Coatings

Research

9169 KiB

Open AccessArticle

Aluminizing via Ionic Liquid Electrodeposition and Pack Cementation: A Comparative Study with Inconel 738 and a CoNiCrAlY

by Luca Tagliaferri, Enrico Berretti, Andrea Giaccherini, Stefano M. Martinuzzi, Francesco Bozza, Martin Thoma, Ugo Bardi and Stefano Caporali

Coatings 2017, 7(6), 83; https://doi.org/10.3390/coatings7060083 - 19 Jun 2017

Cited by 6 | Viewed by 6479

Abstract

A novel aluminizing process based upon room temperature Al-electrodeposition from Ionic Liquids followed by diffusion heat treatment was applied on bare- and CoNiCrAlY-coated Inconel 738 (IN738). The aluminized samples were tested by isothermal oxidation at 1000 °C in air. The microstructural and chemical [...] Read more.

A novel aluminizing process based upon room temperature Al-electrodeposition from Ionic Liquids followed by diffusion heat treatment was applied on bare- and CoNiCrAlY-coated Inconel 738 (IN738). The aluminized samples were tested by isothermal oxidation at 1000 °C in air. The microstructural and chemical evolution of the samples were determined as function of oxidation time and compared with the currently applied coatings obtained via pack cementation. The newly proposed method is suitable for the CoNiCrAlY coating, but not for the bare IN738. In the latter, the formed Al-enriched layer is much thinner and the anticorrosion properties resulted in being reduced. This is probably due to the presence of precipitates, which slow down the aluminum inward diffusion impairing the formation of a well-developed interdiffusion zone (IDZ). Traces of the electrolyte, embedded during the Al-electrodeposition process, can be seen as the origin of these precipitates. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3016 KiB

Open AccessArticle

Studies on the Effect of Arc Current Mode and Substrate Rotation Configuration on the Structure and Corrosion Behavior of PVD TiN Coatings

by Liam Ward, Antony Pilkington and Steve Dowey

Coatings 2017, 7(4), 50; https://doi.org/10.3390/coatings7040050 - 4 Apr 2017

Cited by 18 | Viewed by 6557

Abstract

Thin, hard cathodic arc evaporated (CAE) metal nitride coatings are known to contain defects such as macro-particles, pinholes, voids and increased porosity, leading to reduced corrosion resistance. The focus of this research investigation was to compare the structure and corrosion behaviour of cathodic [...] Read more.

Thin, hard cathodic arc evaporated (CAE) metal nitride coatings are known to contain defects such as macro-particles, pinholes, voids and increased porosity, leading to reduced corrosion resistance. The focus of this research investigation was to compare the structure and corrosion behaviour of cathodic arc evaporated (CAE) TiN coatings deposited on AISI 1020 low carbon steel substrates using a pulsed current arc and a more conventional constant current arc source (DC). The effects of a double (2R) and triple (3R) substrate rotation configuration were also studied. Coating morphology and chemical composition were characterised using optical, SEM imaging and XRD analysis. Focus variation microscopy (FVM), an optical 3D measurement technique, was used to measure surface roughness. Corrosion studies were carried out using potentiodynamic scanning in 3.5% NaCl. Tafel extrapolation was carried out to determine E_corr and I_corr values for the coated samples. In general, increased surface roughness, and to a certain extent, corrosion resistance, were associated with thicker coatings deposited using 2R, compared to 3R rotation configuration. The arc source mode (continuous or pulsed) was shown to have little effect on the corrosion behavior. Corrosion behavior was controlled by the presence of defects, pinholes and macro-particles at lower anodic potentials, while the formation of large pitted regions and aggressive corrosion of the underlying substrate was observed at higher anodic potentials. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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4922 KiB

Open AccessArticle

Development of a Fabrication Process Using Suspension Plasma Spray for Titanium Oxide Photovoltaic Device

by Hsian Sagr Hadi A and Yasutaka Ando

Coatings 2017, 7(3), 40; https://doi.org/10.3390/coatings7030040 - 4 Mar 2017

Viewed by 6297

Abstract

In order to reduce the high costs of conventional materials, and to reduce the power necessary for the deposition of titanium dioxide, titanium tetrabutoxide has been developed in the form of a suspension of TiO2 using water instead of expensive ethanol. To avoid [...] Read more.

In order to reduce the high costs of conventional materials, and to reduce the power necessary for the deposition of titanium dioxide, titanium tetrabutoxide has been developed in the form of a suspension of TiO2 using water instead of expensive ethanol. To avoid sedimentation of hydroxide particles in the suspension, mechanical milling of the suspension was conducted in order to create diffusion in colloidal suspension before using it as feedstock. Consequently, through the creation of a colloidal suspension, coating deposition was able to be conducted without sedimentation of the hydroxide particles in the suspension during the deposition process. Though an amorphous as-deposited coating was able to be deposited, through post heat treatment at 630 °C for 60 min, the chemical structure became anatase rich. In addition, it was confirmed that the post heat treated anatase rich coating had enough photo-catalytic activity to decolor methylene-blue droplets. From these results, this technique was found to have high potential in the low cost photo-catalytic titanium coating production process. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3343 KiB

Open AccessArticle

Influence of the Electrolyte Concentration on the Smooth TiO₂ Anodic Coatings on Ti-6Al-4V

by María Laura Vera, Ángeles Colaccio, Mario Roberto Rosenberger, Carlos Enrique Schvezov and Alicia Esther Ares

Coatings 2017, 7(3), 39; https://doi.org/10.3390/coatings7030039 - 3 Mar 2017

Cited by 9 | Viewed by 6071

Abstract

To obtain smooth TiO₂ coatings for building a new design of Ti-6Al-4V heart valve, the anodic oxidation technique in pre-spark conditions was evaluated. TiO₂ coating is necessary for its recognized biocompatibility and corrosion resistance. A required feature on surfaces in contact [...] Read more.

