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Coatings, Volume 9, Issue 11 (November 2019)

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Open AccessReview
Superhydrophobic Civil Engineering Materials: A Review from Recent Developments
Coatings 2019, 9(11), 753; https://doi.org/10.3390/coatings9110753 (registering DOI) - 13 Nov 2019
Abstract
Superhydrophobic surfaces have drawn attention from scientists and engineers because of their extreme water repellency. More interestingly, these surfaces have also demonstrated an infinite influence on civil engineering materials. In this feature article, the history of wettability theory is described firstly. The approaches [...] Read more.
Superhydrophobic surfaces have drawn attention from scientists and engineers because of their extreme water repellency. More interestingly, these surfaces have also demonstrated an infinite influence on civil engineering materials. In this feature article, the history of wettability theory is described firstly. The approaches to construct hierarchical micro/nanostructures such as chemical vapor deposition (CVD), electrochemical, etching, and flame synthesis methods are introduced. Then, the advantages and limitations of each method are discussed. Furthermore, the recent progress of superhydrophobicity applied on civil engineering materials and its applications are summarized. Finally, the obstacles and prospects of superhydrophobic civil engineering materials are stated and expected. This review should be of interest to scientists and civil engineers who are interested in superhydrophobic surfaces and novel civil engineering materials. Full article
(This article belongs to the Special Issue Low-Adhesion Coatings: Fundamentals and Applications)
Open AccessArticle
Rolling Contact Performance of a Ti-Containing MoS2 Coating Operating Under Ambient, Vacuum, and Oil-Lubricated Conditions
Coatings 2019, 9(11), 752; https://doi.org/10.3390/coatings9110752 (registering DOI) - 13 Nov 2019
Abstract
Solid lubricant molybdenum disulfide (MoS2) coatings have been frequently used to lubricate mechanisms operating in environments where oil and grease lubrication are ineffective. This work evaluated the rolling contact performance of a Titanium-containing MoS2 coating under humid ambient, vacuum, and [...] Read more.
Solid lubricant molybdenum disulfide (MoS2) coatings have been frequently used to lubricate mechanisms operating in environments where oil and grease lubrication are ineffective. This work evaluated the rolling contact performance of a Titanium-containing MoS2 coating under humid ambient, vacuum, and oil-lubricated conditions. Weibull analyses of L50 lifetimes of AISI 52100 steel balls coated with a Ti-MoS2 coating paired with uncoated M50 steel rods were determined to be 3.7, 14.5, and 158.6 million cycles in ambient, vacuum, and oil-lubricated environments, respectively. In the ambient and vacuum tests, failures were determined to be associated with the onset of abrasive wear rather than fatigue or spalling. The L50 lifetimes of tests performed in those environments were found to depend upon the wear rate of the coatings on the balls. That is, the Ti-MoS2 functioned as a barrier to the onset of abrasive wear between the steel alloys until the coating was sufficiently worn away. Under oil-lubricated (boundary lubrication) conditions, L50 was found to depend on the durability and composition of tribofilms formed in-situ on the surfaces of the uncoated M50 rods. The tribofilms were comprised of mixtures of MoS2 crystallites and amorphous hydrocarbon (a-C:H). The crystalline MoS2 in the tribofilm originated from the amorphous Ti-MoS2 coating and likely underwent a thermodynamic phase transition as a result of the applied Hertz stress and frictional heating in the contact. The a-C:H in the tribofilm probably originated from a catalytic scission of the polyalphaolefin (PAO) molecules caused by the d-band character of the Mo or Ti in the coating. Overall, the Ti-MoS2-coated balls were effective at extending the operational lifetimes of M50 rods under ambient, vacuum, and oil-lubricated conditions by an order of magnitude. Full article
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Open AccessFeature PaperArticle
Luminescence of CsI and CsI:Na Films under LED and X-ray Excitation
Coatings 2019, 9(11), 751; https://doi.org/10.3390/coatings9110751 (registering DOI) - 13 Nov 2019
Abstract
In this study, we investigated the luminous properties of undoped cesium iodide (CsI) and Na-doped CsI (CsI:Na) films deposited by thermal vacuum evaporation and treated with different substrate temperatures, post-annealing temperatures, and deposition rates. The quality of the deposited films was evaluated by [...] Read more.
In this study, we investigated the luminous properties of undoped cesium iodide (CsI) and Na-doped CsI (CsI:Na) films deposited by thermal vacuum evaporation and treated with different substrate temperatures, post-annealing temperatures, and deposition rates. The quality of the deposited films was evaluated by their XRD pattern, SEM cross-section/surface morphologies and UV/X-ray luminescence, the spectra of which were used to derive the luminescence mechanism of the deposited films. The 310 nm luminescence demonstrates that the exciting light arises from the electron–hole recombination through the self-trapped exciton (STE) process, which is characteristic of the host polycrystalline CsI. The broad-band luminescence from ~400 to 450 nm demonstrates the other electron–hole recombination between the new energy states created by doping Na in the forbidden gap of CsI. When we deposited higher quality films at a substrate temperature of 200 °C, the undoped CsI films showed preferred crystal orientation at (200), and the CsI:Na films co-evaporated by 1 wt.% NaI at (310) and had the highest UV/X-ray luminescence. Full article
(This article belongs to the Special Issue Functional Thin Films: Design, Fabrication and Applications)
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Open AccessArticle
Electrodeposition of a Ni–P–TiO2/Ti3C2Tx Coating with in situ Grown Nanoparticles TiO2 on Ti3C2Tx Sheets
Coatings 2019, 9(11), 750; https://doi.org/10.3390/coatings9110750 (registering DOI) - 12 Nov 2019
Abstract
Protective coatings have received considerable attention for the surface treatment of devices. Herein, in situ grown nanoparticles, TiO2 on Ti3C2Tx sheets (TiO2/Ti3C2Tx), are prepared by a simple hydrothermal oxidation [...] Read more.
