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Coatings
Volume 15
Issue 7
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Coatings, Volume 15, Issue 7 (July 2025) – 126 articles

Cover Story (view full-size image): Ultraviolet (UV) and visible light contribute significantly to the degradation of many foods by causing detrimental processes such as discoloration, lipid oxidation, generation of off-flavors, and reduced nutritional content. UV radiation, in particular, plays a critical role at the retail level because shelf lighting often emits in the UV-A region. This exposure can ultimately reduce the shelf life of packaged foods. While UV absorbers are commonly used as masterbatch solutions, identifying safer and more effective alternatives remains a priority in the food packaging industry. In this study, we investigate the UV-absorbing capacity of alternative molecules of natural origin incorporated into a biopolymer coating applied to a standard plastic film. View this paper
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19 pages, 3407 KiB  
Article
Surface Property Differences of European Larch Sapwood and Heartwood After Sanding
by Agnieszka Laskowska, Karolina Lipska, Teresa Kłosińska, Anna Piwek and Piotr Boruszewski
Coatings 2025, 15(7), 860; https://doi.org/10.3390/coatings15070860 - 21 Jul 2025
Viewed by 295
Abstract
The sapwood and heartwood of European larch (Larix decidua Mill.) are both used in industrial applications, but they differ in structure and composition, which may lead to surface property differences. This study compared their surface characteristics (on radial and tangential sections) after [...] Read more.
The sapwood and heartwood of European larch (Larix decidua Mill.) are both used in industrial applications, but they differ in structure and composition, which may lead to surface property differences. This study compared their surface characteristics (on radial and tangential sections) after sanding with aluminium oxide papers of four grit sizes (P60, P120, P180, P240). Surface roughness (Ra, Rz), wettability (contact angle with two reference liquids: water and diiodomethane, 3 and 30 s after droplet deposition), surface free energy, and colour parameters (L*, a*, b*) were analysed. Microscopic measurements were also performed to assess anatomical differences between sapwood and heartwood. The results showed no significant differences in roughness (Ra, Rz) between sapwood and heartwood. Measurement direction and sandpaper grit accounted for about 80% of variability in roughness parameters. Wettability was mainly influenced by wood area, with its effect ranging from 55% to 89% depending on measurement time. The sapwood was characterised by the lower wettability on the tangential section, while the heartwood was characterised by the lower wettability on the radial section. This was examined for the contact angle tests performed 3 s after the water droplet had been applied to the wood surface. Such dependencies were not observed after 30 s. Sapwood exhibited higher surface free energy (SFE) values than heartwood. The greatest colour change ΔE, at level 2.59, was noted for the heartwood on the radial section after sanding with P240 sandpaper. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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21 pages, 5914 KiB  
Article
Simple Spin-Coating Preparation of Hydrogel and Nanoparticle-Loaded Hydrogel Thin Films
by Sara Calistri, Chiara Ciantelli, Sebastiano Cataldo, Vincenzo Cuzzola, Roberta Guzzinati, Simone Busi and Alberto Ubaldini
Coatings 2025, 15(7), 859; https://doi.org/10.3390/coatings15070859 - 21 Jul 2025
Viewed by 319
Abstract
Hydrogel films receive significant attention among researchers because they combine increased stimuli responsiveness and faster responses to the already excellent properties of their component materials. However, their preparation is complex and requires that many difficulties are overcome. The present work presents a new [...] Read more.
Hydrogel films receive significant attention among researchers because they combine increased stimuli responsiveness and faster responses to the already excellent properties of their component materials. However, their preparation is complex and requires that many difficulties are overcome. The present work presents a new study regarding the preparation of pure and nanoparticle-loaded alginate-based films by spin-coating. Two-microliter solutions of sodium alginate and calcium chloride with different concentrations were deposited on a glass substrate and subjected to rapid rotations of between 100 and 1000 RPM. Film formation can be achieved by optimizing the ratio between the viscosity of the solutions, depending on their concentrations and the rotation speed. When these conditions are in the right range, a homogeneous film is obtained, showing good adherence to the substrate and uniform thickness. Films containing silver nanoparticles were prepared, exploiting the reaction between sodium borohydride and silver nitrate. The two reagents were added to the sodium alginate and calcium nitrate solution, respectively. Their concentration is the driving force for the formation of a uniform film: particles of about 50 nm that are well-dispersed throughout the film are obtained using AgNO3 at 4 mM and NaBH4 at 2 or 0.2 mM; meanwhile, at higher concentrations, one can also obtain the precipitation of inorganic crystals. Full article
(This article belongs to the Section Thin Films)
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29 pages, 1609 KiB  
Review
Recent Advances in Silver Nanowire-Based Transparent Conductive Films: From Synthesis to Applications
by Ji Li, Jun Luo and Yang Liu
Coatings 2025, 15(7), 858; https://doi.org/10.3390/coatings15070858 - 21 Jul 2025
Viewed by 508
Abstract
Silver nanowire (AgNW)-based transparent conductive films are essential for flexible electronics due to their superior optoelectronic properties and mechanical flexibility. This review examines the characteristics and fabrication methods of AgNW thin films in detail. Among various fabrication techniques, the AgNW thin film produced [...] Read more.
Silver nanowire (AgNW)-based transparent conductive films are essential for flexible electronics due to their superior optoelectronic properties and mechanical flexibility. This review examines the characteristics and fabrication methods of AgNW thin films in detail. Among various fabrication techniques, the AgNW thin film produced by silk-screen printing exhibits the highest quality factor of 568.47, achieving 95.3% visible light transmittance of 95.3% and 13.6 Ω/sq sheet resistance. Ensuring the stability of AgNW films requires the deposition of protective layers through physical or chemical approaches. This review also systematically evaluates the different methods for preparing these protective layers, including their respective advantages and limitations. Furthermore, the review proposes strategies to enhance the conductivity, transparency, and flexibility of AgNW films. Finally, it discusses potential future applications and challenges, offering valuable insights for the development of next-generation flexible transparent electrodes. Full article
(This article belongs to the Special Issue Advanced Thin Films Technologies for Optics, Electronics, and Sensing)
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14 pages, 7306 KiB  
Article
Influence of Gear Set Loading on Surface Damage Forms for Gear Teeth with DLC Coating
by Edyta Osuch-Słomka, Remigiusz Michalczewski, Anita Mańkowska-Snopczyńska, Michał Gibała, Andrzej N. Wieczorek and Emilia Skołek
Coatings 2025, 15(7), 857; https://doi.org/10.3390/coatings15070857 - 21 Jul 2025
Viewed by 239
Abstract
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 [...] Read more.
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 article belongs to the Special Issue Fatigue and Wear Mechanisms of Different Surface Coatings for Industrial Application)
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13 pages, 2686 KiB  
Article
Synergistic Energy Level Alignment and Light-Trapping Engineering for Optimized Perovskite Solar Cells
by Li Liu, Wenfeng Liu, Qiyu Liu, Yongheng Chen, Xing Yang, Yong Zhang and Zao Yi
Coatings 2025, 15(7), 856; https://doi.org/10.3390/coatings15070856 - 20 Jul 2025
Viewed by 324
Abstract
Perovskite solar cells (PSCs) leverage the exceptional photoelectric properties of perovskite materials, yet interfacial energy level mismatches limit carrier extraction efficiency. In this work, energy level alignment was exploited to reduce the charge transport barrier, which can be conducive to the transmission of [...] Read more.
