In the manufacture of graphene-reinforced aluminum composites, powder metallurgy has been the primary production method, proving to be highly effective. The present work addresses the production and characterization of aluminum matrix composites reinforced with graphene-based nanomaterials. The production route employed the powder metallurgy technique and was processed in two stages: first by mixing in different liquid media, and second by using distinct mixing methods. The sintered samples from the first stage were evaluated for their density, and the sintered samples from the second stage were subjected to mechanical microhardness tests. The results of the first stage indicated that among the solvents used for mixing, acetone and ethanol stood out, providing compacts with densification above 92%. In the second stage, Al/rGr composite samples produced by the mechanical mixing method using a helical impeller showed the greatest increase in hardness, achieving a 60.5% increase compared to pure aluminum.
In this experimental study, we present and discuss the effects of 3, 5, and 7 wt.% Si additions on the thermal parameters, phase transformations, microstructural patterns, microhardness, and 3D porous formation in binary Al - 2 wt.% Cu alloy. Through the phase diagram and Thermo-Calc Scheil simulation, one can determine the growth sequence of the phases during the cooling process. With slow cooling curves and its second derivatives, liquidus temperatures can be found. An approach based on the second derivative curve was adopted to determine the onset of solidification and subsequent phase transformations. The experimental results determined with the slow cooling curves are corroborated by those calculated by Thermo-Calc software. A data acquisition system was used to record the experimental slow cooling curves for subsequent thermal analysis. Higher silicon concentrations, shorter solidification range and refined microstructures were key factors acting during solidification, which served to conditions changes in the microhardness and 3D porous formation. The relationships between porosity content with silicon concentration (PC = 1.46%Si0.7813 with R2 = 0.97) and secondary dendritic arm spacing (PC = 1692.7λ2-1.44 with R2 = 0.99) are presented and discussed from experimental equations. This result indicates that porous formation during solidification process is closely connected to the silicon concentrations and dendrite arm spacings.
In this study nylon 66 (N66), glass fiber–reinforced nylon 66 (GFN66), and talc particulate–filled glass fiber–reinforced nylon 66 (T-GFN66) hybrid composites were fabricated using compounding process and injection moulding technique. Test was performed by varying the input factors (impact velocity, impingement angle, and constitute of composite). Study intended to explore the combined effect of input factors on erosion wear rate (EWR) of the composites. Data-driven machine learning (ML) approach was applied to analyse and predict the EWR of the N66 and its hybrid composites. Experimental results showed that EWR increased with increase in impact velocity and decreased with an addition of glass fiber and talc filler contents. T-GFN66 composite exhibited superior erosion wear resistance than N66 and GFN66. Furthermore, experimental data were fed into the four ML models and compared using their performance metrics. It was observed that among all the developed ML models, gradient boosting machine (GBM) model found to be superior in predicting the erosion wear performance of N66 composite with R2 value of 0.9666. Eroded surface topography was analysed using 3D optical profilometer to establish the relationship between surface parameters and EWR. Worn morphology was conducted using field emission scanning electron microscopy (FESEM) to observe wear mechanisms endured by the N66 composites.
Bismuth has become one of the most promising anodes for lithium-ion batteries (LIBs) due to its suitable operating voltage and high volumetric capacity. However, the inevitable volume expansion of bismuth during the charge/discharge cycling process of lithium-ion batteries can lead to severe capacity fading and eventual battery failure. Herein, Bi-Bi2O3/C composite materials were prepared using a combination of solvothermal and calcination methods, and a series of characterization tests were conducted to investigate the effects of different secondary calcination times on the microstructure, composition, electrochemical properties, and the internal structural evolution during the initial charge/discharge cycle of the composite materials. In situ synchrotron radiation small angle X-ray scattering (SAXS) was employed to reveal the multi-level nanostructure evolution of Bi-Bi2O3/C electrode materials during charge/discharge processes. The present work reveals that these SAXS findings provide some new insights into the theoretical mechanism for the development of LIBs.
Accurate fatigue-life prediction under variable-amplitude loading (VAL) is critical for damage-tolerance assessment. This study presents a systematic comparative analysis of experimental data and numerical predictions of crack propagation in SAE-AMS 7475-T7351 alloy. NASGRO, AFGROW, and CRACK 2000 were employed to simulate standardized spectra (TWIST, FALSTAFF) and an actual commercial aeronautical load history, focusing on the calibration of Wheeler, GW, and MGW retardation models. The results demonstrate that calibration parameters (e.g., Rso) are highly spectrum-dependent. Physical analysis revealed that underloads attenuate retardation in the TWIST spectrum but are ineffective in the FALSTAFF spectrum. Discrepancies between the software packages, even with identical parameters, were attributed to varying ΔKth implementations.
