Search Results (1,458)

Accurate prediction of surface roughness and cutting forces in milling aluminum alloys remains challenging under data-scarce conditions, where limited experimental data restricts the application of conventional machine learning models. This study addresses this gap by developing a systematic machine learning framework using 108 milling experiments (repeated to 216 tests) on aluminum alloys AA2024-T351 and AA6061-T6. Five primary machining inputs—material type, spindle speed, feed rate, depth of cut, and tool coating—were used. Through feature engineering, 35 interaction features were generated to capture non-linear relationships. A two-step preprocessing strategy was applied: Winsorization at the 5th and 95th percentiles to handle outliers, followed by hybrid scaling combining RobustScaler and MinMaxScaler. Eight machine learning algorithms, including XGBoost, NGBoost, LightGBM, CatBoost, Random Forest, MLP, SVR, and Least Squares Boosting, were developed and hyperparameter-optimized using the Optuna framework with Tree-structured Parzen Estimator. Models were evaluated using R², MAE, and RMSE on a 70/15/15 train–validation–test split. Results demonstrate that XGBoost achieved the highest predictive accuracy for surface roughness (Ra) (R² = 0.99829) and for resultant cutting force (FN) (R² = 0.997). Feed rate was identified as the dominant machining parameter, accounting for 87.7% of the total importance in predicting surface roughness. SHAP analysis confirmed that engineered interaction features—particularly Feed_Coating and Material_Feed—carry strong physical relevance. Additionally, NGBoost enabled probabilistic regression, providing uncertainty estimates. The proposed framework proves highly effective for multi-output prediction in machining under limited data, offering a robust, interpretable, and industry-ready solution for quality control in aluminum alloy milling operations. Full article

The increasing demand for materials with enhanced properties and high-performance devices has driven substantial research into nanomanufacturing, particularly using carbon nanotubes (CNTs), because of their exceptional properties and high sensitivity to chemical doping. In this way, this work summarizes nanomanufacturing methods for CNT-based devices developed in Brazil, covering the complete cycle from nanocomposite production to functional device assembly across cellulosic, polymeric, and metallic matrix systems. For cellulosic matrices, vacuum filtration enables the production of buckypaper, which is subsequently assembled into chemiresistive, thermoresistive, and thermoelectric devices. For polymeric matrices, 3D printing combined with surface functionalization techniques (spray coating, inverted immersion, and direct immersion) produces piezoresistive robotic sensors, metal-free thermal sensors, and biomedical scaffolds for tissue engineering. For metallic matrices, electrodeposition can produce Cu-CNT-coated aluminum comparable to traditional copper power transmission cables, while arc welding produces stainless steel composites with properties comparable to commercial high-grade steels. These devices have commercial and industrial applications, with low-cost and scalable production methods in comparison with conventional materials. Characterization results demonstrate that CNT integration into diverse matrices successfully bridges nanoscale properties to macroscopic functional devices. Current challenges include uniform CNT dispersion and structural defect control, laboratory to industry scale transition, and long-term device stability under environmental conditions. Future perspectives encompass lab-on-chip systems, wearable devices, 3D-printed smart structures, Internet of Things integration, and machine learning-enhanced analytics. Full article

Chromate-free conversion coatings are increasingly investigated as environmentally acceptable alternatives to conventional chromate conversion coatings for corrosion protection of aluminum alloys. In the present study, the electrochemical behaviour and long-term corrosion stability of several commercial conversion coating systems based on trivalent chromium (TCP), zirconium (ZrCC) and zirconium/titanium (Zr/TiCC) were systematically evaluated on AA3003 aluminum alloy and compared to chromate conversion coating (CCC) CR614. Three TCP coatings (ST650, MC1300 and B30002), two ZrCC (MC1700 and MC160/161), and one Zr/TiCC (B2040) were investigated. Coatings were prepared at pre-selected pH and concentration, but at varying conversion times. The protective performance of the coating was then tested across various exposure conditions using potentiodynamic polarization measurements: (i) after 24 h of exposure to air, (ii) after 24 h of immersion in 3.5 wt.% NaCl solution and (iii) simulated acid rain solution, and (iv) after exposure in a salt spray chamber for 500 h. The protective performance strongly depended on both the conversion conditions and the exposure environment. The optimal conversion times ranged between 40 s and 18 min, depending on the coating type. Differences between the investigated systems remained relatively limited when investigated after exposure to air and immersion in the simulated acid rain solution. However, in chloride-containing environments, substantially greater differentiation between the coatings was observed. Among the investigated systems, TCP coatings exhibited the most favourable overall corrosion performance, particularly after prolonged salt spray exposure, where ST650 and B30002 polarization resistance values were approximately 8800 and 5300 kΩ cm², respectively, together with corrosion current densities as low as 0.0004 and 0.001 μA cm⁻². ZrCC systems MC1700 and MC160/161 also provided significant corrosion protection, achieving polarization resistance values around 2700 and 2400 kΩ cm² after 500 h of salt spray exposure, whereas the Zr/TiCC coating B2040 exhibited poorer long-term performance. The results further demonstrated that prolonged salt spray exposure provides considerably more realistic evaluation of long-term coating protectiveness than short-term electrochemical measurements alone. Overall, optimized TCP and ZrCC systems provided corrosion protection under chloride-containing conditions comparable to or superior to the investigated conventional chromate conversion coating CR614 deposited on AA3003 alloy. Full article

