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Coatings, Volume 14, Issue 5 (May 2024) – 132 articles

Cover Story (view full-size image): Epoxy resin was conjugated with halloysite nanotubes (HNTs) and different types of ZnO nanoparticles (commercial ZnO and modified ZnO-ODTES) to obtain HNT-ZnO/epoxy resin composites. These ZnO nanoparticles were utilized with the intention to enhance the interfacial bonding between the epoxy resin and the reinforcing agent (HNT). The properties of resulted epoxy resin composites were characterized by various methods. The thermal properties of the composite materials were enhanced by the addition of HNT-ZnO nanofillers. It was observed that the epoxy resin modified with HNT and ZnO-ODTES has the highest resistance to scratching by demonstrating good elastic recovery as well as high values for surface hardness and reduced modulus. These findings can pave the way for the development of ZnO-based marine coatings with improved properties. View this paper
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14 pages, 5459 KiB  
Article
Effects of ZrW2O8 Content on the Microstructures and Properties of Composite Coatings Produced by Laser Cladding
by Pengxian Zhang, Chang Liu and Yibin Pang
Coatings 2024, 14(5), 649; https://doi.org/10.3390/coatings14050649 - 20 May 2024
Viewed by 190
Abstract
Addressing the issue of cracking in laser-cladding Ni-based composite coatings with WC particles, this study explored an approach to fabricating a crack-free coating by incorporating ZrW2O8 powder. The influence of varying ZrW2O8 contents on the crack susceptibility, [...] Read more.
Addressing the issue of cracking in laser-cladding Ni-based composite coatings with WC particles, this study explored an approach to fabricating a crack-free coating by incorporating ZrW2O8 powder. The influence of varying ZrW2O8 contents on the crack susceptibility, microstructure, microhardness, wear resistance, and corrosion resistance of Ni60/WC composite coatings was systematically examined. The findings indicate that the ZrW2O8 content significantly impacts the microstructure and functional properties of the coating. Furthermore, it is suggested that the main contributors to preventing crack formation and diffusion are believed to be the pressure interaction caused by the negative expansion effect of ZrW2O8, as well as the in situ phase transition and diffusion toughening of ZrO2 during its decomposition process. The feasibility of achieving crack selfhealing through the addition of specific amounts of ZrW2O8 powder has been conclusively demonstrated. Full article
16 pages, 3266 KiB  
Article
Wear Resistance Behavior of Low-, Mid-, and High-Phosphorus Electroless Ni-P Coatings Heat-Treated in the Air Environment
by Dhani Ram Dhakal, Young Uk Han, Byung Geon Lee, Tae Ho Kim, Gi Bum Jang and Sung Youl Cho
Coatings 2024, 14(5), 648; https://doi.org/10.3390/coatings14050648 - 20 May 2024
Viewed by 269
Abstract
The high-temperature heat treatment of electroless nickel–phosphorus (Ni-P) coatings in an air environment, and its consequences have scarcely been investigated. This work investigated tribological characteristics of the high-temperature, heat-treated, electroless Ni-P coatings on steel substrates with low-, mid-, and high-phosphorus content for which [...] Read more.
The high-temperature heat treatment of electroless nickel–phosphorus (Ni-P) coatings in an air environment, and its consequences have scarcely been investigated. This work investigated tribological characteristics of the high-temperature, heat-treated, electroless Ni-P coatings on steel substrates with low-, mid-, and high-phosphorus content for which the average phosphorus content was 2.4 wt.%, 7.1 wt.%, and 10.3 wt.%, respectively. X-ray fluorescence and energy dispersive spectroscopy were implemented to determine the phosphorus content of the coatings. The oxidation of Ni and the formation of the NiO layer on the coating surface was confirmed by the X-ray diffraction technique. A reciprocating sliding method on a ball-on-flat system was utilized to evaluate the coating’s friction and wear behavior. Among the coatings with varying phosphorus content, a high hardness of 1086 HV was found for high-phosphorus coating when heat-treated at 400 °C in an air environment, and that was decreased to 691 HV when heat-treated at 650 °C. The oxidation of nickel in the electroless Ni-P coating occurred when heat-treated at 400 °C in an air environment, and this phenomenon was increased more when the temperature was increased to 650 °C. The characteristics of the NiO layer that formed on the surface of the heat-treated electroless Ni-P coating were influenced by the concentration of phosphorus, which caused different colors of NiO to be seen on the Ni-P coating surface. A greenish black NiO layer on the low-phosphorus and black NiO layer on the mid- and high-phosphorus Ni-P coating was developed during heat treatment at 650 °C in an air atmosphere. The adhesion and tribological characteristics of the Ni-P coatings were affected by the NiO layer developed on the heat-treated Ni-P coating surfaces. The Ni-P coatings with mid- and high-phosphorus content showed enhanced wear-resistance characteristics when they underwent heat treatment in an air atmosphere at the high temperature of 650 °C. The wear volume obtained for as-plated mid-phosphorus and high-phosphorus Ni-P coatings was 0.111 mm3 and 0.128 mm3, respectively, and that was reduced to 0.031 mm3 and 0.051 mm3, respectively, after the high-temperature heat treatment. Full article
(This article belongs to the Special Issue Advanced Wear-Resistant Materials and Coatings)
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17 pages, 2699 KiB  
Article
Terahertz Nondestructive Measurement of Heat Radiation Performance of Thermal Barrier Coatings Based on Hybrid Artificial Neural Network
by Zhou Xu, Changdong Yin, Yiwen Wu, Houli Liu, Haiting Zhou, Shuheng Xu, Jianfei Xu and Dongdong Ye
Coatings 2024, 14(5), 647; https://doi.org/10.3390/coatings14050647 - 20 May 2024
Viewed by 266
Abstract
Effective control of the micro- and nanostructure of thermal barrier coatings is essential to enhance the thermal radiation performance of the coating, which helps to determine the remaining service life of the coating. This paper proposed a method to measure the radiation properties [...] Read more.
