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Coatings, Volume 13, Issue 11 (November 2023) – 157 articles

Cover Story (view full-size image): This study explores the microcosm of superhydrophobicity by uncovering modified copper foam’s inner structure. Take a closer look at our research through high-resolution SEM images that reveal the superhydrophobic coating on both smooth and rough copper foams. Surface roughness plays a fundamental role in shaping intricate structures. Tree-like silver dendrites and delicate flower-like formations develop on the rough substrates, while smoother samples showcase nanowire morphologies and moss-like Ag dendrites. These microscopic SEM insights provide a comprehensive understanding of our investigation, emphasizing the significance of surface roughness in superhydrophobic performance for oil/water separation applications. View this paper
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13 pages, 1358 KiB  
Article
Paper Coatings Based on Polyvinyl Alcohol and Cellulose Nanocrystals Using Various Coating Techniques and Determination of Their Barrier Properties
Coatings 2023, 13(11), 1975; https://doi.org/10.3390/coatings13111975 - 20 Nov 2023
Viewed by 776
Abstract
The goal of this work was to improve the barrier properties of selected papers against water, grease and oil or gases (water vapor and oxygen) by covering them with biodegradable commercial coating carriers based on cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVOH). The [...] Read more.
The goal of this work was to improve the barrier properties of selected papers against water, grease and oil or gases (water vapor and oxygen) by covering them with biodegradable commercial coating carriers based on cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVOH). The aim was also to obtain cellulose recyclable packaging materials with improved barrier characteristics. The properties of paper coatings based on CNCs and PVOH were characterized. Various paper coating techniques (flexographic printing, rotogravure printing and blade printing) were evaluated with respect to the final properties of the surface-modified paper with different starting grammages (40 g/m2, 70 g/m2, 100 g/m2). Functional properties, such as the barrier against oxygen, water vapor, water and grease; mechanical properties; and seal characterization of coated paper were examined. The results of this study demonstrated that the covering of the paper may improve the water, grease and oil barrier and that the best results were obtained for Gerstar 70 g/m2 coated with J12 coatings using the flexographic technique. Full article
(This article belongs to the Special Issue Advanced Coatings and Films for Food Packing and Storage)
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13 pages, 2923 KiB  
Article
Comparative Study of the Physico-Chemical Properties of Sorbents Based on Natural Bentonites Modified with Iron (III) and Aluminium (III) Polyhydroxocations
Coatings 2023, 13(11), 1974; https://doi.org/10.3390/coatings13111974 - 20 Nov 2023
Viewed by 588
Abstract
A comparative study of the physicochemical properties of natural bentonite clays of Pogodayevo (Republic of Kazakhstan, mod. 1) and Dash-Salakhli (Republic of Azerbaijan, mod. 2) deposits and modification of the bentonite clay with polyhydroxocations of iron (III) and aluminium (III). The amount of [...] Read more.
A comparative study of the physicochemical properties of natural bentonite clays of Pogodayevo (Republic of Kazakhstan, mod. 1) and Dash-Salakhli (Republic of Azerbaijan, mod. 2) deposits and modification of the bentonite clay with polyhydroxocations of iron (III) and aluminium (III). The amount of bentonite in the concentration of iron (aluminum) was 5 mmol Me3+/g. It was established that the modification of natural bentonites using polyhydroxocations of iron (III) (mod. 1_Fe_5-c, mod. 2_Fe_5-c) and aluminum (III) (mod. 1_Al_5-c, mod. 2_Al_5-c) by the method of “co-precipitation” leads to a change in their chemical composition, structural and sorption properties. The results showed that hydroxy-aluminum cations ([Al3O4(OH)24(H2O)12]7+) and poly-hydroxyl-Fe or polyoxo-Fe were intercalated into clay layers, which led to an increase in the values of d001 and specific surface areas compared to those of the original bentonite, from 37 to 120 m2/g for the Pogodaevo bentonite and from 51 to 172 m2/g respectively, for bentonite from the Dash-Salakhli deposit. It is shown that modified sorbents based on natural bentonite are finely porous objects with a predominance of pores of 1.5–8.0 nm in size. As a result, there is a significant increase in the specific surface area of sorbents. Modification of bentonite with polyhydroxocations of iron (III) and aluminum (III) by the “co-precipitation” method also leads to an increase in the sorption capacity of the sorbents obtained with respect to nickel (II) cations. Modified bentonites were used for the adsorption of Ni (II) ions from the model solution. Ni (II) was absorbed in a neutral pH solution. The study of equilibrium adsorption showed that the data are in good agreement with the Langmuir isotherm model. The maximum adsorption capacity of the Ni (II) obtained from the Langmuir equation was 25.0 mg/g (mod. 1_Al_5-c), 18.2 mg/g (mod. 2_Al_5-c) for Al-bentonite and 16.7 mg/g (mod. 1_Fe_5-c), 10.1 (mod. 2_Fe_5-c) for Fe-bentonite. The kinetics of adsorption is considered. The high content of Al-OH anion exchange centers in them determines the higher sorption activity of Al-modified bentonites. Full article
(This article belongs to the Special Issue Surface Coatings and Technology Against Soil Abrasion and Adhesion)
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21 pages, 16224 KiB  
Article
Analysis of Interlayer Crack Propagation and Strength Prediction of Steel Bridge Deck Asphalt Pavement Based on Extended Finite Element Method and Cohesive Zone Model (XFEM–CZM) Coupling
Coatings 2023, 13(11), 1973; https://doi.org/10.3390/coatings13111973 - 20 Nov 2023
Viewed by 597
Abstract
The extended finite element method (XFEM) was employed for the computational modeling of internal defects within a bond layer. Furthermore, a cohesive zone model (CZM) was implemented to characterize the behavior of the bond layer in response to interactions at both the bond [...] Read more.
The extended finite element method (XFEM) was employed for the computational modeling of internal defects within a bond layer. Furthermore, a cohesive zone model (CZM) was implemented to characterize the behavior of the bond layer in response to interactions at both the bond layer/steel plate and bond layer/asphalt paving layer interfaces. The coupling of XFEM and CZM was used for a comprehensive analysis of crack propagation within the bond layer as well as the assessment of phenomena associated with interfacial debonding and delamination. The feasibility and accuracy of the XFEM–CZM coupling method were verified by comparing it with the virtual crack closure technique (VCCT), CZM, XFEM–VCCT, and experiments. A double cantilever beam experimental model was established to simulate the process of interlayer-type cracks expanding from the inside of the bond layer to the interface between the bond layer and the upper and lower layers, causing debonding. This was undertaken to analyze the damage failure mechanism of interlayer-type cracks in asphalt paving layers of steel bridge decks; to discuss the impacts of the initial crack length, the interface stiffness, the interface strength, and the thickness of the bond layer on the performance of the overall interlayer bond strength; and to carry out the significance analysis. The results showed that the initial crack length, interface stiffness, and bond layer thickness had different effects on the expansion path of interlayer cracks. The interlayer strength decreased with an increase in the initial crack length and interface stiffness, increased with an increase in the interface strength, and decreased with an increase in the thickness of the bond layer. The interface stiffness had the most significant effect on the strength. Full article
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15 pages, 5518 KiB  
Article
Effect of Cavitation Water Jet Peening on Properties of AlCoCrFeNi High-Entropy Alloy Coating
Coatings 2023, 13(11), 1972; https://doi.org/10.3390/coatings13111972 - 20 Nov 2023
Viewed by 622
Abstract
High-entropy alloys have been widely used in engineering manufacturing due to their hardness, good wear resistance, excellent corrosion resistance, and high-temperature oxidation resistance. However, it is inevitable that metallurgical defects, such as micro cracks and micro pores, are produced when preparing the coating, [...] Read more.
