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Coatings, Volume 7, Issue 11 (November 2017)

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Cover Story We developed the functional edible film by incorporating borage seed oil (BO) into barnyard millet [...] Read more.
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Open AccessArticle Evolution of Nanostructure and Metastable Phases at the Surface of a HCPEB-Treated WC-6% Co Hard Alloy with Increasing Irradiation Pulse Numbers
Coatings 2017, 7(11), 178; doi:10.3390/coatings7110178
Received: 30 July 2017 / Revised: 7 October 2017 / Accepted: 17 October 2017 / Published: 26 October 2017
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Abstract
This work investigates the mechanisms of the microstructure evolution in the melted surface layers of a WC-6% Co hard alloy when increasing the number of pulses of irradiation by high-current pulsed electron beam (HCPEB) treatment. After one pulse of irradiation, about 50% of
[...] Read more.
This work investigates the mechanisms of the microstructure evolution in the melted surface layers of a WC-6% Co hard alloy when increasing the number of pulses of irradiation by high-current pulsed electron beam (HCPEB) treatment. After one pulse of irradiation, about 50% of the stable hcp WC phase was melted and resolidified into the metastable fcc form (WC1−x). When increasing the numbers of pulse irradiation, the WC phase decomposed into ultrafine-grained WC1−x plus nanosized graphite under our selected energy condition. Because of the rapidity of HCPEB carried under vacuum, the formation of the brittle W2C phase was avoided. In the initial Co-rich areas, where the Co was evaporated, melting and solidification led to the formation of nanostructures Co3W9C4 and Co3W3C. The volume fraction of the nano domains containing WC1−x, Co3W9C4, and Co3W3C phases reached its maximum after 20 pulses of irradiation. The improved properties after 20 pulses are therefore due to the presence of nano graphite that served as lubricant and dramatically decreased the friction coefficient, while the ultrafine-grained carbides and the nano domains contribute to the improvement of the surface microhardness and wear resistance. Full article
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Open AccessArticle Aluminum Templates of Different Sizes with Micro-, Nano- and Micro/Nano-Structures for Cell Culture
Coatings 2017, 7(11), 179; doi:10.3390/coatings7110179
Received: 23 August 2017 / Revised: 19 October 2017 / Accepted: 20 October 2017 / Published: 26 October 2017
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Abstract
This study investigates the results of cell cultures on aluminum (Al) templates with flat-structures, micro-structures, nano-structures and micro/nano-structures. An Al template with flat-structure was obtained by electrolytic polishing; an Al template with micro-structure was obtained by micro-powder blasting; an Al template with nano-structure
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This study investigates the results of cell cultures on aluminum (Al) templates with flat-structures, micro-structures, nano-structures and micro/nano-structures. An Al template with flat-structure was obtained by electrolytic polishing; an Al template with micro-structure was obtained by micro-powder blasting; an Al template with nano-structure was obtained by aluminum anodization; and an Al template with micro/nano-structure was obtained by micro-powder blasting and then anodization. Osteoblast-like cells were cultured on aluminum templates with various structures. The microculture tetrazolium test assay was utilized to assess the adhesion, elongation, and proliferation behaviors of cultured osteoblast-like cells on aluminum templates with flat-structures, micro-structures, nano-structures, and micro/nano-structures. The results showed that the surface characterization of micro/nano-structure of aluminum templates had superhydrophilic property, and these also revealed that an aluminum template with micro/nano-structure could provide the most suitable growth situation for cell culture. Full article
(This article belongs to the Special Issue Surface Engineering of Biomaterials)
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Open AccessArticle Evaluation of Accelerated Ageing Tests for Metallic and Non-Metallic Graffiti Paints Applied to Stone
Coatings 2017, 7(11), 180; doi:10.3390/coatings7110180
Received: 22 September 2017 / Revised: 23 October 2017 / Accepted: 27 October 2017 / Published: 30 October 2017
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Abstract
Graffiti are increasingly observed on urban and peri-urban buildings and their removal requires a huge financial outlay by local governments and agencies. Graffiti are not usually removed immediately, but rather over the passage of time, viz. months or even years. In this study,
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Graffiti are increasingly observed on urban and peri-urban buildings and their removal requires a huge financial outlay by local governments and agencies. Graffiti are not usually removed immediately, but rather over the passage of time, viz. months or even years. In this study, which forms part of a wider research project on graffiti removal, different methods (gravimetric analysis, examination of digital images, colour and infrared measurements) were used to evaluate the performance of accelerated ageing tests (involving exposure to humidity, freeze-thawing cycles and NaCl and Na2SO4 salts) for graffiti painted on stone. Silver (metallic) and black (non-metallic) graffiti spray paints were applied to two types of igneous rock (granite and rhyolitic ignimbrite) and one sedimentary rock (fossiliferous limestone, i.e., biocalcarenite). The metallic and non-metallic graffiti spray paints acted differently on the stone surfaces, both chemically and physically. Older graffiti were found to be more vulnerable to weathering agents. The ageing test with NaCl and particularly Na2SO4, both applied to granite, proved the most severe on the paints, yielding more detrimental and faster artificial ageing of the type of material under study. Full article
(This article belongs to the Special Issue Anti-Graffiti Coatings)
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Open AccessArticle Inhibitory Properties of Neomycin Thin Film Formed on Carbon Steel in Sulfuric Acid Solution: Electrochemical and AFM Investigation
Coatings 2017, 7(11), 181; doi:10.3390/coatings7110181
Received: 11 August 2017 / Revised: 9 October 2017 / Accepted: 25 October 2017 / Published: 31 October 2017
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Abstract
Our study aims to implement a strategy to reduce the carbon steel corrosion rate in a sulfuric acid solution, using an expired drug with adsorption affinity on the metal surface. To investigate the corrosion protection efficiency of an environmental friendly inhibitor, namely neomycin
[...] Read more.
