Coatings

19 pages, 5380 KiB

Open AccessArticle

Biocompatibility of Al₂O₃-Doped Diamond-like Carbon Laparoscope Coatings

by Russell L. Leonard, Anna B. Bull, Fan Xue, Christopher P. Haycook, Sharon K. Gray, Charles W. Bond, Paige E. Bond, Lesa R. Brown, Todd D. Giorgio and Jacqueline A. Johnson

Coatings 2025, 15(4), 437; https://doi.org/10.3390/coatings15040437 (registering DOI) - 7 Apr 2025

Abstract

Laparoscopic lens fogging and contamination pose significant challenges, leading to a reduced surgical field of view. Intraoperative cleaning to address these issues extends the surgical duration and elevates the risk of surgical site infections. The authors propose that a hydrophilic diamond-like carbon (DLC) [...] Read more.

Laparoscopic lens fogging and contamination pose significant challenges, leading to a reduced surgical field of view. Intraoperative cleaning to address these issues extends the surgical duration and elevates the risk of surgical site infections. The authors propose that a hydrophilic diamond-like carbon (DLC) coating would effectively mitigate fogging and fouling, thereby eliminating the requirement for intraoperative cleaning, while the scratch-resistant nature of DLC would provide additional benefits. The present study investigates the efficacy of aluminum oxide (Al₂O₃) as a dopant in diamond-like carbon (DLC) films for antifogging applications. The authors hypothesized that adding oxygen to the DLC matrix would increase surface energy by increased hydrogen bonding, resulting in a highly hydrophilic coating. Varying dopant concentrations were tested to observe their effects on hydrophilicity, transparency, biocompatibility, and wear properties. The doped films displayed a notable improvement in transparency throughout the visible spectrum. Plasma-cleaned samples demonstrated a substantial reduction in contact angles, achieving values less than 8°. The biocompatibility of these films was analyzed with CellTiter-Glo assays; the films demonstrated statistically similar levels of cell viability when compared to the control media. The absence of adenosine triphosphate released by blood platelets in contact with the DLC coatings suggests in vivo hemocompatibility. These films, characterized by high transparency, biocompatibility, and biostability, could be valuable for biomedical applications necessitating transparent coatings. Full article

(This article belongs to the Collection Feature Paper Collection in Bioactive Coatings and Biointerfaces)

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13 pages, 14903 KiB

Open AccessArticle

Al₂O₃/ZnO Multilayer Coatings for Improvement in Functional Properties of Surgical Scalpel Blades

by Magdalena Monika Szindler, Marek Szindler, Jakub Bicz and Krzysztof Matus

Coatings 2025, 15(4), 436; https://doi.org/10.3390/coatings15040436 (registering DOI) - 7 Apr 2025

Abstract

This work aimed to investigate the structure and corrosion resistance of Al₂O₃/ZnO multilayer coatings deposited by ALD on the standard surgical scalpel blades made of carbon steel. The surface topography of the coatings was examined using a scanning electron [...] Read more.

This work aimed to investigate the structure and corrosion resistance of Al₂O₃/ZnO multilayer coatings deposited by ALD on the standard surgical scalpel blades made of carbon steel. The surface topography of the coatings was examined using a scanning electron microscope (SEM), revealing the significant effect of the number of deposited Al₂O₃/ZnO bilayers on the morphology of the multilayer coatings. The XRD method was used for the phase analysis, allowing to confirm the presence of ZnO and ZnAl₂O₄ phases. The presence of the ZnAl₂O₄ structure was also confirmed using a Raman spectrometer. A qualitative analysis of the chemical composition of the obtained coatings was performed using the energy dispersive spectrometry (EDX) method. In order to determine the corrosion resistance, potentiodynamic tests were performed using Ringer’s solution at a temperature of 37 °C. The beneficial effect of increasing the number of deposited Al₂O₃/ZnO bilayers on the corrosion resistance was confirmed, with the lowest corrosion current density value of 2.05 μA/cm² and the highest polarization resistance of 12.15 kΩ obtained in the case of the N72 coating. Full article

(This article belongs to the Special Issue Advances in Corrosion Behaviors and Protection of Coatings)

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19 pages, 1017 KiB

Open AccessArticle

Composite Edible Coating from Arabic Gum and Mango Peel Hydrocolloids Enriched with Mango Seed Extracts for the Preservation of Grapes (Vitis vinifera) During Storage

by Luisa López-Ortiz, Somaris E. Quintana and Luis A. García-Zapateiro

Coatings 2025, 15(4), 435; https://doi.org/10.3390/coatings15040435 (registering DOI) - 7 Apr 2025

Abstract

Composite edible coatings based on arabic gum with mango peel hydrocolloids and mango seed extracts were prepared and used to evaluate grape conservation. Hydroethanolic solutions were used for the obtention of mango seed extracts, by microwave-assisted extraction, with total phenolic compounds (5.48 and [...] Read more.

