Coatings

21 pages, 7758 KB

Open AccessArticle

Electric Field-Assisted Chemical Bath Deposition of ZnO Thin Films: Effects of Field Intensity, Polarity Inversion, and Air Agitation on Film Properties

by Jesús Bladimir Cepero-Rodríguez, Francisco Ramos-Brito, Jorge Noe Angulo-Rocha, Marco Antonio Sánchez-Alejó, Rafael Martínez-Martínez, Enrique Camarillo-García, Erika Lizárraga-Medina, Fernando J. Sánchez-Rodríguez, Castulo Alejo-Armenta, Adrián Canizalez-Román, Santos Jesús Castillo, J. Joel Molina-Duarte and Manuel García-Hipólito

Coatings 2025, 15(10), 1225; https://doi.org/10.3390/coatings15101225 (registering DOI) - 18 Oct 2025

Abstract

This study presents an innovative modification to the chemical bath deposition method for synthesizing zinc oxide thin films by incorporating a high-voltage electric field, with and without electrical polarity inversion, to influence film growth dynamics. Two configurations were developed to assess the effects [...] Read more.

This study presents an innovative modification to the chemical bath deposition method for synthesizing zinc oxide thin films by incorporating a high-voltage electric field, with and without electrical polarity inversion, to influence film growth dynamics. Two configurations were developed to assess the effects of electric field strength, periodic inversion, air agitation, and solution pH on the morphological, structural, and optical properties of ZnO coatings. Morphology studies revealed that particle size, shape, and distribution were strongly dependent on synthesis parameters, with electric field and air injection enabling higher surface coverage and finer nanostructures. Crystalline structural analysis confirmed the formation of the wurtzite ZnO phase, with reduced interplanar spacing and crystallite size under electric fields, especially when polarity was inverted. Optical measurements showed a consistent increase in the band gap (blue shift) and reduced defect-related absorption when electric field is applied. These findings are evidence that controlled electric field application during chemical bath deposition enables precise tuning of ZnO film properties. Full article

(This article belongs to the Special Issue Advanced Ceramic Materials and Coatings: Synthesis, Properties and Applications)

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12 pages, 3708 KB

Open AccessArticle

Impact of BN Buffer Layer Thickness on Interfacial Structure and Band Alignment of a-BN/4H-SiC Heterojunctions

by Yang-Chao Liu, Wen-Jie Chen, Man Luo, Zimo Zhou, Lin Gu, Yi Shen, Xin Qi, Hong-Ping Ma and Qing-Chun Zhang

Coatings 2025, 15(10), 1224; https://doi.org/10.3390/coatings15101224 (registering DOI) - 18 Oct 2025

Abstract

This study provides a comprehensive investigation into the growth behavior of boron nitride (BN) buffer layers on Silicon carbide (SiC) substrates and their influence on interfacial band alignment. BN layers were deposited on semi-insulating SiC by RF magnetron sputtering with deposition times of [...] Read more.

This study provides a comprehensive investigation into the growth behavior of boron nitride (BN) buffer layers on Silicon carbide (SiC) substrates and their influence on interfacial band alignment. BN layers were deposited on semi-insulating SiC by RF magnetron sputtering with deposition times of 2.5, 5, and 7.5 min (these deposition times are specific experimental parameters to adjust the thickness of the amorphous BN layer, not intrinsic material properties of BN). Atomic force microscopy revealed that the surface roughness of the BN layers initially decreased and then increased with thickness, indicating an evolution from nucleation to continuous film formation, followed by surface coarsening. Transmission electron microscopy confirmed the BN thicknesses of approximately 3.25, 4.91, and 7.57 nm, showing that the layers gradually became uniform and compact, thereby improving the structural integrity of the BN/SiC interface. Band alignment was analyzed using the Kraut method, yielding a valence band offset of ~0.36 eV and a conduction band offset of ~2.34 eV for the BN/SiC heterojunction. This alignment indicates that the BN buffer layer introduces a pronounced electron barrier, effectively suppressing leakage, while the relatively small VBO facilitates hole transport across the interface. These findings demonstrate that the BN buffer layer enhances interfacial bonding, reduces defect states, and enables band structure engineering, offering a promising strategy for improving the performance of wide-bandgap semiconductor devices. Full article

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26 pages, 5667 KB

Open AccessArticle

Performance of High-Fluidity Cementitious Grouting Materials with Recycled Waste Glass in Semi-Flexible Pavement Mixture

by Ayman Hassan AL-Qudah, Suhana Koting, Mohd Rasdan Ibrahim, Muna M. Alibrahim and Abdullah I. Al-Mansour

Coatings 2025, 15(10), 1223; https://doi.org/10.3390/coatings15101223 (registering DOI) - 18 Oct 2025

Abstract

Semi-flexible pavement (SFP) relies primarily on the properties of cementitious grouting material (CGM), which plays a crucial role in providing durability and crack resistance. This paper investigates the performance of CGMs containing recycled waste glass (RWG) as a replacement to fine granite aggregate [...] Read more.

Semi-flexible pavement (SFP) relies primarily on the properties of cementitious grouting material (CGM), which plays a crucial role in providing durability and crack resistance. This paper investigates the performance of CGMs containing recycled waste glass (RWG) as a replacement to fine granite aggregate (FGA) and their effect on SFP mixtures. Two high-fluidity glass-cementitious grouts (Glcement grouts) were developed and tested at five RWG replacement levels (0%, 30%, 50%, 70%, and 100%). The results indicated that CGM with 70% RWG provided the most balanced performance, with a flowability of 11.8 s, low drying shrinkage (0.04%), and water absorption not exceeding 1.9%. The mechanical properties were significantly enhanced, achieving a high compressive strength of 121.9 MPa and a high flexural strength of 13.9 MPa. Microstructural analysis confirmed a refined interfacial transition zone with low porosity (5.36%), contributing to superior durability. Furthermore, the SFP mixture injected with Glcement exhibited high mechanical performance, attributed to improved interlocking within voids. In conclusion, replacing FGA with RWG in CGM optimizes both mechanical and durability properties, promoting sustainable and low-carbon pavement construction. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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12 pages, 1298 KB

Open AccessArticle

Effects of 3D Printing Parameters on the Coating Performance of Chinese Lacquer on PLA Substrates

by Yi Xie, Yuemin Feng, Alin Olarescu, Yushu Chen and Xinyou Liu

Coatings 2025, 15(10), 1222; https://doi.org/10.3390/coatings15101222 - 17 Oct 2025

Abstract

This study systematically investigates the influence of 3D printing parameters on the surface morphology and coating performance of polylactic acid (PLA) substrates finished with traditional Chinese lacquer. PLA specimens were fabricated using fused deposition modeling (FDM) with varying print speeds, layer heights, and [...] Read more.