Our study aims to implement a strategy to reduce the carbon steel corrosion rate in a sulfuric acid solution, using an expired drug with adsorption affinity on the metal surface. To investigate the corrosion protection efficiency of an environmental friendly inhibitor, namely neomycin sulfate (NMS), the electrochemical measurements were applied on carbon steel immersed in 1.0 M H2SO4 solution with and without NMS. The protective layer that formed on the steel surface was studied by atomic force microscopy (AFM). The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) showed that the presence of the neomycin sulfate in acid solution leads to the decrease in corrosion current density (icorr) and the increase of polarization resistance (Rp). The mixed mechanism between physical and chemical adsorption of NMS molecules on the steel surface was proposed according to the Langmuir adsorption isotherm. AFM indicated that the NMS molecules contributed to a protective layer formation by their adsorption on the steel surface. The AFM parameters, such as root mean square roughness (Rq), average roughness (Ra), and maximum peak to valley height (Rp−v) revealed that in the presence of NMS a smoother surface of carbon steel was obtained, compared to the steel surface corroded in sulfuric acid blank solution. Full article
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Open AccessArticle Microwave-Assisted Dip Coating of Aloe Vera on Metallocene Polyethylene Incorporated with Nano-Rods of Hydroxyapaptite for Bone Tissue Engineering
Coatings 2017, 7(11), 182; doi:10.3390/coatings7110182
Received: 18 August 2017 / Revised: 13 October 2017 / Accepted: 14 October 2017 / Published: 31 October 2017
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Abstract
Bone tissue engineering widely explores the use of ceramic reinforced polymer-matrix composites. Among the various widely-used ceramic reinforcements, hydroxyapatite is an undisputed choice due to its inherent osteoconductive nature. In this study, a novel nanocomposite comprising metallocene polyethylene (mPE) incorporated with nano-hydroxyapaptite nanorods
[...] Read more.
Bone tissue engineering widely explores the use of ceramic reinforced polymer-matrix composites. Among the various widely-used ceramic reinforcements, hydroxyapatite is an undisputed choice due to its inherent osteoconductive nature. In this study, a novel nanocomposite comprising metallocene polyethylene (mPE) incorporated with nano-hydroxyapaptite nanorods (mPE-nHA) was synthesized and dip coated with Aloe vera after subjecting it to microwave treatment. The samples were characterized using contact angle, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), atomic force microscopy (AFM) and 3D Hirox microscopy scanning. Contact angle results show that the hydrophilicity of mPE-nHA improved notably with the coating of Aloe vera. The surface topology and increase in surface roughness were observed using the SEM, AFM and 3D Hirox microscopy. Blood compatibility assays of pure mPE and the Aloe vera coated nanocomposite were performed. The prothrombin time (PT) was delayed by 1.06% for 24 h Aloe-vera-treated mPE-nHA compared to the pristine mPE-nHA. Similarly, the 24 h Aloe-vera-coated mPE-nHA nanocomposite prolonged the activated partial thromboplastin time (APTT) by 41 s against the control of pristine mPE-nHA. The hemolysis percentage was also found to be the least for the 24 h Aloe-vera-treated mPE-nHA which was only 0.2449% compared to the pristine mPE-nHA, which was 2.188%. To conclude, this novel hydroxyapatite-reinforced, Aloe-vera-coated mPE with a better mechanical and anti-thrombogenic nature may hold a great potential to be exploited for bone tissue engineering applications. Full article
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Open AccessArticle Characterization of Barnyard Millet Starch Films Containing Borage Seed Oil
Coatings 2017, 7(11), 183; doi:10.3390/coatings7110183
Received: 22 September 2017 / Revised: 31 October 2017 / Accepted: 31 October 2017 / Published: 1 November 2017
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Abstract
In this study, barnyard millet starch (BMS) was used to prepare edible films. Antioxidant activity was conferred to the BMS film by incorporating borage seed oil (BO). The physical, optical, and thermal properties as well as antioxidant activities of the films were evaluated.
[...] Read more.
In this study, barnyard millet starch (BMS) was used to prepare edible films. Antioxidant activity was conferred to the BMS film by incorporating borage seed oil (BO). The physical, optical, and thermal properties as well as antioxidant activities of the films were evaluated. The incorporation of BO into the BMS films decreased the tensile strength from 9.46 to 4.69 MPa and increased the elongation at break of the films from 82.49% to 103.87%. Water vapor permeability, water solubility, and moisture content of the BMS films decreased with increasing BO concentration, whereas Hunter b value and opacity increased, L and a values of the films decreased. The BMS films containing BO exhibited antioxidant activity that increased proportionally with increased BO concentration. In particular, the BMS film with 1.0% BO exhibited the highest antioxidant activity and light barrier properties among the BMS films. Therefore, the BMS films with added BO can be used as an antioxidant packaging material. Full article
(This article belongs to the Special Issue Edible Films and Coatings)
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Open AccessArticle Biodegradable Ceramics Consisting of Hydroxyapatite for Orthopaedic Implants
Coatings 2017, 7(11), 184; doi:10.3390/coatings7110184
Received: 11 September 2017 / Revised: 20 October 2017 / Accepted: 27 October 2017 / Published: 3 November 2017
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Abstract
This study aims to analyze hydroxyapatite (HAP) coatings enriched with Mg and Ti prepared by a magnetron sputtering technique on Ti6Al4V substrate. For preparation of the coatings, three magnetron targets (HAP, MgO and TiO2) were simultaneously co-worked. The concentration of Mg
[...] Read more.