Composite edible coatings based on arabic gum with mango peel hydrocolloids and mango seed extracts were prepared and used to evaluate grape conservation. Hydroethanolic solutions were used for the obtention of mango seed extracts, by microwave-assisted extraction, with total phenolic compounds (5.48 and 9.85 GAE/g of extract) and antioxidant activity (<13.03 µmol Trolox/g of extract). The extracts were selected for the development of edible coatings. The rheological properties of edible coating solutions present a non-Newtonian behavior-type shear thinning fluid; the addition of extracts improves their viscoelastic properties, favoring their application into grapes. The coated grapes maintained physicochemical parameters, such as weight, pH, acidity, soluble solids, and color during the 15 days of storage. The results of this research offer the possibility of using by-products from fruit industries, especially mango, to obtain functional ingredients and their application in food systems, taking advantage of their biological activity. Full article

(This article belongs to the Special Issue Trends in Sustainable Food Packaging and Coatings)

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15 pages, 4349 KiB

Open AccessArticle

Research on Titanium Ion Etching Pretreatment Process on Cemented Carbide Before DLC Film Deposition

by Chao Li, Juan Chen and Lei Huang

Coatings 2025, 15(4), 434; https://doi.org/10.3390/coatings15040434 (registering DOI) - 7 Apr 2025

Abstract

Before depositing a thin film, modifying the substrate surface was a crucial step in the film preparation process, having a decisive impact on the final properties of the film. In addition to additive methods such as preparing transition layers, subtractive methods such as [...] Read more.

Before depositing a thin film, modifying the substrate surface was a crucial step in the film preparation process, having a decisive impact on the final properties of the film. In addition to additive methods such as preparing transition layers, subtractive methods such as etching treatment could also enhance the performance of the film. Using titanium ions to etch and pretreat the surface of cemented carbide was an effective optimization method for depositing DLC films. This paper investigated the influence of process parameters for titanium ion etching of cemented carbide on the substrate surface. By varying the substrate negative bias voltage, medium-frequency current, and argon gas flow rate, the etching rate, roughness, and elemental changes of the etched surface were studied. DLC films were then deposited on the etched surfaces to investigate the effect of the changes of surface characteristics on subsequent film deposition. The research revealed that the substrate negative bias voltage had the most significant impact on the etching rate, while the MF current affected the surface roughness. The increase in surface roughness can enhance the deposition rate. The changes in C/W ratio did not exhibit a clear impact pattern on the DLC film. However, an increase in Co element content improved the properties of the DLC film due to the diffusion of sub-surface Co element. Full article

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15 pages, 11630 KiB

Open AccessArticle

Feasible Exploration Study of Anti-Silicon Element Corrosion Coating for C/C Composites

by Haijiang Yu, Huiyong Yang, Deteng Wang, Yixin Xiao, Lianyi Wang, Zhi Chen, Wei Li, Ruiying Luo and Juntong Huang

Coatings 2025, 15(4), 433; https://doi.org/10.3390/coatings15040433 (registering DOI) - 7 Apr 2025

Abstract

This study investigates the fabrication of a ZrSiO₄-based coating (ZSO coating) on substrate surfaces using atmospheric plasma spraying (APS) technology, with ZrSiO₄ as the feedstock material. A comprehensive characterization of the coating systems was conducted, including an in-depth analysis of [...] Read more.

This study investigates the fabrication of a ZrSiO₄-based coating (ZSO coating) on substrate surfaces using atmospheric plasma spraying (APS) technology, with ZrSiO₄ as the feedstock material. A comprehensive characterization of the coating systems was conducted, including an in-depth analysis of phase composition and a systematic evaluation of the effects of spray thickness and heat treatment temperature on phase evolution, microstructural development, and the resulting properties. The coatings’ resistance to silicon corrosion and the associated failure mechanisms were thoroughly examined. The key findings reveal that the plasma-sprayed coatings form a multiphase system composed of ZrSiO₄, along with the decomposition products of ZrO₂ and SiO₂. Optimal performance was observed within a critical thickness range of 154–240 μm. Post-deposition heat treatment at 1500 °C significantly improved the integrity of the coatings, as evidenced by a marked reduction in crack density and porosity, leading to substantial enhancement in densification. The coatings demonstrated outstanding performance in the high-temperature silicon corrosion tests, maintaining structural integrity after 4 h of exposure to molten silicon and its oxides at 1500 °C. Notably, the coatings effectively prevented the penetration of silicon into the C/C substrate, preserving strong interfacial adhesion without the formation of permeable cracks. Furthermore, post-corrosion analysis showed that the surface reaction products could be easily removed, underscoring the coatings’ exceptional protective capability for the underlying C/C substrate. Full article

(This article belongs to the Collection Feature Paper Collection in Plasma Coatings, Surfaces & Interfaces)

