Coatings

2 pages, 1036 KiB

Open AccessCorrection

Correction: Zhou et al. Effect of Zirconium Doping on Electrical Properties of Aluminum Oxide Dielectric Layer by Spin Coating Method with Low Temperature Preparation. Coatings 2020, 10, 620

by Yue Zhou, Zhihao Liang, Rihui Yao, Wencai Zuo, Shangxiong Zhou, Zhennan Zhu, Yiping Wang, Tian Qiu, Honglong Ning and Junbiao Peng

Coatings 2020, 10(10), 918; https://doi.org/10.3390/coatings10100918 - 21 Oct 2020

Viewed by 1250

Abstract

The authors wish to make the following corrections to this paper [...] Full article

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11 pages, 6525 KiB

Open AccessArticle

Fabrication of an Organo-Fluoride–Free Hydrophobic Film Using the Sol-Gel Method by Factors Screening and Poly-Acrylic Acid Addition

by Meng-Wei Shen and Shyi-Tien Chen

Coatings 2020, 10(10), 1011; https://doi.org/10.3390/coatings10101011 - 21 Oct 2020

Cited by 3 | Viewed by 2299

Abstract

Improving silica film’s contact angle (CA) using tetraethoxysilane (TEOS) and iso-butyltrimethoxysilane (iso-BTMS) by the sol-gel method without adding organo-fluoride substances is of interest. Five factors, namely type of solvent, molar ratio and amounts of TEOS and iso-BTMS, mixing intensity, sol aging time, and [...] Read more.

Improving silica film’s contact angle (CA) using tetraethoxysilane (TEOS) and iso-butyltrimethoxysilane (iso-BTMS) by the sol-gel method without adding organo-fluoride substances is of interest. Five factors, namely type of solvent, molar ratio and amounts of TEOS and iso-BTMS, mixing intensity, sol aging time, and presence and absence of poly-acrylic acid (PAA), were assessed to improve the static water CA of the film and its surface quality. Results revealed that when ethanol was used as the dissolving solvent and after adding initial iso-BTMS and TEOS concentrations of 0.0270 and 0.0194 mol/L (molar ratio = 1.39), respectively, without sonication and adding PAA/TEOS weight ratio of 0.029, then the maximum static CA of the film reached 147°, a nearly super-hydrophobic surface. Under given conditions, long-term film durability was observed, and the added PAA prevented the formation of nonhomogeneous film surfaces caused by the highly clustering aggregation of silanols under high pH conditions. Full article

(This article belongs to the Section Liquid–Fluid Coatings, Surfaces and Interfaces)

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16 pages, 4024 KiB

Open AccessArticle

Synthesis and Characterisation of Organo-Modified Silica Nanostructured Films for the Water-Repellent Treatment of Historic Stone Buildings

by Cristian Petcu, Elvira Alexandrescu, Adriana Bălan, Maria Antonia Tănase and Ludmila Otilia Cinteză

Coatings 2020, 10(10), 1010; https://doi.org/10.3390/coatings10101010 - 21 Oct 2020

Cited by 7 | Viewed by 2761

Abstract

This study presents the facile sol-gel synthesis of nanostructured coatings for use in water-repellent treatment of travertine stone. The synthesized materials combine surface roughness characteristics with particular chemical compositions to give different hydrophobicity results. The influence of the silica particle coating precursor on [...] Read more.

This study presents the facile sol-gel synthesis of nanostructured coatings for use in water-repellent treatment of travertine stone. The synthesized materials combine surface roughness characteristics with particular chemical compositions to give different hydrophobicity results. The influence of the silica particle coating precursor on the hydrophobicity of the polymeric film was investigated, and the octyl-modified silane was selected for further fabrication of the hybrid coatings. The water repellent properties, together with composition and structural properties of the silane-based hybrid material were measured on model glass surface. The coating with the best characteristics was subsequently deposited onto the travertine stone. The potential applicability of the nanostructured material was evaluated considering both the properties of the coating film and those of the travertine stone subjected to the treatment. The surface texture of the film, water repellent properties and uniformity were determined using scanning electron microscopy, atomic force microscopy, dynamic light scattering and contact angle measurements. The coating’s potential for use in stone conservation was evaluated by assessing its impact on the stone’s visual aspect. All the results obtained from the different types of analyses showed that the octyl-modified silica nanostructured material was highly hydrophobic and compatible both with the travertine stone and with the requirements for use on cultural heritage monuments. Full article

(This article belongs to the Special Issue Polymer-Based Multifunctional Coatings for Cultural Heritage Protection)

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12 pages, 3813 KiB

Open AccessArticle

Laser Surface Nitriding of Ti–6Al–4V Alloy in Nitrogen–Argon Atmospheres

by Guang Li, Xiaochun Yao, Richard James Wood, Jinchang Guo and Yu Shi

Coatings 2020, 10(10), 1009; https://doi.org/10.3390/coatings10101009 - 21 Oct 2020

Cited by 14 | Viewed by 2621

Abstract

Surface-nitrided layers of Ti–6Al–4V alloy were fabricated using a diode laser in pure and mixed gas atmospheres of nitrogen and argon. The surface morphology, microstructure, hardness, and cracks of the nitrided layers were investigated. In all gas atmospheres, the layers showed smooth and [...] Read more.

