Coatings

23 pages, 38190 KiB

Open AccessEditor’s ChoiceArticle

Effect of Grain Sizes on the Friction and Wear Behavior of Dual-Phase Microstructures with Similar Macrohardness and Composition

by Corentin Penfornis, Abdeljalil Jourani and Pierre-Emmanuel Mazeran

Coatings 2023, 13(3), 533; https://doi.org/10.3390/coatings13030533 - 28 Feb 2023

Cited by 3 | Viewed by 3581

Abstract

The tribological behavior of dual-phase steels have been studied at the macroscopic scale taking the macrohardness as the main material property to control friction and wear. However, the contribution to the macroscopic behavior of the varying properties of the phase at the microscopic [...] Read more.

The tribological behavior of dual-phase steels have been studied at the macroscopic scale taking the macrohardness as the main material property to control friction and wear. However, the contribution to the macroscopic behavior of the varying properties of the phase at the microscopic scale are yet to be fully understood. In this study, dual-phase microstructures with various grain sizes and martensite volume fraction are generated. Microhardness of ferrite and martensite are measured by nanoindentation tests while their friction and wear behavior are studied by conducting scratch tests with various conical tips. Results show that for martensite, friction coefficient and wear resistance are proportional to its carbon content, whatever the martensite grain size. Whereas changing the ferrite grain size has two effects on the tribological behavior of the microstructure. First, the friction and wear resistance of ferrite are related to its grain size through a Hall–Petch relationship. Second, at a given martensite volume fraction, the mean wear resistance changes from the Equal Wear mode to the Equal Pressure mode as the ratio of the contact size to the ferrite grain size increases, while the mean friction coefficient always correlates to the Equal Pressure mode. Full article

(This article belongs to the Special Issue Surface Modification for Improving the Performance of Engineering Components)

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18 pages, 2586 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Controlled Release of β-CD-Encapsulated Thyme Essential Oil from Whey Protein Edible Packaging

by Andreea Lanciu Dorofte, Cristian Dima, Alina Ceoromila, Andreea Botezatu, Rodica Dinica, Iulia Bleoanca and Daniela Borda

Coatings 2023, 13(3), 508; https://doi.org/10.3390/coatings13030508 - 24 Feb 2023

Cited by 5 | Viewed by 2221

Abstract

Whey edible films (EFs) functionalized with essential oils have a high potential to be used on various foods due to their antimicrobial and antioxidant activities. Encapsulation is applied for a better retention of volatiles in EFs; however, the functional properties of EFs are [...] Read more.

Whey edible films (EFs) functionalized with essential oils have a high potential to be used on various foods due to their antimicrobial and antioxidant activities. Encapsulation is applied for a better retention of volatiles in EFs; however, the functional properties of EFs are modified. The properties of EFs containing thyme essential oil (TEO) encapsulated by co-precipitation in β-CD, developed in three formulae, with inclusion complexes (EF/IC1, EF/IC2, and EF/IC3, respectively) in 15:85, 26:74, and 35:65 mass ratios were studied. Thymol is the main volatile in the ICs with TEO/β-CD (50%–60% of the total volatiles). In comparison with EF/TEO, all three formulae with EF/ICs had better, but similar, WVPs (p > 0.05). The EF/IC2 displayed a different FTIR profile than EF/IC1 and EF/IC3, suggesting a smaller number of free functional groups. The EF/IC2 showed better transparency in comparison with EF/IC1 and EF/IC3. All EF/ICs moderately inhibited R. glutinis, with the strongest activity registered by EF/IC3 (p < 0.05), but did not inhibit G. candidum, while showing a strong antibacterial activity against B. cereus. All EF/ICs inhibited 65%–70% of the total free radicals. The EF/ICs ensured a gradual release of VOCs in food simulants, with a higher rate in 95% ethanol than in water. These results have demonstrated the properties of EF/ICs with TEO/β-CD as bioactive packaging systems for foods. Full article

(This article belongs to the Special Issue Edible Coatings and Films for Food and Medical Applications)

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12 pages, 3619 KiB

Open AccessEditor’s ChoiceArticle

The Design and Characterization of New Chitosan, Bioglass and ZnO-Based Coatings on Ti-Zr-Ta-Ag

by Mariana Prodana, Daniela Ionita, Andrei Bogdan Stoian, Ioana Demetrescu, Geanina Valentina Mihai and Marius Enăchescu

Coatings 2023, 13(3), 493; https://doi.org/10.3390/coatings13030493 - 23 Feb 2023

Cited by 4 | Viewed by 3289

Abstract

The starting point of this study is a new alloy with rare metals such as Ta and Zr that has Ag in the composition, proven antibacterial properties. New coatings on Ti-Zr-Ta-Ag capable of improving the alloys’ properties and to be suitable for more [...] Read more.

The starting point of this study is a new alloy with rare metals such as Ta and Zr that has Ag in the composition, proven antibacterial properties. New coatings on Ti-Zr-Ta-Ag capable of improving the alloys’ properties and to be suitable for more applications have yet to be fabricated. New formulations based on chitosan (Ch) and bioglass (BG) were designed as multifunctional coatings to be deposited from suspensions on the mentioned alloy. To make the suspensions used for deposition, several samples were made containing Ch, BG and ZnO in various mass ratios. A number of solutions with different component ratios were produced and analyzed by ζ potential and Dynamic Light Scattering (DLS) to determine the most stable mixture, which was subsequently deposited on the Ti-Zr-Ta-Ag samples. The mixtures and the samples obtained after applying the coating were characterized from a morphological and compositional standpoint using Scanning Electron Microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and Fourier-transform infrared spectroscopy (FT-IR). Further analyses on the properties of the coating were performed using contact angle and roughness analysis. Zeta potential measurements demonstrated evidence of a good stability of the coatings. The size of the ceramic particles is between 1 and 10 μm. From the SEM, the morphology of all the components from the mixture containing chitosan, bioglass and ZnO are shown to be present on the surface. From the FTIR determination, all the functional groups that appear demonstrated evidence of the presence of BG, ZnO and chitosan. The contact angle values of the coated samples are in the hydrophilic domain but are higher compared to the uncoated alloy values. Such behavior is promising in a potential bioapplication. Full article

(This article belongs to the Special Issue Innovations in Hybrid Biomaterials and Coatings)

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22 pages, 3120 KiB

Open AccessEditor’s ChoiceReview

The Development of Cement-Based, Intumescent and Geopolymer Fire-Retardation Coatings for Metal Structures: A Review

by Kaibao Wang and Huirong Le

Coatings 2023, 13(3), 495; https://doi.org/10.3390/coatings13030495 - 23 Feb 2023

Cited by 15 | Viewed by 3460

Abstract

Coating, as one of the significant applications in the building and construction sector, is crucial to prevent steel from reaching critical temperature and fire-induced structural collapse. This article reviews the current use of conventional coatings and assesses the potential use of novel geopolymer [...] Read more.

Coating, as one of the significant applications in the building and construction sector, is crucial to prevent steel from reaching critical temperature and fire-induced structural collapse. This article reviews the current use of conventional coatings and assesses the potential use of novel geopolymer coatings on the metal substrate, particularly on the steel structure. The conventional passive fireproofing systems, including cement-based coatings and intumescent coatings, exhibit unavoidable limitations either due to the high thickness and weight or poor thermal and chemical resistance of the coating. Thus, innovations in conventional and novel coatings are constantly developing and growing rapidly. In recent years, geopolymer coatings have attracted much attention due to their higher mechanical strength and excellent resistance to chemicals and heat. Moreover, the green and environmentally friendly characteristics make geopolymer an admirable coating material for many applications. The main challenge that lies in the development of geopolymer coating is the interfacial bonding with the metal structure. Therefore, the influencing factors, including precursor materials, alkaline activator, and curing processes on the adhesion and thermal and chemical resistance of the geopolymer coating have been well explored. The performance comparison between these coatings indicates that geopolymer coating offers a superior mechanical and thermal performance, along with a substantially lower environmental impact compared with cement-based coating. This suggests that geopolymer coatings have great potential for fire protection on steel structures. Full article

(This article belongs to the Special Issue Protective Composite Coatings: Implementation, Structure, Properties)

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26 pages, 8662 KiB

Open AccessEditor’s ChoiceReview

An Overview of Technological Parameter Optimization in the Case of Laser Cladding

by Kaiming Wang, Wei Liu, Yuxiang Hong, H. M. Shakhawat Sohan, Yonggang Tong, Yongle Hu, Mingjun Zhang, Jian Zhang, Dingding Xiang, Hanguang Fu and Jiang Ju

Coatings 2023, 13(3), 496; https://doi.org/10.3390/coatings13030496 - 23 Feb 2023

Cited by 59 | Viewed by 6859

Abstract

This review examines the methods used to optimize the process parameters of laser cladding, including traditional optimization algorithms such as single-factor, regression analysis, response surface, and Taguchi, as well as intelligent system optimization algorithms such as neural network models, genetic algorithms, support vector [...] Read more.

This review examines the methods used to optimize the process parameters of laser cladding, including traditional optimization algorithms such as single-factor, regression analysis, response surface, and Taguchi, as well as intelligent system optimization algorithms such as neural network models, genetic algorithms, support vector machines, the new non-dominance ranking genetic algorithm II, and particle swarm algorithms. The advantages and disadvantages of various laser cladding process optimization methods are analyzed and summarized. Finally, the development trend of optimization methods in the field of laser cladding is summarized and predicted. It is believed that the result would serve as a foundation for future studies on the preparation of high-quality laser cladding coatings. Full article

(This article belongs to the Section Laser Coatings)

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26 pages, 4768 KiB

Open AccessEditor’s ChoiceReview

Biosensors in Food and Healthcare Industries: Bio-Coatings Based on Biogenic Nanoparticles and Biopolymers

by Melania Popescu and Camelia Ungureanu

Coatings 2023, 13(3), 486; https://doi.org/10.3390/coatings13030486 - 22 Feb 2023

Cited by 15 | Viewed by 5453

Abstract

Biosensors use biological materials, such as enzymes, antibodies, or DNA, to detect specific analytes. These devices have numerous applications in the health and food industries, such as disease diagnosis, food safety monitoring, and environmental monitoring. However, the production of biosensors can result in [...] Read more.

Biosensors use biological materials, such as enzymes, antibodies, or DNA, to detect specific analytes. These devices have numerous applications in the health and food industries, such as disease diagnosis, food safety monitoring, and environmental monitoring. However, the production of biosensors can result in the generation of chemical waste, which is an environmental concern for the developed world. To address this issue, researchers have been exploring eco-friendly alternatives for immobilising biomolecules on biosensors. One solution uses bio-coatings derived from nanoparticles synthesised via green chemistry and biopolymers. These materials offer several advantages over traditional chemical coatings, such as improved sensitivity, stability, and biocompatibility. In conclusion, the use of bio-coatings derived from green-chemistry synthesised nanoparticles and biopolymers is a promising solution to the problem of chemical waste generated from the production of biosensors. This review provides an overview of these materials and their applications in the health and food industries, highlighting their potential to improve the performance and sustainability of biosensors. Full article

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

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10 pages, 1921 KiB

Open AccessEditor’s ChoiceArticle

A Ru-Doped VTi_2.6O_7.2 Anode with High Conductivity for Enhanced Sodium Storage

by Guangwan Zhang, Chunhua Han, Kang Han, Jinshuai Liu, Jinghui Chen, Haokai Wang, Lei Zhang and Xuanpeng Wang

Coatings 2023, 13(3), 490; https://doi.org/10.3390/coatings13030490 - 22 Feb 2023

Cited by 1 | Viewed by 1835

Abstract

Sodium-ion batteries (SIBs) are considered a potential replacement for lithium-ion batteries in the area of low-cost large-scale energy storage. Due to its low operating voltage, high capacity, non-toxicity and low production cost, titanium dioxide is now among the anode materials under investigation and [...] Read more.