Perovskite solar cells (PSCs) leverage the exceptional photoelectric properties of perovskite materials, yet interfacial energy level mismatches limit carrier extraction efficiency. In this work, energy level alignment was exploited to reduce the charge transport barrier, which can be conducive to the transmission of photo-generated carriers and reduce the probability of electron–hole recombination. We designed a dual-transition perovskite solar cell (PSC) with the structure of FTO/TiO2/Nb2O5/CH3NH3PbI3/MoO3/Spiro-OMeTAD/Au by finite element analysis methods. Compared with the pristine device (FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au), the open-circuit voltage of the optimized cell increases from 0.98 V to 1.06 V. Furthermore, the design of a circular platform light-trapping structure makes up for the light loss caused by the transition at the interface. The short-circuit current density of the optimized device increases from 19.81 mA/cm2 to 20.36 mA/cm2, and the champion device’s power conversion efficiency (PCE) reaches 17.83%, which is an 18.47% improvement over the planar device. This model provides new insight for the optimization of perovskite devices. Full article
(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)
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40 pages, 16352 KiB  
Review
Surface Protection Technologies for Earthen Sites in the 21st Century: Hotspots, Evolution, and Future Trends in Digitalization, Intelligence, and Sustainability
by Yingzhi Xiao, Yi Chen, Yuhao Huang and Yu Yan
Coatings 2025, 15(7), 855; https://doi.org/10.3390/coatings15070855 - 20 Jul 2025
Viewed by 637
Abstract
As vital material carriers of human civilization, earthen sites are experiencing continuous surface deterioration under the combined effects of weathering and anthropogenic damage. Traditional surface conservation techniques, due to their poor compatibility and limited reversibility, struggle to address the compound challenges of micro-scale [...] Read more.
As vital material carriers of human civilization, earthen sites are experiencing continuous surface deterioration under the combined effects of weathering and anthropogenic damage. Traditional surface conservation techniques, due to their poor compatibility and limited reversibility, struggle to address the compound challenges of micro-scale degradation and macro-scale deformation. With the deep integration of digital twin technology, spatial information technologies, intelligent systems, and sustainable concepts, earthen site surface conservation technologies are transitioning from single-point applications to multidimensional integration. However, challenges remain in terms of the insufficient systematization of technology integration and the absence of a comprehensive interdisciplinary theoretical framework. Based on the dual-core databases of Web of Science and Scopus, this study systematically reviews the technological evolution of surface conservation for earthen sites between 2000 and 2025. CiteSpace 6.2 R4 and VOSviewer 1.6 were used for bibliometric visualization analysis, which was innovatively combined with manual close reading of the key literature and GPT-assisted semantic mining (error rate < 5%) to efficiently identify core research themes and infer deeper trends. The results reveal the following: (1) technological evolution follows a three-stage trajectory—from early point-based monitoring technologies, such as remote sensing (RS) and the Global Positioning System (GPS), to spatial modeling technologies, such as light detection and ranging (LiDAR) and geographic information systems (GIS), and, finally, to today’s integrated intelligent monitoring systems based on multi-source fusion; (2) the key surface technology system comprises GIS-based spatial data management, high-precision modeling via LiDAR, 3D reconstruction using oblique photogrammetry, and building information modeling (BIM) for structural protection, while cutting-edge areas focus on digital twin (DT) and the Internet of Things (IoT) for intelligent monitoring, augmented reality (AR) for immersive visualization, and blockchain technologies for digital authentication; (3) future research is expected to integrate big data and cloud computing to enable multidimensional prediction of surface deterioration, while virtual reality (VR) will overcome spatial–temporal limitations and push conservation paradigms toward automation, intelligence, and sustainability. This study, grounded in the technological evolution of surface protection for earthen sites, constructs a triadic framework of “intelligent monitoring–technological integration–collaborative application,” revealing the integration needs between DT and VR for surface technologies. It provides methodological support for addressing current technical bottlenecks and lays the foundation for dynamic surface protection, solution optimization, and interdisciplinary collaboration. Full article
(This article belongs to the Special Issue New Insights into Earthen Site Conservation: Methods, Techniques, Management, and Key Case Studies)
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22 pages, 5401 KiB  
Article
Evaluation of Integral and Surface Hydrophobic Modification on Permeation Resistance of Foam Concrete
by Liangbo Ying, Pengfei Yu, Fuping Wang and Ping Jiang
Coatings 2025, 15(7), 854; https://doi.org/10.3390/coatings15070854 - 20 Jul 2025
Viewed by 304
Abstract
To investigate the impermeability of foam concrete in various challenging environments, this study evaluates its water resistance by measuring the water contact angle and water absorption. Polyurethane (PU) was used to fabricate polyurethane foam concrete (PFC), enabling a monolithic hydrophobic modification to improve [...] Read more.
To investigate the impermeability of foam concrete in various challenging environments, this study evaluates its water resistance by measuring the water contact angle and water absorption. Polyurethane (PU) was used to fabricate polyurethane foam concrete (PFC), enabling a monolithic hydrophobic modification to improve the permeation performance of foam concrete. The study also examines the effects of carbonation and freeze–thaw environments on the permeation resistance of PFC. Graphene oxide (GO), KH-550, and a composite hydrophobic coating (G/S) consisting of GO and KH-550 were employed to enhance the permeation resistance of PFC through surface hydrophobic modification. The functionality of the G/S composite hydrophobic coating was confirmed using energy dispersive X-ray spectrometry (EDS) and Fourier transform infrared spectroscopy (FTIR). The results showed the following: (1) The water contact angle of PFC increased by 20.2° compared to that of ordinary foam concrete, indicating that PU-based hydrophobic modification can significantly improve its impermeability. (2) After carbonation, a micro–nano composite structure resembling the surface of a lotus leaf developed on the surface of PFC, further enhancing its impermeability. However, freeze–thaw cycles led to the formation and widening of microcracks in the PFC, which compromised its hydrophobic properties. (3) Surface hydrophobic modifications using GO, KH-550, and the G/S composite coating improved the anti-permeability properties of PFC, with the G/S composite showing the most significant enhancement. (4) GO filled the tiny voids and pores on the surface of the PFC, thereby improving its anti-permeability properties. KH-550 replaced water on the surface of PFC and encapsulated surface particles, orienting its R-groups outward to enhance hydrophobicity. The G/S composite emulsion coating formed a hydrophobic silane layer inside the concrete, which enhanced water resistance by blocking water penetration, reducing microscopic pores in the hydrophobic layer, and improving impermeability characteristics. Full article
(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)
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17 pages, 3228 KiB  
Article
Research on the Laser Ablation Threshold of the Graphene/Aluminum Foil Interface Surface
by Ying Xu, Yi Lv, Dongcheng Zhou, Yixin Chen and Boyong Su
Coatings 2025, 15(7), 853; https://doi.org/10.3390/coatings15070853 - 20 Jul 2025
Viewed by 313
Abstract
The aim was to investigate the impact of laser parameters on the surface morphology of ablated graphene and elucidate the interaction mechanism between carbon materials and femtosecond lasers. A pulsed laser with a wavelength of 1030 nm is employed to infer the ablation [...] Read more.
