Coatings

726 KiB

Open AccessReview

The Porter-Whitesides Discrepancy: Revisiting Odd-Even Effects in Wetting Properties of n-Alkanethiolate SAMs

by Zhengjia Wang, Jiahao Chen, Stephanie Oyola-Reynoso and Martin Thuo

Coatings 2015, 5(4), 1034-1055; https://doi.org/10.3390/coatings5041034 - 21 Dec 2015

Cited by 30 | Viewed by 9177

This review discusses the Porter-Whitesides discrepancy in wetting properties of n-alkanethiolate self-assembled monolayers (SAMs). About 25 years ago, Whitesides and coworker failed to observe any odd-even effect in wetting, however, Porter and his coworker did, albeit in select cases. Most previous studies agreed [...] Read more.

This review discusses the Porter-Whitesides discrepancy in wetting properties of n-alkanethiolate self-assembled monolayers (SAMs). About 25 years ago, Whitesides and coworker failed to observe any odd-even effect in wetting, however, Porter and his coworker did, albeit in select cases. Most previous studies agreed with Whitesides’ results, suggesting the absence of the odd-even effect in hydrophobicity of n-alkanethiolate SAMs. Recent reports have, however, found the odd-even effect in hydrophobicity of n-alkanethiolate SAMs on smooth substrates, indicating that hydrophobicity, and analogous interfacial properties, of n-alkanethiolate SAMs significantly depends on the properties of substrate. Unfortunately, the Whitesides and Porter papers do not report on the quality of the surfaces used. Based on recent work, we inferred that the original discrepancy between Whitesides and Porter can be attributed to the quality of the surface. Odd-even effect of SAMs in charge transport, capacitance, friction, and SAM structure are also discussed in this review to inform the general discussion. The discrepancy between Porter's group and Whitesides’ group could be due to surface roughness, morphology, oxidation, and adventitious contaminants. Full article

(This article belongs to the Special Issue Self-assembled Monolayers and Multilayers (SAMs/SAMTs) for Medicine and Dentistry)

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616 KiB

Open AccessArticle

UV-LED Curing Efficiency of Wood Coatings

by Véronic Landry, Pierre Blanchet, Gabrielle Boivin, Jean-François Bouffard and Mirela Vlad

Coatings 2015, 5(4), 1019-1033; https://doi.org/10.3390/coatings5041019 - 18 Dec 2015

Cited by 18 | Viewed by 9298

Abstract

Ultraviolet light emitting diodes (UV-LEDs) have attracted great interest in recent years. They can be used to polymerize coatings, such as those used for prefinished wood flooring. In this project, two lamps were compared for their suitability to be used on a wood [...] Read more.

Ultraviolet light emitting diodes (UV-LEDs) have attracted great interest in recent years. They can be used to polymerize coatings, such as those used for prefinished wood flooring. In this project, two lamps were compared for their suitability to be used on a wood flooring finishing line: a UV-microwave and a UV-LED lamp. Low heat emission was found for the UV-LED lamp compared to the UV-microwave one. This study also reveals that the 4 W/cm² UV-LED lamp used is not powerful enough to cure UV high solids acrylate coatings while satisfactory results can be obtained for UV water-based formulations. In fact, conversion percentages were found to be low for the high solids coatings, leaving the coatings tacky. Higher conversion percentages were obtained for the UV water-based formulations. As a result, mass loss, hardness, and scratch resistance found for the samples cured by UV-LED were closed to the ones found for the samples cured using the UV microwave lamp. Full article

(This article belongs to the Special Issue Coatings and Sustainability)

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3592 KiB

Open AccessReview

Revisiting the Challenges in Fabricating Uniform Coatings with Polyfunctional Molecules on High Surface Energy Materials

by Stephanie Oyola-Reynoso, Zhengjia Wang, Jiahao Chen, Simge Çınar, Boyce Chang and Martin Thuo

Coatings 2015, 5(4), 1002-1018; https://doi.org/10.3390/coatings5041002 - 18 Dec 2015

Cited by 22 | Viewed by 11354

Abstract

Modifying the chemistry of a surface has been widely used to influence interfacial properties of a material or nature of interaction between two materials. This article provides an overview on the role of polyfunctional molecules, specifically silanes, in surface modification of polar surfaces [...] Read more.

