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Article

19 pages, 17846 KiB

Open AccessEditor’s ChoiceArticle

Effect of Scanning Strategies on Anisotropy of YCF104 Alloy Mechanical Properties by Laser Cladding

by Yu Zhao, Wenkai Shi, Liaoyuan Chen, Wenzheng Wu and Tianbiao Yu

Coatings 2023, 13(5), 842; https://doi.org/10.3390/coatings13050842 - 28 Apr 2023

Cited by 1 | Viewed by 1672

YCF104 alloy specimens were fabricated by laser cladding on #45 steel following three different scanning strategies. The microstructure, phase composition, friction coefficient, microhardness, tensile strength, and compressive strength of the specimens formed by different scanning strategies were investigated. The results show that the [...] Read more.

YCF104 alloy specimens were fabricated by laser cladding on #45 steel following three different scanning strategies. The microstructure, phase composition, friction coefficient, microhardness, tensile strength, and compressive strength of the specimens formed by different scanning strategies were investigated. The results show that the uniformity of laser remelting of solidified layers improved the uniformity of microstructure and refined the grains. The strengthening effect of the Fe–Cr/Mo solid solution was primarily responsible for the high strength. YCF104 cladding specimens exhibit brittle failure, and with the change of metallurgical bonding form in the overlap area, the compressive strength (the maximum value is 3235 MPa) and the tensile strength (specimen via strategy 3 is 527.44 MPa), there appears significant anisotropy. With the improvement of the uniformity of temperature distribution, the friction coefficient as well as the microhardness decreased when the GCr15 was used as the friction pair. The mechanical anisotropy of the coating is related to both the microstructure and metallurgical bonding strength in the overlap area. Full article

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

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17 pages, 11521 KiB

Open AccessEditor’s ChoiceArticle

Microstructure and Properties of Direct Laser-Deposited CeO₂-Modified Cobalt-Based Composite Coatings

by Yan Liu, Hui Han, Tao Ding, Dengwen Hu, Zhenlin Zhang, Hang Lv and Hui Chen

Coatings 2023, 13(5), 834; https://doi.org/10.3390/coatings13050834 - 26 Apr 2023

Viewed by 1515

Abstract

The seawater circulation pump is a significant piece of equipment in coastal nuclear power plants that is susceptible to erosion and corrosion in the seawater. In this work, CeO₂-modified cobalt-based composite coatings were prepared on the surface of martensitic stainless steel [...] Read more.

The seawater circulation pump is a significant piece of equipment in coastal nuclear power plants that is susceptible to erosion and corrosion in the seawater. In this work, CeO₂-modified cobalt-based composite coatings were prepared on the surface of martensitic stainless steel by direct laser deposition. The effect of CeO₂ on the phase composition, microstructure, microhardness, corrosion resistance, and erosion properties of the cobalt-based composite coatings was systematically investigated. While the addition of CeO₂ did not affect the phase composition of the coatings that comprised γ-Co, γ-Ni, M₇C₃, and M₂₃C₆ (M = Cr, W, Fe) metallic carbides, the eutectic organization showed an obvious phenomenon of contiguous aggregation. Microscopic pores were found in the coatings with 2 wt.% CeO₂, and the number of pores increased with the increase in CeO₂ content. Despite the higher self-corrosion potential (−0.27668 V) of cobalt-based alloy coating compared to the substrate (−0.37019 V), indicating enhanced corrosion resistance, the difference in self-corrosion potential among coatings with varying CeO₂ addition amounts is small (0.027 V), and the corrosion current densities are within one order of magnitude (10⁻⁸ A/cm²). These findings suggest that the addition of CeO₂ has no significant impact on the coating’s corrosion resistance. Full article

(This article belongs to the Section Laser Coatings)

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18 pages, 8616 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of CaCO₃-Based Hyperdispersants and Their Application in Aqueous Coatings

by Jue Bai and Yu Li

Coatings 2023, 13(5), 819; https://doi.org/10.3390/coatings13050819 - 23 Apr 2023

Cited by 1 | Viewed by 2161

Abstract

As an essential pigment particle in white water-based coatings, light calcium carbonate (CaCO₃) is difficult to disperse in water-based systems. The hard-to-disperse particles agglomerate, causing the viscosity of the coating to rise, which in turn affects the quality of the coating. [...] Read more.

As an essential pigment particle in white water-based coatings, light calcium carbonate (CaCO₃) is difficult to disperse in water-based systems. The hard-to-disperse particles agglomerate, causing the viscosity of the coating to rise, which in turn affects the quality of the coating. Therefore, in order to obtain efficient dispersion, the hyperdispersant SSS–MPEGA–DMAEA (SMD) has been prepared in this study using sodium styrene sulfonate (SSS), polyethylene glycol monomethyl ether acrylate (MPEGA), and dimethylaminoethyl acrylate (DMAEA) as monomers through aqueous solution polymerization. Firstly, we utilized the central composite design method to conduct mathematical modeling of the monomer ratios so as to optimize the dispersion performance of the hyperdispersants. Secondly, the structural characteristics and molecular weight distribution of SMD were characterized by ¹H NMR spectroscopy and GPC. Then, the effect of SMD on the dispersion of the CaCO₃ slurry was investigated through particle size distribution and TEM measurements. Finally, we applied the SMD in aqueous white coatings and tested the surface properties of the paint film by SEM as well as the stability of the paint film. The results showed that SMD can significantly reduce the viscosity and particle size of the CaCO₃ slurry. The waterborne coatings prepared by SMD had good storage stability and corrosion resistance, so the materials owned broad application prospects. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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24 pages, 3314 KiB

Open AccessEditor’s ChoiceArticle

Influence of Drop Viscosity and Surface Wettability on Impact Outcomes

by Ghokulla Haran Krishnan, Kevin Fletcher and Eric Loth

Coatings 2023, 13(5), 817; https://doi.org/10.3390/coatings13050817 - 23 Apr 2023

Cited by 5 | Viewed by 2894

Abstract

To understand the effects of liquid viscosity and surface wettability on the outcomes for a drop impacting perpendicularly on a dry, clean surface at a normal temperature and pressure, experiments were conducted for a wide variety of droplets and substrate surfaces. These experiments [...] Read more.

