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Coatings, Volume 7, Issue 2 (February 2017)

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Cover Story The endeavor to reduce CO2 emissions associated with the burning of fossil fuels in combination [...] Read more.
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Research

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Open AccessArticle Electroplating of CdTe Thin Films from Cadmium Sulphate Precursor and Comparison of Layers Grown by 3-Electrode and 2-Electrode Systems
Coatings 2017, 7(2), 17; doi:10.3390/coatings7020017
Received: 29 June 2016 / Revised: 3 September 2016 / Accepted: 19 January 2017 / Published: 24 January 2017
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Abstract
Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium
[...] Read more.
Electrodeposition of CdTe thin films was carried out from the late 1970s using the cadmium sulphate precursor. The solar energy group at Sheffield Hallam University has carried out a comprehensive study of CdTe thin films electroplated using cadmium sulfate, cadmium nitrate and cadmium chloride precursors, in order to select the best electrolyte. Some of these results have been published elsewhere, and this manuscript presents the summary of the results obtained on CdTe layers grown from cadmium sulphate precursor. In addition, this research program has been exploring the ways of eliminating the reference electrode, since this is a possible source of detrimental impurities, such as K+ and Ag+ for CdS/CdTe solar cells. This paper compares the results obtained from CdTe layers grown by three-electrode (3E) and two-electrode (2E) systems for their material properties and performance in CdS/CdTe devices. Thin films were characterized using a wide range of analytical techniques for their structural, morphological, optical and electrical properties. These layers have also been used in device structures; glass/FTO/CdS/CdTe/Au and CdTe from both methods have produced solar cells to date with efficiencies in the region of 5%–13%. Comprehensive work carried out to date produced comparable and superior devices fabricated from materials grown using 2E system. Full article
(This article belongs to the Special Issue Thin Film Semiconductors for Photovoltaic Applications)
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Open AccessArticle Influence of the Distribution of a Spray Paint on the Efficacy of Anti-Graffiti Coatings on a Highly Porous Natural Stone Material
Coatings 2017, 7(2), 18; doi:10.3390/coatings7020018
Received: 22 November 2016 / Revised: 10 January 2017 / Accepted: 20 January 2017 / Published: 24 January 2017
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Abstract
Graffiti on facades often has a heavy impact in social and economic terms, particularly when historical and artistic artefacts are affected. To limit the damages to the surfaces, preventive plans are implemented and anti-graffiti coatings are used as a protective measure. In this
[...] Read more.
Graffiti on facades often has a heavy impact in social and economic terms, particularly when historical and artistic artefacts are affected. To limit the damages to the surfaces, preventive plans are implemented and anti-graffiti coatings are used as a protective measure. In this study, the distribution of a spray paint inside a highly porous stone, with and without anti-graffiti protection, was investigated. Two commercial sacrificial anti-graffiti systems were used and an acrylic-based paint was applied as staining agent. Environmental scanning electron microscopy and energy-dispersive X-ray spectroscopy (EDS) microanalysis were performed to characterise, from the morphological and chemical point of view, the anti-graffiti coatings and the paint. Maps of the main elements were acquired to locate the different products inside the stone. Chemical removers were used to clean the stained surfaces, then the effectiveness of the cleaning was assessed by visual observations and colour measurements, as well as on the basis of percentage of residual stain. The obtained results highlighted that the anti-graffiti efficacy strongly depended on the characteristics of the applied coating. This latter usually acted as a barrier, but good results were obtained only where the stain did not remain as a separate layer, but penetrated the protective coating. Microcracks in the anti-graffiti coating were able to nullify the protective action. Full article
(This article belongs to the Special Issue Anti-Graffiti Coatings)
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Open AccessArticle Fabrication of Efficient Cu2ZnSnS4 Solar Cells by Sputtering Single Stoichiometric Target
Coatings 2017, 7(2), 19; doi:10.3390/coatings7020019
Received: 16 December 2016 / Revised: 6 January 2017 / Accepted: 20 January 2017 / Published: 24 January 2017
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Abstract
Low cost single stoichiometric target sputtering of Cu2ZnSnS4 (CZTS) precursor has been adopted to fabricate CZTS solar cells. The effect of a series of deposition pressures and deposition durations on the device performance has been investigated. A 3.74% efficient solar
[...] Read more.