Battery housings are critical structural and safety components in electric vehicles, fulfilling multiple functions related to mechanical protection, crashworthiness, thermal management, fire resistance, electromagnetic shielding, and integration of battery modules into the vehicle body. While metallic housings, particularly aluminum and steel, remain dominant in industrial applications, increasing attention is being given to composite materials as lightweight alternatives capable of improving energy efficiency and extending driving range. However, the growing use of composites in battery enclosures raises important questions regarding recyclability, end-of-life management, and compatibility with circular economy principles. This review critically examines the current state of the art in composite materials used for electric vehicle battery housings, with particular emphasis on glass- and carbon-fiber-reinforced thermoplastics, thermoset composites, sandwich structures, and hybrid multi-material systems. The paper discusses the functional requirements imposed on battery housings and analyzes how these requirements influence material selection and design strategies. Particular attention is devoted to recycling pathways applicable to composite battery enclosures, including mechanical recycling, thermal treatment, chemical recycling, and reuse-oriented approaches, as well as to the limitations associated with mixed-material assemblies, adhesives, coatings, and integrated functions. The review also addresses circular design strategies for battery housings, including design for disassembly, material traceability, modularity, and the incorporation of recycled polymers and secondary reinforcements into new housing systems. Current research gaps are identified in the integration of structural performance, fire safety, manufacturability, and recyclability within a single design framework. The analysis shows that thermoplastic composites currently offer the most promising route toward circular battery enclosures, while thermoset-based systems still face significant challenges in high-value recycling. The paper concludes by outlining future research directions required for the development of lightweight, safe and recyclable composite battery housings aligned with sustainable mobility and circular economy goals. Full article

Plasma electrolytic oxidation (PEO) has emerged as a leading surface engineering technology for improving the tribological and corrosion performance of lightweight structural alloys, including aluminum, magnesium, titanium, and zirconium. Unlike conventional anodizing or line-of-sight deposition processes, PEO forms thick, multiphase ceramic oxide coatings metallurgically bonded to the substrate through plasma-assisted in situ oxidation, enabling treatment of complex and internal geometries that competing technologies cannot reach. The tribological performance of PEO coatings is governed by coupled interactions among electrolyte chemistry, electrical discharge behavior, phase evolution, porosity development, and residual stress state. This review critically evaluates the friction, wear, and tribo-corrosion behavior of PEO coatings under dry sliding, lubricated, high-temperature, marine, and vacuum environments, and systematically examines the influence of processing parameters, microstructural evolution, transfer layer formation, and counterface interactions on coating performance. Hybrid and duplex systems incorporating solid lubricants, polymer impregnation, sol–gel sealing, and multilayer architectures are discussed as strategies to overcome limitations associated with brittleness and surface porosity. Current research challenges, including fatigue degradation, coating defect control, limited cross-study standardization, and incomplete mechanistic understanding of process–microstructure, tribological relationships, are critically assessed. Emerging directions encompassing self-lubricating adaptive coatings, AI-guided process optimization, and multifunctional hybrid architectures are highlighted as pathways toward next-generation surface systems. This review provides a mechanism-based framework for understanding tribological behavior in PEO coatings and identifies critical opportunities for future industrial implementation in aerospace, automotive, marine, biomedical, and energy applications. Full article

