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Coatings, Volume 14, Issue 1 (January 2024) – 151 articles

Cover Story (view full-size image): Optical states generated at the Bragg reflector and metal interface called Tamm plasmon polaritons (TPP) attracted attention due to the in-plane wave vector being smaller than light in a vacuum, thus allowing the direct excitation of TPPs. This property attracts the use of TPPs in various photonic devices, such as optical sensors, bandgap filters, and plasmonic lasers. Plasmonic resonances usually require tens of nanometers thick layers to achieve precise control of plasmonic excitation. This study used an atomic layer deposition (ALD) of the Al2O3 layer for TPP resonance tailoring in the spectra, demonstrating the importance of such a method in plasmonics. View this paper
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19 pages, 10166 KiB  
Article
Visible Light Activation of Gold Nanoparticles Embedded into Titanium Dioxide Surface in Electrospun Polymeric Coatings
by Xabier Sandua, Pedro J. Rivero, Jonathan Calvopiña, José F. Palacio and Rafael Rodríguez
Coatings 2024, 14(1), 151; https://doi.org/10.3390/coatings14010151 - 22 Jan 2024
Viewed by 896
Abstract
This work reports the development of a functional photocatalytic coating based on a combination of polymeric electrospun fibres and nanoparticles that is intended to be activated in the visible light range. In this sense, the resulting fibres can act as an effective matrix [...] Read more.
This work reports the development of a functional photocatalytic coating based on a combination of polymeric electrospun fibres and nanoparticles that is intended to be activated in the visible light range. In this sense, the resulting fibres can act as an effective matrix for the incorporation of titanium dioxide (TiO2) particles, which are covered by gold nanoparticles (AuNPs), in the outer surface of the metal oxide precursor. In the first step of the process, the optical properties of the nanoparticles were determined by UV-Vis spectroscopy. The extension of the visible absorption can be associated to the localized surface plasmon resonance (LSPR) of the metallic AuNPs. In addition, the resultant particle size distribution and average particle diameter was evaluated by dynamic light scattering (DLS) measurements. Furthermore, the phase composition and porosity of the functional particle powder were analysed by an XRD and N2 adsorption test. In the second step, these synthesized particles have been successfully immobilized into a PAA + β-CD electrospun fibre matrix by using the two different deposition methods of dip-coating and solution-casting, respectively. The morphological characterization of the samples was implemented by means of scanning electron microscopy (SEM), showing uniform and homogeneous, free-beaded fibres with a random distribution of the synthesized particles deposited onto the electrospun fibres. Then, the functional coatings were removed from the substrate, and a thermogravimetric (TGA) analysis was carried out for each sample in order to obtain the precursor mass immobilized in the coating. Once the overall mass of precursor was obtained, the percentage of TiO2 particles and AuNPs in the precursor was calculated by using inductively coupled plasma atomic emission spectrometry (ICP-AES). Finally, the photocatalytic activity of both functional solution and electrospun coatings were evaluated in terms of a gradual degradation of rhodamine B (RhB) dye after continuous exposition to a visible-light lamp. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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11 pages, 7449 KiB  
Article
The Preparation and Properties of Thick Bronze Coating Using Friction-Assisted Jet Electrodeposition
by Yilin Yao, Jihua Cheng, Hai Ji, Shiji Zhang, Haozhe Pang, Ya Chen and Zongjun Tian
Coatings 2024, 14(1), 150; https://doi.org/10.3390/coatings14010150 - 22 Jan 2024
Viewed by 792
Abstract
In this study, a novel friction-assisted jet electrodeposition technology was applied to prepare bronze coating on 40CrNiMoA structural steel surfaces. The bronze electrode was designed with internal flow channels and nozzles, and the friction brushes made of alumina and silicon carbide were connected [...] Read more.
In this study, a novel friction-assisted jet electrodeposition technology was applied to prepare bronze coating on 40CrNiMoA structural steel surfaces. The bronze electrode was designed with internal flow channels and nozzles, and the friction brushes made of alumina and silicon carbide were connected to the electrode surface. It was reported that the quality and deposition rate of the thick bronze coatings were significantly improved with friction-assisted jet electrodeposition. The roughness and microstructures were refined, and the deposition rate was up to 100 μm/h when the current density was 8 A/dm2. In addition, the chemical composition was related to current density as the content of tin in the bronze coating made with FJED decreased at a high current density. Moreover, the grain structures were α-CuSn in the solid-solution phase and the average grain size of FJED coatings was refined at a current density of 8 A/dm2. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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15 pages, 4663 KiB  
Article
Impact of Molecular Weight on Anti-Bioadhesion Efficiency of PDMS-Based Coatings
by Mama Aïssata Bangoura, David Mimeau, Eric Balnois, Karine Réhel, Fabrice Azemar and Isabelle Linossier
Coatings 2024, 14(1), 149; https://doi.org/10.3390/coatings14010149 - 21 Jan 2024
Viewed by 1010
Abstract
Silicone elastomer coatings have shown successful fouling release ability in recent years. To further enhance the design of silicone coatings, it is necessary to fully understand the mechanisms that contribute to their performance. The objective of this study was to examine the relationship [...] Read more.
Silicone elastomer coatings have shown successful fouling release ability in recent years. To further enhance the design of silicone coatings, it is necessary to fully understand the mechanisms that contribute to their performance. The objective of this study was to examine the relationship between the molecular weight of polydimethylsiloxane (PDMS) and antibioadhesion efficiency. PDMS-based coatings were prepared via a condensation reaction, with a controlled molecular weight ranging from 0.8 to 10 kg·mol−1. To evaluate changes in surface wettability and morphology, contact angle experiments and atomic force microscopy (AFM) were performed. Finally, the antibioadhesion and self-cleaning performance of PDMS coatings was carried out during in situ immersion in Lorient harbor for 12 months. Despite small variations in surface properties depending on the molecular weight, strong differences in the antibioadhesion performance were observed. According to the results, the best antibioadhesion efficiency was obtained for coatings with an Mn between 2 and 4 kg·mol−1 after 12 months. This paper provides for the first time the impact of the molecular weight of PDMS on antibioadhesion efficiency in a real marine environment. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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42 pages, 24325 KiB  
Review
Overview of Surface Modification Techniques for Titanium Alloys in Modern Material Science: A Comprehensive Analysis
by Kang Gao, Yun Zhang, Junhao Yi, Fang Dong and Pinghu Chen
Coatings 2024, 14(1), 148; https://doi.org/10.3390/coatings14010148 - 21 Jan 2024
Cited by 1 | Viewed by 1391
Abstract
Titanium alloys are acclaimed for their remarkable biocompatibility, high specific strength, excellent corrosion resistance, and stable performance in high and low temperatures. These characteristics render them invaluable in a multitude of sectors, including biomedicine, shipbuilding, aerospace, and daily life. According to the different [...] Read more.
