Programa de Pós-Graduação em Ciência e Engenharia de Materiais
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Master Thesis Desenvolvimento e avaliação de nanofluidos de alumina para recuperação avançada de petróleo em reservatórios areníticos(Universidade Federal do Rio Grande do Norte, 2026-02-24) Rocha, Camila Louyse Oliveira da; Martinelli, Antonio Eduardo; https://orcid.org/0000-0003-3885-9104; http://lattes.cnpq.br/0022988322449627; https://orcid.org/0000-0003-1531-4099; http://lattes.cnpq.br/7793908717511173; Alves, Annelise Kopp; http://lattes.cnpq.br/0064626732086273; http://lattes.cnpq.br/0064626732086273; Paskocimas, Carlos Alberto; https://orcid.org/0000-0002-1915-4291; http://lattes.cnpq.br/2365059843175411; Oliveira, Gregory Vinicius Bezerra de; https://orcid.org/0000-0002-8223-8199; http://lattes.cnpq.br/5656895709723231Enhanced Oil Recovery (EOR) comprises a set of techniques designed to increase oil extraction from reservoirs where primary and secondary recovery methods are limited. Among the strategies employed, nanofluids have gained significant attention, as they combine a base fluid, additives, and nanoparticles capable of modifying critical reservoir properties such as wettability, oil viscosity, and interfacial tension, thereby increasing the recovery factor. Among the nanomaterials applied in EOR, aluminum oxide (Al₂O₃) stands out due to its high stability, large surface area, and chemical versatility, which favor its interaction with fluids and rock surfaces. Coprecipitation is a widely used method for synthesizing Al₂O₃ nanoparticles because it produces homogeneous particles with high purity; however, their tendency to agglomerate in liquid media still limits their performance. To overcome this limitation, the use of anionic polymers such as sodium polyacrylate (PAS) has proven effective by enhancing electrosteric repulsion between particles and consequently improving colloidal stability. In this context, the present study aimed to synthesize γ-Al₂O₃ nanoparticles via coprecipitation, stabilize them through the addition of PAS, and evaluate the performance of the resulting nanofluids in enhanced oil recovery processes in sandstone reservoirs. The nanoparticles were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FEG-SEM), and Brunauer–Emmett– Teller (BET) surface area analysis, while the nanofluids were evaluated in terms of rheological behavior, zeta potential, sedimentation, UV–Vis spectroscopy, dynamic light scattering (DLS), interfacial tension, and wettability. EOR experiments were conducted through conventional recovery followed by the injection of nanofluids containing γ-Al₂O₃ nanoparticles and additive (enhanced recovery), as well as an additional test consisting of conventional recovery followed by polymer solution injection, both performed at a flow rate of 0.5 mL·min⁻¹, with the recovered oil volume determined from the collected effluent samples. The results indicated the initial formation of fibrillar pseudoboehmite with low crystallinity and a high degree of hydration, which was subsequently converted into high-purity nanometric γ-Al₂O₃ with crystallite sizes of approximately 3 nm, spherical morphology, and a specific surface area of 250–270 m²·g⁻¹. The nanofluids exhibited dilatant behavior both in the absence and presence of PAS, while the addition of the polymer increased colloidal stability, promoted a bimodal particle distribution, and caused a reversal of the surface charge. Wettability and interfacial tension measurements showed that the combination of γAl₂O₃ and PAS reduced interfacial tension and altered the rock surface from oleophilic to strongly hydrophilic, particularly at higher alumina concentrations, indicating a synergistic effect between the polymer and the nanoparticles. In the EOR tests, polymer solution injection resulted in a moderate increase in the recovery factor compared with the reference brine, whereas PAS-stabilized nanofluids promoted progressive and concentration-dependent increases in oil recovery, reaching the highest enhanced recovery factors, a performance associated with greater colloidal stability, lower sedimentation, and more effective nanoparticle transport through the porous medium, demonstrating the high