The aim was to investigate the impact of laser parameters on the surface morphology of ablated graphene and elucidate the interaction mechanism between carbon materials and femtosecond lasers. A pulsed laser with a wavelength of 1030 nm is employed to infer the ablation threshold of the surface and interface of graphene coatings formed through ultrasonic spraying. The ablation threshold of the coating–substrate interface is verified by numerical simulation. Incorporating the data of groove width and depth obtained from a three-dimensional profilometer and finite element simulation, an in-depth analysis of the threshold conditions of laser ablation in coating materials is accomplished. The results indicate that when the femtosecond laser frequency is 10 kHz, the pulse width is 290 fs, and the energy density reaches 0.057 J/cm2, the graphene material can be effectively removed. When the energy density is elevated to 2.167 J/cm2, a complete ablation of a graphite coating with a thickness of 1.5 μm can be achieved. The findings of this study validate the evolution law and linear relationship of ablation crater morphology, offering new references for microstructure design and the selection of controllable laser processing parameters. Full article
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24 pages, 4099 KiB  
Article
Dynamic Control of Coating Accumulation Model in Non-Stationary Environment Based on Visual Differential Feedback
by Chengzhi Su, Danyang Yu, Wenyu Song, Huilin Tian, Haifeng Bao, Enguo Wang and Mingzhen Li
Coatings 2025, 15(7), 852; https://doi.org/10.3390/coatings15070852 - 19 Jul 2025
Viewed by 282
Abstract
To address the issue of coating accumulation model failure in unstable environments, this paper proposes a dynamic control method based on visual differential feedback. An image difference model is constructed through online image data modeling and real-time reference image feedback, enabling real-time correction [...] Read more.
To address the issue of coating accumulation model failure in unstable environments, this paper proposes a dynamic control method based on visual differential feedback. An image difference model is constructed through online image data modeling and real-time reference image feedback, enabling real-time correction of the coating accumulation model. Firstly, by combining the Arrhenius equation and the Hagen–Poiseuille equation, it is demonstrated that pressure regulation and temperature changes are equivalent under dataset establishment conditions, thereby reducing data collection costs. Secondly, online paint mist image acquisition and processing technology enables real-time modeling, overcoming the limitations of traditional offline methods. This approach reduces modeling time to less than 4 min, enhancing real-time parameter adjustability. Thirdly, an image difference model employing a CNN + MLP structure, combined with feature fusion and optimization strategies, achieved high prediction accuracy: R2 > 0.999, RMSE < 0.79 kPa, and σe < 0.74 kPa on the test set for paint A; and R2 > 0.997, RMSE < 0.67 kPa, and σe < 0.66 kPa on the test set for aviation paint B. The results show that the model can achieve good dynamic regulation for both types of typical aviation paint used in the experiment: high-viscosity polyurethane enamel (paint A, viscosity 22 s at 25 °C) and epoxy polyamide primer (paint B, viscosity 18 s at 25 °C). In summary, the image difference model can achieve dynamic regulation of the coating accumulation model in unstable environments, ensuring the stability of the coating accumulation model. This technology can be widely applied in industrial spraying scenarios with high requirements for coating uniformity and stability, especially in occasions with significant fluctuations in environmental parameters or complex process conditions, and has important engineering application value. Full article
(This article belongs to the Special Issue Thermal Barrier Coatings: Materials, Processes, Properties and Applications)
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20 pages, 7035 KiB  
Article
Microstructure Evolution Mechanism and Corrosion Resistance of FeCrNi(AlTi)x Medium Entropy Alloy Prepared by Laser Melting Deposition with Al and Ti Content Changes
by Kai Wang, Mingjie Liu, Chuan Liu, Xiaohui Li and Guanghui Shao
Coatings 2025, 15(7), 851; https://doi.org/10.3390/coatings15070851 - 19 Jul 2025
Viewed by 300
Abstract
In order to improve the microstructure and corrosion resistance of entropy alloy in the FeCrNi system, laser melting deposition technology was used as a preparation method to study the effects of different contents of Al and Ti on the microstructure and corrosion resistance [...] Read more.
In order to improve the microstructure and corrosion resistance of entropy alloy in the FeCrNi system, laser melting deposition technology was used as a preparation method to study the effects of different contents of Al and Ti on the microstructure and corrosion resistance of entropy alloy in FeCrNi(AlTi)x (x = 0.17, 0.2, and 0.24). The results show that the addition of Al and Ti elements can change the phase structure of the alloy from a single FCC phase structure to an FCC + BCC biphase structure. The BCC phase volume fraction of FeCrNi(AlTi)0.2 is the highest among the three alloys, reaching 37.5%. With the addition of Al and Ti content, the grain of the alloy will be refined to a certain extent. In addition, the dual-phase structure will also improve the corrosion resistance of the alloy. In 3.5 wt.% NaCl solution, the increase of Al and Ti content can effectively improve the protection of the passivation film on the surface of the entropy alloy in FeCrNi(AlTi)x, effectively inhibit the large-scale corrosion phenomenon on the alloy surface, and thus improve the corrosion resistance of the alloy. In a certain range, increasing the content of Al and Ti elements in the FeCrNi(AlTi)x system can improve the corrosion resistance of the alloy. Full article
(This article belongs to the Special Issue Recent Progress in Thin Films and Surfaces: Deposition, Characterization and Various Applications)
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19 pages, 1343 KiB  
Article
Two-Step Plasma Electrolytic Oxidation of Advanced High-Strength Steel in Aluminate and Silicate Solutions
by Roy Morgenstern, Thomas Mehner and Thomas Lampke
Coatings 2025, 15(7), 850; https://doi.org/10.3390/coatings15070850 - 19 Jul 2025
Viewed by 274
Abstract
This work aims to clarify whether the individual advantages of the two commonly used silicate- and aluminate-based electrolytes for the plasma electrolytic oxidation (PEO) of steel can be combined in a two-step process. The first PEO step was carried out in an aluminate–phosphate [...] Read more.
This work aims to clarify whether the individual advantages of the two commonly used silicate- and aluminate-based electrolytes for the plasma electrolytic oxidation (PEO) of steel can be combined in a two-step process. The first PEO step was carried out in an aluminate–phosphate electrolyte with pulsed voltage and anodic amplitudes between 150 V and 200 V. The second PEO step was carried out at an increased anodic voltage amplitude of 400 V in a silicate–phosphate electrolyte. As a reference, PEO was conducted in a single step in the same silicate–phosphate electrolyte at an increased anodic voltage amplitude of up to 400 V. The microstructural layer analysis was carried out using SEM and EDX analyses, Raman spectroscopy and XRD analysis. Heterogeneous layers containing iron oxide and iron phosphate form in the silicate–phosphate electrolyte at anodic voltage amplitudes up to 300 V by electrochemical reactions. Further increasing the anodic voltage amplitude up to 400 V results in heterogeneous layers, too. PEO in the aluminate–phosphate electrolyte at 150 V causes the formation of thin, amorphous layers mainly consisting of aluminum and iron oxides. At 200 V amplitude, a PEO layer with pronounced open porosity is formed, which primarily consists of the crystalline phases corundum and hercynite. During subsequent PEO in the silicate–phosphate electrolyte, the previously formed layers were replaced by a macroscopically homogeneous layer that is mostly nanocrystalline and may contain amorphous iron(-aluminum) phosphates and oxides as well as silicon oxide. It can be concluded that the two-step PEO process is suitable for the production of more homogeneous PEO layers. Full article
(This article belongs to the Special Issue Plasma Coating and Interface Technology: New Horizons in Surface Science)
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24 pages, 3928 KiB  
Article
Performance Degradation and Fatigue Life Prediction of Hot Recycled Asphalt Mixture Under the Coupling Effect of Ultraviolet Radiation and Freeze–Thaw Cycle
by Tangxin Xie, Zhongming He, Yuetan Ma, Huanan Yu, Zhichen Wang, Chao Huang, Feiyu Yang and Pengxu Wang
Coatings 2025, 15(7), 849; https://doi.org/10.3390/coatings15070849 - 19 Jul 2025
Viewed by 401
Abstract
In actual service, asphalt pavement is subjected to freeze–thaw cycles and ultraviolet radiation (UV) over the long term, which can easily lead to mixture aging, enhanced brittleness, and structural damage, thereby reducing pavement durability. This study focuses on the influence of freeze–thaw cycles [...] Read more.
