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Coatings, Volume 10, Issue 1 (January 2020) – 89 articles

Cover Story (view full-size image): Scaffolding protein layers formed on surfaces of biomaterials after contacting with body fluids play essential roles in determining the fate of cells and tissues adhering to the biomaterials. Our method enables us to evaluate molar compositions of proteins adsorbed from serum or various cell culture media. This information contributes to understanding the mechanism underlying responses of cells to biomaterials. View this paper.
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Open AccessEditorial
Acknowledgement to Reviewers of Coatings in 2019
Coatings 2020, 10(1), 89; https://doi.org/10.3390/coatings10010089 - 20 Jan 2020
Viewed by 756
Abstract
The editorial team greatly appreciates the reviewers who have dedicated their considerable time and expertise to the journal’s rigorous editorial process over the past 12 months, regardless of whether the papers are finally published or not [...] Full article
Open AccessFeature PaperArticle
Meyer-Rod Coated 2D Single-Crystalline Copper Nanoplate Film with Intensive Pulsed Light for Flexible Electrode
Coatings 2020, 10(1), 88; https://doi.org/10.3390/coatings10010088 - 20 Jan 2020
Viewed by 1152
Abstract
Copper is widely used because it is inexpensive, abundant, and highly conductive. However, most copper used in industrial coating processes is in the form of circular powder, which is problematic for large area, high conductive coatings. In this work, 2D single-crystalline Cu nanoplates [...] Read more.
Copper is widely used because it is inexpensive, abundant, and highly conductive. However, most copper used in industrial coating processes is in the form of circular powder, which is problematic for large area, high conductive coatings. In this work, 2D single-crystalline Cu nanoplates (Cu NPLs) were synthesized and a systematic study on coating with large-scale Cu NPLs using a Meyer-rod coating process was performed. The rheological behaviors of the Cu solution with various concentrations, surface tensions, and speeds were analyzed using Ca and Re numbers to optimize coating conditions. In addition, the effect of intensive pulse light (IPL) to sinter the coper film within a 1 s timeframe was also investigated in order to be able to produce an electrode in the shortest possible time which is applicable to industry. Finally, the Meyer-rod coated electrode was utilized in an electrochemical luminescence (ECL) device. Full article
(This article belongs to the Special Issue UV-Curable Coatings for Flexible/Wearable Electronics)
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Open AccessArticle
Electrochromic Properties of Li- Doped NiO Films Prepared by RF Magnetron Sputtering
Coatings 2020, 10(1), 87; https://doi.org/10.3390/coatings10010087 - 20 Jan 2020
Cited by 2 | Viewed by 873
Abstract
In this study: various amounts of Li2CO3 powders were mixed into NiO powders to fabricate the Li- added NiO (NiO:Li) targets. The electrochromic films of LiNiO were deposited on ITO glasses at room temperature (R.T.) by RF magnetron sputtering. The [...] Read more.
In this study: various amounts of Li2CO3 powders were mixed into NiO powders to fabricate the Li- added NiO (NiO:Li) targets. The electrochromic films of LiNiO were deposited on ITO glasses at room temperature (R.T.) by RF magnetron sputtering. The thicknesses of electrochromic LiNiO films were kept about 200 nm. The ECD device was constructed with structure of Glass/ITO/ LiNiO /Gel-electrolyte/ITO/Glass. The results indicated that the optimal electrochromic characteristics of Li0.16Ni0.58O thin films could be obtained by 10 wt% Li2CO3 added NiO target. The optimized characteristics of ECDs could be achieved with the intercalation charge (Q) of 11.93 mC/cm2, the optical density (ΔOD) of 0.38, the transmittance change (ΔT) of 44.1%, and the coloring efficiency (η) of 31.8 cm2/C at the wavelength of 550 nm by setting voltage of 3.2V. The results demonstrate that the doping of Li+ ions into NiO films can effectively enhance the characteristics of ECD devices. The reason may due to the increased amount of charge stored in the electrochromic devices (ECDs). Full article
(This article belongs to the Special Issue Selected Papers from IIKII 2019 Conferences)
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Open AccessArticle
Significance of Arrhenius Activation Energy and Binary Chemical Reaction in Mixed Convection Flow of Nanofluid Due to a Rotating Disk
Coatings 2020, 10(1), 86; https://doi.org/10.3390/coatings10010086 - 20 Jan 2020
Cited by 6 | Viewed by 908
Abstract
This article addresses mixed convective 3D nanoliquid flow by a rotating disk with activation energy and magnetic field. Flow was created by a rotating disk. Velocity, concentration and temperature slips at the surface of a rotating disk were considered. Impacts of Brownian diffusion [...] Read more.
This article addresses mixed convective 3D nanoliquid flow by a rotating disk with activation energy and magnetic field. Flow was created by a rotating disk. Velocity, concentration and temperature slips at the surface of a rotating disk were considered. Impacts of Brownian diffusion and thermophoretic were additionally accounted for. The non-linear frameworks are simplified by suitable variables. The shooting method is utilized to develop the numerical solution of resulting problem. Plots were prepared just to explore that how concentration and temperature are impacted by different pertinent flow parameters. Sherwood and Nusselt numbers were additionally plotted and explored. Furthermore, the concentration and temperature were enhanced for larger values of Hartman number. However, the heat transfer rate (Nusselt number) diminishes when the thermophoresis parameter enlarges. Full article
(This article belongs to the Special Issue Recent Trends in Coatings and Thin Film–Modeling and Application)
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Open AccessArticle
Ultrasonic Sensors-Assisted Corrosion Studies on Surface Coated AlSi9Cu3 Alloy Die Castings
Coatings 2020, 10(1), 85; https://doi.org/10.3390/coatings10010085 - 19 Jan 2020
Cited by 1 | Viewed by 874
Abstract
A novel phenomenon known as Industry X.0 is becoming extremely popular for digitizing and reinventing business organizations through the adaption of rapid and dynamic technological, innovational, and organizational changes for attaining the profitable revenue. This work investigates the die-casted commercially pure aluminum alloyed [...] Read more.
