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Artigo The effect of particle size on structural and catalysts for oxygen evolution reaction of (CoFeNiMnCr)3O4 prepared by controlled synthesis with polyvinylpyrrolidone (PVP)(Journal of Colloid and Interface Science, 2025-02-15) Gomes, Uilame Umbelino; Alves, Ricardo Francisco; Raimundo, Rafael Alexandre; Lima, Bruno Alessandro Silva Guedes de; Loureiro, Francisco José Almeida; Fagg, Duncan Paul; Macedo, Daniel Araújo de; Morales, Marco Antonio; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0001-8958-7263; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0000-0003-4966-7140; https://orcid.org/0000-0002-5050-3859; https://orcid.org/0000-0001-6287-9223; https://orcid.org/0000-0003-0466-1458; https://orcid.org/0000-0002-3098-5731In this study, high-entropy spinel oxides (CoNiMnFeCr)3O4 were synthesized using a PVP-assisted sol–gel method, marking the first report of this approach for producing high-entropy oxides. This method provides new insights into morphology customization through precise temperature control during calcination. Samples were calcined at 800, 900, and 1000 °C, and structural, optical, and electrochemical characterizations were performed to evaluate the impact of synthesis conditions on the oxygen evolution reaction (OER) performance. X-ray diffraction (XRD) confirmed the formation of a single-phase spinel structure with face-centered cubic symmetry. UV–Vis spectroscopy revealed a band gap shift associated with calcination temperature, indicating subtle changes in electronic structure that can influence catalytic behavior. The S-HEO 800 sample exhibited the highest catalytic activity, achieving an overpotential of 316 mV at 10 mA cm−2. Electrochemical tests showed excellent short-term durability, with the electrodes maintaining stable performance for 24 h at 10 mA cm−2. Field emission gun scanning electron microscopy (FEGSEM) analysis revealed that particle size increased with calcination temperature, ranging from 96 nm (S-HEO 800) to 475 nm (S-HEO 1000). X-ray photoelectron spectroscopy (XPS) showed a higher concentration of Cr6+, Cr4+, and Ni3+ ions on the surface of S-HEO 800, correlating with its superior OER performance. Additionally, Raman and FT-IR spectra confirmed the formation of the spinel phase and provided insights into metal–oxygen bonding. Electrochemical impedance spectroscopy (EIS) results indicated that S-HEO 800 exhibited the lowest charge transfer resistance (Rct), further supporting its enhanced catalytic behavior. These findings demonstrate the potential of the PVP-assisted sol–gel method to produce customized high-entropy oxides with tunable morphology, making them promising candidates for energy conversion applications, particularly in water electrolysisArtigo Modulating the microstructural and mechanical characteristics of copper-tungsten carbide composite powders by WC content and milling time(Materials Today Communications, 2025-01) Gomes, Uílame Umbelino; Silva, Thalita Queiroz e; Vieira, Pâmala Samara; Ramundo, Rafael Alexandre; Marques, Anderson Costa; Vasconcelos, Gabriel dos Santos; Mashhadikarimi, Meysam; Senos, Ana Maria de Oliveira Rocha e; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0009-0009-6365-2691; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0000-0002-8846-658X; https://orcid.org/0009-0008-6974-9630; https://orcid.org/0000-0003-4784-9784Composites produced with a copper matrix and reinforced with ceramic and refractory material have applicability in electrical conductors. This study investigated copper powder with addition of different concentrations of tungsten carbide (5, 10, 15 and 20 % by mass) prepared by high-energy milling (HEM) for 1, 2, 5, 10 and 20 h. The powders obtained were characterized by Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD) with Rietveld refinement and Powder Vickers microhardness. The morphology of the powders was changed by HEM, deforming the copper particles due to their ductility. The brittle tungsten carbide particles were fragmented, resulting in a homogeneous distribution in the metal matrix and the production of composite particles. The dispersion, homogenization and particle size were significantly influenced by the milling time and percentage of WC, as well as the different milling mechanisms were identified. The diffractograms revealed characteristic peaks of copper and tungsten carbide, and the Rietveld refinement of the XRD revealed very significant changes in the structures of the studied phases. Vickers microhardness showed a direct relationship with the amount of WC, milling time and dispersion of the WC phase in the Cu matrixArtigo Mechanisms of high-entropy carbide formation (TiVTaNbW)C via high-energy milling: structural, chemical, and spectroscopic analysis(Materials Science and Engineering