potential of PAS-stabilized γ-Al₂O₃ nanofluids for enhanced oil recovery applications.Doctoral Thesis Síntese e caracterização do nanocompósito ZnFe204-Fe203-Zno usando o método de autocombustão e síntese verde(Universidade Federal do Rio Grande do Norte, 2024-03-07) Araújo, Tomaz Rodrigues de; Melo, Dulce Maria de Araújo; Melo, Marcus Antonio de Freitas; https://orcid.org/0000-0003-3697-2859; http://lattes.cnpq.br/5840621182000517; https://orcid.org/0000-0001-9845-2360; http://lattes.cnpq.br/3318871716111536; https://orcid.org/0000-0002-5368-9775; http://lattes.cnpq.br/8089377214120842; Torres, Marco Antonio Morales; http://lattes.cnpq.br/0091292234916055; Braga, Renata Martins; https://orcid.org/0000-0002-6232-0945; http://lattes.cnpq.br/4603529162393328; Albuquerque, Dener da Silva; https://orcid.org/0000-0003-1892-1783; http://lattes.cnpq.br/8570890900553566; Figueredo, Gilvan Pereira de; https://orcid.org/0000-0002-3989-1360; http://lattes.cnpq.br/3730724432445516One of the goals of materials science and engineering is to create conditions for materials to achieve adequate performance for specific applications, and this relates to their properties, as evidenced by characterizations. Therefore, the aim of this work was to improve the textural, morphological, physical, structural, and crystalline properties of the ZnFe2O4-Fe2O3-ZnO nanocomposite using appropriate synthesis methods for this purpose. For this purpose, two types of synthesis were used: the synthesis called microwave-assisted self-combustion and the green synthesis, where it was used residues from the processing of jatobá wood, which has high production, low added value, and few technological applications. The residues (liquid and solid phases) were extracted by a hot process at various temperatures. The liquid portion was used in microwaveassisted self-combustion, replacing water by 50% and 100%; while the solid portion was adapted for green synthesis as a structural driver. The characterization techniques used were: X-ray diffraction, scanning electron microscopy (SEM-EDS and SEMFEG), thermogravimetric analysis (TG/DTG); immediate analysis; calorific value and heat capacity; determination of density in helium gas; cellulose and hemicellulose, lignin and phenolic contents; infrared, Raman, ultraviolet and visible spectroscopy, diffuse reflectance; Mössbauer and magnetic properties, in addition to particle size by light scattering (DLS) and specific area volume pore size (BJH). Furthermore, yield analyses of the extraction and synthesis processes were performed. Immediate analysis shows moisture content below 20%, high percentages of volatiles, and low levels of ash and fixed carbon. The in nature and post-extraction residues exhibit specific heat of 950.13 to 9,091.98 cal/gºC and heat capacity (2,433.10 – 2,504.03 cal/ºC). ZnFe2O4- Fe2O3-ZnO was formed by the green synthesis route and ZnFe2O4-Fe2O3 by microwaveassisted autocombustion. The crystallite size ranged from 14.2 to 26.39 nm, crystallinity from 40.39 to 57.45%, and band-gap from 1.48 to 2.46 eV. Microscopic analyses show diverse morphologies with signs of cavities with consistent orientations. The materials obtained from the liquid portion of the residues (used in the self-combustion synthesis) provided a specific surface area between 80.41-99.74 cm².g-1. Solid waste from the jatobá, used in the green synthesis of nanocomposites, produced stable structures with low ferromagnetic properties and consistent high magnetization, suitable for applications in devices subjected to alternating magnetic fields. The results showed that a ternary nanocomposite was formed, demonstrating a technological application capable of adding value to this class of plant residues.Doctoral Thesis Nb2O5-based functional materials for environmental remediation and sodium-ion batteries(Universidade Federal do Rio Grande do Norte, 2026-02-04) Morais, Débora Ferreira dos Santos; Delmonte, Mauricio Roberto Bomio; Motta, Fabiana Villela da; https://orcid.org/0000-0002-3523-737X; http://lattes.cnpq.br/9918299069511517; https://orcid.org/0000-0001-9016-4217; http://lattes.cnpq.br/9558299312183852; https://orcid.org/0000-0002-8801-9720; http://lattes.cnpq.br/6958079215646587; Andrade Neto, Nivaldo Freire