High-entropy alloys have been widely used in engineering manufacturing due to their hardness, good wear resistance, excellent corrosion resistance, and high-temperature oxidation resistance. However, it is inevitable that metallurgical defects, such as micro cracks and micro pores, are produced when preparing the coating, which affects the overall performance of the alloy to a certain extent. In view of this situation, cavitation water jet peening (CWJP) was used to strengthen the AlCoCrFeNi high-entropy alloy coating. The effect of CWJP impact time on the microstructure and mechanical properties of CWJP were investigated. The results show that CWJP can form an effective hardening layer on the surface layer of the AlCoCrFeNi high-entropy alloy. When the CWJP impact time was 4 h, the microhardness of the surface layer of the specimen was harder than that of 2 h and 6 h, and the CWJP impact time had little effect on the thickness of the hardening layer. Observing the surface of the untreated and CWJP-treated specimens using the EBSD test, it was evident that the microstructure was significantly homogenized, the grains were refined, and the proportion of small-angle grain boundaries increased. The system reveals the grain refinement mechanism of the AlCoCrFeNi high-entropy alloy coating during plastic deformation. This study aims to provide a new surface strengthening method for obtaining high-performance AlCoCrFeNi high-entropy alloy coatings. Full article
(This article belongs to the Special Issue Advanced Coatings for Metals)
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13 pages, 9068 KiB  
Article
A Superhydrophobic Anti-Icing Surface with a Honeycomb Nanopore Structure
Coatings 2023, 13(11), 1971; https://doi.org/10.3390/coatings13111971 - 20 Nov 2023
Cited by 1 | Viewed by 654
Abstract
Recently, the icing disaster of transmission lines has been a serious threat to the safe operation of the power system. A superhydrophobic (SHP) anti-icing surface with a honeycomb nanopore structure was constructed using anodic oxidation technology combined with a vacuum infusion process. When [...] Read more.
Recently, the icing disaster of transmission lines has been a serious threat to the safe operation of the power system. A superhydrophobic (SHP) anti-icing surface with a honeycomb nanopore structure was constructed using anodic oxidation technology combined with a vacuum infusion process. When the current density was 87.5 mA/cm2, the honeycomb porous surface had the best superhydrophobic performance (excellent water mobility), lowest ice-adhesion strength (0.7 kPa) and best anti-frosting performance. Compared with other types of alumina surfaces, the ice-adhesion strength of the SHP surface (87.5 mA/cm2) was only 0.2% of that of the bare surface. The frosting time of the SHP surface (87.5 mA/cm2) was 150 min, which was much slower. The former is attributed to the air cushion within the porous structure and the stress concentration, and the latter is attributed to the self-transition of the droplets and low solid–liquid heat transfer area. After 100 icing or frosting cycles, the SHP surface (87.5 mA/cm2) maintained a low ice-adhesion strength and superhydrophobic performance. This is because the anodic oxidation process forms a hard porous film, and the nano porous structure with a high aspect ratio can store modifiers to realize self-healing. The results indicate that the SHP surface with a honeycomb nanopore structure presents excellent anti-icing performance and durability. Full article
(This article belongs to the Special Issue Durability of Transmission Lines)
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11 pages, 12070 KiB  
Review
Investigation of the Change in Roughness and Microhardness during Laser Surface Texturing of Copper Samples by Changing the Process Parameters
Coatings 2023, 13(11), 1970; https://doi.org/10.3390/coatings13111970 - 20 Nov 2023
Cited by 1 | Viewed by 585
Abstract
The aim of this research is to achieve a high-quality and long-lasting laser marking of ammunition, which is of interest to the defense industry. The study is about the effects of speed, raster pitch and power on the roughness and microhardness of the [...] Read more.
The aim of this research is to achieve a high-quality and long-lasting laser marking of ammunition, which is of interest to the defense industry. The study is about the effects of speed, raster pitch and power on the roughness and microhardness of the marked areas of copper samples. The experiments were carried out with a fiber laser and a copper bromide laser—modern lasers widely used in industrial production. Laser power, scan speed and raster step were varied to determine their effects on the resulting microhardness and surface roughness. The lasers operate in different wavelength ranges, with the optical laser operating at 1064 nm in the near-infrared region and the copper bromide laser at 511 nm and 578 nm in the visible region, allowing the influence of wavelengths on the process to be investigated. The roughness and microhardness velocity dependence for three powers and two pulse durations for the fiber laser were obtained from the experimental data. The dependence of roughness and microhardness on the raster step for both types of lasers was also demonstrated. Full article
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14 pages, 4329 KiB  
Essay
Simulation and Experimental Investigation of Multi-Step Shot Peening for Surface Crack Repair in Aluminum Alloys
Coatings 2023, 13(11), 1969; https://doi.org/10.3390/coatings13111969 - 20 Nov 2023
Viewed by 563
Abstract
This study explores the impact of shot peening residual compressive stress on repairing surface cracks in the 7075-T651 aluminum alloy. Two models were developed for crack repair via shot peening and fatigue test finite element modeling. A multi-step numerical simulation introduced shot peening-induced [...] Read more.
This study explores the impact of shot peening residual compressive stress on repairing surface cracks in the 7075-T651 aluminum alloy. Two models were developed for crack repair via shot peening and fatigue test finite element modeling. A multi-step numerical simulation introduced shot peening-induced residual stress into the fatigue test model, and subsequent simulations analyzed the crack repair mechanism. The research results indicate that increasing pressure and projectile size improve repair effectiveness, but higher pressure causes material damage, and larger projectiles decrease fatigue life. Crack repair effectiveness decreased with higher loading levels, more significantly at higher loads. Experimental and simulation results matched well, validating the simulation model for shot peen repair processes and offering optimization possibilities. Full article
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30 pages, 7307 KiB  
Article
Preparation and Testing of Anti-Corrosion Properties of New Pigments Containing Structural Units of Melamine and Magnesium Cations (Mg2+)
Coatings 2023, 13(11), 1968; https://doi.org/10.3390/coatings13111968 - 19 Nov 2023
Viewed by 723
Abstract
This paper deals with the properties and testing of newly prepared organic pigments based on melamine cyanurate containing magnesium or zinc cations depending on their composition and anticorrosive properties in model coatings. Organic pigments based on melamine cyanurate with Mg2+ in the [...] Read more.
