Coatings

16 pages, 3543 KB

Open AccessArticle

Multifunctional PDMS Composite Coating for Advanced Anti-Icing with Concurrent Mechanical Durability and Corrosion Protection

by Zaixiang Zheng, Shutong Wu, Jiawei Luo, Shengnan Yang, Junnan Cui, Zhimin Cao and Pan Cao

Coatings 2025, 15(8), 979; https://doi.org/10.3390/coatings15080979 - 21 Aug 2025

Viewed by 359

Abstract

Ice accretion on critical transportation infrastructure presents serious operational risks and economic challenges, highlighting the need for sustainable anti-icing solutions. This study develops a strong PDMS-based composite coating on aluminum by incorporating carbon nanotubes (CNTs) and carbon powder, effectively merging passive superhydrophobicity with [...] Read more.

Ice accretion on critical transportation infrastructure presents serious operational risks and economic challenges, highlighting the need for sustainable anti-icing solutions. This study develops a strong PDMS-based composite coating on aluminum by incorporating carbon nanotubes (CNTs) and carbon powder, effectively merging passive superhydrophobicity with photothermal capabilities. We systematically assess how different ratios of CNTs to carbon powder (3:1, 1:1, 1:3) influence surface morphology, wettability, anti-icing performance, mechanical durability, and corrosion resistance. The morphological analysis shows the formation of hierarchical micro/nano-structures, with the optimal 1:3 ratio (designated as P13) resulting in dense, porous agglomerates of intertwined CNTs and carbon powder. P13 demonstrates high-performing superhydrophobicity, with a contact angle of 139.7° and a sliding angle of 9.4°, alongside a significantly extended freezing delay of 180 s at −20 °C. This performance is attributed to reduced water–surface interaction and inhibited ice nucleation. Mechanical abrasion tests indicate remarkable durability, as P13 retains a contact angle of 132.5° and consistent anti-icing properties after enduring 100 abrasion cycles. Electrochemical analysis reveals exceptional corrosion resistance, particularly for P13, which achieves a notable 99.66% corrosion inhibition efficiency by creating a highly tortuous diffusion barrier that protects against corrosive agents. This multifunctional coating effectively utilizes the photothermal properties of CNTs, the affordability of carbon powder, the low surface energy of PDMS, and the thermal conductivity of aluminum, presenting a robust and high-performance solution for anti-icing applications in challenging environments. Full article

(This article belongs to the Special Issue Development and Application of Anti/De-Icing Surfaces and Coatings)

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22 pages, 9271 KB

Open AccessArticle

The Effect of Laser Cleaning on the Cr Coating on the Surface of Steel Tyre Moulds

by Yuan Ren, Jianfeng Li, Yinghao Xue, Liming Wang, Xinqiang Ma, Yongmei Zhu, Xingwei Yao, Li Lin and Wei Cheng

Coatings 2025, 15(8), 978; https://doi.org/10.3390/coatings15080978 - 21 Aug 2025

Viewed by 365

Abstract

To investigate the effect of laser cleaning on the chromium plating of steel tyre moulds, a solid-state laser with an average power of 500 W was used as the cleaning light source. By varying the energy density and the number of pulses applied [...] Read more.

To investigate the effect of laser cleaning on the chromium plating of steel tyre moulds, a solid-state laser with an average power of 500 W was used as the cleaning light source. By varying the energy density and the number of pulses applied to the exact location, the changes in the macro- and micro-morphology of the mould surface, surface element content, and chromium plating thickness before and after laser cleaning were studied. The results show that as the laser energy density increases, the cleaning effect improves significantly. However, when the energy density exceeds

1.02 \times 10^{4}

mJ/cm², cracks appear in the chrome-plated layer. By changing the number of pulses applied to a specific location, it was found that cracks also appear in the chrome-plated layer when the number of pulses exceeds three. These results provide a reference for the practical application of laser cleaning in the cleaning of chrome-plated steel tyre moulds. Full article

(This article belongs to the Section Laser Coatings)

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18 pages, 3320 KB

Open AccessArticle

Numerical and Experimental Investigation of Slot-Die Coating Regimes of Alumina Slurries on Glass and Dried Alumina Layer for Ceramic Additive Manufacturing

by Jeonghong Ha

Coatings 2025, 15(8), 977; https://doi.org/10.3390/coatings15080977 - 21 Aug 2025

Viewed by 458

Abstract

Slurry-based additive manufacturing (AM) enables the fabrication of dense and complex ceramic components through the layer-by-layer deposition of high-solid-content slurries. However, the reliable formation of uniform, defect-free slurry layers remains a bottleneck for process stability and final part quality. In this study, the [...] Read more.

Slurry-based additive manufacturing (AM) enables the fabrication of dense and complex ceramic components through the layer-by-layer deposition of high-solid-content slurries. However, the reliable formation of uniform, defect-free slurry layers remains a bottleneck for process stability and final part quality. In this study, the slot-die coating window for alumina slurry (50 wt%, viscosity = 34 Pa·s) was systematically investigated using volume-of-fluid simulations and experiments, with coating speed (0.7–2.8 mm/s), flow rate (0.6–0.8 mL/min), and coating gap (200–400 μm) as key variables. The coating process exhibited three distinct regimes, namely overflow, stable, and unstable, depending on process conditions. For a coating gap of 200 μm on a glass substrate, stable bead formation was observed over the widest coating speed range without overflow or air entrainment. At higher speeds, dynamic wetting failure induced air entrainment and bead breakage, while lower speeds led to overflow defects. When coating on a dried alumina layer (contact angle, CA = 137

°

), the stable window narrowed significantly compared to the glass substrate (CA = 66.7

°)

, highlighting the substantial influence of substrate wettability on coating stability and defect formation. The results derived in this work offer practical guidance for optimizing process parameters to achieve uniform, defect-free films in multilayer ceramic AM. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology, 3rd Edition)

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20 pages, 11628 KB

Open AccessArticle

Optimized Mix Proportion and Microstructural Mechanism of Foamed Concrete for Internal Molds in Hollow Concrete Components

by Bing Luo, Xu Dong, Rong Li, Dunlei Su, Yuanhui Qiao, Lingqiang Meng and Chenhao Zhang

Coatings 2025, 15(8), 976; https://doi.org/10.3390/coatings15080976 - 21 Aug 2025

Viewed by 389

Abstract

To address the issues of numerous influencing factors on material quality, difficulty in determining the optimal mix proportion, and the need to clarify the formation mechanism when foam concrete is used as an internal mold for prefabricated components, this study conducted orthogonal tests [...] Read more.