This study systematically investigates the influence of 3D printing parameters on the surface morphology and coating performance of polylactic acid (PLA) substrates finished with traditional Chinese lacquer. PLA specimens were fabricated using fused deposition modeling (FDM) with varying print speeds, layer heights, and infill densities, followed by natural lacquer coating and controlled curing. Surface roughness, gloss, adhesion, and wear resistance were evaluated through standardized tests, while microstructural analysis using SEM revealed the interfacial morphology and film uniformity. Results indicate that layer height is the most dominant factor, exerting significant effects on all surface and coating properties. Increasing layer height led to higher surface roughness, which in turn reduced gloss due to enhanced diffuse scattering but improved adhesion and wear resistance through stronger mechanical interlocking. Print speed showed a secondary influence on adhesion, attributed to its effect on interlayer bonding and surface porosity, while infill density exhibited minimal influence except on wear resistance. The application of Chinese lacquer significantly reduced surface irregularities owing to its excellent self-leveling and gap-filling capabilities, producing smooth, durable, and well-adhered coatings. Overall, the study demonstrates that integrating traditional lacquer with modern FDM technology provides a sustainable and high-performance finishing solution for 3D-printed PLA, bridging cultural craftsmanship with advanced additive manufacturing for potential applications in decorative, protective, and eco-friendly products. Full article

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

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14 pages, 4922 KB

Open AccessArticle

Morphological, Compositional and Optical Properties of Cu_xS Films on FTO Glass

by Dominyka Zubrickaite, Asta Bronusiene and Ingrida Ancutiene

Coatings 2025, 15(10), 1221; https://doi.org/10.3390/coatings15101221 - 17 Oct 2025

Abstract

In this study, by varying the concentrations of the precursors used, copper sulfide films were deposited on FTO glass using the sequential ionic layer adsorption and reaction (SILAR) method and the following copper sulfide phases were detected: anilite, djurleite, chalcocite, and yarrowite. It [...] Read more.

In this study, by varying the concentrations of the precursors used, copper sulfide films were deposited on FTO glass using the sequential ionic layer adsorption and reaction (SILAR) method and the following copper sulfide phases were detected: anilite, djurleite, chalcocite, and yarrowite. It was found that the films of copper sulfides are unevenly distributed, that the crystallinity of the films increases with increasing annealing temperature from 100 to 400 °C, and that the particles aggregate into agglomerates. The films formed were found to be dominated by copper sulfides, and the calculated molar ratio of copper to sulfur varied with the concentrations of the precursors used, ranging from 1.4 to 2.2. The values of the band gap energy were not significantly affected by the change in the concentrations of the precursors and the annealing temperature, varying between 1.0 and 1.5 and 1.95–2.15 eV. 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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21 pages, 3811 KB

Open AccessArticle

TEOS-Based Fiber Fabrication via Electrospinning: Influence of Process Parameters and NMC Doping on Functional Properties

by Nida Tezgel, Yıldız Yaralı Özbek, Kristýna Jílková, Martin Havlík Míka, Mária Kolářová and Radovan Fojt

Coatings 2025, 15(10), 1220; https://doi.org/10.3390/coatings15101220 - 17 Oct 2025

Abstract

The main aim of this study is to produce TEOS-based fibers using the electrospinning method with solutions without carrier polymers, unlike most TEOS-based fibers that are produced with polymer additives. This study provides fundamental insights into the production and characterization of TEOS-based fibers [...] Read more.

The main aim of this study is to produce TEOS-based fibers using the electrospinning method with solutions without carrier polymers, unlike most TEOS-based fibers that are produced with polymer additives. This study provides fundamental insights into the production and characterization of TEOS-based fibers and offers a general overview of their potential applications. We investigate the production and overlaying of their morphological, chemical, thermal, and electrochemical properties. The effects of electrospinning parameters such as voltage, flow rate, and solution viscosity on fiber morphology were examined, revealing a strong dependence of fiber diameter and structural uniformity on these parameters. Furthermore, TEOS-based fibers containing nickel–manganese–cobalt oxide (NMC) were fabricated, and their electrochemical behavior was investigated. The analyses indicate that the addition of NMC enhances the electrochemical properties of the TEOS fibers; however, the system still requires further improvement to be effective in energy-storage applications. To investigate how the flow properties of the solution affect fiber generation during electrospinning, viscosity measurements were conducted on the TEOS-based solution. Differential thermal analysis (DTA) was applied to assess the thermal behavior and stability of the fibers at elevated temperatures. The produced fibers were analyzed using various characterization techniques. As a result, thin fibers were successfully produced. Full article

(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)

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13 pages, 2662 KB

Open AccessArticle

Electrodeposition of Fine-Grained Tungsten Coatings on CuCrZr Alloy Substrates from Relatively Low Temperature KF-KCl-WO₃ Molten Salt System

by Xiaoxu Dong, Wenqi Liu, Yusha Li, Zeyu Gao and Yingchun Zhang

Coatings 2025, 15(10), 1219; https://doi.org/10.3390/coatings15101219 - 17 Oct 2025

Abstract

To address the issue in the pure oxide molten salt system Na₂WO₄-WO₃, where the relatively high melting temperature often causes thermal corrosion of the base material and reduces electrodeposition efficiency. A new molten salt system for electrodeposition [...] Read more.

To address the issue in the pure oxide molten salt system Na₂WO₄-WO₃, where the relatively high melting temperature often causes thermal corrosion of the base material and reduces electrodeposition efficiency. A new molten salt system for electrodeposition tungsten coatings on CuCrZr substrates at relatively low temperatures was investigated. The crystal structure and microstructure of the tungsten coatings were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The results indicate that the power supply mode, current density, and duty cycle significantly affect the microstructure, crystalline characteristics, and overall performance of the tungsten coating. Pure tungsten coatings were successfully fabricated on CuCrZr substrates at 943 K. The best electrodeposition parameters were determined to be a current density of 40 mA/cm² and a duty cycle of 40%. Moreover, after prolonged electrodeposition (60 h), the tungsten coatings retained fine grains, with sizes ranging from 2 μm to 6 μm. Full article

(This article belongs to the Special Issue New Functional Coatings and Thin Films for Sensor and Green Energy Technologies)

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24 pages, 7424 KB

Open AccessArticle

Mechanical Consequences of Gap-Graded Soils Subjected to Internal Erosion: The Effect of Mode of Removal of Fine Particles Using Discrete Element Method

by Feng He, Haodong Xu, Yongqing Xu, Shengliang Hu, Maowen Li and Chenxi Tong

Coatings 2025, 15(10), 1218; https://doi.org/10.3390/coatings15101218 - 16 Oct 2025

Abstract

Seepage-induced internal erosion occurs when the hydraulic forces are sufficient to detach fine particles and transport them out of the structure, leading to notable changes in soil characteristics such as particle size distribution, pore size distribution, and pore structure, which will, in turn, [...] Read more.

Seepage-induced internal erosion occurs when the hydraulic forces are sufficient to detach fine particles and transport them out of the structure, leading to notable changes in soil characteristics such as particle size distribution, pore size distribution, and pore structure, which will, in turn, have significant influences on the mechanical properties of soil. In this study, three approaches were utilized to model the erosion-induced loss of fine particles, i.e., deleting fine particles randomly (RM), by contact force (CF), and by coordination number (CN) using the discrete element method (DEM). The impact of each fine particle removal mode on both micro- and macro-mechanical soil properties, including peak strength, dilation, critical state characteristics, average particle coordination number, and contact force distribution, is comprehensively analyzed and compared. The results demonstrate that residual strength was insensitive to removal method, whereas at 10% fines loss, peak strength decreased by up to 17% and the secant stiffness E₅₀ decreased by nearly 48%. This work provides a foundation for simulating the internal erosion of gap-graded soils. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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Graphical abstract

13 pages, 3827 KB

Open AccessArticle

Preparation and Corrosion Resistance of Hydrothermal Coatings on LZ91 Mg–Li Alloy

by Liu Yang, Shiyuan Li, Hao Peng, Hao Jiang, Yong Wang, Yingping Guan and Hongwang Zhang

Coatings 2025, 15(10), 1217; https://doi.org/10.3390/coatings15101217 - 16 Oct 2025

Abstract

A corrosion-resistant coating was fabricated on the surface of LZ91 Mg–Li alloy via a one-step hydrothermal method under varying reaction temperatures (70, 90, 110, and 130 °C). This involved immersing bare Mg–Li alloy substrates in a 10 wt.% Na₂CO₃ aqueous [...] Read more.