Sodium-ion batteries (SIBs) are considered a potential replacement for lithium-ion batteries in the area of low-cost large-scale energy storage. Due to its low operating voltage, high capacity, non-toxicity and low production cost, titanium dioxide is now among the anode materials under investigation and shows the most promise. However, its poor electrical conductivity is one of the main reasons limiting its large-scale application. Herein, we designed a ruthenium-doped anatase-type VTi_2.6O_7.2 ultrafine nanocrystal (Ru-VTO). As the anode of SIBs, Ru-VTO delivers a high specific capacity of 297 mAh g⁻¹ at 50 mA g⁻¹, a long cycle life of 2000 cycles and a high rate capability (104 mAh g⁻¹ at 1000 mA g⁻¹). The excellent performance may be related to the solid-solution interatomic interactions and the enhanced conductivity after ruthenium doping. These studies demonstrate the potential of Ru-VTO as an anode material for advanced SIBs. Full article

(This article belongs to the Collection Feature Papers of Coatings for Energy Applications)

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16 pages, 3709 KiB

Open AccessEditor’s ChoiceArticle

Enhanced Optically–Excited THz Wave Emission by GaAs Coated with a Rough ITO Thin Film

by Anup Kumar Sahoo, Shi-Ying Kang, Peichen Yu and Ci-Ling Pan

Coatings 2023, 13(2), 461; https://doi.org/10.3390/coatings13020461 - 17 Feb 2023

Cited by 3 | Viewed by 2522

Abstract

In this study, we report enhancement of terahertz (THz) radiation with indium-tin-oxide (ITO) thin-film deposited on semi-insulating gallium arsenide substrate (SI-GaAs). The amplitude of THz emission from both ITO/SI-GaAs and bare SI-GaAs substrate as a function of optical pump (i) incident angle, (ii) [...] Read more.

In this study, we report enhancement of terahertz (THz) radiation with indium-tin-oxide (ITO) thin-film deposited on semi-insulating gallium arsenide substrate (SI-GaAs). The amplitude of THz emission from both ITO/SI-GaAs and bare SI-GaAs substrate as a function of optical pump (i) incident angle, (ii) polarization angle, and (iii) power were investigated. The enhancement of peak amplitude of a THz pulse transmitted through the ITO/SI-GaAs sample in comparison to bare SI-GaAs substrate varied from 100% to 0% when the pump incidence angle changed from 0° to 50°. The maximum enhancement ratio of peak amplitude for a coated sample relative to the bare substrate is approximately up to 2.5 times at the minimum pump intensity of 3.6 TW/m² and gradually decreased to one at the maximum pump intensity of 20 TW/m². From outcomes of these studies, together with data on surface and material characterization of the samples, we show that THz emission originates from the ITO/GaAs interfaces. Further, both interface-field-induced transient current and field-induced optical rectification contribute to the observed THz signal. Observed enhancement was tentatively attributed to surface-plasmon-induced local field enhancement, coupled with constructive interference of forward and retro-reflected backward THz emission from the ITO/GaAs interfaces. The polarity-flip reported previously for very thin Au-coated GaAs was not observed. This was explained by the wide-bandgap, transparency and lower free carriers of ITO. For best results, the incident angle should be in the range of 0 to 30° and the incident polarization should be 0 to 45°. We further predict that the ITO thin film of suitable thickness or with engineered nanostructures, post-annealed under optimum conditions may lead to further enhancement of THz radiation from ITO-coated semiconductor surfaces. Full article

(This article belongs to the Special Issue New Advances in Novel Optical Materials and Devices)

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18 pages, 6282 KiB

Open AccessEditor’s ChoiceArticle

Surface Deformation Recovery by Thermal Annealing of Thermal Plasma Sprayed Shape Memory NiTi Alloys

by Sneha Samal, Jan Tomáštík, Radim Čtvrtlík, Lukáš Václavek, Orsolya Molnárová and Petr Šittner

Coatings 2023, 13(2), 433; https://doi.org/10.3390/coatings13020433 - 15 Feb 2023

Cited by 6 | Viewed by 2828

Abstract

The shape memory effect is the most important attribute of shape memory alloys where material can recover to its initial shape after deformation by heating above its transformation temperature. In this article, the thermally induced recovery of well-defined microscopic deformation in a NiTi [...] Read more.

The shape memory effect is the most important attribute of shape memory alloys where material can recover to its initial shape after deformation by heating above its transformation temperature. In this article, the thermally induced recovery of well-defined microscopic deformation in a NiTi shape memory alloy was investigated. Surface deformation was performed by indenting the plasma sprayed NiTi shape memory alloy in a martensitic phase at room temperature using spherical indenters. In this article, a series of indentations, scratch lines and wear lines were made on the surface of two different NiTi shape memory alloys at the micrometre scale using two spherical indenters with different radii. Three-dimensional imaging of indentation topography using scanning confocal microscopy provided direct evidence of the thermally induced martensitic transformation of these plasma sprayed thick films allowing for partial recovery on the micro-scale. The partial recovery is achieved at various indentation depths and for different scratches and wear volumes. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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12 pages, 1306 KiB

Open AccessEditor’s ChoiceArticle

Evaluating the Fungal Pathogens’ Inhibition Efficiency of Composite Film Combined with Antagonistic Yeasts and Sodium Alginate on Peach

by Xiaolong Du, Shaobin Li, An Luo, Xiaoli Yin, Kai Fan, Linyun Mou and Jianlong Li

Coatings 2023, 13(2), 417; https://doi.org/10.3390/coatings13020417 - 12 Feb 2023

Cited by 3 | Viewed by 1929

Abstract

To reduce the indiscriminate use of pesticides and extend the postharvest shelf life of peach fruit (Prunus persica, cv. Baihua) from southeast China, mainly the microbial antagonism of indigenous yeasts was studied and applied in the construction of composite film. In [...] Read more.

To reduce the indiscriminate use of pesticides and extend the postharvest shelf life of peach fruit (Prunus persica, cv. Baihua) from southeast China, mainly the microbial antagonism of indigenous yeasts was studied and applied in the construction of composite film. In this study, 14 yeast strains of 9 genera were screened out from the surface of peaches by isolation, purification, cultivation, and identification. Through an experimental analysis of the in vitro inhibition zone and the in vivo colonizing capacity, 1 × 10⁸ CFU mL⁻¹ of Candida oleophila sp-ELPY12B and Cryptococcus laurentii sp-ELPY15A proved most efficient against the major pathogens and were chosen as candidate fungicides. In combination with Na-alginate film (0.4% glycerin as the plasticizer and 0.1% Tween-80 as the emulsifier), the preservative effects of these composite-treated groups also showed the best antifungal effects, which significantly delayed the postharvest preservation period by about 6–7 d under an ambient temperature of 25 ± 3 °C and a relative humidity of 50–70%. Full article

(This article belongs to the Special Issue Edible Films and Coatings with Tailored Features for Improvement of Food Quality)

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13 pages, 6780 KiB

Open AccessEditor’s ChoiceArticle

Antifouling Coatings Fabricated by Laser Cladding

by Shuwen Wang, Yang Chen, Chunxing Gu, Qingyi Sai, Tianyu Lei and John Williams

Coatings 2023, 13(2), 397; https://doi.org/10.3390/coatings13020397 - 9 Feb 2023

Cited by 21 | Viewed by 2852

Abstract

Laser surface treatment is a very useful technology for the fabrication of functional surfaces. In this study, novel antifouling surfaces are fabricated by laser cladding of TC4 and Ni60 mixed materials in various mass ratios on the surfaces of 316L stainless steel substrates. [...] Read more.

Laser surface treatment is a very useful technology for the fabrication of functional surfaces. In this study, novel antifouling surfaces are fabricated by laser cladding of TC4 and Ni60 mixed materials in various mass ratios on the surfaces of 316L stainless steel substrates. Parametric studies are carried out to investigate the effects of the mixed powder mass ratios and laser cladding parameters on the antifouling performance of the laser clad coatings (LCCs). The antifouling mechanism of the LCCs is investigated by using the water contact angle/surface energy measurement, scanning electron microscope (SEM) surface observation, and phase composition analysis via XRD (X-ray diffractometer) testing. The experimental results show that the LCCs with Ni60/TC4 mass ratio of 3/7 has better antifouling performance in this study. The antifouling performance of the LCC decreases with the increase in laser scanning speed. Surface energy and surface topography have a significant effect on the antifouling performance of LCCs. In order to get the optimal antifouling performance of LCCs, the Ni60/TC4 mass ratio and laser cladding parameters should be optimized. Full article

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10 pages, 1984 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Tribo-Catalytic Conversions of H₂O and CO₂ by NiO Particles in Reactors with Plastic and Metallic Coatings

by Hua Lei, Xuchao Jia, Hongbo Wang, Xiaodong Cui, Yanmin Jia, Linfeng Fei and Wanping Chen

Coatings 2023, 13(2), 396; https://doi.org/10.3390/coatings13020396 - 9 Feb 2023

Cited by 14 | Viewed by 5968

Abstract

NiO has been found to be highly outstanding in producing H₂ and O₂ from H₂O through magnetic stirring, while its capability for the reduction of CO₂ through mechanical stimulation has not been investigated. Presently, NiO particles have been [...] Read more.

NiO has been found to be highly outstanding in producing H₂ and O₂ from H₂O through magnetic stirring, while its capability for the reduction of CO₂ through mechanical stimulation has not been investigated. Presently, NiO particles have been employed to promote the conversion of H₂O and CO₂ enclosed in reactors into flammable gases through magnetic stirring. For a 150 mL glass reactor filled with 50 mL water, 1.00 g of NiO particles, and 1 atm of CO₂, 24 h of magnetic stirring using a home-made Teflon magnetic rotary disk resulted in the formation of 33.80 ppm CO, 10.10 ppm CH₄, and 12,868.80 ppm H₂. More importantly, the reduction of CO₂ was found to be substantially enhanced through coating some polymers and metals on the reactor bottoms, including 25.64 ppm CO and 70.97 ppm CH₄ obtained for a PVC-coated reactor and 30.68 ppm CO, 52.78 ppm CH₄, 3.82 ppm C₂H₆, and 2.18 ppm C₂H₄ obtained for a stainless steel-coated reactor. Hydroxyl radicals were detected using fluorescence spectroscopy for NiO particles under magnetic stirring in water. A tribo-catalytic mechanism has been proposed for the conversion of H₂O and CO₂ into flammable gases by NiO particles under magnetic stirring that is based on the excitation of electron-hole pairs in NiO by mechanical energy absorbed through friction. These findings not only reveal a great potential for mechanical energy to be utilized for CO₂ conversion but are also valuable for fundamental studies. Full article

(This article belongs to the Special Issue Advanced Materials for Electrocatalysis and Energy Storage)

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14 pages, 4988 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Argon/Hydrogen Inductively Coupled Plasma for Carbon Removal over Multilayer Thin Films

by Yi Wang, Tim Gehring, Qihao Jin, Jan Dycke and Rainer Kling

Coatings 2023, 13(2), 368; https://doi.org/10.3390/coatings13020368 - 6 Feb 2023

Cited by 4 | Viewed by 4213

Abstract

Inductively coupled plasma with an argon/hydrogen (Ar/H₂) mixture is a potential solution to many surface treatment problems, especially when encountering carbon contamination in optical X-ray and extreme ultraviolet instruments. Removing carbon contamination on multilayer thin films with Ar/H₂ plasma extends [...] Read more.