B-Advanced Functional Solid-State Materials, 2026-01) Nascimento, Rubens Maribondo do; Marques, Anderson Costa; Silva, Thalita Queiroz e; Vieira, Pâmala Samara; Paula, Celmo Hudson Reis; Lima, Maria José Santos; Filgueira, Marcello; Gomes, Uilame Umbelino; Mashhadikarimi, Meysam; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0001-9094-0044; https://orcid.org/0000-0002-8846-658X; https://orcid.org/0009-0009-6365-2691; https://orcid.org/0000-0001-9918-7087; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0001-5297-0250; https://orcid.org/0000-0003-1449-3654This study reports a two-step high-energy milling (HEM) route for synthesizing equimolar high-entropy carbide (TiVTaNbW)C powders directly from elemental metals and graphite, without post-milling heat treatments. In the first stage, equiatomic Ti0.2V0.2Ta0.2Nb0.2W0.2 alloys were produced by milling for 6, 12, and 18 h; in the second stage, the alloys were milled with graphite (1:1 M ratio) for 6 and 12 h at 500 rpm. The powders were characterized by SEM/EDS, XRD, FTIR, and TOC analysis. XRD confirmed the presence of the high-entropy carbide phase along with minor intermetallic and binary carbide residues. FTIR revealed metal–carbon bonding and surface hydroxyl/carbonate species, consistent with mild surface oxidation during milling. TOC quantified 6.549 wt% C versus the theoretical 9.74 wt%, evidencing a carbon deficit that may contribute to the residual phases. Prolonged milling enhanced elemental homogeneity and reduced crystallite size. These findings confirm the successful formation of a high-entropy carbide phase, demonstrating the potential of this synthesis method for producing homogeneous carbide powdersArtigo Analysis of sintering curves, microstructure, and microhardness of the Cu-WC composite(Materials Research, 2025-09-26) Gomes, Uílame Umbelino; Marques, Anderson Costa; Silva, Thalita Queiroz e; Araújo, Kívia Fabiana Galvão; Lima, Maria José Santos; Vieira, Pâmala Samara; Lourenço, Cleber da Silva; Mashhadikarimi, Meysam; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0002-8846-658X; https://orcid.org/0009-0008-5675-2419; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0009-0009-6365-2691; https://orcid.org/0000-0003-0668-3925; https://orcid.org/0000-0003-1449-3654Composite materials have gained prominence due to their tailored properties for various applications. Cu-WC composites, combining a copper matrix with tungsten carbide reinforcement, are particularly valuable for electrical conductors and heat sinks. This study examined the sintering behavior of Cu-WC composite powder (10%WC) produced via High-Energy Ball Milling (HEBM) at 400 RPM for 2, 10, and 20 hours. The powders were compacted at 150 MPa and sintered at 900°C with a 1-hour isothermal hold. Sintering curves, microstructure, and Vickers microhardness were analyzed. The results showed that longer milling times led to significant powder expansion up to 750°C, followed by greater shrinkage due to diffusion mechanisms. Sintered samples milled for 10 hours displayed improved carbide distribution in the copper matrix. The highest microhardness was achieved at 20 hours of milling, attributed to refined microstructure. Extended milling times enhanced atomic diffusion during sintering, resulting in a more homogeneous structure and increased hardnessArtigo Influence of the high-energy milling and spark plasma sintering on the formation of Cu − Graphite composite with enhanced properties(Journal of Alloys and Compounds Communications, 2025-05) Gomes, Uílame Umbelino; Lourenço, Cleber da Silva; Raimundo, Rafael Alexandre; Silva, Ariadne de Souza; Morales, Marco Antonio; Vitoriano, Jussier de Oliveira; Lima, Maria José Santos; Filgueira, Marcello; Costa, Franciné Alves da; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0003-0668-3925; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0009-0002-9675-0748; https://orcid.org/0000-0002-3098-5731; https://orcid.org/0000-0002-9357-2088; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0001-5297-0250This study explores the effects of high-energy milling and sintering routes on the microstructure and properties of Cu-10wt%Graphite composites. The powders were milled for 10, 30 and 50 h, and sintered either in resistive oven or spark plasma (SPS). The results showed that milling time influenced the particle size, crystallite size, phase composition, dispersion, and homogeneity of the powders. It was also observed that a longer milling time lead to the formation of composite particles of Cu-Cu2O-C with a smaller particle size. Additionally, during the SPS process, the carbo-reduction of the Cu2O phase takes place, resulting in metallic Cu and graphite phases. The SPS sample exhibited improved densification and enhanced microhardness. Sliding wear tests show that the sample sintered via SPS had better