de; http://lattes.cnpq.br/4019473456045745; Cabello, Pedro Lavela; Carreño, Neftalí Lenin Villarreal; https://orcid.org/0000-0002-5780-817X; http://lattes.cnpq.br/4035574249612354The growing demand for sustainable technologies has driven the development of new materials capable of meeting both environmental and energy challenges. In this context, niobium pentoxide (Nb2O5) has been gaining prominence due to its high chemical stability, abundance in Brazil, and versatility of applications. Therefore, this thesis aimed to investigate the multifunctional potential of Nb2O5 in two complementary areas: (i) as a photocatalyst in the degradation of organic pollutants and (ii) as a coating material in sodium-ion battery (SIB) cathodes. In the first step, Nb2O5 was used in the synthesis of new binary and ternary heterojunctions, Ag@AgCl/Nb2O5 and g-C3N4/Ag@AgCl/Nb2O5, obtained through combined precipitation and calcination routes. Structural analyses (XRD, XPS, PL, and EIS) confirmed the formation of oxygen vacancies, metallic silver, and strong interfacial coupling between the phases, resulting in efficient charge separation and broadening of optical absorption into the visible spectrum. The ternary heterojunction NbA75CN exhibited superior photocatalytic performance, eliminating 99.9% of the Rhodamine B (RhB) dye in just 10 minutes of solar irradiation, with high structural and photocatalytic stability after multiple cycles. Furthermore, the material demonstrated significant antimicrobial activity against Staphylococcus aureus and Escherichia coli, highlighting its potential for environmental and health applications. In the second phase, the use of Nb2O5 was evaluated as a coating on NASICON (Na3V2(PO4)3) cathodes synthesized via the citrus sol-gel route. The coating was applied at different concentrations (1%, 3%, and 5%), and morphological and spectroscopic analyses confirmed its homogeneous distribution on the particles. The coated samples exhibited improved electrochemical performance, particularly the NVP@Nb3 material, which exhibited a capacity of 96 mA h g⁻¹ at 3.2 V, corresponding to an energy density of 307.2 Wh kg⁻¹, in addition to 97% capacity retention after 300 cycles and excellent stability at -15°C. This improvement was attributed to reduced interfacial resistance, increased surface capacitive contribution, and greater ionic mobility in the electrode. The results demonstrate the effectiveness of Nb2O5 as a multifunctional material, capable of both promoting efficient pollutant degradation and optimizing electrode performance in SIBs. Thus, this research reinforces the strategic role of Nb2O5 as a key material in the development of clean technologies, aligned with the principles of environmental sustainability and energy transition.Doctoral Thesis Espumas bionanocompósitas sustentáveis de pectina com argilas naturais e modificadas: síntese, caracterização e comparação entre os diferentes tipos de argila e diatomita(2025-08-14) Dantas Neto, José Claudiano; Pergher, Sibele Berenice Castellã; http://lattes.cnpq.br/5249001430287414; https://orcid.org/0000-0003-1586-5747; http://lattes.cnpq.br/6188131429691575; Loiola, Adonay Rodrigues; https://orcid.org/0000-0002-4981-6321; http://lattes.cnpq.br/9807982856173580; Penha, Fábio Garcia; https://orcid.org/0000-0002-5587-873X; http://lattes.cnpq.br/0866082836928725; Nascimento, Rubens Maribondo do; https://orcid.org/0000-0001-9094-0044; http://lattes.cnpq.br/8671649752936793; Fernandes Júnior, Valter José; https://orcid.org/0000-0001-6549-0643; http://lattes.cnpq.br/1595902438130772Bionanocomposites are hybrid materials composed of a natural polymeric matrix and inorganic nanofillers, such as clays, which have emerged as sustainable alternatives to low-density synthetic materials like polystyrene foams. Although widely used, these synthetic foams are environmentally unsustainable due to their non-biodegradable nature and the release of toxic compounds during combustion. In this work, low-density bionanocomposite foams were developed by combining pectin, a biodegradable plantbased biopolymer, with various types of clays: fibrous (palygorskite and sepiolite), lamellar (montmorillonite with and without pillaring, and kaolinite), as well as porous materials