Modifying the chemistry of a surface has been widely used to influence interfacial properties of a material or nature of interaction between two materials. This article provides an overview on the role of polyfunctional molecules, specifically silanes, in surface modification of polar surfaces (bearing soft nucleophiles). An emphasis on the mechanism of the reaction in the presence of adsorbed water, where the modifying reagents are hydrolysable, is discussed. To highlight the complexity of the reaction, modification of paper with trichlorosilanes is highlighted. Preparation of hydrophobic cellulosic paper, and structure–property relations under different treatment conditions is used to highlight that a monolayer is not always formed during the surface modification. Gel-formation via step-growth polymerization suggests that at the right monomer:adsorbed water ratio, a monolayer will not form but rather self-assembly driven particle formation will occur leading to a textured surface. The review highlights recent work indicating that the focus on monolayer formation, is at the very least, not always the case but gel formation, with concomitant self-assembly, might be the culprit in understanding challenges associated with the use of polyfunctional molecules in surface modification. Full article

(This article belongs to the Special Issue Self-assembled Monolayers and Multilayers (SAMs/SAMTs) for Medicine and Dentistry)

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1300 KiB

Open AccessReview

Recent Progress in Gas Barrier Thin Film Coatings on PET Bottles in Food and Beverage Applications

by Masaki Nakaya, Akira Uedono and Atsushi Hotta

Coatings 2015, 5(4), 987-1001; https://doi.org/10.3390/coatings5040987 - 8 Dec 2015

Cited by 46 | Viewed by 12765

Abstract

This article presents a short history and the recent advancement of the development of chemical vapor deposition technologies to form thin film gas barrier coatings on PET bottles and other plastic containers in food and beverage containers. Among different gas barrier enhancement technologies, [...] Read more.

This article presents a short history and the recent advancement of the development of chemical vapor deposition technologies to form thin film gas barrier coatings on PET bottles and other plastic containers in food and beverage containers. Among different gas barrier enhancement technologies, coating can show unique performance where relatively high gas barrier enhancement is possible to various gas permeants. In this article, technologically common and different points of the current thin film coating methods in this field are summarized. This article also refers to recent market situations and technological challenges in the Japanese market. Full article

(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)

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265 KiB

Open AccessReview

Antifungal Edible Coatings for Fresh Citrus Fruit: A Review

by Lluís Palou, Silvia A. Valencia-Chamorro and María B. Pérez-Gago

Coatings 2015, 5(4), 962-986; https://doi.org/10.3390/coatings5040962 - 4 Dec 2015

Cited by 144 | Viewed by 23755

Abstract

According to their origin, major postharvest losses of citrus fruit are caused by weight loss, fungal diseases, physiological disorders, and quarantine pests. Cold storage and postharvest treatments with conventional chemical fungicides, synthetic waxes, or combinations of them are commonly used to minimize postharvest [...] Read more.

According to their origin, major postharvest losses of citrus fruit are caused by weight loss, fungal diseases, physiological disorders, and quarantine pests. Cold storage and postharvest treatments with conventional chemical fungicides, synthetic waxes, or combinations of them are commonly used to minimize postharvest losses. However, the repeated application of these treatments has led to important problems such as health and environmental issues associated with fungicide residues or waxes containing ammoniacal compounds, or the proliferation of resistant pathogenic fungal strains. There is, therefore, an increasing need to find non-polluting alternatives to be used as part of integrated disease management (IDM) programs for preservation of fresh citrus fruit. Among them, the development of novel natural edible films and coatings with antimicrobial properties is a technological challenge for the industry and a very active research field worldwide. Chitosan and other edible coatings formulated by adding antifungal agents to composite emulsions based on polysaccharides or proteins and lipids are reviewed in this article. The most important antifungal ingredients are selected for their ability to control major citrus postharvest diseases like green and blue molds, caused by Penicillium digitatum and Penicillium italicum, respectively, and include low-toxicity or natural chemicals such as food additives, generally recognized as safe (GRAS) compounds, plant extracts, or essential oils, and biological control agents such as some antagonistic strains of yeasts or bacteria. Full article

(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)

780 KiB

Open AccessReview

Non-Conventional Tools to Preserve and Prolong the Quality of Minimally-Processed Fruits and Vegetables

by Maria Rosaria Corbo, Daniela Campaniello, Barbara Speranza, Antonio Bevilacqua and Milena Sinigaglia

Coatings 2015, 5(4), 931-961; https://doi.org/10.3390/coatings5040931 - 26 Nov 2015

Cited by 34 | Viewed by 10554

Abstract

The main topic of this paper is a focus on some non-conventional tools to preserve the microbiological and physico-chemical quality of fresh-cut fruits and vegetables. The quality of fresh-cut foods is the result of a complex equilibrium involving surface microbiota, storage temperature, gas [...] Read more.