values of average coefficient of friction (COF) and rate of wear, indicating the ability of these samples for sliding electrical contacts. The mechanisms and implications of these findings are discussed. This study contributes to the development of novel Cu-graphite based composites for electrical applicationsArtigo Influence of temperature on the APT carborreduction process for obtaining nanocrystalline WC powder from sheelite concentrate(Materials Research, 2025-05-12) Gomes, Uilane Umbelino; Lourenço, Cleber da Silva; Oliveira, Gerlânea Silva; Morais, Luís Matheus Fernandes de; Nascimento, A. B. G. do; Silva, A. S.; Morales, Marco Antonio; Lima, Maria José Santos; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0003-0668-3925; https://orcid.org/0000-0002-3098-5731; https://orcid.org/0000-0001-8957-9204Tungsten carbide (WC) is a highly relevant material due to its exceptional catalytic properties and applications in composite materials and cutting tools. The production of nanocrystalline and ultrafine WC powders contributes to enhanced properties in these applications. Therefore, this study aims to obtain nanocrystalline WC powders with a high surface area from ammonium paratungstate (APT) derived from scheelite concentrate. To achieve this, a gas-solid reaction (carbothermal reduction) of APT was carried out at different temperatures under a mixed H2/CH4 atmosphere. The results showed that the WC powders obtained at 850°C present a higher purity with a crystallite size of 15.8 nm composed of agglomerates of ultrafine particles of 159 μmArtigo Structural, magnetic and electrocatalytic properties of rock salt oxide nanofibers (Ni0.2Mg0.2Zn0.2Cu0.2-xCo0.2+x)O produced by air-heated solution blow spinning (A-HSBS) for oxygen evolution reaction(Applied Surface Science, 2025-02-15) Gomes, Uilame Umbelino; Oliveira Filho, Ronaldo M.; Alves, Ricardo Francisco; Raimundo, Rafael Alexandre; Hortêncio, Johnnys da Silva; Lopes, Caio Matheus Sousa; Nascimento, Emanuel Pereira; Araújo, Allan Jedson Menezes de; Loureiro, Francisco José Almeida; Medeiros, Eliton Souto de; Morales, Marco Antonio; Macedo, Daniel Araújo de; Menezes, Romualdo Rodrigues; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0001-8958-7263; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0000-0002-4028-5499; https://orcid.org/0000-0003-1294-8897; https://orcid.org/0009-0002-9856-9846; https://orcid.org/0000-0003-0386-9329; https://orcid.org/0000-0002-5050-3859; https://orcid.org/0000-0002-9033-9141; https://orcid.org/0000-0002-3098-5731; https://orcid.org/0000-0003-0466-1458; https://orcid.org/0000-0003-4316-2168In this study, we investigated the fabrication of high entropy rock salt (Ni0.2Mg0.2Zn0.2Cu0.2-xCo0.2+x) (x = 0, 0.1, 0.2) nanofibers via air-heated solution blow spinning (A-HSBS). The samples were monophasic, with compositions considering the gradual substitution of non-magnetic Cu by magnetic Co, transitioning samples from high to medium configurational disorder entropy. SEM images revealed that nanofibers were composed of aggregated nanoparticles. XRD showed a gradual reduction in the lattice parameter due to the replacement of Cu by Co. UV–Vis analysis indicated an increase in the band gap from 1.42 to 2.47 eV with increasing Co concentration. Magnetically, the addition of Co caused a positive shift in the Néel transition temperature (TN), increasing from 117 K to 155 K. The oxides exhibited antiferromagnetic behavior (AFM) below TN and displayed a spin glass regime. XPS analysis showed an increase in the charge state of Ni3+ and the presence of Co3+ with the substitution of Cu by Co. The electrocatalytic activity for the oxygen evolution reaction was enhanced in the medium-entropy oxide catalysts (x = 0.2), achieving an overpotential of 326 mV@10 mA cm−2, along with excellent short-term stability for 12 hArtigo Synthesis and characterization of (Fe0.2Ni0.2Co0.2Al0.2Zn0.2)3O4 high entropy oxide as electrocatalyst for oxygen evolution reaction(Journal of Alloys and Compounds, 2025-04-10) Gomes, Uílame Umbelino; Vasconcelos, Gabrel dos Santos; Raimundo, Rafael Alexandre; Lima, Maria José Santos; Arújo, Kívia Fabiana Galvão; Silva, Matheus Duarte da; Macedo, Daniel Araújo de; Karimi, Meysam Mashhadikarimieysam; Huaman, Raquel Checca; Gastelois, Pedro Lana; Morales, Marco Antonio; https://orcid.org/0009-0008-6974-9630; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0003-0466-1458; https://orcid.org/0000-0003-1449-3654; https://orcid.org/0000-0002-8898-2584; https://orcid.org/0000-0001-7849-5013; https://orcid.org/0000-0002-3098-5731In this work, the high entropy oxide (HEO) (Fe0.2Ni0.2Co0.2Al0.2Zn0.2)3O4 was synthesized at 600 ºC (labeled as HEO-600) by sol-gel method assisted with polyvinylpyrrolidone (PVP). Additional samples were produced at higher temperatures and the spinel and rock-salt