Effective control of the micro- and nanostructure of thermal barrier coatings is essential to enhance the thermal radiation performance of the coating, which helps to determine the remaining service life of the coating. This paper proposed a method to measure the radiation properties of thermal barrier coatings by terahertz nondestructive testing technique, using APS-prepared thermal barrier coatings as the object of study. Radiative properties were a comprehensive set of properties characterized by the diffuse reflectance, transmittance, and absorptance of the thermal barrier coating. The coating data in actual service were obtained by scanning electron microscopy and metallographic experiments, and the data were used as the simulation model critical value. The terahertz time-domain simulation data of coatings with different microstructural features were obtained using the finite-different time-domain (FDTD) method. In simulating the real test signals, white noise with a signal-to-noise ratio of 20 dB was added, and fast Fourier transform (FFT), short-time Fourier transform (STFT), and wavelet transform (WT) were used to reduce the noise and compare their noise reduction effects. Different machine learning methods were used to build the model, including support vector machine algorithm (SVM) and k-nearest neighbor algorithm (KNN). The principal component algorithm (PCA) was used to reduce the dimensionality of terahertz time-domain data, and the SVM algorithm and KNN algorithm were optimized using the particle swarm optimization algorithm (PSO) and the ant colony optimization algorithm (ACO), respectively, to improve the robustness of the system. The K-fold cross-validation method was used to construct the model to improve the adaptability of the model. It could be clearly seen that the novel hybrid PCA-ACO-SVM model had superior prediction performance. Finally, this work proposed a novel, convenient, nondestructive, online, safe and highly accurate method for measuring the radiation performance of thermal barrier coatings, which could be used for the judgment of the service life of thermal barrier coatings. Full article
(This article belongs to the Special Issue Smart Coatings)
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15 pages, 23229 KiB  
Article
Comparison of the Erosive Wear Resistance of Ductile Cast Iron Following Laser Surface Melting and Alloying
by Jacek Górka, Aleksandra Lont, Damian Janicki, Tomasz Poloczek and Agnieszka Rzeźnikiewicz
Coatings 2024, 14(5), 646; https://doi.org/10.3390/coatings14050646 - 20 May 2024
Viewed by 285
Abstract
This article presents research results on the influence of the laser surface melting and alloying processes on the erosive wear resistance of ductile cast iron. For the research, an EN-GJS 350-22 ductile cast iron surface was laser-melted and laser-alloyed with titanium powder in [...] Read more.
This article presents research results on the influence of the laser surface melting and alloying processes on the erosive wear resistance of ductile cast iron. For the research, an EN-GJS 350-22 ductile cast iron surface was laser-melted and laser-alloyed with titanium powder in an argon and nitrogen atmosphere. Solid-particle erosion tests were carried out on the laser-melted and -alloyed surface layers and the base material according to the ASTM G76-04 standard with 30° and 90° impingement angles. The erosive wear resistance results were correlated with Vickers hardness and microstructural test results with the use of SEM (scanning electron microscopy), TEM (transmission electron microscopy), EDS (energy dispersive spectroscopy), and XRD (X-ray diffraction). The mechanisms of erosive wear were also analyzed for the laser-treated surface layers and the base material. The research showed that the laser melting and alloying processes with titanium powder had a positive effect on the hardness and erosive wear resistance of the ductile cast iron surface due to microstructure modification. Moreover, despite the lower hardness of the laser-alloyed surface layers, their composite microstructure had a positive impact on the erosive wear resistance in comparison to the laser-melted surface layers. Full article
(This article belongs to the Special Issue Laser-Assisted Coating Techniques and Surface Modifications)
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20 pages, 5191 KiB  
Article
Preparation of n-Tetradecane Phase Change Microencapsulated Polyurethane Coating and Experiment on Anti-Icing Performance for Wind Turbine Blades
by Yiting Wang, He Shen, Zheng Sun, Yan Li and Fang Feng
Coatings 2024, 14(5), 645; https://doi.org/10.3390/coatings14050645 - 19 May 2024
Viewed by 271
Abstract
Icing is a common physical phenomenon, and the icing of wind turbine blades can significantly affect the performance of wind turbines. Therefore, researching methods to prevent icing is of great significance, and the coating method of anti-icing is an effective way to delay [...] Read more.
Icing is a common physical phenomenon, and the icing of wind turbine blades can significantly affect the performance of wind turbines. Therefore, researching methods to prevent icing is of great significance, and the coating method of anti-icing is an effective way to delay icing, with advantages such as low energy consumption and easy implementation. In this study, using the coating method as the background, tetradecane phase change microcapsules were prepared, with a melting enthalpy of 90.8 J/g and a crystallization enthalpy of 96.3 J/g, exhibiting good coverage and energy storage efficiency. After mixing tetradecane phase change microcapsules (PCMS) with polyurethane coating (PUR) and coating them on wind turbine blades, after a 5 min icing wind tunnel test, the coating could significantly delay the icing on the blade surface, with the highest anti-icing rate reaching 60.41%. This indicates that the coating has a good anti-icing effect and provides basic research data for exploring new anti-icing methods. Full article
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10 pages, 10999 KiB  
Article
Protective Properties of Calcareous Deposit Layer for Cathodically Polarized AH36 Steel in Natural Seawater
by Quoc Quang Nong, Van Kien Dong, Van Trieu Nguyen, Van Chi Nguyen, Hong Quan Le and Nhat Linh Cao
Coatings 2024, 14(5), 644; https://doi.org/10.3390/coatings14050644 - 19 May 2024
Viewed by 241
Abstract
A calcareous deposit is a by-product of the cathodic polarization in seawater environments. This study presents the results of evaluating the anticorrosion and anti-macro-biofouling effectiveness of a calcareous deposit layer on the surface of the cathodically polarized AH36 structural steel in tropical seawater. [...] Read more.
A calcareous deposit is a by-product of the cathodic polarization in seawater environments. This study presents the results of evaluating the anticorrosion and anti-macro-biofouling effectiveness of a calcareous deposit layer on the surface of the cathodically polarized AH36 structural steel in tropical seawater. The polarization is induced with initial current densities at which the calcareous deposit layer formed with both aragonite and brucite for 12 months continuously. The protective properties of the layer were compared with those of the passive layer from corrosion products under the same environmental conditions. The macro-biofouling in the tropical seawater is observed in the closed and open surfaces of the steel. The comparison of the anticorrosion property shows that, to some degree, the calcareous deposit layer contributes to surface passivation, as in the case of the corrosion product layer. In addition, the composition of the brucite and aragonite in the calcareous layer in the study plays a role as a macro-biofouling growth-limiting factor. Full article
20 pages, 6184 KiB  
Article
Experimental Evaluation of Ceramic Coatings for Die Protection in Low-Pressure Die-Casting Process
by Ainara López-Ortega, Olatz Areitioaurtena, Elena Fuentes, Amaya Igartua, Luis Merchán, Enrique Pardo, Jessica Montero, Roberto Granado, Ignacio Martinez de la Pera, Joannes Mendizabal and Borja Zabala
Coatings 2024, 14(5), 643; https://doi.org/10.3390/coatings14050643 - 19 May 2024
Viewed by 343
Abstract
One of the most important factors in the LPDC process is the heat transfer during the solidification of the molten alloys, which is responsible for the resulting microstructure and, thus, the quality of the cast piece. The use of foundry coatings has been [...] Read more.
