Search Results (173)

The laser damage resistance of optical films holds significant practical importance, as it largely determines both the maximum power output of laser systems and the overall stability of the entire optical assembly. A comprehensive investigation was conducted to examine the influence of both single additives—acetylacetone (ACAC) and diethanolamine (DEA)—and dual-additive systems, specifically ACAC combined with polyethylene glycol 200 (PEG 200) and DEA combined with PEG 200, on TiO₂ film properties and their laser-induced damage behavior under 1064 nm irradiation. It demonstrated that the films fabricated using ACAC exhibited smoother surfaces. Nevertheless, the sol prepared with DEA was more stable, resulting in films with superior optical properties and an enhanced laser-induced damage threshold (LIDT). The incorporation of dual additives further improved the films’ LIDT. Specifically, the film with DEA and PEG 200 achieved the highest LIDT, reaching 21.5 J/cm². Moreover, all films exhibited defect-induced damage, yet distinct damage morphologies were observed across different samples. The single-additive films predominantly displayed stress-type damage patterns, whereas the dual-additive films manifested melting-type damage characteristics. Furthermore, through a combination of experiments and calculations, it was revealed that the reasons why the film with DEA and PEG 200 achieved the highest LIDT were twofold: first, the high thermal conductivity of DEA reduced the maximum temperature at the defect center within the film; second, the long molecular chains of PEG 200 created a looser film structure that better mitigated damage caused by stress and expansion during laser irradiation. This study presents a promising approach to enhancing the LIDT through the strategic selection of additives with high thermal conductivity while simultaneously incorporating organic compounds with long molecular chains to develop effective dual-additive films. Full article

This paper presents the results of a comprehensive study of the structure, phase composition, thermal corrosion, and tribological properties of multilayer gradient coatings based on YSZ/NiCrAlY obtained using detonation spraying. X-ray phase analysis showed that the coatings consist entirely of metastable tetragonal zirconium dioxide (t’-ZrO₂) phase stabilized by high temperature and rapid cooling during spraying. SEM analysis confirmed the multilayer gradient phase distribution and high density of the structure. Wear resistance, optical profilometry, wear quantification, and coefficient of friction measurements were used to evaluate the operational stability. The results confirm that the structural parameters of the coating, such as porosity and phase gradient, play a key role in improving its resistance to thermal corrosion and CMAS melt, which makes such coatings promising for use in high-temperature applications. It is shown that a dense and thick coating effectively prevents the penetration of aggressive media, providing a high barrier effect and minimal structural damage. Tribological tests in the temperature range from 21 °C to 650 °C revealed that the best characteristics are observed at 550 °C: minimum coefficient of friction (0.63) and high stability in the stage of stable wear. At room temperature and at 650 °C, there is an increase in wear due to the absence or destabilization of the protective layer. Full article

An analysis of the working surfaces of cylindrical gears after scuffing shock tests allowed for the assessment of the effect of loading conditions on the form of damage to the tooth surfaces. Unlike the method of scuffing under severe conditions, where loading is applied gradually, the presented tests employed direct maximum loading—shock loading—without prior lapping of the gears under lower loads. This loading method significantly increases the vulnerability of the analyzed components to scuffing, enabling an evaluation of their limit in terms of operational properties. To identify the changes and the types of the teeth’s working surface damage, the following microscopy techniques were applied: scanning electron microscopy (FE-SEM) with EDS microanalyzer, optical interferential profilometry (WLI), atomic force microscope (AFM), and optical microscopy. The results allowed us to define the characteristic damage mechanisms and assess the efficiency of the applied DLC coatings when it comes to resistance to scuffing in shock scuffing conditions. Tribological tests were performed by means of an FZG T-12U gear test rig in a power circulating system to test cylindrical gear scuffing. The gears were made from 18CrNiMo7-6 steel and 35CrMnSiA nano-bainitic steel and coated with W-DLC/CrN. Full article