To address the issues of numerous influencing factors on material quality, difficulty in determining the optimal mix proportion, and the need to clarify the formation mechanism when foam concrete is used as an internal mold for prefabricated components, this study conducted orthogonal tests to investigate the influence laws of fly ash content, foam content, foaming agent dilution ratio, and water–binder ratio on the dry density and compressive strength of foam concrete, and determined the optimal mix proportion via analysis of variance (ANOVA). Additionally, scanning electron microscopy (SEM) tests were performed to analyze the effects of these four factors on the microscopic pore morphology of foam concrete from a microscopic perspective, thereby revealing its formation mechanism, and engineering applications were carried out. The results show that the primary-to-secondary order of factors affecting the dry density and compressive strength of foam concrete is as follows: foam content (B) > water–binder ratio (D) > foaming agent dilution ratio (C) > fly ash content (A). The optimal mix proportion is 5% fly ash content, 18% foam content, a 30-fold foaming agent dilution ratio, and a water–binder ratio of 0.55. Under this mix proportion, the pore size of foam concrete ranges from 200 μm to 500 μm with uniform distribution, and the pore spacing is between 20 μm and 30 μm, with almost no connected pores. When the foam concrete slurry sets and hardens, hydration products such as calcium silicate hydrate (C-S-H) gel, calcium hydroxide, ettringite (AFt), and monosulfate aluminate (AFm) are generated around the bubbles. The mechanical properties of foam concrete are afforded by the combined action of these hydration products and the pore structure. Full article

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

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13 pages, 1763 KB

Open AccessArticle

Influence of Plasma Nitriding Under Pulsed Nitrogen Flow on Expanded Austenite Formation and Surface Performance of ISO 5832-1 Stainless Steel

by Anna Carolina Sphair, Andrey Matheus Vianna, Carlos Maurício Lepienski, Gelson Biscaia de Souza, Euclides Alexandre Bernardelli and Marcio Mafra

Coatings 2025, 15(8), 975; https://doi.org/10.3390/coatings15080975 - 21 Aug 2025

Viewed by 423

Abstract

Plasma nitriding is a thermo-chemical treatment widely used to improve the tribological properties of austenitic stainless steel, due to the formation of an expanded austenite layer, which presents increased hardness. Although low-temperature plasma nitriding of austenitic stainless steels has been extensively studied in [...] Read more.

Plasma nitriding is a thermo-chemical treatment widely used to improve the tribological properties of austenitic stainless steel, due to the formation of an expanded austenite layer, which presents increased hardness. Although low-temperature plasma nitriding of austenitic stainless steels has been extensively studied in recent years, the reported results consistently show similarly high nitrogen concentrations, owing to the diffusive nature of the process. Excess nitrogen in the expanded austenite can impair the integrity of the treated surface and thus compromise the overall viability of the treatment. In such a context, the present work evaluated the use of intermittent nitrogen flow during plasma nitriding of ISO 5832-1 steel to control nitrogen concentration in the layer formed. Throughout the treatments, alternated cycles were applied between nitrogen flow periods and periods of interruption, which were repeated throughout the process. Different pulse conditions were used, in which the nitrogen flow corresponded to 10%, 15% and 50% of the cycle time. The results indicated that, in the intermittent flow condition with 50% time of nitrogen offer, the layer thickness, nitrogen concentration, and hardness values were very close to those observed in treatments carried out with continuous flow. On the other hand, in the conditions where the nitrogen flow was kept at 10% and 15% of the cycle, more significant differences were observed compared to the results obtained in continuous flow treatments. Nevertheless, those samples presented a substantial improvement in the surface hardness compared with the untreated steel. Therefore, the intermittent nitrogen flow can be used during plasma nitriding to control expanded austenite properties, enabling the design of surface properties. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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15 pages, 5445 KB

Open AccessArticle

Numerical Study on Chemical Vapor Deposition of Aluminide Coatings

by Shihong Xin, Baiwan Su, Qizheng Li and Chonghang Tang

Coatings 2025, 15(8), 974; https://doi.org/10.3390/coatings15080974 - 21 Aug 2025

Viewed by 351

Abstract

To ensure the mechanical performance of gas turbine hollow blades under high-temperature conditions, the application of aluminide high-temperature protective coatings on the inner gas flow channel surfaces of hollow blades via chemical vapor deposition (CVD) has become a critical measure for enhancing blade [...] Read more.

To ensure the mechanical performance of gas turbine hollow blades under high-temperature conditions, the application of aluminide high-temperature protective coatings on the inner gas flow channel surfaces of hollow blades via chemical vapor deposition (CVD) has become a critical measure for enhancing blade safety. This study employs computational fluid dynamics (CFD) to investigate the flow field within CVD reactors and the influences of deposition processes on the chemical reaction rates at sample surfaces, thereby guiding the optimization of CVD reactor design and deposition parameters. Three distinct CVD reactor configurations are examined to analyze the flow characteristics of precursor gases and the internal flow field distributions. The results demonstrate that Model A, featuring a bottom-positioned outlet and an extended inlet, exhibits a larger stable deposition zone with more uniform flow velocities near the sample surface, thereby indicating the formation of higher-quality aluminide coatings. Based on Model A, CFD simulations are conducted to evaluate the effects of process parameters, including inflow velocity, pressure, and temperature, on aluminide coating deposition. The results show that the surface chemical reaction rate increases with inflow velocity (0.0065–6.5 m/s), but the relative change rate (ratio of reaction rate to flow rate) shows a declining trend. Temperature variations (653–1453 K) induce a trapezoidal-shaped trend in deposition rates: an initial increase (653–1053 K), followed by stabilization (1053–1303 K), and a subsequent decline (>1303 K). The underlying mechanisms for this trend are discussed. Pressure variations (0.5–2 atm) reveal that both excessively low and high pressures reduce surface reaction rates, with optimal performance observed near 1 atm. This study provides a methodology and insights for optimizing CVD reactor designs and process parameters to enhance aluminide coating quality on turbine blades. Full article

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

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15 pages, 3999 KB

Open AccessArticle

Effect of Different N₂ Partial Pressures on the Corrosion Properties and Conductivity of NbN_x Coated Titanium Bipolar Plates for PEMFCs

by Bo Dang, Yu Han, Kai Yang, Dong Chen, Mengling Zhan, Feng Ding, Shuqin Li and Pingze Zhang

Coatings 2025, 15(8), 973; https://doi.org/10.3390/coatings15080973 - 20 Aug 2025

Viewed by 353

Abstract

Metal nitride coatings have been considered as a promising approach to improve the performance of metal bipolar plates for proton exchange membrane fuel cells (PEMFCs). In this study, NbN_x coatings with three different ratios of N₂/Ar (1:2, 1:1 and 3:1) [...] Read more.

Metal nitride coatings have been considered as a promising approach to improve the performance of metal bipolar plates for proton exchange membrane fuel cells (PEMFCs). In this study, NbN_x coatings with three different ratios of N₂/Ar (1:2, 1:1 and 3:1) were prepared on TC4 alloy substrates using the double glow plasma alloying technology. The NbN_x coatings are homogeneous and dense, and the phase of the coating transforms from hexagonal β-Nb₂N to δ′-NbN phase as the nitrogen content increases. All coatings demonstrate high protective efficiency, with the coating (N₂/Ar ratio of 3:1) displaying the lowest current density of 8.92 × 10⁻⁶ A/cm² at a working voltage of 0.6 V. The EIS results also show that this coating has the best corrosion resistance. Notably, it also presents the lowest interfacial contact resistance of 7.29 mΩ·cm² at 1.5 MPa and good hydrophobicity. More importantly, this study provides a new idea and method for corrosion-resistant coatings of metal bipolar plates for PEMFC applications. 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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25 pages, 5569 KB

Open AccessArticle

Effect of Indium Doping on the Photoelectric Properties of SnS Thin Films and SnS/TiO₂ Heterojunctions

by Jiahao Leng, Yaoxin Ding, Mingyang Zhang and Jie Shen

Coatings 2025, 15(8), 972; https://doi.org/10.3390/coatings15080972 - 20 Aug 2025

Viewed by 378

Abstract

This study addresses the need for efficient photoelectric materials by fabricating Indium-doped tin sulfide (SnS-In)/titanium dioxide (TiO₂) heterostructure thin films via radio frequency (RF) magnetron sputtering. We systematically investigated the synergistic enhancement of photoelectric properties from both In-doping and the heterostructure [...] Read more.