To obtain smooth TiO₂ coatings for building a new design of Ti-6Al-4V heart valve, the anodic oxidation technique in pre-spark conditions was evaluated. TiO₂ coating is necessary for its recognized biocompatibility and corrosion resistance. A required feature on surfaces in contact with blood is a low level of roughness (R_a ≤ 50 nm) that does not favor the formation of blood clots. The present paper compares the coatings obtained by anodic oxidation of the Ti-6Al-4V alloy using H₂SO₄ at different concentrations (0.1–4 M) as electrolyte and applying different voltages (from 20 to 70 V). Color and morphological analysis of coatings are performed using optical and scanning microscopy. The crystalline phases were analyzed by glancing X-ray diffraction. By varying the applied voltage, different interference colors coatings were obtained. The differences in morphologies of the coatings caused by changes in acid concentration are more evident at high voltages, limiting the oxidation conditions for the desired application. Anatase phase was detected from 70 V for 1 M H₂SO₄. An increase in the concentration of H₂SO₄ decreases the voltage at which the transformation of amorphous to crystalline coatings occurs; i.e., with 4 M H₂SO₄, the anatase phase appears at 60 V. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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4192 KiB

Open AccessArticle

Assessment on the Effects of ZnO and Coated ZnO Particles on iPP and PLA Properties for Application in Food Packaging

by Antonella Marra, Gennaro Rollo, Sossio Cimmino and Clara Silvestre

Coatings 2017, 7(2), 29; https://doi.org/10.3390/coatings7020029 - 17 Feb 2017

Cited by 23 | Viewed by 5813

Abstract

This paper compares the properties of iPP based composites and PLA based biocomposites using 5% of ZnO particles or ZnO particles coated with stearic acid as filler. In particular, the effect of coating on the UV stability, thermostability, mechanical, barrier, and antibacterial properties [...] Read more.

This paper compares the properties of iPP based composites and PLA based biocomposites using 5% of ZnO particles or ZnO particles coated with stearic acid as filler. In particular, the effect of coating on the UV stability, thermostability, mechanical, barrier, and antibacterial properties of the polymer matrix were compared and related to the dispersion and distribution of the loads in the polymer matrix and the strength of the adhesion between the matrix and the particles. This survey demonstrated that, among the reported systems, iPP/5%ZnOc and PLA/5%ZnO films are the most suitable active materials for potential application in the active food packaging field. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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2589 KiB

Open AccessArticle

Silicides and Nitrides Formation in Ti Films Coated on Si and Exposed to (Ar-N₂-H₂) Expanding Plasma

by Isabelle Jauberteau, Richard Mayet, Julie Cornette, Denis Mangin, Annie Bessaudou, Pierre Carles, Jean Louis Jauberteau and Armand Passelergue

Coatings 2017, 7(2), 23; https://doi.org/10.3390/coatings7020023 - 8 Feb 2017

Cited by 17 | Viewed by 7903

Abstract

The physical properties including the mechanical, optical and electrical properties of Ti nitrides and silicides are very attractive for many applications such as protective coatings, barriers of diffusion, interconnects and so on. The simultaneous formation of nitrides and silicides in Ti films improves [...] Read more.

The physical properties including the mechanical, optical and electrical properties of Ti nitrides and silicides are very attractive for many applications such as protective coatings, barriers of diffusion, interconnects and so on. The simultaneous formation of nitrides and silicides in Ti films improves their electrical properties. Ti films coated on Si wafers are heated at various temperatures and processed in expanding microwave (Ar-N₂-H₂) plasma for various treatment durations. The Ti-Si interface is the centre of Si diffusion into the Ti lattice and the formation of various Ti silicides, while the Ti surface is the centre of N diffusion into the Ti film and the formation of Ti nitrides. The growth of silicides and nitrides gives rise to two competing processes which are thermodynamically and kinetically controlled. The effect of thickness on the kinetics of the formation of silicides is identified. The metastable C₄₉TiSi₂ phase is the main precursor of the stable C₅₄TiSi₂ phase, which crystallizes at about 600 °C, while TiN crystallizes at about 800 °C. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3720 KiB

Open AccessArticle

Combustion Synthesis during Flame Spraying (“CAFSY”) for the Production of Catalysts on Substrates

by Galina Xanthopoulou, Amalia Marinou, Konstantinos Karanasios and George Vekinis

Coatings 2017, 7(1), 14; https://doi.org/10.3390/coatings7010014 - 20 Jan 2017

Cited by 5 | Viewed by 5520

Abstract

Combustion-assisted flame spraying (“CAFSY”) has been used to produce catalytically active nickel aluminide coatings on ceramic substrates. Their catalytic activity was studied in CO₂ (dry) reforming of methane, which is particularly significant for environmental protection as well as production of synthesis gas [...] Read more.