Protective coatings have received considerable attention for the surface treatment of devices. Herein, in situ grown nanoparticles, TiO2 on Ti3C2Tx sheets (TiO2/Ti3C2Tx), are prepared by a simple hydrothermal oxidation method possessing the layer structure, which is applied to prepare protective coatings. The Ni–P–TiO2/Ti3C2Tx coating is prepared by electroplating technology, revealing more excellent properties than those of the Ni–P coating. Compared with the Ni–P coating, even though the Ni–P–TiO2/Ti3C2Tx coating holds the rough surface, the wettability is changed from hydrophilic to hydrophobic, owing to the gathering existence of TiO2/Ti3C2Tx on the surface and coarse surface texture. In addition, the participation of TiO2/Ti3C2Tx in the Ni–P coating can improve the capacity of corrosion prevention and decrease the corrosion rate. According to the results of hardness and wear tests, microhardness of the Ni–P–TiO2/Ti3C2Tx coating is approximately 1350 kg mm–2 and the coefficient of friction (COF) of Ni–P–TiO2/Ti3C2Tx coatings is about 0.40, which is much lower than that of Ni–P coatings. Thus, the Ni–P–TiO2/Ti3C2Tx coating can be a promising material to protect the surface of equipment. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
Open AccessFeature PaperArticle
Advanced Analysis of Corroded Solar Reflectors
Coatings 2019, 9(11), 749; https://doi.org/10.3390/coatings9110749 - 11 Nov 2019
Abstract
The corrosion of the reflective layer is one of the main degradation mechanisms of solar reflectors. However, the appropriate assessment of the corroded reflector samples is not accomplished by the current analysis techniques. On the one hand, the reflectance measurement protocol of non-damaged [...] Read more.
The corrosion of the reflective layer is one of the main degradation mechanisms of solar reflectors. However, the appropriate assessment of the corroded reflector samples is not accomplished by the current analysis techniques. On the one hand, the reflectance measurement protocol of non-damaged solar reflectors for concentrating solar thermal technologies is widely addressed in the SolarPACES reflectance guideline. However, this methodology is not adequate for reflectors whose surface is partially corroded by many kind of corrosion agents. In this work, a new measurement technique to properly assess corroded samples was developed. To check the usefulness of the method, several damaged samples (subjected to two accelerated aging tests) were evaluated with the conventional technique and with the improved one. The results showed that a significant discrepancy is observed between the two methods for heavily corroded samples, with average reflectance differences of 0.053 ppt. The visualization of the reflector images illustrated that the improved method is more reliable. On the other hand, both the corrosion products formed and the corrosion rates were identified after each corrosive test. The chemical atmosphere significantly affects the products formed, whereas the corrosion rates are influenced by the test conditions and the reflector quality. Full article
(This article belongs to the Special Issue Surfaces and Interfaces for Renewable Energy)
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Open AccessArticle
Synthesis and Characterization of Nanostructured Polyaniline Thin Films with Superhydrophobic Properties
Coatings 2019, 9(11), 748; https://doi.org/10.3390/coatings9110748 - 11 Nov 2019
Abstract
Polyaniline (PANI) thin films incorporated with TiO2 or ZnO nanoparticles were synthesized via an electrochemical polymerization technique. Cyclic voltammetry (CV) was used to synthesize PANI from a strongly acidic medium (0.5 M H2SO4). The effects of different deposition [...] Read more.
Polyaniline (PANI) thin films incorporated with TiO2 or ZnO nanoparticles were synthesized via an electrochemical polymerization technique. Cyclic voltammetry (CV) was used to synthesize PANI from a strongly acidic medium (0.5 M H2SO4). The effects of different deposition cycles on the morphology, thickness, color, and properties of electrodeposited PANI thin films nanocomposites were investigated. Furthermore, the effects of the nanoparticles concentration on the morphology and water contact angle (CA) of the produced coating were investigated. Field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) were used to investigate the morphological structure. X-ray photoelectron spectroscopy (XPS) was used to study the surface composition of the formed film. The results reveal that the CA of the prepared coating reached 146°. A granular morphology of PANI with a moderate concentration of nanoparticles was obtained. In addition, XPS analysis confirmed the incorporation of the oxide nanoparticles in the matrix. Full article
(This article belongs to the Special Issue Thin-Film Synthesis, Characterization and Properties)
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Open AccessArticle
Tribological Performance of a Ni-Based Composite Coating in Artificial Seawater
Coatings 2019, 9(11), 747; https://doi.org/10.3390/coatings9110747 - 11 Nov 2019
Abstract
NiCrAlY and NiCrAlY-Mo coatings were fabricated by atmospheric plasma spraying (APS). The corrosion-wear performance of the coatings was investigated in artificial seawater and the synergistic mechanism between wear and corrosion were evaluated in detail. Results showed that the diffraction peaks of Ni3 [...] Read more.
NiCrAlY and NiCrAlY-Mo coatings were fabricated by atmospheric plasma spraying (APS). The corrosion-wear performance of the coatings was investigated in artificial seawater and the synergistic mechanism between wear and corrosion were evaluated in detail. Results showed that the diffraction peaks of Ni3Al shifted to the right and the microhardness of the coating was improved from 329.8 HV to 342.5 HV with adding the Mo element. Meanwhile, the NiCrAlY-Mo coating had a lower friction coefficient, with a wear rate of 0.26 and 3.69 × 10−6 mm3/Nm, compared to the NiCrAlY coating with a wear rate of 0.37 and 4.67 × 10−6 mm3/Nm. The NiCrAlY coating had severe corrosion and the corrosion mainly occurred in grain boundary. Adding the Mo element, the Mo element was distributed in the grain boundary and the coating had a lower corrosion rate and visibly slighter corrosion. The NiCrAlY-Mo coating had excellent corrosion-wear properties in artificial seawater. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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Open AccessArticle
Influence of Substrate Shape and Roughness on Coating Microstructure in Suspension Plasma Spray
Coatings 2019, 9(11), 746; https://doi.org/10.3390/coatings9110746 - 11 Nov 2019
Abstract
This study investigated the influence of the substrate shape and roughness on the microstructure of suspension plasma spray (SPS) coatings. For this purpose, an yttria-stabilized zirconia (YSZ) suspension was sprayed on flat and curved stainless-steel substrates by SPS. The suspension was composed of [...] Read more.