One of the most important factors in the LPDC process is the heat transfer during the solidification of the molten alloys, which is responsible for the resulting microstructure and, thus, the quality of the cast piece. The use of foundry coatings has been lately suggested as a proper strategy to control the heat transfer while protecting bonded moulds from aluminium adhesion by providing a barrier between the surface and the liquid metal. LPDC die coating failures usually come from the loss of adherence or excessive wear originated in the successive filling processes, which requires stopping production for the reapplication of the coating. In the present work, coatings with different insulation capabilities have been evaluated, in terms of adherence and wear tests, in order to select the most promising alternative for LPDC die coating. This study confirmed that surface preparation and cleanliness are vital for an adequate adhesion of the coatings to ensure their durability. The results evinced that the use of a primer layer provided a higher adhesion of the coatings and considerably improved their perfomance. The coating that presented the best results in terms of adhesion and wear resistance under different abrasive testing conditions was coating B3. Full article
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14 pages, 3660 KiB  
Article
Investigating the Effectiveness of Novel Repellent Labels Produced from Invasive Plant Species
by Klemen Možina, Zala Mavrič and Urška Vrabič-Brodnjak
Coatings 2024, 14(5), 642; https://doi.org/10.3390/coatings14050642 - 19 May 2024
Viewed by 261
Abstract
Although N,N-diethyl-3-methylbenzamide (DEET) remains the most effective repellent against mosquitoes and ticks, concerns about skin irritation, rashes, and neurological problems in children have driven the search for natural alternatives. The aim of this research was to develop, manufacture, and test prototype stickers derived [...] Read more.
Although N,N-diethyl-3-methylbenzamide (DEET) remains the most effective repellent against mosquitoes and ticks, concerns about skin irritation, rashes, and neurological problems in children have driven the search for natural alternatives. The aim of this research was to develop, manufacture, and test prototype stickers derived from invasive plant species in Europe. These labels contained a coating with encapsulated repellents made from essential oils to protect against mosquito bites and similar blood-sucking insects. Six samples of invasive plant species in Europe such as Japanese knotweed (Fallopia japonica), goldenrod (Solidago gigantea), and black locust (Robinia pseudoacacia) were coated with two essential oil mixtures (of geranium, lavender, and eucalyptus) and were encapsulated on solid carriers for prolonged evaporation. Analysis of the structural properties (weight, thickness, density, and specific volume) were carried out on the coated label samples. Analysis of surface properties (roughness and porosity), capillary absorption, and a comparison of time and evaporation of essential oils were also carried out. Scanning electron microscopy was performed on the samples and the solid carrier with different mixtures of essential oils. The Japanese knotweed sample, coated with a blend of geranium, lavender, and eucalyptus essential oils, showed the highest efficacy and stability. Full article
(This article belongs to the Special Issue Sustainable Coatings for Functional Textile and Packaging Materials)
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15 pages, 8596 KiB  
Article
Influence of Surfactant Types on the Anti-Corrosion Performance of Phosphate Chemical Conversion Coated Mg-8wt.%Li Alloy
by Liji Cui, Baojie Wang, Jiyu Hou, Daokui Xu and Jie Sun
Coatings 2024, 14(5), 641; https://doi.org/10.3390/coatings14050641 - 18 May 2024
Viewed by 237
Abstract
In this work, the morphology, anti-corrosion performance and degradation mechanisms of two phosphate chemical conversion coatings containing the AEO (fatty alcohol polyoxyethylene ether) and AES (fatty alcohol polyoxyethylene ether sodium sulfate) on an as-cast Mg-8wt.%Li alloy were explored and compared. Although two coating [...] Read more.
In this work, the morphology, anti-corrosion performance and degradation mechanisms of two phosphate chemical conversion coatings containing the AEO (fatty alcohol polyoxyethylene ether) and AES (fatty alcohol polyoxyethylene ether sodium sulfate) on an as-cast Mg-8wt.%Li alloy were explored and compared. Although two coating layers had a petal-shaped structure and were composed of leaf-shaped particles, the coating layer of the AES-coated sample was relatively dense due to the smaller size of the formed petal-shaped structure. Based on the electrochemical data and hydrogen evolution measurements, the corrosion protectability of the coating layer on the AES-coated sample was better than that on the AEO-coated sample. The determined corrosion current densities (icorr) of the AES-coated and AEO-coated samples in the 3.5 wt.% NaCl solution were, respectively, 7.8 mA·cm−2 and 11.7 mA·cm−2, whereas the icorr value of the coated sample without a surfactant was 36.2 mA·cm−2. Full article
(This article belongs to the Special Issue Environmental Corrosion of Metals and Its Prevention)
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11 pages, 4425 KiB  
Article
Boosting the Anti-Infection Ability of Titanium Implants by Coating Polydopamine–Curcumin
by Manlong Chen, Wenyi Yu, Qi Shi, Han Wen, Guojing Li, Yunliang Wang, Tao Wang, Shibin Liu and Tingting Yang
Coatings 2024, 14(5), 640; https://doi.org/10.3390/coatings14050640 - 18 May 2024
Viewed by 316
Abstract
To reduce the risk of infection, improving the anti-infection ability of Ti-based implantation has become a very meaningful task. In this work, by employing polydopamine (PDA) as a carrier and curcumin (CUR) as an anti-biotic/inflammatory, a series of Ti-PDA@CURx (x = 0.5, 1.0, [...] Read more.
To reduce the risk of infection, improving the anti-infection ability of Ti-based implantation has become a very meaningful task. In this work, by employing polydopamine (PDA) as a carrier and curcumin (CUR) as an anti-biotic/inflammatory, a series of Ti-PDA@CURx (x = 0.5, 1.0, 1.5, 2.0, 2.5) was successfully fabricated and characterized by scanning electron microscopy, Fourier transform infrared spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, and the water contact angle, where Ti plates were firmly coated by PDA@CUR. The test result of CUR content shows that the maximum loading of CUR in PDA can reach 0.6506%, where the CUR concentration is 1.5 mg/mL. The antibacterial test results demonstrate that Ti-PDA@CUR-x (x = 0.5, 1.0, 1.5, 2.0, 2.5) exhibit significant antibacterial activities against Escherichia coli and S. aureu, where Ti-PDA@CUR1.5 has the highest antibacterial rate of 62.7% against Escherichia coli and 52.6% against S. aureus. The cytotoxicity test shows that Ti-PDA, Ti-PDA@CUR-x (x = 0.5, 1.0, 1.5, 2.0, 2.5) has almost no toxicity. Full article
(This article belongs to the Section Bioactive Coatings and Biointerfaces)
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11 pages, 2270 KiB  
Article
Competitive Mechanism of Alloying Elements on the Physical Properties of Al10Ti15Nix1Crx2Cox3 Alloys through Single-Element and Multi-Element Analysis Methods
by Yu Liu, Lijun Wang, Juangang Zhao, Zhipeng Wang, Ruizhi Zhang, Yuanzhi Wu, Touwen Fan and Pingying Tang
Coatings 2024, 14(5), 639; https://doi.org/10.3390/coatings14050639 - 18 May 2024
Viewed by 254
Abstract
Altering the content of an alloying element in alloy materials will inevitably affect the content of other elements, while the effect is frequently disregarded, leading to subsequent negligence of the common influence on the physical properties of alloys. Therefore, the correlation between alloying [...] Read more.