This study addresses the need for efficient photoelectric materials by fabricating Indium-doped tin sulfide (SnS-In)/titanium dioxide (TiO₂) heterostructure thin films via radio frequency (RF) magnetron sputtering. We systematically investigated the synergistic enhancement of photoelectric properties from both In-doping and the heterostructure design. SnS-In films with controlled In concentrations were prepared by embedding varying numbers of indium pellets into the SnS sputtering target. Our findings reveal that an optimal In doping of 4.93 at% significantly improves the crystalline quality and light absorption of SnS, reducing its band gap from 1.27 eV to 1.13 eV and enhancing carrier concentration and mobility. Subsequently, the optimized SnS-In film combined with TiO₂ formed a heterojunction, achieving a peak photocurrent density of 6.36 µA/cm² under visible light. This is 2.2 and 53.0 times higher than standalone SnS-In and TiO₂ films, respectively. This superior performance is attributed to the optimal In³⁺ doping effectively modulating the SnS band structure and the type-II heterojunction promoting efficient charge separation. This work demonstrates a promising strategy for optoelectronic conversion and photocatalysis by combining In-doping for SnS band structure engineering with TiO₂ heterostructure construction. Full article

(This article belongs to the Special Issue Electrochemical Properties and Applications of Thin Films)

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18 pages, 3254 KB

Open AccessArticle

On the Possibility of Improving Surface Geometrical Texture During High-Performance Machining of Aluminium Without the Use of Coolant

by Szymon Zgrzeblak, Daniel Grochała and Rafał Grzejda

Coatings 2025, 15(8), 971; https://doi.org/10.3390/coatings15080971 - 20 Aug 2025

Viewed by 493

Abstract

Sustainable production and material recycling as well as minimising energy input are the most important challenges of modern production engineering. Despite the accelerating development of incremental shaping technologies, machining is still an indispensable component of many machine part manufacturing processes. Like other manufacturing [...] Read more.

Sustainable production and material recycling as well as minimising energy input are the most important challenges of modern production engineering. Despite the accelerating development of incremental shaping technologies, machining is still an indispensable component of many machine part manufacturing processes. Like other manufacturing techniques, machining also has a significant impact on the environment, which should be reduced. One factor that has a negative impact on energy resources and the environment is the use of cutting fluids during machining. In this study, it was investigated whether it is possible to completely eliminate coolant in high-performance machining of parts made of aluminium and to what extent this limitation would affect changes in the shaped geometrical texture of the surface. To this end, experimental studies were carried out under industrial conditions, the results of which should be used in industrial production. The recommendations developed can influence the economic efficiency of mass production carried out in the automotive, engineering or aerospace sectors. The effect of the coolant on changes in the height indices and the unevenness of the surface geometrical texture as well as on changes in the indices describing its function was investigated. It was demonstrated that it is possible to perform high-performance dry machining without deteriorating surface geometrical texture. The effectiveness of dry milling is limited by the degree of surface unevenness when very high cutting speeds are used. Full article

(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)

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16 pages, 2001 KB

Open AccessArticle

Research on the Performance of Phosphorus-Building-Gypsum-Based Foamed Lightweight Soil in Road Reconstruction

by Wangchao Sun, Yuchen Cao, Fan Yang, Penghao Zhai, Chuizhong Kong and Fang Xu

Coatings 2025, 15(8), 970; https://doi.org/10.3390/coatings15080970 - 20 Aug 2025

Viewed by 419

Abstract

Current research on foamed lightweight soil primarily focuses on mechanical properties and durability, with few studies addressing its hydraulic characteristics and internal pore structure in road reconstruction applications. However, the material’s high porosity and low bulk density may significantly alter its mechanical properties [...] Read more.

Current research on foamed lightweight soil primarily focuses on mechanical properties and durability, with few studies addressing its hydraulic characteristics and internal pore structure in road reconstruction applications. However, the material’s high porosity and low bulk density may significantly alter its mechanical properties and durability under prolonged rainwater exposure, highlighting the importance of investigating its hydraulic characteristics and internal foam structure. Based on the analysis of water absorption and bulk density in phosphogypsum-based foamed lightweight soil, this study further discusses the material’s softening coefficient and internal pore structure through systematic data comparison. Experimental results demonstrate that the unconfined compressive strength (UCS) of both dry and water-soaked specimens increases linearly with dry density. Notably, soaked specimens with 0.5 g/cm³ dry density achieve compliant 7-day UCS values while displaying a steeper strength increase compared to dry specimens. A dry density of 0.64 g/cm³ ensures a softening coefficient exceeding 0.75, confirming the material’s suitability for humid environments. The material contains predominantly small pores (90% ≤ 0.2 mm diameter), with improved bubble distribution at the edges and higher upper porosity. Spherical pores (roundness 0.5–1) enhance mechanical properties, while phosphogypsum (optimal 10% dosage) effectively improves both strength and workability but requires corrosion control due to its hydration products. Full article

(This article belongs to the Special Issue Green and Low-Carbon Buildings: Materials, Technology and Processes and Techniques)

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18 pages, 15121 KB

Open AccessArticle

SEM Image Segmentation Method for Copper Microstructures Based on Enhanced U-Net Modeling

by Shiqi Yang, Jianpeng Zhu, Zhenfeng Cao, Minglai Yang and Ying Wang

Coatings 2025, 15(8), 969; https://doi.org/10.3390/coatings15080969 - 20 Aug 2025

Viewed by 502

Abstract

Grain boundary segmentation in scanning electron microscope (SEM) images of pure copper presents substantial challenges for traditional image processing methods, including constrained segmentation precision and difficulties in identifying elongated grain boundaries and intricate topological structures. To overcome these constraints, this research introduces a [...] Read more.

Grain boundary segmentation in scanning electron microscope (SEM) images of pure copper presents substantial challenges for traditional image processing methods, including constrained segmentation precision and difficulties in identifying elongated grain boundaries and intricate topological structures. To overcome these constraints, this research introduces a comprehensive framework that integrates dataset development, advanced data augmentation, and model optimization to achieve precise grain boundary segmentation. This work proposes three principal innovations. First, a meticulously curated small-scale dataset, combined with a sophisticated adaptive data augmentation strategy, addresses data scarcity and ensures high-quality, robust training data. Second, the U-Net model was refined by incorporating a self-attention mechanism, markedly enhancing its capability to capture global contextual information and accurately detect complex grain boundary features. Third, an optimized stratified K-fold cross-validation method was implemented to ensure equitable data partitioning and reduce overfitting, thereby strengthening the model’s generalization capability. Experimental results demonstrate that the proposed framework delivers exceptional performance on the validation dataset, achieving a global accuracy of 0.96, a Dice coefficient of 0.91, and a mean Intersection over Union (mIoU) of 0.85. These metrics underscore significant advancements in grain boundary segmentation precision for polycrystalline metal systems. The framework validates the power of deep learning in microstructural characterization and establishes a reliable computational tool for quantitative metallographic analysis. It is well-positioned to extend to the microstructural analysis of a broad range of heterogeneous materials, enabling deeper insights into microstructure–property relationships in materials engineering. Full article

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

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19 pages, 7946 KB

Open AccessArticle

Synergistic Disinfection of Photocatalytic Nanomaterials Exposed to UVC, Electricity and Magnetic Fields Against Candida albicans

by María Cristina Grijalva-Castillo, Renee Joselin Saénz-Hernández, Adrián Alberto Cobos-Márquez, Francisco Alonso Herrera-Ojeda, Fernando Efraín Díaz-Chávez, Irving Ricardo Acosta-Galindo, César Leyva-Porras, Alva Rocío Castillo-González, María Alejandra Favila-Pérez, Celia María Quiñonez-Flores, Javier Camarillo Cisneros and Carlos Arzate-Quintana

Coatings 2025, 15(8), 968; https://doi.org/10.3390/coatings15080968 - 19 Aug 2025

Viewed by 560

Abstract

Nosocomial infections caused by Candida albicans pose serious challenges to healthcare systems due to their persistence on medical surfaces and resistance to conventional disinfectants. This study evaluates antifungal properties of SnO₂ doped with silver and cuprite nanoparticles and WO₃ thin films, [...] Read more.