Low cost single stoichiometric target sputtering of Cu2ZnSnS4 (CZTS) precursor has been adopted to fabricate CZTS solar cells. The effect of a series of deposition pressures and deposition durations on the device performance has been investigated. A 3.74% efficient solar cell has been achieved at a base pressure of 1 × 10−4 Torr with a stoichiometric target, which to the authors’ knowledge, is the record efficiency for such a stoichiometric target. Full article
(This article belongs to the Special Issue Thin Film Semiconductors for Photovoltaic Applications)
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Open AccessArticle Interfacial Mechanics Analysis of a Brittle Coating–Ductile Substrate System Involved in Thermoelastic Contact
Coatings 2017, 7(2), 21; doi:10.3390/coatings7020021
Received: 14 November 2016 / Revised: 9 January 2017 / Accepted: 25 January 2017 / Published: 6 February 2017
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Abstract
In this paper, interfacial stress analysis for a brittle coating/ductile substrate system, which is involved in a sliding contact with a rigid ball, is presented. By combining interface mechanics theory and the image point method, stress and displacement responses within a coated material
[...] Read more.
In this paper, interfacial stress analysis for a brittle coating/ductile substrate system, which is involved in a sliding contact with a rigid ball, is presented. By combining interface mechanics theory and the image point method, stress and displacement responses within a coated material for normal load, tangential load, and thermal load are obtained; further, the Green’s functions are established. The effects of coating thickness, friction coefficient, and a coating’s thermoelastic properties on the interfacial shear stress, τxz, and transverse stress, σxx, distributions are discussed in detail. A phenomenon, where interfacial shear stress tends to be relieved by frictional heating, is found in the case of a coating material’s thermal expansion coefficient being less than a substrate material’s thermal expansion coefficient. Additionally, numerical results show that distribution of interfacial stress can be altered and, therefore, interfacial damage can be modified by adjusting a coating’s structural parameters and thermoelastic properties. Full article
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Open AccessArticle Multiscale Computational Fluid Dynamics: Methodology and Application to PECVD of Thin Film Solar Cells
Coatings 2017, 7(2), 22; doi:10.3390/coatings7020022
Received: 13 December 2016 / Revised: 24 January 2017 / Accepted: 25 January 2017 / Published: 8 February 2017
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Abstract
This work focuses on the development of a multiscale computational fluid dynamics (CFD) simulation framework with application to plasma-enhanced chemical vapor deposition of thin film solar cells. A macroscopic, CFD model is proposed which is capable of accurately reproducing plasma chemistry and transport
[...] Read more.
This work focuses on the development of a multiscale computational fluid dynamics (CFD) simulation framework with application to plasma-enhanced chemical vapor deposition of thin film solar cells. A macroscopic, CFD model is proposed which is capable of accurately reproducing plasma chemistry and transport phenomena within a 2D axisymmetric reactor geometry. Additionally, the complex interactions that take place on the surface of a-Si:H thin films are coupled with the CFD simulation using a novel kinetic Monte Carlo scheme which describes the thin film growth, leading to a multiscale CFD model. Due to the significant computational challenges imposed by this multiscale CFD model, a parallel computation strategy is presented which allows for reduced processing time via the discretization of both the gas-phase mesh and microscopic thin film growth processes. Finally, the multiscale CFD model has been applied to the PECVD process at industrially relevant operating conditions revealing non-uniformities greater than 20% in the growth rate of amorphous silicon films across the radius of the wafer. Full article
(This article belongs to the Special Issue Chemical Vapor Deposition)
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Open AccessArticle Silicides and Nitrides Formation in Ti Films Coated on Si and Exposed to (Ar-N2-H2) Expanding Plasma
Coatings 2017, 7(2), 23; doi:10.3390/coatings7020023
Received: 20 September 2016 / Revised: 20 January 2017 / Accepted: 4 February 2017 / Published: 8 February 2017
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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
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Open AccessArticle Using an Atmospheric Pressure Chemical Vapor Deposition Process for the Development of V2O5 as an Electrochromic Material
Coatings 2017, 7(2), 24; doi:10.3390/coatings7020024
Received: 11 November 2016 / Revised: 11 December 2016 / Accepted: 5 February 2017 / Published: 8 February 2017
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Abstract
Vanadium pentoxide coatings were grown by atmospheric pressure chemical vapor deposition varying the gas precursor ratio (vanadium (IV) chloride:water) and the substrate temperature. All samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, cyclic voltammetry, and transmittance measurements. The water flow
[...] Read more.
