Coatings

12 pages, 2080 KiB

Open AccessFeature PaperArticle

X-ray Microanalysis of Precious Metal Thin Films: Thickness and Composition Determination

by Walter Giurlani, Massimo Innocenti and Alessandro Lavacchi

Coatings 2018, 8(2), 84; https://doi.org/10.3390/coatings8020084 - 24 Feb 2018

Cited by 33 | Viewed by 6948

Measuring the thickness and the composition of precious metal thin films is a challenging task. Currently, the available techniques for thickness measurements are either destructive or need heavy assumptions on the nature of the sample, relying on information that are not always available [...] Read more.

Measuring the thickness and the composition of precious metal thin films is a challenging task. Currently, the available techniques for thickness measurements are either destructive or need heavy assumptions on the nature of the sample, relying on information that are not always available with sufficient accuracy. In this paper we propose a new methodology based on X-ray microanalysis that can complement, with better lateral resolution, the use of X-ray Fluorescence, the most widely employed technique for measuring the thickness of electrodeposited coatings. The proposed method employs a combination of energy dispersive microanalysis spectra acquisition and Monte Carlo simulation. The effectiveness of the technique has been demonstrated by the measure of the thickness and the composition of a thin 24 kt gold electroplated film that contained small amount of nickel. Results have been validated by comparing data with those obtained by X-ray fluorescence and the scanning electron microscopy of metallographic cross-sections. Full article

(This article belongs to the Special Issue Development and Characterization of Nanostructured Functional Coatings/Films)

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13 pages, 5592 KiB

Open AccessArticle

Improving the Tribological Properties of Spark-Anodized Titanium by Magnetron Sputtered Diamond-Like Carbon

by Zhaoxiang Chen, Xipeng Ren, Limei Ren, Tengchao Wang, Xiaowen Qi and Yulin Yang

Coatings 2018, 8(2), 83; https://doi.org/10.3390/coatings8020083 - 24 Feb 2018

Cited by 17 | Viewed by 5456

Abstract

Spark-anodization of titanium can produce adherent and wear-resistant TiO₂ film on the surface, but the spark-anodized titanium has lots of surface micro-pores, resulting in an unstable and high friction coefficient against many counterparts. In this study, the diamond-like carbon (DLC) was introduced [...] Read more.

Spark-anodization of titanium can produce adherent and wear-resistant TiO₂ film on the surface, but the spark-anodized titanium has lots of surface micro-pores, resulting in an unstable and high friction coefficient against many counterparts. In this study, the diamond-like carbon (DLC) was introduced into the micro-pores of spark-anodized titanium by the magnetron sputtering technique and a TiO₂/DLC composite coating was fabricated. The microstructure and tribological properties of TiO₂/DLC composite coating were investigated and compared with the anodic TiO₂ mono-film and DLC mono-film. Results show that the DLC deposition significantly decreased the surface roughness and porosity of spark-anodized titanium. The fabricated TiO₂/DLC composite coating exhibited a more stable and much lower friction coefficient than anodic TiO₂ mono-film. Although the friction coefficient of the composite coating and the DLC mono-film was similar under both light load and heavy load conditions, the wear life of the composite coating was about 43% longer than that of DLC mono-film under heavy load condition. The wear rate of titanium with protective composite coating was much lower than that of titanium with DLC mono-film. The superior low friction coefficient and wear rate of the TiO₂/DLC composite coating make it a good candidate as protective coating on titanium alloys. Full article

(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))

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0 pages, 1658 KiB

Open AccessEditor’s ChoiceArticle

RETRACTED: Exploration of Growth Window for Phase-Pure Cubic Boron Nitride Films Prepared in a Pure N₂ Plasma

by Wei Gao, Yujing Li, Yuyuan Zhang and Hong Yin

Coatings 2018, 8(2), 82; https://doi.org/10.3390/coatings8020082 - 24 Feb 2018

Cited by 7 | Viewed by 6009 | Retraction

Abstract

Cubic boron nitride (c-BN) films were prepared via radio frequency (RF) magnetron sputtering from a hexagonal boron nitride (h-BN) target in a pure N₂ plasma. The composition and microstructure morphology of the BN films with different deposition times under pure N₂ [...] Read more.

Cubic boron nitride (c-BN) films were prepared via radio frequency (RF) magnetron sputtering from a hexagonal boron nitride (h-BN) target in a pure N₂ plasma. The composition and microstructure morphology of the BN films with different deposition times under pure N₂ plasma or mixed Ar/N₂ plasma were investigated with respect to the nucleation and growth processes. The pure-phase c-BN growth window was obtained using pure N₂ gas. The effects of pure N₂ gas on the growth mechanism, structural morphology, and internal compressive stress of the as-synthesized c-BN films were studied. Using pure N₂ gas instead of additional Ar resulted in improved microstructure quality and much reduced compressive stress, suggesting a fundamental strategy for achieving high-quality c-BN films. Full article

(This article belongs to the Special Issue Carbon-Related Coatings)

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12 pages, 4478 KiB

Open AccessArticle

Tunnel Oxides Formed by Field-Induced Anodisation for Passivated Contacts of Silicon Solar Cells

by Jingnan Tong, Sean Lim and Alison Lennon

Coatings 2018, 8(2), 81; https://doi.org/10.3390/coatings8020081 - 23 Feb 2018

Cited by 3 | Viewed by 5007

Abstract

Tunnel silicon oxides form a critical component for passivated contacts for silicon solar cells. They need to be sufficiently thin to allow carriers to tunnel through and to be uniform both in thickness and stoichiometry across the silicon wafer surface, to ensure uniform [...] Read more.

Tunnel silicon oxides form a critical component for passivated contacts for silicon solar cells. They need to be sufficiently thin to allow carriers to tunnel through and to be uniform both in thickness and stoichiometry across the silicon wafer surface, to ensure uniform and low recombination velocities if high conversion efficiencies are to be achieved. This paper reports on the formation of ultra-thin silicon oxide layers by field-induced anodisation (FIA), a process that ensures uniform oxide thickness by passing the anodisation current perpendicularly through the wafer to the silicon surface that is anodised. Spectroscopical analyses show that the FIA oxides contain a lower fraction of Si-rich sub-oxides compared to wet-chemical oxides, resulting in lower recombination velocities at the silicon and oxide interface. This property along with its low temperature formation highlights the potential for FIA to be used to form low-cost tunnel oxide layers for passivated contacts of silicon solar cells. Full article

(This article belongs to the Special Issue Advanced Surface Passivation Processes for Solar Cells)

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14 pages, 1059 KiB

Open AccessArticle

The Effect of Xanthan Gum and Flaxseed Mucilage as Edible Coatings in Cheddar Cheese during Ripening

by Afshin Soleimani-Rambod, Shahin Zomorodi, Shahram Naghizadeh Raeisi, Asghar Khosrowshahi Asl and Seyed-Ahmad Shahidi

Coatings 2018, 8(2), 80; https://doi.org/10.3390/coatings8020080 - 23 Feb 2018

Cited by 40 | Viewed by 6955

Abstract

The object of this study was to investigate the possibility of using xanthan gum and flaxseed mucilage as edible coatings for Cheddar cheese during ripening for 90 days. Five samples of Cheddar cheese blocks were coated with different coating materials in triplicate as [...] Read more.

