PPGCEM https://repositorio.ufpb.br/jspui/handle/tede/440 2026-09-25T18:58:33Z 2026-09-25T18:58:33Z Maia, Valéria de Andrade https://repositorio.ufpb.br/jspui/handle/123456789/39188 2026-09-22T06:11:33Z 2025-12-19T00:00:00Z

Título: Produção de fibras hibridas de nylon 66 com cargas minerais via Solution Blow Spinning para reforço de matrizes cimenticias Autor(es): Maia, Valéria de Andrade Orientador: Simões, Thiago Araújo Abstract: The improvement of post-cracking behavior and energy absorption in cementitious matrices has driven the development of small-scale fibrous reinforcements, essential for mitigating the fragility and low toughness inherent in mortars and concrete. Within this technological frontier, this work proposes the production and application of pure and hybrid nylon 66 (PA 66) fibers, containing kaolin or metakaolin, obtained by the Solution Blow Spinning (SBS) technique. Regarding process optimization, the SBS technique demonstrated technical efficiency and economic viability, where adjusted parameters allowed the production of pure nylon 66 fibers with sub-micrometer diameters (average of 162 nm) and smooth morphology. The incorporation of mineral fillers altered the solution rheology, resulting in hybrid nylon 66/kaolin and nylon 66/metakaolin fibers with larger diameters (376 nm and 1.60 µm, respectively) and a rough surface, a desirable characteristic for mechanical locking in the hydrated paste. The incorporation of mineral fillers aimed to mitigate adhesion limitations and promote better fiber-matrix interaction. The produced fibers were added replacing 1% of the mass of Portland cement CPV-ARI. In parallel, the direct addition of metakaolin (1% and 3%) was evaluated to compare the physical fibrous reinforcement with the chemical improvement of the pozzolanic additive. The characterization of the materials involved SEM, FTIR, TG, and XRD. Mechanical performance was evaluated by compression and flexural tensile strength tests at 7 and 28 days, complemented by microstructural analysis. The results showed increased strength for all formulations with fibers. Pure nylon 66 and kaolin-containing composites showed limited performance due to defects and a weak interface. Hybrid nylon 66/metakaolin composites, however, demonstrated more effective reinforcement, associated with synergy between mechanical reinforcement and pozzolanic reactivity. The exclusive addition of metakaolin promoted the greatest increase in strength, resulting in a denser matrix. Microstructural analysis confirmed that the quality of the fiber-matrix interface is crucial in stress transfer, reinforcing the potential of the SBS technique for the development of higher-performance and more durable cementitious composites. Editor: Universidade Federal da Paraíba Tipo: Tese

2025-12-19T00:00:00Z Soares, Clarice Cardoso https://repositorio.ufpb.br/jspui/handle/123456789/38570 2026-07-31T06:35:59Z 2025-08-27T00:00:00Z

Título: Compósitos ferromagnéticos de PDMS e Liga Heusler Ni44Mn44Sn9Cu3 Autor(es): Soares, Clarice Cardoso Orientador: Oliveira, Danniel Ferreira de Abstract: Heusler Ni-Mn-Sn alloys have been widely studied because they present multifunctional properties associated with phase transitions controlled by the magnetic field, such as the metamagnetic shape memory effect, the magnetocaloric effect and exchange polarization. These properties are promising for applications such as magnetic actuators, magnetic refrigeration and high-efficiency sensors. Changing the composition by replacing its components with a fourth element, such as Cu, is an effective way to adapt their properties. However, these materials have limitations such as low machinability, mechanical brittleness and instability of functional properties after processing. To overcome these problems, a strategy involves the production of polymer matrix composite materials reinforced with these metal alloys. In this work, PDMS matrix composites reinforced with Heusler Ni44Mn44Sn9Cu3 alloy particles were produced. The developed materials showed preservation of the polymer chemical structure, thermal stability, reduction of mechanical resistance with the addition of metallic particles, greater flexibility compared to pure Heusler alloys, increase of remanent magnetization and saturation magnetization according to the increase of the alloy content, resulting in improvement of the ferromagnetic response. Thus, the results obtained indicate that the developed composites are favorable candidates for use in flexible devices that require tunable magnetic properties. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2025-08-27T00:00:00Z Martins, Poliana Soares https://repositorio.ufpb.br/jspui/handle/123456789/38564 2026-07-31T06:35:57Z 2025-06-30T00:00:00Z

