Search Results (5,500)

In response to thermal failure risks in ultra-high voltage (UHV) bushing online monitoring devices and maintenance equipment—caused by high heat generation of electronic components and the intrinsically low thermal conductivity of conventional resin encapsulation materials—this study proposes a novel modification strategy based on flash Joule heating (FJH). Distinct from conventional interface modification methods, the proposed approach enables cross-scale, in situ microsoldering between multi-walled carbon nanotubes (MWCNTs) and carbon fibers (CFs), constructing a multiscale reinforcement network with integrated thermal transport and mechanical load transfer pathways. The transient ultra-high-temperature thermal shock generated by FJH not only effectively removes inert impurities on CF surfaces but also drives carbon structural reconstruction, enabling graphitic-level welding of MWCNTs onto the fiber surface. This micro-welded architecture fundamentally differs from traditional filler dispersion or interface coating strategies, which often suffer from the trade-off between interfacial thermal transport and mechanical bonding. By contrast, the FJH-induced carbon–carbon bonded nodes form a continuous conductive and load-bearing network at the micro–nano scale. Characterizations using scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) confirm successful in situ welding of MWCNTs onto CF surfaces. Meanwhile, FJH treatment effectively removes oxygen-containing functional groups and surface impurities. Analysis of carbon bonding evolution indicates that the welding efficiency reaches its maximum at 90 V. Macroscopic performance tests demonstrate that, compared with epoxy resin, the thermal conductivity of the multiscale reinforced system increases by approximately 168%, while the mechanical strength improves by 62.72%. This study provides new theoretical insights and technical pathways for the development of next-generation polymer composite materials with both high thermal conductivity and high mechanical strength. Full article

Background/Objectives: Cardiopulmonary bypass (CPB) facilitates complex cardiac surgery but can damage erythrocyte membranes, impairing microcirculation and oxygen transport. Standard rheological tests assess overall blood properties but fail to define specific cellular mechanisms. In this study, atomic force microscopy (AFM) was employed to characterize morphological, nanostructural, and mechanical changes in erythrocytes following CPB and CPB combined with hypothermic circulatory arrest (HCA). Methods: The study included 14 patients who underwent cardiac surgery with CPB. Patients were divided into two groups. Group 1 underwent heart valve surgery with normothermic CPB (n = 7), and Group 2 underwent aortic arch surgery with CPB combined with HCA and moderate hypothermia (28 °C) (n = 7). Arterial blood samples were collected before the induction of anesthesia and immediately after CPB. The morphology and surface roughness (Rtm) of the erythrocyte membrane were evaluated on air-dried blood smears. Young’s modulus (E) was estimated from force-distance curves on living cells; measurements were performed at 24 °C in PBS. Results: Following CPB, both groups exhibited a decrease in the proportion of discocytes and an increase in echinocytes. In the CPB+HCA group, discocytes were absent after surgery. The mean Rtm increased 1.4-fold in Group 1 and 1.6-fold in Group 2, indicating greater nanostructural membrane damage in the latter. In Group 1, Young’s modulus increased by an average of 1.6 times, indicating increased cell stiffness. In Group 2, the increase was smaller (mean: 1.1 times) and was not statistically significant in some patients. Conclusions: Normothermic CPB primarily affects the nanomechanical properties of erythrocytes, whereas CPB+HCA induces more severe morphological and membrane surface damage while relatively preserving cytoskeletal elasticity. AFM-derived parameters of membrane roughness and cell elasticity may serve as sensitive indicators of erythrocyte biophysical integrity. Full article

Ultrafast laser-induced micro–nano hierarchical structures show broad applicability in optoelectronics, functional surfaces, and biomedicine. However, precisely controlling their formation through light field manipulation remains a relatively unexplored area. This work demonstrates a rapid drilling strategy on silicon using an emission-programmed, high-repetition-rate femtosecond Bessel beam. This spatiotemporal modulation enables a unique manufacturing synergy that integrates subtractive drilling and thermo-fluidic redistribution by the central lobes with additive nanostructuring by the peripheral lobes, directly fabricating a micro–nano hierarchical structure comprising tapered micro-holes, elevated micropillars, and dense nanocoatings. Meanwhile, areal scanning enables programmable geometry control through line interval adjustment. This approach offers new insights into laser-matter interactions and facilitates applications in infrared photodetection or drag-reduction surfaces. Full article