such as diatomite and modified clays. The formulations underwent synthesis optimization and were freeze-dried to produce the foams. The materials were structurally and morphologically characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Physical and mechanical properties were evaluated through compression tests, water absorption and solubility assays, as well as flame resistance tests. The results showed that foams synthesized with pillared clay minerals exhibited higher compressive strength compared to the other materials. Micrographs confirmed the porous structure of the samples, highlighting the influence of both composition and freezing method on the final morphology. Foams frozen with liquid nitrogen absorbed more water without exhibiting significant solubilization. In CO₂ adsorption assays, bionanocomposites containing fibrous clays displayed superior performance, with adsorption capacity more than twice that of the raw materials, indicating strong synergy between the components. The developed foams demonstrate potential to replace synthetic materials in applications requiring low weight, mechanical resistance, and greater environmental safety, reinforcing the technological and ecological appeal of the bionanocomposites produced.Doctoral Thesis Influência da interação de diferentes fontes amiláceas sobre as propriedades do amido termoplástico(Universidade Federal do Rio Grande do Norte, 2025-11-28) Milfont, Carlos Henrique Rodrigues; Ito, Edson Noriyuki; https://orcid.org/0000-0001-7784-9035; http://lattes.cnpq.br/7249500407405478; https://orcid.org/0000-0002-8909-3420; http://lattes.cnpq.br/8351193305080475; Nascimento, Maria Carolina Burgos Costa do; https://orcid.org/0000-0002-4261-1331; http://lattes.cnpq.br/4409025248163428; Mattos, Adriano Lincoln Albuquerque; https://orcid.org/0000-0003-2823-037X; http://lattes.cnpq.br/8866532554464174; Reinaldo, Juciklécia da Silva; https://orcid.org/0000-0002-4228-9709; http://lattes.cnpq.br/0106357784933202; Souza Filho, Men de Sá Moreira de; http://lattes.cnpq.br/4768901375579199This study evaluated the influence of interactions among corn (Mi), cassava (Ma), and potato (Ba) starches on the properties of thermoplastic starch (TPS), considering the limitations of using isolated starches, such as high water susceptibility and low mechanical performance. To investigate these interactions, binary and ternary blends were prepared based on a simplex-centroid experimental design {3,2}, used as a tool to analyze interactions among different starch sources. TPS materials were obtained by casting from gelatinized aqueous dispersions and by extrusion, allowing the effect of the processing method on material properties to be assessed. The starches exhibited amylose contents of 29.52 ± 0.38% (Mi), 18.19 ± 0.68% (Ma), and 34.77 ± 0.29% (Ba), as well as average viscosimetric molar masses (M̅v) of 1.34 × 10⁶, 2.93 × 10⁶, and 6.09 × 10⁵ g·mol⁻¹, respectively. Rheological tests of aqueous solutions indicated higher apparent viscosity and thixotropy values for corn starch, while the blends showed intermediate values of storage modulus (G′), loss modulus (G″), and complex viscosity (|η*|) compared to the pure components. In the films obtained by casting, starch interactions influenced crystallinity and opacity, with higher values observed in formulations rich in potato starch. Ternary blends with higher proportions of Mi and Ba exhibited lower water solubility indices, indicating synergistic effects. Thermal analysis showed that formulations with higher Ma content exhibited greater thermal stability, associated with a higher amylopectin proportion. Mechanical tests indicated an increase in maximum tensile strength in the blends compared to the isolated starches. In extruded TPS, increasing the Ma proportion resulted in smoother and shinier surfaces, but with greater susceptibility to moisture. Thermal and mechanical properties showed intermediate values relative to the pure components, reflecting the combined effect of composition and processing. Overall, the results demonstrated that amylose content, starch molar mass, and processing technique govern the interactions among starch sources, directly impacting TPS properties. Mixture modeling highlighted the