Resumo em Inglês:

This study presents the pequi (Caryocar coriaceum) as a new biomass source for carbon dots synthesis. The pequi almond, usually discarded, was used as the biomass precursor in one-step hydrothermal green synthesis of carbon dots. Pequi-based carbon dots (PQ-CDs) exhibited an estimated height of around 8 nm, with hydroxyl, carbonyl, and amino functional groups confirmed by FTIR, bright blue emission, and a quantum yield of 17.9%. PQ-CDs were employed as fluorescent sensors for Fe3+ ions, based on the quenching of PQ-CDs fluorescence by interaction with Fe3+ ions. The sensor demonstrated a linear relationship between the quenching of PQ-CDs fluorescence and the increase in Fe3+ ion concentration, with a LOD of 1.16 μmol L-1, well below the maximum Fe3+ concentration for drinking water established by the WHO. PQ-CDs are a cost-effective and highly sensitive alternative for Fe3+ ions detection in drinking water samples from the Cariri region.

Resumo em Inglês:

This paper presents a case study regarding the hard turning of tool steel specimens when some insidious surface patterns were observed beyond the usual parallel feed marks. An optical three-dimensional measuring device was used to characterize and compare common reference surfaces and textured profiles. Subsequently, these data were analyzed using an image processing computational tool, through which it was possible to infer that, indeed, the surface with an unusual appearance exhibited a very well-defined orientation texture. The vibration monitoring data during the turning process of the samples were then compared through spectral density analysis of the signal, from which a dominant frequency was observed in the range of 3100 to 3300 Hz for both, but with a considerably higher amplitude peak for the textured one, indicating an unstable cut, i.e., one subjected to excessive vibrations. Finally, the experimental modal analysis performed on the tool used identified a fundamental frequency of the same order of magnitude, which allows for establishing a potentially causal correlation between the occurrence of chatter and the obtaining of the textured surface. This technique may be a pleasant opportunity to improve the tribology performance of tools, as the potential of textures are well presented in recent studies.

Resumo em Inglês:

P91 steels are widely used in power plants. They were developed in a context of increasing process temperatures to increase efficiency and reduce CO2 emissions into the atmosphere. In this sense, the energy industry aims to increase its efficiency and process control, for which temperature control is essential and welding thermocouples in P91 steel pipes may be necessary. In this context, this study aims to evaluate, in a preliminary way, the influence of welding thermocouples in P91 steel specimens subjected to fatigue testing. The results showed that in general there is a decrease in fatigue life, more prominent for 90 and 80% of the load. In addition, the insertion of defects such as welding points increases the probability of the initiation of fatigue cracks in the welded areas due to loss of properties. From 70% of the load onwards, infinite fatigue life was achieved for the welded and as suplied cases, and in both conditions the same fracture shape was obtained, observed macroscopically.

Resumo em Inglês:

This study presents the results of constructing the master curve through dynamic mechanical analysis (DMA) of unidirectional composites made of glass fiber and epoxy resins of classes F and H to evaluate the thermal stability and durability of these materials. For this purpose, the viscoelastic behavior of the polymers and composites was evaluated using the time-temperature superposition (TTS) model, applying the empirical Sigmoidal equation and the Williams-Landel-Ferry (WLF) method to estimate the behavior at different temperatures. This approach allows the extension of experimentally accessible frequencies and the description of the entire relaxation behavior of the polymers. The time-temperature shift factor was determined from the DMA curves, generated from individual isotherms at different oscillation frequencies. It was observed that the viscoelastic behavior depends on both frequency and temperature, with a general equivalence between the behavior related to frequency and temperature during the transition processes. The composite materials manufactured by filament winding were also subjected to physical and thermal characterization through differential scanning calorimetry (DSC) and DMA, ensuring the consistent quality of high-performance structural composites. Once the time-temperature shift factors were described by the model, the master curve could be extrapolated to any desired temperature, reducing the need for extensive empirical testing.

Resumo em Inglês:

Tungsten 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 μm.

Resumo em Inglês:

Over the last decades, high-entropy refractory alloys with shape memory (SM) effect have been increasingly studied. However, identifying the optimal composition among the vast array of potential systems remains a significant challenge for the scientific community. In this work, Ni-Ti alloys are studied via molecular dynamics simulations to determine the range of martensitic phase transformations, with the goal of developing in the future medium- (MEA) and high-entropy alloys (HEA) that exhibit SM behavior. Virtual samples with compositions of Ni(100-x)Tix (45 < x < 55) were created using the LAMMPS software, in a system consisting of 2000 atoms that interacted under the modified embedded atom method (MEAM) interatomic potential. In addition, simulations were also performed on systems with sizes of 4000 and 8000 atoms to assess the effect of system size on the phase transformation behavior. The structural evolution and phase transformations were analyzed by applying heating and cooling rates of 1 K/ps, controlled by the isothermal-isobaric (NPT) ensemble. The compositional range, in atom percent, for martensitic transformations was found to be 47.5 to 52.5% nickel. Martensitic transformations are complex, showing either direct or two-step transformations. At lower temperatures, the phases R and B19’ can be formed as a function of Ni content. In several cases, at intermediate temperatures, the Ni4Ti3 compound forms and influences the phase transformation process. Also, the larger the system size, the lower the phases transformation temperatures.

Resumo em Inglês:

In the present work, we explored the production of Cu-Sn alloy coatings with anti-corrosive properties using simple pulse current (SPC) electrodeposition. The effects of the pulse parameters - pulse frequency (F) and duty cycle (γ) - on the surface characteristics of the coatings produced at a constant average current density value were evaluated to verify the corrosion protection performance of these coating systems in a saline medium. Coatings with small grains, high Sn content, a single Cu6Sn5 phase microstructure, and reduced porosity were obtained by increasing F and γ, improving the cathodic current efficiency and charge transfer resistance in the NaCl 3.5%w/v. The most protective coating, produced at F = 1500 Hz and γ = 50%, showed a Sn content near that of commercial bronze and a charge-transfer resistance of 4097 Ω cm2, which is approximately 2.5 times higher than the resistance of a protective alloy obtained by DC electrodeposition.

Resumo em Inglês:

The 6xxx series alloys [Al-Mg-Si] are valued for their excellent mechanical and electrical properties, making them suitable for power conductors in non-steel core transmission and distribution lines. This study investigates the growth of the dendritic microstructure in the Al-0.6wt%Mg-0.8wt%Si-0.2wt%Fe alloy, specifically under horizontally solidified conditions. We employ both experimental techniques and mathematical modeling to predict the growth of the secondary dendritic arm spacing (SDAS). Samples of the as-cast alloy were obtained using a water-cooled horizontal solidification device. Our research starts with a mathematical model that was originally developed for solidification conditions close to thermodynamic equilibrium (low cooling rates - TR). We extend this model to address non-equilibrium conditions (high TR) by incorporating the reverse diffusion parameter β into our analysis. The experimental relationships for SDAS as functions of TR and local solidification time (tSL) are expressed with the equations: SDAS = constant × (TR)(-1/3) and SDAS = constant × (tSL)(1/3). We found a good agreement between the results from our iterative method and the experimental values. Additionally, we utilized a recently developed theoretical formulation for nonequilibrium nucleation to predict the Gibbs-Thomson coefficient under these conditions.

Resumo em Inglês:

Self-sensing cementitious composites have attracted significant attention in Structural Health Monitoring (SHM) due to their semiconductive and piezoresistive properties, achieved through incorporations conductive fillers such as graphite powder and carbon microfibers. This study evaluated cementitious composites with 0.4%, 0.6%, 0.8%, and 1% of carbon microfibers by mass, analyzing their mechanical, electrical, and microstructural properties. The results indicated that higher fiber contents (0.8% and 1%) increase flexural tensile strength and electrical conductivity. Scanning Electron Microscopy (SEM) reveals void formation around fibers due to their sinuosity. Piezoresistivity analysis demonstrate increased sensitivity to mechanical stress, although the linearity and reproducibility of the piezoresistive response decrease at intermediate fiber contents. Overall, findings confirm the feasibility of developing self‑sensing materials for SHM, while underscoring the need for further studies on durability and large‑scale implementation.

Resumo em Inglês:

Multilayered conversion coatings (MCCs) can be produced on carbon steel via sol-gel dip coating to improve the corrosion resistance of alumina film/conversion coating/carbon steel systems in a saline medium. Nonetheless, the deposition parameters used to produce the MCCs can affect this performance, and the optimum conditions are generally found using univariate studies. In this work, Silica/boehmite (SB) and boehmite/silica (BS) MCCs were produced on carbon steel via sol-gel dip coating, using a central composite experimental design to evaluate the effects of deposition time (t), substrate removal speed (v), and heat treatment time (HT) on corrosion resistance of the complete system in a saline medium. This unprecedented statistical study allowed us to determine optimal MCC deposition conditions for producing coating systems with superior anti-corrosive properties. v and HT had the most significant impact on anticorrosive performance. The SB-MCC system, optimized at t = 116 s, v = 368 mm/min, and HT = 70 min, showed the best corrosion resistance (Rg = 81.6 kΩ cm2). Improved surface roughness and better coverage of sharp structures enhanced alumina adhesion, increasing stability in saline environments compared to BS-MCC/alumina.

Resumo em Inglês:

The aim of this work is to evaluate mechanical and specifically tribological properties of TiO2 (titanium dioxide) coatings on SAE 4140 steel. The substrates were quenched, tempered and plasma nitrided prior to the deposition of the thin films. The TiO2 films were deposited in two different routes: namely reactive and metallic deposition. The samples were characterized by X-ray diffraction (XRD), Vickers microhardness (HV), instrumented indentation, measurement of film thicknesses through scanning electron microscopy (SEM) and film adhesion via Rockwell C indentation (VDI 3198 standard). The tribological behavior was evaluated using pin-on-disc wear tests (ASTM G99-17 standard). Consequently, the tribological performance of samples with and without a TiO2 film was examined, the results indicate that the films increased surface hardness and had good adhesion to the substrate, however, statistically no significant changes were noted in the wear resistance.

Resumo em Inglês:

The ornamental stone industry generates a huge amount of marble waste around the world, which requires sustainable disposal. This investigation aimed to synthesize a new biphasic calcium phosphate-magnesium phosphate bioceramic using marble waste as an alternative carbonate precursor. The phosphate bioceramic was synthesized using a wet chemical precipitation method in different Ca/P ratios. After the synthesis step, the resulting powders were characterized in terms of X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR) and average crystallite size. For the conditions studied, the results showed that the use of marble waste allowed the obtaining of binary mixtures of the type ß-calcium pyrophosphate (ß-Ca2P2O7)/magnesian whitlockite ((CaMg)3(PO4)2). The new biphasic phosphate powders presented average crystallite size in the range of 42.56 nm to 57.55 nm. Thus, marble waste can be recycled to obtain biphasic phosphate bioceramic for medical applications with relevant repercussions on the circular economy.

Resumo em Inglês:

The UNS S41003 (ASTM A1010) is a lean stainless steel with a chromium content of 10.5-11.0%. Its relatively low cost and enhanced corrosion resistance make it a promising alternative to carbon steels in various applications. Depending on the processing route the UNS S41003 with low carbon (<0.02%) and small Ni addition (~0.30%) may present ferritic, martensitic or ferritic-martensitic microstructures. In this work the corrosion resistance was evaluated in specimens processed by three different ways: hot rolling (HR), batch annealing (ANN), and water quenching from 1000ºC (Q). The microstructure of the HR is majoritarily martensitic, but also contains delta (δ) ferrite and fine dispersed carbides. The ANN specimen has equiaxial α ferritic grains with intergranular Cr carbides, and the quenched (Q) was martensitic. Polarization curves were carried out in 0.1M HCl solution. DL-EPR tests were also performed to evaluate the intergranular corrosion susceptibilities. It was observed that the martensitic microstructures have better corrosion than the annealed steel in polarization tests. which was highly susceptible to intergranular attack due to sensitization caused by intergranular Cr carbides.

Resumo em Inglês:

This study investigates the machining performance of trochoidal toolpaths in hardened AISI 4340 steel. Three toolpaths—conventional, horizontal semi-ellipse, and vertical semi-ellipse—were analyzed in terms of machining time and machining forces under dry and flood coolant conditions. Computer Numerical Control (CNC) programs were optimized using circular interpolation and repetition commands to minimize number of command blocks and maintain effective feed rates. Results showed the vertical semi-ellipse trajectory reduced machining time by 18.9% compared to the conventional path, while the horizontal semi-ellipse presented stable machining forces across both dry and wet conditions but had the longest machining time. The use of coolant significantly decreased machining forces in the conventional and vertical semi-ellipse trajectories, enhancing performance. The semi-ellipse paths demonstrated smoother tool transitions and optimized material removal, offering superior force stability. These findings underscore the importance of selecting toolpath geometry and cooling strategies to balance efficiency and stability in industrial machining applications.

Resumo em Inglês:

The use of mineral oil-based fluids in machining processes can lead to social and environmental problems. Therefore, the objective of this study is to perform a comparative technical-economic analysis between biodegradable emulsions based on babassu oil, castor oil and a commercial synthetic fluid during cylindrical turning of SAE 1045 steel. The formulations' impact on tool wear and durability at varying cutting speeds (90, 70 and 50 m/min) and on the surface roughness of the workpiece was analyzed. Economically, the costs per production volume were compared, using data from the machining tests. The tests demonstrated that the babassu oil-based emulsion provided the longest tool life, reaching 65.31 minutes. The synthetic fluid provided the best surface roughness results. In the economic analysis, the synthetic fluid was advantageous at a speed of 90 m/min, and below this value the castor oil-based emulsion stood out.

Resumo em Inglês:

The laser remelting technique on tungsten carbide (12Co–4Cr WC) and chromium carbide (Cr3C2–25NiCr) coatings deposited by HVOF provides improvements in surface properties, such as increased hardness and resistance to abrasive wear. This process uses a laser beam to selectively melt the coating, promoting a uniform and adherent layer. In the present work, tungsten carbide and chromium carbide alloy coatings were deposited on properly prepared SAE 1020 substrates using the high-speed oxy-fuel (HVOF) technique. After deposition, the coatings were remelted with a laser beam, varying the scanning speed and the laser beam power of the ytterbium fiber to obtain a pore- and crack-free coating and better metallurgical anchorage to the substrate. The samples were characterized by scanning electron microscopy (SEM), X-ray diffractogram, ASTM G132 Standard Test Method for Pin Abrasion Testing wear and microhardness. The results show that it was possible to obtain coatings with greater hardness after the laser remelting process, reducing pores or imperfections and metallurgically bonding to the substrate.

Resumo em Inglês:

Current development of hybrid and bioactive materials based on consolidated metallic substrates, such as titanium and its alloys, combined with polymeric and ceramic additives has been promoted. These materials, with an emphasis on hydroxyapatite and polycaprolactone, have a high applicability in tissue replacement and regeneration. Since bacterial contamination and biofilm formation are the main causes of post-surgical complications involving implants, the present work proposes a hybrid coating to address these issues. It incorporates Melaleuca alternifolia essential oil as a natural bactericide, into a polymeric PCL layer. This layer was applied over a bioceramic coating on a commercially pure titanium substrate. The surface evolution of the apatite layer was verified through bioactivity tests in simulated body fluid, verifying a homogeneous layer with appreciable globular morphology. In the microbiological assays by disk-diffusion against Staphylococcus aureus and Escherichia coli, the formation of small halos was observed for both cultures. As a result, it is suggested that the proposed hybrid coating may improve the osseointegration process and biocompatibility, indicating the potentiality of prosthetic application in orthopedic medical devices.

