BDTD - Biblioteca Digital de Teses e Dissertações
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Master Thesis Análises comparativas de fios em blendas contendo uma nova fibra de origem animal com algodão e poliéster(Universidade Federal do Rio Grande do Norte, 2025-11-17) Assunção Neto, Leonel; Nascimento, José Heriberto Oliveira do; https://orcid.org/0000-0001-6804-2854; http://lattes.cnpq.br/7033735079037677; http://lattes.cnpq.br/1520101377305302; Silva, Francisco Claudivan da; http://lattes.cnpq.br/5316555734731599; Morais, João Paulo Saraiva; https://orcid.org/0000-0002-2190-248X; http://lattes.cnpq.br/4050364568559473; Silva, Kesia Karina de Oliveira Souto; https://orcid.org/0000-0002-9705-6750; http://lattes.cnpq.br/4712628443097348This study investigates the use of fishing waste from the flying fish (Hirundichthys affinis), specifically the filaments involved in the production of roe—known as Tobiko—as a new animal-based textile fiber, referred to in this work as Sea’s Silk (SS fiber). The research presents comparative analyses between yarns produced with 100% of the new fiber and its respective blends with cotton (CO), polyester (PES), and their mixtures in different proportions. morphological, chemical, physical, and mechanical analyses were performed, with emphasis on twist, tensile strength, elongation, and yarn count, as well as FTIR, DRX, and TG, in order to compare the performance of yarns produced from the new fiber with already established fibers, in addition to blended yarns. The results showed that, although pure SS fiber has lower strength and uniformity, its blends—especially with polyester—revealed significant improvements in mechanical properties, as well as good elasticity performance. The study concludes that SS fiber is a viable and sustainable alternative for the textile industry, with the potential to add value to a currently underutilized production chain. Furthermore, the use of the fiber offers a sustainable reuse alternative for what was previously an important fishing waste with no added value.Master Thesis Obtenção e caracterização de uma nova fibra natural derivada de resíduo industrial pesqueiro(Universidade Federal do Rio Grande do Norte, 2025-02-24) Maurício, Pedro Paulo Assunção Pereira; Nascimento, José Heriberto Oliveira do; https://orcid.org/0000-0001-6804-2854; http://lattes.cnpq.br/7033735079037677; http://lattes.cnpq.br/4442737668311796; Silva, Francisco Claudivan da; http://lattes.cnpq.br/5316555734731599; Almeida, Raphael Lucas Jacinto; https://orcid.org/0000-0001-7232-2373; http://lattes.cnpq.br/0056534203066666; Araújo, Rubens Capistrano de; http://lattes.cnpq.br/2544026059947892The search for alternative and environmentally friendly textile materials that meet the goals of the UN 2030 agenda for both processes and products has become increasingly frequent in recent years. Therefore, using upcycling to evaluate the potential of industrial waste in obtaining value-added textile materials is one of the most promising paths in scientific research. Thus, this research aims to analyze the potential of a new natural textile fiber, derived from industrial fishing waste, as a promising option for the technical and clothing textile segment. And with the specific objective of developing innovative products in yarn and fabric structures. Structural (XRD, FT-IR), RAMAN, thermal (TGA/DTA) and morphological analyses by SEMFEG, in addition to Classifiber, were performed. A resistance test in an acidic environment was performed, which revealed a resistance superior to that of silk and wool. The characterization of the fiber revealed, in comparison with other natural protein fibers, such as wool and silk, significant similarities, including the Amide I, II and III bands present in the three fibers, in addition to the presence of the chemical elements C, N, O and H. The material then underwent a detergent wash, followed by unraveling through the carding process. After this process, the carded material was subjected to ribbon formation and then to the spinning process. The strength and elongation tests performed on the produced yarn indicated an elasticity of 33% and a tenacity of 3.02 cN/Tex. From the yarn obtained, a mesh with a grammage of 890 g/m² was produced. The thermal insulation test performed on the mesh showed a thermal conductivity of 0.036 W/(m.K), suggesting its potential for applications in professional thermal insulation textiles, both for coatings and clothing. The results obtained demonstrate the great potential of this new natural textile fiber derived from industrial fishing waste. The combination of its mechanical, thermal and chemical properties demonstrates its viability for the production of innovative and sustainable yarns and fabrics. This opens up a new possibility for the use of natural and recycled materials, contributing to innovation and sustainability in the textile industry.Master Thesis Frequency-selective radome absorbers based on interdigital resonators for radar cross section reduction(Universidade Federal do Rio Grande do Norte, 2024-08-26) Macilon, Reilian da Silva; D'Assunção, Adaildo Gomes; http://lattes.cnpq.br/4159638862269940; http://lattes.cnpq.br/0944598472324151; Mendonça, Laercio Martins de; Silva Neto, Valdemir Praxedes da; D'Assunção Júnior, Adaildo Gomes; Silva, Jefferson Costa eIn the midst of increasing advances in the detection capability of modern radar systems, stealth technology