PPGEM https://repositorio.ufpb.br/jspui/handle/tede/4458 2026-04-06T22:20:17Z 2026-04-06T22:20:17Z Silva, David Domingos Soares da https://repositorio.ufpb.br/jspui/handle/123456789/37895 2026-04-02T06:07:14Z 2020-04-14T00:00:00Z

Título: Evaluation of the sigma phase precipitation in duplex stainless steel by nondestructive testing Autor(es): Silva, David Domingos Soares da Orientador: Gomes, Rodinei Medeiros Abstract: Duplex stainless steels (DSS) have a structure composed of α-Fe and γ-Fe in approximately equal volume fractions. Which provides an excellent integration between mechanical properties and corrosion resistance. However, the precipitation of sigma (σ) phase may cause a severe deterioration of these properties, phenomenon known as sigma phase embrittlement. In the present work, the effect of the isothermal aging treatment at 800 °C (temperature in which σ phase can be formed) on metallurgical, corrosion, magnetic and mechanical properties on DSS UNS S31803 was investigated. In addition, two new nondestructive methods for monitoring of sigma phase embrittlement in DSS were proposed and evaluated. The first method is based on the electromechanical impedance (EMI), using piezoelectric sensors. The basic idea of this method is that the increase mechanical stiffness, due to sigma phase embrittlement, will leads to the variation in the EMI signatures. The second method, designated as low-fields magnetic analysis (LFMA) is based on the measurement of magnetic flux density. Once the precipitation of σ phase cause a change in the volume fraction of α-Fe/γ-Fe phases due to α-Fe (ferromagnetic phase) decomposition to precipitate σ (paramagnetic phase). The evaluated techniques present accurate results with high sensitivity and reliability. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2020-04-14T00:00:00Z Sousa, Anderson Aldelyan Ramalho de https://repositorio.ufpb.br/jspui/handle/123456789/37422 2026-01-27T06:05:48Z 2025-03-31T00:00:00Z

Título: Caracterização físico-quimíca do bio-óleo obtido da pirólise do lodo da estação de tratamento de esgoto Autor(es): Sousa, Anderson Aldelyan Ramalho de Orientador: Gomes, Kelly Cristiane Abstract: The Sewage sludge generated in Wastewater Treatment Plants (WWTPs) represents a significant environmental challenge. Pyrolysis emerges as a promising alternative for converting this waste into bio-oil, with energetic potential and industrial applications. This study aimed to evaluate the technical and environmental feasibility of bio-oil obtained from the pyrolysis of sludge generated in WWTPs in Paraíba, Brazil, as a sustainable energy source and industrial raw material. To this end, bio-oil samples obtained from the pyrolysis of sludge from the WWTPs of João Pessoa and Campina Grande, as well as a mixture of both, were analyzed through physicochemical characterizations, thermal stability, and higher heating value (HHV). In addition, a bibliometric and systematic review was conducted to map the scientific production on the subject and identify knowledge gaps. The results showed that the samples exhibit characteristics compatible with liquid fuels, with HHV ranging from 40.09 to 41.50 MJ/kg. Infrared spectroscopy revealed the presence of phenolic compounds and hydrocarbons, contributing to the energy performance. Thermal analyses indicated stability and good performance under different atmospheres. It is concluded that sludge pyrolysis from WWTPs is a viable alternative for energy recovery, contributing to sustainability and environmental management. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2025-03-31T00:00:00Z Nascimento, Meyson Cassio do https://repositorio.ufpb.br/jspui/handle/123456789/37393 2026-01-23T06:07:19Z 2024-05-31T00:00:00Z

Título: Estudo do efeito da adição do elemento prata em ligas quasicristalinas de Al-Cu-Fe em suas propriedades microestruturais Autor(es): Nascimento, Meyson Cassio do Orientador: Cavalcante, Danielle Guedes de Lima Abstract: The advance in research into metallic materials and their alloys has been remarkable in the last two decades, driven by the need to improve characteristics and optimize production costs. In this context, quasicrystals (QC) emerge, metal alloys with long-range ordered structures, but of short periodicity, which have tribological properties similar to those of ceramic materials and prove to be extremely fragile. The introduction of a fourth element into a QC alloy, such as silicon, e.g. stabilises the icosahedral phase, which is aperiodic in all directions. In this study, the impact of the addition of silver on the microstructure of the quasicrystalline alloy Al62,3Cu25,5Fe12,2 was analyzed. The direct addition of silver to the alloy resulted in destabilization of the quasicrystalline phase. To mitigate this, silver was added to replace copper, in the proportions of 0.5%, 1.0%, and 2.5%, resulting in the composition Al65Cu15-xFe12Agx (where x=0, 0.5, 1.0, 2.5, and 10). It was observed that 10% of silver destabilized the quasicrystalline phase, with a predominance of β and Ag2Al phases. With 0.5% and 1.0% silver, the quasicrystalline phase remained stable, despite traces of Ag2Al. The composition with 2.5% silver remained balanced, with icosahedral and Ag2Al quasicrystalline phases stable after 24 hours of treatment. Silver is expected to provide self-lubrication, reducing friction, and antimicrobial action. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2024-05-31T00:00:00Z Melo Neto, Rafael Fernandes de https://repositorio.ufpb.br/jspui/handle/123456789/37352 2026-01-17T06:07:22Z 2025-03-31T00:00:00Z

Título: Análise exergoeconomica da geração de biogás a partir da vinhaça Autor(es): Melo Neto, Rafael Fernandes de Orientador: Santos, Carlos Antônio Cabral dos Abstract: The present study aims to present an exergoeconomic analysis of biogas generation from vinasse, searching in the literature for data on exergy analysis of vinasse biogas combined with data from an economic evaluation of the same biogas. This combination sought to identify optimizations in the process through the exergy costs of the components. Exergy analysis is based on the second law of thermodynamics, highlighting the quality of the energy produced by the thermal system. This analysis is the pillar of the exergoeconomic study. The application of the SPECO method, developed by Valero and Lozano, seeks to quantify the costs of fuels and products generated through the principles of fuel (F) and product (P). The exergoeconomic study analyzes the costs of the exergy and monetary flows of each component of the anaerobic digestion plant. This analysis highlighted the significant costs of the UASB reactor, mainly due to exergy destruction 0.107 R$/s and operating costs 76.74 R$/s. The pump and cooling tower had lower economic impacts, with exergoeconomic factors below 1.2%. The results point to exergy destruction as the main factor for exergy cost, requiring optimization through new technologies or addition of other organic materials. The system is technically feasible, with its economic viability depending on these reductions in exergy losses. Editor: Universidade Federal da Paraíba Tipo: Dissertação

2025-03-31T00:00:00Z