This paper deals with the properties and testing of newly prepared organic pigments based on melamine cyanurate containing magnesium or zinc cations depending on their composition and anticorrosive properties in model coatings. Organic pigments based on melamine cyanurate with Mg2+ in the form of a complex differing in the ratio of melamine and cyanurate units were prepared. Furthermore, a pigment based on melamine citrate with magnesium cation Mg2+, a pigment based on melamine citrate with magnesium cation, and a pigment based on melamine cyanurate with zinc cation were prepared. The properties of Mg-containing organic pigments were also compared with those of selected magnesium-containing inorganic oxide-type pigments. The above-synthesized pigments were characterized by inductively coupled plasma-optical emission spectroscopy, elemental analysis, scanning electron microscopy, and X-ray diffraction. In addition, the basic parameters that are indicative of the applicability of the pigments in the binders of anti-corrosion coatings were determined. The anti-corrosive properties of the tested pigments were verified after application to the epoxy-ester resin-based paint binder in three different concentrations: at pigment volume concentrations of 0.10%, 0.25%, and 0.50%. The anticorrosive effectiveness of pigmented organic coatings was verified by cyclic corrosion tests in a salt electrolyte fog (NaCl + (NH4)2SO4) in an atmosphere containing SO2 and by the electrochemical technique of linear polarization. Finally, the effect of the structure of the pigments on the mechanical resistance of the organic coatings was investigated. The results obtained showed that the new organic pigments exhibit anticorrosive properties, and at the same time, differences in performance were found depending on the structure of the pigments tested. Specifically, the results of cyclic corrosion tests and the electrochemical technique of linear polarization clearly demonstrated that synthesized pigments of the organic type based on melamine cyanurate containing magnesium or zinc cations ensure the anti-corrosion efficiency of the tested organic coatings. The highest anti-corrosion efficiency was achieved by the system pigmented with synthesized melamine cyanurate with magnesium cation (C12H16MgN18O6), whose anti-corrosion efficiency was comparable to the anti-corrosion efficiency of the tested inorganic pigment MgFe2O4, which was prepared by high-temperature solid-phase synthesis. In addition, these organic coatings achieved high mechanical resistance after being tested using the most used standardized mechanical tests. Full article
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12 pages, 14333 KiB  
Article
Effects of Graphene Oxide on Tribological Properties of Micro-Arc Oxidation Coatings on Ti-6Al-4V
Coatings 2023, 13(11), 1967; https://doi.org/10.3390/coatings13111967 - 19 Nov 2023
Cited by 1 | Viewed by 618
Abstract
This paper investigates the effect of graphene oxide (GO) particles on the friction reduction and wear resistance of coatings on a Ti-6Al-4V alloy generated using the micro-arc oxidation (MAO) technique. Different concentrations of GO were added in aluminate–phosphate electrolyte. The composition of the [...] Read more.
This paper investigates the effect of graphene oxide (GO) particles on the friction reduction and wear resistance of coatings on a Ti-6Al-4V alloy generated using the micro-arc oxidation (MAO) technique. Different concentrations of GO were added in aluminate–phosphate electrolyte. The composition of the MAO coatings was investigated using X-ray diffraction and the energy dispersive spectrum. Measurements of the coating’s thickness, hardness, and roughness have also been conducted. Ball-on-disk friction tests under dry conditions were carried out to reveal the tribological behavior of the MAO coating. The results showed that the coating consisted of Al2TiO5 and γ-Al2O3. The addition of GO greatly reduced the friction coefficient by 25%. The coating with 5 g/L of GO particles exhibited the lowest friction coefficient (reduced from 0.47 to 0.35). Moreover, the coating thickness become thicker (from 10 to 20 μm) with an increase in GO concentration from 0 to 10 g/L. The wear mechanism was revealed via worn surface analysis. This study provides a helpful way to improve the surface wear resistance of titanium alloys. Full article
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10 pages, 1222 KiB  
Article
The Emission of Volatile Components during Laboratory Vitrification When Using Fly Ash and Other Waste to Obtain Ceramic Coatings
Coatings 2023, 13(11), 1966; https://doi.org/10.3390/coatings13111966 - 18 Nov 2023
Viewed by 735
Abstract
For decades, a significant amount of research has been conducted on the vitrification of mixtures of all kinds of industrial wastes, especially fly ash, both from thermal power plants and municipal waste incinerators. Although the possibility of creating glass from all types of [...] Read more.
For decades, a significant amount of research has been conducted on the vitrification of mixtures of all kinds of industrial wastes, especially fly ash, both from thermal power plants and municipal waste incinerators. Although the possibility of creating glass from all types of fly ash has been proven through such research, these studies barely focused on the emission of volatile components that takes place during vitrification processes at high temperatures. This is why, after identifying the types of volatilisation that can occur, we characterised the gasses that are emitted during the vitrification of some types of fly ash and other waste in a laboratory furnace. In order to do so, we analysed the Cl2 and SO2 gasses emitted using the DTA/TG/FTIR techniques, as well as the losses of H2O and CO2. The authors also measured the volatilizations directly from the mouth of the furnace using gas chromatography syringes and analysed the possible emission of dioxins. This study is the first analysis of volatile elements of this kind, after numerous vitrifications in recent decades which ignored the volatilisations that occur when using fly ashes. Although the various types of fly ash used generate emissions of Cl2 and SO2, their use as a by-product on an industrial level could be recommended if previous thermal and washing treatments are conducted. These would minimise the above emissions, enabling the use of said fly ash in the production of glasses for commercial frits, even if an efficient industrial-scale gas cleaning system would apply. Furthermore, an appropriate optimised design of its formulation would make it possible to structurally link some of these gaseous components to the glass structure. These types of results will make it possible to calculate the volatilization when vitrifying certain types of industrial waste on an industrial level, although these studies would require prior assessment in a pilot plant. Full article
(This article belongs to the Special Issue Advanced Bioactive Glasses and Ceramic Coatings)
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19 pages, 15365 KiB  
Article
Gradation Optimization Based on Micro-Analysis of Rutting Behavior of Asphalt Mixture
Coatings 2023, 13(11), 1965; https://doi.org/10.3390/coatings13111965 - 18 Nov 2023
Viewed by 713
Abstract
This study investigates the microscopic mechanism of the force on particles of different particle sizes in the asphalt mixture during rutting formation. The gradation was optimized by analyzing the particle force results. The enhanced discrete element method (EDEM) was used to simulate the [...] Read more.
