Coatings

10 pages, 1815 KB

Open AccessArticle

Application of Diethylenetriamine for Electroless Deposition of Cobalt Alloys with Controllable Amount of Boron Using Morpholine Borane as Reducing Agent

by Eugenijus Norkus, Ina Stankeviciene, Aldona Jagminiene, Aldona Balciunaite, Giedrius Stalnionis, Vidas Pakstas and Loreta Tamasauskaite-Tamasiunaite

Coatings 2025, 15(9), 1081; https://doi.org/10.3390/coatings15091081 (registering DOI) - 15 Sep 2025

Abstract

Cobalt–boron (Co–B) coatings containing different amounts of boron were electrolessly deposited using morpholine borane as the reducing agent. Diethylenetriamine (dien) was applied to obtain a controllable amount of boron in the coatings. Depending on the concentration of diethylenetriamine in the solution, the deposited [...] Read more.

Cobalt–boron (Co–B) coatings containing different amounts of boron were electrolessly deposited using morpholine borane as the reducing agent. Diethylenetriamine (dien) was applied to obtain a controllable amount of boron in the coatings. Depending on the concentration of diethylenetriamine in the solution, the deposited coatings contained between 0 and 12 at% of boron. It was shown that diethylenetriamine suppresses the incorporation of boron into Co–B alloys. The same tendency was observed when the solution pH increased. Higher temperatures promote the incorporation of boron into cobalt films. The kinetic data on the electroless deposition process of Co–B alloys under different conditions are presented and discussed. The coatings obtained were characterized by means of XRD, SEM, and AFM methods. Since the use of diethylenetriamine hinders boron incorporation into coatings, pure cobalt films can be obtained. Full article

(This article belongs to the Special Issue Advanced Surface Engineering of Alloys: Coatings and Thin Films)

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14 pages, 1618 KB

Open AccessArticle

Microstructure, Mechanical, and Tribological Properties of Mo₂N/Ag-SiN_x Nanomultilayers with Varying Modulation Periods

by Jing Luan, Lei Wang, Songtao Dong, Fábio Ferreira, Filipe Fernandes, Changpan Mo, Albano Cavaleiro and Hongbo Ju

Coatings 2025, 15(9), 1080; https://doi.org/10.3390/coatings15091080 (registering DOI) - 15 Sep 2025

Abstract

The multilayered Mo₂N/Ag-SiN_x self-lubricant films were designed and deposited using a DC (Direct Current) magnetron sputtering system under mixed gas atmosphere of N₂ and Ar. The modulation ratio (thickness ratio of Mo₂N to Ag-SiN_x) was [...] Read more.

The multilayered Mo₂N/Ag-SiN_x self-lubricant films were designed and deposited using a DC (Direct Current) magnetron sputtering system under mixed gas atmosphere of N₂ and Ar. The modulation ratio (thickness ratio of Mo₂N to Ag-SiN_x) was fixed at 2:1, while the modulation periods (thickness of Mo₂N and its adjacent Ag-SiN_x layer) were set at 20, 40, and 60 nm. The results indicated that all multilayer films, regardless of modulation period, exhibited a combination of face-centered cubic (fcc) and amorphous phases. Specifically, fcc-Mo₂N was detected in the Mo₂N layers, while fcc-Ag and amorphous SiN_x co-existed in the Ag-SiN_x layers. The multilayered architecture induced residual stress and interface strengthening, resulting in hardness values exceeding 21 GPa for all films. Compared to Mo₂N and Ag-SiN_x monolayer films, the multilayer structure significantly enhanced tribological properties at room temperature, particularly in terms of wear resistance. The Mo₂N/Ag-SiN_x multilayer films exhibit ~25% lower friction than Ag-SiN_x, ~3% lower than Mo₂N, and achieve remarkable wear rate reductions of ~71% and ~85% compared to Ag-SiN_x and Mo₂N, respectively, demonstrating superior tribological performance. The synergistic effects of both modulation layers and relative high hardness were key factors contributing to the enhanced tribological behavior. Full article

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18 pages, 4659 KB

Open AccessArticle

Performance Enhancement and Nano-Scale Interaction Mechanism of Asphalt Modified with Solid Waste-Derived Nano-Micro-Powders

by Xiaodong Jia, Yao Ge, Hongzhou Zhu and Kaifeng Zheng

Coatings 2025, 15(9), 1079; https://doi.org/10.3390/coatings15091079 - 15 Sep 2025

Abstract

To investigate the influence patterns and underlying mechanisms of solid waste-derived Nano-Micro-Powder (NMP) materials on asphalt performance, this study selected nano-sized silica fume (a typical industrial solid waste) along with conventionally used hydrated lime and cement powders as representative modifiers. Based on material [...] Read more.

To investigate the influence patterns and underlying mechanisms of solid waste-derived Nano-Micro-Powder (NMP) materials on asphalt performance, this study selected nano-sized silica fume (a typical industrial solid waste) along with conventionally used hydrated lime and cement powders as representative modifiers. Based on material type, dosage, and particle size, the high-temperature rheological properties, low-temperature rheological behavior, and nano-scale mechanical characteristics of NMP-modified asphalt were systematically evaluated through dynamic shear frequency tests, Multiple Stress Creep Recovery (MSCR) tests, Bending Beam Rheometer (BBR) tests, and Atomic Force Microscopy (AFM) measurements. Additionally, the grey relational analysis method was employed to quantify the impact of key nanoparticle characteristics on modified asphalt performance. The results demonstrate the following: (1) With increasing NMP dosage and decreasing particle size, the complex modulus (G*) of modified asphalt increases significantly, while the creep recovery rate (R) rises and non-recoverable creep compliance (J_nr) decreases. The creep stiffness slope (m-value) diminishes under low-temperature conditions. (2) Among different NMP types, silica fume-modified asphalt exhibits the highest G*, R, and m-value parameters. (3) At the nanoscale, adhesion force, modulus, and surface roughness all increase with higher NMP dosage and smaller particle size. Silica fume demonstrates superior performance in these nano-mechanical properties compared to hydrated lime and cement powders. (4) Grey relational analysis reveals that specific surface area shows the strongest correlation with the overall performance of NMP-modified asphalt. Full article

(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)

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12 pages, 2710 KB

Open AccessArticle

A Study of the Properties of Two-Layer Coatings Based on TiO₂-Cr₂O₃/Ta

by Bauyrzhan Rakhadilov, Zhangabay Turar, Dauir Kakimzhanov and Dastan Buitkenov

Coatings 2025, 15(9), 1078; https://doi.org/10.3390/coatings15091078 - 15 Sep 2025

Abstract

In this work, a comparative study of the corrosion resistance and microstructural characteristics of oxide coatings based on TiO₂ and TiO₂ + Cr₂ + Cr₂O₃ both deposited onto and without a tantalum sublayer has been carried out. [...] Read more.