Surface-nitrided layers of Ti–6Al–4V alloy were fabricated using a diode laser in pure and mixed gas atmospheres of nitrogen and argon. The surface morphology, microstructure, hardness, and cracks of the nitrided layers were investigated. In all gas atmospheres, the layers showed smooth and humped regions, and consisted of planar nitrogen titanium (TiN), dendrites, and acicular martensite. The surface roughness was improved dramatically as the nitrogen concentration of the atmosphere was diluted with argon. Overall, the hardness of the nitrided layer was greatest for pure nitrogen and it tended to decrease as the concentration of argon in the atmosphere increased. However, the hardness of the layer for pure nitrogen also decreased rapidly, from the surface to matrix, in comparison to the diluted nitrogen atmospheres. It was shown that the number and size of dendrites, which determine hardness, are controlled by the nitrogen concentration. The dendrites of the nitrided layer were denser and smaller in a pure nitrogen atmosphere, than in diluted nitrogen atmospheres. Longitudinal and transverse cracks were observed in the nitrided layers. These two types of cracks were decreased or even eliminated as the argon concentration of the nitrogen–argon atmosphere was increased. Therefore, by diluting the nitrogen atmosphere with argon, the nitrided layer properties, in terms of surface roughness and cracks, can be improved, but this may also cause a reduction in the layer hardness. Full article

(This article belongs to the Special Issue Advanced Coatings for Resisting Fretting Damage)

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17 pages, 4937 KiB

Open AccessArticle

The Effect of Carbon Ink Rheology on Ink Separation Mechanisms in Screen-Printing

by Sarah-Jane Potts, Chris Phillips, Tim Claypole and Eifion Jewell

Coatings 2020, 10(10), 1008; https://doi.org/10.3390/coatings10101008 - 21 Oct 2020

Cited by 15 | Viewed by 4106

Abstract

Screen-printable carbon-based inks are available in a range of carbon morphologies and concentrations, resulting in various rheological profiles. There are challenges in obtaining a good print when high loading and elasticity functional inks are used, with a trade-off often required between functionality and [...] Read more.

Screen-printable carbon-based inks are available in a range of carbon morphologies and concentrations, resulting in various rheological profiles. There are challenges in obtaining a good print when high loading and elasticity functional inks are used, with a trade-off often required between functionality and printability. There is a limited understanding of how ink rheology influences the ink deposition mechanism during screen-printing, which then affects the print topography and therefore electrical performance. High speed imaging was used with a screen-printing simulation apparatus to investigate the effect of viscosity of a graphite and carbon-black ink at various levels of solvent dilution on the deposition mechanisms occurring during screen-printing. With little dilution, the greater relative volume of carbon in the ink resulted in a greater tendency towards elastic behavior than at higher dilutions. During the screen-printing process this led to the ink splitting into filaments while remaining in contact with both the mesh and substrate simultaneously over a greater horizonal length. The location of separating filaments corresponded with localized film thickness increases in the print, which led to a higher surface roughness (Sz). This method could be used to make appropriate adjustments to ink rheology to overcome print defects related to poor ink separation. Full article

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12 pages, 5431 KiB

Open AccessArticle

Osteogenic and Antibacterial Activity of a Plasma-Sprayed CeO₂ Coating on a Titanium (Ti)-Based Dental Implant

by Jing Yue, Zhichun Jin, Hin Lok Enoch Poon, Guangwei Shang, Haixia Liu, Dan Wang, Shengcai Qi, Fubo Chen and Yuanzhi Xu

Coatings 2020, 10(10), 1007; https://doi.org/10.3390/coatings10101007 - 21 Oct 2020

Cited by 8 | Viewed by 2571

Abstract

Peri-implantitis, often induced by oral pathogens, is one of the main reasons for the clinical failure of dental implants. The aim of this study was to investigate the biocompatibility, osteogeneic, and antibacterial properties of a cerium oxide (CeO₂) coating containing high [...] Read more.

Peri-implantitis, often induced by oral pathogens, is one of the main reasons for the clinical failure of dental implants. The aim of this study was to investigate the biocompatibility, osteogeneic, and antibacterial properties of a cerium oxide (CeO₂) coating containing high proportions of Ce⁴⁺ valences on a titanium-based dental implant biomaterial, Ti-6Al-4V. MC3T3-E1 cells or bone marrow stem cells (BMSCs) were seeded onto Ti-6Al-4V disks with or without CeO₂ coating. Compared to the control, the plasma-sprayed CeO₂ coating showed enhanced cell viability based on cell counting kit-8 (CCK-8) and flow cytometry assays. CCK-8, colony-forming unit test (CFU), and live-dead staining illustrated the antibacterial activity of CeO₂ coating. Additionally, CeO₂ coating upregulated the gene expression levels of osteogenic markers ALP, Bsp and Ocn, with a similar increase in protein expression levels of OCN and Smad 1 in both MC3T3-E1 cells and BMSCs. More importantly, the viability and proliferation of Enterococcus faecalis, Prevotella intermedia, and Porphyromonas gingivalis were significantly decreased on the CeO₂-coated Ti-6Al-4V surfaces compared to non-treated Ti-6Al-4V. In conclusion, the plasma-sprayed CeO₂ coating on the surface of Ti-6Al-4V exhibited strong biocompatibility, antibacterial, and osteogenic characteristics, with potential for usage in coated dental implant biomaterials for prevention of peri-implantitis. Full article

(This article belongs to the Special Issue Bioactive Coatings for Implantable Devices)

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12 pages, 3721 KiB

Open AccessArticle

Comparative Analysis on the Structure and Properties of Iron-Based Amorphous Coating Sprayed with the Thermal Spraying Techniques

by Amjad Iqbal, Sumera Siddique, Moazam Maqsood, Muhammad Atiq Ur Rehman and Muhammad Yasir

Coatings 2020, 10(10), 1006; https://doi.org/10.3390/coatings10101006 - 21 Oct 2020

Cited by 15 | Viewed by 3407

Abstract

Iron-based amorphous coatings are getting attention owing to their attractive mechanical, chemical, and thermal properties. In this study, the comparative analysis between high-velocity oxy-fuel (HVOF) and atmospheric plasma (APS) spraying processes has been done. The detailed structural analysis of deposited coatings were studied [...] Read more.