Combustion-assisted flame spraying (“CAFSY”) has been used to produce catalytically active nickel aluminide coatings on ceramic substrates. Their catalytic activity was studied in CO₂ (dry) reforming of methane, which is particularly significant for environmental protection as well as production of synthesis gas (CO + H₂). By varying the CAFSY processing parameters, it is possible to obtain a range of Ni–Al alloys with various ratios of catalytically active phases on the substrate. The influence of the number of coating layers and the type of substrate on the final catalyst composition and on the catalytic activity of the CAFSY coatings was studied and is presented here. The morphology and microstructure of the composite coatings were determined by scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) elemental analysis, X-ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) specific area analysis. Catalytic tests for dry reforming of methane were carried out using crushed pellets from the coatings at temperatures of 750–900 °C, and gas chromatography showed that methane conversion approached 88% whereas that of carbon dioxide reached 100%. The H₂/CO ratio in the synthesis gas produced by the reaction varied from about 0.7 to over 1.2, depending on the catalyst and substrate type and testing temperature. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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8404 KiB

Open AccessArticle

Numerical and Experimental Investigation on the Spray Coating Process Using a Pneumatic Atomizer: Influences of Operating Conditions and Target Geometries

by Qiaoyan Ye and Karlheinz Pulli

Coatings 2017, 7(1), 13; https://doi.org/10.3390/coatings7010013 - 18 Jan 2017

Cited by 33 | Viewed by 7616

Abstract

This paper presents a numerical simulation of the spray painting process using a pneumatic atomizer with the help of a computational fluid dynamics code. The droplet characteristics that are necessary for the droplet trajectory calculation were experimentally investigated using different shaping air flow [...] Read more.

This paper presents a numerical simulation of the spray painting process using a pneumatic atomizer with the help of a computational fluid dynamics code. The droplet characteristics that are necessary for the droplet trajectory calculation were experimentally investigated using different shaping air flow rates. It was found that the droplet size distribution depends on both the atomizing and the shaping air flow rate. An injection model for creating the initial droplet conditions is necessary for the spray painting simulation. An approach for creating these initial conditions has been proposed, which takes different operating conditions into account and is suitable for practical applications of spray coating simulation using spray guns. Further, tests on complicated targets and complex alignments of the atomizer have been carried out to verify this numerical approach. The results confirm the applicability and reliability of the chosen method for the painting process. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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2221 KiB

Open AccessArticle

Assessment of Environmental Performance of TiO₂ Nanoparticles Coated Self-Cleaning Float Glass

by Martina Pini, Erika Iveth Cedillo González, Paolo Neri, Cristina Siligardi and Anna Maria Ferrari

Coatings 2017, 7(1), 8; https://doi.org/10.3390/coatings7010008 - 12 Jan 2017

Cited by 29 | Viewed by 8523

Abstract

In recent years, superhydrophilic and photocatalytic self-cleaning nanocoatings have been widely used in the easy-to-clean surfaces field. In the building sector, self-cleaning glass was one of the first nanocoating applications. These products are based on the photocatalytic property of a thin layer of [...] Read more.

In recent years, superhydrophilic and photocatalytic self-cleaning nanocoatings have been widely used in the easy-to-clean surfaces field. In the building sector, self-cleaning glass was one of the first nanocoating applications. These products are based on the photocatalytic property of a thin layer of titanium dioxide (TiO₂) nanoparticles deposited on the surface of any kind of common glass. When exposed to UV radiation, TiO₂ nanoparticles react with the oxygen and water molecules adsorbed on their surface to produce radicals leading to oxidative species. These species are able to reduce or even eliminate airborne pollutants and organic substances deposited on the material’s surface. To date, TiO₂ nanoparticles’ benefits have been substantiated; however, their ecological and human health risks are still under analysis. The present work studies the ecodesign of the industrial scale-up of TiO₂ nanoparticles self-cleaning coated float glass production performed by the life cycle assessment (LCA) methodology and applies new human toxicity indicators to the impact assessment stage. Production, particularly the TiO₂ nanoparticle application, is the life cycle phase most contributing to the total damage. According to the ecodesign approach, the production choices carried out have exacerbated environmental burdens. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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17297 KiB

Open AccessArticle

Durability Analysis and Experimental Validation of Environmental Barrier Coating (EBC) Performance Using Combined Digital Image Correlation and NDE

by Ali Abdul-Aziz and Adam C. Wroblewski

Coatings 2016, 6(4), 70; https://doi.org/10.3390/coatings6040070 - 16 Dec 2016

Cited by 10 | Viewed by 6788

Abstract

To understand the failure mechanism or to predict the spallation life of environmental barrier coatings (EBC) on fiber reinforced ceramic matrix composites, the fracture strength of EBC and the process of the crack growth in EBC layers need to be experimentally determined under [...] Read more.