potential of starch blends for the development of biodegradable materials.Master Thesis Síntese e estudo do óxido de alta entropia (Fe0,2,Ni0,2Co0,2Al0,2Zn0,2)3O4 pelo método sol-gel assistido por polivinilpirrolidona (PVP) e sua aplicação como eletrocatalisador para a reação de evolução de oxigênio(Universidade Federal do Rio Grande do Norte, 2025-06-02) Vasconcelos, Gabriel dos Santos; Gomes, Uilame Umbelino; Torres, Marco Antonio Morales; http://lattes.cnpq.br/0091292234916055; http://lattes.cnpq.br/9858094266525225; http://lattes.cnpq.br/2806155952751330; Mashhadikarimi, Meysam; https://orcid.org/0000-0003-1449-3654; http://lattes.cnpq.br/9422624675887080; Silva, Ariadne de Souza; https://orcid.org/0009-0002-9675-0748; http://lattes.cnpq.br/5623381698478389; Raimundo, Rafael Alexandre; https://orcid.org/0000-0002-9943-9464; http://lattes.cnpq.br/9772819884310876High-entropy oxides (HEOs) have emerged as a promising class of functional materials due to their tunable electrochemical and magnetic properties, with potential applications in electrocatalysis, energy storage, and electronic devices. In this context, the present study aims to synthesize and thoroughly characterize the high-entropy oxide (Fe₀.₂Ni₀.₂Co₀.₂Al₀.₂Zn₀.₂)₃O₄, referred to as HEO-600, synthesized at 600 °C via the sol-gel method assisted by polyvinylpyrrolidone (PVP). Additional samples were produced at higher temperatures, revealing the formation of distinct crystalline phases, including spinel-type and rock-salt structures. Structural and compositional characterization was carried out using various techniques, including X-ray diffraction (XRD), field-emission scanning electron microscopy (FEG-SEM) with energy-dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS analysis confirmed the equimolar composition of the elements in the HEO-600 sample, whereas the EDS analysis revealed a homogeneous distribution of cations, corroborating the formation of a uniform solid solution. TEM micrographs showed well-dispersed, non-agglomerated particles with an average size of 9.2 nm. The magnetic properties of the HEO-600 sample were investigated using Mössbauer spectroscopy, direct current (DC) magnetometry, and alternating current (AC) magnetometry. The Mössbauer spectrum indicated that iron ions were distributed between tetrahedral (A) and octahedral (B) sites in a 43% and 57% ratio, respectively, confirming a partially inverted spinel structure. Magnetic susceptibility measurements (DC and AC) revealed superparamagnetic behavior at room temperature, as well as the presence of a spin glass-like phase, with a transition temperature at 206 K. This magnetic phase was suppressed under an external field of approximately 4300 Oe, highlighting the complexity of magnetic interactions in the system. In addition to structural characterization, spectroscopic and electrochemical analyses were performed to evaluate the catalytic potential of the HEO-600 sample for the oxygen evolution reaction (OER). Fourier-transform infrared (FTIR) spectroscopy provided additional information on the vibrational configuration of the system, and the chemical bonds present in the oxide. Electrochemical experiments demonstrated that the HEO-600 sample exhibits promising performance for OER, with an overpotential of 358 mV at a current density of 10 mA cm⁻². This value indicates competitive catalytic activity compared to other transition metal-based high-entropy oxides. Thus, this work significantly contributes to the advance in the understanding of the structural, magnetic, and electrochemical properties of high-entropy oxides. The results obtained not only expand the knowledge of the correlation between synthesis, structure, and properties of these materials but also highlight their potential for technological applications in electrochemical catalysis.Master Thesis Desenvolvimento de nanocompósitos cimentícios a base de nanoplacas de grafeno para aplicações em poços CCS(Universidade Federal do Rio Grande do Norte, 2025-12-12) Silva, Dayanne Gabriella da; Martinelli, Antonio Eduardo; https://orcid.org/0000-0003-3885-9104; http://lattes.cnpq.br/0022988322449627; http://lattes.cnpq.br/3415325334445679; Freitas, Júlio Cézar de