This study aims to analyze hydroxyapatite (HAP) coatings enriched with Mg and Ti prepared by a magnetron sputtering technique on Ti6Al4V substrate. For preparation of the coatings, three magnetron targets (HAP, MgO and TiO2) were simultaneously co-worked. The concentration of Mg added was varied by modifying the power applied to the MgO target. In all coatings, the Ti concentration was maintained constant by keeping the same cathode power fed during the whole deposition. The influence of different Mg dopant contents on the formation of phase, microstructure and morphology of the obtained Ti-doped HAP coatings were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Moreover, the effects of Mg addition upon corrosion, mechanical and biological properties were also investigated. Mg- and Ti-doped HAP coating obtained at low radio-frequency (RF) power fed to the MgO target provided material with high corrosion resistance compared to other coatings and bare alloy. A slight decrease in hardness of the coatings was found after the Mg addition, from 8.8 to 5.7 GPa. Also, the values of elastic modulus were decreased from 87 to 53 GPa, this being an advantage for biomedical applications. The coatings with low Mg concentration proved to have good deformation to yielding and higher plastic properties. Biological test results showed that the novel surfaces exhibited excellent properties for the adhesion and growth of bone cells. Moreover, early adherent vital cell numbers were significantly higher on both coatings compared to Ti6Al4V, suggesting that Mg ions may accelerate initial osteoblast adhesion and proliferation. Full article
(This article belongs to the Special Issue Advanced Biomimetic Calcium Phosphate Coatings)
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Open AccessArticle Study on the Formation of Reaction Phase to Si Addition in Boron Steel Hot-Dipped in Al–7Ni Alloy
Coatings 2017, 7(11), 186; doi:10.3390/coatings7110186
Received: 17 October 2017 / Revised: 30 October 2017 / Accepted: 2 November 2017 / Published: 4 November 2017
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Abstract
In order to reduce the intermetallic compounds formed during the application of an Al–7Ni wt % hot-dip multifunctional coating on boron steel, developed for Tailor Welded Blanks (TWB) and hot stamping, 2–6 wt % Si was added to the coating to change the
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In order to reduce the intermetallic compounds formed during the application of an Al–7Ni wt % hot-dip multifunctional coating on boron steel, developed for Tailor Welded Blanks (TWB) and hot stamping, 2–6 wt % Si was added to the coating to change the reaction layer. The coating was run at 690 °C for 120 s. Al9FeNi phases were formed on the steel interface, Fe2Al5 was formed on the steel, FeAl3 was generated between the existing layers, and flake-type Al2Fe3Si3 was formed in the Fe2Al5 phase, depending on the Si content. In addition, as Si was added to the coating, the thickness of the Fe2Al5 phase decreased and the thickness of the Al9FeNi phase and Al2Fe3Si3 increased. The decrease in the thickness of the Fe2Al5 phase was mainly due to the effect of the Si solid solution and the Al2Fe3Si3 formation in the Fe2Al5 phase. The reason for the growth of Al9FeNi is that the higher the Si content in the coating, the more the erosion of the interface of the steel material due to the coating solution. Therefore, the outflow of Fe into the coating liquid increased. Full article
(This article belongs to the Special Issue Innovative Coatings for Automotive Industry)
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Open AccessArticle Tribological and Wear Performance of Carbide Tools with TiB2 PVD Coating under Varying Machining Conditions of TiAl6V4 Aerospace Alloy
Coatings 2017, 7(11), 187; doi:10.3390/coatings7110187
Received: 5 September 2017 / Revised: 22 October 2017 / Accepted: 1 November 2017 / Published: 4 November 2017
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Abstract
Tribological phenomena and tool wear mechanisms during machining of hard-to-cut TiAl6V4 aerospace alloy have been investigated in detail. Since cutting tool wear is directly affected by tribological phenomena occurring between the surfaces of the workpiece and the cutting tool, the performance of the
[...] Read more.
Tribological phenomena and tool wear mechanisms during machining of hard-to-cut TiAl6V4 aerospace alloy have been investigated in detail. Since cutting tool wear is directly affected by tribological phenomena occurring between the surfaces of the workpiece and the cutting tool, the performance of the cutting tool is strongly associated with the conditions of the machining process. The present work shows the effect of different machining conditions on the tribological and wear performance of TiB2-coated cutting tools compared to uncoated carbide tools. FEM modeling of the temperature profile on the friction surface was performed for wet machining conditions under varying cutting parameters. Comprehensive characterization of the TiB2 coated vs. uncoated cutting tool wear performance was made using optical 3D imaging, SEM/EDX and XPS methods respectively. The results obtained were linked to the FEM modeling. The studies carried out show that during machining of the TiAl6V4 alloy, the efficiency of the TiB2 coating application for carbide cutting tools strongly depends on cutting conditions. The TiB2 coating is very efficient under roughing at low speeds (with strong buildup edge formation). In contrast, it shows similar wear performance to the uncoated tool under finishing operations at higher cutting speeds when cratering wear predominates. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle Determining the Presence of Spalted Wood in Spanish Marquetry Woodworks of the 1500s through the 1800s
Coatings 2017, 7(11), 188; doi:10.3390/coatings7110188
Received: 16 September 2017 / Revised: 25 October 2017 / Accepted: 2 November 2017 / Published: 4 November 2017
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Abstract
The process of using fungal-colored wood (spalted wood) for marquetry and intarsia woodworks in Italy and Germany was very popular from the 1400–1600s, with some instances continuing as late as the 1800s. While spalted marquetry in these countries is relatively well documented, less
[...] Read more.
The process of using fungal-colored wood (spalted wood) for marquetry and intarsia woodworks in Italy and Germany was very popular from the 1400–1600s, with some instances continuing as late as the 1800s. While spalted marquetry in these countries is relatively well documented, less is known about its use in other parts of Europe. One of the primary reasons for this lack of knowledge is the difficulty in identifying spalted wood, especially the blue-green variety produced from Chlorociboria species, from wood dyed with copper-based compounds or other synthetics. The most reliable testing method involves destructive sampling, where a small piece is taken from the work, the pigment extracted, and an analysis performed. Such sampling is simply not feasible, nor often allowed, on ancient artwork. To make a reliable, non-destructive identification of spalted wood, a visual method based on anatomical characteristics of spalted wood was developed to differentiate spalted wood from dyed wood. High-resolution pictures were taken from wooden artifacts containing blue-green colored wood in collections at the National Museum of Decorative Arts (MNAD), the Royal Site Monastery El Escorial and the Bilbao Museum of Fine Arts in Spain. The concentration of pigment in the rays, the color distribution, the size of the piece and the date of production, were analyzed. With the use of this new visual method, it was possible to determine that intarsia artifacts, held in Spain but of Augsburg origin from the 1500–1600s, contained spalted wood details. Meanwhile, Spanish and Italian intarsia artifacts from the 1800s were found to only contain dyed wood. Full article
(This article belongs to the Special Issue Varnishes and Surface Treatments of Historical Wooden Artworks)
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Open AccessArticle Ta–Zr–N Thin Films Fabricated through HIPIMS/RFMS Co-Sputtering
Coatings 2017, 7(11), 189; doi:10.3390/coatings7110189
Received: 31 August 2017 / Revised: 19 October 2017 / Accepted: 2 November 2017 / Published: 4 November 2017
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Abstract
Ta–Zr–N thin films were fabricated through co-deposition of radio-frequency magnetron sputtering and high-power impulse magnetron sputtering (HIPIMS/RFMS co-sputtering). The oxidation resistance of the fabricated films was evaluated by annealing the samples in a 15-ppm O2-N2 atmosphere at 600 °C for
[...] Read more.