Iron-based amorphous coatings are getting attention owing to their attractive mechanical, chemical, and thermal properties. In this study, the comparative analysis between high-velocity oxy-fuel (HVOF) and atmospheric plasma (APS) spraying processes has been done. The detailed structural analysis of deposited coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical and electrochemical properties were investigated by using micro-Vickers hardness testing, pin-on-disc tribometry and potentiodynamic analysis. The microstructure comparison revealed that HVOF-coated samples had better density than that of APS. The porosity in APS-coated samples was 2 times higher than that of HVOF-coated samples. The comparison of tribological properties showed that HVOF-coated samples had 3.9% better hardness than that of coatings obtained via APS. The wear test showed that HVOF-coated samples had better wear resistance in comparison to APS coatings. Furthermore, the potentiodynamic polarization and electrochemical impedance spectroscopy showed that the HVOF-coated samples had better corrosion resistance in comparison to APS-coated samples. Full article

(This article belongs to the Special Issue Plasma Sprayed Coatings)

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14 pages, 7299 KiB

Open AccessArticle

Application of X-rays Diffraction for Identifying Thin Oxide Surface Layers on Zinc Coatings

by George Vourlias

Coatings 2020, 10(10), 1005; https://doi.org/10.3390/coatings10101005 - 20 Oct 2020

Cited by 22 | Viewed by 7802

Abstract

Structural characterization of compound material coatings is usually achieved using time-consuming and destructive techniques such as optical and electrical microscopy, which require the use of grinding processes not always compatible with the material. This paper reports on the effective use of a theoretical [...] Read more.

Structural characterization of compound material coatings is usually achieved using time-consuming and destructive techniques such as optical and electrical microscopy, which require the use of grinding processes not always compatible with the material. This paper reports on the effective use of a theoretical model based on X-ray diffraction to calculate the thickness and composition of thin oxide films formed on the surface of zinc coatings. Zinc coatings are widely used in industrial application as protective layers against the atmospheric corrosion of steel substrates. The thickness of single- and multi-layer coatings is estimated using grazing incidence X-ray diffraction and various incidence angles. The coatings were grown using hot-dip, pack cementation and thermal spray techniques, and their experimental characteristics were compared to the theoretically predicted values of thickness and composition. The results indicate the formation of a thin zinc oxide film on top of each coating, which acts as an isolation layer and protects the surface of the sample against the environmental corrosion. Finally, the penetration depth of the X-rays into the zinc-based coatings for grazing incidence and Bragg–Brentano X-ray diffraction geometries were calculated using theoretical equations and experimentally confirmed. Full article

(This article belongs to the Special Issue Industrial Coatings: Applications and Developments)

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10 pages, 4392 KiB

Open AccessArticle

New Low-Voltage Driving Compensating Pixel Circuit Based on High-Mobility Amorphous Indium-Zinc-Tin-Oxide Thin-Film Transistors for High-Resolution Portable Active-Matrix OLED Displays

by Ching-Lin Fan, Hou-Yen Tsao, Chun-Yuan Chen, Pei-Chieh Chou and Wei-Yu Lin

Coatings 2020, 10(10), 1004; https://doi.org/10.3390/coatings10101004 - 20 Oct 2020

Cited by 11 | Viewed by 3728

Abstract

In recent years, active-matrix organic light-emitting diodes (AMOLEDs) has been the most popular display for portable application. To satisfy the requirement for the application of the portable display, the design of the compensating pixel circuit with the low-voltage driving and low-power consumption will [...] Read more.

In recent years, active-matrix organic light-emitting diodes (AMOLEDs) has been the most popular display for portable application. To satisfy the requirement for the application of the portable display, the design of the compensating pixel circuit with the low-voltage driving and low-power consumption will be requested. In addition to the circuit with the design of the low-voltage driving, high-mobility thin-film transistors as driving device will be also necessary in order to supply larger driving current at low-voltage driving. Therefore, the study presents a new low-voltage driving AMOLED pixel circuit with high-mobility amorphous indium–zinc–tin–oxide (a-IZTO) thin-film transistors (TFTs) as driving device for portable displays with high resolution. The proposed pixel circuit can simultaneously compensate for the threshold voltage variation of driving TFT (ΔV_{TH_TFT}), OLED degradation (ΔV_{TH_OLED}), and the I-R drop of a power line (ΔV_DD). By using AIM-Spice for simulation based on fabricated a-IZTO TFTs with mobility of 70 cm²V⁻¹S⁻¹ as driving devices, we discovered that the error rates of the driving current were all lower than 5.71% for all input data when ΔV_{TH_TFT} = ±1 V, ΔV_DD = 0.5 V, and ΔV_{TH_OLED} = 0.5 V were all considered simultaneously. We revealed that the proposed 5T2C pixel circuit containing a high-mobility a-IZTO TFT as a driving device was suitable for high-resolution portable displays. Full article

(This article belongs to the Special Issue Advances in Thin Film Transistors: Properties and Applications)

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22 pages, 2859 KiB

Open AccessArticle

The Law of Parsimony and the Negative Charge of the Bubbles

by Stoyan I. Karakashev and Nikolay A. Grozev

Coatings 2020, 10(10), 1003; https://doi.org/10.3390/coatings10101003 - 20 Oct 2020

Cited by 5 | Viewed by 2593

Abstract

Why the bubbles are negatively charged? This is almost 100 years old question, which many scientists have striven and still are striving to answer using the latest developments of the MD simulations and various physical analytical methods. We scrutinize with this paper the [...] Read more.