Altering the content of an alloying element in alloy materials will inevitably affect the content of other elements, while the effect is frequently disregarded, leading to subsequent negligence of the common influence on the physical properties of alloys. Therefore, the correlation between alloying elements and physical properties has not been adequately addressed in the existing studies. In response to this problem, the present study focuses on the Al10Ti15Nix1Crx2Cox3 alloys and investigates the competitive interplay among Ni, Cr, and Co elements in the formation of physical properties through a single-element (SE) analysis and a multi-element (ME) analysis based on the first principles calculations and the partial least squares (PLS) regression. The values of C11 and C44 generally increase with the incorporation of Ni or Cr content in light of SE analysis, which is contrary to the inclination of ME analysis in predicting the impact of Ni and Cr elements, and the Ni element demonstrates a pronounced negative competitive ability. The overall competitive relationship among the three alloying elements suggests that increasing the content of Ni and Cr does not contribute to enhancing the elastic constants of alloys, and the phenomenon is also observed in the analysis of elastic moduli. The reason is that the SE analysis fails to account for the aforementioned common influence of multiple alloying elements on the physical properties of alloys. Therefore, the integration of SE analysis and ME analysis is more advantageous in elucidating the hidden competitive mechanism among multiple alloying elements, and offering a more robust theoretical framework for the design of alloy materials. Full article
(This article belongs to the Special Issue Microstructure, Mechanical and Tribological Properties of Alloys)
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24 pages, 12704 KiB  
Article
Effect of Nb Doping on the Electrical Contact Properties of AgNi Contact Materials
by Jingqin Wang, Menghan Wang, Jing Chen and Guanglin Huang
Coatings 2024, 14(5), 638; https://doi.org/10.3390/coatings14050638 - 17 May 2024
Viewed by 290
Abstract
AgNi contact materials have received widespread attention with the acceleration of the process of replacing AgCdO contact materials. However, the practical applications of AgNi contact materials are limited due to its disadvantage of poor resistance to melting welding. Firstly, following the first principles [...] Read more.
AgNi contact materials have received widespread attention with the acceleration of the process of replacing AgCdO contact materials. However, the practical applications of AgNi contact materials are limited due to its disadvantage of poor resistance to melting welding. Firstly, following the first principles of the density functional theory, we simulated and tested an interfacial model of AgNi doped with varying amounts of Nb. Next, we fabricated AgNi electrical contact materials. Subsequently, we conducted electrical contact tests. Finally, the impact of Nb doping on the arc erosion behavior of AgNi electrical contact materials was analyzed. The results indicate that, with an increase in Nb doping content, the electrical contact performance and the degree of arc erosion exhibit a trend of initially decreasing and then increasing, which aligns with the simulation results. The mean values of arc energy, arc duration, and welding force for the material doped with 4.55% Nb were 181.02 mJ, 9.43 mS, and 38.45 cN, respectively. Moreover, the anode is more responsive to changes in Nb content compared to the cathode. The introduction of Nb enhances the viscosity of the molten pool in the AgNi electrical contact. Furthermore, the mechanisms of grain boundary strengthening and solid solution strengthening by Nb improve the weld performance resistance of the contact. Full article
(This article belongs to the Special Issue Manufacturing and Surface Engineering IV)
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11 pages, 6666 KiB  
Article
Application of Laser Remelting Technology in the Case of Cultivator Tines
by István Domokos and Sándor Pálinkás
Coatings 2024, 14(5), 637; https://doi.org/10.3390/coatings14050637 - 17 May 2024
Viewed by 298
Abstract
The effectiveness of farming relies heavily on the condition of machinery and equipment, as well as maintaining the ideal soil conditions for the desired yields. Soil cultivation tools endure substantial stress and wear, emphasizing the need to study their durability surrounding soil contact. [...] Read more.
The effectiveness of farming relies heavily on the condition of machinery and equipment, as well as maintaining the ideal soil conditions for the desired yields. Soil cultivation tools endure substantial stress and wear, emphasizing the need to study their durability surrounding soil contact. Our research focuses on enhancing the lifespan of worn-out ploughshares through various heat treatment methods and hot metal spraying. By remelting the surface of ploughshares using a flame or laser, we aim to identify the most effective treatment for agricultural production. The improved surface treatment of the furrows in field tillers can significantly cut costs and enhance tillage efficiency. Our preliminary findings suggest that the metal spraying and remelting of nickel alloy hold promise for achieving these goals. Full article
(This article belongs to the Section Laser Coatings)
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12 pages, 2403 KiB  
Article
A Novel Approach towards the Preparation of Silk-Fibroin-Modified Polyethylene Terephthalate with High Hydrophilicity and Stability
by Jingyi Fan, Yiwen Zhang, Maoyang Li, Peiyu Ji, Haiyun Tan, Tianyuan Huang, Lanjian Zhuge, Xiaoman Zhang and Xuemei Wu
Coatings 2024, 14(5), 636; https://doi.org/10.3390/coatings14050636 - 17 May 2024
Viewed by 276
Abstract
Silk fibroin (SF) has been widely used in biomedical applications for the hydrophilicity modification of high molecular polymer materials. However, the challenge remains to immobilize SF with high structure stability and strong adhesion strength between SF and the substrate. Here, we propose an [...] Read more.
Silk fibroin (SF) has been widely used in biomedical applications for the hydrophilicity modification of high molecular polymer materials. However, the challenge remains to immobilize SF with high structure stability and strong adhesion strength between SF and the substrate. Here, we propose an effective two-step process for modifying polyethylene terephthalate (PET) with SF: dipping PET film in SF solution and subsequently carrying out plasma-assisted deposition in SF aerosol. The structure and property analysis revealed that the SF-modified PET (PET-SF) prepared using the two-step method exhibited superior structural stability and stronger adhesion strength compared to the dip-coating method and the plasma-assisted deposition method. In addition, PET-SF prepared using the two-step method resulted in a higher concentration of SF and an increased content of active groups on its surface, enhancing its hydrophilicity compared to the other two methods. Additionally, the influence of dipping time and deposition time in the two-step method was investigated. The results demonstrated that the dipping time for 6 h and the deposition time for 3 min resulted in maximum SF grafting amount with a highly stable structure. Furthermore, the PET-SF exhibited satisfactory hydrophilicity when the deposition time was more than 3 min and showed the most hydrophilicity surface at 8 min. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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13 pages, 6356 KiB  
Article
The Effect of Resin Interleafing on the Wedge Peel Strength of CF/PEEK Manufactured by Laser-Assisted In Situ Consolidation
by Ruozhou Wang, Entao Xu and Liwei Wen
Coatings 2024, 14(5), 635; https://doi.org/10.3390/coatings14050635 - 17 May 2024
Viewed by 331
Abstract
In this work, a novel approach involving coating fine PEEK powder on prepreg is introduced to improve wedge peel strength and reduce interlaminar voids. CF/PEEK laminates with resin interleaving are in situ consolidated by laser-assisted fiber placement. The morphology of the powdered surface [...] Read more.