Resumo em Inglês:

Titanium and its alloys are the most commonly used materials for biomedical applications such as implants. The Ti-6Al-4V ELI (Extra Low Interstitial) alloy is particularly desired for its excellent mechanical performance and remarkable biocompatibility. However, infection is a limiting factor after implantation, making it necessary to adopt surface treatment to minimize this process. Bacterial adhesion to the substrate is strongly influenced by surface roughness and wettability. Therefore, the present study aims to evaluate these parameters after dry electropolishing of the Ti-6Al-4V ELI alloy. The Ti-6Al-4V ELI samples were sectioned with Ø = 14 mm and 3 mm thick, followed by sanding with silicon carbide #600, #1200 and #1600. Subsequently, they were sent for dry electropolishing for 30 min with a voltage potential of 13 to 18 V and characterized. Data were processed statistically using ANOVA. The Ra roughness values were statistically significant: 143±24 nm for 17 V compared to 193±18 nm for the control. The wettability test confirmed that all surfaces obtained are considered hydrophilic, favorable for lower bacterial adhesion, with 16 V being the best condition. Contact angle was found to be 77±6° for 16 V and 59±4° for the control. Dry electropolishing is essential for surface enhancement and biomedical applications.

Resumo em Inglês:

Offshore oil and gas exploration in deep areas raises the need to develop equipment monitoring techniques to detect possible defects and prevent catastrophic failures. This work sought to analyze the feasibility of using non-destructive electromagnetic techniques - Magnetic Barkhausen Noise (MBN), Magnetic Hysteresis and Electrical Resistivity - in the identification of predominant stresses, microstructural transformations and mechanical behavior of a steel used in the manufacture of flexible Risers. The material was analyzed as received and cold rolled with 5, 10, 20, and 35% reduction rates. The signals were related to data obtained by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and hardness tests. The results show that with increasing strain, the MBN peak amplitude decreases (95.0%), the energy required to reach magnetic saturation increases (23.2%), and the electrical resistivity increases (41.6%). The variation of these signs indicates an increase in structural heterogeneities, such as elongation of cementite lamellae, increase in dislocation density, and non-homogeneous stress field distribution, which increase the area of sites fixation of magnetic domains and decrease the flow of free electrons. The sensitivity in detecting changes of the techniques in question demonstrates their efficiency in inspecting flexible ducts installed in areas of difficult access.

Resumo em Inglês:

The present study aims to apply the principles of the circular economy by utilizing special inorganic waste, specifically gypsum sludge from a Zn refinery to produce ceramic tiles. Samples containing up to 50% of gypsum sludge were prepared as partial replacements of traditional materials such as clay, feldspar, quartz, and kaolin. The properties of the mixtures were analysed in accordance with ABNT NBR ISO 10545 standards, including tests for water absorption, flexural strength, stain and chemical resistances and deep abrasion resistance (ASTM G65-16). The results indicated that the addition of up to 15% of gypsum sludge maintains acceptable mechanical and physical properties, while higher contents significantly increase porosity and water absorption, compromising structural strength. Thermogravimetric analysis revealed that the thermal decomposition of calcium sulphate promotes the release of SO2 at temperatures above 1120°C, requiring emission controls to meet environmental regulations. To conclude, the incorporation of gypsum sludge in ceramic formulations proved to be technically viable, supporting circular economy principles by lowering production costs, reducing the use of virgin raw materials, and finding a destination to industrial waste. The resulting ceramic bodies exhibited properties compatible with the requirements of ABNT NBR ISO 10545 for wall and low-traffic floor tiles, particularly in terms of water absorption and flexural strength, confirming their suitability for non-structural applications.

Resumo em Inglês:

Laser-based powder bed fusion (PBF-LB) of AlSi10Mg alloys faces non-equilibrium solidification, resulting in a microstructure of α-aluminum phase matrix and an interconnected, fibrous α-silicon-rich phase network. The development of heat treatment (HT) routes tailored specifically for PBF-LB parts are essential, as standardized procedures may not yield optimal results. This study investigates the effect of different HTs on the microstructural characteristics and hardness of AlSi10Mg parts. Analyses revealed that the as-built (AB) microstructure exhibited a typical cellular-dendritic solidification structure. The eutectic α-Si-rich network partially degenerated after direct aging (DA) and stress relieving (SR), while solution annealing (SA), and solution annealing + aging HT erased the solidification microstructure, producing α-Si-rich precipitates dispersed within the α-Al matrix. Columnar grains exhibited preferential epitaxial growth along {001} planes in the <001> direction, with no significant changes observed after HTs. The AB sample displayed a hardness of 122 HV, increasing up to 149 HV after DA. Conversely, SR and SA led to a hardness reduction between 61 and 77 HV. While the DA HT maintains the AB microstructural characteristics with a hardness increase, SR and SA HTs modify the solidification microstructure, reducing hardness.

Resumo em Inglês:

Supermartensitic stainless steels (SMSS) are corrosion resistant alloys used as casing and tubulars in the oil and gas prodution. In this application, mandrels for gas or chemical products injection in the wheel are composed of forged and hot rolled seamless tubes. SMSSs used as tubulars are subjected to sulfide stress corrosion cracking (SSC) in sour services with H2S and high salinity. Nitriding is a thermochemical treatment used to increase hardness and wear resistance of steels. This surface treatment can be used to improve the performance of SMSSs. In this work a forged SMSS grade UNS S41426 steel was plasma nitrided at 350ºC, 400ºC and 570ºC for 5 h, using gas mixture of 75%H2 and 25%N2. The effects of the microstructure were evaluated by X-ray diffraction and scanning electron microscopy. The effects on mechanical properties were evaluated by microhardness and tensile tests, while the susceptibility to SSC was evaluated by slow strain rate testing (SSRT). The average microhardness measured in the surface was 308 HV0.05 in the as received steel, and increased to 341 HV0.05, 441 HV0.05 and 1277 HV0.05 with nitriding at 350oC, 400oC and 570oC, respectively. The results were compared to specimens of SMSS not subjected to nitriding treatment.

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As demand for sustainable agriculture grows, materials like graphene oxide (GO) are gaining attention due to their potential to boost crop productivity and reduce environmental impacts. This study reports the synthesis of GO from sugarcane bagasse using ferrocene as a catalyst. The material was characterized by Raman spectroscopy, FTIR, XRD, and SEM. To evaluate its effects on bean seeds, seed priming was done with GO concentrations of 0, 10, 50, and 100 mg/L, followed by ultrasound treatment and germination tests. Higher GO concentrations (100 mg/L) were phytotoxic, reducing germination rates and speed index (GSI). In contrast, lower concentrations (10 and 50 mg/L) increased moisture content in shoots and roots, positively influencing growth. The highest mean shoot length (13.3 cm) was observed at 50 mg/L, while root length did not differ significantly. These findings highlight GO's potential to improve water retention and growth at optimized concentrations, offering promise as a sustainable agricultural input.

Resumo em Inglês:

Flat heat pipes are highly effective for electronic thermal management, combining compact design with efficient heat transfer. Diffusion bonding is a promising manufacturing method, enabling leak-tight joints without notable plastic deformation. This study examined the effects of bonding temperature and pressure on the quality of miniature copper heat pipe joints. Optical microscopy, microhardness tests, and shear strength evaluations were used for assessment. Optimal results occurred at 875°C and 7MPa. Among four temperatures and three pressures tested, 900°C and 9MPa also yielded strong joints. Bonding time was fixed at 3600s. Good joints showed shear strengths of 5.92–6.17MPa and microhardness of 45–49HV. Interfaces had small, rounded, well-distributed defects that did not impair integrity. Temperature had a greater impact than pressure on joint quality. A flat miniature loop heat pipe made under optimal conditions (875°C, 7MPa, 3600s) displayed high-quality, deformation-free bonding and transferred up to 8W before reaching its operational limit—suitable for electronics.

Resumo em Inglês:

The cost of recycled glass is strongly influenced by its color. Colorless glass is usually more expensive than other glass, then, products generated from recycled glass are costlier if the requirement of colorless cullet is required. Particularly, glass beads (GB) used in horizontal road marks are usually produced from recycled glass, and the standards that regulate GB production for this application emphasize that they must be colorless to guarantee high retrorefletivity. Thus, this work aims to evaluate the effect of GB produced from different cullet colors on the retroreflectivity measurements. The horizontal flame method was used to produce the GB in a granulometry classified as Type-IB. Results demonstrate that physical, chemical and optical properties do not change when microspheres of same characteristics but different colors are used, showing that other sources of glasses can be applied in road marking materials, reducing the overall production costs and consequently, trade costs.

Resumo em Inglês:

UNS S17400 (AISI 17-4PH) is a precipitation hardening steel with several applications in energy generation, oil and gas, aerospace and chemical industries. The hardening effect is mainly produced by the precipitation of copper rich phases (CRP). In this work, the precipitation hardening behavior of 17-4 PH steel was investigated and modelled. One set of samples was solution treated at 1050oC and quenched before aging at 420oC, 440oC, 480oC, 495oC and 550oC for different periods of time. Another set of specimens was solution treated and cold rolled with 35% of reduction before aging at the same conditions of un-deformed samples. This way the effect of previous cold rolling on the kinetics of precipitation was evaluated. The Vickers hardness (HV10) of all specimens were measured to obtain the aging curves (hardness versus aging time), which were modeled by equation (ΔH=Ktn). The activation energies for precipitation were calculated for samples aged with and without cold deformation.

Resumo em Inglês:

The beneficiation of bauxite ore generates significant quantities of tailings, primarily composed of kaolinite and residual gibbsite, the latter still amenable to metallurgical recovery. In this study, bauxite tailings were reprocessed based on particle size classification from 30 µm to 2 µm, obtained by sedimentation. The resulting fractions consisted mainly of fine to ultrafine particles, comprising approximately 80%. These fractions contained gibbsite and kaolinite as the dominant mineral phases, in varying proportions. Chemically, Al2O3 and SiO2 were the major components, with a progressive reduction in Al2O3 and a corresponding increase in SiO2 as particle size decreased. This trend was confirmed by an increasing SiO2/Al2O3 ratio, indicating silica enrichment attributed to kaolinite and alumina depletion associated with gibbsite. The results suggest that gibbsite remains recoverable even in finer fractions, while kaolinite becomes progressively liberated. This behavior supports the potential for reprocessing tailings only to fines particles and reducing the reactive silica.

Resumo em Inglês:

The gradual replacement of petrochemical derivatives with sustainable alternatives is fundamental to reducing environmental impact. Biopolymers such as potato starch stand out for their low cost, biodegradability and sustainability, however, they exhibit hydrophilic properties, leading to poor water resistance and necessitating modifications for improved performance. This study investigated the use of the anionic surfactant saponified sunflower oil (SSO) in the formulation of potato starch films, evaluating its effects on the polymer network and film properties. The films were prepared using the casting method with different dosages of SSO (0.01 g, 0.02 g, 0.04 g, 0.06 g and 0.08 g). Properties such as water vapor permeability (WVP), mechanical behavior, and optical characteristics were analyzed. Micelle formation in the polymer matrix generated vacancies, increasing WVP. At low concentrations, there was a reduction of up to 47.82% in WVP, attributed to the interaction of polar groups in the biopolymer with surfactant monomers, without compromising optical properties. Mechanical properties, such as tensile strength and elasticity, improved at micellar concentrations, to 22.80 MPa and 62.16% respectively. Moreover, this study suggests that the use of additional lipophilic agents may be avoided, reducing costs and broadening post-harvest preservation applications as fruit coatings that extend shelf life.

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In this study, biochar‑derived adsorbent was prepared by pyrolysis of sugarcane bagasse using the activation step with KOH and applied for dye removal. The structural characterization methods, X‑ray diffraction, infrared, and Raman spectroscopy showed that the material is purely carbonaceous. Scanning Electron Microscopy revealed that the material has a rough and irregular morphology with cavities of various sizes. The material showed good efficiency for methylene blue (MB) (96.6%) and methyl orange (MO) (95.1%) removal. The experimental data fit well with a pseudo-second-order model. Based on the Langmuir isotherm, the material exhibits good maximum adsorption capacity for removing MB (8.20 mg/g). The material was able to remove MB at different pH values ​​(3-11), with good removal efficiency (above 60%). The biochar could remove MB in up to 5 cycles with good removal efficiency. The biochar obtained from sugarcane is a potential material for removing dyes from wastewater via adsorption.

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This study evaluates the feasibility of modifying thermoplastic starch using citric acid through extrusion processing. The samples were characterized by FTIR, TGA, XRD, and tensile testing. In the FTIR analysis, carbonyl group formation was observed, indicating esterification between the starch hydroxyl groups and the carboxyl groups of the acid. TGA provided data on the thermal events in the materials. In the tensile test, Young's modulus increased while elongation at break decreased, making the modified starches more rigid and less ductile. XRD analysis revealed structural changes due to the increased acid concentration and the presence of plasticizer. Esterification was effective at citric acid concentrations of 1.0 to 2.5–3.0 wt%, but difficulties in processing and controlling process parameters were noted, as highlighted in previous studies. These results demonstrate the viability of starch modification, although challenges remain in controlling production and achieving the desired characteristics.

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This study investigates the effect of niobium (Nb) addition on the microstructure and mechanical behavior particularly impact toughness of 300-grade maraging steel. Two novel Nb-modified alloys were developed: one with partial substitution of titanium (Ti) by Nb (0.64 wt.%), and another with complete substitution (1.4 wt.% Nb), based on a 1:2 Ti-to-Nb weight ratio. These were compared to a conventional 18Ni300 maraging steel. Thermodynamic and kinetic simulations using Thermo-Calc® and JMatPro® guided the alloy design, revealing that Nb addition favors the formation of Ni3Nb and Laves phases and delays precipitation kinetics compared to Ni3Ti. Microstructural characterization (XRD, SEM, EBSD) confirmed martensite refinement and reduced prior austenite grain size (PAGS) with increasing Nb content. Mechanical testing showed that the partially Nb-modified alloy exhibited the highest impact toughness, reaching 14.4 J, while maintaining a yield strength of 1.61 GPa and ultimate tensile strength (UTS) of 1.68 GPa. The fully Nb-substituted alloy achieved 13.4 J of impact toughness and recovered high strength levels (YS: 1.78 GPa, UTS: 1.83 GPa) comparable to commercial grades.

Resumo em Inglês:

Titanium is extensively applied for dental implants manufacture due to its remarkable mechanical properties, corrosion behavior, and biocompatibility. To further improve these attributes, some TiNb alloys have been developed. This study investigates the Ti-45Nb alloy, aiming to optimize its biomechanical performance and osseointegration properties through micro-arc anodization. The research encompasses the analysis of the alloy's microstructure, surface modification via micro-arc anodization using H2SO4 solutions at concentrations of 1M, 1.5M, and 2M, characterization of surface properties, surface topography and roughness profiling, and surface energy analysis. The findings indicate that the micro-arc anodization treatment with 1.5M H2SO4 solution is the most effective to enhance biomechanical performance and osseointegration of the Ti-45Nb alloy.