This study investigated the influence of the substrate shape and roughness on the microstructure of suspension plasma spray (SPS) coatings. For this purpose, an yttria-stabilized zirconia (YSZ) suspension was sprayed on flat and curved stainless-steel substrates by SPS. The suspension was composed of 20 wt.% YSZ particles in ethanol. After spraying, the morphology of the coatings was characterized by scanning electron microscopy (SEM). The results showed that the substrate shape influences the amount of coating material deposited and microstructural features of the coating. The amount of coating material deposited was seen to decrease as the radius of curvature decreased. Finally, the roughness was found to influence the formation of columnar structure. Full article
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Open AccessArticle
Application of Pullulan and Chitosan Multilayer Coatings in Fresh Papayas
Coatings 2019, 9(11), 745; https://doi.org/10.3390/coatings9110745 - 10 Nov 2019
Abstract
In this work, some multilayer coatings (two-layer, four-layer or six-layer) based on pullulan and chitosan for protecting papayas were prepared by the layer-by-layer technique. The papayas were coated by immersion and stored at 25 °C, 50% relative humidity or up to 14 days. [...] Read more.
In this work, some multilayer coatings (two-layer, four-layer or six-layer) based on pullulan and chitosan for protecting papayas were prepared by the layer-by-layer technique. The papayas were coated by immersion and stored at 25 °C, 50% relative humidity or up to 14 days. Uncoated and monolayer-coated papayas were used as controls. The pullulan/chitosan coatings decreased the papaya weight loss, softening, color change (b*, ΔE), and pH, retarded the fall of titratable acidity and vitamin C, and maintained respiratory rate and soluble solid contents. Sensory quality evaluation demonstrated that pullulan/chitosan coatings effectively preserved papaya flavor and overall acceptance. In general, the four-layer coatings provided the best fruit preservation. In conclusion, multilayer pullulan/chitosan coatings are efficient in maintaining the post-harvest quality and prolonging the shelf life of fresh papaya. Full article
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Open AccessArticle
One-Step Preparation of Nickel Nanoparticle-Based Magnetic Poly(Vinyl Alcohol) Gels
Coatings 2019, 9(11), 744; https://doi.org/10.3390/coatings9110744 - 09 Nov 2019
Abstract
Magnetic nanoparticles (MNPs) are of great interest due to their unique properties, especially in biomedical applications. MNPs can be incorporated into other matrixes to prepare new functional nanomaterials. In this work, we described a facile, one-step strategy for the synthesis of magnetic poly(vinyl [...] Read more.
Magnetic nanoparticles (MNPs) are of great interest due to their unique properties, especially in biomedical applications. MNPs can be incorporated into other matrixes to prepare new functional nanomaterials. In this work, we described a facile, one-step strategy for the synthesis of magnetic poly(vinyl alcohol) (mPVA) gels. In the synthesis, nickel nanoparticles and cross-linked mPVA gels were simultaneously formed. Ni nanoparticles (NPs) were also incorporated into a stimuli-responsive polymer to result in multiresponsive gels. The size of and distribution of the Ni particles within the mPVA gels were controlled by experimental conditions. The mPVA gels were characterized by field emission scanning electron microscope, X-ray diffraction, magnetic measurements, and thermogravimetric analysis. The new mPVA gels are expected to have applications in drug delivery and biotechnology. Full article
(This article belongs to the Special Issue Biointerface Coatings for Biomaterials and Biomedical Applications)
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Open AccessArticle
Condensation Test and Simulation of Superhydrophobic Coatings
Coatings 2019, 9(11), 743; https://doi.org/10.3390/coatings9110743 - 08 Nov 2019
Abstract
Pollution flashover accidents pose a great threat to the safe and stable operation of a power system, and superhydrophobic materials have broad application prospects in the field of pollution flashover prevention of the external insulation of transmission and transformation equipment. In this paper, [...] Read more.
Pollution flashover accidents pose a great threat to the safe and stable operation of a power system, and superhydrophobic materials have broad application prospects in the field of pollution flashover prevention of the external insulation of transmission and transformation equipment. In this paper, [email protected]/SiO2 superhydrophobic coatings were prepared using a spraying method. Superhydrophobicity is defined as an angle larger than 150° and a small roll-off angle smaller than 10°. The static contact angle of the coatings reached 155°, which meant they had excellent superhydrophobic properties. The distribution characteristics of water droplets on superhydrophobic surface were analyzed through a live condensation test, and simulation analysis was carried out. It was found that the distance between water droplets on the superhydrophobic surface was larger, which increased the distance of the arc development; the static contact angle was larger; and the electric field strength at the three-phase junction was lower. Both of them worked together to enhance the pollution flashover voltage of the coating. Full article
Open AccessArticle
Influence of Thermochromic Pigment Powder on Properties of Waterborne Primer Film for Chinese Fir
Coatings 2019, 9(11), 742; https://doi.org/10.3390/coatings9110742 - 08 Nov 2019
Abstract
This study chose organic thermochromic pigment powder and waterborne wood primer as the paint base, and Chinese fir board as the substrate to prepare thermochromic waterborne coatings with different concentrations of thermochromic pigment powder. The best concentration of thermochromic pigment powder for waterborne [...] Read more.