Titanium alloys are acclaimed for their remarkable biocompatibility, high specific strength, excellent corrosion resistance, and stable performance in high and low temperatures. These characteristics render them invaluable in a multitude of sectors, including biomedicine, shipbuilding, aerospace, and daily life. According to the different phases, the alloys can be broadly categorized into α-titanium and β-titanium, and these alloys demonstrate unique properties shaped by their respective phases. The hexagonal close-packed structure of α-titanium alloys is notably associated with superior high-temperature creep resistance but limited plasticity. Conversely, the body-centered cubic structure of β-titanium alloys contributes to enhanced slip and greater plasticity. To optimize these alloys for specific industrial applications, alloy strengthening is often necessary to meet diverse environmental and operational demands. The impact of various processing techniques on the microstructure and metal characteristics of titanium alloys is reviewed and discussed in this research. This article systematically analyzes the effects of machining, shot peening, and surface heat treatment methods, including surface quenching, carburizing, and nitriding, on the structure and characteristics of titanium alloys. This research is arranged and categorized into three categories based on the methods of processing and treatment: general heat treatment, thermochemical treatment, and machining. The results of a large number of studies show that surface treatment can significantly improve the hardness and friction mechanical properties of titanium alloys. At present, a single treatment method is often insufficient. Therefore, composite treatment methods combining multiple treatment techniques are expected to be more widely used in the future. The authors provide an overview of titanium alloy modification methods in recent years with the aim of assisting and promoting further research in the very important and promising direction of multi-technology composite treatment. Full article
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12 pages, 2632 KiB  
Article
Electrochemical Properties of LaMO3(M=Cr, Mn, and Co) Perovskite Materials
by Hongquan Zhao, Qiudong Zhu, Xin Ye, Lei Wang and Songtao Dong
Coatings 2024, 14(1), 147; https://doi.org/10.3390/coatings14010147 - 21 Jan 2024
Viewed by 872
Abstract
The utilization of lanthanide perovskite oxides as electrode materials for supercapacitors has garnered significant interest owing to their excellent electrical conductivity, low cost, and excellent thermal stability. In this study, LaMO3(M=Cr, Mn, and Co) nanoparticles were prepared by the sol–gel method [...] Read more.
The utilization of lanthanide perovskite oxides as electrode materials for supercapacitors has garnered significant interest owing to their excellent electrical conductivity, low cost, and excellent thermal stability. In this study, LaMO3(M=Cr, Mn, and Co) nanoparticles were prepared by the sol–gel method coupled with a calcination process. To evaluate the microstructures, morphologies, and electrochemical properties of the samples, a variety of techniques were employed, including X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area measurements, cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) cycling, and electrochemical impedance spectroscopy (EIS). The results revealed that the LaCoO3 electrodes exhibited a maximum specific capacitance of 118.4 F/g at a current density of 1 A/g, attributed to its higher concentration of oxygen vacancy, larger specific surface area, and lower charge transfer resistance. This discovery substantiates the notion that the electrochemical efficacy is enhanced with the diminishing B-site cation radius in the perovskite LaMO3 system. The charge–discharge process was employed to investigate the anion-intercalation mechanism of LaMO3(M=Cr, Mn, and Co). Full article
(This article belongs to the Topic Properties of the Corroding Interface)
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17 pages, 4276 KiB  
Article
Revolutionizing Construction Safety with Geopolymer Composites: Unveiling Advanced Techniques in Manufacturing Sandwich Steel Structures Using Formwork-Free Spray Technology
by Van Su Le and Kinga Setlak
Coatings 2024, 14(1), 146; https://doi.org/10.3390/coatings14010146 - 21 Jan 2024
Viewed by 896
Abstract
The article discusses the fabrication of sandwich steel and geopolymer structures using spray technology without the need for formwork. In the article, the effects of high temperatures on geopolymer materials are analyzed and their mechanical properties and durability are examined. The importance of [...] Read more.
The article discusses the fabrication of sandwich steel and geopolymer structures using spray technology without the need for formwork. In the article, the effects of high temperatures on geopolymer materials are analyzed and their mechanical properties and durability are examined. The importance of geopolymer coatings for steel protection is also highlighted, and specific features such as the setting time, application process, attachment strength, fire testing, and production costs are analyzed. The materials and methods used in the study are described, including the composition of geopolymer binders and the process of applying geopolymer coatings to steel plates. The research includes test methods such as strength tests, density tests, thermal conductivity tests, accelerated aging tests, microstructure analyses, pore size analyses, and fire resistance tests. The research section concludes with a summary of the chemical and phase composition of the materials and a discussion of the fire resistance of the geopolymer composites (GCs). The results show that GC foams offer excellent thermal insulation, providing up to 75 min of fire resistance with a 6 mm coating, reducing temperatures by 150 °C compared to uncoated steel. GC foams have a density of 670 kg/m3, a thermal conductivity of 0.153 W/m∙K, and a cost effectiveness of USD 250 per cubic meter. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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18 pages, 15413 KiB  
Article
Evaluation of the Wear Properties and Corrosion Resistance of 52100 Steel Coated with Ni/CrC by Cold Spraying
by Fabian Cezar Lupu, Corneliu Munteanu, Sinan Müftü, Marcelin Benchea, Ramona Cimpoesu, Gehn Ferguson, Sam Boese, Patricia Schwartz, Bogdan Istrate and Vlad Nicolae Arsenoaia
Coatings 2024, 14(1), 145; https://doi.org/10.3390/coatings14010145 - 21 Jan 2024
Viewed by 713
Abstract
Coatings deposited by the cold particle gas spray method have shown significant potential for enhancing the properties of metals. We investigated the wear characteristics and corrosion behavior of 52100 steel coated with a mixture of Ni/chromium carbide (Ni/CrC) particles. These coatings exhibited high [...] Read more.
Coatings deposited by the cold particle gas spray method have shown significant potential for enhancing the properties of metals. We investigated the wear characteristics and corrosion behavior of 52100 steel coated with a mixture of Ni/chromium carbide (Ni/CrC) particles. These coatings exhibited high density and were devoid of cracks, closely adhering to the substrate’s surface. Microscratch resistance testing revealed strong resilience, with the apparent friction coefficient exhibiting multiple peaks as the displacement varied. The determination of the friction coefficient, utilizing linear and rotational sliding tests, displayed a brief transition period. This occurred as the apparent contact area expanded until it reached an equilibrium state, with the large asperities being smoothed out and the remaining particles on the sliding track acting as an abrasive material, resulting in higher friction coefficient values. Electro-corrosion tests confirmed the near-intact condition of the deposited layer. Few compounds were detected in the electrolyte solution, resulting in significantly lower oxidation in the layer compared to the base material. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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12 pages, 5843 KiB  
Article
Influence of the Gas Flow Rate on the Crack Formation of AlCoCrNi High-Entropy Metallic Film Fabricated Using Magnetron Sputtering
by Young-Soon Kim, Hae-Jin Park, Young-Seok Kim, Sung-Hwan Hong and Ki-Buem Kim
Coatings 2024, 14(1), 144; https://doi.org/10.3390/coatings14010144 - 21 Jan 2024
Viewed by 721
Abstract
In the present study, the AlCoCrNi high-entropy metallic film was deposited on a Si wafer using a magnetron sputtering system. To capture the effects of the sputtering parameters on the microstructure and mechanical properties of the film, the flow rate of Ar gas [...] Read more.
