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Coatings, Volume 15, Issue 2 (February 2025) – 124 articles

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15 pages, 3461 KiB  
Article
Fabrication of Thermally Stable Heat-Shielding Coated Glass for Solar Glazing via Direct Calcination in Air
by Guangrui Zhang, Xiaoting Qin, Dinghui Wang, Jinqing Li, Wenlong Pan and Jian Yin
Coatings 2025, 15(2), 239; https://doi.org/10.3390/coatings15020239 - 17 Feb 2025
Abstract
The utilization of heat-shielding glazing technologies can efficiently promote carbon emission reductions and energy savings by decreasing solar irradiation into buildings. Although a variety of glazing technologies have been created for solar glazing, either the heat-shielding performance is low, the thermal stability is [...] Read more.
The utilization of heat-shielding glazing technologies can efficiently promote carbon emission reductions and energy savings by decreasing solar irradiation into buildings. Although a variety of glazing technologies have been created for solar glazing, either the heat-shielding performance is low, the thermal stability is poor, or the cost is high. Here, we report a thermally stable heat-shielding coated glass for solar glazing in a simple way via direct calcination of Ce and Sb co-doped SnO2 nanoparticles with polysilazane (PSZ) coatings in air. The resulting coated glass has transmittances of 4.7% at 250–380 nm, 59.3% at 380–780 nm, and 9.7% at 780–2500 nm; excellent environment stability under accelerated aging conditions over 350 h; and also a ca. 50-fold lower fixed cost than commercial low-E glass. Moreover, a coated glass with a high pencil hardness of 9H was also fabricated via further spraying and calcinating of a PSZ coating as the cover layer, which is also the hardest coated solar glaze to our knowledge. The high solar-shielding performance and unprecedented low cost of the Ce and Sb co-doped SnO2-coated glass, as well as the simplicity of its fabrication, exhibit great potential in energy-saving buildings and cars. Full article
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22 pages, 2729 KiB  
Article
Effect of Enzymatic Glycosylation on Film-Processing Properties and Biological Activities of Black Soybean Protein
by Yinglei Zhang, Xue Gong, Jing Wang, Boxin Dou, Lida Hou, Wei Xiao, Jiang Chang and Danting Li
Coatings 2025, 15(2), 238; https://doi.org/10.3390/coatings15020238 - 17 Feb 2025
Viewed by 72
Abstract
In this study, chitooligosaccharides (COS) were introduced into black soybean protein (BSP) using transglutaminase (TG) as a biocatalyst. The film-processing properties and physiological activities of the enzymatically glycosylated black soybean protein (EGBSP) were studied. The results showed that glycosylation decreased the surface hydrophobicity, [...] Read more.
In this study, chitooligosaccharides (COS) were introduced into black soybean protein (BSP) using transglutaminase (TG) as a biocatalyst. The film-processing properties and physiological activities of the enzymatically glycosylated black soybean protein (EGBSP) were studied. The results showed that glycosylation decreased the surface hydrophobicity, absolute value of the zeta potential, its minimum solubility, and film permeability of BSP by 69.86%, 6.04%, 36.68%, and 14.91%, respectively, while increasing the tensile strength and elongation at break of its protein film by 56.57% and 172.68%, respectively. The gel time was shortened, and the acid-induced gel properties of EGBSP were similar to those of BSP. The anticancer effect of EGBSP was evaluated by the tumor inhibition rate, flow cytometry, and morphology observation of an ascites tumor in H22 tumor-bearing mice. The immune organs (spleen, thymus), immune cells (lymphocytes, NK cells), and immune factors (IL-2, IL-12) of H22 tumor-bearing mice were detected to evaluate the immunomodulatory effects of EGBSP. The results showed that medium and high doses of BSP had positive effects on immune enhancement and anti-cancer activity of H22 tumor-bearing mice, while almost all doses of EGBSP showed significant effects. These results indicated that glycosylation significantly improved the anti-cancer effect and immunomodulatory activity of H22 tumor-bearing mice while prolonging their overall survival. In conclusion, the glycosylation method using microbial transglutaminase to catalyze the introduction of chitooligosaccharides into black bean protein can improve the film-processing properties and biological activities of BSP more effectively than the enzyme crosslinking method. Full article
24 pages, 6650 KiB  
Article
Wire Arc Additive Manufacturing of Scalmalloy® (Al-Mg-Sc-Zr): Thermal Management Effects on Direct Age-Hardening Response
by Leandro João da Silva, Douglas Bezerra de Araújo, Ruham Pablo Reis, Frank Palm and Américo Scotti
Coatings 2025, 15(2), 237; https://doi.org/10.3390/coatings15020237 - 17 Feb 2025
Viewed by 26
Abstract
The thermal history of a part deposited via wire arc additive manufacturing (WAAM) and hence its as-built properties can vary significantly depending on the thermal management applied, especially for metallurgically complex materials. Thus, this work aimed to assess the feasibility of processing thin-walled [...] Read more.
The thermal history of a part deposited via wire arc additive manufacturing (WAAM) and hence its as-built properties can vary significantly depending on the thermal management applied, especially for metallurgically complex materials. Thus, this work aimed to assess the feasibility of processing thin-walled Scalmalloy® (Al-Mg-Sc-Zr) structures by WAAM while examining the effects of arc energy and heat dissipation on their response to direct age-hardening heat treatment (without solution annealing). As a complement, the geometry, porosity, and processing time of such parts were also analyzed. The walls were built via the cold metal transfer (CMT) deposition process with different arc energy levels in combination with near-immersion active cooling (NIAC) settings (as thermal management solution), as well as with natural cooling (NC), resulting overall in both low surface waviness and porosity levels. Based on hardness testing, the resultant Scalmalloy® direct-aging response (relative increase in hardness after direct age-hardening from WAAM as-built state) depended more on the arc energy per unit length of deposit applied. In contrast, the other thermal management approaches (NIAC or NC) helped in maintaining Sc in a supersaturated solid solution during deposition. Thus, Scalmalloy® strengthening was demonstrated as feasibly triggered by means of a post-WAAM direct age-hardening heat treatment solely. Additionally, in comparison with a thermally equivalent (same interpass temperature) condition based on NC, the NIAC technique allowed the achievement of such a positive result on direct-aging response with much shorter WAAM processing times, therefore improving productivity. Full article
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17 pages, 5383 KiB  
Article
An Experimental Study on Icing on Superhydrophobic Surfaces of Wind Turbine Blades in Offshore Environments
by Yaoyao Pei, Changwei Cai, Zhi Chen, Wentao Li, Henglin Xiao, Changjie Li and Kai Liu
Coatings 2025, 15(2), 236; https://doi.org/10.3390/coatings15020236 - 16 Feb 2025
Viewed by 177
Abstract
When wind turbines operate in high-latitude offshore regions, ice accumulation on blade surfaces can severely compromise the structural safety of turbines and reduce their power generation efficiency. To mitigate the adverse effects of ice accumulation on wind turbines, it is essential to evaluate [...] Read more.