Título: Caracterização físico-química das argilas caulim (branca) e bentonita (verde) associadas à polpa de acerola (Malpighia emarginata dc) como ativos para o desenvolvimento de uma formulação cosmética facial Autor(es): Martins, Poliana Soares Orientador: Ferreira, Heber Sivini Abstract: There is a growing consumer preference for natural raw materials, such as clays and fruits, in the development of cosmetic products. Clays, composed of minerals, are widely used in cosmetics due to their high adsorption rate, abundance in nature, low environmental impact, low risk of toxicity, high surface area, and excellent ion exchange capacity. Among the most common clays in cosmetics are kaolin (white) and bentonite (green), which offer benefits such as cleansing, adsorption of impurities, toning of the epidermis, hydration, and treatment of dermatitis and acne. Acerola, a fruit rich in vitamin C, has also been widely used in the cosmetics sector for its effectiveness in combating free radicals, in addition to its properties in lightening blemishes, increasing skin elasticity, and photoprotection, due to its high antioxidant potential. The objective of this study was to characterize the physicochemical properties of kaolin (white) and bentonite (green) clays combined with acerola pulp, aiming at their use as active ingredients in a cosmetic facial cream formulation. The clays underwent purification and drying processes via spray dryer, and the acerola fruits underwent pulp removal. Subsequently, they underwent microbiological analysis and were characterized according to their physicochemical properties, revealing a clayey material with a pH above the skin pH, low unit content, fine particle size after purification and drying, and rich in minerals according to XRF analysis. Bentonite presented better results in terms of density, porosity, and flow angle. In the TG and DTA analyses, kaolin showed endothermic peaks, and bentonite showed endothermic and isothermal peaks. The acerola pulp had an acidic pH and high vitamin C content. The clays and acerola pulp showed good application properties in a facial cream formulation with 0.5%, 1.5%, and 3.0% of each active ingredient equally incorporated into the cosmetic. The formulation was subjected to microbiological testing and analyzed for organoleptic, physicochemical, and rheological properties. The cosmetic presented good stability and underwent sensory analysis and in vivo tests approved by the ethics committee. Rheological analysis indicated that the formulation exhibited non-Newtonian pseudoplastic behavior, and the 3% active ingredient concentration best fit the rheological model. In microbiological analyses, the active ingredients did not show bacterial or fungal colony growth. The facial cream, in turn, showed bacterial growth within the limits permitted by law. The facial cream containing clays and acerola pulp obtained promising results in terms of hydration, pores, and skin elasticity. In the sensory analysis, oiliness, firmness, and overall evaluation were the best-rated attributes. In terms of purchasing behavior, it was found that 50% of evaluators would buy the clay cream with acerola. Thus, this study provides relevant information on the use of clay and acerola pulp, demonstrating their benefits for the skin through facial creams containing these active ingredients. This suggests a potential product for application as a facial cream, a promising alternative for the development of innovative, effective, and sustainable cosmetic products. Editor: Universidade Federal da Paraíba Tipo: Tese

2025-06-30T00:00:00Z Nascimento, Jefferson Lira https://repositorio.ufpb.br/jspui/handle/123456789/38555 2026-07-30T06:11:40Z 2026-02-09T00:00:00Z

Título: Avaliação das características termoelétricas e termorresistivas da matriz semicondutora de óxido de zinco dopado com manganês em diferentes concentrações Autor(es): Nascimento, Jefferson Lira Orientador: Torquato, Ramon Alves Abstract: In the current context, scientific and technological development is fundamental to the needs of a modern society, such as information capacity, data speed, energy autonomy, miniaturization of components and equipment, lower production costs, and more efficient systems. In this vision and reality, the world of semiconductor materials plays a fundamental, even essential, role. Therefore, the study of these materials will always have a scientific and technological appeal that attracts the attention of those who conduct research. When dealing with sensing systems and the production of electrical energy, it is something that sparks interest in the results that will be generated. Therefore, in this work we used the zinc oxide (ZnO) semiconductor matrix, which has a wide band gap of ≈ 3,37 eV, so that through the doping process we could evaluate the effect on the thermoresistive and thermoelectric response of this matrix doped with the transition metal manganese (Mn), at concentrations of x = 0,1; 0,2; 0,3; 0,4 and 0,5 mol of Mn+2, in the Zn+2 substitution process, in the Zn1-xMnxO system, using the combustion reaction synthesis route for the production of the systems. The produced systems were calcined, beneficiated, pressed, and sintered at a temperature of 1100 °C at a rate of 10 °C/min. After preparation, their microstructure was analyzed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) with EDS, band gap analysis using Ultraviolet Spectroscopy (UV-Vis), and thermoresistive and thermoelectric responses. The results showed the formation of a second phase, with a dense material whose average particle size increased with increasing Mn+2 concentration. Considering a theoretical value of 3,37 eV for pure ZnO, the band gap width was affected by the addition of the dopant, with the highest value obtained being 2,91 eV for x = 0,3 mol of Mn+2 and the lowest value found being 2,72 eV for x = 0,5 mol, but preserving the semiconductor characteristic even with doping. In the thermoresistive results, a thermistor with a negative thermal coefficient (NTC) was produced, where the minimum β found was at x = 0,1 mol of Mn+2 with 4334K for the 75°C to 100°C test, and the best for x = 0,2 mol Mn+2 resulting in 6396K in the 50°C – 100°C test. Therefore, the results obtained proved satisfactory for this initial study, where we were able to produce high-quality NTC thermistors, reinforced by the ln(ρ) x 1000/T(K) graph, which also demonstrated specific temperature ranges within those analyzed, in which β exceeded commercial values. In the thermoelectric results, we obtained values between -835.53 μV/°C and -57.62 μV/°C and -72.02 μV/°C to - 1.02 μV/°C for pure ZnO doped with 0.5 mol of Mn at temperatures of 50°C and 100°C, respectively. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2026-02-09T00:00:00Z