Oliveira; https://orcid.org/0000-0003-1324-9705; http://lattes.cnpq.br/2357217530716519; Braga, Glauco Soares; http://lattes.cnpq.br/4514550024139119Carbon Capture and Storage (CCS) is a fundamental technology for reducing largescale greenhouse gas emissions. This technique enables the safe confinement of carbon dioxide (CO₂), one of the main contributors to global warming, in deep geological formations, thereby limiting its release into the atmosphere. To implement this technology, it is essential to construct wells that allow the injection of CO₂ captured from industrial sources, ensuring secure storage and preventing its return to the surface. In this context, the cementitious material responsible for zonal isolation and well structural integrity must exhibit high chemical and mechanical resistance, as its degradation by CO₂ can compromise the long-term durability of the system. Thus, the incorporation of nanomaterials such as graphene nanoplatelets (GNPs) into cement pastes emerges as a promising approach, since their two-dimensional lamellar structure and high aspect ratio can enhance the mechanical strength, conductivity, and chemical stability of the cementitious system. Additionally, GNPs offer high scalability and lower cost compared with other graphene-based derivatives. This study aimed to evaluate the effect of different GNP concentrations (0.03%, 0.06%, and 0.09% BWOC) on the mechanical strength, permeability, and chemical resistance of cement pastes. The formulations were subjected to carbonation tests under supercritical CO₂ conditions in an aqueous medium, with evaluations performed after 7, 14, and 28 days of exposure. Complementary analyses, including X-ray Diffraction (XRD), Thermogravimetry (TG), and Scanning Electron Microscopy (SEM), were conducted to identify and quantify hydration and carbonation products formed before and after chemical attack, as well as to assess GNP dispersion within the cement matrix and its influence on product formation. The results showed that GNP-containing pastes exhibited increased compressive strength and reduced permeability, particularly at early curing ages. Carbonation was also slowed by the addition of GNPs, with the 0.06% concentration demonstrating the best performance. Microstructural analysis revealed well-dispersed GNPs in the cement matrix and the presence of carbonation products, while thermal and crystallographic analyses indicated the effect of GNP addition on the formation of compounds before and after CO₂ exposure. Therefore, the results indicate that GNPs present strong potential for the development of cementitious nanocomposites designed for CCS well construction.Doctoral Thesis Avaliação do efeito da temperatura no processo de corte por puncionamento em aços avançados de alta resistência(Universidade Federal do Rio Grande do Norte, 2025-01-24) Gonçalves, Rennáh Francisco Figueiredo; Sousa, Fábio José Pinheiro; https://orcid.org/0000-0002-8381-8806; http://lattes.cnpq.br/9909217959915292; http://lattes.cnpq.br/5292990047030419; Castro, Nicolau Apoena; http://lattes.cnpq.br/3740711945494961; Buschinelli, Augusto José de Almeida; http://lattes.cnpq.br/9684649153800847; Ferreira, Jetson Lemos; Lourenço, Jorge MagnerThis study focuses on the analysis of dual-phase (DP) steels, a category of advanced highstrength steels (AHSS) widely used in the manufacturing of automotive components. AHSS exhibit a microstructural configuration that combines a highly ductile ferritic matrix with a second constituent of high hardness, such as martensite, bainite, or a combination of both, dispersed within the matrix. This microstructural arrangement enables the efficient processing of AHSS through forming processes such as stamping. During the manufacturing of automotive parts, the quality of the cutting edge of these steels is critical, as defects, such as cracks originating from the cutting edges, can lead to failures during production. The present study proposes the use of cryogenic temperatures during the punching cutting process as a strategy to minimize crack nucleation. The hypothesis is that performing the process at low temperatures may alter the plastic deformation mechanism, shifting from shearing to mechanical twinning and cleavage. The work involved a qualitative and quantitative