Coatings

14 pages, 8625 KB

Open AccessArticle

Microstructural Characteristics and Tensile Behavior of Vacuum-Fusion-Welded Joints in 2507 Duplex Stainless-Steel Pipes

by Xia Cao, Lichu Zhou, Lili Zhai and Hong Gao

Coatings 2026, 16(1), 146; https://doi.org/10.3390/coatings16010146 - 22 Jan 2026

Viewed by 207

Abstract

To address the performance deficiencies in welded joints in 2507 duplex stainless-steel pipes under demanding service conditions such as deep-sea operation, this study investigates drawn 2507 duplex stainless-steel pipes. Vacuum-fusion welding coupled with ER2507 wire filling is employed to fabricate the joints. The [...] Read more.

To address the performance deficiencies in welded joints in 2507 duplex stainless-steel pipes under demanding service conditions such as deep-sea operation, this study investigates drawn 2507 duplex stainless-steel pipes. Vacuum-fusion welding coupled with ER2507 wire filling is employed to fabricate the joints. The joint microstructure and tensile behavior are systematically analyzed using microstructural characterization techniques (electron backscatter diffraction and transmission electron microscopy) and uniaxial tensile testing. The results indicate that the joint exhibits a graded microstructure along the welding direction: base metal-heat affected zone-weld metal. The austenite phase fraction in the fusion zone decreases to 27.6%. The joint achieves an ultimate tensile strength of 833.3 MPa and a total elongation of close to 23%, demonstrating an excellent combination of strength and ductility. During tensile deformation, the ferrite and austenite phases undergo coordinated deformation. Strain is distributed relatively uniformly at low strain levels but localized preferentially within the fusion zone at high strain levels. Fractographic analyses reveal a ductile fracture mode. This research provides theoretical support and technical reference for optimizing welding processes and assessing the service safety of 2507 duplex stainless-steel pipes in deep-sea pipeline-engineering applications. Full article

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17 pages, 13859 KB

Open AccessArticle

Research on the BEM Reinforcement Mechanism of the POSF Method for Ocean Stone Construction

by Yuhong Ding, Yujing Lai, Jinxuan Wang, Yili Fu, Li Chen, Tengfei Ma and Ruiming Guan

Coatings 2026, 16(1), 145; https://doi.org/10.3390/coatings16010145 - 22 Jan 2026

Cited by 1 | Viewed by 383

Abstract

The Planting Oysters to Strengthen the Foundation (POSF) method, as a construction technique for coastal stone structures in the Northern Song Dynasty of China (1059), has been preserved to this day. Exploring its long-term reinforcement mechanism can provide theoretical support and practical guidance [...] Read more.

The Planting Oysters to Strengthen the Foundation (POSF) method, as a construction technique for coastal stone structures in the Northern Song Dynasty of China (1059), has been preserved to this day. Exploring its long-term reinforcement mechanism can provide theoretical support and practical guidance for the protection and sustainable development of world marine cultural heritage. This article uses Crustacean Ash Triad Clay (CATC) from Shihu Ancient Wharf in Quanzhou as a case study and conducts a systematic investigation using XRD, Raman, SEM-EDS, FTIR, and 16S rRNA high-throughput sequencing. The results show that CATC has a core skeleton of 94.6% quartz, with potassium feldspar, dolomite, and metal compounds as auxiliary components; that its 19.04% porosity provides enrichment space for positively charged ions and tide-borne microorganisms; that electrostatic adsorption between barnacle adhesive and the material achieves physical reinforcement; and that microbial metabolism promotes dolomite formation, producing chemical reinforcement. Thus, the ternary coupling of Biology–Environment–Materials forms a BEM long-term reinforcement mechanism suitable for low-carbon construction in the ocean. Full article

(This article belongs to the Special Issue New Insights into Everyday Heritage: Surface Analysis and Conservation)

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15 pages, 5220 KB

Open AccessArticle

Feasibility of CaZr₄(PO₄)₆ as Radome TBC Based on Thermophysical and Thermal Cycle Performance Research

by Yunwei Tu, Wenbo Chen, Wei Zhou, Li Liu, Longhui Deng, Jianing Jiang, Shujuan Dong and Xueqiang Cao

Coatings 2026, 16(1), 144; https://doi.org/10.3390/coatings16010144 - 22 Jan 2026

Viewed by 191

Abstract

This paper investigates the feasibility of CaZr₄(PO₄)₆ as a novel thermal barrier coating for SiO_2f/SiO₂, serving as a radome at 1200 °C. Initially, CaZr₄(PO₄)₆ powder undergoes TG-DSC testing across [...] Read more.

This paper investigates the feasibility of CaZr₄(PO₄)₆ as a novel thermal barrier coating for SiO_2f/SiO₂, serving as a radome at 1200 °C. Initially, CaZr₄(PO₄)₆ powder undergoes TG-DSC testing across a temperature range from room temperature to 1200 °C, demonstrating excellent phase stability within this range. Subsequently, the coating’s properties and the thermal cycling performance are examined. The results indicate that the thermal conductivity of CaZr₄(PO₄)₆ falls within the range of 1.05 to 1.02 W·m⁻¹·K⁻¹ (RT ~ 1200 °C), with thermal expansion coefficients of the coating ranging from 2.07 to 5.55 × 10⁻⁶ K⁻¹. Moreover, the thermal cycling lifetime of the CaZr₄(PO₄)₆ coating is evaluated by performing 100 cycles (50 h) at 1200 °C. Mechanical properties are assessed through Vickers and Knoop hardness tests, revealing a fracture toughness of 1.4 Mpa·m^1/2. The primary cause of coating failure and peeling is the excessive internal stress between the coating and the expansion of transverse cracks. Fracture toughness serves as a key performance indicator reflecting the material’s resistance to unstable crack expansion, so the failure of the coating is attributed to the limited fracture toughness and the thermal mismatch stress between the coating and the substrate. Based on the aforementioned research findings, CaZr₄(PO₄)₆ might be the potential coating for SiO_2f/SiO₂ systems. Full article

(This article belongs to the Special Issue Advances in Surface and Coatings Technologies)

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23 pages, 6943 KB

Open AccessArticle

Influence of Nano-Sized Ceramic Reinforcement Content on the Powder Characteristics and the Mechanical, Tribological, and Corrosion Properties of Al-Based Alloy Nanocomposites

by Müslim Çelebi, Aykut Çanakçı and Sezai Kütük

Coatings 2026, 16(1), 143; https://doi.org/10.3390/coatings16010143 - 22 Jan 2026

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Abstract

In this study, B₄C nanoparticles were incorporated into AA2024, one of the aluminum alloys with superior mechanical and wear properties, with the aim of further enhancing its mechanical, tribological, and corrosion performance. The nanocomposites were produced using mechanical milling followed by [...] Read more.

