Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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23 pages, 7526 KiB  
Article
Influence of Material Composition on Structure, Surface Properties and Biological Activity of Nanocrystalline Coatings Based on Cu and Ti
by Damian Wojcieszak, Malgorzata Osekowska, Danuta Kaczmarek, Bogumila Szponar, Michal Mazur, Piotr Mazur and Agata Obstarczyk
Coatings 2020, 10(4), 343; https://doi.org/10.3390/coatings10040343 - 2 Apr 2020
Cited by 7 | Viewed by 3546
Abstract
In this paper, the influence of material composition on structure and surface properties of bioactive coatings based on Cu and Ti is described. Nanocrystalline coatings were prepared by innovative pulsed DC magnetron sputtering. For their preparation, a multi-magnetron system was used in order [...] Read more.
In this paper, the influence of material composition on structure and surface properties of bioactive coatings based on Cu and Ti is described. Nanocrystalline coatings were prepared by innovative pulsed DC magnetron sputtering. For their preparation, a multi-magnetron system was used in order to obtain films with various copper content. The main goal of our work was the complex analysis of biological activity of Cu-Ti films in comparison with their material composition and surface state. Antimicrobial activity (for E. coli and S. aureus), as well as the impact on cell viability (L929 line), were investigated. The physicochemical properties were examined with the aid of X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and atomic absorption spectroscopy. It was found that all prepared films were nanocrystalline and bactericidal, but their cytotoxicity was related to the Cu-content in the film. Complex analysis of the bioactivity was developed in relation to the copper ion migration process. Moreover, manufacturing of antibacterial films with stimulating action on L929 cell line was possible. Full article
(This article belongs to the Special Issue Functional Surfaces for Biomedical Applications)
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9 pages, 1450 KiB  
Article
Local Structure Analysis on Si-Containing DLC Films Based on the Measurement of C K-Edge and Si K-Edge X-ray Absorption Spectra
by Kazuhiro Kanda, Shuto Suzuki, Masahito Niibe, Takayuki Hasegawa, Tsuneo Suzuki and Hedetoshi Saitoh
Coatings 2020, 10(4), 330; https://doi.org/10.3390/coatings10040330 - 30 Mar 2020
Cited by 12 | Viewed by 3705
Abstract
In this paper, the local structure of silicon-containing diamond-like carbon (Si-DLC) films is discussed based on the measurement of C K-edge and Si K-edge near-edge x-ray absorption fine structure (NEXAFS) spectra using the synchrotron radiation of 11 types of Si-DLC film [...] Read more.
In this paper, the local structure of silicon-containing diamond-like carbon (Si-DLC) films is discussed based on the measurement of C K-edge and Si K-edge near-edge x-ray absorption fine structure (NEXAFS) spectra using the synchrotron radiation of 11 types of Si-DLC film fabricated with various synthesis methods and having different elemental compositions. In the C K-edge NEXAFS spectra of the Si-DLC films, the σ* band shrunk and shifted to the lower-energy side, and the π* peak broadened with an increase in the Si content in the Si-DLC films. However, there were no significant changes observed in the Si K-edge NEXAFS spectra with an increase in the Si content. These results indicate that Si–Si bonding is not formed with precedence in Si-DLC film. Full article
(This article belongs to the Special Issue Recent Advances in Carbon/Graphite Coatings)
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14 pages, 2428 KiB  
Article
Poultry Shelf-Life Enhancing Potential of Nanofibers and Nanoparticles Containing Porphyra dioica Extracts
by João Reboleira, Pedro Adão, Sara F. C. Guerreiro, Juliana R. Dias, Rui Ganhão, Susana Mendes, Mariana Andrade, Fernanda Vilarinho, Ana Sanches-Silva, Artur Mateus, Nuno Alves and Susana Bernardino
Coatings 2020, 10(4), 315; https://doi.org/10.3390/coatings10040315 - 26 Mar 2020
Cited by 11 | Viewed by 3718
Abstract
Aqueous extracts of commercially available red macroalgae Porphyra dioica were integrated as inner coatings of food-grade polypropylene (PP) films through use of electrospinning and electrospraying technologies. Two coating formulations (A = 5 wt% P. dioica extract and 7.5 wt% polyvinyl alcohol (PVA); B [...] Read more.
Aqueous extracts of commercially available red macroalgae Porphyra dioica were integrated as inner coatings of food-grade polypropylene (PP) films through use of electrospinning and electrospraying technologies. Two coating formulations (A = 5 wt% P. dioica extract and 7.5 wt% polyvinyl alcohol (PVA); B = 1 wt% P. dioica extract, 1 wt% PVA, and 17% gelatine) were evaluated as to their capacity to delay spoilage of minced chicken breasts, through monitoring of microbial growth (total mesophile aerobic colony counts), colour stability, lipid oxidation (thiobarbituric acid reactive substances (TBARS)), and sensory analysis over a 4-day refrigerated storage. Scanning electron microscopy (SEM) imaging revealed an increased nanofiber and nanoparticle density on extract-enriched fibers, without compromise to their morphology or the homogeneity of the coatings. Total microbial counts on coating B samples was significantly (p < 0.001) reduced compared to uncoated plastic wraps. The coated samples also exhibited fewer colour degradation, though the coatings did not differ substantially from uncoated plastic wrap. Sensory analysis test subjects successfully distinguished the raw samples based on their treatment and gave a positive approval rating (66.7%) to the extract-enriched coatings when asked about edibility post storage. Full article
(This article belongs to the Special Issue Novel Advances in Food Contact Materials)
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12 pages, 34969 KiB  
Article
Multilayer Nanoimprinting to Create Hierarchical Stamp Masters for Nanoimprinting of Optical Micro- and Nanostructures
by Amiya R. Moharana, Helene M. Außerhuber, Tina Mitteramskogler, Michael J. Haslinger and Michael M. Mühlberger
Coatings 2020, 10(3), 301; https://doi.org/10.3390/coatings10030301 - 24 Mar 2020
Cited by 11 | Viewed by 4640
Abstract
Nanoimprinting is a well-established replication technology for optical elements, with the capability to replicate highly complex micro- and nanostructures. One of the main challenges, however, is the generation of the master structures necessary for stamp fabrication. We used UV-based Nanoimprint Lithography to prepare [...] Read more.
Nanoimprinting is a well-established replication technology for optical elements, with the capability to replicate highly complex micro- and nanostructures. One of the main challenges, however, is the generation of the master structures necessary for stamp fabrication. We used UV-based Nanoimprint Lithography to prepare hierarchical master structures. To realize structures with two different length scales, conventional nanoimprinting of larger structures and conformal reversal nanoimprinting to print smaller structures on top of the larger structures was performed. Liquid transfer imprint lithography proved to be well suited for this purpose. We used the sample prepared in such a way as a master for further nanoimprinting, where the hierarchical structures can then be imprinted in one single nanoimprinting step. As an example, we presented a diffusor structure with a diffraction-grating structure on top. Full article
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12 pages, 3045 KiB  
Article
Flame-Retardant Wood Composites Based on Immobilizing with Chitosan/Sodium Phytate/Nano-TiO2-ZnO Coatings via Layer-by-Layer Self-Assembly
by Lin Zhou and Yanchun Fu
Coatings 2020, 10(3), 296; https://doi.org/10.3390/coatings10030296 - 22 Mar 2020
Cited by 60 | Viewed by 6244
Abstract
Composite coatings of inorganic nanomaterials with polyelectrolytes are promising materials for wood modification. Endowing wood with flame retardancy behavior can not only broaden the range of applications of wood, but also improve the safety of wood products. In this work, chitosan/sodium phytate/TiO2 [...] Read more.
Composite coatings of inorganic nanomaterials with polyelectrolytes are promising materials for wood modification. Endowing wood with flame retardancy behavior can not only broaden the range of applications of wood, but also improve the safety of wood products. In this work, chitosan/sodium phytate/TiO2-ZnO nanoparticle (CH/SP/nano-TiO2-ZnO) composite coatings were coated on wood surface through layer-by-layer self-assembly. The morphology and chemical composition of the modified wood samples were analyzed using scanning electron microscopy and energy dispersive spectrometry. The thermal degradation properties and flame retardancy of the samples treated with different assembly structures were observed by thermogravimetric analysis, limiting oxygen test, and combustion test. Due to the presence of an effective intumescent flame retardant system and a physical barrier, the CH/SP/nano-TiO2-ZnO coatings exhibited the best flame retardant performance and required only approximately six seconds for self-extinguishing. The coated samples had a limiting oxygen index of 8.4% greater than the original wood. Full article
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11 pages, 6163 KiB  
Article
SERS Activity of Silver Nanosphere, Triangular Nanoplates, Hexagonal Nanoplates and Quasi-Spherical Nanoparticles: Effect of Shape and Morphology
by Marco Zannotti, Andrea Rossi and Rita Giovannetti
Coatings 2020, 10(3), 288; https://doi.org/10.3390/coatings10030288 - 20 Mar 2020
Cited by 41 | Viewed by 6000
Abstract
In this work, we prepared different morphologies of silver nanoparticles: nanosphere, triangular nanoplates, hexagonal nanoplates, and quasi-spherical shapes, through one-step synthesis. Hydrogen peroxide was used as the oxidizing agent during the reduction of silver nitrate by sodium borohydride, in the presence of tri-sodium [...] Read more.
In this work, we prepared different morphologies of silver nanoparticles: nanosphere, triangular nanoplates, hexagonal nanoplates, and quasi-spherical shapes, through one-step synthesis. Hydrogen peroxide was used as the oxidizing agent during the reduction of silver nitrate by sodium borohydride, in the presence of tri-sodium citrate and poly-vinyl-pyrrolidone. The obtained silver nanoparticles were fully characterized by UV-Vis spectroscopy, Dynamic Light Scattering and Scanning Electron Microscopy, and successfully used as Surface Enhanced Raman Scattering (SERS) substrates. The effect of shape and morphology on the Raman scattering enhancement was evaluated by using methylene blue as target molecules. The Raman measurements demonstrated that the prepared substrates are reliable and sensitive with analytical enhancement factors, estimated to be around 105 with a concentration of methylene blue 1 μM. When triangular and hexagonal nanoplates were tested with different concentrations of analyte, they demonstrated a good linearity in Raman intensity with a good detection of methylene blue 0.1 μM. Full article
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23 pages, 7944 KiB  
Article
Hard Quasicrystalline Coatings Deposited by HVOF Thermal Spray to Reduce Ice Accretion in Aero-Structures Components
by J. Mora, P. García, R. Muelas and A. Agüero
Coatings 2020, 10(3), 290; https://doi.org/10.3390/coatings10030290 - 20 Mar 2020
Cited by 31 | Viewed by 4797
Abstract
Weather hazards, in particular icing conditions, are an important contributing factor in aviation accidents and incidents worldwide. Many different anti-icing strategies are currently being explored to find suitable long-lasting solutions, such as surface engineering, which can contribute to reduce ice accumulation. Quasicrystals (QCs) [...] Read more.