Why the bubbles are negatively charged? This is almost 100 years old question, which many scientists have striven and still are striving to answer using the latest developments of the MD simulations and various physical analytical methods. We scrutinize with this paper the basic literature on this topic and conduct our own analysis. Following the philosophical law of parsimony: “Entities should not be multiplied without necessity”, we assume that the simplest explanation is the right one. It is well known that the negative change of the Gibbs free energy is a solid criterion for spontaneous process. Hence, we calculated the energies of adsorption of OH⁻, H₃O⁺ and HCO₃⁻ ions on the air/water interface using the latest theoretical developments on the dispersion interaction of inorganic ions with the air/water interface. Thus, we established that the adsorption of OH⁻ and HCO₃⁻ ions is energetically favorable, while the adsorption of H₃O⁺ is energetically unfavorable. Moreover, we calculated the change of the entropy of these ions upon their transfer from the bulk to the air/water interface. Using the well-known formula ΔG = ΔH − TΔS, we established that the adsorption of OH⁻ and HCO₃⁻ ions on the air/water interface decreases their Gibbs free energy. On the contrary, the adsorption of H₃O⁺ ions on the air/water interface increases their Gibbs free energy. Thus, we established that both OH⁻ and HCO₃⁻ ions adsorb on the air/water interface, while the H₃O⁺ ions are repelled by the latter. Therefore, electrical double layer (EDL) is formed at the surface of the bubble–negatively charged adsorption layer of OH⁻ and HCO₃⁻ ions and positively charged diffuse layer of H₃O⁺ ions. Full article

(This article belongs to the Special Issue Thin Liquid Films and Dispersed Systems–from Fundamentals to Applications)

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21 pages, 20122 KiB

Open AccessEditor’s ChoiceArticle

Biodegradation and Antimicrobial Properties of Zinc Oxide–Polymer Composite Materials for Urinary Stent Applications

by Chaitra Venkatesh, Marco Laurenti, Marina Bandeira, Eduardo Lanzagorta, Lorenzo Lucherini, Valentina Cauda and Declan M. Devine

Coatings 2020, 10(10), 1002; https://doi.org/10.3390/coatings10101002 - 20 Oct 2020

Cited by 12 | Viewed by 4794

Abstract

Research advancements in the field of urinary stents have mainly been in the selection of materials and coatings to address commonly faced problems of encrustation and bacterial adhesion. In this study, polylactic acid (PLA) and polypropylene (PP) were evaluated with zinc oxide (ZnO) [...] Read more.

Research advancements in the field of urinary stents have mainly been in the selection of materials and coatings to address commonly faced problems of encrustation and bacterial adhesion. In this study, polylactic acid (PLA) and polypropylene (PP) were evaluated with zinc oxide (ZnO) coating to assess its ability to reduce or eliminate the problems of encrustation and bacteria adhesion. PLA and PP films were prepared via twin screw extrusion. ZnO microparticles were prepared using sol-gel hydrothermal synthesis. The as-prepared ZnO microparticles were combined in the form of a functional coating and deposited on both polymer substrates using a doctor blade technique. The ZnO-coated PP and PLA samples as well as their uncoated counterparts were characterized from the physicochemical standpoints, antibacterial and biodegradation properties. The results demonstrated that both the polymers preserved their mechanical and thermal properties after coating with ZnO, which showed a better adhesion on PLA than on PP. Moreover, the ZnO coating successfully enhanced the antibacterial properties with respect to bare PP/PLA substrates. All the samples were investigated after immersion in simulated body fluid and artificial urine. The ZnO layer was completely degraded following 21 days immersion in artificial urine irrespective of the substrate, with encrustations more evident in PP and ZnO-coated PP films than PLA and ZnO-coated PLA films. Overall, the addition of ZnO coating on PLA displayed better adhesion, antibacterial activity and delayed the deposition of encrustations in comparison to PP substrates. Full article

(This article belongs to the Special Issue Recent Developments in Antibacterial and/or Antifouling Surfaces)

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3 pages, 335 KiB

Open AccessEditorial

Fluid Interfaces

by Eduardo Guzmán

Coatings 2020, 10(10), 1000; https://doi.org/10.3390/coatings10101000 - 20 Oct 2020

Cited by 2 | Viewed by 1626

Abstract

Fluid interfaces are promising candidates for the design of new functional materials by confining different types of materials, e.g., polymers, surfactants, colloids, or even small molecules, by direct spreading or self-assembly from solutions. The development of such materials requires a deep understanding of [...] Read more.