In this work, a comparative study of the corrosion resistance and microstructural characteristics of oxide coatings based on TiO₂ and TiO₂ + Cr₂ + Cr₂O₃ both deposited onto and without a tantalum sublayer has been carried out. The coatings were formed through thermal spraying, and their corrosion behaviour was evaluated through potentiodynamic polarisation in 3.5% NaCl solution using a potentiostat–galvanostat in a three-electrode cell. The TiO₂ + Cr₂O₃ composite coating, applied with a tantalum sublayer, had the lowest corrosion current density and the most positive corrosion potential, indicating its high corrosion resistance. The morphology and elemental composition of the coatings were analysed using scanning electron microscopy (SEM) and energy-dispersive analysis (EDX). The microstructural analysis revealed that the coatings with Cr₂O₃ added were characterised by an increased density, a more uniform phase distribution, and improved adhesion to the substrate. The obtained results confirm that combined TiO₂ + Cr₂O₃ coatings with a tantalum sublayer are promising for use in aggressive environments due to their high corrosion resistance and structural stability. Full article

(This article belongs to the Special Issue Advances in Ceramic Materials and Coatings)

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14 pages, 4719 KB

Open AccessArticle

Corrosion Resistance of Ti Coatings, Cr Coatings, and Ti/Cr Multilayer Coatings Prepared on 7050 Aluminum Alloy by Magnetron Sputtering

by Kang Chen, Tao He, Xiangyang Du, Artem Okulov, Catherine Sotova, Yang Ding, Yuqi Wang and Peiyu He

Coatings 2025, 15(9), 1077; https://doi.org/10.3390/coatings15091077 - 14 Sep 2025

Abstract

Al7050 aluminum alloy substrates were coated with Cr, Ti, and Ti/Cr multilayer films via direct current magnetron sputtering to enhance their corrosion resistance. A comprehensive analysis, employing SEM and XRD, characterized the coatings’ morphology and composition, while electrochemical experiments assessed their corrosion performance. [...] Read more.

Al7050 aluminum alloy substrates were coated with Cr, Ti, and Ti/Cr multilayer films via direct current magnetron sputtering to enhance their corrosion resistance. A comprehensive analysis, employing SEM and XRD, characterized the coatings’ morphology and composition, while electrochemical experiments assessed their corrosion performance. The Cr coating, despite exhibiting the largest thickness (588 nm), revealed a porous microstructure with inherent structural weaknesses. Conversely, the Ti coating, while possessing a dense structure, presented a significantly reduced thickness (96 nm). The Ti/Cr multilayer coating, with a thickness of 242 nm, achieved an optimal balance between structural density and overall thickness. Critically, the layered architecture of the Ti/Cr multilayer coating effectively impeded crack propagation and facilitated the formation of tortuous corrosion pathways. This intricate pathway morphology significantly hindered the diffusion of the corrosive medium, resulting in a notably low corrosion current density of 3.83 × 10⁻⁷ A·cm⁻². Comparative analysis revealed that the corrosion current density of the Ti/Cr multilayer coating was substantially lower than that of both the Cr and Ti coatings, demonstrating improvements of 2386% and 222%, respectively. These findings underscore the pivotal role of the multilayer structure in augmenting the corrosion resistance of aluminum alloys by providing a superior barrier to corrosive medium. Full article

(This article belongs to the Special Issue Innovative Coatings for Corrosion Protection of Alloy Surfaces)

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11 pages, 3973 KB

Open AccessArticle

Low-Temperature Deposition of Alumina Films by Ultrasonic Spray Pyrolysis with a Water-Based Precursor

by Anayantzi Luna Zempoalteca, J. A. David Hernández de la Luz, Adan Luna Flores, Alfredo Benítez Lara, Zaira Jocelyn Hernández Simón, Gabriel Omar Mendoza Conde, Karim Monfil Leyva, Javier Flores Méndez, Gustavo M. Minquiz Xolo and José Alberto Luna López

Coatings 2025, 15(9), 1076; https://doi.org/10.3390/coatings15091076 - 13 Sep 2025

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Abstract

Alumina (Al₂O₃) is a key material in inorganic and hybrid electronics due to its excellent dielectric, chemical, and thermal stability properties. In this work, we present the first results of alumina films deposited by ultrasonic spray pyrolysis (USP) at [...] Read more.

Alumina (Al₂O₃) is a key material in inorganic and hybrid electronics due to its excellent dielectric, chemical, and thermal stability properties. In this work, we present the first results of alumina films deposited by ultrasonic spray pyrolysis (USP) at low temperatures (40–100 °C) using water as the sole solvent, followed by an annealing step at 100 °C. The films were characterized by SEM, XRD, EDS, and UV-Vis spectroscopy to evaluate their morphology, structure, composition, and optical properties. Preliminary results show an average thickness of approximately 8 µm, with surface features consisting of agglomerates (average particle size ≈ 7.252 µm) distributed over the film. XRD patterns revealed the presence of tetragonal and orthorhombic phases, while EDS confirmed the presence of aluminum and oxygen with slight compositional variations depending on deposition and annealing conditions. UV-Vis absorption spectra exhibited characteristic bands between 259 nm and 263 nm. These results provide a comprehensive understanding of the optical, structural, and morphological behavior of Al₂O₃ films processed at low temperatures. The motivation for studying these films is to enable more eco-friendly gate oxides for organic MIS structures, as well as functional layers in photonic devices. This approach represents a sustainable and straightforward route for obtaining Al₂O₃ coatings compatible with temperature-sensitive substrates, paving the way for future applications in hybrid and organic electronics. Full article

(This article belongs to the Collection Advanced Optical Films and Coatings)

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13 pages, 3372 KB

Open AccessArticle

Rotating Bending Fatigue Properties of 30CrNi2Mo Steel After Electropulsing-Assisted Ultrasonic Surface Rolling Process

by Dan Liu, Hongsheng Huang, Yalin Shen, Jie Liu, Changsheng Tan, Haonan Fan and Yinglin Ke

Coatings 2025, 15(9), 1075; https://doi.org/10.3390/coatings15091075 - 12 Sep 2025

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Abstract

With the rapid development of mechanical components, increasingly stringent demands are placed on steel properties—particularly tensile strength and rotating bending fatigue resistance. This study systematically investigates the effects of the electropulsing-assisted ultrasonic surface rolling process (EUSRP) on the surface microstructure and fatigue performance [...] Read more.

With the rapid development of mechanical components, increasingly stringent demands are placed on steel properties—particularly tensile strength and rotating bending fatigue resistance. This study systematically investigates the effects of the electropulsing-assisted ultrasonic surface rolling process (EUSRP) on the surface microstructure and fatigue performance of 30CrNi2Mo steel. A fine-grained surface layer (depth: 80 μm) was formed. Lath martensite width decreased significantly from 7 μm to 4 μm after EUSRP treatment, which was significantly refined after electropulsing treatment and an ultrasonic surface-rolling process. Under identical stress amplitudes, the rotating bending fatigue life of EUSRP-treated specimens substantially exceeded that of the as-machined state. Fatigue cracks in the as-machined state consistently initiated at the surface, coalesced, and propagated into large cracks, leading to premature fracture. In EUSRP-treated samples, crack initiation shifted to subsurface regions, delaying failure and extending fatigue life. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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22 pages, 4462 KB

Open AccessArticle

Dynamic Response and Energy Dissipation Mechanisms of Soil–Lightweight Foam Composite Protective Layers Under Impact Loading

by Jianping Gao, Le Liu, Xuefeng Mei, Dengfeng Li, Jianli Wu and Peng Cui

Coatings 2025, 15(9), 1074; https://doi.org/10.3390/coatings15091074 - 12 Sep 2025

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Abstract

Engineering structures often face safety risks under impact or explosion loading, making the design of lightweight and efficient cushioning systems crucial. This study investigates the dynamic response and energy-dissipation characteristics of Expanded Polystyrene (EPS), Expanded Polyethylene (EPE), and soil–foam composite cushion layers under [...] Read more.

