Search Results (196)

General-purpose polystyrene (GPPS) is widely used in packaging and insulation, although its recyclability poses environmental challenges that require circular economy strategies. The objective of this study was to evaluate the mechanical and tribological behavior of virgin GPPS (100%N), a 50% virgin–50% recycled blend (50N–50R), and 100% recycled GPPS (100%R), processed in Mexico under controlled injection molding conditions. Micro-tensile, flexural, surface roughness, and sliding wear (pin-on-disk) tests were conducted in accordance with ASTM/ANSI standards. The results show that virgin GPPS exhibited the highest strength (micro-tensile: 31.1 MPa; flexural: 87.8 MPa), while the 50N–50R blend maintained comparable tensile strength (27.5 MPa) with greater ductility, making it viable for secondary applications. Recycled GPPS exhibited a significant reduction in strength (micro-tensile: 18.6 MPa; flexural: 41.1 MPa), although with greater deformability. In tribological tests, the coefficients of friction were 0.480 (100%N), 0.128 (50N–50R), and 0.143 (100%R), all with relative errors of less than 4%, confirming statistical validity. Surface roughness analysis showed that the virgin material had the most uniform surface (Ra = 1.0 µm), while the blends exhibited greater variation (Ra ≈ 1.2 µm). In conclusion, although recycled GPPS has limitations compared to virgin material, it retains acceptable mechanical and tribological properties for non-structural applications. These findings support its potential in circular economy strategies in Mexico and provide a framework for countries with similar recycling infrastructure conditions. Full article

Contact-angle prediction from literature data is vulnerable to target leakage when solid surface-free-energy descriptors are reconstructed using the liquid, which is later treated as the target. We developed a target-masked workflow that removes the target liquid before fitting nonnegative Owens-Wendt-Rabel-Kaelble components by nonnegative least squares and uses that physical prediction to anchor residual learning. A row-level revision audit re-extracted or excluded mismatched legacy sources before all models were retrained. Development used nested source-group cross-validation; the fixed cross-source external confirmation set was excluded from selection. The revised residual model achieved mean absolute errors of 15.5 degrees in nested validation and 13.2 degrees on that confirmation set. Surface-cluster bootstrap supported improvement over physics, whereas source-cluster uncertainty remained substantial. Diagnostics showed source dependence, sparse roughness, and limited strict unseen-liquid support. The method is therefore positioned as an auditable, risk-aware and reproducible materials-screening tool for surfaces with at least two non-target probes, with explicit out-of-distribution risk and refusal conditions rather than universal transfer claims. Full article

This study investigates the influence of detonation spraying parameters on the microstructure, mechanical properties and tribological performance of self-fluxing Ni–Cr–Fe–Si–B–C coatings deposited on AISI 321 stainless steel substrates. The effects of the barrel filling ratio (48–68%), the oxygen-to-fuel molar ratio (O/C = 1.026–1.856), and the delay time between detonation shots (0–1 s) were systematically evaluated. The coatings were characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), microhardness measurements, instrumented indentation, and ball-on-disk tribological testing. Microstructural investigations revealed that the spraying parameters significantly influence coating thickness, porosity and defect formation. The lowest porosity (0.306 per cent) and the most homogeneous microstructure were obtained at a barrel filling ratio of 48 per cent, an O/C ratio of 1.026 and a shot delay of 1 s. XRD analysis identified a multiphase structure consisting of a Ni₃Fe matrix reinforced by Cr₇C₃ carbides, Ni₃B and CrB borides, and Ni₃₁Si₁₂ silicides. Tribological tests demonstrated that increasing the delay between shots significantly improved wear resistance, reducing the wear rate to 1.89 × 10⁻⁴ mm³/(N × m). The optimised coating exhibited an average coefficient of friction of 0.578 ± 0.093 and a wear rate of 1.03 × 10⁻⁴ mm³/(N × m). Instrumented indentation revealed a hardness of 1049.1 ± 43.4 HV and a Young’s modulus of 215.9 ± 8.5 GPa. The wear mechanism was predominantly abrasive–adhesive, whilst the wear rate of the 100Cr6 counter-body remained low at 1.20 × 10⁻⁵ mm³/(N × m). The results obtained demonstrate that appropriate optimisation of detonation spraying parameters enables the formation of dense Ni–Cr–Fe–B–Si–C coatings with superior mechanical and tribological properties, making them promising candidates for wear-resistant engineering applications. Full article