aims to reduce the radar cross section (RCS) of a platform, making it difficult to detect. Among the principles on which stealth technology is based, active systems have stood out because of the various advantages they present. Due to their spatial filtering characteristics, frequency-selective surfaces (FSSs) have been widely explored as active systems. Considering the strong out-of-passband reflections in various directions, bandpass FSSs can significantly reduce monostatic RCS, however they can cause large bistatic RCS. In this context, a new structure, called frequency-selective radome absorber or frequency-selective rasorber (FSR), has attracted the attention of researchers in recent years. This type of structure combines the design of a bandpass FSS with a resistive absorber FSS, to obtain two absorption bands (A) located on both sides of a transmission band (T), also known as absorption-transmission-absorption (A-T-A). Therefore, it is capable of reducing out-of-passband reflections in other directions. In this work, two dual-polarization A-T-A FSRs based on interdigital resonators (IR) are proposed, whose lossy FSS designs feature elements with four incorporated resistors and different layouts; split-ring and crossed dipole. The two rasorbers presented provide good operational bandwidth, and have passbands around 9.7 GHz and 4.78 GHz, whose minimum insertion losses (IL), at normal incidence, are 1.0 dB and 0.77 dB, respectively. The equivalent circuit models (ECM) for the proposed FSRs are presented with the aim of explaining the parallel resonance in each case. The rasorber prototypes are fabricated with low-cost FR4 substrate in both layers, and measured for demonstration. The results are very coherent when compared to those obtained in the simulations. Due to their symmetries, the presented FSRs have good angular stability. Therefore, it appears that the proposed rasorbers are capable of reducing the RCS of communication systems operating in different bands, contributing to making them stealthy. Finally, performance comparisons with other FSRs implemented with parallel resonance in previous works are presented.Master Thesis Seaweed cosmetics: análise do potencial de um modelo de negócios centrado em cosméticos de algas marinhas(Universidade Federal do Rio Grande do Norte, 2024-07-19) Mariano, Luciana de Almeida; Lima, Adley Antonini Neves de; Carvalho, Zulmara Virginia de; https://orcid.org/0000-0002-3798-3915; http://lattes.cnpq.br/4061809277935577; Abreu, Carlos Alexandre Camargo de; Gouveia, Cinthia Beatrice da Silva TellesCosmetics are synthetic or natural preparations intended for external use and were developed from the discovery of ingredients capable of sustaining the formulations. Over time, knowledge spread and the cosmetics industry emerged, with a billion-dollar market dominated by an oligopoly of multinationals. To get a sense of its magnitude, data from a survey carried out by Business Insider (2017) shows that 182 of the main beauty companies are controlled by 7 majores players, with the top 20 leaders in this sample recording US$186 billion in annual net sales, according to Beauty Packaging (2023). However, research by the Union + Webster agency shows that 87% of Brazilians prefer companies that work with sustainability, a fact that includes individuals who adhere to slow beauty and veganism. Based on this trend, this scientific-entrepreneurial research aims to diagnose opportunities - for business models - centered on algae-based cosmetics and associated with 4.0 enabling technologies. To this end, the research method is centered on exploratory analysis based on techno-logical and market prospecting. With an applied nature and a qualitative and quantitative approach, the study describes and analyzes the prospected data, supported by bibliographic procedures. The results show the dominance of the major economic powers in the patent, economic and marketing areas, with evidence of cosmetological nanomaterials as well as big data, artificial intelligence and the internet of things to optimize the production chain, consumer trends and crop monitoring. Finally, the business modeling of Seaweed Cosmetics helps to support entrepreneurial initiatives involving seaweed in Rio Grande do Norte and supports the production of cosmetics made from the seaweed Gracilaria birdiae.Doctoral Thesis Geração de bioenergia com captura intríseca de CO2 via processo de iG-CLC em planta piloto contínua(Universidade Federal do Rio Grande do Norte, 2024-07-15) Oliveira, Gislane Pinho de; Braga, Renata Martins; Adánez-rubio, Iñaki; https://orcid.org/0000-0002-6232-0945; http://lattes.cnpq.br/4603529162393328; http://lattes.cnpq.br/0670520594680554; Alves, José Luiz Francisco; Melo, Marcus Antônio de Freitas; Melo, Dulce Maria de AraújoThe continuous increase in CO2 emissions and its effect on global warming imposes the need for collaborative actions between scientists and government to implement strategies aimed at reducing CO2 emissions. Among these strategies, carbon capture and storage technologies stand out that, especially when associated with the use of biofuels, as they can achieve a negative balance of CO2 emissions. Chemical looping (CL) is recognized as an energy-efficient approach to capture and store CO2 and has high technological maturity. In these processes, the search for low-cost solid oxygen carriers (OC) is motivated by the loss of OC incurred when