This study investigates the microscopic mechanism of the force on particles of different particle sizes in the asphalt mixture during rutting formation. The gradation was optimized by analyzing the particle force results. The enhanced discrete element method (EDEM) was used to simulate the rutting test, study the correlation state between different particle sizes in the rutting process, and analyze the rutting of asphalt pavement from the aggregate level. From a microscopic perspective, the specific forces acting on particles at different times were determined to investigate the particle size range of stressed particles in two types of asphalt mixtures. Furthermore, the role of particles with different sizes in the rutting process was analyzed. The force limit values of particles with different particle sizes are fitted, and the force of particles in two types of asphalt mixtures is compared and analyzed. After that, the gradation of the asphalt mixture is optimized, and the feasibility of the gradation optimization method is verified by laboratory experiments. The results show that the change rule of the rutting simulation test is gradually transformed from compacted rutting to unstable rutting. The force of the asphalt concrete-13 (AC-13) asphalt mixture is borne by the particles with a radius greater than 1.8 mm. The force of the stone matrix asphalt-13 (SMA-13) asphalt mixture is borne by the particles with a radius greater than 3.6 mm, and the small particle size particles play a filling role. When the particle radius is less than 5.1 mm, the force value of AC-13 asphalt mixture particles is greater than that of SMA-13. When the particle radius exceeds 5.1 mm, the force value of SMA-13 asphalt mixture particles is greater than that of AC-13. The force of particles with a radius of 5.7 mm and 7.3 mm in the SMA-13 asphalt mixture is 30% higher than that in AC-13, and the force limit of particles is proportional to the particle size. The dynamic stability, flexural tensile strength, water immersion residual stability, and freeze-thaw splitting strength ratios of the optimized asphalt mixture are improved compared with those before optimization. The AC-13 asphalt mixture is increased by 8.5%, 9.2%, 1.6%, and 1.9%, respectively, and the SMA-13 asphalt mixture is increased by 10.6%, 7.3%, 0.7%, and 2.1%, respectively. It shows that the grading optimization method is feasible. Full article
(This article belongs to the Special Issue Asphalt Pavement: Materials, Design and Characterization)
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21 pages, 8185 KiB  
Article
Mechanical Performance and Strengthening Mechanism of Polymer Concretes Reinforced with Carbon Nanofiber and Epoxy Resin
Coatings 2023, 13(11), 1964; https://doi.org/10.3390/coatings13111964 - 17 Nov 2023
Viewed by 796
Abstract
To address the issues of the brittleness, low tensile strength, insufficient bond strength, and reduced service life associated with ordinary cement concrete being used as a repair material, a water-based epoxy (WBE) and carbon-nanofiber-reinforced concrete composite repair material was designed, and the mechanical [...] Read more.
To address the issues of the brittleness, low tensile strength, insufficient bond strength, and reduced service life associated with ordinary cement concrete being used as a repair material, a water-based epoxy (WBE) and carbon-nanofiber-reinforced concrete composite repair material was designed, and the mechanical properties, bonding performance, and durability of the concrete modified using WBE and carbon fiber under various WBE contents were investigated and evaluated. In this paper, a self-emulsifying water-based epoxy curing agent with reactive, rigid, flexible, and water-soluble chains was obtained via chemical grafting, involving the incorporation of polyethylene glycol chain segments into epoxy resin molecules. The results demonstrated that a WBE has a contributing effect on improving the weak interfacial bond between the carbon fiber and concrete; moreover, the composite admixture of carbon fiber and WBE improves the mechanical properties and durability of concrete, in which the composite admixture of 1% carbon fiber and 10% WBE has the best performance. The flexural strength and chlorine ion permeability resistance of concrete were slightly reduced after more than 10% admixture, but bond strength, tensile strength, compressive strength, dry shrinkage resistance, and frost resistance were promoted. The addition of WBE significantly retards the cement hydration process while greatly improving the compactness and impermeability of the concrete. Furthermore, the combined effects of WBE and carbon fiber effectively prevented the generation and expansion of cracks. The interaction mechanism and microstructure evolution between the WBE, carbon fiber, and cement hydration were described by clarifying the mineral composition, organic–inorganic interactions, the evolution of the hydration products, and composite morphology at different scales. Carbon fiber and WBE exhibited synergistic effects on the tensile strength, ductility, and crack resistance of concrete. In the formed three-dimensional network structural system of concrete, the WBE formed an organic coating layer on the fiber surface and provided fiber protection as well as interfacial bonding reinforcement for the embedded cement particles. Full article
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16 pages, 4831 KiB  
Article
Fabrication of Piezoelectric ZnO Nanowires on Laser Textured Copper Substrate to Enhance Catalytic Properties
Coatings 2023, 13(11), 1963; https://doi.org/10.3390/coatings13111963 - 17 Nov 2023
Viewed by 749
Abstract
In this work, 3D periodic “grid-type” CuO/Cu2O layers were fabricated on a copper sheet using laser processing techniques, and the laser processing parameters were optimized for favorable ZnO nanowire growth. It was found that ZnO nanowires could be successfully prepared to [...] Read more.
In this work, 3D periodic “grid-type” CuO/Cu2O layers were fabricated on a copper sheet using laser processing techniques, and the laser processing parameters were optimized for favorable ZnO nanowire growth. It was found that ZnO nanowires could be successfully prepared to form a CuO-Cu2O-ZnO heterojunction structure without an extra catalyst or seed layer coating, which could be attributed to the copper oxide active sites induced via laser texturing. ZnO nanowires on laser textured “grid-type” copper substrates demonstrated an effective piezocatalytic performance with different morphologies and the generation of abundant reactive oxygen species in the CuO-Cu2O-ZnO catalytic system, providing a fundamental mechanism for the degradation of organic dye in water. This simple and low-cost method could provide a useful guide for the large-scale efficient and versatile synthesis of immobilized piezoelectric catalysts. Full article
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9 pages, 11133 KiB  
Communication
Effect of Process Pressure on Carbon-Based Thin Films Deposited by Cathodic Arc on Stainless Steel for Bipolar Plates
Coatings 2023, 13(11), 1962; https://doi.org/10.3390/coatings13111962 - 17 Nov 2023
Viewed by 722
Abstract
In this study, three carbon-based coating variants were deposited onto stainless steel substrates, and the process pressure during the carbon layer deposition was varied. We conducted Raman spectroscopy, transmission electron microscopy, interfacial contact resistance measurements, and potentiodynamic polarization tests to examine the effect [...] Read more.
In this study, three carbon-based coating variants were deposited onto stainless steel substrates, and the process pressure during the carbon layer deposition was varied. We conducted Raman spectroscopy, transmission electron microscopy, interfacial contact resistance measurements, and potentiodynamic polarization tests to examine the effect of the process pressure on the properties of the coatings. The structural characterization revealed that all specimens exhibit a highly sp2-bonded structure. However, some structural differences could also be identified. In the TEM cross-section images of the carbon layer variants, these structural differences could be observed. The carbon layer deposited at 0.98 Pa has some distortions in the mainly perpendicular graphitic structure, which agrees with the Raman results. Almost completely vertically oriented graphitic layers exhibit the 0.1 Pa coating variant with a d-spacing similar to pure graphite. Regarding the contact resistance, the process pressure has only minor influence. All coatings variants have very low resistance values below 3 mΩ cm2, even at a compaction force of 50 N cm−2, which can be attributed to the graphite-like structure. The polarization tests show that the corrosion resistance increases with increasing process pressure. The best coating variant has a corrosion current density of approximately 108 A cm−2 and almost 106 A cm−2 at room temperature and 80 °C, respectively. Full article
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14 pages, 3534 KiB  
Article
Studying the Crucial Physical Characteristics Related to Surface Roughness and Magnetic Domain Structure in CoFeSm Thin Films
Coatings 2023, 13(11), 1961; https://doi.org/10.3390/coatings13111961 - 17 Nov 2023
Viewed by 696
Abstract
This study investigated the effects of varying film thicknesses and annealing temperatures on the surface roughness and magnetic domain structure of CoFeSm thin films. The results revealed that as the film thickness increased, both the crystalline size and surface roughness decreased, leading to [...] Read more.