This paper presents the results of an experimental study on the buckling and failure behavior of thin-walled square columns made from PLA and PETG polymers using FDM 3D printing technology. Thin-walled square columns made from thermoplastic materials, intended for use in lightweight load-bearing applications such as structural supports in transportation, construction, and mechanical assemblies, were tested under axial compression from the onset of buckling to complete failure. The novelty of this work lies in the application of an interdisciplinary experimental approach to the analysis of the behavior of thin-walled columns made of PLA and PETG materials during FDM 3D printing under compression until complete failure, as well as the use of acoustic and optical diagnostic methods for a comprehensive assessment of damage. The experimental results are as follows: Buckling load (N): PLA—1175 ± 32, PETG1—1910 ± 34, PETG2—1315 ± 27. Ultimate load (N): PLA—2770, PETG1—4077, PETG2—2847. Maximum strain: PLA—11.35%, PETG1—11.77%, PETG2—10.99%. Among the tested materials, PETG1 exhibited the highest resistance and energy absorption capacity upon failure, making it a favorable choice for manufacturing 3D-printed load-bearing columns. Full article

The use of plastic materials in the maritime industry is increasing day by day. Plastics are particularly preferred in watercraft due to their lightweight, resistance to water-related damage (such as mold and wear), optical clarity, and high corrosion resistance. In recent years, plastics produced by 3D printing have gained prominence in applications traditionally dominated by conventional plastic materials. Therefore, producing marine-grade materials—such as acrylonitrile butadiene styrene (ABS), which has long been used in the maritime sector—through 3D printing, and understanding their long-term performance, has become increasingly important. In this study, the mechanical behavior, surface roughness, and color changes of ABS+ materials in three different colors (yellow, green, and blue) and with three different infill ratios (50%, 75%, and 100%) were investigated after a salt spray test. Following the salt spray exposure, tensile and bending tests, hardness measurements, surface roughness analyses, and color measurements were conducted and compared with reference samples. The results were evaluated based on filament color and infill ratio. This study underscores the importance of color selection—along with mechanical strength—when designing 3D-printed materials for long-term use in saltwater environments. Full article

Structural health monitoring (SHM) plays a vital role in ensuring the safety, durability, and performance of civil infrastructure. This review delves into the significant advancements in optical fiber sensor (OFS) technologies such as Fiber Bragg Gratings, Distributed Temperature Sensing, and Brillouin-based systems, which have emerged as powerful tools for enhancing SHM capabilities. Offering high sensitivity, resistance to electromagnetic interference, and real-time distributed monitoring, these sensors present a superior alternative to conventional methods. This paper also explores the integration of OFSs with Artificial Intelligence (AI), which enables automated damage detection, intelligent data analysis, and predictive maintenance. Through case studies across key infrastructure domains, including bridges, tunnels, high-rise buildings, pipelines, and offshore structures, the review demonstrates the adaptability and scalability of these sensor systems. Moreover, the role of SHM is examined within the broader context of civil and urban infrastructure, where IoT connectivity, AI-driven analytics, and big data platforms converge to create intelligent and responsive infrastructure. While challenges remain, such as installation complexity, calibration issues, and cost, ongoing innovation in hybrid sensor networks, low-power systems, and edge computing points to a promising future. This paper offers a comprehensive amalgamation of current progress and future directions, outlining a strategic path for next-generation SHM in resilient urban environments. Full article

Calcium fluoride (CaF₂) crystals are widely utilized in deep-ultraviolet (DUV) lithography due to their excellent optical properties. The laser-induced degradation and damage of CaF₂ crystals is a critical concern that restricts its extended application. Impurities of CaF₂ crystal are considered a key factor affecting its laser resistance. Establishing the quantitative relationship and mechanism of impurity content impacting the degradation and damage characteristics of CaF₂ crystal is essential. This study investigated the characteristics of different impurity contents affecting the degradation and laser-induced damage thresholds (LIDTs) of CaF₂ crystals under X-ray and 193 nm pulsed laser irradiations, and quantitatively analyzed the degradation process and mechanism. Our findings demonstrate that impurities at ppm levels significantly diminish the transmittance of CaF₂ crystals across various wavelengths following X-ray irradiation. In contrast, these impurities have a negligible effect on the LIDT test results, suggesting distinct damage mechanisms between X-ray and laser irradiation. This study provides valuable insights for optimizing the CaF₂ crystal fabrication process and enhancing irradiation resistance. Full article