high entropy oxides were formed. The characterizations were carried out by XRD, EDS, XPS, TEM, Mössbauer spectroscopy, AC and DC magnetometry, UV–vis, FTIR, and electrochemical experiments. For sample HEO-600, the XPS analysis confirmed the equimolar composition of the sample. The EDS results showed homogeneous distribution of the cations within the sample. The TEM showed non-aggregated particles with size of 9.2 nm. The sample had superparamagnetic behavior at room temperature. The Mössbauer results showed Fe occupancies in the A and B sites of 43 and 57 %, evidencing the formation of a partial inversed spinel. The DC and AC susceptibility data showed the presence of a spin glass phase with onset at 206 K, this magnetic phase was wiped under a field of about 4300 Oe. The electrochemical characterization showed the ability of this sample for oxygen evolution reaction applications. The HEO-600 sample showed overpotential of 358 mV at 10 mA cm−2. This work brings new developments in the understanding of high entropy oxides and provides a useful application as an electrocatalyst in OER processesArtigo Synthesis, structural, and magnetic properties of high-entropy (Fe0.2Co0.2Cu0.2Ni0.2Mn0.2)Nb2O6(Magnetochemistry, 2025-10-28) Gomes, Uilame Umbelino; Silva, Fernando Erick Santos da; Silva, Matheus Duarte da; Araújo, Kívia Fabiana Galvão; Torres, Marco Antonio Morais; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0001-6971-6718; https://orcid.org/0009-0008-1424-4491; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0002-3098-5731n this work, we present the first report on the synthesis via the sol–gel method of a high-entropy (Fe0.2Co0.2Cu0.2Ni0.2Mn0.2)Nb2O6 with columbite–orthorhombic structure. Polyvinylpyrrolidone (PVP), ammonium niobium oxalate, and equimolar amounts of Fe, Co, Cu, Ni, and Mn ions were used. The refinement of the XRD pattern showed the presence of niobate crystallites with an average size of 48.4 nm and a fraction of 7.6 wt% of a spinel-like phase. At temperatures below 5 K, the DC and AC magnetometry results revealed the presence of a ferromagnetic-like phase due to the niobate phase. The Mössbauer spectrum at 300 K showed a paramagnetic and two magnetically ordered components corresponding to the niobate and the spinel-like phases, respectively. The spectral components were typical of Fe3+, indicating the presence of cation vacancies. The elemental mapping obtained from EDS measurements showed compositional homogeneity. The XRF measurements confirmed a composition consistent with nominal values. These results confirm the feasibility of synthesizing entropy-stabilized columbite oxides via the sol–gel route, opening new opportunities for the design of multifunctional ceramics with tunable structural and magnetic properties for high-performance thermal barrier coatings and energy conversion applicationsArtigo Structural and magnetic behavior of milled EUROFER with Nb2O5 additions(Journal of Magnetism and Magnetic Materials, 2025-10-15) Gomes, Uilane Umbelino; Menezes, Roberta Araújo Cavalcante de; Gurgel, Diêgo Pires; Silva, Isaac Barros Tavares da; Melo, Ingryd Kely Cosme; Lima, Maria José Santos; Filgueira, Marcello; Torres, Marco Antonio Morales; Araújo, José Humberto; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0001-6209-7096; https://orcid.org/0000-0002-2351-291X; https://orcid.org/0009-0005-6160-3256; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0001-5297-0250; https://orcid.org/0000-0002-3098-5731; https://orcid.org/0000-0002-3390-8600EUROFER is a ferritic-martensitic steel with reduced activation, it is being used in the construction of nuclear fusion reactors due to its robust mechanical performance when exposed to radiation, neutron and helium bombardment. However, its operational temperature is limited to 500 °C, caused by microstructural changes at higher temperatures. This study investigates the structural and magnetic behavior of EUROFER alloy with the addition of niobium pentoxide (Nb2O5) after 15 h high-energy milling. The aim of this work is to study the microstructure, crystallite size, lattice parameters, and magnetic properties of the composite, using X-ray diffraction, magnetometry and Mössbauer spectroscopy. The results revealed significant reduction in crystallite size and alterations in magnetic properties, including decreased saturation magnetization and increased coercivity, while Mössbauer spectroscopy confirms no oxidation of EUROFER during the milling process and suggests Nb incorporation into the alloy. These findings suggested that the presence of Nb2O5 during the milling process promoted the formation of a new solid solution, making the alloy less susceptible to magnetic fields, an essential characteristic for applications involving exposure to high magnetic fieldsArtigo The influence of thermal processing with