A novel phenomenon known as Industry X.0 is becoming extremely popular for digitizing and reinventing business organizations through the adaption of rapid and dynamic technological, innovational, and organizational changes for attaining the profitable revenue. This work investigates the die-casted commercially pure aluminum alloyed with 9% silicon and 3% copper (AlSi9Cu3) that is produced through the gravity die casting process. Further, the degradation of surface coating on die-casted AlSi9Cu3 alloy was explored. The acrylic paint electrodeposition (ED) coat, 2-coat polyester without primer and 3-coat polyester with epoxy primer powder coatings were used in this study. Moreover, the 3.5 wt.% of sodium chloride (3.5 wt.% of NaCl) test solution was used for electrochemical and salt spray test and the tools used to assess electrochemical properties were electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, and neutral salt spray test (NSS). The microstructure of AlSi9Cu3 after corrosion exposure was investigated; also, the microstructure of coated and uncoated AlSi9Cu3 samples was analyzed by SEM microscopy after corrosion exposure. Besides, the electrochemical studies were also carried out on the Al alloy die casting. It was found that acrylic paint ED coatings exhibited higher corrosion resistance than 2-coat polyester without primer & 3-coat polyester with epoxy primer powder coatings. Acrylic paint ED coating showed higher corrosion resistance in AC and a lower value in DC and 3-coat polyester with epoxy primer powder coating displayed higher corrosion resistance in DC and a lower value in AC. Full article
(This article belongs to the Special Issue Coatings for Machining, Stamping, Moulding and Other Tools)
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Open AccessArticle
Adhesion Effect on the Hyperfine Frequency Shift of an Alkali Metal Vapor Cell with Paraffin Coating Using Peak-Force Tapping AFM
Coatings 2020, 10(1), 84; https://doi.org/10.3390/coatings10010084 - 19 Jan 2020
Cited by 1 | Viewed by 857
Abstract
We have investigated the adhesion effect on the hyperfine frequency shift of an alkali metal vapor cell with paraffin coating using the peak-force tapping AFM (atomic force microscopy) technique by developing a uniform and high-quality paraffin coating method. We observed a relatively uniform [...] Read more.
We have investigated the adhesion effect on the hyperfine frequency shift of an alkali metal vapor cell with paraffin coating using the peak-force tapping AFM (atomic force microscopy) technique by developing a uniform and high-quality paraffin coating method. We observed a relatively uniform temperature field on the substrate can be obtained theoretically and experimentally with the closed-type previse temperature-controlled evaporation method. The roughness and adhesion of the coating surface as low as 0.8 nm and 20 pN were successfully obtained, respectively. Furthermore, the adhesion information dependence of the topography was investigated from the force spectroscopy, which indicates that the adhesion force jumped on the edge of the particles and stepped but remained constant above the particles and steps regardless of their height for paraffin coating. Finally, we can evaluate the relaxation and the hyperfine frequency shift of an alkali metal vapor cell through accurately calculating the surface adsorption energy of the paraffin coating from peak-force tapping information. This finding is crucial for improving the sensitivity of the atomic sensors through directly analyzing the adhesion effect of the paraffin coating films instead of measuring the relaxation times. Full article
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Open AccessArticle
Attempts to Improve the Subsurface Properties of Horizontally-Formed Cementitious Composites Using Tin(II) Fluoride Nanoparticles
Coatings 2020, 10(1), 83; https://doi.org/10.3390/coatings10010083 - 19 Jan 2020
Cited by 2 | Viewed by 871
Abstract
This article presents studies that were performed in order to improve the subsurface properties of horizontally-formed cementitious composites using tin(II) fluoride nanoparticles. The main aim of the study was to solve the problem of the decrease in subsurface properties caused by mortar bleeding [...] Read more.
This article presents studies that were performed in order to improve the subsurface properties of horizontally-formed cementitious composites using tin(II) fluoride nanoparticles. The main aim of the study was to solve the problem of the decrease in subsurface properties caused by mortar bleeding and the segregation of the aggregate along the height of the overlay. The article also aims to highlight the patch grabbing difficulties that occur during the process of forming horizontally-formed cementitious composites. Four specimens were analyzed: one reference sample and three samples modified with the addition of 0.5, 1.0, and 1.5% of tin(II) fluoride nanoparticles in relation to the cement mass. To analyze the mechanical properties of the specimens, non-destructive (ultrasonic pulse velocity) and destructive tests (flexural tensile strength, compressive strength, abrasion resistance, pull-off strength) were performed. It was indicated that due to the addition of the tin(II) fluoride, it was possible to enhance the subsurface tensile strength and abrasion resistance of the tested cementitious composites. To confirm the obtained macroscopic results, the porosity of the subsurface was measured using SEM. It was also shown that the addition of the tin(II) fluoride nanoparticles did not reduce its flexural and compressive strength. The results show that horizontally-formed cementitious composites with the addition of 1.0% of tin(II) fluoride nanoparticles in relation to the cement mass obtained the most effective mechanical performance, especially with regard to subsurface properties. Full article
(This article belongs to the Special Issue Erosion of Nanostructured Coatings)
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Open AccessArticle
Formation of Coatings Based on Titanium Dioxide Nanosolson Polyester Fibre Materials
Coatings 2020, 10(1), 82; https://doi.org/10.3390/coatings10010082 - 19 Jan 2020
Cited by 1 | Viewed by 863
Abstract
In this paper, we show that functionalization of fibrous materials through coating formation is hindered by the need to preserve the capillary-porous system of the fabric and its drapability. Additionally, such coatings must be resistant to abrasion and washing. We consider ways of [...] Read more.
