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Volume 13
Issue 3
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Coatings, Volume 13, Issue 3 (March 2023) – 186 articles

Cover Story (view full-size image): In accordance with the downscaling of semiconducting materials, area-selective atomic layer deposition methods have been proposed to preserve thin-film quality, but there is a lack of quantitative data that relates to surface-scale kinetics and macroscopic fluid dynamics. Multiscale modeling provides an alternative, in silico approach for characterizing thin-layer deposition processes quantitatively, which are essential for their optimization and scale-up in reactor design. This work discusses the architectural multiscale framework, which conjoins ab initio quantum mechanics computations, mesoscopic kinetic Monte Carlo methods, and macroscopic computational fluid dynamics to simulate the behavior of area-selective atomic layer deposition processes for a spatial reactor configuration. View this paper
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15 pages, 3794 KiB  
Article
Mechanical Strengths of Alkali-Activated Blast Furnace Slag Powder with Different Alkali Activators and Plant Fibers
by Jing Zhu, Lizhuo Song, Zijian Qu, Xiaopeng Wang, Zijie Wen, Xiaodong Liu and Hui Wang
Coatings 2023, 13(3), 664; https://doi.org/10.3390/coatings13030664 - 22 Mar 2023
Cited by 1 | Viewed by 1372
Abstract
In this paper, the influence of water glass types, the modulus of water glass, the alkali content, the water consumption, and plant fibers on the mechanical strengths of alkali-activated blast furnace slag powder (BFS) is investigated. Moreover, the fiber types and pretreatment on [...] Read more.
In this paper, the influence of water glass types, the modulus of water glass, the alkali content, the water consumption, and plant fibers on the mechanical strengths of alkali-activated blast furnace slag powder (BFS) is investigated. Moreover, the fiber types and pretreatment on the plant fibers and the measuring temperature on the performance of alkali-activated BFS are further considered. Results indicate that BFS activated by potassium silicate shows higher mechanical strengths than that activated by sodium silicate. The alkali-activated BFS with alkali treatment on fibers is the most advantageous. The modulus of alkali leads to decreasing the compressive strength. A total of 35% water consumption is the most beneficial to the specimens’ flexural and compressive strengths. Samples with 14% potassium silicate show the maximum mechanical strength. Alkali-activated BFS with 1% wheat straw fibers in addition by total volume represents the maximum mechanical strength. The alkali-activated BFS with alkali treatment on fibers is the most advantageous. The addition of potassium silicate can improve the flexural and compressive strengths by the maximum values of 30.4% and 16.8% compared to specimens with sodium silicate. A total of 35% water consumption can increase the flexural and compressive strengths by 33.8% and 32.7%. Full article
(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)
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12 pages, 4465 KiB  
Article
First Approach to ZrB2 Thin Films Alloyed with Silver Prepared by Magnetron Co-Sputtering
by Tomáš Fiantok, Martin Truchlý, Viktor Šroba, Tomáš Roch, Vitalii Izai, Marek Vidiš, Marián Haršáni, Leonid Satrapinskyy and Marián Mikula
Coatings 2023, 13(3), 663; https://doi.org/10.3390/coatings13030663 - 22 Mar 2023
Cited by 2 | Viewed by 1105
Abstract
Hexagonal ZrB2 belongs to the group of ultra-high temperature ceramics representing an important class of materials with the potential to meet the high demands of today’s industry. However, this potential is limited by inherent brittleness and poor tribological properties. Here, the combination [...] Read more.
Hexagonal ZrB2 belongs to the group of ultra-high temperature ceramics representing an important class of materials with the potential to meet the high demands of today’s industry. However, this potential is limited by inherent brittleness and poor tribological properties. Here, the combination of density functional theory and experiment is used to investigate the effect of silver alloying on the mechanical and tribological properties of hexagonal ZrB2 thin films. Calculations indicate strong insolubility of Ag atoms in the ZrB2 metal sublattice and a significant effect on the mechanical properties, pointing out an improvement in ductility and tribological properties but at the cost of reduced hardness. The experiments confirmed the theoretical predictions of the strong insolubility of silver, where the magnetron-sputtered Zr1−xAgxB2+Δ films form a segregated nanostructure consisting of separated hexagonal ZrB2 and cubic Ag phases. With increased Ag content, values of Young’s modulus decrease from EZrB2.31 = 375 GPa to EZr0.26Ag0.74B0.89 = 154 GPa, followed by a decrease in hardness from HZrB2.31 = 30 GPa to a value of HZr0.26Ag0.74B0.89 = 4 GPa. The suppression of crack formation is also shown with the material flow around cube corner indents, indicating enhanced ductility. The improvement of tribological properties was also confirmed when the coefficient of friction (COF) was reduced from COFZrB2.31 ~0.9 to a value of COFZr0.26Ag0.74B0.89 ~0.25 for all counterpart materials—steel (100Cr6), Si3N4, and WC/Co. Full article
(This article belongs to the Section Thin Films)
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18 pages, 8856 KiB  
Article
Influence of Milling Conditions on AlxCoCrFeNiMoy Multi-Principal-Element Alloys
by Diego Delgado Arroyo, Tim Richter, Dirk Schroepfer, Andreas Boerner, Michael Rhode, Thomas Lindner, Bianca Preuß and Thomas Lampke
Coatings 2023, 13(3), 662; https://doi.org/10.3390/coatings13030662 - 22 Mar 2023
Viewed by 1218
Abstract
Multi-Principal-Element or High-Entropy Alloys (MPEAs/HEAs) have gained increasing interest in the past two decades largely due to their outstanding properties such as superior mechanical strength and corrosion resistance. However, research studies on their processability are still scarce. This work assesses the effect of [...] Read more.
