Search Results (588)

Graphene exhibits great potential as an anti-friction coating material in MEMS. However, its underlying microscopic friction-reduction mechanism remains unclear. In this paper, the microstructural evolution and nanomechanical behavior of graphene coatings on copper substrates were systematically investigated by AFM friction experiments and MD simulations. MD simulations reveal that the anti-friction properties of graphene coatings primarily stem from microstructural regulation and load-bearing reinforcement of the substrate. The graphene coatings increase indentation diameter by forming transition radii at the indentation edges, and suppress the plowing effect of the substrate by restricting atomic upward movement, both of which enhance the dislocation density and load-bearing capacity of the substrate. Additionally, graphene coatings also reduce the scratch edge angle, weakening the interlocking effect between the substrate and tip, further lowering the friction force. Experimental results indicate that the tribological behavior of graphene coatings exhibits staged characteristics: graphene coatings show excellent ultrafriction properties under intact structural conditions, while showing a higher friction force in wear and tear states. This research provides a theoretical basis and technical guidance for the development of anti-friction and wear-resistant coatings for micro-nano devices. Full article

Polyurea grease (PU) is widely used in the lubrication of heavy machinery, but it can still suffer from structural or performance degradation under extreme conditions such as high temperatures and heavy loads. This study successfully synthesized a hybrid polyurea grease (LiTFSI-PU) by incorporating lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into polyurea matrix. LiTFSI coordinates with the carbonyl groups (C=O) in the thickener molecules to form weakly Lewis acidic complex, thereby reinforcing the soap fiber network structure. As a result, LiTFSI-PU exhibits increased apparent viscosity under shear. The tribological properties of LiTFSI-PU were evaluated under both ambient and elevated temperature conditions. At a load of 200 N and 150 °C, the average coefficient of friction for the 3 wt% LiTFSI-PU formulation was 0.094, which is 32.3% lower than that of the baseline polyurea grease (PU), while the wear volume was reduced by 77.5%. XPS and FIB-STEM/EDS analyses confirmed that LiTFSI-PU forms a multicomponent protective film in situ during friction, which simultaneously shields the substrate and provides lubrication. The additive strategy proposed in this work offers novel insights for the development of high-performance lubricants suitable for extreme thermomechanical conditions. Full article

This study examined the application of rhyolite filler in agroecological farming systems in the Fourth Colony of Italian Immigration (Quarta Colônia de Imigração Italiana), Rio Grande do Sul, Brazil. The aim was to explore sustainable alternatives to synthetic fertilizers in line with organic agriculture principles. The region’s designation as the Quarta Colônia UNESCO Global Geopark reinforces the relevance of this initiative. The research involved petrographic characterization, incubation experiments, and chemical analyses of rhyolite samples. Incubation tests with pigeon pea and elephant grass assessed combinations of rock filler and poultry litter. The results showed that rhyolite filler supported plant growth, especially with poultry litter, which supplies nitrogen and microorganisms that accelerate mineral weathering. Petrographic observations indicated that elephant grass promoted stronger mineral alteration, likely due to its dense fibrous roots and substrate interaction. Chemical analyses confirmed the rhyolite’s quartz content and trace elements remain within safety limits defined by Brazilian legislation on soil remineralizers. The K₂O content and the base sum (CaO, MgO, and K₂O) also complied with minimum legal requirements. Beyond mineralogical and chemical aspects, the study emphasized the economic feasibility of using locally sourced rock fillers, offering lower costs than synthetic fertilizers and supporting sustainable, resilient agroecological systems. Full article

Spent coffee grounds represent an abundant waste resource with potential for sustainable material applications. This study investigates the use of carbonized spent coffee grounds (CSCG) as fillers in polyurethane (PU) coatings for carbon fiber-reinforced polymer (CFRP) substrates to enhance mechanical durability and anti-icing performance. SCGs were dried, sieved (<100 µm), and oxidatively carbonized in air at 100–300 °C for 60–120 min, then incorporated into PU at 1 or 5 wt.% and applied by spray-coating. A full-factorial design was employed to evaluate the effects of carbonization temperature, particle size, and filler loading. The optimized formulation (300 °C, 100 µm, 5 wt.%) showed the highest water contact angle (103.5°), lowest work of adhesion (55.8 mJ/m²), and improved thermal stability with 60% char yield. Mechanical testing revealed increased tensile modulus with reduced strain, and differential scanning calorimetry indicated an upward shift in glass-transition temperature, suggesting restricted chain mobility. Ice formation at 0 °C was sparse and discontinuous, attributed to lowered polar surface energy, rough surface texture, and porous carbon morphology. These results demonstrate that CSCGs are effective sustainable fillers for PU coatings, offering combined improvements in mechanical, thermal, and anti-icing properties suitable for aerospace, wind power, and other icing-prone applications. Full article

