Search Results (137)

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

Concrete, when used in construction, is prone to internal micro cracks that compromise its strength, flexibility, durability and lifespan. To address this, self-healing concrete technologies using microbial-induced calcium carbonate precipitation (MICP) have gained significant attention. The objective of this study was to focus on the preparation of a bacterial consortium (BV) composed of Bacillus cereus and Vibrio natriegens, selected for their specific characteristics to produce calcium carbonate under alkaline conditions. These bacterial strains with nutrients were added in optimised proportions to the concrete mixes and evaluated their healing potential. The effectiveness of the bacterial consortium on the self-healing potential of concrete was investigated. Similarly, the performance of this consortium was assessed across three different water–cement (w/c) ratios: 0.40, 0.45, and 0.50. These variations were selected to investigate the influence of moisture availability and mixed porosity on bacterial activation and crack healing efficiency. Mechanical tests like flexural strength, split tensile strength and compressive strength were performed to assess the structural recovery. Durability tests such as acid resistance, water absorption, and non-destructive tests like ultrasonic pulse velocity were also performed. Based on these investigations, a 0.40 w/c ratio of bacterial consortia (0.40 BV) showed the best performance. These results indicate that the bacterial consortium can significantly improve the self-healing properties of concrete, particularly at low w/c ratios. Full article

The performance requirements of wear-resistant and anti-corrosion coatings for marine equipment continue to increase. Diamond-like carbon (DLC) film has become a preferred protective material due to its high hardness, low friction and chemical inertia. To reveal the tribocorrosion mechanism of Si-doped DLC films in a seawater environment, a Cr-WC-WC/C transition layer and DLC-Si films with different Si contents were prepared by high-power pulsed magnetron sputtering (HiPIMS) technology on 304 stainless steel. The tribocorrosion tests were carried out under open-circuit potential and dynamic polarization conditions in seawater. The results show that Si doping improved the tribocorrosion resistance of the films. The sample with Si content of 9.26 at.% has the lowest self-corrosion current density, the smallest volume loss, complete wear scar morphology and no obvious substrate exposure. The strengthening mechanism is attributed to Si doping, which induces the formation of a SiO_x passivation film and a hydrated silica gel lubrication layer. This establishes a synergistic solid-chemical lubrication system, inhibits sp² cluster growth, prolongs the diffusion path of corrosive media, and mitigates the damaging wear–corrosion synergy. This study confirms that moderate Si doping can significantly improve the wear resistance and corrosion resistance of DLC films in a seawater environment, and provides a theoretical basis for the design and application of carbon-based protective coatings for marine equipment. Full article

Accurate impact localization on spacecraft structural panels subjected to contact loading by on-orbit servicing robots is critical for real-time structural health monitoring (SHM), yet remains challenging due to heterogeneous elastic wave propagation in complex aluminum structures with stiffener ribs and bonded joints. Conventional Received Signal Strength Indicator (RSSI)-based weighted centroid methods rely on fixed path-loss exponents that cannot accommodate spatially varying wave attenuation, resulting in position-dependent localization errors that worsen significantly near structural discontinuities. This paper proposes a Crow Search Algorithm (CSA)-optimized adaptive weighted centroid algorithm using distributed Fiber Bragg Grating (FBG) sensors, featuring three principal innovations: (i) a novel FBG wavelength-shift-to-RSSI amplitude mapping derived from elastic wave attenuation theory, bridging optical fiber sensing with centroid localization; (ii) per-event online weight optimization via CSA that adapts sensor contributions to each individual impact’s strain-wave signature; and (iii) a multi-objective fitness function simultaneously optimizing localization accuracy, noise robustness, and temporal consistency. The proposed method is validated across 200 impact events distributed over five representative positions on a 1 m³ Al6061 satellite-like structure with 64 FBG sensors (8 × 8 grid, 125 mm pitch), under three Gaussian noise levels (σ = 1%, 3%, 5% of signal RMS), and benchmarked against classical weighted centroid (WC), PSO-WC, GA-WC, DE-WC, and GWO-WC using paired t-tests (p < 0.01). CSA-WC achieves a mean localization error of 4.63 mm—an 83.29% improvement over classical WC and the lowest error among all five compared algorithms—with an average computation time of 0.14 s per event, satisfying real-time monitoring requirements. Full article