In actual service, asphalt pavement is subjected to freeze–thaw cycles and ultraviolet radiation (UV) over the long term, which can easily lead to mixture aging, enhanced brittleness, and structural damage, thereby reducing pavement durability. This study focuses on the influence of freeze–thaw cycles and ultraviolet aging on the performance of recycled asphalt mixtures. Systematic indoor road performance tests were carried out, and a fatigue prediction model was established to explore the comprehensive effects of recycled asphalt pavement (RAP) content, environmental action (ultraviolet radiation + freeze–thaw cycle), and other factors on the performance of recycled asphalt mixtures. The results show that the high-temperature stability of recycled asphalt mixtures decreases with the increase in environmental action days, while higher RAP content contributes to better high-temperature stability. The higher the proportion of old materials, the more significant the environmental impact on the mixture; both the flexural tensile strain and flexural tensile strength decrease with the increase in environmental action time. When the RAP content increased from 30% to 50%, the bending strain continued to decline. With the extension of environmental action days, the decrease in the immersion Marshall residual stability and the freeze–thaw splitting strength became more pronounced. Although the increase in RAP content can improve the forming stability, the residual stability decreases, and the freeze–thaw splitting strength is lower than that before the freeze–thaw. Based on the fatigue test results, a fatigue life prediction model with RAP content and freeze–thaw cycles as independent variables was constructed using the multiple nonlinear regression method. Verification shows that the established prediction model is basically consistent with the change trend of the test data. The research results provide a theoretical basis and optimization strategy for the performance improvement and engineering application of recycled asphalt materials. Full article
(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)
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15 pages, 3200 KiB  
Article
Stress Compensation in TiO2/SiO2 Optical Coatings by Manipulating the Thickness Modulation Ratio
by Bo Wang, Taiqi Wu, Weidong Gao, Gang Hu and Changjun Wang
Coatings 2025, 15(7), 848; https://doi.org/10.3390/coatings15070848 - 19 Jul 2025
Viewed by 292
Abstract
With the rapid advancement of high-precision optical systems, increasingly stringent demands are imposed on the surface figure accuracy of optical components. The magnitude of residual stress in multilayer films directly influences the post-coating surface figure stability of these components, making the control of [...] Read more.
With the rapid advancement of high-precision optical systems, increasingly stringent demands are imposed on the surface figure accuracy of optical components. The magnitude of residual stress in multilayer films directly influences the post-coating surface figure stability of these components, making the control of multilayer film stress a critical factor in enhancing optical surface figure accuracy. In this study, which addresses the process constraints and substrate damage risks associated with conventional annealing-based stress compensation for large-aperture optical components, we introduce an active stress engineering strategy rooted in in situ deposition process optimization. By systematically tailoring film deposition parameters and adjusting the thickness modulation ratio of TiO2 and SiO2, we achieve dynamic compensation of residual stress in multilayer structures. This approach demonstrates broad applicability across diverse optical coatings, where it effectively mitigates stress-induced surface distortions. Unlike annealing methods, this intrinsic stress polarity manipulation strategy obviates the need for high-temperature post-processing, eliminating risks of material decomposition or substrate degradation. By enabling precise nanoscale stress regulation in large-aperture films through controlled process parameters, it provides essential technical support for manufacturing ultra-precision optical devices, such as next-generation laser systems and space-based stress wave detection instruments, where minimal stress-induced deformation is paramount to functional performance. Full article
(This article belongs to the Section Thin Films)
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20 pages, 4241 KiB  
Article
Strontium-Doped Ti3C2Tx MXene Coatings on Titanium Surfaces: Synergistic Osteogenesis Enhancement and Antibacterial Activity Evaluation
by Yancheng Lai and Anchun Mo
Coatings 2025, 15(7), 847; https://doi.org/10.3390/coatings15070847 - 19 Jul 2025
Viewed by 332
Abstract
To improve implant osseointegration while preventing infection, we developed a strontium (Sr)-doped Ti3C2Tx MXene coating on titanium, aiming to synergistically enhance bone integration and antibacterial performance. MXene is a family of two-dimensional transition-metal carbides/nitrides whose abundant surface terminations [...] Read more.
To improve implant osseointegration while preventing infection, we developed a strontium (Sr)-doped Ti3C2Tx MXene coating on titanium, aiming to synergistically enhance bone integration and antibacterial performance. MXene is a family of two-dimensional transition-metal carbides/nitrides whose abundant surface terminations endow high hydrophilicity and bioactivity. The coating was fabricated via anodic electrophoretic deposition (40 V, 2 min) of Ti3C2Tx nanosheets, followed by SrCl2 immersion to incorporate Sr2+. The coating morphology, phase composition, chemistry, hydrophilicity, mechanical stability, and Sr2+ release were characterized. In vitro bioactivity was assessed with rat bone marrow mesenchymal stem cells (BMSCs)—with respect to viability, proliferation, migration, alkaline phosphatase (ALP) staining, and Alizarin Red S mineralization—while the antibacterial efficacy was evaluated against Staphylococcus aureus (S. aureus) via live/dead staining, colony-forming-unit enumeration, and AlamarBlue assays. The Sr-doped MXene coating formed a uniform lamellar structure, lowered the water-contact angle to ~69°, and sustained Sr2+ release (0.36–1.37 ppm). Compared to undoped MXene, MXene/Sr enhanced BMSC proliferation on day 5, migration by 51%, ALP activity and mineralization by 47%, and reduced S. aureus viability by 49% within 24 h. Greater BMSCs activity accelerates early bone integration, whereas rapid bacterial suppression mitigates peri-implant infection—two critical requirements for implant success. Sr-doped Ti3C2Tx MXene thus offers a simple, dual-function surface-engineering strategy for dental and orthopedic implants. Full article
(This article belongs to the Section Surface Coatings for Biomedicine and Bioengineering)
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14 pages, 5535 KiB  
Article
Studies on the Coating Formation and Structure Property for Plasma Electrolytic Oxidation of AZ31 Magnesium Alloy
by Yingting Ye, Lishi Wang, Xinbin Hu and Zhixiang Bu
Coatings 2025, 15(7), 846; https://doi.org/10.3390/coatings15070846 - 19 Jul 2025
Viewed by 302
Abstract
Plasma electrolytic oxidation (PEO) is an advanced electrochemical surface treatment technology. It can effectively improve the corrosion resistance of magnesium and its alloys. This paper aims to form protective PEO coatings on an AZ31 substrate with different electrolytes, while monitoring the micro-discharge evolution [...] Read more.
Plasma electrolytic oxidation (PEO) is an advanced electrochemical surface treatment technology. It can effectively improve the corrosion resistance of magnesium and its alloys. This paper aims to form protective PEO coatings on an AZ31 substrate with different electrolytes, while monitoring the micro-discharge evolution by noise intensity and morphology analysis. By setting the PEO parameters and monitoring process characteristics, such as current density, spark appearance, and noise intensity, it was deduced that the PEO process consists of the following three stages: anodic oxidation, spark discharge, and micro-arc discharge. The PEO oxide coating formed on the AZ31 alloy exhibits various irregular volcano-like structures. Oxygen species are uniformly distributed along the coating cross-section. Phosphorus species tend to be enriched inwards to the coating/magnesium substrate interface, while aluminum piles up towards the surface region. Surface roughness of the PEO coating formed in the silicate-based electrolyte was the lowest in an arithmetic average height (Sa) of 0.76 μm. Electrochemical analysis indicated that the corrosion current density of the PEO coating decreased by about two orders of magnitude compared to that of untreated blank AZ31 substrate, while, at the same time, the open-circuit potential shifted significantly to the positive direction. The corrosion current density of the 10 min/400 V coating was 1.415 × 10−6 A/cm2, approximately 17% lower than that of the 2 min/400 V coating (1.738 × 10−6 A/cm2). For a fixed 10 min treatment, the longer the PEO duration time, the lower the corrosion current density. Finally, the tested potentiodynamic polarization curve reveals the impact of different types of PEO electrolytes and different durations of PEO treatment on the corrosion resistance of the oxide coating surface. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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13 pages, 3980 KiB  
Article
Research on the Synergistic Evolution Law of Microstructure and Properties of Deformed Austenitic Stainless Steel
by Huimin Tao, Yafang Cai, Zi Li, Haiteng Xiu, Zeqi Tong and Mingming Ding
Coatings 2025, 15(7), 845; https://doi.org/10.3390/coatings15070845 - 18 Jul 2025
Viewed by 193
Abstract
Austenitic stainless steel inevitably undergoes deformation during application, and it is necessary to study the properties of deformed steel. This article investigates the evolution of microstructure, mechanical properties, and corrosion resistance of plastic-deformed 304 steel, the evolution law of structure and properties of [...] Read more.