Engineering structures often face safety risks under impact or explosion loading, making the design of lightweight and efficient cushioning systems crucial. This study investigates the dynamic response and energy-dissipation characteristics of Expanded Polystyrene (EPS), Expanded Polyethylene (EPE), and soil–foam composite cushion layers under impact loading, using a Split Hopkinson Pressure Bar (SHPB) testing apparatus. The tests include pure foam layers (lengths ranging from 40 to 300 mm) and a soil–foam composite layer with a total length of 60 mm (soil/foam ratio 1:1 to 1:3), subjected to impact velocities of 9.9–15.4 m/s. The results show that the stress wave propagation velocity of EPE is 149.6 m/s, lower than that of EPS at 249.3 m/s. At higher velocities, the attenuation coefficient for the 40 mm EPE sample reaches as low as 0.22, while EPS is 0.31. Furthermore, the maximum energy absorption coefficient of EPE exceeds 98%, with better stability at high impact velocities. In composite cushion layers, both soil and foam collaborate in energy absorption, but an increased proportion of soil leads to a decrease in energy absorption efficiency and attenuation capacity. Under equivalent ratios, the soil–EPE combination performs better than the soil–EPS combination. By constructing a comprehensive evaluation system based on three indices: stress wave attenuation coefficient, energy absorption coefficient, and energy absorption density, this study quantifies the impact resistance performance of different cushioning layers, providing theoretical and parametric support for material selection in engineering design. Full article

(This article belongs to the Special Issue Development of Low-Carbon Coatings/Materials and Intelligent Construction Protection Technology)

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18 pages, 7636 KB

Open AccessArticle

Ultrasonic-Assisted Spinning V-Groove Moulding Mechanism and Accuracy Research

by Shiqi Chen, Weiqing Wang, Qingshan Jiang, Jiashun Gao, Yongqing Lai, Yuhong Liu, Zhilong Xu and Zhenye Zhao

Coatings 2025, 15(9), 1073; https://doi.org/10.3390/coatings15091073 - 12 Sep 2025

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Abstract

Spinning forming, a new method for processing multi-ribbed pulleys, is increasingly replacing traditional casting and cutting techniques. However, reducing the substantial forming load remains a challenging task. This paper explores the introduction of ultrasonic assistance into the spinning process to examine the V-groove [...] Read more.

Spinning forming, a new method for processing multi-ribbed pulleys, is increasingly replacing traditional casting and cutting techniques. However, reducing the substantial forming load remains a challenging task. This paper explores the introduction of ultrasonic assistance into the spinning process to examine the V-groove formation in multi-ribbed pulleys and combines experimental spinning trials with finite element analysis (FEA) to investigate the process. It assesses how ultrasonic aid affects spinning quality under various static loads by analysing V-groove depth, inclination angle, microhardness, structure, and surface roughness. The results indicate that ultrasonic assistance significantly increases the depth of the V-groove in spinning formation. Initially, the V-groove depth is 197.64 μm, which improves to 410.35 μm with ultrasonic aid, corresponding to a reduction in static load by 185 N. The V-groove angle rises with static load, but with ultrasonic assistance, the angle stabilises, enhancing forming accuracy. At a static load of 700 N, the V-groove angle decreases from 74.32° to 62.96°. Full article

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12 pages, 5463 KB

Open AccessArticle

Interfacial Diffusion and Copper Alloy Layer Wear Mechanism in Cu-20Pb-5Sn/45 Steel Bimetallic Composites

by Yuanyuan Kang, Guowei Zhang, Yanling Hu and Yue Liu

Coatings 2025, 15(9), 1072; https://doi.org/10.3390/coatings15091072 - 12 Sep 2025

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Abstract

Cu-20Pb-5Sn/45 steel bimetallic composites were prepared using the solid–liquid composite method. The interfacial microstructure, bonding strength, and wear performance were systematically characterized to elucidate the mechanisms governing the solid-solution interface and copper alloy layer wear behavior. The results reveal that mutual diffusion of [...] Read more.

Cu-20Pb-5Sn/45 steel bimetallic composites were prepared using the solid–liquid composite method. The interfacial microstructure, bonding strength, and wear performance were systematically characterized to elucidate the mechanisms governing the solid-solution interface and copper alloy layer wear behavior. The results reveal that mutual diffusion of Cu and Fe forms a metallurgically bonded α-(Cu,Ni)/α-Fe interface with a diffusion layer thickness of approximately 10.7 µm and an interfacial shear strength of 227.58 MPa. Under dry sliding conditions, the average coefficient of friction was 0.145, with a wear rate of 7.3665 × 10⁻⁶ mm³/(N·m). The α-(Cu,Ni) matrix was reinforced by hard Cu₃P and Ni-rich phases, which resist frictional shear stresses, while dispersed Pb particles provide self-lubricating properties, while the solid-solution interface hindered dislocation propagation, reducing dislocation pile-up and ensuring stable frictional performance. Full article

(This article belongs to the Special Issue Surface Engineering Processes for Reducing Friction and Wear)

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19 pages, 7791 KB

Open AccessArticle

Comparative Effects of Fine and Conventional Shot Peening on Surface Morphology, Topography, Wettability, and Antibacterial Activity of Biomedical Ti6Al4V Alloy

by Egemen Avcu, Mert Guney, Yasemin Yıldıran Avcu, Mine Sulak, Hüseyin Uzuner, Meltem İlçe Bahadır, Eray Abakay, Mustafa Armağan, Rıdvan Yamanoğlu, Cagatay Elibol and Martin F.-X. Wagner

Coatings 2025, 15(9), 1071; https://doi.org/10.3390/coatings15091071 - 12 Sep 2025

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Abstract

Interest in textured surfaces for biomaterials and implants is increasing, with shot peening emerging as a promising method for surface modification. This study investigates the influence of conventional and fine shot peening on the surface morphology, topography, wettability, and antibacterial properties of biomedical-grade [...] Read more.

Interest in textured surfaces for biomaterials and implants is increasing, with shot peening emerging as a promising method for surface modification. This study investigates the influence of conventional and fine shot peening on the surface morphology, topography, wettability, and antibacterial properties of biomedical-grade Ti6Al4V alloy. Peening was conducted using a custom-built, fully automated system, employing fine (100–200 µm) and coarse (700–1000 µm) shots using well-controlled sets of parameters. Both treatments introduced severe plastic deformation on the surface, resulting in increased roughness. Conventionally shot-peened samples exhibited deeper and wider dimples compared to finely peened ones. Surface wettability shifted from hydrophilic (contact angle: ~4°, untreated) to hydrophobic, reaching contact angles of ~91° and ~100° for fine and conventional shot peening, respectively. Antibacterial assays against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were evaluated by normalizing colony counts to the untreated Ti6Al4V surface. The inherent antibacterial response of Ti6Al4V against E. coli was preserved after both shot peening treatments, showing no notable increase in bacterial proliferation. In contrast, adhesion of S. aureus increased, more notably on fine shot-peened surfaces, indicating a strain-specific response influenced by surface roughness and wettability. In summary, both fine and conventional shot peening altered the surface morphology, topography, and wettability of Ti6Al4V. At the same time, their antibacterial influence was strain-dependent, underscoring the need for careful parameter selection in biomedical applications. Full article

(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications, 2nd Edition)

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30 pages, 8759 KB

Open AccessArticle

Frost Resistance and Life Prediction of Waste Polypropylene Fibre-Reinforced Recycled Aggregate Concrete

by Xuechao Yang, Zehui Zhang, Hsing-Wei Tai, Bangxiang Li, Jiahui Li, Weishen Zhang, Tian Su and Jianping Liu

Coatings 2025, 15(9), 1070; https://doi.org/10.3390/coatings15091070 - 11 Sep 2025

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Abstract

The inherent defects of recycled coarse aggregate (RCA) lead to poor frost resistance in recycled aggregate concrete (RAC), limiting its application in cold coastal regions. Waste polypropylene fibre (WPF), utilized as a reinforcement material, can improve the frost resistance of RAC. This study [...] Read more.