Multi-Principal-Element or High-Entropy Alloys (MPEAs/HEAs) have gained increasing interest in the past two decades largely due to their outstanding properties such as superior mechanical strength and corrosion resistance. However, research studies on their processability are still scarce. This work assesses the effect of different machining conditions on the machinability of these novel alloys, with the objective of advancing the introduction of MPEA systems into industrial applications. The present study focuses on the experimental analysis of finish-milling conditions and their effects on the milling process and resulting surface finish of CoCrFeNi, Al0.3CoCrFeNi and Al0.3CoCrFeNiMo0.2 alloys fabricated via Spark Plasma Sintering. Ball-nose-end milling experiments have been carried out various milling parameters such as cutting speed, feed per cutting edge, and ultrasonic assistance. In situ measurements of cutting forces and temperature on the tool edge were performed during the experiments, and surface finish and tool wear were analyzed afterwards. The results exhibited decreasing cutting forces by means of low feed per cutting edge and reduced process temperatures at low cutting speed, with the use of ultrasonic-assisted milling. It was shown that the machinability of these modern alloys through conventional, as well as modern machining methods such as ultrasonic-assisted milling, is viable, and common theories in machining can be transferred to these novel MPEAs. Full article
(This article belongs to the Special Issue High-Entropy Alloy Coatings and Surface Functionalization)
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12 pages, 7234 KiB  
Article
Decomposition of Fingerprints on Porous TiO2 Thin Films
by Minsu Lee, Hohyeong Kim, Hyungsub Kim, Akash Katoch and Jae Young Park
Coatings 2023, 13(3), 661; https://doi.org/10.3390/coatings13030661 - 22 Mar 2023
Viewed by 1427
Abstract
This study investigated the effect of the mixing ratio of TiO2 nanoparticles (P25) and titanium alkoxide (T-sol) on various properties of TiO2 films. The specific surface area of the TiO2 film was determined using BET analysis, while the microstructure and [...] Read more.
This study investigated the effect of the mixing ratio of TiO2 nanoparticles (P25) and titanium alkoxide (T-sol) on various properties of TiO2 films. The specific surface area of the TiO2 film was determined using BET analysis, while the microstructure and thickness were analyzed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), respectively. Transmittance and pencil hardness tests were conducted to evaluate the transparency and durability of the coating layer, respectively. The results showed that, as the P25 content increased, the specific surface area of the TiO2 film also increased, but this effect decreased as the ratio of T-sol to P25 increased. Additionally, the thickness and surface roughness (Ra) of the coating layer increased as the P25 content increased, with the thickness increasing from 210 to 950 nm and Ra increasing from 51 to 88 nm. However, the transmittance of the coating layer decreased as the P25 content increased, indicating that the films became less transparent. Furthermore, the pencil hardness of the coating layer decreased as the P25 content increased, indicating that the films became less durable. Finally, the oil contact angle decreased as the P25 content increased, indicating that the films became more hydrophilic. Full article
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14 pages, 11239 KiB  
Article
The Microstructure Evolution and Dynamic Recrystallization Mechanism of Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr Alloys during High-Temperature Deformation
by Meng Zhou, Yunzhang Li, Shunlong Tang, Yijie Ban, Yi Zhang, Bin Gan, Xu Li, Lihua Fu, Baohong Tian, Yong Liu and Alex A. Volinsky
Coatings 2023, 13(3), 660; https://doi.org/10.3390/coatings13030660 - 22 Mar 2023
Viewed by 1318
Abstract
Copper alloys with a combination of good electrical conductivity and mechanical properties are widely used in automotive electronics, large-scale integrated circuits, and other fields. In this study, a new type of Cu–Ni–Si alloy with added trace elements of Co and Cr was fabricated. [...] Read more.
Copper alloys with a combination of good electrical conductivity and mechanical properties are widely used in automotive electronics, large-scale integrated circuits, and other fields. In this study, a new type of Cu–Ni–Si alloy with added trace elements of Co and Cr was fabricated. Hot compression tests of this alloy at different temperatures and strain rates were conducted using a Gleeble-1500D simulator. Then, the microstructure transformation and precipitation behaviors of the Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy were studied during a hot deformation process. The results show that the hot deformation behavior of the Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy includes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). The intensity of the texture in the microstructure is decreased, and the randomness of the texture in the microstructure is increased together with the recrystallization progress. The degree of recrystallization of the new Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy is increased when the hot deformation temperature rises. Additionally, the results indicate that there are two types of precipitates which are formed in the alloy during the hot deformation process. These two precipitates can pin dislocations and grain boundaries, and therefore, they significantly improve the hot compression resistance of the Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy. Full article
(This article belongs to the Special Issue Microstructure Evolution, Mechanical Properties, and Applications of Nonferrous Metal Alloys)
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10 pages, 5415 KiB  
Article
Effect of Powder Recycling on the Organization and Mechanical Properties of GH4169 Alloy by Laser Metal Deposition
by Haibo Zhang, Jieshuai Li and Yingqiu Li
Coatings 2023, 13(3), 659; https://doi.org/10.3390/coatings13030659 - 22 Mar 2023
Cited by 1 | Viewed by 1091
Abstract
The purpose of this research is to prepare GH4 169 alloy specimens by laser metal deposition, by investigating the changes in powder morphology, powder particle size, and elemental content during the cycling process. As well as the pore defects and microstructure of deposited [...] Read more.
The purpose of this research is to prepare GH4 169 alloy specimens by laser metal deposition, by investigating the changes in powder morphology, powder particle size, and elemental content during the cycling process. As well as the pore defects and microstructure of deposited samples prepared from recycled powder, we analyzed the changes in powder properties during the cycling process and the effects of using recycled powder on the organization and properties of LMD-deposited specimens. It was shown that the average particle size of the powder increased with the increase in the size of powder recycling, from 59.861 µm in the original powder to 64.144 µm after four cycles, with the phenomenon of powder burnout and satellite ball. The elemental content of the powder changed with the increase in the number of cycles, among which the elemental content of Nb increased significantly from 4.31 wt% of the original powder to 7.97 wt% after four cycles, the proportion of Laves phase in the deposited samples increased, the porosity and pore size increased, the tensile strength of the specimen decreased from 1046 MPa of the original powder to 936 MPa, the tensile strength decreased by 10.5%, and the elongation was increased to 27% from 11% of the original powder. Powder recycling can lead to powder aging and reduce the mechanical properties of the laser metal deposited formed parts. Full article
(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)
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4 pages, 177 KiB  
Editorial
Coating Technology Makes Comprehensive Surface Protection Possible
by Chi Ma
Coatings 2023, 13(3), 658; https://doi.org/10.3390/coatings13030658 - 21 Mar 2023
Cited by 3 | Viewed by 1427
Abstract
The tribology and wear protection of coatings has been an active and rapidly developing area for research and industries in recent years, with innovative coating materials, structures, and fabrication technologies [...] Full article
(This article belongs to the Special Issue Tribological Properties and Wear Protection of Coatings and Alloys)
16 pages, 5935 KiB  
Article
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 3 | Viewed by 1754
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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19 pages, 5690 KiB  
Article
Passivation and pH-Induced Precipitation during Anodic Polarization of Steel in Aluminate Electrolytes as a Precondition for Plasma Electrolytic Oxidation
by Roy Morgenstern, Claudia Albero Rojas, Frank Simchen, Vanessa Meinhold, Thomas Mehner and Thomas Lampke
Coatings 2023, 13(3), 656; https://doi.org/10.3390/coatings13030656 - 20 Mar 2023
Viewed by 1357
Abstract
Potentiodynamic and potentiostatic polarization tests in the potential range between open circuit potential (OCP) − 0.1 V and OCP + 4 V were carried out in aluminate–phosphate electrolytes with an aluminate concentration of 0.2 mol/L and varying phosphates contents between 0 and 0.1 [...] Read more.