To understand the effects of liquid viscosity and surface wettability on the outcomes for a drop impacting perpendicularly on a dry, clean surface at a normal temperature and pressure, experiments were conducted for a wide variety of droplets and substrate surfaces. These experiments included a range of receding contact angles (from ~18° to ~150°) and liquid viscosities (from 1 cp to 45 cp); the broadest such combination is yet published. The surface wettabilities were quantitatively characterized using a new set of definitions: superphillic (θ_rec < 30°), phillic (30° < θ_rec < 90°), phobic (90° < θ_rec < 150°), and superphobic (θ_rec > 150°). Six different outcome regimes were found (including a new beaded deposition outcome) as a function of Ohnesorge number, Weber number, and the cosine of the receding contact angle. The beaded deposition is a hybrid of the well-known splash and deposition outcomes. The critical Weber number that separates the outcome boundaries was found to be significantly influenced by both the Ohnesorge numbers and the receding contact angle. In particular, there is a consistent reduction in the critical Weber number from superphilic to philic to neutral wettability conditions. Interestingly, this same decreasing trend line continues from neutral to phobic to superphobic conditions, but instead, it separates the regimes of deposition and bouncing. At higher Weber numbers, an additional boundary regime was found between splashing and bounce, which also decreased as the surface wettability decreased. This same type of trend was seen for several Ohnesorge numbers, indicating that wetting characterization should be based on the contact angles for the combination of the droplet liquid and the surface. In addition, a new regime map for droplet rebound on superphobic surfaces was obtained from the present and previous results indicating (for the first time) that the total rebound generally occurs for Weber numbers between 2.2 and 32 with Ohnesorge numbers less than 0.17. Additional studies are recommended to explore an even broader range of test conditions (especially intermediate wettability conditions), the separate influence of advancing and/or hysteresis contact angles, and to include the effects of the inclination angle, gas pressure, and heat transfer. Full article

(This article belongs to the Special Issue Liquid–Fluid Interfaces and Dynamics)

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14 pages, 2288 KiB

Open AccessEditor’s ChoiceArticle

Linear and Nonlinear Optical Properties of Iridium Nanoparticles Grown via Atomic Layer Deposition

by Paul Schmitt, Pallabi Paul, Weiwei Li, Zilong Wang, Christin David, Navid Daryakar, Kevin Hanemann, Nadja Felde, Anne-Sophie Munser, Matthias F. Kling, Sven Schröder, Andreas Tünnermann and Adriana Szeghalmi

Coatings 2023, 13(4), 787; https://doi.org/10.3390/coatings13040787 - 18 Apr 2023

Cited by 2 | Viewed by 2510

Abstract

Nonlinear optical phenomena enable novel photonic and optoelectronic applications. Especially, metallic nanoparticles and thin films with nonlinear optical properties offer the potential for micro-optical system integration. For this purpose, new nonlinear materials need to be continuously identified, investigated, and utilized for nonlinear optical [...] Read more.

Nonlinear optical phenomena enable novel photonic and optoelectronic applications. Especially, metallic nanoparticles and thin films with nonlinear optical properties offer the potential for micro-optical system integration. For this purpose, new nonlinear materials need to be continuously identified, investigated, and utilized for nonlinear optical applications. While noble-metal nanoparticles, nanostructures, and thin films of silver and gold have been widely studied, iridium (Ir) nanoparticles and ultrathin films have not been investigated for nonlinear optical applications yet. Here, we present a combined theoretical and experimental study on the linear and nonlinear optical properties of iridium nanoparticles deposited via atomic layer deposition (ALD). Linear optical constants, such as the effective refractive index and extinction coefficient, were evaluated at different growth stages of nanoparticle formation. Both linear and nonlinear optical properties of these Ir ALD coatings were calculated theoretically using the Maxwell Garnett theory. The third-order susceptibility of iridium nanoparticle samples was experimentally investigated using the z-scan technique. According to the experiment, for an Ir ALD coating with 45 cycles resulting in iridium nanoparticles, the experimentally determined nonlinear third-order susceptibility is about χ_Ir⁽³⁾ = (2.4 − i2.1) × 10⁻¹⁷ m²/V² at the fundamental wavelength of 700 nm. The theory fitted to the experimental results predicts a 5 × 10⁶-fold increase around 230 nm. This strong increase is due to the proximity to the Mie resonance of iridium nanoparticles. Full article

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

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13 pages, 3371 KiB

Open AccessEditor’s ChoiceArticle

Bacterial Detection and Differentiation of Staphylococcus aureus and Escherichia coli Utilizing Long-Period Fiber Gratings Functionalized with Nanoporous Coated Structures

by Shuyue He, Jue Wang, Fan Yang, Tzu-Lan Chang, Ziyu Tang, Kai Liu, Shuli Liu, Fei Tian, Jun-Feng Liang, Henry Du and Yi Liu

Coatings 2023, 13(4), 778; https://doi.org/10.3390/coatings13040778 - 17 Apr 2023

Cited by 5 | Viewed by 1784

Abstract

A biosensor utilizing long-period fiber gratings (LPFG) functionalized with nanoporous coated structures was developed for the rapid detection of Staphylococcus aureus (S. aureus) bacteria. The nanoporous structure coatings on the LPFG surface facilitated specific adhesion and interaction with S. aureus, [...] Read more.

A biosensor utilizing long-period fiber gratings (LPFG) functionalized with nanoporous coated structures was developed for the rapid detection of Staphylococcus aureus (S. aureus) bacteria. The nanoporous structure coatings on the LPFG surface facilitated specific adhesion and interaction with S. aureus, resulting in an instantaneous shift in the resonance wavelength (RW) in the transmission spectrum of the LPFG. The LPFG with nanoporous polyelectrolyte coatings exhibited an approximately seven-fold RW shift compared to the bare LPFG under the optimal experiment conditions. By tracking the RW shifts, we were able to monitor the real-time S. aureus adhesion to study the interaction process in detail. The bacterial differentiation and S. aureus specificity of the method was confirmed through a series of studies using Escherichia coli (E. coli). This nanoporous structure-enabled LPFG-based biosensor scheme holds significant promise for rapid, reliable, and low-cost detection of S. aureus for biomedical applications. Full article

(This article belongs to the Special Issue New Advance in Nanoparticles, Fiber, and Coatings)

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17 pages, 4240 KiB

Open AccessEditor’s ChoiceArticle

Novel Hybrid Organic–Inorganic Polymeric Coatings Containing Phosphonium or Acidic Groups for Improving Flame Retardancy of Wood

by Vasilis Koukoumtzis, Georgia C. Lainioti, George A. Voyiatzis and Joannis K. Kallitsis

Coatings 2023, 13(4), 754; https://doi.org/10.3390/coatings13040754 - 9 Apr 2023

Cited by 2 | Viewed by 1707

Abstract

Flame-retardant polymeric coatings with high limiting oxygen index (LOI) were prepared by combining inorganic mineral huntite (H5) and polymeric additives synthesized in the present work into a polymeric formulation. In order to improve the dispersion of the Mg- (and Ca)-based H5 particles, additives [...] Read more.

