Coatings

1337 KiB

Open AccessArticle

Laboratory and Field Studies of Poly(2,5-bis(N-methyl-N-hexylamino)phenylene vinylene) (BAM-PPV): A Potential Wash Primer Replacement for Army Military Vehicles

by Peter Zarras, Christopher E. Miller, Cindy Webber, Nicole Anderson and John D. Stenger-Smith

Coatings 2014, 4(3), 687-700; https://doi.org/10.3390/coatings4030687 - 15 Sep 2014

Cited by 5 | Viewed by 8100

Abstract

In this study, an electroactive polymer (EAP), poly(2,5-bis(N-methyl-N- hexylamino)phenylene vinylene) (BAM-PPV), was tested as an alternative to current hexavalent chromium (Cr(VI))-based Army wash primers. BAM-PPV was tested in both laboratory and field studies to determine its adhesive and corrosion-inhibiting [...] Read more.

In this study, an electroactive polymer (EAP), poly(2,5-bis(N-methyl-N- hexylamino)phenylene vinylene) (BAM-PPV), was tested as an alternative to current hexavalent chromium (Cr(VI))-based Army wash primers. BAM-PPV was tested in both laboratory and field studies to determine its adhesive and corrosion-inhibiting properties when applied to steel and aluminum alloys. The Army Research Laboratory (ARL) tests showed that BAM-PPV combined with an epoxy primer and the Army chemical agent-resistant coating (CARC) topcoat met Army performance requirements for military coatings. After successful laboratory testing, the BAM-PPV was then field tested for one year at the Aberdeen Test Center (ATC). This field testing showed that BAM-PPV incorporated into the Army military coating survived with no delamination of the coating and only minor corrosion on the chip sites. Full article

(This article belongs to the Special Issue Advances in Multifunctional Coatings for Next Generation Applications)

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458 KiB

Open AccessArticle

Antibacterial Activity of TiO₂ Photocatalyst Alone or in Coatings on E. coli: The Influence of Methodological Aspects

by Thomas Verdier, Marie Coutand, Alexandra Bertron and Christine Roques

Coatings 2014, 4(3), 670-686; https://doi.org/10.3390/coatings4030670 - 22 Aug 2014

Cited by 187 | Viewed by 14915

Abstract

In damp environments, indoor building materials are among the main proliferation substrates for microorganisms. Photocatalytic coatings, including nanoparticles of TiO₂, could be a way to prevent microbial proliferation or, at least, to significantly reduce the amount of microorganisms that grow on [...] Read more.

In damp environments, indoor building materials are among the main proliferation substrates for microorganisms. Photocatalytic coatings, including nanoparticles of TiO₂, could be a way to prevent microbial proliferation or, at least, to significantly reduce the amount of microorganisms that grow on indoor building materials. Previous works involving TiO₂ have already shown the inactivation of bacteria by the photocatalysis process. This paper studies the inactivation of Escherichia coli bacteria by photocatalysis involving TiO₂ nanoparticles alone or in transparent coatings (varnishes) and investigates different parameters that significantly influence the antibacterial activity. The antibacterial activity of TiO₂ was evaluated through two types of experiments under UV irradiation: (I) in slurry with physiological water (stirred suspension); and (II) in a drop deposited on a glass plate. The results confirmed the difference in antibacterial activity between simple drop-deposited inoculum and inoculum spread under a plastic film, which increased the probability of contact between TiO₂ and bacteria (forced contact). In addition, the major effect of the nature of the suspension on the photocatalytic disinfection ability was highlighted. Experiments were also carried out at the surface of transparent coatings formulated using nanoparticles of TiO₂. The results showed significant antibacterial activities after 2 h and 4 h and suggested that improving the formulation would increase efficiency. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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1437 KiB

Open AccessArticle

Photocatalytic Activity and Stability of Porous Polycrystalline ZnO Thin-Films Grown via a Two-Step Thermal Oxidation Process

by James C. Moore, Robert Louder and Cody V. Thompson

Coatings 2014, 4(3), 651-669; https://doi.org/10.3390/coatings4030651 - 15 Aug 2014

Cited by 34 | Viewed by 7021

Abstract

The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV) photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form [...] Read more.