When wind turbines operate in high-latitude offshore regions, ice accumulation on blade surfaces can severely compromise the structural safety of turbines and reduce their power generation efficiency. To mitigate the adverse effects of ice accumulation on wind turbines, it is essential to evaluate the effectiveness of various anti-icing measures in offshore environments. Superhydrophobic materials, known for their environmental friendliness, high efficiency, and energy-saving advantages, have been widely used for anti-icing in onshore wind power generation. However, their direct application to offshore wind turbines is limited due to the presence of salt in offshore environments. In this study, laboratory-scale experiments were conducted to investigate the anti-icing performance of superhydrophobic surfaces under winter atmospheric conditions simulating China’s Bohai Sea. The experiments were divided into two phases. In the first phase, the ice accretion process and morphology of superhydrophobic surfaces were analyzed under different operating conditions. The second phase expanded on the first by further examining the icing process of droplets on these surfaces. The results indicate that both the salt content and wind speed significantly affect the anti-icing performance of superhydrophobic surfaces. Additionally, the salt content influences the critical droplet diameter required for detachment. This research provides insights into icing mechanisms and supports the development of anti-icing technologies for offshore wind turbine blades with superhydrophobic surfaces. Full article
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25 pages, 8019 KiB  
Review
Chloride Corrosion Resistance of Steel Fiber-Reinforced Concrete and Its Application in Subsea Tunnel Linings
by Jiguo Liu, Longhai Wei, Qinglong Cui, Heng Shu, Wenbo Peng, Huimin Gong, Yiguo Xue and Min Han
Coatings 2025, 15(2), 235; https://doi.org/10.3390/coatings15020235 - 15 Feb 2025
Viewed by 369
Abstract
The composite performance of steel fiber-reinforced concrete (SFRC) is excellent, and its application potential in subsea tunnel engineering has gradually emerged. This paper discusses three types of laboratory testing methods for studying the corrosion of SFRC induced by chlorides: the ion diffusion method, [...] Read more.
The composite performance of steel fiber-reinforced concrete (SFRC) is excellent, and its application potential in subsea tunnel engineering has gradually emerged. This paper discusses three types of laboratory testing methods for studying the corrosion of SFRC induced by chlorides: the ion diffusion method, electric field migration method, and pre-corrosion method. The similar relationship between short-term accelerated deterioration tests and the natural corrosion process, as well as the experimental setup for simulating the coupling effect of multiple factors, requires further exploration. Furthermore, the mechanisms of steel fibers influencing the chloride corrosion resistance of SFRC are explored from four aspects: type, coating, shape, and dosage. Finally, by examining practical case studies of SFRC in subsea tunnel applications, the challenges posed by the multi-directionality of chloride ion corrosion, the diversity of corrosion sources, and the uneven distribution of steel fibers are highlighted. Future research should focus on enhancing the application of SFRC in subsea tunnel linings. This study provides a reference and basis for promoting the application of SFRC in subsea tunnel engineering and indicates future development directions. Full article
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21 pages, 4193 KiB  
Article
Experimental Study Regarding the Synthesis of Iron Oxide Nanoparticles by Laser Pyrolysis Using Ethanol as Sensitizer; Morpho-Structural Alterations Using Thermal Treatments on the Synthesized Nanoparticles
by Florian Dumitrache, Anca Criveanu, Iulia Lungu, Claudiu Fleaca, Lavinia Gavrila-Florescu, Iuliana Morjan, Ioan Stamatin, Adriana Balan, Vlad Socoliuc and Bogdan Vasile
Coatings 2025, 15(2), 234; https://doi.org/10.3390/coatings15020234 - 15 Feb 2025
Viewed by 170
Abstract
The laser pyrolysis technique was used in the synthesis of magnetic iron oxide nanopowders in the presence of ethanol vapors as a sensitizer. This technique uses the energy from a continuous-wave CO2 laser operating at a 9.25 μm wavelength, which is transferred [...] Read more.
The laser pyrolysis technique was used in the synthesis of magnetic iron oxide nanopowders in the presence of ethanol vapors as a sensitizer. This technique uses the energy from a continuous-wave CO2 laser operating at a 9.25 μm wavelength, which is transferred to the reactive precursors via the excited ethanol molecules, inducing a rapid heating of the argon-entrained Fe(CO)5 vapors in the presence of oxygen. For a parametric study, different samples were prepared by changing the percentages of sensitizer in the reactive mixture. Moreover, the raw samples were thermally treated at different temperatures and their morpho-structural and magnetic properties were investigated. The results indicated a high degree of crystallinity (mean ordered dimension) and enhanced magnetic properties when high percentages of ethanol vapors were employed. On the contrary, at low ethanol concentrations, due to a decrease in the reaction temperature, nanoparticles with a very low size were synthesized. The raw particles have a dimension in the range of 2.5 to 10 nm (XRD and TEM). Most of them exhibited superparamagnetic behavior at room temperature, with saturation magnetization values up to 60 emu/g. The crystalline phase detected in samples is mainly maghemite, with a decreased carbon presence (up to 8 at%). In addition to the expected Fe-OH on the particles surfaces, C (and O) bearing functional groups such as C-OH or C=O that act as a supplementary hydrophilic agent in water-based suspension were detected. Using the as-synthesized and thermally treated nanopowders, water suspensions without or with hydrophilic agents (CMCNa, L-Dopa, chitosan) were prepared by means of a horn ultrasonic homogenizer at 0.5 mg/mL concentrations. DLS analyzes revealed that some powder suspensions maintained stable agglomerates over time, with a mean size of 100 nm, pH values between 4.8 and 5.3, and zeta-potential values exceeding 40 mV. All tested agents greatly improved the stability of 250–450 °C thermally treated NPs, with L-Dopa and Chitosan inducing smaller hydrodynamic sizes. Full article
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27 pages, 12594 KiB  
Article
Chrome Doped Hydroxyapatite Enriched with Amoxicillin Layers for Biomedical Applications
by Carmen Steluta Ciobanu, Daniela Predoi, Simona Liliana Iconaru, Krzysztof Rokosz, Steinar Raaen, Catalin Constantin Negrila, Liliana Ghegoiu, Coralia Bleotu and Mihai Valentin Predoi
Coatings 2025, 15(2), 233; https://doi.org/10.3390/coatings15020233 - 15 Feb 2025
Viewed by 191
Abstract
In the last decade, it has been observed that the field of biomaterials has gained the attention of the researchers. This study presents the physicochemical and biological properties of coatings based on chromium-doped hydroxyapatite (CrHAp) and chromium-doped hydroxyapatite enriched with amoxicillin (CrHApAx). The [...] Read more.