The main topic of this paper is a focus on some non-conventional tools to preserve the microbiological and physico-chemical quality of fresh-cut fruits and vegetables. The quality of fresh-cut foods is the result of a complex equilibrium involving surface microbiota, storage temperature, gas in the headspace and the use of antimicrobials. This paper proposes a short overview of some non-conventional approaches able to preserve the quality of this kind of product, with a special focus on some new ways, as follows: (1) use of edible or antimicrobial-containing coatings (e.g., chitosan-based coatings) on fruits or vegetables; (2) alternative modified atmospheres (e.g., high O₂-modified atmosphere packaging (MAP)) or the use of essential oils in the headspace; (3) conditioning solutions with antimicrobials or natural compounds for fruit salad; and (4) biopreservation and use of a probiotic coating. Full article

(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)

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2704 KiB

Open AccessReview

Bio-Based Coatings for Paper Applications

by Vibhore Kumar Rastogi and Pieter Samyn

Coatings 2015, 5(4), 887-930; https://doi.org/10.3390/coatings5040887 - 20 Nov 2015

Cited by 274 | Viewed by 56408

Abstract

The barrier resistance and wettability of papers are commonly controlled by the application of petroleum-based derivatives such as polyethylene, waxes and/or fluor- derivatives as coating. While surface hydrophobicity is improved by employing these polymers, they have become disfavored due to limitations in fossil-oil [...] Read more.

The barrier resistance and wettability of papers are commonly controlled by the application of petroleum-based derivatives such as polyethylene, waxes and/or fluor- derivatives as coating. While surface hydrophobicity is improved by employing these polymers, they have become disfavored due to limitations in fossil-oil resources, poor recyclability, and environmental concerns on generated waste with lack of biodegradation. Alternatively, biopolymers including polysaccharides, proteins, lipids and polyesters can be used to formulate new pathways for fully bio-based paper coatings. However, difficulties in processing of most biopolymers may arise due to hydrophilicity, crystallization behavior, brittleness or melt instabilities that hinder a full exploitation at industrial scale. Therefore, blending with other biopolymers, plasticizers and compatibilizers is advantageous to improve the coating performance. In this paper, an overview of barrier properties and processing of bio-based polymers and their composites as paper coating will be discussed. In particular, recent technical advances in nanotechnological routes for bio-based nano- composite coatings will be summarized, including the use of biopolymer nanoparticles, or nanofillers such as nanoclay and nanocellulose. The combination of biopolymers along with surface modification of nanofillers can be used to create hierarchical structures that enhance hydrophobicity, complete barrier protection and functionalities of coated papers. Full article

(This article belongs to the Special Issue Coatings and Sustainability)

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293 KiB

Open AccessReview

Natural Pectin Polysaccharides as Edible Coatings

by Arantzazu Valdés, Nuria Burgos, Alfonso Jiménez and María Carmen Garrigós

Coatings 2015, 5(4), 865-886; https://doi.org/10.3390/coatings5040865 - 16 Nov 2015

Cited by 175 | Viewed by 20258

Abstract

The most fashionable trends in food packaging research are targeted towards improvements in food quality and safety by increasing the use of environmentally-friendly materials, ideally those able to be obtained from bio-based resources and presenting biodegradable characteristics. Edible films represent a key area [...] Read more.