The photocatalytic activity and stability of thin, polycrystalline ZnO films was studied. The oxidative degradation of organic compounds at the ZnO surface results from the ultraviolet (UV) photo-induced creation of highly oxidizing holes and reducing electrons, which combine with surface water to form hydroxyl radicals and reactive oxygen species. Therefore, the efficiency of the electron-hole pair formation is of critical importance for self-cleaning and antimicrobial applications with these metal-oxide catalyst systems. In this study, ZnO thin films were fabricated on sapphire substrates via direct current sputter deposition of Zn-metal films followed by thermal oxidation at several annealing temperatures (300–1200 °C). Due to the ease with which they can be recovered, stabilized films are preferable to nanoparticles or colloidal suspensions for some applications. Characterization of the resulting ZnO thin films through atomic force microscopy and photoluminescence indicated that decreasing annealing temperature leads to smaller crystal grain size and increased UV excitonic emission. The photocatalytic activities were characterized by UV-visible absorption measurements of Rhodamine B dye concentrations. The films oxidized at lower annealing temperatures exhibited higher photocatalytic activity, which is attributed to the increased optical quality. Photocatalytic activity was also found to depend on film thickness, with lower activity observed for thinner films. Decreasing activity with use was found to be the result of decreasing film thickness due to surface etching. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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1296 KiB

Open AccessArticle

Thermal Conductivity Analysis and Lifetime Testing of Suspension Plasma-Sprayed Thermal Barrier Coatings

by Nicholas Curry, Kent VanEvery, Todd Snyder and Nicolaie Markocsan

Coatings 2014, 4(3), 630-650; https://doi.org/10.3390/coatings4030630 - 15 Aug 2014

Cited by 124 | Viewed by 14630

Abstract

Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma [...] Read more.

Suspension plasma spraying (SPS) has become an interesting method for the production of thermal barrier coatings for gas turbine components. The development of the SPS process has led to structures with segmented vertical cracks or column-like structures that can imitate strain-tolerant air plasma spraying (APS) or electron beam physical vapor deposition (EB-PVD) coatings. Additionally, SPS coatings can have lower thermal conductivity than EB-PVD coatings, while also being easier to produce. The combination of similar or improved properties with a potential for lower production costs makes SPS of great interest to the gas turbine industry. This study compares a number of SPS thermal barrier coatings (TBCs) with vertical cracks or column-like structures with the reference of segmented APS coatings. The primary focus has been on lifetime testing of these new coating systems. Samples were tested in thermo-cyclic fatigue at temperatures of 1100 °C for 1 h cycles. Additional testing was performed to assess thermal shock performance and erosion resistance. Thermal conductivity was also assessed for samples in their as-sprayed state, and the microstructures were investigated using SEM. Full article

(This article belongs to the Special Issue High Temperature Coatings)

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Graphical abstract

481 KiB

Open AccessArticle

Self-Cleaning Photocatalytic Polyurethane Coatings Containing Modified C₆₀ Fullerene Additives

by Jeffrey G. Lundin, Spencer L. Giles, Robert F. Cozzens and James H. Wynne

Coatings 2014, 4(3), 614-629; https://doi.org/10.3390/coatings4030614 - 13 Aug 2014

Cited by 17 | Viewed by 7617

Abstract

Surfaces are often coated with paint for improved aesthetics and protection; however, additional functionalities that impart continuous self-decontaminating and self-cleaning properties would be extremely advantageous. In this report, photochemical additives based on C₆₀ fullerene were incorporated into polyurethane coatings to investigate their [...] Read more.