The paper presents the results of the research on the spectral reflectance characteristics of colorimetric standards and the practical verification of the Helmholtz principle of reversibility of measurement geometries. The studies were conducted in the calibration laboratory of the Central Office of Measures (GUM) using a spectrophotometer equipped with a multi-angle accessory, enabling measurements over a wide range of angular configurations. Ceramic standards from the DM05 set, Teflon standards, and an enameled reference standard were analyzed. For each sample, measurements were performed in pairs of inverse angular geometries, x°:0° and 0°:x°, and then the relative deviations (differences between nominally reciprocal configurations) from the Helmholtz principle of reciprocity were determined. The studies provide a basis for a better understanding of the reflectance properties of the standards and for assessing the measurement capabilities of spectrophotometers operating in directional geometry. Full article

Traditional methane sensors based on metal oxide semiconductors typically require high operating temperatures (200–400 °C), which not only leads to high power consumption but also often results in detection limits that struggle to fall below 5 ppm. To achieve room-temperature operation with lower detection limit, this work proposed a surface acoustic wave (SAW) methane sensor using monolayer graphene oxide (GO) film. The GO material was prepared by a modified Hummers method combined with liquid-phase exfoliation and characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The sensor was constructed by drop-casting the GO dispersion onto the delay line region of a Y-cut quartz SAW device. Results showed that the GO sensor exhibited a low detection limit of 1 ppm and a sensitivity of 0.046 mV/ppm in the range of 100–1000 ppm, which was 2.2 times higher than that of multilayer graphite (0.021 mV/ppm). The response and recovery times for 500 ppm methane were 16.7 s and 66.4 s, respectively. Good repeatability and selectivity were also demonstrated. This work presents a simple and effective approach for room-temperature methane detection using monolayer GO on SAW devices. Full article

This study evaluated how silicone release liners come away from butyl hot-melt pressure-sensitive adhesive (HMPSA) sealants. An application-specific integration peel test was conducted based on FINAT FTM 10 geometry. It kept the 180° geometry, the 300 mm/min crosshead speed, and the cN/25 mm reporting convention, but used 90 mm butyl-sealant strips in place of a standard reference adhesive tape. The reported values are therefore apparent/effective separation forces for the tested liner–butyl constructions, not standard FINAT datasheet release-force values. Three double-sided silicone-coated PET liners (Rossella, Dolpap, Crosil 42) and seven commercial butyl sealants (C1E, U2E, C1EN, T1E, T2E, T1EN, T2EN) were tested on both liner sides. Two descriptors summarized each force–displacement trace: the mean apparent separation force and an operational slip-stick peak count based on positive residual-force excursions. Most combinations stayed below about 18 cN/25 mm. An increase was observed for T1EN, and a much larger one for Rossella/U2E. In both cases, high, diffuse stress was accompanied by volumetric deformations, fibrillation, and unstable detachment, rather than clean detachment at the phase boundary. Dolpap was the most stable and the most symmetric. Crosil 42 stayed in the low-force range but showed a few material-specific side differences. Taken together, the mean force and the peak count form a reproducible relative screen for selecting actual liner–butyl pairs, one that complements rather than replaces standard release-liner datasheet testing. Full article

Icing phenomena on wind turbine blades and components are a major problem, causing downtimes that increase maintenance costs, reducing the blade’s lifespan, or in severe cases, even leading to component damage. A nanofiber-based bi-layer liquid-infused surface (BLIS) coating was prepared and characterized, combining good adhesion to wind turbine blades with low ice adhesion. The BLIS coating was produced by a new method combining electrospinning and a heat treatment step, containing a poly ethyl-2-cyanoacrylate (PECA)-based adhesive layer, a slippery layer of poly vinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) copolymer, and an infiltrated perfluoropolyether lubricant. Thermogravimetric analysis (TGA) was used to ensure the thermal stability of the polymers in the nanofiber coating layers and to optimize the heat treatment process of the layers. Microstructural changes were studied by scanning electron microscopy (SEM) and surface roughness measurements. Contact angle measurements and sliding velocity tests on wind turbine blade segments at icing conditions of 0 °C and +5 °C indicate that the water sliding properties of the BLIS coating were improved compared to uncoated blades. In addition, coated blade segments showed a 50% lower ice adhesion strength than uncoated blades. Full article