In this work, a novel approach involving coating fine PEEK powder on prepreg is introduced to improve wedge peel strength and reduce interlaminar voids. CF/PEEK laminates with resin interleaving are in situ consolidated by laser-assisted fiber placement. The morphology of the powdered surface is obtained using an optical profilometer, and the surface roughness and volume of added resin are calculated accordingly. Interface and surface temperature are measured during the layup process. Thermal history indicates that very short bonding time is the dominating factor for voids and limited interlayer strength. Laminate porosity and microscopic features are characterized with an optical microscope. The porosity of resin-interleaved laminates decreases to 3.7%, while the resin content only increases by 4.5% in the meantime. This is because interlayer resin particles rapidly melt under laser heating and quickly fill the voids between layers. The wedge peel strength of resin-interleaved laminates can increase by 30.1% without a repass treatment. This could be attributed to the increase in resin intimate contact and reduction in interlayer voids. Full article
(This article belongs to the Special Issue Surface Science of Degradation and Surface Protection)
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10 pages, 1721 KiB  
Article
Optical Limiting from CdSe-Based Multiphase Polymer Nanocomposite Films
by Leah M. Eversole, Richard Adjorlolo, Jack Francis Renaud and Mithun Bhowmick
Coatings 2024, 14(5), 634; https://doi.org/10.3390/coatings14050634 - 17 May 2024
Viewed by 291
Abstract
Closely packed nanoparticles in polymer films are interesting materials where collective as interactive optical properties could be tuned based on nanoparticle proximity, surface morphology, types of encapsulation and matrix parameters. Two types of polymers (polymethylmethacrylate (PMMA) and polyvinyl alcohol (PVA))-based nanocomposite films featuring [...] Read more.
Closely packed nanoparticles in polymer films are interesting materials where collective as interactive optical properties could be tuned based on nanoparticle proximity, surface morphology, types of encapsulation and matrix parameters. Two types of polymers (polymethylmethacrylate (PMMA) and polyvinyl alcohol (PVA))-based nanocomposite films featuring dual-colored emission peaks (~578 nm and ~650 nm) were fabricated from CdSe quantum dots to study their viability in optoelectronic applications. Using a 405 nm excitation laser, the evolution of photoluminescence (PL) intensities and peak wavelengths were examined as a function of increasing excitation intensity. While PL intensities showed systematic saturation and quenching, the emission wavelengths were found to be linearly red shifting with increasing excitation intensities in the PMMA films. The 650 nm emitting QDs seem to tune the PL saturation behavior in these films, as opposed to the PVA-based materials, where no such impact was seen. The material system could be a low-cost, low-maintenance alternative for future mesoscale sensing and light-emitting device applications. Full article
(This article belongs to the Special Issue Coatings for Advanced Devices)
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14 pages, 8667 KiB  
Article
Improvement of X-ray Photoelectric Conversion Performance of MAPbI3 Perovskite Crystals by Ionic Liquid Treatment
by Xueqiong Su, Ruimin Wang, Huimin Yu, Jin Wang, Ruixiang Chen, He Ma and Li Wang
Coatings 2024, 14(5), 633; https://doi.org/10.3390/coatings14050633 - 16 May 2024
Viewed by 191
Abstract
Although perovskite has great potential in optoelectronic devices, the simultaneous satisfaction of material stability and high performance is still an issue that needs to be solved. Most perovskite optoelectronic devices use quantum dot spin coating or the gas-phase growth of perovskite thin films [...] Read more.
Although perovskite has great potential in optoelectronic devices, the simultaneous satisfaction of material stability and high performance is still an issue that needs to be solved. Most perovskite optoelectronic devices use quantum dot spin coating or the gas-phase growth of perovskite thin films as the photoelectric conversion layer. Due to stability limitations, these materials often experience a significant decrease in photoelectric conversion efficiency when encountering liquid reagents. The self-assembled growth of hybrid perovskite crystals determines superior lattice ordering and stability. There are three types of ionic liquids—[Emim]BF4, EMIMNTF2, and HMITFSI—that can effectively enhance the X-ray photoelectric conversion performance of hybrid perovskite crystal CH3NH3PbI3 (MAPbI3), and the enhancement in the photocurrent leads to an improvement in the sensitivity of X-ray detectors. We soak the perovskite crystals in an ionic liquid and perform two treatment methods: electrification and dilution with ETOH solution. It is interesting to find that MAPbI3 perovskite single crystal materials choose the same optimized ionic liquid species in X-ray detection and photovoltaic power generation applications, and the effect is quite the opposite. Compared with untreated MAPbI3 crystals, the average photocurrent density of Electrify-HMITFSI MAPbI3 increased by 826.85% under X-ray excitation and the sensitivity of X-ray detectors made from these treated MAPbI3 crystals significantly increased by 72.6%, but the intensity of the PL spectrum decreased to 90% of the untreated intensity. Full article
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20 pages, 8146 KiB  
Article
Effective Promotion of Micro Damping of GO Hybrid PU–PF Copolymer Grinding Wheels on Precision Machining
by Shaoling Xia, Hongying Zhang, Jixian Xu, Yingliang Liu, Cong Liu, Shengdong Guo, Xudong Song, Jin Peng, Yu Jia and Jialu Li
Coatings 2024, 14(5), 632; https://doi.org/10.3390/coatings14050632 - 16 May 2024
Viewed by 285
Abstract
The influence of damping and friction performance of grinding wheels on precision grinding was explored for the first time. GO hybrid PU-modified PF copolymers were prepared by in situ synthesis and adopted as a matrix for fabricating grinding wheels. FT-IR, DSC, TG, and [...] Read more.
The influence of damping and friction performance of grinding wheels on precision grinding was explored for the first time. GO hybrid PU-modified PF copolymers were prepared by in situ synthesis and adopted as a matrix for fabricating grinding wheels. FT-IR, DSC, TG, and mechanical property tests showed the optimal modification when PU content was 10 wt% and GO addition was 0.1 wt%. Damping properties were investigated by DMA, and tribological characteristics were measured by sliding friction and wear experiments. The worn surfaces and fracture morphologies of GO hybrid PU–PF copolymers were observed by SEM. Distribution of components on the worn surfaces was explored by Raman mapping and EDS. The research results revealed that the PU component tended to be dispersed around the edges of corundum abrasives acting as a buffer layer of abrasive particles, which could provide micro-damping characteristics for abrasives, making the grinding force more stable during precision machining and facilitating a smoother surface quality of the workpiece. Full article
(This article belongs to the Special Issue Enhanced Mechanical Properties of Metals by Surface Treatments)
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16 pages, 3547 KiB  
Article
Well-Dispersed CoNiO2 Nanosheet/CoNi Nanocrystal Arrays Anchored onto Monolayer MXene for Superior Electromagnetic Absorption at Low Frequencies
by Leiyu Du, Renxin Xu, Yunfa Si, Wei Zhao, Hongyi Luo, Wei Jin and Dan Liu
Coatings 2024, 14(5), 631; https://doi.org/10.3390/coatings14050631 - 16 May 2024
Viewed by 317
Abstract
Developing microwave absorbers with superior low-frequency electromagnetic wave absorption properties is one of the foremost important factors driving the boom in 5G technology development. In this study, via a simple hydrothermal and pyrolysis strategy, randomly interleaved CoNiO2 nanosheets and uniformly ultrafine CoNi [...] Read more.