Surfaces are often coated with paint for improved aesthetics and protection; however, additional functionalities that impart continuous self-decontaminating and self-cleaning properties would be extremely advantageous. In this report, photochemical additives based on C₆₀ fullerene were incorporated into polyurethane coatings to investigate their coating compatibility and ability to impart chemical decontaminating capability to the coating surface. C₆₀ exhibits unique photophysical properties, including the capability to generate singlet oxygen upon exposure to visible light; however, C₆₀ fullerene exhibits poor solubility in solvents commonly employed in coating applications. A modified C₆₀ containing a hydrophilic moiety was synthesized to improve polyurethane compatibility and facilitate segregation to the polymer–air interface. Bulk properties of the polyurethane films were analyzed to investigate additive–coating compatibility. Coatings containing photoactive additives were subjected to self-decontamination challenges against representative chemical contaminants and the effects of additive loading concentration, light exposure, and time on chemical decontamination are reported. Covalent attachment of an ethylene glycol tail to C₆₀ improved its solubility and dispersion in a hydrophobic polyurethane matrix. Decomposition products resulting from oxidation were observed in addition to a direct correlation between additive loading concentration and decomposition of surface-residing contaminants. The degradation pathways deduced from contaminant challenge byproduct analyses are detailed. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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7385 KiB

Open AccessArticle

Noise Reduction Properties of an Experimental Bituminous Slurry with Crumb Rubber Incorporated by the Dry Process

by Moisés Bueno, Jeanne Luong, Fernando Terán, Urbano Viñuela, Víctor F. Vázquez and Santiago E. Paje

Coatings 2014, 4(3), 602-613; https://doi.org/10.3390/coatings4030602 - 11 Aug 2014

Cited by 12 | Viewed by 7038

Abstract

Nowadays, cold technology for asphalt pavement in the field of road construction is considered as an alternative solution to conventional procedures from both an economic and environmental point of view. Among these techniques, bituminous slurry surfacing is obtaining an important role due to [...] Read more.

Nowadays, cold technology for asphalt pavement in the field of road construction is considered as an alternative solution to conventional procedures from both an economic and environmental point of view. Among these techniques, bituminous slurry surfacing is obtaining an important role due to the properties of the obtained wearing course. The functional performance of this type of surfaces is directly related to its rough texture. Nevertheless, this parameter has a significant influence on the tire/road noise generation. To reduce this undesirable effect on the sound performance, new designs of elastic bituminous slurries have been developed. Within the FENIX project, this work presents the acoustical characterization of an experimental bituminous slurry with crumb rubber from wasted automobile tires incorporated by the dry process. The obtained results show that, under controlled operational parameters, the close proximity sound levels associated to the experimental slurry are considerably lower than those emitted by a conventional slurry wearing course. However, after one year of supporting traffic loads and different weather conditions, the evaluated bituminous slurry, although it conserves the original noise reduction properties in relation to the conventional one, noticeably increases the generated sound emission. Therefore, it is required to continue improving the design of experimental surfaces in order to enhance its long-term performance. Full article

(This article belongs to the Special Issue Low-Noise Road Surfaces)

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792 KiB

Open AccessArticle

Tuning the Photocatalytic Activity of Anatase TiO₂ Thin Films by Modifying the Preferred <001> Grain Orientation with Reactive DC Magnetron Sputtering

by B. Stefanov and L. Österlund

Coatings 2014, 4(3), 587-601; https://doi.org/10.3390/coatings4030587 - 8 Aug 2014

Cited by 24 | Viewed by 10016

Abstract

Anatase TiO₂ thin films were deposited by DC reactive magnetron sputtering on glass substrates at 20 mTorr pressure in a flow of an Ar and O₂ gas mixture. The O₂ partial pressure (P_O₂) was varied from [...] Read more.