To understand the failure mechanism or to predict the spallation life of environmental barrier coatings (EBC) on fiber reinforced ceramic matrix composites, the fracture strength of EBC and the process of the crack growth in EBC layers need to be experimentally determined under standard or simulated engine operating conditions. The current work considers a multi layered barium strontium aluminum silicate (BSAS)-based EBC-coated, melt infiltrated silicon carbide fiber reinforced silicon carbide matrix composite (MI SiC/SiC) specimen that was tensile tested at room temperature. Numerous tests were performed under tensile loading conditions, and the specimen was loaded until failure under pre-determined stress levels. The specimen was examined with optical microscopy, scanning electron microscopy (SEM), computed tomography (CT) scan, and digital image correlation (DIC) camera. Observation from the computed tomography scanning, the SEM, and the optical microscopy did not offer conclusive information concerning the cracks that spawned during the tests. However, inspection with the DIC camera offered some indication that cracks had developed and allowed their detection and the location of their initiation site. Thus, this study provides detailed discussion of the results obtained from the experimental investigation and the nondestructive evaluation (NDE), and it also includes assessment of the stress response predicted by analytical modeling and their impact on EBC durability and crack growth formation under complex loading settings. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3303 KiB

Open AccessArticle

Characterization and Photovoltaic Properties of BiFeO₃ Thin Films

by Yasuhiro Shirahata and Takeo Oku

Coatings 2016, 6(4), 68; https://doi.org/10.3390/coatings6040068 - 8 Dec 2016

Cited by 18 | Viewed by 7744

Abstract

Bismuth ferrite (BiFeO₃) thin films were prepared by a spin-coating method. Crystal structure and optical properties of the BiFeO₃ films were evaluated using X-ray diffraction. The lattice constants, crystallite size, and energy gap of BiFeO₃ films depended on the [...] Read more.

Bismuth ferrite (BiFeO₃) thin films were prepared by a spin-coating method. Crystal structure and optical properties of the BiFeO₃ films were evaluated using X-ray diffraction. The lattice constants, crystallite size, and energy gap of BiFeO₃ films depended on the concentration of the BiFeO₃ precursor solution. BiFeO₃/CH₃NH₃PbI₃ photovoltaic devices were fabricated to investigate photovoltaic properties of BiFeO₃. Current density–voltage characteristics of the photovoltaic devices showed rectifying behavior, indicating that BiFeO₃ worked as an electron transport layer in CH₃NH₃PbI₃-based photovoltaic devices. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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4740 KiB

Open AccessArticle

Improving the Performance of Clear Coatings on Wood through the Aggregation of Marginal Gains

by Philip D. Evans, Stephan Vollmer, Joseph Doh Wook Kim, George Chan and Sara Kraushaar Gibson

Coatings 2016, 6(4), 66; https://doi.org/10.3390/coatings6040066 - 26 Nov 2016

Cited by 22 | Viewed by 10775

Abstract

Remarkable increases in the performance of complex systems can be achieved by a collective approach to optimizing individual factors that influence performance. This approach, termed the aggregation of marginal gains, is tested here as a means of improving the performance of exterior clear-coatings. [...] Read more.

Remarkable increases in the performance of complex systems can be achieved by a collective approach to optimizing individual factors that influence performance. This approach, termed the aggregation of marginal gains, is tested here as a means of improving the performance of exterior clear-coatings. We focused on five factors that influence clear-coating performance: dimensional stability of wood; photostability of the wood surface; moisture ingress via end-grain; coating flexibility and photostability; and finally coating thickness. We performed preliminary research to select effective wood pre-treatments and durable clear-coatings, and then tested coating systems with good solutions to each of the aforementioned issues (factors). Red oak and radiata pine panels were modified with PF-resin, end-sealed, and thick acrylic, alkyd or spar varnishes were applied to the panels. Panels were exposed to the weather and the level of coating defects was assessed every year over a 4-year period. All of the coatings are performing well on PF-modified pine after 4 years’ outdoor exposure. In contrast, coatings failed after 2 years on unmodified pine and they are failing on PF-modified oak. We conclude that our approach shows promise. Future research will build on the current work by developing solutions to additional factors that influence clear-coating performance. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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10728 KiB

Open AccessArticle

Corrosion Testing of Thermal Spray Coatings in a Biomass Co-Firing Power Plant

by Maria Oksa, Jarkko Metsäjoki and Janne Kärki

Coatings 2016, 6(4), 65; https://doi.org/10.3390/coatings6040065 - 24 Nov 2016

Cited by 13 | Viewed by 7930

Abstract

Large-scale use of biomass and recycled fuel is increasing in energy production due to climate and energy targets. A 40% cut in greenhouse gas emission compared to 1990 levels and at least a 27% share of renewable energy consumption are set in EU [...] Read more.

Large-scale use of biomass and recycled fuel is increasing in energy production due to climate and energy targets. A 40% cut in greenhouse gas emission compared to 1990 levels and at least a 27% share of renewable energy consumption are set in EU Energy Strategy 2030. Burning fuels with high content of corrosive species such as chlorine and heavy metals causes deterioration of boiler components, shortened lifetime, limited availability of a plant and hence higher maintenance and investment costs and lower thermal and economic efficiency. Coatings can be applied to protect the critical boiler components against high temperature corrosion. In this study, five thermal spray coatings were tested in an actual biomass co-firing boiler for 1300 h with a measurement probe. The coatings were analyzed after the exposure by metallographic means and scanning electron microscope/energy-dispersive X-ray spectroscope (SEM/EDX). The deposits formed on the specimens were analyzed by X-ray fluorescence. At 550 °C, the coatings showed excellent corrosion performance compared to reference material ferritic steel T92. At 750 °C, tube material A263 together with NiCr and NiCrTi had the highest corrosion resistance. To conclude, thermal spray coatings can offer substantial corrosion protection in biomass and recycled fuel burning power plants. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3511 KiB