A corrosion-resistant coating was fabricated on the surface of LZ91 Mg–Li alloy via a one-step hydrothermal method under varying reaction temperatures (70, 90, 110, and 130 °C). This involved immersing bare Mg–Li alloy substrates in a 10 wt.% Na₂CO₃ aqueous solution for 3 h. The microstructure, elemental distribution, and phase composition of the as-prepared coatings were systematically characterized using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The corrosion resistance was evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization measurements. The results revealed that the hydrothermal treatment led to the formation of a dense nanostructured coating composed of fine nanosheets, with their morphology and population density being highly dependent on the reaction temperature. Phase analysis confirmed that the coating primarily consisted of Mg(OH)₂, MgCO₃, and Li₂CO₃. The electrochemical tests demonstrated that the coatings substantially enhanced the corrosion resistance of the alloy. Additionally, the corrosion resistance decreased in the following order: 130 °C > 110 °C > 90 °C > 70 °C > bare LZ91 substrate. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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21 pages, 3658 KB

Open AccessReview

An Overview of Metallic Abradable Coatings in Gas Turbine Engines

by Kaue Bertuol, Bruno Edu Arendarchuck and Pantcho Stoyanov

Coatings 2025, 15(10), 1216; https://doi.org/10.3390/coatings15101216 - 16 Oct 2025

Viewed by 19

Abstract

This review presents a comprehensive overview of metallic abradable coatings and the advanced testing methodologies used to evaluate their performance in gas turbine engines. Abradable materials are engineered to act as sacrificial coatings, enabling minimal blade tip wear while maintaining tight clearances between [...] Read more.

This review presents a comprehensive overview of metallic abradable coatings and the advanced testing methodologies used to evaluate their performance in gas turbine engines. Abradable materials are engineered to act as sacrificial coatings, enabling minimal blade tip wear while maintaining tight clearances between rotating blades and stationary components. Such functionality is critical in aerospace applications, where engines operate at high rotational speeds and across wide temperature ranges. The review examines the principal factors governing the design and selection of metallic-based abradable coatings, including material composition, thermal stability, and microstructural tailoring through the addition of phase modifiers, porosity formers, and solid lubricants. The performance of various metallic matrix materials is also discussed concerning their operational temperature ranges and wear characteristics. Particular attention is given to abradability evaluation methods, emphasizing the need to replicate engine-representative conditions to capture blade–coating interactions, frictional behavior, and wear mechanisms. This review consolidates advances in material compositions, microstructural engineering, and experimental testing, integrating perspectives from materials science, tribology, and methodology to guide the development of next-generation turbine coatings. It specifically addresses the lack of a unified review linking material design, thermal spray processes, and performance evaluation by summarizing key compositions, microstructures, and testing methods. Full article

(This article belongs to the Special Issue Research Progress and Prospect of Functional Thin Films & Hard Protective Coatings)

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18 pages, 9928 KB

Open AccessArticle

Simulation and Experimental Study of γ-TiAl Alloy Cutting with scCO₂-MQL Based on Modified Heat Transfer Coefficient

by Limin Shi, Xuehao Zhao, Lixin Cui, Haonan Chen and Erliang Liu

Coatings 2025, 15(10), 1215; https://doi.org/10.3390/coatings15101215 - 16 Oct 2025

Viewed by 91

Abstract

Current heat transfer coefficient models for scCO₂-MQL exhibit critical limitations because they neglect the Mach disk phenomenon and the effects of radial velocity distribution in the scCO₂ jets. These theoretical deficiencies result in significant deviations in the thermal predictions, limiting [...] Read more.

Current heat transfer coefficient models for scCO₂-MQL exhibit critical limitations because they neglect the Mach disk phenomenon and the effects of radial velocity distribution in the scCO₂ jets. These theoretical deficiencies result in significant deviations in the thermal predictions, limiting the application potential of scCO₂-MQL technology in γ-TiAl machining applications. This study establishes a modified heat transfer coefficient model incorporating Mach disk and radial velocity distribution correction factors to characterise complex jet flow behaviour. Based on the modified heat transfer coefficient model, comprehensive simulation and experimental investigations were conducted to analyse cutting forces, cutting temperatures, stress distributions, and serrated chip formation during scCO₂-MQL machining of γ-TiAl alloys. Results demonstrate that the modified model achieves superior predictive accuracy, with average relative error reductions of 21.8% for cutting force predictions and 37.3% for temperature predictions compared to conventional models. The developed modified heat transfer coefficient model establishes a foundation for the widespread application of scCO₂-MQL cutting of γ-TiAl alloys. Full article

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

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22 pages, 10080 KB

Open AccessArticle

Laser Fabricated MgO-TiO₂ Based Photocatalytic Antifogging and Self-Cleaning Surface in Air

by Zhenze Zhai, Feiyue Zhang, Yongjian Gao, Longze Chen, Jia Liu, Yu Wang, Chaoran Sun and Hongtao Cui

Coatings 2025, 15(10), 1214; https://doi.org/10.3390/coatings15101214 - 15 Oct 2025

Viewed by 158

Abstract

A cost-effective laser marker was employed to fabricate a superhydrophilic, photocatalytic Mg-Ti-based surface on glass under ambient conditions. The photocatalytic layer was first deposited via laser processing, followed by partial laser etching to generate micro/nanostructures on the surface. This method preserves partial photocatalytic [...] Read more.

A cost-effective laser marker was employed to fabricate a superhydrophilic, photocatalytic Mg-Ti-based surface on glass under ambient conditions. The photocatalytic layer was first deposited via laser processing, followed by partial laser etching to generate micro/nanostructures on the surface. This method preserves partial photocatalytic functionality while enhancing surface roughness and introducing unique nanostructures, enabling the sample to simultaneously exhibit antifogging, self-cleaning capabilities, and high light transmittance. The optimal sample was achieved by tuning laser processing parameters, including repetition rate and scanning hatch distance. It maintained a water contact angle (WCA) of 0° after 15 days of outdoor exposure, which only increased to 21.2° after 30 days. In comparison, the WCA of reference glass increased from an initial 23.3° to 63.9° over the same period. Furthermore, the amount of dust accumulated on the optimal sample was significantly lower—by up to 43%—than that on the reference glass over one month under both indoor and outdoor conditions. After a single spray cleaning, the dust removal efficiency of the indoor-stored optimal sample reached 70%, which was 56% higher than that of the reference. For samples stored outdoors, a single spray removed 67% of the dust from the optimal surface, compared to only 26% for the reference, highlighting its excellent self-cleaning performance. Additionally, the optimal also showcased remarkable antifogging property, which had been maintained over the one-month exposure period without visible degradation. Moreover, the optimal sample exhibited a 2% enhancement in broadband light transmittance across the 400–1000 nm wavelength range, demonstrating strong potential for photovoltaic applications. The simultaneous achievement of antireflection, antifogging, and self-cleaning performance under both indoor and outdoor conditions over a one-month period has rarely been reported in the literature. Full article

(This article belongs to the Special Issue Applications of Self-Cleaning Photocatalytic Coatings)

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12 pages, 3666 KB

Open AccessArticle

Development and Experimental Validation of a Filament-Assisted Chemical Vapor Deposition (FACVD) Reactor Using a Plastic Chamber

by Him Chan Kang, Jeong Heon Lee and Jae B. Kwak

Coatings 2025, 15(10), 1213; https://doi.org/10.3390/coatings15101213 - 15 Oct 2025

Viewed by 134

Abstract

This study explored the feasibility of using a plastic vacuum chamber for the Filament-Assisted Chemical Vapor Deposition (FACVD) of polymer thin films. Traditional chemical vapor deposition (CVD) methods often require high vacuum and elevated temperatures, which limit their use for heat-sensitive and flexible [...] Read more.