Flame-retardant polymeric coatings with high limiting oxygen index (LOI) were prepared by combining inorganic mineral huntite (H5) and polymeric additives synthesized in the present work into a polymeric formulation. In order to improve the dispersion of the Mg- (and Ca)-based H5 particles, additives containing phosphonium and acidic groups were employed to homogenize the inorganic fillers into the polymer matrix. Specific blend combinations of the commercial matrix Ecrovin^® LV 340 eco with huntite and the additives poly(benzyltriphenylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSBTPB60) and poly(hexadecyltributylphosphonium-co-4-styrene sulfonic acid) P(SSH-co-SSTBHDPB80), combining acidic and phosphonium groups, led to LOI values of 34.5% and 33.5%, respectively. The novel flame-retardant polymeric coatings inhibited the combustion of the coated wood substrates, which is attributed to the combination of acidic groups that promote the dispersion of inorganic filler in the polymer matrix and phosphonium groups that support the increase in LOI values. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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18 pages, 4683 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparison of the Mechanical Properties and Corrosion Resistance of the Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN Coatings

by He Tao, Valery Zhylinski, Alexey Vereschaka, Vadzim Chayeuski, Huo Yuanming, Filipp Milovich, Catherine Sotova, Anton Seleznev and Olga Salychits

Coatings 2023, 13(4), 750; https://doi.org/10.3390/coatings13040750 - 8 Apr 2023

Cited by 7 | Viewed by 2271

Abstract

In this work, the mechanical properties and corrosion resistance of Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings deposited by the physical vapor deposition (PVD) method on Ti-6Al-4V alloy were compared. The phase composition of the coatings, their hardness and fracture resistance in scratch tests [...] Read more.

In this work, the mechanical properties and corrosion resistance of Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings deposited by the physical vapor deposition (PVD) method on Ti-6Al-4V alloy were compared. The phase composition of the coatings, their hardness and fracture resistance in scratch tests were determined, and their structural characteristics were also studied using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The diffraction spectra were made using an automatic X-ray diffractometer. The value of the adhesive component of the friction coefficient f_adh of the pair “coated and uncoated Ti-6Al-4V alloy” was investigated in the temperature range of 20–900 °C. The lowest value of f_adh was detected for the Zr-ZrN coating at temperatures below 400 °C, while for the Mo-MoN coating it was observed at temperatures above 700 °C. The polarization curves of the coated and uncoated samples were performed in a 3% aqueous NaCl solution. The level of corrosion of the Ti-6Al-4V alloy samples with Cr-CrN, Ti-TiN, Zr-ZrN, and Mo-MoN coatings was evaluated using the Tafel extrapolation method, the iteration method, and the polarization resistance method. The results obtained with these methods indicate that the Zr-ZrN coated sample has the best corrosion resistance in the 3 wt.% NaCl solution, with a corrosion current density of 0.123 μA/cm². Full article

(This article belongs to the Special Issue Corrosion Effects and Smart Coatings of Corrosion Protection)

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21 pages, 8544 KiB

Open AccessEditor’s ChoiceArticle

Thermoelectric and Structural Properties of Transparent Sb-Doped ZnO Thin Films Sputtered in a Confocal Geometry

by Helder Filipe Faria, Joana Margarida Ribeiro, Torben Boll and Carlos José Tavares

Coatings 2023, 13(4), 735; https://doi.org/10.3390/coatings13040735 - 4 Apr 2023

Cited by 5 | Viewed by 2472

Abstract

This study focuses on understanding the influence of low Sb doping on ZnO’s electrical, optical, and thermoelectrical properties, while also studying its structural and morphological parameters. For this, several ZnO films with varying Sb target current densities, in the range of 0–0.27 mA/cm [...] Read more.

This study focuses on understanding the influence of low Sb doping on ZnO’s electrical, optical, and thermoelectrical properties, while also studying its structural and morphological parameters. For this, several ZnO films with varying Sb target current densities, in the range of 0–0.27 mA/cm², were produced by DC magnetron sputtering in a confocal geometry. As a result, thin ZnO:Sb films with an average transparency in the visible region greater than 80% are obtained, revealing for optimized conditions an absolute Seebeck coefficient of 100 μV/K and a respective power factor of 1.1 mW∙m⁻¹∙K⁻² at 300 K, effectively modifying the electrical, optical, and thermoelectrical properties of the material and ensuring its suitability for heat harvesting applications. From atom probe tomography experiments, a larger Zn content is registered at triple junctions of the grain boundary, which matches the approximately 25 nm crystallite grain size derived from the X-ray diffraction analysis. Full article

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

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20 pages, 7211 KiB

Open AccessEditor’s ChoiceArticle

Impact of High Concentrations of Cellulose Fibers on the Morphology, Durability and Protective Properties of Wood Paint

by Massimo Calovi and Stefano Rossi

Coatings 2023, 13(4), 721; https://doi.org/10.3390/coatings13040721 - 31 Mar 2023

Cited by 13 | Viewed by 1843

Abstract

This work aims to reveal the effect of a high amount of cellulose fibers on the durability and protective behavior of a bio-based wood paint. The influence of the filler on the morphology of the coatings was investigated by scanning electron microscopy observations, [...] Read more.

This work aims to reveal the effect of a high amount of cellulose fibers on the durability and protective behavior of a bio-based wood paint. The influence of the filler on the morphology of the coatings was investigated by scanning electron microscopy observations, while the durability of the paint was evaluated by exposing the samples to UV-B radiation and continuous thermal shocks. Infrared spectroscopy analysis, colorimetric inspections, adhesion tests and scanning electron microscope observations were employed to assess the role of the high concentrations of fillers in affecting the resilience of the acrylic matrix. Moreover, the impact of the filler on the barrier performance of the coatings was estimated using a liquid resistance test and a water uptake test. Finally, the mechanical properties of hardness and abrasion resistance of the layers were evaluated by means of the Buchholz Hardness Indentation test and the Scrub test. Ultimately, this study demonstrates the pros and cons of using large amounts of cellulose fibers as filler in wood paint: the work warns against the excessive use of these fibers, which need a threshold limit so as not to significantly change the coating’s structure and thereby weaken its protective properties. Full article

(This article belongs to the Special Issue Recent Advances in Wood Coatings)

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13 pages, 4614 KiB

Open AccessEditor’s ChoiceArticle

Atmospheric Plasma and UV Polymerisation for Developing Sustainable Anti-Adhesive Polyethylene Terephthalate (PET) Surfaces

by Tugce Caykara, Sara Fernandes, Adelaide Braga, Joana Rodrigues, Ligia Raquel Rodrigues and Carla Joana Silva

Coatings 2023, 13(4), 715; https://doi.org/10.3390/coatings13040715 - 31 Mar 2023

Cited by 3 | Viewed by 1839

Abstract

Enhancing the hydrophilicity of polymeric materials is an important step for achieving anti-adhesiveness. Thus, in this study, atmospheric plasma as a pre-treatment was combined with a UV grafting process to obtain a durable surface modification on polyethylene terephthalate (PET). The most promising conditions [...] Read more.