Ta–Zr–N thin films were fabricated through co-deposition of radio-frequency magnetron sputtering and high-power impulse magnetron sputtering (HIPIMS/RFMS co-sputtering). The oxidation resistance of the fabricated films was evaluated by annealing the samples in a 15-ppm O2-N2 atmosphere at 600 °C for 4 and 8 h. The mechanical properties and surface roughness of the as-deposited and annealed thin films were evaluated. The results indicated that the HIPIMS/RFMS co-sputtered Ta–Zr–N thin films exhibited superior mechanical properties and lower surface roughness than did the conventional direct current-sputtered Ta–Zr–N thin films and HIPIMS-fabricated ZrNx thin films in both the as-deposited and annealed states. Full article
(This article belongs to the Special Issue Thin Film Deposition and Characterization Techniques)
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Open AccessArticle Role of Phase Composition of PEO Coatings on AA2024 for In-Situ LDH Growth
Coatings 2017, 7(11), 190; doi:10.3390/coatings7110190
Received: 14 October 2017 / Revised: 30 October 2017 / Accepted: 1 November 2017 / Published: 6 November 2017
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Abstract
Plasma electrolytic oxidation (PEO) is an environmentally friendly anodizing technique leading to the formation of a ceramic-like coatings under high-voltage discharges. Layered double hydroxides (LDHs) were grown directly on γ, α, and amorphous Al2O3 powders, respectively, in order to investigate
[...] Read more.
Plasma electrolytic oxidation (PEO) is an environmentally friendly anodizing technique leading to the formation of a ceramic-like coatings under high-voltage discharges. Layered double hydroxides (LDHs) were grown directly on γ, α, and amorphous Al2O3 powders, respectively, in order to investigate the phase responsible for in-situ LDH growth on PEO coating. Furthermore, it is shown that LDH growth is limited by the high tortuosity of the PEO layer and the accessibility of Al ( OH ) 4 anions from the substrate covered with thin amorphous aluminum oxide, through the pores. Full article
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Open AccessArticle Friction and Wear Behavior of an Ag–Mo Co-Implanted GH4169 Alloy via Ion-Beam-Assisted Bombardment
Coatings 2017, 7(11), 191; doi:10.3390/coatings7110191
Received: 12 September 2017 / Revised: 25 October 2017 / Accepted: 2 November 2017 / Published: 6 November 2017
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Abstract
Ag, Mo, and Ag–Mo were respectively implanted into GH4169 alloy substrates without heating via ion-beam-assisted bombardment technology (IBAB). In addition, the wear performance under low sliding speed and applied load were researched at room temperature (RT). A small amount silver molybdate phase could
[...] Read more.
Ag, Mo, and Ag–Mo were respectively implanted into GH4169 alloy substrates without heating via ion-beam-assisted bombardment technology (IBAB). In addition, the wear performance under low sliding speed and applied load were researched at room temperature (RT). A small amount silver molybdate phase could be detected on the surface of the co-implanted GH4169 alloy bombarded by a high-energy ion beam. The average friction coefficients under the steady wear state had almost no change at all. Compared with the un-implanted GH4169 alloys, the wear rate of the GH4169 alloys with co-implantation of Ag and Mo was reduced by 75%. A large amount of the silver molybdate phase could be generated due to the tribo-reaction on the worn surface during sliding. It benefits the formation of continuous oxide layers as lubrication and protected layers, leading to the change in the predominant wear mechanism from abrasion and adhesion wear to oxidation wear. Full article
(This article belongs to the Special Issue Coatings Tribology)
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Open AccessArticle Visible-Light-Driven, Dye-Sensitized TiO2 Photo-Catalyst for Self-Cleaning Cotton Fabrics
Coatings 2017, 7(11), 192; doi:10.3390/coatings7110192
Received: 28 July 2017 / Revised: 30 October 2017 / Accepted: 3 November 2017 / Published: 6 November 2017
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Abstract
We report here the photo-catalytic properties of dye-sensitized TiO2-coated cotton fabrics. In this study, visible-light-driven, self-cleaning cotton fabrics were developed by coating the cotton fabrics with dye-sensitized TiO2. TiO2 nano-sol was prepared via the sol-gel method and the
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We report here the photo-catalytic properties of dye-sensitized TiO2-coated cotton fabrics. In this study, visible-light-driven, self-cleaning cotton fabrics were developed by coating the cotton fabrics with dye-sensitized TiO2. TiO2 nano-sol was prepared via the sol-gel method and the cotton fabric was coated with this nano-sol by the dip-pad–dry-cure method. In order to enhance the photo-catalytic properties of this TiO2-coated cotton fabric under visible light irradiation, the TiO2-coated cotton fabric was dyed with a phthalocyanine-based reactive dye, C.I. Reactive Blue 25 (RB-25), as a dye sensitizer for TiO2. The photo-catalytic self-cleaning efficiency of the resulting dye/TiO2-coated cotton fabrics was evaluated by degradation of Rhodamine B (RhB) and color co-ordinate measurements. Dye/TiO2-coated cotton fabrics show very good photo-catalytic properties under visible light. Full article
(This article belongs to the Special Issue Advances in Functional Inorganic Coatings)
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Open AccessArticle In Situ Synthesis and Electrophoretic Deposition of NiO/Ni Core-Shell Nanoparticles and Its Application as Pseudocapacitor
Coatings 2017, 7(11), 193; doi:10.3390/coatings7110193
Received: 29 September 2017 / Revised: 30 October 2017 / Accepted: 4 November 2017 / Published: 8 November 2017
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Abstract
A simple, low cost and transferable colloidal processing method and the subsequent heat treatment has been optimized to prepare binder-free electrodes for their application in supercapacitors. NiO/Ni core–shell hybrid nanostructures have been synthetized by heterogeneous precipitation of metallic Ni nanospheres onto NiO nanoplatelets
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A simple, low cost and transferable colloidal processing method and the subsequent heat treatment has been optimized to prepare binder-free electrodes for their application in supercapacitors. NiO/Ni core–shell hybrid nanostructures have been synthetized by heterogeneous precipitation of metallic Ni nanospheres onto NiO nanoplatelets as seed surfaces. The electrophoretic deposition (EPD) has been used to shape the electroactive material onto 3D substrates such as Ni foams. The method has allowed us to control the growth and the homogeneity of the NiO/Ni coatings. The presence of metallic Nickel in the microstructure and the optimization of the thermal treatment have brought several improvements in the electrochemical response due to the connectivity of the final microstructure. The highest specific capacitance value has been obtained using a thermal treatment of 325 °C during 1 h in Argon. At this temperature, necks formed among ceramic-metallic nanoparticles preserve the structural integrity of the microstructure avoiding the employment of binders to enhance their connectivity. Thus, a compromise between porosity and connectivity should be established to improve electrochemical performance. Full article
(This article belongs to the Special Issue Electrophoretic Deposition)
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Open AccessArticle Fabrication of an Anisotropic Superhydrophobic Polymer Surface Using Compression Molding and Dip Coating