Equiaxed and rounded pore cellular metals with five different size ranges based on an aluminium-silicon alloy were fabricated by a soluble particle infiltration technique, in order to evaluate and compare their energy absorption capacity under impact and quasi-static compression. Under compression, the equiaxed cellular metal with the smallest pore size (4-4.75 mm) recorded the highest energy absorption (4.9 MJ/m3). In addition, the equiaxed pore cellular metals exhibited an energy absorption capacity 68.2% higher than that of the rounded pore ones. Under impact, for a standard strain of 9.8%, the highest energy absorption capacity was presented in the equiaxed cellular metal with the largest pore size (9.5-11.2 mm). In turn, the energy absorption in equiaxed pore cellular metals was 53.1% higher than that of the rounded pore ones. Cellular metals of both pore shapes showed a higher energy absorption capacity under impact. Therefore, it is concluded that this property varies depending on the shape and size of the pore, but also with the deformation rate.
There is potential to improve corrosion resistance of AA7085 aluminium alloy by adding ultra-high temperature ceramic particles such as TiB2 and by using better T6 ageing conditions. AA7085 composites with 3–9 wt.% TiB2 particles were fabricated by the stir-casting method. T6 heat treatment of 525 °C solutionising, then artificial ageing at 230 °C for 10 hours was performed. Hardness assessment, 3.5 wt.% NaCl immersion corrosion for 24 hours, 48 hours and 72 hours, and Optical microscopy and SEM analysis studies as indicates the fine distribution of TiB2 particles. The AT9 sample achieved a maximum hardness of 122 HV, about 35% higher than the base AA7085. The lowest corrosion rate was observed for the AT9 composite at 230 °C ageing rate of 0.12 mm yr-1 at 72 hours. TiB2 particles inhibited pit initiation and promoted the formation of an Al-rich passivation layer. At higher ageing, pitting was observed to increase due to the reduction of over-ageing precipitates. The AA7085 composite reinforced with 9 wt.% TiB2 and artificially aged at 230 °C improved the corrosion resisting behaviour. The TiB2-Al matrix interface and the formation of a dense passivation layer are the key mechanisms for the enhanced corrosion resistance process.
The formation of scale deposits in pipelines within the oil and gas sector is a recurring challenge that impacts operational efficiency and incurs various associated costs. Understanding the processes of mineral formation and dissolution that contribute to these deposits is essential for the implementation of effective control and mitigation strategies. This study used thermodynamic simulations to predict mineral species present in inorganic scale deposits in saline water systems within the oil and gas industry in order to provide background knowledge for future scale inhibition studies. To this end, the software The Geochemist’s Workbench was employed to construct stability diagrams, taking into account thermodynamic parameters such as pH, temperature, and pressure, through focusing on a high-bicarbonate, low-sulfate formation water, a common but challenging scenario where carbonate scaling dominates. Through the thermodynamic simulations, the software suggested the precipitation of Witherite (BaCO3), Strontianite (SrCO3), and Dolomite (CaMg(CO3)2), which were not expected for the present scenario, due to the low concentrations of Ba, Mg and Sr. Thus it was suggested that such results did not take into consideration the precipitation kinetics and the amount of crystalized material. In addition to the simulations, the systems were analyzed through static tests, and the resulting precipitates were characterized using optical microscopy, X-ray diffraction, and thermal analysis. The thermodynamic simulation results were compared with the experimental data, enabling an assessment of the consistency between the theoretical models and the observed results.
Three different regions in the heat-affected zone are formed when the shielding gas mixture during the GMAW procedure is argon-rich. The microstructural characterization and corrosion susceptibility of different heat-affected zone (HAZ) regions in welds of UNS S31803(2205) duplex stainless steel (DSS), were evaluated by optical images, scanning electron microscopy and transmission electron microscopy. The pitting susceptibility of the different regions in the HAZ was evaluated by pitting corrosion tests in an acidified ferric chloride solution. The analyzed HAZ regions showed different HAZ dimensions and microstructural aspects as grain size, phase fractions, morphologies and compositions that influenced the pitting resistance. The HAZ region induced by the lower cooling rate showed larger ferrite grain size. In this region, the Widmanstätten and intragranular austenite fractions were higher, indicating greater susceptibility to pitting corrosion. The weld with the highest heat input showed the lowest resistance to pitting corrosion.