study of the microstructures of the cutting edges of DP780 steel, obtained by punching at cryogenic and ambient temperatures. Tests conducted demonstrated the feasibility of the punching process at cryogenic temperatures for AHSS (DP780). Using electron backscatter diffraction (EBSD) in a scanning electron microscope (SEM), the analysis revealed significant changes, including a reduction in the regions of plastic deformation and an increase in the fracture zone in samples tested at temperatures below -150 ºC, compared to those tested at ambient temperature. The quantitative results indicated the effectiveness of this method in reducing plastic deformation at the cutting edges of DP780 by up to 37% when performed at cryogenic temperatures (≤ -150 °C) and a punching speed of 725 mm/s. Although the results of the hole expansion test did not show a significant influence when comparing punching temperatures, the strain distribution and fracture morphology indicated that the reduction in temperature led to a lower level of strain hardening at the cutting edges and a more homogeneous distribution of cracks along the cutting perimeter in samples punched at -125 °C. It is possible that, with adjustments to cutting process parameters, such as die clearance, hole expansion values could be increased with the application of cryogenic punching.Master Thesis Formulação de tintas nanométricas funcionais de TiNb2O7(Universidade Federal do Rio Grande do Norte, 2025-06-12) Rodrigues, Rayssa Ribeiro; Martinelli, Antonio Eduardo; https://orcid.org/0000-0003-3885-9104; http://lattes.cnpq.br/0022988322449627; http://lattes.cnpq.br/4144399849996058; Paskocimas, Carlos Alberto; https://orcid.org/0000-0002-1915-4291; http://lattes.cnpq.br/2365059843175411; Mendes, Armando Monte; https://orcid.org/0000-0002-3442-9927; http://lattes.cnpq.br/3173204192281049; Macedo, Daniel Araújo de; http://lattes.cnpq.br/1027496814443777The search for new battery materials has intensified with the aim of increasing efficiency, storage capacity, and device compactness. Among the promising anode materials, TiNb₂O₇ (NTO) stands out, as it exhibits a high theoretical capacity (~388 mAh g⁻¹), which corresponds to the maximum charge that can be stored per gram of material during charge and discharge cycles. In addition, NTO presents high cyclic stability, meaning it is capable of maintaining its performance over multiple cycles, which is essential for battery durability. However, material selection is not the only crucial factor for battery performance; manufacturing methods also play a fundamental role. Although significant advances have been achieved in recent decades, the modernization of manufacturing techniques remains underexplored due to limitations of conventional methods. In this context, 3D printing, or additive manufacturing especially through the Direct Ink Writing (DIW) technique emerges as an innovative approach for fabricating battery components, enabling the creation of miniaturized electrodes with complex geometries and high surface area, which directly contributes to the optimization of properties related to electrical conductivity and ion storage. In the DIW technique, ink formulation is a key factor in ensuring ideal printing characteristics. The lack of information about such formulations highlights the need for further research in this area. Therefore, the present work proposes the development of a functional nanometric ink for application in the DIW technique, aimed at fabricating miniaturized electrodes for lithium-ion batteries. The goal is to make the process measurable, ensure good printability, and preserve the structural properties of the printed parts after sintering. For this purpose, the resin incorporates TiNb₂O₇ (NTO) as one of its components, obtained through synthesis. A hydrothermal synthesis route was adopted to produce high-purity NTO nanoparticles, ensuring morphological control key requirements for developing good electrochemical properties. After this step, the material was calcined, and the resulting powder was used in the preparation of inks for 3D printing. The printed samples were initially evaluated dimensionally and then subjected to a sintering process. Subsequently, structural and morphological