The object of this study was to investigate the possibility of using xanthan gum and flaxseed mucilage as edible coatings for Cheddar cheese during ripening for 90 days. Five samples of Cheddar cheese blocks were coated with different coating materials in triplicate as follows: Coated with polyvinyl acetate as control (C), coated with 0.5% xanthan gum (XG), coated with 0.75% flaxseed mucilage (FM1), coated with 1% flaxseed mucilage (FM2), and coated with 1.25% flaxseed mucilage (FM3). All samples were kept at 8 ± 2 °C in a cold room for 90 days. The statistical analysis of the results showed that the moisture content of the samples decreased and the protein content increased during the ripening period (P < 0.01). The pH, acidity, fat in dry matter, and TCA-SN/TN of samples were significantly affected by xanthan gum and flaxseed mucilage treatment (P < 0.01). The free fatty acid composition of samples was significantly affected by edible coatings. Edible coatings affected the growth of non-starter lactic acid bacteria and the total mesophilic aerobic bacteria in a non-significant manner (P > 0.01). The growth of starter bacteria was significantly altered under the effect of edible coating materials (P < 0.05). Tyrosine and tryptophan contents as an index of proteolysis, lipolysis, and sensory evaluation of samples were not significantly different. Full article

(This article belongs to the Special Issue Films and Coatings for Food and Health Applications)

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17 pages, 5900 KiB

Open AccessArticle

Alkoxylated β-Naphthol as an Additive for Tin Plating from Chloride and Methane Sulfonic Acid Electrolytes

by Simona P. Zajkoska, Antonio Mulone, Wolfgang E. G. Hansal, Uta Klement, Rudolf Mann and Wolfgang Kautek

Coatings 2018, 8(2), 79; https://doi.org/10.3390/coatings8020079 - 21 Feb 2018

Cited by 11 | Viewed by 6273

Abstract

β-naphthol was one of the first additives introduced for smooth and homogeneous tin electrodeposition. Although it can be oxidized under the plating conditions, forming either 1,2-napthoquinone or polymeric materials based on naphthioxides, it is still in use. In this work, an investigation of [...] Read more.

β-naphthol was one of the first additives introduced for smooth and homogeneous tin electrodeposition. Although it can be oxidized under the plating conditions, forming either 1,2-napthoquinone or polymeric materials based on naphthioxides, it is still in use. In this work, an investigation of its more stable form, alkoxylated β-naphthol (ABN), on tin plating is undertaken. For this purpose, chloride based (pH ~5) and methane sulfonic acid (MSA, pH ~0.5) electrolytes, including ABN, were prepared. Reaction kinetics were studied by polarization, Tafel measurements, and cyclic voltammetry. Tin electrodeposits were obtained on flat brass substrates. Surface morphology and preferred crystal orientation were studied by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). In both studied electrolytes ABN acts as an inhibitor but in the case of the chloride electrolyte it is more pronounced. In the MSA electrolyte this effect was overlaid by the presence of tin-citrate complexes. In the chloride-based electrolyte, ABN has a grain refining effect, while in the MSA electrolyte an increase of ABN concentration leads to a slight enlargement of the average grain size. X-ray analysis shows a constant decrease of the (101) intensity with increasing concentration of ABN for the sample deposited from both baths. Full article

(This article belongs to the Special Issue Thin Films and Patterned Structures by Electrochemical Methods)

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9 pages, 2862 KiB

Open AccessArticle

Chemical Vapor Transport Deposition of Molybdenum Disulfide Layers Using H₂O Vapor as the Transport Agent

by Shichao Zhao, Jiaxin Weng, Shengzhong Jin, Yanfei Lv and Zhenguo Ji

Coatings 2018, 8(2), 78; https://doi.org/10.3390/coatings8020078 - 21 Feb 2018

Cited by 8 | Viewed by 7284

Abstract

Molybdenum disulfide (MoS₂) layers show excellent optical and electrical properties and have many potential applications. However, the growth of high-quality MoS₂ layers is a major bottleneck in the development of MoS₂-based devices. In this paper, we report a [...] Read more.

Molybdenum disulfide (MoS₂) layers show excellent optical and electrical properties and have many potential applications. However, the growth of high-quality MoS₂ layers is a major bottleneck in the development of MoS₂-based devices. In this paper, we report a chemical vapor transport deposition method to investigate the growth behavior of monolayer/multi-layer MoS₂ using water (H₂O) as the transport agent. It was shown that the introduction of H₂O vapor promoted the growth of MoS₂ by increasing the nucleation density and continuous monolayer growth. Moreover, the growth mechanism is discussed. Full article

(This article belongs to the Special Issue Graphene and Other 2D Layered Nanomaterial-Based Films: Synthesis, Properties and Applications)

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6 pages, 531 KiB

Open AccessCommunication

A Note on the Dyeing of Wool Fabrics Using Natural Dyes Extracted from Rotten Wood-Inhabiting Fungi

by Vicente A. Hernández, Felipe A. Galleguillos, Nicole Sagredo and Ángela Machuca

Coatings 2018, 8(2), 77; https://doi.org/10.3390/coatings8020077 - 19 Feb 2018

Cited by 11 | Viewed by 6397

Abstract

Fungal isolates obtained from rotten wood samples were identified and selected by their ability to produce fungal dyes in liquid media. Fungal isolates produced natural extracellular dyes with colors ranging from red to orange, yellow and purple. Dyes from two of these fungi, [...] Read more.