Potentiodynamic and potentiostatic polarization tests in the potential range between open circuit potential (OCP) − 0.1 V and OCP + 4 V were carried out in aluminate–phosphate electrolytes with an aluminate concentration of 0.2 mol/L and varying phosphates contents between 0 and 0.1 mol/L. The pH was adjusted between 11.5 and 12.0 due to phosphate and optional KOH addition. A high-strength, dual-phase steel, which is relevant for lightweight construction, served as the substrate material. The layer microstructure was investigated by optical and scanning electron microscopy. Energy-dispersive X-ray spectroscopy and Raman spectroscopy were used for element and phase analyses. We found that iron hydroxides or oxides are initially formed independently of the electrolyte composition at low potentials. At around 1 V vs. standard hydrogen electrode (SHE), the current density suddenly increases as a result of oxygen evolution, which causes a significant reduction in the pH value. Precipitation leads to the formation of porous layers with thicknesses of 10 µm to 20 µm. In the case of a pure aluminate solution, the layer mainly consists of amorphous alumina. When adding phosphate to the electrolyte, the layer additionally contains the hydrous phosphate evansite. At the highest phosphate content in the electrolyte, the highest P content and the most pronounced crack network were observed. Full article
(This article belongs to the Special Issue Plasma Electrolytic Oxidation (PEO) Coatings, 2nd Edition)
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16 pages, 21828 KiB  
Article
Ti3C2@g-C3N4/TiO2 Ternary Heterogeneous Photocatalyst for Promoted Photocatalytic Degradation Activities
by Yuxin Bai, Shasha Xu, Jing Chen, Xun Sun, Shan Zhao, Jingcai Chang and Zuoli He
Coatings 2023, 13(3), 655; https://doi.org/10.3390/coatings13030655 - 20 Mar 2023
Cited by 6 | Viewed by 1538
Abstract
Ternary heterojunction photocatalysts can improve the transport and separation of photogenerated electrons and holes, which could promote their reduction and oxidation properties for environmental and energy applications. In this research, the ternary photocatalyst Ti3C2@TiO2/g-C3N4 [...] Read more.
Ternary heterojunction photocatalysts can improve the transport and separation of photogenerated electrons and holes, which could promote their reduction and oxidation properties for environmental and energy applications. In this research, the ternary photocatalyst Ti3C2@TiO2/g-C3N4 was successfully synthesized via direct electrostatic self-assembly during hydrothermal process. Ti3C2 MXene was used to optimize the interfacial carrier transport and separation between the interfaces. The obtained ternary heterostructured photocatalyst had a higher photocatalytic degradation performance for removing rhodamine B (RhB) and 4-chlorophenol (4-CP). The synergistic effect of heterojunction between g-C3N4 and TiO2 and Schottky barrier presented among TiO2 and Ti3C2 suppressed the recombination of the photogenerated electron–hole pairs. Moreover, the Ti3C2 can serve as an active site for the adsorption and activation of organic pollutants resulting from sufficient functional groups (F− here). Full article
(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)
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15 pages, 8721 KiB  
Article
Characterization of Nitrogen-Doped TiO2 Films Prepared by Arc Ion Plating without Substrate Heating in Various N2/O2 Gas Mixture Ratios
by Hsing-Yu Wu, Wen-Chun Huang, Jyh-Liang Wang, Guo-Yu Yu, Yung-Shin Sun and Jin-Cherng Hsu
Coatings 2023, 13(3), 654; https://doi.org/10.3390/coatings13030654 - 20 Mar 2023
Viewed by 1163
Abstract
Nitrogen-doped TiO2 films exhibit good photocatalytic ability in the visible (VIS) light region. This study reports the fabrication of these films using arc ion plating (AIP) in different ratios of nitrogen partial pressure (PN2) to oxygen partial pressure (PO2 [...] Read more.
Nitrogen-doped TiO2 films exhibit good photocatalytic ability in the visible (VIS) light region. This study reports the fabrication of these films using arc ion plating (AIP) in different ratios of nitrogen partial pressure (PN2) to oxygen partial pressure (PO2) without substrate heating and/or applied bias. This approach allows a significant broadening of the range of possible substrates to be used. X-ray diffraction (XRD) patterns indicate that these films deposited at room temperature are amorphous, and surface electron microscope (SEM) and atomic force microscope (AFM) images show that they have rough surfaces. Their transmittance and optical properties are measured with a spectrometer and ellipsometer, respectively. In addition, the bandgap energies of these amorphous films are derived by the ellipsometer from the Tauc–Lorentz (TL) model. The results indicate that the N-doped TiO2 film with a PN2/PO2 ratio of 1/4 attains the narrowest bandgap and the highest absorbance in the visible region. It can be attributed to the prominent Ti–N peaks observed in the sample’s Ti and N X-ray photoelectron spectroscopy (XPS) spectra. In addition, verified with the methylene blue (MB) test, this sample exhibits the best photocatalytic performance for its narrowest energy gap. Full article
(This article belongs to the Special Issue Design, Manufacturing and Measurement of Optical Film Coatings II)
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12 pages, 4079 KiB  
Communication
Cleaning Effect of Atmospheric-Plasma-Sprayed Y2O3 Coating Using Piranha Solution Based on Contamination Particle Measurement
by Hyuksung Kwon, Minjoong Kim, Jongho So, Seonjeong Maeng, Jae-Soo Shin and Ju-Young Yun
Coatings 2023, 13(3), 653; https://doi.org/10.3390/coatings13030653 - 20 Mar 2023
Cited by 1 | Viewed by 1441
Abstract
A Y2O3 coating was prepared using the atmospheric plasma spraying (APS) technique. On exposing the coating to CF4/O2/Ar plasma, a fluorine contamination layer (YOxFy) was formed, which was the main cause of [...] Read more.