Optical-based sensors have been widely used for various applications, including biosensing, civil structural health monitoring, and humidity sensing. Fiber Bragg Grating (FBG) is one of the optical-based sensing approaches that are commonly used in these applications. The effect of hygroscopic coating on different grating profiles, including uniform, apodized, and tilted FBG, was investigated by connecting the FBG to a light source and optical spectrum analyzer (OSA). The reflected wavelength of the FBG, captured by the OSA at increasing and decreasing relative humidity ranging from 40 to 80% RH were recorded. Tin dioxide (SnO₂) is one of the metal oxides with a hygroscopic nature, which is suitable to act as a coating material for FBG. For improved sensitivity, the HMT-enhanced technique was applied in this study to modify the surface morphology of SnO₂, increasing the porosity of the nanostructure for water adsorption and desorption. The result showed that the sensitivity and linearity of the FBG-based humidity sensor can be enhanced via HMT-enhanced SnO₂ nanostructure coating onto uniform FBG. A sensitivity of 1.30 pm/%RH and 1.52 pm/%RH was reported during incremental and decremental RH, respectively, and a fitting coefficient of >0.97 was recorded. This approach demonstrated the feasibility of hygroscopic coating on FBG to enable broad applications across various humidity sensing industries such as agriculture, pharmaceutical, and semiconductors. Full article

Recent advances in polymeric composites emphasize the incorporation of natural and mineral fillers to enhance sustainability while maintaining mechanical performance. Studies have shown that lignocellulosic residues and nanostructured clays can improve stiffness and thermal stability, although interfacial compatibility remains a key challenge. This study investigates the mechanical behavior of epoxy composites reinforced with eucalyptus powder and montmorillonite clay, aiming to develop sustainable materials with reduced environmental impact. Formulations containing 5%, 10%, and 20% by volume of each particulate, as well as hybrid combinations, were produced and tested for impact, flexural, and compressive strength. Higher particulate contents were not explored, as fractions above 20% considerably increased viscosity, hindering proper mixing and specimen fabrication. Scanning electron microscopy (SEM) revealed irregular morphologies and heterogeneous dispersion of both fillers. The reduction in impact strength observed across all formulations was mainly attributed to poor interfacial adhesion and void formation, as no chemical or surface treatments were applied to enhance compatibility between the particulates and the epoxy matrix. Conversely, compressive strength improved at low filler contents (5–10%), suggesting a more efficient load transfer under compressive stress. Composites with up to 10% particulate presented a viable balance between mechanical performance and sustainability, showing potential for non-structural applications such as panels, coatings, and eco-friendly construction components. Overall, the results highlight the feasibility of using natural and mineral particulates as sustainable reinforcements, albeit with performance constraints at higher loadings. Full article

This study aims to develop an innovative electrochemical genosensor based on activated biochar (ABC) derived from the biomass of the seaweed Sargassum spp. The synthesis process begins with the pyrolysis of Sargassum spp. at 500 °C to obtain biochar (BC), which is chemically activated with nitric acid (HNO₃). The physicochemical properties of the resulting material, such as morphology and surface area, were characterized using techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and the Brunauer–Emmett–Teller (BET) method for surface area. BET results showed an increase in surface area from 22.9367 ± 0.0879 m²/g (BC) to 159.2915 ± 2.2641 m²/g (ABC). For the development of the genosensor, a hydrolyzed collagen gel matrix enriched with ABC is created. This nanostructured, biocompatible mixture is used to immobilize a DNA probe on a graphite electrode, employing the large surface area of ABC and the formation of a functional HC-based coating. The system’s viability was evaluated by cyclic voltammetry (CV), which showed changes in the maximum anodic peak current (Ipa) during fabrication: 27.78 ± 1.87 μA for the bare electrode, 35.25 ± 1.24 μA for ABC 30%, and 39.25 ± 1.84 μA for HC + ABC 30%. After ssDNA immobilization and hybridization to dsDNA, Ipa decreased to 28.81 ± 1.565 μA and 23.10 ± 1.25 μA, respectively. Finally, hematoxylin (Hx) was used as an intercalating indicator from hybridization, reducing the maximum anodic peak current to 15.51 ± 1.13 μA, consistent with additional interfacial limitations associated with dsDNA formation. Overall, the developed system demonstrates a sustainable, promising platform for molecular diagnostics in electrochemical DNA biosensor development. Full article