Inductively coupled plasma with an argon/hydrogen (Ar/H₂) mixture is a potential solution to many surface treatment problems, especially when encountering carbon contamination in optical X-ray and extreme ultraviolet instruments. Removing carbon contamination on multilayer thin films with Ar/H₂ plasma extends the lifetime of the above devices. To further investigate the reaction between plasma and carbon, both optical emission spectroscopy and finite element method with multiphysics fields were employed. The results demonstrated that the intensities of the Balmer lines were in good agreement with the densities of the radical hydrogen atoms from the simulation model, showing a dependence on the mixing ratio. At an electrical input power of 165 W and a total pressure of 5 Pa, an optimum mixing ratio of about 35 ± 5 % hydrogen produced the highest density of hydrogen radicals, coinciding with the highest carbon removal rate. This shows that the carbon removal with Ar/H₂ plasma was mainly controlled by the density of hydrogen radicals, and the mixing ratio showed a significant impact on the removal rates. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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17 pages, 3114 KiB

Open AccessEditor’s ChoiceReview

A Review on Ceramic Matrix Composites and Environmental Barrier Coatings for Aero-Engine: Material Development and Failure Analysis

by Guangwu Fang, Xiguang Gao and Yingdong Song

Coatings 2023, 13(2), 357; https://doi.org/10.3390/coatings13020357 - 4 Feb 2023

Cited by 35 | Viewed by 5345

Abstract

Ceramic matrix composites with environmental barrier coatings (CMC/EBCs) are the most promising material solution for hot section components of aero-engines. It is necessary to access relevant information and knowledge of the physical properties of various CMC and EBCs, the characteristics of defects and [...] Read more.

Ceramic matrix composites with environmental barrier coatings (CMC/EBCs) are the most promising material solution for hot section components of aero-engines. It is necessary to access relevant information and knowledge of the physical properties of various CMC and EBCs, the characteristics of defects and damages, and relevant failure mechanisms. Then, effective failure prediction models can be established. Individually assessing the failure of CMC and EBCs is not a simple task. Models considering the synergetic effect of coating properties and substrate fibrous architecture are more reasonable and more challenging. This paper offers a review and a detailed description of the materials features, failure mechanism, and failure modeling for both CMC substrate and EBC coatings. The various methods for failure analyses and their pros and cons are discussed. General remarks on technical development for failure modeling are summarized subsequently. Full article

(This article belongs to the Section Laser Coatings)

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18 pages, 4118 KiB

Open AccessEditor’s ChoiceArticle

Graphitic Layered Structures Enhancing TiNT Catalyst Photo-Electrochemical Behaviour

by Rosalba Passalacqua, Salvatore Abate, Federica De Luca, Siglinda Perathoner and Gabriele Centi

Coatings 2023, 13(2), 358; https://doi.org/10.3390/coatings13020358 - 4 Feb 2023

Cited by 1 | Viewed by 2037

Abstract

The increasing knowledge in nanoscience and materials technology promoted the development of advanced materials with enhanced and unusual properties suitable for sustainable applications ranging from energy to environmental purposes. Here are presented some results from our current investigations on composite semiconducting materials. The [...] Read more.

The increasing knowledge in nanoscience and materials technology promoted the development of advanced materials with enhanced and unusual properties suitable for sustainable applications ranging from energy to environmental purposes. Here are presented some results from our current investigations on composite semiconducting materials. The investigated composites have been prepared from different nitrogen precursors and thin films of TiO₂ nanotubes. The synergy between hetero-structures based on graphitic-C₃N₄ and thin films of titania nanotubes obtained by anodisation was studied. The composites have been characterised with several complementary techniques to evidence the relation between photo-behaviour and the composition of the samples. This study allows new insights into the nature of the specific enhanced properties due to this synergy among the two compounds. The g-C₃N₄/TiNT heterojunctions showed enhanced photo-electrochemical properties observed from the photocurrent measurements. The as-prepared composites have been investigated as cathode materials in the electrocatalytic reduction of oxalic acid (OX), evidencing the capability of tuning the reaction toward glycolic acid with respect to the pristine TiNT array. The observed Faradic efficiency (FE) for the composites follows the trend: TiNT-U₆ > TiNT-M₆ > TiNT-MU₁₈. TiNT-U₆ shows the best performances (FE_GC = 63.7%; FE_GO = 15.5%; OX conversion = 61. 4%) after 2 h of reaction. The improved photo-electrochemical properties make these materials suitable for H₂ production, solar-light-driven water splitting, and CO₂ reduction applications. Full article

(This article belongs to the Collection Feature Papers of Coatings for Energy Applications)

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11 pages, 5509 KiB

Open AccessEditor’s ChoiceArticle

Improved Performance of Perovskite Deep-Ultraviolet Photodetector Using FAPb(I/Br)₃ as Light Absorption Layer

by Soo Beom Hong, Sangmo Kim and Hyung Wook Choi

Coatings 2023, 13(2), 341; https://doi.org/10.3390/coatings13020341 - 2 Feb 2023

Cited by 2 | Viewed by 2026

Abstract

Constitutive engineering by adding halide anions is one effective way to improve the performance of photodetectors by adjusting the bandgap. In this study, a mixed-anion perovskite thin film was facile fabricated by post-processing of a pure FAPbI₃ film with a formamidinium bromide [...] Read more.

Constitutive engineering by adding halide anions is one effective way to improve the performance of photodetectors by adjusting the bandgap. In this study, a mixed-anion perovskite thin film was facile fabricated by post-processing of a pure FAPbI₃ film with a formamidinium bromide (FABr) solution. In addition, the manufactured thin film was used as the light absorption layer, SnO₂-SDBS as the electron transport layer, and spiro-OMeTAD as the hole injection layer to fabricate a deep ultraviolet(UV) photodetector. The device exhibited a response of 43.8 mA/W⁻¹, a detectability of 3.56 × 10¹³ Jones, and an external quantum efficiency of 38%. Therefore, this study is promising for various applications in the deep-UV wavelength region. Full article

(This article belongs to the Special Issue Optical Thin Film and Photovoltaic (PV) Related Technologies)

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26 pages, 24284 KiB

Open AccessEditor’s ChoiceReview

Polymer@SiO₂ Core–Shell Composite Particles: Preparation and Application

by Na Wang, Hongbin Zhou, Junfang Ren, Gui Gao, Gengrui Zhao, Yawen Yang, Honggang Wang and Jinqing Wang

Coatings 2023, 13(2), 334; https://doi.org/10.3390/coatings13020334 - 1 Feb 2023

Cited by 4 | Viewed by 4624

Abstract

In recent years, core–shell composite particles with organic polymer as the core and inorganic SiO₂ as the shell have attracted widespread attention and prompted robust scientific endeavors. The encapsulation of SiO₂ can endow the polymer core with a variety of important [...] Read more.

In recent years, core–shell composite particles with organic polymer as the core and inorganic SiO₂ as the shell have attracted widespread attention and prompted robust scientific endeavors. The encapsulation of SiO₂ can endow the polymer core with a variety of important properties, and is of great significance for the synthesis of multi–functional materials, having favorable application prospects in coating, polishing, medical, optical, magnetic, lubrication and other fields. In this paper, the recent advances in the preparation of core–shell polymer@SiO₂ composite particles are reviewed. From the perspective of interface bonding mechanisms between the core and the shell, this paper mainly focused on the following five aspects: Pickering stabilization, acid–base interaction, charge interaction, bridging of coupling agent, hydrogen bonding, and other actions. Additionally, applications of core–shell polymer@SiO₂ particles are also discussed. It is expected that this article can provide scientific guidance for the preparation of polymer@SiO₂ core–shell particles, further enriching their species and broadening their applications. Full article

(This article belongs to the Special Issue Thermal and Mechanical Properties of Polymer Based Materials and Adhesives)

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23 pages, 9090 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Motile Gyrotactic Micro-Organisms for the Bioconvection Peristaltic Flow of Carreau–Yasuda Bionanomaterials

by Zahid Nisar and Humaira Yasmin

Coatings 2023, 13(2), 314; https://doi.org/10.3390/coatings13020314 - 31 Jan 2023

Cited by 32 | Viewed by 2377

Abstract

Nanofluids are considered as an effective way to enhance the thermal conductivity of heat transfer fluids. Additionally, the involvement of micro-organisms makes the liquid more stable, which is important in nanotechnology, bio-nano cooling systems, and bio-microsystems. Therefore, the current investigation focused on the [...] Read more.

Nanofluids are considered as an effective way to enhance the thermal conductivity of heat transfer fluids. Additionally, the involvement of micro-organisms makes the liquid more stable, which is important in nanotechnology, bio-nano cooling systems, and bio-microsystems. Therefore, the current investigation focused on the examination of the thermodynamic and mass transfer of a Carreau–Yasuda magnetic bionanomaterial with gyrotactic micro-organisms, which is facilitated by radiative peristaltic transport. A compliant/elastic symmetric channel subject to partial slip constraints was chosen. The features of viscous dissipation and ohmic heating were incorporated into thermal transport. We use the Brownian and thermophoretic movement characteristics of the Buongiorno nanofluid model in this study. A set of nonlinear ordinary differential equations are created from the partial differential equations that control fluid flow. The governing system of differential equations is solved numerically via the shooting technique. The results of pertinent parameters are examined through velocity, temperature, motile micro-organisms, concentration, and heat transfer rate. Full article

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25 pages, 5727 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review on Superhydrophobic Surface with Anti-Icing Properties in Overhead Transmission Lines

by Bo Li, Jie Bai, Jinhang He, Chao Ding, Xu Dai, Wenjun Ci, Tao Zhu, Ruijin Liao and Yuan Yuan

Coatings 2023, 13(2), 301; https://doi.org/10.3390/coatings13020301 - 28 Jan 2023

Cited by 51 | Viewed by 5669

Abstract

The icing on overhead transmission lines is one of the largest threats to the safe operation of electric power systems. Compared with other security accidents in the electric industry, a sudden ice disaster could cause the most serious losses to electric power grids. [...] Read more.

The icing on overhead transmission lines is one of the largest threats to the safe operation of electric power systems. Compared with other security accidents in the electric industry, a sudden ice disaster could cause the most serious losses to electric power grids. Among the numerous de-icing and anti-icing techniques for application, direct current ice-melting and mechanical de-icing schemes require power cuts and other restrictive conditions. Superhydrophobic coating technology has been widely focused for good anti-icing properties, low cost and wide application range. However, the special structure of curved transmission lines, complicated service environments, and variated electric performance could significantly limit the application of superhydrophobic anti-icing coatings on overhead transmission lines. In particular, superhydrophobic surfaces can be achieved by combining the rough micro-nano structure and modification agents with low surface energy. Compared with superhydrophobic coatings, superhydrophobic surfaces will not increase the weight of the substrate and have good durability and stability in maintaining the robust structure to repeatedly resist aging, abrasion, corrosion and corona damages, etc. Therefore, this review summarizes the theoretical basis of anti-icing behavior and mechanisms, influencing factors of anti-icing properties, potential techniques of superhydrophobic surfaces on transmission lines, and, finally, presents future development challenges and prospects of superhydrophobic surfaces in the anti-icing protection of overhead transmission lines. Full article

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

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23 pages, 8402 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Heterostructure Films of SiO₂ and HfO₂ for High-Power Laser Optics Prepared by Plasma-Enhanced Atomic Layer Deposition

by Shawon Alam, Pallabi Paul, Vivek Beladiya, Paul Schmitt, Olaf Stenzel, Marcus Trost, Steffen Wilbrandt, Christian Mühlig, Sven Schröder, Gabor Matthäus, Stefan Nolte, Sebastian Riese, Felix Otto, Torsten Fritz, Alexander Gottwald and Adriana Szeghalmi

Coatings 2023, 13(2), 278; https://doi.org/10.3390/coatings13020278 - 26 Jan 2023

Cited by 9 | Viewed by 4128

Abstract

Absorption losses and laser-induced damage threshold (LIDT) are considered to be the major constraints for development of optical coatings for high-power laser optics. Such coatings require paramount properties, such as low losses due to optical absorption, high mechanical stability, and enhanced damage resistance, [...] Read more.