This study investigated the effects of varying film thicknesses and annealing temperatures on the surface roughness and magnetic domain structure of CoFeSm thin films. The results revealed that as the film thickness increased, both the crystalline size and surface roughness decreased, leading to a reduction in coercivity (Hc) and improved magnetic contrast performance. Energy-dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of cobalt (Co), iron (Fe), and samarium (Sm) within the thin films. Notably, the 40 nm Co40Fe40Sm20 thin film annealed at 200 °C exhibited lower sheet resistance (Rs) and resistivity (ρ), indicating higher conductivity and a relatively higher maximum magnetic susceptibility (χac) at 50 Hz. These findings suggest that these films are well suited for low-frequency magnetic components due to their increased spin sensitivity. The 40 nm Co40Fe40Sm20 thin film, subjected to annealing at 200 °C, displayed a distinct stripe domain structure characterized by prominently contrasting dark and bright patterns. It exhibited the lowest Hc and the highest saturation magnetization (Ms), leading to a significant improvement in their soft magnetic properties. It is proposed that the surface roughness of the CoFeSm thin films plays a crucial role in shaping the magnetic properties of these thin magnetic films. Full article
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12 pages, 5826 KiB  
Article
One-Step Synthesis of Nitrogen-Doped Porous Carbon Derived from Biomass for Lithium-Ion Battery
Coatings 2023, 13(11), 1960; https://doi.org/10.3390/coatings13111960 - 17 Nov 2023
Viewed by 730
Abstract
Bamboo shoot is renewable biomass rich in carbon and nitrogen. To take advantage of its sources of carbon and nitrogen, hierarchical porous nitrogen-doped carbon materials derived from bamboo shoot were acquired via a one-step method in this study. The obtained carbons were characterized [...] Read more.
Bamboo shoot is renewable biomass rich in carbon and nitrogen. To take advantage of its sources of carbon and nitrogen, hierarchical porous nitrogen-doped carbon materials derived from bamboo shoot were acquired via a one-step method in this study. The obtained carbons were characterized by using XRD, Raman, N2 sorption, SEM, TEM, XPS, etc. The carbon calcinated at 700 °C with KHCO3 treatment (BSC) displays a large surface area (1475.5 m2 g−1) and typically porous structure from micro- to macropores, a self-nitrogen content, and many defects, which could offer transport channels and active sites for lithium ions while used as carbon anode. Based on the above features and the synergistic effects among them, BSC exhibits the typical electrochemical performance of a carbon-based anode material, with a specific capacity as high as 611.3 mA h g−1 (a Coulombic efficiency of 98.7%) after 100 cycles at a current density of 0.1 A g−1. Meanwhile, it also has a good rate performance and excellent cycling properties (436.1 mA h g−1 after 300 cycles at 0.1 A g−1) compared with NBSC (carbon directly carbonized at 700 °C). Thus, it is promising for further improvements made to porous carbon derived from biomass and used as anode in the application of energy storage, and could be a guideline for the preparation of high-value-added carbon materials derived from biomass. Full article
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12 pages, 2133 KiB  
Article
Effect of Sodium Lauryl Sulfate on the Properties of the Electrodeposited Invar Alloy
Coatings 2023, 13(11), 1959; https://doi.org/10.3390/coatings13111959 - 16 Nov 2023
Viewed by 615
Abstract
In the OLED display manufacturing process, a fine metal mask (FMM) is used for the RGB side-by-side in precise positions. An Invar alloy with exceptionally low thermal expansion was used as the FMM material to prevent the deformation of the FMM by heat [...] Read more.
In the OLED display manufacturing process, a fine metal mask (FMM) is used for the RGB side-by-side in precise positions. An Invar alloy with exceptionally low thermal expansion was used as the FMM material to prevent the deformation of the FMM by heat during the deposition process. The thickness of the FMM must be reduced to less than 10 microns to manufacture high-resolution OLED displays, making it essential to apply a bottom-up electrodeposition process. Moreover, controlling the interfacial energy of the cathode substrate and the electrolyte is necessary to achieve ion electrodeposition and peeling of the ultra-thin Fe-Ni plated on the cathode substrate during electrodeposition. Therefore, this study investigated the effect on the properties of the electrodeposited Fe-Ni alloy by controlling the amount of SLS content, which acts as a surfactant. The amount of SLS content was maintained in the range of 0 to 1 g/L, and the composition homogeneity, microstructure, and surface defects of the electrodeposited Fe-Ni alloy were investigated. Under low pH conditions, the composition was insignificantly changed depending on the difference in the amount of SLS content, and a uniform composition was observed. The findings of this research offer valuable insights for optimizing the electrodeposition process, which is crucial for producing high-resolution OLED displays with ultra-thin FMM, advancing display technology. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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21 pages, 4312 KiB  
Article
An Experimental Study and Adaptability Evaluation of Chain Extender Component in Water Reducer on the Sulfate Corrosion Resistance of Ordinary Concrete
Coatings 2023, 13(11), 1958; https://doi.org/10.3390/coatings13111958 - 16 Nov 2023
Cited by 1 | Viewed by 634
Abstract
In Shanxi Province, China, concrete foundations of substations are widely exposed to environments with sulfate erosion, which results in severe damage. There are various avenues to enhance sulfate resistance, and one promising approach involves optimizing high-performance water reducers. Chain extender, which is an [...] Read more.