In this study, B₄C nanoparticles were incorporated into AA2024, one of the aluminum alloys with superior mechanical and wear properties, with the aim of further enhancing its mechanical, tribological, and corrosion performance. The nanocomposites were produced using mechanical milling followed by powder metallurgy techniques. The effects of nano-sized B₄C additions on powder characteristics, microstructure, and physical, mechanical, tribological, and corrosion properties were systematically investigated through microhardness, density, SEM, XRD, bulk hardness, wear, and corrosion tests. B₄C was added at weight fractions of 0–2 wt.%, and all samples were mechanically milled for 8 h. The results revealed a gradual reduction in powder particle size and a corresponding increase in particle microhardness with increasing B₄C content. The sample reinforced with 2 wt.% nano-B₄C exhibited an approximately 80% increase in hardness and around a 55% improvement in tensile strength compared to the unreinforced alloy. Wear resistance was significantly enhanced, showing up to an 8-fold improvement under a 5 N load and a 6-fold improvement under a 25 N load. Furthermore, corrosion resistance nearly doubled with the addition of B₄C nanoparticles. Full article

(This article belongs to the Special Issue Mechanical, Corrosion, and Wear Properties of Metallic Materials/Coatings)

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21 pages, 8249 KB

Open AccessFeature PaperArticle

A Reasoned Diagnostic Procedure to Support the Restoration of the 17th Century Stucco Altar Dedicated to St. Michael the Archangel in Barbarano Romano (Viterbo, Italy)

by Claudia Pelosi, Marta Cristofori, Luca Lanteri, Giorgio Capriotti, Antonella Casoli, Marianna Potenza, Marta Sardara and Armida Sodo

Coatings 2026, 16(1), 142; https://doi.org/10.3390/coatings16010142 - 22 Jan 2026

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Abstract

The 17th-century stucco altar dedicated to St. Michael the Archangel is an interesting, but very damaged, artwork located in the complex of St. Angel in the little town of Barbarano Romano in Central Italy. During the recent and quite necessary restoration carried out [...] Read more.

The 17th-century stucco altar dedicated to St. Michael the Archangel is an interesting, but very damaged, artwork located in the complex of St. Angel in the little town of Barbarano Romano in Central Italy. During the recent and quite necessary restoration carried out by University of Tuscia students on the Conservation and Restoration of Cultural Heritage Master’s program, some problems with the surface coating were encountered in the cleaning phase. Diagnostic and scientific analyses were crucial to better understanding the composition of these materials to perform the safest and most efficient cleaning procedures. The first of many steps required by this approach was an in situ analysis, starting from on-site analysis and diagnostic documentation through X-ray fluorescence spectroscopy and ultraviolet fluorescence photography, followed by laboratory investigations. The latter included µ-Raman and Fourier transform infrared spectroscopies, gas chromatography coupled with mass spectrometry, and scanning electron microscopy equipped with an energy-dispersive detector. Each technique provided useful data to determine the chemical composition of the white surface coating, which was found to be a non-original overpaint containing lead and organic binder. This overpaint had been applied to retouch the white stucco during a previous restoration project. All this new information contributed to achieving the final decision to remove this layer. Full article

(This article belongs to the Special Issue Heritage Conservation and Restoration: Surface Treatments, Coatings and Sustainable Approaches)

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22 pages, 51561 KB

Open AccessArticle

Effect of V Content on Microstructure and Properties of TiNbZrV_x Medium-Entropy Alloy Coatings on TC4 Substrate by Laser Cladding

by Wen Zhang, Ying Wu, Chuan Yang, Yongsheng Zhao, Zhenhong Wang, Jia Yang, Wei Feng, Yang Deng, Junjie Zhang, Qingfeng Xian, Xingcheng Long, Zhirong Liang and Hui Chen

Coatings 2026, 16(1), 141; https://doi.org/10.3390/coatings16010141 - 22 Jan 2026

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Abstract

In order to improve the wear resistance of titanium alloy and apply it to the high-speed train brake disc, TiNbZrV_x (x = 0, 0.2, 0.4, 0.6, 0.8) refractory medium-entropy alloy coatings were prepared on Ti-6Al-4V (TC4) substrate. The effect of V content [...] Read more.

In order to improve the wear resistance of titanium alloy and apply it to the high-speed train brake disc, TiNbZrV_x (x = 0, 0.2, 0.4, 0.6, 0.8) refractory medium-entropy alloy coatings were prepared on Ti-6Al-4V (TC4) substrate. The effect of V content on the microstructure, mechanical properties, and friction and wear properties of the coatings was studied. TiNbZrV_x coatings achieved good metallurgical bonding with the substrate, forming BCC and B2 phases and AlZr₃ intermetallic compound (IMC). From TiNbZr coating to TiNbZrV_0.8 coating, V promotes element segregation and new phase formation, which decreased the average grain size from 85.055 μm to 56.515 μm, increased the average hardness from 265.5 HV to 343.4 HV, and reduced the room temperature (RT) wear rate by 97.8%. However, the ductility of the coatings decreased from 15.7% to 5.8% because the grain boundary precipitates changed the dislocation arrangement, and the tensile fracture mode changed from ductile fracture to brittle fracture. Abrasive wear was the main wear mode at RT, and adhesive wear and oxidation wear were the main wear modes at elevated temperature. The COF at elevated temperature was lower than that at RT, because a large number of friction pair components were transferred to the coating surface at high temperature and were repeatedly rolled to form a dense film, which played a certain lubricating role. Full article

(This article belongs to the Section High-Energy Beam Surface Engineering and Coatings)

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25 pages, 2841 KB

Open AccessArticle

Mechanistic Insights into Asphalt Natural Aging: Microstructural and Micromechanical Transformations Under Diverse Climates

by Shanglin Song, Xiaoyan Ma, Xiaoming Kou, Lanting Feng, Yatong Cao, Fukui Zhang, Haihong Zhang and Huiying Zhang

Coatings 2026, 16(1), 140; https://doi.org/10.3390/coatings16010140 - 21 Jan 2026

Viewed by 186

Abstract

Understanding mechanisms of asphalt in the process of natural aging is crucial for predicting its long-term durability and optimizing performance under diverse environmental conditions. Despite its importance, the microstructural and micromechanical changes induced by natural aging remain poorly understood, particularly under varying climatic [...] Read more.