A Y2O3 coating was prepared using the atmospheric plasma spraying (APS) technique. On exposing the coating to CF4/O2/Ar plasma, a fluorine contamination layer (YOxFy) was formed, which was the main cause of process drift and contamination particle generation on the APS–Y2O3 coating surface. To remove the YOxFy layer on the coating surface, a piranha solution, which is a mixture of sulfuric acid and hydrogen peroxide, was employed for cleaning. The piranha solution was found to be an excellent medium for removing the YOxFy layer. The amount of contamination particle generated could be reduced by approximately 37% after cleaning with a 3:1 piranha solution compared with before cleaning. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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12 pages, 4344 KiB  
Article
Effects of Surface Modification and Heat Treatment on the Storage and Application Properties of Waterborne Zinc-Based Paint
by Liran Liu, Yangtao Zhou, Qingpeng Li, Yuejun Yin, Wei Zhang and Na Wang
Coatings 2023, 13(3), 652; https://doi.org/10.3390/coatings13030652 - 20 Mar 2023
Viewed by 1155
Abstract
The high activity of metallic zinc particles with water, and consequently the short pot lift of a mixed waterborne organic zinc-rich paint, are the most well-known problem for their application. In this study, zinc powders were modified by silane-crosslinked potassium silicate and the [...] Read more.
The high activity of metallic zinc particles with water, and consequently the short pot lift of a mixed waterborne organic zinc-rich paint, are the most well-known problem for their application. In this study, zinc powders were modified by silane-crosslinked potassium silicate and the paint’s pot life was prolonged. Electron microscopy analysis showed that the zinc spheres in the waterborne paint were encapsulated by the shell consisted of silane-crosslinked potassium silicate and resin. The modification allowed the paint stay fluid after storage for 36 h. Nevertheless, the thickened shell was found to deteriorate the cathodic protection provided by the zinc particles. As a repair strategy, the post-heat treatment performing on the coating could awaken the protective effect of zinc powders. The anti-corrosion performance of the repaired coatings was confirmed by electrochemical tests and salt spray tests. Full article
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14 pages, 5251 KiB  
Article
Synthesis of Multicomponent Coatings by Electrospark Alloying with Powder Materials
by Valentin Mihailov, Natalia Kazak, Sergiu Ivashcu, Evgenii Ovchinnikov, Constantin Baciu, Anatoli Ianachevici, Raimundas Rukuiza and Audrius Zunda
Coatings 2023, 13(3), 651; https://doi.org/10.3390/coatings13030651 - 20 Mar 2023
Cited by 3 | Viewed by 1335
Abstract
The results of systematic studies of the electrospark alloying process with the introduction of dispersed materials into plasma of low-voltage pulsed discharges are presented. Technological methods have been developed for supplying the powder material straight into the treatment zone through a hollow electrode [...] Read more.
The results of systematic studies of the electrospark alloying process with the introduction of dispersed materials into plasma of low-voltage pulsed discharges are presented. Technological methods have been developed for supplying the powder material straight into the treatment zone through a hollow electrode of an anode or from the side, with the electrode-anode periodically contacting the substrate of cathode. It has been established that under the same energy regimes, when powder materials were introduced into the discharge zone, the increase in the mass of the cathode per time unit increases from 10 to 15 times or more. This study presents the process of synthesis of carbide phases (TiC and WC) during electrospark alloying of steel substrates with electrodes made of Ti, W, and graphite, with additional supply powders of these materials into the processing zone. A process has been developed for the synthesis of ternary compounds, so-called MAX-phases: Ti2AlC, Ti2AlN and Ti3SiC2 by electrospark alloying with powder compositions TiAlC, TiAlN and TiSiC. These MAX phases exhibit a unique combination of properties that are characteristic of both metals and ceramics. Energy modes of the processing were optimized, which resulted in high-quality coatings with the maximum content of carbide phases and ternary compounds. It has been established that the energy of electrical pulses during electrospark alloying, when powders of materials are fed into the interelectrode gap, ranges from 0.8 to 3.0 J, depending on their thermal physical properties. High wear and corrosion resistant characteristics of C45 structural steel with such electrospark coatings are obtained. The wear of steel with coatings in comparison with uncoated steel decreased by an average of 5.5–6.0 times. It was estimated the high corrosion resistance of 40X13 steel coated with TiC and WC in 3% NaCl solution. The corrosion current for these coatings is 0.044 and 0.075 A/cm2, respectively, and is significantly less than for coatings made of TiAlC, TiAlN, and TiSiC compositions. X-ray phase and optical metallographic microscopy analyses enabled the display of the amorphous-crystalline nature of the coatings. Full article
(This article belongs to the Special Issue Coatings and Surface Modification for Tribological Applications)
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17 pages, 3025 KiB  
Article
Study on Thixotropic Properties of Asphalt Mastics Based on Energy Viewpoint
by Xiaoyan Ma, Yubo Wang, Junpeng Hou, Yanping Sheng, Wanpeng Zheng and Shujuan Wu
Coatings 2023, 13(3), 650; https://doi.org/10.3390/coatings13030650 - 20 Mar 2023
Cited by 3 | Viewed by 1184
Abstract
An asphalt mastic has thixotropic characteristics that significantly influence its fatigue and healing performance. Therefore, understanding the thixotropy of an asphalt mastic is clearly of great importance. However, research in this area is still in the early stages. This study focuses on self-heating [...] Read more.