In Shanxi Province, China, concrete foundations of substations are widely exposed to environments with sulfate erosion, which results in severe damage. There are various avenues to enhance sulfate resistance, and one promising approach involves optimizing high-performance water reducers. Chain extender, which is an integral component of a water reducer, serves as a pore-blocking agent to effectively counter sulfate erosion. This study delves into the impact of a chain extender in the water reducer on the sulfate resistance and adaptability of ordinary concrete. The assessment begins with gauging the sensitivity of concrete to sulfate erosion, utilizing a 0–1 scoring method. Comparable conditions are maintained, allowing for a direct comparison between concrete with and without chain extender based on predefined criteria. A score of 1 denotes superior performance, while a score of 0 indicates a poorer performance. Following the evaluation of each criterion, scores are aggregated by the water reducer type, with higher scores signaling superior adaptability. The findings highlight that chain extender enhances the internal porosity of concrete, resulting in a more compact microstructure, heightened impermeability, and improved resistance to sulfate erosion. Its influence on mixture performance, however, is marginal. From an erosion product standpoint, using the semi-immersion method, chemical erosion predominates in the immersion zone, while both chemical and physical erosion are observed in the alternate wet–dry zone. Employing a 0–1 scoring method, Water Reducer 3# (with chain extender) scores 20 points, whereas Water Reducer 3#–1 (without chain extender) scores 4 points. Taking into consideration all factors, the chain extender demonstrates excellent adaptability to ordinary concrete. To validate the effectiveness of the 0–1 scoring method, it is applied to assess fly ash and slag double-blended concrete. Water Reducer 3# (with chain extender) scores 13 points, while Water Reducer 3#–1 (without chain extender) scores 10 points. Taking all aspects into consideration, the chain extender component exhibits commendable adaptability to fly ash and slag double-blended concrete. Full article
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12 pages, 5066 KiB  
Article
Kinetic Analysis of Oxygen Evolution on Spin-Coated Thin-Film Electrodes via Electrochemical Impedance Spectroscopy
Coatings 2023, 13(11), 1957; https://doi.org/10.3390/coatings13111957 - 16 Nov 2023
Viewed by 956
Abstract
Sustainable and renewable energy technologies have attracted significant attention for reducing greenhouse emissions in the shift from fossil fuels. The production of green hydrogen from water electrolysis is considered an environmentally friendly strategy for a decarbonized economy. We examine the activities of the [...] Read more.
Sustainable and renewable energy technologies have attracted significant attention for reducing greenhouse emissions in the shift from fossil fuels. The production of green hydrogen from water electrolysis is considered an environmentally friendly strategy for a decarbonized economy. We examine the activities of the hydrogen and oxygen evolution reactions (HER and OER) using spin-coated thin-film electrodes with Pt/C and IrO2 nano-electrocatalysts under acidic conditions. The nano-electrocatalysts are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The electrocatalytic activities of nanoscale Pt/C and IrO2 are close to those of commercial Pt/C and superior to commercial IrO2, resulting in improved overall water splitting performance. Furthermore, the OER kinetics analysis using the IrO2 electrode is conducted using EIS measurements with distribution of relaxation time (DRT) analysis, resulting in a comparable exchange current density to that from the Tafel slope method (6.7 × 10−2 mA/cm2 versus 5.1 × 10−2 mA/cm2), demonstrating the validity of the kinetics analysis. This work provides a general strategy for preparing novel and highly active OER electrode materials for water electrolysis. Full article
(This article belongs to the Special Issue Advanced Electrochemical Surface Properties)
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13 pages, 2521 KiB  
Review
Research Progress on the Application of Graphene Quantum Dots
Coatings 2023, 13(11), 1956; https://doi.org/10.3390/coatings13111956 - 16 Nov 2023
Viewed by 750
Abstract
Graphene quantum dots (GQDs) are sets of carbon quantum dots derived from graphene or graphene oxide, and they have obvious graphene lattice properties. The number of layers in GQDs is generally no more than five layers, and the diameter size of GQDs is [...] Read more.
Graphene quantum dots (GQDs) are sets of carbon quantum dots derived from graphene or graphene oxide, and they have obvious graphene lattice properties. The number of layers in GQDs is generally no more than five layers, and the diameter size of GQDs is generally less than 10 nm. GQDs have stable photoluminescence characteristics, high specific surface areas, high conductivity levels and adjustable band gaps, and they can be used in sensing systems such as ion detection sensing, optical biosensing, electrochemical biosensing and electronic sensing. Based on the research status of GQDs in recent years and the application background of sensing systems, this review paper focuses on the synthesis strategies, sizes, chemical compositions, crystal structures, optical properties and sensor applications of GQDs. Full article
(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)
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29 pages, 13794 KiB  
Article
Study of Decay Mechanisms and Rules of Recycled Asphalt Pavement via a Full-Scale Experiment
Coatings 2023, 13(11), 1955; https://doi.org/10.3390/coatings13111955 - 16 Nov 2023
Viewed by 607
Abstract
Under the influence of long-term vehicle loads and large attenuation degrees, asphalt pavement performance gradually decreases, which leads to failure in fulfilling the appropriate requirements and, in turn, may affect driving safety. The purpose of this paper was to study the attenuation mechanism [...] Read more.
Under the influence of long-term vehicle loads and large attenuation degrees, asphalt pavement performance gradually decreases, which leads to failure in fulfilling the appropriate requirements and, in turn, may affect driving safety. The purpose of this paper was to study the attenuation mechanism and rule of styrene–butadiene–styrene (SBS)-modified recycled asphalt pavement, so as to determine the applicable position and rational utilization of recycled asphalt mixture. To achieve this goal, two structures were designed, and full-scale experiments were carried out. The performance of the field test road based on accelerated loading testing (ALT) was analyzed through field monitoring data. The fatigue characteristics of stone matrix asphalt-13 (SMA-13) and asphalt concrete-20 (AC-20) mixtures before and after accelerated loading were studied via the trabecular bending fatigue test and dynamic modulus test. The microscopic components in the asphalt mixtures were determined via thin-layer chromatography on chromarods with flame ionization detection (TLC-FID). The results showed that the fatigue properties of recycled asphalt mixture can meet the requirements of ordinary asphalt mixtures and meet the technical standards of asphalt pavement design. With the increase in loading times, the British pendulum number (BPN) value of the two structures tended to be stable, and the BPN of Plan 2 was six less than that of Plan 1. Under the same test conditions, the fatigue life sequence of the recycled asphalt mixture under different loading frequencies was 20 Hz > 10 Hz > 5 Hz. The contents of four components in the reclaimed asphalt mixture were similar to those in the ordinary asphalt mixture. The light component of the reclaimed asphalt mixture of SMA-13 was reduced by 11.69%, and the light component of the ordinary asphalt mixture of SMA-13 was reduced by 15.29% through the full-scale test. In summary, recycled asphalt mixture should not be applied to the upper layer of pavement but can be rationalized in the middle layer and the bottom layer of pavement. Full article
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21 pages, 11551 KiB  
Article
Effect of Oxygen-Evaporation-Preventative Post-Annealing Gas Conditions on NiO Thin Films
Coatings 2023, 13(11), 1954; https://doi.org/10.3390/coatings13111954 - 15 Nov 2023
Viewed by 655
Abstract
In this study, NiO films were fabricated through radio frequency sputtering with various oxygen flow rates and processed via rapid thermal annealing under Ar, O2, and N2 atmospheres. The electrical, optical, and crystallographic properties of the NiO films were influenced [...] Read more.