Vanadium pentoxide coatings were grown by atmospheric pressure chemical vapor deposition varying the gas precursor ratio (vanadium (IV) chloride:water) and the substrate temperature. All samples were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, cyclic voltammetry, and transmittance measurements. The water flow rate was found to affect the crystallinity and the morphological characteristics of vanadium pentoxide. Dense stacks of long grains of crystalline oxide are formed at the highest amount of water utilized for a substrate temperature of 450 °C. Accordingly, it was indicated that for higher temperatures and a constant gas precursor ratio of 1:7, the surface morphology becomes flattened, and columnar grains of uniform size and shape are indicated, keeping the high crystalline quality of the material. Hence, it was possible to define a frame of operating parameters wherein single-phase vanadium pentoxide may be reliably expected, including a gas precursor ratio of 1:7 with a substrate temperature of >450 °C. The as-grown vanadium pentoxide at 550 °C for a gas precursor ratio of 1:7 presented the best electrochemical performance, including a diffusion coefficient of 9.19 × 10−11 cm2·s−1, a charge density of 3.1 mC·cm−2, and a coloration efficiency of 336 cm2·C−1. One may then say that this route can be important for the growth of large-scale electrodes with good performance for electrochromic devices. Full article
(This article belongs to the Special Issue Chemical Vapor Deposition)
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Open AccessArticle Coating Qualities Deposited Using Three Different Thermal Spray Technologies in Relation with Temperatures and Velocities of Spray Droplets
Coatings 2017, 7(2), 27; doi:10.3390/coatings7020027
Received: 21 December 2016 / Revised: 23 January 2017 / Accepted: 10 February 2017 / Published: 16 February 2017
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Abstract
Three guns based on different thermal spray technologies—namely, gas flame spray, wire arc spray, and wire plasma spray—were operated at each best cost–performance condition, and the resulting spray droplets and deposited coating qualities were investigated. For the former, a simple optical monitoring system
[...] Read more.
Three guns based on different thermal spray technologies—namely, gas flame spray, wire arc spray, and wire plasma spray—were operated at each best cost–performance condition, and the resulting spray droplets and deposited coating qualities were investigated. For the former, a simple optical monitoring system was used to measure temperatures and velocities of spray droplets ejected from the guns. On the other hand, for the latter, qualities of coating layers on substrates—namely, surface roughness, atomic composition, hardness, adhesive strength, and porosity—were characterized. Then, these coating qualities were discussed with respect to the measured temperatures and velocities of spray droplets, which revealed novel features in the coatings that have not been seen before, such as atomic composition and hardness strongly dependent on temperature and environments of droplets towards the substrates, and porosity on velocity of droplets impinging onto the substrates. Full article
(This article belongs to the Special Issue Thermal Spray Technology)
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Open AccessArticle Improving the Wear Resistance of Moulds for the Injection of Glass Fibre–Reinforced Plastics Using PVD Coatings: A Comparative Study
Coatings 2017, 7(2), 28; doi:10.3390/coatings7020028
Received: 31 December 2016 / Revised: 8 February 2017 / Accepted: 9 February 2017 / Published: 16 February 2017
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Abstract
It is well known that injection of glass fibre–reinforced plastics (GFRP) causes abrasive wear in moulds’ cavities and runners. Physical vapour deposition (PVD) coatings are intensively used to improve the wear resistance of different tools, also being one of the most promising ways
[...] Read more.
It is well known that injection of glass fibre–reinforced plastics (GFRP) causes abrasive wear in moulds’ cavities and runners. Physical vapour deposition (PVD) coatings are intensively used to improve the wear resistance of different tools, also being one of the most promising ways to increase the moulds’ lifespan, mainly when used with plastics strongly reinforced with glass fibres. This work compares four different thin, hard coatings obtained using the PVD magnetron sputtering process: TiAlN, TiAlSiN, CrN/TiAlCrSiN and CrN/CrCN/DLC. The first two are monolayer coatings while the last ones are nanostructured and consist of multilayer systems. In order to carry out the corresponding tribological characterization, two different approaches were selected: A laboratorial method, using micro-abrasion wear tests based on a ball-cratering configuration, and an industrial mode, analysing the wear resistance of the coated samples when inserted in a plastic injection mould. As expected, the wear phenomena are not equivalent and the results between micro-abrasion and industrial tests are not similar due to the different means used to promote the abrasion. The best wear resistance performance in the laboratorial wear tests was attained by the TiAlN monolayer coating while the best performance in the industrial wear tests was obtained by the CrN/TiAlCrSiN nanostructured multilayer coating. Full article
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Open AccessArticle Assessment on the Effects of ZnO and Coated ZnO Particles on iPP and PLA Properties for Application in Food Packaging
Coatings 2017, 7(2), 29; doi:10.3390/coatings7020029
Received: 15 November 2016 / Revised: 9 January 2017 / Accepted: 8 February 2017 / Published: 17 February 2017
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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
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Open AccessArticle Effects of Rare Earth Elements on Properties of Ni-Base Superalloy Powders and Coatings
Coatings 2017, 7(2), 30; doi:10.3390/coatings7020030
Received: 25 October 2016 / Revised: 6 January 2017 / Accepted: 23 January 2017 / Published: 16 February 2017
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Abstract
NiCrMoY alloy powders were prepared using inert gas atomization by incorporation of rare earth elements, such as Mo, Nb, and Y into Ni60A powders, the coatings were sprayed by oxy-acetylene flame spray and then remelted with high-frequency induction. The morphologies, hollow particle ratio,
[...] Read more.