This study chose organic thermochromic pigment powder and waterborne wood primer as the paint base, and Chinese fir board as the substrate to prepare thermochromic waterborne coatings with different concentrations of thermochromic pigment powder. The best concentration of thermochromic pigment powder for waterborne primer film on Chinese fir surface was explored. The experimental results showed that the color-changing property of the primer film was the best when the concentration of pigment powder in primer film was 5.0%–10%. There was a negative correlation between the gloss of the primer and the concentration of pigment powder. The gloss of the primer film was the highest when the concentration of pigment powder was 5%. When the concentration of pigment powder is 0%–20% and 25.0%–30%, the adhesion of the coating is grade 0 and grade 1, respectively. The resistance to the impact of primer film increased with the increase of concentration of pigment powder, but the resistance to the impact of primer film with 0%–30% of thermochromic pigment powder concentration was similar. Scanning electron microscopy showed that the higher the concentration of thermochromic pigment powder, the more particles and agglomeration. When the concentration of pigment powder was 5%, the distribution of particles was uniform and no agglomeration, and the microstructure of primer film was the best. Infrared spectroscopy showed that there was no difference in the composition of the paint film from 0% to 30%. The results showed that the comprehensive property of waterborne primer film on Chinese fir was better when the pigment concentration was 5%. Waterborne thermochromic primer film provides a potential application for the development of intelligent furniture in different temperature ranges. Full article
(This article belongs to the Special Issue Paints and Paint Additives)
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Open AccessArticle
Analysis of a Thin Layer Formation of Third-Grade Fluid
Coatings 2019, 9(11), 741; https://doi.org/10.3390/coatings9110741 - 08 Nov 2019
Abstract
In present learning, surface protection layer progression of a third-grade fluid (TGF) is examined. Fluid transport within the micro passage made by the firm bladehas beenpresented. Main system of equations of fluidity have been narrated and streamlined by means of lubrication approximation theory [...] Read more.
In present learning, surface protection layer progression of a third-grade fluid (TGF) is examined. Fluid transport within the micro passage made by the firm bladehas beenpresented. Main system of equations of fluidity have been narrated and streamlined by means of lubrication approximation theory (LAT). Here, approximate solutions of velocity, pressure gradient, and coating depth have been presented. Results of coating and layer forming have been tabulated and discussed as well. It is observed that the transport properties of third-order fluid delivers an instrument to regulate flow velocity, pressure, and affect the final coated region. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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Open AccessFeature PaperArticle
Anti-Graffiti Behavior of Oleo/Hydrophobic Nano-Filled Coatings Applied on Natural Stone Materials
Coatings 2019, 9(11), 740; https://doi.org/10.3390/coatings9110740 - 07 Nov 2019
Abstract
In recent years, graffiti writings are increasingly regarded as a form of art. However, their presence on historic building remains a vandalism and different strategies have been developed to clean or, preferably, protect the surfaces. In this study, an experimental nano-filled coating, based [...] Read more.
In recent years, graffiti writings are increasingly regarded as a form of art. However, their presence on historic building remains a vandalism and different strategies have been developed to clean or, preferably, protect the surfaces. In this study, an experimental nano-filled coating, based on fluorine resin containing SiO2 nano-particles, and two commercial products have been applied on compact and porous calcareous stones, representative of building materials used in the Mediterranean basin, and their anti-graffiti ability has been analyzed. All the tested experimental and commercial coatings exhibited high hydrophobicity and oleophobicity, thus meeting one of the basic requirements for anti-graffiti systems. The effects of staining by acrylic blu-colored spray paint and felt-tip marker were, then, assessed; the properties of the treated stone surfaces after cleaning by acetone were also investigated. Visual observations, contact angle measurements and color evaluations were performed to this aim. It was found that the protective coatings facilitated the spray paint removal; however high oleophobicity or paint repellence did not guarantee a complete cleaning. The stain from the felt-tip marker was confirmed to be extremely difficult to remove. The cleaning with a neat unconfined solvent promoted the movement of the applied polymers (and likely of the paint, as well) in the porous structure of the stone substrate. Full article
(This article belongs to the Special Issue Water and Oil Repellent Surfaces)
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Open AccessArticle
Water Saving in CSP Plants by a Novel Hydrophilic Anti-Soiling Coating for Solar Reflectors
Coatings 2019, 9(11), 739; https://doi.org/10.3390/coatings9110739 - 07 Nov 2019
Abstract
In this work, results of the outdoor exposure campaign of a newly developed hydrophilic anti-soiling coating for concentrated solar thermal power (CSP) mirrors are presented. The material was exposed for nearly two years under realistic outdoor conditions and the influence of two different [...] Read more.
In this work, results of the outdoor exposure campaign of a newly developed hydrophilic anti-soiling coating for concentrated solar thermal power (CSP) mirrors are presented. The material was exposed for nearly two years under realistic outdoor conditions and the influence of two different cleaning techniques was evaluated. Mirror samples were analyzed during exposure and their reflectance and cleanliness were measured. The performance of the anti-soiling coated mirror samples was compared to conventional uncoated silvered-glass mirrors. The coatings showed appropriate anti-soiling and easy-to-clean behavior, with a mean cleanliness gain of 1 pp and maximum values under strong soiling conditions of up to over 7 pp. Cleanliness of the coated samples stayed higher throughout the whole campaign before and after cleaning, resulting in lower soiling rate compared to the reference material. Taking into account these values and supposing a threshold for cleaning of 96%, the number of cleaning cycles could be decreased by up to 11%. Finally, the coated material showed negligible degradation, not exceeding the degradation detected for the reference material. Full article
(This article belongs to the Special Issue Surfaces and Interfaces for Renewable Energy)
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Open AccessArticle
Preparation of Intumescent Fire Protective Coating for Fire Rated Timber Door
Coatings 2019, 9(11), 738; https://doi.org/10.3390/coatings9110738 - 06 Nov 2019
Abstract
Intumescent flame-retardant coating (IFRC) provides a protective barrier to heat and mass transfer for the most efficient utilization of a wide variety of passive fire protection systems at the recent development. This article highlights the fire-resistance, physical, chemical, mechanical, and thermal properties of [...] Read more.