In the present study, the AlCoCrNi high-entropy metallic film was deposited on a Si wafer using a magnetron sputtering system. To capture the effects of the sputtering parameters on the microstructure and mechanical properties of the film, the flow rate of Ar gas injected into the chamber (5, 7, and 8 sccm) was controlled. All films were identified as being of BCC phase with compositions of near equiatomic proportions, regardless of the gas flow rates. Nano-scale clusters were observed on the surfaces of all films, and nano-cracks were found in the film deposited at the Ar gas flow rate of 8 sccm, unlike the films deposited at the gas flow rates of 5 and 7 sccm. Detailed microstructural analysis of film deposition at an Ar gas flow rate of 8 sccm indicated that the void boundaries contribute to the formation of nano-cracks. The nano-indentation results indicated that the Ar gas flow rate 5 sccm specimen, with the smallest cluster size at the topmost surface, showed the highest hardness (12.21 ± 1.05 GPa) and Young’s modulus (188.1 ± 11 GPa) values. Full article
(This article belongs to the Special Issue Advanced High-Entropy Materials and Coatings)
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12 pages, 2086 KiB  
Article
Composite Right/Left-Handed Leaky-Wave Antenna with Electrical Beam Scanning Using Thin-Film Ferroelectric Capacitors
by Roman Platonov, Andrey Altynnikov, Andrey Komlev, Andrey Tumarkin and Andrey Kozyrev
Coatings 2024, 14(1), 143; https://doi.org/10.3390/coatings14010143 - 21 Jan 2024
Viewed by 726
Abstract
This article presents a wide-angle-scanning leaky-wave antenna (LWA) based on a composite right/left-handed (CRLH) transmission line. In contrast to traditional semiconductor elements, thin-film ferroelectric capacitors were implemented in the CRLH unit cells to enable electric beam scanning. The proposed CRLH LWA has a [...] Read more.
This article presents a wide-angle-scanning leaky-wave antenna (LWA) based on a composite right/left-handed (CRLH) transmission line. In contrast to traditional semiconductor elements, thin-film ferroelectric capacitors were implemented in the CRLH unit cells to enable electric beam scanning. The proposed CRLH LWA has a single-layer design without metalized vias and is compatible with PCB and thin-film technologies. To fabricate the CRLH LWA prototype, dielectric material substrates and thin-film ferroelectric capacitors were manufactured, and their characteristics were investigated. Double-sided metalized fluoroplast-4 reinforced with fiberglass with a permittivity of 2.5 was used as a substrate for CRLH LWA prototyping. A solid solution of barium strontium titanate (BaxSr1xTiO3) with a composition of x=0.3 was used as a ferroelectric material in electrically tunable capacitors. The characteristics of the manufactured ferroelectric thin-film capacitors were measured at a frequency of 1 GHz using the resonance method. The capacitors have a tunability of about two and a quality factor of about 50. The antenna prototype consists of ten units with a total length of 1.25 wavelengths at the operating frequency of close to 2.4 GHz. The experimental results demonstrate that the main beam can be shifted within the range of −40 to 16 degrees and has a gain of up to 3.2 dB. The simple design, low cost, and excellent wide-angle scanning make the proposed CRLH LWA viable in wireless communication systems. Full article
(This article belongs to the Section Thin Films)
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15 pages, 16308 KiB  
Article
Tetrahedral Amorphous Carbon Coatings with Al Incorporation Deposited by a Hybrid Technique of Sputtering and Arc Evaporation
by Wei Dai, Yunzhan Shi, Qimin Wang and Junfeng Wang
Coatings 2024, 14(1), 142; https://doi.org/10.3390/coatings14010142 - 21 Jan 2024
Viewed by 708
Abstract
In this paper, tetrahedral amorphous carbon (ta-C) coatings containing Al were deposited by a hybrid technique of sputtering and arc evaporation. The influence of Al incorporation in the structure and properties of the ta-C coatings were studied as a function of the Al [...] Read more.
In this paper, tetrahedral amorphous carbon (ta-C) coatings containing Al were deposited by a hybrid technique of sputtering and arc evaporation. The influence of Al incorporation in the structure and properties of the ta-C coatings were studied as a function of the Al concentration. It is found that Al tends to form a Al-O-C bond when the Al concentration is small. An Al-C bond was detected when the Al concentration is high. Al can facilitate the graphitization of the ta-C coatings and the graphite cluster size as well as the sp2/sp3 ratio of the coatings increase as the Al concentration increases. The decline of the sp3 fraction causes the drop in the hardness of the coatings. The incorporation of Al can effectively decrease the residual stress of the ta-C coatings. During friction tests, Al can facilitate the formation of the sp2-rich graphitic tribo-layer and decrease the friction coefficient. Nevertheless, the decline of the hardness due to the Al incorporation will result in the increase in the wear rate of the coating. It is believed that the ta-C coating with a proper concentration of Al appears to achieve a good comprehensive performance with high hardness, low residual stress, and a low friction coefficient and wear rate. Full article
(This article belongs to the Special Issue Advances in Deposition and Characterization of Hard Coatings)
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15 pages, 15094 KiB  
Article
Formation and Electrochemical Properties of Heterostructured Electrodes Based on Cu2O and CuCo2O4
by Anna A. Murashkina, Aida V. Rudakova, Tair V. Bakiev, Alexei V. Emeline and Detlef W. Bahnemann
Coatings 2024, 14(1), 141; https://doi.org/10.3390/coatings14010141 - 20 Jan 2024
Viewed by 909
Abstract
Individual (FTO/Cu2O and FTO/CuCo2O4) and heterostructured (FTO/BiVO4/Cu2O, FTO/BiVO4/CuCo2O4, and FTO/CuCo2O4/Cu2O) electrodes were successfully formed using the electrodeposition method on copper-containing compounds. [...] Read more.
Individual (FTO/Cu2O and FTO/CuCo2O4) and heterostructured (FTO/BiVO4/Cu2O, FTO/BiVO4/CuCo2O4, and FTO/CuCo2O4/Cu2O) electrodes were successfully formed using the electrodeposition method on copper-containing compounds. The morphology of the synthesized electrode systems, which affect the electrochemical properties, was determined. A comparative study of the electrochemical and photoelectrochemical properties of the individual and heterostructured electrodes showed that the modification of the BiVO4 electrode surface with Cu2O and CuCo2O4 oxides led to a significant increase in its efficiency as a photoanode. The deposition of Cu2O nanoclusters onto CuCo2O4 nanoflakes increased the electrochemical stability of the electrode while maintaining its high capacitance. Full article
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21 pages, 9909 KiB  
Article
Mutual Impact of Four Organic Calcium Salts on the Formation and Properties of Micro-Arc Oxidation Coatings on AZ31B Magnesium Alloys
by Changtian Chen, Xiaoting Shi, Shufang Zhang, Youliang Shen, Ying Zhao, Rongfa Zhang and Rongfang Zhao
Coatings 2024, 14(1), 140; https://doi.org/10.3390/coatings14010140 - 20 Jan 2024
Viewed by 808
Abstract
Calcium phosphate (Ca–P) coatings provide an effective approach in current research and the clinical application of Mg alloys by endowing them with improved corrosion resistance, biocompatibility, and even bioactivity. Ca-containing coatings were prepared on AZ31B magnesium alloys using the micro-arc oxidation (MAO) technique [...] Read more.