NiCrMoY alloy powders were prepared using inert gas atomization by incorporation of rare earth elements, such as Mo, Nb, and Y into Ni60A powders, the coatings were sprayed by oxy-acetylene flame spray and then remelted with high-frequency induction. The morphologies, hollow particle ratio, particle-size distribution, apparent density, flowability, and the oxygen content of the NiCrMoY alloy powders were investigated, and the microstructure and hardness of the coatings were evaluated by optical microscopy (OM). Due to incorporation of the rare earth elements of Mo, Nb, or Y, the majority of the NiCrMoY alloy particles are near-spherical, the minority of which have small satellites, the surface of the particles is smoother and hollow particles are fewer, the particles exhibit larger apparent density and lower flowability than those of particles without incorporation, i.e., Ni60A powders, and particle-size distribution exhibits a single peak and fits normal distribution. The microstructure of the NiCrMoY alloy coatings exhibits finer structure and Rockwell hardness HRC of 60–63 in which the bulk- and needle-like hard phases are formed. Full article
(This article belongs to the Special Issue Coatings for Corrosion Mitigation)
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Open AccessArticle Microstructural Changes of Al Hot-Dipped P91 Steel during High-Temperature Oxidation
Coatings 2017, 7(2), 31; doi:10.3390/coatings7020031
Received: 30 December 2016 / Revised: 6 February 2017 / Accepted: 13 February 2017 / Published: 17 February 2017
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Abstract
The 9Cr-1Mo steel (ASTM P91) was hot-dip aluminized, and its microstructural changes during oxidation were studied. Before oxidation, the coating consisted of (Al-rich topcoat containing a small amount of Al5Fe2 and Al13Fe4)/(Al13Fe4-rich,
[...] Read more.
The 9Cr-1Mo steel (ASTM P91) was hot-dip aluminized, and its microstructural changes during oxidation were studied. Before oxidation, the coating consisted of (Al-rich topcoat containing a small amount of Al5Fe2 and Al13Fe4)/(Al13Fe4-rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer containing a small amount of Al9Cr4 precipitates), from the surface. During oxidation at 700–900 °C for 20–100 h, Al diffused inward and the substrate elements migrated outward to broaden and soften the coating, and also to transform (high Al)-Fe intermetallics to (low Al)-Fe intermetallics. The phases in the coating progressively transformed during oxidation as follows; (Al-rich topcoat)/(Al5Fe2–rich, Al13Fe4-containing alloy layer)/(Al5Fe2 alloy layer)→(α-Al2O3 scale)/(Al13Fe4–rich, Al5Fe2-containing layer)/(Al5Fe2 layer)/(AlFe interlayer)→(α-Al2O3 scale)/(AlFe–rich, Al5Fe2-containing layer)/(AlFe layer)/(AlFe3 layer))→((α-Al2O3, Fe2O3)-mixed scale)/(AlFe3 layer)/(Fe(Al) layer) from the surface. As the oxidation progressed, the scale changed from α-Al2O3 to the (α-Al2O3, Fe2O3)-mixture, which provided the necessary oxidation resistance. Full article
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Open AccessArticle Damping Optimization of Hard-Coating Thin Plate by the Modified Modal Strain Energy Method
Coatings 2017, 7(2), 32; doi:10.3390/coatings7020032
Received: 17 December 2016 / Revised: 10 February 2017 / Accepted: 10 February 2017 / Published: 17 February 2017
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Abstract
Due to the medium and small damping characteristics of the hard coating compared with viscoelastic materials, the classical modal strain energy (CMSE) method cannot be applied to the prediction of damping characteristics of hard-coating composite structure directly. In this study, the CMSE method
[...] Read more.