Fungal isolates obtained from rotten wood samples were identified and selected by their ability to produce fungal dyes in liquid media. Fungal isolates produced natural extracellular dyes with colors ranging from red to orange, yellow and purple. Dyes from two of these fungi, Talaromyces australis (red) and Penicillium murcianum (yellow), were extracted and used to dye wool samples in a Data Color Ahiba IR Pro-Trade (model Top Speed II) machine. The protein nature of wool interacted well with the fungal dyes producing colors suitable for textile applications when used to a concentration of 0.1 g·L⁻¹. Results on color fastness when washing confirmed the affinity of the dyes with wool as the dyed samples kept their color in acceptable ranges after washing, without the implementation of mordanting pretreatments or the use of fixing agents. Full article

(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)

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35 pages, 10290 KiB

Open AccessReview

Design of Nanostructured Functional Coatings by Using Wet-Chemistry Methods

by Pedro J. Rivero, Jose A. Garcia, Iban Quintana and Rafael Rodriguez

Coatings 2018, 8(2), 76; https://doi.org/10.3390/coatings8020076 - 14 Feb 2018

Cited by 23 | Viewed by 6592

Abstract

This review reports the implementation of novel nanostructured functional coatings by using different surface engineering techniques based on wet chemistry. In the first section, the theoretical fundaments of three techniques such as sol-gel process, layer-by-layer (LbL) assembly and electrospinning will be briefly described. [...] Read more.

This review reports the implementation of novel nanostructured functional coatings by using different surface engineering techniques based on wet chemistry. In the first section, the theoretical fundaments of three techniques such as sol-gel process, layer-by-layer (LbL) assembly and electrospinning will be briefly described. In the second section, selected applications in different potential fields will be presented gathering relevant properties such as superhydrophobicity, biocide behavior or applications in the field of optical fiber sensors. Full article

(This article belongs to the Special Issue Nanostructured Functional Coatings)

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11 pages, 14155 KiB

Open AccessArticle

The Fracture of Plasma-Treated Polyurethane Surface under Fatigue Loading

by Ilya A. Morozov, Alexander S. Mamaev, Mikhail V. Bannikov, Anton Yu. Beliaev and Irina V. Osorgina

Coatings 2018, 8(2), 75; https://doi.org/10.3390/coatings8020075 - 14 Feb 2018

Cited by 20 | Viewed by 4048

Abstract

Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading. [...] Read more.

Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading. The influence of the strain amplitude and the plasma treatment regime on damage character is discussed. Surface defects are studied in unloaded and stretched states of the material. As a result of fatigue loading, transverse cracks (with closed overlapping edges as well as with open edges deeply propagating into the polymer) and longitudinal folds which are break and bend inward, appear on the surface. Hard edges of cracks cut the soft polymer which is squeezed from the bulk to the surface. The observed damages are related to the high stiffness of the modified surface and its transition to the polymer substrate. Full article

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9 pages, 4614 KiB

Open AccessArticle

Study on the Properties of 1319 nm Ultra-High Reflector Deposited by Electron Beam Evaporation Assisted by an Energetic RF Ion Source

by Songwen Deng, Gang Li, Feng Wang, Qipeng Lv, Long Sun and Yuqi Jin

Coatings 2018, 8(2), 74; https://doi.org/10.3390/coatings8020074 - 14 Feb 2018

Cited by 2 | Viewed by 4147

Abstract

Ultra-high reflectors, working as a critical optical component, has been widely applied as a cavity mirror in fine optical systems such as laser gyro, F-P interferometer, etc. For decades, ion beam sputtering (IBS) technology, which can deposit ultra-low loss and dense layers, has [...] Read more.

Ultra-high reflectors, working as a critical optical component, has been widely applied as a cavity mirror in fine optical systems such as laser gyro, F-P interferometer, etc. For decades, ion beam sputtering (IBS) technology, which can deposit ultra-low loss and dense layers, has been commonly believed to be the only and irreplaceable method to fabricate ultra-high reflectors. Thus, reports on other methods are rare and a reflectivity above 99.99% obtained by evaporation technology (including ion assisted evaporation) has not been seen yet. In the present study, an energetic radio frequency (RF) ion source was introduced during the electron beam evaporation process, which improved the layer quality dramatically. An ultra-high reflector at 1319 nm with reflectivity of 99.992% (measured by cavity-ring down method) was successfully deposited on a φ100 mm × 25 mm single crystal silicon substrate whose surface roughness was approximately 0.420 nm. The surface figure of the reflector was accurately controlled superior to 1/6λ (λ = 632.8 nm). The measured absorption was approximately 3–5 ppm and the calculated scatter based on surface roughness measurement was approximately 6.64 ppm. Total loss of the reflector was systematically discussed. This study showed that it is possible to apply electron beam evaporation in ultra-high reflector manufacture and the method is capable of depositing reflectors with an aperture larger than φ600 mm which is the maximum capacity of current IBS technology. Full article

(This article belongs to the Special Issue Applications of Optical Thin Film Coatings)

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21 pages, 2542 KiB

Open AccessArticle

Damping Oriented Design of Thin-Walled Mechanical Components by Means of Multi-Layer Coating Technology

by Giuseppe Catania and Matteo Strozzi

Coatings 2018, 8(2), 73; https://doi.org/10.3390/coatings8020073 - 13 Feb 2018

Cited by 25 | Viewed by 5463

Abstract

The damping behaviour of multi-layer composite mechanical components, shown by recent research and application papers, is analyzed. A local dissipation mechanism, acting at the interface between any two different layers of the composite component, is taken into account, and a beam model, to [...] Read more.

The damping behaviour of multi-layer composite mechanical components, shown by recent research and application papers, is analyzed. A local dissipation mechanism, acting at the interface between any two different layers of the composite component, is taken into account, and a beam model, to be used for validating the known experimental results, is proposed. Multi-layer prismatic beams, consisting of a metal substrate and of some thin coated layers exhibiting variable stiffness and adherence properties, are considered in order to make it possible to study and validate this assumption. A dynamical model, based on a simple beam geometry but taking into account the previously introduced local dissipation mechanism and distributed visco-elastic constraints, is proposed. Some different application examples of specific multi-layer beams are considered, and some numerical examples concerning the beam free and forced response are described. The influence of the multilayer system parameters on the damping behaviour of the free and forced response of the composite beam is investigated by means of the definition of some damping estimators. Some effective multi-coating configurations, giving a relevant increase of the damping estimators of the coated structure with respect to the same uncoated structure, are obtained from the model simulation, and the results are critically discussed. Full article

(This article belongs to the Special Issue Manufacturing and Surface Engineering)

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9 pages, 3567 KiB

Open AccessArticle

Effect of Hexagonal Phase Content on Wear Behaviour of AlTiN Arc PVD Coatings

by Joern Kohlscheen and Christian Bareiss

Coatings 2018, 8(2), 72; https://doi.org/10.3390/coatings8020072 - 13 Feb 2018

Cited by 17 | Viewed by 5181

Abstract

In this study, the effect of increasing aluminum content and magnetic steering field strength on the structure and wear behavior of arc PVD AlTiN coatings is discussed. Deposition was done by means of an industrial-scale PVD unit for tool coating. The aluminium content [...] Read more.