Anatase TiO₂ thin films were deposited by DC reactive magnetron sputtering on glass substrates at 20 mTorr pressure in a flow of an Ar and O₂ gas mixture. The O₂ partial pressure (P_O₂) was varied from 0.65 mTorr to 1.3 mTorr to obtain two sets of films with different stoichiometry. The structure and morphology of the films were characterized by secondary electron microscopy, atomic force microscopy, and grazing-angle X-ray diffraction complemented by Rietveld refinement. The as-deposited films were amorphous. Post-annealing in air for 1 h at 500 °C resulted in polycrystalline anatase film structures with mean grain size of 24.2 nm (P_O₂ = 0.65 mTorr) and 22.1 nm (P_O₂ = 1.3 mTorr), respectively. The films sputtered at higher O₂ pressure showed a preferential orientation in the <001> direction, which was associated with particle surfaces exposing highly reactive {001} facets. Films sputtered at lower O₂ pressure exhibited no, or very little, preferential grain orientation, and were associated with random distribution of particles exposing mainly the thermodynamically favorable {101} surfaces. Photocatalytic degradation measurements using methylene blue dye showed that <001> oriented films exhibited approximately 30% higher reactivity. The measured intensity dependence of the degradation rate revealed that the UV-independent rate constant was 64% higher for the <001> oriented film compared to randomly oriented films. The reaction order was also found to be higher for <001> films compared to randomly oriented films, suggesting that the <001> oriented film exposes more reactive surface sites. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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828 KiB

Open AccessConcept Paper

Metallization on FDM Parts Using the Chemical Deposition Technique

by Azhar Equbal and Anoop Kumar Sood

Coatings 2014, 4(3), 574-586; https://doi.org/10.3390/coatings4030574 - 5 Aug 2014

Cited by 37 | Viewed by 7791

Abstract

Metallization of ABS (acrylonitrile-butadiene-styrene) parts has been studied on flat part surfaces. These parts are fabricated on an FDM (fused deposition modeling machine) using the layer-wise deposition principle using ABS as a part material. Electroless copper deposition on ABS parts was performed using [...] Read more.

Metallization of ABS (acrylonitrile-butadiene-styrene) parts has been studied on flat part surfaces. These parts are fabricated on an FDM (fused deposition modeling machine) using the layer-wise deposition principle using ABS as a part material. Electroless copper deposition on ABS parts was performed using two different surface preparation processes, namely ABS parts prepared using chromic acid for etching and ABS parts prepared using a solution mixture of sulphuric acid and hydrogen peroxide (H₂SO₄/H₂O₂) for etching. After surface preparations using these routes, copper (Cu) is deposited electrolessly using four different acidic baths. The acidic baths used are 5 wt% CuSO₄ (copper sulfate) with 15 wt% of individual acids, namely HF (hydrofluoric acid), H₂SO₄ (sulphuric acid), H₃PO₄(phosphoric acid) and CH₃COOH (acetic acid). Cu deposition under different acidic baths used for both the routes is presented and compared based on their electrical performance, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). The result shows that chromic acid etched samples show better electrical performance and Cu deposition in comparison to samples etched via H₂SO₄/H₂O₂. Full article

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2308 KiB

Open AccessReview

Recent Photocatalytic Applications for Air Purification in Belgium

by Elia Boonen and Anne Beeldens

Coatings 2014, 4(3), 553-573; https://doi.org/10.3390/coatings4030553 - 31 Jul 2014

Cited by 126 | Viewed by 14170

Abstract

Photocatalytic concrete constitutes a promising technique to reduce a number of air contaminants such as NO_x and VOC’s, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, the urban environment, etc. Ideally, the photocatalyst, titanium dioxide, [...] Read more.