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17 pages, 7865 KiB

Open AccessArticle

Repair Bond Strength and Surface Roughness Evaluation of CAD/CAM Materials After Various Surface Pretreatments

by Burcu Dikici, Elif Türkeş Başaran, Nazlı Şirinsükan and Esra Can

Coatings 2025, 15(4), 432; https://doi.org/10.3390/coatings15040432 (registering DOI) - 7 Apr 2025

Abstract

This study assessed the repair shear bond strength (SBS; MPa) and surface roughness (Ra; μm) of aged hybrid ceramic (Cerasmart270, GC) and nano-hybrid ceramic (Grandio Blocs, Voco) CAD/CAM blocks after different surface pretreatment methods. In this study, 2 mm thick Cerasmart270 and Grandio [...] Read more.

This study assessed the repair shear bond strength (SBS; MPa) and surface roughness (Ra; μm) of aged hybrid ceramic (Cerasmart270, GC) and nano-hybrid ceramic (Grandio Blocs, Voco) CAD/CAM blocks after different surface pretreatment methods. In this study, 2 mm thick Cerasmart270 and Grandio Blocs were cut into slabs (Isomet; n = 80 per group). Following aging for six months, the specimens in each CAD/CAM material were randomly divided into four groups (n: 20 each) according to the surface pretreatments: control (no pretreatment), Er:YAG laser, sandblasting, and bur grinding. A total of 10 specimens in each CAD/CAM material pretreatment group were used for Ra evaluation (Perthometer Mahr), while the other 10 were for SBS. After the application of a silane primer (G-Multi Primer, GC) and universal adhesive (G2-Bond, GC), composite build-ups (Filtek Z250; 3MESPE) were performed for the SBS evaluation. After storage in distilled water for 24 h, SBS was evaluated with a universal testing machine (Instron). SBS and Ra data were analyzed with two-way ANOVA and Tukey’s post hoc tests (p < 0.05). SBS was significantly affected by the surface pretreatment methods (p = 0.0001) and by the types of CAD/CAM material (p = 0.005). Bur grinding showed the highest SBS for both CAD/CAM materials, while the control groups yielded significantly lower SBS than bur grinding and sandblasting (p < 0.05). Er:YAG lasers did not significantly enhance the SBS compared to the control group. Sandblasting presented significantly higher SBS than lasers only in Grandio Blocs (p < 0.05). The surface pretreatment methods significantly influenced Ra (p = 0.0001); however, no significant interaction was found between the types of CAD/CAM material and the surface pretreatments (p > 0.05). Control groups exhibited, significantly, the lowest Ra for both materials (p = 0.0001), while no significant differences were observed between the other pretreatment methods. Bur grinding was identified as the most effective pretreatment method for repairing hybrid ceramic CAD/CAM materials. Full article

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

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21 pages, 5911 KiB

Open AccessArticle

Ultra-Thin Films of CdS Doped with Silver: Synthesis and Modification of Optical, Structural, and Morphological Properties by the Doping Concentration Effect

by Juan P. Molina-Jiménez, Sindi D. Horta-Piñeres, S. J. Castillo, J. L. Izquierdo and D. A. Avila

Coatings 2025, 15(4), 431; https://doi.org/10.3390/coatings15040431 (registering DOI) - 7 Apr 2025

Abstract

Obtaining wide energy-gap semiconductor ultra-thin films is an important aspect for their application in sulfide-based solar cells. By reducing the optical losses associated with light reflection and exhibiting absorption edge shifts towards short wavelengths, these layers can optimize the amount of photons interacting [...] Read more.

Obtaining wide energy-gap semiconductor ultra-thin films is an important aspect for their application in sulfide-based solar cells. By reducing the optical losses associated with light reflection and exhibiting absorption edge shifts towards short wavelengths, these layers can optimize the amount of photons interacting with the active photovoltaic material, which increases the conversion efficiency of the solar cell. Ultra-thin CdS films were prepared by a low-cost chemical synthesis and the impact of silver doping on the optical, structural, and morphological properties was evaluated. SEM micrographs revealed that the layers are ultra-thin, homogeneous and uniform, with a reduction in particle size with increasing doping concentration. X-ray diffraction data confirmed the crystallization of CdS in the hexagonal phase for all prepared samples. A low concentration contributed to the formation of Ag₂S in the monoclinic phase according to the diffractograms. The optical properties of the thin films revealed an absorption edge shift that increased the CdS band gap from 2.267 ± 0.007 to 2.353 ± 0.005 eV with increasing doping concentration, improving the spectral transmittance response. These results make these layers particularly useful for implementation in next-generation flexible photovoltaic devices. Full article

(This article belongs to the Special Issue Thin-Film Synthesis, Characterization and Properties)

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15 pages, 3380 KiB

Open AccessArticle

Study on the Effect of Coal Gangue Particle Size Distribution for the Preparation of Kaolin by Shaking Table Separation

by Xinkai Hou, Wenjuan Ji, Hao Li, Xiaoqi Fan and Ying Wang

Coatings 2025, 15(4), 430; https://doi.org/10.3390/coatings15040430 (registering DOI) - 6 Apr 2025

Abstract

The presence of pyrite in coal gangue significantly degrades the performance of its prepared kaolin in ceramic and coating applications. Implementing separation techniques to remove pyrite can markedly enhance the quality of kaolin products. However, there is no research on the effect of [...] Read more.