Super duplex stainless steels (SDSS) have a microstructure composed of approximately equal fractions of ferrite and austenite. However, depending on the chemical composition and thermomechanical conditions, precipitation of deleterious intermetallic phases may occur, compromising their properties. This work investigated the influence of isothermal aging time and temperature on the phase transformation of a super duplex steel subjected to heat treatments at 700°C, 800°C and 900°C, for 1 and 2 hours, with water cooling. Initially, all samples were solubilized at 1100°C for 30 minutes for microstructural homogenization. The innovative scanning magnetic microscopy (SMM) technique was used to access variations in remaining magnetization, whose application in steel phase detection has received relatively limited attention in the literature. However, the image processing in SDSS proposed in this work had not yet been reported in the literature, giving the study a pioneering character. Since variations in magnetic properties can result from microstructural changes, this technique, although still requiring further experimentation, presents interesting results. For validation, the results were compared with established methods, such as ferritoscope, vibrating sample magnetometry (VSM), X-ray Diffraction (XRD) and optical microscopy (OM). The results demonstrate that increasing the aging time and temperature promotes a significant reduction in the ferrite fraction (ferromagnetic), accompanied by the dispersed formation of the σ phase and partial transformation into austenite (paramagnetic). Differences between the characterization methods, especially at advanced stages of aging, suggest the possible presence of intermetallic deleterious phases or finely dispersed carbides. As a main result, magnetic techniques are promising for the thorough processing of SDSS.
This study compiles experimental knowledge on the surface preparation and painting of SAE 4150 steel parts using a waterborne coating based on a thermosetting polyester–amino resin as a replacement for a conventional solvent-based coating system. Tests, analyses, and process adjustments were conducted in a production environment, aiming to optimize adhesion and coating resistance. The variables evaluated included the type of mechanical cleaning process (grinding or brushing), the type and concentration of chemical cleaning agents (degreasers), the application of a zirconium-based nanoconversion coating, the dry film thickness of the coating, and the paint curing temperature. This study elucidates the combined effects of surface roughness, film thickness, curing conditions, and alkaline exposure on the chemical degradation mechanisms of polyester–amino waterborne coatings applied to steel substrates. Optimal process parameters were achieved using a brushing process with a medium brush grit size of 100, chemical cleaning with an alkaline degreaser at a 1% concentration, and painting with a dry film thickness of 30 µm followed by curing at 175ºC. The use of a nanoconversion coating was not justified, since the substrate roughness obtained after brushing was sufficient to ensure adequate paint adhesion. The results demonstrated that the waterborne paint outperformed the solvent-based paint originally used in the production line, while also providing a more sustainable solution in terms of environmental impact and occupational safety.
This study investigates the complementary modulation of chitosan/keratin hydrogels through the combined use of hexamethylene diisocyanate (HDI) and Pluronic F-68, aiming to tailor mechanical stability, porosity, and biological performance for wound healing applications. Covalent crosslinking by HDI enhanced network integrity and mechanical resistance, while Pluronic F-68 promoted micelle-templated porosity, increased hydration, and improved permeability. The hydrogels exhibited compressive strength values ranging from 33.5 to 65.9 MPa, swelling capacities of up to approximately 160%, and porosity values approaching 60%, depending on composition. Increasing HDI content reduced solubility to approximately 15%, indicating improved structural stability. All formulations were cytocompatible, maintaining cell viability above 70%, with Pluronic-containing systems reaching values close to 100%. These results demonstrate that the independent control of crosslinking density and porosity enables the identification of compositional balance zones that reconcile mechanical integrity and biological response, supporting the rational design of adaptable hydrogel platforms for wound healing.