Absorption losses and laser-induced damage threshold (LIDT) are considered to be the major constraints for development of optical coatings for high-power laser optics. Such coatings require paramount properties, such as low losses due to optical absorption, high mechanical stability, and enhanced damage resistance, to withstand high-intensity laser pulses. In this work, heterostructures were developed by sub-nanometer thin films of SiO₂ and HfO₂ using the plasma-enhanced atomic layer deposition (PEALD) technique. Thin-film characterization techniques, such as spectroscopic ellipsometry, spectrophotometry, substrate curvature measurements, X-ray reflectivity, and Fourier transform infrared spectroscopy, were employed for extracting optical constants, residual stress, layer formation, and functional groups present in the heterostructures, respectively. These heterostructures demonstrate tunable refractive index, bandgap, and improved optical losses and LIDT properties. The films were incorporated into antireflection coatings (multilayer stacks and graded-index coatings) and the LIDT was determined at 355 nm wavelength by the R-on-1 method. Optical absorptions at the reported wavelengths were characterized using photothermal common-path interferometry and laser-induced deflection techniques. Full article

(This article belongs to the Special Issue Optical Properties of Crystals and Thin Films)

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11 pages, 3789 KiB

Open AccessEditor’s ChoiceArticle

Single-Layer MoS₂: A Two-Dimensional Material with Negative Poisson’s Ratio

by Yucheng Zhu, Xiaofei Cao, Yuan Tan, Yao Wang, Jun Hu, Baotong Li and Zhong Chen

Coatings 2023, 13(2), 283; https://doi.org/10.3390/coatings13020283 - 26 Jan 2023

Cited by 10 | Viewed by 3536

Abstract

Negative Poisson’s ratio (NPR) materials have broad applications such as heat dissipation, vibration damping, and energy absorption because of their designability, lightweight quality, and high strength ratio. Here, we use first-principles calculations to find a two-dimensional (2D) auxetic material (space group R [...] Read more.

Negative Poisson’s ratio (NPR) materials have broad applications such as heat dissipation, vibration damping, and energy absorption because of their designability, lightweight quality, and high strength ratio. Here, we use first-principles calculations to find a two-dimensional (2D) auxetic material (space group R

\bar{3}

m), which exhibits a maximum in-plane NPR of −0.0846 and a relatively low Young’s modulus in the planar directions. Calculations show that the NPR is mainly related to its unique zigzag structure and the strong interaction between the 4d orbital of Mo and the 3p orbital of S. In addition, molecular dynamics (MD) simulations show that the structure of this material is thermodynamically stable. Our study reveals that this layered MoS₂ can be a promising 2D NPR material for nanodevice applications. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Performance Enhancement of Electrode and Biomaterial Coatings)

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10 pages, 8986 KiB

Open AccessEditor’s ChoiceArticle

Room Temperature Synthesis of Branched ZnO Nanowires Array with Tunable Morphology

by Wei Zhao, Hsiang-Shun Chang, Kefu Yao and Yang Shao

Coatings 2023, 13(2), 275; https://doi.org/10.3390/coatings13020275 - 25 Jan 2023

Cited by 1 | Viewed by 1692

Abstract

Herein, a novel method is proposed to synthesize B-ZnO NWA by simply immersing the Zn NWA in NaOH solution at room temperature (25 °C). Based on the systematic investigation of various factors that affect the growth of B-ZnO NWA, the growth mechanism of [...] Read more.

Herein, a novel method is proposed to synthesize B-ZnO NWA by simply immersing the Zn NWA in NaOH solution at room temperature (25 °C). Based on the systematic investigation of various factors that affect the growth of B-ZnO NWA, the growth mechanism of B-ZnO NWA is clarified. Guided by the growth mechanism, the control of the morphology of B-ZnO NWA is achieved by adjusting the pore structure of anodized aluminum oxide templates, hot-pressing parameters, NaOH concentration, solution temperature, and immersion time. In contrast to previous reports, the prepared B-ZnO NWA has hollow trunks, which can further increase the specific area of B-ZnO NWA. Considering the facile, environmental, and low-cost synthesis, the prepared B-ZnO NWA with tunable morphology has great prospects in a wide range of applications, especially those related to the conversion and utilization of solar energy, which are gaining increasing interest nowadays. Full article

(This article belongs to the Collection Feature Papers of Coatings for Energy Applications)

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44 pages, 10027 KiB

Open AccessEditor’s ChoiceReview

A Review of Advances in Cold Spray Additive Manufacturing

by Rodolpho Fernando Vaz, Andrea Garfias, Vicente Albaladejo, Javier Sanchez and Irene Garcia Cano

Coatings 2023, 13(2), 267; https://doi.org/10.3390/coatings13020267 - 23 Jan 2023

Cited by 59 | Viewed by 13804

Abstract

Cold Spray Additive Manufacturing (CSAM) produces freeform parts by accelerating powder particles at supersonic speed which, impacting against a substrate material, trigger a process to consolidate the CSAM part by bonding mechanisms. The literature has presented scholars’ efforts to improve CSAM materials’ quality, [...] Read more.

Cold Spray Additive Manufacturing (CSAM) produces freeform parts by accelerating powder particles at supersonic speed which, impacting against a substrate material, trigger a process to consolidate the CSAM part by bonding mechanisms. The literature has presented scholars’ efforts to improve CSAM materials’ quality, properties, and possibilities of use. This work is a review of the CSAM advances in the last decade, considering new materials, process parameters optimization, post-treatments, and hybrid processing. The literature considered includes articles, books, standards, and patents, which were selected by their relevance to the CSAM theme. In addition, this work contributes to compiling important information from the literature and presents how CSAM has advanced quickly in diverse sectors and applications. Another approach presented is the academic contributions by a bibliometric review, showing the most relevant contributors, authors, institutions, and countries during the last decade for CSAM research. Finally, this work presents a trend for the future of CSAM, its challenges, and barriers to be overcome. Full article

(This article belongs to the Special Issue Advanced Cold Spraying Technology)

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13 pages, 782 KiB

Open AccessEditor’s ChoiceReview

Changes in Strength Parameters of Composite Cements as Affected by Storage Temperature—A Review of the Literature

by Joanna Giełzak, Beata Dejak, Jerzy Sokołowski and Kinga Bociong

Coatings 2023, 13(2), 244; https://doi.org/10.3390/coatings13020244 - 20 Jan 2023

Cited by 3 | Viewed by 2489

Abstract

Fixed restorations are now among the most common restorations in modern dental prosthodontics. The current view in prosthodontics of maximum preparation economy is causing an increased interest in the mechanical properties of cements. Among the most important properties of materials used for indirect [...] Read more.

Fixed restorations are now among the most common restorations in modern dental prosthodontics. The current view in prosthodontics of maximum preparation economy is causing an increased interest in the mechanical properties of cements. Among the most important properties of materials used for indirect cementation are mechanical properties, i.e., hardness and compressive strength. These properties can change as a result of changes in physical factors. The purpose of this study was to analyze the available literature on the effect of conditioning temperature of cements used for cementation of indirect fixed restorations on the durability of their bonding to dental tissues and their mechanical and physical properties. The following databases were used: Mendeley, PubMed, ResearchGate, National Library of Medicine, and Google Scholar. Analysis of the available literature was carried out according to the Prisma diagram program. Forty-eight articles were selected, which were the following types of studies: clinical reports, research article, and review articles. Some studies indicated that mechanical properties, such as flexural strength, polymerization shrinkage, and conversion factor, did not change after heating the composite material. According to some researchers, preheating the composite material increased its conversion degree, which consequently led to an increase in hardness and fracture toughness, an increase in flexural strength and an increase in elastic modulus, and an increase in abrasion resistance. Studies on changes in the mechanical and physical properties of composite materials, as well as composite cements, have not always provided clear answers, as there are still no laboratory and clinical studies that fully confirm the benefits of heating composite cements. Conducting studies evaluating the effect of elevated storage temperature on the strength parameters of cements, in conjunction with the type of material and its composition, could provide answers to many clinical questions that are still unresolved. If the benefits of heating cements were unequivocally confirmed in laboratory studies, this could open up many possibilities for improving the retention of fixed prosthetic restorations. Full article

(This article belongs to the Special Issue Surface Properties of Dental Materials and Instruments, 2nd Edition)

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12 pages, 8469 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Characterization of Hydroxyapatite/Chitosan Composite Coating Obtained from Crab Shells on Low-Modulus Ti–25Nb–8Sn Alloy through Hydrothermal Treatment

by Hsueh-Chuan Hsu, Shih-Ching Wu, Chien-Yu Lin and Wen-Fu Ho

Coatings 2023, 13(2), 228; https://doi.org/10.3390/coatings13020228 - 18 Jan 2023

Cited by 12 | Viewed by 2504

Abstract

In this study, hydroxyapatite/chitosan (HA/CS) composite coatings were prepared by hydrothermal treatment on the surface of low-modulus Ti–25Nb–8Sn alloy to improve the surface bioactivity of the alloy. HA, the main mineral composition of the human skeleton, has excellent bioactivity and is often used [...] Read more.

In this study, hydroxyapatite/chitosan (HA/CS) composite coatings were prepared by hydrothermal treatment on the surface of low-modulus Ti–25Nb–8Sn alloy to improve the surface bioactivity of the alloy. HA, the main mineral composition of the human skeleton, has excellent bioactivity and is often used as a surface coating on biometal implants. CS, a natural polymer with good antibacterial, hydrophilic and non-toxic characteristics, is often used as dermal regeneration templates, hemostatic agents and drug delivery systems. In this experiment, a natural crab shell was used as a raw material to prepare the HA/CS composite coating by alkali treatment and hydrothermal reaction at various temperatures. The microstructure, morphology and phase composition of the coating surfaces were analyzed by XRD, SEM, and FTIR, and the sample coated with HA/CS was soaked in simulated body fluid (SBF) to evaluate its bioactivity. The experimental results showed that the HA/CS composite coatings through hydrothermal treatment at various temperatures can be successfully fabricated on the surface of the Ti alloy. HA on the coating surface exhibited mainly spherical particles and contained A- and B-type carbonate. When the hydrothermal temperature was up to 200 °C, the spherical particles were approximately 20–40 nm. An ultrasonic vibration test was used to evaluate the adhesion of the coatings, showing that the CS exhibited significantly improved adhesion capacity to the substrate. After being soaked in SBF for 7 days, apatite was deposited on the entire surfaces of the HA/CS coatings, indicating that the coating possesses excellent bioactivity. Full article

(This article belongs to the Special Issue Synthetic and Biological-Derived Hydroxyapatite Implant Coatings)

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9 pages, 4258 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Tunnel Magnetoresistance-Based Sensor for Biomedical Application: Proof-of-Concept

by Crina Ghemes, Oana-Georgiana Dragos-Pinzaru, Mihai Tibu, Mihaela Lostun, Nicoleta Lupu and Horia Chiriac

Coatings 2023, 13(2), 227; https://doi.org/10.3390/coatings13020227 - 18 Jan 2023

Cited by 5 | Viewed by 3180

Abstract

The aim of this work was to investigate and prove the possibility of the real-time detection of magnetic nanoparticles (MNPs) distributed in solid material by using a tunnel magnetoresistance-based (TMR) sensor. Following the detection tests of FeCrNbB magnetic nanoparticles distributed in transparent epoxy [...] Read more.