Open AccessArticle

Thermally Sprayed Aluminum Coatings for the Protection of Subsea Risers and Pipelines Carrying Hot Fluids

by Nataly Ce and Shiladitya Paul

Coatings 2016, 6(4), 58; https://doi.org/10.3390/coatings6040058 - 8 Nov 2016

Cited by 15 | Viewed by 7266

Abstract

This paper reports the effect of boiling synthetic seawater on the performance of damaged Thermally Sprayed Aluminum (TSA) on carbon steel. Small defects (4% of the sample’s geometric surface area) were drilled, exposing the steel, and the performance of the coating was analyzed [...] Read more.

This paper reports the effect of boiling synthetic seawater on the performance of damaged Thermally Sprayed Aluminum (TSA) on carbon steel. Small defects (4% of the sample’s geometric surface area) were drilled, exposing the steel, and the performance of the coating was analyzed for corrosion potential for different exposure times (2 h, 335 h, and 5000 h). The samples were monitored using linear polarization resistance (LPR) in order to obtain their corrosion rate. Scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) were used for post-test characterization. The results showed that a protective layer of Mg(OH)₂ formed in the damaged area, which protected the underlying steel. Additionally, no coating detachment from the steel near the defect region was observed. The corrosion rate was found to be 0.010–0.015 mm/year after 5000 h in boiling synthetic seawater. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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1574 KiB

Open AccessArticle

Cellular Automata Modelling of Photo-Induced Oxidation Processes in Molecularly Doped Polymers

by David M. Goldie

Coatings 2016, 6(4), 55; https://doi.org/10.3390/coatings6040055 - 4 Nov 2016

Cited by 1 | Viewed by 4091

Abstract

The possibility of employing cellular automata (CA) to model photo-induced oxidation processes in molecularly doped polymers is explored. It is demonstrated that the oxidation dynamics generated using CA models exhibit stretched-exponential behavior. This dynamical characteristic is in general agreement with an alternative analysis [...] Read more.

The possibility of employing cellular automata (CA) to model photo-induced oxidation processes in molecularly doped polymers is explored. It is demonstrated that the oxidation dynamics generated using CA models exhibit stretched-exponential behavior. This dynamical characteristic is in general agreement with an alternative analysis conducted using standard rate equations provided the molecular doping levels are sufficiently low to prohibit the presence of safe-sites which are impenetrable to dissolved oxygen. The CA models therefore offer the advantage of exploring the effect of dopant agglomeration which is difficult to assess from standard rate equation solutions. The influence of UV-induced bleaching or darkening upon the resulting oxidation dynamics may also be easily incorporated into the CA models and these optical effects are investigated for various photo-oxidation product scenarios. Output from the CA models is evaluated for experimental photo-oxidation data obtained from a series of hydrazone-doped polymers. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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6364 KiB

Open AccessArticle

Atmospheric Plasma Spraying of Single Phase Lanthanum Zirconate Thermal Barrier Coatings with Optimized Porosity

by Georg Mauer, Linnan Du and Robert Vaßen

Coatings 2016, 6(4), 49; https://doi.org/10.3390/coatings6040049 - 18 Oct 2016

Cited by 25 | Viewed by 6963

Abstract

The shortcomings at elevated operation temperatures of the standard material yttria-stabilized zirconia (YSZ) for thermal barrier coatings (TBCs) have initiated many research activities seeking alternatives. One candidate is the pyrochlore lanthanum zirconate La₂Zr₂O₇ (LZ), which is phase-stable to [...] Read more.

The shortcomings at elevated operation temperatures of the standard material yttria-stabilized zirconia (YSZ) for thermal barrier coatings (TBCs) have initiated many research activities seeking alternatives. One candidate is the pyrochlore lanthanum zirconate La₂Zr₂O₇ (LZ), which is phase-stable to its melting point. At the same time, it shows a lower thermal conductivity and a lower sintering tendency when compared to YSZ. Because of its low thermal expansion coefficient and poor toughness, it is applied in combination with YSZ in double layer TBC systems. It is the current state of knowledge that LZ is prone to lanthanum depletion if processed by plasma spraying. The process conditions have to be selected carefully to avoid this. Furthermore, the amount and morphology of the coating porosity is essential for a good thermo-mechanical performance. In this work, the development and testing of LZ/YSZ double layer TBC systems is described. Initially, suitable basic parameters (torch, plasma gas composition, and power) were tested with respect to coating stoichiometry. Then, microstructures were optimized by adjusting feed rate, spray distance, and by selecting a more appropriate feedstock. Powder particles and coatings were characterized by digital image analysis. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3911 KiB

Open AccessCommunication

Atmospheric-Pressure Plasma Jet Processed Pt-Decorated Reduced Graphene Oxides for Counter-Electrodes of Dye-Sensitized Solar Cells

by Ting-Hao Wan, Yi-Fan Chiu, Chieh-Wen Chen, Cheng-Che Hsu, I-Chun Cheng and Jian-Zhang Chen

Coatings 2016, 6(4), 44; https://doi.org/10.3390/coatings6040044 - 13 Oct 2016

Cited by 24 | Viewed by 6721

Abstract

Ultrafast atmospheric-pressure plasma jet (APPJ) processed Pt-decorated reduced graphene oxides (rGOs) were used as counter-electrodes in dye-sensitized solar cells (DSSCs). Pastes containing rGO, ethyl cellulose, terpineol, and chloroplatinic acid were screen-printed and sintered by nitrogen dc-pulse APPJs. Pt nanodots were uniformly distributed on [...] Read more.