This study explored the feasibility of using a plastic vacuum chamber for the Filament-Assisted Chemical Vapor Deposition (FACVD) of polymer thin films. Traditional chemical vapor deposition (CVD) methods often require high vacuum and elevated temperatures, which limit their use for heat-sensitive and flexible substrates. FACVD enables polymer deposition under mild vacuum and temperature conditions, providing an opportunity to utilize plastic vacuum chambers as cost-effective and easily machinable alternatives to metallic chambers. In this study, a custom-designed acrylic chamber was fabricated and integrated into an FACVD system. Glycidyl methacrylate (GMA) and tert-butyl peroxide (TBPO) were considered as the monomer and initiator, respectively, for creating thin films under a low-temperature and moderate-vacuum deposition process. Polymeric film (pGMA) contains reactive epoxy groups that allow versatile post-polymerization modifications and are widely applied in coatings and biomedical fields. Preliminary experiments demonstrated the successful growth of pGMA thin films, with Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) confirming the characteristic polymer features, including the disappearance of the C=C stretching band as direct evidence of polymerization. Ellipsometry determines a uniformity of film thickness of approximately 85% for the 4-inch wafers’ area, with deposition rates in the range of 18–26 nm/h. These results highlight the potential of polymer-based chambers as cost-effective and versatile alternatives to advanced vapor-phase polymerization processes. 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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18 pages, 8338 KB

Open AccessArticle

Influence of Laser Power on Crack Evolution During Selective Laser Melting Manufacturing Process of Aluminum–Lithium Alloys

by Haibin Ji, Ke Lin, Yingjie Gao, Shuai Wei and Caiyun Shi

Coatings 2025, 15(10), 1212; https://doi.org/10.3390/coatings15101212 - 14 Oct 2025

Viewed by 325

Abstract

Aluminum–lithium alloys, as promising next-generation aerospace materials, exhibit outstanding properties, such as high strength, low density, excellent cryogenic performance, and superior corrosion resistance. In this study, aluminum–lithium alloy powders were processed via selective laser melting to systematically investigate the effects of processing parameters [...] Read more.

Aluminum–lithium alloys, as promising next-generation aerospace materials, exhibit outstanding properties, such as high strength, low density, excellent cryogenic performance, and superior corrosion resistance. In this study, aluminum–lithium alloy powders were processed via selective laser melting to systematically investigate the effects of processing parameters on manufacturing quality, microstructure, microhardness, residual stress, and tensile properties, with a particular emphasis on crack initiation and evolution. The results demonstrate that increasing laser power significantly improves specimen densification and reduces surface roughness. Moreover, the number of cracks decreases while their average length increases with elevated laser power. The maximum microhardness of 106.8 HV was achieved at the highest laser power, which also corresponded to the optimal tensile performance. These findings provide valuable insights into the relationship between laser parameters, microstructural evolution, and mechanical behavior, offering practical guidance for optimizing process parameters in the SLM fabrication of Al-Li alloy components for aerospace applications. Full article

(This article belongs to the Section Laser Coatings)

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29 pages, 23723 KB

Open AccessArticle

Active Surfaces in Sensor Technologies Utilizing Ceramic Nanotube-Conducting Polymer Composites Containing Embedded Gold Nanoparticles

by Alexandru Florentin Trandabat, Romeo Cristian Ciobanu and Oliver Daniel Schreiner

Coatings 2025, 15(10), 1211; https://doi.org/10.3390/coatings15101211 - 14 Oct 2025

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Abstract

This study describes the approach to develop hybrid nanostructures made of four varieties of ceramic nanotubes and three types of conductive polymers embedded with gold nanoparticles through a novel technique, which can exhibit distinct sensory properties not documented in the existing literature. Atomic [...] Read more.

This study describes the approach to develop hybrid nanostructures made of four varieties of ceramic nanotubes and three types of conductive polymers embedded with gold nanoparticles through a novel technique, which can exhibit distinct sensory properties not documented in the existing literature. Atomic force microscopy (AFM) analysis highlighted the characteristics of their surface roughness, identifying which could be the best choice for electrochemical electrodes depending on their surface structure. The incorporation of gold nanoparticles modifies the surface structure and forces the original grains to create voids that allow the gold particles to penetrate deeper and gather in small clusters, which in turn leads to a minor increase in grain size and localized sharpening of the peaks. The analysis mainly identified the peaks that were higher in relation to the valleys to identify a Gaussian distribution. It turned out that the configuration of ZnO nanotubes in the composites leads to the highest Ra values, with Al₂O₃ nanotubes coming in second place. Regarding the contribution of conducting polymers, PANI:EB presented the highest importance for all composites, while P3HT was relevant in several other cases. The evaluation of the electrode roughness, as described in this paper, is essential for the evaluation of its potential electrochemical activity and acts as a reliable measure that goes beyond the role of the evaluation of the active surface area (EASA). In our opinion, the evaluation of the EASA by traditional approaches described in the literature is not relevant for sensor applications, since the evaluation of the electrode surface structure must be performed before electrochemical tests, because the general electrochemical tests designed for sensor applications do not evaluate the EASA. Consequently, a thorough assessment of the electrode surface structure is advised, choosing the optimal electrodes according to this design, and additional data obtained from cyclic voltammetry will finally ascertain the true EASA and the actual performance of the respective electrode for identifying the target molecules. Full article

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

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18 pages, 3511 KB

Open AccessArticle

Nb₂CT_x Mxene—Pistachio Shell-Filled Chitosan Coatings on Zn Biomaterial for In Vitro Corrosion and Bioactivity Improvement

by Mehmet Topuz and Fatma Coskun Topuz

Coatings 2025, 15(10), 1210; https://doi.org/10.3390/coatings15101210 - 14 Oct 2025

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Abstract

This study aims to enhance the corrosion resistance and bioactivity of zinc surfaces through the development of chitosan–pistachio shell (CPM) coatings reinforced with Nb₂CT_x MXene. The approach introduces a sustainable pathway by incorporating waste pistachio shells as a natural, eco-friendly [...] Read more.