Understanding mechanisms of asphalt in the process of natural aging is crucial for predicting its long-term durability and optimizing performance under diverse environmental conditions. Despite its importance, the microstructural and micromechanical changes induced by natural aging remain poorly understood, particularly under varying climatic influences. This study addresses this gap by analyzing the effects of natural aging on asphalt’s microscopic properties and identifying key indicators that govern its degradation. Asphalt samples were subjected to natural aging across five climatically distinct regions over 6, 12, and 18 months. Atomic force microscopy (AFM) was employed to characterize surface roughness, adhesion forces, and DMT modulus, while correlation analysis and principal component analysis (PCA) were used to identify relationships among micromechanical indicators and streamline the dataset. The results reveal that natural aging induces irreversible transformations in asphalt’s microstructure, driven by the combined effects of temperature, UV radiation, humidity, and oxygen. These processes promote the evolution of “Bee structures,” increase surface roughness, and accelerate phase separation, alongside chemical modifications such as oxidation and polymerization, leading to progressive material hardening and stiffness. Significant regional and temporal variations in adhesion forces and DMT modulus were observed, reflecting the cumulative impact of environmental factors on asphalt’s aging dynamics. Correlation analysis demonstrated strong associations between surface roughness and “Bee structure” area, while mechanical properties such as stiffness and adhesion were largely decoupled from morphological features. Environmental factors interact in complex ways to drive asphalt aging. Humidity enhances adhesion and stiffness via water-induced capillary forces, while temperature reduces surface roughness and adhesion through molecular reorganization. UV radiation accelerates oxidative degradation, promoting surface erosion and stiffness loss, while altitude modulates these dynamics by influencing temperature and UV exposure. Full article

(This article belongs to the Special Issue Advances in Asphalt and Concrete Coatings)

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12 pages, 3165 KB

Open AccessArticle

Influencing Factors of the Bending Properties of Resin-Treated Flattened Bamboo and Its Decorative Characteristics

by Penghui Chen, Jianglong Wu, Yingyue Yu, Hong Chen and Wei Xu

Coatings 2026, 16(1), 139; https://doi.org/10.3390/coatings16010139 - 21 Jan 2026

Viewed by 249

Abstract

Cracking frequently occurs during the pressing process of flattened bamboo, significantly reducing yield rates. To address the lack of effective strategies for the mechanical reutilisation of cracked flattened bamboo, an epoxy resin-based treatment approach was proposed to improve both mechanical and decorative performance, [...] Read more.

Cracking frequently occurs during the pressing process of flattened bamboo, significantly reducing yield rates. To address the lack of effective strategies for the mechanical reutilisation of cracked flattened bamboo, an epoxy resin-based treatment approach was proposed to improve both mechanical and decorative performance, inspired by resin-based decorative composites. Crack filling and full-cell impregnation methods were then systematically evaluated. This work is the first to systematically compare crack filling and full-cell impregnation strategies across different bamboo radial positions, with a simultaneous evaluation of mechanical performance and decorative properties. The results show that bamboo radial position has a pronounced influence on bending performance. The outer layer exhibits markedly higher bending strength and Young’s modulus than the inner layer, with mean differences of approximately 134 MPa and 13.3 GPa, respectively. Crack filling results in a measurable improvement in the bending performance of cracked flattened bamboo, whereas full-cell impregnation leads to a reduction in the bending properties of the outer layer. These results suggest that crack filling represents a more mechanically efficient and cost-effective treatment strategy. Resin treatment increases surface colour variation but minimally impacts yellowing resistance performance. These findings demonstrate that resin-treated flattened bamboo with cracks supports the resource utilisation of waste bamboo and shows potential for decorative and interior material applications. Full article

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

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19 pages, 28667 KB

Open AccessArticle

Electrochemical and Optical Insights into Interfacial Connection for Fast Pollutant Removal: Experimental Study of g-C₃N₄/BiOCl Heterojunction for Rhb and MO Photodegradation

by Hadja Kaka Abanchime Zenaba, Mi Long, Xue Liu, Mengying Xu, Wen Luo and Tian Zhang

Coatings 2026, 16(1), 138; https://doi.org/10.3390/coatings16010138 - 21 Jan 2026

Viewed by 462

Abstract

Developing efficient heterojunction photocatalysts is essential to address the challenge of degrading persistent organic pollutants. In this study, a multi-scale characterization strategy was employed to investigate the implications of interfacial connectivity between synthesized graphitic carbon nitride (g-C₃N₄) /bismuth oxychloride [...] Read more.

Developing efficient heterojunction photocatalysts is essential to address the challenge of degrading persistent organic pollutants. In this study, a multi-scale characterization strategy was employed to investigate the implications of interfacial connectivity between synthesized graphitic carbon nitride (g-C₃N₄) /bismuth oxychloride (BiOCl)e removal of Rhodamine B (RhB) and Methyl Orange (MO). Morpho-structural characterizations, including Scanning/Transmission Electron Microscopy (SEM/TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and N₂ physisorption (Brunauer–Emmett–Teller (BET)) analyses, confirmed the successful construction of an intimate interfacial contact between g-C₃N₄ and BiOCl. The optimized composite (15% g-C₃N₄/BiOCl), prepared via a one-step hydrothermal method, exhibited enhanced photocatalytic performance following pseudo-first-order kinetics described by the Langmuir–Hinshelwood model, with apparent rate constants of 0.166 min⁻¹ for MO and 0.519 min⁻¹ for RhB. Under visible-light irradiation, degradation efficiencies of 98% for MO (120 min) and 99% for RhB (35 min) were achieved, outperforming the pristine components. Complementary optical and electrochemical analyses indicate improved light absorption and charge-separation efficiency in the heterojunction system. In addition, the photocatalyst demonstrated good operational stability over four consecutive cycles, maintaining 91.70% activity for MO and 99.76% for RhB. Overall, this work highlights the synergistic photocatalytic g-C₃N₄/BiOCl heterojunction and provides a valuable insight to guide the design of advanced materials for pollutant remediation. Full article

(This article belongs to the Special Issue Coatings for Batteries and Energy Storage)

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5 pages, 182 KB

Open AccessEditorial

New Insights in Surface Engineering, Coatings, and Tribology

by Esteban Broitman, Martín Flores, Germán Prieto and Giuseppe Pintaude

Coatings 2026, 16(1), 137; https://doi.org/10.3390/coatings16010137 - 20 Jan 2026

Viewed by 282

Abstract

This Special Issue, “Surface Engineering, Coatings, and Tribology”, was open for submissions from the entire community and incorporates a selection of studies presented at the VIII National Symposium and First Latin American Meeting on Surface Engineering and Tribology [...] Full article

(This article belongs to the Special Issue Surface Engineering, Coatings and Tribology)

16 pages, 7231 KB

Open AccessArticle

Underwater Performance of Eco-Friendly Choline-Based Ionic Liquid Coatings Applied on Stone Surfaces

by Marika Luci, Filomena De Leo, Mirko Mutalipassi, Teresa Romeo, Silvestro Greco, Chiara Giommi, Lorenzo Evola, Mauro Francesco La Russa, Michela Ricca, Donatella de Pascale, Clara Enza Urzì, Sandra Lo Schiavo, Christian Galasso, Nadia Ruocco and Silvestro Antonio Ruffolo

Coatings 2026, 16(1), 136; https://doi.org/10.3390/coatings16010136 - 20 Jan 2026

Viewed by 302

Abstract

In the marine environment, numerous factors endanger the preservation of underwater rock surfaces as well as submerged archeological artifacts, including physical, chemical, and biological processes. Limestone and marble are common materials used in artifacts due to their availability and long-term durability. However, such [...] Read more.