Fluid interfaces are promising candidates for the design of new functional materials by confining different types of materials, e.g., polymers, surfactants, colloids, or even small molecules, by direct spreading or self-assembly from solutions. The development of such materials requires a deep understanding of the physico-chemical bases underlying the formation of layers at fluid interfaces, as well as the characterization of the structures and properties of such layers. This is of particular importance, because the constraints associated with the assembly of materials at the interface lead to the emergence of equilibrium and dynamic features in the interfacial systems that are far from those found in traditional 3D materials. These new properties are of importance in many scientific and technological fields, such as food science, cosmetics, biology, oil recovery, electronics, drug delivery, detergency, and tissue engineering. Therefore, the understanding of the theoretical and practical aspects involved in the preparation of these interfacial systems is of paramount importance for improving their usage for designing innovative technological solutions. Full article

(This article belongs to the Special Issue Fluid Interfaces)

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10 pages, 3920 KiB

Open AccessArticle

Properties of Titanium Oxide Coating on MgZn Alloy by Magnetron Sputtering for Stent Application

by Shusen Hou, Weixin Yu, Zhijun Yang, Yue Li, Lin Yang and Shaoting Lang

Coatings 2020, 10(10), 999; https://doi.org/10.3390/coatings10100999 - 19 Oct 2020

Cited by 24 | Viewed by 2877

Abstract

Constructing surface coatings is an effective way to improve the corrosion resistance and biocompatibility of magnesium alloy bioabsorbable implants. In this present work, a titanium oxide coating with a thickness of about 400 nm was successfully prepared on a MgZn alloy surface via [...] Read more.

Constructing surface coatings is an effective way to improve the corrosion resistance and biocompatibility of magnesium alloy bioabsorbable implants. In this present work, a titanium oxide coating with a thickness of about 400 nm was successfully prepared on a MgZn alloy surface via a facile magnetron sputtering route. The surface features were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and the contact angle method. The corrosion behavior and biocompatibility were evaluated. The results indicated that the amorphous TiO₂ coating with a flat and dense morphology was obtained by magnetron-sputtering a titanium oxide target. The corrosion current density decreased from 1050 (bare MgZn alloy) to 49 μA/cm² (sample with TiO₂ coating), suggesting a significant increase in corrosion resistance. In addition, the TiO₂ coating showed good biocompatibilities, including significant reduced hemolysis and platelet adhesion, and increased endothelial cell viability and adhesion. Full article

(This article belongs to the Special Issue Bioactive Coatings for Implantable Devices)

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21 pages, 8715 KiB

Open AccessArticle

Microstructure and Inertial Characteristics of MHD Suspended SWCNTs and MWCNTs Based Maxwell Nanofluid Flow with Bio-Convection and Entropy Generation Past a Permeable Vertical Cone

by Zahir Shah, Ebraheem Alzahrani, Muhammad Jawad and Umair Khan

Coatings 2020, 10(10), 998; https://doi.org/10.3390/coatings10100998 - 19 Oct 2020

Cited by 31 | Viewed by 2826

Abstract

In this research work, our goal is to scrutinize the case, where water-based nanofluids having single-wall and multi-wall carbon nanotubes (CNTs) flow through a vertical cone. The second law of thermodynamic is taken for the aim of scheming effective heat storage units. The [...] Read more.

In this research work, our goal is to scrutinize the case, where water-based nanofluids having single-wall and multi-wall carbon nanotubes (CNTs) flow through a vertical cone. The second law of thermodynamic is taken for the aim of scheming effective heat storage units. The body package is layered in convective heat and diluted permeable medium. The effects of Joule heating, rotary microorganisms, heat generation/absorption, chemical reactions, and heat radiation increase the novelty of the established model. By using a local similarity transformation technique, the partial differential equations (PDEs) change into a coupled differential equation. By using the numerical technique, bvp4c, to get the solution of the conservation equations and their relevant boundary conditions. The parameters appearing in the distribution analysis of the alliance are scrutinized in detail, and the consequences are depicted graphically. It can be perceived that in the situation of composed nanotubes, the velocity of fluid decreases as the magnetic field is increased. Full article

(This article belongs to the Special Issue Fluid Interfaces)

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12 pages, 3244 KiB

Open AccessArticle

Hybrid ZrO₂/Cr₂O₃ Epoxy Nanocomposites as Organic Coatings for Steel

by Ayman M. Atta, Mona A. Ahmed, Ashraf M. El-Saeed, Ossama M. Abo-Elenien and Maher A. El-Sockary

Coatings 2020, 10(10), 997; https://doi.org/10.3390/coatings10100997 - 19 Oct 2020

Cited by 13 | Viewed by 2408

Abstract

Mixed ZrO₂ and Cr₂O₃ nanoparticles (NPs) were prepared using a liquid phase chemical technique and applied as reinforced filler for epoxy coatings with different weight ratios ranged from 0.5 to 2.5 wt.% to protect carbon steel from corrosion. The [...] Read more.

Mixed ZrO₂ and Cr₂O₃ nanoparticles (NPs) were prepared using a liquid phase chemical technique and applied as reinforced filler for epoxy coatings with different weight ratios ranged from 0.5 to 2.5 wt.% to protect carbon steel from corrosion. The ZrO₂/Cr₂O₃ NPs were used to catalyze the curing of the epoxy composite films to modify their mechanical and thermal characteristics on the steel surface. The crystalline structure, particle sizes, and surface morphologies of the prepared ZrO₂ and Cr₂O₃ NPs were characterized to investigate their chemical composition and dispersion. The thermal stability of epoxy ZrO₂/Cr₂O₃ coating films was investigated by thermogravimetric analysis (TGA), and the mechanical properties of the cured epoxy films were also studied. The dispersion of the Cr₂O₃/ZrO₂ NPs into the epoxy matrix was investigated by scanning electron microscope (SEM), dynamic mechanical analysis (DMA) and TGA analyses. The results of salt spray test, used to investigate the anticorrosion performance of the epoxy coatings) were combined with thermal characteristics to confirm that the addition of Cr₂O₃/ZrO₂ NPs significantly improved the corrosion resistance and the thermal stability of epoxy coating. The mechanical properties, adhesion, hardness, impact strength, flexibility and abrasion resistance were also improved with the addition of ZrO₂/Cr₂O₃ NPs filler content. Full article