An asphalt mastic has thixotropic characteristics that significantly influence its fatigue and healing performance. Therefore, understanding the thixotropy of an asphalt mastic is clearly of great importance. However, research in this area is still in the early stages. This study focuses on self-heating as one of the biasing performances of asphalt material by analyzing the viscosity, stress, and hysteresis loops the of asphalt mastics under cyclic shear loading. Twelve types of asphalt mastics fabricated with asphalt, as well as different types of mineral filler, were selected to examine thixotropy. In addition, the filler/asphalt ratio was examined via the hysteresis technique to analyze the hysteresis loop and the viscosity–shear rate. The thixotropic potential function was also studied from the energy viewpoint. The results show that asphalt mastics with different asphalt binders, mineral fillers, and filler volume fractions showed hysteresis loops for shear stress versus shear rate diagrams. With an increase in the loading times of the cyclic load, the area of the hysteresis loop gradually decreases, and the hysteresis area most likely features a relatively stable value. The thixotropy of the asphalt can be significantly reduced by adding filler, and different types of mineral filler can slightly influence the thixotropy. The viscosity decreases with an increase in the shear rate, and it gradually recovers with a decrease in the shear rate. The greater the filler/asphalt ratio, the greater the viscosity, and the faster the viscosity’s descent is with the prolongation of time. Due to the existence of a higher amount of filler content, the recovery of a viscosity crack is more difficult. For asphalt mastics with high filler/asphalt ratios, the thixotropic mechanism can be explained via particle agglomeration and the depolymerization theory. For asphalt mastics with low and medium filler/asphalt ratios, the thixotropic mechanism can be explained via the particle chain theory. The damage and recovery of the internal structure of an asphalt mastic can be characterized by the structural failure potential function and the structural recovery potential function, respectively. Full article
(This article belongs to the Special Issue Asphalt Pavement: Materials, Design and Characterization)
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12 pages, 3330 KiB  
Article
Dispersion of Carbon Nanotubes Improved by Ball Milling to Prepare Functional Epoxy Nanocomposites
by Ziqi Gao, Quanjiabao Han, Jianbang Liu, Kangbo Zhao, Yin Yu, Yuanyuan Feng and Sensen Han
Coatings 2023, 13(3), 649; https://doi.org/10.3390/coatings13030649 - 20 Mar 2023
Cited by 2 | Viewed by 1965
Abstract
There has been an increase in interest in developing functional polymer composites based on green chemistry principles. The purpose of this study was to investigate the preparation of functional epoxy/carbon nanotube nanocomposites using ball milling methods. In contrast to mechanical mixing, ball milling [...] Read more.
There has been an increase in interest in developing functional polymer composites based on green chemistry principles. The purpose of this study was to investigate the preparation of functional epoxy/carbon nanotube nanocomposites using ball milling methods. In contrast to mechanical mixing, ball milling promoted good dispersion of CNTs within the epoxy matrix, thereby improving their mechanical properties and electrical conductivity. In epoxy nanocomposites with ball milling, Young’s modulus and tensile strength were increased by 653% and 150%, respectively, when CNT loading was 1.0 vol%. Additionally, the ball milling of CNTs improves their dispersion, resulting in a low percolation threshold at 0.67 vol%. The epoxy/CNT film sensor that was produced using the ball milling approach not only exhibited high reliability and sensitivity to mechanical strains and impact loads, but also possessed the ability to self-detect damage, such as cracks, and accurately locate them. This study marks a notable milestone in the advancement of functional epoxy/CNT composites through the ball milling approach. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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42 pages, 22234 KiB  
Article
Analysis of the Dynamic Thermal Barrier in Building Envelopes
by Veronika Mučková, Daniel Kalús, Daniela Koudelková, Mária Kurčová, Zuzana Straková, Martin Sokol, Rastislav Ingeli and Patrik Šťastný
Coatings 2023, 13(3), 648; https://doi.org/10.3390/coatings13030648 - 19 Mar 2023
Viewed by 1410
Abstract
This article focuses on the investigation of the dynamic thermal barrier (TB) and dynamic thermal resistance (DTR) of the building envelope. The aim is to analyze the DTR as a function of the temperature change of the heat transfer medium supplied to the [...] Read more.
This article focuses on the investigation of the dynamic thermal barrier (TB) and dynamic thermal resistance (DTR) of the building envelope. The aim is to analyze the DTR as a function of the temperature change of the heat transfer medium supplied to the dynamic TB layer and to determine the energy potential of several materially different fragments of the building envelope. The functions of TB and DTR depend on the uniform and continuous maintenance of temperature in a given layer of the building structure. The methodology is based on the analysis and synthesis of thermal resistance calculation, wall heating, and computer simulation. The research results show that the relatively low mean temperature of the heat transfer medium of approximately θm = 17 °C delivered to the TB layer represents RDTR = up to 30 ((m2·K)/W) for an equivalent dynamic thermal insulation thickness of 1000 mm for a required standard resistance of RSTANDARD = 6.50 ((m2·K)/W) of the individual fragments analyzed with static thermal insulation of 65 to 210 mm. The energy potential of a thermal barrier (TB) represents an increase of approximately 500% in the thermal resistance and up to 1500% in the thickness of the dynamic thermal insulation. Further research on the dynamic thermal barrier and verification of the results of the parametric study will continue with comprehensive computer simulations and experimental measurements on the test cell. Full article
(This article belongs to the Special Issue Fabrication, Properties Characterization and Application of Thermal Protective Coatings)
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17 pages, 8899 KiB  
Article
Synergistic Effects of Multiple Heterojunctions and Dopant Atom for Enhancing the Photocatalytic Activity of C-Modified Zn-Doped TiO2 Nanofiber Film
by Ying Lu, Xiangge Qin and Jinzhong Hong
Coatings 2023, 13(3), 647; https://doi.org/10.3390/coatings13030647 - 19 Mar 2023
Viewed by 1337
Abstract
To design efficient photocatalytic systems, it is necessary to inhibit the compounding of electron-hole pairs and promote light absorption in photocatalysts. In this paper, semiconductor heterojunction systems of C-modified Zn-doped TiO2 composite nanomaterials with nanofiber structures were synthesized by electrospinning and hydrothermal [...] Read more.