Ultrafast atmospheric-pressure plasma jet (APPJ) processed Pt-decorated reduced graphene oxides (rGOs) were used as counter-electrodes in dye-sensitized solar cells (DSSCs). Pastes containing rGO, ethyl cellulose, terpineol, and chloroplatinic acid were screen-printed and sintered by nitrogen dc-pulse APPJs. Pt nanodots were uniformly distributed on the rGO flakes. When using Pt-decorated rGOs as the counter electrodes of DSSCs, the efficiency of the DSSC first increased and then decreased as the APPJ processing time increased. Nitrogen APPJs can effectively remove organic binders and can reduce chloroplatinic acid to Pt, thereby improving the efficiency of DSSCs. However, over-calcination by APPJ can damage the graphenes and degrade the DSSCs. The addition of Pt mainly improves the fill factor, which thereby increases the efficiency of DSSCs. The optimized APPJ processing time was merely 9 s owing to the vigorous interaction among the rGOs, chloroplatinic acid and nitrogen APPJs. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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7601 KiB

Open AccessArticle

Feasibility of Coloring Bamboo with the Application of Natural and Extracted Fungal Pigments

by Sarath M. Vega Gutierrez, Patricia T. Vega Gutierrez, Auna Godinez, Lauren Pittis, Megan Huber, Savannah Stanton and Sara C. Robinson

Coatings 2016, 6(3), 37; https://doi.org/10.3390/coatings6030037 - 30 Aug 2016

Cited by 23 | Viewed by 6074

Abstract

Fungal pigments, specifically those generated from spalting fungi, are being developed for broader use in the wood and textile industry, and due to their coloration properties, may also be useful as aesthetic bamboo dyes. This paper evaluates the potential use of fungal pigments [...] Read more.

Fungal pigments, specifically those generated from spalting fungi, are being developed for broader use in the wood and textile industry, and due to their coloration properties, may also be useful as aesthetic bamboo dyes. This paper evaluates the potential use of fungal pigments in bamboo (Phyllostachys spp.), and compares the difference between natural spalting and the direct application of extracted fungal pigments of three known spalting fungi: Scytalidium cuboideum, Scytalidium ganodermophthorum, and Chlorociboria aeruginosa. Bamboo was significantly spalted by S. cuboideum under live inoculation, while the other two fungi did not colonize. For the direct application of fungal pigments, bamboo did not develop internal pigmentation with any pigment, but did develop visible surface color for S. cuboideium and C. aeruginosa. Light microscopy and scanning electron microscopy confirmed the presence of hyphae in bamboo vessels and parenchyma. An HPLC analysis for simple sugars showed the presence of glucose but no sucrose. Results indicate that the extracted pigments of the aforementioned fungi are ideal for the surface treatment of bamboo, while only direct inoculation of S. cuboideum is appropriate for internal coloration. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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8724 KiB

Open AccessArticle

Non-Cyanide Electrodeposited Ag–PTFE Composite Coating Using Direct or Pulsed Current Deposition

by Raymond Sieh and Huirong Le

Coatings 2016, 6(3), 31; https://doi.org/10.3390/coatings6030031 - 26 Jul 2016

Cited by 5 | Viewed by 7823

Abstract

The effects of FC-4 cationic surfactant on electrodeposited Ag–PTFE composite coating using direct or pulsed currents were studied using scanning electron microscope (SEM), energy dispersive X-ray (EDS), optical microscope, and a linear tribometer. FC-4:PTFE in various ratios were added to a non-cyanide succinimide [...] Read more.

The effects of FC-4 cationic surfactant on electrodeposited Ag–PTFE composite coating using direct or pulsed currents were studied using scanning electron microscope (SEM), energy dispersive X-ray (EDS), optical microscope, and a linear tribometer. FC-4:PTFE in various ratios were added to a non-cyanide succinimide silver complex bath. Direct or pulsed current method was used at a constant current density to enable comparison between both methods. A high incorporation rate of PTFE was successfully achieved, with pulsed current being highly useful in increasing the amount of PTFE in the composite coating. The study of coating wear under sliding showed that a large majority of the electrodeposited coatings still managed to adhere to the substrate, even after 10 wear cycles of sliding tests. Performance improvements were achieved on all the samples with a coefficient of friction (CoF) between 0.06 and 0.12. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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1811 KiB

Open AccessArticle

A Surface Photovoltage Study of Surface Defects on Co-Doped TiO₂ Thin Films Deposited by Spray Pyrolysis

by Henry Wafula, Albert Juma, Thomas Sakwa, Robinson Musembi and Justus Simiyu

Coatings 2016, 6(3), 30; https://doi.org/10.3390/coatings6030030 - 22 Jul 2016

Cited by 6 | Viewed by 5494

Abstract

Surface photovoltage (SPV) spectroscopy is a powerful tool for studying electronic defects on semiconductor surfaces, at interfaces, and in bulk for a wide range of materials. Undoped and Cobalt-doped TiO₂ (CTO) thin films were deposited on Crystalline Silicon (c-Si) and Flourine doped [...] Read more.

