http://repositorio.ufc.br/handle/riufc/494 Thu, 09 Apr 2026 01:05:52 GMT 2026-04-09T01:05:52Z http://repositorio.ufc.br/handle/riufc/68318 Título: The effect of copper addition on the corrosion resistance of cast duplex stainless steel Autor(es): Lima, Hillane Mirelle Lopes Ferreira de; Tavares, Sérgio Souto Maior; Martins, Marcelo; Araújo, Walney Silva Abstract: In this study, the effects of the addition of 3.01% Cu on the corrosion behaviour of cast duplex stainless steel aged for 1 h at different temperatures between 450 and 600 °C was investigated by electrochemical tests in 0.6 M NaCl, 0.3 M H2SO4 and 0.6 M NaCl + 0.3 M H2SO4. A short ageing time increases the hardness and mechanical resistance of the Cu-containing steel by precipitation hardening. Potentiodynamic polarization and electrochemical impedance spectroscopy results show that the effect of Cu addition depends on the media studied. In addition, critical pitting temperature (CPT) measurements revealed that steel with 3.01% Cu has a lower pitting corrosion resistance. On the other hand, for both steels, the short time ageing caused a slight increase in CPT values. Tipo: Artigo de Periódico Tue, 01 Jan 2019 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/68318 2019-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/68317 Título: Análise do uso de resíduo da siderurgia para aplicação em cerâmica vermelha através da caracterização química e mineralógica Autor(es): Silva, Laís Cândido da; Barreiras, Alessandra Farias Formiga Queiroga; Albuquerque, José Silvio Veras; Medeiros, Samuel Lucas Santos; Nogueira, Ricardo Emílio Ferreira Quevedo; Ferreira, Hilder Caldas; Ferreira, Marcos Vinícius da Silva; Rios, Maria Alexsandra de Sousa Abstract: The chemical composition of ceramics has a deep impact on our understanding of their physical and chemical properties. This work performed a chemical and mineralogical characterization of clay mixtures with incorporation of a residue from the steel industry. The clay mixtures could be used in the brick production. Two types of clays were mixed with the proportion of 1:1 and the residue were incorporated with the proportions of 5%, 10%, 15%, and 20%. Each material had their chemical composition analysed before the burning step. Five specimens were used to analyse their mineralogical composition after the burning step at the temperature of 800 °C. The tests performed to make the characterization were: X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). The XFR analysis showed that the main components of the clays are the silicon oxide (SiO2) and the aluminium oxide (Al2O3), and for the residue, the main components are the iron oxides, represented by iron content (T-Fe). The XRD analysis showed the quartz as the most abundant mineral in clays, but that hematite, the most abundant mineral in the residue, appeared more as the amount of residue increased in the sample. Thermal Analysis confirmed the expected peaks in clays and identified an exothermic reaction in the sample with residue. The increase in the percentage of residue caused changes in the chemical composition of the samples, however, these variations were not remarkable, which suggests the red clay industry could add the residue in its production. Tipo: Artigo de Periódico Fri, 01 Jan 2021 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/68317 2021-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/68316 Título: Double-layer technique for welding subsea joints without post welding heat treatment Autor(es): Oliveira, George Luiz Gomes de; Miranda, Hélio Cordeiro de; Miranda, Edvan Cordeiro de; Pinheiro, Pedro Helton Magalhães Abstract: Welded joints for subsea systems are usually buttered with a nickel alloy, heat-treated and then joined together. Although the majority of these joints have been successful throughout their service, some have suffered catastrophic failure, leading to investigations into the possible causes. The use of heat treatment has been considered the primary cause for failure in this type of joint. The main objective of this article is, with background on the methodology used on Double-Layer Controlled Deposition Technique – DL-CDT, along with the LPTS decision diagrams, to determine the relations between the buttering parameters that allow the welding of subaquatic joints, and the low need for heat treatment. MIG single-bead-on-plate welding was executed on samples of AISI 8630M steel. The welded samples were submitted to metallographic analyses of their geometric and microstructural characteristics and the confection of decision diagrams. Among the 200 possible relationships between the buttering parameters, only one presented positive gaps over all criteria. Grain refinements were observed in the HAZ of joints buttered for the parameters approved by the decision diagrams, while for the joints submitted to the Post Welding Heat Treatment (PWHT) peaks of microhardness on the buttering interface were found, which may result in fragilization of that region. Tipo: Artigo de Periódico Sat, 01 Jan 2022 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/68316 2022-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/68315 Título: Caracterização mecânica e morfológica de fibras de coco tratadas superficialmente para utilização como reforço em polímeros Autor(es): Nunes, João Vitor da Silveira; Silva, Edson Xavier Batista da; Miranda, Matheus Henrique Pires; Rios, Alexandre de Souza; Deus, Ênio Pontes de Abstract: Due to the environmental issue, the demand for materials that use more natural and renewable resources increased, such as natural fibers reinforced polymers. Surface treatments are performed for better adhesion of the fiber to the polymer matrix, the most common is mercerization through NaOH solution. Coconut fiber was analyzed under four conditions: varying between treated and untreated, oven dried and naturally dried. Then they were analyzed by tensile test, scanning electron microscopy (SEM) and x-ray tomography to study the mechanical and morphological characteristics and observe the adhesion to the polymer. After the chemical treatment, lignin and hemicellulose were removed from the fiber surface. In the treated and dried fibers, micro-cracks appeared that could compromise the mechanical properties. By processing the images of the fiber cross-sections, an effective area between 39.6% and 43.3% was obtained. For fibers below 300 µm, the tensile strength converges to 20 to 60 MPa and the modulus of elasticity between 1 and 3 GPa. The treatments increased the tensile strength and modulus of elasticity of the fibers, contributing to the use of coconut fiber as reinforcement in polymers. Tipo: Artigo de Periódico Sat, 01 Jan 2022 00:00:00 GMT http://repositorio.ufc.br/handle/riufc/68315 2022-01-01T00:00:00Z