solid biofuels are employed. In this context, this study aims to select, characterize and evaluate the energy potential of different biomasses and the reactivity of low-cost mineral materials as solid oxygen carriers for application in chemical looping combustion process with gasification in situ (iG-CLC) in pilot plant with continuous power supply with a technology readiness level (TRL) 4. The biomasses were characterized by proximate, ultimate, thermogravimetric analysis, analytical flash pyrolysis and determination of calorific value. The OCs were characterized using X-ray diffraction and fluorescence techniques, scanning electron microscopy, determination of crushing strength, and attrition rate. Their reactivities with CH4, H2 and CO were evaluated in thermobalance performing redox cycles at 900 °C and in a semi-continuous fluidized bed reactor (FBR) at 850, 900 and 950 °C. The reactivity during iG-CLC process of the selected OC was evaluated in FBR at 900°C feeding char of the selected biomass; and in a 0.5 kWh pilot plant with continuous biomass feed. The selected biomass showed high calorific value (18 MJ/kg), high volatile + fixed carbon content (67%) and ashes with high K and Ca content, which can catalyze gasification reactions. All OCs showed low friction rate and good crushing strength, except for Mn, which is why it was submitted to calcination. The OCs Fe2, Fe3 and MnT1000 (Mn calcined at 1000 °C) demonstrated favorable attributes such as adequate crushing strength (>1 N), minimum attrition rate (<7%), good oxygen transport capacity (3.3%, 1.7% and 3.4%, respectively) and high reactivity in thermobalance. They also showed excellent performance in FBR with CO and H2, without agglomeration, good reoxidation rate and lifetime ranging from 3000h to 10500 hours. Notably, due to the excellent performance of the MnT1000 with CO and H2, it is a promising candidate for application in the iGCLC process. The iG-CLC tests in FBR indicates that an oxygen-to-biomass ratio greater than 30 promotes complete combustion of the gasification products, while lower values promote incomplete combustion. The iG-CLC tests in a continuous pilot plant indicate that an increase of the temperature of the fuel reactor or a decrease in the oxygen-biomass ratio increases the CO2 capture efficiency (>87%) and the combustion efficiency (>85%) while the excess oxygen has little influence on the process. The MnT1000 stood out as an oxygen carrier, did not suffer agglomeration in any of the tests, presented high performance, high reactivity, resistance, is environmentally friendly and low-cost. The application of a highly reactive low-cost TSO in iG-CLC processes using biomass stands out as an energy-efficient alternative to produce energy with intrinsic CO2 capture with a negative CO2 emissions balance.Master Thesis Síntese de bioaditivo à base de lignina para aplicação em cimentação de poços de petróleo(Universidade Federal do Rio Grande do Norte, 2024-03-01) Carvalho, José Valderisso Alfredo de; Braga, Renata Martins; https://orcid.org/0000-0002-6232-0945; http://lattes.cnpq.br/4603529162393328; https://orcid.org/0000-0002-7979-5576; http://lattes.cnpq.br/5531387692306284; Padilha, Carlos Eduardo de Araújo; Freitas, Júlio Cézar de Oliveira; Santiago, Rodrigo César; Costa, Bruno Leonardo de SenaCementing plays a fundamental role in the construction of oil wells, as it is directly linked to their integrity and durability. A slury used for this purpose is typically composed of water, cement, and additives. Additives are essential materials for adjusting the physical and chemical properties of the slury, making it suitable for the peculiar temperature and pressure conditions found in wells. Additives can be synthesized from inorganic and natural compounds, one of which is lignin, a polymer present in lignocellulosic biomass. It has low commercial value however, when subjected to structural modification processes, it can acquire exceptional characteristics that make it highly valuable and suitable for various industrial applications. Thus, this research aimed to develop a bioadditive from green coconut lignin, via oxidative modification, for application in oil well cementing slurries. Lignin was extracted through alkaline pretreatment of green coconut biomass, and its structural modification was carried out through the oxidation process. After the synthesis process, unmodified lignin (LNM) and oxidized lignin (LOX) were characterized using Zeta potential, Fourier-transform infrared spectroscopy, UV spectrophotometry, and thermogravimetric analysis (TGA/DTG). The lignins were validated as retarder additives by the thickening time test, and the dispersant capacity was evaluated through rheology testing. The developed additive was compared to a commercial additive through a primary cementing simulation, where the slurries were evaluated with tests of rheology, static filtration, and thickening time. In characterization, the opening of aromatic rings and the increase in surface charge were confirmed in LOX. LOX provided greater retardation of setting time than LNM. A dosage of 0.5% of LOX resulted in a setting time of over 2 hours (50% more than the reference slury), validating it as a retarder additive. Additionally, LOX showed dispersant effect as a secondary property and contributed to reducing the rheological parameters of cement slurries. Technological application showed that LOX can modify