The paper investigates the structure and properties of titanium carbide-based composite coatings produced by flame spraying. The relevance of the study is associated with the need to improve the wear resistance and mechanical properties of components operating under abrasive and impact loading conditions in the metallurgical and machine-building industries. A composite powder mixture consisting of titanium carbide, copper, and aluminum was used as the coating material. Titanium carbide acted as a strengthening phase, while copper and aluminum served as damping and binding components. The coating was deposited onto a 30KhGS steel substrate using a 6 PM-II Powder Flame Spray System. Sedimentation analysis, scanning electron microscopy, energy-dispersive analysis, microhardness measurements, and wear resistance tests were carried out. The results demonstrated that the powder mixture has a predominantly fine-dispersed structure favorable for coating formation. The obtained coating exhibited a heterogeneous composite structure with uniformly distributed titanium carbide particles within the metallic matrix. The microhardness of the coating reached HV 770. Wear resistance tests showed insignificant weight loss after 10,000–30,000 abrasion cycles, indicating high wear resistance of the developed coating. It was established that the proposed composite composition contributes to the improvement of the strength characteristics, microhardness, and tribological properties of the surface layer. Full article

Al₂O₃:Cr³⁺ coatings were synthesized on tungsten substrates by plasma electrolytic oxidation in a phosphate-aluminate electrolyte containing dispersed Cr₂O₃ nanoparticles, and their structural, photoluminescent, and temperature-sensing properties were investigated. The coatings exhibited a typical porous PEO morphology with a uniform thickness of approximately 31 μm, and EDS analysis confirmed the incorporation of Cr species from the electrolyte, with Cr content increasing with the concentration of Cr₂O₃ particles. XRD analysis showed that the coatings were composed predominantly of α-Al₂O₃, with minor contributions from metastable γ-Al₂O₃, confirming that our previously established process for forming the thermodynamically stable α-Al₂O₃ phase directly on a non-aluminum substrate remains robust upon the introduction of dopant nanoparticles. The Al₂O₃:Cr³⁺ coatings displayed characteristic ruby-like photoluminescence, including broad excitation bands associated with the ⁴A₂⟶⁴T₁ and ⁴A₂⟶⁴T₂ transitions and sharp R-line emission arising from the spin-forbidden ²E⟶⁴A₂ transition. The strongest emission was obtained for coatings prepared with 0.05 g/L Cr₂O₃, while higher concentrations resulted in concentration quenching. Temperature-dependent photoluminescence revealed two complementary thermometric mechanisms: R-line spectral shifting and thermally induced redistribution between the ²E and ⁴T₂ emissions. The deconvolution-based intensity-ratio approach provided a stronger temperature response than simple spectral partitioning, demonstrating the potential of PEO-derived Al₂O₃:Cr³⁺ coatings on tungsten as robust luminescent temperature-sensing layers. Full article

Aluminum alloys are attractive for oil production, refining, and hydrocarbon-processing equipment because of their low density, high specific strength, and heat-transfer properties; however, their use is limited by localized corrosion in chloride-, sulfur-, and water-containing environments. This review analyzes combined anodic oxide/polymer and anodic oxide/fluoropolymer coating systems as surface-engineering approaches for improving corrosion resistance, adhesion, and durability of aluminum alloys under such conditions. The reviewed data show that coating performance is governed by anodic oxide morphology, pore sealing or polymer impregnation, and oxide/polymer interfacial stability. Quantitative results indicate that anodizing and pore widening can increase aluminum/polyamide lap-shear strength from 5.0 to 17.4 MPa, while optimized interfacial treatment can provide 22.5 ± 0.5 MPa before aging and 18.1 ± 0.2 MPa after humid aging. Corrosion data show that anodizing can increase the polarization resistance of aluminum alloy 6061 in seawater from 17.2 kΩ·cm² to 2.24 MΩ·cm². For wear-related durability, optimized anodizing can increase the critical scratch load from 37.3 to 118.9 N. These values provide practical benchmarks for designing anodic oxide/polymer systems for complex oilfield and hydrocarbon-processing environments. Full article

The accurate characterization of low-power near-infrared LEDs typically requires costly radiometric equipment, limiting broader accessibility. This study proposes a low-cost indirect method for comparative NIR LED characterization based on the thermal response of black-coated aluminum absorbing targets monitored by a commercial MLX90614 contactless temperature sensor integrated with an ESP32 acquisition system. The absorbed optical power was estimated from a steady-state energy-balance model combining convective and radiative heat transfer, with geometry-dependent effective coefficients derived for 10 mm and 15 mm diameter targets. Experiments were conducted using 850 nm and 940 nm LEDs at drive currents between 30 mA and 100 mA. The absorbed power increased linearly with the drive current and electrical input power across all configurations, with R² values of 0.995–0.997 and 0.996–0.999, respectively. The 15 mm targets exhibited higher capture ratios (10.4–11.9%) compared to the 10 mm targets (8.4–9.4%). The combined measurement uncertainty ranged from 13% at high drive currents to nearly 70% at low drive currents, with the temperature-rise sensitivity being the dominant factor; within the recommended operating range (≥70 mA for 10 mm and ≥80 mA for 15 mm targets), the uncertainty remained below 25%. The proposed platform enables reliable comparative characterization of low-power NIR emitters using exclusively off-the-shelf components. Full article