In the marine environment, numerous factors endanger the preservation of underwater rock surfaces as well as submerged archeological artifacts, including physical, chemical, and biological processes. Limestone and marble are common materials used in artifacts due to their availability and long-term durability. However, such surfaces provide a suitable substrate for the settlement of micro- and macro-organisms, causing so-called biofouling, which significantly contributes to stone deterioration. Previous studies have demonstrated the applicability of antifouling coatings containing ionic liquids (ILs) on marble surfaces and assessed their durability for up to 15 days under submerged environments. To further corroborate these results, additional physical studies (colorimetric, contact angles, capillarity water absorption measurements, and UV aging) were carried out on treated limestone. Washout tests were also performed on both lithotypes to verify the coatings’ stability under medium-term underwater exposures. The results of these investigations are reported here. Our data confirm that the application of IL-based coatings had no effect on the intrinsic properties of the limestone surfaces, as previously reported for marble, including resistance to daily UV irradiation. In addition, laboratory tests demonstrated good coating durability against seawater erosive action for up to 6 months. Full article

(This article belongs to the Special Issue Heritage Conservation and Restoration: Surface Treatments, Coatings and Sustainable Approaches)

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16 pages, 3029 KB

Open AccessArticle

Durable Anti-Icing Slippery Surface with Y-Shaped Composite Porous Structure Prepared by Two-Step Anodic Oxidation

by Chanxi Yan, Gaoping Liu, Qing Zhu, Yashi Zhou and Yuan Yuan

Coatings 2026, 16(1), 135; https://doi.org/10.3390/coatings16010135 - 20 Jan 2026

Viewed by 237

Abstract

Ice accumulation on power transmission lines poses serious threats to operational safety and can lead to substantial social and economic impacts. While various anti-icing coatings have been investigated, their performance is often limited by the effectiveness and durability of anti-icing. Slippery lubricant-infused porous [...] Read more.

Ice accumulation on power transmission lines poses serious threats to operational safety and can lead to substantial social and economic impacts. While various anti-icing coatings have been investigated, their performance is often limited by the effectiveness and durability of anti-icing. Slippery lubricant-infused porous surfaces (SLIPSs) have shown remarkable anti-icing properties and durability, aided by their lubricant-infused and self-healing capability. In this study, SLIPSs were successfully fabricated on aluminum substrates using a two-step anodization process. The effects of the anodizing parameter of the current density on pore diameter and depth at each stage were systematically investigated. Compared to untreated aluminum and superhydrophobic coatings (SHCs), SLIPSs presented good anti-icing properties. First, at −6 °C, droplets slid off the surface completely within 4340.5 ms without pinning, indicating sustained droplet-shedding capability. It also significantly delayed ice formation, extending the freezing time to 80 min—eight times longer than that of the untreated surface. Moreover, the SLIPSs also exhibited ultra-low ice adhesion, with an initial strength of only 6.93 kPa. Meanwhile, after 100 frosting–defrosting cycles, SLIPSs could still maintain low ice adhesion strength (<20 kPa). The prepared SLIPS with a Y-shaped pore structure demonstrates good potential for anti-icing. Full article

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

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17 pages, 4326 KB

Open AccessArticle

Influence and Optimization of Process Parameters on Surface Roughness of Selective Laser Melting of 316L Stainless Steel

by Pin Dong, Kamonpong Jamkamon and Suppawat Chuvaree

Coatings 2026, 16(1), 134; https://doi.org/10.3390/coatings16010134 - 20 Jan 2026

Cited by 1 | Viewed by 310

Abstract

To achieve better surface quality in selective laser melting (SLM), this study used 316L stainless steel powder and conducted a systematic design experiment to investigate the influence mechanism of process parameters on the surface roughness of the top and vertical surfaces. Response surface [...] Read more.

To achieve better surface quality in selective laser melting (SLM), this study used 316L stainless steel powder and conducted a systematic design experiment to investigate the influence mechanism of process parameters on the surface roughness of the top and vertical surfaces. Response surface methodology (RSM) was then used for parameter optimization. The results showed that scanning speed has the greatest impact on surface roughness, followed by laser power, while scanning spacing has the least impact. The lowest surface roughness was observed when the volumetric energy density was between 65 J/mm³ and 90 J/mm³. The optimal combination of process parameters was a scanning speed of 637 mm/s, a hatch spacing of 0.08 mm, and a laser power of 191 W. Under these conditions, the surface roughness of the top and vertical surfaces were 4.96 μm and 6.58 μm, respectively, validating the effectiveness of the model. Full article

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

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24 pages, 8813 KB

Open AccessArticle

Research on the Mechanism of Steel Slag Fine Aggregate Damaging the Volume Stability of Cement-Based Materials

by Haoran Zhai, Aizhu Liu, Huiqing Yang, Dong Gao, Chunguang Liu, Wenda Yan and Whengyu Du

Coatings 2026, 16(1), 132; https://doi.org/10.3390/coatings16010132 - 20 Jan 2026

Viewed by 377

Abstract

With the depletion of natural sand and gravel resources and increasing emphasis on environmental protection, natural aggregates suitable for concrete production are becoming increasingly scarce. Steel slag, a by-product of steelmaking, is produced in substantial quantities yet remains underutilized due to its low [...] Read more.

With the depletion of natural sand and gravel resources and increasing emphasis on environmental protection, natural aggregates suitable for concrete production are becoming increasingly scarce. Steel slag, a by-product of steelmaking, is produced in substantial quantities yet remains underutilized due to its low recycling rate. Owing to the high strength and excellent compatibility of steel slag particles with cementitious materials, they demonstrate significant potential as a replacement for natural river sand in fine aggregate applications. However, the volumetric instability of steel slag has long been a major impediment to its widespread adoption in cement-based composites. This study examines the stability performance of cement mortar containing steel slag aggregate, with the objective of clarifying the mechanisms responsible for dimensional instability resulting from steel slag incorporation. When the replacement level exceeds 40%, the dimensional stability of the mortar deteriorates markedly. The initial contents of free CaO (f-CaO) and free MgO (f-MgO) in the steel slag were determined to be 1.58% and 1.14%, respectively. Following 50 h of hydrothermal treatment, 69.6% of f-CaO and 44.3% of f-MgO had hydrated, causing internal volumetric expansion and subsequent particle fracturing. Under elevated temperature conditions, over-burned lime demonstrated 220% volumetric expansion and completed its reaction within 40 min, consequently impairing early-age stability. In contrast, periclase (dead-burned MgO) exhibited 34% expansion and attained a reaction degree of merely 13.3%, suggesting a more substantial impact on long-term stability. For each mixture, linear expansion measurements were performed on n = 5 independent specimens, and results are reported as mean ± standard deviation. Full article

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

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29 pages, 521 KB

Open AccessReview

Application of Electromagnetic Ultrasonic Testing Technology in Pipeline Defects

by Qingsheng Lan, Riteng Sun, Wenbin Tang, Chunyan Zhang, Yu Liu, Yu Wang, An Lei, Changhui Huang, Shanglong Li, Zhichao Cai and Bo Feng

Coatings 2026, 16(1), 133; https://doi.org/10.3390/coatings16010133 - 19 Jan 2026

Viewed by 479

Abstract

Pipelines, as critical carriers for energy transportation, are prone to defects such as cracks and corrosion during long-term operation. Traditional testing methods exhibit limitations in various aspects, while electromagnetic ultrasonic testing technology, leveraging its advantages of non-contact operation and couplant-free application, has emerged [...] Read more.