Calcium phosphate (Ca–P) coatings provide an effective approach in current research and the clinical application of Mg alloys by endowing them with improved corrosion resistance, biocompatibility, and even bioactivity. Ca-containing coatings were prepared on AZ31B magnesium alloys using the micro-arc oxidation (MAO) technique and a combination of ethylenediaminetetraacetic acid calcium disodium (EDTA–Ca), calcium glycerophosphate (GP–Ca), calcium gluconate (CaGlu2), and calcium lactate (CaLac2) as the Ca source in a near-neutral solution. The respective and mutual impacts of the four calcium salts on the formation and properties of the coatings were investigated. Experimental results indicated that GP–Ca was more decisive than EDTA–Ca, CaGlu2, and CaLac2 in the formation, morphology, and, therefore, the corrosion resistance of the coatings. GP–Ca alone could not effectively incorporate Ca2+ ions into the coatings but it could combine with EDTA–Ca, CaGlu2, and CaLac2 to bring a synergistic effect in improving the Ca content of the coatings. The bifunctional structure of CaGlu2 and CaLac2, containing hydroxyl groups and carboxylic groups with anchoring effects, enabled them to enhance the Ca content of the coatings. However, due to minor differences in functional group orientation, CaGlu2 was a little more efficient than CaLac2 in increasing Ca content, while CaLac2 was a little more efficient than CaGlu2 in improving the corrosion resistance of the coatings. Finally, the total concentration of the four calcium salts, [Ca2+]T, should be controlled at a proper level; otherwise, excessively high [Ca2+]T would produce localized microbumps originating from coating ablation, eventually deteriorating the corrosion resistance of the coatings. Full article
(This article belongs to the Special Issue Advances in Corrosion-Resistant Coatings, 2nd Edition)
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32 pages, 18782 KiB  
Review
Effects of Rare Earths on Microstructure and Wear Resistance in Metal Additive Manufacturing: A Review
by Dingding Xiang, Di Wang, Tingfang Zheng and Yu Chen
Coatings 2024, 14(1), 139; https://doi.org/10.3390/coatings14010139 - 20 Jan 2024
Cited by 2 | Viewed by 950
Abstract
Rare earth elements (REEs) doping technology can effectively control the microstructure and improve the quality and performance of materials. This paper summarizes the research progress of REEs in metal additive manufacturing (MAM) in recent years and briefly introduces the effects of REEs on [...] Read more.
Rare earth elements (REEs) doping technology can effectively control the microstructure and improve the quality and performance of materials. This paper summarizes the research progress of REEs in metal additive manufacturing (MAM) in recent years and briefly introduces the effects of REEs on the molten pool fluidity, purified structure, and interfacial bonding between the molten cladding layer and substrate. It focuses on the mechanism of the role of REEs in the refinement and homogenization of microstructures, including grain growth, columnar to equiaxed transition (CET), and elemental segregation. The reasons for the influence of REEs on the homogenization of the structure and elemental segregation are analyzed. The effects of REE type, content, and dimension on hardness and wear resistance are investigated. Finally, tribological applications of REEs in biological and high-temperature environments are summarized, and the impact of REEs-modified alloys is summarized and prospected. Full article
(This article belongs to the Special Issue Tribological Properties and Wear Protection of Coatings and Alloys)
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13 pages, 3189 KiB  
Article
Exploring the Influence of the Deposition Parameters on the Properties of NiTi Shape Memory Alloy Films with High Nickel Content
by André V. Fontes, Patrícia Freitas Rodrigues, Daniela Santo and Ana Sofia Ramos
Coatings 2024, 14(1), 138; https://doi.org/10.3390/coatings14010138 - 20 Jan 2024
Viewed by 715
Abstract
NiTi shape memory alloy films were prepared by magnetron sputtering using a compound NiTi target and varying deposition parameters, such as power density, pressure, and deposition time. To promote crystallization, the films were heat treated at a temperature of 400 °C for 1 [...] Read more.
NiTi shape memory alloy films were prepared by magnetron sputtering using a compound NiTi target and varying deposition parameters, such as power density, pressure, and deposition time. To promote crystallization, the films were heat treated at a temperature of 400 °C for 1 h. For the characterization, scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, synchrotron X-ray diffraction, and nanoindentation techniques were used on both as-deposited and heat-treated films. Apart from the morphology and hardness of the as-deposited films that depend on the deposition pressure, the power applied to the target and the deposition pressure did not seem to significantly influence the characteristics of the NiTi films studied. After heat treatment, austenitic (B2) crystalline superelastic films with exceptionally high nickel content (~60 at.%) and vein-line cross-section morphology were produced. The crystallization of the films resulted in an increase in hardness, Young’s modulus, and elastic recovery. Full article
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16 pages, 14656 KiB  
Article
Investigation of Microhole Quality of Nickel-Based Single Crystal Superalloy Processed by Ultrafast Laser
by Dongxu Zhang, Zhichao Song, Zhuang Luo, Xiaoyue Guo and Zhixun Wen
Coatings 2024, 14(1), 137; https://doi.org/10.3390/coatings14010137 - 20 Jan 2024
Viewed by 807
Abstract
The geometric accuracy and surface quality of thin-film cooling holes have a significant impact on the cooling efficiency and fatigue life of aeroengine turbine blades. In this paper, we conducted experimental research on the processing of nickel-based single-crystal high-temperature alloy DD6 flat plates [...] Read more.
The geometric accuracy and surface quality of thin-film cooling holes have a significant impact on the cooling efficiency and fatigue life of aeroengine turbine blades. In this paper, we conducted experimental research on the processing of nickel-based single-crystal high-temperature alloy DD6 flat plates using different femtosecond laser processes. Our focus was on analyzing the effects of various laser parameters on the geometric accuracy results of microholes and the quality of the surfaces and inner walls of these holes. The results demonstrate that femtosecond laser processing has great influence on the geometrical accuracy and surface quality results of film cooling holes. Notably, the average laser power, focus position, and feed volume exert a significant influence on the geometric accuracy results of microholes. For instance, a higher laser power can damage the microhole wall, thereby leading to the formation of tiny holes and cracks. Additionally, microholes exhibit optimal roundness and taper values when using a zero defocus volume. Moreover, increasing the feed distance results in enhanced entrance and exit roundness, whereas scanning speed has a negligible impact on microhole roundness. Full article
(This article belongs to the Special Issue Advanced Surface Technology and Application)
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23 pages, 8101 KiB  
Article
Reliability Evaluation of EB-PVD Thermal Barrier Coatings in High-Speed Rotation and Gas Thermal Shock
by Weiliang Yan, Cong Li, Zhiyuan Liu, Chunyu Cheng and Li Yang
Coatings 2024, 14(1), 136; https://doi.org/10.3390/coatings14010136 - 19 Jan 2024
Viewed by 751
Abstract
The uncertain service life of thermal barrier coatings (TBCs) imposes constraints on their secure application. In addressing this uncertainty, this study employs the Monte Carlo simulation method for reliability evaluation, quantifying the risk of TBC peeling. For reliability evaluation, the failure mode needs [...] Read more.