In this study, the effect of increasing aluminum content and magnetic steering field strength on the structure and wear behavior of arc PVD AlTiN coatings is discussed. Deposition was done by means of an industrial-scale PVD unit for tool coating. The aluminium content in the AlTi source material was increased from 67 to 73 at.%. We applied two settings of the magnetic field that steers the arc across the cathode surface thereby evaporating the AlTi alloy differently. The resulting coating thickness ranged from 3.5 to about 7 µm. Cemented tungsten carbide was used as substrate material. Coating properties like hardness, adhesion, and crystal phases were analyzed by indentation and X-ray diffraction, respectively. The wear behaviour of the different AlTiN hard coatings were investigated in two ways. In a first idealized test, cyclic impacting was done applying a constant force. The resulting wear pattern was quantified by an Alicona multi-focus microscope. A second wear test was done by metal cutting under realistic conditions. Fly milling of ductile cast iron (EN-GJS-700) was performed with regular interruptions in order to measure the increasing wear mark. As expected, aluminium contents above 67 at.% (in the metal fraction of the coating) lead to a decreased wear resistance as the soft hexagonal phase exceeds values of a few vol.%. However, it was found that the formation of the hexagonal phase can be effectively influenced and delayed by increasing the magnetic steering field at the cathode. The wear behavior observed in cyclic impact testing corresponds well to results obtained with the more complex loading situation encountered in milling. Full article

(This article belongs to the Special Issue Coatings for Cutting Tools)

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15 pages, 4755 KiB

Open AccessArticle

Arc-Sprayed Fe-Based Coatings from Cored Wires for Wear and Corrosion Protection in Power Engineering

by Korobov Yury, Michael Filiрpov, Aleksey Makarov, Irina Malygina, Natalia Soboleva, Davide Fantozzi, Milanti Andrea, Heli Koivuluoto and Petri Vuoristo

Coatings 2018, 8(2), 71; https://doi.org/10.3390/coatings8020071 - 13 Feb 2018

Cited by 16 | Viewed by 5035

Abstract

High wear and corrosion of parts lead to an increase in operating costs at thermal power plants. The present paper shows a possible solution to this problem through the arc spraying of protective coatings. Cored wires of the base alloying system Fe-Cr-C were [...] Read more.

High wear and corrosion of parts lead to an increase in operating costs at thermal power plants. The present paper shows a possible solution to this problem through the arc spraying of protective coatings. Cored wires of the base alloying system Fe-Cr-C were used as a feedstock. Rise of wear- and heat-resistance of the coatings was achieved by additional alloying with Al, B, Ti, and Y. The wear and heat resistance of the coatings were tested via a two-body wear test accompanied by microhardness measurement and the gravimetric method, respectively. A high-temperature corrosion test was performed at 550 °C under KCl salt deposition. The porosity and adhesion strengths of the coatings were also evaluated. The microstructure was investigated with a scanning electron microscope (SEM) unit equipped with an energy dispersive X-ray (EDX) microanalyzer, and the phase composition was assessed by X-ray diffractometry. The test results showed the positive influence of additional alloying with Y on the coating properties. A comparison with commercial boiler materials showed that the coatings have the same level of heat resistance as austenite steels and are an order of magnitude higher than that of pearlite and martensite-ferrite steels. The coatings can be applied to wear- and heat-resistant applications at 20–700 °C. Full article

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10 pages, 3944 KiB

Open AccessArticle

Corrosion Resistance and Durability of Superhydrophobic Copper Surface in Corrosive NaCl Aqueous Solution

by Chun-Wei Yao, Divine Sebastian, Ian Lian, Özge Günaydın-Şen, Robbie Clarke, Kirby Clayton, Chiou-Yun Chen, Krishna Kharel, Yanyu Chen and Qibo Li

Coatings 2018, 8(2), 70; https://doi.org/10.3390/coatings8020070 - 11 Feb 2018

Cited by 44 | Viewed by 8101

Abstract

Artificial superhydrophobic copper surfaces play an important role in modern applications such as self-cleaning and dropwise condensation; however, corrosion resistance and durability often present as major concerns in such applications. In this study, the anti-corrosion properties and mechanical durability of superhydrophobic copper surface [...] Read more.

Artificial superhydrophobic copper surfaces play an important role in modern applications such as self-cleaning and dropwise condensation; however, corrosion resistance and durability often present as major concerns in such applications. In this study, the anti-corrosion properties and mechanical durability of superhydrophobic copper surface have been investigated. The superhydrophobic copper surfaces were achieved with wet chemical etching and an immersion method to reduce the complexity of the fabrication process. The surface structures and materials were characterized using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectrometer (FTIR). The corrosion resistance and mechanical properties of the superhydrophobic copper surface were characterized after immersing surfaces in a 3.5 wt % NaCl solution. The chemical stability of the superhydrophobic copper surface in the NaCl solution for a short period of time was also evaluated. An abrasion test and an ultrasound oscillation were conducted to confirm that the copper surface contained durable superhydrophobic properties. In addition, an atomic force microscope was employed to study the surface mechanical property in the corrosion conditions. The present study shows that the resulting superhydrophobic copper surface exhibit enhanced corrosion resistance and durability. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings)

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8 pages, 1672 KiB

Open AccessArticle

Effects of the Oxide Coating Thickness on the Small Flaw Sizing Using an Ultrasonic Test Technique

by Xiujuan Miao, Xiongbing Li, Hongwei Hu, Guangjun Gao and Shuzeng Zhang

Coatings 2018, 8(2), 69; https://doi.org/10.3390/coatings8020069 - 9 Feb 2018

Cited by 5 | Viewed by 4333

Abstract

When magnesium alloys are tested using ultrasonic techniques, their oxide coating will affect the transmitted ultrasonic energy and the accuracy of the flaw sizing. In this work, the effects of the coating thickness on the flaw sizing are investigated. An ultrasonic measurement model [...] Read more.