Developing microwave absorbers with superior low-frequency electromagnetic wave absorption properties is one of the foremost important factors driving the boom in 5G technology development. In this study, via a simple hydrothermal and pyrolysis strategy, randomly interleaved CoNiO2 nanosheets and uniformly ultrafine CoNi nanocrystals are anchored onto both sides of a single-layered MXene. The absorption mechanism demonstrated that the hierarchical heterostructure prevents the aggregation of MXene nanoflakes and magnetic crystallites. In addition, the introduction of the double-magnetic phase of CoNiO2/CoNi arrays can not only enhance the magnetic loss capacity but also generate larger void spaces and abundant heterogeneous interfaces, collectively promoting impedance-matching and furthering microwave attenuation capabilities at a low frequency. Hence, the reflection loss of the optimal absorber (M–MCNO) is −45.33 dB at 3.24 GHz, which corresponds to a matching thickness of 5.0 mm. Moreover, its EAB can entirely cover the S-band and C-band by tailoring the matching thickness from 2 to 7 mm. Satellite radar cross-section (RCS) simulations demonstrated that the M–MCNO can reduce the RCS value to below −10 dB m2 over a multi-angle range. Thus, the proposed hybrid absorber is of great significance for the development of magnetized MXene composites with superior low-frequency microwave absorption properties. Full article
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15 pages, 5132 KiB  
Review
Recent Advances in the Deposition of Aluminide Coatings on Nickel-Based Superalloys: A Synthetic Review (2019–2023)
by Mateusz Kopec
Coatings 2024, 14(5), 630; https://doi.org/10.3390/coatings14050630 - 16 May 2024
Viewed by 279
Abstract
Thermal barrier coatings (TBCs) are widely used to improve the oxidation resistance and high-temperature performance of nickel-based superalloys operating in aggressive environments. Among the TBCs, aluminide coatings (ACs) are commonly utilized to protect the structural parts of jet engines against high-temperature oxidation and [...] Read more.
Thermal barrier coatings (TBCs) are widely used to improve the oxidation resistance and high-temperature performance of nickel-based superalloys operating in aggressive environments. Among the TBCs, aluminide coatings (ACs) are commonly utilized to protect the structural parts of jet engines against high-temperature oxidation and corrosion. They can be deposited by different techniques, including pack cementation (PC), slurry aluminizing or chemical vapor deposition (CVD). Although the mentioned deposition techniques have been known for years, the constant developments in materials sciences and processing stimulates progress in terms of ACs. Therefore, this review paper aims to summarize recent advances in the AC field that have been reported between 2019 and 2023. The review focuses on recent advances involving improved corrosion resistance in salty environments as well as against high temperatures ranging between 1000 °C and 1200 °C under both continuous isothermal high-temperature exposure for up to 1000 h and cyclic oxidation resulting from AC application. Additionally, the beneficial effects of enhanced mechanical properties, including hardness, fatigue performance and wear, are discussed. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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17 pages, 32510 KiB  
Article
First-Principles and Experimental Study of Ge, V, Ta-Doped AgNi Electrical Contact Materials
by Jingqin Wang, Yixuan Zhang, Menghan Wang, Jing Chen and Guanglin Huang
Coatings 2024, 14(5), 629; https://doi.org/10.3390/coatings14050629 - 16 May 2024
Viewed by 315
Abstract
To explore the stability, electrical, and mechanical characteristics of undoped AgNi alongside AgNi doped with elemental Ge, V, and Ta, we performed calculations on their electronic structures using density functional theory from first-principles. We also prepared AgNi(17) and AgNi-x(Ge, V, Ta) electrical contact [...] Read more.
To explore the stability, electrical, and mechanical characteristics of undoped AgNi alongside AgNi doped with elemental Ge, V, and Ta, we performed calculations on their electronic structures using density functional theory from first-principles. We also prepared AgNi(17) and AgNi-x(Ge, V, Ta) electrical contact materials using the powder metallurgy technique, and they were subsequently assessed experimentally. The electrical properties of these materials were evaluated under a 24 V/15 A DC-resistive load using the JF04D contact material testing system. A three-dimensional morphology scanner was employed to examine the contact surface and investigate the erosion patterns of the materials. Our findings indicate that doping with metal elements significantly enhanced the mechanical properties of electrical contacts, including conductivity and hardness, and optimizes arc parameters while improving resistance to arc erosion. Notably, AgNi-Ge demonstrated superior conductivity and arc erosion resistance, showing significant improvements over the undoped AgNi contacts. This research provides a theoretical foundation for selecting doping elements aimed at enhancing the performance of AgNi electrical contact materials. Full article
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20 pages, 12458 KiB  
Article
Temporal and Spatial Variation Study on Corrosion of High-Strength Steel Wires in the Suspender of CFST Arch Bridge
by Luming Deng and Yulin Deng
Coatings 2024, 14(5), 628; https://doi.org/10.3390/coatings14050628 - 16 May 2024
Viewed by 314
Abstract
The corrosion and degradation behavior of high-strength steel wires during service directly affect the safety and usability of suspenders in steel pipe concrete arch bridges. In this study, three different types of specimens were fabricated using steel wires extracted from the suspenders of [...] Read more.
The corrosion and degradation behavior of high-strength steel wires during service directly affect the safety and usability of suspenders in steel pipe concrete arch bridges. In this study, three different types of specimens were fabricated using steel wires extracted from the suspenders of an 11-year-old in-service arch bridge and subjected to accelerated corrosion tests with acetic acid. Considering the differential diffusion processes of corrosion factors caused by varying degrees of damage to the suspender sheath, the spatial corrosion variability of steel wires at different positions within the suspender cross-section was investigated. Experimental results indicated a two-stage characteristic in the corrosion process of individual galvanized steel wire samples. In the first corrosion stage, the microstructure on the corroded steel wire surface evolved from a dense crystalline structure to a porous one. In the second corrosion stage, corrosion products accumulate on the steel wire substrate, subsequently further aggregating into sheet-like structures. The maximum pitting factor of individual steel wire samples from a specific area could be described by a Type I extreme value distribution. In the time-dependent model that was established, the location parameter and scale parameter exhibited an exponential decrease during the first corrosion stage and a linear decrease during the second corrosion stage. In the absence of sheath protection, the coefficient of variation in corrosion among adjacent steel wires in the suspender followed a normal distribution. The spatial corrosion variability of the wires inside the suspender is significantly influenced by the shape of the suspender sheath damage. As the corrosion time increased, the overall discrepancy in corrosion levels among different layers of wires diminished. Full article
(This article belongs to the Special Issue Corrosion and Corrosion Prevention in Extreme Environments)
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11 pages, 11337 KiB  
Article
The Effects of Induction Plasma Spheroidization on the Properties of Yttrium-Stabilized Zirconia Powders and the Performance of Corresponding Thermal Barrier Coatings for Gas Turbine Engine Applications
by Haoran Peng, Yueguang Yu, Jianxin Dong, Tianjie Shi, Kang Yuan, Zheng Yan and Botian Bai
Coatings 2024, 14(5), 627; https://doi.org/10.3390/coatings14050627 - 16 May 2024
Viewed by 304
Abstract
To modify the structure of thermal barrier coatings and improve their high-temperature resistance, induction plasma spheroidization (IPS) technology was applied to regulate the structure of YSZ powders in this study. The surface morphology, particle size distribution, phase composition, and internal microstructure of the [...] Read more.