Weather hazards, in particular icing conditions, are an important contributing factor in aviation accidents and incidents worldwide. Many different anti-icing strategies are currently being explored to find suitable long-lasting solutions, such as surface engineering, which can contribute to reduce ice accumulation. Quasicrystals (QCs) are metallic materials, but with similar properties to those of ceramic materials, such as low thermal and electrical conductivities, and high hardness. In particular, QCs that have low surface energy are commercially used as coatings to replace polytetrafluoroethylene (PTFE), also known as Teflon, on frying pans, as they do not scratch easily. PTFE exhibits excellent anti-wetting and anti-icing properties and therefore QCs appear as good candidates to be employed as ice-phobic coatings. Al-based QCs have been applied by High Velocity Oxyfuel (HVOF) thermal spray on typically used aeronautic materials, such as Ti and Al alloys, as well as steels. The coatings have been characterized and evaluated, including the measurement of hardness, roughness, wetting properties, ice accretion behavior in an icing wind tunnel (IWT), and ice adhesion by a double lap shear test. The coatings were studied, both as-deposited, as well as after grinding, in order to study the effect of the surface roughness and morphology on the ice accretion and adhesion properties. The QC coating was compared with PTFE and two polyurethane (PU)-based commercial paints, one of them known to have anti-icing properties, and the results indicate an ice accretion reduction relative to these two materials, and ice adhesion lower than bare AA6061-T6, or the PU paint in the ground version of one of the two QCs. Since the QC coatings are hard (GPa Vickers hardness > 5), a durable behavior is expected. Full article
(This article belongs to the Special Issue Anti-Icing Coatings and Surfaces)
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15 pages, 2011 KiB  
Article
Composite Ferroelectric Coatings Based on a Heat-Resistant Polybenzoxazole Polymer Matrix
by Nikolay Mukhin, Irina Sokolova, Dmitry Chigirev, Lyudmila Rudaja, Galina Lebedeva, Rene Kastro, Maxim Bol’shakov, Marc-Peter Schmidt and Soeren Hirsch
Coatings 2020, 10(3), 286; https://doi.org/10.3390/coatings10030286 - 19 Mar 2020
Cited by 5 | Viewed by 3331
Abstract
The polycondensation of 5,5-methylene bis(2-aminophenol) and the mixture of diamines 5,5-methylene bis(2-aminophenol) and 4,4-(hexafluoroisopropylidene)dianiline (molar ratio 0.8:0.2) with isophthaloyl dichloride was used to synthesize a new heat resistant binder of the composites for microelectronics: poly(o-hydroxyamide) (POA) and poly(amido-o-hydroxy amide) [...] Read more.
The polycondensation of 5,5-methylene bis(2-aminophenol) and the mixture of diamines 5,5-methylene bis(2-aminophenol) and 4,4-(hexafluoroisopropylidene)dianiline (molar ratio 0.8:0.2) with isophthaloyl dichloride was used to synthesize a new heat resistant binder of the composites for microelectronics: poly(o-hydroxyamide) (POA) and poly(amido-o-hydroxy amide) (POA-F). The thermal stability of synthesized polymer coatings, as well as based on them photosensitive compositions with a naphthoquinondiazide photosensitive component were studied in the temperature range from 100 to 500 °C. Ferroelectric composites with nanodispersed lead titanate zirconate powder filler were formed based on these polymer matrices. By manipulating the conditions of the polymer formation, we obtained matrices with different stiffnesses, which reflected on the properties of the composite. The electrophysical parameters of the synthesized polymer and ferroelectric composite coatings were measured in the frequency range from 0.1 Hz to 1.5 GHz and the temperature range from 0 to 300 °C. The frequency and temperature stability of the dielectric constant of ferroelectric composite coatings up to 10 MHz and 300 °C, respectively, are noted. The influence of the composition and structure of the polymer matrix and the grain/matrix interfaces on the thermal stability of the dielectric parameters of composite films is estimated. The shift of the phase transition region toward higher temperatures in the composite structure, as well as the sufficient rigidity of the poly(benzoxazole) matrix, provide high temperature and frequency stability of the dielectric constant of the studied composites. Full article
(This article belongs to the Special Issue Ferroelectric Thin Films and Devices)
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17 pages, 6760 KiB  
Article
Properties of Tool Steels and Their Importance When Used in a Coated System
by Bojan Podgornik, Marko Sedlaček, Borut Žužek and Agnieszka Guštin
Coatings 2020, 10(3), 265; https://doi.org/10.3390/coatings10030265 - 12 Mar 2020
Cited by 17 | Viewed by 5783
Abstract
The introduction of new light-weight high-strength materials, which are difficult to form, increases demands on tool properties, including load-carrying capacity and wear resistance. Tool properties can be improved by the deposition of hard coatings but proper combination and optimization of the substrate properties [...] Read more.
The introduction of new light-weight high-strength materials, which are difficult to form, increases demands on tool properties, including load-carrying capacity and wear resistance. Tool properties can be improved by the deposition of hard coatings but proper combination and optimization of the substrate properties are required to prepare the tool for coating application. The aim of this paper is to elaborate on tool steel substrate properties correlations, including hardness, fracture toughness, strength and surface quality and how these substrate properties influence on the coating performance. Results show that hardness of the steel substrate is the most influential parameter for abrasive wear resistance and load-carrying capacity, which is true for different types of hard coatings. However, high hardness should also be accompanied by sufficient fracture toughness, especially when it comes to very hard and brittle coatings, thus providing a combination of high load-carrying capacity, good fatigue properties and superior resistance against impact wear. Duplex treatment and formation of a compound layer during nitriding can be used as an additional support interlayer, but its brittleness may result in accelerated coating cracking and spallation if not supported by sufficient core hardness. In terms of galling resistance, even for coated surfaces substrate roughness and topography have major influence when it comes to hard ceramic coatings, with reduced substrate roughness and coating post-polishing providing up to two times better galling resistance. Full article
(This article belongs to the Special Issue Surface Topography Effects on Functional Properties of PVD Coatings)
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9 pages, 4992 KiB  
Article
Biocompatibility Evaluation and Enhancement of Elastomeric Coatings Made Using Table-Top Optical 3D Printer
by Giedre Grigaleviciute, Daiva Baltriukiene, Virginija Bukelskiene and Mangirdas Malinauskas
Coatings 2020, 10(3), 254; https://doi.org/10.3390/coatings10030254 - 10 Mar 2020
Cited by 6 | Viewed by 3863
Abstract
In this experimental report, the biocompatibility of elastomeric scaffold structures made via stereolithography employing table-top 3D printer Ember (Autodesk) and commercial resin FormLabs Flexible (FormLabs) was studied. The samples were manufactured using the standard printing and development protocol, which [...] Read more.
In this experimental report, the biocompatibility of elastomeric scaffold structures made via stereolithography employing table-top 3D printer Ember (Autodesk) and commercial resin FormLabs Flexible (FormLabs) was studied. The samples were manufactured using the standard printing and development protocol, which is known to inherit cytotoxicity due to remaining non-polymerized monomers, despite the polymerized material being fully biocompatible. Additional steps were taken to remedy this problem: the fabricated structures were soaked in isopropanol and methanol under different conditions (temperature and duration) to leach out the non-polymerized monomers. In addition, disc-shaped 3D-printed structures were UV exposed to assure maximum polymerization degree of the material. Post-processed structures were seeded with myogenic stem cells and the number of live cells was evaluated as an indicator for the material biocompatibility. The straightforward post-processing protocol enhanced the biocompatibility of the surfaces by seven times after seven days soaking in isopropanol and methanol and was comparable to control (glass and polystyrene) samples. This proposes the approach as a novel and simple method to be widely applicable for dramatic cytotoxicity reduction of optically 3D printed micro/nano-scaffolds for a wide range of biomedical studies and applications. Full article
(This article belongs to the Special Issue Thin Film Laser Damage, Ablation, Deposition and Structuring)
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13 pages, 642 KiB  
Article
Wettability of Wood Surface Layer Examined From Chemical Change Perspective
by Eva Annamaria Papp, Csilla Csiha, Adam Nandor Makk, Tamas Hofmann and Levente Csoka
Coatings 2020, 10(3), 257; https://doi.org/10.3390/coatings10030257 - 10 Mar 2020
Cited by 10 | Viewed by 3109
Abstract
The effect of artificial ageing on spruce (Picea abies), beech (Fagus sylvatica L.), birch (Betula pendula), and sessile oak (Quercus petraea) wood surfaces were investigated using qualitative (total phenolic and total soluble carbohydrate content) chemical examination [...] Read more.
The effect of artificial ageing on spruce (Picea abies), beech (Fagus sylvatica L.), birch (Betula pendula), and sessile oak (Quercus petraea) wood surfaces were investigated using qualitative (total phenolic and total soluble carbohydrate content) chemical examination methods. During ageing (∑240h), the influence of surface chemistry modifications was monitored by contact angle measurements of polar, dispersive (distilled water), and dispersive (diiodomethane) liquids. The results clearly show the relation between the ratio of main chemical components of the wood surface layer and surface wettability during artificial radiation. The identified surface chemistry modifications cause more significant change in the contact angle of polar and dispersive liquid, relative to the change of dispersive liquid contact angle. Chemical changes of the wood surface layer are due to the degradation of the main wood components (cellulose, hemicelluloses, and lignin) which can be properly monitored by total phenolic (TPC) and total soluble carbohydrate content (TSCC) measurements. Full article
(This article belongs to the Special Issue Advances in Surface Modification and Treatment of Wood)
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12 pages, 6150 KiB  
Article
Layer-by-Layer Deposition of Hyaluronan and Quercetin-Loaded Chitosan Nanoparticles onto Titanium for Improving Blood Compatibility
by Xingda Wu, Cuijuan Liu, Hongpeng Chen, Yanfang Zhang, Lin Li and Nan Tang
Coatings 2020, 10(3), 256; https://doi.org/10.3390/coatings10030256 - 9 Mar 2020
Cited by 12 | Viewed by 4010
Abstract
Surface modification is an effective way to improve the hemocompatibility of biomaterials. Quercetin has significant anticoagulation and antithrombotic effects, and thus it is a promising candidate agent for the surface modification of blood-contacting materials. In this study, quercetin was successfully encapsulated in tripolyphosphate–chitosan [...] Read more.