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12 pages, 3344 KiB

Open AccessArticle

Ultrasonic Treatment Induced Fluoride Conversion Coating without Pores for High Corrosion Resistance of Mg Alloy

by Sheng Li, Laihua Yi, Xiongxiang Zhu and Tongfang Liu

Coatings 2020, 10(10), 996; https://doi.org/10.3390/coatings10100996 - 19 Oct 2020

Cited by 8 | Viewed by 2336

Abstract

Fluoride conversion (MgF₂) coating with facile preparation and good adhesion is promising to protect Mg alloy, but defects of pores in the coating lead to limited corrosion resistance. In this study, a compact and dense MgF₂ coating was prepared by [...] Read more.

Fluoride conversion (MgF₂) coating with facile preparation and good adhesion is promising to protect Mg alloy, but defects of pores in the coating lead to limited corrosion resistance. In this study, a compact and dense MgF₂ coating was prepared by the combination of fluoride treatment and ultrasonic treatment. The ultrasonically treated MgF₂ coating showed a compact and dense structure without pores at the frequency of 28 kHz. The chemical compositions of the coating were mainly composed of F and Mg elements. The corrosion potential of the ultrasonically treated Mg alloy shifted towards the noble direction in the electrochemical tests. The corrosion current density decreased due to the protectiveness of MgF₂ coating without defects of pores or cracks. During immersion tests for 24 h, the ultrasonically treated Mg alloy exhibited the lowest H₂ evolution (0.32 mL/cm²) and pH value (7.3), which confirmed the enhanced anti-corrosion ability of MgF₂ coating. Hence, the ultrasonically treated fluoride coating had great potentials for their use in anti-corrosion applications of Mg alloy. Full article

(This article belongs to the Special Issue Anticorrosion Protection of Nonmetallic and Metallic Coatings II)

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25 pages, 4177 KiB

Open AccessReview

Recent Development of Corrosion Factors and Coating Applications in Biomass Firing Plants

by Duoli Wu, Ziyi Yuan, Su Liu, Jiayin Zheng, Xinlong Wei and Chao Zhang

Coatings 2020, 10(10), 1001; https://doi.org/10.3390/coatings10101001 - 19 Oct 2020

Cited by 9 | Viewed by 2747

Abstract

Due to global warming, biomass fuels are gradually being used to replace fossil fuels. However, high-temperature biomass corrosion is a crucial issue affecting its future application. In this article, different factors affecting boiler performance are summarized from various studies to guide the optimization [...] Read more.

Due to global warming, biomass fuels are gradually being used to replace fossil fuels. However, high-temperature biomass corrosion is a crucial issue affecting its future application. In this article, different factors affecting boiler performance are summarized from various studies to guide the optimization of boiler parameters in practical applications, such as corrosive components and boiler temperatures. Meanwhile, different coating formation methods and materials are summarized to provide better protection strategies. The potential coating materials for future research are also discussed. The addition of other elements, such as Ti, Mo, and W, has the potential to accelerate the formation of oxide layers during high-temperature corrosion and directly slow down the corrosion rate. Future studies should focus on these elements containing materials. Full article

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12 pages, 3201 KiB

Open AccessArticle

Low Weight Hollow Microspheres of Iron with Thin Dielectric Coating: Synthesis and Microwave Permeability

by Anastasia Kosevich, Elizaveta Petrusevich, Sergey Maklakov, Andrey Naboko, Evgeniy Kolesnikov, Dmitry Petrov, Polina Zezyulina, Konstantin Pokholok, Dmitry Filimonov and Mangui Han

Coatings 2020, 10(10), 995; https://doi.org/10.3390/coatings10100995 - 18 Oct 2020

Cited by 4 | Viewed by 2219

Abstract

Spray pyrolysis of an aqueous solution of iron nitrate, proceeded with reduction of the product in hydrogen, gave iron powder with micron-sized hollow particles. Coating these iron particles with SiO₂ through tetraethyl orthosilicate hydrolysis prevented interparticle electrical contacts and suppressed DC percolation. [...] Read more.

Spray pyrolysis of an aqueous solution of iron nitrate, proceeded with reduction of the product in hydrogen, gave iron powder with micron-sized hollow particles. Coating these iron particles with SiO₂ through tetraethyl orthosilicate hydrolysis prevented interparticle electrical contacts and suppressed DC percolation. This material shows a high ferromagnetic resonance frequency of 18 GHz, low permittivity, and weighs 20% less than common carbonyl iron. Potential microwave applications are for inductors and electromagnetic interference shielding designs. Full article

(This article belongs to the Special Issue Functional Nanofilms: From Fundamentals to Applications)

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10 pages, 2671 KiB

Open AccessArticle

Voltage-Tunable UVC–UVB Dual-Band Metal–Semiconductor–Metal Photodetector Based on Ga₂O₃/MgZnO Heterostructure by RF Sputtering

by Jie-Si Jheng, Chun-Kai Wang, Yu-Zung Chiou, Sheng-Po Chang and Shoou-Jinn Chang

Coatings 2020, 10(10), 994; https://doi.org/10.3390/coatings10100994 - 17 Oct 2020

Cited by 7 | Viewed by 2564

Abstract

Dual-band metal–semiconductor–metal (MSM) photodetectors (PDs) with a Ga₂O₃/MgZnO heterostructure were fabricated by radio frequency (RF) sputtering, which can detect ultraviolet C (UVC) and ultraviolet B (UVB) bands individually by controlling different bias voltages. A PD with the annealing temperature [...] Read more.