The aim of this work was to investigate and prove the possibility of the real-time detection of magnetic nanoparticles (MNPs) distributed in solid material by using a tunnel magnetoresistance-based (TMR) sensor. Following the detection tests of FeCrNbB magnetic nanoparticles distributed in transparent epoxy resin (EPON 812) and measuring the sensor output voltage changes at different particle concentrations, the detection ability of the sensor was demonstrated. For the proposed TMR sensor, we measured a maximum magnetoresistance ratio of about 53% and a sensitivity of 1.24%/Oe. This type of sensor could facilitate a new path of research in the field of magnetic hyperthermia by locating cancer cells. Full article

(This article belongs to the Special Issue Ceramic and Metallic Biomaterials. Application in Medical Sciences)

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10 pages, 8999 KiB

Open AccessEditor’s ChoiceArticle

Hydrothermal Preparation of TiO₂/Graphite Nanosheets Composites and Its Effect on Electrothermal Behavior

by Chunyu Wang, Weiyao Tian, Sibo Kang, Bo Zhong, Chunlin Qin and Hongyang Wang

Coatings 2023, 13(2), 226; https://doi.org/10.3390/coatings13020226 - 18 Jan 2023

Cited by 4 | Viewed by 2109

Abstract

Nowadays, carbon materials are supposed to replace the resistance wire made of metal alloy to be the next generation of heat-generating materials due to their excellent electrical conductivity and corrosion resistance. In this study, TiO₂/graphite nanosheets (GNs) composite was prepared by [...] Read more.

Nowadays, carbon materials are supposed to replace the resistance wire made of metal alloy to be the next generation of heat-generating materials due to their excellent electrical conductivity and corrosion resistance. In this study, TiO₂/graphite nanosheets (GNs) composite was prepared by chemical exfoliation and hydrothermal methods. XRD, FTIR, and Raman spectra confirm TiO₂ particles are on the surface of GNs. SEM photographs show TiO₂ nanoparticles covering the surface of the GNs uniformly. We used TiO₂/GNs and sodium silicate to produce the electrothermal film coated on the glass. As compared to raw GNs, the heating rate and maximum temperature have greatly improved. In order to find the reasons for the improvement, the BET and zeta potential of TiO₂/GNs were tested, and we found that the enhancement of the surface area and the dispersion to the composite by TiO₂ particles and sodium silicate make the distribution of GNs more uniform. Full article

(This article belongs to the Special Issue Thermal and Mechanical Properties of Polymer Based Materials and Adhesives)

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14 pages, 4111 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

All-Inkjet-Printed Ti₃C₂ MXene Capacitor for Textile Energy Storage

by Eugenio Gibertini, Federico Lissandrello, Luca Bertoli, Prisca Viviani and Luca Magagnin

Coatings 2023, 13(2), 230; https://doi.org/10.3390/coatings13020230 - 18 Jan 2023

Cited by 9 | Viewed by 2916

Abstract

The emerging wearable electronics integrated into textiles are posing new challenges both in materials and micro-fabrication strategies to produce textile-based energy storage and power source micro-devices. In this regard, inkjet printing (IJP) offers unique features for rapid prototyping for various thin-film (2D) devices. [...] Read more.

The emerging wearable electronics integrated into textiles are posing new challenges both in materials and micro-fabrication strategies to produce textile-based energy storage and power source micro-devices. In this regard, inkjet printing (IJP) offers unique features for rapid prototyping for various thin-film (2D) devices. However, all-inkjet-printed capacitors were very rarely reported in the literature. In this work, we formulated a stable Ti₃C₂ MXene aqueous ink for inkjet printing current-collector-free electrodes on TPU-coated cotton fabric, together with an innovative inkjet-printable and UV-curable solvent-based electrolyte precursor. The electrolyte was inkjet-printed on the electrode’s surface, and after UV polymerization, a thin and soft gel polymer electrolyte (GPE) was obtained, resulting in an all-inkjet-printed symmetrical capacitor (a-IJPSC). The highest ionic conductivity (0.60 mS/cm) was achieved with 10 wt.% of acrylamide content, and the capacitance retention was investigated both at rest (flat) and under bending conditions. The flat a-IJPSC textile-based device showed the areal capacitance of 0.89 mF/cm² averaged on 2k cycles. Finally, an array of a-IJPSCs were demonstrated to be feasible as both a textile-based energy storage and micro-power source unit able to power a blue LED for several seconds. Full article

(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)

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9 pages, 2250 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Dual-Type Flexible-Film Thermoelectric Generators Using All-Carbon Nanotube Films

by Ryota Konagaya and Masayuki Takashiri

Coatings 2023, 13(1), 209; https://doi.org/10.3390/coatings13010209 - 16 Jan 2023

Cited by 12 | Viewed by 3363

Abstract

The long-term stability of n-type single-walled carbon nanotubes (SWCNTs) in air makes all-carbon thermoelectric generators (TEGs) viable. To increase the performance of TEGs, we developed a dual-type flexible-film thermoelectric generator (DFTEG). The vacuum filtering was used to form p- and n-type SWCNT films [...] Read more.

The long-term stability of n-type single-walled carbon nanotubes (SWCNTs) in air makes all-carbon thermoelectric generators (TEGs) viable. To increase the performance of TEGs, we developed a dual-type flexible-film thermoelectric generator (DFTEG). The vacuum filtering was used to form p- and n-type SWCNT films from ethanol-based dispersion and water-based solutions with cationic surfactant, respectively. DFTEGs were fabricated as follows: strip-shaped p- and n-type SWCNT films were attached on the top and back sides of a polyimide substrate, respectively, and were connected alternately in series by bending copper tapes on the edge of the polyimide substrate. The thermoelectric performance was measured after attaching the DFTEG outside a beaker full of water, where the water surface reached the center of the DFTEG. For a 10 mm long film and 15 p-n pairs, the DFTEG had an output voltage of 40 mV and a maximum power of 891 nW at a temperature difference of 25 K. The measured thermoelectric performance was significantly higher than that of the single-type TEG for almost the same SWCNT films. This result demonstrates that thermoelectric performance can be improved by using DFTEGs that are fabricated with optimum structural designs. Full article

(This article belongs to the Collection Feature Paper Collection in Thin Films)

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15 pages, 3415 KiB

Open AccessEditor’s ChoiceArticle

Abrasive and Erosive Wear of TI6Al4V Alloy with Electrospark Deposited Coatings of Multicomponent Hard Alloys Materials Based of WC and TiB₂

by Todor Penyashki, Georgi Kostadinov, Mara Kandeva, Valentin Kamburov, Antonio Nikolov and Rayna Dimitrova

Coatings 2023, 13(1), 215; https://doi.org/10.3390/coatings13010215 - 16 Jan 2023

Cited by 9 | Viewed by 2335

Abstract

In the present work, abrasive and erosive wear of wear-resistant composite coatings with a complex structure and different phase compositions deposited on titanium surfaces was studied. The coatings were obtained by electrospark deposition (ESD) using two types of hard-alloy compositions: WC–TiB₂–B [...] Read more.

In the present work, abrasive and erosive wear of wear-resistant composite coatings with a complex structure and different phase compositions deposited on titanium surfaces was studied. The coatings were obtained by electrospark deposition (ESD) using two types of hard-alloy compositions: WC–TiB₂–B₄C–Co–Ni–Cr–Si–B and TiB₂–TiAl reinforced with dispersed nanoparticles of ZrO₂ and NbC. The influence of the ESD process parameters on the roughness, thickness, composition, structure and coefficient of friction of the coated surfaces was investigated, and their role in protecting the titanium surfaces from wear was clarified. Dense coatings with the presence of newly formed wear-resistant phases and crystalline-amorphous structures were obtained, with roughness, thickness and microhardness that can be varied by the ESD modes in the range Ra = 2.5 ÷ 4.5 µm, δ = 8 ÷ 30 µm and HV 8.5 ÷ 14.0 GPa. The new coatings were found to reduce the abrasive and erosive wear of the coated surfaces by up to four times. The influence of the geometric characteristics, composition and structure of coatings on the wear intensity and wear resistance of coatings was studied. Full article

(This article belongs to the Special Issue Coatings and Surface Modification for Tribological Applications)

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19 pages, 2632 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Laser Obtained Superhydrophobic State for Stainless Steel Corrosion Protection, a Review

by Kirill A. Emelyanenko, Alexandre M. Emelyanenko and Ludmila B. Boinovich

Coatings 2023, 13(1), 194; https://doi.org/10.3390/coatings13010194 - 15 Jan 2023

Cited by 46 | Viewed by 5612

Abstract

Stainless steel has become an integral part of modern engineering materials and daily life due to its mechanical efficiency, strength, recyclability, high resistance to oxidation and corrosive attack, which make it the ideal material for many kinds of applications. At the same time, [...] Read more.

Stainless steel has become an integral part of modern engineering materials and daily life due to its mechanical efficiency, strength, recyclability, high resistance to oxidation and corrosive attack, which make it the ideal material for many kinds of applications. At the same time, steel suffers from certain types of corrosion, such as intergranular corrosion, or contact corrosion that develops when stainless steel comes into contact with carbon steel or another metal with a different electrochemical potential. Finally, pitting corrosion is a serious problem often occurring when stainless steel parts work in sea water. This paper provides a brief overview of methods for protecting stainless steel from corrosion using a new approach based on superhydrophobization of the surface of stainless steel using laser processing followed by the deposition of a layer of a substance with a low surface energy. The review discusses the mechanisms of corrosion protection by such coatings and the properties of superhydrophobic coatings presented in the literature. Superhydrophobic protective coatings on stainless steel have been shown to significantly reduce corrosion, with some demonstrating a decrease in corrosion current of up to 156 times. However, a more comprehensive analysis of the mechanisms contributing to this effect, as well as a comparison with anti-corrosion coatings on other metals, suggests that the combination of these mechanisms has the potential to create even more durable and effective surfaces for corrosion protection of stainless steel. Full article

(This article belongs to the Collection Feature Paper Collection in Corrosion, Wear and Erosion)

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16 pages, 6883 KiB

Open AccessEditor’s ChoiceArticle

High Temperature Oxidation and Oxyacetylene Ablation Properties of ZrB₂-ZrC-SiC Ultra-High Temperature Composite Ceramic Coatings Deposited on C/C Composites by Laser Cladding

by Kaijin Huang, Yahao Xia and Aihua Wang

Coatings 2023, 13(1), 173; https://doi.org/10.3390/coatings13010173 - 12 Jan 2023

Cited by 8 | Viewed by 2705

Abstract

In order to improve the high temperature oxidation and ablation resistance of C/C composites, ZrB₂-ZrC-SiC ultra-high temperature composite ceramic coatings were prepared on C/C composites by laser cladding using Zr, B₄C, and Si as raw materials. The microstructure of [...] Read more.

In order to improve the high temperature oxidation and ablation resistance of C/C composites, ZrB₂-ZrC-SiC ultra-high temperature composite ceramic coatings were prepared on C/C composites by laser cladding using Zr, B₄C, and Si as raw materials. The microstructure of the coating was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Air isothermal oxidation (1600 °C, 80 min) and oxyacetylene flame ablation (2400 kW/m², 300 s) were used to evaluate the high-temperature oxidation and ablation properties of the coating, respectively. The results show that the microstructure of laser cladding coating is a totem of black and white. The white part is mainly the first solidified high melting point ZrB₂ phase, and the black part is the latter solidified eutectic structure, which is mainly composed of ZrB₂(ZrB₁₂)-ZrC or ZrB₂(ZrB₁₂)-SiC two phases. After oxidation at 1600 °C and 80 min, the coating is mainly composed of ZrO₂ and ZrSiO₄ phases, and ZrSiO₄ is basically distributed among ZrO₂ particles. The high temperature oxidation and ablation properties of the coating are better than the C/C composite matrix, and the mass ablation rate of the coating is about 1/4 of the latter. Full article

(This article belongs to the Special Issue Laser Cladding Coatings: Microstructure, Properties, and Applications)

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11 pages, 2170 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

In Situ and Ex Situ Raman Studies of Cysteine’s Behavior on a Titanium Surface in Buffer Solution

by Dominika Święch, Natalia Piergies, Gaetano Palumbo and Czesława Paluszkiewicz

Coatings 2023, 13(1), 175; https://doi.org/10.3390/coatings13010175 - 12 Jan 2023

Cited by 4 | Viewed by 3036

Abstract

In this paper, surface-enhanced Raman spectroscopy (SERS) was used to investigate the adsorption process of cysteine (Cys). Studies were carried out in the presence of phosphate-buffered saline solution (PBS), at pH 7.4, and acidified to pH 5, 3, and 1, on the surface [...] Read more.