This study aims to enhance the corrosion resistance and bioactivity of zinc surfaces through the development of chitosan–pistachio shell (CPM) coatings reinforced with Nb₂CT_x MXene. The approach introduces a sustainable pathway by incorporating waste pistachio shells as a natural, eco-friendly additive within a biopolymer matrix. Comprehensive structural and surface characterizations confirmed the homogeneous dispersion of Nb₂CT_x and the successful fabrication of the hybrid coating. Electrochemical analyses in simulated body fluid demonstrated that the CPM coatings markedly improved the corrosion protection of zinc by shifting the corrosion potential to more noble values, reducing current density and increasing polarization resistance. Impedance results further indicated enhanced charge transfer resistance and stable diffusion-controlled behavior. The coatings also exhibited stronger adhesion, higher hydrophilicity, and improved surface compatibility. After immersion in simulated body fluid, the formation of a dense apatite layer on the CPM surface confirmed the coating’s excellent bioactivity. These findings demonstrate that Nb₂CT_x-reinforced CPM coatings significantly enhance the functional performance of zinc, combining corrosion resistance, biocompatibility, and mechanical stability. Moreover, the use of pistachio shell waste underscores the potential of sustainable biomaterials in developing environmentally friendly coatings for biomedical applications. Full article

(This article belongs to the Special Issue Metallic Materials and Alloys: Corrosion Protection, Mechanical Properties and Applications)

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16 pages, 6717 KB

Open AccessArticle

A Novel Organic–Inorganic Composite with Outstanding Comprehensive Reinforcement Properties for Dealing with Salt Efflorescence of Pottery

by Tao Tan, Nuo Xu, Xinyuan Su, Rui Chu, Zhanhui Peng, Shukun Shen, Zhihui Jia, Yajun Zhou, Huiping Xing, Yuhu Li and Xiaolian Chao

Coatings 2025, 15(10), 1209; https://doi.org/10.3390/coatings15101209 - 14 Oct 2025

Viewed by 263

Abstract

Salt efflorescence is always a main barrier for pottery cultural relic conservation. This study presents an innovative two-step process for enhancing the reinforced strength of efflorescence pottery. The first step involves forming a cross-linked mesh structure on the weathered surfaces using ethyl orthosilicate [...] Read more.

Salt efflorescence is always a main barrier for pottery cultural relic conservation. This study presents an innovative two-step process for enhancing the reinforced strength of efflorescence pottery. The first step involves forming a cross-linked mesh structure on the weathered surfaces using ethyl orthosilicate hydrolysate as an organic reinforcement material. In the second step, a two-component inorganic reinforcement material is developed to transform the destructive salt into a filling reinforcement material. The reinforcement pottery was comparatively investigated by XRD, color difference analysis, penetration depth measurements, mechanical strength tests, permeability assessment, and surface morphology characterization. The results demonstrate that the optimized reinforcement material exhibits high water permeability (up to 2.5 cm in penetration depth), stable color variation (ΔE up to 1.44), and excellent mechanical properties (17.01 MPa compressive strength and 2.66 MPa flexural strength). This work presents a promising technique for enhancing the structural interlocking between reinforcement pottery, which is crucial for mitigating dominant salt damage, and suggests an effective strategy that is applicable to the protection of cultural relics. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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21 pages, 4323 KB

Open AccessArticle

Synergistic Enhancement of Microbial Fuel Cell Performance via Hierarchical NiCo₂O₄/Polypyrrole-Modified Carbon Felt Anode

by Yuchu Chen, Jiuming Lei, Zhijie Wang, Xiangquan Kong, Ting Zhang, Yishuai Li, Xianheng Yang, Jinlong Zuo, Jie Li and Yuyang Wang

Coatings 2025, 15(10), 1208; https://doi.org/10.3390/coatings15101208 - 14 Oct 2025

Viewed by 302

Abstract

In this study, a carbon felt (CF)-based ternary composite anode was developed through the decoration of nickel cobaltite (NiCo₂O₄) nano-needles and subsequent in situ electropolymerization of polypyrrole (PPy). The structural and electrochemical properties of the modified electrodes were systematically [...] Read more.

In this study, a carbon felt (CF)-based ternary composite anode was developed through the decoration of nickel cobaltite (NiCo₂O₄) nano-needles and subsequent in situ electropolymerization of polypyrrole (PPy). The structural and electrochemical properties of the modified electrodes were systematically characterized. The CF/NiCo₂O₄/PPy anode demonstrated significantly enhanced bioelectrochemical activity, achieving a peak current density of 96.0 A/m² and a steady-state current density of 28.9 A/m², which were 4.85 and 5.90 times higher than those of bare carbon felt, respectively. Geobacteriaceae is a type of electrogenic bacteria. It was hardly detected on the bare CF substrate; however, in the ternary CF/NiCo2O4/PPy electrode, the relative abundance of Geobacteriaceae significantly increased to 43%. Moreover, the composite electrode exhibited superior charge storage performance, with a total charge (Q_t) of 32,509.0 C/m² and a stored charge (Q_s) of 3609.0 C/m² measured under a 1000 s charging/discharging period. The MFC configured with the CF/NiCo₂O₄/PPy anode reached a maximum power density of 1901.25 mW/m² at an external resistance of 200 Ω, nearly six times that of the unmodified CF-based MFC. These improvements are attributed to the synergistic interaction between the pseudocapacitive NiCo₂O₄ and conductive PPy, which collectively facilitate electron transfer, promote microbial colonization, and enhance interfacial redox kinetics. This work provides an effective strategy for designing high-performance MFC electrodes with dual functionality in energy storage and power delivery. Full article

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19 pages, 7868 KB

Open AccessArticle

Numerical Investigation of Ice Crystal Effects on Aircraft Icing Under Mixed-Phase Conditions

by Huijie Li, Afang Jin, Bo Yang, Mingzhao Li and Shuhao Zhou

Coatings 2025, 15(10), 1207; https://doi.org/10.3390/coatings15101207 - 14 Oct 2025

Viewed by 247

Abstract

This study presents numerical simulations of ice crystal accretion on aircraft surfaces under mixed-phase icing conditions, where ice crystals coexist with supercooled water droplets. The Finite Element Navier–Stokes Analysis Program (FENSAP-ICE) suite, incorporating the Discrete Roughness Optimization Program in 3D (DROP3D) and Ice [...] Read more.

This study presents numerical simulations of ice crystal accretion on aircraft surfaces under mixed-phase icing conditions, where ice crystals coexist with supercooled water droplets. The Finite Element Navier–Stokes Analysis Program (FENSAP-ICE) suite, incorporating the Discrete Roughness Optimization Program in 3D (DROP3D) and Ice Accretion Simulation in 3D (ICE3D) solvers, was applied to the Common Research Model with Natural Laminar Flow (CRM-NLF) to examine the effects of crystal size, aspect ratio, and concentration on ice growth. The results show that the presence of ice crystals produces smoother, more uniform, and substantially thicker ice compared with droplet-only cases, where distinct horns and roughness dominate. At peak growth locations, the predicted ice thickness increases by up to 75% under mixed-phase conditions. Quantitative analyses reveal that increasing crystal diameter from 50 μm to 200 μm raises ice growth by 25%–75%, increasing aspect ratios from 0.05 to 1 increases growth by 20%–75%, and raising concentrations from 0.25 to 2 kg/m³ enhances growth by nearly 450%. These findings demonstrate the critical role of ice crystals in promoting layered ice accumulation, clarify the mechanisms driving mixed-phase icing, and provide theoretical guidance for advancing anti-icing and de-icing technologies in aviation. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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18 pages, 2083 KB

Open AccessArticle

Adsorption and Desorption Characteristics of Nano-Metal-Modified Zeolite for Removal of Oxygenated Volatile Organic Compounds

by Yue Wang, Hairong Jiang, Wenhui Wei, Zhengao Zhang, Xiaowei Wang, Minglu Zhang and Lianhai Ren

Coatings 2025, 15(10), 1206; https://doi.org/10.3390/coatings15101206 - 13 Oct 2025

Viewed by 243

Abstract

Oxygenated volatile organic compounds are key precursors of secondary photochemical pollutants. To enhance their removal, NaY–zeolite was modified with nano-sized metals (Fe, Ti, Si, or Ce) using impregnation and sol–gel methods. Dynamic adsorption experiments were conducted to evaluate the adsorption of ethanol, acetaldehyde, [...] Read more.