The presence of pyrite in coal gangue significantly degrades the performance of its prepared kaolin in ceramic and coating applications. Implementing separation techniques to remove pyrite can markedly enhance the quality of kaolin products. However, there is no research on the effect of material particle size distribution on the separation effect in the current study on shaking table separation. For this reason, the coal gangue was crushed to different maximum particle sizes in this study, and its particle size distribution was fitted and analyzed. Based on the fitting results, the Rosin–Rammler–Sperling–Bennet (RRSB) distribution with a uniformity coefficient n of 0.74 was used to study the influence of the characteristic particle size d_e on the separation effect. Fuller distribution with distribution modulus q of 0.45 was also used to study the impact of maximum particle size d_max. The results showed that the Fuller distribution reduced the contents of SO₃ and Fe₂O₃ by 30.85% and 25.71%, respectively, compared with the raw materials. In comparison, the RRSB distribution reduced the contents of SO₃ and Fe₂O₃ by 41.01% and 30.85%, respectively, indicating that the separation effect of the RRSB distribution was better than that of the Fuller distribution. In addition, when the characteristic particle size d_e of the RRSB distribution was 37–42 μm, the content of SO₃ and Fe₂O₃ in the tailings varied very little, and the separation effect was stable. This study demonstrates that the particle size distribution significantly influences the separation efficiency of the shaking table, providing a novel idea for enhancing shaking table separation processes. Future studies may further explore the effect of another parameter or two-parameter coupling of RRSB distribution and Fuller distribution on the separation effect of the shaking table. Full article

(This article belongs to the Special Issue Ceramic and Glass Material Coatings)

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15 pages, 2518 KiB

Open AccessArticle

VOC Emission Spectrum and Industry-Specific Analysis in the Industrial Coating Industry of Hangzhou, China

by Wei Tang, Yang Xia, Ping He, Shenwei Tao, Qiyi Zhang, Dongrui Wang and Jinpeng Lin

Coatings 2025, 15(4), 429; https://doi.org/10.3390/coatings15040429 (registering DOI) - 4 Apr 2025

Abstract

This study conducted an on-site monitoring of 28 representative coating enterprises in Hangzhou City and successfully constructed the localized component spectrum of volatile organic compounds (VOC) emissions from the industrial coating industry. These coating enterprises, which have a total VOC emission of approximately [...] Read more.

This study conducted an on-site monitoring of 28 representative coating enterprises in Hangzhou City and successfully constructed the localized component spectrum of volatile organic compounds (VOC) emissions from the industrial coating industry. These coating enterprises, which have a total VOC emission of approximately 7113 tons, accounting for 17.6% of the city’s total industrial VOC emissions, primarily emit benzene derivatives, ketones, esters, and halogenated hydrocarbons. Using the maximum incremental reactivity (MIR) method, the ozone formation potential (OFP) was calculated based on the annual VOC emissions from the industry. The OFP values for the different types of enterprises had significant variations, with the general equipment manufacturing, metal products, and electrical machinery industries exhibiting the highest contributions. Research results indicate that differentiated management approaches are needed for specific emission characteristics in each sub-industry, including promoting the use of water-based paints and clean production technologies, adopting efficient volatile organic compound treatment technologies, and establishing stricter emission standards with regular monitoring of highly reactive compounds. These measures are crucial for achieving more effective environmental management and continuous improvement of air quality. Full article

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14 pages, 3801 KiB

Open AccessArticle

Synthesis and Characterization of Silane-Coupled Sodium Silicate Composite Coatings for Enhanced Anticorrosive Performance

by Minghui Liu, Zhiwen Tan, Shengda Xu, Yuantao Zhao, Haoran Wang, Shitao Zhang, Rong Ma, Tao Jiang, Zhen Ma, Ning Zhong and Wenge Li

Coatings 2025, 15(4), 428; https://doi.org/10.3390/coatings15040428 (registering DOI) - 4 Apr 2025

Abstract

Ships and offshore equipment operating in marine environments often face issues such as seawater corrosion and biofouling, leading to significant economic losses. To address the corrosion problems of ships and offshore equipment, heavy-duty anticorrosive coatings are widely used for corrosion protection in marine [...] Read more.