In this paper, we show that functionalization of fibrous materials through coating formation is hindered by the need to preserve the capillary-porous system of the fabric and its drapability. Additionally, such coatings must be resistant to abrasion and washing. We consider ways of solving these problems by analysing the formation of a stable coating based on photoactive titanium dioxide on a polyester fibre material as an example. The purpose of such coatings is to destroy coloured organic contaminants when the fabric is exposed to sunlight. We show that a polyester fabric with a titanium dioxide coating can become highly photochemically active and capable of inhibiting the vital activity of gram-negative bacteria and remaining soft and breathable at the same time. We also determined that depositing a titanium dioxide coating does not reduce the polyester fabric tensile strength. Polyester fabrics with photoactive properties can be widely used as decorative and trimming materials—for housing decoration, production of curtains and other decorative interior design elements. Full article
(This article belongs to the Special Issue Functional Coatings for Textile Applications)
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Open AccessArticle
Theoretical Uniformity Analysis and Improvement of Spray Deposition by Mixing Nozzles with Heating Conditions
Coatings 2020, 10(1), 81; https://doi.org/10.3390/coatings10010081 - 19 Jan 2020
Viewed by 750
Abstract
Spray coating is widely used in the manufacture of deposited layers of electronic devices due to its unique advantages of high-speed deposition over a large area. To improve the spray deposition process for further low-cost and uniform production, the uniformity of the spray [...] Read more.
Spray coating is widely used in the manufacture of deposited layers of electronic devices due to its unique advantages of high-speed deposition over a large area. To improve the spray deposition process for further low-cost and uniform production, the uniformity of the spray deposition should be systematically investigated. The current study, however, mainly focuses on the experimental trials with few numerical directions especially for the mixing nozzle sprayers with heating conditions. In the paper, we conduct a theoretical study on the uniformity of the internal and external mixing nozzles. The influencing factors include the initial angle, the total ink flow rate, the transporting gas velocity and the distance from the nozzle to the substrate. Then, the orthogonal test method is adopted to obtain the optimal combination of the parameters. Finally, the effects of different heating modes on the uniformity have been further studied. The results show that these factors influence the uniformity with the two types of nozzles to a different degree. The evaporation of the atomized droplets can effectively improve the uniformity in a certain temperature range. The heating temperature with the highest uniformity is various depending on the heating modes, which should be carefully addressed during the actual production. Full article
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Open AccessEditor’s ChoiceArticle
Effect of Zr Target Current on the Mechanical and Tribological Performance of MoS2–Zr Composite Lubricating Coatings
Coatings 2020, 10(1), 80; https://doi.org/10.3390/coatings10010080 - 18 Jan 2020
Cited by 3 | Viewed by 679
Abstract
To improve the tribological properties of pure MoS2 coating, the MoS2–Zr composite lubricating coatings were prepared on the WC/TiC/Co carbide surface utilizing radio frequency magnetron sputtering method combining with multiple arc ion plating technology. The effects of different Zr target [...] Read more.
To improve the tribological properties of pure MoS2 coating, the MoS2–Zr composite lubricating coatings were prepared on the WC/TiC/Co carbide surface utilizing radio frequency magnetron sputtering method combining with multiple arc ion plating technology. The effects of different Zr target currents on the surface morphologies, roughness, Zr content, adhesive force, thickness, microhardness and tribological behaviors of the composite coatings were systematically investigated. Results showed that the properties of MoS2 coating can be remarkably enhanced through co-deposition of a certain amount of Zr. As the Zr target current increased, the Zr content, surface roughness, thickness, and micro-hardness gradually increased, while the adhesive force of coatings increased first and then decreased. The friction behaviors and wear modes of the composite coatings both varied obviously with the increase of Zr current. The mechanism was mainly attributed to the different components and mechanical properties of the coatings caused by various Zr current. Full article
(This article belongs to the Section Tribology)
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Open AccessArticle
Photocatalytic Properties of Copper Nitride/Molybdenum Disulfide Composite Films Prepared by Magnetron Sputtering
Coatings 2020, 10(1), 79; https://doi.org/10.3390/coatings10010079 - 18 Jan 2020
Cited by 1 | Viewed by 746
Abstract
Cu3N/MoS2 composite films were prepared by magnetron sputtering under different preparation parameter, and their photocatalytic properties were investigated. Results showed that the composite films surface was uniform and had no evident cracks. When the sputtering power of MoS2 increased [...] Read more.
Cu3N/MoS2 composite films were prepared by magnetron sputtering under different preparation parameter, and their photocatalytic properties were investigated. Results showed that the composite films surface was uniform and had no evident cracks. When the sputtering power of MoS2 increased from 2 W to 8 W, the photocatalytic performance of the composite films showed a trend of increasing first and then decreasing. Among these films, the composite films with MoS2 sputtering power of 4 W showed the best photocatalytic degradation performance. The photocatalytic degradation rate of methyl orange at 30 min was 98.3%, because the MoS2 crystal in the films preferentially grew over the Cu3N crystal, thereby affecting the growth of the Cu3N crystal. The crystallinity of the copper nitride also increased. During photocatalytic degradation, the proper amount of MoS2 reduced the band gap of Cu3N, and the photogenerated electron hole pairs were easily separated. Thus, the films produces additional photogenerated electrons and promotes the degradation reaction of the composite films on methyl orange solution. Full article
(This article belongs to the Section Thin Films)
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Open AccessArticle
Surface Functionalization of Wool via Microbial-Transglutaminase as Bio-Mordant to Improve Dyeability with Madder in the Presence of Alum
Coatings 2020, 10(1), 78; https://doi.org/10.3390/coatings10010078 - 17 Jan 2020
Cited by 2 | Viewed by 767
Abstract
Herein, the wool fabric was mordanted with alum, treated with microbial transglutaminase (m-TGase), and then dyed with madder. Different concentrations of alum and m-TGase were used to find out the optimum condition to achieve the best color after dyeing the wool fabrics with [...] Read more.