This study investigates the application of polymer inclusion membranes (PIMs) for the removal/recovery of 1H-benzotriazole from aqueous solutions, via facilitated transport mechanism, using tri-n-octylamine as a carrier and NaOH as a stripping agent. The process efficiency was analyzed using 1H-benzotriazole flux and permeability through the membrane, its recovery percentage, and the transport process kinetic constant. PIM containing 40% cellulose triacetate, 30% o-nitrophenyl octyl ether and 30% tri-n-octylamine yielded the best results for all four parameters studied due to the role of o-nitrophenyl octyl ether and tri-n-octylamine in reducing the cellulose triacetate polarity, which leads to carrier solubilization on the plasticizer, creating continuous pathways within the membrane and facilitating 1H-benzotriazole transport. Reduced graphene oxide inclusion as the fourth PIM component increases its hydrophobicity, promoting continuous pathway formation and enhancing 1H-benzotriazole transport, which leads to an increase of 10% to 20% in the values of the four parameters analyzed. Ultrasound use in membrane preparation leads to a further increase of 9% to 20% in the values of the four parameters analyzed because the cavitation effect improves the molecular mixing of membrane components and results in a less ordered configuration of cellulose triacetate molecules, thereby reducing their crystallinity degree. All of this significantly improves the interaction between the membrane components and pathway formation, enhancing 1H-benzotriazole transport through the membrane. Full article

The surface treatment of inner walls in large-aspect-ratio tubes plays a pivotal role in ensuring long-term stable operation of equipment. Although traditional methods like electroplating are widely used, they often suffer from limited protection, poor adhesion, and environmental drawbacks. Magnetron sputtering (MS) represents a promising alternative; however, few studies have successfully developed coatings that balance high hardness with strong adhesion on the inner walls of tubes featuring large length-to-diameter ratios. In this study, we deposited Cr coating on the inner wall of a tube with an aspect ratio of 13.3 using MS technology, and regulated the process to enhance the hardness and adhesion strength of the coating. By systematically varying the bias voltage, the microstructure and properties of the coating were effectively tailored. Results show that a bias voltage of −200 V promotes pronounced (110) preferred orientation in the Cr coating, yielding an optimal combination of high hardness (~11.54 GPa) and a low coefficient of friction (~0.4). Furthermore, scratch testing revealed robust coating–substrate adhesion strength, with initial failure loads exceeding 50 N under various bias conditions. These findings demonstrate that optimizing the bias voltage during MS deposition is an effective approach for fabricating high-performance Cr coatings, providing a viable strategy to improve the durability and reliability of high-end equipment. Full article

The thermochemical diffusion treatment of boronitrocarburizing in a single stage was conducted on AISI 1018 steel using the powder-packing method. The treatment was performed at temperatures of 1123 K, 1173 K, and 1223 K for 8 h. The specimens were characterized using Scanning Electron Microscopy (SEM), Energy-Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) enabling a superficial elemental analysis of B, N, and C diffusion into the substrate. The tribological effects of friction and wear under dry conditions were analyzed through a pin-on-disc test, employing an aluminum oxide (Al₂O₃) sphere and a profilometer to measure mass loss. The study concluded that the sample treated at 1173 K exhibited the best tribological performance, showing the lowest coefficient of friction ($\mu \approx 0.1216$), while the samples treated at 1123 K and 1223 K exhibited coefficients of friction of $\mu \approx 0.1611$ and $\mu \approx 0.1856$, respectively. All treated samples showed a reduction in the coefficient of friction compared to the control sample ($\mu \approx 0.558$). Full article

Fused Filament Fabrication (FFF) is a widely used additive manufacturing technology due to its versatility, low cost, and broad material compatibility. However, achieving high dimensional accuracy in FFF parts remains challenging because dimensional deviations are affected by material shrinkage, process parameters, and part geometry. This study analyses the dimensional deviations of PLA hollow cylindrical specimens manufactured by FFF, with particular attention to the different behaviour of outer and inner diameters. The methodology combines an iterative design-adjustment procedure with a neural-network-based compensation approach. First, specimens with different geometries were printed and measured to evaluate the evolution of dimensional error after successive design corrections. Then, the influence of print speed and layer thickness was analysed through the volumetric material flow rate, and the resulting data were used to train separate feedforward neural networks for the outer and inner diameters. The results showed that outer and inner diameters followed different deviation trends, confirming that they should be analysed independently. Print speed, layer thickness, and material flow affected dimensional accuracy in different ways depending on the measured diameter. The proposed neural network approach provided a practical means of estimating compensated design diameters within the experimental domain analysed, reducing the need for repeated trial and error adjustments. However, the results should be interpreted within the experimental limits of the study, particularly regarding the use of a single material, a single printer, and a limited validation dataset. Overall, the study provides a practical workflow for improving dimensional accuracy in FFF parts and highlights the importance of diameter-specific compensation strategies. Full article

The catalytic influence of γ-aminobutyric acid (GABA) on Zn²⁺ electroreduction at a mercury electrode was investigated in an acetate buffer. Electrochemical measurements, including DC polarography and differential capacity, indicate that GABA facilitates charge transfer through the formation of “cap-pair” surface bridges. This acceleration is reflected in a systematic increase in the standard rate constant and the transfer coefficient. Molecular dynamics simulations complement these findings by characterizing the conformational properties of GABA, showing a transition toward more folded forms in concentrated environments. Moreover, MD simulations demonstrate that GABA reduces the Zn²⁺ solvation number, providing a structural pathway that lowers the dehydration barrier prior to charge transfer. These observations correlate with the measured decrease in diffusion coefficients as the neurotransmitter concentration increases. The results establish a direct link between the zwitterionic adsorption of GABA and the reduction in the energetic barrier in the zinc electroreduction process. Full article