characterizations were carried out, including X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FEG-SEM). Thermal analyses such as Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) were also performed. In addition to these electrochemical analyses focused on the oxygen evolution reaction (OER) were carried out to evaluate the functional behavior of the electrodes. The results demonstrated that it was possible to obtain NTO through hydrothermal synthesis and to produce nanometric inks compatible with a modified bioprinter for electrode fabrication. The formulated resin, composed of a polyvinyl alcohol (PVA) solution and alcohol as the base, showed good printability and maintained dimensional stability of the structures after printing.Doctoral Thesis Produção de hidrogênio a partir da reforma a seco metano utilizando perovskitas LaNiO3 como precursores catalíticos: da análise bibliométrica ao machine learning(Universidade Federal do Rio Grande do Norte, 2025-07-22) Favacho, Vanessa Santana Silva; Melo, Dulce Maria de Araújo; Medeiros, Rodolfo Luiz Bezerra de Araújo; http://lattes.cnpq.br/7274621195761563; https://orcid.org/0000-0001-9845-2360; http://lattes.cnpq.br/3318871716111536; https://orcid.org/0000-0002-2332-4476; http://lattes.cnpq.br/4158005957721927; Vasconcelos, Bruna Rêgo de; https://orcid.org/0000-0002-8328-0399; http://lattes.cnpq.br/8976568859799716; Figueredo, Gilvan Pereira de; https://orcid.org/0000-0002-3989-1360; http://lattes.cnpq.br/3730724432445516; Delmonte, Mauricio Roberto Bomio; https://orcid.org/0000-0001-9016-4217; http://lattes.cnpq.br/9558299312183852; Braga, Renata Martins; https://orcid.org/0000-0002-6232-0945; http://lattes.cnpq.br/4603529162393328Dry reforming of methane (DRM) is a catalytic reaction that uses two greenhouse gases (CH4 and CO2) to produce syngas, a mixture of H2 and CO. A bibliometric analysis on perovskites synthesized by the hydrothermal method was carried out and revealed that LaNiO3 has been employed as a catalytic precursor in DRM. However, this bibliometric analysis also showed a scarcity of studies directly relating synthesis parameters to morphology and catalytic activity. Therefore, the objective of this study is to investigate the influence of variables such as pH (9–13), time (6–24 h), temperature (160–200 °C), pressure (autogenous–85 bar), and the use of soft templates (cetyltrimethylammonium bromide and citric acid) on the morphology of LaNiO3 synthesized via the hydrothermal method, and to evaluate the relationship between these parameters and performance in DRM. A preliminary study indicated that pH is a key variable in the synthesis of LaNiO3, influencing particle morphology and, consequently, catalytic performance. Based on the bibliometric analysis and the preliminary results, a full factorial design of experiments (DoE) combined with machine learning (ML) was applied to explore the interactions between synthesis and reaction variables, as well as catalyst properties and performance. The results showed that the DRM reaction temperature was the most significant factor affecting catalytic performance, with higher temperatures (800 °C) leading to greater H2 yields (74–80%). Moreover, higher reaction temperatures also resulted in lower carbon deposition; however, the deposited carbon was more ordered (ID/IG = 0.56–0.79) and more crystalline (48–68 nm), making its removal and catalyst regeneration more difficult. The synthesis pH also proved to be a fundamental variable, where a more alkaline pH (13) positively influenced H2 yield (up to 10% higher) and negatively impacted carbon deposition (>57 wt%). The highest H2 yields were obtained with fresh catalysts containing between 20% and 100% of the LaNiO3 phase, associated with crystallite sizes in the range of 25 to 35 nm. The highest carbon depositions were observed in fresh catalysts containing between 60–100% of the LaNiO3 phase, small crystallite sizes (<30 nm), high reduction degrees (>60%), and low reduction temperatures (<540 °C). Finally, the synergistic effect between pH and synthesis pressure was also evaluated, identifying that the sample synthesized at pH 9 under 85 bar exhibited the best performance, with high H2 yield (76–77%) and moderate carbon deposition (20.43 wt%).