The most fashionable trends in food packaging research are targeted towards improvements in food quality and safety by increasing the use of environmentally-friendly materials, ideally those able to be obtained from bio-based resources and presenting biodegradable characteristics. Edible films represent a key area of development in new multifunctional materials by their character and properties to effectively protect food with no waste production. The use of edible films should be considered as a clean and elegant solution to problems related with waste disposal in packaging materials. In particular, pectin has been reported as one of the main raw materials to obtain edible films by its natural abundance, low cost and renewable character. The latest innovations in food packaging by the use of pectin-based edible films are reviewed in this paper, with special focus on the use of pectin as base material for edible coatings. The structure, properties related to the intended use in food packaging and main applications of pectins are herein reported. Full article

(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)

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3698 KiB

Open AccessReview

The Search for Durable Exterior Clear Coatings for Wood

by Philip D. Evans, Jonathan G. Haase, A. Shakri B.M. Seman and Makoto Kiguchi

Coatings 2015, 5(4), 830-864; https://doi.org/10.3390/coatings5040830 - 12 Nov 2015

Cited by 87 | Viewed by 17339

Abstract

The goal of a durable exterior clear coating has eluded generations of coatings technologists, despite long-standing desire amongst the public for such a coating. The journey towards this goal initially focused on modifications to coating formulation, but took a completely different direction when [...] Read more.

The goal of a durable exterior clear coating has eluded generations of coatings technologists, despite long-standing desire amongst the public for such a coating. The journey towards this goal initially focused on modifications to coating formulation, but took a completely different direction when it was found that a UV-transparent silicone clear coating on wood modified with chromic acid met consumer expectations of coating durability. This finding sparked world-wide interest in wood pre-treatments as a way of enhancing the durability of clear coatings. This interest initially focused on transition metal compounds, but has now shifted in the direction of organic and inorganic photostabilizers or even more drastic pre-treatments. Pre-treatments that dimensionally stabilize wood, protect it from microbial degradation and photostabilize lignin, when combined with flexible, photostable, coatings provide the next way-stop on the journey towards achieving the goal of durable exterior clear coatings for wood. This paper reviews this journey, drawing upon our research and that of other groups who have focused on this elusive goal. Full article

(This article belongs to the Special Issue Wood Coatings)

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1390 KiB

Open AccessArticle

Natural Deposit Coatings on Steel during Cathodic Protection and Hydrogen Ingress

by Wayne R. Smith and Shiladitya Paul

Coatings 2015, 5(4), 816-829; https://doi.org/10.3390/coatings5040816 - 12 Nov 2015

Cited by 17 | Viewed by 6938

Abstract

The calcareous coating formed during cathodic protection (CP) in seawater is known to reduce the current demand by hindering the transport of species required to support the cathodic reactions and, thereby, improve the economic performance of CP systems. There is, however, uncertainty as [...] Read more.

The calcareous coating formed during cathodic protection (CP) in seawater is known to reduce the current demand by hindering the transport of species required to support the cathodic reactions and, thereby, improve the economic performance of CP systems. There is, however, uncertainty as to whether the coating reduces hydrogen uptake or indeed enhances it. To ascertain this, two sets of samples were polarized at −1.1 V (standard calomel electrode, SCE) in 3.5% w/v NaCl and synthetic seawater (ASTM D1141) at 20 °C and the diffusible hydrogen content measured over a period of 530 h. Under such conditions reports suggest a deposit with two distinct layers, comprising an initial brucite layer followed by an aragonite layer. Contrary to other findings, a fine initial layer containing Ca and Mg followed by a brucite layer was deposited with a few specks of Ca-containing zones in synthetic seawater. The hydrogen uptake was found to occur within the initial 100 h of exposure in synthetic seawater whilst it continued without the benefit of a deposit coating, i.e., in 3.5 wt % NaCl solution. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)

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2195 KiB

Open AccessArticle

On the Novel Biaxial Strain Relaxation Mechanism in Epitaxial Composition Graded La1−_xSr_xMnO₃ Thin Film Synthesized by RF Magnetron Sputtering

by Yishu Wang, Minghui Zhang and Efstathios I. Meletis

Coatings 2015, 5(4), 802-815; https://doi.org/10.3390/coatings5040802 - 11 Nov 2015

Cited by 2 | Viewed by 6165

Abstract

We report on a novel method to fabricate composition gradient, epitaxial La1−_xSr_xMnO₃ thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La1−_xSr_xMnO₃, and pure LaMnO3 [...] Read more.