Oxygenated volatile organic compounds are key precursors of secondary photochemical pollutants. To enhance their removal, NaY–zeolite was modified with nano-sized metals (Fe, Ti, Si, or Ce) using impregnation and sol–gel methods. Dynamic adsorption experiments were conducted to evaluate the adsorption of ethanol, acetaldehyde, and ethyl acetate under various condition modifications, including of the impregnation concentration, treatment time, and calcination temperature. The structural and surface properties of the modified zeolites were characterized by N₂ adsorption–desorption isotherm, X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR) analyses. The results indicated that the metal-loaded zeolites exhibited significantly higher adsorption capacities than the unmodified NaY–zeolite. Among them, silicon-modified zeolite showed the best performance, with its adsorption capacities for ethanol, acetaldehyde, and ethyl acetate increasing from 32.4, 72.4, and 123.0 mg·g⁻¹ to 49.82, 88.94, and 207.02 mg·g⁻¹, corresponding to improvements of 37%, 23%, and 70%. The optimal modification conditions involved the use of silicon as the modifier with a 7% impregnation concentration, a 12 h impregnation time, and calcination at 350 °C; the zeolite modified under these conditions was characterized by a good adsorption capacity and low preparation cost. This study suggests newly designed adsorber materials suitable for highly efficient treatment of oxygenated volatile organic compounds. Full article

(This article belongs to the Special Issue Surface Structure and Adsorption Properties of Mesoporous Materials for Pollutant Removal)

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11 pages, 3402 KB

Open AccessArticle

Synergistic Enhancement of Stain Resistance in Exterior Wall Coatings Using SiO₂-TiO₂ Composite Overlay

by Lian-Jie Dong, Hong-Ke Pan, Cheng-Di Li, Shuo-Peng Cao, Yong-Chun Ma and Jia-Hong Luo

Coatings 2025, 15(10), 1205; https://doi.org/10.3390/coatings15101205 - 13 Oct 2025

Viewed by 239

Abstract

Architectural exterior wall coatings require a balance of elasticity, stain resistance, and durability. Although nano-SiO₂ enhances fracture resistance in elastic coatings, its limited hydrophobicity allows pollutant adhesion. Nano-TiO₂ can photocatalytically degrade organics but is often encapsulated by the polymer matrix, reducing [...] Read more.

Architectural exterior wall coatings require a balance of elasticity, stain resistance, and durability. Although nano-SiO₂ enhances fracture resistance in elastic coatings, its limited hydrophobicity allows pollutant adhesion. Nano-TiO₂ can photocatalytically degrade organics but is often encapsulated by the polymer matrix, reducing its effectiveness. This study introduces a SiO₂-TiO₂ composite topcoat applied via aqueous dispersion to overcome these limitations. Experimental results demonstrate that the composite coating significantly outperforms single-component modifications, improving stain resistance by 21.3% after 12 months of outdoor exposure. The surface remains brighter with markedly reduced pollutant accumulation. Mechanistically, SiO₂ serves as an inert mesoporous carrier that improves the dispersion and photostability of TiO₂, minimizing agglomeration and photocorrosion. Its inherent hardness and hydrophobicity reduce physical adsorption sites. Together, SiO₂ and TiO₂ create a nanoscale rough surface that enhances hydrophobicity through a lotus-like effect. Under UV irradiation, TiO₂ generates radicals that decompose organic pollutants and inhibit microbial growth, enabling efficient self-cleaning with rainwater. This synergistic mechanism addresses the limitations of individual nanoparticles, successfully integrating elasticity with long-term anti-fouling and durability. This composite demonstrates a significant advancement in stain resistance and overall durability, offering potential applications in energy-efficient and environmentally sustainable building technologies. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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13 pages, 5859 KB

Open AccessArticle

Influences of SiO₂ Additions on the Structures and Thermal Properties of AlTaO₄ Ceramics as EBC Materials

by Bingyan Wu, Luyang Zhang, Lin Chen, Jiankun Wang, Zipeng Gao and Jing Feng

Coatings 2025, 15(10), 1204; https://doi.org/10.3390/coatings15101204 - 13 Oct 2025

Viewed by 267

Abstract

Ceramic matrix composites (CMCs) are extensively utilized in aero engines due to their high-temperature stability; however, they are prone to environmental corrosion at high temperatures, and environmental barrier coatings (EBCs) are necessary to resist oxidation and corrosion. Among various EBC materials, AlTaO₄ [...] Read more.

Ceramic matrix composites (CMCs) are extensively utilized in aero engines due to their high-temperature stability; however, they are prone to environmental corrosion at high temperatures, and environmental barrier coatings (EBCs) are necessary to resist oxidation and corrosion. Among various EBC materials, AlTaO₄ offers high cost-effectiveness and low thermal expansion coefficients (TECs), but its resistance to SiO₂ erosion and high-temperature stability remain unclear. We investigated the influences of SiO₂ additions on the structures and thermal properties of AlTaO₄; and AlTaO₄ mixtures containing 10 wt.% SiO₂ were kept at 1400 °C for 30–120 h. AlTaO₄ exhibited excellent high-temperature phase stability, and SiO₂ dissolved into AlTaO₄ to generate a solid solution. XRD Rietveld refinement was employed to confirm the position of Si in the lattices, while SEM and EDS characterizations demonstrated the homogeneous distribution of Si, Al, and Ta elements. At 1200 °C, the TECs of SiO₂-AlTaO₄ (4.65 × 10⁻⁶ K⁻¹) were close to those of SiC (4.5–5.5 × 10⁻⁶ K⁻¹). Additionally, the addition of SiO₂ could reduce TECs of AlTaO₄, a feature that helped alleviate the interface thermal stress between AlTaO₄ and the Si bond coat in the EBC systems. At 900 °C, the thermal conductivity was reduced by 26.9% compared to that of AlTaO₄, and the lowest value was 1.65 W·m⁻¹·K⁻¹. Accordingly, SiO₂ will enter the lattices of AlTaO₄ after heat treatments at 1400 °C, and SiO₂ additions will reduce the thermal conductivity and TECs of AlTaO₄, which is beneficial for its EBC applications. Full article

(This article belongs to the Section Ceramic Coatings and Engineering Technology)

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27 pages, 1777 KB

Open AccessReview

A Review of the Developments in Capacity-Uprating Conductors for Overhead Transmission Lines

by Bo Li, Quan Hu, Ruyue Guo, Jin Hu, Zhouzhuang Fen, Xujiang Hua, Tao Zhu and Yuan Yuan

Coatings 2025, 15(10), 1203; https://doi.org/10.3390/coatings15101203 - 13 Oct 2025

Viewed by 360

Abstract

Globally escalating electricity demand necessitates substantial power grid capacity expansion. Current transmission line capacity enhancement technologies are seriously constrained by factors including limited accuracy of computational models, elevated line losses, requirements for new line construction, and substantial capital investment. Capacity-uprating conductors, recognized for [...] Read more.