Optimizing laser welding of dissimilar materials is critical for aerospace applications, where high-performance joints are required under stringent weight and reliability constraints. This study presents a multiphysics modeling framework for predicting heat flux and residual stress development in laser-welded AA6013/Ti-6Al-4V dissimilar joints. A finite element model was implemented in COMSOL Multiphysics to simulate transient heat transfer, thermal gradients, and thermo-mechanical stress evolution, and was validated against experimentally measured thermal cycles, yielding deviations of 2.5–6%. The results demonstrate that heat input (HI) and beam offset strongly govern the temperature field, residual-stress distribution, and intermetallic-compound (IMC) formation at the Al/Ti interface. For condition T7 (HI = 9.6 J/mm; offset = 0.3 mm), the model predicted a peak temperature of 5950 K in the high-energy interaction region. A comparison between conditions T6 and T9 showed that, under identical beam intensity, reducing the welding speed increased the energy absorbed by the titanium side, with a 22% reduction in heat dissipated by conduction relative to T6. Residual stresses decreased with distance from the laser path; for a fixed offset, increasing HI increased compressive residual stress, reaching a maximum of 26 MPa (≈10% of the AA6013 yield strength) at HI = 24 J/mm and remaining nearly constant thereafter. In addition, higher cooling rates reduced IMC thickness from approximately 7 µm to 3 µm, indicating improved metallurgical conditions. Overall, the validated model provides a predictive tool for selecting process parameters to minimize residual stresses and control IMC growth, supporting the development of aerospace-grade AA6013/Ti-6Al-4V dissimilar laser welds.
Copper with higher electrical conductivity, reinforced with high-performance ceramic particulates, is suitable for use in industrial electrical contacts, connectors, and thermal management systems due to its tailorable mechanical properties, which improve its wear resistance accordingly. The stronger effect of particle mixing and sintering temperature variation is tailoring the mechanical properties, allowing the copper matrix to be met for the desired applications. The influence of sintering temperature and alumina particulate ratio on the microstructure, compressive strength, ultimate tensile strength, flexural strength, and micro hardness of copper–alumina composites were systematically studied. Copper matrices were reinforced with 5, 10, 15, and 20 vol.% alumina powder and sintered at three different temperatures: 750 °C, 800 °C, and 850 °C. The composite containing 15 vol.% alumina sintered at 750 °C exhibited the highest compressive strength. The maximum ultimate tensile strength was observed in the composite with 20 vol. % alumina sintered at 850 °C. The greatest flexural strength was achieved with 5 vol.% alumina at 850 °C, while the highest micro hardness was recorded in the composite containing 15 vol.% alumina sintered at 800 °C.
In the present investigation, aluminium Metal Matrix Composites (MMCs) were synthesized by reinforcing nano TiO2 particles at varying weight percentages (0.5 ,1.5,2.5 and 3.5 wt%) into an AA6061 molten aluminium matrix using the stir casting method. The synthesized composites were characterized using optical microscopic analysis, Scanning Electron Microscopy (SEM) and X- ray diffraction (XRD). The hardness and tensile properties of the composites were evaluated. The analysis of mechanical properties revealed that the T6 composite containing 0.5 wt% nano TiO2 particles had a maximum hardness of 79.6 BHN compared to other T6 samples and as well as ac-cast samples. Ultimate tensile strength and yield strength of T6 composite containing 0.5 wt% TiO2 was found to be (180 MPa and 135 MPa) higher than other T6 composites and as cast samples. Fractography of Al MMC containing 0.5 wt% nano TiO2 particles revealed ductile -brittle fracture mode in the T6 condition.
Selecting materials for metallic structures such as transmission towers requires careful consideration of environmental dynamics, climate change, atmospheric variations, and human activity, all of which directly affect corrosion behavior. Relying on generic or incomplete data can lead to premature material degradation and increased maintenance costs. This study focuses on a 1,150 km transmission line spanning the Brazilian states of Ceará, Piauí, and Maranhão, where material selection was initially based on theoretical estimates of atmospheric aggressiveness (C3 category). However, frequent maintenance and component replacements indicated underestimated corrosivity. To improve understanding, environmental parameters (humidity, salinity, precipitation, and wind) were monitored, and field corrosion rates were determined using AISI 1020 and galvanized steel samples. Complementary analyses included electrochemical testing, microstructural evaluation, and accelerated aging under industrial and saline conditions. Additionally, an artificial intelligence tool based on feedforward neural networks was developed to enable rapid corrosivity classification through RGB/HSV image analysis, without requiring long-term field exposure or specialized equipment. After one year, the environment was reclassified as C5–Cx (extreme aggressiveness). These results highlight the importance of location-specific assessments over general assumptions and demonstrate how AI-based tools can enhance decision-making and maintenance strategies for more resilient power transmission infrastructure in a changing climate.