Resumo em Inglês:

Films for controlled drug release are systems that allow the prolonged and sustainable release of the therapeutic principle into the tissue to be treated. This research aims to develop polyvinyl alcohol (PVA) films crosslinked with citric acid (CA) and reinforced with microcellulose obtained from mango seeds for controlled drug release applications. The mango seeds used were pretreated (PMS), hydrolyzed (HMS), and chemically bleached (BMS). The films were prepared using each of these seed samples through the solution casting method and were characterized using Fourier-transform infrared spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), and UV-Vis spectrophotometry. For controlled release tests, a model drug (Paracetamol, PC) was used. Additionally, the solubility and swelling characteristics of the films were evaluated. FTIR analyses revealed the effect of crosslinking between PVA and CA in the films, as well as the presence of PC. Furthermore, swelling and solubility tests confirmed that the films undergo physicochemical changes due to the crosslinking process and the type of seed used. SEM images showed that the films possess a homogeneous surface, which is desirable for ensuring controlled drug release. The concentration of the drug released from the film in a phosphate buffer solution was analyzed by UV-Vis spectrophotometry, showing that the PVA films reinforced with mango seeds exhibited sustained release. The findings of this research suggest that PVA films crosslinked with CA and reinforced with mango seeds have suitable properties for controlled drug release applications.

Resumo em Inglês:

UNS S41003 stainless steel is a lean stainless steel with 10.5-11% Cr, low carbon (<0.03%C), and small Ni addition. The composition is such that, depending on the processing route, the microstructure can be ferritic, martensitic, or ferritic-martensitic. Specimens acquired from the steelmaker were produced by hot rolling, with and without batch annealing. Two other sets of specimens were created by heat treating at 1000°C followed by water quenching. The microstructures of the four groups of specimens were characterized by scanning electron microscopy (SEM) with electron backscattered scanning diffraction (EBSD). The mechanical properties were measured by tensile tests, hardness, and impact toughness. This study demonstrates the optimal combination of mechanical resistance and toughness in hot rolling samples, which presented a fine grain size of martensite with fine carbides and 23.3% of elongated δ-ferrite. The hot rolled samples show a yield strength 6.2% higher than the quenched samples, and 152.1% higher than the annealed ones. The hot rolled steel presents a higher impact toughness, 31.7 J, 16.1% superior to the annealed material. The quenching heat treatments decreased the %δ ferrite and increased the grain size. The material annealed has a microstructure of equiaxial α-ferrite grains and intergranular chromium carbides.

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This work investigated the charge transport behavior at the interface between a Pt-Ir metal contact and transparent zinc oxide (ZnO) electrodes with one, four, and eight ZnO layers. Electrostatic force microscopy (EFM), Kelvin probe force microscopy (KPFM), and conducting atomic force microscopy (c-AFM) techniques were employed to explore the nanoscale surface electrical properties. The variation in thickness led to changes in the type of contact formed between metal and semiconductor, which went from ohmic to rectifier with the increase in the number of layers. The modulation in the type of contact formed was mainly due to the presence of grain boundaries (GB) during film formation. The influence of the thickness synthesis parameter on the optoelectronic and charge transport properties of conductive and transparent ZnO electrodes is demonstrated, and its importance in the formation of metal- semiconductor (M-S) contacts that make zinc oxide a versatile semiconductor.

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This work investigated the corrosion inhibition of carbon steel in 0.1 mol L-1 Na2SO4 by lyophilized extracts of garlic white peel (GP) and centrifugation residue of Isabel grape juice (CGJ) using gravimetric tests, polarization curves, electrochemical impedance spectroscopy, and scanning electron microscopy. Initially, the DPPH (2,2-diphenyl-picrylhydrazyl) method analyzed the extracts for antioxidant activity. Considering the capacity to scavenge the DPPH free radical (% DPPH consumed), the GP and GJC lyophilized extracts presented values ​​of 12.64 and 8.47, respectively. The inhibition efficiency exceeded 96% and 88% after 24 h of immersion in the saline medium containing 300 mg L-1 of the GP and CGJ, respectively. These results indicate that producing such extracts is an excellent alternative for using these agro-industrial wastes, as they showed promising results as corrosion inhibitors for carbon steel in the corrosive environment studied.

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Bisphenol A (BPA), commonly found in plastics and epoxy resins, poses serious risks to human and animal health, particularly affecting reproduction and hormonal balance. This study investigates the removal of BPA from water using modified Moringa oleifera seed husks (H-MOH300) as a sustainable adsorbent. The husks were chemically activated with phosphoric acid and thermally treated at 300°C, yielding a BET surface area of 380 m2 g−1 and a pore volume of 0.282 cm3 g−1. SEM analysis showed a porous and fibrous morphology, while XRD indicated a crystalline nature. FTIR identified hydroxyl, aromatic, and carboxylic functional groups. The process followed the Langmuir isotherm model, achieving a maximum adsorption capacity of 27.5 mg g−1 at 22°C. Thermodynamic analysis indicated a spontaneous, endothermic process driven by electrostatic and π-π interactions. Regeneration tests up to 5 cycles confirmed H-MOH300’s reusability, demonstrating its potential as a cost-effective, eco-friendly solution for BPA removal.

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The continuous growth of the global population, coupled with new food safety regulations, has driven the demand for packaging that extends food shelf life. In this context, active packaging, which incorporates functional compounds to prolong shelf life without direct addition to the food, emerges as a sustainable alternative. The widespread use of plastic packaging significantly contributes to environmental pollution, fostering increasing interest in the development of biodegradable materials. These materials offer several advantages, including low cost, ease of processing, and renewable origin. This study developed a polymeric film based on cassava starch incorporated with silver nanoparticles (AgNPs) for potential applications in food packaging. The incorporation of AgNPs conferred antimicrobial properties to the film while also enhancing its mechanical strength. The results demonstrated that the developed material exhibits promising performance, comparable to commercial PVC film, while providing a more sustainable solution for food preservation.

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This study investigates failures in solder joints of Ball Grid Array (BGA) components using destructive techniques such as cross-section, dye and pry, and chemical etching with metallographic reagents. Discarded printed circuit boards (PCBs) from the University of the State of Amazonas (UEA) were reused, with a focus on the SAC305 alloy. The samples were analyzed using optical microscopy. The dye and pry analysis revealed fractures in the intermetallic compound (IMC) layer and "Type E" staining (according to IPC-TM-650 2.4.53). Cross-section confirmed cracks in the IMC layer and macrovoids at the solder-PCB interface, including shrinkage voids associated with solidification, as per IPC-7095E standards. The microstructure of the SAC305 alloy exhibited silver and copper precipitates within a dendritic tin matrix. The research highlights the importance of destructive testing for evaluating solder joint reliability, preventing failures in electronic components.

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In the electric sector, power transmission lines, substations, and associated equipment are highly susceptible to environmental aggressiveness, necessitating updated and efficient monitoring systems. This study analyzed the corrosion rate of metals in a 1,150 km power transmission line spanning Ceará, Piauí, and Maranhão in northeastern Brazil. Carbon and galvanized steel coupons were exposed for one year, with corrosion assessed through mass and thickness loss. The results, combined with local meteorological data such as temperature, humidity, and precipitation rates, were used to train, test, and validate a feed-forward neural network model. The model showed good prediction accuracy, particularly for galvanized steel, with low mean absolute and mean squared errors, enabling reliable forecasts. For carbon steel, although predictions exhibited slightly lower accuracy, they were still adequate for classifying local atmospheric corrosivity levels. Furthermore, the model successfully generated corrosion maps for both metals, enabling detailed visual analysis across the entire transmission line.

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The main characteristics of a superduplex stainless steel (SDSS) are the biphasic microstructure composed by ferrite and austenite, and the pitting resistance equivalent (PRE) higher than 40. The mechanical properties and corrosion resistance are optimized with austente:ferrite proportions close to 1:1, and the absence of other phases. The UNS S39274 grade is a W-alloyed SDSS used in critical services in the Exploration & Production of the Oil & Gas Industry, such as in Oil Country Tubular Goods (OCTG). This material can be used for tubes that work with high pressure (until 138MPa) and corrosive environments (with CO2 and H2S). To achieve a high mechanical strength, the seamless tubes are cold drawn. Short duration and low temperature aging can further improve the mechanical resistance of SDSSs. This work was focused on the investigation of short duration aging at 400 and 475oC of the UNS S39274 steel, comparing two initial conditions: cold worked and solution treated. The objective and main contribution of this study was to determine the effect of work hardening on the low-temperature aging, specifically the ferrite phase decomposition by δ→α+α' reaction, where α’ is a nanometric Cr-rich precipitate. The effects on mechanical properties (hardness, tensile, and impact toughness) and pitting corrosion resistance were determined. The activation energy for precipitation (Ea) was obtained through Differential Scanning Calorimetry (DSC). In addition, Transmission Electronic Microscopy (TEM) images show the presence of α' inside ferrite grains of specimen aged at 475oC for 8 hours.

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This work evaluated the application of sugarcane bagasse waste in the manufacture of porous ceramic supports for filtration membrane. Kaolinitic clay and sugarcane bagasse waste from the Campos dos Goytacazes-RJ region used as raw materials were characterized regarding their chemical, mineralogical and thermal behavior. Four clayey formulations containing up to 25 wt.% of bagasse waste were prepared, extruded, dried and fired at 950 ºC, 1000 ºC and 1050 °C. The fired supports were characterized by water absorption, apparent porosity, apparent density, linear shrinkage, mechanical strength, mercury porosimetry and microstructural analysis. It was found that the incorporation of bagasse waste increased the total porosity by up to 31 %. The results also showed that the porous support produced with 20 wt.% of sugarcane bagasse waste and fired at 1000 °C has potential for application in low-cost ceramic membranes. These results suggest a highly attractive way for the sustainable valorization of sugarcane bagasse waste.

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The study of engineered wood products has expanded due to their production from renewable raw materials. While wood products have traditionally seen limited use in Brazil, they have gained significant traction over the past two decades, fueled by new products and technological advancements. Among emerging materials, nanocellulose has shown promise due to its potential to enhance the adhesive performance and mechanical properties of wood-based panels. This study aimed to incorporate cellulose nanofibers obtained by mechanical defibrillation of pulp from the extraction of the Eucalyptus grandis by kraft process in proportions of 0% and 5% into a castor oil-based polyurethane adhesive commercial to produce plywood panels. The mechanical properties of the panels were analyzed, specifically focusing on static bending strength both parallel and perpendicular to the wood fibers, as well as bond quality through shear testing along the glue line. Results indicated that adding nanocellulose to the polyurethane resin significantly enhanced the mechanical performance of the plywood panels. Additionally, it was observed that using eucalyptus wood veneers with polyurethane resin alone already resulted in improved mechanical properties compared to conventional adhesives. Thermal analysis, suggested that nanocellulose incorporation increased the resin's thermal stability, potentially contributing to enhanced durability. Further studies are recommended to explore the viability of nanocellulose at different proportions and its long-term effects on adhesive performance.

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This work investigates the fatigue failure mode of a shaft used in a conveyor system for mining applications through visual inspection, metallographic examination, fracture analysis, and mechanical testing. It was observed that a misalignment of about 5° between the shaft and the conveyor drum system promoted intensive contact with the parts. The combination of misalignment and overload was the leading cause of the localized plastic deformation, which resulted in the shaft fracture. A metallurgical examination revealed ferritic and pearlitic microstructures for an AISI 4140 grade steel. This suggested that the heat treatment on the steel was not adequate for the application. Therefore, it can be inferred that no preventive or corrective maintenance inspections were performed during the shaft's operational production period.

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Carbon steel is widely used as a metallic material, despite its limited corrosion resistance. To enhance its anti-corrosion properties, organic coatings such as epoxy are commonly applied due to their barrier mechanism. This study investigates the corrosion resistance of epoxy coatings reinforced with various ratios of iron oxides and goethite as anticorrosive pigments. The research aims to evaluate the adhesion and anticorrosive properties of waste mineral goethite (α-FeOOH) pigments in comparison to micaceous and red iron oxides. Coating morphology and chemical element distribution were analyzed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). Electrochemical characterization techniques—including electrochemical impedance spectroscopy (EIS), linear and potentiodynamic polarization, and accelerated salt spray corrosion tests—were employed. Additionally, coating adherence was assessed via pull-off tests. Results demonstrated that goethite-based paints exhibited anticorrosive performance comparable to industrially used red and micaceous iron oxides, regardless of pigment concentration. The results of EIS showed that the 5% goethite formulation reached an impedance modulus of |Z|0.01Hz ≈ 1011 Ω·cm2 after 90 days. However, salt spray results showed that the area with corrosion products around the incision in the painted test specimens was quantified, showing the smallest reduction in corroded areas for the samples with 10 and 20% goethite concentration applied to the coating. These findings highlight the potential of mining waste goethite as a sustainable and effective anticorrosive pigment when properly optimized.

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This article presents an electrochemical sensor designed for the identification of thymine, one of the nitrogenous bases in deoxyribonucleic acid, crucial for diagnosing damage and health issues such as cancer. The sensor was fabricated using a graphite electrode modified by electrodeposition of brilliant cresyl blue dye in a phosphate-buffered solution, employing cyclic voltammetry. The modified electrode was characterized by atomic force microscopy, revealing changes in surface morphology that facilitated the detection of thymine with a limit of 0.25 µM, demonstrating enhanced oxidation currents. The sensor’s selectivity was tested in the presence of interferents. The use of graphite-based electrochemical sensors for thymine detection has gained attention due to their sensitivity, low cost, ease of fabrication and disposal, and the growing demand for innovative technologies in medical and technological fields.

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Adjustments and changes in concrete formulations aim to improve physical and mechanical properties. This research analysed the influence of the addition of graphene oxide (GO) to reactive powder concretes (RPC) on their structure and properties. The addition of GO (0.025% and 0.050% by cement weight) resulted in significant improvements in the mechanical and microstructural properties of the RPC, increasing compressive (up to 19.14%) and flexural strength (up to 11.80%), as well as a reducing water absorption and porosity. Statistical analyses (ANOVA and Tukey's ad hoc test) confirmed the significance of the results. Scanning electron microscopy (SEM) showed greater formation of C-S-H around the GO nanosheets, resulting in an increase of mechanical strength. It was concluded that the addition of GO helps the RPC allowing a greater homogeneity in the mixture, enhancing mechanical strength (up to around 130 MPa at 28 days of curing), and reducing the RPC porosity and water absorption.

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Nanostructured materials containing iron oxide and carbon were synthesised using chitosan and iron chloride as chemical precursors in different proportions. These materials were applied as adsorbents and methanol sensors. The sample's characterisation used thermal analysis, temperature-programmed oxidation, infrared spectroscopy, X-ray diffraction, temperature-programmed reduction, Raman spectroscopy, and scanning electron microscopy. The characterisations confirmed the formation of a sp2 carbon matrix with iron embedded within it. The presence of functional groups on the carbon structure was also confirmed, and they were introduced through treatment with an acidic solution to produce the sensor. The sensor’s response to methanol was measured at different temperatures and concentrations. The results suggest good response and reproducibility of the sensor, which was synthesised using a straightforward method. The adsorption of methylene blue from an aqueous solution indicated a strong affinity between the adsorbent and the adsorbate, and the material's magnetic properties facilitate the extraction of the adsorbent.