Ships and offshore equipment operating in marine environments often face issues such as seawater corrosion and biofouling, leading to significant economic losses. To address the corrosion problems of ships and offshore equipment, heavy-duty anticorrosive coatings are widely used for corrosion protection in marine environments due to their long-term effectiveness, cost-efficiency, and excellent applicability. In this study, silane coupling agent (KH-560) was employed to modify sodium silicate, and the modified sodium silicate was then incorporated as a reinforcing phase into polyurethane to ultimately prepare a modified sodium silicate/polyurethane coating. The feasibility of the modified sodium silicate/polyurethane coating was investigated by characterizing its conventional physicochemical properties, weather resistance, acid and alkali resistance, and salt spray corrosion resistance. Experimental results indicate that the silane coupling agent acts as a bridge between the organic and inorganic interfaces through the hydrolysis and condensation reactions of its bifunctional groups, forming an interfacial layer connected by hydrogen bonds and covalent bonds, thereby improving the compatibility between the organic resin and inorganic sodium silicate. Comprehensive performance analysis revealed that when the content of modified sodium silicate was 60 wt%, the coating hardness reached 4H. Additionally, electrochemical tests demonstrated that the coating exhibited higher impedance (9.62 × 10⁴ Ω/cm²) and lower corrosion current density (5.82 × 10⁻⁷ A/cm²). This study provides a theoretical and experimental basis for the development of high-performance anticorrosive coatings for marine applications. Full article

(This article belongs to the Special Issue Advances in Protective Coatings: Materials, Fabrication, Corrosion and Applications)

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10 pages, 1757 KiB

Open AccessArticle

Ab Initio MD Study of the Mechanism of Carbonization of Si(001) Surfaces with Methane at High Temperatures

by Dobromir A. Kalchevski, Dimitar V. Trifonov, Stefan K. Kolev, Hristiyan A. Aleksandrov, Dimitar A. Dimov, Valentin N. Popov and Teodor I. Milenov

Coatings 2025, 15(4), 427; https://doi.org/10.3390/coatings15040427 - 4 Apr 2025

Abstract

This study employs ab initio metadynamics to simulate the carbonization of Si(001) surfaces with chemical vapor deposition at a temperature of 1423 K. We reveal the complete reaction mechanism, including the beginning of silicon carbide crystal formation. The existence of surficial native oxide [...] Read more.

This study employs ab initio metadynamics to simulate the carbonization of Si(001) surfaces with chemical vapor deposition at a temperature of 1423 K. We reveal the complete reaction mechanism, including the beginning of silicon carbide crystal formation. The existence of surficial native oxide is incorporated into the theoretical model. The mechanism determination includes clarification of all intermediate products and transition states. The free-energy surface of the reaction chain has been found. Carbonization initiates with alkylated surface products and continues with consecutive dehydrogenation steps. Carbon is integrated in the volume, near the crystal surface, only if no covalent interactions with hydrogen atoms remain. The native oxide was not found to prohibit the process of carbonization. The oxygen atoms have certain surface mobility at high temperatures. It was revealed that hypervalency of carbon atoms is possible in transition state structures. The theoretical activation free energy of the rate-determining step was found to be only 166 kJ/mol. This work sheds light on the advantage of the practical use of Si(001) substrates for the synthesis of silicon carbide and Si-O-C glasses using direct carbonization via chemical vapor deposition. We also aim to enable more methodical designs of future synthetic routes and better-informed decisions for experimental investigations. Full article

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16 pages, 5858 KiB

Open AccessArticle

Ag NP-Decorated Glass Surfaces for Sensing in Medical Applications

by Cornelia-Ioana Ilie, Angela Spoială, Ludmila Motelica, Liliana Marinescu, Zeno Ghizdăveț, Doina-Roxana Trușcă, Ovidiu-Cristian Oprea, Denisa Ficai and Anton Ficai

Coatings 2025, 15(4), 426; https://doi.org/10.3390/coatings15040426 - 3 Apr 2025

Abstract

In recent decades, applications related to sensing have grown increasingly, transforming and expanding their fields into innovative research. Lately, researchers have demonstrated that immobilizing metal nanoparticles on glass-based platforms may render innovative perspectives for sensing applications. As a result, the focus of this [...] Read more.

In recent decades, applications related to sensing have grown increasingly, transforming and expanding their fields into innovative research. Lately, researchers have demonstrated that immobilizing metal nanoparticles on glass-based platforms may render innovative perspectives for sensing applications. As a result, the focus of this study was to develop glass-based platforms functionalized with silver nanoparticles, intending them to be utilized in sensing applications. The purpose of using glass-based platforms is due to their availability and eco-friendly features, which will make them suitable for such applications. The study uses a glass-based platform functionalized/modified with organosilanes (such as mercaptoalkyl trialkoxysilane), which can have a high affinity for Ag NPs. By decorating the glass surface with Ag NPs, it becomes active for the adsorption of the mercapto derivatives and further usage in sensing applications (specific drugs with an antitumoral, anti-hypertensive, antiarthritic role, neurotransmitters, etc.) but also for specific classes of pollutants for environmental applications. Therefore, the desired purpose of this study was to develop glass-based platforms decorated with Ag NPs and their further use in the selective adsorption of thioderivatives (cysteine was selected as a model component) even from a mixture of amino acids (cysteine, alanine, and threonine). Full article