Dual-band metal–semiconductor–metal (MSM) photodetectors (PDs) with a Ga₂O₃/MgZnO heterostructure were fabricated by radio frequency (RF) sputtering, which can detect ultraviolet C (UVC) and ultraviolet B (UVB) bands individually by controlling different bias voltages. A PD with the annealing temperature of Ga₂O₃ at 600 °C can improve the crystal quality of Ga₂O₃ thin film and exhibit the least persistent photoconductivity (PPC) effect. However, a PD with the annealing temperature of Ga₂O₃ at 600 °C cannot achieve a voltage-tunable dual-band characteristic. On the contrary, the PD without annealing can suppress the carriers from the bottom layer of MgZnO thin film at a lower bias voltage of 1 V. At this time, the peak responsivity at 250 nm was mainly dominated by the top layer of Ga₂O₃ thin film. Then, as the bias voltage increased to 5 V, the peak detection wavelength shifted from 250 (UVC) to 320 nm (UVB). In addition, the PD with a 25 nm–thick SiO₂ layer inserted between Ga₂O₃ and MgZnO thin film can achieve a broader operating bias voltage range for dual-band applications. Full article

(This article belongs to the Special Issue Advances in Thin Film Transistors: Properties and Applications)

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12 pages, 34716 KiB

Open AccessArticle

Fabrication and Characterization of Ceramic Coating on Al7075 Alloy by Plasma Electrolytic Oxidation in Molten Salt

by Alexander Sobolev, Tamar Peretz and Konstantin Borodianskiy

Coatings 2020, 10(10), 993; https://doi.org/10.3390/coatings10100993 - 17 Oct 2020

Cited by 19 | Viewed by 3347

Abstract

The fabrication of a ceramic coating on the metallic substrate is usually applied to achieve the improved performance of the material. Plasma electrolytic oxidation (PEO) is one of the most promising methods to reach this performance, mostly wear and corrosion resistance. Traditional PEO [...] Read more.

The fabrication of a ceramic coating on the metallic substrate is usually applied to achieve the improved performance of the material. Plasma electrolytic oxidation (PEO) is one of the most promising methods to reach this performance, mostly wear and corrosion resistance. Traditional PEO is carried out in an aqueous electrolyte. However, the current work showed the fabrication and characterization of a ceramic coating using PEO in molten salt which was used to avoid disadvantages in system heating-up and the formation of undesired elements in the coating. Aluminum 7075 alloy was subjected to the surface treatment using PEO in molten nitrate salt. Various current frequencies were applied in the process. Coating investigations revealed its surface porous structure and the presence of two oxide layers, α-Al₂O₃ and γ-Al₂O₃. Microhardness measurements and chemical and phase examinations confirmed these results. Potentiodynamic polarization tests and electrochemical impedance spectroscopy revealed the greater corrosion resistance for the coated alloy. Moreover, the corrosion resistance was increased with the current frequency of the PEO process. Full article

(This article belongs to the Special Issue Plasma Electrolytic Oxidation (PEO) Coatings)

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21 pages, 5628 KiB

Open AccessFeature PaperArticle

In Vivo Assessment of Bone Enhancement in the Case of 3D-Printed Implants Functionalized with Lithium-Doped Biological-Derived Hydroxyapatite Coatings: A Preliminary Study on Rabbits

by Liviu Duta, Johny Neamtu, Razvan P. Melinte, Oana A. Zureigat, Gianina Popescu-Pelin, Diana Chioibasu, Faik N. Oktar and Andrei C. Popescu

Coatings 2020, 10(10), 992; https://doi.org/10.3390/coatings10100992 - 17 Oct 2020

Cited by 12 | Viewed by 2882

Abstract

We report on biological-derived hydroxyapatite (HA, of animal bone origin) doped with lithium carbonate (Li-C) and phosphate (Li-P) coatings synthesized by pulsed laser deposition (PLD) onto Ti6Al4V implants, fabricated by the additive manufacturing (AM) technique. After being previously validated by in vitro cytotoxicity [...] Read more.

We report on biological-derived hydroxyapatite (HA, of animal bone origin) doped with lithium carbonate (Li-C) and phosphate (Li-P) coatings synthesized by pulsed laser deposition (PLD) onto Ti6Al4V implants, fabricated by the additive manufacturing (AM) technique. After being previously validated by in vitro cytotoxicity tests, the Li-C and Li-P coatings synthesized onto 3D Ti implants were preliminarily investigated in vivo, by insertion into rabbits’ femoral condyles. The in vivo experimental model for testing the extraction force of 3D metallic implants was used for this study. After four and nine weeks of implantation, all structures were mechanically removed from bones, by tensile pull-out tests, and coatings’ surfaces were investigated by scanning electron microscopy. The inferred values of the extraction force corresponding to functionalized 3D implants were compared with controls. The obtained results demonstrated significant and highly significant improvement of functionalized implants’ attachment to bone (p-values ≤0.05 and ≤0.00001), with respect to controls. The correct placement and a good integration of all 3D-printed Ti implants into the surrounding bone was demonstrated by performing computed tomography scans. This is the first report in the dedicated literature on the in vivo assessment of Li-C and Li-P coatings synthesized by PLD onto Ti implants fabricated by the AM technique. Their improved mechanical characteristics, along with a low fabrication cost from natural, sustainable resources, should recommend lithium-doped biological-derived materials as viable substitutes of synthetic HA for the fabrication of a new generation of metallic implant coatings. Full article