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Rail transport is one of the main freight transportation modes in Brazil, responsible for transporting about 92% of all extracted ore to ports via railways. However, it incurs high maintenance costs, exceeding $1.5 billion annually, with most of this amount allocated to rolling stock maintenance. This study investigates the influence of vanadium (V) microalloying on the wear and rolling contact fatigue (RCF) performance of cast Class D railway wheels. Using a twin-disc tribometer simulating wheel-rail contact, a vanadium-microalloyed wheel (CD-V) was compared against a conventional wheel (CD). Key parameters evaluated included mass loss, plastically deformed layer thickness, and crack characteristics. While the CD-V wheel showed slightly lower mass loss, the difference compared to the CD wheel was not statistically significant. However, the slightly increased hardness of the CD-V wheel seems to led to greater wear on the rail counterbody, indicating a trade-off. In contrast, vanadium addition demonstrated significant benefits for RCF resistance. The CD-V wheel exhibited a thinner plastically deformed subsurface layer and superior crack morphology, characterized by shorter surface cracks, lower-angle and shallower subsurface cracks. These RCF improvements suggest that vanadium microalloying in cast wheels could offer advantages in operations where shelling resistance is a primary concern.

Resumo em Inglês:

As a strategy to reduce socio-environmental impacts, the incorporation of waste or natural fibers from various sources into the formulation of composites has proven to be an attractive and sustainable alternative. In the development of nanocomposites specifically, the use of coconut fiber waste at the nanoscale has been explored both for its ability to enhance the mechanical properties of materials and as a way to add value to an agro-industrial residue that would otherwise be discarded into the environment. In this context, the present work aimed to develop epoxy matrix nanocomposites using nanocellulose extracted from coconut husk fiber. The polymer matrix used was an epoxy system composed of diglycidyl ether of bisphenol A/diethylenetriamine (DGEBA/DETA), with a hardener-to-resin ratio of 16:100 (16 phr). The nanocellulose was extracted through chemical treatments of the coconut husk, using sodium hydroxide (NaOH) and sodium hypochlorite (NaClO) to remove lignin, hemicellulose, and other impurities. Subsequently, to eliminate the amorphous region of cellulose and obtain nanofibrils, the material underwent acid hydrolysis with sulfuric acid (H2SO4). The nanocomposites were prepared in an open mold by incorporating nanocellulose at weight fractions of 0, 1.25, 2.5, and 5% relative to the total mass of the epoxy system. The obtained materials were characterized through compression strength tests, Izod impact resistance, and thermal stability analysis (thermogravimetry). The results showed the influence of nanocellulose addition on the mechanical and thermal properties of the epoxy system, demonstrating the technical feasibility of applying this material as reinforcement in composites within the evaluated context.

Resumo em Inglês:

In countries with continental dimensions like Brazil, railways transport production from inland regions to ports and the international market. It is essential to note that researchers and engineers in the railway sector are constantly striving to reduce operational and maintenance costs associated with wheel-rail contact while maintaining high standards of quality, safety, and operational predictability. In this context, wheels are one of the most costly components in railway acquisition and maintenance, representing a significant factor in transport safety. Additionally, their manufacturing process can involve either forging or casting. Therefore, the manufacturing process can offer the best cost-benefit ratio to meet the diverse demands of the railway sector — longer wear/fatigue life with lower costs. This study aimed to analyze the effects of the manufacturing process of the cast and forged microalloyed railway wheels, with similar microstructure, hardness, and equivalent carbon content, on the metallurgical defects formation and tribological properties. To support material characterization, optical microscopy, scanning electron microscopy, hardness measurements, ASTM E45 standards for evaluating metallurgical defects, twin-disc wear tests, Raman spectroscopy, and statistical analyses were conducted to compare the defects and cracks developed in railway steels.

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One of the most effective approaches for the densification of titanium aluminides processed by powder metallurgy involves the addition of elements that induce the formation of a liquid phase during sintering. This work investigated the sintering behavior and creep resistance of Ti-45Al (in at.%) with ternary Co or Ni additions. Conventional sintering under a high vacuum atmosphere led to densifications of approximately 90% of the theoretical density in the Ti-45Al-2Co and Ti-45Al-2Ni alloys, while binary Ti-45Al was limited to a maximum of 57%. Microstructural analysis revealed the formation of equilibrium intermetallics γ-TiAl and α2-Ti3Al, along with Ni- and Co-rich regions concentrated at the boundaries of primary particles. Compression creep tests at 800°C under a 120 MPa load demonstrated a significant increase in mechanical strength, especially with the addition of Co, which showed 1% of plastic deformation in approximately 18 hours.

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Polyethylene Terephthalate (PET), known nationally as Polyester (PES), is the most used fiber in the textile sector and stands out compared to natural fibers and other synthetic fibers due to its constant rise in production and consumption. In the search for sustainability in the textile industry, ionizing radiation presents itself as an environmentally correct process for modifying the properties of polyester fiber, through the formation of reactive species. This work aims to analyze the influence of ionizing radiation on the physicochemical properties of PES microfiber textile multifilaments. The samples were analyzed for toughness and elongation resistance, Thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). The Cobalt-60 gamma irradiation process was effective in altering the properties of the microfiber multifilament analyzed, thus exposing important information on the effects of radiation applied to the polyester textile microfiber to adapt it to the demands of the end consumer.

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The development of β-metastable Ti alloys aims to replace materials like Ti-6Al-4V, which contain cytotoxic elements, with alloys that offer better biocompatibility. The Ti-xMo-yNb system has been studied for its promising characteristics, such as low Young's modulus, good ductility, excellent corrosion resistance in bodily fluids, and bone biocompatibility. This study evaluated the electrochemical behavior of the Ti-12Mo-25Nb alloy compared to the Ti-xMo-30Nb alloys (x = 10 or 12 wt.%) in Ringer’s solution. The alloys were produced by arc melting with a non-consumable tungsten electrode in an argon atmosphere, followed by homogenization at 950°C for 1 hour and water quenching. The microstructure was analyzed using X-ray diffraction and optical microscopy, while mechanical properties were evaluated by Vickers microhardness and Young’s modulus via the impulse excitation technique. Electrochemical characterization was performed by polarization between -2.0 and +2.0 V (vs SCE) at 10 mV•s-1. The results showed that all alloys had a single β-phase microstructure, with a hardness/modulus ratio between 2.6 and 2.8, indicating a good balance between strength and elasticity. Corrosion resistance in Ringer's solution showed that increased Mo content raised corrosion potential, promoting passive films but reduced active corrosion resistance. In contrast, higher Nb content improved passivation.

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This study aimed to enhance solar distillation systems through the incorporation of photothermal materials. The adopted methodology involved integrating these materials into the solar stills to improve solar radiation absorption, thereby increasing the water temperature. As a result, internal temperature profiles reached up to 70 °C. Additionally, thermal imaging was employed to support the thermal behavior analysis of the system. The productivity of distilled water increased by 16% for the distiller (D2) containing gravel and by 3% for D3 with marbles, compared to the control unit (D1), which had no added materials. The highest thermal efficiency was observed in D1, reaching 52.8%, followed by D2 with 52.7% and D3 with 36.9%. Physicochemical and bacteriological analyses were conducted before and after the distillation process to assess water quality, including the presence of microorganisms. The results confirmed that the incorporation of photothermal materials was effective in enhancing salt and microorganism removal from the treated water.

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This study aims to evaluate the wear and rolling contact fatigue performance of two lives of the same railway wheel: one with a bainitic microstructure and the other with a pearlitic microstructure, both tested against the same commercial premium rail. Tests were conducted using a Twin Disc tribometer. The results demonstrated that bainite exhibits superior wear resistance, with a 34% lower mass loss compared to pearlite under identical conditions. Additionally, the bainitic microstructure showed greater resistance to rolling contact fatigue, as surface cracks were smaller in size compared to those observed in the pearlitic microstructure. The counterbody also performed better when tested against the bainitic specimen.

Resumo em Inglês:

Ti-based amorphous alloys are promising for biomedical applications due to their high mechanical strength, low modulus of elasticity, corrosion resistance, and biocompatibility. This study primarily utilized molecular dynamics simulations to investigate the glass-forming behavior of Ti53Cu39Ni8 and Ti50Cu42Ni8 alloys, using the LAMMPS code with a hybrid potential composed of the modified embedded atom method and Lennard-Jones potentials. Structural properties were analyzed using X-ray diffraction, pair distribution functions, and Voronoi polyhedra. The variation in viscosity with temperature in the supercooled liquid during cooling was calculated using the Green-Kubo method. Liquidus (TL) and solidus (TS) temperatures were determined from heating curves obtained at a rate of 1 K/ps. The glass transition temperatures (Tg) were obtained from cooling curves and compared with experimental measurements. Simulated and experimental XRD results confirmed that both alloys are fully amorphous, with TL, TS, and Tg increasing with higher titanium content. The reduced glass transition temperatures (Trg = Tg/Tₗ) were 0.437 for Ti53Cu39Ni8 and 0.430 for Ti50Cu42Ni8. The viscosity change was more pronounced in the Ti50Cu42Ni8 alloy, indicating greater thermal stability of the supercooled liquid near Tg, attributed to an increase in icosahedral clusters, reaching a 6% volume fraction at 300 K. Additionally, the predicted values of Tg from the simulations are in good agreement with experimental measurements.

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Poly(N-vinylcaprolactam) (PNVCL) is a biocompatible and thermoresponsive polymer, which presents changes in solubility at temperatures close to the physiological temperature, making it a promising biomaterial. However, its application is limited due to difficult processability in the molten state and brittleness in the solid state. To overcome these characteristics, the present work developed polymeric blends of PNVCL and poly(lactic acid) (PLA), which is a biodegradable and biocompatible polymer, varying mass concentrations of PNVCL by 40, 50 and 60%. Scanning electron microscopy (SEM) showed the formation of a heterogeneous morphology, with spherical domains dispersed in a matrix phase. Nevertheless, Fourier Transform Infrared Spectromicroscopy (micro-FTIR) analysis indicated the presence of both polymers in both phases, with a predominance of PNVCL in the dispersed phase and PLA in the matrix phase. All mixtures produced were thermoresponsive and exhibited a reversible change in optical properties with temperature, going from transparent to opaque upon heating.

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This study investigates the electrospinning of cellulose acetate propionate (CAP) and the optimization of processing parameters to produce nanofibrous membranes with advanced functionality. CAP, a biodegradable and semi-synthetic polymer, offers exceptional thermal and mechanical properties, making it a promising material for applications in filtration, wound dressing, and containment membranes. The research systematically explores the influence of solution properties, such as polymer concentration and solvent ratios, as well as electrospinning conditions, including voltage, flow rate, and collector distance, on the morphology and uniformity of the nanofibers. Differential Scanning Calorimetry (DSC) was utilized to evaluate the thermal transitions of the material, confirming its suitability for use in applications requiring thermal stability and flexibility. The results reveal that the optimized electrospinning parameters lead to defect-free and highly uniform nanofibrous membranes, tailored for specific advanced applications. This work underscores the significance of CAP as a sustainable alternative to conventional synthetic polymers and highlights the critical role of process optimization in achieving desired material properties. The findings contribute to the growing demand for eco-friendly and high-performance materials, offering innovative solutions for industries such as healthcare and environmental remediation. This research establishes a robust foundation for further advancements in CAP-based nanotechnology.

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LPBF is an additive manufacturing technique that allows the building of complex geometries. Its process parameters directly influence the microstructure of the material. Inconel 718 is a nickel-based superalloy with excellent mechanical properties and oxidation resistance at elevated temperatures. However, when built by AM, its anisotropic microstructural character can influence the oxidation resistance, impairing the mechanical integrity. This work investigates the effects of high temperature exposure on the LPBF IN718. Samples manufactured with two different scanning strategies and with and without age-hardening heat treatment were prepared in three different orientations: X, Y and Z, and subjected to oxidation tests at 1000 °C for 24 h in order to measure the mass variation and characterize their surfaces. Conventional forged samples were used for comparison. ANOVA, OM, SEM-EDS and XRD analyses showed a strong influence of both parameters on the oxidation of all faces. The samples produced using 0° angle had better performance compared to 67°, with less mass gain. Heat treatment promoted grain recrystallization, improving the resistance to oxidation in some cases. Faces X and Y presented similar mass gains at 0°, with better performance for non-treated samples. Face Z showed the lowest mass gain, with better performance for treated samples.

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The search for environmentally friendly energy management systems has become fundamental regarding the growing use of fossil fuel by the energy sector and its impacts on the environment. In this sense, latent heat thermal energy storage (LHTES) is a promising technology for recovering, storing, and subsequently using the heat generated from renewable sources, which in turn can make industrial facilities more efficient and reduce CO2 emissions. The proposed numerical model aims to provide auxiliary tools for the design of thermal reservoirs by considering the kinetics and controlling parameters of phase transformations to better equate supply and demand. A medium temperature PCM ~900K and a previously developed numerical model are carried out to simulate the solidification process of Al-Cu-Mg-Fe alloys. The numerical model is coupled with theoretical SDAS predictions, enabling this model to be applied to investigate different heat extraction scenarios, considering a wide range of Biot and Fourier numbers.

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Great efforts have been made to develop new energy sources that can replace conventional energy sources that rely on fossil resources. The present study aims to develop electrocatalysts of Titanium Niobate doped with Graphene at concentrations of 0.01%, 0.02% and 0.05%, to produce hydrogen through the electrolysis of natural seawater, using the dip-coating technique. The electrocatalysts were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), diffuse reflectance and linear voltammetry to analyze the thermal properties, morphology, band gap and electrolytic performance, respectively. The films were tested in an electrolytic cell known as Hoffman's voltmeter with natural seawater as the electrolyte, their efficiency in generating hydrogen was evaluated by gas chromatography. Preliminary results have shown that catalysts are effective in the electrolysis of water, producing hydrogen with significant percentages of the element, making it a promising alternative for sustainable fuel generation.

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The significant generation of urban solid waste by the construction sector demands strategies to mitigate its environmental impacts. This study investigated the use of polypropylene (PP) fibers from raffia bags, repurposed as reinforcement in concrete. Thermal and spectroscopic analyses were performed to characterize the recycled fibers. For the concrete, the tests included axial compressive strength, flexural tensile strength, Slump Test, and capillary water absorption. Four different concrete mixes were evaluated, one as reference and three others incorporating 0.3% by weight of different recycled PP fibers, relative to the cement mass. Incorporating recycled PP fibers into the concrete mix led to an enhancement in tensile strength by up to 15.56%, alongside a reduction in water absorption by 7.81%. However, no significant improvement in compressive strength was observed. The results indicated the potential of recycled PP fibers as reinforcement for concrete, although further studies are needed to determine the optimal addition percentage.

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This study describes the production of electrospun polylactic acid (PLA) membranes followed by expansion based on supercritical technology. The influence of electrospinning process on fiber morphology and physical characteristics was analyzed. The most promising membranes, i.e., those with lowest number of defects, were subjected to expansion process using supercritical CO2 (scCO2). Membranes were characterized in terms of morphology by scanning electron microscopy and microtomography. Polymer characteristics such as thermal transitions and degree of crystallinity were evaluated by differential scanning calorimetry and X-ray diffraction. The expansion process promoted an increase in fibers diameter and in the surface area. The degree of PLA crystallinity was very low in the electrospun fibers and showed an increase in the expanded fibers. The cell viability was evaluated and showed viability above 70% being considered non-cytotoxic material. The two techniques, which are commonly used separately, resulted in a three-dimensional structure with potential application in scaffolds.