In the last decade, it has been observed that the field of biomaterials has gained the attention of the researchers. This study presents the physicochemical and biological properties of coatings based on chromium-doped hydroxyapatite (CrHAp) and chromium-doped hydroxyapatite enriched with amoxicillin (CrHApAx). The coatings were obtained for the first time using the dip coating technique, beginning from dense suspensions of CrHAp and CrHApAx. The obtained layers were then analyzed by various methods in order to have a comprehensive overview of their physicochemical properties. Stability studies performed using ultrasound measurements showed that the CrHAp suspension has very good stability (S = 6.86·10−6 s−1) compared to double-distilled water. The CrHApAx suspension (S = 0.00025 s−1) shows good but weaker stability compared to that of the CrHAp suspension. Following XRD studies, a single hydroxyapatite-specific phase was observed in the CrHAp sample, while in the case of the CrHApAx sample, an amoxicillin-specific peak was also observed. The AFM results showed that the CrHAp coatings had a surface topography of a homogenous and uniform layer, with no significant cracks and fissures, while the CrHApAx coatings exhibited a surface morphology of homogenous layers formed of particles conglomerates. The biocompatibility of CrHAp and CrHApAx coatings was assessed using the MG63 cell line. The cytotoxicity of the coatings was evaluated by measuring cell viability with the aid of an MTT assay after 24, 48, and 72 h of incubation with the CrHAp and CrHApAx coatings. The results demonstrated that both CrHAp and CrHApAx coatings exhibited good biocompatibility for all the tested time intervals. The in vitro antibacterial activity of the coatings was also assessed against Pseudomonas aeruginosa 27853 ATCC (P. aeruginosa) bacterial cells. The potential of P. aeruginosa bacterial cells to adhere and develop on the surfaces of CrHAp and CrHApAx coatings was also investigated using AFM analysis. The findings of the biological assays suggest that CrHAp and CrHApAx coatings could be considered as promising candidates for biomedical applications, including the development of novel antimicrobial materials. Full article
(This article belongs to the Special Issue Advanced Biomaterials and Coatings)
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13 pages, 5021 KiB  
Article
The Effect of Surface Pretreatments on the Reliability of Glass Bonded Joints
by Nikol Bachurová, Jan Kudláček, Jiří Kuchař and Jaroslav Červený
Coatings 2025, 15(2), 232; https://doi.org/10.3390/coatings15020232 - 15 Feb 2025
Viewed by 203
Abstract
This paper focuses on the evaluation of the surface pretreatment of glass specimens and its effect on the strength of bonded joints. The experimental portion of this study includes the testing of three types of surface treatments (degreasing, blasting and etching) and the [...] Read more.
This paper focuses on the evaluation of the surface pretreatment of glass specimens and its effect on the strength of bonded joints. The experimental portion of this study includes the testing of three types of surface treatments (degreasing, blasting and etching) and the use of three types of adhesives (two-component epoxy, instant cyanoacrylate and two-component acrylate). Surface roughness measurements and bond strength testing using the pull-off test and shear tests were performed on the samples. The results showed that surface etching in conjunction with the Auratech AR 708 acrylic adhesive provided the highest bond strength. These findings contribute to the development of more reliable and stronger bonded joints for industrial applications. Scientific knowledge lies in determining the effect of appropriate glass surface treatment on adhesive adhesion under load with respect to joint aging due to environmental effects (UV, temperature, humidity) for transparent adhesives. This study provides an assessment of the effect of surface cleanliness on adhesion to glass. Full article
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14 pages, 3625 KiB  
Article
Insight into the Morphology, Hydrophobicity and Swelling Behavior of TiO2-Reinforced Polyurethane
by Ivan S. Stefanović, Jasna V. Džunuzović, Enis S. Džunuzović, Danijela V. Randjelović, Vladimir B. Pavlović, Andrea Basagni and Carla Marega
Coatings 2025, 15(2), 231; https://doi.org/10.3390/coatings15020231 - 14 Feb 2025
Viewed by 267
Abstract
In this research, the structure, morphology, hydrophobicity and swelling behavior of a polyurethane (PU) network and its composites (PUCs) were examined. PUCs were synthesized by the incorporation of different percentages (0.5, 1 and 2 wt.%) of unmodified or surface-modified TiO2 nanoparticles into [...] Read more.
In this research, the structure, morphology, hydrophobicity and swelling behavior of a polyurethane (PU) network and its composites (PUCs) were examined. PUCs were synthesized by the incorporation of different percentages (0.5, 1 and 2 wt.%) of unmodified or surface-modified TiO2 nanoparticles into a PU network based on polycaprolactone, aliphatic hyperbranched polyester and isophorone diisocyanate. In order to improve interfacial interactions, the surface of the TiO2 nanoparticles was chemically modified with lauryl gallate. The impact of the presence and content of unmodified or surface-modified TiO2 nanoparticles on the cross-sectional and surface morphology, swelling behavior and hydrophobicity of the PU network was assessed by different experiments. The obtained findings revealed that the incorporation of TiO2 nanoparticles brought a more pronounced irregular cross-sectional and rougher surface morphology, better microphase separation, higher values of the equilibrium swelling degree in tetrahydrofuran and toluene, and altered water contact angles compared to the neat PU. Based on the collected results, the practical applicability of the prepared PUCs may be in the area of protective coatings. Full article
(This article belongs to the Special Issue Recent Innovations in Polyurethane Coatings and Films)
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24 pages, 18456 KiB  
Article
Influence of Post-Printing Polymerization Time on Flexural Strength and Microhardness of 3D Printed Resin Composite
by Shaima Alharbi, Abdulrahman Alshabib, Hamad Algamaiah, Muath Aldosari and Abdullah Alayad
Coatings 2025, 15(2), 230; https://doi.org/10.3390/coatings15020230 - 14 Feb 2025
Viewed by 259
Abstract
Background: The adoption of 3D printing in restorative dentistry is increasing, with the post-curing duration of a material being identified as a key determinant of its performance. This study evaluated the effect of the post-polymerization time on the flexural strength (FS) and Vickers [...] Read more.