In this paper, surface-enhanced Raman spectroscopy (SERS) was used to investigate the adsorption process of cysteine (Cys). Studies were carried out in the presence of phosphate-buffered saline solution (PBS), at pH 7.4, and acidified to pH 5, 3, and 1, on the surface of Ti for implant application. In situ SERS spectra obtained for the Cys/Ti solution system, after 24 h of immersion time, indicated that the buffer solution strongly influences the adsorption behavior of Cys on the Ti surface. This results in a decrease in Cys adsorption on the Ti surface, in the range of pH 7.4 to 3. The strong interaction between a sulfur atom of Cys and a Ti surface was observed only at pH = 1, under strongly acidic conditions. In contrast, ex situ SERS spectra recorded for the same samples but in a dried Cys/Ti system show a completely different behavior of Cys on the Ti surface. Formation of a disulfide (S-S) bond has occurred as a result of the dimerization or aggregation of Cys molecules on the Ti surface. Detailed analysis of the adsorption behavior of Cys on the Ti surface can be very important in the preparation of bioactive materials (i.e., coated by organic layers). Full article

(This article belongs to the Special Issue Novel Approaches on the Coatings Materials: Biomedical and Industrial Applications)

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11 pages, 3059 KiB

Open AccessEditor’s ChoiceArticle

Antifrictional Effects of Group IVB Elements Deposited as Nanolayers on Anodic Coatings

by Tadas Matijošius, Giedrius Stalnionis, Gedvidas Bikulčius, Sigitas Jankauskas, Laurynas Staišiūnas and Svajus Joseph Asadauskas

Coatings 2023, 13(1), 132; https://doi.org/10.3390/coatings13010132 - 10 Jan 2023

Cited by 2 | Viewed by 1703

Abstract

The utilization of anodized aluminum (Al) components would contribute greatly to combat against dry friction if good tribological properties could be attained. Despite its hardness, the wear rate of anodic coatings presents a major problem in many applications, including automotive, aerospace and high-tech [...] Read more.

The utilization of anodized aluminum (Al) components would contribute greatly to combat against dry friction if good tribological properties could be attained. Despite its hardness, the wear rate of anodic coatings presents a major problem in many applications, including automotive, aerospace and high-tech industries. Recently, nanolayers of Ti demonstrated high tribological effectiveness and unusually low dry friction on anodic coatings. However, few researchers focus on the tribological characterization of nanolayers of other elements. In this study, nanolayers of Ti, Zr, Hf, Cu, Cr, Nb and Sn were deposited on anodized 1050 and 6082 alloys by magnetron sputtering and Atomic Layer Deposition. Major attention was devoted to surface roughness and hardness measurements, because of their importance for static friction. The results showed that structural, chemical and other intrinsic properties of nanolayers of Group IVB elements in many cases led to significant friction reduction, when compared to those of Cu, Cr and Hf. Nanolayers of 15 nm to 75 nm thicknesses appeared most effective tribologically, while 180 nm or thicker layers progressively lost their ability to sustain low dynamic friction. Deposition of nanoscale structures could provide advantages for the anodized Al industry in protection against incidental friction and wear. Full article

(This article belongs to the Special Issue Coatings and Surface Modification for Tribological Applications)

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10 pages, 3179 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Functionally Gradient Material Fabrication Based on Cr, Ti, Fe, Ni, Co, Cu Metal Layers via Spark Plasma Sintering

by Oleg O. Shichalin, Evgeniy K. Papynov, Igor Yu. Buravlev, Anastasiya A. Buravleva, Sergey V. Chuklinov, Ekaterina A. Gridasova, Anton V. Pogodaev, Valreiia A. Nepomnyushchaya, Zlata E. Kornakova, Alexey O. Lembikov, Danila V. Gritsuk, Olesya V. Kapustina, Sofia S. Gribanova and Yun Shi

Coatings 2023, 13(1), 138; https://doi.org/10.3390/coatings13010138 - 10 Jan 2023

Cited by 5 | Viewed by 3101

Abstract

The paper presents a method of obtaining functionally graded material (FGM) of heterogeneous (layered) type based on joined metals Cr-Ti-Fe-Co-Ni-Cu using spark plasma sintering (SPS) technology. The structure, elemental and phase composition of FGM obtained on the basis of joined metals with different [...] Read more.

The paper presents a method of obtaining functionally graded material (FGM) of heterogeneous (layered) type based on joined metals Cr-Ti-Fe-Co-Ni-Cu using spark plasma sintering (SPS) technology. The structure, elemental and phase composition of FGM obtained on the basis of joined metals with different values of the temperature coefficient of linear expansion (CTLE) were studied by SEM, EDS and XRD methods with regard to the phase states of the alloy system. Based on the Vickers microhardness data, the evaluation of the mechanical characteristics of FGM in the whole sample body and locally at the contact boundaries of the joined metals was carried out. The results of the study are new and represent a potential for FGM, as well as functionally graded coatings (FGC), which have special physical, chemical and mechanical properties and are highly demanded for the manufacture of structures and products for industrial applications. Full article

(This article belongs to the Special Issue Trends in Spark Plasma Sintering of Advanced Materials)

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15 pages, 1914 KiB

Open AccessEditor’s ChoiceArticle

Development of Catalyst-Free Self-Healing Biobased UV-Curable Coatings via Maleate Monoester Transesterification

by Xixi Yu, Yun Hu, Wen Lei, Chengguo Liu and Yonghong Zhou

Coatings 2023, 13(1), 110; https://doi.org/10.3390/coatings13010110 - 7 Jan 2023

Cited by 11 | Viewed by 2336

Abstract

Developing environmentally friendly UV-curable polymers with multi-functionality is very significant for sustainable development and environmental protection. In this work, a novel tung-oil-based UV-curable oligomer (TOMAH) was synthesized by Diels–Alder and ring-opening reactions via microwave technology. Subsequently, catalyst-free self-healing UV-curable materials based on a [...] Read more.

Developing environmentally friendly UV-curable polymers with multi-functionality is very significant for sustainable development and environmental protection. In this work, a novel tung-oil-based UV-curable oligomer (TOMAH) was synthesized by Diels–Alder and ring-opening reactions via microwave technology. Subsequently, catalyst-free self-healing UV-curable materials based on a maleate monoester transesterification (MMETER) were developed by co-photopolymerization of TOMAH and hydroxyethyl methacrylate (HEMA). The obtained UV-cured materials possessed a high glass transition temperature (T_g > 81 °C), excellent adhesion (grade 1), and flexibility (2 mm). Particularly, the outstanding photopolymerization activity of the UV-curable resins was proved by UV-curing kinetics. In addition, dynamic transesterifications occurred without an external catalyst at a moderate temperature, resulting in good self-healing properties (with a scratch-repair efficiency of 78.6–93.3%) and shape-memory properties for the obtained UV-cured materials. This work combines the multiple advantages of biomass raw material, microwave synthesis technology, UV-curing method, and multifunctional polymers, thus providing an innovative strategy to fabricate sustainable and intelligent coatings. Full article

(This article belongs to the Section Bioactive Coatings and Biointerfaces)

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16 pages, 5415 KiB

Open AccessEditor’s ChoiceArticle

In Vitro Investigation of Corrosion Control of Magnesium with Degradable Polycaprolactone Coatings for Cardiovascular Grafts

by Sara Knigge, Marc Mueller, Lara Fricke, Tobias Schilling and Birgit Glasmacher

Coatings 2023, 13(1), 94; https://doi.org/10.3390/coatings13010094 - 4 Jan 2023

Cited by 6 | Viewed by 3254

Abstract

Magnesium is a promising metal for resorbable cardiovascular implants due to its high biocompatibility, high corrosion tendency, and mechanical properties. However, adapting its corrosion rate to the physiological healing processes is required to ascertain a safe graft function. A protective polymeric layer is [...] Read more.

Magnesium is a promising metal for resorbable cardiovascular implants due to its high biocompatibility, high corrosion tendency, and mechanical properties. However, adapting its corrosion rate to the physiological healing processes is required to ascertain a safe graft function. A protective polymeric layer is supposed to slow down the corrosion rate of magnesium. Additionally, coatings can improve the host’s tissue interaction with the implant by implementing the local delivery of antibiotic drugs and growth or cell adhesion factors. However, little is known about the interaction of polymer-based coatings, their degradation, and magnesium corrosion. This study examines the corrosion mechanism of magnesium protected by spin coatings and electrospun fiber coatings under physiological conditions. Pure magnesium specimens were coated with polycaprolactone (PCL). The corrosion of the coated magnesium was evaluated using an immersion test in simulated body fluid. Spin coatings provided efficient protection against corrosive attacks and a significantly lower corrosion rate by 75% compared to uncoated magnesium. In contrast, fiber coatings did not provide relevant corrosion protection. On the other hand, magnesium corrosion caused the accelerated degradation of the PCL layer. A reliable and safe implant function is vital, especially in cardiovascular applications. Magnesium coating, therefore, should be carried out with spin coatings. Full article

(This article belongs to the Special Issue Multifunctional Coatings on Medical Devices)

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14 pages, 1613 KiB

Open AccessEditor’s ChoiceArticle

The Application of Rubber Aggregate-Combined Permeable Concrete Mixture in Sponge City Construction

by Bowen Qi, Shouwu Gao and Peilong Xu

Coatings 2023, 13(1), 87; https://doi.org/10.3390/coatings13010087 - 3 Jan 2023

Cited by 33 | Viewed by 4226

Abstract

Permeable concrete is a new type of pavement material, which can effectively improve the urban flood discharge system, and is of great significance to the construction of sponge city. In order to optimize the use effect of permeable concrete and improve the application [...] Read more.

Permeable concrete is a new type of pavement material, which can effectively improve the urban flood discharge system, and is of great significance to the construction of sponge city. In order to optimize the use effect of permeable concrete and improve the application value of permeable concrete in permeable road engineering, the combination of rubber aggregate and permeable concrete is proposed, and the mix ratio of rubber permeable concrete mixture material is designed, which is applied to the engineering of pavement in Hunan Province, and its comprehensive pavement performance is analyzed and evaluated. The results show that the rubber permeable concrete has the best performance when the water cement ratio is 0.3, the designed porosity is 15%, the rubber particle size is 16 mesh, the rubber content is 15% and the coarse aggregate ratio is 4:6. The removal rates of suspended solids and metal pollutants are 0.65 and 0.72, respectively, which are increased by 0.23 and 0.19, respectively, compared with ordinary permeable concrete. This shows that rubber permeable concrete improves the ecological benefits of permeable concrete pavement, gives full play to the economic benefits of waste rubber products, reduces the construction cost of permeable concrete pavement, and provides assistance for promoting the construction of sponge city. Full article

(This article belongs to the Topic Properties of the Corroding Interface)

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20 pages, 10512 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Al₂O₃, ZnO and TiO₂ Atomic Layer Deposition Grown Thin Films on the Electrochemical and Mechanical Properties of Sputtered Al-Zr Coating

by Elias Kaady, Roland Habchi, Mikhael Bechelany, Elia Zgheib and Akram Alhussein

Coatings 2023, 13(1), 65; https://doi.org/10.3390/coatings13010065 - 30 Dec 2022

Cited by 5 | Viewed by 5492

Abstract

The 316L stainless steels, often used in turbine blades for naval and marine applications, usually suffer from localized pitting corrosion after long exposure to chlorinated environments. The aluminum-zirconium coatings deposited by magnetron sputtering technique can be used to ensure cathodic protection for steels. [...] Read more.