To improve the laser-induced damage resistance of 7075 aluminum alloy, a typical aerospace material, a laser-resistant coating material for the surface of 7075 aluminum alloy was prepared in this paper. The performance of 7075 aluminum alloy coated with this coating was analyzed and tested by combining numerical simulation and experimental verification. The test results show that under the same laser irradiation conditions and geometric dimensions, the breakdown time of 7075 aluminum alloy coated with the laser-resistant coating is prolonged by 541.6%, and its laser-induced damage resistance is significantly improved. Full article

Emissivity is a parameter allowing the assessment of thermal/optical properties of active pharmaceutical ingredients (APIs). ε reflects radiative properties, changes with product aging, and correlates with surface characteristics. This study analyzed the thermal emissivity of commercial tablets—extended-release tablets with metformin hydrochloride (from two manufacturers: XR I and XR II), coated (Co) tablets with ibuprofen, and chewable (Ch) tablets with sodium aluminum dihydroxycarbonate—and compared unexpired vs. expired products. We used the ET 100 emissometer (Surface Optics Corporation, USA; IR range 1.5–21 µm) to measure directional–hemispherical reflectance (DHR) at 300 K, and on the basis of these values, directional thermal emissivity at 20° (DTE20) and 60° (DTE60) and hemispherical thermal emissivity (HTE) were calculated. Then, emissivity parameters were evaluated at 500 K, 800 K, and 1200 K. The DHR values at a 60° angle differed between unexpired and expired XR II tablets across all spectral bands and for XR I tablets, except in the 3.0–4.0 micron range. In turn, for DHR at 20°, high effect sizes were demonstrated between unexpired and expired Ch tablets for 1.5–2.0, 2.0–3.5, 4.0–5.0, and 5.0–10.5 microns. For the DHR at 60°, the high effect size between unexpired and expired Ch tablets was found at 1.5–2.0, 2.0–3.5, and 4.0–5.0 microns. At 300 K, XR I and XR II tablets showed comparable DTE20, DTE60, and HTE. The Ch tablets had higher DTE20 than XR I and XR II (0.968 vs. 0.954 and 0.958, respectively; p < 0.001) and Co tablets (0.968 vs. 0.930; p < 0.001). The Co tablets had the highest DTE60 mean values (0.941 vs. 0.926 for Ch, p < 0.001; 0.926 for XR I, p < 0.001; 0.932 for XR II, p = 0.001). The HTE value was the highest for Ch tablets (p < 0.001 vs. others). During thermal modeling of the emissivity parameters, all DTE20, DTE60, and HTE values decreased with temperature, reaching their lowest values at 1200 K. The largest relative decrease in HTE values (over 15%) between the standard measurement temperature of 300 K and the modeled temperature of 1200 K was found for Ch tablets. Tablets with different release profiles show distinct DTE20, DTE60, and HTE values, suggesting that emissivity may serve as a rapid, non-destructive screening tool that could support further pharmaceutical evaluation during storage. However, emissivity alone does not establish pharmaceutical quality, and the present findings should be interpreted as proof-of-concept rather than as validation of a stand-alone quality-control method. Full article

The choice of brass as the substrate due to its widespread use in soft non-ferrous industrial components such as bearings and electrical connectors creates the primary basis of novelty in this study. While prior tribological studies on titanium aluminum nitride (TiAlN) coatings is primarily focused on hard substrates such as steel and WC–Co, this work addresses the research gap by presenting a systematic investigation of the combined influence of sputtering power and working pressure on TiAlN coatings deposited on brass. Application of TiAlN coatings on brass surfaces was accomplished using magnetron sputtering. Within the scope of this study, the influence of sputtering power and working pressure on the tribological and structural attributes of TiAlN films is evaluated. The analysis of surface morphology is carried out using scanning electron microscopy (SEM), while structural characteristics revealed a progressive increment in the intensity of the (103) and (107) peaks with variation in deposition parameters. An analysis was conducted to evaluate the tribological properties of the TiAlN coating using a pin-on-disk tribometer. The study involved varying the speeds, loads, and sliding lengths. The optimized condition achieved wear reduction as high as 22% compared to uncoated brass at a sliding distance of 785 m, which highlights the strong dependence of wear performance on deposition parameters. The wear rates of TiAlN-coated brass ranged between 1.03 × 10⁻³ and 5.87 × 10⁻⁴ mm³/Nm depending on parameters like load, sliding distance and speed. Conversely, TiAlN-coated brass pins prepared at varying power showed wear rates ranging from 1.83 × 10⁻⁴ to 5.87 × 10⁻⁴ mm³/Nm. These findings demonstrate that optimization of TiAlN coating parameters on brass can significantly enhance wear resistance, which ultimately improves the durability and performance of engineering components in tribological applications. Full article