Background: The adoption of 3D printing in restorative dentistry is increasing, with the post-curing duration of a material being identified as a key determinant of its performance. This study evaluated the effect of the post-polymerization time on the flexural strength (FS) and Vickers microhardness (VHN) of a 3D-printed composite. Methods: Specimens of Formlabs Permanent Crown Resin were 3D printed and divided into four groups according to their post-curing time: no post-curing time and 20, 40, and 60 min post-curing time. Flexural strength testing was carried out using a three-point test of 40 bar-shaped specimens (n = 10/group), followed by fractography observations under a scanning electron microscope (SEM). Vicker microhardness testing was also conducted with 40 disk-shaped specimens (n = 10/group). The inorganic filler content was measured using the ash method, and the filler morphology was characterized under an SEM. Statistical analyses were performed using adjusted ANOVA and regression tests. Results: The highest median FS values were observed at 40 min post-curing (133.07 MPa), with significant differences across all groups (p < 0.0001). The highest median VHN values were found at 40 min post-curing (32.09 VHN), with significant differences between groups (p < 0.0001). A significant positive correlation (rho = 0.7488; p < 0.0001) was found between the flexural strength and Vickers hardness with changing post-curing durations. The 3D resin composite had an average filler content of 66.82% based on weight. Conclusions: With the limitation of the current in vitro setup, a post-polymerization time of 40 min was shown to lead to the best material performance. The post-printing polymerization time significantly affects the Vickers hardness and FS of 3D Formlabs Permanent Crown Resin. Further research should explore the effects of different resin compositions, clinical conditions, and curing protocols to enhance the general applicability of these findings. Clinical implications: Extending the post-printing polymerization time does not inherently result in improved material properties. A considered adjustment of the post-curing time can significantly impact the mechanical properties of a 3D-printed composite. Full article
(This article belongs to the Special Issue Advances in Polymer Composites, Coatings and Adhesive Materials)
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27 pages, 5214 KiB  
Review
Research Progress on Surface Modification of Titanium Implants
by Yifei Wu, Keming Wan, Jianhua Lu, Changyong Yuan, Yuwei Cui, Rongquan Duan and Jun Yu
Coatings 2025, 15(2), 229; https://doi.org/10.3390/coatings15020229 - 14 Feb 2025
Viewed by 282
Abstract
Implants made of titanium and its alloys are currently widely used in the human body. A series of surface modification methods developed nowadays enable titanium alloy implants to serve effectively in the human body for a long time. This paper reviews three different [...] Read more.
Implants made of titanium and its alloys are currently widely used in the human body. A series of surface modification methods developed nowadays enable titanium alloy implants to serve effectively in the human body for a long time. This paper reviews three different types of surface modification technologies for biomedical titanium alloys: physical, chemical, and biological, with particular attention to the assistance of these three technologies on the biological properties of titanium alloys. The physical method can change the surface morphology of titanium implants and prepare specific coatings for the implants, such as oxide films, bioactive molecules, drugs, etc. Chemical and biological surface modification technologies can minimize bacterial adhesion on the implant surface, improve the integration of soft tissue around the implant, prevent the occurrence of peri-implantitis, and accelerate the process of damage repair. An ideal titanium implant surface should balance the optimal surface morphology, chemical properties, and bionic characteristics to accelerate bone integration, enhance stability, and reduce peri-implant inflammation. Future research should focus on combining technologies, exploring interactions at the cellular and molecular levels, and conducting extensive in vitro and in vivo studies to verify the effectiveness and safety of modified surfaces. The progress in these fields will help overcome the existing limitations, improve the performance of implants, and obtain better clinical results. Full article
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19 pages, 4973 KiB  
Article
The Effect of Air Void on the Laboratory Properties of Polyurethane Mixtures
by Yunhao Zhou, Shijie Ma, Chenghua Gan, Wenjian Wang, Peihan Yu, Xiangzhuo Zheng, Peiyu Zhang, Bokai Liu and Haisheng Zhao
Coatings 2025, 15(2), 228; https://doi.org/10.3390/coatings15020228 - 14 Feb 2025
Viewed by 246
Abstract
Polyurethane (PU) materials, with their excellent mechanical properties, durability, and fatigue resistance, hold promise for addressing the challenges of aging, environmental pollution, and segregation during the storage of modified asphalt mixtures, thereby extending the lifespan of pavements and enhancing the level of service. [...] Read more.
Polyurethane (PU) materials, with their excellent mechanical properties, durability, and fatigue resistance, hold promise for addressing the challenges of aging, environmental pollution, and segregation during the storage of modified asphalt mixtures, thereby extending the lifespan of pavements and enhancing the level of service. Although studies have been conducted on the road performance of PU mixtures that compared them with asphalt mixtures, there is relatively less research on how the air void of PU mixtures affects their performance. This study systematically investigates the dynamic characteristics and road performance of dense-graded PU mixtures at three air void ranges—1%–3%, 3%–5%, and 5%–7%—and verifies the effectiveness through statistical methods. The research results show that air voids have a significant impact on road performance. Compared to low air voids, high air voids can increase high-temperature performance by 12%–33%. However, higher air voids also lead to a significant decrease in resistance to water damage, with a reduction of about 9%–24%. When the air void is in the range of 3%–5%, the mixture has better dynamic stability. Therefore, when designing PU mixtures, a reasonable air void should be selected based on engineering conditions to achieve the optimal pavement structure combination and save investment. This study provides a scientific basis for the design and application of PU mixtures and lays the foundation for further understanding of their performance mechanisms. Full article
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22 pages, 10125 KiB  
Article
Wear Study of Bulk Cargo Vehicle Body Materials Used to Transport Dolomite
by Vytenis Jankauskas, Audrius Žunda, Artūras Katinas and Simona Tučkutė
Coatings 2025, 15(2), 227; https://doi.org/10.3390/coatings15020227 - 14 Feb 2025
Viewed by 288
Abstract
Steel and aluminum alloys are used to manufacture the bodies of bulk material handling machines. The aluminum body enables a higher load mass and thus reduces transport costs. However, the greater abrasion of aluminum alloys leads to more frequent repairs to the underside [...] Read more.
Steel and aluminum alloys are used to manufacture the bodies of bulk material handling machines. The aluminum body enables a higher load mass and thus reduces transport costs. However, the greater abrasion of aluminum alloys leads to more frequent repairs to the underside of the body, as the abrasion parameters of aluminum are lower. This study, which used three different methods to evaluate abrasive wear (erosive/impact wear, abrasive wear in the mass of the free abrasive and abrasion test according to ASTM G65), showed that the most significant influence on the wear of 3004 series aluminum is the grain size of the abrasive. Only under erosive/impact wear conditions with abrasive particles of 2.0–5.0 and 5.0–8.0 mm is aluminum competitive with Hardox 450 in terms of volumetric wear, with aluminum exhibiting 1.3–1.4 times the wear rate of steel. Tests on the abrasive mass of the grinding fraction in question have shown that the volumetric wear of aluminum is 0.2–2.3 times higher at very low contact loads. In contrast, aluminum wears 7.5 and 4 times more than steel in the ASTM G65 test (0.1–0.4 mm fraction) at low and medium contact loads. Only in exceptional cases is the aluminum floor of bulk material handling equipment competitive with hardened steel in terms of wear intensity. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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11 pages, 2161 KiB  
Article
P-Doped Metal–Organic Framework (MOF)-Derived Co3O4 Nanowire Arrays Supported on Nickle Foam: An Efficient Urea Electro-Oxidation Catalyst
by Yong Liu, Junqing Ma, Yifei Pei, Xinyue Han, Xinyuan Ren, Yanfang Liang, Can Li, Tingting Liang, Fang Wang and Xianming Liu
Coatings 2025, 15(2), 226; https://doi.org/10.3390/coatings15020226 - 14 Feb 2025
Viewed by 225
Abstract
The urea electro-oxidation reaction (UOR) is emerging as a new energy conversion technology and a promising method for alleviating water eutrophication problems. However, a rationally designed structure of the electrode materials is urgently required to achieve high UOR performance. Herein, P-doped MOF-derived Co [...] Read more.