Enhancing the hydrophilicity of polymeric materials is an important step for achieving anti-adhesiveness. Thus, in this study, atmospheric plasma as a pre-treatment was combined with a UV grafting process to obtain a durable surface modification on polyethylene terephthalate (PET). The most promising conditions for the atmospheric plasma process were found to be 15 kW power and 4 m/min speed, leading to a contact angle reduction from 70 ± 6° to approximately 30°. However, it was observed that these values increased over time due to the ageing and washing of the PET surface, ultimately causing it to recover its initial contact angle. Therefore, the plasma-pre-treated PET samples were further modified through a UV grafting process using sodium acrylate (NaAc) and 3-sulfopropyl acrylate potassium salts (KAc). The grafted acrylate PET samples exhibited contact angles of 8 ± 3° and 28 ± 13° for NaAc and KAc, respectively, while showing durability in ageing and washing tests. The dry film thicknesses for both samples were found to be 28 ± 2 μm. Finally, the anti-adhesive properties of the NaAc- and KAc-treated surfaces were evaluated using an Escherichia coli expressing YadA, an adhesive protein from Yersinia. The modified PET surfaces were highly effective in reducing bacterial adhesion by more than 90%. Full article

(This article belongs to the Special Issue Functional Coatings for Textile Applications)

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33 pages, 35756 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Galvanizing on the Surface Quality and Part Precision of S235J0 Alloy Machined by Turning

by Sandor Ravai-Nagy, Aurel Mihail Titu and Alina Bianca Pop

Coatings 2023, 13(4), 701; https://doi.org/10.3390/coatings13040701 - 30 Mar 2023

Cited by 1 | Viewed by 2114

Abstract

This scientific paper aims to determine the optimal economic roughness of galvanized surfaces by studying the influence of turning surface roughness on the quality of galvanizing. The thickness of the zinc layer, its corrosion resistance, and the precision of the galvanized parts were [...] Read more.

This scientific paper aims to determine the optimal economic roughness of galvanized surfaces by studying the influence of turning surface roughness on the quality of galvanizing. The thickness of the zinc layer, its corrosion resistance, and the precision of the galvanized parts were also examined. S235J0 steel samples were processed using a turning operation to obtain different roughness values. Three galvanizing technologies, galvanic galvanizing, hot dip galvanizing, and hot dip galvanizing with centrifugation, were used in the experiments. The surface evolution from turning to zinc layer deposition was monitored, and parts were subjected to salt spray corrosion resistance testing. Statistical analysis confirmed the stability of the technologies used and the accuracy of the experimental data. Optimal roughness ranges for galvanizing were determined based on the quality of the surface before galvanizing and the galvanizing technology used. The findings show that avoiding small roughness values leads to savings in the machining phases. From the dimensional accuracy perspective, the parts have smaller dimensions after galvanizing, and the dimensional accuracy decreases. The study confirms that steel parts are protected from corrosion, and degradation of the zinc layer is more advanced in sections with less roughness. The optimal surface roughness values before galvanizing were determined to be Ra < 3.657 m in the case of HDG, Ra < 3.344 m in the case of HDG+C, and Ra > 2.928 μm in the case of ZP. The conclusions drawn from this study introduce new directions of research. Full article

(This article belongs to the Special Issue Surface Modification of Magnesium, Aluminum Alloys, and Steel)

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15 pages, 5093 KiB

Open AccessEditor’s ChoiceArticle

Multiscale Wear Simulation in Textured, Lubricated Contacts

by Michael Maier, Michael Pusterhofer and Florian Grün

Coatings 2023, 13(4), 697; https://doi.org/10.3390/coatings13040697 - 29 Mar 2023

Cited by 3 | Viewed by 2028

Abstract

Specific surface textures may reduce the friction and increase the lifting forces in lubricated contacts. For the detrimental operating condition of mixed friction, wear is induced by the solid contact. In this study, a methodology for wear calculation in textured, lubricated contacts is [...] Read more.

Specific surface textures may reduce the friction and increase the lifting forces in lubricated contacts. For the detrimental operating condition of mixed friction, wear is induced by the solid contact. In this study, a methodology for wear calculation in textured, lubricated contacts is presented that considers the wear-induced surface topography evolution. Based on the Reynolds differential equation, the mass-conserving cavitation model according to Jakobsson, Floberg, and Olsson (JFO), a wear-dependent asperity contact pressure curve and the wear equation according to Archard, wear in a wedge-shaped, textured lubrication gap was calculated. The results show the wear behavior of textured lubrication gaps. Based on the wear simulations, the tribological behavior of the textured surfaces compared to smooth surfaces is discussed. It is evident that textures, which improve the tribological performance in the hydrodynamic lubrication regime, are not necessarily associated with low wear values in a lubrication condition in the mixed friction regime. The analysis of the wear-dependent parameters initially showed a ‘recovery’ of the tribological system with increasing wear until the performance decreased again after a specific reversal point. This behavior is attributed to the relative position of the surface textures in the lubrication gap. Full article

(This article belongs to the Special Issue Friction, Wear, Lubrication and Mechanics of Surfaces and Interfaces)

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12 pages, 5384 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Thermoelectric and Structural Properties of Sputtered AZO Thin Films with Varying Al Doping Ratios

by Muhammad Isram, Riccardo Magrin Maffei, Valeria Demontis, Leonardo Martini, Stiven Forti, Camilla Coletti, Vittorio Bellani, Andrea Mescola, Guido Paolicelli, Alberto Rota, Stefania Benedetti, Alessandro di Bona, Joana M. Ribeiro, Carlos J. Tavares and Francesco Rossella

Coatings 2023, 13(4), 691; https://doi.org/10.3390/coatings13040691 - 28 Mar 2023

Cited by 3 | Viewed by 2266

Abstract

Nanomaterials can be game-changers in the arena of sustainable energy production because they may enable highly efficient thermoelectric energy conversion and harvesting. For this purpose, doped thin film oxides have been proven to be promising systems for achieving high thermoelectric performances. In this [...] Read more.

Nanomaterials can be game-changers in the arena of sustainable energy production because they may enable highly efficient thermoelectric energy conversion and harvesting. For this purpose, doped thin film oxides have been proven to be promising systems for achieving high thermoelectric performances. In this work, the design, realization, and experimental investigation of the thermoelectric properties exhibited by a set of five Al:ZnO thin films with thicknesses of 300 nm and Al doping levels ranging from 2 to 8 at.% are described. Using a multi-technique approach, the main structural and morphological features of the grown thin films are addressed, as well as the electrical and thermoelectrical transport properties. The results show that the samples exhibited a Seebeck coefficient absolute value in the range of 22–33 μV/K, assuming their maximum doping level was 8 at.%, while the samples’ resistivity was decreased below 2 × 10⁻³ Ohm·cm with a doping level of 3 at.%. The findings shine light on the perspectives of the applications of the metal ZnO thin film technology for thermoelectrics. Full article

(This article belongs to the Special Issue Thermoelectric Thin Films for Thermal Energy Harvesting)

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11 pages, 4272 KiB

Open AccessEditor’s ChoiceArticle

Inkjet Printing of High Aspect Ratio Silver Lines via Laser-Induced Selective Surface Wetting Technique

by Iseok Sim, Seongju Park, Kwon-Yong Shin, Chanwoo Yang, Heuiseok Kang, Jun Young Hwang and Seung-Jae Moon

Coatings 2023, 13(4), 683; https://doi.org/10.3390/coatings13040683 - 27 Mar 2023

Cited by 4 | Viewed by 2181

Abstract

The field of printed electronics for highly integrated circuits and energy devices demands very fine and highly conductive electric interconnections. In this study, conductive lines having a high cross-sectional aspect ratio were printed via the inkjet printing of Ag nanoparticle inks assisted by [...] Read more.