Nosocomial infections caused by Candida albicans pose serious challenges to healthcare systems due to their persistence on medical surfaces and resistance to conventional disinfectants. This study evaluates antifungal properties of SnO₂ doped with silver and cuprite nanoparticles and WO₃ thin films, as well as cobalt (CoFe₂O₄) and cobalt–nickel (Co_0.5Ni₀.₅Fe₂O₄) ferrite nanoparticles, activated by ultraviolet C (UVC) radiation, direct electric current (up to 100 V), and magnetic fields. SnO₂ films were synthesized by Spray Pyrolysis and WO₃ by Sputtering deposition, Ferrites nanoparticles by sol–gel, while metallic nanoparticles were synthetized via chemical reduction. Characterization consisted mainly of SEM, TEM, and XRD, and their antimicrobial activity was tested against C. albicans. WO₃ films achieved 86.2% fungal inhibition after 5 min of UVC exposure. SnO₂ films doped with nanoparticles reached 100% inhibition when combined with UVC and 100 V. Ferrite nanoparticles alone showed moderate activity (21.9%–40.4%) but exhibited strong surface adhesion to fungal cells, indicating potential for magnetically guided antifungal therapies. These results demonstrate the feasibility of using multifunctional nanomaterials for rapid, non-chemical disinfection. The materials are low-cost, scalable, and adaptable to hospital settings, making them promising candidates for reducing healthcare-associated fungal infections through advanced surface sterilization technologies. Full article

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

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20 pages, 16428 KB

Open AccessArticle

Influence of B₂O₃ on Reactive and Non-Reactive Wetting Behavior of CaO-SiO₂-MgO-Al₂O₃-B₂O₃ System

by Dalibor Novák, Lenka Řeháčková, Vlastimil Novák, Dalibor Matýsek and Pavlína Peikertová

Coatings 2025, 15(8), 967; https://doi.org/10.3390/coatings15080967 - 19 Aug 2025

Viewed by 449

Abstract

Boron oxide is introduced into slag as a flux, significantly lowering the liquidus temperature; however, this advantage is accompanied by several undesirable consequences. This study aims to evaluate the impact of boron oxide addition on the wetting reactivity of the CaO-SiO₂-MgO-Al [...] Read more.

Boron oxide is introduced into slag as a flux, significantly lowering the liquidus temperature; however, this advantage is accompanied by several undesirable consequences. This study aims to evaluate the impact of boron oxide addition on the wetting reactivity of the CaO-SiO₂-MgO-Al₂O₃-B₂O₃ slag system, particularly on platinum and graphite substrates, which are commonly utilized for wettability investigations of such systems. The slag system was modified to incorporate varying concentrations of B₂O₃, reaching up to 30 wt%, with the addition of this oxide at the expense of CaO and SiO₂ in a constant ratio, while the contents of Al₂O₃ and MgO remained unchanged. High-temperature wettability tests were conducted at temperatures up to 1550 °C under a flow of high-purity argon atmosphere (99.9999%). For the platinum substrate, the results indicated non-reactive wetting, characterized by a decrease in wetting angles with increasing temperature and boron oxide content. Conversely, for the graphite substrate, the nature of wetting varied, resulting in either reactive or non-reactive behavior depending on the B₂O₃ content. Following the high-temperature experiments, additional analyses were performed using scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). Furthermore, the powdered oxide systems underwent characterization through Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRPD). Full article

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

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14 pages, 10136 KB

Open AccessArticle

The Influence of Plasma-Carburizing Temperature on the Microstructure and Properties of DLC/Carbonitride Wear-Resistant and Friction-Reducing Functional Layer

by Jiawei Yao, Yiming Ma, Peiwu Cong, Fuyao Yan, Wenlin Lu, Yanxiang Zhang, Mufu Yan and Jingbo Ma

Coatings 2025, 15(8), 966; https://doi.org/10.3390/coatings15080966 - 19 Aug 2025

Viewed by 268

Abstract

M50 steel is widely used in the manufacturing of high-end bearing components for aero-engine shafts, where an excellent surface performance is required to withstand harsh service conditions. In this study, plasma carburizing at different temperatures varying from 410 to 570 °C was performed [...] Read more.

M50 steel is widely used in the manufacturing of high-end bearing components for aero-engine shafts, where an excellent surface performance is required to withstand harsh service conditions. In this study, plasma carburizing at different temperatures varying from 410 to 570 °C was performed on pre-nitrided M50 steel to investigate the influence of the temperature on the structural evolution and mechanical behavior of the self-lubricating functional layer. The microstructure, phase composition, hardness, and wear resistance of the carburized samples were fully characterized using scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, a nano-indenter, and other analytical techniques. The carbon-rich film with nano-domains contains a significant amount of sp³ bonds at low carburizing temperatures, exhibiting a Diamond-like carbon (DLC) film character. With the rise in the carburizing temperature, the initially distinct interface between the carbon-rich film and the compound layer gradually disappears as the nitrides are progressively replaced by carbides; the sp³ bond of the film is decreased, which reduces the hardness and wear resistance. Samples carburized at 490 °C with a homogeneous surface layer consisting of DLC film and a compound layer showed a low friction coefficient (about 0.22) and a 60% reduction in the wear rate compared with the nitrided specimen. The formation of a surface carbon-enriched layer also plays a role in avoiding oxidative wear. Full article

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

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18 pages, 4309 KB

Open AccessArticle

Fabrication of Biomimetical TiO₂@PVDF Composite Membrane with Omniphobicity via In-Situ Growth and Its Anti-Fouling Performance

by Wei Zhang, Xuran Zhu, Baoan Li, Boyang Hu, Leyu Shen, Yanzong Meng and Haifeng Gao

Coatings 2025, 15(8), 965; https://doi.org/10.3390/coatings15080965 - 19 Aug 2025

Viewed by 449

Abstract

Commercial hydrophobic membranes encounter severe problems such as membrane wetting and membrane fouling under extreme conditions, which affect membrane separation performance. To enhance the anti-fouling abilities of hydrophobic membranes, a composite membrane with omniphobic characteristics was fabricated successfully in this paper. Titanium dioxide [...] Read more.

Commercial hydrophobic membranes encounter severe problems such as membrane wetting and membrane fouling under extreme conditions, which affect membrane separation performance. To enhance the anti-fouling abilities of hydrophobic membranes, a composite membrane with omniphobic characteristics was fabricated successfully in this paper. Titanium dioxide (TiO₂) nanoparticles were in-situ grown via the hydrothermal synthesis method, and then fluorosilane with low surface energy was grafted on polyvinylidene fluoride (PVDF) membranes. Subsequently, the morphologies, chemical compositions, wetting properties and structural parameters of composite membranes were characterized systematically. Various contaminants were added to the feed to investigate the anti-fouling and anti-wetting performances of the composite membrane in membrane distillation tests. The results showed that butyl titanate was first hydrolyzed to form titanium hydroxide (Ti(OH)₄) and then it was dehydrated to form TiO₂ in the hydrothermal environment. TiO₂ crystals continued to grow and formed rough morphology with micro-nano synergistic distribution, which is similar to a “sunflower” disk composed of cubic clusters and nanopillars. Meanwhile, fluorosilane successfully was grafted onto TiO₂. The contact angles of deionized water, 0.4 mM sodium dodecyl sulfate (SDS) solution and 0.2% v/v mineral oil emulsion on the composite membrane surface were 167.3°, 162.0° and 158.5°, respectively, endowing the composite membrane with excellent omniphobic features. In direct contact membrane distillation (DCMD) tests, the composite membrane exhibited a relatively stable membrane permeate flux, and the salt rejection rate almost reached 100%. The mixture, consisting of inorganic salts, organic substances, surfactants and oil emulsions, was used as feed. In contrast, the commercial PVDF membrane flux decreased drastically and even dropped to 0 due to the membrane fouling and wetting. As for the pristine PVDF membrane, the membrane surface was covered with pollutants and membrane pores were blocked. Therefore, it was proved that the omniphobic composite membrane possesses outstanding anti-fouling and anti-wetting performance. Full article