Globally escalating electricity demand necessitates substantial power grid capacity expansion. Current transmission line capacity enhancement technologies are seriously constrained by factors including limited accuracy of computational models, elevated line losses, requirements for new line construction, and substantial capital investment. Capacity-uprating conductors, recognized for their superior current-carrying performance and cost-effective retrofitting, represent one of the most viable solutions for transmission augmentation. However, their large-scale deployment remains impeded by increased line losses and high costs. This review systematically analyses critical constraints on transmission line ampacity through computational modeling and elucidates conductor heat dissipation pathways. Based on this foundation, we synthesize recent advancements in capacity-uprating conductors across three key dimensions: structural optimization, material engineering, and passive radiative cooling technologies. We concurrently evaluate their applications in power transmission projects and explore promising future development directions. This review aims to provide a theoretical foundation, guiding next-generation capacity enhancement solutions for grid modernization. Full article

(This article belongs to the Special Issue Durability of Transmission Lines)

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14 pages, 1423 KB

Open AccessArticle

Electric and Thermal Performance Evaluation of a Serpentine-Pipe PVT Solar Collector

by Miaoxian Lyu, Haoyun Ke, Jianyong Zhan and Jicheng Zhou

Coatings 2025, 15(10), 1202; https://doi.org/10.3390/coatings15101202 - 12 Oct 2025

Viewed by 234

Abstract

The promotion and application of a solar photovoltaic thermal (PVT) collector is increasingly favored. In this paper, a solar PVT collector with a serpentine pipe has been investigated by using the double iteration strategy. The simulation results are in good agreement with the [...] Read more.

The promotion and application of a solar photovoltaic thermal (PVT) collector is increasingly favored. In this paper, a solar PVT collector with a serpentine pipe has been investigated by using the double iteration strategy. The simulation results are in good agreement with the experimental data. The effects of ambient temperature, solar irradiance, distance between pipes, pipe diameter and mass flow rate on the thermal efficiency and photoelectric conversion efficiency (PCE) are discussed. Specifically, the results show that with an increase in the ambient temperature, the thermal efficiency of the collectors increases and the PCE decreases. By contrast, as the inlet water temperature decreases, the heat dissipation capacity is enhanced, which in turn both improves its thermal efficiency and PCE. Furthermore, the reduction in the distance between pipes also helps to improve thermal efficiency. However, when the distance between pipes is reduced to 0.1 m, the reduction in the thermal efficiency is not significant. It is worth noting that there exists an optimal solution to the influence of the pipe diameter on the thermal performance of the collector. This implies that the large pipe diameter will reduce the thermal efficiency to some extent. In addition, as the mass flow rate increases, the thermal efficiency is improved, and the plate temperature and outlet water temperature decrease simultaneously, with a greater decrease in outlet water temperature. Full article

(This article belongs to the Special Issue Thin Layers for Applications in Photovoltaic Solar Cells)

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24 pages, 3803 KB

Open AccessReview

Review of Preparation and Key Functional Properties of Micro-Arc Oxidation Coatings on Various Metal Substrates

by Ningning Li, Huiyi Wang, Qiuzhen Liu, Zhenjie Hao, Da Xu, Xi Chen, Datian Cui, Lei Xu and Yaya Feng

Coatings 2025, 15(10), 1201; https://doi.org/10.3390/coatings15101201 - 12 Oct 2025

Viewed by 365

Abstract

Micro-arc oxidation (MAO) technology demonstrates remarkable advantages in fabricating ceramic coatings on lightweight alloys. For aluminum alloys, MAO rapidly forms dense, pore-free ceramic layers within minutes, significantly enhancing corrosion and wear resistance at low processing costs. In magnesium alloys, optimized electrolyte compositions and [...] Read more.

Micro-arc oxidation (MAO) technology demonstrates remarkable advantages in fabricating ceramic coatings on lightweight alloys. For aluminum alloys, MAO rapidly forms dense, pore-free ceramic layers within minutes, significantly enhancing corrosion and wear resistance at low processing costs. In magnesium alloys, optimized electrolyte compositions and process parameters enable composite coatings with a combination of high hardness and self-lubrication properties, while post-treatments like laser melting or corrosion inhibitors extend salt spray corrosion resistance. Titanium alloys benefit from MAO coatings with exceptional interfacial bonding strength and mechanical performance, making them ideal for biomedical implants and aerospace components. Notably, dense ceramic oxide films grown in situ via MAO on high-entropy alloys (HEAs) triple surface hardness and enhance wear/corrosion resistance. However, MAO applications on steel require pretreatments like aluminizing, thermal spraying, or ion plating. Current challenges include coating uniformity control, efficiency for complex geometries, and long-term stability. Future research focuses on multifunctional coatings (self-healing, antibacterial) and eco-friendly electrolyte systems to expand engineering applications. Full article

(This article belongs to the Special Issue Advances in Alloy Surface Mechanics: The Effects of Coating Technologies on Performance)

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18 pages, 4685 KB

Open AccessArticle

Comparison of Microstructure and Properties of CoCrMo Coatings Prepared by High-Speed and Conventional Laser Cladding

by Tianyu Wang, Qingquan Li, Fengping Huo, Haitao Chen and Tongzhou Xu

Coatings 2025, 15(10), 1200; https://doi.org/10.3390/coatings15101200 - 12 Oct 2025

Viewed by 322

Abstract

High-speed laser cladding technology is an innovative process that reduces costs and enhances coating quality. In this study, CoCrMo wear-resistant coatings were fabricated on a 40Cr steel substrate using high-speed laser cladding technology and compared to CoCrMo coatings produced by traditional methods. The [...] Read more.

High-speed laser cladding technology is an innovative process that reduces costs and enhances coating quality. In this study, CoCrMo wear-resistant coatings were fabricated on a 40Cr steel substrate using high-speed laser cladding technology and compared to CoCrMo coatings produced by traditional methods. The effects of both processes on the microstructure, nanoindentation characteristics, and wear behavior of CoCrMo coatings were examined. The results show that the phase compositions of both coatings include γ-Co solid solution and ε-Co solid solution. The high cooling rate of high-speed laser cladding significantly suppressed Mo precipitation, enhancing Mo solid solution strengthening. Additionally, the fine-grain strengthening effect induced by the high cooling rate contributed significantly to the coatings’ mechanical properties. The nano-hardness of the HS-CoCrMo coatings reached approximately 5.18 ± 0.23 GPa, 1.2 times higher than that of the N-CoCrMo coatings. Furthermore, the generalized hardness, H/E ratio, and H³/E² ratio of HS-CoCrMo coatings were improved. This increase in nano-hardness significantly boosted the wear resistance of HS-CoCrMo coatings, yielding an average friction coefficient of approximately 0.466, with wear volume and specific wear rate values of 6.55 × 10⁶ μm³ and 0.87 × 10⁻⁵ mm³/N·m, respectively, outperforming the N-CoCrMo coatings. The main wear mechanisms for the HS-CoCrMo coatings were abrasive wear, adhesive wear, and oxidative wear. In conclusion, high-speed laser cladding technology produces high-performance, wear-resistant coatings with high productivity, offering broader application prospects for the metallurgical and power industries, while effectively reducing production cycles and usage costs. Full article

(This article belongs to the Special Issue Laser Additive Manufacturing: Materials, Technologies, and Applications)

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14 pages, 5210 KB

Open AccessArticle

Study on Discharge Behavior of Hollow Tungsten Arc Coaxially Assisted by Fiber Laser Welding

by Zheng Lei, Zongtao Zhu, Hui Chen and Xu Zhao

Coatings 2025, 15(10), 1199; https://doi.org/10.3390/coatings15101199 - 12 Oct 2025

Viewed by 286

Abstract

In this study, a processing platform based on hollow tungsten arc coaxially assisted by fiber laser (HTAAL) was developed. The HTAAL discharge process was analyzed through physical experiments and numerical simulations. The coupling effect between the laser and the hollow tungsten arc (HTA) [...] Read more.