The field of printed electronics for highly integrated circuits and energy devices demands very fine and highly conductive electric interconnections. In this study, conductive lines having a high cross-sectional aspect ratio were printed via the inkjet printing of Ag nanoparticle inks assisted by a laser-induced selective surface wetting technique: a hydrophobic layer of self-assembled monolayer-treated ZnO nanorods was coated on a glass substrate and selectively ablated by a laser to form micro-channels for the inkjet, whose surface energy changed from 36.3 mJ/m² to 51.5 mJ/m² before and after the laser irradiation. With the varying width of the laser-ablated channels and pitch of jetted ink drops, the 3D shapes of the printed silver lines were measured to investigate their effects on the widths, heights, and uniformities of the printed patterns. The results showed that the present technique realized a uniform line of 35 μm width and 0.46 μm average thickness, having an aspect ratio of 0.013, which is 7.6 times higher than that printed on bare glass. Full article

(This article belongs to the Special Issue Printed Functional Thin Films for Electronic, Optoelectronic and Sensing Applications)

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19 pages, 5421 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Curing Temperature and Thickness of Polybutyl Methacrylate Siloxane Coatings on the Corrosion Protection of Structural Steel S355

by Damir Hamulić, Gregor Medoš, Dorota Korte, Peter Rodič and Ingrid Milošev

Coatings 2023, 13(4), 675; https://doi.org/10.3390/coatings13040675 - 26 Mar 2023

Cited by 4 | Viewed by 1922

Abstract

This study aimed to determine the effects of coating thickness and curing temperature on the properties of a polybutyl methacrylate-siloxane coating deposited on structural steel S355. First, the thermal properties of the sol as a function of temperature were investigated using thermogravimetric analysis [...] Read more.

This study aimed to determine the effects of coating thickness and curing temperature on the properties of a polybutyl methacrylate-siloxane coating deposited on structural steel S355. First, the thermal properties of the sol as a function of temperature were investigated using thermogravimetric analysis coupled with mass spectrometry and differential scanning calorimetry. After coating deposition on structural steel S355 using a dip-coating process, the coating composition and porosity were evaluated using Fourier transform infrared spectroscopy and photothermal beam deflection spectroscopy. In the second part, coating thickness, topography, and corrosion properties were studied as functions of withdrawal rate during deposition. The corrosion properties of variously prepared coatings were evaluated using electrochemical impedance measurements in 3.5 wt.% NaCl and salt spray testing according to the ASTM B117 standard. An elevated curing temperature (at 150 °C) of the polybutyl methacrylate siloxane sol-gel coating impairs greater crosslinking and lower porosity, while the optimal thickness of 4 μm is achieved with the appropriate withdrawal rate to obtain a homogeneous, defect-free surface. Under these optimal conditions, the protection of structural steel against corrosion in a chloride environment lasting for more than 6 months can be achieved. Full article

(This article belongs to the Special Issue New Developments of Protective Coatings, Organic Polymers, and Surface Analysis)

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17 pages, 11204 KiB

Open AccessEditor’s ChoiceArticle

Characterization and Control of Residual Stress in Plasma-Sprayed Silicon Coatings on SiC/SiC Composites

by Mengqiu Guo, Yongjing Cui, Changliang Wang, Jian Jiao, Xiaofang Bi and Chunhu Tao

Coatings 2023, 13(4), 674; https://doi.org/10.3390/coatings13040674 - 26 Mar 2023

Cited by 4 | Viewed by 1831

Abstract

In order to reveal the relationship between residual stress in Si layers of SiC/SiC composites and the different parameters used in their preparation, the residual stress of the coating surface was tested using X-ray sin²ψ technology and laser Raman spectroscopy. Then, [...] Read more.

In order to reveal the relationship between residual stress in Si layers of SiC/SiC composites and the different parameters used in their preparation, the residual stress of the coating surface was tested using X-ray sin²ψ technology and laser Raman spectroscopy. Then, the Raman shift–stress coefficient (P) and the Raman shift with free stress (ω₀) were calculated as −201.41 MPa/cm⁻¹ and 520.591 cm⁻¹ via linear fitting with the least squares method. The results showed that all the as-sprayed Si coatings exhibited tensile stress on the surface, ranging from 53.5 to 65.9 MPa. The parameters of the spraying distance and second gas (H₂) flow rate were considered to be the most important for controlling the residual stress on the coating surface. Additionally, the surface tensile stress of the Si layers could be eliminated and even changed into compressive stress by annealing above 800 °C. Furthermore, the residual stress distribution in the cross-section of the Si layers was evaluated using laser Raman spectroscopy. Additionally, the particle characteristics, such as in-flight velocity and temperature, were investigated using a diagnostic system. The results of this research contribute to increasing the understanding and control of residual stress in APS Si bond layers. Full article

(This article belongs to the Special Issue Thermal Spray Coatings)

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16 pages, 5935 KiB

Open AccessEditor’s ChoiceArticle

Tailored Biobased Resins from Acrylated Vegetable Oils for Application in Wood Coatings

by Sabine Briede, Oskars Platnieks, Anda Barkane, Igors Sivacovs, Armands Leitans, Janis Lungevics and Sergejs Gaidukovs

Coatings 2023, 13(3), 657; https://doi.org/10.3390/coatings13030657 - 20 Mar 2023

Cited by 4 | Viewed by 2914

Abstract

The modern coating market is dominated by acrylic, polyurethane, and polyester polymer resins produced from unsustainable fossil resources. Herein, we propose the preparation of resins from biobased components to produce functional and solvent-free wood coatings with enhanced performance properties. Acrylated rapeseed, linseed, and [...] Read more.