The urea electro-oxidation reaction (UOR) is emerging as a new energy conversion technology and a promising method for alleviating water eutrophication problems. However, a rationally designed structure of the electrode materials is urgently required to achieve high UOR performance. Herein, P-doped MOF-derived Co3O4 nanowire arrays grown on nickel foam (P-Co3O4/NF) are successfully synthesized via the growth of Co-MOF and subsequent calcination followed by phosphorization treatment. Owing to the optimized electronic structure, the as-prepared P-Co3O4/NF composite exhibits much higher UOR electrocatalytic performance than the undoped Co3O4/NF sample. Beyond this, the meticulous structure of the one-dimensional nanowire arrays and the three-dimensional skeleton structure of nickel foam contribute to the enhanced electrocatalytic activity and stability toward UOR. As a result, the P-Co3O4/NF composite displays a low overpotential of 1.419 V vs. RHE at 50 mA cm−2, a small Tafel slope of 82 mV dec−1, as well as favorable long-term stability over 65,000 s in 1.0 M KOH with 1.0 M urea. This work opens a new avenue in designing non-precious electrocatalysts for high-performance urea electro-oxidation reactions. Full article
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15 pages, 5437 KiB  
Article
Deposition and Characterization of Zinc–Tin Oxide Thin Films with Varying Material Compositions
by Stanka Spasova, Vladimir Dulev, Alexander Benkovsky, Vassil Palankovski, Ekaterina Radeva, Rumen Stoykov, Zoya Nenova, Hristosko Dikov, Atanas Katerski, Olga Volobujeva, Daniela Lilova and Maxim Ganchev
Coatings 2025, 15(2), 225; https://doi.org/10.3390/coatings15020225 - 13 Feb 2025
Viewed by 299
Abstract
Zinc–tin oxide (ZTO) thin films (ZnO)x(SnO2)1−x with different material composition x (0 < x < 1) are deposited by spin coating on glass substrates at room temperature. The Differential Scanning Calorimetry (DSC) data of the precursor compounds show [...] Read more.
Zinc–tin oxide (ZTO) thin films (ZnO)x(SnO2)1−x with different material composition x (0 < x < 1) are deposited by spin coating on glass substrates at room temperature. The Differential Scanning Calorimetry (DSC) data of the precursor compounds show gradual phase transitions up to 480 °C. These data are used for an appropriate regime for thermal annealing of the layers. X-ray photoelectron spectroscopy (XPS) data show mixed oxide compound formation in states Zn2+, Sn4+ and O2− of the constituents. Optical investigation manifests high transmittance above 80% in the visible spectral range and an optical band gap of 3.3–3.7 eV. The work functions vary between 4.1 eV and 5 eV, depending on the annealing, with deviations less than 1% for surface 1 mm2 scans. Stack devices ITO/ZTO/metal with different metal contacts are formed. The I–V (current–voltage) measurements of the fabricated stacks exhibit Ohmic or nonlinear behavior, depending on the material composition and the work function levels. Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology, 2nd Edition)
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14 pages, 3565 KiB  
Article
Microstructure and Properties of Ti-5Al-2.5Sn Alloy with Higher Carbon Content
by Agnieszka Szkliniarz and Wojciech Szkliniarz
Coatings 2025, 15(2), 224; https://doi.org/10.3390/coatings15020224 - 13 Feb 2025
Viewed by 288
Abstract
This study investigates the characteristics of the Ti-5Al-2.5Sn-0.2C alloy, an alpha titanium alloy containing approximately 0.2 wt% carbon—a concentration significantly exceeding the standard allowable limit of 0.08 wt%. The Ti-5Al-2.5Sn-0.2C alloy was melted in a vacuum induction furnace with a cold copper crucible, [...] Read more.
This study investigates the characteristics of the Ti-5Al-2.5Sn-0.2C alloy, an alpha titanium alloy containing approximately 0.2 wt% carbon—a concentration significantly exceeding the standard allowable limit of 0.08 wt%. The Ti-5Al-2.5Sn-0.2C alloy was melted in a vacuum induction furnace with a cold copper crucible, processed into bar form through hot rolling, and subsequently annealed under standard conditions. The microstructure and mechanical properties of the Ti-5Al-2.5Sn-0.2C alloy were systematically compared with those of the Ti-5Al-2.5Sn alloy (Grade 6), which possesses a similar chemical composition. The results revealed that the addition of 0.2 wt% carbon significantly influences the alloy’s solidification process, phase transformation temperatures, phase composition, and phase lattice parameters. Moreover, the carbon addition enhances key mechanical properties, including tensile strength, yield strength, hardness, and wear resistance, as well as creep and oxidation resistance. While a slight reduction in plasticity and increase in impact energy were observed, the alloy remained within the permissible range defined by existing standards. Full article
(This article belongs to the Special Issue Advanced Light Metals: Microstructure, Properties, and Applications)
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18 pages, 7701 KiB  
Article
Shear Failure Analysis of 3D Seven-Directional Braided Composites
by Bingnan Dang, Ju Tang, Yan Shang and Deng’an Cai
Coatings 2025, 15(2), 223; https://doi.org/10.3390/coatings15020223 - 13 Feb 2025
Viewed by 252
Abstract
According to the “four-step” braiding technique, this paper analyzed the movement laws of internal space yarns in the projection plane and in space, and established a 3D seven-direction braided composite material solid finite element model by combining the observed yarn directions on the [...] Read more.
