http://repositorio.ufc.br/handle/riufc/29278 2026-04-09T00:46:07Z 2026-04-09T00:46:07Z Mattos, Samuel Sousa http://repositorio.ufc.br/handle/riufc/85082 2026-03-05T16:51:10Z 2026-01-01T00:00:00Z

Título: Glicoaldeído no meio interestelar: proposta de mecanismo químico de formação e análise teórica acerca de sua viabilidade termodinâmica Autor(es): Mattos, Samuel Sousa Abstract: Astrochemistry is a scientific field that stands out for the identification and study of chemical processes in the interstellar medium (ISM), with one of its main objects of study being complex organic molecules, which are generally associated with biomolecule synthesis processes. With this in mind, glycolaldehyde (GA) becomes the focus of this work due to its possible connections to reaction processes associated with prebiotic chemistry. Furthermore, the precursor used for a possible route to the synthesis of GA was ethanol, an alcohol already detected in the ISM and with a possible abundance correlation with GA itself. Thus, a four-step reaction mechanism was proposed, and the energetic feasibility of the proposal was analyzed through thermodynamic parameters of the reactions. These data were obtained using the theoretical methods DFT and CCSD(T), based on the M06-2X functional and the aug-cc-pVTZ basis set. The combined level of theory was denoted as CCSD(T)//M06-2X/cc-pVTZ. Based on this level of theory, several types of calculations were performed in order to obtain thermodynamic parameters for the system. The combined level of theory demonstrated superiority in the results, given the effectiveness of CCSD(T) for systems involving weakly localized radicals. Thus, based on the analysis of the thermodynamic data, steps 1, 2.1, and 4 exhibited considerable energy barriers along with an endothermic character for the reactions, while step 3, in addition to being exothermic, maintained a lower barrier than the other steps. Furthermore, step 2 did not yield results due to the inefficacy of the optimizations of the proposed stationary states. Therefore, in view of the thermodynamic data, the considered mechanism, and the extreme conditions employed, the theoretical analysis of the synthesis of glycolaldehyde from ethanol resulted in the infeasibility of the process. Tipo: TCC

2026-01-01T00:00:00Z Sousa, Samile Karen de Oliveira http://repositorio.ufc.br/handle/riufc/85081 2026-03-05T16:45:20Z 2026-01-01T00:00:00Z

Título: Avaliação do desempenho do formato de 2-hidroxietilamônio como inibidor de corrosão acelerada por escoamento (FAC) em aço carbono Autor(es): Sousa, Samile Karen de Oliveira Abstract: Flow-Accelerated Corrosion (FAC) represents a critical challenge for the integrity of carbon steel pipelines in the oil and gas sector, with the application of corrosion inhibitors being one of the primary methods employed for its mitigation. This work evaluated the performance of the protic ionic liquid (PIL) 2-hydroxyethylammonium formate as an inhibitor for 1020 carbon steel in a saline medium, consisting of a 3.5% NaCl solution under continuous flow. For the experiments, a closed-loop system (flow loop) with one-inch PVC piping was used, operating at a flow rate of 650 L/h. Tests were conducted at temperatures of 25, 35, 45, and 55 °C, at intervals of 4, 8, and 12 h. The inhibitor's efficiency at a concentration of 500 ppm and the assessment of surface wear were investigated through gravimetric techniques and Computational Fluid Dynamics (CFD), complemented by optical microscopy (OM) and X- ray diffraction (XRD). The system's hydrodynamics proved to be a determinant factor in the degradation rate; CFD simulations indicated that samples subjected to parallel flow experienced higher shear stresses, accelerating both mechanical and chemical wear. The inhibitor showed low resistance to shear stress at ambient temperatures, with efficiencies lower than those reported in static regimes. The best efficiency, 70.14%, was achieved at 45 °C, possibly due to a transition in the adsorption mechanism from physical to chemical, making the protective film more robust. XRD analysis identified lepidocrocite as the majority phase and evidenced that the inhibitor favored the formation of goethite, a more stable corrosion product. It is concluded that, although 2-hydroxyethylammonium formate demonstrates protective potential, its effectiveness under constant flow is highly dependent on temperature and the stability of the film formed, reinforcing the need for operational condition optimization to enable its use in dynamic industrial systems. Tipo: TCC

2026-01-01T00:00:00Z Monteiro, Rayssa Gabrielly Freitas http://repositorio.ufc.br/handle/riufc/85080 2026-03-05T16:44:18Z 2026-01-01T00:00:00Z

Título: A influência da adição de cobre no processo corrosivo do aço duplex 2205 Autor(es): Monteiro, Rayssa Gabrielly Freitas Abstract: This study aimed to evaluate the influence of different copper contents on the corrosion behavior of duplex stainless steel 2205 when exposed to sodium chloride–containing media under different pH conditions, since the literature indicates that the effect of copper on the corrosion resistance of this material does not exhibit a consistent trend as a function of its content. The analyzed samples consisted of duplex stainless steel 2205 without copper addition and with 2 wt.% and 4 wt.% Cu additions. The investigation was carried out at room temperature (25 °C) using electrochemical techniques, including open circuit potential (OCP) monitoring, linear potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), as well as optical microscopy analyses for metallographic surface evaluation after the tests. The results indicated that decreasing pH increased the aggressiveness of the environment for all samples, promoting shifts in the potential toward more negative values and intensifying localized corrosion. The addition of 2 wt.% Cu proved to be beneficial, especially under more acidic conditions, showing higher electrochemical stability, more noble corrosion potential values, and higher impedance modulus at low frequencies, which are associated with increased stability of the passive film. In contrast, the sample containing 4 wt.% Cu did not show a proportional improvement in corrosion performance, suggesting that higher copper contents may compromise material stability. Overall, the study exhibited a qualitative and quantitative approach, allowing the establishment of relationships between copper content, medium acidity, and the corrosion behavior of duplex stainless steel 2205, providing technical support for the selection and application of this material in aggressive industrial environments. Tipo: TCC

2026-01-01T00:00:00Z Nascimento, Alice Maria Pereira do http://repositorio.ufc.br/handle/riufc/85079 2026-03-05T16:28:26Z 2026-01-01T00:00:00Z

Título: Síntese e caracterização preliminar de um nanocomposto a base de resíduos da extração do suco dos frutos do cajueiro Autor(es): Nascimento, Alice Maria Pereira do Abstract: The large volume of residues generated by the cashew agroindustry, especially the peduncle bagasse rich in mineral elements and organic structures, highlights the need for strategies that promote its reuse and valorization. In this context, this study aimed to synthesize and preliminarily characterize a nanocomposite based on fibers from cashew fruits, targeting its potential application as an agricultural nanofertilizer. Carbon quantum dots were obtained through hydrothermal synthesis using cashew bagasse powder and citric acid as carbon sources, ethylenediamine as a passivating agent, and Hoagland nutrient solution as the reaction medium and as a source of micro- and macronutrients for plants. Material characterization involved mineralogical, gravimetric, and spectroscopic analyses, including ultraviolet–visible absorption spectroscopy, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. The results confirmed the formation of carbon quantum dots with fluorescent behavior, exhibiting characteristic absorption and emission bands, as well as the presence of oxygenated and nitrogenated functional groups on the nanoparticle surface. The obtained quantum yield was 15.91, which is consistent with values reported for biomass-derived materials. The mineral composition of the residue revealed the presence of macro- and micronutrients relevant to plant development. Therefore, the synthesized nanocomposite demonstrated potential for agricultural application, combining nanostructured properties with the valorization of agroindustrial residues, in alignment with the principles of sustainability and green chemistry. Tipo: TCC

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