We report on a novel method to fabricate composition gradient, epitaxial La1−_xSr_xMnO₃ thin films with the objective to alleviate biaxial film strain. In this work, epitaxial, composition gradient La1−_xSr_xMnO₃, and pure LaMnO3 and La_0.67Sr_0.33MnO₃ thin films were deposited by radio frequency (RF) magnetron sputtering. The crystalline and epitaxy of all films were first studied by symmetric θ–2θ X-ray diffraction (XRD) and low angle XRD experiments. Detailed microstructural characterization across the film thickness was conducted by high-resolution transmission electron microscopy and electron diffraction. Four compositional gradient domains were observed in the La1−_xSr_xMnO₃film ranging from LaMnO3 rich to La_0.67Sr_0.33MnO₃ at the surface. A continuous reduction in the lattice parameter was observed accompanied by a significant reduction in the out-of-plane strain in the film. Fabrication of the composition gradient La1−_xSr_xMnO₃ thin film was found to be a powerful method to relieve biaxial strain under critical thickness. Besides, the coexistence of domains with a composition variance is opening up various new possibilities of designing new nanoscale structures with unusual cross coupled properties. Full article

(This article belongs to the Special Issue Recent Aspects of Thin Films Deposited by Magnetron Sputtering and Emerging Applications)

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1693 KiB

Open AccessReview

Coating Acetylated Wood

by Roger Rowell and Ferry Bongers

Coatings 2015, 5(4), 792-801; https://doi.org/10.3390/coatings5040792 - 6 Nov 2015

Cited by 18 | Viewed by 6843

Abstract

Wood exposed to the outdoor environment is susceptible to weathering due to a series of chemical, biological and physical processes. Acetylation of wood is known to reduce cell wall moisture content, improve dimensional stability and durability against fungal decay. As a result of [...] Read more.

Wood exposed to the outdoor environment is susceptible to weathering due to a series of chemical, biological and physical processes. Acetylation of wood is known to reduce cell wall moisture content, improve dimensional stability and durability against fungal decay. As a result of these improvements, less stress is created between the coating and the wood surface improving the performance of the coating and increasing its useful lifetime. This paper is a review of research done on the chemistry of the acetylation process, the coating performance of acetylated wood and concentrates on the factors influencing coating performance. Full article

(This article belongs to the Special Issue Wood Coatings)

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476 KiB

Open AccessReview

Active Packaging Coatings

by Luis J. Bastarrachea, Dana E. Wong, Maxine J. Roman, Zhuangsheng Lin and Julie M. Goddard

Coatings 2015, 5(4), 771-791; https://doi.org/10.3390/coatings5040771 - 6 Nov 2015

Cited by 132 | Viewed by 18000 | Correction

Abstract

Active food packaging involves the packaging of foods with materials that provide an enhanced functionality, such as antimicrobial, antioxidant or biocatalytic functions. This can be achieved through the incorporation of active compounds into the matrix of the commonly used packaging materials, or by [...] Read more.

Active food packaging involves the packaging of foods with materials that provide an enhanced functionality, such as antimicrobial, antioxidant or biocatalytic functions. This can be achieved through the incorporation of active compounds into the matrix of the commonly used packaging materials, or by the application of coatings with the corresponding functionality through surface modification. The latter option offers the advantage of preserving the packaging materials’ bulk properties nearly intact. Herein, different coating technologies like embedding for controlled release, immobilization, layer-by-layer deposition, and photografting are explained and their potential application for active food packaging is explored and discussed. Full article

(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)

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1825 KiB

Open AccessArticle

Synthesis of a pH- and Thermo- Responsive Binary Copolymer Poly(N-vinylimidazole-co-N-vinylcaprolactam) Grafted onto Silicone Films

by Ángela Obando-Mora, Claudia A. Acevedo-Gutiérrez, Jesica G Pérez-Cinencio, Francis S. Sánchez-Garzón and Emilio Bucio

Coatings 2015, 5(4), 758-770; https://doi.org/10.3390/coatings5040758 - 30 Oct 2015

Cited by 5 | Viewed by 6395

Abstract

This work focuses on the effects of gamma-ray irradiation conditions on the stimuli-responsiveness of silicone rubber (SR) substrates grafted with N-vinylcaprolactam (NVCL) and N-vinylimidazole (NVIM), modified by the simultaneously polymerization and grafting method, which is expected to result in valuable new applications in [...] Read more.