To design efficient photocatalytic systems, it is necessary to inhibit the compounding of electron-hole pairs and promote light absorption in photocatalysts. In this paper, semiconductor heterojunction systems of C-modified Zn-doped TiO2 composite nanomaterials with nanofiber structures were synthesized by electrospinning and hydrothermal methods. The composite nanofiber film was thoroughly characterized and the morphology, structure, chemical phases and optical properties were determined. Scanning electron microscopy confirmed that the nanofiber diameter was 150–200 nm and the C particles were uniformly modified on the smooth nanofiber surfaces. X–ray diffraction patterns and Raman show TiO2 as a typical anatase, modified C as graphite and Zn as ZnOcrystals. Moreover, the entry of Zn and C into the TiO2 lattice increases the crystal defects. Meanwhile, TiO2, ZnO and graphite form multiple heterojunctions, providing pathways for photogenerated carrier transfer. These synergistic effects inhibit the recombination of electron-hole pairs and provide more reaction sites, thus improving the photocatalytic efficiency. UV-Vis diffuse reflectance spectroscopy and fluorescence spectroscopyimply that these synergistic effects lead to improved optical properties of the composite. Using organic dyes (methylene blue, methyl orange, rhodamine Bandmalachite green) as simulated pollutants, the composite nanofiber film exhibited good photocatalytic activity for all dyes due to the significantly large specific surface area, small size effect and synergistic effects of multiple heterojunctions and dopant atom. In addition, the nanofiber film has good reusability and stability for the photodegradation of organic dyes, so it has potential for industrial applications. Full article
(This article belongs to the Special Issue Functional Nanomaterials in Catalysis for Environmental and Energy Application)
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12 pages, 5843 KiB  
Article
Study on Fatigue Performance of 2200 MPa High-Strength Wire of Main Cables Based on FE-SAFE
by Hongtao Li, Zhubing Zhou, Sen Liu, Leyong Wei, Jun Zhao and Han Su
Coatings 2023, 13(3), 646; https://doi.org/10.3390/coatings13030646 - 19 Mar 2023
Viewed by 1523
Abstract
In order to estimate the fatigue life of 2200 MPa high-strength steel wire for main cables at the outlet of the cable saddle, a fatigue loading test of a single steel wire was designed, and the value of the friction coefficient in finite [...] Read more.
In order to estimate the fatigue life of 2200 MPa high-strength steel wire for main cables at the outlet of the cable saddle, a fatigue loading test of a single steel wire was designed, and the value of the friction coefficient in finite element simulation and the scale factor in fatigue life analysis were determined. The fatigue life of the steel wire was analyzed by two-stage modelling. The results showed that the fatigue life of steel wire can be simulated effectively when the friction coefficient is 0.21 and the scale factor is 1.15. The fatigue life of 2200 MPa main cable wire at the saddle outlet is 4.78 million loading cycles. The research results laid a foundation for practical engineering application of high-strength steel wire for 2200 MPa main cables. Full article
(This article belongs to the Special Issue Heat Treatment and Surface Engineering of Tools and Dies)
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11 pages, 2095 KiB  
Article
Evaluation of the Thickness of Each Layer of Cu/Al Laminate Using Laser Ultrasonic
by Baoping Ji, Haonan Zhang, Jianshu Cao and Qingdong Zhang
Coatings 2023, 13(3), 645; https://doi.org/10.3390/coatings13030645 - 18 Mar 2023
Cited by 1 | Viewed by 1464
Abstract
A new method of detecting the thickness of each layer of Cu/Al laminates based on laser ultrasound was proposed for the online non-contact measurement of the thickness of each layer of Cu/Al laminates during the rolling process. This method utilized a laser to [...] Read more.
A new method of detecting the thickness of each layer of Cu/Al laminates based on laser ultrasound was proposed for the online non-contact measurement of the thickness of each layer of Cu/Al laminates during the rolling process. This method utilized a laser to excite and detect ultrasounds remotely and then obtains the transit time of the longitudinal wave pulse in the copper layer and aluminum layer to calculate their thicknesses. The finite element method was used for investigating the propagation behavior of longitudinal wave in Cu/Al laminate, and the minimum thickness of the copper layer that can be detected by this method was analyzed. The laser ultrasonic experimental platform was set up in the laboratory, and a sample of Cu/Al laminate with step shape was made. The experimental results demonstrate that the laser ultrasound can realize the non-contact and high-precision detection of the thickness of each layer of Cu/Al laminates and has the potential of online thickness measurement. Full article
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21 pages, 2583 KiB  
Review
Recent Progress in Perovskite Solar Cells: Status and Future
by Ying Chen, Man Zhang, Fuqiang Li and Zhenyuan Yang
Coatings 2023, 13(3), 644; https://doi.org/10.3390/coatings13030644 - 18 Mar 2023
Cited by 8 | Viewed by 5146
Abstract
The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has seen effective performance upgrades, showing remarkable academic research and commercial application value. Compared with commercial silicon cells, the PCE gap is narrowing. However, the stability, cost, and large-scale production are still far [...] Read more.
The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has seen effective performance upgrades, showing remarkable academic research and commercial application value. Compared with commercial silicon cells, the PCE gap is narrowing. However, the stability, cost, and large-scale production are still far behind. For scale-up preparing high-efficiency and stable PSCs, there is a variety of related research from each functional layer of perovskite solar cells. This review systematically summarizes the recent research on the functional layers, including the electron transport layer, perovskite layer, hole transport layer, and electrode. The common ETL materials, such as TiO2, SnO2, and ZnO, need doping and a bi-layer ETL to promote their property. Large-scale and low-cost production of perovskite layers with excellent performance and stability has always been the focus. The expensive and instability problems of Spiro-OMeTAD and electrode materials remain to be solved. The main problems and future development direction of them are also discussed. Full article
(This article belongs to the Special Issue Optical Thin Film and Photovoltaic (PV) Related Technologies)
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12 pages, 3665 KiB  
Article
Study on Corrosion Resistance of LDH/Micro-Arc Oxidation Composite Superhydrophobic Coatings on AZ31 Magnesium Alloy
by Dongjie Liu, Jing Liu, Guangyu Liu, Yuntao Xie and Zongfan Duan
Coatings 2023, 13(3), 643; https://doi.org/10.3390/coatings13030643 - 18 Mar 2023
Cited by 6 | Viewed by 1327
Abstract
Because of some defects such as holes and cracks, the corrosion resistance of micro-arc oxidation coating needs to be improved by surface modification. In this paper, LDH/MAO film with a micro-/nano-structure is constructed on the surface of AZ31 magnesium alloy by controlling the [...] Read more.