When magnesium alloys are tested using ultrasonic techniques, their oxide coating will affect the transmitted ultrasonic energy and the accuracy of the flaw sizing. In this work, the effects of the coating thickness on the flaw sizing are investigated. An ultrasonic measurement model is employed to predict the flaw response signal, and the reflected and transmitted ultrasonic energy in the coated surface are corrected by modifying the reflection and transmission coefficients related to the effects of the coating thickness. The effectiveness of these coefficients and the ultrasonic measurement model are verified through experiments. With the correction of the coating thickness effects, the flaw-sizing curves predicted using the ultrasonic measurement model are provided. The flaws in magnesium alloy specimens with different coating thicknesses are tested, and the determined flaw sizes from these curves agree well with the actual sizes, which reveals the effectiveness of the proposed work. This work provides an effective tool to improve the flaw sizing performance using ultrasonic techniques in practical applications. Full article

(This article belongs to the Special Issue Advanced Nondestructive Evaluation and Characterization of Surface)

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12 pages, 7397 KiB

Open AccessArticle

Multifunctional Surface Modification of Mulberry Silk Fabric via PNIPAAm/Chitosan/PEO Nanofibers Coating and Cross-Linking Technology

by Jia Li, Boxiang Wang, Jie Lin, Dehong Cheng and Yanhua Lu

Coatings 2018, 8(2), 68; https://doi.org/10.3390/coatings8020068 - 9 Feb 2018

Cited by 8 | Viewed by 6411

Abstract

Multifunctional mulberry silk fabrics with excellent temperature- and pH-sensitivity, antibacterial properties and permeability are successfully prepared by surface modification with PNIPAAm/chitosan/poly(ethylene oxide) nanofibers. The nanofibers deposited on the surface of mulberry silk fabric are produced by the electrospinning technique. The surface properties of [...] Read more.

Multifunctional mulberry silk fabrics with excellent temperature- and pH-sensitivity, antibacterial properties and permeability are successfully prepared by surface modification with PNIPAAm/chitosan/poly(ethylene oxide) nanofibers. The nanofibers deposited on the surface of mulberry silk fabric are produced by the electrospinning technique. The surface properties of mulberry silk fabrics were changed by coating process and glutaraldehyde vapor cross-linking technology. The PNIPAAm/chitosan/PEO nanofibers have good apparent morphology and uniform fiber diameter. The contact angle of modified mulberry silk obviously increases with the increasing temperature. The bacterial reduction rates of modification of mulberry silk against E. coli and S. aureus all reach above 80%. Permeability test results show that it can largely improve the poor permeability of coated fabric by intelligent nanofiber modification technology. The air permeability of temperature- and pH-sensitivity mulberry silk fabric modified with PNIPAAm/chitosan/PEO nanofibers, which has reached about 5.1 × 10² L/m²/s, is higher than that of the silk fabric coated with PNIPAAm/chitosan/PEO solution that reached 1.5 × 10² L/m²/s. The nanofibers coated with mulberry silk fabrics show outstanding temperature- and pH-sensitivity, antibacterial properties and permeability, and may be a potential application in medical care, intelligent materials and textiles. Full article

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24 pages, 11696 KiB

Open AccessReview

Porous Zinc Oxide Thin Films: Synthesis Approaches and Applications

by Marco Laurenti and Valentina Cauda

Coatings 2018, 8(2), 67; https://doi.org/10.3390/coatings8020067 - 9 Feb 2018

Cited by 74 | Viewed by 16305

Abstract

Zinc oxide (ZnO) thin films have been widely investigated due to their multifunctional properties, i.e., catalytic, semiconducting and optical. They have found practical use in a wide number of application fields. However, the presence of a compact micro/nanostructure has often limited the resulting [...] Read more.

Zinc oxide (ZnO) thin films have been widely investigated due to their multifunctional properties, i.e., catalytic, semiconducting and optical. They have found practical use in a wide number of application fields. However, the presence of a compact micro/nanostructure has often limited the resulting material properties. Moreover, with the advent of low-dimensional ZnO nanostructures featuring unique physical and chemical properties, the interest in studying ZnO thin films diminished more and more. Therefore, the possibility to combine at the same time the advantages of thin-film based synthesis technologies together with a high surface area and a porous structure might represent a powerful solution to prepare ZnO thin films with unprecedented physical and chemical characteristics that may find use in novel application fields. Within this scope, this review offers an overview on the most successful synthesis methods that are able to produce ZnO thin films with both framework and textural porosities. Moreover, we discuss the related applications, mainly focused on photocatalytic degradation of dyes, gas sensor fabrication and photoanodes for dye-sensitized solar cells. Full article

(This article belongs to the Collection Surface and Interface Science and Engineering for the Society of the Future)

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12 pages, 6944 KiB

Open AccessArticle

Hydrogen Permeation, and Mechanical and Tribological Behavior, of CrN_x Coatings Deposited at Various Bias Voltages on IN718 by Direct Current Reactive Sputtering

by Egor B. Kashkarov, Aleksei Obrosov, Alina N. Sutygina, Elena Uludintceva, Andrei Mitrofanov and Sabine Weiß

Coatings 2018, 8(2), 66; https://doi.org/10.3390/coatings8020066 - 9 Feb 2018

Cited by 11 | Viewed by 5178

Abstract

In the current work, the microstructure, hydrogen permeability, and properties of chromium nitride (CrN_x) thin films deposited on the Inconel 718 superalloy using direct current reactive sputtering are investigated. The influence of the substrate bias voltage on the crystal structure, mechanical, [...] Read more.

In the current work, the microstructure, hydrogen permeability, and properties of chromium nitride (CrN_x) thin films deposited on the Inconel 718 superalloy using direct current reactive sputtering are investigated. The influence of the substrate bias voltage on the crystal structure, mechanical, and tribological properties before and after hydrogen exposure was studied. It was found that increasing the substrate bias voltage leads to densification of the coating. X-ray diffraction (XRD) results reveal a change from mixed fcc-CrN + hcp-Cr₂N to the approximately stoichiometric hcp-Cr₂N phase with increasing substrate bias confirmed by wavelength-dispersive X-ray spectroscopy (WDS). The texture coefficients of (113), (110), and (111) planes vary significantly with increasing substrate bias voltage. The hydrogen permeability was measured by gas-phase hydrogenation. The CrN coating deposited at 60 V with mixed c-CrN and (113) textured hcp-Cr₂N phases exhibits the lowest hydrogen absorption at 873 K. It is suggested that the crystal orientation is only one parameter influencing the permeation resistance of the CrN_x coating together with the film structure, the presence of mixing phases, and the packing density of the structure. After hydrogenation, the hardness increased for all coatings, which could be related to the formation of a Cr₂O₃ oxide film on the surface, as well as the defect formation after hydrogen loading. Tribological tests reveal that hydrogenation leads to a decrease of the friction coefficient by up to 40%. The lowest value of 0.25 ± 0.02 was reached for the CrN_x coating deposited at 60 V after hydrogenation. Full article

(This article belongs to the Special Issue Surface Preparation and Treatments for Enhancing the Coating Performance)

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16 pages, 9940 KiB

Open AccessArticle

New Electrospun Polystyrene/Al₂O₃ Nanocomposite Superhydrophobic Coatings; Synthesis, Characterization, and Application

by Ahmed Bahgat Radwan, Aboubakr M. Abdullah, Adel M. A. Mohamed and Mariam A. Al-Maadeed

Coatings 2018, 8(2), 65; https://doi.org/10.3390/coatings8020065 - 8 Feb 2018

Cited by 37 | Viewed by 6541

Abstract

The effect of electrospinning operational parameters on the morphology, surface roughness, and wettability of different compositions of electrospun polystyrene (PS)–aluminum oxide (Al₂O₃) nanocomposite coatings was investigated using different techniques. For example, a scanning electron microscope (SEM) coupled with an [...] Read more.