Surface photovoltage (SPV) spectroscopy is a powerful tool for studying electronic defects on semiconductor surfaces, at interfaces, and in bulk for a wide range of materials. Undoped and Cobalt-doped TiO₂ (CTO) thin films were deposited on Crystalline Silicon (c-Si) and Flourine doped Tin oxide (SnO₂:F) substrates by chemical spray pyrolysis at a substrate temperature of 400 °C. The concentration of the Co dopant in the films was determined by Rutherford backscattering spectrometry and ranged between 0 and 4.51 at %. The amplitude of the SPV signals increased proportionately with the amount of Co in the films, which was a result of the enhancement of the slow processes of charge separation and recombination. Photogenerated holes were trapped at the surface, slowing down the time response and relaxation of the samples. The surface states were effectively passivated by a thin In₂S₃ over-layer sprayed on top of the TiO₂ and CTO films. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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3818 KiB

Open AccessArticle

Wear Behaviour of Nanostructured Polymer-Based Safety Films on Soda-Lime Glass

by C. N. Panagopoulos, E. P. Georgiou, G. S. Tradas and K. I. Giannakopoulos

Coatings 2016, 6(3), 26; https://doi.org/10.3390/coatings6030026 - 8 Jul 2016

Cited by 3 | Viewed by 5102

Abstract

The wear behaviour of bare and polymer-coated soda-lime glass specimens sliding against 440C stainless steel counterfaces was investigated with the aid of a pin-on-disk apparatus. The selected polymeric coatings were commercially supplied safety films, which are nowadays extensively applied on glass in the [...] Read more.

The wear behaviour of bare and polymer-coated soda-lime glass specimens sliding against 440C stainless steel counterfaces was investigated with the aid of a pin-on-disk apparatus. The selected polymeric coatings were commercially supplied safety films, which are nowadays extensively applied on glass in the automotive and construction industry. One of their main failures is the degradation of their properties due to wear. In this work, the frictional behaviour of these coatings on glass were evaluated and compared to those of bare soda-lime glass. Correlations have been also made between the worn surfaces and weight loss in order to investigate the effect of wear conditions (speed, load) on the wear behaviour of these tribosystems. In addition, during the dry wear of soda-lime glass sliding against stainless steel counterfaces, the dominant wear mechanisms were found to be localized adhesion and abrasion, whereas, in the case of the multilayered polymeric coatings localized adhesion, deformation and tearing were observed. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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1917 KiB

Open AccessArticle

Mechanical Color Reading of Wood-Staining Fungal Pigment Textile Dyes: An Alternative Method for Determining Colorfastness

by Eric M. Hinsch and Sara C. Robinson

Coatings 2016, 6(3), 25; https://doi.org/10.3390/coatings6030025 - 4 Jul 2016

Cited by 29 | Viewed by 7001

Abstract

Colorfastness to washing and crocking (color loss due to rubbing) are essential qualities for any dye/fabric combination that will be used for garments or upholstery. In this study, colorfastness to washing and crocking of fabrics dyed with wood-staining fungal pigments was compared to [...] Read more.

Colorfastness to washing and crocking (color loss due to rubbing) are essential qualities for any dye/fabric combination that will be used for garments or upholstery. In this study, colorfastness to washing and crocking of fabrics dyed with wood-staining fungal pigments was compared to colorfastness of commercial dyes using an alternative mechanical testing method. Overall, wood-staining fungal pigments out performed commercial dyes for colorfastness to washing and wet and dry crocking. Xylindein was the most colorfast dye. Draconin red yielded inconsistent results, and the yellow pigment required a mordant to achieve any colorfastness. This study showed that the mechanical color reading method, along with statistical analysis, provided an objective, repeatable gauge of colorfastness, although visual inspection is also needed for practical purposes. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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2909 KiB

Open AccessArticle

Thermal Protection of Carbon Fiber-Reinforced Composites by Ceramic Particles

by Baljinder Kandola, Forkan Sarker, Piyanuch Luangtriratana and Peter Myler

Coatings 2016, 6(2), 22; https://doi.org/10.3390/coatings6020022 - 1 Jun 2016

Cited by 21 | Viewed by 8910

Abstract

The thermal barrier efficiency of two types of ceramic particle, glass flakes and aluminum titanate, dispersed on the surface of carbon-fiber epoxy composites, has been evaluated using a cone calorimeter at 35 and 50 kW/m², in addition to temperature gradients through [...] Read more.

