurements through the integration of transparent and conducting oxides in the multilayer structures can greatly enhance the biosensors’ sensitivity. Furthermore, the integration of polymeric substrates may bring powerful advantages in comparison with silicon based ones. The biosensors will have a lower production costs being possible to disposable them after use (“one use sensor chip”). This research work represents a preliminary study about the influence of substrate temperature on the overall properties of ITO thin films deposited by DC magnetron sputtering onto 0,5 mm thick PMMA sheets.