The availability of fossil resources decreases over the years, constituting a problem that needs to be properly treated. In this context, it is necessary the exploration of alternative and renewable sources of energy, particularly the use of solar energy incident on the planet. The aim of this work is to examine the feasibility of the application of sugarcane bagasse ash as a precursor material for obtaining an inorganic polymer that will form the absorber film for use in solar collectors for medium and high temperature. Through mechanical particle size separation of ash and its physicochemical characterization, it was possible to prove that the chemical and mineralogical composition of the raw material is favorable for use in alkaline synthesis Furthermore, the ash particle size large achieved the best results of properties optical and microstructural, favoring its application to obtain films to be applied to selective surface. It was also observed that the metallic copper substrate had the best interaction with the film providing the best results in absorption of ultraviolet visible region.

High performance solar collectors are those with high selectivity surfaces, high solar radiation absorption and that do not thermally reemit to the external environment. Strategies to enhance this performance might involve surface porosity modification. In this work, a plasma treatment technique called plasma electrolytic oxidation (PEO) has been tested to produce porosity on aluminium surfaces in a controlled manner. The porosity control was made by varying the intensity, frequency and duty cycle of the applied voltage pulses. The aluminium sample was placed in a solution of 1 g/L Na 2 SiO 3. Voltage of 500 V and current density of 0.17 A cm 2 was applied between electrodes. Three duty cycles were used: 33.33%, 50.00% and 67.77%. After treatment, the size, number and distribution of pores were evaluated. These parameters were correlated with both surface reflectance and optical absorbance. It was possible to control the porosity by controlling the electrical parameters of the process. While the mean pore size was directly related to the duty cycle, the inverse occurred for the number of pores. Surface treated with duty cycle of 33.33% presented higher values of absorption for all wavelength range.

In petroleum wells, the adhesion between the steel and the cementitious coating material is responsible for ensuring the efficiency of the mechanical point of view and of the thermodynamic stability of steels, protecting them against corrosion, preventing the escape of fluids inside and hydraulically isolating the structure against infiltration. The push-out test is used to measure the level of adhesion between the steel and cement. In this paper, the numerical simulation of steelcement interface was performed to reproduce the mechanical behavior of this interface used a cohesive zone model combined with Coulomb's law for friction. The proposed model was implemented in CAST3M software. The numerical results obtained with the proposed model were compared with experimental results of push-out test. The comparison between the force versus displacement curves, obtained experimentally and numerically, validated the proposed model.

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