High-entropy fluorite oxides offer exceptional tunability of structure and functionality through controlled multi-cation substitution. In this work, Ce-Zr-Pr-Sm-Eu-based high-entropy oxides, with systematically varied Pr content, were synthesized using a modified sol–gel citrate method to investigate the influence of Pr incorporation on lattice structure, defect formation, and photocatalytic performance. All compositions crystallized in a single-phase cubic fluorite structure, where increasing Pr concentration induced gradual lattice expansion and microstrain due to the substitution of larger Pr³⁺ ions. Morphological and surface analyses revealed porous nanostructures at moderate Pr levels, while excessive Pr promoted densification and reduced surface accessibility. Spectroscopic studies confirmed the coexistence of Pr³⁺/Pr⁴⁺ and Ce³⁺/Ce⁴⁺ redox couples, strong 4f–2p orbital hybridization, and enhanced defect-related electronic states that narrowed the optical bandgap. The optimized Pr-doped composition exhibited almost 100% degradation of methylene blue under UV light over 30 min, untypical for semiconductors with a narrower bandgap, and is enabled by efficient charge separation and redox cycling between Ce and Pr centers. Full article

Concrete is widely employed in structural engineering; however, its porous nature renders it vulnerable to chloride ingress and salt freezing cycles, ultimately compromising its durability. To address this, a penetrating primer based on tetraethyl orthosilicate (TEOS) was prepared in an ethanol-water co-solvent system, and a hydrophobic topcoat of isooctyltriethoxysilane (IOTES) was obtained via emulsification. A layered application on concrete surfaces yielded a TEOS–IOTES dual-coating protection system designed to enhance water repellency and thereby improve resistance to chloride penetration and salt freeze–thaw damage. Test results show that the dual coating markedly increased hydrophobicity, giving a water contact angle of 130° and reducing water absorption rate to below 0.01 mm/min^0.5. Compared with single-layer treatments, the dual coating significantly lowered the free chloride diffusion coefficient (reached 83.74%). In terms of salt freezing cycle resistance, the dual-coating protection delayed surface scaling and increased the critical number of freeze–thaw cycles required for damage by 40%. Microstructural analyses indicate that the TEOS primer generates nano-SiO₂ and C-S-H gels, refining pores and densifying the matrix, while the IOTES topcoat forms a durable hydrophobic layer that suppresses moisture and deleterious ion transport. The synergistic “densification–hydrophobization” mechanism substantially enhances concrete durability, offering a cost-effective and efficient surface-protection strategy with promising application potential. Full article

The presence of corrosion on metal substrates can compromise the integrity of a structure. In this study, discrete fiber Bragg grating (FBG) sensing technology is used to monitor the corrosion process of a Cu surface in a corrosive environment. The surface morphology and nanostructures of corrosion products are observed to reveal their forms or structures. The results show that corrosion products are composed of loose or dense collections of micrometer/nanometer-sized particles in a crystalline state. Furthermore, this study experimentally explores how localized corrosion affects the sensing signal between an optical fiber and a corroded copper substrate. This phenomenon is also theoretically modeled using contact mechanics, enabling a semi-quantitative calculation of how corrosive particles influence Bragg wavelength. The wavelength shift trends of the four monitoring points over a period of 10 days were similar under the same corrosive environment. Results show that fiber Bragg grating sensors can identify the corrosion process in real time using wavelength demodulation methods. This study will lay the foundation for subsequent work on the precise monitoring of copper corrosion using fiber Bragg grating sensors. Full article