(This article belongs to the Special Issue Surface Wetting and Functionalization of Composite Films and Coatings for Modern Applications)

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2 pages, 750 KB

Open AccessCorrection

Correction: He et al. Mechanism and Structural Defects of Zinc Film Deposited on a Copper Substrate: A Study via Molecular Dynamics Simulations. Coatings 2025, 15, 174

by Xin He, Xiangge Qin and Lan Zhan

Coatings 2025, 15(8), 964; https://doi.org/10.3390/coatings15080964 - 19 Aug 2025

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Abstract

In the original publication [...] Full article

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15 pages, 3430 KB

Open AccessArticle

3D Printed Parts Exhibit Superior Elastic Properties to Milled Ones

by Laisvidas Striška, Dainius Vaičiulis, Sonata Tolvaišienė, Dainius Udris, Nikolajus Kozulinas, Rokas Astrauskas, Arūnas Ramanavičius and Inga Morkvėnaitė

Coatings 2025, 15(8), 963; https://doi.org/10.3390/coatings15080963 - 19 Aug 2025

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Abstract

While many studies on fused filament fabrication (FFF)-printed polymers focus on ultimate tensile strength or failure analysis, the elastic region of the stress–strain curve is frequently overlooked. However, in most engineering applications, components operate well within the elastic range. In mechanical joints, support [...] Read more.

While many studies on fused filament fabrication (FFF)-printed polymers focus on ultimate tensile strength or failure analysis, the elastic region of the stress–strain curve is frequently overlooked. However, in most engineering applications, components operate well within the elastic range. In mechanical joints, support frames, and other load-bearing structures, stiffness and elastic response are more critical than post-failure behavior, as these properties determine system performance during standard operating conditions before any damage occurs. This study examines the elastic properties of acrylonitrile butadiene styrene (ABS) components fabricated via FFF, with a focus on the impact of printing orientation and nozzle temperature. Tensile tests were performed according to ISO 527-2:1993, and the results were compared to those of milled ABS parts (referred to as FT). Two print orientations were studied: XT, where the layers are oriented perpendicular to the loading direction, and ZT, where the layers are aligned parallel to the loading direction (load-aligned). The study reveals that printing orientation has a significant impact on mechanical behavior. The specimens printed in the ZT orientation exhibited superior elastic modulus and tensile strength compared to the XT specimens and also outperformed the milled FT parts. At 245 °C, the ZT specimens achieved an average tensile strength of 41.0 MPa, substantially higher than the FT’s 31.1 MPa. Moreover, the ZT had approximately 12.6% higher elastic moduli than the FT (1.97 GPa ZT compared to 1.74 GPa FT). Although the FT parts showed higher strain at break, the ZT-printed parts demonstrated a stiffness and strength that suggest their viability as replacements for machined components in load-bearing applications. Full article

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

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31 pages, 6372 KB

Open AccessArticle

First-Order Structural Modal Damping Ratio Identification by Withdrawing Amplitudes of Free Decaying Responses

by Shuai Luo, Youjie Nong, Gang Hou and Qiuwei Yang

Coatings 2025, 15(8), 962; https://doi.org/10.3390/coatings15080962 - 19 Aug 2025

Viewed by 437

Abstract

In the field of structural engineering, accurate identification of modal damping ratio is the key to structural dynamic response analysis. In order to accurately identify the modal damping ratio of the structure, this study proposes a method to identify the first-order modal damping [...] Read more.

In the field of structural engineering, accurate identification of modal damping ratio is the key to structural dynamic response analysis. In order to accurately identify the modal damping ratio of the structure, this study proposes a method to identify the first-order modal damping ratio of the structure by analyzing the free attenuation response of the acceleration signal. By intercepting the free attenuation section from the structural dynamic response output, the amplitude is extracted, and the logarithmic estimation slope of the amplitude is fitted by the least square method to establish a theoretical model for identifying the first-order modal damping ratio. The results show that the method has high accuracy and good stability when the modal damping ratio is in the range of 0.00500~0.06400, and different nodes have little effect on the accuracy of identification. When the modal damping ratio is in the range of 0.06400~0.07000, the accuracy of the method is relatively low and the stability is relatively poor, but it is still within the acceptable range. When the damping ratio is greater than 0.07000 or less than 0.00500, the accuracy may be reduced. In order to further verify the effectiveness of the method, it is applied to the damping identification of a steel arch bridge project. The dynamic response of the bridge under random excitation and El Centro seismic wave excitation is analyzed by using the recommended value and identification value of the first-order damping ratio. The results show that the method can accurately and reliably identify the first-order modal damping ratio, which is significantly different from the empirical modal damping ratio. The identified modal damping ratio can more accurately describe the dynamic response of the structure after long-term use, while the recommended value is not applicable. This method can be applied to the modal damping ratio identification of other structural types, which reflects that the modal damping ratio identification method proposed in this study has certain engineering significance. It is worth noting that the accuracy of identification will be reduced when the modal damping ratio is less than 0.00500 or more than 0.07000, and it may not even be applicable if the modal damping ratio is too small or too large. This method has higher requirements for acceleration signals. In engineering, it may be affected by noise and other factors, resulting in reduced identification accuracy. In practical engineering, it is necessary to improve the identification accuracy of first-order modal damping ratio by changing the interception point of the free attenuation section of the acceleration signal and the screening of the amplitude. Full article

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

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18 pages, 8227 KB

Open AccessArticle

The Influence of PEO Process Parameters on the Mechanical and Sclerometric Properties of Coatings on the Ultralight Magnesium Alloy LA141

by Mateusz Niedźwiedź, Joanna Korzekwa, Marek Bara, Sławomir Kaptacz, Krzysztof Aniołek, Maciej Sowa and Wojciech Simka

Coatings 2025, 15(8), 961; https://doi.org/10.3390/coatings15080961 - 18 Aug 2025

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Abstract

This study explores the influence of significant manufacturing parameters, i.e., peak current density and frequency, on the oxide coatings’ micromechanical and sclerometric properties. The parameter levels were determined using a full experimental design with two variables at three levels. Plasma electrolytic oxidation (PEO) [...] Read more.