This work focuses on the effects of gamma-ray irradiation conditions on the stimuli-responsiveness of silicone rubber (SR) substrates grafted with N-vinylcaprolactam (NVCL) and N-vinylimidazole (NVIM), modified by the simultaneously polymerization and grafting method, which is expected to result in valuable new applications in the near future. The modification of silicone rubber was carried out via γ-ray radiation in order to graft a binary copolymer, poly(N-vinylimidazole-co-N-vinylcaprolactam), by the pre-irradiation method, to obtain pH- and thermo-responsive materials. The grafting yield was found to be directly proportional to the dose and monomers concentration. The biomaterials were characterized by using Fourier-transform infrared attenuated total reflection (FTIR-ATR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and swelling; and their stimuli behavior was evaluated by lower critical solution temperature (LCST) and pH critical studies. Full article

(This article belongs to the Special Issue Self-assembled Monolayers and Multilayers (SAMs/SAMTs) for Medicine and Dentistry)

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5308 KiB

Open AccessReview

Novel Development of Biocompatible Coatings for Bone Implants

by Nicholas Yue Hou, Hiran Perinpanayagam, Mohammad Sayem Mozumder and Jesse Zhu

Coatings 2015, 5(4), 737-757; https://doi.org/10.3390/coatings5040737 - 30 Oct 2015

Cited by 26 | Viewed by 8105

Abstract

Prolonged life expectancy also results in an increased need for high-performance orthopedic implants. It has been shown that a compromised tissue-implant interface could lead to adverse immune-responses and even the dislodging of the implant. To overcome these obstacles, our research team has been [...] Read more.

Prolonged life expectancy also results in an increased need for high-performance orthopedic implants. It has been shown that a compromised tissue-implant interface could lead to adverse immune-responses and even the dislodging of the implant. To overcome these obstacles, our research team has been seeking ways to decrease the risk of faulty tissue-implant interfaces by improving the biocompatibility and the osteo-inductivity of conventional orthopedic implants using ultrafine particle coatings. These particles were enriched with various bioactive additives prior to coating, and the coated biomaterial surfaces exhibited significantly increased biocompatibility and osteoinductivity. Physical assessments firstly confirmed the proper incorporation of the bioactive additives after examining their surface chemical composition. Then, in vitro assays demonstrated the biocompatibility and osteo-inductivity of the coated surfaces by studying the morphology of attached cells and their mineralization abilities. In addition, by quantifying the responses, activities and gene expressions, cellular evaluations confirmed the positive effects of these polymer based bioactive coatings. Consequently, the bioactive ultrafine polymer particles demonstrated their ability in improving the biocompatibility and osteo-inductivity of conventional orthopedic implants. As a result, our research team hope to apply this technology to the field of orthopedic implants by making them more effective medical devices through decreasing the risk of implant-induced immune responses and the loosening of the implant. Full article

(This article belongs to the Special Issue Advanced Biomimetic Calcium Phosphate Coatings)

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1788 KiB

Open AccessArticle

Reversible Switching of Icing Properties on Pyroelectric Polyvenylidene Fluoride Thin Film Coatings

by Dirk Spitzner, Ute Bergmann, Sabine Apelt, Richard A. Boucher and Hans-Peter Wiesmann

Coatings 2015, 5(4), 724-736; https://doi.org/10.3390/coatings5040724 - 20 Oct 2015

Cited by 15 | Viewed by 6650

Abstract

In this work a new approach for ice repellent coatings is presented. It was shown that the coatings cause a decrease or increase in the freezing temperature of water depending on the alignment of an external electric field. For this coating the commonly [...] Read more.

In this work a new approach for ice repellent coatings is presented. It was shown that the coatings cause a decrease or increase in the freezing temperature of water depending on the alignment of an external electric field. For this coating the commonly used pyroelectric polymer polyvenylidene fluoride was deposited as a thin film on glass. The samples were dip-coated and subsequently thermally-treated at 140 °C for 1 h. All samples were found to cause a reduction of the icing temperature of water on their surface in comparison to uncoated glass. On several samples an external electric field was applied during this thermal treatment. The field application was found to cause a remarkable reduction of the icing temperature where a maximum lowering of the freezing temperature of 3 K compared to uncoated glass could be achieved. The actual achieved reduction of the icing temperature was observed to depend on the polarity of the field applied during the thermal treatment. Furthermore, a repetition of the thermal treatment under oppositely directed electric fields led to a switchable freezing behavior of water according to the direction of the applied field. With an increasing number of cycles of switching of the icing property a slight training effect towards lower freezing temperatures was observed. Full article

