Special Issue "Five Years of Coatings: Coatings Science and Technology for the 21st Century"

A special issue of Coatings (ISSN 2079-6412).

Deadline for manuscript submissions: closed (20 September 2016)

Special Issue Editor

Guest Editor
Dr. Alessandro Lavacchi

Istituto di Chimica dei Composti OrganoMetallici (ICCOM-CNR), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Firenze, Italy
E-Mail
Phone: 00390555225250
Interests: electrodeposition of materials for renewable energy production; surface engineering; corrosion and corrosion protection; thermal barriers coatings; electron microscopy (SEM, TEM); X-ray techniques for surface structure and composition (XPS, XRF, XRD); electroless deposition of metals and cermets; simulation and modelling of complex electrochemical systems

Special Issue Information

Dear Colleagues,

Coatings has ended its fifth year of publication. In this time, the journal has experienced a steady growth and it is now affirmed as a leading platform for scientific papers in the fields of materials science and the technology of coatings. To celebrate the journal, I have the honor to edit a new featured Special Issue. The Special Issue will collect original research papers from the frontier of research, as well as review articles from prominent scholars highlighting the state-of-the-art of science and technology. I invite researchers and technologists, whose work focuses on coatings and related applications, to contribute with papers disseminating their excellent research findings. We are looking forward to receiving your work.

Dr. Alessandro Lavacchi
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Coatings is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (27 papers)

View options order results:
result details:
Displaying articles 1-27
Export citation of selected articles as:

Research

Jump to: Review, Other

Open AccessArticle Aluminizing via Ionic Liquid Electrodeposition and Pack Cementation: A Comparative Study with Inconel 738 and a CoNiCrAlY
Received: 1 May 2017 / Revised: 6 June 2017 / Accepted: 15 June 2017 / Published: 19 June 2017
PDF Full-text (9169 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Studies on the Effect of Arc Current Mode and Substrate Rotation Configuration on the Structure and Corrosion Behavior of PVD TiN Coatings
Received: 21 September 2016 / Revised: 7 March 2017 / Accepted: 30 March 2017 / Published: 4 April 2017
Cited by 2 | PDF Full-text (3016 KB) | HTML Full-text | XML Full-text
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 Ecorr and Icorr 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
Figures

Figure 1

Open AccessArticle Development of a Fabrication Process Using Suspension Plasma Spray for Titanium Oxide Photovoltaic Device
Received: 20 September 2016 / Revised: 24 February 2017 / Accepted: 1 March 2017 / Published: 4 March 2017
PDF Full-text (4922 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Influence of the Electrolyte Concentration on the Smooth TiO2 Anodic Coatings on Ti-6Al-4V
Received: 16 January 2017 / Revised: 27 February 2017 / Accepted: 28 February 2017 / Published: 3 March 2017
Cited by 3 | PDF Full-text (3343 KB) | HTML Full-text | XML Full-text
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 (Ra ≤ 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
Figures

Figure 1

Open AccessArticle Assessment on the Effects of ZnO and Coated ZnO Particles on iPP and PLA Properties for Application in Food Packaging
Received: 15 November 2016 / Revised: 9 January 2017 / Accepted: 8 February 2017 / Published: 17 February 2017
Cited by 5 | PDF Full-text (4192 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Silicides and Nitrides Formation in Ti Films Coated on Si and Exposed to (Ar-N2-H2) Expanding Plasma
Received: 20 September 2016 / Revised: 20 January 2017 / Accepted: 4 February 2017 / Published: 8 February 2017
Cited by 4 | PDF Full-text (2589 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Combustion Synthesis during Flame Spraying (“CAFSY”) for the Production of Catalysts on Substrates
Received: 7 November 2016 / Revised: 22 December 2016 / Accepted: 13 January 2017 / Published: 20 January 2017
Cited by 3 | PDF Full-text (3720 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Numerical and Experimental Investigation on the Spray Coating Process Using a Pneumatic Atomizer: Influences of Operating Conditions and Target Geometries
Received: 1 December 2016 / Revised: 28 December 2016 / Accepted: 5 January 2017 / Published: 18 January 2017
Cited by 3 | PDF Full-text (8404 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Assessment of Environmental Performance of TiO2 Nanoparticles Coated Self-Cleaning Float Glass
Received: 5 September 2016 / Revised: 21 December 2016 / Accepted: 3 January 2017 / Published: 12 January 2017
Cited by 8 | PDF Full-text (2221 KB) | HTML Full-text | XML Full-text | Supplementary Files
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
Figures