According to the “four-step” braiding technique, this paper analyzed the movement laws of internal space yarns in the projection plane and in space, and established a 3D seven-direction braided composite material solid finite element model by combining the observed yarn directions on the surface and side of the preform. Based on the 3D Hashin criterion, a progressive damage failure analysis method was adopted to study the shear failure mechanism of 3D seven-direction braided composites. The effect of braided angles on the elastic properties and crack propagation path of the fabric was discussed. The failure modes and mechanisms of 3D seven-directional braided composites were also observed and analyzed by electron microscope and scanning electron microscope. The results show that the shear failure mode is mainly caused by matrix failure, interface damage, and fiber fracture and pull-out. The fiber cross-sections at the shear fracture surface are at a certain angle, indicating that the fibers are subjected to both transverse and axial stresses during the shear process. It also can be seen that the initial damage occurs at the interface between the matrix and the fiber bundle. As the crack propagates, tensile damage occurs inside the fiber bundle, forming cracks and eventually leading to the failure of the entire structure. The accuracy of proposed method for predicting 3D seven-directional braided composites was verified by the shear experimental results. Full article
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22 pages, 2243 KiB  
Article
Thermal Friction Contact Analysis of Graded Piezoelectric Coatings Under Conductive Punch Loading
by Xinyu Zhou, Jing Liu and Jiajia Mao
Coatings 2025, 15(2), 222; https://doi.org/10.3390/coatings15020222 - 13 Feb 2025
Viewed by 301
Abstract
In this paper, we investigate the thermal friction sliding contact of a functionally graded piezoelectric material (FGPM)-coated half-plane subjected to a rigid conductive cylindrical punch. This study considers the effect of the thermal convection term in heat conduction. The thermo-electro-elastic material parameters of [...] Read more.
In this paper, we investigate the thermal friction sliding contact of a functionally graded piezoelectric material (FGPM)-coated half-plane subjected to a rigid conductive cylindrical punch. This study considers the effect of the thermal convection term in heat conduction. The thermo-electro-elastic material parameters of the coating vary exponentially along its thickness direction. Utilizing thermoelastic theory and Fourier integral transforms, the problem is formulated into Cauchy singular integral equations of the first and second kinds with surface stress, contact width, and electric displacement as the unknown variables. The numerical solutions for the contact stress, electric displacement, and temperature field of the graded coating surface are obtained using the least-squares method and iterative techniques. It can be observed that the thermo-electro-elastic contact behavior of the coating surface undergoes significant changes as the graded index varies from −0.5 to 0.5, the friction coefficient ranges from 0.1 to 0.5, and the sliding velocity changes from 0.01 m/s to 0.05 m/s. The results indicate that adjusting the graded index of the coating, the sliding speed of the punch, and the friction coefficient can improve the thermo-electro-elastic contact damage of the material’s surface. Full article
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13 pages, 12364 KiB  
Article
Constructing Micro-/Nano-Aramid Pulp (MAP)–Epoxy Coatings on Laser-Engraved Titanium Alloy Surfaces for Stronger Adhesive Bonding with Carbon Fiber-Reinforced Polymer Panel
by Haibo Zhu, Fei Cheng, Shihao Zuo, Jinheng Zhang, Wenyi Huang, Tangrui Fan and Xiaozhi Hu
Coatings 2025, 15(2), 221; https://doi.org/10.3390/coatings15020221 - 13 Feb 2025
Viewed by 385
Abstract
A shape-controllable laser-engraving treatment (LET) and aramid pulp (AP)-reinforced resin pre-coating (RPC) were used on a titanium (Ti) alloy surface to construct micro-/nano-aramid pulp and epoxy (MAPE) coatings for greater bonding strength with carbon fiber-reinforced polymers (CFRPs). The array pits of regular hexagon [...] Read more.
A shape-controllable laser-engraving treatment (LET) and aramid pulp (AP)-reinforced resin pre-coating (RPC) were used on a titanium (Ti) alloy surface to construct micro-/nano-aramid pulp and epoxy (MAPE) coatings for greater bonding strength with carbon fiber-reinforced polymers (CFRPs). The array pits of regular hexagon on the Ti alloy surface were engraved and vertical spaces between the array pits were created to place the AP-reinforced epoxy for stronger mechanical interlocking. The specimen treated with laser engraving (side length of 0.3 mm) and AP-reinforced RPC yielded the greatest bonding strength of 27.1 MPa, 67.4% higher than the base strength. The failure modes of the Ti-CFRPs composites changed from debonding failure at the Ti/epoxy surface to fiber-damaged failure of the laminated CFRPs panels. The shape-controllable LET and simple AP-reinforced RPC were confirmed as the most feasible and effective combined methods for use on titanium alloy surfaces for manufacturing stronger Ti-CFRPs composites, which exhibited the potential for application in other metal–matrix-bonding composite systems. Full article
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9 pages, 2573 KiB  
Article
Influence of Laser Remelting on Creep Resistance in Ti-6Al-4V Alloy with Thermal Barrier Coating
by Filipe Estevão de Freitas, Roberta Aguiar Luna da Silva, Renata Jesuina Takahashi, Adriano Gonçalves dos Reis, Aline Gonçalves Capella and Danieli Aparecida Pereira Reis
Coatings 2025, 15(2), 220; https://doi.org/10.3390/coatings15020220 - 12 Feb 2025
Viewed by 307
Abstract
Ti-6Al-4V alloys with a thermal barrier coating (TBC) have been applied in aeronautical components as turbine blades to provide oxidation resistance and thermal protection, enabling higher operating temperatures and extending component lifespan. Research into TBCs with laser surface modification has investigated improving their [...] Read more.
Ti-6Al-4V alloys with a thermal barrier coating (TBC) have been applied in aeronautical components as turbine blades to provide oxidation resistance and thermal protection, enabling higher operating temperatures and extending component lifespan. Research into TBCs with laser surface modification has investigated improving their mechanical and thermal properties. This study assessed the creep behavior of Ti-6Al-4V alloy with a TBC, where the coating was applied via CO2 laser-remelted plasma spraying. Creep tests were conducted at a constant temperature and a load ranging from 500 to 700 °C at 125 MPa. The microstructure and fractography of the specimens were also investigated. The investigation also included microstructural and fractographic analyses of the specimens. The results indicate that the laser-remelted TBC provided effective thermal protection and increased oxidation resistance, with the stationary creep rate at 600 °C reduced by 50% and the creep rupture life extended by 20%. Observations revealed typical ductile fractures characterized by equiaxed dimples and a homogeneous microstructure with an equiaxed dual-phase (α+β) structure near the fracture zone. Full article
(This article belongs to the Special Issue Laser-Assisted Processes and Thermal Treatments of Materials)
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2 pages, 118 KiB  
Editorial
Coatings for Advanced Devices
by Xu Long
Coatings 2025, 15(2), 219; https://doi.org/10.3390/coatings15020219 - 12 Feb 2025
Viewed by 281
Abstract
The continuous evolution of coating materials is critically important to driving innovative technologies in various domains, especially advanced electrical devices [...] Full article
(This article belongs to the Special Issue Coatings for Advanced Devices)
21 pages, 9502 KiB  
Article
Environmental Impact of Physical Vapour Deposition and Plasma-Enhanced Chemical Vapour Deposition Technologies for Deposition of Diamond-Like Carbon Coatings for Green Tribology
by Larissa Ihara, Guizhi Wu, Albano Cavaleiro, Ardian Morina and Liuquan Yang
Coatings 2025, 15(2), 218; https://doi.org/10.3390/coatings15020218 - 12 Feb 2025
Viewed by 583
Abstract
With low friction and high hardness, diamond-like carbon (DLC) coatings are a prominent surface engineering solution for tribosystems in various applications. Their versatility stems from their varying composition, facilitated by different deposition techniques, which affect their properties. However, environmental impact is often overlooked [...] Read more.
