Desenvolvimento de tinta inorgânica de cura fosfática a partir de resíduo de anodização de alumínio

Dissertação apresentada ao Programa de Pós-Graduação em Ciência e Engenharia de Materiais da Universidade do Extremo Sul Catarinense - UNESC, para a obtenção do título de Mestre em Ciência e Engenharia de Materiais.A anodização é um processo eletroquímico que modifica a superfície do alumínio. O objetivo é acelerar a formação de uma a cobertura regular e controlada de alumina, melhorando propriedades como resistência a corrosão, abrasão e isolamento elétrico. Este processo gera grandes quantidades de resíduo que por tratamento adequado pode ser valorizado como matéria prima para utilização em materiais que necessitam de alumínio em sua composição. Neste trabalho foram obtidas tintas inorgânicas a base de fosfato de alumínio utilizando o resíduo do processo de anodização de alumínio (RAA) e matérias primas comerciais como referência. As tintas produzidas foram compostas pelo ligante mono alumínio fosfato (MAF) e pela carga, Al2O3. O RAA foi lavado e usado como hidróxido de alumínio (Al(OH)3) na produção de MAF. O RAA lavado foi calcinado a 1300 e 1500 °C para ser convertido em Al2O3 e ser utilizado como carga. As tintas produzidas foram aplicadas sobre substratos cerâmicos e avaliado o desempenho por ensaio de resistência ao desgaste, pino-sobre-disco. As tintas produzidas com MAF obtido do RAA tiveram desempenho equivalente às tintas produzidas com MAF obtido do hidróxido de alumínio comercial. As tintas produzidas com Al2O3 obtido pela calcinação do RAA 1300 °C apresentaram desempenho inferior. As tintas produzidas com Al2O3 obtido pela calcinação do RAA a 1500 °C apresentaram resultado equivalente ás tintas produzidas com Al2O3 comercial. O RAA calcinado a 1500 °C apresentou área de superfície específica (B.E.T) igual a 1,54 (±0,02) m2/g e o Al2O3 de referência 1,1 m2/g. Em ambos apenas fase alfa-alumina foi detectada por DRX. O RAA calcinado a 1300 °C apresentou B.E.T de 8,25 (±0,03) m2/g e além de fase alfa-alumina, alumina de transição foi detectada. O desempenho inferior do RAA calcinado a 1300 °C pode ser relacionado com a maior reatividade do Al2O3 obtido, que possuí fase de transição da alumina e a maior área de superfície. As analises realizadas por MEV revelaram microtrincas na estrutura das tintas produzidas com RAA calcinado a 1300 °C. Pode ser concluído que é possível produzir tintas inorgânicas a partir do RAA, porém deve ser evitada a utilização de aluminas de maior reatividade como carga.Anodising is an electrochemical process that modifies the aluminum surface. The goal is accelerate the formation of a regular and controlled layer of alumina, improving properties such as corrosion resistance, abrasion, and electrical insulation. This process generates large amounts of waste that by appropriate treatment can be valued as a raw material for use in materials that require aluminum in its composition. In this work, inorganic aluminum phosphate coatings were obtained using waste of anodizing aluminum process (RAA) and commercial raw materials as a reference. The coatings produced were composed by monoaluminum phosphate binder (MAF) and the load Al2O3. The RAA was washed and used as aluminum hydroxide (Al(OH)3) on MAF production. The RAA was washed and calcined at 1300 and 1500 °C to be converted into Al2O3 and used as filler. The coatings produced were applied on ceramic substrates and evaluated the performance by wear resistance, pin-on-disc. The coatings produced with MAF obtained from RAA presented equivalent performance to coatings produced with MAF obtained from commercial aluminum hydroxide. The coatings produced with Al2O3 obtained by calcining the RAA 1300 °C showed lower performance. The coatings produced with Al2O3 obtained by calcination RAA at 1500 °C showed equivalent performance that produced with commercial Al2O3. The RAA calcined at 1500 °C showed a specific surface area (B.E.T.) equal to 1.54 ( ± 0.02) m2/g and the reference Al2O3, 1.1 m2 /g. In either, only alpha-alumina phase was detected by XRD. The RAA calcined at 1300 °C showed a B.E.T of 8.25 (±0.03) m2/g and addition to alpha-phase alumina, transition alumina was detected . The underperformance of the RAA calcined at 1300 °C can be related to the greater reactivity of Al2O3 obtained, which possess transitional alumina phase and larger surface area. The analyzes performed by SEM revealed microcracks in the structure of the coatings produced with RAA calcined at 1300 °C. It can be concluded that it is possible to produce inorganic coating from the RAA, but the use of alumina as filler of higher reactivity must be avoided

Solid-State Luminescence with a Large Stokes Shift in Starch Functionalized with Low-Content ESIPT Dye

Herein, we present the preparation of solid-state photoactive starches with a large Stokes shift, along with the resulting materials. In this investigation, 2-(2′-hydroxyphenyl)benzazole derivatives responsive to intramolecular proton transfer in the excited state (ESIPT) were covalently bonded to the polymeric structure of starch through a reaction involving an isothiocyanate group and the hydroxyl groups of starch. These compounds exhibit absorption at approximately 350 nm, which is related to fully spin- and symmetry-allowed π → π* electronic transitions, and solid-state fluorescence at approximately 500 nm, which features a significant separation between the absorption and emission maxima (~9000 cm−1). Due to the minimal use of fluorophores in functionalized starch preparation, this modification does not affect the original properties of the starch. Finally, photoactive starch-based films with significantly high transparency were successfully produced

Production and Weathering Exposure of Thermochromic Coatings Used as Sensors to Protect Electricity Distribution Systems

Currently, the overheating detection of electric system components is performed using thermal imaging devices, which depend on on-site regulation parameters, require skilled operators and suitable weather conditions. The development and application of innovative technologies to monitor hotspots has highlighted the use of sensors based on thermosensitive materials. In this study, a temperature sensor with thermochromic coating was developed. Thermochromic sensors covered with a varnish layer and nano-titanium oxide, in addition to thermochromic paint, were produced. A 23 experimental design was established to assess the performance of thermochromic sensors under artificial weathering conditions. Color measurements of the coatings were performed using the CIELAB method. Fourier-transform infrared (FTIR), UV-Vis (Ultraviolet-Visible), (thermogravimetric TGA, and Differential Scanning Calorimetry (DSC) analyses were performed on the sensors exposed to photodegradation to detect changes in the thermochromic coatings. The sensors exposed to thermodegradation, and salt spray weathering showed ΔE (total color difference) values below 1.50 points in the presence of TiO2. In comparison, the sensors exposed to photodegradation showed ΔE values above 10 points, and UV-Vis analysis revealed changes in the chemical structure of the coatings. These results demonstrate that the varnish layer and TiO2 can help minimize the degradation effects of temperature, light, and salinity

Resumos concluídos - Engenharia Química

Resumos concluídos - Engenharia Químic

Resumos concluídos - Engenharia de Materiais

Resumos concluídos - Engenharia de Materiai