Avaliação das propriedades capacitivas de recobrimentos de sol-gel aplicados sobre alumínio anodizado

Abstract

The development of the electronics industry with the miniaturization of devices creates a demand for new energy storage systems, such as capacitors. In the search for these new systems, the study of materials for use as capacitors has a fundamental role. This work aims at the development of a coating with capacitive properties on aluminum alloy, using as pretreatment the anodizing process, which roughness formed on the sample can assist in coating adhesion. Coatings were produced from the sol-gel process, which forms thin coatings in a simple and economical way. The aluminum samples obtained from soft drinks cans were sanded for the removal of its internal and external coatings after undergone a surface treatment by means of anodizing process, which was conducted at three different times (15, 20, and 30 minutes). This surface treatment was evaluated by the technique of Pontentiostatic Polarization (PP), indicating the best conditions of anodizing process for the deposition of solgel. The capacitance for this surface treatment was assessed using Electrochemical Impedance Spectroscopy (EIS) over a period of six days in 3,0 % NaCl solution at pH 2.7. Both analyzes identified the anodizing 15 min as the best condition for the treatment. Samples with and without anodization were then coated with eight different sol-gel compositions, and from the capacitance ratings of each coating was determined by EIA the best composition for adding a new oxide, ruthenium oxide (RuO2), in order to increase the capacitance of the coating. Samples with this final composition was evaluated by EIA, determining the capacitance of the coating, chronocoulometry, to identify the behavior and loading, X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) evaluating the sample surface. EIS measurements indicating a smaller capacitance for samples coated with the sol-gel in relation to the anodized samples, however chronocoulometry was verified by loading and unloading surface, which indicated a dielectric behavior of the sol-gel, cause it kept the charging load on the establishment of a potential opposite to that applied. The analysis of XRD and AFM confirmed the anodizing action due to the presence of pseudo-boehmite and roughness of the sample, and the appointment of an amorphous region for samples with sol-gel, which had more flat surfaces.