The modern coating market is dominated by acrylic, polyurethane, and polyester polymer resins produced from unsustainable fossil resources. Herein, we propose the preparation of resins from biobased components to produce functional and solvent-free wood coatings with enhanced performance properties. Acrylated rapeseed, linseed, and grapeseed oils were prepared via a one-step synthesis and used as a basis for the control of resin viscosity and fatty acid content. A combination of vegetable oil acrylates was used as a matrix and the biobased monomer propoxylated glycerol triacrylate (GPT) was selected to tailor the properties of the UV crosslinked network. During polymerization, the GPT monomer induced a two-phase microstructure as indicated by an SEM analysis. The possibility of generating a tailored microstructure in the final material was examined in this study. The addition of GPT increased the storage modulus by up to five-fold, crosslink density by up to two-fold at 20 °C, and glass transition temperature by up to 10.2 °C. Pull-off adhesion tests showed a strength of 1.21 MPa. In addition, the photo-oxidation effect on samples, i.e., aging, was assessed with microhardness, sliding friction, and optical microscopy. Coatings showed a microhardness value up to 250 MPa, while a coefficient of friction (μ) was in the range of 0.21 to 0.88. Full article

(This article belongs to the Special Issue Bio-Based and Bio-Inspired Polymers and Composites)

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14 pages, 4498 KiB

Open AccessEditor’s ChoiceArticle

Behaviour of Thermochromic Coatings under Thermal Exposure

by Zuzana Tatíčková, Jan Kudláček, Michal Zoubek and Jiří Kuchař

Coatings 2023, 13(3), 642; https://doi.org/10.3390/coatings13030642 - 18 Mar 2023

Cited by 4 | Viewed by 1778

Abstract

Interactive thermochromic coatings based on Leuco dye are most commonly used in research for building cooling applications. The coatings developed by the authors are primarily aimed at industrial applications on metal substrates, mainly for safety reasons. Thanks to a higher transition temperature associated [...] Read more.

Interactive thermochromic coatings based on Leuco dye are most commonly used in research for building cooling applications. The coatings developed by the authors are primarily aimed at industrial applications on metal substrates, mainly for safety reasons. Thanks to a higher transition temperature associated with a significant change in shade, they have the potential to prevent burns and can be used as an element of active protection in exposed areas. Interactive thermochromic materials with different base matrices and two dispersion methods have been monitored and tested over the long term to gain an overall impression of their behaviour and applicability. The monitoring of colour characteristics helps to understand the behaviour of the thermochromic pigment in different primer matrices. The values of L*, a*, and b* and the spectral curves measured by a spectrophotometer were compared. Colour differences between the cold and heated conditions were also evaluated. ΔE* values for acrylate polyol reached up to 39. For waterborne paint, they varied according to the method of dispersion—when using a saw tooth stirrer, ΔE* was 23, and when mixing with a rotor-stator device, up to 56. Similarly, for the polyurethane matrix: ΔE* went up to 39 for stirring with a saw tooth stirrer while ΔE* was 64 for the rotor-stator. From the measurement of the behaviour of the coatings during temperature exposure, it can be concluded that most of the samples show a decrease in the transition temperature. Monitoring the behaviour of coatings during cooling is important for choosing a suitable base matrix that will ensure the long-term functionality of the coating and declare the temperature range of its use for safety applications. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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18 pages, 3309 KiB

Open AccessEditor’s ChoiceArticle

Titanium Implant Alloy Modified by Electrochemically Deposited Functional Bioactive Calcium Phosphate Coatings

by Jozefina Katić, Sara Krivačić, Željka Petrović, Dajana Mikić and Marijan Marciuš

Coatings 2023, 13(3), 640; https://doi.org/10.3390/coatings13030640 - 17 Mar 2023

Cited by 10 | Viewed by 2763

Abstract

Calcium phosphate-based (CaP) bioceramic materials are widely used in the field of bone regeneration, both in orthopaedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The formation of CaP coatings on high-strength implant materials such as titanium alloys combines the [...] Read more.

Calcium phosphate-based (CaP) bioceramic materials are widely used in the field of bone regeneration, both in orthopaedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The formation of CaP coatings on high-strength implant materials such as titanium alloys combines the superior mechanical properties of metals with the osteoconductive properties of CaP materials. In this work, the electrochemically assisted deposition of CaP coatings on the titanium alloy, TiAlNb, which is commonly used commercially as an implant material in orthopaedic devices, was examined. The barrier properties (electronic properties) of unmodified and CaP-modified titanium alloy were tested in situ in a simulated physiological solution, Hanks’ solution, under in vitro conditions of real implant applications using electrochemical impedance spectroscopy (EIS). The morphology and microstructure of the obtained CaP deposit were characterised by scanning electron microscopy (SEM) and chemical composition was assessed by energy dispersive X-ray spectroscopy (EDS) and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The aim was to investigate the effect of calcium phosphate CaP coating on the corrosion resistance of the titanium TiAlNb alloy and to understand better the deposition process in the production of bioactive functional coatings on metallic implant materials. Full article

(This article belongs to the Special Issue Biomimetic Approaches in Coatings Synthesis)

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18 pages, 3372 KiB

Open AccessEditor’s ChoiceArticle

Direct Liquid Reactor-Injector of Nanoparticles: A Safer-by-Design Aerosol Injection for Nanocomposite Thin-Film Deposition Adapted to Various Plasma-Assisted Processes

by Guillaume Carnide, Laura Cacot, Yohan Champouret, Vincent Pozsgay, Thomas Verdier, Adèle Girardeau, Marjorie Cavarroc, Andranik Sarkissian, Anne-Françoise Mingotaud, Constantin Vahlas, Myrtil Louise Kahn, Nicolas Naudé, Luc Stafford and Richard Clergereaux

Coatings 2023, 13(3), 630; https://doi.org/10.3390/coatings13030630 - 16 Mar 2023

Cited by 3 | Viewed by 1973

Abstract

The requirements of nanocomposite thin films, having non-aggregated nanoparticles homogeneously dispersed in the matrix, have been realized using a new method of Direct Liquid Reactor-Injector (DLRI) of nanoparticles. In this approach, unlike conventional aerosol-assisted plasma deposition, the nanoparticles are synthesized before their injection [...] Read more.

The requirements of nanocomposite thin films, having non-aggregated nanoparticles homogeneously dispersed in the matrix, have been realized using a new method of Direct Liquid Reactor-Injector (DLRI) of nanoparticles. In this approach, unlike conventional aerosol-assisted plasma deposition, the nanoparticles are synthesized before their injection as an aerosol into plasma. In our experiments, we have used two different plasma reactors, namely an asymmetric low-pressure RF plasma reactor and a parallel plate dielectric barrier discharge at atmospheric pressure. Our results have shown that DLRI can be easily coupled with various plasma processes as this approach allows the deposition of high-quality multifunctional nanocomposite thin films, with embedded nanoparticles of less than 10 nm in diameter. Hence, DLRI coupled with plasma processes meets the specifications for the deposition of multifunctional coatings. Full article

(This article belongs to the Special Issue Functionalities of Polymer-Based Nanocomposite Films and Coatings)

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13 pages, 2496 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Development of a Surface Treatment to Achieve Long-Lasting Antimicrobial Properties and Non-Cytotoxicity through Simultaneous Incorporation of Ag and Zn via Two-Step Micro-Arc Oxidation

by Yusuke Tsutsumi, Harumi Tsutsumi, Tomoyo Manaka, Peng Chen, Maki Ashida, Hideki Katayama and Takao Hanawa

Coatings 2023, 13(3), 627; https://doi.org/10.3390/coatings13030627 - 16 Mar 2023

Cited by 1 | Viewed by 1774

Abstract

A customized micro-arc oxidation (MAO) treatment technique was developed to obtain antibacterial properties with no toxicity on Ti surfaces. A two-step MAO treatment was used to fabricate a specimen containing both Ag and Zn in its surface oxide layer, and the optimal incorporation [...] Read more.