To modify the structure of thermal barrier coatings and improve their high-temperature resistance, induction plasma spheroidization (IPS) technology was applied to regulate the structure of YSZ powders in this study. The surface morphology, particle size distribution, phase composition, and internal microstructure of the conventional agglomerated and spheroidized powders were characterized using scanning electron microscopy and focused ion beam analysis methods. The results showed that the microstructure of the powders presented uneven evolution in the induction plasma stream. Due to the existence of the temperature gradient along the radial direction of the powders, the IPS powders consisted of outer dense shells and internal porous cores. The mechanical property of such shell–core structure was analyzed by using the finite elemental simulation method. In addition, coatings were prepared using the IPS powders and the agglomerated powders. The IPS coating showed improved water-cooling thermal cycling resistance compared to the conventional coating. Full article
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17 pages, 5180 KiB  
Article
Performance of Atmospheric Plasma-Sprayed Thermal Barrier Coatings on Additively Manufactured Super Alloy Substrates
by Madhura Bellippady, Stefan Björklund, Xin-Hai Li, Robert Frykholm, Bjorn Kjellman, Shrikant Joshi and Nicolaie Markocsan
Coatings 2024, 14(5), 626; https://doi.org/10.3390/coatings14050626 - 15 May 2024
Viewed by 388
Abstract
This work represents a preliminary study of atmospheric plasma-sprayed (APS) Yttria-Stabilized Zirconia (YSZ)-based thermal barrier coatings (TBCs) deposited on forged and additive manufactured (AM) HAYNES®282® (H282) superalloy substrates. The effect of different feedstock morphologies and spray gun designs with radial [...] Read more.
This work represents a preliminary study of atmospheric plasma-sprayed (APS) Yttria-Stabilized Zirconia (YSZ)-based thermal barrier coatings (TBCs) deposited on forged and additive manufactured (AM) HAYNES®282® (H282) superalloy substrates. The effect of different feedstock morphologies and spray gun designs with radial and axial injection on APS-deposited YSZ layer characteristics such as microstructure, porosity content, roughness, etc., has been investigated. The performance of TBCs in terms of thermal cycling fatigue (TCF) lifetime and erosion behaviour were also comprehensively investigated. In view of the high surface roughness of as-built AM surfaces compared to forged substrates, two different types of NiCoCrAlY bond coats were examined: one involved high-velocity air fuel (HVAF) spraying of a finer powder, and the other involved APS deposition of a coarser feedstock. Despite the process and feedstock differences, the above two routes yielded comparable bond coat surface roughness on both types of substrates. Variation in porosity level in the APS topcoat was observed when deposited using different YSZ feedstock powders employing axial or radial injection. However, the resultant TBCs on AM-derived substrates were observed to possess similar microstructures and functional properties as TBCs deposited on reference (forged) substrates for any given YSZ deposition process and feedstock. Full article
(This article belongs to the Special Issue Advances in Thermal Spray Coatings: Technologies and Applications)
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10 pages, 5978 KiB  
Article
A Manufacturing Method for High-Reliability Multilayer Flexible Electronics by Electrohydrodynamic Printing
by Geng Li, Shang Wang, Jiayue Wen, Shujun Wang, Yuxin Sun, Jiayun Feng and Yanhong Tian
Coatings 2024, 14(5), 625; https://doi.org/10.3390/coatings14050625 - 15 May 2024
Viewed by 346
Abstract
To meet the demand for higher performance and wearability, integrated circuits are developing towards having multilayered structures and greater flexibility. However, traditional circuit fabrication methods using etching and lamination processes are not compatible with flexible substrates. As a non-contact printing method in additive [...] Read more.
To meet the demand for higher performance and wearability, integrated circuits are developing towards having multilayered structures and greater flexibility. However, traditional circuit fabrication methods using etching and lamination processes are not compatible with flexible substrates. As a non-contact printing method in additive manufacturing, electrohydrodynamic printing possesses advantages such as environmental friendliness, sub-micron manufacturing, and the capability for flexible substrates. However, the interconnection and insulation of different conductive layers become significant challenges. This study took composite silver ink as a conductive material to fabricate a circuit via electrohydrodynamic printing, applied polyimide spraying to achieve interlayer insulation, and drilled micro through-holes to achieve interlayer interconnection. A 200 × 200 mm2 ten-layer flexible circuit was thus prepared. Furthermore, we combined a finite element simulation with reliability experiments, and the prepared ten-layer circuit was found to have excellent bending resistance and thermal cycling stability. This study provides a new method for the manufacturing of low-cost, large-sized, multilayer flexible circuits, which can improve circuit performance and boost the development of printed electronics. Full article
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9 pages, 4309 KiB  
Article
Precise Analysis of the Differences in the Laser-Activated Energy Density of Aluminum Nitride Ceramics under Various Gas Bath Environments
by Haitao Zhang, Yingming Wang, Jing Shao, Hao Dong, Zhiyuan Sun, Suli Han, Changqing Xie, Ping Song, Shufeng Sun and Zhenwei Nie
Coatings 2024, 14(5), 624; https://doi.org/10.3390/coatings14050624 - 15 May 2024
Viewed by 320
Abstract
Laser activation can lead to the formation of a layer of aluminum on the surface of aluminum nitride ceramics, thereby preparing metal circuits. Under various gas environments, there are differences in the aluminum layers precipitated by laser-activated aluminum nitride ceramics. The existing literature [...] Read more.
Laser activation can lead to the formation of a layer of aluminum on the surface of aluminum nitride ceramics, thereby preparing metal circuits. Under various gas environments, there are differences in the aluminum layers precipitated by laser-activated aluminum nitride ceramics. The existing literature uses the width of the metal layer to characterize this difference, and these data are very imprecise. Usually, laser energy density is used to describe this processing difference. However, the existing concept of laser energy density is an average value and is not suitable for the threshold of laser activation, because the intensity gradient of the focused Gaussian beam is large, and different intensity distributions represent different energy levels. This article applied a precise concept of laser energy density that sees it as being proportional to light intensity and can be used to evaluate the difference in laser energy density required for the decomposition of aluminum nitride ceramics under various gas bath conditions precisely. Due to the strong energy of a focused Gaussian beam, it is not possible to directly obtain the intensity distribution. Here, the intensity distribution of the collimated beam was used to indirectly obtain the intensity distribution of the focused Gaussian beam, and the threshold values for laser activation under different gas baths were calculated. It was found that the minimum energy density in air increased by 12.5%, and the minimum energy density in nitrogen increased by 3%, using the minimum energy density required for laser activation in argon as the reference. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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15 pages, 13232 KiB  
Article
An Experimental Study of Surface Icing Characteristics on Blade Airfoil for Offshore Wind Turbines: Effects of Chord Length and Angle of Attack
by Dong Liang, Pengyu Zhao, He Shen, Shengbing Yang, Haodong Chi, Yan Li and Fang Feng
Coatings 2024, 14(5), 623; https://doi.org/10.3390/coatings14050623 - 15 May 2024
Viewed by 441
Abstract
Offshore wind turbines operating in frigid and humid climates may encounter icing on the blade surface. This phenomenon adversely impacts the aerodynamic efficiency of the turbine, consequently diminishing power generation efficacy. Investigating the distribution characteristics of icing on the blade surface is imperative. [...] Read more.