Austenitic stainless steel inevitably undergoes deformation during application, and it is necessary to study the properties of deformed steel. This article investigates the evolution of microstructure, mechanical properties, and corrosion resistance of plastic-deformed 304 steel, the evolution law of structure and properties of steel is revealed. As a result, it was found that with the increase in deformation, the grains of 304 steel were destroyed, and many small subgrains were generated internally, resulting in a significant decrease in grain size. At the same time, the content of martensitic transformation in stainless steel increased significantly. The characteristics of the surface passivation film of stainless steel also change during the deformation process. Meanwhile, with the increase in deformation, the nanohardness and wear resistance of 304 steel gradually increase, but its corrosion resistance gradually decreases. Analysis suggests that microstructural changes such as grain size and phase transformation in stainless steel lead to an improvement in its mechanical properties, while the generation of defects during deformation and changes in surface passivation film characteristics result in a deterioration of its corrosion resistance. This study can provide a reference for the forming and performance optimization of metals and has high theoretical significance and practical value. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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19 pages, 4571 KiB  
Article
Modified Asphalt Prepared by Coating Rubber Powder with Waste Cooking Oil: Performance Evaluation and Mechanism Analysis
by Jianwei Zhang, Meizhu Chen, Yuan Yan, Muyan Han and Yuechao Zhao
Coatings 2025, 15(7), 844; https://doi.org/10.3390/coatings15070844 - 18 Jul 2025
Viewed by 302
Abstract
Waste cooking oil (WCO) plays different roles in modified asphalt and significantly affects the performance of the binder. However, a systematic comparative study is still lacking in the existing research. This study investigates the effects of WCO used as a swelling agent for [...] Read more.
Waste cooking oil (WCO) plays different roles in modified asphalt and significantly affects the performance of the binder. However, a systematic comparative study is still lacking in the existing research. This study investigates the effects of WCO used as a swelling agent for rubber powder (RP) and as a compatibilizer in rubber powder-modified asphalt (RPMA) on the performance of modified asphalt. Specifically, the microstructure and functional groups of WCO-coated RP were first characterized. Then, RPMAs with different RP dosages were prepared, and the storage stability and rheological properties of RPMAs were thoroughly investigated. Finally, the flue gas emission characteristics of different RPMAs at 30% RP dosing were further analyzed, and the corresponding inhibition mechanisms were proposed. The results showed that the RP coated by WCO was fully solubilized internally, and the WCO formed a uniform and continuous coating film on the RP surface. Comparative analysis revealed that when WCO was used as a swelling agent, the prepared S-RPMA exhibited superior storage stability. At a 30% RP content, the softening point difference value of S-RPMA was only 1.8 °C, and the reduction rate of the segregation index reached 40.91%. Surprisingly, after WCO was used to coat the RP, the average concentrations of VOCs and H2S in S-RPMA30 were reduced to 146.7 mg/m3 and 10.6 ppm, respectively, representing decreases of 20.8% and 22.1% compared with the original RPMA30. These findings demonstrate that using WCO as a swelling agent enhances both the physical stability and environmental performance of RPMA, offering valuable insights for the rational application and optimization of WCO incorporation methods in asphalt modification. It also makes meaningful contributions to the fields of coating science and sustainable materials engineering. Full article
(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)
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22 pages, 12507 KiB  
Article
Research on the Friction Prediction Method of Micro-Textured Cemented Carbide–Titanium Alloy Based on the Noise Signal
by Hao Zhang, Xin Tong and Baiyi Wang
Coatings 2025, 15(7), 843; https://doi.org/10.3390/coatings15070843 - 18 Jul 2025
Viewed by 402
Abstract
The vibration and noise of friction pairs are severe when cutting titanium alloy with cemented carbide tools, and the surface micro-texture can significantly reduce noise and friction. Therefore, it is very important to clarify the correlation mechanism between friction noise and friction force [...] Read more.
The vibration and noise of friction pairs are severe when cutting titanium alloy with cemented carbide tools, and the surface micro-texture can significantly reduce noise and friction. Therefore, it is very important to clarify the correlation mechanism between friction noise and friction force for processing quality control. Consequently, investigating the underlying mechanisms that link friction noise and friction is of considerable importance. This study focuses on the friction and wear acoustic signals generated by micro-textured cemented carbide–titanium alloy. A friction testing platform specifically designed for the micro-textured cemented carbide grinding of titanium alloy has been established. Acoustic sensors are employed to capture the acoustic signals, while ultra-depth-of-field microscopy and scanning electron microscopy are utilized for surface analysis. A novel approach utilizing the dung beetle algorithm (DBO) is proposed to optimize the parameters of variational mode decomposition (VMD), which is subsequently combined with wavelet packet threshold denoising (WPT) to enhance the quality of the original signal. Continuous wavelet transform (CWT) is applied for time–frequency analysis, facilitating a discussion on the underlying mechanisms of micro-texture. Additionally, features are extracted from the time domain, frequency domain, wavelet packet, and entropy. The Relief-F algorithm is employed to identify 19 significant features, leading to the development of a hybrid model that integrates Bayesian optimization (BO) and Transformer-LSTM for predicting friction. Experimental results indicate that the model achieves an R2 value of 0.9835, a root mean square error (RMSE) of 0.2271, a mean absolute error (MAE) of 0.1880, and a mean bias error (MBE) of 0.1410 on the test dataset. The predictive performance and stability of this model are markedly superior to those of the BO-LSTM, LSTM–Attention, and CNN–LSTM–Attention models. This research presents a robust methodology for predicting friction in the context of friction and wear of cemented carbide–titanium alloys. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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17 pages, 4636 KiB  
Article
Chip Flow Direction Modeling and Chip Morphology Analysis of Ball-End Milling Cutters
by Shiqiang Zhou, Anshan Zhang, Xiaosong Zhang, Maiqi Han and Bowen Liu
Coatings 2025, 15(7), 842; https://doi.org/10.3390/coatings15070842 - 18 Jul 2025
Viewed by 281
Abstract
Ball-end milling cutters are normally used for complex surface machining. During the milling process, the tool posture and cutting parameters of the ball-end milling cutters have a significant impact on chip formations and morphological changes. Based on the Cutter Workpiece Engagement (CWE) model, [...] Read more.