The 316L stainless steels, often used in turbine blades for naval and marine applications, usually suffer from localized pitting corrosion after long exposure to chlorinated environments. The aluminum-zirconium coatings deposited by magnetron sputtering technique can be used to ensure cathodic protection for steels. In this work, we study the influence of atomic layer deposited (ALD) Al₂O₃, ZnO, and TiO₂ thin films on the structural, mechanical, and electrochemical properties of Al-Zr (4 at.% Zr) magnetron sputtered coatings. The morphology, preferred orientation growth, mechanical properties, wettability, and corrosion resistance were investigated. The change in the sputtered Al-Zr morphology is mainly due to the insertion of the ALD layer. The Al-Zr layer deposited on ZnO and TiO₂ layers presented a distinctive morphology. The agglomerate particles of AlZr/Al₂O₃/AlZr, AlZr/ZnO/AlZr and AlZr/TiO₂/AlZr coatings exhibited a cauliflower shape. For ALD/PVD coatings, the insertion of an ALD oxide layer promoted the intensity of the peaks corresponding to the (111) crystallographic orientation. The nanoindentation measurements confirmed the enhancement in the mechanical properties, where the hardness increased by about 75%. The ALD oxide layers promoted the hydrophobicity of the coatings. The electrochemical characterization in a 3.5 wt.% NaCl solution also confirmed the role of the ALD oxides layers in delaying the pitting corrosion of the Al-Zr coating by widening the passive region and enhancing the protective efficiency of the passive film. Full article

(This article belongs to the Special Issue Chemical/Physical Vapor Deposition Coatings on Metallic Substrates)

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30 pages, 2701 KiB

Open AccessEditor’s ChoiceReview

Steel Surface Defect Recognition: A Survey

by Xin Wen, Jvran Shan, Yu He and Kechen Song

Coatings 2023, 13(1), 17; https://doi.org/10.3390/coatings13010017 - 22 Dec 2022

Cited by 106 | Viewed by 9757

Abstract

Steel surface defect recognition is an important part of industrial product surface defect detection, which has attracted more and more attention in recent years. In the development of steel surface defect recognition technology, there has been a development process from manual detection to [...] Read more.

Steel surface defect recognition is an important part of industrial product surface defect detection, which has attracted more and more attention in recent years. In the development of steel surface defect recognition technology, there has been a development process from manual detection to automatic detection based on the traditional machine learning algorithm, and subsequently to automatic detection based on the deep learning algorithm. In this paper, we discuss the key hardware of steel surface defect detection systems and offer suggestions for related options; second, we present a literature review of the algorithms related to steel surface defect recognition, which includes traditional machine learning algorithms based on texture features and shape features as well as supervised, unsupervised, and weakly supervised deep learning algorithms (Incomplete supervision, inexact supervision, imprecise supervision). In addition, some common datasets and algorithm performance evaluation metrics in the field of steel surface defect recognition are summarized. Finally, we discuss the challenges of the current steel surface defect recognition algorithms and the corresponding solutions, and our future work focus is explained. Full article

(This article belongs to the Special Issue Solid Surfaces, Defects and Detection)

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11 pages, 3667 KiB

Open AccessEditor’s ChoiceArticle

A Two-Dimensional Guidance Strategy to Fabricate Perovskite Gadolinium Aluminate Ceramic Film

by Tao Zhang, Lu Chen, Jing Yao and Qi Zhu

Coatings 2022, 12(12), 1927; https://doi.org/10.3390/coatings12121927 - 8 Dec 2022

Cited by 1 | Viewed by 2011

Abstract

Gadolinium aluminate is an effective host for doping with various ions, and it can emit various colors. However, it is not easy to prepare transparent ceramics of gadolinium aluminate using traditional methods, although transparent ceramics are very suitable for solid lighting. In this [...] Read more.

Gadolinium aluminate is an effective host for doping with various ions, and it can emit various colors. However, it is not easy to prepare transparent ceramics of gadolinium aluminate using traditional methods, although transparent ceramics are very suitable for solid lighting. In this work, a two-dimensional guidance strategy has been successfully carried out for perovskite-structured aluminate ceramic film. Through the two-dimensional interfacial reaction, GdAlO₃:Eu³⁺ (GAP:Eu³⁺) transparent ceramic films were successfully fabricated using nanosheets exfoliated from layered gadolinium hydroxide, a rare earth source. The final films were tested by characterization techniques, including XRD, SEM, TEM, FT-IR, PLE/PL spectroscopy, temperature-dependent PL spectroscopy, and luminescence decay analysis. The perovskite film of transparent ceramics can be obtained by calcining LRH nanosheets on the substrate of amorphous alumina at 1550 °C in air with a reaction time of 2 h. During the interface reaction, temperature-dependent element diffusion takes the dominant role, and increased reactants take in the reaction with increasing calcination temperature. The grain for ceramic film is only 2–5 μm, which is much smaller than that for bulk ceramic. This is mainly due to the lower temperature and the interface diffusion. Ceramic film has a high transmittance larger than 90% at the visible range. Upon UV excitation at 254 nm, the film exhibits intense emission at the red wavelength range. The outcomes described in this work may have wide implications for transparent ceramics and layered rare-earth hydroxides. Full article

(This article belongs to the Special Issue Ceramic Films and Coatings: Properties and Applications)

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19 pages, 8925 KiB

Open AccessEditor’s ChoiceArticle

Microsurfacing Pavement Solutions with Alternative Aggregates and Binders: A Full Surface Texture Characterization

by Sergio Copetti Callai, Manuel De Rose, Piergiorgio Tataranni, Christina Makoundou, Cesare Sangiorgi and Rosolino Vaiana

Coatings 2022, 12(12), 1905; https://doi.org/10.3390/coatings12121905 - 6 Dec 2022

Cited by 7 | Viewed by 1948

Abstract

The road surface texture is responsible for controlling several quality/safety road indicators, such as friction, noise, and fuel consumption. Road texture can be classified into different wavelengths, and it is dependent on the material used in the paving solution. With the aim of [...] Read more.

The road surface texture is responsible for controlling several quality/safety road indicators, such as friction, noise, and fuel consumption. Road texture can be classified into different wavelengths, and it is dependent on the material used in the paving solution. With the aim of evaluating and characterizing the surface texture of a microsurfacing road pavement, six microsurfacing samples were made in the laboratory with both traditional materials (basaltic aggregates and bituminous emulsion) and with innovative materials from recycling procedures (crumb rubber (CR) and artificial engineered aggregate (AEA)). The characterization was performed through the use of a conoscopic holography profilometer with high precision and post-processing of the profiles detected through consolidated algorithms (ISO standards). We found that the aggregate type plays a very important role in the pavement texture. The binder agent seems to be highly important, but more studies regarding this are necessary. The use of crumb rubber as an aggregate proved to be feasible, and the texture parameters that were obtained were in accordance with the benchmark ones. In addition, the study shows that the use of artificial engineered aggregates does not impair the surface texture. Finally, the use of the texture parameters defined by the ISO standards, together with a statistical analysis, could be useful for defining the surface texture characteristics of microsurfacing. Full article

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25 pages, 4317 KiB

Open AccessEditor’s ChoiceArticle

Influence of Post-Deposition Thermal Treatments on the Morpho-Structural, and Bonding Strength Characteristics of Lithium-Doped Biological-Derived Hydroxyapatite Coatings

by L. Duta, G. E. Stan, G. Popescu-Pelin, I. Zgura, M. Anastasescu and F. N. Oktar

Coatings 2022, 12(12), 1883; https://doi.org/10.3390/coatings12121883 - 4 Dec 2022

Cited by 9 | Viewed by 2944

Abstract

We report on hydroxyapatite (HA) of biological-origin doped with lithium carbonate (LiC) and lithium phosphate (LiP) coatings synthesized by Pulsed laser deposition onto Ti6Al4V substrates fabricated by the Additive manufacturing technique. A detailed comparison from the structural, morphological, chemical composition, wetting behavior and [...] Read more.

We report on hydroxyapatite (HA) of biological-origin doped with lithium carbonate (LiC) and lithium phosphate (LiP) coatings synthesized by Pulsed laser deposition onto Ti6Al4V substrates fabricated by the Additive manufacturing technique. A detailed comparison from the structural, morphological, chemical composition, wetting behavior and bonding strength standpoints of as-deposited (NTT) and post-deposition thermal-treated (TT) coatings at temperatures ranging from 400 to 700 °C (i.e., TT400–TT700), was performed. Structural investigations indicated a complete crystallization of the initially amorphous HA-based layers at temperatures in excess of 500 °C. The morphological analyses emphasized the rough appearance of the film surfaces, consisting of particulates whose dimensions increased at higher temperatures, with an emphasis on LiC coatings. AFM investigations evidenced rough surfaces, with a clear tendency to increase in corrugation with the applied temperature, in the case of LiC coatings. A hydrophobic behavior was observed for control, NTT and TT400 samples, whilst a radical shift towards hydrophilicity was demonstrated for both types of structures at higher temperatures. In the case of TT500–TT700 coatings, the pull-out adherence values increased considerably compared to control ones. Taking into consideration the obtained results, the positive influence of post-deposition thermal treatments (performed at higher temperatures) on the physical–chemical and mechanical properties of LiC and LiP coatings was indicated. Alongside these improved characteristics observed at elevated temperatures, the sustainable nature of the used BioHA materials should recommend them as viable alternatives to synthetic HA ones for bone implant applications. Full article

(This article belongs to the Special Issue Synthetic and Biological-Derived Hydroxyapatite Implant Coatings)

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13 pages, 4747 KiB

Open AccessEditor’s ChoiceArticle

Effect of Annealing on the Microstructure, Opto-Electronic and Hydrogen Sensing Properties of V₂O₅ Thin Films Deposited by Magnetron Sputtering

by Michał Mazur, Szymon Kiełczawa and Jarosław Domaradzki

Coatings 2022, 12(12), 1885; https://doi.org/10.3390/coatings12121885 - 4 Dec 2022

Cited by 4 | Viewed by 2442

Abstract

This paper reports results of investigations on selected properties of vanadium oxide thin films deposited using gas impulse magnetron sputtering and annealed at temperatures in the range of 423 K to 673 K. Post-process annealing was shown to allow phase transition of as-deposited [...] Read more.

