https://repositorio.ufu.br/handle/123456789/5166 2026-08-31T09:28:18Z https://repositorio.ufu.br/handle/123456789/49829 Title: Análise térmica e óptica de íons de Nd e Yb em matriz PANK e seus efeitos para aplicações ópticas inovadoras Abstract: The present work employs thermoluminescent methodologies applied to a phosphate glass (PANK) matrix doped with Nd³⁺ and Yb³⁺ rare-earth ions, aiming to determine the thermo-optical properties of the system, whose concentrations, in weight percentage, were systematically varied according to the xNd (4–x)Yb ratio, with x = 0, 1, 2, 3, and 4. The experimental analyses consisted of investigating the excitation and de-excitation processes of the 4f electrons of the dopant ions through measurements of the luminescence peak, the emission ratio of each band, and the de-excitation lifetime. The obtained results enabled the evaluation of luminescence dynamics, energy transfer processes between the ions, the enhancement of emissive bands as a function of temperature variation, and the identification of potential technological applications of the material. Among the employed techniques, absorbance, photoluminescence (PL), and average lifetime measurements are highlighted. 2026-05-22T00:00:00Z https://repositorio.ufu.br/handle/123456789/49581 Title: Estudo de geração de vapor de água mediado por folhas de grafeno oxidado e grafeno oxidado reduzido Abstract: This work investigates photothermal conversion and steam generation in nanofluids based on graphene oxide (GO) and reduced graphene oxide (rGO), obtained via reduction with L-ascorbic acid (ALA) and palladium chloride (PdCl2). The study focused on the correlation between modifications in the material's electronic and morphological structure and its thermal transport and optical absorption properties. Characterization via electron microscopy, Raman spectroscopy, and UV–Vis indicated that PdCl2 promotes the restoration of the graphitic lattice and sheet stacking, whereas ALA tends to keep the sheets more separated, resulting in a less compact morphology. Thermal Lens measurements revealed non-monotonic behavior of thermal diffusivity regarding the dispersed phase concentration: a reduction in diffusivity was observed at low concentrations relative to the base fluid, followed by an increase at higher concentrations. Although the exact causes of this behavior require further investigation, the data suggest a complex interaction between heat transport in the solvent and the presence of the nanostructures. In evaporation tests, the highest efficiencies (up to ∼70%) were not associated solely with the highest degree of structural ordering, but rather with hybrid samples combining high optical absorption with moderate thermal diffusivity, which favors the localization of thermal energy at the liquid-vapor interface. The results demonstrate that controlling aggregation and optical properties is crucial for optimizing solar-thermal energy conversion systems. 2026-02-19T00:00:00Z https://repositorio.ufu.br/handle/123456789/49576 Title: Permeabilidade seletiva de água e metanol através de filmes ultrafinos de rGO/Polímero: uma investigação computacional Abstract: The search for clean and sustainable energy sources, driven by the growing energy demand and the problems caused by the use of fossil fuels, poses the challenge of developing technologies capable of replacing the polluting energy matrix (1). In this context, the Direct Methanol Fuel Cell (DMFC) stands out as an alternative, non-intermittent, and portable energy source, with low 𝐶𝑂2 emissions, no release of other polluting gases, and the ability to operate under conditions close to room temperature (2). Reduced graphene oxide (rGO) wrapped with poly(styrene sulfonate) (PSS) leads to the formation of a stable hybrid material (GPSS). This composite enables the fabrication of ultrathin films with promising barrier properties for DMFC applications, aiming to prevent methanol crossover poisoning, one of the major challenges of this technology (3). Experimental evidence shows that polymer electrolyte membranes of DMFCs coated with ultrathin GPSS-based films exhibit a significant reduction in methanol permeation and an increase in the cell’s power density. In this context, the objective of this work was to study the mechanism behind the methanol barrier provided by GPSS, which still allows the permeation of water and protons (4). To that end, classical Molecular Dynamics simulations were employed to investigate the structural and dynamic properties of GPSS at different polymer ionization fractions in a solvent composed of water, methanol, and hydronium. Regarding structural properties, the influence of the sulfonation fraction on the self-assembly of the layered film was discussed, including its effect on the PSS conformation and the distribution of rGO sheets, as well as the nature of the PSS–rGO interactions. As for the dynamic properties, the impact of GPSS structure on solvent diffusion was analyzed, and the mechanisms leading to the selective diffusion of methanol were elucidated. 2025-10-01T00:00:00Z https://repositorio.ufu.br/handle/123456789/49503 Title: Alunos com altas habilidades e superdotação (AH/SD): considerações sobre a afetividade e o ambiente escolar 2026-08-05T00:00:00Z