In this study, NiO films were fabricated through radio frequency sputtering with various oxygen flow rates and processed via rapid thermal annealing under Ar, O2, and N2 atmospheres. The electrical, optical, and crystallographic properties of the NiO films were influenced by their oxygen content in each film. As the oxygen content, carrier concentration, and resistivity increased, transmittance and mobility decreased. The carrier mobility of the NiO film in the p-type layer of the photodetector requires improvement. Rapid thermal annealing (RTA) has been widely used to improve the crystallinity and mobility of films. However, the reduction in oxygen content during RTA causes a decrease in the carrier concentration and transmittance of NiO films. Regarding the aim of preventing a reduction in oxygen content in the NiO films due to the RTA process, an O2 atmosphere (compared with Ar and N2 atmospheres) was identified as the optimal condition for mobility (3.42 cm2/V·s) and transmittance (50%). Full article
(This article belongs to the Section Thin Films)
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25 pages, 14023 KiB  
Article
Cold Spray Process for Co-Deposition of Copper and Aluminum Particles
Coatings 2023, 13(11), 1953; https://doi.org/10.3390/coatings13111953 - 15 Nov 2023
Viewed by 798
Abstract
Mixed-particle spraying has been applied to various aspects of industrial cold spraying for a long time. Due to the complexity of mixed-particle simulations, most studies only consider dozens of particles when considering particle collisions. This paper combines computational fluid dynamics and a discrete [...] Read more.
Mixed-particle spraying has been applied to various aspects of industrial cold spraying for a long time. Due to the complexity of mixed-particle simulations, most studies only consider dozens of particles when considering particle collisions. This paper combines computational fluid dynamics and a discrete element method to analyze the entire trajectories of mixed particles. With simulations involving over one hundred thousand particles, we accurately tracked the three-dimensional positions and velocities of each particle, effectively visualizing their journey from feeder to substrate. By comparing the particles’ velocities to their critical velocities, we could directly assess the deposition efficiency, achieving a comprehensive and accurate simulation of the complete cold spray process. The numerical model was validated using a multi-experimental analysis. The particle distribution and deposition area from the numerical model matched well with the experimental data. It was found that the mutual collision of copper and aluminum particles increased the number of copper particles, surpassing the critical velocity in the mixed powder by 24.2%. When copper particles and aluminum particles collided, the displacement of aluminum particles was more than three times that of copper particles in the direction perpendicular to the jet. This collision caused the aluminum particles to be more dispersed. Full article
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15 pages, 6870 KiB  
Article
Microstructure and Tribological Performance of HVAF-Sprayed Ti-6Al-4V Coatings
Coatings 2023, 13(11), 1952; https://doi.org/10.3390/coatings13111952 - 15 Nov 2023
Viewed by 708
Abstract
Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must [...] Read more.
Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must be dense to provide the required in-service functionalities, such as resistance to wear. The High Velocity Air Fuel (HVAF) thermal spray technique deposits dense coatings with reduced concern for oxide inclusions. This work presents an investigation of the microstructure, dry sliding, and solid particle erosive wear performance of four different coatings engineered through the configuration of the nozzle of an HVAF spray gun, based on the length of the nozzle and the size of the nozzle exit. A long nozzle length and wide nozzle exit mean increased inflight dwell time and reduced average inflight temperature for the sprayed particles, respectively—a reversed configuration means the opposite. The tested coatings showed a porosity of less than 2%. The sliding and erosion wear performance of the densest of the coatings compares to that of the bulk material tested under the same conditions. Electron microscopy was used to investigate the driving mechanisms for the performance of the respective coatings. The implications of the results are discussed for the potential adoption of HVAF-sprayed coatings in metal component repair. Full article
(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)
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11 pages, 7048 KiB  
Article
Tribological Performance and Scuffing Resistance of Cast-Iron Cylinder Liners and Al-Si Alloy Cylinder Liners
Coatings 2023, 13(11), 1951; https://doi.org/10.3390/coatings13111951 - 15 Nov 2023
Cited by 1 | Viewed by 692
Abstract
In order to better determine the applicable working conditions of Al-Si alloy cylinder liners and cast-iron cylinder liners, their tribological performance and scuffing resistance are discussed in this paper. After wear and scuffing tests, it was found that cast-iron cylinder liners had better [...] Read more.
In order to better determine the applicable working conditions of Al-Si alloy cylinder liners and cast-iron cylinder liners, their tribological performance and scuffing resistance are discussed in this paper. After wear and scuffing tests, it was found that cast-iron cylinder liners had better wear resistance and better scuffing resistance, but poor friction performance. Al-Si alloy cylinder liners had weaker wear resistance and scuffing resistance, but excellent friction performance. The wear mechanism of cast-iron cylinder liners is slight adhesive wear, and they are suitable for traditional fuel engines and turbocharged engines with high load, high power, and high stability. The wear mechanism of Al-Si alloy cylinder liners was a mixture of adhesive wear and abrasive wear, and they are suitable for engines that are lightweight, efficient, and energy-saving, and operate at high speeds. Full article
(This article belongs to the Special Issue Thin Films for Tribological Applications)
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20 pages, 21260 KiB  
Article
Graded Minimal Surface Structures with High Specific Strength for Broadband Sound Absorption Produced by Laser Powder Bed Fusion
Coatings 2023, 13(11), 1950; https://doi.org/10.3390/coatings13111950 - 15 Nov 2023
Viewed by 738
Abstract
In this research, a design method for triply periodic minimal surface (TPMS) structures with a high specific strength for broadband sound absorption is proposed. The graded TPMS structures are controlled by linear, quadratic, and sine functions. Homogeneous TPMSs and graded TPMSs were manufactured [...] Read more.
In this research, a design method for triply periodic minimal surface (TPMS) structures with a high specific strength for broadband sound absorption is proposed. The graded TPMS structures are controlled by linear, quadratic, and sine functions. Homogeneous TPMSs and graded TPMSs were manufactured by laser powder bed fusion (LPBF) with AlSi7Mg powder, and acoustic impedance tube, compression, and digital image correlation (DIC) tests were applied to obtain the sound absorption and compression properties. The sound absorption coefficient of a homogeneous gyroid increases as the height and offset thickness of the surface increase, and it increases as element size decreases. The sound absorption peak shifts to low frequencies as the height of the structure increases. The average sound absorption coefficient at 1/3 octave from 500 to 6300 Hz of the graded TPMS with a porosity from 60.51 to 77.59% (surface of incident sound wave to rigid backing) is superior to that of the graded TPMS with a porosity from 77.59 to 60.51%, but the latter has a broadband sound absorption coefficient. The compression and DIC results of graded TPMS also show excellent mechanical properties and energy absorption characteristics. Full article
(This article belongs to the Special Issue Recent Development in Post-processing for Additive Manufacturing)
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20 pages, 6379 KiB  
Article
Effects and Consequences of an Alkali-Induced Cathodic Environment on Coating Aging
Coatings 2023, 13(11), 1949; https://doi.org/10.3390/coatings13111949 - 15 Nov 2023
Viewed by 722
Abstract
The use of organic coatings in conjunction with cathodic protection (CP) for buried structures is the usual method for protecting steel against corrosion. When the organic coating loses its protective ability, regardless of the reason, the CP becomes the active protection, leading to [...] Read more.