(This article belongs to the Special Issue Anti-Icing Coatings and Surfaces)

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2382 KiB

Open AccessArticle

Tailoring a High Temperature Corrosion Resistant FeNiCrAl for Oxy-Combustion Application by Thermal Spray Coating and HIP

by Jarkko Metsäjoki, Maria Oksa, Satu Tuurna, Juha Lagerbom, Jouko Virta, Sanni Yli-Olli and Tomi Suhonen

Coatings 2015, 5(4), 709-723; https://doi.org/10.3390/coatings5040709 - 16 Oct 2015

Cited by 6 | Viewed by 6694

Abstract

Oxy-fuel combustion combined with CCS (carbon capture and storage) aims to decrease CO₂ emissions in energy production using fossil fuels. Oxygen firing changes power plant boiler conditions compared to conventional firing. Higher material temperatures and harsher and more variable environmental conditions cause [...] Read more.

Oxy-fuel combustion combined with CCS (carbon capture and storage) aims to decrease CO₂ emissions in energy production using fossil fuels. Oxygen firing changes power plant boiler conditions compared to conventional firing. Higher material temperatures and harsher and more variable environmental conditions cause new degradation processes that are inadequately understood at the moment. In this study, an Fe-Ni-Cr-Al alloy was developed based on thermodynamic simulations. The chosen composition was manufactured as powder by gas atomization. The powder was sieved into two fractions: The finer was used to produce thermal spray coatings by high velocity oxy-fuel (HVOF) and the coarser to manufacture bulk specimens by hot isostatic pressing (HIP). The high temperature corrosion properties of the manufactured FeNiCrAl coating and bulk material were tested in laboratory conditions simulating oxy-combustion. The manufacturing methods and the results of high temperature corrosion performance are presented. The corrosion performance of the coating was on average between the bulk steel references Sanicro 25 and TP347HFG. Full article

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2587 KiB

Open AccessArticle

Development of 3D Multicomponent Model for Cold Spray Process Using Nitrogen and Air

by Muhammad Faizan Ur Rab, Saden Zahiri, Syed H. Masood, Mahnaz Jahedi and Romesh Nagarajah

Coatings 2015, 5(4), 688-708; https://doi.org/10.3390/coatings5040688 - 16 Oct 2015

Cited by 17 | Viewed by 9741

Abstract

Cold spray is a unique coating technology that allows for solid state deposition of particles under atmospheric pressure. In this paper, a three dimensional, Computational Fluid Dynamics (CFD) multicomponent model is developed to estimate cold spray gas conditions involving both nitrogen and air. [...] Read more.

Cold spray is a unique coating technology that allows for solid state deposition of particles under atmospheric pressure. In this paper, a three dimensional, Computational Fluid Dynamics (CFD) multicomponent model is developed to estimate cold spray gas conditions involving both nitrogen and air. Calibration of the model followed by validation is accomplished by considering the thermal history of substrate exposed to cold spray supersonic jet. The developed holistic multicomponent model is effective in determining the state of gas and particles from injection point to the substrate surface with the advantage of optimizing very rapid cold spray deposition in nanoseconds. The validation of k-ε type CFD multicomponent model is done by using the temperature measured for a titanium substrate exposed to cold spray nitrogen at 800 °C and 3 MPa. Heat transfer and radiation are considered for the de Laval nozzle used in cold spray experiments. The calibrated multicomponent model has successfully estimated the state of propellant gas for the chosen high pressure and high temperature cold spray conditions. Moreover, the multicomponent model predictions are in good agreement with a previous holistic three dimensional cold spray model in which only nitrogen was used as the surrounding as well as the propellant gas. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)

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1265 KiB

Open AccessReview

Molybdenum Nitride Films: Crystal Structures, Synthesis, Mechanical, Electrical and Some Other Properties

by Isabelle Jauberteau, Annie Bessaudou, Richard Mayet, Julie Cornette, Jean Louis Jauberteau, Pierre Carles and Thérèse Merle-Méjean

Coatings 2015, 5(4), 656-687; https://doi.org/10.3390/coatings5040656 - 13 Oct 2015

Cited by 113 | Viewed by 19722

Abstract

Among transition metal nitrides, molybdenum nitrides have been much less studied even though their mechanical properties as well as their electrical and catalytic properties make them very attractive for many applications. The δ-MoN phase of hexagonal structure is a potential candidate for an [...] Read more.