Photocatalytic concrete constitutes a promising technique to reduce a number of air contaminants such as NO_x and VOC’s, especially at sites with a high level of pollution: highly trafficked canyon streets, road tunnels, the urban environment, etc. Ideally, the photocatalyst, titanium dioxide, is introduced in the top layer of the concrete pavement for best results. In addition, the combination of TiO₂ with cement-based products offers some synergistic advantages, as the reaction products can be adsorbed at the surface and subsequently be washed away by rain. A first application has been studied by the Belgian Road Research Center (BRRC) on the side roads of a main entrance axis in Antwerp with the installation of 10.000 m² of photocatalytic concrete paving blocks. For now however, the translation of laboratory testing towards results in situ remains critical of demonstrating the effectiveness in large scale applications. Moreover, the durability of the air cleaning characteristic with time remains challenging for application in concrete roads. From this perspective, several new trial applications have been initiated in Belgium in recent years to assess the “real life” behavior, including a field site set up in the Leopold II tunnel of Brussels and the construction of new photocatalytic pavements on industrial zones in the cities of Wijnegem and Lier (province of Antwerp). This paper first gives a short overview of the photocatalytic principle applied in concrete, to continue with some main results of the laboratory research recognizing the important parameters that come into play. In addition, some of the methods and results, obtained for the existing application in Antwerp (2005) and during the implementation of the new realizations in Wijnegem and Lier (2010–2012) and in Brussels (2011–2013), will be presented. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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960 KiB

Open AccessArticle

Wetting, Solubility and Chemical Characteristics of Plasma-Polymerized 1-Isopropyl-4-Methyl-1,4-Cyclohexadiene Thin Films

by Jakaria Ahmad, Kateryna Bazaka, Michael Oelgemöller and Mohan V. Jacob

Coatings 2014, 4(3), 527-552; https://doi.org/10.3390/coatings4030527 - 31 Jul 2014

Cited by 28 | Viewed by 8490

Abstract

Investigations on the wetting, solubility and chemical composition of plasma polymer thin films provide an insight into the feasibility of implementing these polymeric materials in organic electronics, particularly where wet solution processing is involved. In this study, thin films were prepared from 1-isopropyl-4-methyl-1,4-cyclohexadiene [...] Read more.

Investigations on the wetting, solubility and chemical composition of plasma polymer thin films provide an insight into the feasibility of implementing these polymeric materials in organic electronics, particularly where wet solution processing is involved. In this study, thin films were prepared from 1-isopropyl-4-methyl-1,4-cyclohexadiene (γ-Terpinene) using radio frequency (RF) plasma polymerization. FTIR showed the polymers to be structurally dissimilar to the original monomer and highly cross-linked, where the loss of original functional groups and the degree of cross-linking increased with deposition power. The polymer surfaces were hydrocarbon-rich, with oxygen present in the form of O–H and C=O functional groups. The oxygen content decreased with deposition power, with films becoming more hydrophobic and, thus, less wettable. The advancing and receding contact angles were investigated, and the water advancing contact angle was found to increase from 63.14° to 73.53° for thin films prepared with an RF power of 10 W to 75 W. The wetting envelopes for the surfaces were constructed to enable the prediction of the surfaces’ wettability for other solvents. The effect of roughness on the wetting behaviour of the films was insignificant. The polymers were determined to resist solubilization in solvents commonly used in the deposition of organic semiconducting layers, including chloroform and chlorobenzene, with higher stability observed in films fabricated at higher RF power. Full article

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7558 KiB

Open AccessArticle

Electrochemical Characterization of Multilayer Cr/CrN-Based Coatings

by Fabio C. Caiazzo, Valentina Sisti, Stefano P. Trasatti and Sergio Trasatti

Coatings 2014, 4(3), 508-526; https://doi.org/10.3390/coatings4030508 - 31 Jul 2014

Cited by 13 | Viewed by 7753

Abstract

In this work, a series of mono-and multilayer coatings were considered. They consisted of CrN and Cr prepared by physical vapor deposition with a cathodic arc. The most common steels for molds of plastics were chosen as substrates: X37CrMoV5-1 (SMV3), X2NiCoMo18-8-5 (MARVAL M1), [...] Read more.