Figure 1

Open AccessArticle Durability Analysis and Experimental Validation of Environmental Barrier Coating (EBC) Performance Using Combined Digital Image Correlation and NDE
Received: 27 September 2016 / Revised: 2 December 2016 / Accepted: 7 December 2016 / Published: 16 December 2016
PDF Full-text (17297 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Characterization and Photovoltaic Properties of BiFeO3 Thin Films
Received: 19 August 2016 / Revised: 2 December 2016 / Accepted: 5 December 2016 / Published: 8 December 2016
Cited by 4 | PDF Full-text (3303 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Improving the Performance of Clear Coatings on Wood through the Aggregation of Marginal Gains
Received: 17 September 2016 / Revised: 12 November 2016 / Accepted: 21 November 2016 / Published: 26 November 2016
Cited by 7 | PDF Full-text (4740 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Corrosion Testing of Thermal Spray Coatings in a Biomass Co-Firing Power Plant
Received: 20 September 2016 / Revised: 31 October 2016 / Accepted: 19 November 2016 / Published: 24 November 2016
PDF Full-text (10728 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Thermally Sprayed Aluminum Coatings for the Protection of Subsea Risers and Pipelines Carrying Hot Fluids
Received: 20 September 2016 / Revised: 29 October 2016 / Accepted: 1 November 2016 / Published: 8 November 2016
Cited by 5 | PDF Full-text (3511 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Cellular Automata Modelling of Photo-Induced Oxidation Processes in Molecularly Doped Polymers
Received: 24 August 2016 / Revised: 21 October 2016 / Accepted: 2 November 2016 / Published: 4 November 2016
PDF Full-text (1574 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Atmospheric Plasma Spraying of Single Phase Lanthanum Zirconate Thermal Barrier Coatings with Optimized Porosity
Received: 16 August 2016 / Revised: 7 October 2016 / Accepted: 14 October 2016 / Published: 18 October 2016
Cited by 9 | PDF Full-text (6364 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessCommunication Atmospheric-Pressure Plasma Jet Processed Pt-Decorated Reduced Graphene Oxides for Counter-Electrodes of Dye-Sensitized Solar Cells
Received: 31 July 2016 / Revised: 30 September 2016 / Accepted: 10 October 2016 / Published: 13 October 2016
Cited by 18 | PDF Full-text (3911 KB) | HTML Full-text | XML Full-text
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
Figures

Graphical abstract

Open AccessArticle Feasibility of Coloring Bamboo with the Application of Natural and Extracted Fungal Pigments
Received: 18 July 2016 / Revised: 15 August 2016 / Accepted: 18 August 2016 / Published: 30 August 2016
Cited by 9 | PDF Full-text (7601 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Non-Cyanide Electrodeposited Ag–PTFE Composite Coating Using Direct or Pulsed Current Deposition
Received: 25 April 2016 / Revised: 12 July 2016 / Accepted: 22 July 2016 / Published: 26 July 2016
Cited by 2 | PDF Full-text (8724 KB) | HTML Full-text | XML Full-text
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
Figures

Graphical abstract

Open AccessArticle A Surface Photovoltage Study of Surface Defects on Co-Doped TiO2 Thin Films Deposited by Spray Pyrolysis
Received: 20 May 2016 / Revised: 12 July 2016 / Accepted: 14 July 2016 / Published: 22 July 2016
Cited by 3 | PDF Full-text (1811 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Wear Behaviour of Nanostructured Polymer-Based Safety Films on Soda-Lime Glass
Received: 27 May 2016 / Revised: 16 June 2016 / Accepted: 23 June 2016 / Published: 8 July 2016
Cited by 3 | PDF Full-text (3818 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessArticle Mechanical Color Reading of Wood-Staining Fungal Pigment Textile Dyes: An Alternative Method for Determining Colorfastness
Received: 17 May 2016 / Revised: 15 June 2016 / Accepted: 27 June 2016 / Published: 4 July 2016
Cited by 8 | PDF Full-text (1917 KB) | HTML Full-text | XML Full-text | Supplementary Files
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
Figures

Figure 1

Open AccessArticle Thermal Protection of Carbon Fiber-Reinforced Composites by Ceramic Particles
Received: 7 April 2016 / Revised: 9 May 2016 / Accepted: 20 May 2016 / Published: 1 June 2016
Cited by 4 | PDF Full-text (2909 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Review

Jump to: Research, Other

Open AccessReview State of the Art of Antimicrobial Edible Coatings for Food Packaging Applications
Received: 6 January 2017 / Revised: 9 March 2017 / Accepted: 10 April 2017 / Published: 19 April 2017
Cited by 16 | PDF Full-text (809 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessReview Corrosion Protection Systems and Fatigue Corrosion in Offshore Wind Structures: Current Status and Future Perspectives
Received: 6 December 2016 / Revised: 24 January 2017 / Accepted: 25 January 2017 / Published: 11 February 2017
Cited by 4 | PDF Full-text (6538 KB) | HTML Full-text | XML Full-text
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
Figures

Figure 1

Open AccessReview Surface-Engineered Fire Protective Coatings for Fabrics through Sol-Gel and Layer-by-Layer Methods: An Overview
Received: 12 June 2016 / Revised: 21 July 2016 / Accepted: 27 July 2016 / Published: 29 July 2016
Cited by 10 | PDF Full-text (1053 KB) | HTML Full-text | XML Full-text
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
Figures

Graphical abstract

Other

Jump to: Research, Review

Open AccessErratum Erratum: Panagopoulos, C.N., et al. Wear Behaviour of Nanostructured Polymer-Based Safety Films on Soda-Lime Glass. Coatings 2016, 6, 26
Received: 1 December 2016 / Revised: 1 December 2016 / Accepted: 1 December 2016 / Published: 14 December 2016
PDF Full-text (137 KB) | HTML Full-text | XML Full-text
Coatings EISSN 2079-6412 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top