H2 atmosphere on the physical properties and microstructure for use in electrolytic capacitors of Nb(Materials Research, 2025-08-04) Gomes, Uilane Umbelino; Silva, Ariadne de Souza; Vasconcelos, Gabriel dos Santos; Vitoriano, Jussier de Oliveira; Silva, Giovanna Xavier de Souza; Araújo, Kívia Fabiana Galvão; Lourenço,Cleber da Silva; Lima, Maria José Santos; Morales, Marco Antonio; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0009-0002-9675-0748; https://orcid.org/0009-0008-6974-9630; https://orcid.org/0000-0002-9357-2088; https://orcid.org/0009-0008-1894-2430; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0003-0668-3925; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0002-3098-5731This study evaluated the effect of thermal processing in hydrogen (H2) and argon (Ar) atmospheres on the physical and microstructural properties of niobium (Nb) powders for electrolytic capacitors. Nb powders were treated at 750 °C, 850 °C and 950 °C with isothermal holds of 60 min and 120 min—samples H2-850-120 and Ar-850-120 denote the H2 and Ar atmospheres—using a heating rate of 10 °C/min. Powders were compacted at 150 MPa and sintered at 1200 °C under H2. XRD confirmed predominant βH phase and minor NbO in H2-treated powders, while Ar-treated samples exhibited stronger NbO reflections. FEG-SEM micrographs showed finer grains and reduced porosity in H2-850-120. These results demonstrate that hydrogen-atmosphere processing yields Nb powders with improved homogeneity, particle size reduction and densification—key attributes for enhanced capacitor performanceArtigo Performance of quasicrystalline particles as reinforcements in copper matrix composites: microstructural and mechanical properties(Materials Letters, 2025-10-15) Gomes, Uílame Umbelino; Costa, Ingrid Mayara Figueiredo da; Raimundo, Rafael Antonio; Silva, Thalita Queiroz e; Vieira, Pâmala Samara; Alves, Ricardo Francisco; Feitosa, Francisco Riccelly Pereira; Araújo Júnior, Francisco Wlaudy Erimar Lourenço de; Cavalcante, Danielle de Guedes Lima; Lima, Bruno Alessandro Silva Guedes de; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0000-0002-9943-9464; https://orcid.org/0009-0008-5675-2419; https://orcid.org/0009-0009-6365-2691; https://orcid.org/0000-0001-8958-7263; https://orcid.org/0000-0001-7630-0067; https://orcid.org/0000-0001-6088-5478; https://orcid.org/0000-0003-1975-311X; https://orcid.org/0000-0003-4966-7140This work investigates the use of quasicrystalline particles (AlCuFe, AlCuFeB, AlCuFeSi) as reinforcements in copper matrix composites to enhance mechanical properties. Composite powders were produced by high-energy milling and analyzed by XRD, SEM/FESEM, and Vickers microhardness tests. Results showed that adding AlCuFeSi significantly reduced crystallite size and particle size, while markedly increasing microhardness—reaching ∼ 90 HV after 10 h of milling. The study underscores AlCuFeSi’s effectiveness in inducing residual stresses and crystalline defects, greatly improving material strength and making it highly promising for various technological applicationsArtigo CuNb2O6 particles obtained via solid-state reaction and application as electrocatalyst for oxygen evolution reaction(Ceramics-Switzerland, 2025-05-13) Gomes, Uilane Umbelino; Araújo, Kívia Fabiana Galvão de; Lorenço, Cleber da Silva; Souza, Vitor Manoel Silva Fernandes de; Silva, Matheus Duarte da; Vasconcelos, Gabriel dos Santos; Lima, Maria José Santos; Santos, Jakeline Raiane Dora dos; Gomes, Kelly Cristina; Loureiro, Francisco J. A.; Morales, Marco Antonio; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0003-0668-3925; https://orcid.org/0009-0000-1496-4853; https://orcid.org/0009-0008-1424-4491; https://orcid.org/0009-0008-6974-9630; https://orcid.org/0000-0001-8957-9204; https://orcid.org/0000-0002-1983-8298; orcid.org/0000-0002-0255-8740; https://orcid.org/0000-0002-5050-3859; https://orcid.org/0000-0002-3098-5731Copper niobate (CuNb2O6) is an important compound due to its low cost and polymorphism, presenting monoclinic and orthorhombic phases, which leads to unique physical–chemical properties. The electrochemical performance of efficient electrocatalysts for the oxygen evolution reaction (OER) is of importance in order to produce hydrogen gas from water. In this context, this work reports the synthesis of CuNb2O6 particles by high-energy milling for 5 and 10 h, and subsequent thermal treatment at 900 °C for 3 h. The samples were characterized by XRD, XRF, FESEM, RAMAN, UV–Vis, and FT-IR techniques, and were applied as electrocatalysts for the OER. The samples had both monoclinic and orthorhombic crystalline phases. The band gaps were in the range of 1.92 to 2.06 eV. In the application for the OER, the particles obtained by 5 and 10 h of milling exhibited overpotentials of 476 and 347 mV vs. RHE at 10 mA cm−2, respectively. In