Surface modification is an effective way to improve the hemocompatibility of biomaterials. Quercetin has significant anticoagulation and antithrombotic effects, and thus it is a promising candidate agent for the surface modification of blood-contacting materials. In this study, quercetin was successfully encapsulated in tripolyphosphate–chitosan nanoparticles (TCs) based on the ionic gelation of chitosan with tripolyphosphate (TPP) anions. Then, hyaluronan acid (HA)/quercetin-loaded TPP–chitosan nanoparticle (QTCs) films, in addition to HA/TCs films, were prepared separately using an electrostatic layer-by-layer self-assembly technique. The encapsulation of quercetin in the chitosan nanoparticles was confirmed by UV spectra. The quercetin-loaded multilayer coatings were also successfully self-assembled, as confirmed by the UV spectra and contact angle measurements. Platelet adhesion experiments were carried out with platelet-enriched plasma so as to evaluate the blood compatibility of the different samples. There were many platelets on the surfaces of the glass and HA/TC-coated titanium, which were partially activated but not aggregated. Meanwhile, many more platelets were observed on the uncoated titanium surfaces, most of which developed pseudopodia. By contrast, the platelet adhesion and activation were reduced remarkably on the surface of the HA/QTC-coated titanium. These results showed that the multilayer coatings containing quercetin could act as potential biomaterials to improve the anticoagulation performance of blood-contacting materials. Full article
(This article belongs to the Special Issue Multifunctional Coatings on Medical Devices)
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16 pages, 4585 KiB  
Article
Electrophoretic Deposition and Characteristics of Chitosan–Nanosilver Composite Coatings on a Nanotubular TiO2 Layer
by Michał Bartmański, Łukasz Pawłowski, Andrzej Zieliński, Aleksandra Mielewczyk-Gryń, Gabriel Strugała and Bartłomiej Cieślik
Coatings 2020, 10(3), 245; https://doi.org/10.3390/coatings10030245 - 6 Mar 2020
Cited by 23 | Viewed by 4387
Abstract
The surface treatment of titanium implants has been applied mainly to increase surface bioactivity and, more recently, to introduce antibacterial properties. To this end, composite coatings have been investigated, particularly those based on hydroxyapatite. The present research was aimed at the development of [...] Read more.
The surface treatment of titanium implants has been applied mainly to increase surface bioactivity and, more recently, to introduce antibacterial properties. To this end, composite coatings have been investigated, particularly those based on hydroxyapatite. The present research was aimed at the development of another coating type, chitosan–nanosilver, deposited on a Ti13Zr13Nb alloy. The research comprised characterization of the coating’s microstructure and morphology, time-dependent nanosilver dissolution in simulated body fluid, and investigation of the nanomechanical properties of surface coatings composed of chitosan and nanosilver, with or without a surface-active substance, deposited at different voltages for 1 min on a nanotubular TiO2 layer. The microstructure, morphology, topography, and phase composition were examined, and the silver dissolution rate in simulated body fluid, nanoscale mechanical properties, and water contact angle were measured. The voltage value significantly influenced surface roughness. All specimens possessed high biocompatibility. The highest and best adhesion of the coatings was observed in the absence of a surface-active substance. Silver dissolution caused the appearance of silver ions in solution at levels effective against bacteria and below the upper safe limit value. Full article
(This article belongs to the Special Issue Multifunctional Coatings on Medical Devices)
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10 pages, 4541 KiB  
Article
Sensitivity Improvement of Quantum Dot-Blended Hybrid Detector for X-ray Imaging
by Seahong Kim, Jehoon Lee and Jungwon Kang
Coatings 2020, 10(3), 222; https://doi.org/10.3390/coatings10030222 - 1 Mar 2020
Cited by 7 | Viewed by 3065
Abstract
This study investigated the characteristics of an indirect-type hybrid X-ray detector with a conjugated polymer poly(3-hexylthiophene) (P3HT) and CdSe quantum dot (QD) blended active layer. To improve detection sensitivity, the optimal blending ratio of P3HT:CdSe QDs, ligand exchange effect, and optimal process condition [...] Read more.
This study investigated the characteristics of an indirect-type hybrid X-ray detector with a conjugated polymer poly(3-hexylthiophene) (P3HT) and CdSe quantum dot (QD) blended active layer. To improve detection sensitivity, the optimal blending ratio of P3HT:CdSe QDs, ligand exchange effect, and optimal process condition of the active layer were examined. The detector with a P3HT:CdSe QDs = 1:5 blended active layer showed the highest collected charge density (CCD) and highest sensitivity under X-ray irradiation. The replacement of a trioctylphosphine (TOP) ligand by a pyridine ligand effectively assisted the charge transport and reduced the QD aggregation, increasing the detection sensitivity of the detector by 75% after the ligand exchange. To further improve the sensitivity of the proposed detector, the optimized process conditions of the active layer were studied. The sensitivity of the detector with an active layer of about 80 nm thickness formed by a double-coating method showed the highest CCD of 62.5 nA/cm2, and the highest sensitivity of 0.14 mA/Gy∙cm2. Due to additional pyridine treatment between the double-coating processes, the surface roughness of the active layer decreased, and the CCD and sensitivity subsequently increased. Full article
(This article belongs to the Special Issue Coatings and Interfaces)
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55 pages, 4199 KiB  
Review
The Sealing Step in Aluminum Anodizing: A Focus on Sustainable Strategies for Enhancing Both Energy Efficiency and Corrosion Resistance
by Stanley Udochukwu Ofoegbu, Fábio A.O. Fernandes and António B. Pereira
Coatings 2020, 10(3), 226; https://doi.org/10.3390/coatings10030226 - 1 Mar 2020
Cited by 57 | Viewed by 27488
Abstract
Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones [...] Read more.
Increasing demands for environmental accountability and energy efficiency in industrial practice necessitates significant modification(s) of existing technologies and development of new ones to meet the stringent sustainability demands of the future. Generally, development of required new technologies and appropriate modifications of existing ones need to be premised on in-depth appreciation of existing technologies, their limitations, and desired ideal products or processes. In the light of these, published literature mostly in the past 30 years on the sealing process; the second highest energy consuming step in aluminum anodization and a step with significant environmental impacts has been critical reviewed in this systematic review. Emphasis have been placed on the need to reduce both the energy input in the anodization process and environmental implications. The implications of the nano-porous structure of the anodic oxide on mass transport and chemical reactivity of relevant species during the sealing process is highlighted with a focus on exploiting these peculiarities, in improving the quality of sealed products. In addition, perspective is provided on plausible approaches and important factors to be considered in developing sealing procedures that can minimize the energy input and environmental impact of the sealing step, and ensure a more sustainable aluminum anodization process/industry. Full article
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17 pages, 6499 KiB  
Article
One-Step Deposition of Polyester/TiO2 Coatings by Atmospheric Pressure Plasma Jet on Wood Surfaces for UV and Moisture Protection
by Ghiath Jnido, Gisela Ohms and Wolfgang Viöl
Coatings 2020, 10(2), 184; https://doi.org/10.3390/coatings10020184 - 19 Feb 2020
Cited by 14 | Viewed by 4571
Abstract
In this work, polyester/TiO2 coatings on wood surfaces were prepared in one step via two deposition methods by using an atmospheric pressure plasma jet technique with the aim to further enhance the stabilization of the wood surfaces against UV-radiation and moisture. The [...] Read more.
In this work, polyester/TiO2 coatings on wood surfaces were prepared in one step via two deposition methods by using an atmospheric pressure plasma jet technique with the aim to further enhance the stabilization of the wood surfaces against UV-radiation and moisture. The first method, based on the combination of plasma spray powder (PSP) coating and liquid precursor plasma spraying (LPPS) coating techniques, used polyester powder and titanium tetraisopropoxide (TTIP) liquid precursor as feedstock. In the second method, the polyester/TiO2 coatings were prepared by using a mixed powder of polyester micro-particles and TiO2 nano-particles as feedstock and applied via plasma spray powder coating technique. The surface topology and morphology of the wood samples were observed by scanning electron microscopy (SEM). The SEM results showed the presence of a rough structure after coating with polyester/TiO2. The surface chemical compositions of the samples were characterized by X-ray photoelectron spectroscopy and by Fourier transform infrared spectroscopy. The wetting behaviour of the coated wood surfaces was studied by measuring the water contact angle. After coating a hydrophilic wood surface with polyester/TiO2 prepared via (PSP + LPPS), it showed excellent water repellency; the wood surfaces were transformed from hydrophilic to superhydrophobic, while the polyester/TiO2 coating prepared via (PSP) was hydrophilic. Protection against UV radiation-induced colour changes was determined by UV tests and photo-assisted analysis using the CIELab colour system. The abrasion test results indicated that the polyester-containing films had good abrasion resistance and good adhesion to the wood substrates. Full article
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16 pages, 8247 KiB  
Article
Roles of Graphene Additives in Optimizing the Microstructure and Properties of Ni–Cr–Graphene Coatings
by Liang Meng, Qinyou Hu, Chaojian Shi and Changhai Huang
Coatings 2020, 10(2), 104; https://doi.org/10.3390/coatings10020104 - 24 Jan 2020
Cited by 10 | Viewed by 2740
Abstract
The electrodeposition technique was used to fabricate graphene and Cr particle-reinforced Ni–Cr–graphene coatings. The Rietveld refinement was utilized to analyze the microstructure of Ni deposits in the coatings. The properties including micro-hardness and corrosion behaviors of the coatings were also tested. Results showed [...] Read more.
The electrodeposition technique was used to fabricate graphene and Cr particle-reinforced Ni–Cr–graphene coatings. The Rietveld refinement was utilized to analyze the microstructure of Ni deposits in the coatings. The properties including micro-hardness and corrosion behaviors of the coatings were also tested. Results showed that the addition of graphene particles contributed to the dendrite like structure on the surface of the Ni–Cr–graphene coating. The crystallite size and [200] texture of the Ni deposits in the Ni–Cr–graphene coatings were significantly decreased by the graphene particles. The crystallite size of 149.8 nm in the Ni-25–Cr-0–graphene coating was reduced to 35 nm in the Ni-25–Cr-8–graphene coating due to the addition of 8 g/L graphene to the electrolyte. The microstructure evolution of the Ni–Cr–graphene coatings brought about an enhancement in micro-hardness and corrosion resistance of the coatings. The micro-hardness of the coatings was improved from 260.1 HV0.2 of the pure Ni coating to 285.9 HV0.2 of the Ni-25–Cr-0–graphene coating and continually to 461.8 HV0.2 of the Ni-25–Cr-8–graphene coating. In corrosion solution (3.5 wt.% NaCl), the corrosion current (6.22 μA/cm2) of the Ni-25–Cr-0–graphene coating could be decreased by about an order of magnitude through the addition of graphene particles, which was 0.33 μA/cm2 for the Ni-25–Cr-8–graphene coating. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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14 pages, 8295 KiB  
Article
Effect of Zr Target Current on the Mechanical and Tribological Performance of MoS2–Zr Composite Lubricating Coatings
by Wenlong Song, Zixiang Xia, Shoujun Wang and Qingge Zhang
Coatings 2020, 10(1), 80; https://doi.org/10.3390/coatings10010080 - 18 Jan 2020
Cited by 6 | Viewed by 2604
Abstract
To improve the tribological properties of pure MoS2 coating, the MoS2–Zr composite lubricating coatings were prepared on the WC/TiC/Co carbide surface utilizing radio frequency magnetron sputtering method combining with multiple arc ion plating technology. The effects of different Zr target [...] Read more.