The thermal barrier efficiency of two types of ceramic particle, glass flakes and aluminum titanate, dispersed on the surface of carbon-fiber epoxy composites, has been evaluated using a cone calorimeter at 35 and 50 kW/m², in addition to temperature gradients through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. Two techniques of dispersing ceramic particles on the surface have been employed, one where particles were dispersed on semi-cured laminate and the other where their dispersion in a phenolic resin was applied on the laminate surface, using the same method as used previously for glass fiber composites. The morphology and durability of the coatings to water absorption, peeling, impact and flexural tension were also studied and compared with those previously reported for glass-fiber epoxy composites. With both methods, uniform coatings could be achieved, which were durable to peeling or water absorption with a minimal adverse effect on the mechanical properties of composites. While all these properties were comparable to those previously observed for glass fiber composites, the ceramic particles have seen to be more effective on this less flammable, carbon fiber composite substrate. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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Review

Jump to: Research, Other

809 KiB

Open AccessReview

State of the Art of Antimicrobial Edible Coatings for Food Packaging Applications

by Arantzazu Valdés, Marina Ramos, Ana Beltrán, Alfonso Jiménez and María Carmen Garrigós

Coatings 2017, 7(4), 56; https://doi.org/10.3390/coatings7040056 - 19 Apr 2017

Cited by 177 | Viewed by 22562

Abstract

The interest for the development of new active packaging materials has rapidly increased in the last few years. Antimicrobial active packaging is a potential alternative to protect perishable products during their preparation, storage and distribution to increase their shelf-life by reducing bacterial and [...] Read more.

The interest for the development of new active packaging materials has rapidly increased in the last few years. Antimicrobial active packaging is a potential alternative to protect perishable products during their preparation, storage and distribution to increase their shelf-life by reducing bacterial and fungal growth. This review underlines the most recent trends in the use of new edible coatings enriched with antimicrobial agents to reduce the growth of different microorganisms, such as Gram-negative and Gram-positive bacteria, molds and yeasts. The application of edible biopolymers directly extracted from biomass (proteins, lipids and polysaccharides) or their combinations, by themselves or enriched with natural extracts, essential oils, bacteriocins, metals or enzyme systems, such as lactoperoxidase, have shown interesting properties to reduce the contamination and decomposition of perishable food products, mainly fish, meat, fruits and vegetables. These formulations can be also applied to food products to control gas exchange, moisture permeation and oxidation processes. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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6538 KiB

Open AccessReview

Corrosion Protection Systems and Fatigue Corrosion in Offshore Wind Structures: Current Status and Future Perspectives

by Seth J. Price and Rita B. Figueira

Coatings 2017, 7(2), 25; https://doi.org/10.3390/coatings7020025 - 11 Feb 2017

Cited by 110 | Viewed by 23228

Abstract

Concerns over reducing CO₂ emissions associated with the burning of fossil fuels in combination with an increase in worldwide energy demands is leading to increased development of renewable energies such as wind. The installation of offshore wind power structures (OWS) is one [...] Read more.

Concerns over reducing CO₂ emissions associated with the burning of fossil fuels in combination with an increase in worldwide energy demands is leading to increased development of renewable energies such as wind. The installation of offshore wind power structures (OWS) is one of the most promising approaches for the production of renewable energy. However, corrosion and fatigue damage in marine and offshore environments are major causes of primary steel strength degradation in OWS. Corrosion can reduce the thickness of structural components which may lead towards fatigue crack initiation and buckling. These failure mechanisms affect tower service life and may result in catastrophic structural failure. Additionally, environmental pollution stemming from corrosion’s by-products is possible. As a result, large financial investments are made yearly for both the prevention and recovery of these drawbacks. The corrosion rate of an OWS is dependent on different characteristics of attack which are influenced by access to oxygen and humidity. Structural degradation can occur due to chemical attack, abrasive action of waves, and microorganism attacks. Inspired by technological and scientific advances in recent years, the purpose of this paper is to discuss the current protective coating system technologies used to protect OWS as well as future perspectives. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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1053 KiB

Open AccessReview

Surface-Engineered Fire Protective Coatings for Fabrics through Sol-Gel and Layer-by-Layer Methods: An Overview

by Giulio Malucelli

Coatings 2016, 6(3), 33; https://doi.org/10.3390/coatings6030033 - 29 Jul 2016

Cited by 77 | Viewed by 9633

Abstract

Fabric flammability is a surface-confined phenomenon: in fact, the fabric surface represents the most critical region, through which the mass and heat transfers, responsible for fueling the flame, are controlled and exchanged with the surroundings. More specifically, the heat the fabric surface is [...] Read more.

Fabric flammability is a surface-confined phenomenon: in fact, the fabric surface represents the most critical region, through which the mass and heat transfers, responsible for fueling the flame, are controlled and exchanged with the surroundings. More specifically, the heat the fabric surface is exposed to is transferred to the bulk, from which volatile products of thermal degradation diffuse toward the surface and the gas phase, hence feeding the flame. As a consequence, the chemical and physical characteristics of the fabric surface considerably affect the ignition and combustion processes, as the surface influences the flux of combustible volatile products toward the gas phase. In this context, it is possible to significantly modify (and improve) the fire performance of textile materials by “simply” tailoring their surface: currently, one of the most effective approaches exploits the deposition of tailored coatings able to slow down the heat and mass transfer phenomena occurring during the fire stages. This paper reviews the current state of the art related to the design of inorganic, hybrid, or organic flame-retardant coatings suitable for the fire protection of different fabric substrates (particularly referring to cotton, polyester, and their blends). More specifically, the use of sol-gel and layer-by-layer (LbL) methods is thoroughly discussed; then, some recent examples of flame retardant coatings are presented, showing their potential advances and their current limitations. Full article

(This article belongs to the Special Issue Five Years of Coatings: Coatings Science and Technology for the 21st Century)

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