The effect of electrospinning operational parameters on the morphology, surface roughness, and wettability of different compositions of electrospun polystyrene (PS)–aluminum oxide (Al₂O₃) nanocomposite coatings was investigated using different techniques. For example, a scanning electron microscope (SEM) coupled with an energy dispersive X-ray (EDX) unit, a Fourier transform infrared (FTIR) spectrometer, an atomic force microscope (AFM), and water contact angle (WCA), and contact angle hysteresis (CAH) measurements using the sessile droplet method, were used. The latter used 4 µL of distilled water at room temperature. PS/Al₂O₃ nanocomposite coatings exhibited different morphologies, such as beaded fibers and microfibers, depending on the concentration ratio between the PS and Al₂O₃ nanoparticles and the operational parameters of the electrospinning process. The optimum conditions to produce a nanocomposite coating with the highest roughness and superhydrophobic properties (155° ± 1.9° for WCA and 3° ± 4.2° for CAH) are 2.5 and 0.25 wt % of PS and Al₂O₃, respectively, 25 kV for the applied potential and 1.5 mL·h⁻¹ for the solution flow rate at 35 °C. The corrosion resistance of the as-prepared coatings was investigated using the electrochemical impedance spectroscopy (EIS) technique. The results have revealed that the highly porous superhydrophobic nanocomposite coatings (SHCs) possess a superior corrosion resistance that is higher than the uncoated Al alloy by three orders of magnitude. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings)

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10 pages, 2554 KiB

Open AccessArticle

Application of Graphene-Oxide-Modified Polyacrylate Polymer for Controlled-Release Coated Urea

by Wenjun Yuan, Yazhen Shen, Fei Ma and Changwen Du

Coatings 2018, 8(2), 64; https://doi.org/10.3390/coatings8020064 - 8 Feb 2018

Cited by 7 | Viewed by 6606

Abstract

Polyacrylate polymer (PA) was modified with graphene oxide (GO) and the obtained composites were applied as coatings for controlled-release coated urea (CRU). The physicochemical properties of the different PA/GO coatings were characterized in detail and the nitrogen-release characteristics of the obtained CRU samples [...] Read more.

Polyacrylate polymer (PA) was modified with graphene oxide (GO) and the obtained composites were applied as coatings for controlled-release coated urea (CRU). The physicochemical properties of the different PA/GO coatings were characterized in detail and the nitrogen-release characteristics of the obtained CRU samples were determined in water at 25 °C. The experimental results revealed that addition of GO to PA reduced the swelling degree from 83.01% to 46.35% and improved its mechanical properties (the Young’s modulus was improved from 31.52 to 34.97 MPa and the glass transition temperature was increased from 4.21 to 6.11 °C), thus dramatically slowing down the cumulative nutrient release from the CRU fertilizer from 87.25% to 59.71%. These results suggest that GO enhances the properties of PA for CRU applications, which shows that GO-modified PA is a good coating material. Full article

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17 pages, 4194 KiB

Open AccessEditor’s ChoiceReview

Recent Advances in Graphene-Based Free-Standing Films for Thermal Management: Synthesis, Properties, and Applications

by Feng Gong, Hao Li, Wenbin Wang, Dawei Xia, Qiming Liu, Dimitrios V. Papavassiliou and Ziqiang Xu

Coatings 2018, 8(2), 63; https://doi.org/10.3390/coatings8020063 - 7 Feb 2018

Cited by 46 | Viewed by 9829

Abstract

Thermal management in microelectronic devices has become a crucial issue as the devices are more and more integrated into micro-devices. Recently, free-standing graphene films (GFs) with outstanding thermal conductivity, superb mechanical strength, and low bulk density, have been regarded as promising materials for [...] Read more.

Thermal management in microelectronic devices has become a crucial issue as the devices are more and more integrated into micro-devices. Recently, free-standing graphene films (GFs) with outstanding thermal conductivity, superb mechanical strength, and low bulk density, have been regarded as promising materials for heat dissipation and for use as thermal interfacial materials in microelectronic devices. Recent studies on free-standing GFs obtained via various approaches are reviewed here. Special attention is paid to their synthesis method, thermal conductivity, and potential applications. In addition, the most important factors that affect the thermal conductivity are outlined and discussed. The scope is to provide a clear overview that researchers can adopt when fabricating GFs with improved thermal conductivity and a large area for industrial applications. Full article

(This article belongs to the Special Issue Graphene and Other 2D Layered Nanomaterial-Based Films: Synthesis, Properties and Applications)

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16 pages, 15299 KiB

Open AccessArticle

Improvements of Piezo-Actuated Stick–Slip Micro-Drives: Modeling and Driving Waveform

by Xuan-Ha Nguyen, Tien-Hiep Mau, Ingo Meyer, Bao-Lam Dang and Hong-Phuc Pham

Coatings 2018, 8(2), 62; https://doi.org/10.3390/coatings8020062 - 7 Feb 2018

Cited by 19 | Viewed by 7020

Abstract

Modeling and waveform optimization are important research topics for piezo-actuated stick–slip micro-drives. In this paper, the dynamics of piezo-actuated stick–slip micro-drives (PASSMDs) are theoretically investigated. We introduce an extended model taking the dynamics of the piezo actuators into account. The model combines the [...] Read more.