To improve the tribological properties of pure MoS2 coating, the MoS2–Zr composite lubricating coatings were prepared on the WC/TiC/Co carbide surface utilizing radio frequency magnetron sputtering method combining with multiple arc ion plating technology. The effects of different Zr target currents on the surface morphologies, roughness, Zr content, adhesive force, thickness, microhardness and tribological behaviors of the composite coatings were systematically investigated. Results showed that the properties of MoS2 coating can be remarkably enhanced through co-deposition of a certain amount of Zr. As the Zr target current increased, the Zr content, surface roughness, thickness, and micro-hardness gradually increased, while the adhesive force of coatings increased first and then decreased. The friction behaviors and wear modes of the composite coatings both varied obviously with the increase of Zr current. The mechanism was mainly attributed to the different components and mechanical properties of the coatings caused by various Zr current. Full article
(This article belongs to the Section Tribology)
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9 pages, 3792 KiB  
Article
A Highly Efficient Visible Absorber Coating on a Curved Substrate
by Ruoqian Gao, Heshig Bayan, Fei Yang, Yanchao Wang, Zhen Liu, Hai Liu, Zhenfeng Shen, Qiang Li, Zizheng Li, Xiaoyi Wang and Haigui Yang
Coatings 2020, 10(1), 71; https://doi.org/10.3390/coatings10010071 - 13 Jan 2020
Cited by 1 | Viewed by 3154
Abstract
In this study, we propose and fabricate a perfect absorber on a planar substrate using alternate silicon dioxide and ultrathin metallic lossy chromium (Cr) films. Furthermore, we transfer the absorber to a curved substrate via an optimization design of symmetric structures. The absorber [...] Read more.
In this study, we propose and fabricate a perfect absorber on a planar substrate using alternate silicon dioxide and ultrathin metallic lossy chromium (Cr) films. Furthermore, we transfer the absorber to a curved substrate via an optimization design of symmetric structures. The absorber exhibits a highly efficient absorption and large incident-angular tolerance characteristics in the whole visible region. We investigate each layer contribution to the absorption theoretically, and find that ultrathin (~5 nm) lossy Cr films play a dominant absorptive role. Using the effective interface method, we calculate the phase difference on the lossy Cr front surface. It is close to the destructive interference condition, from which we clarify why the proposed structures can produce a highly efficient absorption. Full article
(This article belongs to the Section Thin Films)
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10 pages, 6940 KiB  
Article
Investigation of Photoelastic Property and Stress Analysis for Optical Polyimide Membrane through Stress Birefringence Method
by Guohan Gao, Danbo Mao, Renkui Jiang, Zhiwei Li, Xin Liu, Baiping Lei, Jiang Bian, Shibin Wu and Bin Fan
Coatings 2020, 10(1), 56; https://doi.org/10.3390/coatings10010056 - 9 Jan 2020
Cited by 7 | Viewed by 3406
Abstract
Optical polyimide (PI) membranes have been increasingly attractive in optoelectronic substrate and optical element material applications. Controlled stress distribution is very important to optical PI membrane-based optics. However, nondestructive absolute stress measurement inside optical PI membranes remains challenging. In this letter, we adopted [...] Read more.
Optical polyimide (PI) membranes have been increasingly attractive in optoelectronic substrate and optical element material applications. Controlled stress distribution is very important to optical PI membrane-based optics. However, nondestructive absolute stress measurement inside optical PI membranes remains challenging. In this letter, we adopted the stress birefringence method to experimentally investigate the correlation between stress and retardation in uniaxially, biaxially, and circularly stretched PI membranes. The calculated value of the photoelastic coefficient was found to be around 400 nm/Mpa·cm. A theoretical model was established where the retardation angle is the negative arctan of the principal stress ratio in the biaxially stretched membrane. We also found that the average retardation angle is an important parameter for evaluating the uniformity of stretching force in the circularly stretched membrane. This work provides a better understanding of the stress birefringence measurement of membrane materials. Full article
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19 pages, 8226 KiB  
Article
Studies of Polylactic Acid and Metal Oxide Nanoparticles-Based Composites for Multifunctional Textile Prints
by Meram S. Abdelrahman, Sahar H. Nassar, Hamada Mashaly, Safia Mahmoud, Dalia Maamoun, Mohamed El-Sakhawy, Tawfik A. Khattab and Samir Kamel
Coatings 2020, 10(1), 58; https://doi.org/10.3390/coatings10010058 - 9 Jan 2020
Cited by 48 | Viewed by 5084
Abstract
A novel approach toward the production of multifunctional printed technical textiles is reported. Three different metal oxides nanoparticles including titanium dioxide, magnesium oxide, and zinc oxide were prepared and characterized. Both natural wool and synthetic acrylic fibers were pretreated with the prepared metal [...] Read more.
A novel approach toward the production of multifunctional printed technical textiles is reported. Three different metal oxides nanoparticles including titanium dioxide, magnesium oxide, and zinc oxide were prepared and characterized. Both natural wool and synthetic acrylic fibers were pretreated with the prepared metal oxide nanoparticles followed by printing using polylactic acid based paste containing acid or basic dyestuffs. Another route was applied via post-treatment of the targeted fabrics with the metal oxide nanoparticles after running the printing process. The color strength (K/S) and colorfastness properties of pretreated and post-treated printed fabrics were evaluated and compared with untreated printed fabrics. The presence of nanoparticles on a fabric surface during the coating process was found to significantly increase the color strength value of the coated textile substrates. The increased K/S value depended mainly on the nature and concentration of the applied metal oxide, as well as the nature of colorant and fabric. In addition, the applied metal oxide nanoparticles imparted the printed fabrics with good antibacterial activity, high ultraviolet protection, photocatalytic self-cleaning, and improved colorfastness properties. Those results suggest that the applied metal oxide-based nanoparticles could introduce ideal multifunctional prints for garments. Full article
(This article belongs to the Special Issue Novel Coatings for Smart Textile Fabrics for Enhanced Functions)
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25 pages, 308 KiB  
Review
Urinary Catheter Coating Modifications: The Race against Catheter-Associated Infections
by Marissa J. Andersen and Ana L. Flores-Mireles
Coatings 2020, 10(1), 23; https://doi.org/10.3390/coatings10010023 - 29 Dec 2019
Cited by 69 | Viewed by 16958
Abstract
Urinary catheters are common medical devices, whose main function is to drain the bladder. Although they improve patients’ quality of life, catheter placement predisposes the patient to develop a catheter-associated urinary tract infection (CAUTI). The catheter is used by pathogens as a platform [...] Read more.
Urinary catheters are common medical devices, whose main function is to drain the bladder. Although they improve patients’ quality of life, catheter placement predisposes the patient to develop a catheter-associated urinary tract infection (CAUTI). The catheter is used by pathogens as a platform for colonization and biofilm formation, leading to bacteriuria and increasing the risk of developing secondary bloodstream infections. In an effort to prevent microbial colonization, several catheter modifications have been made ranging from introduction of antimicrobial compounds to antifouling coatings. In this review, we discuss the effectiveness of different coatings in preventing catheter colonization in vitro and in vivo, the challenges in fighting CAUTIs, and novel approaches targeting host–catheter–microbe interactions. Full article
(This article belongs to the Special Issue Recent Developments in Antibacterial and/or Antifouling Surfaces)
15 pages, 1893 KiB  
Article
Superconducting HfO2-YBa2Cu3O7−δ Nanocomposite Films Deposited Using Ink-Jet Printing of Colloidal Solutions
by Hannes Rijckaert, Pablo Cayado, Rainer Nast, Javier Diez Sierra, Manuela Erbe, Pedro López Dominguez, Jens Hänisch, Klaartje De Buysser, Bernhard Holzapfel and Isabel Van Driessche
Coatings 2020, 10(1), 17; https://doi.org/10.3390/coatings10010017 - 26 Dec 2019
Cited by 26 | Viewed by 5554
Abstract
To reduce the fabrication costs while maximizing the superconducting and pinning properties of YBa2Cu3O7−δ (YBCO) nanocomposite films, the drop-on-demand ink-jet printing technique was used to deposit colloidal YBCO inks onto LaAlO3 substrates. These inks containing preformed HfO [...] Read more.
To reduce the fabrication costs while maximizing the superconducting and pinning properties of YBa2Cu3O7−δ (YBCO) nanocomposite films, the drop-on-demand ink-jet printing technique was used to deposit colloidal YBCO inks onto LaAlO3 substrates. These inks containing preformed HfO2 nanocrystals were carefully adjusted, prior to the jettability, as the droplet formation depends on the rheological properties of the inks themselves. After carefully adjusting printing parameters, 450-nm thick pristine YBCO films with a self-field critical current density (Jc) of 2.7 MA cm² at 77 K and 500-nm thick HfO2-YBCO nanocomposite films with a self-field Jc of 3.1 MA·cm² at 77 K were achieved. The final HfO2-YBCO nanocomposite films contained dispersed BaHfO3 particles in a YBCO matrix due to the Ba2+ reactivity with the HfO2 nanocrystals. These nanocomposite films presented a more gradual decrease of Jc with the increased magnetic field. These nanocomposite films also showed higher pinning force densities than the pristine films. This pinning enhancement was related to the favorable size and distribution of the BaHfO3 particles in the YBCO matrix. Full article
(This article belongs to the Special Issue Superconducting Films and Nanostructures)
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11 pages, 15929 KiB  
Article
Delayed Formation of Thermally Grown Oxide in Environmental Barrier Coatings for Non-Oxide Ceramic Matrix Composites
by Hagen Klemm, Katrin Schönfeld and Willy Kunz
Coatings 2020, 10(1), 6; https://doi.org/10.3390/coatings10010006 - 19 Dec 2019
Cited by 9 | Viewed by 4026
Abstract
The oxidation and corrosion behavior at elevated temperatures of a SiCF/SiC(N) composite with two plasma-sprayed environmental barrier coating (EBC) systems were studied. After both processes, the formation of a silica-based thermally grown oxide (TGO) layer was observed. The formation of this [...] Read more.
The oxidation and corrosion behavior at elevated temperatures of a SiCF/SiC(N) composite with two plasma-sprayed environmental barrier coating (EBC) systems were studied. After both processes, the formation of a silica-based thermally grown oxide (TGO) layer was observed. The formation of this TGO caused two principal failure mechanisms of the EBC. Firstly, spallation of the EBC induced by stresses from volume expansion and phase transformation to crystalline SiO2 was observed. Water vapor corrosion of the TGO with gap formation in the top region of the TGO was found to be a second failure mechanism. After a burner rig test of the Al2O3-YAG EBC system, this corrosion process was observed at the TGO surface and in the volume of the Al2O3 bond coat. In the case of the second system, Si-Yb2Si2O7/SiC-Yb2SiO5, the formation of the TGO could be delayed by introducing an additional intermediate layer based on Yb2Si2O7 filled with SiC particles. The SiC particles in the intermediate layer were oxidized and served as getter to reduce the permeation of oxidants (O2, H2O) into the material. In this way, the formation of the TGO and the failure mechanisms caused by their formation and growth could be delayed. Full article
(This article belongs to the Special Issue Environmental Barrier Coatings)
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14 pages, 1197 KiB  
Review
Innovative Wood Surface Treatments Based on Nanotechnology
by Antonios N. Papadopoulos and Hamid R. Taghiyari
Coatings 2019, 9(12), 866; https://doi.org/10.3390/coatings9120866 - 16 Dec 2019
Cited by 68 | Viewed by 7864
Abstract
This work reviewed innovative wood surface treatments based on nanotechnology. It is well documented in the literature that the cell walls of wood present significant porosity; this porosity is on a molecular scale. The main reason for the use of nanotechnology in wood [...] Read more.
