INFLUENCE OF WEATHERING ON THE ELECTROCHEMICAL AND MORPHOLOGICAL CHARACTERISTICS OF CEO2 AND CEO2:V2O5 SOLGEL THINFILMS
Rótulo Weathering, Electrochromism, Smart, window, CeO2, V2O5
ResumoIn order to obtain a better control on the temperature and lighting for residential and commercial buildings, different technologies have been created. The objective is to reduce costs related to electricity in the use of air conditioners and/or artificial lighting. One of these technologies are the smart windows, devices that emerge as great alternatives, due to the characteristic of changing coloration as desired, reducing the transmission of radiation and light due to the redox reactions that occur in the chemical species involved. These devices are based in the electrochromism, a property characterized by the reversible change of color when submitted to an external potential and are composed of several layers with different functions. The objectives of the work are to produce films of CeO2 and CeO2:V2O5 that work as one of these layers, analyze its properties, submit it to a weathering process and then reevaluate these properties. To prepare the sol of CeO2, cerium chloride heptahydrate, citric acid and ethyl alcohol were stirred for 30 minutes. For the CeO2:V2O5 sol, vanadium isopropoxide was added to the first sol and stirred for 10 minutes. The sols were deposited through the spin-coating technique in a fluorine tin oxide (FTO) conductive glass substrate and then submitted to a heat treatment during 30 minutes at 450 °C. A Climate Aging Chamber UV Accelerated Weathering Tester were used to simulate the natural exposure of the materials to the environment and weathering process. The films were analyzed before being placed in the chamber and then reanalyzed after the equivalent incubation period. The cyclic voltammetry presented a greater area for the doped film, which means that there are more ways for the movement of the ions. Through the chronocoulometry, it was possible to understand the amount of charges that were inserted and extracted in the films. The reanalyzes showed some variations in these values during the whole process, but at the end of the 900 simulated days, the CeO2:V2O5 still presented some interesting values for this application, slightly lower than the initial ones, but not significantly. The Electrochemical Impedance Spectroscopy were also performed in order to understand the process of charge transfer in the film. The Nyquist plot presented curves with the angulation close to 45°, suggesting that this process is through diffusion. The morphological properties were evaluated through Scanning Electronic Microscopy and presented a reduction on the degradation and on the exposure effects when doping the film. It is possible to conclude that even after 2.5 years of exposure to the weathering, the material continues performing well and presenting promising electrochemical properties, which is important for the proposed application of this type of material.
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BALBONI, R.; MONTEIRO CHOLANT, C.; USZACKI KRÜGER, L.; MOREIRA JAVIER LEMOS, R.; ANDREAZZA, R.; ANTONIO OROPESA AVELLANEDA, C. INFLUENCE OF WEATHERING ON THE ELECTROCHEMICAL AND MORPHOLOGICAL CHARACTERISTICS OF CEO2 AND CEO2:V2O5 SOLGEL THINFILMS. Anais do Salão Internacional de Ensino, Pesquisa e Extensão, v. 12, n. 2, 20 nov. 2020.