(This article belongs to the Collection Feature Paper Collection in 'Surface Coatings for Biomedicine and Bioengineering')

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24 pages, 7784 KiB

Open AccessArticle

Enhancing the Surface Integrity of a Laser Powder Bed Fusion Inconel 718 Alloy by Tailoring the Microstructure and Microrelief Using Various Finishing Methods

by Dmytro Lesyk, Bohdan Mordyuk, Silvia Martinez, Vitaliy Dzhemelinskyi, Daniel Grochala, Andriy Kotko and Aitzol Lamikiz

Coatings 2025, 15(4), 425; https://doi.org/10.3390/coatings15040425 - 3 Apr 2025

Abstract

Heat-performance nickel-based superalloys are commonly applied in various critical industries. In this work, test samples in the form of turbine blades were manufactured by means of laser powder bed fusion (LPBF) 3D technology. This research focused on comparison of the influences of various [...] Read more.

Heat-performance nickel-based superalloys are commonly applied in various critical industries. In this work, test samples in the form of turbine blades were manufactured by means of laser powder bed fusion (LPBF) 3D technology. This research focused on comparison of the influences of various surface finishing methods. The mechanical surface post-processing of the LPBF-manufactured Inconel 718 alloy samples consisted of ultrasonic impact treatment (UIT), ultrasonic shot peening (USP), shot peening (SP), and barrel finishing (BF). The surface microrelief was evaluated using a high-precision laser profilometer, while the microstructural features were studied by light optical microscopy (LOM), scanning/transmission electron microscopy (SEM/TEM), and X-ray diffraction (XRD). Potentiodynamic polarization tests were also conducted to compare the surface finishing methods in terms of corrosion resistance improvement of the LPBF-manufactured 718 alloy samples. The effects of the surface microstructure and hardening intensity in combination with residual stresses and surface relief coupled with roughness profile shapes on the room temperature corrosion behavior of plastically deformed 718 alloy specimens manufactured by LPBF were studied. The corrosion rate (CR) of the LPBF-manufactured samples was reduced after post-processing: BF (~16 μm/year), USP (~15 μm/year), SP (~6.5 μm/year), and UIT (~5.5 μm/year). The experimental trends also agreed well with the theoretical trends of uniform corrosion of the studied alloy. Full article

(This article belongs to the Special Issue Laser Surface Engineering: Technologies and Applications)

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10 pages, 3133 KiB

Open AccessArticle

Effect of Substrate Negative Bias on the Composition and Structure of nc-Cu/a-C:H Nanocomposite Films Deposited by FCVA

by Qingyan Hou, Xiao Ouyang, Shuai Wu, Pan Pang, Yifan Zhang, Qian Li, Lin Chen, Xiaoyue Jin, Xu Zhang and Bin Liao

Coatings 2025, 15(4), 424; https://doi.org/10.3390/coatings15040424 - 2 Apr 2025

Abstract

Copper-doped hydrogenated amorphous carbon (Cu-doped a-C:H) films were synthesized using copper as the cathode and C₂H₂ as the precursor. The result shows that the negative bias voltage can affect the composition and microstructure of nanocomposite films. With bias voltage increasing, [...] Read more.

Copper-doped hydrogenated amorphous carbon (Cu-doped a-C:H) films were synthesized using copper as the cathode and C₂H₂ as the precursor. The result shows that the negative bias voltage can affect the composition and microstructure of nanocomposite films. With bias voltage increasing, Cu content first increases in the range of 50~300 V and then declines with higher voltage, while the deposition rate decreases continuously. The stress and sp³ content present a similar trend with the bias voltage, increasing during the range from 50 V to 200 V and then decreasing with higher voltage. Full article

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

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15 pages, 8675 KiB

Open AccessArticle

Nb Microalloying Enhances the Grain Stability of SAE8620H Gear Steel During High-Temperature Carburizing

by Xiangyu Zhang, Huasong Liu, Bingjun Lu, Yu Zhang, Qianshui Zhao, Zhiran Yan, Shuo Gong, Xiaodong Guo, Dong Pan, Pei Xu, Yang Wang and Kaimeng Wang

Coatings 2025, 15(4), 423; https://doi.org/10.3390/coatings15040423 - 2 Apr 2025

Abstract

In modern industries, gears function as pivotal transmission elements whose operational performance is directly dependent on the microstructural characteristics of gear steels. While high-temperature carburizing (950–1050 °C) substantially improves process efficiency through accelerated carbon diffusion, it inevitably promotes austenite grain coarsening. This study [...] Read more.