Pipelines, as critical carriers for energy transportation, are prone to defects such as cracks and corrosion during long-term operation. Traditional testing methods exhibit limitations in various aspects, while electromagnetic ultrasonic testing technology, leveraging its advantages of non-contact operation and couplant-free application, has emerged as a significant direction for pipeline integrity assessment. This paper analyzes the advantages of EMAT guided wave testing technology in achieving long-distance and rapid screening of pipelines, as well as the strengths of bulk wave testing technology in high-precision quantitative evaluation. It also examines the unique value of obliquely incident SV waves in the directional identification of weld defects. Furthermore, the paper discusses the potential of integrating EMAT with multiple technologies, demonstrating how multi-physical field synergy enhances detection reliability. Finally, it summarizes the remaining challenges in practical engineering applications, providing references for advancing the field toward intelligent and high-precision development. Full article

(This article belongs to the Special Issue Corrosion Monitoring, Prevention and Prediction of Urban Buried Infrastructures)

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18 pages, 4195 KB

Open AccessArticle

Preparation and Performance Study of Modified Graphene Oxide/Polyurethane Anti-Corrosion Coating

by Shudi Zhang, Xinya Wei, Na Xiao, Jiahui Bing, Jialin Dong, Jiacheng Ma and Tao Zhang

Coatings 2026, 16(1), 131; https://doi.org/10.3390/coatings16010131 - 19 Jan 2026

Viewed by 288

Abstract

To address the corrosion and degradation of metallic materials in seawater, tidal, and similar environments, this study employs lysine (C₆H₁₄N₂O₂) to modify graphene oxide (GO) via a hydrothermal process. The modified graphene oxide (f-GO) and [...] Read more.

To address the corrosion and degradation of metallic materials in seawater, tidal, and similar environments, this study employs lysine (C₆H₁₄N₂O₂) to modify graphene oxide (GO) via a hydrothermal process. The modified graphene oxide (f-GO) and poly(l-lysine) (PL) composite was characterized structurally and functionally using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) to characterize its structure and properties. A composite coating was prepared using modified graphene oxide (f-GO) and polyurethane (PU), which underwent electrochemical testing, hardness testing, corrosion rate testing, adhesion testing, impact resistance testing, and salt spray corrosion resistance testing. Experimental results indicate that C-N stretching vibration peaks appeared at all reaction temperatures. At 85 °C, f-GO85 exhibited optimal modification with a layer spacing of 1.471 nm, 72% transmittance, and superior thermal stability, confirming successful lysine grafting onto the GO surface. Corrosion resistance testing of the composite coating revealed enhanced adhesion and impact resistance, reduced corrosion rate, decreased corrosion current density in polarization curves, positive shift in corrosion potential, and higher impedance values in impedance curves, indicating improved coating density and corrosion resistance. Salt spray tests demonstrated that incorporating lysine-modified graphene oxide significantly improved the anti-corrosion performance of polyurethane coatings. Optimal corrosion resistance was achieved when the modified graphene oxide content was 0.2 wt%. Full article

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

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4 pages, 150 KB

Open AccessEditorial

Sustainable and Resilient Pavements—Insights from Innovative Coatings and Materials

by Hao Wu, Xiaobao Chen and Weimin Song

Coatings 2026, 16(1), 130; https://doi.org/10.3390/coatings16010130 - 19 Jan 2026

Viewed by 483

Abstract

As the global community intensifies its focus on the circular economy and environmental resilience, the science and technology of pavement coating materials have reached a critical inflection point [...] Full article

(This article belongs to the Special Issue Science and Technology of Pavement Coatings Materials)

45 pages, 5089 KB

Open AccessReview

A Review on the Synthesis Methods, Properties, and Applications of Polyaniline-Based Electrochromic Materials

by Ge Cao, Yan Ke, Kaihua Huang, Tianhong Huang, Jiali Xiong, Zhujun Li and He Zhang

Coatings 2026, 16(1), 129; https://doi.org/10.3390/coatings16010129 - 19 Jan 2026

Viewed by 859

Abstract

Polyaniline (PANI), characterized by its proton-coupled redox mechanism and multicolor reversibility, is widely investigated for adaptive optical interfaces. Compared to inorganic oxides, PANI offers advantages in cost-effectiveness, mechanical flexibility, and molecular tunability; however, its practical implementation faces challenges related to kinetic limitations and [...] Read more.

Polyaniline (PANI), characterized by its proton-coupled redox mechanism and multicolor reversibility, is widely investigated for adaptive optical interfaces. Compared to inorganic oxides, PANI offers advantages in cost-effectiveness, mechanical flexibility, and molecular tunability; however, its practical implementation faces challenges related to kinetic limitations and environmental instability. This review presents a comprehensive analysis of PANI-based electrochromic materials, examining the intrinsic correlations among synthesis methodologies, microstructural characteristics, and optoelectronic performance. Synthesis strategies, including chemical oxidative polymerization, electrochemical deposition, and template-assisted techniques, are evaluated. Emphasis is placed on resolving the trade-off between optical contrast and switching kinetics by constructing high-surface-area porous nanostructures and inducing chain ordering via functional dopants to shorten ion diffusion paths and reduce charge transfer resistance. Fundamental electrochromic properties are subsequently discussed, with specific attention to degradation mechanisms triggered by environmental factors, such as pH drift, and stabilization strategies involving electrolyte engineering and composite design. Furthermore, the review addresses the evolution of applications from single-band monochromatic displays to dual-band smart windows for decoupled visible/near-infrared regulation and multifunctional integrated systems, including electrochromic supercapacitors and adaptive thermal management textiles. Finally, technical challenges regarding long-term durability, neutral color development, and large-area manufacturing are summarized to outline future research directions for PANI-based optical systems. Full article

(This article belongs to the Special Issue Advanced Coating Materials and Manufacturing Technologies for Enhancing Robotic Capabilities)

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12 pages, 7889 KB

Open AccessArticle

Growth Process and Formation Mechanism of Oxide Films for FSX-414 Alloy: Comparing External Surface and Narrow Crevice During Long-Term Oxidation at 900 °C

by Junjie Wu, Changlin Yang, Fan Zhao, Yi Zeng, Jianping Lai, Jiaxin Yu, Yingbo Guan, Zhenhuan Gao and Xiufang Gong

Coatings 2026, 16(1), 128; https://doi.org/10.3390/coatings16010128 - 19 Jan 2026

Viewed by 479

Abstract

Welding repair of cracks in FSX-414 cobalt-based alloy, used in high-temperature components, poses significant challenges due to the presence of surface oxide films within the cracks. By comparing the formation of oxide films on the external surface and inside the narrow crevice of [...] Read more.