Offshore wind turbines operating in frigid and humid climates may encounter icing on the blade surface. This phenomenon adversely impacts the aerodynamic efficiency of the turbine, consequently diminishing power generation efficacy. Investigating the distribution characteristics of icing on the blade surface is imperative. Hence, this study undertook icing wind tunnel tests on segments of DU25 airfoil, a prevalent type for offshore wind turbines, to examine such characteristics as different chord lengths and angles of attack. The results show a simultaneous increase in the blade icing area and growth rate of the net icing area with augmenting the chord length and angles of attack. The total icing area rate decreases by a factor of two when the chord length is doubled. The relative positioning of icing and the average icing thickness remain consistent across the airfoil blades with varying chord lengths. Comparing the icing shapes on blades of varying scales shows a similarity ranging from 84.06% to 88.72%. The results of this study provide insight into the icing characteristics of offshore wind turbines. Full article
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17 pages, 3740 KiB  
Article
Magnetron-Sputtered Long-Term Superhydrophilic Thin Films for Use in Solid-State Cooling Devices
by Maria Barrera, Olaf Zywitzki, Thomas Modes and Fred Fietzke
Coatings 2024, 14(5), 622; https://doi.org/10.3390/coatings14050622 - 14 May 2024
Viewed by 351
Abstract
Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The [...] Read more.
Pulse-magnetron-sputtered long-term superhydrophilic coatings have been synthesized to functionalize the surfaces of solid-state cooling devices, e.g., electrocaloric heat pumps, where not only a complete wetting of the surface by a fluid is intended, but also fast wetting and dewetting processes are required. The coatings consist of a (Ti,Si)O2 outer layer that provides lasting hydrophilicity thanks to the mesoporous structure, followed by an intermediate WO3 film that enables the reactivation of the wettability through visible light irradiation, and a W underlayer which can work as a top electrode of the electrocaloric components thanks to its suitable electrical and thermal conductivity properties. Process parameter optimization for each layer of the stack as well as the influence of the microstructure and composition on the wetting properties are presented. Finally, water contact angle measurements, surface energy evaluations, and a contact line dynamics assessment of evaporating drops on the coatings demonstrate that their enhanced wetting performance is attributed not only to their intrinsic hydrophilic nature but also to their porous microstructure, which promotes wicking and spreading at the nanometric scale. Full article
(This article belongs to the Section Thin Films)
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16 pages, 1608 KiB  
Article
Evaluation of Edible Coatings from Components from Chlorella vulgaris and Comparison with Conventional Coatings
by Alexandra Mari, Charilaos Fafalis and Magdalini Krokida
Coatings 2024, 14(5), 621; https://doi.org/10.3390/coatings14050621 - 14 May 2024
Viewed by 347
Abstract
The present customer demand for ready-to-eat food items with higher nutritious value and longer shelf life necessitates creative solutions. An edible coating is a sustainable packaging solution that can prevent food deterioration and preserve food quality. Proteins, starch, and the addition of plasticizers [...] Read more.
The present customer demand for ready-to-eat food items with higher nutritious value and longer shelf life necessitates creative solutions. An edible coating is a sustainable packaging solution that can prevent food deterioration and preserve food quality. Proteins, starch, and the addition of plasticizers are used to create edible coatings. The aim of this study was to develop coating solutions that can best preserve food using isolated starch and proteins from Chlorella vulgaris, and then compare them to coatings that comprise conventional ingredients like chitosan and starch. A number of criteria pertaining to the coatings’ mechanical, optical, thermal, and physical properties were tested. The alternative coatings performed just as well as the conventional ones, with the protein algal coating exhibiting the best thermal, optical, and physical qualities. The food product that needs to be coated can determine which coating is ideal. In conclusion, edible coatings derived from Chlorella vulgaris offer a sustainable solution to preserve ready-to-eat food items, showcasing comparable performance to conventional coatings. Full article
(This article belongs to the Section Coatings for Food Technology and System)
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14 pages, 7363 KiB  
Article
Microstructure and Properties of CoCrFeNiMnTix High-Entropy Alloy Coated by Laser Cladding
by Shibang Ma, Congzheng Zhang, Liang Li and Yinhai Yang
Coatings 2024, 14(5), 620; https://doi.org/10.3390/coatings14050620 - 14 May 2024
Viewed by 327
Abstract
In this study, laser cladding of CoCrFeNiMnTix (x is the proportion of the mass of a material, x = 0.0, 0.2, 0.4, 0.6, 0.8) high-entropy alloy (HEA) composite powder coating on 45 steel substrate was studied by using the method of [...] Read more.
In this study, laser cladding of CoCrFeNiMnTix (x is the proportion of the mass of a material, x = 0.0, 0.2, 0.4, 0.6, 0.8) high-entropy alloy (HEA) composite powder coating on 45 steel substrate was studied by using the method of preplaced powder. The phase composition, morphology, microhardness, corrosion resistance and wear properties of CoCrFeNiMnTix high entropy alloy were analyzed by XRD, SEM, microhardness tester, electrochemical workstation and reciprocating friction wear tester, respectively. The influences of Ti concentration on structure and properties of CoCrFeNiMn HEA laser cladding coating were discussed. The macromorphology of CoCrFeNiMnTix HEA coating layer becomes worse with the increase in Ti quantity. The coating layer is a face-centered cubic solid solution phase. The microstructure of the coating layer is dominated by dendrites and equiaxed crystals. The average microhardness of the coating layer grows with the increases in Ti content, and CoCrFeNiMnTi0.8 can reach 823 HV. The friction coefficient of the cladding coating gradually reduces and the wear resistance adds as Ti content rises; the friction coefficients of CoCrFeNiMnTi0.6 and CoCrFeNiMnTi0.8 cladding coating are similar, at 0.835 and 0.828, respectively. Adhesive and abrasive wear are the two basic types of cladding coating wear. In 3.5 wt.% NaCl solution, the corrosion potential of cladding coating increases with increases in Ti content, the corrosion potential of CoCrFeNiMnTi0.8 is about 244 mV higher than that of CoCrFeNiMnTi0, and the density of corrosion current drops to 3.41 × 10−6 A/cm2 from 7.17 × 10−5 A/cm2. Full article
(This article belongs to the Section Laser Coatings)
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