Coatings 2017, 7(11), 194; doi:10.3390/coatings7110194
Received: 12 October 2017 / Revised: 4 November 2017 / Accepted: 7 November 2017 / Published: 10 November 2017
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Abstract
Many studies of anisotropic wetting surfaces with directional structures inspired from rice leaves, bamboo leaves, and butterfly wings have been carried out because of their unique liquid shape control and transportation. In this study, a precision mechanical cutting process, ultra-precision machining using a
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Many studies of anisotropic wetting surfaces with directional structures inspired from rice leaves, bamboo leaves, and butterfly wings have been carried out because of their unique liquid shape control and transportation. In this study, a precision mechanical cutting process, ultra-precision machining using a single crystal diamond tool, was used to fabricate a mold with microscale directional patterns of triangular cross-sectional shape for good moldability, and the patterns were duplicated on a flat thermoplastic polymer plate by compression molding for the mass production of an anisotropic wetting polymer surface. Anisotropic wetting was observed only with microscale patterns, but the sliding of water could not be achieved because of the pinning effect of the micro-structure. Therefore, an additional dip coating process with 1H, 1H, 2H, 2H-perfluorodecythricholosilanes, and TiO2 nanoparticles was applied for a small sliding angle with nanoscale patterns and a low surface energy. The anisotropic superhydrophobic surface was fabricated and the surface morphology and anisotropic wetting behaviors were investigated. The suggested fabrication method can be used to mass produce an anisotropic superhydrophobic polymer surface, demonstrating the feasibility of liquid shape control and transportation. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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Open AccessArticle Nucleation and Growth of Intermetallic Compounds Formed in Boron Steel Hot-Dipped in Al–Ni alloy
Coatings 2017, 7(11), 195; doi:10.3390/coatings7110195
Received: 17 October 2017 / Revised: 9 November 2017 / Accepted: 10 November 2017 / Published: 10 November 2017
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Abstract
The formation mechanism of intermetallic compounds formed in boron steel hot-dipped in Al–7Ni (wt %) at 690 °С for 10–120 s was studied by identifying the intermetallic phases and investigating the growth process. Initially, a Fe3O4 oxide layer formed on
[...] Read more.
The formation mechanism of intermetallic compounds formed in boron steel hot-dipped in Al–7Ni (wt %) at 690 °С for 10–120 s was studied by identifying the intermetallic phases and investigating the growth process. Initially, a Fe3O4 oxide layer formed on the steel. The oxide layer separated into multiple layers sporadically; following this, the Al–Ni molten alloy permeated into the region of the oxide layer breakdown and formed the Al9FeNi (T, monoclinic, space group: P21/c) phase on the steel surfaces. The Al9FeNi (T) phase formed from the reaction between the Al–Ni molten alloy and Fe eluted from the steel; this phase not only acts as an Al interdiffusion channel, but also as a barrier for Fe; and facilitates only grain growth without a significant change in thickness. Inside the steel, the Fe2Al5 (η, orthorhombic, space group: Cmcm) phase grows along the c-axis in the [001] direction; and has a long columnar structure. The Fe3AlC (κ, Cubic, space group: Pm3m) phase is formed owing to a reduction in the Al concentration and the simultaneous diffusion and discharge of C toward the steel interface, as C cannot dissolve in the Fe2Al5 (η) phase. Full article
(This article belongs to the Special Issue Innovative Coatings for Automotive Industry)
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Open AccessArticle Effective Postharvest Preservation of Kiwifruit and Romaine Lettuce with a Chitosan Hydrochloride Coating
Coatings 2017, 7(11), 196; doi:10.3390/coatings7110196
Received: 28 August 2017 / Revised: 8 November 2017 / Accepted: 9 November 2017 / Published: 11 November 2017
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Abstract
Kiwifruits and romaine lettuce, among the most horticulturally-consumed fresh products, were selected to investigate how to reduce damage and losses before commercialization. The film-forming properties, physico-chemical, and morphological characteristics, as well as the antimicrobial response against Botrytis cinerea and Pectobacterium carotovorum subsp. carotovorum
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Kiwifruits and romaine lettuce, among the most horticulturally-consumed fresh products, were selected to investigate how to reduce damage and losses before commercialization. The film-forming properties, physico-chemical, and morphological characteristics, as well as the antimicrobial response against Botrytis cinerea and Pectobacterium carotovorum subsp. carotovorum of chitosan hydrochloride (CH)-based coatings were investigated. The results underlined the film-forming capability of this CH that maintained its physico-chemical characteristics also after dissolution in water. Morphological investigations by FESEM (Field Emission Scanning Electron Microscopy) underlined a well-distributed and homogeneous thin coating (less than 3–5 μm) on the lettuce leaves that do not negatively affect the food product functionality, guaranteeing the normal breathing of the food. FESEM images also highlighted the good distribution of CH coating on kiwifruit peels. The in vitro antimicrobial assays showed that both the mycelial growth of Botrytis cinerea and the bacterial growth of Pectobacterium carotovorum subsp. carotovorum were totally inhibited by the presence of CH, whereas in vivo antimicrobial properties were proved for 5–7 days on lettuce and until to 20–25 days on kiwifruits, demonstrating that the proposed coating is able to contrast gray mold frequently caused by the two selected plant pathogens during postharvest phases of fruit or vegetable products. Full article
(This article belongs to the Special Issue Food and Beverage Packaging Coatings 2017)
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Open AccessArticle Characterization of Hydroxyapatite (HA) Sputtering Targets by APS Methods
Coatings 2017, 7(11), 197; doi:10.3390/coatings7110197
Received: 29 June 2017 / Revised: 29 October 2017 / Accepted: 7 November 2017 / Published: 11 November 2017
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Abstract
Radio frequency (RF) sputtering is a potential medical device coating technology that is commercializable; however, a suitable commercialized target for sputtering the hydroxyapatite (HA) coating onto titanium medical devices is more important. Therefore, this study used three HA targets in conducting sputtering experiments
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Radio frequency (RF) sputtering is a potential medical device coating technology that is commercializable; however, a suitable commercialized target for sputtering the hydroxyapatite (HA) coating onto titanium medical devices is more important. Therefore, this study used three HA targets in conducting sputtering experiments for HA films, which were manufactured in a laboratory by using three different processes: cold pressing and sintering (CPS), hot isostatic pressing (HIP), and atmospheric plasma spraying (APS). Subsequently, the sputtering performance of each type of target and the properties of the HA films were assessed to develop an appropriate process for modifying the surfaces of medical devices. The experimental results showed that the APS target, with a density of approximately 2.83 g/cm3, was suitable for use in HA sputtering. Additionally, the APS target could withstand a high discharge power over 300 W, whereas the CPS target could nearly endure a power below 70 W. The APS target, with Ca/P ratio of 2.401, consisted of a combination of HA, α-tricalcium phosphate (α-TCP), β-TCP, and tetracalcium phosphate phases (TTCP). In addition to being able to perform at a high sputtering power of more than 300 W, the APS target achieved a higher deposition rate than did the CPS target. This study shows that the processing technology used for the APS target is a potential method for applying HA sputtering for the surface modification of artificial aggregates. Full article