The prediction of the compressive strength (CS) for sustainable concrete reinforced with graphene nanoplatelets (GNPs) is difficult as a result of nonlinear interactions between chemical composition, dispersion state, and curing conditions. To address this, an interpretable ensemble machine learning framework is developed to provide accurate predictions of CS. The major input parameters used are sand content, graphene diameters, graphene thicknesses, and percentages of GNP to sand (GNP%; w/w), water-to-cement ratio W/C, ultrasonication period UST time (s), curing age CA day(s), while the CS (in MPa) is the target output. The random forest (RF) and XGBoost (XGB) models are incorporated into two novel metaheuristic optimization techniques, the Drawer-based optimization algorithm (DOA) and the Giant Trevally Optimizer (GTO), to enhance hyperparameter tuning and generalization. For all models, DOA XGB hybrids are the most predictive, with testing R² values up to 0.98; RMSE of around 2.9 MPa; MAE is approximately 2.0 MPa, and well over 97% within ±20% prediction error boundaries. The explainable artificial intelligence methodologies like Shapley Additive exPlanations (SHAP), Local Interpretable Model-Agnostic Explanations (LIME), partial dependence plots, and Individual Conditional Expectation plots reveal curing age and graphene thickness as the dominant parameters. High strengths above 70 MPa are always achieved from higher curing age, w/c ratio (from 0.3 to 0.4), and graphene dosage (from 0.5 to 2.5%). A Python GUI is developed for efficient and accurate strength predictions suitable for practical applications. The proposed approach provides a robust, interpretable, and efficient alternative to extensive testing for GNP-reinforced concrete. Full article

Epilepsy is associated with impaired reproductive function and testicular pathologies. Intermittent fasting (IF) is a nonpharmacological metabolic intervention with anti-inflammatory and antioxidant effects. This study investigated the protective effects of IF on testicular damage in a genetic absence epilepsy rat model (GAERS), focusing on histomorphology, oxidative stress parameters, and hormonal profiles. Testicular tissues from Wistar control (WC), Wistar + IF (WIF), GAERS control (GC), and GAERS + IF (GIF) groups (total n = 20; 5 rats per group) were evaluated using hematoxylin and eosin and Periodic Acid–Schiff staining. Apoptosis and spermatogenic cell integrity were assessed using caspase-3, P-element-induced wimpy testis (PIWI), and Deleted in Azoospermia-Like (DAZL) immunohistochemistry. Johnsen’s score, seminiferous tubule diameter, and epithelial thickness were quantified. Oxidative stress markers, including catalase, malondialdehyde, glutathione, myeloperoxidase, and superoxide dismutase, were measured using spectrophotometric methods, and serum testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) levels were determined using ELISA kits. The GC group showed significantly reduced Johnsen scores, tubular diameters, and epithelial thickness, along with disrupted basement membrane integrity and increased caspase-3 immunoreactivity. IF significantly improved histological parameters, restored basement membrane integrity, reduced apoptosis, and increased PIWI and DAZL expression in the GIF group. IF also ameliorated oxidative stress and elevated reproductive hormone levels, indicating positive modulation of the hypothalamic–pituitary–gonadal axis. In conclusion, IF reduces oxidative stress and preserves seminiferous tubules and hormonal function in genetic absence epilepsy, highlighting its potential as a supportive nonpharmacological approach to protect male reproductive health. Full article