This study explores the influence of significant manufacturing parameters, i.e., peak current density and frequency, on the oxide coatings’ micromechanical and sclerometric properties. The parameter levels were determined using a full experimental design with two variables at three levels. Plasma electrolytic oxidation (PEO) was conducted on an ultralight LA141 magnesium alloy in an alkaline ternary electrolyte. Coating performance was characterized by measuring hardness (HIT) and Young’s modulus (EIT), as well as three loads significant to coating failure: L_c1, the initiation of Hertzian tensile cracks; L_c2, the initiation of cohesive coating failure; and L_c3, full delamination of the coating. Scratch testing was complemented by profilographic analysis to provide isometric surface images. Statistical analysis was then employed to ascertain correlations of process parameters with the developed mechanical and sclerometric properties. Full article

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

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22 pages, 3484 KB

Open AccessArticle

Investigation of the Mixed Super-Early-Strength Agent of Mechanical and Hydration Properties of Concrete

by Huanqin Liu, Nuoqi Shi, Zhifa Yu, Yonglin Zhu and Xu Fu

Coatings 2025, 15(8), 960; https://doi.org/10.3390/coatings15080960 - 18 Aug 2025

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Abstract

This paper discusses the potential of adding a self-made super-early-strength agent to produce quick-setting, quick-hardening, and high-strength concrete. A super-early-strength agent is prepared by mixing triethanolamine (TEA), aluminum sulfate (Al₂(SO₄)₃·18H₂O), formic acid (HCOOH), and sodium [...] Read more.

This paper discusses the potential of adding a self-made super-early-strength agent to produce quick-setting, quick-hardening, and high-strength concrete. A super-early-strength agent is prepared by mixing triethanolamine (TEA), aluminum sulfate (Al₂(SO₄)₃·18H₂O), formic acid (HCOOH), and sodium fluoride (NaF) with a water-reducing agent in different proportions. In this paper, the effects of super-early-strength agent ratio and dosage, water–binder ratio, silica fume content, and cementitious material content on the setting time and compressive strength of high-strength concrete were studied. The hydration characteristics were evaluated by X-ray diffraction (XRD) and TG-DSC thermal analysis. The results show that the high-strength concrete prepared by 42.5R ordinary Portland cement mixed with appropriate amount of silica fume and self-made super-early-strength agent has a compressive strength of 10 MPa in 6 h, a compressive strength of 40 MPa in 1 day, a compressive strength of not less than 80 MPa in 28 days, and a compressive strength of not shrinking in 180 days. Using conventional raw materials and general process methods, the concrete prepared according to the preparation method of this experiment can significantly shorten the setting time and improve the compressive strength. However, it is difficult to form concrete when the amount of super-early-strength agent is too large. Nevertheless, this study provides a theoretical basis for large-scale and high-value utilization of the potential of super-early-strength agents and development to improve efficiency. At the same time, it provides a reference for the application of coating technology in rapid repair engineering. Full article

(This article belongs to the Special Issue Effective Coating Barriers for Protection of Reinforced Concrete, 2nd Edition)

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16 pages, 4617 KB

Open AccessArticle

Preparation via Wet Chemical Method, Characterization, and Antimicrobial and Antifungal Properties of Benzalkonium Chloride-Modified Montmorillonite

by Shirong Xu, Feng Yang, Changchun Liu, Taotao Yu, Zexiong Zhou, Hong Sun, Kunmao Li, Xiaoli Zhan, Mingkui Shi, Soyeon Kim, Guping Tang, Hongzhen Bai and Kenji Ogino

Coatings 2025, 15(8), 959; https://doi.org/10.3390/coatings15080959 - 18 Aug 2025

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Abstract

This study reports the preparation of benzalkonium chloride-modified montmorillonite (MMT-1227) via a wet chemical method and systematically investigates its structural characteristics and antimicrobial/antifungal properties. The modified montmorillonite was comprehensively characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric [...] Read more.

This study reports the preparation of benzalkonium chloride-modified montmorillonite (MMT-1227) via a wet chemical method and systematically investigates its structural characteristics and antimicrobial/antifungal properties. The modified montmorillonite was comprehensively characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) surface area analysis. The results confirmed the successful intercalation of benzalkonium chloride into montmorillonite layers, leading to altered surface morphology, increased interlayer spacing, and enhanced hydrophobicity. Antimicrobial assays demonstrated that MMT-1227 exhibits potent activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with inhibition zone diameters of 15.6 ± 0.2 mm and 17.7 ± 0.2 mm, respectively, and minimum inhibitory concentrations (MIC) of 1 mg/mL and 0.5 mg/mL. When incorporated into latex paint at a mass fraction of 0.3%, MMT-1227 achieved a 99.9% antibacterial rate against both strains after 24 h. Additionally, fungal resistance testing in accordance with GB/T 1741-2020 revealed that the modified paint films completely inhibited the growth of eight common mold strains (e.g., Aspergillus niger, Trichoderma viride), achieving a resistance grade of 0. These findings validate that benzalkonium chloride modification endows montmorillonite with excellent antimicrobial and antifungal properties, highlighting its potential as a high-performance additive for functional coatings and related antimicrobial materials. Full article

(This article belongs to the Special Issue Recent Advances in Antibacterial Composite Coatings)

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17 pages, 3794 KB

Open AccessFeature PaperArticle

Synergistic Effect of In₂O₃-rGO Hybrid Composites for Electrochemical Applications

by Alina Matei, Cosmin Obreja, Cosmin Romaniţan, Oana Brîncoveanu, Marius Stoian and Vasilica Țucureanu

Coatings 2025, 15(8), 958; https://doi.org/10.3390/coatings15080958 - 16 Aug 2025

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Abstract

In the present paper, the interaction between metal oxide nanoparticles and carbon materials was studied, and the results showed a synergetic effect, leading to an improvement in the properties of the obtained hybrid composites. The In₂O₃ NPs were prepared by [...] Read more.

In the present paper, the interaction between metal oxide nanoparticles and carbon materials was studied, and the results showed a synergetic effect, leading to an improvement in the properties of the obtained hybrid composites. The In₂O₃ NPs were prepared by the precipitation method and thermal treatment at 550 °C. The composites were obtained using an ex situ method, by mixing the In₂O₃ NPs with reduced oxide graphene (rGO) in a ratio of 10:1. The structural, morphological, and chemical composition studies of the In₂O₃ NPs and In₂O₃-rGO composites were investigates by FTIR and EDX spectroscopy, SEM microscopy, and XRD analysis. These techniques have highlighted the obtaining of In₂O₃ of high purity, and crystallinity, with the mean particle size in the range of 8–25 nm, but also, the dispersion of In₂O₃ NPs onto rGO sheets. We examined the influence of the In₂O₃ nanostructure morphology and In₂O₃-rGO composites on the electrochemical properties using cyclic voltammetry. The surface properties of the In₂O₃ and composite films were studied by contact angles, which indicate the maintenance of the hydrophilic nature. The obtained results establish the synergy between the main components to form In₂O₃-rGO, which can be used for the development of biosensors to enhance the device performance. Full article

(This article belongs to the Special Issue Smart Coatings: Adapting to the Future)

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10 pages, 7355 KB

Open AccessArticle

Study on the Influence of Heat Input on Microstructure and Properties of Q420C Steel Welded Joints

by Hanxin Long, Guoping Wang, Pingxin Wang, Jinjun Ma, Xiong Luo and Huan He

Coatings 2025, 15(8), 957; https://doi.org/10.3390/coatings15080957 - 16 Aug 2025

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Abstract

The occurrence of the welding heat-affected zone in Q420C steel may lead to a reduction in the toughness of the welded joint and disruption of high strength-toughness combination of Q420C. This study investigates the microstructure and mechanical properties of Q420C steel welded joints [...] Read more.