The quality of the feedstock powder plays a key role in determining the properties of coatings produced by cold spray (CS). However, most commercially available powders are not specifically designed for CS, which makes it difficult to tailor powder characteristics for optimal performance. In this study, we examined the cold sprayability of five copper (Cu) powders manufactured using electrolysis, gas atomization, and mechanical grinding. The powders were characterized in terms of their microstructure, particle shape, and size distribution to evaluate how the production method influences powder properties. Powder flowability was measured using a shear cell test, while mechanical properties and deformability relevant to CS were assessed through nano-indentation. The results showed that gas-atomized powders with equiaxed grain structures offered the best combination of flowability and deformability, making them the most suitable for CS. Their spherical particle shape resulted in a lower surface area compared to the irregular electrolytic powder, which reduced inter-particle surface forces and allowed for smoother powder flow. Nano-indentation measurements indicated that the mechanically ground powder with ultra-fine grains and the gas-atomized powder containing fine dendrites had the highest nano-hardness values (HIT = 2.1 ± 0.15 GPa and 1.6 ± 0.1 GPa, respectively). In contrast, the porous electrolytic Cu powder showed the lowest hardness (HIT = 0.7 ± 0.2 GPa). These trends were confirmed by microstructural analysis of the deposited coatings. Coatings produced from the irregular electrolytic powder exhibited limited particle deformation, weak inter-particle bonding, and the highest porosity. Conversely, spherical gas-atomized powders produced much denser coatings. In particular, the powder with the most uniform spherical shape and no microsatellite particles resulted in the lowest coating porosity due to its superior deformation behavior upon impact. Full article

In mechanical engineering, interest in reliable and practicable technologies for nano- and microstructuring of tool surfaces is increasing. Femtosecond laser structuring offers a promising approach that combines high processing speeds with high precision. However, a knowledge gap remains regarding the optimal process parameters for achieving specific surface patterns on hot-work tool steel substrates. The current study aims to investigate the effects of laser scanning parameters on the formation of self-organized surface structures and the resulting topography and morphology. Therefore, samples were irradiated using a 300 fs laser with linearly polarized light (λ = 1030 nm). Scanning electron microscopy revealed four structure types: laser-induced periodic surface structures (LIPSSs), micrometric ripples, micro-crater structures, and pillared microstructures. The results for surface area and line roughness indicate that high laser pulse overlaps lower the strong ablation threshold more effectively than high scanning line overlaps, promoting the formation of pillared microstructures. For efficient ablation and increased surface roughness, higher pulse overlaps are therefore advantageous. In contrast, at low fluences, higher scanning line overlaps support a more homogeneous formation of nanostructures and reduce waviness. Full article

High-entropy alloys (HEAs) represent one of the most promising emerging material families, particularly for advanced surface engineering applications. In this work, a near-high-entropy alloy (near-HEA) coating was produced on a 316L stainless steel substrate using laser metal deposition (LMD) from a powder mixture of Inconel 625, Cr and Mo, without the intentional addition of Fe. Due to dilution from the substrate, the resulting alloy contained elevated Fe content while maintaining Cr, Ni and Mo concentrations within the generally accepted compositional range of HEAs. The deposited layer exhibited a dual-phase microstructure consisting of a face-centered cubic (FCC) phase and a highly distorted tetragonal phase forming a periodic network with a characteristic length scale of several hundred nanometers. The hardness of the coating increased to approximately three times that of the substrate, reaching values of 600–700 HV. To further modify the surface properties, laser-induced periodic surface structures (LIPSS) were generated on the polished coating using femtosecond pulsed laser irradiation at different energy densities. The morphology and subsurface structure of the resulting periodic patterns were investigated by scanning electron microscopy. LIPSS with characteristic dimensions ranging from the micrometer to nanometer scale were successfully produced. Cross-sectional analyses revealed that the underlying dual-phase microstructure remained continuous within the laser-structured regions, indicating that LIPSS formation occurred predominantly via metallic ablation without significant phase transformation or amorphization. These results demonstrate the combined applicability of LMD and femtosecond laser structuring for producing mechanically enhanced, micro- and nanostructured near-HEA coatings with potential for advanced surface-related functionalities. Full article