Objectives: Given the limitations of body mass index (BMI) as a metric and the lack of data on the relationship between various anthropometric indices of obesity and immune fitness (IF), this study aimed at exploring the possible association between various anthropometric indicators and the immune fitness among an adult sample of the Saudi population residing in Makkah. Methods: A structured self-reported questionnaire, with questions covering age, sex, anthropometric and immune fitness assessment data, was distributed online to a convenience sample of target population. The Immune Status Questionnaire (ISQ) was utilized to assess respondents’ IF over the past 12 months, while perceived momentary immune fitness (PMIF) was measured using a single-item scale. A total of 1135 responses were included in the study. Results: Overall, 530 male (46.7%) and 605 female (53.3%) respondents were included in the analysis. Of these, 478 (42.1%) had a normal BMI, and 343 (30.2%) were classified as overweight, 184 (16.2%) as obese, and 130 (11.5%) as underweight. Participants with reduced ISQ score (<6) were more likely to be underweight (p < 0.001), have a high weight-adjusted waist index (WWI) (p = 0.035), and exhibit an increased conicity index (C index) (p = 0.037) compared to those with an ISQ score ≥ 6. After controlling for age and sex, weight (p = 0.003), height (p < 0.001), and WWI (p = 0.01) were found to have significant correlations with past-year IF, while only height (p = 0.004) showed a significant positive correlation with PMIF. A multiple linear regression analysis revealed that sex and height and waist circumference (WC) were significant predictors of IF. Specifically, males and those who were taller had higher IF scores. Whereas individuals with high-risk WC values reported lower IF scores than those with low-risk WC. Conclusions: Sex (male) and anthropometric measures (lower WC, and taller height) were the most informative predictors of higher IF scores. The findings highlight the association between anthropometric measures and IF. A deeper understanding of these associations can inform the development of targeted interventions aimed at improving IF and overall health outcomes. Full article

This review provides a comprehensive evaluation of the key technologies and latest advances in cemented carbide bearings for marine environments, such as navigation equipment and deep-sea operations. Given the rigorous performance requirements imposed on bearings by the extreme conditions of marine environments, including high hydrostatic pressure, seawater corrosion and abrasive wear, this paper explores the developments within carbide material systems. It focuses on analyzing the limitations of traditional WC-Co alloys in seawater, as well as the potential and challenges of alternative binder systems such as WC-Ni and WC-high Entropy Alloys (HEAs) in enhancing corrosion resistance and comprehensive mechanical properties. Building on this foundation, the research sorts out the tribological behavior of cemented carbides under seawater lubrication, explaining the influence of the tribocorrosion mechanism on friction characteristics. Meanwhile, it also explores reliability enhancement strategies through surface modifications like coatings and texturing, and discusses the challenges associated with life prediction models. Through tribopair experiments between cemented carbides and various bearing materials, the application orientation of cemented carbides is clarified, which provides a selection framework for carbide bearing applications in different marine scenarios. Finally, the paper summarizes the current technological bottlenecks and core scientific issues, offering insights for future research and development directions in this field. Full article

To gain deeper insight into the protective mechanism of tungsten carbide/diamond-like carbon (WC/DLC) duplex coatings, this study employed high-velocity oxygen-fuel (HVOF) combined with linear ion source (LIS) technology to deposit the WC/DLC duplex coating on the Ti₆Al₄V substrate. Their tribocorrosion behaviors were thoroughly investigated. The results show that the dense, uniform, and chemically inert DLC top layer acts as an effective barrier, preventing the corrosive medium from penetrating into the underlying WC cermet layer through pores. Consequently, the duplex coating exhibits a lower I_corr of 3.54 × 10⁻⁸ A/cm², compared with that of the single WC coating (1.08 × 10⁻⁶ A/cm²), demonstrating significantly improved corrosion resistance. Moreover, the DLC coating offers excellent tribological performance owing to the high hardness and self-lubricating characteristics. After depositing the DLC top layer on the HVOF-sprayed WC cermet, the COF is reduced to ~0.08, and the wear rate reaches only 5.64 × 10⁻⁸ mm³/N·m, indicating notably enhanced tribocorrosion resistance. In short, in such HVOF-PVD/CVD duplex coating systems, the PVD/CVD functional layer can improve the tribocorrosion performance of the HVOF interlayer by leveraging its intrinsic advantages, such as high hardness, low friction, dense and uniform microstructure, and chemical inertness. Full article