The occurrence of the welding heat-affected zone in Q420C steel may lead to a reduction in the toughness of the welded joint and disruption of high strength-toughness combination of Q420C. This study investigates the microstructure and mechanical properties of Q420C steel welded joints under three heat in-puts of 25 kJ/cm, 100 kJ/cm, 200 kJ/cm, and 300 kJ/cm, with high-strength matching adopted for the welded joints, Charpy impact tests at 0 °C, −20 °C, and −40 °C were conducted on the weld metal, fusion line(FL), and heat-affected zone (HAZ). The weld metal maintains high impact toughness across all tested temperatures. However, increasing the heat input leads to coarsening of the microstructure in the overheated zone of the HAZ, accompanied by the formation of ferrite. At a heat input of 300 kJ/cm, significant amounts of coarse intergranular ferrite and intragranular blocky ferrite develop in the overheated zone. These microstructural changes result in a marked reduction in the impact toughness of both the fusion zone and HAZ, and the fracture mode shifts from ductile to cleavage fracture. To ensure adequate impact toughness of Q420C welded joints, the welding heat input should be kept below 200 kJ/cm. Full article

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

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23 pages, 6732 KB

Open AccessArticle

Tailoring Tribological Properties and Corrosion Resistance of Self-Lubricating Ti-Mo-N Coatings Prepared by Arc Depositions

by Chenwei Wang, Jing Liu, Gang Liu, Liyuan Xue and Keren Zhang

Coatings 2025, 15(8), 956; https://doi.org/10.3390/coatings15080956 - 16 Aug 2025

Viewed by 424

Abstract

Ti-Mo-N coatings were deposited on GCr15 bearing steel using arc ion plating. The effect of deposition bias on the coating microstructure, mechanical properties, tribological behavior, and electrochemical corrosion resistance was systematically investigated. The coating prepared at −120 V bias showed optimal overall performance. [...] Read more.

Ti-Mo-N coatings were deposited on GCr15 bearing steel using arc ion plating. The effect of deposition bias on the coating microstructure, mechanical properties, tribological behavior, and electrochemical corrosion resistance was systematically investigated. The coating prepared at −120 V bias showed optimal overall performance. It achieved the lowest friction coefficient (0.308) and lowest wear rate (1.99 × 10⁻⁶ mm³/N·m). The significant improvement in tribological performance is attributed to the lubricating phase formed during the friction process. XPS analysis confirmed the layered MoO₃ formation within the wear scar. Deposition bias also significantly influenced the coating texture. At −120 V, the coating exhibited the strongest (111) crystal plane preferred orientation. This texture strongly correlated with performance enhancement. Regarding electrochemical corrosion, the −120 V coating displayed the lowest corrosion current density (3.62 × 10⁻⁹ A/cm²) and best corrosion resistance. Its corrosion morphology showed no obvious pitting, grooves, or other damage features. The results demonstrate the critical role of deposition bias in tailoring Ti-Mo-N coating properties. This research provides essential experimental support and a theoretical basis for designing wear- and corrosion-resistant protective coatings on bearing steel. Full article

(This article belongs to the Special Issue Electrodeposition, Sustainability, Characterization and Application of Metals and Alloy Coatings)

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13 pages, 116127 KB

Open AccessArticle

Experimental Study on Static Ice Adhesion Characteristics of Wind Turbine Blade Surfaces After Sand Erosion

by Lei Shi, Hongliang Chen, Shaolong Wang, Liang Zhang and Xinwei Kou

Coatings 2025, 15(8), 955; https://doi.org/10.3390/coatings15080955 - 15 Aug 2025

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Abstract

To investigate how sand erosion impacts the anti-icing performance of wind turbine blade surfaces, this study experimentally examines the individual and interactive effects of four key factors—the freezing temperature, separation temperature, surface roughness of eroded blade coatings, and loading rate on ice adhesion [...] Read more.

To investigate how sand erosion impacts the anti-icing performance of wind turbine blade surfaces, this study experimentally examines the individual and interactive effects of four key factors—the freezing temperature, separation temperature, surface roughness of eroded blade coatings, and loading rate on ice adhesion properties.The results from single-factor analyses reveal that the ice adhesion strength increases linearly with decreasing separation temperature. A more nuanced relationship emerges when considering the freezing temperature relative to the separation temperature: when the freezing temperature exceeds the separation temperature, the adhesion strength rises linearly as the separation temperature drops; conversely, when the freezing temperature is lower than the separation temperature, the adhesion strength decreases linearly with falling separation temperature. Higher loading rates correlate with reduced ice adhesion, while increased surface roughness induced by sand erosion leads to greater adhesion strength. Orthogonal array testing demonstrates the hierarchy of these factors’ influence on post-erosion ice adhesion, as follows: separation temperature > loading rate > freezing temperature > surface roughness of sand-eroded coatings. Notably, the separation temperature and loading rate exert the most significant effects. Furthermore, a regression equation for ice adhesion strength is established based on orthogonal test results, which can effectively predict ice adhesion strength under untested parameter combinations. These findings provide critical foundational data and a reliable theoretical tool to inform the development and optimization of practical de-icing systems in engineering applications. Full article

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

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17 pages, 2842 KB

Open AccessArticle

Hygrosensitive Response and Characteristics of Copolymer Coatings with Potential for Humidity Monitoring

by Katerina Lazarova, Silvia Bozhilova, Martina Docheva, Ketrin Pavlova, Gergana Alexieva, Darinka Christova and Tsvetanka Babeva

Coatings 2025, 15(8), 954; https://doi.org/10.3390/coatings15080954 - 14 Aug 2025

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Abstract

Newly developed hygrosensitive poly(vinyl alcohol) derivatives comprising grafted poly(N,N-dimethylacrylamide) chains of varied length and graft density are presented. The optical, sensing, and hydration properties of these copolymer thin films prepared by spin-coating were systematically studied. Refractive indices (n), absorption coefficients ( [...] Read more.

Newly developed hygrosensitive poly(vinyl alcohol) derivatives comprising grafted poly(N,N-dimethylacrylamide) chains of varied length and graft density are presented. The optical, sensing, and hydration properties of these copolymer thin films prepared by spin-coating were systematically studied. Refractive indices (n), absorption coefficients (k), and thicknesses (d) were calculated via curve fitting of the reflection spectra. Reflectance measurements across a relative humidity range of 5% to 95% were used to evaluate the humidity sensing behavior. Coating swelling exceeding 100% was observed. Hydration levels under high humidity conditions were studied using a quartz crystal microbalance method. This revealed approximately 24% water content in the polymer with the higher grafting density and shorter PDMA chains compared to around 31% in the copolymer with longer PDMA brushes that were loosely grafted The potential application of these copolymers as responsive materials for advanced humidity sensing is discussed. A combined optical and gravimetric approach for characterizing the humidity sensing properties of thin nanosized coatings is demonstrated, providing opportunities for advanced characterization of new functional materials, thus broadly contributing to the state of the art of sensor technologies. 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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17 pages, 4140 KB

Open AccessArticle

Photocatalytic Performance of 3D-Printed Triply Periodic Minimal Surface Photocatalytic Reactors

by Xi Chen, Chenxi Zhang, Qi Chen, Xiao Chen and Ningning Li

Coatings 2025, 15(8), 953; https://doi.org/10.3390/coatings15080953 - 14 Aug 2025

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Abstract

To overcome poor catalyst recovery and inefficient mass transfer in photocatalytic water treatment, this study presents novel Triply Periodic Minimal Surface (TPMS) photocatalytic reactors (PCRs) fabricated via Stereolithography (SLA) 3D printing. Five TiO₂-loaded reactors (Fischer-Radin-Dunn (FRD), Neovius (N), Diamond (D), I-graph [...] Read more.