Due to the medium and small damping characteristics of the hard coating compared with viscoelastic materials, the classical modal strain energy (CMSE) method cannot be applied to the prediction of damping characteristics of hard-coating composite structure directly. In this study, the CMSE method was modified in order to be suitable for this calculation, and then the damping optimization of the hard-coating thin plate was carried out. First, the solution formula of modified modal strain energy (MMSE) method was derived and the relevant calculation procedure was proposed. Then, based on the principle that depositing the hard coating on the locations where modal strain energy is higher, the damping optimization method and procedure were presented. Next, a cantilever thin plate coated with Mg-Al hard coating was taken as an example to demonstrate the solution of the modal damping parameters for the composite plate. Finally, the optimization of coating location was studied according to the proposed method for the cantilever thin plate, and the effect of the coating area on the damping characteristics of hard-coating plate was also discussed. Full article
(This article belongs to the Special Issue Mechanical Behavior of Coatings and Engineered Surfaces)
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Open AccessArticle Static and Dynamic Magnetization Investigation in Permalloy Electrodeposited onto High Resistive N-Type Silicon Substrates
Coatings 2017, 7(2), 33; doi:10.3390/coatings7020033
Received: 19 December 2016 / Revised: 13 February 2017 / Accepted: 15 February 2017 / Published: 20 February 2017
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Abstract
The present study reports on the development of permalloy thin films obtained by electrodeposition onto low-doped n-type silicon substrates. While changing from non-percolated clusters into percolated thin films upon increasing the electrodeposition time, the static and dynamic magnetic properties of the as-obtained structures
[...] Read more.
The present study reports on the development of permalloy thin films obtained by electrodeposition onto low-doped n-type silicon substrates. While changing from non-percolated clusters into percolated thin films upon increasing the electrodeposition time, the static and dynamic magnetic properties of the as-obtained structures were investigated. We found the experimental magnetic results to be in very good agreement with the simulations performed by solving the Landau-Lifshitz for the dynamics of the magnetic moment. For short electrodeposition times we found the static and dynamic magnetization behavior of the as-formed nanoclusters evidencing vortex magnetization with random chirality and polarization, which is explained in terms of dipolar interaction minimization. Indeed, it is herein emphasized that recent applications of ferromagnetic materials in silicon-based spintronic devices, such as logic and bipolar magnetic transistors and magnetic memories, have revived the possible utilization of low cost and simple electrodeposition techniques for the development of these upcoming hetero-nanostructured devices. Full article
(This article belongs to the Special Issue Thin Films and Patterned Structures by Electrochemical Methods)
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Review

Jump to: Research

Open AccessReview Recent Developments in Accelerated Antibacterial Inactivation on 2D Cu-Titania Surfaces under Indoor Visible Light
Coatings 2017, 7(2), 20; doi:10.3390/coatings7020020
Received: 15 September 2016 / Revised: 5 January 2017 / Accepted: 23 January 2017 / Published: 6 February 2017
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Abstract
This review focuses on Cu/TiO2 sequentially sputtered and Cu-TiO2 co-sputtered catalytic/photocatalytic surfaces that lead to bacterial inactivation, discussing their stability, synthesis, adhesion, and antibacterial kinetics. The intervention of TiO2, Cu, and the synergic effect of Cu and TiO2
[...] Read more.