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Ladle furnace slag (LFS) is a byproduct from steel refining with high calcium oxides and hydroxides contents, making it viable as a supplementary cementitious material (SCM), enhancing microstructure and mechanical properties, particularly in mortars. Therefore, this work evaluated the replacement of 30% of ordinary Portland cement (OPC) with LFS in coating mortars, combined with a water-retaining admixture as well as the pozzolanic addition of Metakaolin (MK). The mortars followed a 1:6 (binder:aggregate) ratio, and the tests evaluated their properties in the fresh and hardened state, such as the water retention and mechanical properties, along with microstructure characterization to investigate the effects of the binder blends. At 28 days, LFS incorporation ensured water retention, less compacted matrix and greater capacity of deformation absorption, which are properties particularly beneficial for masonry mortars. MK’s pozzolanic reactions resulted in pore refinement; however, the improvements in nominal strength were not statistically significant.

Resumo em Inglês:

Chitosan has gained considerable attention in recent years as a versatile material with applications in many fields, including food, pharmaceuticals, tissue engineering, and agriculture. The degree of deacetylation (DD) is a critical parameter of the properties and functionality of chitosan, influencing its solubility, bioactivity and suitability for various applications. Accurate determination of DD is crucial as it directly affects the behavior of the material in different environments. However, high-precision methods for DD measurement are often costly and difficult to access, posing a challenge for both academic research and industrial applications. In this study, we evaluated the DD of commercial chitosan using a variety of widely available techniques, including potentiometric titration (PT), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-Vis spectroscopy, and X-ray diffraction (XRD). Despite observed differences between methods, all techniques effectively quantified DD, shedding light on factors such as sample solubility, moisture content, baseline correction, and instrument accuracy that contribute to these differences. By demonstrating the feasibility and reliability of simple and accessible techniques for DD determination, this study provides valuable insights for improving the use of chitosan in both research and industry, making these materials more accessible for a wide range of applications.

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The increase in population has intensified the demand for water resources, leading to scarcity due to constraints in their availability, extraction, and sustainable utilization across various regions of the world. This study aimed to evaluate the performance of asymmetric pyramid-shaped solar stills units enhanced with photothermal materials to improve distilled water yield. Three identical solar still systems were constructed, with sensible heat storage materials incorporated into the trays of two of the units. In the first solar still unit (SS1), ceramic tiles were used as the heat storage medium; in the second (SS2), granite was employed; and in the third (SS3), no additional material was introduced. The corresponding distilled water outputs were 2424.80 mL.m-2 for SS1, 2992.00 mL.m-2 for SS2, and 2121.00 mL.m-2 for SS3. The incorporation of granite and ceramic tiles in the solar still units led to efficiency increases of 23% and 7%, respectively, compared to the reference system. Following the solar still process, significant reductions were observed in physicochemical parameters, particularly sodium, which decreased by 97%, 96%, and 96% in SS1, SS2, and SS3, respectively. All remaining parameters were also reduced and remained within acceptable potable water standards.

Resumo em Inglês:

Amongst the byproducts of steel industry is ladle furnace slag (LFS), with a chemical composition similar to limes, especially in the high content of calcium oxide and hydroxides. Its binding potential is improved with finer texture, making it viable for use as a supplementary cementitious material (SCM). Therefore, this study investigated the effects of a total replacement of hydrated lime (HL) for LFS in masonry mortars, also exploring whether pozzolanic addition of metakaolin (MK) could enhance it, tested both at 28 and 180 days. The experimental results, obtained at 28 and 180 days, showed that the replacing HL for LFS improved the mechanical properties of the mortars, due to the greater amount of compounds of LFS also present in the OPC, but not in the HL, such as Fe2O3, Al2O3 and SiO2. These findings suggest the potential of LFS for application in masonry mortar promoting strategies of circular economy.

Resumo em Inglês:

Due to the possible consequences of the greenhouse effect for future generations, solar energy has emerged as a promising alternative due to its great energy potential, especially for Brazil, which is in a privileged geographical position on the planet. The aim of this study is the deposition of Pt/FTO on the counter electrode of dye-sensitized solar cells (DSSC), as there are few studies in the literature on this area, and evaporation deposition is normally used. The counter electrode used was platinum deposited on FTO by chronoamperometry. The tests were performed in triplicate, at 90, 600 and 1800 seconds on AutoLab equipment, model PGSTAT302N. The solar cell was assembled in a sandwich format, with an active area of 0.23 cm2, so we attempted to develop a method for electrodeposition of platinum, using chronoamperometry, obtaining a PCE of 0.517% for deposition in 600 seconds.

Resumo em Inglês:

The tensile armor of flexible marine pipelines, responsible for the flow of oil and gas, is composed of the helical arrangement of steel wires subjected to complex stress modes that can cause unpredictable failures. Electromagnetic non-destructive testing (NDT) techniques are suitable for monitoring microstructural, morphological, and mechanical properties changes in deformed or heat-treated steels. In this study, a steel used in the manufacture of flexible Risers subjected to different heat treatments, with time and temperature variation, was investigated by SEM, XRD, and DSC, and related to the behavior of MBN, Magnetic Hysteresis, and Electrical Resistivity signals. The results indicate that the recovery process occurs in the spheroidizing at 600 and 700 °C; however, the behavior of the MBN envelope and the DSC curves suggest that the recrystallization only occurs in the treatments at 700 and 800 °C. The MBN peak has greater amplitude and lower energy to reach saturation due to the increased mobility of domain walls in spheroidized microstructure. In normalizing, the MBN peak was lower and the electrical resistivity higher, as the pearlitic microstructure and the multiplication of grain boundaries in recrystallization cause greater impediment to the movement of domain walls and the flow of free electrons.

Resumo em Inglês:

Modifying the surface of β-Ti alloys using the electrochemical anodizing process makes it possible to produce TiO2 nanotubes and nanopores that favor better bioactivity and cell-implant interaction. The use of elements that benefit biological properties, such as Nb and Si, makes the whole process even more advantageous. However, the microstructural and compositional characteristics of β-Ti alloys affect the formation, organization and uniformity of nanotubes. Therefore, this study produced Ti-35Nb-xSi alloys and analyzed the microstructure and formation of TiO2 nanostructures in the as-cast and water quenched (WQ) conditions. The results showed that the addition of Si reduced the precipitation of the ɷ-phase, making the β-phase more stable and formed the (Ti,Nb)5Si3 compound for as-cast and (Ti,Nb)3Si compound for WQ. The growth of nanostructured and hydrophilic layers was benefited from the chemical homogeneity of the substrate after heat treatment, with Si-rich regions affecting nanotube formation and the size of their diameters.

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This work investigates the production of microporous wool hybrid membranes using polyamide 66 yarns from industrial waste and vanadium pentoxide (V2O5), with the aim of applying this technology in the treatment of effluents, especially in the removal of textile dyes. The membranes were produced by phase inversion and characterized by several tests, such as water absorption, porosity and microfiltration efficiency. The results showed that the membranes containing 3% and 5% V2O5 presented superior performance compared to the pure PA 66 membrane, achieving stabilized water fluxes above of 193 Kg.m-2.h-1 and high rejection coefficients, reaching 99.97%. These findings highlight the potential of hybrid membranes as an efficient and economical alternative for effluent treatment.

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This study developed membranes based on babassu coconut mesocarp and evaluated the impact of honey (80% w/w – MM80 and 100% w/w – MM100) and glycerol (30% w/w – MG30 and 40% w/w – MG40) as plasticizers on their mechanical properties, wetting, and swelling behavior. The membranes were characterized using SEM, TG/DTG, and FTIR. Micrographs showed that plasticized membranes (MG30, MG40, MM80, MM100) had more homogeneous surfaces than the pure membrane (MP). All membranes were hydrophilic, with MM80 and MM100 being more polar. Plasticized membranes showed reduced swelling due to pore filling by plasticizers. Thermal analysis revealed two events for MP (dehydration and polymer degradation), while plasticized membranes displayed an additional event linked to plasticizer release. Regarding mechanical properties, MP demonstrated brittle behavior with high tensile strength (20.08 MPa) and low elongation at break (3.79%). In contrast, the MM80 and MG30 excelled, showing better mechanical properties, with elongation at break values of 10.60% and 16.95%, in addition to the tensile strengths of 11.66 MPa and 10.32 MPa, respectively.

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This study evaluates the biotechnological potential of isolated microorganisms for the solubilization of critical and valuable metals in LED lamp waste through a biometallurgical process, called bioleaching or biomineration, which occurs with the production of metabolites by microorganisms capable of transforming metals from the solid phase to the liquid phase. Seven different bacteria from LED waste were isolated. Among them, six samples were identified as belonging to the Bacillus genus. The pH increase indicates that the solubilization of the metals occurred through cyanogenesis. Cellular viability was monitored throughout the process, with viable cells existing for up to 30 days of experiment. The Scanning Electron Microscopy images showed changes in the LED particles size after the bioleaching process, confirming the degradation of the material from the metabolites produced by the microorganism during the process.

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Anionic clay-type materials with layered double hydroxide (LDH) structures in the MgAlFe and ZnAlFe ternary systems were successfully synthesized via co-precipitation, utilizing bauxite tailings from the Amazon region as the starting material. X-ray diffraction (XRD) confirmed the formation of well-defined LDH phases, with basal reflections indicative of the effective incorporation of divalent and trivalent cations into the lamellar structure. Scanning electron microscopy (SEM) revealed distinct morphological differences: MgAlFe LDHs exhibited rough, disordered surfaces, while ZnAlFe variants formed larger, plate-like aggregates. Raman and FTIR (ATR) spectroscopy identified characteristic vibrational bands, reflecting the influence of metallic composition on the structural organization of the materials. This study demonstrates a sustainable and efficient route for the synthesis of anionic clays from industrial waste, emphasizing their potential for technological and environmental applications.

Resumo em Inglês:

The use of lightweight concrete with expanded clay has increased as an alternative for reducing the self-weight of structures. Consequently, techniques that facilitate the analysis of the mechanical and elastic properties, such as ultrasonic pulse velocity (UPV), have gained relevance. Despite this, there is still a lack of studies focusing on the elastic properties of this type of concrete through UPV methods, particularly the dynamic modulus of elasticity (Ed) and Poisson's coefficient. This study aimed to determine the Ed and Poisson's coefficient of concrete containing expanded clay, based on the ASTM C597-16 standard and the stiffness matrix method. Strong correlations between static modulus of elasticity (E) and Ed were observed, with exceptions related to the stiffness matrix method. Nevertheless, this method provided the most suitable Poisson's coefficient for the material studied. The Ed values fell within the expected range, confirming the effectiveness of ultrasonic testing for lightweight concrete.

Resumo em Inglês:

The application of thermal barrier coatings (TBC) on titanium alloys has been widely used in aircraft turbines to maintain their properties such as low density, mechanical strength, while also enabling higher operational temperatures and thermal efficiency. Corrosion and hot oxidation damage the TBC, which consist of a metallic substrate, a metallic coating (bond coat, BC), a thermally grown oxide (TGO), and a ceramic topcoat. This study assessed the oxidation behavior of Ti-6Al-4V with and without BC and TBC. Oxidation tests were conducted cyclically in air at temperatures of 500, 600, and 800 °C in an automatic furnace, in which each cycle consisted of 60 minutes at the target temperature followed by 10 minutes at room temperature. After 100 thermal cycles, the samples were analyzed using scanning electron microscopy (SEM), optical microscopy (OM), and X-ray diffraction (XRD). With increasing temperature, the uncoated Ti-6Al-4V alloy showed the formation of titanium oxides on the surface and an approximate 20% increase in grain size. In contrast, the TBC system demonstrated greater durability under high temperature conditions and showed no evidence of delamination.

Resumo em Inglês:

Basic magnesium sulfate cement (BMSC) is a non-conventional binder with advantages such as fire resistance, lightweight properties, and low alkalinity, widely used in lightweight panels. However, the effects of cellulosic fiber incorporation on the hydration mechanisms and mechanical performance of BMSC remains insufficiently explored. This study evaluates the effects of incorporating different dosages of bleached eucalyptus fibers (EB) on the physical, mechanical, and microstructural properties of BMSC composites. Additionally, it examines their influence on hydration reactions and phase formation to determine optimal compositions for construction applications. The composites were analyzed using mechanical tests, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and DIC. Results indicate that the 5-1-7 phase enhances mechanical strength through a space-filling effect, while fiber incorporation increases porosity and alters phase distribution. Higher fiber contents led to increased porosity and a reduction in compressive strength, whereas flexural strength and energy absorption were improved due to fiber-bridging effects. These findings highlight the potential of optimizing fiber dosage to balance strength and toughness in BMSC composites for construction applications.

Resumo em Inglês:

This study focused on the preparation of electrospun poly(vinyl chloride)/silica membranes featuring the in situ formation of modified silica nanodomains during the electrospinning process, using organosilane precursors, with the purpose to develop new adsorbents for oil-spill cleanup. The membranes were fabricated from poly(vinyl chloride) solutions in a 50/50 (v/v) tetrahydrofuran/dimethylformamide mixture, incorporating 3, 4, and 5 wt% of either (3-aminopropyl)triethoxysilane (APTS) or 3-(triethoxysilyl)propyl isocyanate (TEPI) as precursors. The resulting membranes were characterized by scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and differential scanning calorimetry, which confirmed the successful formation of silica nanodomains via an in situ sol-gel process during electrospinning. Additionally, contact angle measurements and oleophilic behavior were evaluated. The contact angle of the PVC membranes (136.8o) tended to decrease with the incorporation of silica nanodomains with isocyanate (126o) or amino (125.4o) groups. The membranes exhibited excellent oil sorption performance and tunable hydrophobicity, with the sample prepared with 5 wt% APTS showing the highest performance, underscoring their potential for oil/water separation applications.

Resumo em Inglês:

We synthesized and characterized electrospun polystyrene (PS) membranes functionalized with graphene oxide (fGO) and polypyrrole (PPy) for the removal of Eriochrome Black T (EBT) dye from aqueous media. The membranes were prepared via electrospinning, followed by air plasma treatment to improve hydrophilicity, enabling uniform coating with fGO and in situ polymerized PPy. Characterization using SEM, XRD, FTIR, and UV-Vis spectroscopy confirmed the successful incorporation of fGO and PPy. Adsorption experiments evaluated the effects of pH, interaction time, dye concentration, temperature, and ionic strength. The highest adsorption capacity (qe) of 110 mg g−1 was achieved at pH 2 and room temperature, with equilibrium in 150 minutes. Kinetic and isotherm modeling indicated that adsorption follows the pseudo-second-order and Langmuir models, suggesting monolayer adsorption. The thermodynamic analysis confirmed an endothermic and spontaneous process, with a maximum qe of 473.3 mg g−1 at 333 K. The membrane remained effective for at least six adsorption/desorption cycles, and adsorption efficiency increased in saline solutions, demonstrating its potential for real wastewater treatment.