This study first assessed the friction and wear properties of two polytetrafluoroethylene materials sliding against electroplated chrome and high-velocity oxy-fuel-sprayed WC-10Co-4Cr coatings. Subsequently, the sealing performance of three different structure seals made from these two polytetrafluoroethylene materials was investigated on both electroplated chrome and high-velocity oxy-fuel-sprayed WC-10Co-4Cr coatings. The study results indicate the following: in terms of changes in the counter-face surface roughness, both the electroplated chrome and high-velocity oxy-fuel-sprayed WC-10Co-4Cr surfaces exhibited an increase in surface roughness after sliding, demonstrating the phenomenon of “soft material wearing hard material.” Moreover, the changes in surface roughness were greater after sliding against wollastonite mineral-filled polytetrafluoroethylene than against polyether ether ketone-filled polytetrafluoroethylene, indicating that wollastonite mineral-filled polytetrafluoroethylene was more likely to cause damage to the metal surface. Regarding the friction coefficient and wear amount, under dry friction conditions, both materials exhibited higher friction coefficients but lower wear rates on high-velocity oxy-fuel-sprayed WC-10Co-4Cr surfaces, while showing lower friction coefficients but higher wear rates on electroplated chrome surfaces. This behavior was related to the ease of transfer film formation and the stability of the transfer films formed by polytetrafluoroethylene materials on the two surfaces. In terms of the products’ sealing performance, test results showed that, for composite seals with polytetrafluoroethylene as the counter-face, sealing performance was better on high-velocity oxy-fuel-sprayed WC-10Co-4Cr surfaces than on electroplated chrome surfaces. For seals with rubber as the counter-face, there was little difference in sealing performance between high-velocity oxy-fuel-sprayed WC-10Co-4Cr and electroplated chrome surfaces. Full article

To prepare a high-performance Fe-based laser cladding coating, herein, various Fe60/WC/Y₂O₃ coatings are deposited on the surface of 42CrMo steel plate via a laser cladding technique. The WC dosage is fixed as 10 wt%, while the dosage of Y₂O₃ ranges from 0 to 7.5 wt%. The influences of Y₂O₃ dosage on the coating hardness, wear resistance, and corrosion resistance are investigated. With the addition of Y₂O₃, the feature peak of WC disappears, and the peaks of M₂₃C₆ gradually weaken, indicating that Y₂O₃ promotes the decomposition of WC and suppresses the formation of new metal carbides. When the dosage of Y₂O₃ is 2.5 wt%, a grid-like structure is formed on the coating surface, suggesting uniform distribution of decomposed W within the Fe matrix. When the Y₂O₃ dosage exceeds 5 wt%, a large amount of CO₂ gas is released, leading to an increase in surface pores. Through a comparison, the optimal dosage of Y₂O₃ is 2.5 wt%, and the resulting 3# coating has the highest hardness of 861.97 HV. Moreover, the 3# coating also shows the minimum friction coefficient and the minimum wear volume, reflecting its superior wear resistance. The polished coating serves as a working electrode, and the corrosion resistance is tested in 3.5% NaCl solution. The sample containing 2.5 wt% Y₂O₃ has the highest corrosion potential and the lowest corrosion current density, indicating excellent corrosion resistance. The enhanced performance is ascribed to the improved surface quality and the formation of a W-reinforced grid structure. The high-performance coating has promising application potential in material and component repair. Full article

Zirconia, also known as zirconium dioxide ZrO₂, is well known for its good mechanical properties, like its inertness, good wear resistance, high temperature resistance and good strength. To enhance the mechanical properties of many materials, a technique known as transformation toughening is widely used today. This research focuses on achieving an optimized composition of zirconia and alumina Al₂O₃ to achieve zirconia-toughened alumina ZTA with a maximum density and other mechanical properties using a cost-effective and time-efficient approach. Doing so will make it possible to make more and more use of this valuable ceramic. The curing of zirconia and alumina samples with 3d—printing resins in silicone dies was performed so that we could obtain the optimum ratio of the resin and ZTA powder that would produce the most desirable results and properties. For 3d printing, ZTA samples with 19% zirconia ZrO₂ were used with alumina at two different temperatures (i.e., Sample 1, consisting of three pellets weighing 5–6 g, was sintered at 1500 °C, and Sample 2, also containing three pellets weighing 5 g (approx.), was sintered at 1600 °C). The green-state preparation of these samples (Sample 1 and Sample 2) was performed using milling media of WC balls/ethanol and a milling ratio of 1:3, and a milling time of 4 h 100 rpm was used while drying at 80 °C for 5.5 h. The relative density (70%) and Vickers hardness (14–17 GPa) were obtained for Al₂O₃/ZrO₂/MgO samples. Mechanical properties like hardness and strength strongly depend on the holding time, the rate of the temperature increase while sintering and the sintering temperature itself. Full article