Ball-end milling cutters are normally used for complex surface machining. During the milling process, the tool posture and cutting parameters of the ball-end milling cutters have a significant impact on chip formations and morphological changes. Based on the Cutter Workpiece Engagement (CWE) model, this study establishes a chip flow model for ball-end milling cutters with consideration of the tool posture variation. The machining experiments of Ti-6Al-4V with a 15° inclined plane and different feed directions were carried out. The influence mechanism of time-varying tool posture on chip formation was systematically investigated. The results reveal an interaction between the chip flow direction and the cutting velocity direction. The included angle between the chip flow directions at the maximum and minimum contact points in the CWE area affects the degree of chip curling, with a smaller angle leading to weaker curling. This research provides a theoretical foundation for the optimization of posture parameters of ball-end milling cutters and expounds on the influence of the chip flow angle on chip deformation. Full article
(This article belongs to the Special Issue Cutting Performance of Coated Tools)
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29 pages, 7122 KiB  
Article
Experimental Study on Two Types of Novel Prefabricated Counterfort Retaining Wall: Performance Characteristics and Earth Pressure Reduction Effect of Geogrids
by Ao Luo, Yutao Feng, Detan Liu, Junjie Wang, Shi Wang, Huikun Ling and Shiyuan Huang
Coatings 2025, 15(7), 841; https://doi.org/10.3390/coatings15070841 - 18 Jul 2025
Viewed by 279
Abstract
Conventional cast-in-place counterfort retaining walls, while widely used to support the fill body in geotechnical engineering cases, suffer from extended construction cycles and environmental impacts that constrain their usage more widely. In this study, in order to overcome these limitations, the performance of [...] Read more.
Conventional cast-in-place counterfort retaining walls, while widely used to support the fill body in geotechnical engineering cases, suffer from extended construction cycles and environmental impacts that constrain their usage more widely. In this study, in order to overcome these limitations, the performance of two types of innovative prefabricated counterfort retaining wall system—a monolithic design and a modular design—was investigated through physical modeling. The results reveal that failure mechanisms are fundamentally governed by the distribution of stress at the connection interfaces. The monolithic system, with fewer connections, concentrates stress and is more vulnerable to cracking at the primary joints. In contrast, the modular system disperses loads across numerous connections, reducing localized stress. Critically, this analysis identified a construction-dependent failure mode: incomplete contact between the foundation and the base slab induces severe bending moments that can lead to catastrophic failure. Furthermore, this study shows that complex stress states due to backfill failure can induce detrimental tensile forces on the wall structure. To address this, a composite soil material–wall structure system incorporating geogrid reinforcement was developed. This system significantly enhances the backfill’s bearing capacity and mitigates adverse loading. Based on the comprehensive analysis of settlement and structural performance, the optimal configuration involves concentrating geogrid layers in the upper third of section of the backfill, with sparser distribution below. Full article
(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)
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25 pages, 2929 KiB  
Article
Modified Water-Dispersion Compositions Based on Synthesized Dispersions and Hollow Glass Microspheres with Improved Protective Characteristics
by Meiram M. Begentayev, Erzhan I. Kuldeyev, Ruslan E. Nurlybayev, Zaure N. Altayeva, Yelzhan S. Orynbekov, Axaya S. Yestemessova, Aktota A. Murzagulova, Alinur A. Iskakov, Aidos A. Joldassov and Zhanar O. Zhumadilova
Coatings 2025, 15(7), 840; https://doi.org/10.3390/coatings15070840 - 18 Jul 2025
Viewed by 351
Abstract
During the operation of structures, the components and materials from which they are made are exposed to various environmental, technological, and operational impacts. In this context, the use of a modified water-dispersion composition containing finely dispersed fillers with enhanced protective and performance characteristics [...] Read more.
During the operation of structures, the components and materials from which they are made are exposed to various environmental, technological, and operational impacts. In this context, the use of a modified water-dispersion composition containing finely dispersed fillers with enhanced protective and performance characteristics proves to be effective. This article examines the development of a paint-and-coating composition using hollow glass microspheres and modified diatomite as finely dispersed fillers. The influence of technological factors on the properties of coating materials based on a synthesized acrylic dispersion and fillers—such as modified diatomite and hollow glass microspheres ranging from 20 to 100 μm in size with a bulk density of 0.107–0.252 g/cm3—is analyzed. The optimal formulation of the coating materials was determined to ensure the required coating quality. Experimental results demonstrate the improved strength and hardness of the coating due to the use of acrylic dispersion obtained through an emulsifier-free method and modifiers in the form of finely dispersed fillers. It has been established that the resulting samples also exhibit high adhesion to mineral and metallic substrates, along with excellent corrosion resistance. Moreover, the incorporation of acrylic dispersion contributes to increased elasticity of the coating, resulting in improved resistance to washing and abrasion. The developed protective material can be applied to a variety of surfaces, including walls, ceilings, and roofs of buildings and structures, pipelines, and many other applications. Thus, modified water-dispersion compositions based on synthesized acrylic dispersion showed the following results: resistance to sticking—5, which is the best; chemical resistance and gloss level with standard single-phase acrylic dispersion—no destruction or change in gloss. The adhesion of coatings cured under natural conditions and under the influence of UV radiation was 1 point. The developed formulations for obtaining water-dispersion paint and varnish compositions based on synthesized polymer dispersions, activated diatomite, and hollow glass microspheres, meet all the regulatory requirements for paint and varnish materials in terms of performance, and in terms of economic indicators, the cost of 1 kg of paint is 30% lower than the standard. Full article
(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)
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11 pages, 4974 KiB  
Article
Effect of Modulation Period on the Microstructure and Tribological Properties of AlCrTiVNbN/TiSiN Nano Multilayer Films
by Hongjuan Yan, Haoran Wang, Xiaona Li, Zhaoliang Dou and Fengbin Liu
Coatings 2025, 15(7), 839; https://doi.org/10.3390/coatings15070839 - 17 Jul 2025
Viewed by 252
Abstract
The impact of modulation periods on the microstructure, as well as the tribological and mechanical characteristics of the AlCrTiVNbN/TiSiN nano multilayer films, was investigated. The films were prepared with modulation periods ranging from 4 nm to 7 nm, and their properties were explored [...] Read more.
The impact of modulation periods on the microstructure, as well as the tribological and mechanical characteristics of the AlCrTiVNbN/TiSiN nano multilayer films, was investigated. The films were prepared with modulation periods ranging from 4 nm to 7 nm, and their properties were explored using X-ray diffraction (XRD), scanning electron microscope (SEM), nanoindentation, and a tribological tester. All nano multilayer films revealed a face-centered cubic (FCC) structure with a preferred planar direction of (200). As the modulation period increased, the XRD peak moved to higher angles, and the interplanar distance decreased. Also, the mechanical properties deteriorated, and the COF rose monotonically as a result. The nano multilayer film with a modulation period equal to 4 nm exhibited a smooth surface with minimal small particles, the highest hardness of 15.51 ± 0.16 GPa and elastic modulus of 182.89 ± 2.38 GPa, the highest values for the ratios of H/E and H3/E2, the lowest average friction coefficient of 0.73, and a wear rate equal to (8.2 9 ± 0.18) × 10−8 mm3·N−1·m−1. The improvement in the properties of the film was ascribed to the coherent growth and alternating stress field between the AlCrTiVNbN and TiSiN layers. Full article
(This article belongs to the Special Issue Surface Protection for Metal Materials)
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15 pages, 4734 KiB  
Article
Research on the Terahertz Modulation Performance of VO2 Thin Films with Surface Plasmon Polaritons Structure
by Tao Chen, Qi Zhang, Jin Wang, Jiran Liang and Weibin Zhou
Coatings 2025, 15(7), 838; https://doi.org/10.3390/coatings15070838 - 17 Jul 2025
Viewed by 278
Abstract
This paper focuses on the switching and modulation techniques of terahertz waves, develops VO2 thin-film materials with an SPP structure, and uses terahertz time-domain spectroscopy (THz-TDS) to study the semiconductor–metal phase transition characteristics of VO2 thin films, especially the photoinduced semiconductor–metal [...] Read more.