In this study, a processing platform based on hollow tungsten arc coaxially assisted by fiber laser (HTAAL) was developed. The HTAAL discharge process was analyzed through physical experiments and numerical simulations. The coupling effect between the laser and the hollow tungsten arc (HTA) was examined, the factors influencing HTAAL discharge stability were identified, and the coupling mechanism was explained separately. The findings showed that laser power had a significant impact on HTAAL discharge behavior. As laser power increased, the arc discharge exhibited different types. The variations in discharge were attributed to differences in several aspects, including discharge mode, current density distribution, high-temperature zone shape, arc conductivity, and the effect of laser plasma under different laser power conditions. Full article

(This article belongs to the Special Issue Advanced Surface Technology and Application)

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17 pages, 3861 KB

Open AccessArticle

Substrate Temperature-Induced Crystalline Phase Evolution and Surface Morphology in Zirconium Thin Films Deposited by Pulsed Laser Ablation

by Berdimyrat Annamuradov, Zikrulloh Khuzhakulov, Mikhail Khenner, Jasminka Terzic, Danielle Gurgew and Ali Oguz Er

Coatings 2025, 15(10), 1198; https://doi.org/10.3390/coatings15101198 - 11 Oct 2025

Viewed by 319

Abstract

Zirconium (Zr) thin films were deposited on silicon (Si) substrates via pulsed laser deposition (PLD) using a 248 nm excimer laser. The effects of substrate temperature on film morphology and crystallinity were systematically investigated. X-ray diffraction (XRD) revealed that the Zr(100) plane exhibited [...] Read more.

Zirconium (Zr) thin films were deposited on silicon (Si) substrates via pulsed laser deposition (PLD) using a 248 nm excimer laser. The effects of substrate temperature on film morphology and crystallinity were systematically investigated. X-ray diffraction (XRD) revealed that the Zr(100) plane exhibited the strongest orientation at 400 °C while Zr (002) was maximum at 500 °C. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses demonstrated an increase in surface roughness with temperature, with the smoothest surface observed at lower temperatures and significant island formation at 500 °C due to the transition to 3D growth. At 500 °C, interdiffusion effects led to the formation of zirconium silicide at the Zr/Si interface. To further interpret the experimental findings, computational modeling was employed to analyze the transition from 2D layer-by-layer growth to 3D island formation at elevated temperatures. Using a multi-parameter kinetics-free model based on free energy minimization, the critical film thickness for this transition was determined to be ~1–2 nm, aligning well with experimental observations. A separate kinetic model of island nucleation and growth predicts that this shift is driven by the kinetics of adatom surface diffusion. Additionally, the kinetic simulations revealed that, at 400 °C, adatom diffusivity optimally balances crystallization and surface energy minimization, yielding the highest film quality. At 500 °C, the rapid increase in diffusivity leads to the proliferation of 3D islands, consistent with the roughness trends observed in SEM and AFM data. These findings underscore the critical role of deposition parameters in tailoring Zr thin films for applications in advanced coatings and electronic devices. Full article

(This article belongs to the Collection Collection of Papers on Thin Film Deposition)

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28 pages, 8557 KB

Open AccessArticle

Surface Optimization of Additively Manufactured (AM) Stainless Steel Components Using Combined Chemical and Electrochemical Post-Processing

by Pablo Edilberto Sanchez Guerrero, Andrew Grizzle, Daniel Fulford III, Juan Estevez Hernandez, Lucas Rice and Pawan Tyagi

Coatings 2025, 15(10), 1197; https://doi.org/10.3390/coatings15101197 - 11 Oct 2025

Viewed by 303

Abstract

The design and production of goods have been completely transformed by additive manufacturing (AM), which makes it possible to create components with intricate and complex geometries that were previously impossible or impractical to produce. However, current technologies continue to produce coarse-surfaced metal components [...] Read more.

The design and production of goods have been completely transformed by additive manufacturing (AM), which makes it possible to create components with intricate and complex geometries that were previously impossible or impractical to produce. However, current technologies continue to produce coarse-surfaced metal components that typically exhibit fatigue properties, resulting in component failure and unfavorable friction coefficients on the printed part. Therefore, to improve the surface quality of the fabricated parts, post-processing of AM-created components is required. With emphasis on electroless nickel plating, ChemPolishing (CP), and ElectroPolishing (EP), this study investigates post-processing methods for stainless steel that is additively manufactured (AM). The rough surfaces created by additive manufacturing (AM) restrict direct use. While ElectroPolishing (EP) achieves high material removal rates but may not be consistent, ChemPolishing (CP) offers uniform smoothening. Nickel plating enhances additive manufacturing (AM) products’ resistance to wear and scratches and corrosion protection. To optimize nickel deposition, medium (6%–9%) and high (10%–13%) phosphorus nickel was tested using the L9 Taguchi design of experiments (DOE). Mechanical properties, including scratch resistance and adhesion, were evaluated using the TABER 5900 reciprocating (Taber Industries, North Tonawanda, NY, USA) abraser apparatus, a 5 N scratch test, and ASTM B-733 thermal shock method. Surface analysis was performed with the KEYENCE VHX-7000 microscope (Keyence Corporation, Itasca, IL, USA), and chemical composition before and after nickel deposition was assessed via the ThermoFisher Phenom XL scanning electron microscope (SEM, Thermo Fisher Scientific, Waltham, MA, USA) Optimal processing conditions, determined using Qualitek-4 software, Version 20.1.0 revealed improvements in both surface finish and mechanical robustness. This comprehensive analysis underscores the potential of nickel-coated additive manufacturing (AM) parts for enhanced performance, offering a pathway to more durable and efficient additive manufacturing (AM) applications. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation, 2nd Edition)

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19 pages, 7441 KB

Open AccessArticle

The Influence Mechanism of the Hardness Homogeneity of the Grind-Hardening Layer on Its Wear Resistance

by Yu Guo, Minghe Liu and Yiming Zhang

Coatings 2025, 15(10), 1196; https://doi.org/10.3390/coatings15101196 - 11 Oct 2025

Viewed by 210

Abstract

Due to the random factors that influence grinding stability, hardness distribution appears in inhomogeneity at different locations on the hardened layer in grind-hardening technology. It may affect the wear resistance of parts. Therefore, in order to explore the influence mechanism of hardness homogeneity [...] Read more.

Due to the random factors that influence grinding stability, hardness distribution appears in inhomogeneity at different locations on the hardened layer in grind-hardening technology. It may affect the wear resistance of parts. Therefore, in order to explore the influence mechanism of hardness homogeneity on the wear resistance comprehensively, grind-hardening and friction experiments on AISI 1045 steel are carried out. Then, the causes of inhomogeneous hardness distribution are analyzed, and the influence of hardness homogeneity on wear resistance is also discussed. Combining the Archard wear model, the wear process of the hardened layer is simulated for analyzing the effect of contact stress distribution and action range on material loss in the worn area and finally realizing the prediction of the wear depth. The results show that the difference in microstructure distribution caused by the nonlinear variation in grinding force is the fundamental reason for the hardness inhomogeneity of the hardened layer. The hardness homogeneity results in the wear resistance of the cut-out end being superior to that of cut-in end. Additionally, the error between the predictive and the experimental value of the wear depth with different parameters is between 3.6% and 11.3%, thereby verifying the effectiveness of the theoretical research. Full article

(This article belongs to the Special Issue Advances of Hard Material Processing Technologies for Surface and Interface Improvement)

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