Herein, the wool fabric was mordanted with alum, treated with microbial transglutaminase (m-TGase), and then dyed with madder. Different concentrations of alum and m-TGase were used to find out the optimum condition to achieve the best color after dyeing the wool fabrics with aqueous extract of madder. FT-IR spectroscopy and scanning electron microscopy (SEM) methods were applied to characterize the as-prepared samples. Contact angle measurements showed that the water uptake capability was increased in the case of the wool sample treated with alum and enzyme. Moreover, the samples were assessed for color strength (K/S) and color fastness. Our results showed that the optimal condition to get the highest color value was for the sample with 10% owf (of weight of fabric) alum and 5% owf m-TGase. Furthermore, it was found that there was a critical concentration for enzyme so that an increase in m-TGase amount would cause damage to the scales of fibers. The best condition of the dyeing process was discussed in this study, and also the proposed mechanism was presented. Indeed, treatment of wool with m-TGase led to a reduction in the amount of consumed alum, while investigations in color performances demonstrated the enhancement in color fastness, as well as color strength. Full article
(This article belongs to the Special Issue Functional Coatings for Textile Applications)
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Open AccessArticle
Surface Properties of Beech Wood after CO2 Laser Engraving
Coatings 2020, 10(1), 77; https://doi.org/10.3390/coatings10010077 - 16 Jan 2020
Cited by 3 | Viewed by 920
Abstract
The paper deals with the properties of a beech wood surface treated by CO2 laser engraving. The studied concerns were the discoloration, changes to morphology assessed through roughness and waviness parameters, and surface wetting with standard liquids (water and diiodomethane), with the [...] Read more.
The paper deals with the properties of a beech wood surface treated by CO2 laser engraving. The studied concerns were the discoloration, changes to morphology assessed through roughness and waviness parameters, and surface wetting with standard liquids (water and diiodomethane), with the aim of determining the wood surface free energy. The results have confirmed that the studied properties of the beech wood surface varied significantly, which were affected by the laser beam power P and raster density n. With increasing P and n, the lightness L* (expressed in CIE L*a*b* color space) decreased significantly. We also observed significant variation in the color coordinates a* and b*. At 8% laser power, the roughness and waviness parameters measured parallel as well as perpendicular to the grain increased proportionally with the increasing raster density. However, 4% laser power was not associated with distinct changes. Increasing the raster density reduced beech wood surface wetting equally with water and with diiodomethane. This was reflected in the higher contact angle values. The wood surface exhibited higher hydrophobicity at 4% laser power. At this power, the increasing raster density was reflected in the decreasing surface free energy, due to its polar component decrease. At 8% laser power, the changes in surface free energy were very minor from the practical viewpoint. The results suggest a potential good adhesion between film-forming materials and wood. However, the gluing performance may be negatively affected by the high roughness attained at 8% laser power and at higher raster densities. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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Open AccessArticle
Effects of Process Parameters on Geometrical Characteristics, Microstructure and Tribological Properties of TiB2 Reinforced Inconel 718 Alloy Composite Coatings by Laser Cladding
Coatings 2020, 10(1), 76; https://doi.org/10.3390/coatings10010076 - 16 Jan 2020
Cited by 2 | Viewed by 731
Abstract
The TiB2 reinforced Inconel 718 alloy composite coatings were prepared on carbon steel by laser cladding. The energy input (the ratio of laser power and scanning speed, E) was introduced to investigate the effects of process parameters on geometrical characteristics, microstructure and [...] Read more.
The TiB2 reinforced Inconel 718 alloy composite coatings were prepared on carbon steel by laser cladding. The energy input (the ratio of laser power and scanning speed, E) was introduced to investigate the effects of process parameters on geometrical characteristics, microstructure and tribological properties of composite coatings. The results show that the dilution rate decreases and the contact angle increases, respectively, as E decreases from 200.00 J/mm to 80.00 J/mm, which causes the decrease of the boding strength from 1.91 GPa to 0.39 GPa. The composite coatings contain the phases of γ-(Ni, Fe), Laves, TiB2, TiB, TiC, Ni3B, CrB4 and Cr23C6. As E decreases from 200.00 J/mm to 133.33 J/mm, the primary dendrite arm spacing (PDAS) and the Laves content of the composite coating decrease for the increase of cooling rate, leading to the increase of microhardness, the improvement of tribological properties and the change of wear mechanism from the severe multi-plastic deformation wear, adhesive wear and oxidative wear to the slight abrasive wear. However, as E decreases from 133.33 J/mm to 80.00 J/mm, for the weak Marangoni convection, TiB2 particles are prone to aggregate in the top of the composite coating which causes the increase of the PDAS and the Laves content, leading to the decrease of the microhardness and the degradation of tribological properties, and the wear mechanism change to the multi-plastic deformation wear and abrasive wear gradually. Full article
(This article belongs to the Section Tribology)
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Open AccessArticle
Enhanced Photoelectrochemical Properties from Mo-Doped TiO2 Nanotube Arrays Film
Coatings 2020, 10(1), 75; https://doi.org/10.3390/coatings10010075 - 15 Jan 2020
Cited by 4 | Viewed by 861
Abstract
Mo-doped TiO2 nanotube arrays are prepared successfully by a combined method of direct current (DC) magnetron sputtering and anodic oxidation. The doping amount of Mo can be modified by changing the number of molybdenum blocks on the Ti target while a Ti–Mo [...] Read more.
Mo-doped TiO2 nanotube arrays are prepared successfully by a combined method of direct current (DC) magnetron sputtering and anodic oxidation. The doping amount of Mo can be modified by changing the number of molybdenum blocks on the Ti target while a Ti–Mo alloy film is prepared by magnetron sputtering on a metal Ti substrate, following a Mo-doped TiO2 nanotube array grown by anodization. Morphology test shows that the doping of Mo could inhibit the phase transition and growth of crystal of TiO2. X-ray photoelectron spectroscopy (XPS) results show that Mo has successfully been embedded in the TiO2 crystal lattice and mainly exists in the valence states of Mo6+. Mo-doping samples show slightly increased visible light absorption as the red shift of TiO2 absorption edge with the band gap dropping from 3.24 to 3.16 eV with 0.5 at.% Mo doping. The enhanced photocurrent is demonstrated for a 0.5 at.% Mo-doped TiO2 electrode. Through photoelectric performance testing under UV-visible light irradiation, the nanotube array film with a Mo-doped content of 0.5% produced the maximum photocurrent density, which is about four times the undoped TiO2 nanotube array film, exhibiting a considerable photoelectric effect gain. The controllable Mo doping TiO2 nanotube array film prepared by this combining technique is expected as a promising material for efficient applications in photoelectric conversion. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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Open AccessArticle
Sensitivity Analysis of Rotor/Stator Interactions Accounting for Wear and Thermal Effects within Low- and High-Pressure Compressor Stages
Coatings 2020, 10(1), 74; https://doi.org/10.3390/coatings10010074 - 15 Jan 2020
Cited by 1 | Viewed by 719
Abstract
In the current design of turbomachines, engine performance is improved by reducing the clearances between the rotating components and the stator, which allows for loss decrease. Due to these clearance reductions, contact events may occur between the rotor and the stator. An abradable [...] Read more.