The inherent defects of recycled coarse aggregate (RCA) lead to poor frost resistance in recycled aggregate concrete (RAC), limiting its application in cold coastal regions. Waste polypropylene fibre (WPF), utilized as a reinforcement material, can improve the frost resistance of RAC. This study systematically analyzes the influence of WPF on the frost resistance of RAC and establishes a life prediction model. The results indicate that the damage to concrete in a saline freeze–thaw environment is significantly greater than that in a freshwater environment. WPF mitigates the development of freeze–thaw damage in RAC effectively by bridging microcracks and segmenting interconnected pores, thereby optimizing the pore structure and enhancing the matrix compactness. After 125 freeze–thaw cycles, the attenuation amplitude of the relative dynamic elastic modulus (RDEM) for RAC incorporated with WPF decreased by 9.69% and 5.77% in freshwater and saline environments, respectively, while the compressive strength increased by 20.65% and 18.57%. Concurrently, the negative mass growth rate of RAC in freshwater decreased by 20.62%, and the mass loss in the salt solution decreased by 5.84%. Furthermore, life predictions based on both RDEM and the compressive strength loss rate demonstrate that WPF extends the service life of RAC. Notably, the RDEM-based prediction yields a longer life but corresponds to a larger strength loss, whereas the prediction based on the compressive strength loss rate, although slightly shorter, corresponds to a more stable residual strength. Full article

(This article belongs to the Special Issue Development of Low-Carbon Coatings/Materials and Intelligent Construction Protection Technology)

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17 pages, 2868 KB

Open AccessArticle

Study on the Influence of ZM Modifier on the Rheological Properties and Microstructural Characteristics of Asphalt

by Yining Wang, Zhen Zang and Wenyuan Xu

Coatings 2025, 15(9), 1069; https://doi.org/10.3390/coatings15091069 - 11 Sep 2025

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Abstract

As traffic load continuously rises and climatic conditions increasingly vary, the performance of conventional base asphalt can no longer satisfy the needs of modern road engineering in low-temperature cracking resistance, high-temperature stability, and long-term durability. Therefore, the development of novel and efficient asphalt [...] Read more.

As traffic load continuously rises and climatic conditions increasingly vary, the performance of conventional base asphalt can no longer satisfy the needs of modern road engineering in low-temperature cracking resistance, high-temperature stability, and long-term durability. Therefore, the development of novel and efficient asphalt modifiers holds significant engineering value and practical importance. In this study, modified asphalt was prepared using varying dosages of ZM modifier (direct-injection asphalt mixture modified polymer additive). A series of experiments was executed to assess its influence on asphalt properties. First, fundamental property tests were implemented to determine the regulating effect of the ZM modifier on basic physical performances, like the softening point and penetration of the base asphalt. Penetration tests at different temperatures were performed to calculate the penetration index, thereby assessing the material’s temperature sensitivity. Subsequently, focusing on temperature as a key factor, tests on temperature sweep, and multiple stress creep recovery (MSCR) were implemented to delve into the deformation resistance and creep recovery behavior of the modified asphalt under high-temperature conditions. In addition, bending beam rheometer (BBR) experiments were introduced to attain stiffness modulus and creep rate indices, which were applied to appraise the low-temperature rheological performance. Aside from Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) was utilized to explore the mechanism by which the ZM modifier influences the asphalt’s functional group composition and microstructure. Our findings reveal that the ZM modifier significantly increases the asphalt’s softening point and penetration index, reduces penetration and temperature sensitivity, and enhances high-temperature stability. Under high-temperature conditions, the ZM modifier adjusts the viscoelastic balance of asphalt, hence enhancing its resistance to flow deformation and its capacity for creep recovery. In low-temperature environments, the modifier increases the stiffness modulus of asphalt and improves its crack resistance. FTIR analyses reveal that the ZM modifier does not introduce new functional groups, indicating a physical modification process. However, by enhancing the cross-linked structure and increasing the hydrocarbon content within the asphalt, it strengthens the adhesion between the asphalt and aggregates. Overall, the asphalt’s performance improvement positively relates to the dosage of the ZM modifier, providing both theoretical basis and experimental support for its application in road engineering. Full article

(This article belongs to the Special Issue Surface Treatments and Coatings for Asphalt and Concrete)

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28 pages, 4543 KB

Open AccessArticle

Development and Evaluation of a Bioactive Halophilic Bacterial Exopolysaccharide-Based Coating Material to Extend Shelf Life and Mitigate Citrus Canker Disease in Citrus limon L.

by Chandni Upadhyaya, Hiren Patel, Ishita Patel and Trushit Upadhyaya

Coatings 2025, 15(9), 1068; https://doi.org/10.3390/coatings15091068 - 11 Sep 2025

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Abstract

Halophilic isolates were screened to mitigate postharvest losses caused by citrus canker disease in lemon fruits. Among all isolates, SWIS03, isolated from the Sambhar Salt Lake in Rajasthan, India, exhibited the highest exopolysaccharide production, with good stability and antibacterial activity against Xanthomonas citri [...] Read more.

Halophilic isolates were screened to mitigate postharvest losses caused by citrus canker disease in lemon fruits. Among all isolates, SWIS03, isolated from the Sambhar Salt Lake in Rajasthan, India, exhibited the highest exopolysaccharide production, with good stability and antibacterial activity against Xanthomonas citri. Isolate SWIS03 was identified as halophilic Bacillus licheniformis DET601. It produced a very high EPS content in optimized sterilized seawater-based minimal media fortified with 2.5% sucrose and 0.3% beef extract, which was purified through repeated deproteinization and Sephadex G-75 chromatography. HPTLC analysis of composition check indicated the presence of glucose, mannose, and galactose. FTIR analysis also confirmed the presence of sugar and bound water, as well as the presence of hydroxyl, amine, amide, and methyl groups. Rheological characterization revealed a pseudoplastic nature, making it suitable for uniform coating. EPS was reported to have bioactive properties, including antioxidant activity (84.7 ± 1.75% DPPH scavenging potential), antimicrobial activity against human pathogens, and a noncytotoxic nature, which are essential for use in edible coatings. The effect of EPS coating formulation on healthy lemon fruits resulted in shelf-life extension of up to 26.6 ± 1.14 days and 18.0 ± 1.41 days at 4 °C and 30 °C in coated lemons, respectively, as demonstrated by physiological parameters such as % weight loss, firmness, titratable acidity, and shelf life of lemons. Also, EPS coating preserved the quality of fruits in terms of phenolic compounds and Vitamin C content, and reduced lipid peroxidation during storage. Biocontrol potential of halophilic EPS coating on lemon fruits revealed an 86.50% and 68.64% reduction in % disease incidence compared to uncoated fruits at 4 °C and 30 °C, respectively. Similarly, a significantly lower disease incidence (46.80% at 4 °C and 67.03% at 30 °C) was also reported compared to paraffin-coated (positive control) lemons. Consequently, halophilic Bacillus licheniformis DET601 EPS is an effective coating material for citrus fruits to prevent canker disease in post-harvest settings for agricultural and food industry applications. Full article

(This article belongs to the Special Issue Advances in Food Technology: Bioactive Films and Coatings for Food Packaging)

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12 pages, 2429 KB

Open AccessArticle

Amphoteric Doping Effect of Ho³⁺ on the Performance of Medium-Temperature-Sintered PLZT Energy Storage Ceramics

by Yue Xu, Qingwei Liao, Shuhan Zhang, Xinyu Liu, Haoran Zhang and Lei Qin

Coatings 2025, 15(9), 1067; https://doi.org/10.3390/coatings15091067 - 11 Sep 2025

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Abstract

The development of dielectric capacitors with high energy-storage density and ultrafast discharge capability is essential for next-generation pulsed power systems. In this work, (Pb, La, Ho, Zr, Ti)O₃ (PLZTH) ceramics were fabricated via medium-temperature sintering (950–1100 °C) combined with Ho³⁺ doping [...] Read more.