Welding repair of cracks in FSX-414 cobalt-based alloy, used in high-temperature components, poses significant challenges due to the presence of surface oxide films within the cracks. By comparing the formation of oxide films on the external surface and inside the narrow crevice of FSX-414 alloys preserved at 900 °C for up to 1000 h, we found that the oxide film growth rate on the external surface was slightly larger than that inside the narrow crevice, and the latter slowed down after 672 h. Additionally, the oxide films on both surfaces were mainly composed of O and Cr elements, providing excellent protection to the underlying metal and resulting in minimal internal oxidation. A compositional transition region formed between the oxide film and the base metal. The width of the transition region decreased with heating duration and was narrower in the external surface sample, leading to a steeper composition gradient between the oxide film and the inner metal. With prolonged exposure, increasing numbers of “pores” rich in W and O appeared near the oxide films, creating channels that connect the oxide layer with the internal metal and accelerate material degradation. “Pores” extended deeper into the metal within the narrow crevice compared to those on the surface. Prior to welding repair, channels composed of W and O near the oxide films must be cleaned along with the oxide layer itself, and the removal of oxide from narrow cracks poses greater difficulty. 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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5 pages, 390 KB

Open AccessEditorial

Special Issue: “New Functional Coatings and Thin Films for Sensor and Green Energy Technologies”

by Gergana Alexieva

Coatings 2026, 16(1), 127; https://doi.org/10.3390/coatings16010127 - 19 Jan 2026

Viewed by 489

Abstract

The new challenges we face in modern life, such as the increasing need to monitor health, food quality, and environmental control, along with the strategic areas related to clean energy, require the development of a wide range of products and technological applications [...] [...] Read more.

The new challenges we face in modern life, such as the increasing need to monitor health, food quality, and environmental control, along with the strategic areas related to clean energy, require the development of a wide range of products and technological applications [...] 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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12 pages, 3279 KB

Open AccessArticle

Regulation of Droplet Spreading Behavior by Superhydrophobic Meshes Under Fluid Penetration Phenomena

by Lijie Sun, Shuang Chen and Bo Li

Coatings 2026, 16(1), 126; https://doi.org/10.3390/coatings16010126 - 18 Jan 2026

Viewed by 235

Abstract

Droplet impact on porous mesh surfaces is a common phenomenon in fields such as thermal management systems, biomedical manufacturing, and precision agriculture. As a substrate with microstructures, the mesh surface allows liquid penetration upon droplet impact. The resulting loss of liquid mass significantly [...] Read more.

Droplet impact on porous mesh surfaces is a common phenomenon in fields such as thermal management systems, biomedical manufacturing, and precision agriculture. As a substrate with microstructures, the mesh surface allows liquid penetration upon droplet impact. The resulting loss of liquid mass significantly alters the impact dynamics of the residual droplet on the surface. This study experimentally compares the behavior of water droplets impacting superhydrophobic mesh surfaces with different pore sizes against that on smooth surfaces. It focuses on analyzing how liquid penetration affects parameters such as spreading time (

t_{s}

), maximum spreading factor (

β_{m a x}

), contact time (

t_{c}

), and droplet height (

h

). The results show that the substantial liquid loss induced by large-pore meshes directly leads to a marked decrease in spreading time and maximum spreading factor. Furthermore, the “pancake bouncing” phenomenon observed on the superhydrophobic mesh surfaces significantly shortens the contact time, providing a new perspective for minimizing the contact duration between droplets and solid surfaces. By establishing the correlation between pore size and droplet impact behavior, this study provides key structural design guidelines for applications such as advanced printing systems and efficient pesticide spraying, thereby achieving the goal of proactively regulating liquid dynamics through surface microstructure. Full article

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

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18 pages, 2670 KB

Open AccessArticle

High-Efficient Photocatalytic and Fenton Synergetic Degradation of Organic Pollutants by TiO₂-Based Self-Cleaning PES Membrane

by Shiying Hou, Yuting Xue, Wenbin Zhu, Min Zhang and Jianjun Yang

Coatings 2026, 16(1), 125; https://doi.org/10.3390/coatings16010125 - 18 Jan 2026

Viewed by 365

Abstract

In this study, we aimed to develop a high-performance, anti-fouling ultrafiltration membrane by integrating photocatalytic and Fenton-like functions into a polymer matrix, in order to address the critical challenge of membrane fouling and achieve simultaneous separation and degradation of organic pollutants. To this [...] Read more.

In this study, we aimed to develop a high-performance, anti-fouling ultrafiltration membrane by integrating photocatalytic and Fenton-like functions into a polymer matrix, in order to address the critical challenge of membrane fouling and achieve simultaneous separation and degradation of organic pollutants. To this end, a novel Fe-V_O-TiO₂-embedded polyethersulfone (PES) composite membrane was designed and fabricated using a facile phase inversion method. The key innovation lies in the incorporation of Fe-V_O-TiO₂ nanoparticles containing abundant bulk-phase single-electron-trapped oxygen vacancies, which not only modulate membrane morphology and hydrophilicity but also enable sustained generation of reactive oxygen species for the pollutant degradation under light irradiation and H₂O₂. The optimized Fe-V_O-TiO₂-PES-0.04 membrane exhibited a significantly enhanced pure water flux of 222.6 L·m⁻²·h⁻¹ (2.2 times higher than the pure PES membrane) while maintaining a high bovine serum albumin (BSA) retention of 93% and an improved hydrophilic surface. More importantly, the membrane demonstrated efficient and stable synergistic Photocatalytic-Fenton activity, achieving 82% degradation of norfloxacin (NOR) and retaining 75% efficiency after eight consecutive cycles. A key finding is the membrane’s Photocatalytic-Fenton-assisted self-cleaning capability, with an 80% flux recovery after methylene blue (MB) fouling, which was attributed to in situ reactive oxygen species (·OH) generation (verified by ESR). This work provides a feasible strategy for designing multifunctional membranes with enhanced antifouling performance and extended service life through built-in catalytic self-cleaning. Full article

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

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14 pages, 2317 KB

Open AccessArticle

Shrimp-Derived Chitosan for the Formulation of Active Films with Mexican Propolis: Physicochemical and Functional Evaluation of the Biomaterial

by Alejandra Delgado-Lozano, Pedro Alberto Ledesma-Prado, César Leyva-Porras, Lydia Paulina Loya-Hernández, César Iván Romo-Sáenz, Carlos Arzate-Quintana, Manuel Román-Aguirre, María Alejandra Favila-Pérez, Alva Rocío Castillo-González and Celia María Quiñonez-Flores

Coatings 2026, 16(1), 124; https://doi.org/10.3390/coatings16010124 - 17 Jan 2026

Viewed by 308

Abstract

The development of functional biomaterials based on natural polymers has gained increasing relevance due to the growing demand for sustainable and bioactive alternatives for biomedical and technological applications. In this study, chitosan was obtained from shrimp exoskeletons and used to formulate active films [...] Read more.