chronopotentiometry experiments for 15 h, the samples exhibited excellent chemical stability. The electrochemical performance of the sample milled for 10 h showed superior performance (347 mV vs. RHE) when compared with electrocatalysts of the same type, demonstrating that the methodology used to synthesize the samples is promising for energy applicationsArtigo Development of a method for the synthesis of ammoniacal niobium oxalate trihydrate for use as a precursor in chemical reactions(Materials Research, 2025-08-22) Gomes, Uilane Umbelino; Souza, Vitor Manoel Silva Fernandes de; Duarte, Vinícius Gomes de Sousa; Araújo, Kivia Fabiana Galvão; Oliveira, Gerlânea Silva; Pergher, Sibele Berenice Castellã; Lima, Maria José dos Santos; https://orcid.org/0000-0002-5825-958X; https://orcid.org/0000-0002-4074-0762; https://orcid.org/0009-0000-1496-4853; https://orcid.org/0000-0002-7197-2582; https://orcid.org/0000-0001-8957-9204In this project, a method was developed to synthesize ammoniacal niobium oxalate (NH4)(NbO(C2O4)(H2O)ᵧ)·XH2O, aimed at its application in the preparation of niobium-incorporated materials. This transition metal exhibits excellent properties and is widely available in Brazil. Its versatility makes it essential for metal alloys and electronic components. The synthesis was based on physical and chemical processes, including fusion, decantation, filtration, and complexation, using niobium pentoxide and potassium bisulfate. Rigorous procedures were implemented to ensure precursor quality. Material characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and thermogravimetric analysis (TGA), which collectively confirmed the material's morphology, structure, and thermal stability. The results confirmed the efficient synthesis of high-purity niobium oxalate, with the developed method demonstrating technical feasibility by preserving the material's essential physicochemical properties, as verified by the characterization techniques. Key innovations included replacing acid leaching with a more efficient method, implementing neutral-pH decantation instead of traditional acidic processes, and the strategic use of an aqueous acetic acid solution in the washing step. This combination of advancements enabled a 75% reduction in water consumption during the washing stage, thus establishing a significantly more sustainable synthesis protocol for producing this precursor without compromising final product qualityArtigo Optimizing surface properties of AISI 409 stainless steel through duplex treatment consisting of plasma nitriding and vanadium-based deposition(ACS Omega, 2025-07-16) Silva, André Felipe Soares do Monte e; Almeida, Larissa Solano de; Silva, Leandro Almeida; Rossino, Luciana Sgarbi; Nunes, Maelson Sousa; Libório, Maxwell Santana; Costa, Thércio Henrique de Carvalho; Bandeira, Rafael Marinho; Sousa, Rômulo Ribeiro Magalhães de; https://orcid.org/0000-0001-7429-4273; https://orcid.org/0000-0001-6858-1524; https://orcid.org/0000-0003-2755-8349; https://orcid.org/0000-0002-0060-8943; https://orcid.org/0000-0003-1579-8775; https://orcid.org/0000-0002-4362-7466; https://orcid.org/0000-0003-2062-6505This study proposes a surface modification methodology for AISI 409 stainless steel by combining cathodic cage plasma nitriding (CCPN) and deposition (CCPD), evaluating the benefits of this duplex treatment over individual treatments. The mechanical strength, tribological behavior, and corrosion resistance of the treated surfaces were investigated in relation to processing parameters and resulting microstructures. Analyses were performed using XRD, SEM, Vickers microhardness, ball-on-disc testing, and corrosion testing in a 3.5% NaCl solution. The duplex treatment at 400 and 450 °C, consisting of CCPN followed by CCPD, promoted significant surface modifications. Nitriding resulted in a thick layer of Fe3N, Fe4N, and CrN, increasing hardness and wear resistance, with final improvements of 5.7 and 33.5 times, respectively. The subsequent VN deposition enhanced corrosion resistance, shifting the potential from −396 mV to −221 mV, indicating reduced electrochemical activity. These results confirm the treatment’s potential for automotive exhaust systems, requiring lightweight, durable materials in aggressive environmentsArtigo Analysis of the photocatalytic activity and adsorption of CuS nanoparticles synthesized by chemical Route for the degradation of organic contaminants(ACS Omega, 2025-07-11) Costa, Thércio Henrique de Carvalho; Silva, Crislaine Beatriz Guedes da; Lima, Luciano Lucas Fernandes; Araújo, Antônio Marcos Urbano de; Vieira, Pâmala Samara; Garcia, Ramón Raudel Peña; Silva, André Felipe Soares do Monte e; Sousa, Rômulo Ribeiro Magalhães de; Leite, Amanda Melissa Damião; Libório, Maxwell