Because of some defects such as holes and cracks, the corrosion resistance of micro-arc oxidation coating needs to be improved by surface modification. In this paper, LDH/MAO film with a micro-/nano-structure is constructed on the surface of AZ31 magnesium alloy by controlling the composition and concentration of the hydrothermal solution. The superhydrophobic surface is successfully constructed by coating an OTES modifier on the surface of LDH/MAO film by the spin-coating method. The surface morphologies, contact angles, and corrosion resistance of composite coatings are tested. The results show that the OTES-LDH/MAO composite coatings of magnesium alloy can seal the defects in the MAO film well to achieve a superhydrophobic effect and better corrosion resistance. Compared with a MgO ceramic film, the water contact angle of OTES-LDH/MAO composite coatings is increased from 38° to 155°; the corrosion potential increases by 0.7 V, the corrosion current density and polarization resistance decreases and increases by four orders of magnitude, respectively; and the corrosion resistance becomes much higher than that of MAO film. Full article
(This article belongs to the Special Issue Advances in Epitaxial Thin Films: Materials and Applications)
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14 pages, 4498 KiB  
Article
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 3 | Viewed by 1331
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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10 pages, 9261 KiB  
Article
Water-Free SbOx ALD Process for Coating Bi2Te3 Particles
by Sebastian Lehmann, Fanny Mitzscherling, Shiyang He, Jun Yang, Martin Hantusch, Kornelius Nielsch and Amin Bahrami
Coatings 2023, 13(3), 641; https://doi.org/10.3390/coatings13030641 - 18 Mar 2023
Cited by 1 | Viewed by 1284
Abstract
We developed a water-free atomic layer deposition (ALD) process to homogeneously deposit SbOx using SbCl5 and Sb-Ethoxide as precursors, and report it here for the first time. The coating is applied on Bi2Te3 particles synthesized via the solvothermal [...] Read more.
We developed a water-free atomic layer deposition (ALD) process to homogeneously deposit SbOx using SbCl5 and Sb-Ethoxide as precursors, and report it here for the first time. The coating is applied on Bi2Te3 particles synthesized via the solvothermal route to enhance the thermoelectric properties (i.e., Seebeck coefficient, thermal and electrical conductivity) via interface engineering. The amorphous character of the coating was shown by the missing reflexes on the X-ray diffractograms (XRD). A shift from the oxidation state +III to +V of the Sb species was observed using X-ray photoelectron spectroscopy (XPS), indicating increased thickness of the SbOx coating layer. Additionally, a peak shift of the Sb 3d5/2 + O 1s peak indicated increased n-type doping of the material. Electrical measurements of spark plasma-sintered bulk samples confirmed the doping effect on the basis of decreased specific resistivity with increasing SbOx layer thickness. The Seebeck coefficient was improved for the coated sample with 500 cycles of SbOx, while the total thermal conductivity was reduced, resulting in enhancement of the zT. The results distinctly show that surface engineering via powder ALD is an effective tool for improving key properties of thermoelectric materials like electrical conductivity and the Seebeck coefficient. Full article
(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)
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18 pages, 3309 KiB  
Article
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 7 | Viewed by 1675
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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13 pages, 3523 KiB  
Communication
Characterization of CdxTeyOz/CdS/ZnO Heterostructures Synthesized by the SILAR Method
by Yana Suchikova, Sergii Kovachov, Ihor Bohdanov, Elena Popova, Aleksandra Moskina and Anatoli Popov
Coatings 2023, 13(3), 639; https://doi.org/10.3390/coatings13030639 - 17 Mar 2023
Cited by 19 | Viewed by 1454
Abstract
CdxTeyOz/CdS/ZnO heterostructures were obtained by the SILAR method using ionic electrolytes. A CdS film was formed as a buffer layer for better adhesion of the cadmium-tellurium oxides to the substrate surface. In turn, the ZnO substrate was previously prepared by electrochemical etching to [...] Read more.
CdxTeyOz/CdS/ZnO heterostructures were obtained by the SILAR method using ionic electrolytes. A CdS film was formed as a buffer layer for better adhesion of the cadmium-tellurium oxides to the substrate surface. In turn, the ZnO substrate was previously prepared by electrochemical etching to form a rough textured surface. In addition, an annealing mode was used in an oxygen stream to complete the oxidation process of the heterostructure surface. The resulting nanocomposite was investigated using RAMAN, XRD, SEM, and EDX methods. We assume that the oxides CdO and TeO4 initially form on the surface and later evolve into TeO2 and TeO3 when saturated with oxygen. These oxides, in turn, are the components of the ternary oxides CdTeO3 and CdTe3O8. It should be noted that this mechanism has not been fully studied and requires further research. However, the results presented in this article make it possible to systematize the data and experimental observations regarding the formation of cadmium-tellurium films. Full article
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10 pages, 3404 KiB  
Communication
Al2O3 Ultra-Thin Films Deposited by PEALD for Rubidium Optically Pumped Atomic Magnetometers with On-Chip Photodiode
by Florival M. Cunha, Manuel F. Silva, Nuno M. Gomes and José H. Correia
Coatings 2023, 13(3), 638; https://doi.org/10.3390/coatings13030638 - 17 Mar 2023
Cited by 1 | Viewed by 1749
Abstract
This communication shows the recipe for plasma-enhanced atomic layer deposition (PEALD) Al2O3 ultra-thin films with thicknesses below 40 nm. Al2O3 ultra-thin films were deposited by PEALD to improve the rubidium optically pumped atomic magnetometers’ (OPMs) cell lifetime. [...] Read more.