The uncertain service life of thermal barrier coatings (TBCs) imposes constraints on their secure application. In addressing this uncertainty, this study employs the Monte Carlo simulation method for reliability evaluation, quantifying the risk of TBC peeling. For reliability evaluation, the failure mode needs to be studied to determine failure criteria. The failure mode of high-speed rotating TBCs under gas thermal shock was studied by combining fluid dynamics simulations and experiments. Based on the main failure mode, the corresponding failure criterion was established using the energy release rate, and its limit state equation was derived. After considering the dispersion of parameters, the reliability of TBCs was quantitatively evaluated using failure probability and sensitivity analysis methods. The results show that the main mode is the fracture of the ceramic layer itself, exhibiting a distinctive top-down “step-like” thinning and peeling morphology. The centrifugal force emerges as the main driving force for this failure mode. The failure probability value on the top side of the blade is higher, signifying that coating failure is more likely at this location, aligning with the experimental findings. The key parameters influencing the reliability of TBCs are rotation speed, temperature, and the thermal expansion coefficient. This study offers a valuable strategy for the secure and reliable application of TBCs on aeroengine turbine blades. Full article
(This article belongs to the Special Issue Preparation and Failure Mechanism of Thermal Barrier Coatings)
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12 pages, 3620 KiB  
Article
In-Depth Understanding of the Chemical Stripping Mechanism of AlSiY Coatings on Nickel Superalloys by First-Principles Calculation
by Hongying Li, Chaoyong Luo, Ce Zhang, Lei Wu, Xiaolong Zhou, Chengsong Zhang, Yang Wang and Zhiwu Wang
Coatings 2024, 14(1), 135; https://doi.org/10.3390/coatings14010135 - 19 Jan 2024
Viewed by 620
Abstract
In order to repair a failed AlSiY coating on aeroengine turbine components, the AlSiY coating was stripped using a nitric acid-based removal reagent. The homogeneity of chemical stripping was evaluated and the stripping mechanism was clarified using first-principles calculations. The effects of hydrofluoric [...] Read more.
In order to repair a failed AlSiY coating on aeroengine turbine components, the AlSiY coating was stripped using a nitric acid-based removal reagent. The homogeneity of chemical stripping was evaluated and the stripping mechanism was clarified using first-principles calculations. The effects of hydrofluoric acid (HF) and chromium trioxide (CrO3) on the homogeneity of chemical stripping were investigated by calculating the electronic work functions (EWFs) of the stripped surfaces. The results showed that the stripped surfaces of the AlSiY coating exhibited a serrated appearance when it was etched by a single nitric acid solution, indicating severely inhomogeneous stripping. With the addition of HF and/or CrO3, the homogeneity of chemical stripping could be greatly improved, which was attributed to the increased EWF of the (200) surface and the decreased EWF of the (110) surface, causing the corrosion cathode to transition from the (110) surface to the (200) surface. The HF+CrO3+HNO3 mixed reagent was the optimal combination for the uniform stripping of the AlSiY coating, while the inner layer was not broken. The Al atoms on the surface could be preferentially removed due to the strong bonding with acid ions. The research method proposed in the present work will provide a new means to design chemical removal reagents. Full article
(This article belongs to the Special Issue Coating Technologies Involving Surface Adsorption and Diffusion)
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12 pages, 5382 KiB  
Article
Evolution of Microstructure and Mechanical Properties of Novel Al-Mg-Mn-Ag-Cr-Zr Alloy
by Huan Wang, Tao Liu, Yanli Wu and Cheng Guo
Coatings 2024, 14(1), 134; https://doi.org/10.3390/coatings14010134 - 19 Jan 2024
Viewed by 707
Abstract
In order to reinforce the mechanism of Ag in 5xxx aluminum alloys with low magnesium, research on the microstructure and mechanical properties of an Al-Mg-Mn-Ag-Cr-Zr alloy was conducted using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness measurement, and [...] Read more.
In order to reinforce the mechanism of Ag in 5xxx aluminum alloys with low magnesium, research on the microstructure and mechanical properties of an Al-Mg-Mn-Ag-Cr-Zr alloy was conducted using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), hardness measurement, and tensile testing. The as-cast microscopic structure of the alloy comprises the Al6(Mn, Fe) phase and the T-Mg32(Al, Ag)49 phase. Changes in the characteristics of the investigated alloy were clear during the aging process. Based on the findings obtained from TEM and SAED analysis, it was evident that the predominant strengthening phase during the peak-aged stage is the β″ phase, observed when the alloy is aged for 24 h at 160 °C. The β″ phase had a L12-type crystal lattice architecture and presented a completely coherent relevance with the Al-matrix. The lattice parameter, a, of the β″ phase was 0.408 nm. The mechanical properties of the peak-aged alloy increased greatly as compared to the as-quenched alloy. The tensile strength exhibited a rise from 410 MPa to 449 MPa, representing a 9.5% increase, while the yield strength demonstrated an increase from 185 MPa to 273 MPa, indicating a significant enhancement of 47.5%. The method used in the present study has solved the problem of 5xxx aluminum alloys not being heat treatable for strengthening to a significant degree, considerably improving the alloy strength. In addition, new methods and foundations for exploiting new-type Al-Mg based alloys and developing high-strength aluminum alloys are provided in this study. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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11 pages, 3861 KiB  
Article
Preparation of Metal–Organic-Framework-Derived Fe-CN@CoCN Nanocomposites and Their Microwave Absorption Performance
by Shuning Ren, Pengfei Ju, Haojie Yu, Bohua Nan, Li Wang, Aizhen Lian, Xusheng Zang and Hongyu Liang
Coatings 2024, 14(1), 133; https://doi.org/10.3390/coatings14010133 - 19 Jan 2024
Viewed by 760
Abstract
Microwave technology is commonly used in many fields such as wireless communication and medical treatment, which are closely related to social development. However, electromagnetic pollution caused by microwaves is gradually increasing and the demand for high-performance microwave absorption materials is also increasing. Porous [...] Read more.