A customized micro-arc oxidation (MAO) treatment technique was developed to obtain antibacterial properties with no toxicity on Ti surfaces. A two-step MAO treatment was used to fabricate a specimen containing both Ag and Zn in its surface oxide layer, and the optimal incorporation conditions were determined. Surface characterization by EDS was performed followed by the antibacterial properties against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) and osteogenic cell compatibility evaluations. In addition, metal ion release tests were performed to evaluate the contents of Ag and Zn and the ion release behavior in order to simulate practical usage. MAO-treated specimens prepared using proper concentrations of Ag and Zn (0.5Ag-5Zn: 0.5 mM AgNO₃ and 5.0 mM ZnCl, respectively) exhibited excellent antibacterial properties against E. coli and S. aureus and no toxicity to MC3T3-E1 in antibacterial and cytotoxic evaluations, respectively. The antibacterial property of 0.5Ag-5Zn against S. aureus was sustained even after two months of immersion in physiological saline, simulating the in vivo environment. Full article

(This article belongs to the Special Issue Biomimetic Approaches in Coatings Synthesis)

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16 pages, 7047 KiB

Open AccessEditor’s ChoiceArticle

Microstructure, Mechanical Properties, Wear and Erosion Performance of a Novel High Entropy Nitride (AlCrTiMoV)N Coating Produced by Cathodic Arc Evaporation

by Alex Lothrop, Qi Yang and Xiao Huang

Coatings 2023, 13(3), 619; https://doi.org/10.3390/coatings13030619 - 14 Mar 2023

Cited by 1 | Viewed by 1564

Abstract

(AlCrTiMoV)N high entropy nitride film was prepared on 17-4PH stainless steel substrate using cathodic arc evaporation (CAE). The composition, microstructure, and thermal stability were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Mechanical properties such as hardness [...] Read more.

(AlCrTiMoV)N high entropy nitride film was prepared on 17-4PH stainless steel substrate using cathodic arc evaporation (CAE). The composition, microstructure, and thermal stability were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Mechanical properties such as hardness and Young’s modulus and coating performance against wear and erosion were also evaluated. The results show that the (AlCrTiMoV)N coating assumes a single-phased solid solution B1 FCC structure. It has excellent thermal stability and retains its structure with no decomposition observed up to a temperature of 1000 °C. The hardness and elastic modulus are measured as 21.3 GPa and 304 GPa, respectively. The coating contains some metallic droplets. As a potential protective coating, the (AlCrTiMoV)N coating has a lower wear rate but a higher erosion rate when compared to the TiN baseline coating. Full article

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

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15 pages, 6721 KiB

Open AccessEditor’s ChoiceArticle

Coating of Leather with Dye-Containing Antibacterial and Conducting Polypyrrole

by Fahanwi Asabuwa Ngwabebhoh, Oyunchimeg Zandraa, Tomáš Sáha, Jaroslav Stejskal, Dušan Kopecký, Miroslava Trchová and Jiří Pfleger

Coatings 2023, 13(3), 608; https://doi.org/10.3390/coatings13030608 - 13 Mar 2023

Cited by 4 | Viewed by 1937

Abstract

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic [...] Read more.

In the search for functional organic biomaterials, leather constituted by collagen fibers was coated with a conducting polymer, polypyrrole. The coating was carried out during the oxidation of pyrrole in an aqueous solution of poly(N-vinylpyrrolidone) in the presence of five organic dyes: crystal violet, neutral red, methyl orange, acriflavine, and methylene blue. This technique ensures the uniform coating of collagen fibers with polypyrrole and incorporation of organic dyes. The surface morphology was observed with scanning electron microscopy and the transverse profile, reflecting the penetration of the conducting phase into the leather body with optical microscopy. While the polypyrrole coating endows leather with electrical conductivity, organic dyes are expected to affect the polymer morphology and to provide an antibacterial effect. The lowest sheet resistance and antibacterial activity were obtained with crystal violet. This type of coating was characterized in more detail. Infrared spectroscopy confirmed the coating of collagen fibers with polypyrrole and dye incorporation. Mechanical properties were extended to the cyclic bending of the leather at various angles over 5000 cycles. The relative resistance changes were a few percent, indicating good electrical stability during repeated mechanical stress. Full article

(This article belongs to the Special Issue Functional Polymer Films and Their Applications)

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11 pages, 2835 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Physico-Mechanical Properties of a Newly Developed Base Material Containing Mineral Trioxide Aggregate

by Keigo Nakamura, Noriko Horasawa, Toshiyuki Okuse, Ryutaro Uchikawa, Katsumitsu Shimada, Akihiro Kuroiwa, Satoshi Murakami, Hiromasa Hasegawa and Atsushi Kameyama

Coatings 2023, 13(3), 597; https://doi.org/10.3390/coatings13030597 - 11 Mar 2023

Viewed by 1840

Abstract

The aim of this study was to evaluate the physico-mechanical properties of a new cavity base material containing mineral trioxide aggregate, LA-T1, prototyped by Neo Dental Chemical Products for indirect restoration. Three base materials, LA-T1, Cavios (CAV, Neo Dental Chemical Products), and Bulk [...] Read more.