Electropolishing is an essential process for the surface treatment of metallic materials. To determine the appropriate replacement timing of electropolishing solutions for their efficient use and improved productivity, it is important to periodically analyze the amounts of dissolved metals in the solutions. However, these solutions are typically highly corrosive, and on-site analytical techniques that can be easily applied at production sites have not yet been established. In this study, we demonstrated microvolume liquid analysis using low-energy laser-induced breakdown spectroscopy (LIBS) combined with a porous silicon substrate fabricated by metal-assisted etching (metal-assisted chemical etching) and a non-contact gas-blowing pretreatment. In the analysis of electropolishing solutions used for niobium superconducting cavities and stainless steel products, emission lines of niobium and of iron and chromium were successfully detected after blowing the respective microdroplet samples on porous silicon, and linear correlations were observed between the spectral line intensity and the polished amounts. The present results provide a basis for future on-site application of LIBS to highly corrosive electropolishing solutions in the metal finishing industry. Full article

This paper investigates the different relaxation channels of a single symmetric top NH₃ and a spherical top CH₄ molecule trapped at low temperature in a clathrate hydrate nano-cage in the infrared absorption domain of their vibrational degrees of freedom. The approach utilizes the Born–Oppenheimer approximation and the extended site inclusion model applied to CO₂ in a previous work, which was based on pairwise atom–atom effective interaction potentials. The calculations show that trapping the methane or ammonia molecule is energetically more favorable in a type sI clathrate structure than in an sII one, and entropic considerations show that methane can be released much more easily than ammonia from clathrate hydrate nano-cages. In the small (s) and large (l) nano-cages with the sI structure, the CH₄ molecule exhibits a more or less perturbed rotational motion, while the NH₃ molecule shows a strongly hindered orientational motion that tends to a three-dimension librational motion (oscillation motion) around its orientational equilibrium configuration. The calculated orientational energy level schemes are quite different from those of the molecular free rotation. In the static field inside the cage, degenerate ${\nu }_3$ and ${\nu }_4$ vibrational modes of methane and ammonia molecules are shifted and split. Moreover, for ammonia molecules, the ${\nu }_1$ and ${\nu }_2$ modes are shifted, and the inversion motion is no longer allowed. The non-radiative and radiative relaxation channels of CH₄, NH₃ and CO₂ in clathrate nano-cages are discussed with reference to the matrix isolation spectroscopic results. Upon laser excitation, then, from the energy levels calculated for the different degrees of freedom, NH₃ and CO₂ are expected to fluoresce, while for CH₄, non-radiative relaxation should lead to evaporation at the surface of clathrates. Experimental setups are suggested to localize and study these species underneath ice surfaces on distant planets or planetesimals from mobile detectors such as drones or CubeSats equipped with appropriate laser sources and telescopes with 2D imaging detectors. Full article

ZnSe nanoparticles were synthesized via the sustainable laser fragmentation in liquids (LFL) technique using a Nd:YAG laser at 1064 nm. The pulse energy was varied to study its effect on the particle size and vibrational properties. UV–Vis absorption spectra show a blue shift in the absorption edge with a decreasing pulse energy. The sample processed at the lowest pulse energy has the smallest nanoparticles (10.3 nm average), reaches an optical band gap of 2.83 eV, and exhibits a high-energy shoulder attributed to spin–orbit-related transitions. Raman spectra reveal a strong enhancement of the surface phonon mode (231–234 cm⁻¹), where its intensity surpasses that of the longitudinal optical mode, demonstrating the dominant role of surface atoms in the vibrational response. TEM confirms a wide size distribution, i.e., centered at 10.3 ± 6.4 nm, which can account for the simultaneous observation of bulk-like and quantum-confined optical and Raman features. These results show that the pulse energy effectively tunes the nanoparticle size and phonon behavior, positioning LFL as a clean and versatile method for producing ZnSe nanostructures with relevant properties for optoelectronic applications. Full article