This work reviewed innovative wood surface treatments based on nanotechnology. It is well documented in the literature that the cell walls of wood present significant porosity; this porosity is on a molecular scale. The main reason for the use of nanotechnology in wood science and technology is the unique characteristic of nano-based materials to effectively penetrate deeply into wood substrates, which, in turns, results in the alteration of their surface chemistry. This subsequently causes an improvement in wood properties. Any potential change in the wood properties due to treatment with nanomaterials is based on the higher interfacial area which is developed due to the treatment. This occurs because the number of particles is significantly reduced to the nanoscale. The nanomaterials improve the properties of wood as a raw material and alter its original features to a limited extent. However, their potential impact on both health and the environment should be addressed by applying tools such as life-cycle assessments. This will avoid mistakes being made in which new technologies are released on the market prior to an impact assessment having been carried out. Full article
(This article belongs to the Collection Advanced Surface Coating of Nanoparticles)
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12 pages, 3412 KiB  
Article
Laser-Assisted Surface Texturing of Ti/Zr Multilayers for Mesenchymal Stem Cell Response
by Suzana Petrović, Davor Peruško, Evangelos Skoulas, Janez Kovač, Miodrag Mitrić, Jelena Potočnik, Zlatko Rakočević and Emmanuel Stratakis
Coatings 2019, 9(12), 854; https://doi.org/10.3390/coatings9120854 - 13 Dec 2019
Cited by 7 | Viewed by 3175
Abstract
The formation of an ordered surface texture with micro and nanometer features on Ti/Zr multilayers is studied for better understanding and improvement of cell integration. Nanocomposite in form 30×(Ti/Zr)/Si thin films was deposited by ion sputtering on Si substrate for biocompatibility investigation. Surface [...] Read more.
The formation of an ordered surface texture with micro and nanometer features on Ti/Zr multilayers is studied for better understanding and improvement of cell integration. Nanocomposite in form 30×(Ti/Zr)/Si thin films was deposited by ion sputtering on Si substrate for biocompatibility investigation. Surface texturing by femtosecond laser processing made it possible to form the laser-induced periodic surface structure (LIPSS) in each laser-written line. At fluence slightly above the ablation threshold, beside the formation of low spatial frequency-LIPSS (LSFL) oriented perpendicular to the direction of the laser polarization, the laser-induced surface oxidation was achieved on the irradiated area. Intermixing between the Ti and Zr layers with the formation of alloy in the sub-surface region was attained during the laser processing. The surface of the Ti/Zr multilayer system with changed composition and topography was used to observe the effect of topography on the survival, adhesion and proliferation of the murine mesenchymal stem cells (MSCs). Confocal and SEM microscopy images showed that cell adhesion and their growth improve on these modified surfaces, with tendency of the cell orientation along of LIPSS in laser-written lines. Full article
(This article belongs to the Special Issue Surface Topography Effects on Functional Properties of PVD Coatings)
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12 pages, 4387 KiB  
Article
Structure Investigation of Titanium Metallization Coating Deposited onto AlN Ceramics Substrate by Means of Friction Surfacing Process
by Tomasz Chmielewski, Michał Hudycz, Arkadiusz Krajewski, Tadeusz Sałaciński, Beata Skowrońska and Rafał Świercz
Coatings 2019, 9(12), 845; https://doi.org/10.3390/coatings9120845 - 10 Dec 2019
Cited by 21 | Viewed by 3658
Abstract
The article presents selected properties of a titanium metallization coating deposited on aluminum nitride (AlN) ceramics surface by means of the friction surfacing method. Its mechanism is based on the formation of a joint between the surface of an AlN ceramics substrate and [...] Read more.
The article presents selected properties of a titanium metallization coating deposited on aluminum nitride (AlN) ceramics surface by means of the friction surfacing method. Its mechanism is based on the formation of a joint between the surface of an AlN ceramics substrate and a thin Ti coating, involving a kinetic energy of friction, which is directly converted into heat and delivered in a precisely defined quantity to the resulting joint. The largest effects on the final properties of the obtained coating include the high affinity of titanium for oxygen and nitrogen and a relatively high temperature for the deposition process. The titanium metallization coating was characterized in terms of surface stereometric structure, thickness, surface morphology, metallographic microstructural properties, and phase structure. The titanium coating has a thickness ranging from 3 to 7 μm. The phase structure of the coating surface (XPS investigated) is dominated by TiNxOy with the presence of TiOx, TiN, metallic Ti, and AlN. The phase structure deeper below the surface (XRD investigated) is dominated by metallic Ti with additional AlN particles originating from the ceramic substrate due to friction by titanium tools. Full article
(This article belongs to the Special Issue Recent Advances in Friction Stir Processed Coatings)
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17 pages, 25332 KiB  
Article
Optimization of Friction Stir Process Parameters for Enhancement in Surface Properties of Al 7075-SiC/Gr Hybrid Surface Composites
by Namdev Ashok Patil, Srinivasa Rao Pedapati, Othman Bin Mamat and Abdul Munir Hidayat Syah Lubis
Coatings 2019, 9(12), 830; https://doi.org/10.3390/coatings9120830 - 6 Dec 2019
Cited by 18 | Viewed by 3955
Abstract
Friction stir processing (FSP) has evolved as an important technique in fabrication of metal matrix composites. The surface properties enhancement is obtainable by insertion of desired discontinuous particular reinforcements into base alloy using FSP. Despite having high specific strength, more applications of Al [...] Read more.
Friction stir processing (FSP) has evolved as an important technique in fabrication of metal matrix composites. The surface properties enhancement is obtainable by insertion of desired discontinuous particular reinforcements into base alloy using FSP. Despite having high specific strength, more applications of Al alloys are restricted due to their poor surface properties under various loading conditions. In this study, the main focus is on enhancing the microhardness and wear properties of Al 7075 base alloy by means of uniform dispersion of silicon carbide and graphite (SiC/Gr) nano particles into the base alloy using the FSP technique. The tool rotational speed (w: 500, 1000, 1500 rpm), tool traverse speed (v: 20, 30, 40 mm/min), reinforcement particles hybrid ratio (HR: 60:40, 75:25, 90:10) and volume percentage (vol%: 4%, 8%, 12%) are used as independent parameters. The effect of these parameters on microstructure, micro hardness and wear properties of surface composites are studied in detail. For desired wear rate and microhardness as responses, the aforementioned independent parameters are optimized using response surface methodology (RSM). The significance of factors and their interactions for maximizing hardness and minimizing wear rate and coefficient of friction (COF) were determined. Analysis of variance (ANOVA) for responses has been carried out, and the models were found to be significant in all three responses. The minimum wear rate of 0.01194 mg/m was obtained for parameters w 1500 rpm, v 40 mm/min, HR 60:40, vol% 4 (Run 10). The maximum micro hardness of 300 HV obtained for parameters w 1000 rpm, v 30 mm/min, HR 75:25, vol% 12 (Run 14). The presence and uniform distribution of SiC and Gr into the base alloy was confirmed through field-emission scanning electron microscopy (FESEM) imaging, energy-dispersive X-ray spectroscopy (EDX) and mapping tests. The wear rate and COF decreased significantly due to graphitized mechanically mixed layer developed at the sliding contacts. The microhardness of resultant composites observed to be dependent on effect of the independent parameters on extent of inherent precipitates dissolution and grain size strengthening in the resultant materials. Full article
(This article belongs to the Special Issue Recent Advances in Friction Stir Processed Coatings)
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13 pages, 3405 KiB  
Article
Effect of Powder Mixture Composition on the Deposition Efficiency in Cold Spay: Modelling and Experimental Validation
by E. Lapushkina and A. Sova
Coatings 2019, 9(12), 832; https://doi.org/10.3390/coatings9120832 - 6 Dec 2019
Cited by 5 | Viewed by 3099
Abstract
In this paper, a new semiempirical probability model, allowing for prediction of the composition of multimaterial cold spray coating in dependence on the initial percentage of blend components, is developed and applied. The proposed modeling approach takes into account the deposition efficiencies and [...] Read more.
In this paper, a new semiempirical probability model, allowing for prediction of the composition of multimaterial cold spray coating in dependence on the initial percentage of blend components, is developed and applied. The proposed modeling approach takes into account the deposition efficiencies and the particle sizes of each component of the spraying powder blend. The experimental validation using several Cu/Cr2C3NiCr mixtures with different percentages of copper and cermet powders showed that the simulation results were in a good agreement with the experimental data. It was demonstrated that the deposition efficiency of the Cr2C3NiCr cermet powder strongly decreased when its mass percentage in the Cu/Cr2C3NiCr mixture increased from 5% to 75%. It was also shown that the dependence of the Cr2C3NiCr content in the coating on the initial percentage in the blend was nonlinear and the standard rule of mixtures was not applicable for prediction of copper–cermet coating composition. Full article
(This article belongs to the Special Issue Cold Spraying: Recent Trends and Future Views)
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17 pages, 3165 KiB  
Review
Atomic Layer Deposition of Inorganic Films for the Synthesis of Vertically Aligned Carbon Nanotube Arrays and Their Hybrids
by Guang-Jie Yuan, Jie-Fei Xie, Hao-Hao Li, Hong-Liang Lu and Ying-Zhong Tian
Coatings 2019, 9(12), 806; https://doi.org/10.3390/coatings9120806 - 1 Dec 2019
Cited by 5 | Viewed by 3701
Abstract
Vertically aligned carbon nanotube arrays (VACNTs) have many excellent properties and show great potential for various applications. Recently, there has been a desire to grow VACNTs on nonplanar surfaces and synthesize core-sheath-structured VACNT–inorganic hybrids. To achieve this aim, atomic layer deposition (ALD) has [...] Read more.
Vertically aligned carbon nanotube arrays (VACNTs) have many excellent properties and show great potential for various applications. Recently, there has been a desire to grow VACNTs on nonplanar surfaces and synthesize core-sheath-structured VACNT–inorganic hybrids. To achieve this aim, atomic layer deposition (ALD) has been extensively applied, especially due to its atomic-scale thickness controllability and excellent conformality of films on three-dimensional (3D) structures with high aspect ratios. In this paper, the ALD of catalyst thin films for the growth of VACNTs, such as Co3O4, Al2O3, and Fe2O3, was first mentioned. After that, the ALD of thin films for the synthesis of VACNT–inorganic hybrids was also discussed. To highlight the importance of these hybrids, their potential applications in supercapacitors, solar cells, fuel cells, and sensors have also been reviewed. Full article
(This article belongs to the Special Issue Surface Functionalization by ALD Technology)
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10 pages, 3745 KiB  
Article
Investigation of High Voltage Anodic Plasma (HVAP) Ag-DLC Coatings on Ti50Zr with Different Ag Amounts
by Andrei Bogdan Stoian, Cristina Surdu-Bob, Alexandru Anghel, Daniela Ionita and Ioana Demetrescu
Coatings 2019, 9(12), 792; https://doi.org/10.3390/coatings9120792 - 26 Nov 2019
Cited by 5 | Viewed by 2631
Abstract
The paper presents the investigation of a series of silver-incorporated diamond-like carbon (Ag-DLC) coatings with increasing Ag content on Ti50Zr and deposited using high voltage anodic plasma (HVAP). The coatings surface properties were analyzed with scanning electron microscope (SEM), atomic force microscope (AFM), [...] Read more.