In the current design of turbomachines, engine performance is improved by reducing the clearances between the rotating components and the stator, which allows for loss decrease. Due to these clearance reductions, contact events may occur between the rotor and the stator. An abradable coating is deposited along the stator circumference as a sacrificial material to lower the contact severity. However, experiments highlighted the occurrence of rotor/stator interactions with high wear depth on the abradable coating as well as high temperature increases within the abradable coating following contacts. This work focuses on the sensitivity analysis of rotor/stator interactions with respect to the rotor angular speed and the initial clearances between the rotor and the stator, taking into account thermal effects within the abradable coating. Convergence analyses are first conducted to validate the numerical model. Then, after a calibration of the thermal model of the abradable coating based on two experimental test cases, the numerical model is used to investigate the cross effects of the angular speed and the initial clearances on the obtained rotor/stator interactions. Full article
(This article belongs to the Special Issue Tribological Behavior of Functional Surface: Models and Methods)
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Open AccessArticle
Corrosion and Wear Resistance of Fe-Based Amorphous Coatings
Coatings 2020, 10(1), 73; https://doi.org/10.3390/coatings10010073 - 14 Jan 2020
Cited by 5 | Viewed by 1196
Abstract
Fe-based amorphous coatings were prepared on the surface of 45 steel substrates via supersonic plasma spraying and laser cladding. The corrosion and wear behavior of the two different coatings were investigated. Compared with supersonic plasma spraying, laser cladding resulted in coatings with a [...] Read more.
Fe-based amorphous coatings were prepared on the surface of 45 steel substrates via supersonic plasma spraying and laser cladding. The corrosion and wear behavior of the two different coatings were investigated. Compared with supersonic plasma spraying, laser cladding resulted in coatings with a relatively denser structure, lower porosity, less cracks, and a good metallurgical bond with the substrate. Thanks to these properties, coatings produced by laser cladding exhibit a higher ability to resist uniform corrosion and better friction and wear performance than plasma-sprayed coatings. Full article
(This article belongs to the Special Issue Tribological Behavior of Functional Surface: Models and Methods)
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Open AccessArticle
Insulating Thermal and Water-Resistant Hybrid Coating for Fabrics
Coatings 2020, 10(1), 72; https://doi.org/10.3390/coatings10010072 - 14 Jan 2020
Cited by 3 | Viewed by 878
Abstract
Organic–inorganic hybrid (ceramer) coatings were synthesized and deposited on the polyester nonwoven fabrics through the sol–gel process. This promoted the formation of an insulating barrier that was able to enhance the thermal stability and the hydrophobicity of fabrics. The hybrid phase is made [...] Read more.
Organic–inorganic hybrid (ceramer) coatings were synthesized and deposited on the polyester nonwoven fabrics through the sol–gel process. This promoted the formation of an insulating barrier that was able to enhance the thermal stability and the hydrophobicity of fabrics. The hybrid phase is made of an organic network arising from different alkoxysilane precursors (trimethoxymethylalkoxysilane (TMEOS), 3-aminopropyl-trimethoxyalkoxysilane (APTMS), and tetraethylorthosilicate (TEOS)) and inorganic phase made of titanium dioxide TiO2 nanoparticles (NPs) and, in some cases, coated by P-based compound. The characterization of hybrid phase at liquid (size distribution and zeta potential of dispersed nanoparticles), dried state (crystalline phase, thermogravimetric (TGA), and Fourier transform infrared spectroscopic (FTIR) analyses), and on deposited coatings (contact angle, burn-out tests) aimed to find a correlation between the physicochemical properties of ceramer and functional performances of coated fabrics (thermal stability and hydrophobicity). The results showed that all ceramer formulations were able to improve the char formation after burn-out, in particular the highest thermal stability was obtained in the presence of TMEOS precursor and TiO2 NPs coated by P-based compound, which also provided the highest hydrophobicity. In conclusion, we presented an environmentally friendly and easily scalable process for the preparation of ceramer formulations capable of being formed into transparent, thermal-resistant, and hydrophobic fabric coatings, whose functions are extremely challenging for the textile market. Full article
(This article belongs to the Special Issue Advanced Hybrid Coatings and Thin Films for Surface Functionalization)
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Open AccessEditor’s ChoiceArticle
A Highly Efficient Visible Absorber Coating on a Curved Substrate
Coatings 2020, 10(1), 71; https://doi.org/10.3390/coatings10010071 - 13 Jan 2020
Viewed by 838
Abstract
In this study, we propose and fabricate a perfect absorber on a planar substrate using alternate silicon dioxide and ultrathin metallic lossy chromium (Cr) films. Furthermore, we transfer the absorber to a curved substrate via an optimization design of symmetric structures. The absorber [...] Read more.