The development of functional biomaterials based on natural polymers has gained increasing relevance due to the growing demand for sustainable and bioactive alternatives for biomedical and technological applications. In this study, chitosan was obtained from shrimp exoskeletons and used to formulate active films enriched with Mexican propolis, aiming to evaluate the influence of the extract on the physicochemical and functional properties of the resulting biomaterial. Propolis was incorporated into the chitosan film-forming solution at a final concentration of 1.0% (v/v). The propolis employed met the requirements of the Mexican Official Standard NOM-003-SAG/GAN-2017 regarding flavonoid content, total phenolic compounds, and antimicrobial activity; additionally, it was evaluated through antioxidant activity, hemolysis, and acute toxicity (LD₅₀) assays to provide a broader biological and safety assessment. The extracted chitosan exhibited a degree of deacetylation of 74% and characteristic FTIR spectral features comparable to those of commercial chitosan, confirming the quality of the obtained polymer. Chitosan–propolis films exhibited antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans, whereas pure chitosan films showed no inhibitory effect. Thermal analyses (TGA/DSC) revealed a slight reduction in thermal stability due to the incorporation of thermolabile polyphenolic compounds, along with increased thermal complexity of the system. SEM observations demonstrated reduced microbial adhesion and marked morphological damage in microorganisms exposed to the functionalized films. Overall, the incorporation of Mexican propolis enabled the development of a hybrid biomaterial with enhanced antimicrobial performance and potential application in wound dressings and bioactive coatings. Full article

(This article belongs to the Special Issue Coatings with Natural Products)

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4 pages, 168 KB

Open AccessEditorial

The Hidden Threats of Biofouling and Microbiologically Influenced Corrosion—Implications for Coatings Science and Sustainable Infrastructure

by Elisabete R. Silva and Guangming Jiang

Coatings 2026, 16(1), 123; https://doi.org/10.3390/coatings16010123 - 16 Jan 2026

Viewed by 532

Abstract

Biofouling and microbiologically influenced corrosion (MIC) pose profound allied threats, both visible and invisible, across global industrial and societal infrastructures, encompassing both stationary and mobile systems, such as maritime shipping, aquaculture, offshore and onshore energy platforms, desalination and wastewater treatment and distribution systems [...] Read more.

Biofouling and microbiologically influenced corrosion (MIC) pose profound allied threats, both visible and invisible, across global industrial and societal infrastructures, encompassing both stationary and mobile systems, such as maritime shipping, aquaculture, offshore and onshore energy platforms, desalination and wastewater treatment and distribution systems [...] Full article

(This article belongs to the Special Issue Environmentally-Friendly Coatings towards Biofouling Control and Microbiologically Influenced Corrosion (MIC) Inhibition)

4 pages, 151 KB

Open AccessEditorial

Editorial Insight on Special Issue “Recent Developments on Functional Coatings for Industrial Applications, Volume II”

by Luigi Calabrese and Edoardo Proverbio

Coatings 2026, 16(1), 122; https://doi.org/10.3390/coatings16010122 - 16 Jan 2026

Viewed by 496

Abstract

The topic of functional coating technology has seen an increasing interest in recent years, driven by the promising perspective to enhance engineered materials [...] Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications, Volume II)

14 pages, 5336 KB

Open AccessArticle

Time-Dependent Microstructural Transformation and Interfacial Phase Evolution in TLP Bonding of CM247LC Superalloy

by Jaehui Bang, Hyukjoo Kwon, Taewon Park and Eunkyung Lee

Coatings 2026, 16(1), 121; https://doi.org/10.3390/coatings16010121 - 16 Jan 2026

Viewed by 280

Abstract

The bonding behavior of the Ni-based superalloy CM247LC during transient liquid phase (TLP) bonding is strongly governed by filler metal chemistry, particularly boron activity. In this study, the time-dependent bonding mechanisms of CM247LC joints fabricated using a high-boron MBF-80 filler and a low-boron [...] Read more.

The bonding behavior of the Ni-based superalloy CM247LC during transient liquid phase (TLP) bonding is strongly governed by filler metal chemistry, particularly boron activity. In this study, the time-dependent bonding mechanisms of CM247LC joints fabricated using a high-boron MBF-80 filler and a low-boron MBF-20 filler are systematically compared to clarifying the transition between reaction-dominated brazing and diffusion-assisted TLP bonding. Microstructural analyses reveal that MBF-80 promotes the formation of a persistent, reaction-stabilized interlayer characterized by strong boron localization and the development of boron-rich intermetallic reaction products. These features kinetically suppress diffusion-assisted homogenization and prevent isothermal solidification, resulting in pronounced chemical and mechanical discontinuities across the joint. In contrast, MBF-20 enables progressive boron depletion, suppression of stable intermetallic accumulation, and interfacial smoothing, leading to diffusion-assisted chemical redistribution and partial isothermal solidification. This evolution is accompanied by gradual convergence of hardness profiles toward that of the CM247LC base metal, indicating improved mechanical continuity. These results demonstrate that joint hardness alone is insufficient for evaluating bonding quality in CM247LC. Instead, controlled microstructural evolution governed by low-boron filler chemistry is essential for achieving chemically and mechanically compatible joints. The present work establishes a clear mechanistic link between filler metal composition and bonding behavior, providing guidance for the design of reliable TLP bonding strategies in Ni-based superalloys. Full article

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

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21 pages, 4861 KB

Open AccessArticle

Synthesis and Characterization of ITO Films via Forced Hydrolysis for Surface Functionalization of PET Sheets

by Silvia del Carmen Madrigal-Diaz, Laura Cristel Rodríguez-López, Isaura Victoria Fernández-Orozco, Saúl García-López, Cecilia del Carmen Díaz-Reyes, Claudio Martínez-Pacheco, José Luis Cervantes-López, Ibis Ricárdez-Vargas and Laura Lorena Díaz-Flores

Coatings 2026, 16(1), 120; https://doi.org/10.3390/coatings16010120 - 16 Jan 2026

Viewed by 297

Abstract

Transparent conductive oxides (TCOs), such as indium tin oxide (ITO), are essential for flexible electronics; however, conventional vacuum-based deposition is costly and thermally aggressive for polymers. This study investigated the surface functionalization of PET substrates with ITO thin film-based forced hydrolysis as a [...] Read more.

Transparent conductive oxides (TCOs), such as indium tin oxide (ITO), are essential for flexible electronics; however, conventional vacuum-based deposition is costly and thermally aggressive for polymers. This study investigated the surface functionalization of PET substrates with ITO thin film-based forced hydrolysis as a low-cost, reproducible alternative.