The paper presents the investigation of a series of silver-incorporated diamond-like carbon (Ag-DLC) coatings with increasing Ag content on Ti50Zr and deposited using high voltage anodic plasma (HVAP). The coatings surface properties were analyzed with scanning electron microscope (SEM), atomic force microscope (AFM), and contact angle determinations. Electrochemical tests were performed in Afnor artificial saliva and evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. Based on these properties, comparisons of coatings performance were linked with the amount of deposited Ag. Increasing the Ag content led to the increase of the corrosion resistance and to the decrease of the forces exhibited on the surface. The hydrophobic character of the coating with the highest Ag amount could prevent thrombosis, thus suggesting its possible use for medical implants. Full article
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24 pages, 7322 KiB  
Article
Impact of Aggressive Media on the Properties of Polymeric Coatings with Solidification Products as Fillers
by Jakub Hodul, Lenka Mészárosová, Tomáš Žlebek, Rostislav Drochytka and Zdeněk Dufek
Coatings 2019, 9(12), 793; https://doi.org/10.3390/coatings9120793 - 26 Nov 2019
Cited by 6 | Viewed by 2786
Abstract
Dealing with waste materials, particularly hazardous waste, is a serious problem. Disposal areas keep growing, and the costs incurred are high. Disposing of such waste reduces negative environmental impacts and offers considerable financial savings. This paper focuses on the possibilities of incorporating pollutants [...] Read more.
Dealing with waste materials, particularly hazardous waste, is a serious problem. Disposal areas keep growing, and the costs incurred are high. Disposing of such waste reduces negative environmental impacts and offers considerable financial savings. This paper focuses on the possibilities of incorporating pollutants found in hazardous wastes as fillers in coatings based on polymers (epoxide and polyurethane). These coatings are intended mainly for concrete and metal bases and offer secondary protection against adverse weather conditions. Important physical and mechanical properties of the newly developed materials were determined; they include surface hardness, impact resistance, tensile properties, and chemical resistance. These properties were also compared to those of the reference filler. At the same time, the influence of aggressive media on the properties of these materials was observed, in particular on flexural characteristics. The microstructures of the developed coatings were tested using a high-resolution optical microscope, before and after exposure to the chemicals. The positive effect of using progressive fillers, such as solidified hazardous waste (a solidification product (SF)), was witnessed by their constructive contribution to the materials’ physical and mechanical properties. The use of solidification products is unambiguously advantageous from technical, ecological, and economical stand points (utilization of hazardous waste as a progressive filler instead of landfilling, improvement of tensile properties, reduction in the price of coating system, and incorporation of the pollutants into the polymer matrix). Full article
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10 pages, 2349 KiB  
Article
Thermoelectric Properties of Zinc-Doped Indium Tin Oxide Thin Films Prepared Using the Magnetron Co-Sputtering Method
by Ho Yun Lee, Im Jeong Yang, Jang-Hee Yoon, Sung-Ho Jin, Seohan Kim and Pung Keun Song
Coatings 2019, 9(12), 788; https://doi.org/10.3390/coatings9120788 - 24 Nov 2019
Cited by 6 | Viewed by 3855
Abstract
The thermoelectric properties of In−Sn−O (ITO) thin films were estimated in relation to microstructures with various zinc concentrations. The zinc-doped ITO (ITO:Zn) thin films were amorphized with increasing zinc concentration. The carrier density (n) of the thin films decreased as the [...] Read more.
The thermoelectric properties of In−Sn−O (ITO) thin films were estimated in relation to microstructures with various zinc concentrations. The zinc-doped ITO (ITO:Zn) thin films were amorphized with increasing zinc concentration. The carrier density (n) of the thin films decreased as the zinc content increased, which could be attributed to a decline in oxygen vacancies. The highest Seebeck coefficient (S, 64.91 μV/K) was obtained with an ITO film containing 15.33 at.% of Zn due to the low n value, which also exhibited the highest power factor (234.03 μW K−2 m−1). However, the highest thermoelectric figure of merit value (0.0627) was obtained from the film containing 18.26 at.% of Zn because of both low n and the lowest thermal conductivity (κ) (1.085 W m−1·K−1). The total κ decreased as increasing zinc concentration in the thin films. It was confirmed that the decrease of total κ was dominated by electron κ rather than lattice κ. Full article
(This article belongs to the Section Thin Films)
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15 pages, 12609 KiB  
Article
Luminescence of CsI and CsI:Na Films under LED and X-ray Excitation
by Jin-Cherng Hsu and Yu-Shen Ma
Coatings 2019, 9(11), 751; https://doi.org/10.3390/coatings9110751 - 13 Nov 2019
Cited by 10 | Viewed by 4924
Abstract
In this study, we investigated the luminous properties of undoped cesium iodide (CsI) and Na-doped CsI (CsI:Na) films deposited by thermal vacuum evaporation and treated with different substrate temperatures, post-annealing temperatures, and deposition rates. The quality of the deposited films was evaluated by [...] Read more.
In this study, we investigated the luminous properties of undoped cesium iodide (CsI) and Na-doped CsI (CsI:Na) films deposited by thermal vacuum evaporation and treated with different substrate temperatures, post-annealing temperatures, and deposition rates. The quality of the deposited films was evaluated by their XRD pattern, SEM cross-section/surface morphologies and UV/X-ray luminescence, the spectra of which were used to derive the luminescence mechanism of the deposited films. The 310 nm luminescence demonstrates that the exciting light arises from the electron–hole recombination through the self-trapped exciton (STE) process, which is characteristic of the host polycrystalline CsI. The broad-band luminescence from ~400 to 450 nm demonstrates the other electron–hole recombination between the new energy states created by doping Na in the forbidden gap of CsI. When we deposited higher quality films at a substrate temperature of 200 °C, the undoped CsI films showed preferred crystal orientation at (200), and the CsI:Na films co-evaporated by 1 wt.% NaI at (310) and had the highest UV/X-ray luminescence. Full article
(This article belongs to the Special Issue Functional Thin Films: Design, Fabrication and Applications)
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8 pages, 2455 KiB  
Article
Leakage Current Conduction Mechanism of Au-Pt-Ti/ HfO2-Al2O3/n-InAlAs Metal-Oxide-Semiconductor Capacitor under Reverse-Biased Condition
by He Guan and Shaoxi Wang
Coatings 2019, 9(11), 720; https://doi.org/10.3390/coatings9110720 - 1 Nov 2019
Cited by 1 | Viewed by 2888
Abstract
Au-Pt-Ti/high-k/n-InAlAs metal-oxide-semiconductor (MOS) capacitors with HfO2-Al2O3 laminated dielectric were fabricated. We found that a Schottky emission leakage mechanism dominates the low bias conditions and Fowler–Nordheim tunneling became the main leakage mechanism at high fields with reverse biased condition. [...] Read more.
Au-Pt-Ti/high-k/n-InAlAs metal-oxide-semiconductor (MOS) capacitors with HfO2-Al2O3 laminated dielectric were fabricated. We found that a Schottky emission leakage mechanism dominates the low bias conditions and Fowler–Nordheim tunneling became the main leakage mechanism at high fields with reverse biased condition. The sample with HfO2 (4 m)/Al2O3 (8 nm) laminated dielectric shows a high barrier height ϕB of 1.66 eV at 30 °C which was extracted from the Schottky emission mechanism, and this can be explained by fewer In–O and As–O states on the interface, as detected by the X-ray photoelectron spectroscopy test. These effects result in HfO2 (4 m)/Al2O3 (8 nm)/n-InAlAs MOS-capacitors presenting a low leakage current density of below 1.8 × 10−7 A/cm2 from −3 to 0 V at 30 °C. It is demonstrated that the HfO2/Al2O3 laminated dielectric with a thicker Al2O3 film of 8 nm is an optimized design to be the high-k dielectric used in Au-Pt-Ti/HfO2-Al2O3/InAlAs MOS capacitor applications. Full article
(This article belongs to the Special Issue Metal-Semiconductor and Insulator-Semiconductor Interfaces)
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6 pages, 1249 KiB  
Article
Thin Films of Tolane Aggregates for Faraday Rotation: Materials and Measurement
by Maarten Eerdekens, Ismael López-Duarte, Gunther Hennrich and Thierry Verbiest
Coatings 2019, 9(10), 669; https://doi.org/10.3390/coatings9100669 - 16 Oct 2019
Cited by 5 | Viewed by 2974
Abstract
We present organic, diamagnetic materials based on structurally simple (hetero-)tolane derivatives. They form crystalline thin-film aggregates that are suitable for Faraday rotation (FR) spectroscopy. The resulting new materials are characterized appropriately by common spectroscopic (NMR, UV-Vis), microscopy (POM), and XRD techniques. The spectroscopic [...] Read more.
We present organic, diamagnetic materials based on structurally simple (hetero-)tolane derivatives. They form crystalline thin-film aggregates that are suitable for Faraday rotation (FR) spectroscopy. The resulting new materials are characterized appropriately by common spectroscopic (NMR, UV-Vis), microscopy (POM), and XRD techniques. The spectroscopic studies give extremely high FR activities, thus making these materials promising candidates for future practical applications. Other than a proper explanation, we insist on the complexity of designing efficient FR materials starting from single molecules. Full article
(This article belongs to the Special Issue Optical Thin Films and Structures: Design and Advanced Applications)
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19 pages, 487 KiB  
Review
Cactus Mucilage for Food Packaging Applications
by Rim Gheribi and Khaoula Khwaldia
Coatings 2019, 9(10), 655; https://doi.org/10.3390/coatings9100655 - 11 Oct 2019
Cited by 61 | Viewed by 7951
Abstract
Natural polymers have been widely investigated for the development of eco-friendly materials. Among these bio-polymers, cactus mucilage is attracting increasing interest regardless of the plant species or the plant organ used for extraction. Mucilage, which is a highly branched heteropolysaccharide, has been previously [...] Read more.