In this study, we propose and fabricate a perfect absorber on a planar substrate using alternate silicon dioxide and ultrathin metallic lossy chromium (Cr) films. Furthermore, we transfer the absorber to a curved substrate via an optimization design of symmetric structures. The absorber exhibits a highly efficient absorption and large incident-angular tolerance characteristics in the whole visible region. We investigate each layer contribution to the absorption theoretically, and find that ultrathin (~5 nm) lossy Cr films play a dominant absorptive role. Using the effective interface method, we calculate the phase difference on the lossy Cr front surface. It is close to the destructive interference condition, from which we clarify why the proposed structures can produce a highly efficient absorption. Full article
(This article belongs to the Section Thin Films)
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Open AccessArticle
Effect of Different Color Paste on Properties of Fluorine Resin/Aluminum Infrared Low Emissivity Coating
Coatings 2020, 10(1), 70; https://doi.org/10.3390/coatings10010070 - 13 Jan 2020
Cited by 3 | Viewed by 916
Abstract
The effect of the four kinds of red, dark yellow, purple, and black pastes on the properties of fluorine resin/aluminum low emissivity coating was studied. The infrared emissivity coatings with red and black pastes were higher than the coatings with dark yellow and [...] Read more.
The effect of the four kinds of red, dark yellow, purple, and black pastes on the properties of fluorine resin/aluminum low emissivity coating was studied. The infrared emissivity coatings with red and black pastes were higher than the coatings with dark yellow and purple pastes. The hardness of the coatings with red, dark yellow, and purple color pastes was 6H, and that with black pastes was 6B. The adhesion and impact resistance of dark yellow coating was better, followed by red and purple, and the adhesion and impact resistance of black coating was the worst. Electrochemical polarization curves indicated that fluorine resin coatings with purple paste had better corrosion resistance. After the salt water resistance test, there was no obvious loss of light in the coatings with the four kinds of color pastes. The purple paste coating had no obvious loss of light and less bubble, suggesting that the fluorine resin/aluminum low emissivity coating with purple paste had better performance. The results of this study provide a new prospect for the application of infrared low emissivity coating in infrared stealth and compatibility with visible light. Full article
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Open AccessReview
State-of-the-Art Green Roofs: Technical Performance and Certifications for Sustainable Construction
Coatings 2020, 10(1), 69; https://doi.org/10.3390/coatings10010069 - 13 Jan 2020
Cited by 2 | Viewed by 1323
Abstract
Green roof systems, a technology which was used in major ancient buildings, are currently becoming an interesting strategy to reduce the negative impact of traditional urban development caused by ground impermeabilization. Only regarding the environmental impact, the application of these biological coatings on [...] Read more.
Green roof systems, a technology which was used in major ancient buildings, are currently becoming an interesting strategy to reduce the negative impact of traditional urban development caused by ground impermeabilization. Only regarding the environmental impact, the application of these biological coatings on buildings has the potential of acting as a thermal, moisture, noise, and electromagnetic barrier. At the urban scale, they might reduce the heat island effect and sewage system load, improve runoff water and air quality, and reconstruct natural landscapes including wildlife. In spite of these significant benefits, the current design and construction methods are not completely regulated by law because there is a lack of knowledge of their technical performance. Hence, this review of the current state of the art presents a proper green roof classification based on their components and vegetation layer. Similarly, a detailed description from the key factors that control the hydraulic and thermal performance of green roofs is given. Based on these factors, an estimation of the impact of green roof systems on sustainable construction certifications is included (i.e., LEED—Leadership in Energy and Environment Design, BREEAM—Building Research Establishment Environmental Assessment Method, CASBEE—Comprehensive Assessment System for Built Environment Efficiency, BEAM—Building Environmental Assessment Method, ESGB—Evaluation Standard for Green Building). Finally, conclusions and future research challenges for the correct implementation of green roofs are addressed. Full article
(This article belongs to the Special Issue Advanced Coatings for Buildings) Printed Edition available
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Open AccessFeature PaperArticle
Micro-Patterning of Magnetron Sputtered Titanium Dioxide Coatings and Their Efficiency for Photocatalytic Applications
Coatings 2020, 10(1), 68; https://doi.org/10.3390/coatings10010068 - 12 Jan 2020
Cited by 3 | Viewed by 884
Abstract
Titanium dioxide thin films were deposited onto sola-lime glass substrates by reactive magnetron sputtering. Fine stainless steel mesh sheets with different aperture sizes were applied as masks over glass substrates to allow the deposition of the coatings with micro-patterned structures and, therefore, enhanced [...] Read more.
Titanium dioxide thin films were deposited onto sola-lime glass substrates by reactive magnetron sputtering. Fine stainless steel mesh sheets with different aperture sizes were applied as masks over glass substrates to allow the deposition of the coatings with micro-patterned structures and, therefore, enhanced surface area. Non-patterned titania films were deposited for comparison purposes. The titanium dioxide films were post-deposition annealed at 873 K for crystallinity development and then extensively analysed by a number of analytical techniques, including scanning electron microscopy (SEM)/energy-dispersive X-ray spectroscopy (EDX), optical and stylus profilometry, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy. The photocatalytic activity of non-patterned and micro-patterned titania films was assessed under UV light irradiation by three different methods; namely methylene blue, stearic acid, and oleic acid degradation. The results revealed that the micro-patterned coatings significantly outperformed non-patterned titania in all types of photocatalytic tests, due to their higher values of surface area. Increasing the aperture of the stainless steel mesh resulted in lower photocatalytic activity and lower surface area values, compared to the coatings deposited through a smaller aperture mesh. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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Open AccessArticle
Surface Morphological Features of Molybdenum Irradiated by a Single Laser Pulse
Coatings 2020, 10(1), 67; https://doi.org/10.3390/coatings10010067 - 11 Jan 2020
Cited by 2 | Viewed by 899
Abstract
Molybdenum (Mo) is considered a plasma facing material alternative to tungsten (W) for manufacturing the divertor armours of International Thermonuclear Experimental Reactor (ITER). Transient thermal loads of high energy occurring in a tokamak during the service life have been simulated through a single [...] Read more.