Intumescent flame-retardant coating (IFRC) provides a protective barrier to heat and mass transfer for the most efficient utilization of a wide variety of passive fire protection systems at the recent development. This article highlights the fire-resistance, physical, chemical, mechanical, and thermal properties of the IFRC using a Bunsen burner, furnace, Scanning Electron Microscope, freeze-thaw stability test, Instron Micro Tester, and thermogravimetric analysis (TGA) test. The five IFRC formulations were mixed with vermiculite and perlite for the fabrication of fire-resistant timber door prototypes in this research project. Additionally, the best fire-resistance performance of the fire-rated door prototype was selected and compared with a commercial prototype under the fire endurance test. An inventive fire-rated door prototype (P2), with a low density of 636.45 kg/m3, showed an outstanding fire-resistance rating performance, resulting in temperature reduction by up to 54.9 °C, as compared with that of the commercial prototype. Significantly, a novel fire-rated timber door prototype with the addition of formulating intumescent coating has proven to be efficient in preventing fires and maintaining its integrity by surviving a fire resistance period of 2 h. Full article
(This article belongs to the Special Issue Advances in Flame Retardant Materials and Surfaces)
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Open AccessArticle
Effect of Interlayer Thickness on Nano-Multilayer Coating Performance during High Speed Dry Milling of H13 Tool Steel
Coatings 2019, 9(11), 737; https://doi.org/10.3390/coatings9110737 - 06 Nov 2019
Abstract
The TiAlCrSiYN-based family of physical vapor deposition (PVD) coatings were systematically designed through the incorporation of TiAlCrN interlayer to increase coating adhesion and consequently the tool life for extreme conditions that arise during dry high-speed milling of hardened tool steels. The investigation in [...] Read more.
The TiAlCrSiYN-based family of physical vapor deposition (PVD) coatings were systematically designed through the incorporation of TiAlCrN interlayer to increase coating adhesion and consequently the tool life for extreme conditions that arise during dry high-speed milling of hardened tool steels. The investigation in the present paper intends to explain the effect of TiAlCrN interlayer thickness on the overall coating properties and cutting performance. A comprehensive characterization of the structure and properties of the coatings has been performed using focused ion beam (FIB), scanning electron microscope (SEM), X-ray powder diffraction (XRD), nanoindentation, ramped load scratch test, repetitive load wear test, and nano-impact test. The wear test at a subcritical load of 1.5 N showed that there was a gradual improvement in coating adhesion to the substrate as the interlayer thickness increased from 100 to 500 nm. However, the wear performance, being related to the ability of the coating layer to exhibit minimal surface damage under operation, was found to be associated with micro-mechanical characteristics (such as hardness, elastic modulus). Around a 40% increase in the cutting performance with 300 nm interlayer exhibited that a substantial increase in tool life can be achieved through interlayer thickness variation, by obtaining a balance between mechanical and tribological properties of the studied coatings. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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Open AccessArticle
Effect of Transglutaminase Cross-Linking in Protein Isolates from a Mixture of Two Quinoa Varieties with Chitosan on the Physicochemical Properties of Edible Films
Coatings 2019, 9(11), 736; https://doi.org/10.3390/coatings9110736 - 06 Nov 2019
Abstract
The growing demand for minimally processed foods with a long shelf life and environmentally friendly materials has forced industry to develop new technologies for food preservation and handling. The use of edible films has emerged as an alternative solution to this problem, and [...] Read more.
The growing demand for minimally processed foods with a long shelf life and environmentally friendly materials has forced industry to develop new technologies for food preservation and handling. The use of edible films has emerged as an alternative solution to this problem, and mixtures of carbohydrates and proteins, may be formulated to improve their properties. The objective of this work was to evaluate the effect of protein cross-linking with transglutaminase (TG) of two varieties of quinoa protein isolate (Chenopodium quinoa) [Willd (QW), and Pasankalla (QP)] on the physicochemical and barrier properties of edible films based on chitosan (CT)-quinoa protein. The evaluated properties were water vapor permeability (WVP), solubility, adsorption, roughness determined by atomic force microscopy, and the interactions among the main film components determined by Raman spectroscopy. The results indicated that TG interacted with lysine of QW and QP. CT:QW (1:5, w/w) showed the lowest solubility (14.02 ± 2.17% w/w). WVP varied with the composition of the mixture. The WVP of CT:quinoa protein ranged from 2.85 to 9.95 × 10−11 g cm Pa−1 cm−2 s−1 without TG, whereas adding TG reduced this range to 2.42–4.69 × 10−11 g cm Pa−1 cm−2 s−1. The addition of TG to CT:QP (1:10, w/w) reduced the film surface roughness from 8.0 ± 0.5 nm to 4.4 ± 0.3 nm. According to the sorption isotherm, the addition of TG to CT-QW films improved their stability [monolayer (Xm) = 0.13 ± 0.02 %]. Films with a higher amount of cross-linking showed the highest improvement in the evaluated physical properties, but interactions among proteins that were catalyzed by TG depended on the protein source and profile. Full article
(This article belongs to the Special Issue Edible Films and Coatings: Fundamentals and Applications)
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Open AccessArticle
A New Assistant Method for Characterizing Ablation Resistance of ZrC-SiC Dispersive Biphasic Coating on C/C Composites
Coatings 2019, 9(11), 735; https://doi.org/10.3390/coatings9110735 - 06 Nov 2019
Abstract
To optimize the ablation resistance of ZrC coating, ZrC-SiC dispersive biphasic coating was prepared by chemical vapor co-deposition. The ablation resistances of the coatings were carried out by oxyacetylene flame tests. Compared with double-layered ZrC/SiC coating, the ablation resistance of ZrC-SiC coating was [...] Read more.