The aim of this study was to evaluate the physico-mechanical properties of a new cavity base material containing mineral trioxide aggregate, LA-T1, prototyped by Neo Dental Chemical Products for indirect restoration. Three base materials, LA-T1, Cavios (CAV, Neo Dental Chemical Products), and Bulk Base Hard (BBH, Sun Medical), were examined. The depth of cure, microshear bond strength with a resin-based luting cement, and the compressive strength of these materials were investigated. The depth of cure of LA-T1 was similar to that of CAV, while the depth of cure of BBH was above the measurement limit. The distance from the base material to the light source, 0 mm and 4 mm, did not significantly affect the depth of cure of all materials. The microshear bond strength of LA-T1 bonded to a resin-based luting cement was slightly higher than that of CAV and similar to that of BBH, both of which were bonded to the same luting cement under the same conditions. The compressive strength of LA-T1 was similar to that of CAV but less than that of BBH. The results of this study indicate that LA-T1 has properties that are similar to those of CAV and thus can be clinically applied. Full article

(This article belongs to the Special Issue Biomimetic Approaches in Coatings Synthesis)

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18 pages, 4459 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Deposition Temperature on the Structure, Mechanical, Electrochemical Evaluation, Degradation Rate and Peptides Adhesion of Mg and Si-Doped Hydroxyapatite Deposited on AZ31B Alloy

by Anca Constantina Parau, Mihaela Dinu, Cosmin Mihai Cotrut, Iulian Pana, Diana Maria Vranceanu, Lidia Ruxandra Constantin, Giuseppe Serratore, Ioana Maria Marinescu, Catalin Vitelaru, Giuseppina Ambrogio, Dennis Alexander Böhner, Annette G. Beck-Sickinger and Alina Vladescu (Dragomir)

Coatings 2023, 13(3), 591; https://doi.org/10.3390/coatings13030591 - 9 Mar 2023

Cited by 5 | Viewed by 1664

Abstract

Degradable and non-degradable biomaterials are two categories that can be used to classify the existing biomaterials, being a solution for eliminating a second surgical intervention of the implant when the tissue has properly recovered. In the present paper, the effect of deposition temperature [...] Read more.

Degradable and non-degradable biomaterials are two categories that can be used to classify the existing biomaterials, being a solution for eliminating a second surgical intervention of the implant when the tissue has properly recovered. In the present paper, the effect of deposition temperature on the structure, morphology, hardness, electrochemical evaluation, degradation properties and functional peptides adhesion of Mg and Si-doped hydroxyapatite was investigated. The coatings were obtained by RF magnetron sputtering technique at room temperature (RT) and 200 °C on AZ31B alloy substrate. Results showed that an increase in deposition temperature led to an improvement in hardness and reduced modulus of about 47%. From an electrochemical point of view, a comparative assessment of corrosion resistance was made as a function of the immersion medium used, highlighting the superior behaviour revealed by the coating deposited at elevated temperature when immersed in DMEM medium (i_corr~12 µA/cm², R_coat = 705 Ω cm², R_ct = 7624 Ω cm²). By increasing the deposition temperature up to 200 °C, the degradation rate of the coatings was slowed, more visible in the case of DMEM, which had a less aggressive effect after 14 days of immersion. Both deposition temperatures are equally suitable for further bio-inspired coating with a mussel-derived peptide, to facilitate biointegration. Full article

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

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13 pages, 1983 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Nano-Silver–Silver Ion Composite Antibacterial Agents for Green Powder Coatings

by Haiping Zhang, Jixing Cui, Jesse Zhu, Yuanyuan Shao and Hui Zhang

Coatings 2023, 13(3), 575; https://doi.org/10.3390/coatings13030575 - 7 Mar 2023

Cited by 2 | Viewed by 2315

Abstract

Nano-silver is characterized by broad-spectral, strong and stable antibacterial properties, which make it a promising material in coating applications. However, the efficiency of nano-silver is generally low in the coating of films. Here, we developed a series of highly active and durable silver [...] Read more.

Nano-silver is characterized by broad-spectral, strong and stable antibacterial properties, which make it a promising material in coating applications. However, the efficiency of nano-silver is generally low in the coating of films. Here, we developed a series of highly active and durable silver ions–nano-silver antimicrobial agents for powder coatings. To optimize antimicrobial activity and durability, two different nano-silver generation methods, i.e., in situ and ex situ methods combined with different carrier materials, i.e., zeolite with high ion-exchange ability and montmorillonite of layered structure were adopted and investigated. All four antibacterial additives show high activity with a reduction rate of over 99.99% and R value of over 5. The ex situ generated nano-silver antibacterial agents with both carriers exhibit higher activity in the initial antibacterial property and antibacterial durability that the coating films are able to maintain over 99% antimicrobial reduction after 20 cycles (1200 times) of soap solution wiping. They also show a lower yellowish color difference of less than three compared to the films with in situ generation method. The one with montmorillonite as carrier shows the stronger antibacterial property with an R value of 5.88 and slightly better film appearance of lower color difference, smaller reduction in gloss and increase in haze as compared to zeolite carrier due to the layered structure. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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13 pages, 13057 KiB

Open AccessEditor’s ChoiceArticle

NiCo Prussian-Blue-Derived Cobalt–Nickel-Layered Double Hydroxide with High Electrochemical Performance for Supercapacitor Electrodes

by Qihao Yin, Bo Gao, Haiyang Fu and Liang Hu

Coatings 2023, 13(3), 554; https://doi.org/10.3390/coatings13030554 - 4 Mar 2023

Cited by 4 | Viewed by 2155

Abstract

High-performance electrode materials are crucial to the improvement of the supercapacitor performance index. Ni₂Co₁HCF@CoNi-LDH composites with a core–shell structure were prepared by a combination of coprecipitation and constant potential electrodeposition, and the microscopic morphology and phase composition of the [...] Read more.

High-performance electrode materials are crucial to the improvement of the supercapacitor performance index. Ni₂Co₁HCF@CoNi-LDH composites with a core–shell structure were prepared by a combination of coprecipitation and constant potential electrodeposition, and the microscopic morphology and phase composition of the composites were characterized by XRD, SEM, FTIR and XPS. The results showed that the NiCo Prussian blue (Ni₂Co₁HCF) was grown on the nickel foam (NF) substrate by in situ etching, while the nickel–cobalt double hydroxide (CoNi-LDH) was covered on the NiCo Prussian blue surface by electrodeposition, and the composite still retained the cubic skeleton morphology of the NiCo Prussian blue. The electrochemical properties of the composites were investigated using a three-electrode system in 2 M KOH. The results showed that their discharge specific capacity was as high as 1937 F·g⁻¹ at a current density of 1 A·g⁻¹ and still had 81.3% capacity retention at 10 A·g⁻¹, and they exhibited an excellent rate capability. The capacity retention rate was 87.1% after 1000 cycles at 5 A·g⁻¹ and, thus, the composite material has good application prospects as a supercapacitor electrode material. Full article

(This article belongs to the Special Issue Coating Electrode Materials for Next-Generation Energy Storage)

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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 1 | Viewed by 3020

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 3 | Viewed by 1693

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 3 | Viewed by 2825

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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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 1402

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 2 | Viewed by 1921

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 4 | Viewed by 2296

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 2 | Viewed by 1484

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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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 9 | Viewed by 5376

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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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 18 | Viewed by 2317

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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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 1 | Viewed by 2688

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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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 1544

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 1 | Viewed by 1594

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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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 25 | Viewed by 1975

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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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 2 | Viewed by 2932

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 6 | Viewed by 2836

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

Viewed by 1272

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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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 8 | Viewed by 1939

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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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 1 | Viewed by 1629

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 4 | Viewed by 2168

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, 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 4 | Viewed by 2220

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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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 6 | Viewed by 2716

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 1937

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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