Natural polymers have been widely investigated for the development of eco-friendly materials. Among these bio-polymers, cactus mucilage is attracting increasing interest regardless of the plant species or the plant organ used for extraction. Mucilage, which is a highly branched heteropolysaccharide, has been previously studied for its chemical composition, structural features, and biotechnological applications. This review highlights the mucilage application in the food packaging industry, by developing films and coatings. These cactus-based biomaterials will be discussed for their functional properties and their potential in preserving food quality and extending shelf life. Full article
(This article belongs to the Special Issue Novel Advances in Food Contact Materials)
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16 pages, 6241 KiB  
Article
Investigation of Protective Performance of a Mg-Rich Primer Containing Aluminum Tri-Polyphosphate on AZ91D Magnesium Alloy in Simulated Acid Rain
by Xiangyu Lu, Sichen Sun, Qiqi Fan, Xiangjun Pei, Yuchao Dun, Xingguo Feng, Chen Zou and Wang Lu
Coatings 2019, 9(10), 649; https://doi.org/10.3390/coatings9100649 - 9 Oct 2019
Cited by 9 | Viewed by 2830
Abstract
Mg-rich primer (MRP) containing aluminum tri-polyphosphate functions via a galvanic mechanism to protect AZ91D alloy from corrosion in the 3 wt % NaCl solution. However, its protective performance can be strongly affected by the testing environment. Therefore, it is important to investigate the [...] Read more.
Mg-rich primer (MRP) containing aluminum tri-polyphosphate functions via a galvanic mechanism to protect AZ91D alloy from corrosion in the 3 wt % NaCl solution. However, its protective performance can be strongly affected by the testing environment. Therefore, it is important to investigate the performance of the primer on magnesium alloys in an acid rain environment. In the present study, the protective performance of MRP with or without aluminum tri-polyphosphate was investigated via open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) in the simulated acid rain. Compared to the primer without aluminum tri-polyphosphate, the MRP containing aluminum tri-polyphosphate pigments exhibited better protective performance in the simulated acid rain condition. In the initial stage, the acidic condition prompted the aluminum tri-polyphosphate pigments to release phosphates and H+ to form magnesium phosphates on Mg particles, retarding their consumption rate. The Mg-rich primer with aluminum tri-polyphosphate can provide cathodic protection to AZ91D alloy for about 49 days in the simulated acid rain solution. Simultaneously, the corrosion products of Mg particles, magnesium oxides and phosphates, precipitated on the Mg particles and improved the stability of the primer. In addition, a protective film, consisting of magnesium oxides and phosphates, formed on the AZ91D substrate. Consequently, all these factors contributed to the long cathodic protection and improved corrosion resistance of MRP containing aluminum tri-polyphosphate in the simulated acid rain. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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9 pages, 4944 KiB  
Article
Preparation of Micro-Patterned CaMn7O12 Ceramic Films via a Photosensitive Sol-Gel Method
by Yunwei Wang, Gaoyang Zhao, Chuanbao Wu and Zongfan Duan
Coatings 2019, 9(10), 650; https://doi.org/10.3390/coatings9100650 - 9 Oct 2019
Cited by 4 | Viewed by 2742
Abstract
Mn/acetylacetone chelate was synthesized using Mn(CH3COO)2·4H2O as raw material, methanol as the solvent, and acetylacetone as the chelating agent. The ultraviolet (UV)-absorption peak of the synthesized chelate was found around 298 nm. CaMn7O12 sol [...] Read more.
Mn/acetylacetone chelate was synthesized using Mn(CH3COO)2·4H2O as raw material, methanol as the solvent, and acetylacetone as the chelating agent. The ultraviolet (UV)-absorption peak of the synthesized chelate was found around 298 nm. CaMn7O12 sol was subsequently prepared using the Mn/AcAc chelate as the Mn source and calcium nitrate as the calcium source. The UV test indicates that the CaMn7O12 sol has the UV-sensitive characteristics. Owing to its photo-sensitivity, micro-patterned CaMn7O12 ceramic film can be prepared without photoresist, only through dip-coating, drying, UV-irradiation, solvent-washing, and heat treatment. The magnetic test result indicates that the micro-patterned CaMn7O12 ceramic film has a saturation magnetization of 112.8 emu/cm3, which is close to that of non-patterned CaMn7O12 ceramic film. Full article
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11 pages, 6162 KiB  
Article
Thermal Fatigue Failure Behavior of Surface/Interface of Plasma Cladding Layer
by Yang Li, Na Tan, Guo Jin, Xiufang Cui and Qiu Li
Coatings 2019, 9(10), 646; https://doi.org/10.3390/coatings9100646 - 6 Oct 2019
Cited by 4 | Viewed by 2539
Abstract
Co-based coating was prepared by plasma cladding on FV520B substrates. Microstructure of the coatings was observed by scanning electron microscope. Finite element simulation as a predictive method to research the stress distributed after thermal cycling. Thermal fatigue resistance of the coating-substrate was evaluated [...] Read more.
Co-based coating was prepared by plasma cladding on FV520B substrates. Microstructure of the coatings was observed by scanning electron microscope. Finite element simulation as a predictive method to research the stress distributed after thermal cycling. Thermal fatigue resistance of the coating-substrate was evaluated at temperature of 600 °C, 700 °C, 800 °C, and 900 °C. Results indicate that the surface/interface structure has excellent thermal fatigue resistance at 600 °C, and the thermal fatigue crack initiated near the interface and extended along the grain boundary. The difference of expansion coefficient of the coating and substrate is small near 600 °C, and the difference increased when the temperature climbed above 600 °C. The diffuse elements could be found near the interface after the thermal cycle, and the dislocations and precipitated phase were observed. Full article
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15 pages, 14452 KiB  
Article
A Micropitting Study Considering Rough Sliding and Mild Wear
by Ye Zhou, Caichao Zhu and Huaiju Liu
Coatings 2019, 9(10), 639; https://doi.org/10.3390/coatings9100639 - 3 Oct 2019
Cited by 13 | Viewed by 2896
Abstract
Micropitting is a typical surface contact fatigue in rolling–sliding contact. The kinematic sliding is of great significance in the initiation and progression of micropitting. A numerical surface fatigue model considering rolling–sliding contact and surface evolution is developed based on mixed-EHL (elastohydrodynamic lubrication) theory, [...] Read more.
Micropitting is a typical surface contact fatigue in rolling–sliding contact. The kinematic sliding is of great significance in the initiation and progression of micropitting. A numerical surface fatigue model considering rolling–sliding contact and surface evolution is developed based on mixed-EHL (elastohydrodynamic lubrication) theory, rainflow cycle counting method and Archard’s law. Surface evolution is evaluated using Archard’s wear law based on measured teeth surface topography. Surface damage is determined via the Palmgren–Miner line rule and Goodman diagrams. The effect of rolling speed and surface roughness are discussed in detail. Results show that stress micro-cycles are introduced by rough sliding in the rolling–sliding contact. The mild wear reduces the height of asperities, the maximum pressure and alleviates subsurface stress concentration. For rolling–sliding contact, the faster moving surface dominates the composite height of asperities, then decides the fluctuations of pressure, as well as stress ranges. The combination of surface topography should be considered in the surface design. Full article
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11 pages, 1963 KiB  
Article
Effect of Rare Earth Oxides on Microstructure and Corrosion Behavior of Laser-Cladding Coating on 316L Stainless Steel
by Zezhou Xu, Zhiying Wang, Jian Chen, Yanxin Qiao, Junwei Zhang and Yueming Huang
Coatings 2019, 9(10), 636; https://doi.org/10.3390/coatings9100636 - 2 Oct 2019
Cited by 20 | Viewed by 3509
Abstract
The effect of rare earth oxides on the microstructure and corrosion behavior of laser-cladding coating on 316L stainless steel was investigated using hardness measurements, a polarization curve, electrochemical impedance spectroscopy (EIS), a salt spray test, X-ray diffraction, optical microscopy, and scanning electron microscopy [...] Read more.
The effect of rare earth oxides on the microstructure and corrosion behavior of laser-cladding coating on 316L stainless steel was investigated using hardness measurements, a polarization curve, electrochemical impedance spectroscopy (EIS), a salt spray test, X-ray diffraction, optical microscopy, and scanning electron microscopy (SEM). The results showed that the modification of rare earth oxides on the laser-cladding layer caused minor changes to its composition but refined the grains, leading to an increase in hardness. Electrochemical and salt spray studies indicated that the corrosion resistance of the 316L stainless steel could be improved by laser cladding, especially when rare earth oxides (i.e., CeO2 and La2O3) were added as a modifier. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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12 pages, 1943 KiB  
Article
HiPIMS and DC Magnetron Sputter-Coated Silver Films for High-Temperature Durable Reflectors
by Sophie Gledhill, Kevin Steyer, Charlotte Weiss and Christina Hildebrandt
Coatings 2019, 9(10), 593; https://doi.org/10.3390/coatings9100593 - 20 Sep 2019
Cited by 9 | Viewed by 4279
Abstract
High-temperature durable mirrors based on a protected silver sputter coating are attractive for secondary reflector applications in concentrated solar thermal power plants. In this paper, silver films are deposited by high-power impulse magnetron sputtering (HiPIMS) and standard direct current (DC) magnetron sputtering, either [...] Read more.
High-temperature durable mirrors based on a protected silver sputter coating are attractive for secondary reflector applications in concentrated solar thermal power plants. In this paper, silver films are deposited by high-power impulse magnetron sputtering (HiPIMS) and standard direct current (DC) magnetron sputtering, either as exposed discretely deposited films or in-sequence-deposited thin film systems, where the silver is protected and embedded between adhesion and barrier layers. The unprotected silver films and equivalent protected silver thin film systems are compared and characterized as deposited and after 400 °C oven temperature exposure. The reflectance is measured and grazing incident X-ray diffraction (GIXRD) and scanning electron microscopy (SEM) pictures were taken. The HiPIMS silver film, sputtered with a peak current of 200 A and an approximately equivalent average power density to the DC magnetron sputtered silver, exhibits higher reflectance (and conductivity). Increasing the power density further, yields silver films with lower reflectance, correlating to a reduced grain size. In the protected silver film system, the reflectance does not improve, due to the presence of a less reflective top adhesion layer. The protected film system, with the 200 A HiPIMS, is, however, more durable at 400 °C than the DC magnetron sputtered equivalent. Full article
(This article belongs to the Special Issue Surfaces and Interfaces for Renewable Energy)
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14 pages, 8782 KiB  
Article
Antimicrobial Efficacy of Low Concentration PVP-Silver Nanoparticles Deposited on DBD Plasma-Treated Polyamide 6,6 Fabric
by Ana Isabel Ribeiro, Dilara Senturk, Késia Karina Silva, Martina Modic, Uros Cvelbar, Gheorghe Dinescu, Bogdana Mitu, Anton Nikiforov, Christophe Leys, Irina Kuchakova, Mike De Vrieze, António Pedro Souto and Andrea Zille
Coatings 2019, 9(9), 581; https://doi.org/10.3390/coatings9090581 - 14 Sep 2019
Cited by 25 | Viewed by 4368
Abstract
In this study, a low concentration (10 μg·mL−1) of poly(N-vinylpyrrolidone) (PVP)-coated silver nanoparticles (AgNPs) were deposited by spray and exhaustion (30, 70 and 100 °C) methods onto untreated and dielectric barrier discharge (DBD) plasma-treated polyamide 6,6 (PA66) fabric. DBD plasma-treated samples [...] Read more.