To optimize the ablation resistance of ZrC coating, ZrC-SiC dispersive biphasic coating was prepared by chemical vapor co-deposition. The ablation resistances of the coatings were carried out by oxyacetylene flame tests. Compared with double-layered ZrC/SiC coating, the ablation resistance of ZrC-SiC coating was evaluated. On the basis of similar mass ablation rates of the two coatings, a new assistant method for characterizing the thermal protecting effect of coatings on carbon-carbon composites (C/C) composites was proposed. The thermal protecting ability of the coating was accurately reflected by the changes of hardness and elastic modulus of C/C substrate below the central region of ablated coatings before and after ablation. The ablation processes of two kinds of coatings were also discussed. The results showed that the hardness and elastic modulus of the C/C substrate protected by ZrC-SiC coating were higher than that of C/C coated with ZrC/SiC coating. The result convincingly illustrated the thermal protecting ability of ZrC-SiC coating was much better than that of ZrC/SiC coating, which attributed to the formation of Zr-Si-O glass. Full article
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Open AccessArticle
Tribological Properties of Mo2N Films at Elevated Temperature
Coatings 2019, 9(11), 734; https://doi.org/10.3390/coatings9110734 - 06 Nov 2019
Abstract
Mo2N films were synthesized using the reactive magnetron sputtering system in a mixture of argon and nitrogen, and the tribological properties were investigated at different testing temperatures against an Al2O3 counterpart. The relative intensity ratio (RIR) method was [...] Read more.
Mo2N films were synthesized using the reactive magnetron sputtering system in a mixture of argon and nitrogen, and the tribological properties were investigated at different testing temperatures against an Al2O3 counterpart. The relative intensity ratio (RIR) method was used to calculate the weight fraction of the tribo-film (MoO3) on the wear tracks of the films. The results showed that the average friction coefficient first increased from 0.30 at 25 °C to 0.53 at 200 °C, and then decreased to 0.29 at 550 °C, while the wear rate decreased from 2.1 × 10−6 mm3/Nmm at 25 °C to 5.3 × 10−7 mm3/Nmm at 200 °C and then increased to 3.1 × 10−5 mm3/Nmm at 550 °C. The weight fraction of tribo-film was mainly attributed to changes in the average friction coefficient and the wear rate. Besides this, the relative humidity also influenced the tribological properties at 25–200 °C. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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Open AccessFeature PaperArticle
Influence of Polymer Composition and Substrate on the Performance of Bioinspired Coatings with Antibacterial Activity
Coatings 2019, 9(11), 733; https://doi.org/10.3390/coatings9110733 - 05 Nov 2019
Abstract
A series of methacrylic copolymers bearing thiazolium cationic groups and catechol moieties were evaluated as antibacterial coatings on a variety of materials including aluminum and plastics such as polycarbonate, poly(methyl methacrylate), and silicone rubber. The thermal properties of the copolymers were first studied [...] Read more.
A series of methacrylic copolymers bearing thiazolium cationic groups and catechol moieties were evaluated as antibacterial coatings on a variety of materials including aluminum and plastics such as polycarbonate, poly(methyl methacrylate), and silicone rubber. The thermal properties of the copolymers were first studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The cationic copolymers were thermally stable up to 200 °C and presented glass transition temperatures values well above 100 °C; thus, an acceptable thermal behavior for typical biomedical applications. The cationic copolymers with variable content of the adhesive anchoring N-(3,4-dihydroxyphenethyl) methacrylamide (DOMA) units were coated onto the metal and polymeric substrates by drop casting and the adhesive properties of the obtained coatings were further evaluated as a function of DOMA content and substrate. Optical profilometry, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectra, and antimicrobial studies reveal that the coatings adhere stronger to metal substrates than to the polymeric substrates. The copolymers with higher content of DOMA, 24 mol.%, resist solvent erosion treatment when coated onto all substrates and exhibit antimicrobial activity against Gram-positive S. aureus bacteria after this erosion treatment. In contrast, copolymers with low content, 9 mol.% of DOMA, only remain attached onto the aluminum metal substrate after solvent treatment, while on polymeric substrates the coatings are almost removed and do not show any efficacy against S. aureus bacteria. Full article
(This article belongs to the Special Issue Recent Developments in Antibacterial and/or Antifouling Surfaces)
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Open AccessArticle
Selection of Optimum Binder for Silicon Powder Anode in Lithium-Ion Batteries Based on the Impact of Its Molecular Structure on Charge–Discharge Behavior
Coatings 2019, 9(11), 732; https://doi.org/10.3390/coatings9110732 - 05 Nov 2019
Abstract
The high-capacity and optimal cycle characteristics of the silicon powder anode render it essential in lithium-ion batteries. The authors attempted to obtain a composite material by coating individual silicon particles of µm-order diameter with conductive carbon additive and resin to serve as a [...] Read more.
The high-capacity and optimal cycle characteristics of the silicon powder anode render it essential in lithium-ion batteries. The authors attempted to obtain a composite material by coating individual silicon particles of µm-order diameter with conductive carbon additive and resin to serve as a binder of an anode in a lithium-ion battery and thus improve its charge–discharge characteristics. Structural strain and hardness due to stress on the binder resin were alleviated by the adhesion between silicon or copper foil as a collector and the binder resin, preventing the systematic deterioration of the anode composite matrix immersed in electrolyte compositions including Li salt and fluoride. Moreover, the binder resin itself was confirmed to play a role of active material with occlusion and release of Li-ion. Furthermore, charge–discharge characteristics of the silicon powder anode active material strongly depend on the type of binder resin used; therefore, the binder resin used as composite material in rechargeable batteries should be carefully selected. Some resins for binding silicon particles were investigated for their mechanical and electrochemical properties, and a carbonized polyimide obtained a good charge–discharge cyclic property in a lithium-ion battery. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
Open AccessArticle
One-Step Method for Preparing Dispersive Tea Polyphenol/Graphene Nanosheets Enhanced with Anticorrosion Performance
Coatings 2019, 9(11), 731; https://doi.org/10.3390/coatings9110731 - 05 Nov 2019
Abstract
Water-dispersible and anticorrosion nanocomposites have attracted extensive attention. In this study, tea polyphenol (TP)/graphene (GE) was fabricated with a one-step route. The preparation and modification of graphene nanosheets was carried out by graphene employing tea polyphenols as reduction and functionalization reagents. Our study [...] Read more.