(This article belongs to the Special Issue Dental Implant Surface: Science and Technology)
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Open AccessArticle Effect of Microstructure on the Thermal Conductivity of Plasma Sprayed Y2O3 Stabilized Zirconia (8% YSZ)
Coatings 2017, 7(11), 198; doi:10.3390/coatings7110198
Received: 23 September 2017 / Revised: 29 October 2017 / Accepted: 5 November 2017 / Published: 13 November 2017
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Abstract
In this paper, the effect of microstructure on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs) is investigated. Nine freestanding samples deposited on aluminum alloys are studied. Cross-section morphology such as pores, cracks, m-phase
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In this paper, the effect of microstructure on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs) is investigated. Nine freestanding samples deposited on aluminum alloys are studied. Cross-section morphology such as pores, cracks, m-phase content, grain boundary density of the coated samples are examined by scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). Multiple linear regressions are used to develop quantitative models that describe the relationship between the particle parameters, m-phase content and features of the microstructure such as porosity, crack-porosity, and the length density of small and big angle-cracks. Moreover, the relationship between the microstructure and thermal conductivity is investigated. Results reveal that the thermal conductivity of the coating is mainly determined by the microstructure and grain boundary density at room temperature (25 °C), and by the length density of big-angle-crack, monoclinic phase content and grain boundary density at high temperature (1200 °C). Full article
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Open AccessArticle Electrophoretic Deposition as a New Bioactive Glass Coating Process for Orthodontic Stainless Steel
Coatings 2017, 7(11), 199; doi:10.3390/coatings7110199
Received: 6 October 2017 / Revised: 8 November 2017 / Accepted: 10 November 2017 / Published: 13 November 2017
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Abstract
This study investigated the surface modification of orthodontic stainless steel using electrophoretic deposition (EPD) of bioactive glass (BG). The BG coatings were characterized by spectrophotometry, scanning electron microscopy with energy dispersive X-ray spectrometry, and X-ray diffraction. The frictional properties were investigated using a
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This study investigated the surface modification of orthodontic stainless steel using electrophoretic deposition (EPD) of bioactive glass (BG). The BG coatings were characterized by spectrophotometry, scanning electron microscopy with energy dispersive X-ray spectrometry, and X-ray diffraction. The frictional properties were investigated using a progressive load scratch test. The remineralization ability of the etched dental enamel was studied according to the time-dependent mechanical properties of the enamel using a nano-indentation test. The EPD process using alternating current produced higher values in both reflectance and lightness. Additionally, the BG coating was thinner than that prepared using direct current, and was completely amorphous. All of the BG coatings displayed good interfacial adhesion, and Si and O were the major components. Most BG-coated specimens produced slightly higher frictional forces compared with non-coated specimens. The hardness and elastic modulus of etched enamel specimens immersed with most BG-coated specimens recovered significantly with increasing immersion time compared with the non-coated specimen, and significant acid-neutralization was observed for the BG-coated specimens. The surface modification technique using EPD and BG coating on orthodontic stainless steel may assist the development of new non-cytotoxic orthodontic metallic appliances having satisfactory appearance and remineralization ability. Full article
(This article belongs to the Special Issue Surface Engineering of Biomaterials)
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Open AccessArticle Effect of Initial Surface Roughness on Cavitation Erosion Resistance of Arc-Sprayed Fe-Based Amorphous/Nanocrystalline Coatings
Coatings 2017, 7(11), 200; doi:10.3390/coatings7110200
Received: 23 September 2017 / Revised: 18 October 2017 / Accepted: 1 November 2017 / Published: 14 November 2017
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Abstract
The arc spraying process was used to prepare Fe-based amorphous/nanocrystalline coating. The cavitation erosion behaviors of FeNiCrBSiNbW coatings with different surface roughness levels were investigated in distilled water. The results showed that FeNiCrBSiNbW coating adhered well to the substrate, and was compact with
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The arc spraying process was used to prepare Fe-based amorphous/nanocrystalline coating. The cavitation erosion behaviors of FeNiCrBSiNbW coatings with different surface roughness levels were investigated in distilled water. The results showed that FeNiCrBSiNbW coating adhered well to the substrate, and was compact with porosity of less than 2%. With increasing initial surface roughness, the coatings showed an increase in mass loss of cavitation erosion damage. The amount of pre-existing defects on the initial surface of the coatings was found to be a significant factor for the difference in the cavitation erosion behavior. The cavitation erosion damage for the coatings was a brittle erosion mode. The evolution of the cavitation erosion mechanism of the coatings with the increase of the initial surface roughness was micro-cracks, pits, detachment of fragments, craters, cracks, pullout of the un-melted particle, and massive exfoliations. Full article
(This article belongs to the Special Issue Coatings for Harsh Environments)
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Open AccessArticle Mechanical and Spectroscopic Analysis of Retrieved/Failed Dental Implants
Coatings 2017, 7(11), 201; doi:10.3390/coatings7110201
Received: 26 September 2017 / Revised: 26 October 2017 / Accepted: 10 November 2017 / Published: 15 November 2017
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Abstract
The purpose of this study was to examine surface alterations and bone formation on the surface of failed dental implants (Straumann [ST] and TiUnite [TiUn]) removed due to any biological reason. In addition, failure analysis was performed to test mechanical properties. Dental implants