Modeling and waveform optimization are important research topics for piezo-actuated stick–slip micro-drives. In this paper, the dynamics of piezo-actuated stick–slip micro-drives (PASSMDs) are theoretically investigated. We introduce an extended model taking the dynamics of the piezo actuators into account. The model combines the whole macroscopic movement of the drive’s runner and actuators and the microscopic behavior of the frictional contacts in a hybrid dynamic simulation. The macroscopic movements are described via Newtonian mechanics, while the microscopic behavior is computed using the method of dimensionality reduction. Two important characteristics of the drive, the critical actuation amplitude and the force generation, are systematically analyzed. The numerical simulation results show a fine agreement with experimental data of the previously published work. The critical actuation amplitude is found to depend on the behavior of the guiding contacts, the dynamics of the actuators and their interaction. Furthermore, a novel driving waveform, which allows us to increase the operational velocity for the drive, is proposed. The waveform is derived by exploiting micro-vibration and considering the dynamic contact status. Simulation results show that the average velocity of the drive is heightened by about

15 %

. The performance of the drive is therefore improved. Full article

(This article belongs to the Special Issue Piezoresistive and Piezoelectric Thin Films for Sensors)

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10 pages, 2751 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Analysis of the Influence of the Use of Cutting Fluid in Hybrid Processes of Machining and Laser Metal Deposition (LMD)

by Magdalena Cortina, Jon Iñaki Arrizubieta, Eneko Ukar and Aitzol Lamikiz

Coatings 2018, 8(2), 61; https://doi.org/10.3390/coatings8020061 - 7 Feb 2018

Cited by 15 | Viewed by 5919

Abstract

Hybrid manufacturing processes that combine additive and machining operations are gaining relevance in modern industry thanks to the capability of building complex parts with minimal material and, many times, with process time reduction. Besides, as the additive and subtractive operations are carried out [...] Read more.

Hybrid manufacturing processes that combine additive and machining operations are gaining relevance in modern industry thanks to the capability of building complex parts with minimal material and, many times, with process time reduction. Besides, as the additive and subtractive operations are carried out in the same machine, without moving the part, dead times are reduced and higher accuracies are achieved. However, it is not clear whether the direct material deposition after the machining operation is possible or intermediate cleaning stages are required because of the possible presence of residual cutting fluids. Therefore, different Laser Metal Deposition (LMD) tests are performed on a part impregnated with cutting fluid, both directly and after the removal of the coolant by techniques such as laser vaporizing and air blasting. The present work studies the influence of the cutting fluid in the LMD process and the quality of the resulting part. Resulting porosity is evaluated and it is concluded that if the part surface is not properly clean after the machining operation, deficient clad quality can be obtained in the subsequent laser additive operation. Full article

(This article belongs to the Special Issue Surface Preparation and Treatments for Enhancing the Coating Performance)

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12 pages, 5552 KiB

Open AccessArticle

Influence of TiO₂-Coating Layer on Nanoporous Alumina Membranes by ALD Technique

by Lourdes Gelde, Ana L. Cuevas, María Del Valle Martínez de Yuso, Juana Benavente, Víctor Vega, Ana Silvia González, Víctor M. Prida and Blanca Hernando

Coatings 2018, 8(2), 60; https://doi.org/10.3390/coatings8020060 - 7 Feb 2018

Cited by 13 | Viewed by 5205

Abstract

Geometrical, chemical, optical and ionic transport changes associated with ALD of TiO₂-coating on the porous structure of two nanoporous alumina membranes (NPAMs), which were obtained by the two-step aluminum anodization method but with different pore size and porosity, are presented. Chemical [...] Read more.

Geometrical, chemical, optical and ionic transport changes associated with ALD of TiO₂-coating on the porous structure of two nanoporous alumina membranes (NPAMs), which were obtained by the two-step aluminum anodization method but with different pore size and porosity, are presented. Chemical and morphological changes were determined by analyzing XPS spectra and SEM images, showing practically total coverage of the NPAMs surface and leading to a reduction in the geometrical parameters of both samples, while SAED and high resolution TEM measurements allowed us to determine the crystalline structure and thickness of the TiO₂-coating, with the latter confirmed by depth-profile XPS analysis. Spectroscopic ellipsometry measurements were also carried out in order to detect changes in characteristic optical parameters (refractive index, n, and extinction coefficient, k), due to the TiO₂-coating of NPAMs. Considering the common application of NPAMs in solute/ion diffusion processes, the effect of the TiO₂-coverage on electrochemical parameters was analyzed by measuring the concentration potential with a typical model electrolyte (KCl solutions), leading to an increase of the electropositive character for both kinds of samples. Full article

(This article belongs to the Special Issue Nanostructured Functional Coatings)

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14 pages, 8809 KiB

Open AccessArticle

Improvement of Wear Performance of Nano-Multilayer PVD Coatings under Dry Hard End Milling Conditions Based on Their Architectural Development

by Shahereen Chowdhury, Ben D. Beake, Kenji Yamamoto, Bipasha Bose, Myriam Aguirre, German S. Fox-Rabinovich and Stephen C. Veldhuis

Coatings 2018, 8(2), 59; https://doi.org/10.3390/coatings8020059 - 5 Feb 2018

Cited by 25 | Viewed by 6130

Abstract

The TiAlCrSiYN-based family of PVD (physical vapor deposition) hard coatings was specially designed for extreme conditions involving the dry ultra-performance machining of hardened tool steels. However, there is a strong potential for further advances in the wear performance of the coatings through improvements [...] Read more.

The TiAlCrSiYN-based family of PVD (physical vapor deposition) hard coatings was specially designed for extreme conditions involving the dry ultra-performance machining of hardened tool steels. However, there is a strong potential for further advances in the wear performance of the coatings through improvements in their architecture. A few different coating architectures (monolayer, multilayer, bi-multilayer, bi-multilayer with increased number of alternating nano-layers) were studied in relation to cutting-tool life. Comprehensive characterization of the structure and properties of the coatings has been performed using XRD, SEM, TEM, micro-mechanical studies and tool-life evaluation. The wear performance was then related to the ability of the coating layer to exhibit minimal surface damage under operation, which is directly associated with the various micro-mechanical characteristics (such as hardness, elastic modulus and related characteristics; nano-impact; scratch test-based characteristics). The results presented exhibited that a substantial increase in tool life as well as improvement of the mechanical properties could be achieved through the architectural development of the coatings. Full article

(This article belongs to the Special Issue Coatings for Cutting Tools)

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16 pages, 16762 KiB

Open AccessArticle

Mechanical and Barrier Properties of Potato Protein Isolate-Based Films

by David Schäfer, Matthias Reinelt, Andreas Stäbler and Markus Schmid

Coatings 2018, 8(2), 58; https://doi.org/10.3390/coatings8020058 - 5 Feb 2018

Cited by 16 | Viewed by 5277

Abstract

Potato protein isolate (PPI) was studied as a source for bio-based polymer films. The objective of this study was the determination of the packaging-relevant properties, including the mechanical properties and barrier performance, of casted potato protein films. Furthermore, the films were analyzed for [...] Read more.