Molybdenum (Mo) is considered a plasma facing material alternative to tungsten (W) for manufacturing the divertor armours of International Thermonuclear Experimental Reactor (ITER). Transient thermal loads of high energy occurring in a tokamak during the service life have been simulated through a single laser pulse delivered by a Nd:YAG/Glass laser, and the effects have then been examined through scanning electron microscopy (SEM) observations. An erosion crater forms in correspondence with the laser spot due to the vaporization and melting of the metal, while all around a network of cracks induced by thermal stresses is observed. The findings have been compared to results of similar experiments on W and literature data. The morphology of the crater and the surrounding area is different from that of W: the crater is larger and shallower in the case of Mo, while its walls are characterized by long filaments, not observed in W, because the lower viscosity and surface tension of Mo allow an easier flow of the liquid metal. Most importantly, the volume of Mo ablated from the surface by the single laser pulse is about ten times that of W. This critical aspect is of particular relevance and leads us to conclude that W remains the best solution for manufacturing the armours of the ITER divertor. Full article
(This article belongs to the Special Issue Metal Surfaces)
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Open AccessReview
From Extremely Water-Repellent Coatings to Passive Icing Protection—Principles, Limitations and Innovative Application Aspects
Coatings 2020, 10(1), 66; https://doi.org/10.3390/coatings10010066 - 11 Jan 2020
Cited by 5 | Viewed by 1391
Abstract
The severe environmental conditions in winter seasons and/or cold climate regions cause many inconveniences in our routine daily-life, related to blocked road infrastructure, interrupted overhead telecommunication, internet and high-voltage power lines or cancelled flights due to excessive ice and snow accumulation. With the [...] Read more.
The severe environmental conditions in winter seasons and/or cold climate regions cause many inconveniences in our routine daily-life, related to blocked road infrastructure, interrupted overhead telecommunication, internet and high-voltage power lines or cancelled flights due to excessive ice and snow accumulation. With the tremendous and nature-inspired development of physical, chemical and engineering sciences in the last few decades, novel strategies for passively combating the atmospheric and condensation icing have been put forward. The primary objective of this review is to reveal comprehensively the major physical mechanisms regulating the ice accretion on solid surfaces and summarize the most important scientific breakthroughs in the field of functional icephobic coatings. Following this framework, the present article introduces the most relevant concepts used to understand the incipiency of ice nuclei at solid surfaces and the pathways of water freezing, considers the criteria that a given material has to meet in order to be labelled as icephobic and clarifies the modus operandi of superhydrophobic (extremely water-repellent) coatings for passive icing protection. Finally, the limitations of existing superhydrophobic/icephobic materials, various possibilities for their unconventional practical applicability in cryobiology and some novel hybrid anti-icing systems are discussed in detail. Full article
(This article belongs to the Special Issue Anti-Icing Coatings and Surfaces)
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Open AccessArticle
Preparation of Cross-Linkable Waterborne Polyurethane-Acrylate Coating Films with Multifunctional Properties
Coatings 2020, 10(1), 65; https://doi.org/10.3390/coatings10010065 - 11 Jan 2020
Cited by 3 | Viewed by 970
Abstract
Self-migration or unstable phase inversion occurs when the application conditions are varied, which limits the application of polyurethane-acrylate (PUA) composite films. In this paper, cross-linked polyurethane/poly(methyl methacrylate-co-borneol acrylate) shell microspheres were prepared by using the seeded emulsion polymerization method. The core-shell structure of [...] Read more.
Self-migration or unstable phase inversion occurs when the application conditions are varied, which limits the application of polyurethane-acrylate (PUA) composite films. In this paper, cross-linked polyurethane/poly(methyl methacrylate-co-borneol acrylate) shell microspheres were prepared by using the seeded emulsion polymerization method. The core-shell structure of these samples was identified by dynamic light scattering (DLS) and high-resolution transmission electron microscope (HR-TEM). Moreover, HR-TEM images indicated that the core-shell structure of the microsphere does not undergo complete phase inversion. In addition, with increasing content of borneol acrylate in the shell, the water resistance and antibacterial adhesion of films were improved. The X-ray photoelectron spectroscopy (XPS), Energy Dispersive Spectrometer (EDS), water contact angle (CA) measurements, antibacterial and anti-adhesion tests demonstrate that the C/N ratios of films from the inside to the upper surface had an obvious gradient in growth, indicating the shell component (polyborneol acrylate) was predominantly present at the surface of films after coalescence in cross-linked core-shell PUA. It was found that a suitable degree of cross-linking contributes to the segregation of the hydrophobic component (borneol groups) on the film surface. As a consequence, the excellent water resistance, cytocompatibility, and antibacterial properties endowed this series of polymer materials with promising application potential in the biomedical field. Full article
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Open AccessArticle
Antireflection Coating on PMMA Substrates by Atomic Layer Deposition
Coatings 2020, 10(1), 64; https://doi.org/10.3390/coatings10010064 - 10 Jan 2020
Cited by 3 | Viewed by 1562
Abstract
Antireflection coatings (ARC) are essential for various optical components including such made of plastics for high volume applications. However, precision coatings on plastics are rather challenging due to typically low adhesion of the coating to the substrate. In this work, optimization of the [...] Read more.
Antireflection coatings (ARC) are essential for various optical components including such made of plastics for high volume applications. However, precision coatings on plastics are rather challenging due to typically low adhesion of the coating to the substrate. In this work, optimization of the atomic layer deposition (ALD) processes towards conformal optical thin films of Al2O3, TiO2 and SiO2 on poly(methyl methacrylate) (PMMA) has been carried out and a five-layer ARC is demonstrated. While the uncoated PMMA substrates have a reflectance of nearly 8% in the visible (VIS) spectral range, this is reduced below 1.2% for the spectral range of 420–670 nm by applying a double-side ARC. The total average reflectance is 0.7%. The optimized ALD coatings show a good adhesion to the PMMA substrates even after the climate test. Microscopic analysis on the cross-hatch areas on PMMA after the climate test indicates very good environmental stability of the ALD coatings. These results enable a possible route by ALD to deposit uniform, crack free, adhesive and environmentally durable thin film layers on sensitive thermoplastics like PMMA. Full article
(This article belongs to the Special Issue Surface Functionalization by ALD Technology)
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Open AccessArticle
Influence of the Thickness of a Nanolayer Composite Coating on Values of Residual Stress and the Nature of Coating Wear
Coatings 2020, 10(1), 63; https://doi.org/10.3390/coatings10010063 - 10 Jan 2020
Cited by 8 | Viewed by 898
Abstract
The article discusses the influence of the thickness of the wear-resistant layer of the Zr-ZrN-(Zr,Al,Si)N nanolayer composite coating on the values of residual stress and the nature of coating wear. The study focused on coatings with wear-resistant layer thicknesses of 2.0, 4.3, 5.9, [...] Read more.