Waste materials have emerged as attractive low-cost feedstocks for adsorbent development in environmental remediation and materials engineering. Organic wastes are particularly rich in cellulose, hemicellulose, lignin, and pectin, which provide reactive oxygenated groups such as hydroxyls and carboxyls. While inorganic wastes offer stability, lower water retention makes them promising candidates. This study explores the functionalization of waste-derived organic and inorganic matrices using two amine-based agents: 3-aminopropyltrimethoxysilane (APTMS) and polyethylenimine (PEI). The materials were categorized as organic (orange peel, corn cob) or inorganic (silica gel, eggshell) and subjected to a pretreatment process involving drying, grinding, and sieving; inorganic substrates additionally underwent acid activation with citric acid. Surface modification was carried out in ethanolic (APTMS) or aqueous (PEI) media. To assess their suitability and processability as particulate sorbents, drying kinetics, physicochemical properties (FTIR, ζ-potential, pH, conductivity, Boehm titration), and flow characteristics (Carr and Hausner indices) were evaluated. The findings enable a comparative analysis of the functionalization efficiency and elucidate the relationship between substrate type (organic vs. inorganic) and its performance as a modified adsorbent. This approach advances the development of novel sorbent matrices for greenhouse gas mitigation while reinforcing circular economy principles through the valorization of low-cost, readily available waste materials. Full article

As modern industrialization accelerates, traditional metallic materials face challenges in meeting critical surface protection requirements. Constrained by their physicochemical properties, these materials exhibit significant performance degradation. This leads to frequent peeling of surface coatings on critical components. Polyetheretherketone (PEEK) is a high-performance semi-crystalline thermoplastic used in advanced engineering applications. Its composite coating systems have emerged as a promising alternative to metallic coatings. This paper systematically reviews the recent advances in coating preparation techniques for PEEK composites. The current status of the use of mainstream preparation methods such as thermal spray technology, rapid prototyping and electrophoretic deposition is highlighted. The strengths and weaknesses of each method are also compared. Critical parameters including substrate roughness, temperature, and substrate elasticity are systematically examined. The effects of these variables are evaluated with respect to critical performance indicators, including porosity levels and interfacial bonding strength of PEEK composite coatings. A comparative investigation was carried out on different reinforcement materials. Their interfacial interactions with the matrix are examined in detail at the microscopic level. The impact of these modification strategies on coating performance was comprehensively evaluated. Full article

Silica fiber-reinforced silica aerogel (SFRSA) has low dielectric constant, light weight and high temperature resistance characteristics, making it one of the preferred materials for heat-resistant absorptive layers on the surfaces of high-speed aircraft. However, due to its ultra-high porosity, poor rigidity, and sensitivity to organic solvents, existing machining and chemical etching processes struggle to achieve patterned preparation of metallic layers on aerogel substrates. In order to address this issue, the present study employs femtosecond laser etching of the metal layer on the SFRSA surface. Orthogonal experiments were conducted to analyze the impact of different laser process parameters on the etching quality. With straightness as the primary factor, the optimal process parameters obtained were a laser power set to 2.15 W, a laser etching speed of 200 mm/s, and a laser etching time of 9. This achieved an etching width of 26.16 μm, a heat-affected zone of 39.16 μm, and straightness of 7.9 μm. Finally, Raman spectroscopy was used to study laser-ablated samples; thermogravimetric analysis (TGA) and Pyrolysis-Gas Chromatography–Mass Spectrometry analysis (Py-GC-MS) were employed to investigate the changes in the metal layer at high temperatures. A compositional analysis was conducted, revealing a decrease in carbon content within the etched region following laser ablation. The production of CO₂ gas and surface oxidation indicated that laser etching primarily operates via a photothermal mechanism. Full article

Polyaspartic ester polyurea (PEP) elastomers are highly promising for self-healable protective coatings in industrial applications, yet their broader adoption is limited by insufficient mechanical and corrosion resistance. Herein, we develop a multifunctional PEP nanocomposite by incorporating Jeffamine D2000-functionalized graphene nanoplatelets (F-GNPs), prepared through a one-step mechanochemical process. This strategy promotes strong interfacial bonding and uniform dispersion, yielding synergistic property enhancements. At an optimal loading of 0.3 wt%, the PEP/F-GNP nanocomposite exhibited a substantial performance enhancement, with its tensile and tear strengths augmented by 263.0% and 64.2%, respectively. Moreover, the resulting coating delivered an 84.0% boost in impact resistance on aluminum alloy, along with enhanced substrate adhesion. Electrochemical and salt spray tests further confirmed its exceptional anti-corrosion performance. While the reinforcement strategy presented a classic trade-off with self-healing, it is critical to note that the nanocomposite preserved a high healing efficiency of 83.3% after impact damage. Overall, this scalable interfacial engineering strategy simultaneously enhances the material’s mechanical robustness and protective performance, while striking a favorable balance with its intrinsic self-healing capability, paving the way for next-generation coatings. Full article