Aqueous dispersions of colloidal silica (CS) are commonly employed in high-alumina refractory castables to prepare in situ mullite, behaving simultaneously as a liquid medium, binder, and SiO2-source. Despite such technological interest, CS was not explored as a uniaxial pressing additive to replace organic binders and promote earlier strengthening during sintering. This study mixed alumina particles with varying amounts of CS to compare structures composed of the same raw materials, shaped by different processing techniques. Such compositions were pressed as bars or cast into cylinders, and their microstructure and physical properties evolution were assessed during sintering (700-1500ºC). Cast samples developed a homogeneous microstructure comprised of alumina particles surrounded by a gelled CS phase; in contrast, the pressed samples generated SiO2-rich spherical clusters, originating from the original CS droplets, surrounded by alumina. Such a heterogeneous microstructure persisted during sintering, when the silica nanoparticles crystallized before forming mullite. Directly cast samples developed a granular microstructure of alumina-mullite, with traces of cristobalite. In pressed samples, regions with higher SiO2 concentration developed acicular mullite crystals, imbibed in a matrix of alumina and cristobalite. Increasing the CS content in both cases enhanced porosity and decreased strength after sintering at temperatures above 1100 °C.
Poly(lactic acid) (PLA)-based films containing 0.5 and 1.5 wt% of TiO2 or ZnO nanoparticles were prepared by solvent casting and evaluated in terms of thermal, mechanical, optical, structural, and ecotoxicological performance, targeting food packaging applications. X-ray diffraction and scanning electron microscopy revealed that low nanoparticle contents promoted partial crystalline ordering and relatively homogeneous dispersion, whereas higher loadings led to agglomeration and reduced crystallinity. Thermogravimetric analysis showed that the incorporation of 0.5 wt% TiO2 increased the onset decomposition temperature of PLA from 303.3 to 322.8 °C. In contrast, higher nanoparticle contents and all ZnO-containing films exhibited reduced thermal stability and lower glass transition temperatures, with Tg decreasing from 51.3 °C (PLA) to 44.0 °C for PLA15ZnO. Nanoindentation demonstrated a significant increase in nanohardness for all nanocomposites, reaching improvements of up to ~27% compared to neat PLA. Optical analysis showed effective UV-shielding below 400 nm and preservation of visible-light transmittance above ~85% for films containing 0.5 wt% ZnO, whereas higher TiO2 contents induced pronounced opacity and color changes. Germination assays using lettuce and cucumber indicated concentration-dependent phytotoxic effects for TiO2, while ZnO showed neutral or slightly positive effects at low concentrations.
Transparent conductive oxide (TCO) thin films are crucial for modern electronic devices. Among them, amorphous indium-zinc-tin oxide (IZTO) films have attracted considerable interest due to their potential for flexible applications. This work systematically investigates the influence of oxygen partial pressure and oxidative annealing on the properties of IZTO films. IZTO films deposited at 3% oxygen partial pressure exhibited a low sheet resistance of 19.5 Ω/□, high visible (TVIS = 83.6%) and near-infrared (TNIR = 90.0%) transmittance. After oxidative annealing, IZTO films showed an increased sheet resistance of 29.2 Ω/□, and a high Hall mobility of 51.4 cm2·V−1·s−1, while retaining excellent optical transparency. All the films showed amorphous phase and smooth surface structure. These results are valuable for developing high-performance, transparent amorphous electrodes in flexible optoelectronic applications.
Durability and corrosion resistance are essential requirements in the development of aerospace components, and the optimization of anodizing processes stands out as an effective strategy to enhance the corrosion performance of aluminum alloys used in this sector. In this context, the present study provides new insights into the effect of the presence of different carboxylic acids (oxalic, citric, and succinic) in a sulfuric acid-based anodizing electrolyte on the corrosion resistance of the AA2024-T3 aluminum alloy. The anodic oxide films were characterized using microscopy and electrochemical analyses to assess their morphological and corrosion-resistant behavior. The results indicated the formation of oxide films with different surface morphologies, uniform thickness ranging from 16.7 to 23.8 & micro;m, and satisfactory protection against corrosion in NaCl media (0.1 mol.L-1), especially with regard to treatment with oxalic acid (OSA), which, compared to other treatments with carboxylic acids (citric - CSA, and succinic - SSA) and the standard treatment (sulfuric acid - SA), maintained the highest protective performance of the coating over 21 days of immersion.