Water-dispersible and anticorrosion nanocomposites have attracted extensive attention. In this study, tea polyphenol (TP)/graphene (GE) was fabricated with a one-step route. The preparation and modification of graphene nanosheets was carried out by graphene employing tea polyphenols as reduction and functionalization reagents. Our study adopted a nontoxic reductant without an extra functionalization reagent. This method is convenient, inexpensive, and environmentally friendly. The final functionalized graphene nanosheets had a single-layer structure. For evaluating performance, Raman spectroscopy was adapted for evaluating π–π interactions between TP and graphene. Elemental and structural composition was analyzed using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Sample morphology was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results indicated that the TP could effectively augment the dispersive performance of graphene in the solution. The durable anticorrosion capacity of the epoxy matrix noticeably increased after adding the appropriate amount of tea polyphenols–graphene (TPG) (0.3 wt.%). Electrochemical impedance spectroscopy (EIS) studies showed that the impedance of artificial defects was enhanced. The anticorrosion property was attributed to the uniform dispersion of graphene by adding TP. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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Open AccessArticle
Influence of the Thickness of Multilayer Composite Nano-Structured Coating Ti–TiN–(Ti,Al,Si)N on the Tool Life of Metal-Cutting Tools and the Nature of Wear
Coatings 2019, 9(11), 730; https://doi.org/10.3390/coatings9110730 - 05 Nov 2019
Abstract
This article discusses the influence of the thickness of a nano-structured wear-resistant layer of the Ti–TiN–(Ti,Al,Si)N multilayer composite coating on its mechanical and performance properties. The study was focused on the coatings with the following thicknesses of its wear-resistant layers: 2, 3.5, 5, [...] Read more.
This article discusses the influence of the thickness of a nano-structured wear-resistant layer of the Ti–TiN–(Ti,Al,Si)N multilayer composite coating on its mechanical and performance properties. The study was focused on the coatings with the following thicknesses of its wear-resistant layers: 2, 3.5, 5, 7, 11, and 15 μm. The relation between the thickness of a wear-resistant layer and the time of its deposition was investigated, and the effect of the above thickness on hardness and wear resistance in scratch testing was considered. Cutting tests were conducted in turning steel C45 with carbide inserts with the coatings under study at various cutting speeds (vc = 250, 300 and 350 m/min). The study found the value of thickness of wear-resistant layer providing the longest tool life at various cutting speeds. The differences in the nature of wear for the coatings with various thicknesses of wear-resistant layers were considered. Full article
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Open AccessArticle
Synthesis, Characterization, and Corrosion Inhibition Potential of Novel Thiosemicarbazone on Mild Steel in Sulfuric Acid Environment
Coatings 2019, 9(11), 729; https://doi.org/10.3390/coatings9110729 - 04 Nov 2019
Abstract
Corrosion of a material by reaction with a corrosive environment is a common problem across many industries. Iraq is an oil country and corrosion represents a large portion of the total costs for oil producing and a natural potential hazard associated with oil [...] Read more.
Corrosion of a material by reaction with a corrosive environment is a common problem across many industries. Iraq is an oil country and corrosion represents a large portion of the total costs for oil producing and a natural potential hazard associated with oil production and transportation. The synthesis of novel thiosemicarbazone, namely 2-(2,4-dimethoxybenzylidene)hydrazinecarbothioamide (DMBHC), was conducted and the chemical structure was elucidated via the 1H and 13C NMR (Nuclear magnetic resonance), and FT-IR (Fourier-transform infrared) spectroscopic spectroscopic techniques in addition to carbon, hydrogen, and nitrogen analyses (CHN analyses). The inhibition properties of the investigated thiosemicarbazone were evaluated for mild steel (MS) corrosion in 1N H2SO4 using electrochemical impedance spectroscopy (EIS), weight loss method, and scanning electron microscopy (SEM). Electrochemical and weight loss techniques revealed that the tested thiosemicarbazone acted as a superior inhibitor for the acidic corrosion of MS and the efficiency increased with increasing concentrations. The EIS results revealed that thiosemicarbazone demonstrated the highest inhibition efficiency of 94.86%, at a concentration of 0.5 mM. Results from the weight loss technique suggested that the thiosemicarbazone acted as a mixed type corrosion inhibitor. The impact of temperature on the mechanism of inhibition of the new synthesized inhibitor of the surface of MS in 1N H2SO4 was investigated at various temperatures (30–60 °C) where the inhibitive efficiency diminished with increasing temperatures. The mechanism of inhibition was additionally verified with the methodological data. Full article
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Open AccessArticle
Crack Sensitivity Control of Nickel-Based Laser Coating Based on Genetic Algorithm and Neural Network
Coatings 2019, 9(11), 728; https://doi.org/10.3390/coatings9110728 - 03 Nov 2019
Abstract
This paper aimed to establish a nonlinear relationship between laser cladding process parameters and the crack density of a high-hardness, nickel-based laser cladding layer, and to control the cracking of the cladding layer via an intelligent algorithm. By using three main process parameters [...] Read more.
This paper aimed to establish a nonlinear relationship between laser cladding process parameters and the crack density of a high-hardness, nickel-based laser cladding layer, and to control the cracking of the cladding layer via an intelligent algorithm. By using three main process parameters (overlap rate, powder feed rate, and scanning speed), an orthogonal experiment was designed, and the experimental results were used as training and testing datasets for a neural network. A neural network prediction model between the laser cladding process parameters and coating crack density was established, and a genetic algorithm was used to optimize the prediction results. To improve their prediction accuracy, genetic algorithms were used to optimize the weights and thresholds of the neural networks. In addition, the performance of the neural network was tested. The results show that the order of influence on the coating crack sensitivity was as follows: overlap rate > powder feed rate > scanning speed. The relative error between the predicted value and the experimental value of the three-group test genetic algorithm-optimized neural network model was less than 9.8%. The genetic algorithm optimized the predicted results, and the technological parameters that resulted in the smallest crack density were as follows: powder feed rate of 15.0726 g/min, overlap rate of 49.797%, scanning speed of 5.9275 mm/s, crack density of 0.001272 mm/mm2. Therefore, the amount of crack generation was controlled by the optimization of the neural network and genetic algorithm process. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
Open AccessArticle
Lightning Performance of Copper-Mesh Clad Composite Panels: Test and Simulation
Coatings 2019, 9(11), 727; https://doi.org/10.3390/coatings9110727 - 02 Nov 2019
Abstract
:According to simulation lightning experiments and eddy current analysis results, a three-dimensional finite element model of composite laminated plates with shield is established. By applying electric-thermal boundary and the coupling relationship between them, the lightning strike damage results under the protection of shield [...] Read more.