Santana; https://orcid.org/0000-0001-7429-4273; https://orcid.org/0000-0003-4671-6170; https://orcid.org/0000-0001-8994-0418; https://orcid.org/0009-0009-6365-2691; https://orcid.org/0000-0001-9725-5234; https://orcid.org/0000-0003-2062-6505; https://orcid.org/0000-0003-1597-4230; https://orcid.org/0000-0003-1579-8775The treatment of industrial and domestic wastewater is an urgent environmental need. In this context, the photocatalytic activity of semiconductors offers a promising route for degrading organic contaminants. CuS nanoparticles were chemically synthesized using thiourea and copper sulfate in varying concentrations to investigate how precursor ratios affect the chemical composition, structural and morphological features, and optical-electronic properties. The photocatalytic degradation of methylene blue under low-power visible light (10 W), without H2O2 and using a low catalyst dose, showed promising results. Samples with lower sulfate content reached ∼78% degradation, while those with 0.20 M thiourea and 0.15–0.20 M sulfate achieved up to 99%. Mesoporous and macroporous structures (3.85–50 nm) promoted adsorption without hindering photocatalytic efficiency, indicating that, in certain samples, the combined morphological and electronic features enhanced dye removalArtigo A novel technology to deposition diamond-like carbon thin films: cathodic cylinder plasma deposition(JOM, 2025-07-16) Costa, Thércio Henrique de Carvalho; Araújo, Anthunes Íkaro de; Nascimento, Igor Oliveira; Feitor, Michelle Cequeira; Libório, Maxwell Santana; Linhares, Álvaro Albueno da Silva; Vieira, Pâmala Samara; Alves, Salete Martins; https://orcid.org/0000-0001-7429-4273; https://orcid.org/0000-0003-0458-2557; https://orcid.org/0000-0002-4850-9493; https://orcid.org/0009-0007-8181-7280; https://orcid.org/0000-0003-1579-8775; https://orcid.org/0009-0009-6365-2691; https://orcid.org/0009-0002-0627-0530; https://orcid.org/0000-0002-2659-4746This study investigates the influence of deposition temperature on the formation of diamond-Like carbon (DLC) films on AISI 4340 steel using the cathodic cylinder plasma deposition (CCyPD) technique. The films were deposited in an acetylene atmosphere at 350°C, 400°C, and 450°C, and the samples were characterized using Raman spectroscopy, X-ray diffraction (XRD), Vickers hardness testing, and friction coefficient measurements. The results indicate that increasing the deposition temperature significantly impacts the microstructure and tribological properties of the DLC films. At 450°C, the films exhibited higher hardness due to the increased concentration of sp3 carbon, which led to a denser and more rigid structure. However, a notable reduction in film thickness was observed, likely due to increased carbon deposition efficiency and structural densification. The film deposited at 400°C demonstrated the optimal balance between hardness and wear resistance. These findings highlight the critical role of temperature control in optimizing the mechanical and tribological properties of DLC films for various industrial applicationsArtigo Corrosion resistance of SAE 5160 steel deposited by duplex simultaneous treatment with hastelloy cathodic cage(Lubricants, 2025-04-12) Costa, Thércio Hentique de Carvalho; Brito, Marcos Cristino de Sousa; Pereira, Juliermes Carvalho; Silva, Lauriene Gonçalves da Luz; Monção, Renan Matos; Sousa, Ediones Maciel de; Sampaio, Weslley Rick Viana; Nascimento, Igor Oliveira; Araújo, Anthunes Íkaro de; Feitor, Michelle Cequeira; Sousa, Rômulo Ribeiro Magalhães de; https://orcid.org/0000-0001-7429-4273; https://orcid.org/0000-0002-0524-5117; https://orcid.org/0009-0006-1406-6184; https://orcid.org/0000-0003-4893-9976; https://orcid.org/0000-0002-0721-6766; https://orcid.org/0000-0003-2062-6505; https://orcid.org/0000-0003-3268-0197; https://orcid.org/0000-0001-5174-1077; https://orcid.org/0000-0003-0458-2557; https://orcid.org/0000-0002-4850-9493SAE 5160 steel, classified as high-strength, low-alloy steel, is widely used in the automotive sector due to its excellent mechanical strength and ductility. However, its inherently low corrosion resistance limits its broader application. This study explores the application of the cathodic cage plasma deposition (CCPD) technique to enhance the corrosion resistance of SAE 5160 steel. The treatment was performed using a Hastelloy cathodic cage under two atmospheric conditions: hydrogen-rich (75%H2/25%N2) and nitrogen-rich (25%H2/75%N2). Comprehensive analyses revealed significant improvements in surface properties and corrosion resistance. The hydrogen-rich condition (H25N) facilitated the formation of Cr0.4Ni0.6 and CrN phases, associated with a nanocrystalline structure (37.6 nm) and a thicker coating (45.5 μm), resulting in polarization resistance over 290 times greater than that of untreated steel. Conversely, nitrogen-rich treatment (H75N) promoted the formation of Fe3N and Fe4N