S n O_{2}

nanoparticles were synthesized by forced hydrolysis at 180 °C for 3 h and 6 h, yielding crystalline nanoparticles with a cassiterite phase and an average crystallite size of 20.34 nm. The process showed high reproducibility, enabling consistent structural properties without complex equipment or high-temperature treatments. The

S n O_{2}

sample obtained at 3 h was incorporated into commercial

{I n}_{2} O_{3}

to form a mixed In–Sn–O oxide, which was subsequently deposited onto PET substrates by spin coating onto UV-activated PET. The resulting 1.1 µm ITO films demonstrated good adhesion (4B according to ASTM D3359), a low resistivity of 1.27 × 10⁻⁶ Ω·m, and an average optical transmittance of 80% in the visible range. Although their resistivity is higher than vacuum-processed films, this route provides a superior balance of mechanical robustness, featuring a hardness of (H) of 3.8 GPa and an elastic modulus (E) of 110 GPa. These results highlight forced hydrolysis as a reproducible route for producing ITO/PET thin films. The thickness was strategically optimized to act as a structural buffer, preventing crack propagation during bending. Forced hydrolysis-driven PET sheet functionalization is an effective route for producing durable ITO/PET electrodes that are suitable for flexible sensors and solar cells. Full article

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

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21 pages, 4628 KB

Open AccessArticle

Effect of Inclined Angles and Contouring Parameters on Upskin Surface Characteristics of Parts Made by Laser Powder-Bed Fusion

by Nismath Valiyakath Vadakkan Habeeb and Kevin Chou

Coatings 2026, 16(1), 119; https://doi.org/10.3390/coatings16010119 - 16 Jan 2026

Viewed by 376

Abstract

Surface finish plays a critical role in the tribological performance of additively manufactured engineering components. In exploring part characteristics in laser powder-bed fusion (L-PBF), this study investigates the effect of contouring strategies on the upskin surface of inclined specimens (30°, 45°, and 60°) [...] Read more.

Surface finish plays a critical role in the tribological performance of additively manufactured engineering components. In exploring part characteristics in laser powder-bed fusion (L-PBF), this study investigates the effect of contouring strategies on the upskin surface of inclined specimens (30°, 45°, and 60°) made with L-PBF, using post- and pre-contouring strategies with various levels of process parameters. The surface data of fabricated inclined specimens were acquired by white-light interferometry, followed by a quantitative analysis using surface images. The results show that post-contouring leads to better surface finishes, with the lowest S_a of 8.68 µm attained at the highest laser power (195 W) and the slowest scan speed (500 mm/s) on 30°-inclined specimens, likely due to increased remelting and less step-edges. In contrast, pre-contouring produces distinct surface textures on the upskin of L-PBF specimens, resulting in a rougher surface morphology, with a maximum S_a of 33.39 µm also from 30°-inclined specimens at the lowest power (100 W) and the highest speed (2000 mm/s), suggesting an insufficient remelting of surface defects. In comparative analysis, in general, post-contouring yields smoother upskin surfaces, with a 17%–30% reduction in S_a, than those from equivalent pre-contouring conditions, highlighting the potential of scan sequences for optimizing L-PBF to improve the surface finish of inclined structures. Full article

(This article belongs to the Special Issue Surface Topography Measurement Analysis of Additively Manufactured Modern Materials and Coatings)

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18 pages, 17892 KB

Open AccessReview

Review of Preparing Low-Dielectric Epoxy Resin Composites

by Jingwei Liu, Pingping Ming, Zijian Zhou, Tianyong Zhang, Qifeng Liu and Bing Du

Coatings 2026, 16(1), 118; https://doi.org/10.3390/coatings16010118 - 15 Jan 2026

Viewed by 473

Abstract

The rapid advancement of fifth-generation (5G) communication technologies has increased the demand for high-frequency circuits that offer high signal transmission rates and low latency. Traditional epoxy resin materials, characterized by their high dielectric constant (εr) and dielectric loss (tanδ), lead to significant signal [...] Read more.

The rapid advancement of fifth-generation (5G) communication technologies has increased the demand for high-frequency circuits that offer high signal transmission rates and low latency. Traditional epoxy resin materials, characterized by their high dielectric constant (εr) and dielectric loss (tanδ), lead to significant signal attenuation and reflection in high-frequency applications, thus limiting their suitability for modern communication devices. Accordingly, reducing the dielectric constant and dielectric loss of epoxy resins has become a prominent research focus in materials science. This paper reviews various methods for developing low-dielectric epoxy resin composites, emphasizing strategies to reduce polarization and material density. It subsequently provides a concise analysis of the advantages and current challenges associated with each technique and offers insights into potential future research directions. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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20 pages, 1485 KB

Open AccessArticle

SPH Simulation of Multiple Droplets Impact and Solidification on a Cold Surface

by Lujie Yuan, Qichao Wang and Hongbing Xiong

Coatings 2026, 16(1), 117; https://doi.org/10.3390/coatings16010117 - 15 Jan 2026

Viewed by 315

Abstract

The impact and solidification of multiple molten droplets on a cold substrate critically influence the quality and performance of thermally sprayed coatings. We present a Smoothed Particle Hydrodynamics (SPH) model that couples fluid-solid interaction, wetting, heat transfer and phase change to simulate multi-droplet [...] Read more.

The impact and solidification of multiple molten droplets on a cold substrate critically influence the quality and performance of thermally sprayed coatings. We present a Smoothed Particle Hydrodynamics (SPH) model that couples fluid-solid interaction, wetting, heat transfer and phase change to simulate multi-droplet impact and freezing. The model is validated against benchmark cases, including the Young–Laplace relation, wetting dynamics, single-droplet impact and the Stefan solidification problem, showing good agreement. Using the validated model, we investigate two droplets—either centrally or off-centrally—impacting on a cold surface. Simulations reveal two distinct solidification patterns: convex pattern (CVP), which results in a mountain-like splat morphology, and concave pattern (CCP), which leads to a valley-like shape. The criterion for the two patterns is explored with two dimensionless numbers, the Reynolds number

R e

and the Stefan number

S t e

. When

R e \leq 17.8

, droplets tend to solidify in CVP; at higher Reynolds numbers

R e \geq 18.8

, they tend to solidify in CCP. The transition between the two patterns is primarily governed by

R e

, with

S t e

exerting a secondary influence. For example, when droplets have

R e = 9.9

and

S t e = 5.9

, they tend to solidify in a convex pattern, whereas at

R e = 19.8

and

S t e = 5.9

, they tend to solidify in a concave pattern. Also, the solidification state of the first droplet greatly influences the subsequent spreading and solidification of the second droplet. A parametric study on CCP cases with varying vertical and horizontal offsets shows that larger vertical offsets accelerate solidification and reduce the maximum spreading factor. For small vertical distances, the solidification time increases with horizontal offset by more than 29%; for large vertical distances the change is minor. These results clarify how droplet interactions govern coating morphology and thermal evolution during thermal spraying. Full article

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

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