Low combustion efficiency is a challenge of aluminum (Al) particles in solid propellants, especially in small solid rocket motors. Therefore, it is necessary to adjust the combustion performance of Al to improve the energy release of solid propellants. Here, a core–shell structured Al-based composite Al@IL/FG with high combustion efficiency has been prepared through ionic liquid (IL) and fluorinated graphene (FG) coating. It is seen that IL can form a smooth coating layer on the surface of Al particles and encapsulate fluorinated graphene inside the coating layer. Thermal analysis results show that the coating layer can lower the reaction temperature of Al in the solid propellants due to the surface activation reaction between the Al and IL/FG. After substituting Al@IL/FG with Al, the residual Al content in the condensed combustion products of solid propellants decreased by 11.37%. In addition, compared with Al-based propellant, the d (0.5) of condensed combustion products of Al@IL/FG-based solid propellant was reduced from 69.157 to 21.559 μm. These results indicate that Al@IL/FG has a higher combustion efficiency than Al in solid propellants. Full article

To address the inherent drawbacks of micro-arc oxidation (MAO), this study employed MAO combined with sol–gel processing to fabricate ZrO₂/Al₂O₃-CeO₂ composite coatings on ZrH_1.8 surfaces, aiming to solve the hydrogen evolution problem of zirconium hydride (ZrH_1.8) materials in high-temperature environments. By adjusting the aluminum concentration in the sol (0.1~0.5 mol/L), a series of composite thin films were prepared on the ZrH_1.8 surface using MAO combined with dip-coating, and their surface morphology and phase composition were characterized. The microstructure, morphology, and hydrogen barrier performance of the thin films were systematically analyzed using scanning electron microscopy (SEM), XRD, laser confocal microscopy, and quadrupole mass spectrometry. The results showed that the composite coating had a low surface porosity, with a maximum hydrogen permeation reduction factor (PRF) of 18.1. When the aluminum concentration was 0.4 mol/L, the relative content of tetragonal ZrO₂ (T-ZrO₂) reached 13.88%, the surface porosity was as low as 4.87%, and the initial temperature of hydrogen loss was increased to 730 °C. Mechanism analysis indicated that CeO₂ may stabilize the tetragonal phase (T-ZrO₂) of ZrO₂ through solid solution effects and inhibit the phase transformation to monoclinic phase (M-ZrO₂), thereby reducing cracks caused by volume expansion. Meanwhile, the synergistic effect of the MAO densified layer and the sol–gel sealed porous layer significantly reduced the coating porosity and blocked hydrogen diffusion paths, thus achieving excellent hydrogen barrier performance under high-temperature conditions. Full article

In this work, a non-standardized hypereutectic aluminum–silicon alloy AlSi21Cu5MgCr intended for the automotive industry is presented. The modification of the alloy is performed with the conventional modifier phosphorus in an amount of 0.04 wt%. The applied metallurgical treatment is the basis for the obtained modified structure. It has been established that after conducting the T6 heat treatment, the free silicon crystals are reduced to 26.9 µm, and the eutectic silicon crystals are spherical in shape and have dimensions not exceeding 8 µm. The macrohardness of the studied alloy is 168.5HV_10/10, a value significantly higher than that required for this type of alloy, which is in the range of 95 ÷ 137 HV (90 ÷ 130 HB). The microhardness of the α-phase in the composition of the eutectic is 154 µHV_50/10, which indicates that after quenching a saturated solid solution was fixed, and during the artificial aging process secondary strengthening phases were formed and separated. A CrAlN hard coating was deposited on the alloy surface. The mechanical properties of the coating were characterized by a hardness of 14 GPa, whereas the AlSi21Cu5MgCr substrate had a hardness of 2 GPa. The results showed considerable improvement of the hardness of the new alloy and well-tuned elastic–plastic properties. The obtained adhesive properties are compatible with this class of materials. The composition of the CrAlN hard coating is homogeneously distributed on the alloy surface and the morphology is improved. The investigations showed that CrAlN hard coatings could successfully be applied for the modification of the surface of AlSIMgCu alloys. Full article