Surface roughness is a key tribological property commonly characterized by the power spectral density (PSD) of surface topography. However, the recent Surface Topography Challenge demonstrated that measurements of identical surfaces may yield PSD curves differing by several orders of magnitude depending on the laboratory and measurement method. Such discrepancies can arise from measurement artifacts, including spike-like outliers and macroscopic surface curvature. In this work, we analyze these effects and propose a correction procedure for recovering the intrinsic roughness spectrum. The method combines nonlinear median filtering for artifact detection with robust PSD reconstruction based on multiple one-dimensional surface sections. Outliers are removed in real space, the macroscopic shape is eliminated by detrending, and the PSD is obtained as the median of spectra from individual line scans. Tests on synthetic surfaces with known roughness spectra contaminated by curvature and artificial spikes demonstrate that the method reliably recovers the original spectrum even when artifacts dominate the raw data. Application to experimentally measured surfaces further indicates that some apparent roughness features may originate from measurement noise and stitching artifacts rather than the true surface structure. Full article

Rolling bearings operate under complex contact conditions, and their tribological and dynamic behaviors are highly sensitive to their lubrication performance. Based on previous studies on surface texturing, three types of representative textures (wholly distributed dimples, locally distributed dimples, and grooves) with optimized parameters were fabricated on the shaft washers using the laser marking method. This was done to investigate the synergistic effect of surface textures and polytetrafluoroethylene (PTFE) nano-additives on the tribological and friction-induced vibration performance of cylindrical roller thrust bearings under starved lubrication. Lubricating oils containing various mass fractions (0.5 wt%, 1.0 wt%, and 3.0 wt%) of PTFE nano-additives were prepared and employed. The coefficients of friction (COFs), wear losses, worn morphologies, and time/frequency-domain vibration responses were analyzed. The results show that the appropriate integration of surface textures and solid lubricant additives can establish a highly effective synergy for rolling bearings under starved lubrication. PTFE nano-additives significantly improved the tribological performance of the smooth bearings and those with dimples (both wholly distributed and locally distributed), with the optimal performance observed at a mass fraction of 3.0 wt%. In contrast, the tribological performance of the groove-textured bearings noticeably deteriorated with the addition of PTFE nano-particles, especially at higher mass fractions. The bearing with wholly distributed dimples exhibited the best overall tribological performance at a mass fraction of 3.0 wt%, achieving a 61.8% reduction in the average COF, a 99.6% reduction in wear loss, and significantly suppressed vibration amplitudes. Full article

This study aims to investigate the static performance of water-lubricated rubber bearings (WLRBs) with axial grooves. To achieve this objective, an analytical approach is employed that combines a modified Reynolds equation, accounting for surface groove effects and rubber deformation, with a Winkler model and finite element analysis of pressure distribution. By developing a fluid–structure interaction model that incorporates rubber liner deformation, this research reveals the interaction between WLRB geometry and steady-state performance parameters. The investigation evaluates the influence of geometric characteristics, including groove shape, number, and size, on the performance of elastomeric liner WLRBs, while assessing optimal groove depths under various conditions. The study analyzes five distinct groove geometries, including semi-cylindrical, rectangular prism, and three pyramidal types with different apex positions, in a six-groove bearing configuration, presenting their qualitative effects on the behavior of the examined bearings. The key findings indicate that increasing groove size or quantity reduces maximum pressure and load-carrying capacity while elevating friction coefficients. As groove count rises, supporting surfaces diminish, causing pressure distribution to intensify and minimum film thickness to decrease under a specified external load. A notable result reveals that when groove depth exceeds film thickness, performance becomes geometry-independent; however, shallower grooves exhibit significant geometric effects. Additionally, the study identifies groove ends as critical functional zones where film thickness reduction substantially enhances pressure distribution and static performance. Comparative analysis shows that longitudinal grooves with triangular cross sections outperform semi-circular and rectangular variants, with the backward triangular configuration demonstrating superior characteristics due to optimal end-film properties. In conclusion, this research provides a detailed understanding of how groove geometry influences the static performance of WLRBs, highlighting the importance of groove design, particularly at the groove ends, in optimizing bearing functionality. The findings offer valuable insights for the design and selection of groove configurations in water-lubricated rubber bearing applications. Full article