Microwave technology is commonly used in many fields such as wireless communication and medical treatment, which are closely related to social development. However, electromagnetic pollution caused by microwaves is gradually increasing and the demand for high-performance microwave absorption materials is also increasing. Porous materials obtained by the pyrolysis of metal–organic frameworks (MOFs) at high temperatures exhibit good conductivity and magnetism, and the original skeleton structure of MOFs can be maintained; thus, MOF-derived materials can be considered viable candidates of microwave absorption materials. In this paper, Fe-CN@CoCN materials were prepared by pyrolyzing a ferrocene (Fc)-doped core–shell zeolite imidazole framework (Fc-ZIF-8@ZIF-67) at 700, 800, and 900 °C for 2 h in an Ar atmosphere. The obtained Fe-CN@CoCN-0.25-700 nanocomposite exhibited excellent microwave absorption (MA) performance with a minimum reflection loss (RLmin) of −42.27 dB at 5.68 GHz and an effective absorption bandwidth (EAB, RL < −10 dB) of 4.80 GHz at a thickness of 2.5 mm. The Fe-CN@CoCN-0.25-800 nanocomposite possessed optimized MA properties with an RLmin of −40.78 dB at 12.56 GHz and an EAB of 4.16 GHz at relatively low thickness of 2 mm. Fe-CN@CoCN nanocomposites are expected to be efficient materials for microwave absorption coatings. Full article
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12 pages, 3439 KiB  
Article
Aluminum Co-Deposition via DC Magnetron Sputtering for Enhanced Pitting Resistance of Copper–Nickel Alloys
by Sang-Du Yun, Yeonwon Kim, Jun-Seok Lee, Jung-Pil Noh, Beom-Soo Kim, Jae-Sung Kwon, Sung-Woong Choi and Jeong-Hyeon Yang
Coatings 2024, 14(1), 132; https://doi.org/10.3390/coatings14010132 - 19 Jan 2024
Viewed by 824
Abstract
To investigate the improvements in the resistance of Cu–Ni alloys to surface pitting corrosion, Cu–Ni thin films containing Al were fabricated via DC magnetron sputtering. The morphologies of the fabricated samples were obtained using a scanning electron microscopy, which yielded information on the [...] Read more.
To investigate the improvements in the resistance of Cu–Ni alloys to surface pitting corrosion, Cu–Ni thin films containing Al were fabricated via DC magnetron sputtering. The morphologies of the fabricated samples were obtained using a scanning electron microscopy, which yielded information on the crystal size and sample surface before and after corrosion tests. X-ray diffraction was employed for the structural characterization of the as-deposited films, and vibrational spectroscopy was used to verify the corrosion products. The corrosion behaviors of the Cu–Ni and Cu–Ni–Al samples were examined using electrochemical polarization and cyclic corrosion tests. The Al co-deposited samples showed a refined crystal size as compared to the Cu–Ni sample, suggesting that they are more susceptible to the formation of a passivation film. The corrosion current density of the Cu–Ni–Al was reduced, and the corrosion potential was lower than that without Al content. The negative shift in the corrosion potential of the Al-containing samples indicates that the Al2O3 film suppressed the cathodic reaction, resulting in a decrease in the corrosion rate. These results are consistent with the cyclic corrosion test results, in which no pitting corrosion is observed in the Cu–Ni–Al sample. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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13 pages, 2622 KiB  
Article
Carbon Dot-Titanium Dioxide (CD/TiO2) Nanocomposites: Reusable Photocatalyst for Sustainable H2 Production via Photoreforming of Green Organic Compounds
by Pinelopi P. Falara, Maria Antoniadou, Adamantia Zourou, Elias Sakellis and Konstantinos V. Kordatos
Coatings 2024, 14(1), 131; https://doi.org/10.3390/coatings14010131 - 19 Jan 2024
Viewed by 1037
Abstract
The present work focuses on TiO2 modification with carbon dots (CDs) using a hydrothermal process, which results in the synthesis of CD/TiO2 nanocomposite photocatalysts characterized by exceptional optoelectronic properties. The structural and physicochemical properties of the obtained nanocomposites, which contained varying [...] Read more.
The present work focuses on TiO2 modification with carbon dots (CDs) using a hydrothermal process, which results in the synthesis of CD/TiO2 nanocomposite photocatalysts characterized by exceptional optoelectronic properties. The structural and physicochemical properties of the obtained nanocomposites, which contained varying amounts of CDs, were precisely assessed. HR-TEM analysis showed that the prepared nanocomposites consisted of rod-shaped TiO2 nanoparticles and CDs well-dispersed on their surface. The optical properties of the nanocomposites were studied using UV–vis diffuse reflectance spectroscopy. All CD/TiO2 samples presented decreased energy gap values compared with bare TiO2 samples; the band gap was further decreased as the CD concentration rose. Electrochemical measurements revealed that the presence of CDs improved the photocurrent response of the TiO2, presumably due to enhanced charge separation and decreased recombination. The synthesized nanomaterials were used as photocatalysts to produce hydrogen via the photoreforming of ethanol and glycerol green organic compounds, under 1-sun illumination. The photocatalytic experiments confirmed that the optimum loading of CDs corresponded to a percentage of 3% (w/w). Ethanol photoreforming led to a H2 production rate of 1.7 μmol∙min−1, while in the case of the glycerol sacrificial agent, the corresponding rate was determined to be 1.1 μmol∙min−1. The recyclability study revealed that the photocatalyst exhibited consistent stability during its reuse for hydrogen production in the presence of both ethanol and glycerol. Full article
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10 pages, 4795 KiB  
Communication
Shoulder-Restricted Friction Deposition for Aluminum Alloy Coatings on Titanium Alloys
by Yuanhang Guo, Jihong Dong, Zongliang Lv, Yuming Xie, Yongxian Huang and Xiangchen Meng
Coatings 2024, 14(1), 130; https://doi.org/10.3390/coatings14010130 - 19 Jan 2024
Viewed by 805
Abstract
In order to solve the problem of a thin deposition layer on the titanium alloy in the traditional friction surfacing process of dissimilar Ti/Al metals, new shoulder-restricted friction deposition (SRFD) equipment was successfully developed by introducing a restricted shoulder. Using a laser to [...] Read more.
In order to solve the problem of a thin deposition layer on the titanium alloy in the traditional friction surfacing process of dissimilar Ti/Al metals, new shoulder-restricted friction deposition (SRFD) equipment was successfully developed by introducing a restricted shoulder. Using a laser to roughen the titanium substrate, the process verification of Al deposition onto TC4 was realized. The material utilization was close to 100%, and a deposition layer with a thickness of 0.8 mm and a strong bonded interface was obtained. The peel strength of the triple-layer deposited joints was 121 MPa. Full article
(This article belongs to the Topic Development of Friction Stir Welding and Processing)
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13 pages, 10244 KiB  
Article
Effects of Fibre-Reinforced Plastic Wedge-Stick Slope on the Performance of Wind-Turbine Blade Root Connections
by Yuanrong Sun, Yihang Qu, Congli Hu, Peiyu Qi, Huawei Liu and Jianbo Li
Coatings 2024, 14(1), 129; https://doi.org/10.3390/coatings14010129 - 18 Jan 2024
Viewed by 807
Abstract
Bushing-insert connections have emerged as efficient blade root connection designs. Bushing-insert connections with fibre-reinforced plastic (FRP) wedge-sticks enhance the strength and stability of the blade root, prevent stress concentration at the blade root, and improve the service life and reliability of the blade. [...] Read more.