In this work, a series of mono-and multilayer coatings were considered. They consisted of CrN and Cr prepared by physical vapor deposition with a cathodic arc. The most common steels for molds of plastics were chosen as substrates: X37CrMoV5-1 (SMV3), X2NiCoMo18-8-5 (MARVAL M1), X105CrCoMo18-2 (N690) and X40CrMo15 (X13T6). The samples were made with surface state conditions reproducing the main finishes required for molding of plastics: mirror, electro-eroded, sandblasted and ground finish. The coatings were characterized morphologically and chemically. The corrosion behavior of bare and coated steels was evaluated by electrochemical methods. Full article

(This article belongs to the Special Issue Electrochemical Interfaces and Electrodeposition—In Honour of M. Luisa Foresti on the Occasion of Her Retirement)

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2773 KiB

Open AccessArticle

Transparent, Adherent, and Photocatalytic SiO₂-TiO₂ Coatings on Polycarbonate for Self-Cleaning Applications

by Sanjay S. Latthe, Shanhu Liu, Chiaki Terashima, Kazuya Nakata and Akira Fujishima

Coatings 2014, 4(3), 497-507; https://doi.org/10.3390/coatings4030497 - 29 Jul 2014

Cited by 81 | Viewed by 14781

Abstract

Photocatalytic TiO₂ coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards [...] Read more.

Photocatalytic TiO₂ coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards water and photocatalytic SiO₂-TiO₂ coatings on polycarbonate (PC) substrate for self-cleaning applications. The silica barrier layer was applied on UV-treated PC substrate before spin coating the SiO₂-TiO₂ coatings. The effect of different vol% of SiO₂ in TiO₂ and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail. The coatings prepared from 7 vol% of SiO₂ in TiO₂ showed smooth, crack-free surface morphology and low surface roughness compared to the coatings prepared from the higher vol% of SiO₂ in TiO₂. The water drops on this coating acquires a contact angle less than 10° after UV irradiation for 30 min. All the coatings prepared from different vol% (7 to 20) of SiO₂ in TiO₂ showed high transparency in the visible range. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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3317 KiB

Open AccessArticle

A Study of a Powder Coating Gun Near Field: Particle Flow in an Isothermal Staggered Concentric Air Jet

by Graham Payne, Darko Matovic and Edward Grandmaison

Coatings 2014, 4(3), 465-496; https://doi.org/10.3390/coatings4030465 - 29 Jul 2014

Cited by 2 | Viewed by 8043

Abstract

An experimental study of inert particle dispersion in an isothermal concentric air jet near field was conducted for cases of standard non-staggered and alternative staggered jet nozzles, each taken from a polymer powder flame deposition gun. The experimental work consisted of analysis of [...] Read more.

An experimental study of inert particle dispersion in an isothermal concentric air jet near field was conducted for cases of standard non-staggered and alternative staggered jet nozzles, each taken from a polymer powder flame deposition gun. The experimental work consisted of analysis of high speed digital images of the inert two phase isothermal jet flow, illuminated by a laser light sheet along and across the jet axis. The analysis of particle spread in the jet, represented by families of particle density distributions, clearly showed that the staggered nozzles resulted in a better-focused flow, with narrower distributions in the near field, and in the elimination of the recirculation zone that disrupted the particle flow in a non-staggered nozzle arrangement. In all cases, histograms of the cross-sectional particle area density were found to be approximately Gaussian. It was also found that there was a wide variation in the size and shape of the ground polymer particles used and these two characteristics caused a wide variation in the radial and axial velocities of the particles. Despite the differences between single-phase numerical simulations and experimental results, reported in Payne et al. [1], the introduction of particles into a numerical model produced satisfactory agreement with the particle velocities found experimentally. Full article

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727 KiB

Open AccessArticle

The GM1 Ganglioside Forms GM1-Rich Gel Phase Microdomains within Lipid Rafts

by Lucia Becucci, Francesco Vizza, Yolanda Duarte and Rolando Guidelli

Coatings 2014, 4(3), 450-464; https://doi.org/10.3390/coatings4030450 - 16 Jul 2014

Cited by 1 | Viewed by 6016

Abstract

Mercury-supported, self-assembled monolayers (SAMs) of the sole dioleoylphosphatidylcholine (DOPC) and of a raft-forming mixture of DOPC, cholesterol (Chol) and palmitoylsphingomyelin (PSM) of (59:26:15) mol% composition, were investigated by electrochemical impedance spectroscopy (EIS), both in the absence and in the presence of the monosialoganglioside [...] Read more.