This paper reports results of investigations on selected properties of vanadium oxide thin films deposited using gas impulse magnetron sputtering and annealed at temperatures in the range of 423 K to 673 K. Post-process annealing was shown to allow phase transition of as-deposited films from amorphous to nanocrystalline V₂O₅ with crystallite sizes in the range of 23 to 27 nm. Simultaneously, annealing resulted in an increase in surface roughness and grain size. Moreover, a decrease in transparency was observed in the visible wavelength range of approximately 50% to 30%, while the resistivity of formed vanadium pentoxide thin films was almost unchanged and was in the order of 10² Ω·cm. Simultaneously, the best optoelectronic performance, testified by evaluated figure of merit parameter, indicated the as-deposited amorphous films. Performed Seebeck coefficient measurements indicated the electron type of electrical conduction of each prepared thin film. Furthermore, gas sensing properties towards diluted hydrogen were investigated for annealed V₂O₅ thin films, and it was found that the highest senor response was obtained for a thin film annealed at 673 K and measured at operating temperature of 623 K. Full article

(This article belongs to the Special Issue Optical Properties of Crystals and Thin Films)

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12 pages, 2490 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Electrodeposition of Copper Oxides as Cost-Effective Heterojunction Photoelectrode Materials for Solar Water Splitting

by Tai-Hsin Yin, Bu-Jine Liu, Yu-Wei Lin, Yi-Syuan Li, Chih-Wei Lai, Yu-Pin Lan, Changsik Choi, Han-Chen Chang and YongMan Choi

Coatings 2022, 12(12), 1839; https://doi.org/10.3390/coatings12121839 - 28 Nov 2022

Cited by 18 | Viewed by 5111

Abstract

Photoelectrocatalytic hydrogen production is crucial to reducing greenhouse gas emissions for carbon neutrality and meeting energy demands. Pivotal advances in photoelectrochemical (PEC) water splitting have been achieved by increasing solar light absorption. P-type Cu-based metal oxide materials have a wide range of energy [...] Read more.

Photoelectrocatalytic hydrogen production is crucial to reducing greenhouse gas emissions for carbon neutrality and meeting energy demands. Pivotal advances in photoelectrochemical (PEC) water splitting have been achieved by increasing solar light absorption. P-type Cu-based metal oxide materials have a wide range of energy band gaps and outstanding band edges for PEC water splitting. In this study, we first prepared Cu₂O thin films using electrodeposition and fabricated a heterojunction structure of CuO/Cu₂O by controlling annealing temperatures. The surface morphological, optical, and electrochemical properties were characterized using various analytical tools. X-ray and Raman spectroscopic approaches were used to verify the heterojunction of CuO/Cu₂O, while surface analyses revealed surface roughness changes in thin films as the annealing temperatures increased. Electrochemical impedance spectroscopic measurements in conjunction with the Mott–Schottky analysis confirm that the CuO/Cu₂O heterojunction thin film can boost photocurrent generation (1.03 mA/cm² at 0 V vs. RHE) via enhanced light absorption, a higher carrier density, and a higher flat band potential than CuO and Cu₂O thin films (0.92 and 0.08 mA/cm², respectively). Full article

(This article belongs to the Special Issue Advanced Electrochemical Surface Properties)

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17 pages, 6463 KiB

Open AccessEditor’s ChoiceArticle

Photocatalytic Performance of ZnO/Ag(NPs) Nanocomposite Thin Films under Natural Conditions

by Mouna Khiari, Michaël Lejeune, Mickaël Gilliot, Florica Lazar and Aomar Hadjadj

Coatings 2022, 12(11), 1782; https://doi.org/10.3390/coatings12111782 - 21 Nov 2022

Cited by 2 | Viewed by 2247

Abstract

The original technique developed for the direct incorporation and efficient dispersion of silver metal NPs into ZnO precursor solution allowed us to elaborate nanocomposite thin films with a large effective surface area for interaction with the external environment as well as a large [...] Read more.

The original technique developed for the direct incorporation and efficient dispersion of silver metal NPs into ZnO precursor solution allowed us to elaborate nanocomposite thin films with a large effective surface area for interaction with the external environment as well as a large surface area for metal–semiconductor interaction suitable for surface photocatalysis reactions. Such photocatalysts have the advantage of being in solid form, combining the benefits of the semiconductor material and the metallic nanoparticles embedded in it, while being eco-friendly. Their photocatalytic performance was analyzed under different operating conditions. The improved photocatalytic performance, stability, and reusability of the nanocomposite were demonstrated under both laboratory and natural conditions of use. The results of the present study provide interesting perspectives for the application of these photocatalysts in water treatment. Full article

(This article belongs to the Special Issue Recent Advances in Functional Transparent Semiconductor Films and Coatings)

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17 pages, 4281 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Insights into the Electrical Characterization of Graphene-like Materials from Carbon Black

by Raffaella Ferraiuolo, Michela Alfe, Valentina Gargiulo, Giovanni Piero Pepe, Francesco Tafuri, Alessandro Pezzella, Giovanni Ausanio and Domenico Montemurro

Coatings 2022, 12(11), 1788; https://doi.org/10.3390/coatings12111788 - 21 Nov 2022

Cited by 2 | Viewed by 2732

Abstract

A new class of graphene-related materials (GRMs) obtained as water suspensions through a two-step oxidation/reduction of a nanostructured carbon black, namely graphene-like (GL) materials, has recently emerged. GL materials undergo self-assembly in thin amorphous films after drying upon drop-casting deposition on different surfaces. [...] Read more.

A new class of graphene-related materials (GRMs) obtained as water suspensions through a two-step oxidation/reduction of a nanostructured carbon black, namely graphene-like (GL) materials, has recently emerged. GL materials undergo self-assembly in thin amorphous films after drying upon drop-casting deposition on different surfaces. The GL films, with thicknesses of less than a micron, were composed of clusters of nanoparticles each around 40 nm in size. The exploitation of the GL films for different options (e.g., bioelectronic, sensoristic, functional filler in composite) requires a deep characterization of the material in terms of their electric transport properties and their possible interaction with the surface on which they are deposited. In this work, a careful electrical characterization of GL films was performed at room temperature and the results were compared with those achieved on films of benchmark graphenic materials, namely graphene oxide (GO) materials, obtained by the exfoliation of graphite oxide, which differ both in morphology and in oxidation degree. The results indicate a non-linear current–voltage relationship for all the investigated films. The extrapolated dielectric constant (ε) values of the investigated GRMs (GL and GO materials) agree with the experimental and theoretically predicted values reported in the literature (ε~2–15). Because similar conductance values were obtained for the GL materials deposited on glass and silicon oxide substrates, no significant interactions of GL materials with the two different substrates were highlighted. These results are the starting point for boosting a feasible use of GL materials in a wide spectrum of applications, ranging from electronics to optics, sensors, membranes, functional coatings, and biodevices. Full article

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16 pages, 10896 KiB

Open AccessEditor’s ChoiceArticle

High Temperature Low Friction Behavior of h-BN Coatings against ZrO₂

by Qunfeng Zeng

Coatings 2022, 12(11), 1772; https://doi.org/10.3390/coatings12111772 - 19 Nov 2022

Cited by 11 | Viewed by 3071

Abstract

This paper presents high temperature low friction behaviors of the h-BN coatings, which were deposited on high-speed tool steel by radio frequency magnetron sputtering. A tribometer was used to investigate high temperature tribological properties of h-BN coatings against ZrO₂ from 500 °C [...] Read more.

This paper presents high temperature low friction behaviors of the h-BN coatings, which were deposited on high-speed tool steel by radio frequency magnetron sputtering. A tribometer was used to investigate high temperature tribological properties of h-BN coatings against ZrO₂ from 500 °C to 800 °C. The surface morphology, mechanical properties and chemical states of the worn surface of the friction pair were characterized and investigated systemically. The experimental results show that h-BN coatings are of significant importance to improve high temperature tribological properties of steel. Moreover, it is found that high temperature super low friction of the friction pairs is successfully achieved due to tribochemistry, which plays a key role in forming the in-situ generated Fe₂O₃/h-BN composites on the worn surface of h-BN coatings. CoFs of the friction pair are as super low as about 0.02 at 800 °C and around 0.03 at 600 °C at the stable stage. The high temperature super low friction mechanism of the friction pair is discussed in detail. The present study opens a new strategy to achieve high temperature super low friction of the friction system during sliding. Full article

(This article belongs to the Special Issue Technologies of Coatings and Surface Hardening for Tool Industry II)

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17 pages, 3663 KiB

Open AccessEditor’s ChoiceArticle

Chemical Structure, Optical and Dielectric Properties of PECVD SiCN Films Obtained from Novel Precursor

by Evgeniya Ermakova, Konstantin Mogilnikov, Igor Asanov, Anastasiya Fedorenko, Irina Yushina, Vadim Kichay, Eugene Maksimovskiy and Marina Kosinova

Coatings 2022, 12(11), 1767; https://doi.org/10.3390/coatings12111767 - 18 Nov 2022

Cited by 6 | Viewed by 4243

Abstract

A phenyl derivative of hexamethyldisilazane—bis(trimethylsilyl)phenylamine—was first examined as a single-source precursor for SiCN film preparation by plasma enhanced chemical vapor deposition. The use of mild plasma (20 W) conditions allowed the preparation of highly hydrogenated polymeric-like films. The synthesis was carried out under [...] Read more.

A phenyl derivative of hexamethyldisilazane—bis(trimethylsilyl)phenylamine—was first examined as a single-source precursor for SiCN film preparation by plasma enhanced chemical vapor deposition. The use of mild plasma (20 W) conditions allowed the preparation of highly hydrogenated polymeric-like films. The synthesis was carried out under an inert He atmosphere or under that of NH₃ with the deposition temperature range from 100 to 400 °C. The chemical bonding structure and elemental composition were characterized by Fourier-transform infrared spectroscopy, energy-dispersive X-ray analysis and X-ray photoelectron spectroscopy. The surface morphology was investigated by scanning electron microscopy. Ellipsometric porosimetry, a unique high-precision technique to investigate the porosity of thin films, was applied to examine the porosity of SiCN samples. The films were found to possess a morphologically homogenous dense defect-free structure with a porosity of 2–3 vol.%. SiCN films were studied in terms of their optical and dielectric properties. Depending on the deposition conditions the refractive index ranged from 1.53 to 1.78. The optical bandgap obtained using UV-Vis spectroscopy data varied from 2.7 eV for highly hydrogenated polymeric-like film to 4.7 eV for cross-linked nitrogen-rich film. The dielectric constant was found to decrease from 3.51 to 2.99 with the rise of hydrocarbon groups’ content. The results obtained in this study were compared to the literature data to understand the influence of precursor design to the optical and electrical properties of the films. Full article

(This article belongs to the Special Issue Coatings and Thin Film for Chemical Vapor Deposition (CVD) Application)

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29 pages, 4262 KiB

Open AccessEditor’s ChoiceReview

Magnetron Sputtering of Transition Metal Nitride Thin Films for Environmental Remediation

by Linda Aissani, Akram Alhussein, Abdul Wasy Zia, Gcina Mamba and Sami Rtimi

Coatings 2022, 12(11), 1746; https://doi.org/10.3390/coatings12111746 - 14 Nov 2022

Cited by 30 | Viewed by 7408

Abstract

The current economic and ecological situation encourages the use of steel to push the technological limits and offer more cost-effective products. The enhancement of steel properties like wear, corrosion, and oxidation resistance is achieved by the addition of small amounts of chemical elements [...] Read more.

The current economic and ecological situation encourages the use of steel to push the technological limits and offer more cost-effective products. The enhancement of steel properties like wear, corrosion, and oxidation resistance is achieved by the addition of small amounts of chemical elements such as Cr, Ni, Si, N, etc. The steel surface can be protected by different treatments such as heating and coating, among others. For many decades, coatings have been an effective solution to protect materials using thin hard films. Several technologies for thin film deposition have been developed. However, some of them are restricted to certain fields because of their complex operating conditions. In addition, some deposition techniques cannot be applied to a large substrate surface type. The magnetron sputtering deposition process is a good option to overcome these challenges and can be used with different substrates of varying sizes with specific growth modes and for a wide range of applications. In this review article, we present the sputtering mechanism and film growth modes and focus on the mechanical and tribological behavior of nitride thin films deposited by the magnetron sputtering technique as a function of process conditions, particularly bias voltage and nitrogen percentage. The biomedical properties of transition metal nitride coatings are also presented. Full article

(This article belongs to the Special Issue Bio-Based Packaging Films: Development, Characterization, and Application)

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