With low friction and high hardness, diamond-like carbon (DLC) coatings are a prominent surface engineering solution for tribosystems in various applications. Their versatility stems from their varying composition, facilitated by different deposition techniques, which affect their properties. However, environmental impact is often overlooked in coating design. The objective of this paper is to assess the resource efficiency of four different common deposition techniques, thus identifying critical factors for sustainable DLC deposition. The coatings were deposited in one single chamber, enabling a direct comparison of the resource consumption of each technology. Expenditure of electric energy and consumables per volumetric output accounted for the environmental impact of manufacturing the coatings, which was evaluated across the indicators of damage to human health, damage to ecosystems, and resource scarcity. Electric energy use, dictated by deposition rate, was demonstrated to be the most significant factor contributing to the environmental impact. The environmental impact of PECVD and μW-PECVD was comparable and remarkably lower than that of dcMS and HiPIMS, the latter being the least energy efficient process, with the lowest output rate but highest energy expenditure. Thus, μW-PECVD could be considered the ‘greenest’ production method. These findings are consequential for coaters to efficiently produce good-quality DLCs with low environmental impact. Full article
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12 pages, 2317 KiB  
Article
Residual Stress Model in Laser Direct Deposition Based on Energy Equation
by Manping Cheng, Xi Zou, Muhong Gong, Tengfei Chang, Qi Cao and Houlai Ju
Coatings 2025, 15(2), 217; https://doi.org/10.3390/coatings15020217 - 12 Feb 2025
Viewed by 380
Abstract
In this paper, 316 L stainless steel deposited samples were fabricated by direct layer deposition (DED) using both continuous-wave (CW) and pulsed-wave (PW) laser modes. Effects of laser modes on residual stress of deposited samples were investigated. On this basis, a mathematical model [...] Read more.
In this paper, 316 L stainless steel deposited samples were fabricated by direct layer deposition (DED) using both continuous-wave (CW) and pulsed-wave (PW) laser modes. Effects of laser modes on residual stress of deposited samples were investigated. On this basis, a mathematical model of thermal stress evolution during DED was established for the first time based on the energy equation. The variation law of thermal stress on the top of the substrate under multi-material and multi-process conditions was qualitatively predicted and the corresponding residual stress reduction mechanism has been studied using this model. Meanwhile, in situ thermal strain evolution is used to prove the correctness of the mathematical model. This model lays the foundation for predicting the thermal stress evolution and the magnitude of the residual stress of deposited samples under multi-material and process conditions during DED. Full article
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19 pages, 6409 KiB  
Article
Material Textile Design as a Trigger for Transdisciplinary Collaboration: Coating Bio-Based Textiles Using Waste from the Wood Industry
by Jimena Alarcón Castro, Riccardo Balbo, Carla Joana Silva, Catalina Fuenzalida Fernández and Florencia Alarcón Carrasco
Coatings 2025, 15(2), 216; https://doi.org/10.3390/coatings15020216 - 11 Feb 2025
Viewed by 455
Abstract
Waste production is a worldwide concern due to its adverse impact on the environment, as well as on the health of living beings. Sustainable development states the urgent need to implement actions to gradually replace fossil resources, including the use of renewable raw [...] Read more.
Waste production is a worldwide concern due to its adverse impact on the environment, as well as on the health of living beings. Sustainable development states the urgent need to implement actions to gradually replace fossil resources, including the use of renewable raw materials such as residues and secondary raw materials from other industries as a promising alternative to replace fossil resources. This research explores an approach focused on the design of renewable materials by developing a bio-based textile coating with the use of sawdust from radiata pine, which is the result of industrial wood transformation processes. The methodology adopted a transdisciplinary approach, integrating knowledge from design, engineering, and sociology disciplines. A perceived sawdust quality study was carried out in its original format, while two different coated textile substrates were developed, using knife-over-roller and spray coating processes, which were evaluated from user acceptance and functional performance points of views. Finally, a clothing prototype for workwear, using the bio-based coatings, was developed, employing a mono-material design concept (i.e., using the same material in all its forms). The results obtained from users and laboratory studies favour the knife-over-roller coating and the removable clothing design, which provides improved usability performance. The obtained conclusions highlight that transdisciplinary collaboration is essential to address complex challenges in the development of solutions, placing the design of material as a necessary prior action in the design process of final products. Full article
(This article belongs to the Special Issue Advances in Coated Fabrics and Textiles)
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24 pages, 7771 KiB  
Article
In-Flight Particle Oxidation Evolution in HVAF: A Numerical Study
by Sokhna Awa Bousso Diop, Aleksandra Nastic, Ali Dolatabadi, Reza Attarzadeh and Christian Moreau
Coatings 2025, 15(2), 215; https://doi.org/10.3390/coatings15020215 - 11 Feb 2025
Viewed by 380
Abstract
Oxygen present in the High Velocity Air-Fuel (HVAF) process can react with the in-flight metallic particles and cause their oxidation. A grown brittle oxide shell on metallic micro-size particles can reduce their deposition efficiency and impair the coating’s final deposited properties/microstructure. In the [...] Read more.
Oxygen present in the High Velocity Air-Fuel (HVAF) process can react with the in-flight metallic particles and cause their oxidation. A grown brittle oxide shell on metallic micro-size particles can reduce their deposition efficiency and impair the coating’s final deposited properties/microstructure. In the current study, the oxide growth of MCrAlY particles, where M stands for Nickel (Ni) and Cobalt (Co), during their flight in the HVAF process has been numerically modeled and validated with experimental single-particle depositions. A thorough theoretical oxide layer growth background is also presented. The utilized oxidation development follows the Mott–Cabrera theory for very thin films, which uses the particle surrounding temperature and oxygen partial pressure to track and describe the oxide growth. The obtained results provide a good correlation between the HVAF system design, the operating conditions, and surface oxidation phenomena observed using focus ion beam scanning electron microscope (FIB/SEM) analysis on collected particles. Furthermore, the particle’s degree of oxidation in HVAF is compared to High Velocity Oxy-Fuel (HVOF) to demonstrate the influence of combustion processes on oxidation level. Full article
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14 pages, 2831 KiB  
Article
Upscaled Multilayer Dispersion Coating Application for Barrier Packaging: PLAX and bioORMOCER®
by Eetu Nissinen, Adina Anghelescu-Hakala, Roosa Hämäläinen, Pauliina Kivinen, Ferdinand Somorowsky, Jani Avellan and Rajesh Koppolu
Coatings 2025, 15(2), 214; https://doi.org/10.3390/coatings15020214 - 11 Feb 2025
Viewed by 418
Abstract
The shift from fossil-based packaging materials to more sustainable alternatives is driven by evolving environmental regulations aiming for enhanced recyclability and biodegradability. Dispersion coatings, as opposed to extrusion-based approaches, offer significant advantages by reducing the coat weights, but generally, multiple coating layers are [...] Read more.