Mercury-supported, self-assembled monolayers (SAMs) of the sole dioleoylphosphatidylcholine (DOPC) and of a raft-forming mixture of DOPC, cholesterol (Chol) and palmitoylsphingomyelin (PSM) of (59:26:15) mol% composition, were investigated by electrochemical impedance spectroscopy (EIS), both in the absence and in the presence of the monosialoganglioside GM1. The impedance spectra of these four SAMs were fitted by a series of parallel combinations of a resistance and a capacitance (RC meshes) and displayed on plots of ωZ′ against −ωZ″, where Z′ and Z″ are the in-phase and quadrature components of the impedance and ω is the angular frequency. A comparison among these different impedance spectra points to the formation of GM1-rich gel phase microdomains within the lipid rafts of the DOPC/Chol/PSM mixture, thanks to the unique molecular-level smooth support provided by mercury, which allows EIS to detect the protruding gel phase microdomains by averaging them over a macroscopically large area. Full article

(This article belongs to the Special Issue Electrochemical Interfaces and Electrodeposition—In Honour of M. Luisa Foresti on the Occasion of Her Retirement)

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1412 KiB

Open AccessArticle

Photocatalytic TiO₂ and Doped TiO₂ Coatings to Improve the Hygiene of Surfaces Used in Food and Beverage Processing—A Study of the Physical and Chemical Resistance of the Coatings

by Parnia Navabpour, Soheyla Ostovarpour, Carin Tattershall, Kevin Cooke, Peter Kelly, Joanna Verran, Kathryn Whitehead, Claire Hill, Mari Raulio and Outi Priha

Coatings 2014, 4(3), 433-449; https://doi.org/10.3390/coatings4030433 - 15 Jul 2014

Cited by 18 | Viewed by 8670

Abstract

TiO₂ coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO₂ coatings were investigated as self-cleaning surfaces for beverage processing. The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated [...] Read more.

TiO₂ coatings deposited using reactive magnetron sputtering and spray coating methods, as well as Ag- and Mo-doped TiO₂ coatings were investigated as self-cleaning surfaces for beverage processing. The mechanical resistance and retention of the photocatalytic properties of the coatings were investigated over a three-month period in three separate breweries. TiO₂ coatings deposited using reactive magnetron sputtering showed better mechanical durability than the spray coated surfaces, whilst the spray-deposited coating showed enhanced retention of photocatalytic properties. The presence of Ag and Mo dopants improved the photocatalytic properties of TiO₂ as well as the retention of these properties. The spray-coated TiO₂ was the only coating which showed light-induced hydrophilicity, which was retained in the coatings surviving the process conditions. Full article

(This article belongs to the Special Issue Photocalytic Coatings for Air-Purifying, Self-Cleaning and Antimicrobial Properties)

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1524 KiB

Open AccessArticle

Enhanced Adhesion of Continuous Nanoporous Au Layers by Thermochemical Oxidation of Glassy Carbon

by Lori Ana Bromberg, Jiaxin Xia, Ryan Rooney and Nikolay Dimitrov

Coatings 2014, 4(3), 416-432; https://doi.org/10.3390/coatings4030416 - 9 Jul 2014

Cited by 11 | Viewed by 7431

Abstract

The fabrication of a nanoporous gold (NPG)-based catalyst on a glassy carbon (GC) support results normally in large isolated and poorly adhering clusters that suffer considerable material loss upon durability testing. This work exploits thermochemical oxidation of GC, which, coupled with the utilization [...] Read more.

