Avaliação da influência dos parâmetros de fabricação e da adição de camadas antirreflexivas em filmes absorvedores de Cr-Cr2O3 obtidos via magnetron sputtering

• Autor(a) principal: Galvão, Gabriela Oliveira
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/24496
• topic: Energia solar; Filmes absorvedores; Magnetron sputtering; Cromo negro; Sílica; Alumina; Solar energy; Absorbing films; Black chromium; CNPQ::ENGENHARIAS::ENGENHARIA MECANICA

The growth in the field of solar energy faces several barriers due to its high cost and operational limitations of energy harvesting systems. An alternative to optimize the performance of solar thermal conversion systems comes from the application of selective surfaces on the absorber plates. This work proposes to produce absorbent films based on chromium (Cr-Cr2O3) on stainless steel substrates with different surface treatments (electropolished and cleaned with a degreasing bath) and to evaluate the effect of adding anti-reflective layers (AR) of silica (SiO2) and alumina (Al2O3) on their optical properties. The black chromium films were produced by the Magnetron sputtering technique from the variation of three deposition parameters (working distance, power and time). After their manufacture, the films obtained with the parameters that provided the highest absorbances, which were above 70%, were covered with the anti-reflective layers of SiO2 and Al2O3, separately. The samples were submitted to the cross-hatch adhesion test and characterized using UV-vis Spectrophotometry, Fourier Transform Infrared Spectroscopy (FTIR) and Optical Profilemetry. The results showed that the black chromium coatings produced contributed to a significant increase in the level of solar absorption in relation to the non-deposited substrate, mainly in those deposited on the cleaned substrate with a degreasing bath. Regarding the deposition parameters, the highest working power (100 W) and the shortest deposition time (30 minutes) provided films with the highest absorbances for both working distances (110 and 150 mm). The black chromium films selected showed absorbance levels between 70.87% and 74.31%, with small standard deviations, indicating high reproducibility of the deposition technique. The inclusion of anti-reflective coatings kept the films' absorptive properties practically stable, but caused a significant reduction in the emissivity of the analyzed coatings, with silica providing the greatest reduction at all analyzed temperatures. The estimated band gaps had values ranging from 1.18 to 4.74 eV. The highest band gap values are associated with the presence of Cr-Cr2O3. Fourier Transform Infrared Spectroscopy (FTIR) showed characteristic bands of vibration of Cr2O3 and Si-O-Si bonds. The results of Optical Profilemetry indicate that the absorbance of the coatings was favored by the higher roughness of the substrates cleaned with a degreasing bath. The adhesion test showed excellent adhesion of the films to the substrate.