The article discusses the influence of the thickness of the wear-resistant layer of the Zr-ZrN-(Zr,Al,Si)N nanolayer composite coating on the values of residual stress and the nature of coating wear. The study focused on coatings with wear-resistant layer thicknesses of 2.0, 4.3, 5.9, and 8.5 µm, deposited using filtered cathodic vacuum arc deposition (FCVAD) technology. The X-ray diffraction (XRD) method based on the anisotropy of the elasticity modulus was used to find the values of the residual stress. The nature of the formation of interlayer delamination under the influence of residual compressive stress was studied using a scanning electron microscope (SEM). When the wear-resistant layers had a thickness of 2.0–5.9 μm, tensile stress formed, which decreased with an increase in the thickness of the coating. When the thickness of a wear-resistant layer was 8.5 μm, compressive stress formed. Under the action of compressive stress, periodic interlayer delamination formed, with a pitch of about 10 binary nanolayers. A mathematical model is proposed to describe the nature of the formation of interlayer delamination under the influence of compressive residual stress, including in the presence of a microdroplet embedded in the coating structure. Full article
(This article belongs to the Special Issue Stress in Thin Films and Coatings)
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Open AccessArticle
Improvement of the Turbine Blade Surface Phase Structure Recovered by Plasma Spraying
Coatings 2020, 10(1), 62; https://doi.org/10.3390/coatings10010062 - 10 Jan 2020
Cited by 1 | Viewed by 781
Abstract
This paper presents the results of research on the construction, technological parameters and criteria that control the process of formation of optimal phase structure of austenitic- and martensitic-class material for steam turbine blades. The hypothesis that the established correlation could increase the quality [...] Read more.
This paper presents the results of research on the construction, technological parameters and criteria that control the process of formation of optimal phase structure of austenitic- and martensitic-class material for steam turbine blades. The hypothesis that the established correlation could increase the quality of blade recovery and its resistance against dynamic and vibrational loads was proved. The efficiency of the developed implantation method for the recovery of steam turbine blades was demonstrated. The optimal technological parameters of the process of laser plasma recovery were established empirically, allowing the development of the system for the fine tuning of the phase composition of austenitic- and martensitic-class steel. Full article
(This article belongs to the Special Issue Surface Treatment of Metals)
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Open AccessReview
Non-Vital Tooth Bleaching Techniques: A Systematic Review
Coatings 2020, 10(1), 61; https://doi.org/10.3390/coatings10010061 - 09 Jan 2020
Cited by 1 | Viewed by 1550
Abstract
This systematic review aimed to describe and characterize internal tooth bleaching techniques, conventional (walking-bleach) and combined (inside–outside), referring to their efficacy. The research was conducted on the main databases: PubMed, Cochrane Library, EMBASE, and Web of Science. Only randomized controlled trials and cohort [...] Read more.
This systematic review aimed to describe and characterize internal tooth bleaching techniques, conventional (walking-bleach) and combined (inside–outside), referring to their efficacy. The research was conducted on the main databases: PubMed, Cochrane Library, EMBASE, and Web of Science. Only randomized controlled trials and cohort studies were considered, on humans of 18 years old or older. A Population, Intervention, Comparison, Outcome (PICO) question was designed to evaluate the scientific evidence. The quality of each randomized controlled trial and cohort study was evaluated using the Cochrane Handbook for Systematic Reviews of Interventions and the Methodological Index for Non-Randomized Studies (ROBINS-I), respectively. The walking-bleach and the combined techniques were both effective at the end of the treatment, obtaining similar aesthetic results. Regardless of the technique used, internal tooth bleaching is an effective procedure, with good aesthetic results, in the treatment of non-vital teeth. The cervical barrier is a standard of care in internal bleaching techniques and should be used. Considering the similarity in the esthetic results obtained in both techniques, the concentrations used for both, and since the biocompatibility of the bleaching agent is more important than its efficiency or speed in obtaining results, the combined technique should be considered the method of choice rather than the walking-bleach technique. Full article
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Open AccessFeature PaperArticle
Transformations in CrFeCoNiCu High Entropy Alloy Thin Films during In-Situ Annealing in TEM
Coatings 2020, 10(1), 60; https://doi.org/10.3390/coatings10010060 - 09 Jan 2020
Cited by 2 | Viewed by 1136
Abstract
In-situ TEM-heating study of the microstructural evolution of CrFeCoNiCu high entropy alloy (HEA) thin films was carried out and morphological and phase changes were recorded. Post annealing investigation of the samples was carried out by high resolution electron microscopy and EDS measurements. The [...] Read more.
In-situ TEM-heating study of the microstructural evolution of CrFeCoNiCu high entropy alloy (HEA) thin films was carried out and morphological and phase changes were recorded. Post annealing investigation of the samples was carried out by high resolution electron microscopy and EDS measurements. The film is structurally and morphologically stable single phase FCC HEA up to 400 °C. At 450 °C the formation of a BCC phase was observed, however, the morphology of the film remained unchanged. This type of transformation is attributed to diffusionless processes (martensitic or massive). From 550 °C fast morphological and structural changes occur, controlled by volume diffusion processes. Fast growing of a new intermetallic phase is observed which contains mainly Cr and has large unit cell due to chemical ordering of components in <100> direction. The surface of the films gets covered with a CrO-type layer, possibly contributing to corrosion resistance of these. Full article
(This article belongs to the Special Issue Structure and Phase Transformations in Thin Films)
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