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The purpose of this study was to examine surface alterations and bone formation on the surface of failed dental implants (Straumann [ST] and TiUnite [TiUn]) removed due to any biological reason. In addition, failure analysis was performed to test mechanical properties. Dental implants (n = 38) from two manufacturers were collected and subjected to chemical cleaning. The presence of newly formed hydroxyapatite bone around failed implants was evaluated using micro-Raman spectroscopy. Scanning electron microscopy was used to identify surface defects. Mechanical testing was performed using a Minneapolis servo-hydraulic system (MTS) along with indentation using a universal testing machine and average values were recorded. A statistical analysis of mechanical properties was done using an unpaired t test, and correlation between observed defects was evaluated using Chi-square (p = 0.05). Apatite-formation was evident in both implants, but was found qualitatively more in the ST group. No significant difference was found in indentation between the two groups (p > 0.05). The percentage of “no defects” was significantly lower in the ST group (71%). Crack-like and full-crack defects were observed in 49% and 39% of TiUn. The ST group showed 11,061 cycles to failure as compared with 10,021 cycles in the TiUnite group. Implant failure mechanisms are complex with a combination of mechanical and biological reasons and these factors are variable with different implant systems. Full article
(This article belongs to the Special Issue Dental Implant Surface: Science and Technology)
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Open AccessArticle Wear Transition of CrN Coated M50 Steel under High Temperature and Heavy Load
Coatings 2017, 7(11), 202; doi:10.3390/coatings7110202
Received: 22 September 2017 / Revised: 3 November 2017 / Accepted: 15 November 2017 / Published: 20 November 2017
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Abstract
The combination of high temperature indentation and wear test provides a useful way to investigate wear of CrN coating and wear transition mechanisms. In this paper, the high temperature hardness of CrN coatings and load bearing capacity, Lb, of CrN coated
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The combination of high temperature indentation and wear test provides a useful way to investigate wear of CrN coating and wear transition mechanisms. In this paper, the high temperature hardness of CrN coatings and load bearing capacity, Lb, of CrN coated M50 disks were determined from spherical indentation at temperatures up to 500 °C. Wear tests with different normal loads were carried out at the same temperatures as the indentation tests. The results show that wear mechanism of CrN coating changes with external load, P, and temperature, T. Under a tested condition of P < Lb and T < 315 °C, abrasive is the dominant wear mechanism for CrN coating. Under a tested condition of P < Lb and T ≥ 315 °C, wear of CrN coating transitions into mild oxidation wear due to the lubricating effect of chromium oxide film. Under a tested condition of P > Lb and T < 315 °C, wear of CrN coating was controlled by coating fracture. Under a tested condition of P > Lb and T ≥ 315 °C, wear of CrN coating transitions into the severe wear mode, due to the tensile fracture of oxidation films, thereby leading to adhesion between CrN coating and tribo-counterpart. The presented method can be helpful in predicting permissible load and working temperature in tribological applications of CrN coating. Full article
(This article belongs to the Special Issue Coatings for Harsh Environments)
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Open AccessArticle Corrosion and Thermal Fatigue Behaviors of TiC/Ni Composite Coating by Self-Propagating High-Temperature Synthesis in Molten Aluminum Alloy
Coatings 2017, 7(11), 203; doi:10.3390/coatings7110203
Received: 18 September 2017 / Revised: 20 October 2017 / Accepted: 13 November 2017 / Published: 18 November 2017
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Abstract
TiC/Ni composite coatings on H13 steel plates were fabricated in situ by self-propagating high-temperature synthesis and combined with a pseudo-heat isostatic press. The microstructure of the coating was characterized by X-ray diffraction and scanning electron microscopy. The microhardness, corrosion, and thermal fatigue behaviors
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TiC/Ni composite coatings on H13 steel plates were fabricated in situ by self-propagating high-temperature synthesis and combined with a pseudo-heat isostatic press. The microstructure of the coating was characterized by X-ray diffraction and scanning electron microscopy. The microhardness, corrosion, and thermal fatigue behaviors of the coating were investigated by a microhardness test, immersion test, and thermal fatigue test, respectively. The results showed that the in situ coating consisted of TiC and Ni binder phases. Spheroidal TiC particles were enveloped by a nearly continuous Ni binder phase. Coating showed good metallurgical bonding in the interface. The corrosive mechanism of the coating surface in molten aluminum alloy involves the Ni binder phase being etched by aluminum to form AlNi3 and the oxidization of the TiC-reinforced phase. The corrosive mechanism that occurred at the front of the corrosion involves the Ni binder phase of the coating being etched by aluminum to form AlNi3, while the TiC skeleton still maintains the original organizational structure. Hot fatigue cracks began at the defective tips of the coating and propagated in the TiC-reinforced phase. The crack is a trans-granular fracture, which is the result of brittle rupture. Full article
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Open AccessArticle Inactivation of Listeria in Foods Packed in Films Activated with Enterocin AS-48 plus Thymol Singly or in Combination with High-Hydrostatic Pressure Treatment
Coatings 2017, 7(11), 204; doi:10.3390/coatings7110204
Received: 16 October 2017 / Revised: 5 November 2017 / Accepted: 15 November 2017 / Published: 18 November 2017
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Abstract
The aim of the present study was to determine the efficacy of films activated with enterocin AS-48 plus thymol singly, or in combination with high-hydrostatic pressure (HHP) on the inactivation of Listeria innocua in sea bream fillets and in fruit puree stored under
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The aim of the present study was to determine the efficacy of films activated with enterocin AS-48 plus thymol singly, or in combination with high-hydrostatic pressure (HHP) on the inactivation of Listeria innocua in sea bream fillets and in fruit puree stored under refrigeration for 10 days. L. innocua proliferated in control fish fillets during storage. The activated film reduced viable Listeria counts in fillets by 1.76 log cycles and prevented growth of survivors until mid-storage. Application of HHP treatment to fillets packed in films without antimicrobials reduced Listeria counts by 1.83 log cycles, but did not prevent the growth of survivors during storage. The combined treatment reduced viable counts by 1.88 log cycles and delayed growth of survivors during the whole storage period. L. innocua survived in puree during storage. The activated film reduced Listeria counts by 1.80 and 2.0 log cycles at days 0 and 3. After that point, Listeria were below the detection limit. No viable Listeria were detected in the purees after application of HHP treatment singly, or in combination with the activated film. Results from the study indicate that the efficacy of activated films against Listeria is markedly influenced by the food type. Full article
Open AccessArticle Improvement of Power Factor of CoSb3 Thermoelectric Thin Films via Microstructure Optimization
Coatings 2017, 7(11), 205; doi:10.3390/coatings7110205
Received: 31 October 2017 / Revised: 15 November 2017 / Accepted: 16 November 2017 / Published: 18 November 2017
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Abstract