Long-term stability and laser-induced damage resistance of optical components in the UV region are critical for enhancing their performance in UV high-power laser applications. This study evaluates the laser-induced damage threshold (LIDT) of commercially available UV optical windows with anti-reflective (AR) coating, produced through various coating techniques and designed for high-power lasers. A third-harmonic (343 nm) wavelength with good beam quality was generated in the picosecond regime to investigate the LIDT of optical components. The LIDT for each sample was measured under controlled conditions and compared based on their coating techniques. The sample coated with Al₂O₃/SiO₂ through ion beam sputtering has the best LIDT value, of 0.6 J/cm², among the tested samples, based on the hundred-thousand-pulses methodology. The damage threshold curve and the corresponding damage morphology are discussed in detail, and these findings provide insights into the durability and susceptibility of UV optics for advanced laser systems available in the market. Full article

Photodynamic inactivation of bacteria offers a promising alternative to counteract the trend towards the development of resistance, which, if left uncontrolled, will lead to the death of 10 million people per year by 2050. Its advantage over antibiotics is the site-specific mode of action due to the photosensitizer (PS) and the low risk of developing resistance. This is primarily prevented by the damage of the bacteria, which also destroy internal structures such as nucleic acid, proteins, and lipids. A promising and still little-researched PS is chlorophyllin (CHL), a chlorophyll derivative. This study investigated its mode of action on Bacillus subtilis growth using optical density (OD) measurements. It was shown that the PS is highly effective even at low concentrations and short irradiation durations. Here, 1 mg/L and an irradiation duration of 1 min were sufficient to inhibit the growth of the Gram-positive bacterium Bacillus subtilis for several hours. Full article

The development of self-healing coatings represents a promising approach to enhance the durability of metal substrates exposed to corrosive environments, demanding thorough in situ investigations. In this study, poly(urea–formaldehyde–melamine) (PUF) microcapsules containing linseed oil (LO) were synthesized via in situ polymerization to act as healing agents in protective coatings. The microcapsules were characterized using scanning electron microscopy (SEM), optical microscopy (OM), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The capsules exhibited a regular spherical morphology with an average diameter of 96 µm and an LO encapsulation efficiency of 81 wt%. TGA confirmed their thermal stability up to 200 °C, while FTIR verified the successful encapsulation of LO. For performance evaluation, 10 wt% of the microcapsules was incorporated into an epoxy matrix and applied to carbon steel. Corrosion resistance was evaluated using electrochemical impedance spectroscopy (EIS) in 0.1 mol/L of NaCl solution over 500 h. The coating with microcapsules exhibited a |Z|_0.01 of 10⁶ Ω·cm², higher than the 10⁴ Ω·cm² observed for the coating without microcapsules, indicating improved barrier properties. Raman spectroscopy confirmed the auto-oxidation of LO at damaged areas, evidencing the self-healing mechanism. Although full barrier recovery was not achieved, the system effectively delayed corrosion progression. Full article

Lithium niobate (LiNbO₃), a multifunctional crystalline material, has critical importance in advancing holographic storage systems. However, persistent challenges such as optical damage, limited diffraction efficiency, and slow response kinetics hinder its practical implementation. This work systematically examines the correlation between the Zn²⁺ dopant concentration and the defect architecture, photodamage resistance, and holographic storage properties of Zn:Cu:Fe:LiNbO₃ crystals, employing advanced characterization techniques to elucidate structure–property relationships and optimize performance metrics. The experimental data reveal a pronounced Zn²⁺ doping concentration dependence in both photodamage resistance and holographic storage capabilities. Notably, Zn:Cu:Fe:LiNbO₃ crystals doped with 7 mol% Zn²⁺ achieve a substantial 416-fold improvement in photodamage resistance (786.55 J/cm²) relative to the 1 mol% doped variant. Concurrently, these optimally doped crystals demonstrate superior holographic storage performance, characterized by a response time of 196.4 s, a dynamic range of 9.81, a diffraction efficiency of 66.7%, and a sensitivity of 1.04. The observed performance enhancement is fundamentally attributed to Zn²⁺ doping, which concomitantly suppresses intrinsic defect formation and tailors the spatial distribution of Fe³⁺/Cu²⁺ photorefractive centers within the crystal lattice. These mechanistic insights establish critical guidelines for the rational design of next-generation holographic storage materials with optimized photorefractive response and defect engineering capabilities. Full article