The development of dielectric capacitors with high energy-storage density and ultrafast discharge capability is essential for next-generation pulsed power systems. In this work, (Pb, La, Ho, Zr, Ti)O₃ (PLZTH) ceramics were fabricated via medium-temperature sintering (950–1100 °C) combined with Ho³⁺ doping to systematically tailor their energy-storage properties. This processing strategy not only mitigates Pb volatilization but also enhances compatibility with base-metal electrodes such as Ni and Cu. In addition, Ho³⁺ ions exhibit amphoteric doping behavior, which contributes to the enhancement of relaxor characteristics and grain refinement. H4 ceramic delivers an outstanding recoverable energy-storage density (W_rec) of 0.91 J/cm³ and a high energy efficiency (η) of 87% under 216 kV/cm, along with a power density (P_D) of 28.8 MW/cm³ and an ultrafast discharge time (t_0.9) of only 4.97 ns at 180 kV/cm. This study not only proposes a viable route toward high-performance medium-temperature-sintered PLZT ceramics but also elucidates the effective mechanism of Ho³⁺ amphoteric doping in modulating the relaxor state and properties of perovskite-based ceramics. Full article

(This article belongs to the Special Issue Advances in Nanostructured Thin Films and Coatings, 3rd Edition)

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27 pages, 51271 KB

Open AccessArticle

Surface Damage Detection and Analysis for Reduction-Fired Cyan Square Bricks in Jiangnan Gardens via YOLOv12

by Lina Yan, Yile Chen, Xingkang Jia and Liang Zheng

Coatings 2025, 15(9), 1066; https://doi.org/10.3390/coatings15091066 - 11 Sep 2025

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Abstract

As an outstanding UNESCO World Heritage Site, the Jiangnan gardens feature both exquisite and fragile components. Reduction-fired cyan square bricks, serving as crucial paving materials, are long-term exposed to natural and anthropogenic factors, making them prone to various types of surface damage and [...] Read more.

As an outstanding UNESCO World Heritage Site, the Jiangnan gardens feature both exquisite and fragile components. Reduction-fired cyan square bricks, serving as crucial paving materials, are long-term exposed to natural and anthropogenic factors, making them prone to various types of surface damage and urgently requiring efficient, non-destructive detection methods to support scientific conservation. Traditional manual inspection methods suffer from low efficiency, strong subjectivity, and potential disturbance to the fragile heritage structures. This study focuses on developing an intelligent detection method based on advanced computer vision, employing the YOLOv12 object detection model to achieve non-contact, automated identification of typical tile surface damage types in the Jiangnan gardens (such as cracking, stains, water stains, and wear). A total of 691 images of reduction-fired cyan square bricks collected on-site were used as training samples. The main conclusions of this study are as follows: (1) By constructing a dataset containing multiple samples and multiple scenes of reduction-fired cyan square brick images in Jiangnan gardens, the YOLOv12 model was trained and optimized, enabling it to accurately identify subtle damage features under complex texture backgrounds. (2) Overall indicators: Through the comparison of the confusion matrices of the four key training nodes, model C (the 159th epoch, highest mAP50–95) has the most balanced overall performance in multiple categories, with an accuracy of 0.73 for cracking, 0.77 for wear, 0.60 for water stain, and 0.65 for stains, which can meet basic detection requirements. (3) Difficulty of discrimination: Compared with stains and water stains, cracking and wear are easier to distinguish. Experimental results indicate that the detection method is feasible and effective in identifying the surface damage types of reduction-fired cyan square bricks in Jiangnan gardens. This research provides a practical and efficient “surface technology” solution for the preventive protection of cultural heritage, contributing to the sustainable preservation and management of world heritage. Full article

(This article belongs to the Special Issue Solid Surfaces, Defects and Detection, 2nd Edition)

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12 pages, 28822 KB

Open AccessArticle

Microstructure, Esthetics and Engineering Performance of TiN Coatings Deposited by Multi-Arc Ion Plating

by Yan Wang, Tao Fang, Xiaofan Zheng and Huanghuang Jin

Coatings 2025, 15(9), 1065; https://doi.org/10.3390/coatings15091065 - 11 Sep 2025

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Abstract

Despite extensive research on the effect of nitrogen flow rate on titanium nitride (TiN) coating properties, its influence on esthetic and engineering performance through microstructure control remains insufficiently explored. To simultaneously meet the requirements for surface strengthening and decorative esthetics in high-end stainless-steel [...] Read more.

Despite extensive research on the effect of nitrogen flow rate on titanium nitride (TiN) coating properties, its influence on esthetic and engineering performance through microstructure control remains insufficiently explored. To simultaneously meet the requirements for surface strengthening and decorative esthetics in high-end stainless-steel crafts, TiN coatings were deposited on 304L stainless-steel substrates using multi-arc ion plating. The regulatory mechanisms and synergistic evolution laws of nitrogen flow rates (100, 200, and 300 sccm) on the microstructure, decorative properties (color and gloss), and engineering performance (adhesion strength, hardness, wear resistance, and corrosion resistance) of the coatings were investigated. At a nitrogen flow rate of 200 sccm, the coating exhibited a uniform and dense columnar crystal structure, as well as a saturated golden hue with high surface gloss. Additionally, the film–substrate adhesion, microhardness, tribological properties, and corrosion resistance reached optimal levels. In contrast, excessively low (100 sccm) or high (300 sccm) nitrogen flow rates resulted in coarse particles and blurred grain boundaries owing to uncontrolled droplet ejection or target poisoning, respectively, thereby deteriorating both appearance and engineering performance. These findings can inform the optimization of TiN coatings, enabling the design of surfaces that simultaneously meet esthetic and high-performance engineering requirements. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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17 pages, 9095 KB

Open AccessArticle

Electrochemical Corrosion Behavior of SiO₂ Superhydrophobic Inhibitor in Al7075

by Jesús Manuel Jáquez-Muñoz, Luis Eduardo Vázquez-Nuñez, Betania Sánchez-Santamaria, José Saúl Arias-Cerón, Jaime Gonzalo Santana-Esquivel, Abel Diaz-Olivares, Luis Enrique Arambula-Miranda, Martha Guadalupe Carrera-Rámirez, Aurora Abigail López-Ibarra and Delfino Cornejo-Monroy

Coatings 2025, 15(9), 1064; https://doi.org/10.3390/coatings15091064 - 11 Sep 2025

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Abstract

The automotive industry has been employing Al alloys to reduce the weight of chassis; however, this can present some corrosion problems. In this research, we study the electrochemical behavior of SiO₂ superhydrophobic on Al 7075. The electrochemical techniques employed were cyclic potentiodynamic [...] Read more.