Resumo em Inglês:

Aluminum (Al) parts for the electrical industry are subjected to cyclic loads, making their fatigue life critical. Owing to its properties, AlSi10Mg alloy is largely employed in this field. Additive manufacturing (AM) is rising as a new technology to fulfill the demand for spare parts. Laser Directed Energy Deposition (L-DED) and Laser Powder Bed Fusion (L-PBF) can manufacture customized components with larger dimensions and greater geometric resolution, respectively. However, there are challenges in processing AlSi10Mg by AM, like controlling oxygen and moisture atmosphere contents, which negatively affect the processability and component properties. To ensure multilayer parts with appropriate microstructure and mechanical properties, L-DED and L-PBF processing parameters must be properly investigated. In this context, processing parameters and build strategies for an AlSi10Mg alloy were developed for L-DED and L-PBF. The performance of AM-manufactured AlSi10Mg was benchmarked to reference casting. Archimedes’ density, optical microscopy porosity, computed tomography, optical and scanning electron microscopy, hardness, tensile, Charpy impact, and VHCF tests were performed. The results suggest comparable VHCF performance, despite the slight differences observed in mechanical properties, porosity, and microstructure characteristics between L-PBF and L-DED specimens.

Resumo em Inglês:

The present work addresses the different manufacturing routes through which a 1075 pearlitic steel can pass in order to improve its resistance to severe corrosion conditions. Taking into account the use of this material in marine environments, such as offshore oil exploration pipelines, this type of steel must have a microstructure resistant to such conditions. Thus, this eutectoid steel was evaluated in its condition as received and subsequently submitted to cold rolling and full annealing, to change its microstructure, namely, with reductions of 25 and 50% with subsequent heat treatment of 900°C in both reductions and with two different times. After evaluating their microstructures and noticing significant changes in their crystallographic textures, through SEM/EBSD techniques such as Cube, Goss and Brass components, these samples were subjected to electrochemical tests to evaluate their corrosion resistance in a synthetic seawater solution, highlighting the highest polarization resistance for the Goss component and family of plans {011}. Subsequently, a 24-hour immersion test was used for each sample in the synthetic seawater solution and the presence of oxides and salts that attenuated corrosion on the surface of the sample with a family of {011} planes like Akaganeite (β-FeOOH) and Ferroxyhyte (δ-FeOOH) were confirmed by Raman spectroscopy.

Resumo em Inglês:

The biological response to metallic biomaterials is strongly influenced by surface properties such as topography and wettability. This study evaluated the influence of roughness and contact angle on the cellular viability of pre-osteoblasts (MC3T3-E1) cultured on commercially pure titanium (grade 4), Ti-6Al-4V ELI, and Ti-12Mo-6Zr-2Fe (TMZF) alloy. Samples were machined by facing on a lathe using fixed parameters without coolant, and subsequently polished and characterized by confocal microscopy. Wettability tests were performed using the sessile drop method with varying droplet volumes and fitting methods using an optical tensiometer. Biological assays were conducted at 24, 48, and 72 hours using resazurin. Results showed that the combination of arithmetic roughness (0.6 and 1.3 µm) and hydrophilic behavior enhanced cell adhesion and proliferation, particularly on the TMZF alloy. Topographic symmetry (Rsk) and kurtosis (Rku) were more strongly correlated with biological response than mean roughness (Ra). The findings suggest that surface features and wettability properties act synergistically to modulate cell behavior and play a key role for biocompatibility and the development of optimized surfaces for biomedical applications.

Resumo em Inglês:

The municipality of Bragança, Pará, Brazil, is renowned for its artisanal ceramic production, where chamotte is reused as a substitute for clay materials. In this study, test specimens were formulated and produced with clay partially replaced by chamotte in proportions ranging from 0% to 25%, and sintered between 600°C to 1000°C. Both the clay and chamotte underwent technological characterization. The specimens were subjected to physical and mechanical analyses. The raw materials consist of quartz, illite, kaolinite, and K-feldspar, with SiO2 and Al2O3 as the predominant chemical components. The clay is clayed silt, exhibits an appropriate plasticity index, and undergoes structural transformations as the temperature increases, confirming its suitability for ceramic applications. The best results were obtained with 5% to 15% chamotte in ceramics sintered at 900°C, reaching a mechanical strength of 7 MPa. The data on various technological properties indicate the feasibility of producing artisanal ceramics incorporating chamotte.

Resumo em Inglês:

The characterization of surface roughness in rock aggregates is essential for geotechnical engineering, directly influencing pavement performance and durability. This study compared three roughness analysis techniques: the Aggregate Imaging Measurement System (AIMS), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). Samples of volcanic rock (SUL) and plutonic rock (MIN) were analysed using all three techniques, revealing discrepancies in the results. AIMS presented limitations in representing materials with micrometric roughness and substantially coarse grain sizes, such as the MIN aggregate, where dominant minerals influenced the texture due to wavelet processing. AFM proved to be an efficient roughness characterization technique, quantifying parameters such as average roughness (Ra), root mean square roughness (Rq), surface skewness (Rsk), and surface kurtosis (Rku), but was limited to small scanning areas. The results reveal potential inconsistencies in traditional classification systems, particularly their inability to detect variations in rocks with different textures and granulometries. Data obtained from AFM and SEM demonstrated greater sensitivity, revealing features not identified by AIMS, especially in fine-grained materials like the SUL rock. Therefore, integrating micro- and nanoscale analyses is proposed as a complementary approach to overcome the limitations of conventional methods.

Resumo em Inglês:

This study investigates the influence of austenitizing temperature on the retained austenite content and hardness of SAE 52100 steel. Nine samples were subjected to different austenitizing temperatures (760–920°C) followed by oil quenching. Microstructural and mechanical characterization techniques, including X-ray diffraction (XRD), ferritoscopy, electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and hardness test Rockwell were employed. The results indicate that the retained austenite content increases with higher austenitizing temperatures, and TEM and EBSD analyses revealed a reduction in carbide content at higher temperatures, along with an increase in martensite formation. Since ferritoscopy measures magnetic (martensite) versus non-magnetic (retained austenite + carbides) phases, the detected martensite fraction increased as the retained austenite decreased. Hardness measurements showed a direct correlation with austenitizing temperature, with the highest Rockwell hardness observed at 880 °C.

Resumo em Inglês:

We report the development and characterization of flexible polystyrene/polypyrrole-organophilic montmorillonite (PS/PPy-OMMT) membranes tailored for resistive humidity sensing applications. The membranes were produced by electrospinning polystyrene (PS), followed by in situ incorporation of polypyrrole (PPy) and organophilic montmorillonite (OMMT). The successful integration of PPy and OMMT on the PS fiber surfaces was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD), and Energy Dispersive X-ray Spectroscopy (EDX) analyses. The resulting membranes showed a strong sensor response of 397% over a relative humidity range of 11% to 97%, highlighting their potential for advanced humidity sensing applications.

Resumo em Inglês:

Double acid etching (DAE) is a consolidated method of surface modification for implants, however there are few studies on its application in newer alloys. The topography and surface composition influence the long-term success of dental implants, favoring retention and osseointegration. Beta titanium alloys emerge as an alternative with a low modulus of elasticity, high resistance to corrosion and better mechanical properties, in addition to being composed of biocompatible elements. In the present research, the influence of the acid etching process on cold-deformed and aged Ti-xNb-ySn alloys (x= 35 and 42 and y= 0 and 2) was studied. The samples were subjected to a two-step treatment with different combinations of acids. The surface roughness parameters were quantified using a rugosimeter, the topography was studied by scanning electron microscopy, and the wettability was determined by the sessile drop method. The results revealed that the two-step acid treatment altered the topography of the alloy, increasing the surface area and consequently the osseointegration potential.

Resumo em Inglês:

This study investigates the modification of acrylonitrile butadiene styrene (ABS) filaments with polypyrrole (PPy) to enable their use in additive manufacturing applications requiring electrical conductivity. PPy was incorporated into ABS via melt extrusion at concentrations from 0 to 60 wt.% to address the material’s inherently low conductivity. The resulting filaments were characterized using UV-Vis spectroscopy, FTIR, SEM, TGA, DMA, and EIS. At 60 wt.% PPy, impedance decreased by two orders of magnitude, although continuous conductive pathways were not fully established. To overcome this limitation, an additional PPy coating was applied to the filament surface, yielding a five-order reduction in impedance and markedly enhanced electrical performance. TGA results showed improved thermal stability with increasing PPy content, while DMA indicated reduced mechanical strength, especially between 75 °C and 100 °C. These results highlight the potential of PPy-coated ABS filaments as conductive materials for energy-related additive manufacturing applications, balancing conductivity with acceptable thermal and mechanical properties.

Resumo em Inglês:

The Monel 400 alloy, composed primarily of nickel and copper, offers excellent corrosion resistance but exhibits relatively low wear resistance, limiting its durability in demanding applications such as maritime industries, pumps, and valves. To address this, boriding thermochemical treatment was applied to enhance the surface hardness and wear resistance of the alloy. The process used a boriding powder containing 90% B4C and 10% KBF4 at 900 °C for 4 hours, avoiding silicon activators to prevent the formation of less hard nickel silicides. The resulting boride layer, predominantly Ni2B, Ni3B, and Ni4B3, was characterized using X-ray diffraction (XRD) and evaluated for adhesion via Rockwell C indentation (VDI 3198 standard). Wear performance was assessed through pin-on-disk tests on treated and untreated samples, analyzing wear rates, removed volume, and surface roughness using profilometry, confocal microscopy, and SEM. The borided layer achieved a hardness of up to 1600 HV0,01, demonstrating significantly improved wear resistance while maintaining strong adhesion to the substrate. This study highlights the potential of boriding as an effective treatment to extend the service life of Monel 400 in abrasive environments.

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Water pollution, characterized by the release of harmful substances into water bodies, affects water quality and negatively impacts people, animals, and the environment. Its causes include industrial waste, mining, domestic sewage, and radioactive residues. This study aimed to obtain membranes using the immersion-precipitation method, with pure polyamide 66 (PA66) and PA66 with 5%, 7%, and 10% clay. The membranes were analyzed for water absorption capacity, porosity, average and maximum pore radius, bubble point, contact angle, and water and effluent flows. The addition of clay reduced water absorption and porosity due to the clay’s barrier effect. The bubble point indicated an increase in the maximum pore radius, except with 10% clay due the possible agglomeration formation. The average pore radius increased with the clay percentage, with 5% showing the highest value. Flows decreased over time, but higher clay content improved flows and efficiency, achieving retention above 99.5% for dye particles.

Resumo em Inglês:

This study investigated the efficiency of different natural-source additives as coupling agents in sustainable composites based on post-consumer high-density polyethylene (HDPEpc) reinforced with 30 wt.% curauá fiber (CF). The effects of citric acid (CA), pine rosin (PR), and pine lignin (PL) were evaluated in comparison to a conventional synthetic agent, maleic anhydride-grafted polyethylene (MAPE). Mechanical tests — tensile, flexural, and Izod impact — demonstrated that the addition of natural-source additives resulted in significant improvements in the mechanical properties compared to the composite without additives. The performance of the composite with the addition of PR was statistically similar to that of the composite compatibilized with MAPE. The results highlight the potential of PR, a natural resin, as a coupling agent, suggesting a viable, renewable, and more environmentally suitable alternative to synthetic coupling agents, thereby contributing to the development of more sustainable thermoplastic composites.

Resumo em Inglês:

As-cast TiNb alloys with different Y additions were studied, which promoted the formation of Y2O3. Its particles were responsible for grain refinement, the smallest reduction of which was 82% for the TiNb0.6Y alloy, that had the highest volume fraction and the highest E. The hardness of the alloys, on the other hand, was reduced by the depletion of O in the matrix, leading to a loss of solid solution strengthening. Anodic polarization showed that the TiNb0.1Y alloy had higher icrit and lower Eb values, whose lower resistance was confirmed by chronoamperometry. EIS showed that the TiNb0.2Y alloy had the largest capacitive arc diameter and one of the largest phase angles, pointing to the greater resistivity and stability of the passive layer, while Mott-Schottky analysis revealed n-type semiconductor properties in the passive films, whose film formed on the TiNb0.2Y alloy showed the lowest donor density, confirming its greater corrosion resistance.

Resumo em Inglês:

In 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 quality.

Resumo em Inglês:

This research explored a new approach that uses a waste material, polyamide 66 (PA66), as a raw material in the manufacture of membranes for the treatment of textile effluents. Membranes were produced by combining PA66 with silicon carbide (SiC) using the phase inversion technique, in the presence of magnesium chloride, using different solvents such as formic acid and hydrochloric acid. The SiC was characterized using X-ray diffraction and the grain size of the sample was measured. The membranes were characterized using various techniques, including water absorption, porosity, bubble point, average pore radius, contact angle, chemical resistance, water flow and effluent flow. The water-dye separation tests revealed a significant reduction in concentration. All the membranes showed a yield of over 99%, which demonstrates the potential of these membranes for this application.

Resumo em Inglês:

Research with aluminum alloys containing Bi has been developed in recent decades due to the great potential that these alloys present for the manufacture of components subjected to friction conditions. In the literature there are many doubts to be clarified about the interrelationship between the microstructure, mechanical properties, and wear resistance of unsteady-state directionally solidified multicomponent Al-Cu alloys, with high Cu content and containing Bi. Thus, this work aimed to investigate the effect of eutectic spacings (λE) on the hardness and wear resistance in the Al-33Cu-3.2Bi (wt.%) alloy by means of a water-cooled device. Rockwell B hardness (HRB) and micro-abrasive wear tests using a fixed rotating sphere, were carried out on solidified samples in positions from the heat transfer interface. In the wear tests, two durations were evaluated: 7 minutes and 28 minutes. The wear parameters evaluated were worn volume (VD) and wear rate (TD). After the aforementioned tests, the HRB, VD and TD values were correlated with the measured λE values. The results showed that finer microstructures, that is, smaller λE, promoted higher HRB values. On the other hand, VD and TD decreased for coarser microstructures, i.e., presented high wear resistance for higher λE values.

Resumo em Inglês:

The MOF MIL-100(Fe) was successfully synthesized using both a conventional solvothermal method and an innovative green synthesis approach. It was characterized using FTIR, PXRD, TG-DTA, BET, and SEM techniques, and tested for hydrogen production through the hydrolysis of sodium borohydride (NaBH4). The catalyst produced through a green synthesis approach demonstrated superior catalytic performance, achieving a hydrogen generation rate of 443.46 mL min−1 gcat−1 at 340.15 K, with an activation energy of 16.2 kJ mol−1, and good recyclability over multiple cycles. This is attributed to its higher specific surface area (1224 m2/g) and greater porosity than the solvothermal synthesized material, which presented a higher activation energy (19.0 kJ mol−1). These findings position MIL-100(Fe) synthesized via green methods as a promising candidate for sustainable hydrogen production.

Resumo em Inglês:

Contaminants of emerging concern have received considerable attention due to their potential adverse effects on aquatic systems, flora, fauna, and human health. Azo dyes represent a significant category of toxic organic contaminants. Heterogeneous photocatalysis offers an effective green alternative for the degradation of organic pollutants, particularly in wastewater treatment. This research aimed to synthesize and characterize nanostructured zinc oxide films to develop a UV-light activated photocatalyst capable of degrading organic compounds. The films were synthesized via the sol-gel method, and deposited on borosilicate glass substrates by spray coating and spray pyrolysis techniques. The samples underwent heat treatment at varying times and temperatures. The photocatalytic efficiency was evaluated by the methyl orange dye discoloration under UVA radiation. Wurtzite structure was observed in all conditions. Differences in surface morphology, band gap energies, and photocatalytic performance were also noted. Both methods enabled the production of UVA-photoactived films.