Grey cast iron brake discs with lamellar graphite (GJL) offer excellent strength and thermal conductivity but are prone to wear and dust emissions. To mitigate these issues, a multilayer coating was applied via Laser Metal Deposition (LMD), comprising a 316L stainless steel base layer and a WC-reinforced top layer. This study examines the microstructural evolution of the coatings under simulated thermomechanical and corrosive conditions using a brake shock corrosion test. Microstructural characterization was performed via Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), focusing on grain size, orientation, and texture before and after testing. EBSD analysis revealed significant grain coarsening, with sizes increasing from below 20 µm to 30–60 µm, and a shift toward <101> texture. Hardness measurements showed a reduction in the WC-reinforced layer from 478 HV to 432 HV and in the 316L base layer from 232 HV to 223 HV, confirming the influence of thermomechanical stress. SEM analysis revealed a transition from horizontal cracks—caused by residual stress during LMD—to vertical microcracks propagating from the substrate, activated by braking-induced loads. These findings provide insights into the microstructural response of LMD coatings under realistic service conditions and underscore the importance of grain boundary control in designing durable brake disc systems. Full article

Perovskite solar cells (PSCs) rarely report, on a single-device platform, concurrent gains in optoelectronic efficiency and buried-interface mechanical robustness—two prerequisites for flexible and roll-to-roll (R2R) integration. We engineered a nanoplate-structured fluorine-doped tin oxide (NP-FTO) front electrode that couples light management with three-dimensional interfacial anchoring, and we quantified both photovoltaic (PV) and nanomechanical metrics on the same device stack. Relative to planar FTO, the NP-FTO PSCs achieved PCE of up to 25.65%, with simultaneous improvements in Voc (to 1.196 V), Jsc (up to 26.35 mA cm⁻²), and FF (to 82.65%). Nanoindentation revealed a ~28% increase in reduced modulus and >70% higher hardness, accompanied by a ~32% reduction in maximum indentation depth, indicating enhanced load-bearing capacity consistent with the observed FF gains. The low-temperature, solution-compatible NP-FTO interface is amenable to R2R manufacturing and flexible substrates, offering a unified route to bridge high PCE with reinforced interfacial mechanics toward integration-ready perovskite modules. Full article

Amphistegina lobifera, a symbiont-bearing benthic foraminifera native to the Indo-Pacific, is expanding its distribution range in the Mediterranean Sea due to ysian migration through the Suez Canal. This study investigates the colonization dynamics and ecological impact of A. lobifera on Pantelleria Island, which is located in the Central Mediterranean. Nine samples were collected from various substrates at different depths (−4 to −20 m) and analysed for composition, abundance, and ecological diversity. Results reveal a significant dominance of A. lobifera, especially in shallow unvegetated substrates, with relative abundances exceeding 50%. Conversely, more vegetated substrates host more diverse and balanced assemblages. Diversity indices are consistently lower where A. lobifera is dominant, indicating reduced biodiversity. Comparison with similar studies in Malta, Linosa, and Corfu confirms a 20% relative abundance threshold for A. lobifera as indicative of potential ecological imbalance. The results suggest that it represents a growing threat to native microbenthic biodiversity and reinforce its usefulness as a bioindicator species. Pantelleria represents a key transition zone for monitoring the dynamics of invasive species in the Mediterranean, and this study highlights the urgent need for long-term surveillance of benthic biodiversity. Full article

Cold gas dynamic spraying (CGDS) enables the production of protective coatings without melting or oxidation. In this study, Al–Zn–TiO₂ composite powders were prepared by wet agglomeration with binders and by dry mechanical mixing, and deposited onto mild steel substrates. COMSOL simulations of gas dynamics and particle acceleration identified optimal parameters (0.6 MPa, 600 °C, 15 mm, 90°), which were then validated experimentally. Coatings formed under these conditions exhibited dense microstructures, minimal porosity (~0.5%), and continuous, defect-free interfaces with the substrate. SEM and XRD confirmed solid-state bonding without new phase formation. Corrosion tests in 3.5% NaCl revealed a tenfold reduction in corrosion current density compared to bare steel, resulting from synergistic sacrificial (Zn), barrier (Al), and reinforcing/passivating (TiO₂) effects. Tribological tests demonstrated reduced friction (CoF ≈ 0.4–0.5) and wear volume. Compared with reported Al- or Zn-based cold- and thermal-sprayed coatings, the optimized Al–Zn–TiO₂ system shows superior performance, highlighting its potential for industrial anti-corrosion and wear-resistant applications. Full article