Bushing-insert connections have emerged as efficient blade root connection designs. Bushing-insert connections with fibre-reinforced plastic (FRP) wedge-sticks enhance the strength and stability of the blade root, prevent stress concentration at the blade root, and improve the service life and reliability of the blade. However, studies on the failure mechanisms of the FRP wedge-sticks in bushing-insert connections are scarce. Hence, in this study, the influence of the FRP wedge-stick on the structural performance of the blade root was analysed by changing the slope of the FRP wedge-stick’s inclined surface at a constant thickness. The finite element method, sample testing, and full-size blade testing method were employed, and structural verification was conducted using an 84.5 m blade. The results reveal that the contact area of the inclined surface can be increased by reducing the slope of the FRP wedge-stick. This increase in area reduces the stress transmitted to each node of the FRP wedge-stick and blade root, prevents delamination of the FRP wedge-stick and blade root, and enhances the reliability of the blade root connection. Full article
(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)
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14 pages, 6687 KiB  
Article
Microstructure and Properties of FeAlC-x(WC-Co) Composite Coating Prepared through Plasma Transfer Arc Cladding
by Baiyang Chen, Bo Zhang, Daming Zhao, Peihu Gao, Anton Naumov, Qibao Li, Fei Li, Zhong Yang, Yongchun Guo, Jianping Li, Baolong Wu, Jinyuan Gong and Jiawei Liu
Coatings 2024, 14(1), 128; https://doi.org/10.3390/coatings14010128 - 18 Jan 2024
Viewed by 792
Abstract
Tungsten carbide (WC) is widely used in wear-resistant parts due to its excellent wear resistance. Iron-based alloys are used in the repair and remanufacturing of engine components due to their good compatibility with iron-based workpieces. In order to enhance the wear resistance of [...] Read more.
Tungsten carbide (WC) is widely used in wear-resistant parts due to its excellent wear resistance. Iron-based alloys are used in the repair and remanufacturing of engine components due to their good compatibility with iron-based workpieces. In order to enhance the wear resistance of engine components in service under abrasive conditions, composite coatings have been prepared for cast iron engine components by adding WC-Co to iron-based powders. This study investigates the microstructure and wear properties of composite coatings of iron-based alloys reinforced with different contents of WC particles. The composite coatings mainly contained γ-Fe, α-Fe, WC and Fe3W3C. With the addition of the WC-Co strengthening phase, the average hardness of the FeAlC-x(WC-Co) composite coatings increases from 524 HV0.2 to 814 HV0.2. Wear test results showed that when the WC addition was 20%, it had the lowest frictional coefficient of 0.5 and the lowest wear mass loss of 1.3 mg. Compared to the original Fe-based alloy coatings, the WC particle-reinforced FeAlC composite coatings display improved wear resistance on a reduced friction basis, mainly benefiting from the high wear resistance of the graphite solid lubrication phase and carbides in the cladding. Full article
(This article belongs to the Section Tribology)
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20 pages, 3582 KiB  
Review
Progress on the Properties of Ceramic Phase-Reinforced High-Entropy Alloy Composite Coatings Produced via Laser Cladding
by Haoran Zhang, Yaowei Yong, Fuwei Wang, Yuan Liang, Lin Liu, Hong Liu and Yang Gao
Coatings 2024, 14(1), 127; https://doi.org/10.3390/coatings14010127 - 18 Jan 2024
Viewed by 1295
Abstract
The production of ceramic phase-reinforced high-entropy alloy composite coatings with excellent mechanical properties, high-temperature oxidation resistance, and corrosion resistance via laser cladding is a new hotspot in the field of surface engineering. However, as high-entropy alloys have a wide range of constituent systems [...] Read more.
The production of ceramic phase-reinforced high-entropy alloy composite coatings with excellent mechanical properties, high-temperature oxidation resistance, and corrosion resistance via laser cladding is a new hotspot in the field of surface engineering. However, as high-entropy alloys have a wide range of constituent systems and different kinds of ceramic particles are introduced in different ways that give the coatings unique microscopic organization, structure, and synthesized performance, it is necessary to review the methods of preparing ceramic phase-reinforced high-entropy alloys composite coatings via laser cladding. In this paper, the latest research progress on laser cladding technology in the preparation of ceramic phase-reinforced high-entropy alloy composite coatings is first reviewed. On this basis, the effects of ceramic particles, alloying elements, process parameters, and the microstructure and properties of the coatings are analyzed with the examples of the in situ generation method and the externally added method. Finally, research gaps and future trends are pointed out, serving as a reference for the subsequent research, application, and development of the preparation of ceramic phase-reinforced high-entropy alloy composite coatings. Full article
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11 pages, 3617 KiB  
Article
Improved Heat Dissipation of Dip-Coated Single-Walled Carbon Nanotube/Mesh Sheets with High Flexibility and Free-Standing Strength for Thermoelectric Generators
by Katsuma Miura, Takuya Amezawa, Saburo Tanaka and Masayuki Takashiri
Coatings 2024, 14(1), 126; https://doi.org/10.3390/coatings14010126 - 18 Jan 2024
Cited by 1 | Viewed by 802
Abstract
Single-walled carbon nanotubes (SWCNTs) are promising thermoelectric materials used in thermoelectric generators (TEGs) to power sensors. However, the limitation of SWCNTs is their high thermal conductivity, which makes it difficult to create a sufficient temperature difference. In this study, we fabricated dip-coated SWCNT/mesh [...] Read more.
Single-walled carbon nanotubes (SWCNTs) are promising thermoelectric materials used in thermoelectric generators (TEGs) to power sensors. However, the limitation of SWCNTs is their high thermal conductivity, which makes it difficult to create a sufficient temperature difference. In this study, we fabricated dip-coated SWCNT/mesh sheets using an SWCNT dispersion. Several types of mesh materials were tested, and the most suitable material was polyphenylene sulfide (PPS). SWCNTs were uniformly deposited on the PPS mesh surface without filling the mesh openings. The SWCNT/PPS mesh sheets exhibited flexibility and free-standing strength. When the edge of the SWCNT/PPS mesh sheets were heated, a higher temperature gradient was produced compared with that of the conventional SWCNT film owing to the increase in heat dissipation. A flexible and free-standing TEG with an area of 1200 mm2, fabricated using SWCNT/PPS mesh sheets, exhibited an output voltage of 31.5 mV and maximum power of 631 nW at a temperature difference of 60 K (Tlow: 320 K). When the TEG was exposed to wind at 3 m/s, temperature difference further increased, and the performance of the TEG increased by a factor of 1.3 for output voltage and 1.6 for maximum power. Therefore, we demonstrated that the TEG’s performance could be improved using SWCNT/PPS mesh sheets. Full article
(This article belongs to the Special Issue Thermoelectric Thin Films for Thermal Energy Harvesting)
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21 pages, 24896 KiB  
Article
The Influence of the Q-SUN and UV-B Irradiation on the Antiviral Properties of the PP Films Covered with the Coatings Based on ZnO Nanoparticles and TiO2
by Małgorzata Mizielińska and Artur Bartkowiak
Coatings 2024, 14(1), 125; https://doi.org/10.3390/coatings14010125 - 17 Jan 2024
Viewed by 744
Abstract
The purpose of this research was to analyze the antiviral activity of coatings based on ZnO nanoparticles and TiO2. The goal was also to investigate the influence of accelerated UV-B and Q-SUN irradiation on their effectiveness. The results of the performed [...] Read more.