The automotive industry has been employing Al alloys to reduce the weight of chassis; however, this can present some corrosion problems. In this research, we study the electrochemical behavior of SiO₂ superhydrophobic on Al 7075. The electrochemical techniques employed were cyclic potentiodynamic polarization (CPP), performed at a scan rate of 60 mV/s from −800 to 800 mV vs. OCP, and electrochemical impedance spectroscopy (EIS) at ±10 mV with frequencies ranging from 10 mHz to 100 kHz, as per ASTM G61 and ASTM G106. The electrolytes employed were NaCl and H₂SO₄ at 3.5 wt.% simulating marine and industrial atmospheres. The results showed that the coating presented an efficiency of 81% when exposed to NaCl, but the corrosion in this medium is localized. In H₂SO₄, the corrosion type is uniform. Full article

(This article belongs to the Special Issue Advanced Hydrophobic Surfaces and Anti-Corrosion Coatings: Design, Fabrication, and Performance)

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17 pages, 3957 KB

Open AccessArticle

High-Strength, Stable, and Energy-Efficient Bacterial Nanocellulose Composite Films for Building-Integrated Photovoltaics Facade System

by Chenguang Wang, Libin Deng and Yanjie Zhou

Coatings 2025, 15(9), 1063; https://doi.org/10.3390/coatings15091063 - 10 Sep 2025

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Abstract

Bacterial nanocellulose (BNC) composite films have emerged as promising candidates for sustainable building materials, yet their practical application in building-integrated photovoltaics (BIPV) facade systems is hindered by insufficient mechanical strength, poor environmental stability, and limited energy efficiency. Here, we developed bacterial nanocellulose/zinc oxide–phenolic [...] Read more.

Bacterial nanocellulose (BNC) composite films have emerged as promising candidates for sustainable building materials, yet their practical application in building-integrated photovoltaics (BIPV) facade systems is hindered by insufficient mechanical strength, poor environmental stability, and limited energy efficiency. Here, we developed bacterial nanocellulose/zinc oxide–phenolic resin (BNC/ZnO–PF) composite films with high-strength, stability, and energy efficiency for BIPV facade system through a simple strategy. Specifically, we first prepared BNC films, then in-situ grew ZnO nanoparticles on BNC films via ultrasound assistance, and finally hot-pressed the BNC/ZnO films with PF resin. The BNC/–PF composite films exhibit high mechanical strength (tensile strength of 93.8 MPa), exceptional sturdiness (wet strength of 92.3 MPa), and thermal properties, demonstrating their durability for long-term outdoor applications. Furthermore, the BNC/ZnO–PF composite films show high transparency (86.47%) and haze (82.02%) in the visible light range, enabling effective light propagation and scattering, as well as soft, uniform, and large-area light distribution. Meanwhile, a low thermal conductivity of 21.7 mW·m⁻¹·K⁻¹ can effectively impede the transfer of high outdoor temperatures into the room, significantly reducing the energy consumption demands of heating and cooling systems. Coupled with its ability to en-hance the photovoltaic conversion efficiency of solar cells by 12.9%, this material can serve as the core encapsulation layer for BIPV facades. While enabling build-ing-integrated photovoltaic power generation, through the synergistic effect of light management and thermal insulation, it is expected to reduce comprehensive building energy consumption, providing a new solution for building energy efficiency under carbon neutrality goals. Full article

(This article belongs to the Section Thin Films)

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13 pages, 3321 KB

Open AccessArticle

Plasma Controlled Growth Dynamics and Electrical Properties of Ag Nanofilms via RF Magnetron Sputtering

by Jiali Chen, Yanyan Wang, Tianyuan Huang, Peiyu Ji and Xuemei Wu

Coatings 2025, 15(9), 1062; https://doi.org/10.3390/coatings15091062 - 10 Sep 2025

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Abstract

Silver thin films are widely utilized in plasmonic, electronic, and catalytic devices due to their excellent conductivity, optical properties, and surface activity. However, the nanostructure and performance of Ag films are highly dependent on deposition parameters, particularly during radio-frequency magnetron sputtering (RF-MS). In [...] Read more.

Silver thin films are widely utilized in plasmonic, electronic, and catalytic devices due to their excellent conductivity, optical properties, and surface activity. However, the nanostructure and performance of Ag films are highly dependent on deposition parameters, particularly during radio-frequency magnetron sputtering (RF-MS). In this study, we systematically investigate the effects of RF power, sputtering time, and substrate type on the growth behavior, crystallinity, and electrical conductivity of Ag films. Optical emission spectroscopy (OES) and Langmuir probe diagnostics were employed to analyze the plasma environment, revealing the evolution of electron temperature and plasma density with varying RF powers. Structural characterizations using XRD, SEM, and AFM demonstrate that higher RF power results in reduced grain size, increased film density, and improved crystallinity, while deposition time influences film thickness and grain coalescence. Substrate material also plays a key role, with Cu substrates promoting better crystallinity due to improved lattice matching. Electrical measurements show that denser films with larger grains exhibit lower sheet resistance. These findings provide a comprehensive understanding of the plasma–film interplay and offer strategic insights for optimizing silver nanofilms in high-performance optoelectronic and catalytic systems. Full article

(This article belongs to the Special Issue Advanced Plasma Surface Treatments and Their Applications in Coating Technologies)

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22 pages, 4592 KB

Open AccessReview

Defect Engineering of ZnIn₂S₄ Photocatalysts for Enhanced Hydrogen Evolution Reaction

by Fangying Hong, Tong Jing, Sen Wang and Zuoli He

Coatings 2025, 15(9), 1061; https://doi.org/10.3390/coatings15091061 - 10 Sep 2025

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Abstract

ZnIn₂S₄, a visible-light-responsive layered sulfide photocatalyst with a suitable bandgap (~2.4 eV), exhibits considerable potential for the photocatalytic hydrogen evolution reaction (PHER) due to its low toxicity, excellent stability, and appropriate band alignment. Nevertheless, its practical deployment is limited [...] Read more.

ZnIn₂S₄, a visible-light-responsive layered sulfide photocatalyst with a suitable bandgap (~2.4 eV), exhibits considerable potential for the photocatalytic hydrogen evolution reaction (PHER) due to its low toxicity, excellent stability, and appropriate band alignment. Nevertheless, its practical deployment is limited by inherent issues such as rapid charge carrier recombination, scarce surface-active sites, and slow oxidation kinetics. Defect engineering strategies—including sulfur, zinc, and indium vacancies, as well as heteroatom doping—have been developed to mitigate these shortcomings. This review not only summarizes recent advances in these strategies but also elucidates the fundamental physicochemical mechanisms behind the enhanced photocatalytic performance. A systematic quantitative evaluation is presented, highlighting improvements in critical performance metrics such as hydrogen evolution rate, light absorption range, apparent quantum yield (AQY), and charge separation efficiency. Furthermore, the review offers a critical perspective on the current state of defect-engineered ZnIn₂S₄ systems. Promising future research pathways are outlined, with emphasis on atomic-precision synthesis and operando characterization techniques. Finally, we discuss persistent challenges in the field, including reproducibility in synthesis, long-term operational stability, and scalability toward industrial hydrogen production. Full article

(This article belongs to the Special Issue Advanced Thin Films, Surface and Interface in Photocatalytic Applications)

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3 pages, 184 KB

Open AccessComment

Comment on Rasool et al. Spectral Relaxation Methodology for Chemical and Bioconvection Processes for Cross Nanofluid Flowing Around an Oblique Cylinder with a Slanted Magnetic Field Effect. Coatings 2022, 12, 1560

by Asterios Pantokratoras

Coatings 2025, 15(9), 1060; https://doi.org/10.3390/coatings15091060 - 10 Sep 2025

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Abstract

In the present comment, the units presented in the Nomenclature section in [...] Full article

18 pages, 7299 KB

Open AccessArticle

Self-Repairing Polyurethane–Urea Coating for Wind Turbine Blades: Modeling and Analysis

by Yulin Sun, Leon Mishnaevsky, Jr., Katharina Koschek and Florian Sayer

Coatings 2025, 15(9), 1059; https://doi.org/10.3390/coatings15091059 - 10 Sep 2025

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Abstract

This study investigates a UDETA-modified polyurethane–urea (PUU) self-healing coating for wind turbine blades, focusing on its ability to autonomously repair surface erosion damage under realistic environmental conditions. A multiphysics finite element model was developed to couple temperature, moisture, and stress effects on crack [...] Read more.