In modern industries, gears function as pivotal transmission elements whose operational performance is directly dependent on the microstructural characteristics of gear steels. While high-temperature carburizing (950–1050 °C) substantially improves process efficiency through accelerated carbon diffusion, it inevitably promotes austenite grain coarsening. This study investigates the effect of Nb microalloying on grain stability in SAE8620H gear steel during high-temperature carburizing. Experimental steels with varying Nb contents were prepared via vacuum induction suspension melting, followed by hot rolling, solution treatment, and pseudo-carburizing. Thermodynamic calculations, optical microscopy, transmission electron microscopy, and energy-dispersive spectroscopy were employed to analyze the mechanisms. Thermodynamic results revealed that higher Nb content retains more Nb(C, N) phases at elevated temperatures, effectively suppressing grain coarsening. Without preheating, increased Nb content refined grains but exhibited limited inhibition at high temperatures. Preheating (1330 °C × 10 min + water quenching) promoted uniform and fine Nb(C, N) precipitates, significantly enhancing grain refinement. When Nb content exceeded 0.053 wt.%, grain coarsening was fully inhibited under 1050 °C × 2 h carburizing. This study establishes the optimal Nb content range, elucidates the micro-mechanisms, and proposes a preheating process to improve high-temperature carburizing performance in gear steels. Full article

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

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17 pages, 4174 KiB

Open AccessArticle

Synergistic Titanium Intercalation in WO₃ Architectures to Enhance Electrochromic Performance for Smart Windows

by Rutuja U. Amate, Pritam J. Morankar, Namita A. Ahir and Chan-Wook Jeon

Coatings 2025, 15(4), 422; https://doi.org/10.3390/coatings15040422 - 2 Apr 2025

Abstract

We report the successful synthesis of amorphous titanium-engineered tungsten oxide (WTi) films via a facile and cost-effective electrodeposition method. Unlike conventional high-temperature or vacuum-based techniques, our approach enables a scalable, all-solution process, ensuring efficiency and sustainability. X-ray diffraction (XRD) confirmed the amorphous nature [...] Read more.

We report the successful synthesis of amorphous titanium-engineered tungsten oxide (WTi) films via a facile and cost-effective electrodeposition method. Unlike conventional high-temperature or vacuum-based techniques, our approach enables a scalable, all-solution process, ensuring efficiency and sustainability. X-ray diffraction (XRD) confirmed the amorphous nature of all films, a key factor in enhancing ion diffusion for superior electrochromic (EC) performance. Field-emission scanning electron microscopy (FESEM) revealed that an optimized nanoparticle network facilitates rapid charge transport and ion intercalation, while uncontrolled nucleation and grain growth hinder EC efficiency. By precisely tuning the Ti concentration, the optimized 3 at% WTi-3 film achieved outstanding EC properties, including an impressive optical modulation of 85% at 600 nm, exceptional reversibility of 95.61%, and a high coloration efficiency of 51.55 cm²/C. This study underscores the pivotal role of amorphous engineering and dopant concentrations in advancing high-performance EC materials, paving the way for next-generation smart windows and energy-efficient displays. Our findings highlight a transformative strategy for low-cost, high-efficiency EC devices, demonstrating unprecedented performance through precision-engineered material design. Full article

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20 pages, 7408 KiB

Open AccessArticle

Etching and Precursor Effects on Plasma-Modified Waste Polyethylene Terephthalate (PET) to Laccase Immobilization Applied in Catechol Biodegradation for Water Treatment

by Reyna Orsua-Gaona, Rosa Idalia Narro-Céspedes, Anna Ilina, Luis Fernando Mora-Cortés, Yadira Karina Reyes-Acosta, Gustavo Soria-Arguello, Cynthia Luevano-Martínez, Miriam Paulina Luévanos-Escareño and Claudia Gabriela Cuellar-Gaona

Coatings 2025, 15(4), 421; https://doi.org/10.3390/coatings15040421 - 2 Apr 2025

Abstract

Polyethylene terephthalate (PET) is a polyester used in the beverage bottling industry that generates a serious pollution problem. Films were obtained to reuse discarded PET bottles, and their surface was modified to determine their effectiveness in supporting the immobilization of the laccase enzyme [...] Read more.