Among transition metal nitrides, molybdenum nitrides have been much less studied even though their mechanical properties as well as their electrical and catalytic properties make them very attractive for many applications. The δ-MoN phase of hexagonal structure is a potential candidate for an ultra-incompressible and hard material and can be compared with c-BN and diamond. The predicted superconducting temperature of the metastable MoN phase of NaCl-B1-type cubic structure is the highest of all refractory carbides and nitrides. The composition of molybdenum nitride films as well as the structures and properties depend on the parameters of the process used to deposit the films. They are also strongly correlated to the electronic structure and chemical bonding. An unusual mixture of metallic, covalent and ionic bonding is found in the stoichiometric compounds. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology—Feature Papers)

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768 KiB

Open AccessArticle

Fabrication and Characterization of a Perovskite-Type Solar Cell with a Substrate Size of 70 mm

by Takeo Oku, Taisuke Matsumoto, Atsushi Suzuki and Kohei Suzuki

Coatings 2015, 5(4), 646-655; https://doi.org/10.3390/coatings5040646 - 13 Oct 2015

Cited by 24 | Viewed by 10811

Abstract

A perovskite-type solar cell with a substrate size of 70 mm × 70 mm was fabricated by a simple spin-coating method using a mixed solution. The photovoltaic properties of the TiO₂/CH₃NH₃PbI₃-based photovoltaic devices were investigated [...] Read more.

A perovskite-type solar cell with a substrate size of 70 mm × 70 mm was fabricated by a simple spin-coating method using a mixed solution. The photovoltaic properties of the TiO₂/CH₃NH₃PbI₃-based photovoltaic devices were investigated by current density-voltage characteristic and incident photon to current conversion efficiency measurements. Their short-circuit current densities were almost constant over a large area. The photoconversion efficiency was influenced by the open-circuit voltage, which depended on the distance from the center of the cell. Full article

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

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Open AccessReview

A Comprehensive Review on Fluid Dynamics and Transport of Suspension/Liquid Droplets and Particles in High-Velocity Oxygen-Fuel (HVOF) Thermal Spray

by Mehdi Jadidi, Sara Moghtadernejad and Ali Dolatabadi

Coatings 2015, 5(4), 576-645; https://doi.org/10.3390/coatings5040576 - 13 Oct 2015

Cited by 65 | Viewed by 16654

Abstract

In thermal spraying processes, molten, semi-molten, or solid particles, which are sufficiently fast in a stream of gas, are deposited on a substrate. These particles can plastically deform while impacting on the substrate, which results in the formation of well-adhered and dense coatings. [...] Read more.

In thermal spraying processes, molten, semi-molten, or solid particles, which are sufficiently fast in a stream of gas, are deposited on a substrate. These particles can plastically deform while impacting on the substrate, which results in the formation of well-adhered and dense coatings. Clearly, particles in flight conditions, such as velocity, trajectory, temperature, and melting state, have enormous influence on the coating properties and should be well understood to control and improve the coating quality. The focus of this study is on the high velocity oxygen fuel (HVOF) spraying and high velocity suspension flame spraying (HVSFS) techniques, which are widely used in academia and industry to generate different types of coatings. Extensive numerical and experimental studies were carried out and are still in progress to estimate the particle in-flight behavior in thermal spray processes. In this review paper, the fundamental phenomena involved in the mentioned thermal spray techniques, such as shock diamonds, combustion, primary atomization, secondary atomization, etc., are discussed comprehensively. In addition, the basic aspects and emerging trends in simulation of thermal spray processes are reviewed. The numerical approaches such as Eulerian-Lagrangian and volume of fluid along with their advantages and disadvantages are explained in detail. Furthermore, this article provides a detailed review on simulation studies published to date. Full article

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Coatings, Volume 5, Issue 4 (December 2015) – 21 articles , Pages 576-1055

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