This study investigates a UDETA-modified polyurethane–urea (PUU) self-healing coating for wind turbine blades, focusing on its ability to autonomously repair surface erosion damage under realistic environmental conditions. A multiphysics finite element model was developed to couple temperature, moisture, and stress effects on crack healing, and a Gaussian process regression (GPR) model was trained on 35 experimental data points to predict the mobile fraction and healing thresholds with high accuracy (R² = 0.79, MAE = 0.059). The diffusion coefficient of water in the PUU matrix was determined as 11.03 × 10⁻⁷ mm²/s, and stress-driven moisture accumulation at crack tips was shown to accelerate crack healing. Erichsen cupping test simulations were conducted to reproduce experimental crack patterns, demonstrating brittle behavior in dehydrated coatings with a Young’s modulus of 50 MPa and critical principal strains of 0.48. An exponential healing function was incorporated into the computational model and validated against experiments, predicting significant crack healing within 24 h of humidity exposure. These findings provide quantitative design criteria for self-healing coatings, enabling the selection of UDETA content, thickness, and curing strategies to extend wind turbine blade service life while reducing maintenance costs. Full article

(This article belongs to the Special Issue Synthesis, Characterization, and Applications of Innovative Polymer Coatings and Films)

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19 pages, 2958 KB

Open AccessArticle

Crashworthiness Design with a New Optimization Criterion for Multilevel Thin-Walled Structures

by Zhifang Deng, Mengni Liu, Zheyi Zhang and Jianghua Feng

Coatings 2025, 15(9), 1058; https://doi.org/10.3390/coatings15091058 - 10 Sep 2025

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Abstract

This paper proposes and investigates a novel multilevel thin-walled energy-absorbing structure. The proposed design demonstrates superior energy absorption capability compared to conventional single-stage structures through its additional energy-absorbing mechanism that activates after the initial peak force. Based on the Super Folding Element (SFE) [...] Read more.

This paper proposes and investigates a novel multilevel thin-walled energy-absorbing structure. The proposed design demonstrates superior energy absorption capability compared to conventional single-stage structures through its additional energy-absorbing mechanism that activates after the initial peak force. Based on the Super Folding Element (SFE) theory, we derive theoretical calculation expressions to characterize the structure’s behavior. Dynamic impact experiments validate the theoretical model. Furthermore, we introduce an innovative allowable criterion for structural optimization and implement multi-objective crashworthiness optimization to identify the optimal configuration. The optimization results exhibit remarkable consistency with both numerical simulations and theoretical predictions, confirming the effectiveness of our approach. Full article

(This article belongs to the Section Thin Films)

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17 pages, 2901 KB

Open AccessArticle

A Green Plasma-Based Micro-Nanotexturing Method to Realize Stable Superhydrophobic and Superhydrophilic Thin PET Films

by Vasiliki Tselepi, Dimitrios Nioras, Evangelos Gogolides and Kosmas Ellinas

Coatings 2025, 15(9), 1057; https://doi.org/10.3390/coatings15091057 - 9 Sep 2025

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Abstract

Polyethylene terephthalate (PET) is widely used in food packaging, biomedical, and optical applications, but its inherent wettability limitations can hinder its performance in extreme environments. To this end, several methods have been developed to improve PET wetting properties. Yet, most of the methods [...] Read more.

Polyethylene terephthalate (PET) is widely used in food packaging, biomedical, and optical applications, but its inherent wettability limitations can hinder its performance in extreme environments. To this end, several methods have been developed to improve PET wetting properties. Yet, most of the methods proposed are wet and involve the use of chemical reagents, whereas, in most of the dry-based methods, such as plasma-based methods, which can easily tune the wetting properties of polymeric materials such as PET, achieving long-term stability, especially in extreme wetting states (superhydrophilicity and superhydrophobicity), remains a challenge. In this work, oxygen plasma etching is used to micro-nanotexture thin and, therefore, flexible PET films (thickness: 50 μm) for three different time durations of 4, 6, and 12 min followed by a C₄F₈ plasma deposition of a hydrophobic film or a hydrophilic poly (ethylene glycol) coating depending on the wettability profile targeted. Using this dry and, therefore, “green” and simple two step method, durable superhydrophilic and superhydrophobic surfaces that last for at least one year have been successfully realized. Finally, it is also shown that wetting control can be achieved without significantly affecting the inherent optical properties of the PET film (texturing duration up to 6 min), highlighting the multifunctionality of the plasma micro-nanotextured PET film. Full article

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17 pages, 2025 KB

Open AccessArticle

Analysis of AC and DC Interference in One Buried Gas Pipeline

by Zaifeng Wang, Haishan Liu, Jianqing Liu, Yang Liu, Yu Ding and Jie Zhang

Coatings 2025, 15(9), 1056; https://doi.org/10.3390/coatings15091056 - 9 Sep 2025

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Abstract

The complex interference created by several sources for pipelines has not been sufficiently studied. In this study, four types of interference sources were monitored and analyzed. AC voltage monitoring, DC potential monitoring, current density monitoring, and excavation observation and measurement for test pieces [...] Read more.

The complex interference created by several sources for pipelines has not been sufficiently studied. In this study, four types of interference sources were monitored and analyzed. AC voltage monitoring, DC potential monitoring, current density monitoring, and excavation observation and measurement for test pieces and the decouplers were employed to assess the AC/DC interference of one real buried pipeline in situ. The peak value obtained from the second measurement at Pile 33 decreased from 1341.8 V to 143.7 V, indicating that the 1341.8 V in the first measurement may be caused by a sudden grounding of the electrode, while the 143.7 V may be caused by the normal induced voltage. The most negative DC interference potential between the pipeline and the Cu/CuSO₄ reference electrode was −11.946 V. The most positive DC interference potential between the pipeline and the Cu/CuSO₄ reference electrode was 4.862 V. Pile 3 had a maximum DC current density of 240 mA/m², and Pile 4 had a maximum AC current density of 0.615 A/m². After excavating the test piece at Pile 3, the point with maximum DC interference, there were obvious pitting corrosion characteristics, and the corrosion products were mainly γ-FeOOH and Fe₃O₄. It indicated that the coupling of long-term higher positive DC current density or (DC potential) and short-term higher transient AC voltage or (AC current density) may lead to corrosion. After excavating the test piece at the point with maximum AC interference, namely, Pile 4, there were no significant AC or DC corrosion characteristics. This finding suggested that the combination of long-term low AC current voltage or (low AC current density) and long-term more negative low DC current density or (DC potential) did not result in obvious corrosion. The decouplers in this measurement significantly reduced AC interference above 2 V, but the isolation of transient AC shocks and AC interference below 2 V were not significant. During analysis of AC and DC interference, in addition to considering the value of the interference, the duration time of the interference was also an important factor. Instantaneous sharp peaks cannot represent the long-term average voltage or potential current density. The average value should be used as the main basis for judgement, and the instantaneous value should be used as the secondary basis for judgement. Full article

(This article belongs to the Special Issue Surface Protection for Metal Materials)

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17 pages, 5243 KB

Open AccessArticle

Morphology and Wear Resistance of Laser-Clad Fe-Cr-Nb-C Alloy Coatings

by Min Chen, Haoran Zhou, Xuyang Liu, Zhongxue Feng, Xuan Xiao, Liu Weng, Yang Yang and Yan Jiang

Coatings 2025, 15(9), 1055; https://doi.org/10.3390/coatings15091055 - 8 Sep 2025

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Abstract

Fe-Cr-Nb-C wear-resistant alloy coatings were successfully fabricated on high-carbon forged steel via coaxial powder feeding laser cladding. The evolution of microstructure and wear resistance with varying Nb content was systematically investigated. The results indicate that appropriate NbC addition markedly modifies the distribution of [...] Read more.