Resumo em Inglês:

The reinforcement of cementitious matrices with structural fibers in concrete production imposes restrictions on the workability of fresh concrete compared to that without fiber addition. Several international standards have sought to develop and evaluate better methods for this technology. In Brazil, the most recent standards have continued to analyze the workability of concrete using the traditional slump test method. This work, which investigated three different types of fibers in three different dosages, shows that the flow table method can be better used to measure the effect of different levels and types of structural fibers in concrete. The results showed that when plastic concrete receives the addition of fibers, its workability is little changed under energy, which is the principle of the flow method and the practical application using vibrators, but there is a loss of this property when measured using the traditional slump test method. When this workability was corrected using the slump test method, the water content of the concrete mixes increased. The comparative results showed that the analysis of the impact of structural fiber dosage by combining the two methods can support the development of concretes using only the slump test method.

Resumo em Inglês:

This study aimed to evaluate the influence of yerba mate extract (YM) (1%, 10%, 20% w/w) and malic acid (MA) (0.5% w/w) on the mechanical response of potato starch-glycerol based films (PS), targeting disposable packaging applications. YM incorporation decreased the Young's modulus and tensile strength of the films proportional to its content, while increasing elongation at break. The effect of MA was found to be synergistic, further reducing rigidity and improving flexibility. DMA analysis indicated that molecular relaxations shifted to lower temperatures with increasing YM content and MA addition, suggesting a plasticizer-like behavior. SEM images revealed surface homogeneity in MA formulations, confirming better additive-matrix compatibility, as well as the presence of nanoparticles at higher YM concentrations. These findings demonstrate that the combination of YM and MA in starch-based matrices is effective in producing flexible films, with MA20YM formulation (0.5% MA and 20% YM) showing the best overall performance.

Resumo em Inglês:

This study evaluates the photocatalytic performance of ZnO/PS and ZnO-ALE/PS nanofilters, in which zinc oxide (ZnO) nanoparticles were green-synthesized using Aloe vera extract (ALE) and subsequently incorporated into polystyrene (PS) nanofibers. These nanofilters operate as a dual-function system, providing both a physical barrier for particulate retention and photocatalytic degradation of dyes under UV irradiation. The ZnO-ALE/PS filters exhibited enhanced dye removal efficiency compared to filters prepared with conventionally synthesized ZnO. UV-Vis spectroscopy revealed a distinct shift in the absorption spectrum, with ZnO@ALE showing pronounced absorption near 210 nm, overlapping with the characteristic ZnO peak at 360 nm, suggesting plasmonic band contributions. Structural and compositional analyses by SEM, FTIR, and EDS confirmed the successful integration and morphological optimization of the nanofibers for water purification applications. These findings demonstrate the potential of green-synthesized ZnO-ALE/PS nanofilters as an efficient, sustainable, and environmentally friendly approach for wastewater treatment, with broad relevance in the fields of nanotechnology and environmental remediation.

Resumo em Inglês:

Magneto-Rheological Elastomers (MREs) are composite materials combining a solid matrix and a dispersion of magnetizable particles (typically silicone rubber and carbonyl iron). Due to their magneto-sensitivity, which induces changes in the intrinsic viscoelastic properties of the samples when exposed to an external magnetic field, they are classified as "intelligent" materials. This research explores different stress-strain regimes in controlled-force tests, which provided a deeper understanding of the relationship between applied stress and the magnetic field's influence on the material’s viscosity and shear modulus modeled by the Kelvin Voigt Model with 3.91% error. By assuming a linear variation between these regimes, an error of 4.8% was achieved, demonstrating the feasibility of data simulation even with different input values for a single geometry. Sample fabrication techniques were developed using custom molds and devices created via 3D printing, which minimized bubble formation and resulted in a fabrication error of 5.19%. The errors obtained are considered satisfactory for the application of the material in vibration control technologies for structures, as safety factors in such applications are generally higher. The characterization results reaffirm the material's potential for technology development, with an average maximum gain of 275.48% for shear modulus and 218.07% for viscosity across stress-strain regimes.

Resumo em Inglês:

Chloride ions are the primary aggressive agents responsible for the corrosion of reinforced concrete structures and, consequently, the reduction of their service life, which entails high repair costs. These ions penetrate the concrete through its porous network and depassivate the steel reinforcement, even in small quantities. The adoption of specific binders modifies the cementitious matrix, potentially hindering the progression of these ions. As a chloride detection technique, X-ray fluorescence (XRF) can be employed, which, in addition to identifying the elements present in a sample, allows the creation of intensity distribution maps. Thus, this study aimed to evaluate how the XRF technique can contribute to understanding chloride penetration and to identify which cement types most effectively hinder their advancement. To accelerate chloride ion migration, two methods were employed: ASTM C1202 and NT Build 492. Eight different types of cement were analyzed, and the results indicated high resistance to chloride penetration in cements containing slag and pozzolan, while cements with filler exhibited lower resistance.

Resumo em Inglês:

The present study investigates the influence of different organic additives on PLA/PBAT blends, focusing on enhancing their thermal, mechanical, rheological, and microstructural properties for biodegradable packaging applications. Five additives were tested: citric acid, lauric acid, gum rosin, cellulose nanocrystals, and poly(vinyl acetate) (PVAc). The blends were prepared in an internal mixing chamber and injection molded for mechanical testing. Characterizations included mechanical tests (tensile, flexural, Izod impact), thermal analyses (DSC, TGA), rheological assessments (torque, melt flow index), and SEM. Among the additives, PVAc showed the most promising results, improving phase dispersion through a core-shell structure and enhancing tensile strength (11.9%), toughness (32%), and flexural stress (26.5%). These results highlight PVAc as the most promising additive for optimizing the performance of PLA/PBAT blends. This study provides valuable insights into developing sustainable materials with improved properties for biodegradable packaging.

Resumo em Inglês:

This study evaluates the incorporation of electroplating sludge waste into red ceramics as a sustainable and safe alternative for waste management. The raw materials were collected and characterized, and a 23 factorial design was applied with sludge contents of 0%, 10%, and 20%, firing temperatures of 850, 950, and 1050 °C, and residence times of 60, 120, and 180 minutes. Ceramic specimens were formed by hydraulic pressing and tested for flexural strength, water absorption, linear shrinkage, and heavy metal leaching. Although sludge incorporation slightly reduced mechanical performance and increased water absorption and shrinkage, all results remained within regulatory limits. Importantly, leaching tests demonstrated a significant reduction in the mobility of Cr and Ni, indicating the effective immobilization of these hazardous elements. These findings underscore the potential of electroplating sludge as a raw material in red ceramics, serving both as a recycling route and a strategy for environmental risk mitigation.

Resumo em Inglês:

Zinc-rich paint technologies are demanded for the anti-corrosive maintenance of buried metal structures used in the Brazilian electricity sector. In these cases, however, the cleaning treatment, usually carried out by mechanical and manual tools, cannot remove the corrosion product completely, impairing the cathodic protection offered by these paints. Nowadays, different commercial zinc-rich paint technologies are provided to overcome this problem. In this work, the anti-corrosive performance of seven commercial zinc-rich paint technologies was evaluated using electrochemical tests in a saline solution, and the most promising paints concerning their cathodic protection effects were submitted to performance tests in painting systems. The electrochemical results revealed that although the graphene-containing paint (Zcgraf) could provide a barrier anti-corrosive effect, only the traditional epoxy paint (Zn) and that containing ceramic particles (Zcer) showed improved cathodic protection properties. In performance evaluation, these selected zinc-rich paints showed superior anti-corrosive performance compared to the reference epoxy mastic aluminum paint (EMA). Therefore, both Zn and Zcer paints may efficiently replace EMA paint under maintenance conditions.

Resumo em Inglês:

When machining metallic materials, especially when face milling tool steel, annealing heat treatment is recommended for good machinability. The entry strategy of the cutting tool into the material plays a fundamental role in the tool. This study evaluated the direct and rolling entry strategies in the face milling of annealed SAE D2 steel, under dry conditions. The tests were performed at a 3-axis vertical machining center with programming developed in CAM. The rolling strategy resulted in a greater volume of material removed compared to the direct entry, for a stipulated wear of 0.3 mm. The average roughness (Ra) was similar between the strategies. The progressive flank and rake surface wear were evaluated by scanning electron microscopy (SEM) and energy dispersive X-ray (EDS), identifying adhesion as the predominant wear mechanism.

Resumo em Inglês:

The use of pro-oxidant additives in the processing of HDPE is a viable alternative for reducing the impacts caused by the accumulation of polymer waste in the environment, since they favor the thermal oxidation and photooxidation of macromolecules. However, these additives can affect the mechanical recyclability of the polymer, as they are exposed to high temperatures during reprocessing. This study evaluated the consequences of the presence of these additives in the multiple reprocessing of two different types of oxo-biodegradable HDPE, obtained by adding d2wTM and benzoin. After 5 reprocessing cycles, these additives caused a greater increase in oxygenated functional groups, which reduced the contact angle with distilled water. Additionally, thermal oxidation led to a greater loss of mechanical properties in samples with pro-oxidant additives when compared to HDPE reprocessed without these additives. These alterations were accompanied by a progressive increase in the yellowness index, compatible with the changes observed.

Resumo em Inglês:

This study investigates the design, synthesis, and characterization of novel high-entropy alloys (HEAs) in the NbTiCrAl system, focusing on the compositions NbTi, Nb7Ti7Cr2, Nb7Ti7Al2, Nb7Ti7Cr1Al1, and Nb3Ti3Cr1Al1. Microstructural analysis identified a single-phase BCC solid solution with dendritic structure, where compositional segregation is driven by melting point differences, with Ti, Cr, and Al migrating to interdendritic regions. Mechanical testing demonstrated that Cr and Al additions significantly improved hardness and strength, with Nb3Ti3Cr1Al1 exhibiting the highest microhardness (387.9 ± 6.1 HV0.5) and compressive yield strength (986.4 ± 70.0 MPa). Statistical analysis through a 22 full-factorial + central point design and ANOVA indicated that Cr predominantly influences the mechanical properties, with minimal interaction from Al. Multivariable linear regression models were developed to predict mechanical performance. These findings underscore the importance of Cr and Al balance for phase stability and mechanical properties, establishing the NbTiCrAl system as a promising candidate for advanced structural applications.

Resumo em Inglês:

Gelcasting is a versatile forming technique suitable for preparing composite materials with various powders, including metallic and ceramic particles, at any solids concentration. Despite its potential, the application of gelcasting to produce metal matrix composites reinforced with alumina and graphene remains limited. This study investigates the gelcasting of AISI 310 stainless steel composites reinforced with 1, 3, and 5 vol.% nanosized alumina and 0.5 vol.% graphene nanoplatelets (GNPs). Rheological behavior and particle interactions were analyzed to ensure uniform dispersion. Thermal analysis determined optimal sintering conditions, avoiding densification issues. Compression and microhardness tests revealed yield strengths of up to 285 MPa at room temperature (RT) and 140 MPa at 800 °C, exceeding ASTM A351/A351M-18e1 standards. Microstructural refinement and homogeneous alumina distribution were achieved, with 3 vol.% alumina providing the best performance. The gelcasting process proved effective for producing dense, mechanically robust composites at a low cost.

Resumo em Inglês:

The development of multifunctional packaging addresses the demand for solutions that combine protection, sustainability, and functionalities such as antimicrobial activity. In this context, films of hybrid composites (HC) based on a poly(lactic acid)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) blend - PLA/PHBV (70/30 wt/wt), sepiolite nanoparticles (SEP, 5 phr), and different contents (3 and 5 phr) of micrometric zinc oxide (ZnO) were produced via melt mixing and compression molding. The influence of ZnO content on rheological, thermal, mechanical, and water vapor permeability properties, as well as its role as an antimicrobial agent, was evaluated. Despite ZnO acting as a catalyst for PLA degradation during processing, the HC with 3 phr of ZnO demonstrated significant improvements, including a 16% in elastic modulus and a 21% increase in tensile strength (compared to PLA/PHBV blend), an 85% reduction in water vapor permeability (compared to PLA/PHBV/SEP nanocomposite), good processability, and effective inhibition of bacterial growth on the film surface. These results highlight the potential of HC with 3 phr of ZnO for producing multifunctional packaging using conventional melt-processing techniques.

Resumo em Inglês:

This study explores the sustainable use of refractory clay (RC), a low-cost byproduct of the mining industry in southeastern Brazil, as a flame-retardant additive in acrylonitrile-styrene-butadiene (ABS) composites. Composites containing 10 - 20 wt% RC were prepared via twin-screw extrusion and injection molding. Their thermal stability (TGA, DSC), mechanical performance (tensile, flexural, and impact tests), heat deflection temperature (HDT), morphology (SEM), and flammability behavior (UL-94V and UL-94HB) were evaluated. The incorporation of 20 wt% RC significantly enhanced flammability resistance, reducing the linear burning rate to 33.4 mm/min and enabling self-extinguishing behavior under both horizontal and vertical burning tests. These improvements were achieved without compromising the mechanical or thermal properties of ABS. The use of RC presents a sustainable and effective strategy to improve fire safety in polymer systems while adding value to an industrial waste material.

Resumo em Inglês:

In parallel with the exploitation of natural resources and the large amount of waste generated during the production of natural stones, the development of artificial materials offers less harmful alternatives to the environment, with enhanced properties and greater control over these characteristics. This study aims to develop epoxy matrix composites using a by-product from lactic acid production called industrial gypsum. This material was incorporated in two configurations: with and without processing in a ball mill. The composite plates were produced using the vibration and vacuum compaction method, followed by hot pressing for 25 minutes at a temperature of 90°C, with post-curing at 70°C. The processing allowed a 9% reduction in resin content. The physical and thermal properties were not affected by the resin content reduction due to the gypsum processing. Improvements in compressive strength, impact resistance, and wear properties were observed, attributed to the more uniform structure achieved after processing.

Resumo em Inglês:

The Water-Gas Shift reaction is a key step in hydrogen production and requires chromium-free catalysts that perform under various conditions, including with contaminants. The applicability of the Co/Nb2O5 catalyst for the WGS reaction was evaluated in the absence and presence of H2S. The low dispersion of metallic cobalt may be attributed to the strong metal-support interaction, indicated by the surface enrichment of niobium and the presence of reduced species, as confirmed by X-ray photoelectron spectroscopy analysis. Diffuse reflectance infrared Fourier transform spectra obtained during the in situ reaction indicated CO adsorption on partially reduced cobalt sites, and XPS also revealed the presence of unreduced cobalt on the surface. In situ experiments were consistent with the catalytic activity tests, suggesting that the catalyst is more suitable for the High-Temperature Shift range. The catalyst exhibited good initial activity, but showed a tendency to deactivate over time and low tolerance to sulfur.

Resumo em Inglês:

Composite 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 hardness.

Resumo em Inglês:

Plastic waste contributes negatively to the environment by increasing space occupation, creating health hazards on land, in the air, and at sea. For this reason, they need to be disposed of properly so that they can be recycled efficiently. To combat these impacts and reduce environmental pollution, this project aims to study the recycling process of polypropylene (PP) from industrial waste scraps and polypropylene from urban solid waste (MSW) using ionizing radiation from 0 to 500 kGy. Irradiation processing showed efficiency when compared to other recycling processes, promoting the molecular shearing of PP, reaching ideal lengths of shorter chains to be used as a carrier for additives for adhesives and plastics, and/or to be used as a flow modifier for injecting parts. Ionizing radiation above 100 kGy initiated the formation of cross-links, cross-linking the PP that could be used as fillers for asphalt, construction, and other applications, or as a fuel energy source, contributing to the ecosystem, without changes in the curly lettuce after ecotoxicity tests. The use of ionizing radiation in polymer processing has a great advantage when compared to other plastic recycling systems.