The fabrication of a nanoporous gold (NPG)-based catalyst on a glassy carbon (GC) support results normally in large isolated and poorly adhering clusters that suffer considerable material loss upon durability testing. This work exploits thermochemical oxidation of GC, which, coupled with the utilization of some recent progress in fabricating continuous NPG layers using a Pd seed layer, aims to enhance the adhesion to the GC surface. Thermochemical oxidation causes interconnected pores within the GC structure to open and substantially improves the wettability of the GC surface, which are both beneficial toward the improvement of the overall quality of the NPG deposit. It is demonstrated that thermochemical oxidation neither affects the efficiency of the Au_0.3Ag_0.7 alloy (NPG precursor) deposition nor hinders the achievement of continuity in the course of the NPG fabrication process. Furthermore, adhesion tests performed by a rotating disk electrode setup on deposits supported on thermochemically-oxidized and untreated GCs ascertain the enhanced adhesion on the thermochemically-oxidized samples. The best adhesion results are obtained on a continuous NPG layer fabricated on thermochemically-oxidized GC electrodes seeded with a dense network of Pd clusters. Full article

(This article belongs to the Special Issue Electrochemical Interfaces and Electrodeposition—In Honour of M. Luisa Foresti on the Occasion of Her Retirement)

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3397 KiB

Open AccessArticle

Fabrication of CdS/CdTe-Based Thin Film Solar Cells Using an Electrochemical Technique

by I. M. Dharmadasa, P. A. Bingham, O. K. Echendu, H. I. Salim, T. Druffel, R. Dharmadasa, G. U. Sumanasekera, R. R. Dharmasena, M. B. Dergacheva, K. A. Mit, K. A. Urazov, L. Bowen, M. Walls and A. Abbas

Coatings 2014, 4(3), 380-415; https://doi.org/10.3390/coatings4030380 - 27 Jun 2014

Cited by 102 | Viewed by 15981

Abstract

Thin film solar cells based on cadmium telluride (CdTe) are complex devices which have great potential for achieving high conversion efficiencies. Lack of understanding in materials issues and device physics slows down the rapid progress of these devices. This paper combines relevant results [...] Read more.

Thin film solar cells based on cadmium telluride (CdTe) are complex devices which have great potential for achieving high conversion efficiencies. Lack of understanding in materials issues and device physics slows down the rapid progress of these devices. This paper combines relevant results from the literature with new results from a research programme based on electro-plated CdS and CdTe. A wide range of analytical techniques was used to investigate the materials and device structures. It has been experimentally found that n-, i- and p-type CdTe can be grown easily by electroplating. These material layers consist of nano- and micro-rod type or columnar type grains, growing normal to the substrate. Stoichiometric materials exhibit the highest crystallinity and resistivity, and layers grown closer to these conditions show n → p or p → n conversion upon heat treatment. The general trend of CdCl₂ treatment is to gradually change the CdTe material’s n-type electrical property towards i-type or p-type conduction. This work also identifies a rapid structural transition of CdTe layer at 385 ± 5 °C and a slow structural transition at higher temperatures when annealed or grown at high temperature. The second transition occurs after 430 °C and requires more work to understand this gradual transition. This work also identifies the existence of two different solar cell configurations for CdS/CdTe which creates a complex situation. Finally, the paper presents the way forward with next generation CdTe-based solar cells utilising low-cost materials in their columnar nature in graded bandgap structures. These devices could absorb UV, visible and IR radiation from the solar spectrum and combine impact ionisation and impurity photovoltaic (PV) effect as well as making use of IR photons from the surroundings when fully optimised. Full article

(This article belongs to the Special Issue Novel Thin Film Materials for Photovoltaic Applications)

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Coatings, Volume 4, Issue 3 (September 2014) – 17 articles , Pages 380-700

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