In this study, a low concentration (10 μg·mL−1) of poly(N-vinylpyrrolidone) (PVP)-coated silver nanoparticles (AgNPs) were deposited by spray and exhaustion (30, 70 and 100 °C) methods onto untreated and dielectric barrier discharge (DBD) plasma-treated polyamide 6,6 (PA66) fabric. DBD plasma-treated samples showed higher AgNP deposition than untreated ones for all methods. After five washing cycles, only DBD plasma-treated samples displayed AgNPs on the fabric surface. The best-performing method was exhaustion at 30 °C, which exhibited less agglomeration and the best antibacterial efficacy against S. aureus (4 log reduction). For E. coli, the antimicrobial effect showed good results in all the exhaustion samples (5 log reduction). Considering the spray method, only the DBD plasma-treated samples showed some bacteriostatic activity for both strains, but the AgNP concentration was not enough to have a bactericidal effect. Our results suggest DBD plasma may be a low cost and chemical-free method for the preparation of antibacterial textiles, allowing for the immobilization of a very low—but effective—concentration of AgNPs. Full article
(This article belongs to the Special Issue Functional Coatings for Textile Applications)
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13 pages, 4038 KiB  
Article
Ultra-Long-Term Reliable Encapsulation Using an Atomic Layer Deposited HfO2/Al2O3/HfO2 Triple-Interlayer for Biomedical Implants
by Changzheng Li, Maarten Cauwe, Yang Yang, David Schaubroeck, Lothar Mader and Maaike Op de Beeck
Coatings 2019, 9(9), 579; https://doi.org/10.3390/coatings9090579 - 12 Sep 2019
Cited by 25 | Viewed by 5183
Abstract
Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up [...] Read more.
Long-term packaging of miniaturized, flexible implantable medical devices is essential for the next generation of medical devices. Polymer materials that are biocompatible and flexible have attracted extensive interest for the packaging of implantable medical devices, however realizing these devices with long-term hermeticity up to several years remains a great challenge. Here, polyimide (PI) based hermetic encapsulation was greatly improved by atomic layer deposition (ALD) of a nanoscale-thin, biocompatible sandwich stack of HfO2/Al2O3/HfO2 (ALD-3) between two polyimide layers. A thin copper film covered with a PI/ALD-3/PI barrier maintained excellent electrochemical performance over 1028 days (2.8 years) during acceleration tests at 60 °C in phosphate buffered saline solution (PBS). This stability is equivalent to approximately 14 years at 37 °C. The coatings were monitored in situ through electrochemical impedance spectroscopy (EIS), were inspected by microscope, and were further analyzed using equivalent circuit modeling. The failure mode of ALD Al2O3, ALD-3, and PI soaking in PBS is discussed. Encapsulation using ultrathin ALD-3 combined with PI for the packaging of implantable medical devices is robust at the acceleration temperature condition for more than 2.8 years, showing that it has great potential as reliable packaging for long-term implantable devices. Full article
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10 pages, 4105 KiB  
Article
Design and Preparation of a 6-Channel Fan-Shaped Integrated Narrow-Band Filter in the Mid-Infrared Band
by Yingbu Duan, Changlong Cai, Haifeng Liang, Tiantian Jia and Shujing Yin
Coatings 2019, 9(9), 567; https://doi.org/10.3390/coatings9090567 - 5 Sep 2019
Cited by 16 | Viewed by 3055
Abstract
A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed on the basis of the Fabray–Perot (FP) theory and was fabricated using e-beam thermal evaporation. The central wavelength was modulated by modifying the FP cavity thickness using the combination mask method. [...] Read more.
A six-channel fan-shaped integrated narrow-band filter on a silicon substrate was designed on the basis of the Fabray–Perot (FP) theory and was fabricated using e-beam thermal evaporation. The central wavelength was modulated by modifying the FP cavity thickness using the combination mask method. Germanium and zinc sulfide were selected as the high and low refractive index film materials, respectively. Its average peak transmission reached 83.3%, the cut-off transmittance was less than 1%, and the full width at half maximum (FWHM) changed from 55 and 94 nm, and the central wavelength positioning accuracy error was less than 0.35%. Furthermore, transmittance was also calculated inversely, using the thickness of each layer of films, in order to deduce the reason of the decrease in peak transmittance. Thickness deviation of each layer and interface scattering contributed to the decrease of peak transmittance. Compared with the same type of products in the market, our filter showed better properties than that of some published and commercial filter. Full article
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13 pages, 29092 KiB  
Article
High Temperature Wear Behavior of Titanium Nitride Coating Deposited Using High Power Impulse Magnetron Sputtering
by Chin-Chiuan Kuo, Yu-Tse Lin, Adeline Chan and Jing-Tang Chang
Coatings 2019, 9(9), 555; https://doi.org/10.3390/coatings9090555 - 29 Aug 2019
Cited by 41 | Viewed by 5900
Abstract
Titanium nitride (TiN) coating has been used in various application as it gives excellent performance in many aspects. It has been proven to prolong machining tool life since the mid-1960s. Industrial deposition processes of TiN, including magnetron sputtering, arc ion plating, and chemical [...] Read more.
Titanium nitride (TiN) coating has been used in various application as it gives excellent performance in many aspects. It has been proven to prolong machining tool life since the mid-1960s. Industrial deposition processes of TiN, including magnetron sputtering, arc ion plating, and chemical vapor depositions, have their individual advantages and limitations. Due to the rising demands of the dry machining technique, the massive amount of heat generated from the friction of cutting tools against the surface of a work piece has become the main issue to overcome. Oxidation of TiN, which occurs around 400 °C, puts a limit on the applications of the coatings. Comparing TiN tool coatings deposited by arc evaporation, the novel high-power impulse magnetron sputtering (HiPIMS) technology provides smoother film surface, denser structure and subsequent corrosion resistance. Therefore, this research aims to investigate the wear behavior of TiN thin film deposited by HiPIMS at high temperature. The influences of the coating properties on the wear resistance of coatings at high temperature are also investigated. The results show that the HiPIMS technique enables a denser epitaxial-grown TiN coating with higher surface hardness and adhesion in contrast with TiN coating deposited using direct current (DC) magnetron sputtering techniques, which provides a higher wear resistance. Full article
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15 pages, 2920 KiB  
Review
Fused Deposition Modelling as a Potential Tool for Antimicrobial Dialysis Catheters Manufacturing: New Trends vs. Conventional Approaches
by Essyrose Mathew, Juan Domínguez-Robles, Eneko Larrañeta and Dimitrios A. Lamprou
Coatings 2019, 9(8), 515; https://doi.org/10.3390/coatings9080515 - 14 Aug 2019
Cited by 31 | Viewed by 11407
Abstract
The rising rate of individuals with chronic kidney disease (CKD) and ineffective treatment methods for catheter-associated infections in dialysis patients has led to the need for a novel approach to the manufacturing of catheters. The current process requires moulding, which is time consuming, [...] Read more.
The rising rate of individuals with chronic kidney disease (CKD) and ineffective treatment methods for catheter-associated infections in dialysis patients has led to the need for a novel approach to the manufacturing of catheters. The current process requires moulding, which is time consuming, and coated catheters used currently increase the risk of bacterial resistance, toxicity, and added expense. Three-dimensional (3D) printing has gained a lot of attention in recent years and offers the opportunity to rapidly manufacture catheters, matched to patients through imaging and at a lower cost. Fused deposition modelling (FDM) in particular allows thermoplastic polymers to be printed into the desired devices from a model made using computer aided design (CAD). Limitations to FDM include the small range of thermoplastic polymers that are compatible with this form of printing and the high degradation temperature required for drugs to be extruded with the polymer. Hot-melt extrusion (HME) allows the potential for antimicrobial drugs to be added to the polymer to create catheters with antimicrobial activity, therefore being able to overcome the issue of increased rates of infection. This review will cover the area of dialysis and catheter-related infections, current manufacturing processes of catheters and methods to prevent infection, limitations of current processes of catheter manufacture, future directions into the manufacture of catheters, and how drugs can be incorporated into the polymers to help prevent infection. Full article
(This article belongs to the Special Issue Advances in Antimicrobial Coatings)
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11 pages, 2525 KiB  
Article
Study on Local Residual Stress in a Nanocrystalline Cr2O3 Coating by Micro-Raman Spectroscopy
by Qiu Li, Yanrong Gou, Tie-Gang Wang, Tingyi Gu, Qiang Yu and Lijie Wang
Coatings 2019, 9(8), 500; https://doi.org/10.3390/coatings9080500 - 7 Aug 2019
Cited by 20 | Viewed by 4354
Abstract
Residual stress in coatings often affects the service performance of coatings, and the residual stresses in some local areas even lead to premature failure of coatings. In this work, we characterized the residual stress of local micro-areas of a nanocrystalline Cr2O [...] Read more.
Residual stress in coatings often affects the service performance of coatings, and the residual stresses in some local areas even lead to premature failure of coatings. In this work, we characterized the residual stress of local micro-areas of a nanocrystalline Cr2O3 coating deposited on a Si wafer through micro-Raman spectroscopy, including the depositional edge zone where the electrode was placed, the micro-area containing Cr2O3 macroparticles, and other micro-areas vulnerable to cracks. To accurately measure the thickness of the coating, we combined optical interferometry and direct measurement by a profilometer. The results indicate the existence of in-plane tensile residual stress on the Cr2O3 coating. In thick coatings, the residual stress is independent of the coating thickness and is stable between 0.55 GPa and 0.75 GPa. As the coating thickness is less than 0.8 μm, the residual stress is directly related to the coating thickness. This in-plane tensile stress is considered as the origin of the observed microcrack, which can partially release the stress. Full article
(This article belongs to the Special Issue Stress in Thin Films and Coatings)
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13 pages, 3858 KiB  
Article
Antireflection, Superhydrophilic Nano-Porous SiO2 Coating based on Aerosol Impact Spray Deposition Technique for Solar PV Module
by Kamran Alam, Saddam Ali, Abdul Saboor, Muhammad Salman, Maoz, Muhammad Humayun, Muhammad Sadiq and Muhammad Arif
Coatings 2019, 9(8), 497; https://doi.org/10.3390/coatings9080497 - 6 Aug 2019
Cited by 20 | Viewed by 4888
Abstract
In this research, silica nano-particles are deposited over the borosilicate glass and silicon wafer substrates by indigenously developed Aerosol impact deposition assembly using SiH4, oxygen, and helium as precursors. The coating process involves deionization of gases leading towards nucleation sites for [...] Read more.
In this research, silica nano-particles are deposited over the borosilicate glass and silicon wafer substrates by indigenously developed Aerosol impact deposition assembly using SiH4, oxygen, and helium as precursors. The coating process involves deionization of gases leading towards nucleation sites for silica in the presence of plasma, while tuning the pressure difference between reaction and deposition chamber controls the coating thickness, porosity, and refractive index. The deposited coating layer on the substrate enhanced the transmittance to 99.6% at 600 nm wavelength. The induced porous nature and the graded index of the coated layer as observed from the AFM and SEM resulted in superhydrophilic behavior with a water contact angle of near to 0°. The super-hydrophilicity of the coating contains self-cleaning properties, suggesting an improvement of the performance of solar PV modules as well. Full article
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