This review focuses on Cu/TiO2 sequentially sputtered and Cu-TiO2 co-sputtered catalytic/photocatalytic surfaces that lead to bacterial inactivation, discussing their stability, synthesis, adhesion, and antibacterial kinetics. The intervention of TiO2, Cu, and the synergic effect of Cu and TiO2 on films prepared by a colloidal sol-gel method leading to bacterial inactivation is reviewed. Processes in aerobic and anaerobic media leading to bacterial loss of viability in multidrug resistant (MDR) pathogens, Gram-negative, and Gram-positive bacteria are described. Insight is provided for the interfacial charge transfer mechanism under solar irradiation occurring between TiO2 and Cu. Surface properties of 2D TiO2/Cu and TiO2-Cu films are correlated with the bacterial inactivation kinetics in dark and under light conditions. The intervention of these antibacterial sputtered surfaces in health-care facilities, leading to Methicillin-resistant Staphylococcus Aureus (MRSA)-isolates inactivation, is described in dark and under actinic light conditions. The synergic intervention of the Cu and TiO2 films leading to bacterial inactivation prepared by direct current magnetron sputtering (DCMS), pulsed direct current magnetron sputtering (DCMSP), and high power impulse magnetron sputtering (HIPIMS) is reported in a detailed manner. Full article
(This article belongs to the Special Issue Multifunctional Organic-Inorganic Hybrid Thin Films and Coatings)
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Open AccessReview Corrosion Protection Systems and Fatigue Corrosion in Offshore Wind Structures: Current Status and Future Perspectives
Coatings 2017, 7(2), 25; doi:10.3390/coatings7020025
Received: 6 December 2016 / Revised: 24 January 2017 / Accepted: 25 January 2017 / Published: 11 February 2017
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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
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Open AccessReview Surface Enhanced Raman Scattering Substrates Made by Oblique Angle Deposition: Methods and Applications
Coatings 2017, 7(2), 26; doi:10.3390/coatings7020026
Received: 29 December 2016 / Revised: 24 January 2017 / Accepted: 6 February 2017 / Published: 15 February 2017
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Abstract
Surface Enhanced Raman Spectroscopy presents a rapid, non-destructive method to identify chemical and biological samples with up to single molecule sensitivity. Since its discovery in 1974, the technique has become an intense field of interdisciplinary research, typically generating >2000 publications per year since
[...] Read more.
Surface Enhanced Raman Spectroscopy presents a rapid, non-destructive method to identify chemical and biological samples with up to single molecule sensitivity. Since its discovery in 1974, the technique has become an intense field of interdisciplinary research, typically generating >2000 publications per year since 2011. The technique relies on the localised surface plasmon resonance phenomenon, where incident light can couple with plasmons at the interface that result in the generation of an intense electric field. This field can propagate from the surface from the metal-dielectric interface, so molecules within proximity will experience more intense Raman scattering. Localised surface plasmon resonance wavelength is determined by a number of factors, such as size, geometry and material. Due to the requirements of the surface optical response, Ag and Au are typical metals used for surface enhanced Raman applications. These metals then need to have nano features that improve the localised surface plasmon resonance, several variants of these substrates exist; surfaces can range from nanoparticles in a suspension, electrochemically roughened electrodes to metal nanostructures on a substrate. The latter will be the focus of this review, particularly reviewing substrates made by oblique angle deposition. Oblique angle deposition is the technique of growing thin films so that the material flux is not normal to the surface. Films grown in this fashion will possess nanostructures, due to the atomic self-shadowing effect, that are dependent mainly on the deposition angle. Recent developments, applications and highlights of surface enhanced Raman scattering substrates made by oblique angle deposition will be reviewed. Full article
(This article belongs to the Special Issue Recent Advances in Optical Coatings)
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Open AccessReview SnS Thin Film Solar Cells: Perspectives and Limitations
Coatings 2017, 7(2), 34; doi:10.3390/coatings7020034
Received: 27 December 2016 / Revised: 14 February 2017 / Accepted: 16 February 2017 / Published: 22 February 2017
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Abstract
Thin film solar cells have reached commercial maturity and extraordinarily high efficiency that make them competitive even with the cheaper Chinese crystalline silicon modules. However, some issues (connected with presence of toxic and/or rare elements) are still limiting their market diffusion. For this
[...] Read more.
Thin film solar cells have reached commercial maturity and extraordinarily high efficiency that make them competitive even with the cheaper Chinese crystalline silicon modules. However, some issues (connected with presence of toxic and/or rare elements) are still limiting their market diffusion. For this reason new thin film materials, such as Cu2ZnSnS4 or SnS, have been introduced so that expensive In and Te, and toxic elements Se and Cd, are substituted, respectively, in CuInGaSe2 and CdTe. To overcome the abundance limitation of Te and In, in recent times new thin film materials, such as Cu2ZnSnS4 or SnS, have been investigated. In this paper we analyze the limitations of SnS deposition in terms of reproducibility and reliability. SnS deposited by thermal evaporation is analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and atomic force microscopy. The raw material is also analyzed and a different composition is observed according to the different number of evaporation (runs). The sulfur loss represents one of the major challenges of SnS solar cell technology. Full article
(This article belongs to the Special Issue Thin Film Semiconductors for Photovoltaic Applications)
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