:According to simulation lightning experiments and eddy current analysis results, a three-dimensional finite element model of composite laminated plates with shield is established. By applying electric-thermal boundary and the coupling relationship between them, the lightning strike damage results under the protection of shield are realistically simulated with the commercial finite element analysis software, ABAQUS. Considering the coupling effect of heat, electricity, and force during lightning strike, the load distribution field of copper mesh and carbon fiber panel with lightning current inducted is analyzed. Comparing the thermal stress distribution of the specimen surface under various current loads, it is shown that the stress of carbon fiber panel is significantly lower than the one of the copper screen when the specimen structure suffers heavy current, since the copper network plays a role of endergonic protection. Simulation data are consistent with the test results, thus the method can be used for other similar research. Full article
(This article belongs to the Special Issue Thin Films for Thermoelectric Applications)
Open AccessArticle
A Surface Modifier for the Production of Selectively Activated Amino Surface Groups
Coatings 2019, 9(11), 726; https://doi.org/10.3390/coatings9110726 - 02 Nov 2019
Abstract
The formation of self-assembled monolayers with the possibility of selective activation is an important goal of surface chemistry. In this work, a new surface modifier which creates amino surfaces based on aminopropylsilatrane (APS) with a protected amino group was obtained. The utilization of [...] Read more.
The formation of self-assembled monolayers with the possibility of selective activation is an important goal of surface chemistry. In this work, a new surface modifier which creates amino surfaces based on aminopropylsilatrane (APS) with a protected amino group was obtained. The utilization of protected APS allows producing a self-assembled monolayer (SAM) and obtaining reactive surface amino groups at distinct times. Furthermore, a precise selective deprotection with a further modification of the activated amino groups could be performed without affecting the protected groups. To demonstrate the practical applicability of this modifier, a trinitrotoluene-sensitive sensor based on an ion-sensitive field-effect transistor (ISFET) was obtained. Full article
(This article belongs to the Section Thin Films)
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Open AccessArticle
Mangrove Inspired Anti-Corrosion Coatings
Coatings 2019, 9(11), 725; https://doi.org/10.3390/coatings9110725 - 01 Nov 2019
Abstract
Marine corrosion accounts for one-third of the total corrosion cost and has been one of the greatest challenges for modern society. Organic coatings are known as the most widely used protective means. An effective control of the transport of corrosive substances is the [...] Read more.
Marine corrosion accounts for one-third of the total corrosion cost and has been one of the greatest challenges for modern society. Organic coatings are known as the most widely used protective means. An effective control of the transport of corrosive substances is the key to the anti-corrosion performance. In nature, the mangrove survives and thrives in marine tidal zones despite high salinity and humidity. We first showed that the mangrove leaves have salt glands that can secrete excessive ions to control the ion transport in and out. Inspired by this, we proposed a design of bio-inspired, anti-corrosion coating that mimics this functional feature, and fabricated the bipolar, hydrophobic coatings by doping ion-selective resins and constructing surface structures, which restrict the transport of corrosive substances and the electrochemical corrosion at the coating/metal interface. Our results show that the bio-inspired coatings effectively block and control the transport of both the Na+ and Cl, and, together with the hydrophobic surface, the coating system exhibits significantly improved anti-corrosion properties, more than a three orders of magnitude decrease in corrosion current density when compared with the control group (epoxy varnish). Therefore, the mangrove-inspired coatings show a promising protective strategy for the ever-demanding corrosion issues plaguing modern industries. Full article
(This article belongs to the Special Issue Biointerface Coatings for Biomaterials and Biomedical Applications)
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Open AccessArticle
Influence of Ultrasonic Excitation Sealing on the Corrosion Resistance of HVOF-Sprayed Nanostructured WC-CoCr Coatings under Different Corrosive Environments
Coatings 2019, 9(11), 724; https://doi.org/10.3390/coatings9110724 - 01 Nov 2019
Abstract
The corrosion behavior of unsealed and sealed high-velocity oxygen-fuel (HVOF)-sprayed nanostructured WC-CoCr cermet coatings under different corrosive environments was investigated using scanning electron microscopy (SEM), open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Ultrasonic excitation sealing with aluminum phosphate was [...] Read more.
The corrosion behavior of unsealed and sealed high-velocity oxygen-fuel (HVOF)-sprayed nanostructured WC-CoCr cermet coatings under different corrosive environments was investigated using scanning electron microscopy (SEM), open circuit potential (OCP), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Ultrasonic excitation sealing with aluminum phosphate was performed in an external ultrasonic bath with the frequency of 40 kHz at atmospheric pressure and room temperature. SEM micrographs revealed that the exposed area of the coating was effectively reduced by the coverage of aluminum phosphate sealant on the majority of pores. Electrochemical measurements demonstrated that the sealant with the help of ultrasonic energy could shift the corrosion potential to a more noble direction, reduce the corrosion current density, increase the resistance of charge transfer, and effectively improve the corrosion resistance of the coating in both 3.5 wt % NaCl and 1 mol·L−1 HCl solutions. Full article
(This article belongs to the Special Issue Corrosion and Electrochemical Behavior of Metals Coating)
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