The purpose of this research was to analyze the antiviral activity of coatings based on ZnO nanoparticles and TiO2. The goal was also to investigate the influence of accelerated UV-B and Q-SUN irradiation on their effectiveness. The results of the performed analysis demonstrated that only one of four coatings containing nanoparticles demonstrated high antiviral activity. Q-SUN irradiation had a positive influence on the antiviral properties of the other three coatings. After 24 h of accelerated irradiation, these coatings demonstrated moderate antiviral effectiveness, confirming that Q-SUN irradiation improved the properties of the active layers (by activating ZnO nanoparticles and TiO2). Unfortunately, after 48 h of irradiation, the activity of the coatings decreased, confirming that the irradiation time should not be too long. Comparing the influence of the UV-B irradiation on the coating activity to the Q-SUN irradiation, it has to be mentioned that UV-B irradiation (24 h) also improved the antiviral properties of the three coatings, which were not active before irradiation. However, it decreased the activity of the coating that was active before UV aging. Unfortunately, none of those analyzed coatings were active after 48 h of UV-B irradiation, confirming that the irradiation time should be shorter. Full article
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34 pages, 11868 KiB  
Review
Eco-Sustainable Approaches to Prevent and/or Eradicate Fungal Biodeterioration on Easel Painting
by Agustí Sala-Luis, Haizea Oliveira-Urquiri, Pilar Bosch-Roig and Susana Martín-Rey
Coatings 2024, 14(1), 124; https://doi.org/10.3390/coatings14010124 - 17 Jan 2024
Viewed by 1463
Abstract
Eliminating and controlling fungal biodeterioration is one of the most important challenges of easel painting conservation. Historically, the pathologies produced by biodeterioration agents had been treated with non-specific products or with biocides specially designed for conservation but risky for human health or the [...] Read more.
Eliminating and controlling fungal biodeterioration is one of the most important challenges of easel painting conservation. Historically, the pathologies produced by biodeterioration agents had been treated with non-specific products or with biocides specially designed for conservation but risky for human health or the environment due to their toxicity. In recent years, the number of research that studied more respectful solutions for the disinfection of paintings has increased, contributing to society’s efforts to achieve the Sustainable Development Goals (SDGs). Here, an overview of the biodeterioration issues of the easel paintings is presented, critically analyzing chemical and eco-sustainable approaches to prevent or eradicate biodeterioration. Concretely, Essential Oils and light radiations are studied in comparison with the most used chemical biocides in the field, including acids, alcohols, and quaternary ammonium salts. This review describes those strategies’ biocidal mechanisms, efficiency, and reported applications in vitro assays on plates, mockups, and real scale. Benefits and drawbacks are evaluated, including workability, easel painting material alterations, health risks, and environmental sustainability. This review shows innovative and eco-friendly methods from an easel painting conservation perspective, detecting its challenges and opportunities to develop biocontrol strategies to substitute traditional chemical products. Full article
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32 pages, 12789 KiB  
Article
SEM-Guided Finite Element Simulation of Thermal Stresses in Multilayered Suspension Plasma-Sprayed TBCs
by Mohamed Amer, Ahmed Abdelgawad, Nicholas Curry, Muhammad Arshad, Qamar Hayat, Vit Janik, Jon Nottingham and Mingwen Bai
Coatings 2024, 14(1), 123; https://doi.org/10.3390/coatings14010123 - 17 Jan 2024
Viewed by 890
Abstract
This study presents novel insights into thermal stress development and crack propagation mechanisms in single- and multilayered suspension plasma-sprayed (SPS) coatings of gadolinium zirconate (GZ) and yttria-stabilized zirconia (YSZ), thermally treated at 1150 °C. By combining image processing with finite element simulation, we [...] Read more.
This study presents novel insights into thermal stress development and crack propagation mechanisms in single- and multilayered suspension plasma-sprayed (SPS) coatings of gadolinium zirconate (GZ) and yttria-stabilized zirconia (YSZ), thermally treated at 1150 °C. By combining image processing with finite element simulation, we pinpointed sites of high-stress concentration in the coatings, leading to specific cracking patterns. Our findings reveal a dynamic shift in the location of stress concentration from intercolumnar gaps to pores near the top coat/thermally grown oxide (TGO) interface with TGO thickening at elevated temperatures, promoting horizontal crack development across the ceramic layers. Significantly, the interface between the ceramic layer and TGO was found to be a critical area, experiencing the highest levels of both normal and shear stresses. These stresses influence failure modes: in double-layer SPS structures, relatively higher shear stresses can result in mode II failure, while in single-layer systems, the predominant normal stresses tend to cause mode I failure. Understanding stress behavior and failure mechanisms is essential for enhancing the durability of thermal barrier coatings (TBCs) in high-temperature applications. Therefore, by controlling the interfaces’ roughness along with improving interfacial toughness, the initiation and propagation of cracks can be delayed along these interfaces. Moreover, efforts to optimize the level of microstructural discontinuities, such as intercolumnar gaps and pores, within the creaming layer and close to the TGO interface should be undertaken to reduce crack formation in the TBC system. Full article
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15 pages, 4542 KiB  
Article
The Constitutive Equation-Based Recrystallization Mechanism of Ti-6Al-4V Alloy during Superplastic Forming
by Caihong Chang and Junzhou Yang
Coatings 2024, 14(1), 122; https://doi.org/10.3390/coatings14010122 - 16 Jan 2024
Cited by 1 | Viewed by 721
Abstract
The present paper is concerned with the dynamic recrystallization of the Ti-6Al-4V alloy. Electron Backscatter Diffraction (EBSD) observations are performed after high-temperatures tensile tests, with the temperature ranging from 700 to ~950 °C, and the strain rates varying between 10−4 and 10 [...] Read more.
The present paper is concerned with the dynamic recrystallization of the Ti-6Al-4V alloy. Electron Backscatter Diffraction (EBSD) observations are performed after high-temperatures tensile tests, with the temperature ranging from 700 to ~950 °C, and the strain rates varying between 10−4 and 10−2/s. Based on the analysis of flow behavior, the dominant mechanism is identified, and a mechanism map is proposed. In particular, the conditions of 890 °C and strain rates ranging from 10−3 to ~10−2/s serve as the delineating boundary of dynamic recovery (DRV) and dynamic recrystallization (DRX). For superplastic deformation, the dominant softening mechanism is DRV. Consequently, the occurrence of continuous dynamic recrystallization (CDRX) can naturally be ascribed to the process of grain refinement. Then, a multi-scales physical-based constitutive model of CDRX is developed, demonstrating a good agreement is obtained between the experimental and calculated grain sizes, so the above model could be used to describe the grain growth for superplastic deformation. In conclusion, DRV and DRX in the superplastic forming of Ti-6Al-4V are studied in this study, the condition boundaries of their occurrence are distinguished, and a constitutive equation-based CDRX recrystallization mechanism is given, which might be employed in the fracture mechanism research. Full article
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