This communication shows the recipe for plasma-enhanced atomic layer deposition (PEALD) Al2O3 ultra-thin films with thicknesses below 40 nm. Al2O3 ultra-thin films were deposited by PEALD to improve the rubidium optically pumped atomic magnetometers’ (OPMs) cell lifetime. This requirement is due to the consumption of the alkali metal (rubidium) inside the vapor cells. Moreover, as a silicon wafer was used, an on-chip photodiode was already integrated into the fabrication of the OPM. The ALD parameters were achieved with a GPC close to 1.2 Å/cycle and the ALD window threshold at 250 °C. The PEALD Al2O3 ultra-thin films showed a refractive index of 1.55 at 795 nm (tuned to the D1 transition of rubidium for spin-polarization of the atoms). The EDS chemical elemental analysis showed an atomic percentage of 58.65% for oxygen (O) and 41.35% for aluminum (Al), with a mass percentage of 45.69% for O and 54.31% for Al. A sensitive XPS surface elemental composition confirmed the formation of the PEALD Al2O3 ultra-thin film with an Al 2s peak at 119.2 eV, Al 2p peak at 74.4 eV, and was oxygen rich. The SEM analysis presented a non-uniformity of around 3%. Finally, the rubidium consumption in the coated OPM was monitored. Therefore, PEALD Al2O3 ultra-thin films were deposited while controlling their optical refractive index, crystalline properties, void fraction, surface roughness and thickness uniformity (on OPM volume 1 mm × 1 mm × 0.180 mm cavity etched by RIE), as well as the chemical composition for improving the rubidium OPM lifetime. Full article
(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)
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20 pages, 7254 KiB  
Article
Influence of Plasma Electrolytic Oxidation of Cast Al-Si Alloys on Their Phase Composition and Abrasive Wear Resistance
by Mykhailo Student, Iryna Pohrelyuk, Juozas Padgurskas, Volodymyr Posuvailo, Volodymyr Hvozdets’kyi, Khrystyna Zadorozhna, Halyna Chumalo, Halyna Veselivska, Ihor Kovalchuk and Andrii Kychma
Coatings 2023, 13(3), 637; https://doi.org/10.3390/coatings13030637 - 17 Mar 2023
Cited by 4 | Viewed by 1266
Abstract
The microhardness and abrasive wear resistance of cast Al-Si alloys after plasma-electrolytic oxidation (PEO) in a weakly alkaline basic electrolyte (3 g/L KOH + 2 g/L Na2SiO3), as well as with the addition of H2O2, [...] Read more.
The microhardness and abrasive wear resistance of cast Al-Si alloys after plasma-electrolytic oxidation (PEO) in a weakly alkaline basic electrolyte (3 g/L KOH + 2 g/L Na2SiO3), as well as with the addition of H2O2, were determined. X-ray analysis showed that the PEO layer comprises two oxide phases, namely α-Al2O3 and γ-Al2O3, as well as sillimanite -Al2O3 · SiO2 and a small percentage of mullite -3 Al2O3 · 2SiO2. Silicon is present in the structure of the oxide layer, and its percentage is greater than that of the alloys in their initial state. It has been shown that the characteristics of PEO layers on AK9 and AK12 silumins synthesized in an electrolyte of basic composition increase (microhardness up to 900–1000 HV and abrasive wear resistance by 14–57 times). The formation of PEO layers in the base electrolyte with the addition of 3 g/L of hydrogen peroxide intensifies the synthesis process and promotes the formation of high-temperature oxide phases (in particular, corundum). The abrasive wear resistance of both silumins with PEO layers synthesized in such an electrolyte increases by 30–70%. Full article
(This article belongs to the Special Issue Coatings and Surface Modification for Tribological Applications)
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18 pages, 6007 KiB  
Article
Direct Energy Depositions of a 17-4 PH Stainless Steel: Geometrical and Microstructural Characterizations
by Cindy Morales, Mattia Merlin, Annalisa Fortini and Alessandro Fortunato
Coatings 2023, 13(3), 636; https://doi.org/10.3390/coatings13030636 - 17 Mar 2023
Cited by 6 | Viewed by 1487
Abstract
Direct energy deposition (DED) is a widely accepted additive manufacturing process and a possible alternative to the subtractive manufacturing processes due to its high flexibility in fabricating new 3D parts. DED enables the manufacture of complex parts without using costly and time-consuming conventional [...] Read more.
Direct energy deposition (DED) is a widely accepted additive manufacturing process and a possible alternative to the subtractive manufacturing processes due to its high flexibility in fabricating new 3D parts. DED enables the manufacture of complex parts without using costly and time-consuming conventional processes, even though building parameters need to be accurately determined. In the present investigation, the effect of different process parameters on geometrical features, quality, microstructure, and microhardness of 17-4 PH stainless steel single tracks deposited onto an AISI 316L stainless steel substrate was investigated. Four sets of process parameters, considering different values of laser power, scanning speed, and powder feed rate, were selected in the manufacturing strategy, and specimens drawn from each single-track deposition were analyzed by stereomicroscopy, optical microscopy (OM), scanning electron microscopy (SEM-EDS), and X-ray diffraction (XRD). The results show that the optimized geometrical features of the track, together with the best microstructural and hardness properties, were obtained with the highest values of the laser energy input. Full article
(This article belongs to the Special Issue Surface Treatments for Stainless Steels)
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19 pages, 4197 KiB  
Review
High-Entropy Alloy Films
by Kaixuan Cui and Yong Zhang
Coatings 2023, 13(3), 635; https://doi.org/10.3390/coatings13030635 - 17 Mar 2023
Cited by 6 | Viewed by 2475
Abstract
High-entropy alloy films have the same excellent properties as high-entropy alloys and can better realize the practical applications of high-entropy alloys. This paper takes the high-entropy alloy films as the object of discussion. The preparation process, microstructure, hardness, wear resistance and corrosion resistance [...] Read more.
High-entropy alloy films have the same excellent properties as high-entropy alloys and can better realize the practical applications of high-entropy alloys. This paper takes the high-entropy alloy films as the object of discussion. The preparation process, microstructure, hardness, wear resistance and corrosion resistance of high-entropy alloy films are mainly discussed and the influence of nitridation, sputtering power, substrate temperature, substrate bias and other factors on the phase structure of alloy films is analyzed. High-entropy alloy films can be prepared using magnetron sputtering, laser cladding, pulsed laser deposition, detonation spraying, electrochemical deposition and other processes. High-entropy alloy films tend to form a solid solution and amorphous state, and their hardness is far higher than that of traditional films. Among them, the hardness of high-entropy alloy nitride films can reach the standard of superhard films. Wear resistance is usually proportional to hardness. Due to the corrosion-resistant elements and amorphous structure, some high-entropy alloy films have better corrosion resistance than stainless steel. High-entropy alloy films have shown profound development prospects in the fields of wear-resistant coatings for tools, corrosion protection, diffusion barrier and photothermal conversion coatings. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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