Potato protein isolate (PPI) was studied as a source for bio-based polymer films. The objective of this study was the determination of the packaging-relevant properties, including the mechanical properties and barrier performance, of casted potato protein films. Furthermore, the films were analyzed for cross-linking properties depending on the plasticizer concentration, and compared with whey protein isolate (WPI)-based films. Swelling tests and water sorption isotherm measurements were performed to determine the degree of swelling, the degree of cross-linking, and the cross-linking density using the Flory–Rehner approach. The effects of different plasticizer types and contents on compatibility with potato protein were studied. Glycerol was the most compatible plasticizer, as it was the only plasticizer providing flexible standalone films in the investigated concentration range after three weeks of storage. Results indicated that increasing glycerol content led to decreasing cross-linking, which correlated in an inversely proportional manner to the swelling behavior. A correlation between cross-linking and functional properties was also reflected in mechanical and barrier characterization. An increasing number of cross-links resulted in higher tensile strength and Young’s modulus, whereas elongation was unexpectedly not affected. Similarly, barrier performance was significantly improved with increasing cross-linking. The overall superior functional properties of whey protein-based films were mainly ascribed to their higher percentage of cross-links. This was primarily attributed to a lower total cysteine content of PPI (1.6 g/16 g·N) compared to WPI (2.8 g/16 g·N), and the significant lower solubility of potato protein isolate in water at pH 7.0 (48.1%), which was half that of whey protein isolate (96%). Comparing on an identical glycerol level (66.7% (w/w protein)), the performance of potato protein isolate was about 80% that of whey protein isolate regarding cross-linking, as well as mechanical and barrier properties. Full article

(This article belongs to the Special Issue Films and Coatings for Food and Health Applications)

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9 pages, 11816 KiB

Open AccessArticle

Surface Modification of Sol-Gel Silica Antireflective Coatings by F-PMHS: A Simple Method for Improvement of Amphiphobicity

by Wensheng Lin, Yingying Sun, Jiaxian Zheng, Yanmei Zheng, Lianghong Yan, Bo Jiang, Wenbin Yang, Hanxian Chen and Xinxiang Zhang

Coatings 2018, 8(2), 57; https://doi.org/10.3390/coatings8020057 - 5 Feb 2018

Cited by 13 | Viewed by 6291

Abstract

Sol-gel silica antireflective coatings (ARCs) with improved amphiphobicity were simply fabricated on BK7 glass substrates via fluorinated-poly(methylhydrogen)siloxane (F-PMHS) surface modification by the dip-coating method. The results of Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) showed that F-PMHS were covalently bonded to [...] Read more.

Sol-gel silica antireflective coatings (ARCs) with improved amphiphobicity were simply fabricated on BK7 glass substrates via fluorinated-poly(methylhydrogen)siloxane (F-PMHS) surface modification by the dip-coating method. The results of Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS) showed that F-PMHS were covalently bonded to the surface of ARCs. F-PMHS modification significantly improved hydrophobicity and oleophobicity of silica ARCs by increasing their water contact angles from 27° to 105° and oil contact angles from 17° to 45°. In addition to the improved amphiphobicity, the modified ARCs also possessed excellent transmittance. Most importantly, it was found that with increasing F-PMHS content the atom amounts and porous property of modified ARCs were almost unchanged. This result had been shown to be associated with the changes of optical property and amphiphobicity for silica ARCs, and the details were discussed. Full article

(This article belongs to the Special Issue Applications of Optical Thin Film Coatings)

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11 pages, 13468 KiB

Open AccessArticle

Investigation of Electrochemically Deposited and Chemically Reduced Platinum Nanostructured Thin Films as Counter Electrodes in Dye-Sensitized Solar Cells

by Chih-Hung Tsai, Yu-Chen Hsiao and Ping-Yuan Chuang

Coatings 2018, 8(2), 56; https://doi.org/10.3390/coatings8020056 - 1 Feb 2018

Cited by 5 | Viewed by 5861

Abstract

In this paper, we demonstrated that platinum (Pt) counter electrodes (CEs) fabricated using electrochemical deposition and chemical reduction can replace conventional high-temperature thermally decomposed Pt electrodes. In this study, Pt electrodes were fabricated using thermal decomposition, electrochemical deposition, and chemical reduction, and the [...] Read more.

In this paper, we demonstrated that platinum (Pt) counter electrodes (CEs) fabricated using electrochemical deposition and chemical reduction can replace conventional high-temperature thermally decomposed Pt electrodes. In this study, Pt electrodes were fabricated using thermal decomposition, electrochemical deposition, and chemical reduction, and the influence of the different Pt counter electrodes on the efficiency of the dye-sensitized solar cells (DSSCs) was analyzed. The properties of the various Pt CEs were analyzed using scanning electron microscopy (SEM), surface area analysis, X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). DSSCs with various Pt CEs were characterized using current density-voltage (J-V), incident photo-current conversion efficiency (IPCE), and EIS measurements. The results show that the power conversion efficiencies of these three types of DSSC devices were between 7.43% and 7.72%. The DSSCs based on the Pt electrode fabricated through electrochemical deposition exhibited the optimal power conversion efficiency. Because the processes of electrochemical deposition and chemical reduction do not require high-temperature sintering, these two methods are suitable for the fabrication of Pt on flexible plastic substrates. Full article

(This article belongs to the Special Issue Thin Films and Patterned Structures by Electrochemical Methods)

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13 pages, 1195 KiB

Open AccessArticle

Simple Coatings to Render Polystyrene Protein Resistant

by Marcelle Hecker, Matthew Sheng Hao Ting and Jenny Malmström

Coatings 2018, 8(2), 55; https://doi.org/10.3390/coatings8020055 - 1 Feb 2018

Cited by 12 | Viewed by 9092

Abstract

Non-specific protein adsorption is detrimental to the performance of many biomedical devices. Polystyrene is a commonly used material in devices and thin films. Simple reliable surface modification of polystyrene to render it protein resistant is desired in particular for device fabrication and orthogonal [...] Read more.

Non-specific protein adsorption is detrimental to the performance of many biomedical devices. Polystyrene is a commonly used material in devices and thin films. Simple reliable surface modification of polystyrene to render it protein resistant is desired in particular for device fabrication and orthogonal functionalisation schemes. This report details modifications carried out on a polystyrene surface to prevent protein adsorption. The trialed surfaces included Pluronic F127 and PLL-g-PEG, adsorbed on polystyrene, using a polydopamine-assisted approach. Quartz crystal microbalance with dissipation (QCM-D) results showed only short-term anti-fouling success of the polystyrene surface modified with F127, and the subsequent failure of the polydopamine intermediary layer in improving its stability. In stark contrast, QCM-D analysis proved the success of the polydopamine assisted PLL-g-PEG coating in preventing bovine serum albumin adsorption. This modified surface is equally as protein-rejecting after 24 h in buffer, and thus a promising simple coating for long term protein rejection of polystyrene. Full article

(This article belongs to the Special Issue Advanced Coatings for Buildings)

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