The aim of this article is to provide a parametric analysis of the thermal behavior of green roofs, focusing on the influence of the thickness of the vegetation substrate and the type of supporting structure. The simulation model is implemented on the roof structure of an industrial hall in Dubnica nad Váhom, Slovakia, which was created and successfully validated based on real measurements of temperatures and climatic conditions during eight days in September 2023. After validating the model, a series of simulations of three structural variants was performed over three days in the summer. The results demonstrated that the greatest impact on reducing temperature fluctuations was achieved by increasing the thickness of the vegetation substrate (variant V2), which contributed to a reduction in heat flows fluctuations of up to 82% and caused a favorable phase shift in maximum temperatures. The introduction of a reinforced concrete supporting structure (variant V1) brought a partial improvement in the lower layers, while the combined variant (V3) demonstrated the best results—stabilization of temperatures and heat flows throughout the structure, eliminating overheating and cooling of the interior, and overall improvement in the thermal balance of the roof system. The results point to the high potential of green roofs in improving the thermal properties of buildings in summer conditions. Full article

The continuous discharge voltage waveform and phenomena between the electrode and substrate were explored in this paper to study the ultrasonic electro-spark deposition process. Additionally, the impact of ultrasonics on the ultrasonic electro-spark deposition process and the properties of the deposition layer were examined. The results show that the charge–discharge frequency of the ultrasonic electro-spark deposition process was commensurate with the discharge frequency of the ultrasonic electro-spark deposition power source, and the voltage waveform was stable. When ultrasonics is introduced, the molten droplet spray trajectory is efficiently guided, resulting in the spark spray trajectory displaying notable directional concentration characteristics. During a single charging and discharging phase, the electrode and substrate made roughly 15 mechanical contacts, 1 of which was discharging, and the remaining 14 were mechanically contacted reinforcement. The surface of the ultrasonic electro-spark deposition layer exhibited a sputtering morphology with no surface cracks. Phase structures such as Co₃W₃C, Fe₃W₃C, Fe₆W₆C, WC, and W₂C constituted the majority of the ultrasonic electro-spark deposition layer’s microstructure and showed strong metallurgical bonds with the substrate. The ultrasonic electro-spark deposition layer has a surface roughness of 2.554 μm, a cross-section porosity of 1.3%, and a maximum microhardness of 1038.8 HV_0.025. Comparative analysis demonstrates that the addition of ultrasonics can significantly enhance the deposition layer’s quality and performance. When compared to the electro-spark deposition layer, the surface roughness of the ultrasonic electro-spark deposition layer decreases by roughly 61.4%, the cross-sectional porosity decreases by around 57.5%, and the maximum microhardness increases by about 15.5%. Many cracks and much high surface roughness in the conventional electro-spark deposition layer are resolved by the ultrasonic electro-spark deposition technique, which is crucial for cold drawing mold surface strengthening. Full article

Silent information regulator type 1 (SIRT1), a NAD⁺-dependent deacetylase, is a central regulator of cancer cell adaptation to oxidative stress and senescence. By deacetylating redox-sensitive transcription factors, such as p53, FOXOs, PGC-1α, and NF-κB, SIRT1 suppresses apoptosis, delays senescence, enhances mitochondrial function, and attenuates pro-inflammatory senescence-associated secretory phenotypes. These mechanisms collectively promote tumor progression and contribute to resistance to therapy. Reactive oxygen species (ROS), long regarded as damaging byproducts, are now recognized as critical modulators of cancer biology. Although moderate ROS levels drive oncogenic signaling, excessive ROS accumulation triggers DNA damage, oxidative stress, and senescence. To survive these hostile conditions, cancer cells reinforce antioxidant defenses and exploit the NAD⁺–SIRT1 axis to maintain redox balance and evade senescence. The objective of this review was to provide an integrated framework linking SIRT1-mediated deacetylation to redox regulation and senescence control in cancer. We synthesized mechanistic insights into SIRT1 interactions with its substrates, highlighted cancer type-specific functions in ovarian, breast, liver, lung, and gastrointestinal malignancies, and critically evaluated the dual role of SIRT1 as both a longevity factor and an oncogenic driver. Finally, we explored the therapeutic implications of the pharmacological inhibition of SIRT1 as a strategy to restore senescence, increase ROS vulnerability, and overcome therapy resistance. This synthesis underscores the potential of the SIRT1–redox–senescence axis as a promising target in precision oncology. Full article