This paper focuses on the switching and modulation techniques of terahertz waves, develops VO2 thin-film materials with an SPP structure, and uses terahertz time-domain spectroscopy (THz-TDS) to study the semiconductor–metal phase transition characteristics of VO2 thin films, especially the photoinduced semiconductor–metal phase transition characteristics of silicon-based VO2 thin films. The optical modulation characteristics of silicon-based VO2 thin films to terahertz waves under different light excitation modes, such as continuous light irradiation at different wavelengths and femtosecond pulsed laser irradiation, were analyzed. Combining the optical modulation characteristics of silicon-based VO2 thin films with the filtering characteristics of SPP structures, composite structures of VO2 thin films with metal hole arrays, composite structures of VO2 thin films with metal block arrays, and silicon-based VO2 microstructure arrays were designed. The characteristics of this dual-function device were tested experimentally. The experiment proves that the VO2 film material with an SPP structure has a transmission rate dropping sharply from 32% to 1% under light excitation; the resistivity changes by more than six orders of magnitude, and the modulation effect is remarkable. By applying the SPP structure to the VO2 material, the material can simultaneously possess modulation and filtering functions, enhancing its optical performance in the terahertz band. Full article
(This article belongs to the Section Thin Films)
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15 pages, 4160 KiB  
Article
Investigation of the Structure and Electrochemical Performance of Perovskite Oxide La1−xCaxCrO3 Utilized as Electrode Materials for Supercapacitors
by Xu Guo, Xin Sun, Lei Wang, Yanxin Qiao and Songtao Dong
Coatings 2025, 15(7), 837; https://doi.org/10.3390/coatings15070837 - 17 Jul 2025
Viewed by 502
Abstract
Lanthanide perovskite materials are promising candidates for supercapacitor applications. In this study, a series of La1−xCaxCrO3 (x = 0–0.2) materials were prepared by sol-gel method, incorporating bivalent ions calcium at A-site. La0.85Ca0.15CrO3 exhibited [...] Read more.
Lanthanide perovskite materials are promising candidates for supercapacitor applications. In this study, a series of La1−xCaxCrO3 (x = 0–0.2) materials were prepared by sol-gel method, incorporating bivalent ions calcium at A-site. La0.85Ca0.15CrO3 exhibited the lowest charge transfer resistance and highest specific surface area. At 1 A/g, La0.85Ca0.15CrO3 achieved a maximum specific capacitance of 306 F/g, about 2.3 times higher than that of the LaCrO3 (133 F/g). Based on the observed data, a mechanism involving oxygen anion charge storage during the charging-discharging process is proposed. After 5000 long cycle, the coulomb efficiency of the electrode remains above 94%. These results demonstrate that Ca-substituted compounds exhibit significant potential for A-site engineering in supercapacitor applications. Full article
(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)
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33 pages, 4942 KiB  
Review
A Review of Crack Sealing Technologies for Asphalt Pavement: Materials, Failure Mechanisms, and Detection Methods
by Weihao Min, Peng Lu, Song Liu and Hongchang Wang
Coatings 2025, 15(7), 836; https://doi.org/10.3390/coatings15070836 - 17 Jul 2025
Viewed by 410
Abstract
Asphalt pavement cracking represents a prevalent form of deterioration that significantly compromises road performance and safety under the combined effects of environmental factors and traffic loading. Crack sealing has emerged as a widely adopted and cost-effective preventive maintenance strategy that restores the pavement’s [...] Read more.
Asphalt pavement cracking represents a prevalent form of deterioration that significantly compromises road performance and safety under the combined effects of environmental factors and traffic loading. Crack sealing has emerged as a widely adopted and cost-effective preventive maintenance strategy that restores the pavement’s structural integrity and extends service life. This paper presents a systematic review of the development of crack sealing technology, conducts a comparative analysis of conventional sealing materials (including emulsified asphalt, hot-applied asphalt, polymer-modified asphalt, and rubber-modified asphalt), and examines the existing performance evaluation methodologies. Critical failure mechanisms are thoroughly investigated, including interfacial bond failure resulting from construction defects, material aging and degradation, hydrodynamic scouring effects, and thermal cycling impacts. Additionally, this review examines advanced sensing methodologies for detecting premature sealant failure, encompassing both non-destructive testing techniques and active sensing technologies utilizing intelligent crack sealing materials with embedded monitoring capabilities. Based on current research gaps, this paper identifies future research directions to guide the development of intelligent and sustainable asphalt pavement crack repair technologies. The proposed research framework provides valuable insights for researchers and practitioners seeking to improve the long-term effectiveness of pavement maintenance strategies. Full article
(This article belongs to the Special Issue Development and Characterization of New Construction Materials and Coatings)
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11 pages, 9979 KiB  
Article
The Microstructure Evolution of a Ni-Based Superalloy Turbine Blade at Elevated Temperature
by Xuyang Wang, Yanna Cui, Yang Zhou, Ze Li, Yuzhu Zhao and Jun Wang
Coatings 2025, 15(7), 835; https://doi.org/10.3390/coatings15070835 - 17 Jul 2025
Viewed by 266
Abstract
GTD 111 has been employed in first-stage blades in different gas turbines. The study of microstructural evolution is essential for the lifetime assessment and development of turbine blades. The microstructural stability of a 130 MW gas turbine first-stage blade at 800 °C was [...] Read more.
GTD 111 has been employed in first-stage blades in different gas turbines. The study of microstructural evolution is essential for the lifetime assessment and development of turbine blades. The microstructural stability of a 130 MW gas turbine first-stage blade at 800 °C was studied. The microstructure’s evolution was analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermodynamic calculation. As thermal exposure time increases, the shape of γ′ precipitates changes from square to spherical. During thermal exposure, MC particles formed and coarsened along the grain boundaries, and primary MC carbide decomposed into the η phase and M23C6. The stability of MC carbide at the grain boundaries was lower than that within the grains. MC carbide precipitated at the grain boundaries tends to grow along the boundaries and eventually forms elongated carbide. High-resolution transmission electron microscopy (HRTEM) images indicate that the orientation of the γ′ precipitate changes during the coarsening process. The GTD 111 alloy can be deformed through dislocation shearing at 800 °C. The hardness value initially increases, then decreases with further exposure, which is related to the reduced precipitation strengthening by γ′ precipitates and the reduction in the hardness of the γ matrix. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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18 pages, 3307 KiB  
Article
Temperature-Related Containment Analysis and Optimal Design of Aluminum Honeycomb Sandwich Aero-Engine Casings
by Shuyi Yang, Ningke Tong and Jianhua Zuo
Coatings 2025, 15(7), 834; https://doi.org/10.3390/coatings15070834 - 17 Jul 2025
Viewed by 261
Abstract
Aero-engine casings with excellent impact resistance are a practical requirement for ensuring the safe operation of aero-engines. In this paper, we report on numerical simulations of broken rotating blades impacting aluminum honeycomb sandwich casings under different temperatures and optimization of structural parameters. Firstly, [...] Read more.