Fe-Cr-Nb-C wear-resistant alloy coatings were successfully fabricated on high-carbon forged steel via coaxial powder feeding laser cladding. The evolution of microstructure and wear resistance with varying Nb content was systematically investigated. The results indicate that appropriate NbC addition markedly modifies the distribution of grain and boundary carbides. As Nb content increases from 2.5 wt% to 3.5 wt%, nanoscale rod-like NbC precipitates form uniformly along boundaries, effectively suppressing the formation of brittle Cr₂₃C₆ precipitation. Semi-coherent NbC/matrix interfaces and NbC-induced grain refinement reduce adhesive/abrasive wear, thereby improving hardness and wear resistance. At 4.5 wt% Nb, discrete micron-sized NbC particles form within the grains, yielding optimal performance. However, excessive Nb (≥5.5 wt%) causes NbC agglomeration, inducing stress concentrations and large spallation pits that deteriorate wear resistance. This work highlights NbC morphology as a key factor for tailoring coating properties. Full article

(This article belongs to the Section Laser Coatings)

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20 pages, 13751 KB

Open AccessArticle

Laser Cleaning Process for Low-Pressure Turbine Blade Paint Removal with Remelting Suppression

by Xihuai Wang, Yaochen Ding, Qiujuan Chen, Hongying Li, Li Wang and Mingdi Wang

Coatings 2025, 15(9), 1054; https://doi.org/10.3390/coatings15091054 - 8 Sep 2025

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Abstract

This study aims to develop an efficient laser cleaning process for removing paint coatings from low-pressure turbine blades while suppressing substrate remelting, focusing on elucidating the underlying paint removal mechanisms on coated aluminum alloy substrates. A pulsed fiber laser (1064 nm, 100 ns) [...] Read more.

This study aims to develop an efficient laser cleaning process for removing paint coatings from low-pressure turbine blades while suppressing substrate remelting, focusing on elucidating the underlying paint removal mechanisms on coated aluminum alloy substrates. A pulsed fiber laser (1064 nm, 100 ns) was used to perform single-factor and orthogonal experiments, with laser power (70–100 W), scanning speed (1000–3000 mm/s), and repetition frequency (150–300 kHz) as the main variables. The energy density for each of the 16 orthogonal test samples ranged from 11.9 to 51.0 J/cm². Complete paint removal without substrate damage was achieved within an optimal energy density window of approximately 17–27 J/cm² (e.g., 23.8 J/cm²), whereas higher values above 35 J/cm² (e.g., 35.7 J/cm²) frequently caused localized remelting and pitting. The optimized parameter combination (90 W, 1500 mm/s, 300 kHz) achieved 98% paint removal efficiency in four passes with no observable substrate degradation. Mechanistic analysis indicated that low-to-moderate energy densities promoted interfacial debonding and controlled film ablation, while high energy densities led to substrate melting and reflow. This work clarifies the quantitative correlation between laser parameters, paint removal mechanisms, and remelting suppression, providing a scientific basis for turbine blade maintenance applications. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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20 pages, 8748 KB

Open AccessArticle

Effect of Basalt Fibers on the Performance of CO₂-Cured Recycled Aggregate Concrete Composite Slab–Column Assemblies with Bolted Connections Under NaCl Erosion

by Di Wang, Yuanfeng Wu, Zhiqiang Xu, Na Xu, Chuanqi Li, Xu Tian, Feiting Shi and Hui Wang

Coatings 2025, 15(9), 1053; https://doi.org/10.3390/coatings15091053 - 8 Sep 2025

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Abstract

Basalt fibers possess high tensile strength and excellent corrosion resistance, properties that may enhance the chloride resistance of recycled aggregate concrete (RAC) structures. Nevertheless, the effects of basalt fibers on RAC structures under chloride attack remain poorly understood. This study investigates mass loss [...] Read more.

Basalt fibers possess high tensile strength and excellent corrosion resistance, properties that may enhance the chloride resistance of recycled aggregate concrete (RAC) structures. Nevertheless, the effects of basalt fibers on RAC structures under chloride attack remain poorly understood. This study investigates mass loss and the deterioration of key mechanical properties in basalt fiber-reinforced RAC composite slab–column assemblies (RAC composite assemblies) subjected to NaCl freeze–thaw cycles (F-Cs) and dry–wet alternations (D-As) and further explores the damage mechanisms of the concrete matrix through microscopic characterization. The results show that, compared with NaCl F-Cs, NaCl D-As have a more pronounced impact on the performance degradation of RAC composite slab–column assemblies. Moreover, basalt fibers effectively mitigate the deterioration of RAC composite assemblies in chloride-rich environments, particularly under NaCl D-As, where their protective effect is more evident. At 2.5 vol% fiber content, impact toughness peaked at an 83.7% improvement after 30 D-As, while flexural toughness showed a maximum enhancement of 773.6% after 100 F-Cs. Scanning electron microscopy energy-dispersive spectroscopy (SEM-EDS) analysis revealed a marked increase in Cl content within RAC, with NaCl D-As causing more severe erosion than NaCl F-Cs. Additionally, basalt fibers significantly inhibited chloride ion penetration and associated erosion in RAC. These findings provide valuable insights into utilizing basalt fibers to enhance the durability of RAC in coastal infrastructure exposed to chloride attacks. Further research on long-term performance and fiber parameter optimization is needed to support practical implementation. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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21 pages, 2796 KB

Open AccessArticle

Study on Ultrasonic Vibration Lapping of 9310 Small-Size Internal Spline After Heat Treatment

by Zemin Zhao, Jinshilong Huang, Qiang Liu, Zhian Zhang and Fangcheng Li

Coatings 2025, 15(9), 1052; https://doi.org/10.3390/coatings15091052 - 8 Sep 2025

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Abstract

As a key component of aero transmission systems, internal splines suffer from problems of low efficiency and poor precision in traditional lapping processes due to geometric deformation and high hardness after heat treatment. To address this, this study proposes an ultrasonic vibration lapping [...] Read more.

As a key component of aero transmission systems, internal splines suffer from problems of low efficiency and poor precision in traditional lapping processes due to geometric deformation and high hardness after heat treatment. To address this, this study proposes an ultrasonic vibration lapping technology, which combines the synergistic mechanism of high-frequency vibration and free abrasive particles to achieve efficient and precise machining of small-sized hardened internal splines. By establishing an abrasive grain impact trajectory model and a rolling abrasive grain material removal model, the mechanisms of micro-cutting and impact removal of abrasive particles under ultrasonic vibration are revealed. Based on the local resonance theory, a longitudinal ultrasonic vibration system is designed, and its resonant frequency is optimized through finite element modal analysis. An ultrasonic lapping experimental platform is built, and heat-treated 9310 internal spline samples are used for experimental verification. The results show that, compared with traditional manual lapping, ultrasonic vibration lapping significantly improves the tooth profile and tooth lead deviations. After measurement, following ultrasonic vibration lapping, both the total tooth profile deviation and tooth lead deviation of the internal spline meet the Grade 6 accuracy requirements specified in GB/T 3478.1-2008 Cylindrical straight-tooth involute splines (Metric Module, Tooth Side Fit)—Part 1: General. This study confirms that ultrasonic vibration lapping can effectively correct the geometric accuracy of tooth surfaces and suppress thermal damage, and provides an innovative solution for the high-quality repair of aero transmission components. Full article

(This article belongs to the Special Issue Cutting Performance of Coated Tools)

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