To overcome poor catalyst recovery and inefficient mass transfer in photocatalytic water treatment, this study presents novel Triply Periodic Minimal Surface (TPMS) photocatalytic reactors (PCRs) fabricated via Stereolithography (SLA) 3D printing. Five TiO₂-loaded reactors (Fischer-Radin-Dunn (FRD), Neovius (N), Diamond (D), I-graph Wrapped Package (IWP), Gyroid (G)) with hierarchical porosity were designed. Using methylene blue (MB) as the target pollutant, the photocatalytic degradation performance of TPMS-PCRs is evaluated and Computational Fluid Dynamics (CFD) hydrodynamic simulations are conducted to analyze their flow characteristics under both horizontal and rotational flow fields. The catalytic efficiency of TPMS reactors is influenced not only by pore characteristics, specific surface area, and inter-pore connectivity, but also by the flow velocities on both the reactor surface and within its internal channels. The FRD-type TPMS-PCR loaded with 2.5 wt% TiO₂ exhibited optimal photocatalytic performance, achieving 95.36% degradation efficiency under rotational flow within 2.5 h, compared to 88.2% under horizontal flow. Remarkably, after five degradation cycles, its efficiency further improved to 96.7%, demonstrating its excellent stability. The rotational flow field enhanced the average flow velocity by approximately sixfold compared to horizontal flow, with the D-type reactor reaching a maximum surface velocity of 5.3 × 10⁻² m/s. Full article

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

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20 pages, 3199 KB

Open AccessArticle

The Application of a Simple Synthesis Process to Obtain Trirutile-Type Cobalt Antimonate Powders and the Study of Their Electrical Properties in Propane Atmospheres for Use in Gas Sensors

by Lucía Ivonne Juárez Amador, Héctor Guillén Bonilla, Alex Guillén Bonilla, José Trinidad Guillén Bonilla, Verónica María Rodríguez Betancourtt, Jorge Alberto Ramírez Ortega, Antonio Casillas Zamora and Emilio Huizar Padilla

Coatings 2025, 15(8), 952; https://doi.org/10.3390/coatings15080952 - 14 Aug 2025

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Abstract

The dynamic response in propane atmospheres at different voltages was investigated for samples made from powders of the semiconductor oxide CoSb₂O₆ synthesized using the microwave-assisted colloidal method. Powders of the compound calcined at 700 °C were studied with X-ray diffraction, [...] Read more.

The dynamic response in propane atmospheres at different voltages was investigated for samples made from powders of the semiconductor oxide CoSb₂O₆ synthesized using the microwave-assisted colloidal method. Powders of the compound calcined at 700 °C were studied with X-ray diffraction, confirming the CoSb₂O₆ crystalline phase. The microstructural characteristics of the oxide were analyzed using scanning and transmission electron microscopy (SEM/TEM), revealing a high abundance of nanorods, nanoplates, and irregular nanoparticles. These nanoparticles have an average size of ~21 nm. Using UV-Vis, absorption bands associated with the electronic transitions of the CoSb₂O₆’s characteristic bonds were identified, which yielded a bandgap value of ~1.8 eV. Raman spectroscopy identified vibrational bands corresponding to the oxide’s Sb–O and Co–O bonds. Dynamic sensing tests at 300 °C confirmed the material’s p-type semiconductor behavior, showing an increase in resistance upon exposure to propane. Critically, these tests revealed that the sensor’s baseline resistance and overall response are tunable by the applied voltage (1–12 V), with the highest sensitivity observed at the lowest voltages. This establishes a clear relationship between the electrical operating parameters and the sensing performance. The samples exhibited good operational stability, capacity, and efficiency, along with short response and recovery times. Extra-dry air (1500 cm³/min) was used as the carrier gas to stabilize the films’ surfaces during propane detection. These findings lead us to conclude that the CoSb₂O₆ could serve as an excellent gas detector. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures Deposition Techniques)

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33 pages, 3734 KB

Open AccessArticle

Preparation and Performance Characterization of Melamine-Formaldehyde-Microencapsulated Waterborne Topcoat–Brass Powder–Waterborne Acrylic Coating

by Wenjing Chang, Yan Han, Xiaoxing Yan and Jun Li

Coatings 2025, 15(8), 951; https://doi.org/10.3390/coatings15080951 - 14 Aug 2025

Viewed by 617

Abstract

A novel self-healing brass powder/waterborne acrylic decorative coating for wooden substrates was developed, in which γ-methacryloxypropyltrimethoxysilane (KH570)-modified brass powder (with a coupling agent concentration of 6% and reaction solution pH of 5) was employed as the filler, and melamine-formaldehyde (MF) resin-encapsulated water-based paint [...] Read more.

A novel self-healing brass powder/waterborne acrylic decorative coating for wooden substrates was developed, in which γ-methacryloxypropyltrimethoxysilane (KH570)-modified brass powder (with a coupling agent concentration of 6% and reaction solution pH of 5) was employed as the filler, and melamine-formaldehyde (MF) resin-encapsulated water-based paint microcapsules were utilized as the healing agent. The brass powder content and the core–wall ratio of the topcoat microcapsules were identified as the predominant factors affecting both the optical and mechanical properties of the self-healing brass powder/waterborne acrylic coating on Basswood surfaces. Therefore, the brass powder content was selected as the primary influencing factor. With concentration gradients of 0.5%, 1%, 3%, 5%, 7%, 9%, and 10%, and under constant conditions of 3% microcapsule content and room temperature curing, the effect of brass powder content on the properties of self-healing microcapsule coatings with different core–wall ratios was investigated. The waterborne acrylic wood coating containing 3% brass powder and 3% microcapsules with a core–wall ratio of 0.58:1 exhibited superior overall performance. This optimized formulation not only maintained excellent optical properties but also significantly enhanced mechanical performance, while preserving outstanding aging resistance, liquid resistance, and self-healing capability. The coating demonstrated the following comprehensive performance metrics: a glossiness of 24.0 GU, color difference (ΔE) of 2.13, chromatic aberration (ΔE*) of 13.68, visible light reflectance of 0.5879, dominant wavelength of 587.47 nm, visible light transmittance of 74.33%, pencil hardness of H grade, impact resistance of 2 kg·cm, adhesion rating of class 2, surface roughness of 2.600 μm, along with excellent aging resistance and liquid resistance properties, while achieving a self-healing efficiency of 19.62%. The coating also exhibited a smooth and uniform microscopic morphology, with the chemical bonds of both the modified brass powder and microcapsules remaining intact within the coating matrix. Full article

(This article belongs to the Special Issue Novel Microcapsule Technology in Coatings)

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26 pages, 3914 KB

Open AccessReview

Research Progress of Single-Mode Quantum Cascade Lasers

by Jiewei Zheng, Dongxin Xu, Qi Wu, Chi Zhang, Yishui Lin, Mingkun Yuan and Yi Qu

Coatings 2025, 15(8), 950; https://doi.org/10.3390/coatings15080950 - 13 Aug 2025

Viewed by 546

Abstract

Quantum cascade lasers (QCLs) are important laser sources in the mid-infrared band. Among them, single-mode quantum cascade lasers show significant advantages in key performance such as output wavelength stability and narrow linewidth. These lasers have broad application prospects in fields such as gas [...] Read more.

Quantum cascade lasers (QCLs) are important laser sources in the mid-infrared band. Among them, single-mode quantum cascade lasers show significant advantages in key performance such as output wavelength stability and narrow linewidth. These lasers have broad application prospects in fields such as gas detection, component analysis, and medical diagnosis. Single-mode quantum cascade lasers are mainly achieved through distributed feedback (DFB) gratings and distributed Bragg reflector (DBR) gratings. This paper presents the basic principles of quantum cascade lasers and summarizes the research progress of distributed feedback quantum cascade lasers and distributed Bragg reflector quantum cascade lasers in recent years, respectively. Finally, an in-depth discussion and outlook on the development direction and research trends of single-mode quantum cascade lasers are presented. Full article

(This article belongs to the Special Issue Advancements in Lasers: Applications and Future Trends)

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