Aero-engine casings with excellent impact resistance are a practical requirement for ensuring the safe operation of aero-engines. In this paper, we report on numerical simulations of broken rotating blades impacting aluminum honeycomb sandwich casings under different temperatures and optimization of structural parameters. Firstly, an impact test system with adjustable temperature was established. Restricted by the temperature range of the strain gauge, ballistic impact tests were carried out at 25 °C, 100 °C, and 200 °C. Secondly, a finite element (FE) model including a pointed bullet and an aluminum honeycomb sandwich plate was built using LS-DYNA. The corresponding simulations of the strain–time curve and damage conditions showed good agreement with the test results. Then, the containment capability of the aluminum honeycomb sandwich aero-engine casing at different temperatures was analyzed based on the kinetic energy loss of the blade, the internal energy increment of the casing, and the containment state of the blade. Finally, with the design objectives of minimizing the casing mass and maximizing the blade kinetic energy loss, the structural parameters of the casing were optimized using the multi-objective genetic algorithm (MOGA). Full article
(This article belongs to the Special Issue Surface Modification, Repairing and Forming of Metallic Materials by Additive Manufacturing)
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20 pages, 24228 KiB  
Article
Surface Treatments on Cobalt–Chromium Alloys for Layering Ceramic Paint Coatings in Dental Prosthetics
by Willi-Andrei Uriciuc, Maria Suciu, Lucian Barbu-Tudoran, Adrian-Ioan Botean, Horea Florin Chicinaș, Miruna-Andreea Anghel, Cătălin Ovidiu Popa and Aranka Ilea
Coatings 2025, 15(7), 833; https://doi.org/10.3390/coatings15070833 - 17 Jul 2025
Viewed by 544
Abstract
Ceramic dental prosthetics with internal metal structures are made from a cobalt–chromium alloy that is coated with ceramic. This study aims to validate surface treatments for the metal that enhance the adhesion of the ceramic coating under masticatory forces. Surface conditioning is performed [...] Read more.
Ceramic dental prosthetics with internal metal structures are made from a cobalt–chromium alloy that is coated with ceramic. This study aims to validate surface treatments for the metal that enhance the adhesion of the ceramic coating under masticatory forces. Surface conditioning is performed using mechanical methods, like sandblasting (SB), and thermal methods, such as oxidation (O). The ceramic coating is applied to the metal component following the conditioning process, which can be conducted using either a single method or a combination of methods. Each conditioned sample undergoes characterization through various techniques, including drop shape analysis (DSA), scanning electron microscopy (SEM), X-ray diffraction (EDX), and atomic force microscopy (AFM). After the ceramic coating is applied and subjected to thermal sintering, the metal–ceramic samples are mechanically tested to assess the adhesion of the ceramic layer. The research findings, illustrated by scanning electron microscopy (SEM) images of the metal structures’ surfaces, indicate that alloy powder particles ranging from 10 to 50 µm were either adhered to the surfaces or present as discrete dots. Particles that exceed the initial design specifications of the structure can be smoothed out using sandblasting or mechanical finishing techniques. The energy-dispersive spectroscopy (EDS) results show that, after sandblasting, fragments of aluminum oxide remain trapped on the surface of the metal structures. These remnants are considered impurities, which can negatively impact the adhesion of the ceramic to the metal substrate. The analysis focuses on the exfoliation of the ceramic material from the deformed metal surfaces. The results emphasize the significant role of the sandblasting method and the micro-topography it creates, as well as the importance of the oxidation temperature in the treatment process. Drawing on 25 years of experience in dental prosthetics and the findings from this study, this publication aims to serve as a guide for applying the ceramic bonding layer to metal surfaces and for conditioning methods. These practices are essential for enhancing the adhesion of ceramic materials to metal substrates. Full article
(This article belongs to the Special Issue Corrosion and Corrosion Prevention in Extreme Environments)
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17 pages, 4572 KiB  
Article
Numerical Analysis of Impingement Jet Combined Cooling with Film Cooling Holes and Thermal Barrier Coatings Using the Decoupling Method
by Siqi Liao, Li Shi, Xiao Tan, Changce Wang, Yue Luo, Rongli Deng, Haoyu Zhang, Chenwei Zheng and Jinfeng Peng
Coatings 2025, 15(7), 832; https://doi.org/10.3390/coatings15070832 - 16 Jul 2025
Viewed by 275
Abstract
This study investigates the impact of thermal barrier coatings (TBCs) on the individual contributions of cooling components in impingement-jet combined cooling under low Reynolds number conditions. Using decoupled methods, numerical simulations were conducted for cylindrical, fan-shaped, and conical hole geometries. The results show [...] Read more.
This study investigates the impact of thermal barrier coatings (TBCs) on the individual contributions of cooling components in impingement-jet combined cooling under low Reynolds number conditions. Using decoupled methods, numerical simulations were conducted for cylindrical, fan-shaped, and conical hole geometries. The results show that without TBCs, the conical hole provides the best cooling performance, while the fan-shaped hole performs the worst. After applying TBCs, the cooling effectiveness of the cylindrical and conical holes remains largely unchanged, but the fan-shaped hole shows significant improvement, with performance comparable to the conical hole. The cylindrical hole keeps a uniform shape, leading to increased velocity and preventing stable film formation. In contrast, the expanding flow passages of the fan-shaped and conical holes promote a gradual decrease in flow velocity, supporting stable film formation and effective thermal protection. Impingement cooling accounts for more than 75% of the overall cooling effectiveness for across hole types. For cylindrical and conical holes, the TBCs primarily enhance in-hole cooling, while for the fan-shaped hole, it increases in-hole cooling effectiveness and shifts film cooling effectiveness from negative to positive, significantly improving its overall contribution. Full article
(This article belongs to the Section Ceramic Coatings and Engineering Technology)
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20 pages, 4234 KiB  
Article
Study on the Flocculation Characteristics of Protein in Modified Chitosan Membrane and Mung Bean Vermicelli Wastewater
by Zhisheng Liu, Guang Li, Xiaoyu Zhang, Wenjing Li, Tianyi Yang, Zhijie Wang, Jinlong Zuo and Yuyang Wang
Coatings 2025, 15(7), 831; https://doi.org/10.3390/coatings15070831 - 16 Jul 2025
Viewed by 291
Abstract
This study addresses the challenge of chitosan (CS) being difficult to dissolve in water due to its highly ordered crystalline structure. Chitosan is modified with chloroacetic acid to reduce its crystallinity and enhance its water solubility. Through single-factor experiments, the optimal conditions for [...] Read more.
This study addresses the challenge of chitosan (CS) being difficult to dissolve in water due to its highly ordered crystalline structure. Chitosan is modified with chloroacetic acid to reduce its crystallinity and enhance its water solubility. Through single-factor experiments, the optimal conditions for preparing carboxymethyl chitosan film (CMCS) were determined: under conditions of 50 °C, a cellulose substrate (CS) concentration of 18.75 g/L, a NaOH concentration of 112.5 g/L, and a chloroacetic acid concentration of 18.75 g/L, the reaction proceeded for 5 h. Under these conditions, the resulting carboxymethyl chitosan film exhibited the best flocculation effect, forming chitosan films in water that had flocculation activity toward mung bean starch protein wastewater. The successful introduction of carboxyl groups at the N and O positions of the chitosan molecular chain, which reduced the crystallinity of chitosan and enhanced its water solubility, was confirmed through analysis using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The prepared carboxymethyl chitosan film (CMCS) was applied in the flocculation recovery of protein. Through single-factor and response surface experiments, the optimal process conditions for flocculating and recovering protein with CMCS were determined: a CMCS dosage of 1.1 g/L, a reaction time of 39.6 min, a reaction temperature of 42.7 °C, and a pH of 5.2. Under these conditions, the protein recovery rate reached 56.97%. The composition and amino acid profile of the flocculated product were analyzed, revealing that the mung bean protein flocculated product contained 62.33% crude protein. The total essential amino acids (EAAs) accounted for 52.91%, non-essential amino acids (NEAAs) for 47.09%, hydrophobic amino acids for 39.56%, and hydrophilic amino acids for 12.67%. The ratio of aromatic to branched-chain amino acids was 0.31, and the ratio of basic to acidic amino acids was 1.68. These findings indicate that the recovered product has high surface activity and good protein stability, foaming ability, and emulsifying properties. Full article
(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)
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