The shift from fossil-based packaging materials to more sustainable alternatives is driven by evolving environmental regulations aiming for enhanced recyclability and biodegradability. Dispersion coatings, as opposed to extrusion-based approaches, offer significant advantages by reducing the coat weights, but generally, multiple coating layers are needed to meet functional performance requirements. This study explores the application of upscaled multilayer dispersion coatings comprising polylactic acid-based coating (PLAX) and hybrid nanomaterial lacquer (bioORMOCER®) on commercial base papers for barrier packaging using semi-pilot reverse gravure and industrial-scale rod coaters. One multilayer structure demonstrated a low water vapour transmission rate (WVTR), achieving a WVTR of 12 g/(m2·day) under standard conditions and a 78% reduction of WVTR compared to the substrate under elevated humidity. The other multilayer structure exhibited an excellent oxygen transmission rate (OTR) of 2.3 cc/(m2·day·bar) at dry conditions, which is comparable to conventional high-performance alternatives. Both multilayer coatings enhanced the grease and mineral oil barriers significantly, as heptane vapour transmission rate (HVTR) reductions exceeded 97%. The multilayer coatings demonstrated strong potential for scalable production of sustainable, high-barrier packaging materials. These findings highlight the capability of dispersion coatings to replace traditional fossil-based barriers, advancing the development of environmentally friendly packaging solutions. Full article
(This article belongs to the Special Issue Sustainable Coatings for Functional Textile and Packaging Materials)
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1 pages, 129 KiB  
Retraction
RETRACTED: Yang et al. Influence of DETA on Thermal and Corrosion Protection Properties of GPTMS-TEOS Hybrid Coatings on Q215 Steel. Coatings 2023, 13, 1145
by Shuanqiang Yang, Zhenzhen Jia, Jinjia Xu and Ruoyu Hong
Coatings 2025, 15(2), 213; https://doi.org/10.3390/coatings15020213 - 11 Feb 2025
Viewed by 220
Abstract
The journal retracts the article titled “Influence of DETA on Thermal and Corrosion Protection Properties of GPTMS-TEOS Hybrid Coatings on Q215 Steel” [...] Full article
21 pages, 5030 KiB  
Article
Effect of Annealing Temperature on Residual Stress and Microstructure of Ni60A Laser Cladding Repaired Gear
by Xin Zhao, Wenlei Sun, Jingqi Huang, Yuzhu Wu, Yuer Lu and Shuai Wang
Coatings 2025, 15(2), 212; https://doi.org/10.3390/coatings15020212 - 10 Feb 2025
Viewed by 432
Abstract
Laser cladding faces several challenges, including cracking, fracture, deformation, and interlayer delamination, which hinder its widespread application in part repair. Residual stress within the workpiece is a key factor contributing to these issues. To enhance the quality of laser cladding gear tooth repairs, [...] Read more.
Laser cladding faces several challenges, including cracking, fracture, deformation, and interlayer delamination, which hinder its widespread application in part repair. Residual stress within the workpiece is a key factor contributing to these issues. To enhance the quality of laser cladding gear tooth repairs, the study integrates numerical modeling and experimental approaches to examine how varying annealing temperatures influence the residual stress and microstructural changes in Ni60A cladding layers. A theoretical model was established to simulate the laser cladding process and the subsequent annealing treatment utilized in gear repairs. The model was used to study the variations in temperature and stress fields at different annealing temperatures, analyze the effect of temperature gradient on residual stress, and examine the distribution of residual stress. Cladding experiments were then performed under various annealing conditions, with hardness and residual stress measurements taken from the fifth cladding layer. The results demonstrated that residual stress in the samples significantly decreased after annealing, from 781.63 MPa (RT) to 572.24 MPa (400 °C), 494.42 MPa (600 °C), and 393.83 MPa (800 °C). This indicates that the annealing process effectively reduces the residual stress in the workpiece. The residual stress values obtained from experiments showed a deviation of less than 7% from the simulation results, confirming the accuracy of the model. The highest average microhardness of 764.39 HV0.5 was observed at 600 °C. Microstructural analysis of the cladding layer revealed significant grain refinement after annealing, with previously aggregated phases transforming into a uniformly dispersed structure. Energy Dispersive Spectroscopy (EDS) analysis confirmed the presence of boron (B) in the annealed samples, which contributes to grain refinement and enhances the annealing effect. Full article
(This article belongs to the Section Laser Coatings)
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2 pages, 164 KiB  
Comment
Comment on Rooman et al. Entropy Optimization on Axisymmetric Darcy–Forchheimer Powell–Eyring Nanofluid over a Horizontally Stretching Cylinder with Viscous Dissipation Effect. Coatings 2022, 12, 749
by Asterios Pantokratoras
Coatings 2025, 15(2), 211; https://doi.org/10.3390/coatings15020211 - 10 Feb 2025
Viewed by 235
Abstract
The concentration shown in Equation (4) in [1] is given as follows:(1)wCr+uCz=DB2Cr2+1rCr+DTT2Tr2+1rTr [...] Full article
11 pages, 4230 KiB  
Article
Achieving Transparency and Minimizing Losses of Rough Additively Manufactured Optical Components by a Dip-Coating Surface Finish
by Abhijeet Shrotri, Sascha Preu and Oliver Stübbe
Coatings 2025, 15(2), 210; https://doi.org/10.3390/coatings15020210 - 10 Feb 2025
Viewed by 445
Abstract
Additive manufacturing of optical, electrical, and mechanical components is a beneficial approach for the rapid prototyping of components and error elimination, with short turnaround times. However, additively manufactured components usually have rough surfaces that need post-processing, particularly for optical components, where the surface [...] Read more.
Additive manufacturing of optical, electrical, and mechanical components is a beneficial approach for the rapid prototyping of components and error elimination, with short turnaround times. However, additively manufactured components usually have rough surfaces that need post-processing, particularly for optical components, where the surface roughness must be a small fraction of the wavelength. We demonstrate an innovative and economical approach by dip-coating with the same resin used for printing in a simple post-processing step, providing high transparency to the 3D-printed optical components and reducing surface roughness while achieving perfect index matching of the coating layer. The surface roughness of the 3D-printed optical components drops to 5 nm (arithmetic average) after the dip-coating process. We observed significant performance enhancements after comparing the unprocessed optical components and the dip-coated optical components, including optical transparency and a shiny surface finish for previously rough surfaces. Full article
(This article belongs to the Topic Surface Engineering and Micro Additive Manufacturing)
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