phases, achieving a dense but thinner layer (19.6 μm) with polarization resistance approximately 20 times higher than that of untreated steel. These findings underscore the effectiveness of CCPD as a versatile and scalable surface engineering technique capable of tailoring the properties of SAE 5160 steel for use in highly corrosive environments. This study highlights the critical role of optimizing gas compositions and treatment parameters, offering a foundation for advancing plasma-assisted technologies and alloying strategies. The results provide a valuable framework for developing next-generation corrosion-resistant materials, promoting the longevity and reliability of high-strength steels in demanding industrial applicationsArtigo Enhancing wear resistance of AISI 1045 steel through duplex plasma treatment with vanadium cage(JOM, 2025-02) Silva, Lucas Pereira da; Libório, Maxwell Santana; Sousa, Ediones Maciel de; Silva, Lauriene Gonçalves da Luz; Monção, Renan Matos; Brito, Marcos Cristino de Sousa; Costa, Thércio Henrique de Carvalho; Almeida, Larissa Solano de; Rossino, Luciana Sgarbi; Sousa, Rômulo Ribeiro Magalhães de; https://orcid.org/0000-0001-7429-4273; https://orcid.org/0000-0003-1579-8775; https://orcid.org/0000-0002-5595-2207; https://orcid.org/0000-0001-5174-1077; https://orcid.org/0000-0001-9097-9950; https://orcid.org/0000-0003-4893-9976; https://orcid.org/0000-0002-0524-5117; https://orcid.org/0000-0001-6858-1524; https://orcid.org/0000-0003-2755-8349; https://orcid.org/0000-0003-2062-6505AISI 1045 steel is widely used in mechanical parts of industrial equipment. However, its surface mechanical properties can be improved to increase this steel's applicability and service life. This study proposes an evaluation of the feasibility of duplex treatment concerning plasma nitriding (PN) and cathodic cage plasma deposition (CCPD) for reducing wear on AISI 1045 steel. X-ray diffraction, roughness, Vickers hardness, scanning electron microscopy, and wear test results showed that duplex treatment (PN + CCPD) caused the formation of nitride phases responsible for surface hardening, a significant increase in wear resistance for samples subjected to PN and duplex treatment. However, the sample subjected to duplex treatment showed a hardness 77.2% higher than that of the sample that was only nitrided and a greater depth of surface modification, giving the duplex treatment mechanical advantages due to the longer period of time required for AISI 1045 mechanical partsArtigo Effects of plasma treatment on drag reduction and wettability properties of Sylgard®184(Applied Physics A-Materials science & Processing, 2025-01) Lima, Luiz Henrique Pinheiro de; Medeiros Neto, João Freire; Lima, Jackson Silva; Rangel, Jonathan Ferreira; Lima, Luciano Lucas Fernandes; Queiroz, José César Augusto de; Feitor, Michelle Cequeira; Bessa, Kleiber Lima de; Costa, Thércio Henrique de Carvalho; https://orcid.org/0000-0001-7429-4273; https://orcid.org/0000-0001-9560-2538; https://orcid.org/0000-0003-4671-6170; https://orcid.org/0000-0003-3149-6830; https://orcid.org/0000-0002-4850-9493; https://orcid.org/0000-0002-4133-0298This study investigates the surface modification of Sylgard®184 polydimethylsiloxane (PDMS) samples through plasma treatments using two configurations: a mixed gas composition (acetylene, argon, and chloroform) and pure argon. The primary objective was to evaluate how these treatments affect the physicochemical properties of the surfaces and their drag-reduction capabilities. Analyses conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) revealed diverse morphologies and chemical compositions resulting from different treatment parameters. Key findings indicate that an optimal combination of surface roughness and hydrophobic functional groups, notably Si–CH3, and C = C bonds, is crucial for achieving superhydrophobic surfaces and effective drag reduction. Samples treated with the mixed gas configuration exhibited enhanced drag reduction capabilities, particularly those treated at 0.08 A for 60 min, which showed balanced roughness and film uniformity. Conversely, argon-treated samples displayed variable performance depending on treatment conditions, with the 0.08 A for 60 min of treatment demonstrating consistent drag reduction, especially at higher Reynolds numbers. The correlation between viscous sublayer thickness and surface roughness underscored the significance of surface morphology in fluid–surface interactions. While high roughness increased flow resistance under turbulent conditions, moderate roughness maintained drag reduction efficiency. These findings highlight the practical importance of optimizing plasma treatment parameters to develop effective superhydrophobic surfaces for various applications, contributing to advancements in industries where drag reduction is critical