Skutterudite CoSb3 has emerged as one of the most studied candidate materials for thermoelectric applications. In this work, CoSb3 thin films were prepared by radio frequency sputtering, and their microstructure was investigated with emphasis on the effect of target composition and
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Skutterudite CoSb3 has emerged as one of the most studied candidate materials for thermoelectric applications. In this work, CoSb3 thin films were prepared by radio frequency sputtering, and their microstructure was investigated with emphasis on the effect of target composition and deposition temperature. The goal was to enhance the thermoelectric properties of CoSb3 thin films via microstructure optimization. Results showed that the Sb content of films gradually decreased with increasing deposition temperature. Although the thin films prepared by the target with a Co and Sb element ratio of 1:3.5 approached the ideal stoichiometric ratio, they showed poor thermoelectric properties due to the formation of an additional Sb phase. By contrast, the thin films obtained with insufficient Sb showed a single CoSb3 phase and good thermoelectric properties. The mechanism behind this difference was studied accordingly. The power factor of the thin films was enhanced due to their dense structure and good crystallization. Full article
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Open AccessArticle Suppression of Graphene Nucleation by Turning Off Hydrogen Supply Just before Atmospheric Pressure Chemical Vapor Deposition Growth
Coatings 2017, 7(11), 206; doi:10.3390/coatings7110206
Received: 17 October 2017 / Revised: 7 November 2017 / Accepted: 9 November 2017 / Published: 20 November 2017
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Abstract
To exploit the extraordinary property of graphene in practical electrical and optical devices, it is necessary to produce large-sized, single-crystal graphene. Atmospheric pressure chemical vapor deposition (APCVD) on polycrystalline Cu surface is a promising scalable route of graphene synthesis but the unavoidable multiple
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To exploit the extraordinary property of graphene in practical electrical and optical devices, it is necessary to produce large-sized, single-crystal graphene. Atmospheric pressure chemical vapor deposition (APCVD) on polycrystalline Cu surface is a promising scalable route of graphene synthesis but the unavoidable multiple nucleation limits their reachable domain size. Here, we report that effective suppression of nucleation was achieved by only turning off hydrogen supply before introduction of the carbon source for graphene growth. The density of graphene decreased from 72.0 to 2.2 domains/cm2 by turning off hydrogen for 15 min. X-ray photoelectron spectroscopy and Raman spectroscopy studies show that the Cu surface was covered with 3–4 nm thick highly crystalline Cu2O, which would be caused by oxidation by residual oxidative gasses in the chamber during the turning off period. It was also revealed that elevating the temperature in Ar followed by annealing in H2/Ar before turning off hydrogen led to the enlargement of the Cu domain, resulting in the further suppression of nucleation. By optimizing such growth parameters in the CVD process, a single-crystal graphene with ~2.6 mm in diameter was successfully obtained. Full article
(This article belongs to the Special Issue Chemical Vapor Deposition)
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Open AccessArticle Investigation of Droplet Atomization and Evaporation in Solution Precursor Plasma Spray Coating
Coatings 2017, 7(11), 207; doi:10.3390/coatings7110207
Received: 12 October 2017 / Revised: 9 November 2017 / Accepted: 17 November 2017 / Published: 21 November 2017
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Abstract
Solution precursor plasma spray (SPPS) is a novel and promising technique in producing nanostructured coatings. This technique involves complex heat, mass and momentum transfer among the liquid feedstock, droplets, plasma jet and the coating material. Nevertheless, the droplet atomization and evaporation in the
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Solution precursor plasma spray (SPPS) is a novel and promising technique in producing nanostructured coatings. This technique involves complex heat, mass and momentum transfer among the liquid feedstock, droplets, plasma jet and the coating material. Nevertheless, the droplet atomization and evaporation in the plasma jet is one of the most essential parts to obtain the desired coating architecture. In the present work, a three-dimensional two-way-coupled Eulerian-Lagrangian code is used to simulate the interactions between the solution precursor and plasma. In order to obtain a more realistic understanding regarding droplet atomization and vaporization, the flash-boiling effect is modeled by an improved vaporization model. This model could provide accurate details for the droplet pyrolysis and help to optimize the solution precursor plasma spray process. We show that the fragmentation of the liquid stock and its vaporization mainly dominate the spraying details and can be decisive to the coating quality. We further investigate their role in SPPS and separately probe their inner link with the flow field relating to the distinctive area when droplets are flying through the thermal flow field. Our studies reveal that ethanol droplets, compared to those of water, show a superior characteristics in SPPS, owing to the low boiling point and low surface tension, conducive to the evaporation and atomization of droplets. In addition, the mixture of the plasma gas with hydrogen breaks the droplets more thoroughly compared to the pure plasma. The numerical results were compared and found to agree well with previous experimental and simulation work. Full article
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Review

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Open AccessReview Surface Texturing of CVD Diamond Assisted by Ultrashort Laser Pulses
Coatings 2017, 7(11), 185; doi:10.3390/coatings7110185
Received: 1 August 2017 / Revised: 10 October 2017 / Accepted: 28 October 2017 / Published: 3 November 2017
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Abstract
Diamond is a wide bandgap semiconductor with excellent physical properties which allow it to operate under extreme conditions. However, the technological use of diamond was mostly conceived for the fabrication of ultraviolet, ionizing radiation and nuclear detectors, of electron emitters, and of power
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Diamond is a wide bandgap semiconductor with excellent physical properties which allow it to operate under extreme conditions. However, the technological use of diamond was mostly conceived for the fabrication of ultraviolet, ionizing radiation and nuclear detectors, of electron emitters, and of power electronic devices. The use of nanosecond pulse excimer lasers enabled the microstructuring of diamond surfaces, and refined techniques such as controlled ablation through graphitization and etching by two-photon surface excitation are being exploited for the nanostructuring of diamond. On the other hand, ultrashort pulse lasers paved the way for a more accurate diamond microstructuring, due to reduced thermal effects, as well as an effective surface nanostructuring, based on the formation of periodic structures at the nanoscale. It resulted in drastic modifications of the optical and electronic properties of diamond, of which “black diamond” films are an example for future high-temperature solar cells as well as for advanced optoelectronic platforms. Although experiments on diamond nanostructuring started almost 20 years ago, real applications are only today under implementation. Full article
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