In this work, we present a new graphene-based sensor designed to monitor a set of photovoltaic panels on a sound-absorbing screen in terms of their potential mechanical damage. The innovative design of the photovoltaic module and consequently its sound-reflecting and sound-absorbing parameters play a vital role. The light transmittance of the sensor layer composed of graphene flakes in a cellulose matrix, confirmed by optical studies, allows its use directly over the photovoltaic cells. All the sensors are interconnected with metallic connections to reduce their internal resistance on larger surfaces. The sensor state is monitored through the resistance value as a zero-one operation/damaged response. Two sensor damage, scenarios, repetitive scratching, and cutting-out were described. The sensor measurements were performed in the potential ranging from 2.1 to 51.1 V, and the current response allowed to calculate the total resistance. The change in sensor resistance ranged between 9.3 and 24.1%, depending on the damaged area. The resistance for the scratched surface oscillated between 25 and 26 Ω, whereas the cut-out surface showed values more than 1.5 times higher. The proposed sensor based on graphene, cellulose, and ethylene–vinyl acetate allows the registration of immediate information about the destruction or theft of a power node. Full article

This review paper explores the properties of graphene-based transparent electrodes for space solar cell applications. The space environment is extreme due to high-energy radiation, high vacuum and alternating temperature, which are responsible for damaging the atomic structure of materials, and so it influences the performance of a device. In this context, using a physical description of graphene, we analyze its electrical and optical properties, like transmittance and sheet resistance, in order to obtain innovative transparent electrodes that can perform in extreme conditions. In this sense, graphene can be a good candidate for this kind of application. Full article

EV motors and machine elements operate at higher speeds, generate significant heat and noise (vibration), and subject lubricants (bearings) to multiple degrading factors, requiring thermal stability, wear protection, mitigating wear mechanisms like pitting and scuffing, and low electrical conductivity to prevent arcing damage to bearings. This study evaluates the tribological performance of four types of greases—PUEs, PUPao, PUEth (polyurea-based), and LiPAO (lithium–calcium complex-based)—to determine their suitability for electric motor bearings. Key performance metrics include tribological properties, electrical resistivity, leakage, bearing noise, and wear behavior. A four-ball wear test ranks the greases by scar diameter as PUPao < PUEs < PUEth < LiPAO, while the coefficient of friction is observed in the range of 0.15–0.18, with LiPAO exhibiting the lowest friction. Electrical resistivity tests reveal that PUEs grease has the lowest resistivity. Electrical leakage tests, conducted with a voltage differential across bearings, assess pitting damage, with PUEth and LiPAO showing evidence of surface pitting. Optical microscopy and scanning electron microscopy analysis is carried out to examine the pitting. In bearing noise tests, PUEs demonstrates the lowest noise levels, whereas LiPAO produces the highest. Visual and microscopic examination of the greases further characterizes their lubricating properties. Based on overall performance, the greases are ranked in suitability for electric motor applications as PUEs > PUPao > PUEth > LiPAO. The findings highlight the critical need for selecting appropriate grease formulations to ensure optimal bearing performance under varying operational conditions. Full article

Metabolic syndrome (MetS)—a cluster of conditions including obesity, hypertension, dyslipidemia, and insulin resistance—is increasingly recognized as a key risk factor for the development of various eye diseases. The metabolic dysfunctions associated with this syndrome contribute to vascular and neurodegenerative damage within the eye, influencing disease onset and progression. Understanding these links highlights the importance of early diagnosis and management of metabolic syndrome to prevent vision loss and improve ocular health outcomes. This review explores the intricate interplay between metabolic syndrome, chronic low-grade inflammation, and eye diseases such as diabetic retinopathy, age-related macular degeneration, glaucoma, and dry eye syndrome. It highlights how inflammatory mediators, oxidative damage, and metabolic dysregulation converge to compromise ocular structures, including the retina, optic nerve, and ocular surface. We discuss the molecular and cellular mechanisms underpinning these associations and examine evidence from clinical and experimental studies. Given the rising global prevalence of metabolic syndrome, addressing this connection is crucial for improving overall patient outcomes and quality of life. Future research should focus on delineating the precise mechanisms linking these diseases as well as exploring targeted interventions that address both metabolic and ocular health. Full article