Resumo em Inglês:

In this study, polyamide 6 (PA 6), polyamide 6.6 (PA 6.6), and polypropylene (PP) polymers were irradiated with an e-beam (EB) (100 and 200 kGy doses, 100 kGy.s-1 dose rate, at room temperature) to evaluate the effects on radiochemical crosslinking. Mechanical analyses (tensile, flexural, and tribological tests), thermal characterizations (TGA, DSC, and glow wire test), and FTIR spectroscopy were performed. Results demonstrated that PA 6.6 irradiated at 200 kGy exhibited a 6.8% increase in tensile strength at break, being the only material showing improvement in yield point. All samples displayed reduced elongation after irradiation. In flexural resistance tests, both irradiated PA 6 and PA 6.6 showed enhanced properties, while in tribological evaluations, only PA 6.6 (100 kGy) presented a reduced friction coefficient. Thermal analyses revealed that irradiated PA 6.6 showed increased onset degradation temperature, while all polymers exhibited decreased melting temperature. The crystallinity percentage increased in both irradiated PA 6.6 and PP, and only PA 6.6 (200 kGy) resisted all temperature levels in the glow wire test. It was concluded that PA 6.6 demonstrated superior post-irradiation performance, showing more enhanced properties compared to PA 6 and PP.

Resumo em Inglês:

Due to the growing demand for water resources and their well-documented scarcity, low-cost and easy-to-implement alternatives for water treatment are essential to meet human needs. In this context, the present study aims to present the results of a cost analysis regarding the use of low-cost thermally absorbent materials in solar desalination systems, with the goal of achieving greater water productivity in an efficient and economically viable manner. Three desalinators were designed to operate simultaneously for comparative analysis. The first still (D1) was operated without any photothermal material, serving as a control; the second (D2) was filled with gravel, and the third (D3) with glass beads. The results showed that the use of these materials increased the productivity of distilled water by 38.32% in D2 and 16.63% in D3. The thermal efficiency observed was 42.46% in D2 and 35.33% in D3. Additionally, the cost per liter of water produced decreased by 25% and 8.33% for the systems using gravel and glass beads, respectively. The application of these materials in solar distillation systems demonstrated an excellent cost-benefit ratio.

Resumo em Inglês:

This study proposes a sustainable approach to repurposing plastic waste, focusing on nonwoven fabric (NWF) from disposable caps used in historic mine tours. These caps are essential for maintaining hygiene when sharing helmets but generate significant waste. Blends of virgin polypropylene (PP) and recycled NWF (rNWF) were developed with 25%, 50%, and 75%wt using thermokinetic homogenization, extrusion, and hot compression. The blends and control samples’ mechanical, physical, structural, and thermal properties were evaluated. Tests revealed that stiffness increases with rNWF addition, while tensile strength decreases. The 50rNWF blend (50% NWF) stood out with a higher modulus of elasticity than virgin PP in both tensile (1.42 GPa vs. 1.22 GPa) and flexural (1.51 GPa vs. 1.28 GPa) tests. These results highlight 50rNWF as a promising substitute for PP, reducing environmental impacts and promoting the circular economy.

Resumo em Inglês:

This article analyzes a failure of a disc brake used in the Stock Car Pro Series. It focuses on a phase transformation in the pearlitic gray cast iron, commonly occurring during heat treatment. Telemetry data from the racing team, along with samples of brake discs, were utilized for this study. The aim was to explore the potential causes leading to catastrophic wear and failure of the component under real racing conditions. The analyzed brake disc exhibited catastrophic wear due to abrasion, adherence, and material transfer between the disc and brake pads. Through metallographic investigation using optical and scanning electron microscopy, a phase transformation was identified in the outer layer of the brake disc, which may have contributed to its reduced lifespan. Surface hardness was evaluated using a Vickers microhardness tester, revealing that rapid temperature increases induced tensile and compressive stresses, resulting in austenitization and eutectoid transformation in the cooling process.

Resumo em Inglês:

The construction of cisterns — reservoirs specifically designed for the collection, storage, and conservation of water — has emerged as a significant strategy for mitigating water scarcity in arid regions. A widely adopted form of cistern construction involves the use of cementitious composite panels. This study investigates the mechanical properties of cementitious composites incorporating rubber waste, expanded vermiculite, and sisal fibres. Three distinct mortar formulations were developed and evaluated in terms of water absorption, voids index, specific mass, compressive strength, flexural tensile strength, dynamic modulus of elasticity, and damping factor. Relative to the reference mixture, the incorporation of sisal fibres (SF) in conjunction with rubber and vermiculite resulted in a 12–16% reduction in density, a 29.5–30.4% decrease in the dynamic modulus of elasticity, and a 2.5–9.0% increase in the damping factor. Despite an observed reduction of approximately 40% in compressive strength, the values remained within the acceptable range for structural applications. These findings substantiate the technical viability and environmental benefits of the proposed mortars for the sustainable construction of cisterns.

Resumo em Inglês:

The utilization of niobium oxide and its compounds has seen significant growth in recent years, with applications in ion exchangers, adsorbents, catalysts, supports, photocatalysts, and components of lithium and sodium batteries and capacitors. Brazil, having the world's largest niobium reserves, aims to lead in related technologies. This study synthesized mesoporous Nb2O5 microspheres via emulsification/internal gelation from reactive NbCl5, developing a method to stabilize niobium pentachloride in aqueous solution. The microspheres were characterized for morphology, structural integrity (SEM), crystalline structure (XRD), and specific surface area and porosity (gas adsorption, N2). Additionally, TiO2 microspheres (from TiCl4) and their mixtures with Nb2O5 in mol ratios 81/19 and 93/7 were obtained and characterized. The stabilization of NbCl5 in aqueous solution was efficient, enabling the synthesis of Nb2O5 microspheres and their TiO2 mixtures.

Resumo em Inglês:

The valorization of mineral sector tailings can reduce environmental impacts and create economic opportunities, aligning with the concept of responsible mining. This study proposes using spodumene concentration tailings combined with white clay for ceramic production. The clay sample was chemically characterized (XRF), while the tailings sample was characterized chemically (ICP-OES and XRF), mineralogically (XRD), and physically. Test specimens with varying tailings percentages (0–30%) were pressed at 28 MPa, dried at 110°C, and sintered at 1100°C. The clay primarily consists of Si and Al, while the tailings feature particles with an average diameter of 81.2 µm, a surface area of 2.25 m2/g, and a mineralogical composition of silicates and aluminosilicates, with 1.44% thermogravimetric decomposition up to 1000°C. Incorporating tailings showed an inverse relationship with water absorption and a direct relationship with apparent density and mechanical strength, likely due to feldspars acting as fluxing agents during sintering. Mineralogical analysis of ceramic bricks revealed that tailings incorporation promoted phase transformations, reducing quartz content while increasing mullite and cristobalite due to fluxing agents (e.g., albite, spodumene) and partial feldspar decomposition at sintering temperatures. These findings support the feasibility of using these tailings to produce high-quality ceramics.

Resumo em Inglês:

Previous results on the use of recycled polyethylene terephthalate (rPET) in the formation of corrosion-resistant films showed the possibility of providing a low-cost solution to some corrosion problems in the industry. However, to the best of our knowledge, no work has yet studied the thermomechanical incorporation of plasticizers on PET films for anticorrosion applications. Thus, in this work, a thermomechanical route was tested, for the first time, aiming at the production of anticorrosive PET-based adhesive films. A series of characterization methods were used to investigate the influence of the plasticizer addition to the thermal, mechanical, electrochemical and anticorrosive properties of the PET-based films produced. It was found that the 100% PET sample showed better mechanical and corrosion resistance performance compared to the plasticized ones, being comparable to or even better than benchmark tapes commercialized by 3M, maintaining impedance values consistently above 10 GΩ.cm2 for frequencies below 1 Hz and phase angle near 90º over a broad range of frequencies in the EIS tests.

Resumo em Inglês:

The development of sustainable materials, such as high-performance biopolymers, faces the challenge of high quality control costs, given that their mechanical properties depend on the fiber arrangement within the matrix. To overcome this barrier, this work proposes the use of Artificial Intelligence, specifically Computer Vision, to create a virtualization of the material's microstructure from simple images. This virtual representation serves as a basis for the efficient generation of numerical models using the Finite Element Method (FEM) and the Extended Finite Element Method (XFEM). In this context, the paper introduces the aiMat framework, which integrates Computer Vision and FEM/XFEM modules to optimize the process. The main contribution of this work, therefore, derives from the harmonious integration of these techniques, establishing a more efficient and accessible workflow for modeling composite materials.

Resumo em Inglês:

First-principles calculations based on the density functional theory (DFT) represent a sophisticated technique to investigate the mechanical strength of materials in general, although underexplored in polymeric structures such as high-performance thermoplastic polymers. In this study, DFT calculations were systematically conducted to evaluate the effects of strain on the structure of polyether ether ketone, determining the maximum elasticity modulus in a perfect alignment condition of the polymer chain. The atom positions and arrangement of the polymer chains were set based on total energy and force minimizations. The four lowest energy structures were stretched up to 10 Å per monomer, and the results have shown a mean elasticity modulus of 5.93±0.74 GPa, which we attribute to the upper limit for aligned and stretched polymeric chains.

Resumo em Inglês:

The increasing demand for sustainable materials has highlighted the importance of biocomposites; however, their computational analysis is challenging due to the high cost associated with traditional methods such as the Finite Element Method (FEM). This study introduces a computationally efficient approach for analyzing the mechanical behavior of chitosan/nanocellulose biocomposites using Physics-Informed Neural Networks (PINNs). By embedding the governing equations of 2D linear elasticity directly into the network's loss function alongside reference data from FEM simulations, the PINN is trained to predict displacement fields. The methodology involves training the network on data from one microstructure and validating it on five distinct, unseen microstructures. Results demonstrate high predictive accuracy, with an average R² value exceeding 0.92 across validation sets, and a significant post-training reduction in analysis time, achieving an inference speed-up approximately 5.4 times that of the FEM solver. This work establishes PINNs as a promising tool for accelerating the analysis and development cycle of sustainable biocomposite materials.

Resumo em Inglês:

This work used ammonium heptamolybdate as a precursor to obtain molybdenum carbide (Mo2C) at temperatures of 600°C, 650°C and 700°C, using isotherms of 60 min, 90 min and 120 min. The samples were characterized by thermogravimetric (TG), X-ray diffraction (XRD), Rietveld refinement and scanning electron microscopy (SEM). The results revealed that Mo2C formation was strongly dependent on the source temperature and isotherm duration. Characteristic diffraction peaks of molybdenum carbide were identified in samples synthesized at 700 °C for 60 minutes and 120 minutes, indicating that this temperature was crucial for demonstrating complete carburization under the tested conditions. Conversely, samples processed at lower temperatures showed incomplete reactions, with precursor phases and residual byproducts, indicating the need for greater energy transport and reaction time to promote complete transformation into pure Mo2C. These results reinforce the importance of simultaneously optimizing temperature and isotherm parameters to tailor the phase purity and microstructural properties of molybdenum carbide for advanced applications.

Resumo em Inglês:

The improper disposal of gypsum waste impacts the environment, causing pollution of the soil, groundwater and atmospheric air, requiring sustainable solutions for its management. This study proposed the reuse of this waste from the plaster industry in the process of calcining the gypsum mineral. 0, 30 and 50% by mass of the waste was incorporated into the ore calcination process, varying the temperature by 160 and 180 ºC. The gypsum obtained was characterized according to NBR 13207 (ABNT, 2017). The results showed that the recycled gypsum complies with the standards, with workability between 10 and 20 min, surface hardness above 20 N/mm2 and compressive strength up to 16.65% higher than commercial gypsum. It can be concluded that the method used to reuse gypsum waste is viable and can help reduce social and environmental impacts, as it adds value to the recycled material.

Resumo em Inglês:

The aim of this work was to obtain the W-20wt%Cu composite from the precursors powders APT and NCu. The APT-8.54wt%NCu composition was milled for 20 hours and reduced at 700 °C, 750 °C, 800 °C, 850 °C for 30 minutes, and at 800 °C for 60 minutes, all under a hydrogen flow of 300 ml/min. The samples were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and Energy Dispersive Spectroscopy (EDS). The results indicated a decrease in oxide phases as the temperature increased. The Complete elimination of oxides was observed at 800 °C after 60 minutes of isothermal dwell.

Resumo em Inglês:

Cationic hemicelluloses (CH), derived from corn husks, represents a renewable organic resource and the utilization of lignocellulosic residues is crucial for environmental sustainability. In the present research, hemicelluloses were extracted from corn husks using the delignification by OxiOrganosolv method. ETA was used as the cationizing agent in the cationization process. Delignified corn husks exhibited low lignin content (3.90%), higher cellulose (48.89%) and hemicellulose (34.97%) contents, achieving an hemicellulose recovery rate of 86%. FTIR of CH showed an increased intensity in the methyl group band at 1476 cm−1, with degree of substitution of 0.413, indicating cationization. CH was applied as flocculant in dosages ranging from 0.5-4.0 ppm, pH levels from 5-11. The optimal condition were achieved in 3.0 ppm CH and coagulation pH 9.16, achieving 66.3% and 89.2% removal of apparent color and turbidity, respectively. CH extracted and synthesized from the agro-industrial residue is alternative coagulant for raw water treatment.

Resumo em Inglês:

This study evaluated the impact of silanized cobalt ferrite (CoFe2O4@SiO2) concentration (5% vs. 10%) and genipin crosslinking on chitosan microcapsules loaded with deslorelin acetate. The genipin-crosslinked, 5% ferrite formulation (MQGγF5) showed higher swelling (~450%) and porosity (70%) despite lyophilization-induced collapse, linked to interstitial free volume from crosslinking. It also exhibited a magnetic response of 13.37 emu.g−1, confirming functionality. The 10% ferrite counterpart (MQGγF10) displayed compact morphology and reduced porosity (~50%) and swelling (~193%), reflecting robust nanoparticle-polymer interactions. Non-crosslinked microcapsules exhibited intermediate behaviors. These results highlight the tunability of microcapsule properties through ferrite loading and crosslinking, providing a foundation for designing microcapsules for controlled drug delivery in veterinary applications.

Resumo em Inglês:

This study characterized emerald mining tailings from the city of Nova Era, Minas Gerais, Brazil. Analyses included granulometry, density, and moisture content, along with leaching tests, XRF analysis, and chemical composition assessment using an EDS detector coupled with SEM. Additionally, stereomicroscope and SEM imaging were performed, as well as XRD analyses. The granulometric analysis revealed that 46.49% of the particles were smaller than 0.85 mm. XRF analysis identified Mg, K, and Ca in the sample. Leaching tests indicated levels below 1 ppm for potentially toxic metals As, Cd, and Pb. XRD analyses identified the following mineral phases: phlogopite, quartz, actinolite, kaolinite, and vermiculite. These findings indicate that the tailings could serve as a potential soil remineralizer; however, further agronomic testing is required to confirm their suitability for agricultural use.