Programa de Pós-Graduação em Ciência e Engenharia de Materiais - PPGCEM/Ananindeua

URI Permanente desta comunidadehttps://repositorio.ufpa.br/handle/2011/12420

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Acesso aberto (Open Access)
Avaliação da eficácia dos óleos essenciais das especies piper divaricatum e eugenia caryophyllus como inibidores de corrosão em aço carbono
(Universidade Federal do Pará, 2023-07-13) MONTEIRO, Heloise Leal; PAULA, Marcos Vinicius da Silva; http://lattes.cnpq.br/7538211324097974; MAIA, Ana Áurea Barreto; http://lattes.cnpq.br/0820112425394964; https://orcid.org/0000-0002-1880-1442
This research reports the evaluation of essential oils (EOs) such as those from the plant Piper divaricatum and Clove (button) Eugenia caryophyllus, as green corrosion inhibitors in metallic materials precisely in this work, carbon steel, these oils being considered environmentally sustainable. Corrosion tests were carried out in corrosive media such as 1M HCl and 3.5% NaCl, the concentrations used for both essential oils were 0.5g/L; 1g/L; 2g/L and 4g/L, for periods of time such as 24h and 7 days. The method used to evaluate the efficiency of the oils was gravimetric (weight loss). The Scanning Electron Microscopy technique of the field emission gun type (SEM-FEG) was conducted to investigate the surface of the specimen, while its chemical composition was obtained through Electron Dispersion Spectroscopy (EDS). In this work, several aspects were discussed, such as the efficiency in relation to the time exposed to the test specimen to corrosive media and factors such as the adsorption isotherm of the oils on the metal surface, in addition to calculations of the corrosion rate of the test specimens in the absence and presence of inhibitors and their relationship with the oil concentrations used. The studies indicated that the essential oils of Piper divaricatum and Clove (Eugenia caryophyllus) showed excellent results in an acid medium of up to 98.3% for the concentration of 2g/L of Piper divaricatum EO in 24h, and 89.5% for the concentration of 1g/L of Eugenia caryophyllus EO in 7 days. In the neutral medium, the highest percentages of inhibition were 61.1% for the concentration of 0.5g/L of EO from Piper divaricatum in 24h, and 83.3% for the concentration of 1g/L of EO from Eugenia caryophyllus in 24h. the isotherms of the oils followed the Langmuir adsorption model, where both oils adsorbed on the metal surface, the best results of isotherms were for the acid medium, for the neutral medium due to the high variability of the data it was not possible to establish a consistent correlation. In view of the proposed results, it was possible to conclude that the essential oils of P. divaricatum and E. caryophyllus have the potential to be used as corrosion inhibitors mainly in an acid medium, thus providing new alternatives in order to reduce the toxicity of this process in comparison to inhibitors already on the market.
Acesso aberto (Open Access)
Caracterização do tecido fibroso de tururi e avaliação de propriedades mecânicas de compósitos de matriz poliéster reforçados com tecido fibroso de tururi
(Universidade Federal do Pará, 2023-01-30) SANTOS, Avener Gleidson Andrade; CÂNDIDO, Verônica Scarpini; http://lattes.cnpq.br/8274665115727809; https://orcid.org/0000-0002-3926-0403
In recent decades, the search for materials with high mechanical performance and that are in accordance with sustainability requirements has become increasing. In the context of sustainability, the United Nations (UN) established in 2015 the Sustainable Development Goals (SDGs), in order to guide the paths to sustainable development. The use of waste to produce new materials is beneficial, because the use of these materials represents a solution for environmentally friendly disposal, thus covering the requirements established by the SDGs. The use of natural fibers in the production of new materials has increased significantly in the last decade. The use of natural fibers as reinforcement in polymer matrix composites is already well established. This is due to the fact that some fibers have high mechanical performance and good thermal stability, two highly attractive properties in composite materials. Composites reinforced with natural fibers have a vast field of application, and can be used in civil construction, aerospace, and automotive industries, among others. In this scenario, the use of tururi fabric as a reinforcement agent in composites of polymeric matrix emerges as a viable alternative for sustainable disposal of this waste coming from the harvesting stage of its fruits. Thus, this study aims to characterize the tururi fibrous tissue by optical microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis and Fourier transform infrared spectroscopy (FTIR), as well as to determine physical properties such as density, moisture content and weight. The composites were produced using a 2.5, 5.0 and 7.5% by mass percentage of reinforcement. Additionally, tensile, flexural and charpy impact tests were performed. The characterizations revealed that the tururi fibrous tissue is composed of fibers of various diameters and has regions of bifurcation, indicating that the tissue can act in different ways when incorporated as reinforcement. The density, moisture content and weight had average values of 1.17 g/cm3, 16.58% and 146.61 g/m2, respectively. The thermal analysis revealed good thermal stability for the tururi fabric. The mechanical tests pointed out that as the incorporation of reinforcement occurred, the composites tested in traction had a loss of resistance, presenting a loss of 15MPa in relation to the matrix. When requested in flexion the composites reinforced with up to 2.5% showed better mechanical performance, with values of 63.9 MPa. The impact test revealed that the energy absorption capacity increased by 371% compared to the matrix, which indicates that the fabric acted as a good reinforcement agent.

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