the properties of cement slurries in a manner compatible with a commercial retarder additive. Its application together with other additives resulted in a slight increase in the rheological parameters of the slurries and contributed to reducing filtrate. Regarding thickening time, with just 0.1% of LOX, it was possible to delay the setting time by 71 minutes (31%) more than the reference slury. These results suggest that LOX is a promising alternative retarder additive that, in addition to benefiting the oil and gas industry, contributes to adding value to green coconut waste.Doctoral Thesis Modelo de apoio à decisão para desativação ou prolongamento da vida útil de parques eólicos onshore(Universidade Federal do Rio Grande do Norte, 2024-04-25) Agra Neto, João; Gonzalez, Mário Orestes Aguirre; Andrade, Humberto Dionisio de; Almeida, Mariana Rodrigues de; http://lattes.cnpq.br/7356242205950550; Barbalho, Sanderson César Macedo; Santanna, Vanessa CristinaThe number of onshore wind farms reaching the end of their useful life in various parts of the world is on the increase and requires their owners to make a decision on whether or not to continue operating them. The present thesis aims to develop a decision-making model regarding the extension of the useful life or deactivation of onshore wind farms. The research method included four stages: 1) construction of the state of the art based on theoretical research narrative and systematic literature review, 2) systematization of the factors and variables that influence decision-making at the end of the life cycle of onshore wind farms, 3) conceptual modeling, and 4) validation of the decision-making model by means of a questionnaire survey with managers of wind farms in operation and a focus group with experts. As a result, the model presents eleven possible alternatives inserted in two scenarios: the deactivation and completion of operational activities and the extension of useful life of the farm. The factors and variables that influence the decision-making process are: external factors (national energy guidelines, public policies and regulatory aspects, logistical and infrastructural aspects, and technological development in the sector) and internal factors (economic-financial aspects, operational aspects, environmental aspects, regional aspects, and human resources). The model also includes: 1) the process for developing the technical and economic feasibility study to support the decision to decommission or extend the useful life of onshore wind farms, and 2) the relational approach to conducting the technical and economic feasibility study. It is concluded that wind farms that reach maturity of more than 12 years should be studied in order to make a decision on whether to decommission or continue their operation, taking into account the factors internal and external to the wind farm included in the model. We believe that the proposal in this thesis can serve as a reference for academic studies as well as for decision-makers at wind farms in operation.Doctoral Thesis Novo sistema de pasta solúvel em ácido para perda de circulação em reservatórios carbonáticos macroporosos(Universidade Federal do Rio Grande do Norte, 2023-08-17) Braga, Glauco Soares; Freitas, Júlio Cézar de Oliveira; https://orcid.org/0000-0003-1324-9705; http://lattes.cnpq.br/2357217530716519; http://lattes.cnpq.br/4514550024139119; Martinelli, Antônio Eduardo; https://orcid.org/0000-0003-3885-9104; http://lattes.cnpq.br/0022988322449627; Curbelo, Fabíola Dias da Silva; Aum, Pedro Tupã Pandava; Santiago, Rodrigo CésarPre-salt drilling has brought huge challenges, not least circulation losses. Any loss of circulation increases the total cost when added to the non-productive time (NPT) to contain the problem. When drilling pre-salt carbonate reservoirs, there is a risk of severe loss of drilling fluid when invading macroporosity intervals, reaching loss rates of more than 700 barrels/hour. The vast majority of the time, traditional fighting techniques are not effective against severe circulation losses in carbonate reservoirs with vugulars, and it is necessary to fight with cement paste. Cement plugs are effective in combating loss of circulation in reservoirs, but they cause irreversible damage. To replace cement, it was necessary to study and develop new alternative materials that could be reversible in terms of damage to the formation when applied to combat loss of circulation in the reservoir. Acid-soluble paste systems formulated with a water/hemihydrate ratio were studied to assess their potential as a buffer against loss. The paste systems were first studied using consistometry under conditions of 9500 psi and 54 °C, mechanical strength tests, and phase identification by x-ray diffraction of the systems cured at 9500 psi and 80 °C. The results indicate that the consistometry time and mechanical strength are consistent with the intended application. The cured paste systems underwent a static acid attack test in 9 and 15% HCl, with total dissolution of the specimen. The effects of the saturated CO2 atmosphere on the specimens for a period of 30 and 45 days were also evaluated. The results indicate that the specimens have undergone changes in their microstructure, causing physico-chemical alterations to the specimens. The paste systems studied showed great innovative potential for application as a solution to combat loss of circulation in vug zones.