Machining hard metals presents various challenges, especially with materials like WC-Co, known for their exceptional hardness and wear resistance, making them ideal for cutting tools. Among machining methods, Electrical Discharge Machining (EDM) stands out for its ability to machine hard materials with no mechanical damage, which is critical for machining fragile components. For form shape machining symmetrical parts like WC-Co bars, electrical discharge turning (EDT) could be applied. Despite its potential, limited research exists on deep form turning of hard metals like WC-Co using EDT. This study addresses that gap by comparing the final geometrical outcomes of two EDT setups: vertical and horizontal tool electrode configurations. Additionally, the impact of workpiece rotational speed on surface quality was examined. Results showed that the vertical tool electrode setup produced more accurate geometries and smoother surfaces. Furthermore, increasing the workpiece’s rotational speed improved flushing efficiency, resulting in reduced surface roughness and a cleaner machined surface. Full article

Diabetes mellitus (DM) is a complex chronic disease, with a prevalence that has reached alarming proportions in recent decades. In this study, we aimed to analyze the association of type 2 diabetes mellitus (T2DM) with certain insulin resistance (IR) indicators, according to the gender of the participants enrolled in the PREDATORR study. Biomarkers such as the triglyceride–glucose (TyG) index and its derivates, triglyceride-to-high-density lipoprotein cholesterol (TG/HDL-c), and metabolic score for insulin resistance (METS-IR), as well as recent indicators, like cholesterol, HDL, the glucose (CHG) index and its derivates, CHG–body mass index (CHG-BMI), and CHG–waist circumference (CHG-WC), as well as its newly proposed derivates, such as CHG–waist-to-height ratio (CHG-WHtR), CHG–neck circumference (CHG-NC), and CHG–neck-to-height ratio (NHtRs were analyzed in 2080 subjects, divided into two groups, according to gender). Univariate and multivariate logistic regression was used to identify the relationships between IR indicators and T2DM. Regardless of gender, all the analyzed indicators presented statistically significantly higher values in T2DM (+) compared to T2DM (−). For both studied groups, CHG–WHtR had the largest AUROC curve: in males, the AUROC curve was 0.809, the cut-off value being 3.22, with a 70.7% sensitivity and 75.3% specificity; in females, the AUROC curve was 0.840, the cut-off value was 3.20, with a 79.3% sensitivity and 75.5% specificity, respectively. Regardless of gender, the age-adjusted model for multivariate logistic regression analysis demonstrated that TyG and CHG were predictive factors for T2DM. Full article

This study investigates the influence of pectin and copper incorporation on the catalytic properties of Pd/ZnO catalysts in the liquid-phase hydrogenation of 2-hexyn-1-ol and photocatalytic hydrogen evolution. A series of monometallic Pd/ZnO catalysts with varying pectin contents (0–8.1 wt%) and bimetallic PdCu-Pec/ZnO catalysts with different Pd to Cu mass ratios (3:1, 1:1, 1:3) were synthesized via sequential adsorption of the polymer and metal ions onto ZnO. The catalysts were characterized using TGA, EDX, IR spectroscopy, XRD, TEM, UV–Vis DRS, and XPS. Characterization confirmed successful modification and changes in surface properties. Pectin modification improved the distribution of Pd nanoparticles on the surface of ZnO, resulting in the enhanced catalytic performance of Pd-Pec/ZnO in both hydrogenation and hydrogen evolution reactions compared to unmodified Pd/ZnO. In contrast, copper addition led to a deterioration of catalytic properties in both processes, likely due to the inhibited reduction of Pd caused by Pd–Cu interactions. Among the catalysts studied, Pd-Pec/ZnO with low pectin content (1.8 wt%) exhibited the highest activity in both reactions. The hydrogenation of 2-hexyn-1-ol to cis-2-hexen-1-ol proceeded with high selectivity (96%) at a rate (W_C≡C) of 3.3 × 10⁻⁶ mol/s, and the catalyst retained its activity over 30 consecutive runs. In the photocatalytic hydrogen evolution reaction, the rate reached 1.11 mmol/(h·g_cat) and the catalyst maintained ~94% of its initial activity after three consecutive runs. These findings demonstrate the potential of biopolymer-modified ZnO composites for the design of multifunctional catalysts combining hydrogenation and photocatalytic activity. Full article