The use of organic coatings in conjunction with cathodic protection (CP) for buried structures is the usual method for protecting steel against corrosion. When the organic coating loses its protective ability, regardless of the reason, the CP becomes the active protection, leading to a specific local environment. This environment can be characterized by high alkalinity, which can be detrimental for the coated structure, either by weakening the steel–coating interface or by the chemical aging of the coating. Thus, the coating must be compatible with CP and able to sustain aging under an alkaline environment. In this study, the susceptibility to alkaline aging and its consequences in regards to coating performance have been investigated for two commercial coatings used for buried structures—fusion bonded epoxy (FBE) and liquid epoxy (LE)—in free membrane and coated steel configurations. The results showed a clear impact of alkaline aging on the studied LE, leading to a significant reduction in coating resistance and ultimately, failure of the steel–coating interface, whereas the studied FBE remained stable. The presented results relate to a precise formulation of LE and FBE; however, the proposed chemical method appears to be relevant and shows the necessity of considering such specific aging results for coating specifications and improvements. Full article
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14 pages, 8003 KiB  
Article
Effect of Bias Voltage on Structure, Mechanical Properties, and High-Temperature Water Vapor Corrosion of AlCrNbSiTi High Entropy Alloy Coatings
Coatings 2023, 13(11), 1948; https://doi.org/10.3390/coatings13111948 - 15 Nov 2023
Viewed by 702
Abstract
Fuel cladding tubes are devices used in reactors to encapsulate fuel clots and transmit heat to coolants. However, zirconium alloy materials which are widely used in the fuel cladding pipe of pressurized water reactors have noticeable safety risks in resisting design basis accidents. [...] Read more.
Fuel cladding tubes are devices used in reactors to encapsulate fuel clots and transmit heat to coolants. However, zirconium alloy materials which are widely used in the fuel cladding pipe of pressurized water reactors have noticeable safety risks in resisting design basis accidents. Therefore, it is very important to improve the corrosion resistance of fuel envelope tubes to high-temperature water vapor oxidation. High-entropy alloys are considered to be a potential protective coating material for cladding tubes. In this study, AlCrNbSiTi high-entropy alloy (HEA) coatings were prepared by magnetron sputtering at different bias voltages. The effect of bias on coating morphologies, structure, mechanical properties, and resistance to high-temperature water vapor corrosion were studied. Experimental results showed that the bias significantly affects the coating surface roughness. In terms of mechanical properties, the sample at 50 V bias exhibited maximum hardness and elastic modulus of 18.2 GPa and 232.4 GPa, respectively. The highest adhesive force of the coating to the substrate of 36 N was obtained at 100 V bias. The optimum water vapor corrosion resistance of the AlCrNbSiTi HEA coating was achieved at 50 V bias, in which sample-point corrosion was the main corrosion failure mechanism. Full article
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13 pages, 22917 KiB  
Article
Microstructure and Properties of Inconel 718 Coatings with Different Laser Powers on the Surface of 316L Stainless Steel Substrate
Coatings 2023, 13(11), 1947; https://doi.org/10.3390/coatings13111947 - 15 Nov 2023
Viewed by 652
Abstract
Laser cladding is a new method to prepare coatings with good quality. Laser power is one of the main factors affecting the quality of laser cladding coatings. An appropriate laser power helps obtain a high-performance laser cladding coating. In order to obtain coatings [...] Read more.
Laser cladding is a new method to prepare coatings with good quality. Laser power is one of the main factors affecting the quality of laser cladding coatings. An appropriate laser power helps obtain a high-performance laser cladding coating. In order to obtain coatings with good quality, an experiment with different laser powers was designed in this research. Three Inconel 718 coatings with different laser powers were prepared on the surface of a 316L stainless steel substrate. And the effect of different laser powers (1400, 1600, and 1800 W) on the microstructure, phases, and element distribution of coatings (L1–L3) was investigated by SEM, EDS, XRD, and a wear and friction tester. Meanwhile, the microhardness and friction and wear properties of different coatings were analyzed. The results show that the coatings’ phases were the same and composed of γ~(Fe, Ni) solid solution, Ni3Nb, (Nb0.03Ti0.97)Ni3, MCX (M = Cr, Nb, Mo), and so on. The background zones in the L1–L3 coatings were mainly the Fe and Ni elements. The irregular blocks in the coating were rich in Cr, Mo, and Nb, which formed the MCX (M = Cr, Nb, Mo) phase. When laser powers were 1400, 1600, and 1800 W, the average microhardness of the three coatings was 685.6, 604.6, and 551.9 HV0.2, respectively. The L1 coating had the maximum microhardness, 707.5 HV0.2, because the MCX (M = Cr, Nb, Mo)-reinforced phase appeared on the upper part of the coating. The wear rates were 3.65 × 10−5, 2.97 × 10−5, and 6.98 × 10−5 mm3·n−1·m−1. The wear mechanism of the three coatings was abrasive wear and adhesive wear. When the laser power was 1600 W, the coating had the minimum wear rate, which exhibited the best wear resistance. When the laser power was 1600 W, the upper part of the coating to the bonding zone was mainly composed of equiaxed crystals, dendrites, cellular crystals, columnar crystals, and planar crystals. The fine crystals and compounds caused a decrease in wear volume, and they had the most optimal wear resistance. Full article
(This article belongs to the Special Issue Advances in Deposition and Characterization of Hard Coatings)
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18 pages, 19459 KiB  
Article
Electrophoretic Deposition of ZnO-Containing Bioactive Glass Coatings on AISI 316L Stainless Steel for Biomedical Applications
Coatings 2023, 13(11), 1946; https://doi.org/10.3390/coatings13111946 - 14 Nov 2023
Cited by 1 | Viewed by 895
Abstract
The main objective of this investigation was to study the implications of incorporating zinc oxide nanoparticles into the matrix of a bioactive glass for the bioactivity and structural properties of the deposited coating. ZnO-containing bioactive glass was coated on an AISI 316L stainless [...] Read more.
The main objective of this investigation was to study the implications of incorporating zinc oxide nanoparticles into the matrix of a bioactive glass for the bioactivity and structural properties of the deposited coating. ZnO-containing bioactive glass was coated on an AISI 316L stainless steel substrate using the electrophoretic deposition technique. AISI 316L stainless steel is a biomedical grade steel, which is widely used in different biomedical applications. For the electrophoretic deposition, voltages and times were chosen in the range of 15–40 V and 15–120 min, respectively. The microstructure, phase composition, and surface roughness of coated samples were analyzed in this investigation. Moreover, the corrosion behavior and the MTT (mitochondrial activity) of samples were studied. Results showed a uniform distribution of elements such as silicon and calcium, characteristic of bioactive glass 58S5, in the coating as well as the uniform distribution of Zn inside the ZnO-containing samples. The findings showed that the deposited ZnO-containing bioactive glass is a hydrophilic surface with a relatively rough surface texture. The results of the MTT and antibacterial effects showed that the deposited layers have promising cell viability. Full article
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