Polyethylene terephthalate (PET) is a polyester used in the beverage bottling industry that generates a serious pollution problem. Films were obtained to reuse discarded PET bottles, and their surface was modified to determine their effectiveness in supporting the immobilization of the laccase enzyme applied to a catechol biodegradation assay. Radiofrequency (RF) plasma was used to modify the PET surface using different precursors: (a) with the use of air as precursor, the effect of the etching caused by the air on the greater or lesser immobilization was observed; (b) with the use of ethylenediamine, a mixture of N₂/H_2, or aniline as precursors, it was observed which of these three precursors presented the greater or lesser number of amino groups deposited on the PET surface. After plasma modification, the films were cross-linked with glutaraldehyde to immobilize the laccase enzyme. Finally, the catechol test was performed. It was found that the best etching time using air as a precursor was 90 min, and the precursor that caused a higher insertion of amino groups on the surface was ethylenediamine, which reached a density of amino groups of 3.98 ± 0.10 g·mm⁻². The highest percentage of laccase immobilization achieved on the surface of ethylenediamine-modified PET was 97.30%. In the catechol assay, the highest retention was 86.11%. This research reveals how the effect of plasma increases the surface area on a PET surface and, in conjunction with ethylenediamine as the best precursor of the three precursors evaluated, can immobilize a greater amount of enzyme and oxidize more catechol. There is no scientific evidence from previous studies that used air plasma technology to erode and then used three different precursors to modify a surface to immobilize the laccase enzyme and remove a water contaminant. Full article

(This article belongs to the Special Issue Advanced Technology in Environmental Remediation and Resource Utilization, 2nd Edition)

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15 pages, 5372 KiB

Open AccessArticle

Self-Crosslinking Waterborne Acrylate Modified Emulsified Asphalt via DAAM-ADH: A Dual-Enhanced Solution for Pavement Performance

by Jianhui Xu, Zhaoyi He, Haiying Li, Shutong Tang, Jie Wang, Jing Dang and Yuanyuan Li

Coatings 2025, 15(4), 420; https://doi.org/10.3390/coatings15040420 - 1 Apr 2025

Abstract

Emulsified asphalt is widely used for pavement maintenance due to its ease of application. However, its use is limited by poor high-temperature stability and low bonding strength. This study attempted to prepare a self-crosslinking waterborne acrylate (SWA)-type admixture using a diacetone acrylamide (DAAM)-adipic [...] Read more.

Emulsified asphalt is widely used for pavement maintenance due to its ease of application. However, its use is limited by poor high-temperature stability and low bonding strength. This study attempted to prepare a self-crosslinking waterborne acrylate (SWA)-type admixture using a diacetone acrylamide (DAAM)-adipic dihydrazide (ADH) crosslinking system and applied it to emulsified asphalt to ultimately obtain self-crosslinking waterborne acrylate-modified emulsified asphalt (AMEA). The research explored the effects of SWA on the fundamental properties, rheological characteristics, microscopic morphology, and bonding performance of AMEA. Results indicated that SWA undergoes self-crosslinking reactions during the demulsification process, forming a continuous and stable network structure that significantly enhances the strength of emulsified asphalt while improving softening point and high-temperature stability. Rheological analysis revealed that within the 10–15 phr dosage range, the influence of frequency on emulsified asphalt was minimized, with notable improvements in high-temperature elastic recovery and deformation resistance. Particularly when the dosage exceeds 10 phr, the material demonstrates adaptability to high-traffic environments. Pull-off tests demonstrated that SWA can increase the interlayer bonding strength of emulsified asphalt by over 50%. However, SWA exhibits some negative impact on the low-temperature ductility of emulsified asphalt, necessitating cautious dosage control during application. This novel self-crosslinking waterborne acrylate-modified emulsified asphalt, with its excellent bonding performance and superior high-temperature stability, emerges as a crucial material choice for pavement preventive maintenance. Full article

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

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14 pages, 8738 KiB

Open AccessArticle

Fabrication of a Hydrophobic Coating Using Acacia mearnsii De Wild Tannin Melamine Formaldehyde Microcapsules

by Ana Paula Steigleder and Liane Roldo

Coatings 2025, 15(4), 419; https://doi.org/10.3390/coatings15040419 - 1 Apr 2025

Abstract

The aim of this study is to develop and investigate the effect of applying microcapsules containing a melamine formaldehyde resin shell and a tannin extract as a core to form a hydrophobic coating. The microcapsules were obtained by in situ polymerization. Morphological analysis [...] Read more.

The aim of this study is to develop and investigate the effect of applying microcapsules containing a melamine formaldehyde resin shell and a tannin extract as a core to form a hydrophobic coating. The microcapsules were obtained by in situ polymerization. Morphological analysis was performed by focused ion beam/scanning electron microscopy. The chemical composition of the tannin extract, the melamine formaldehyde resin, and the polymeric microcapsules with the core of the tannin extract was determined by Fourier transform infrared spectroscopy. The thermal stability of tannin, melamine formaldehyde resin, and tannin microcapsules was investigated by thermogravimetric analysis. In addition, the durability of the coating over time was tested in an environmental test chamber. The polymeric microcapsules containing tannin extract are quasi-spherical, rough, and dense, with a diameter ranging from 1 to 5 μm and a shell thickness of 50 nm. The coating exhibited a hierarchical structure with improved hydrophobic properties, resulting in a contact angle of up to 148°. Full article

(This article belongs to the Special Issue Synthesis and Application of Functional Polymer Coatings)

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