(This article belongs to the Special Issue Physical Vapor Deposited Biomedical Coatings)

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14 pages, 3642 KiB

Open AccessArticle

Deposition of Titanium Dioxide Coating by the Cold-Spray Process on Annealed Stainless Steel Substrate

by Noor irinah Omar, Santirraprahkash Selvami, Makoto Kaisho, Motohiro Yamada, Toshiaki Yasui and Masahiro Fukumoto

Coatings 2020, 10(10), 991; https://doi.org/10.3390/coatings10100991 - 17 Oct 2020

Cited by 17 | Viewed by 3824

Abstract

The surface of most metals is covered with thin native oxide films. It has generally been believed that to achieve bonding, the oxide covering the surface of metallic particles or metal substrates must be broken and removed by adiabatic shear instability (ASI), whether [...] Read more.

The surface of most metals is covered with thin native oxide films. It has generally been believed that to achieve bonding, the oxide covering the surface of metallic particles or metal substrates must be broken and removed by adiabatic shear instability (ASI), whether induced at the particle–substrate interface or at the particle–particle interface. The aim of the present research is to investigate the correlation between the remaining oxide amorphous layer and substrate-deformation with the adhesion strength of cold-sprayed TiO₂ coatings towards the bonding mechanism involved. Relevant experiments were executed using stainless steel (SUS 304), subjected to various annealing temperatures and cold-sprayed with TiO₂ powder. The results indicate an increasing trend of coating adhesion strength with increasing annealed substrate temperature. The influence of substrate plastic deformation and atomic intermixing at the remaining amorphous oxide layer is discussed as the factors contributing to the increasing adhesion strength of cold-sprayed TiO₂ coatings. Full article

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

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16 pages, 6413 KiB

Open AccessArticle

Obtaining, Evaluation, and Optimization of Doxycycline-Loaded Microparticles Intended for the Local Treatment of Infectious Arthritis

by Maria Minodora Marin, Mădălina Georgiana Albu Kaya, Horia Iovu, Cristina Elena Stavarache, Ciprian Chelaru, Rodica Roxana Constantinescu, Cristina-Elena Dinu-Pîrvu and Mihaela Violeta Ghica

Coatings 2020, 10(10), 990; https://doi.org/10.3390/coatings10100990 - 17 Oct 2020

Cited by 6 | Viewed by 2402

Abstract

Compared to the classical systemic administration, the local drug release has some advantages, such as lack of systemic toxicity and associated side effects, increased patient compliance, and a low rate of bacterial resistance. Biopolymers are widely used to design sustained drug delivery systems [...] Read more.

Compared to the classical systemic administration, the local drug release has some advantages, such as lack of systemic toxicity and associated side effects, increased patient compliance, and a low rate of bacterial resistance. Biopolymers are widely used to design sustained drug delivery systems and biomaterials for tissue engineering. Type II collagen is the indispensable component in articular cartilage and plays a critical role in the growth and proliferation process of chondrocytes. Thus, type II collagen has drawn more attention and interest in the treatment and research of the cartilage regeneration. The aim of this study was to obtain, characterize, and optimize the microcapsules formulation based on type II collagen, sodium alginate, and sodium carboxymethyl cellulose loaded with doxycycline as an antibiotic model drug that could be incorporated further in hydrogels to improve the localized therapy of septic arthritis. The new synthesized microcapsules were assessed by spectral (FT-IR), morphological (optical microscopy), and biological analysis (enzymatic biodegradation, antimicrobial activity). The size distribution of the obtained microcapsules was determined using optical microscopy. The drug encapsulation efficiency was also determined. To optimize the microcapsules’ composition, some physical-chemical and biological analyses were subjected to an optimization technique based on experimental design, response surface methodology, and the Taguchi technique, and the adequate formulations were selected. The results obtained recommend these new microcapsules as promising drug systems to be further incorporated in type II collagen hydrogels used for septic arthritis. Full article

(This article belongs to the Special Issue Micro- and Nano-Coatings for Technological and Biomedical Applications)

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21 pages, 5415 KiB

Open AccessArticle

Influence of Sludge Initial pH on Bioleaching of Excess Sludge to Improve Dewatering Performance

by Shaonan Lin, Mingyan Shi, Jiade Wang, Huijie Zhu and Guicheng Wen

Coatings 2020, 10(10), 989; https://doi.org/10.3390/coatings10100989 - 16 Oct 2020

Cited by 2 | Viewed by 1994

Abstract

pH has an important effect on the physiological activity of eosinophilic microorganisms. Therefore, this study used excess sludge produced by the mixed treatment of leachate and municipal sewage to explore the impact of different sludge initial pH on microbial biochemical reactions associated with [...] Read more.

pH has an important effect on the physiological activity of eosinophilic microorganisms. Therefore, this study used excess sludge produced by the mixed treatment of leachate and municipal sewage to explore the impact of different sludge initial pH on microbial biochemical reactions associated with the performance of excess sludge dehydration. Shake-flask tests were performed using inoculated microorganisms and fresh excess sludge in 500 mL Erlenmeyer flasks at a ratio of 1:4, with the addition of 2 g/L S⁰ and 6 g/L FeS₂ as energy sources. Erlenmeyer flasks were shaken for 72 h at 180 rpm and 28 °C, in a reciprocating constant homeothermic oscillating water-bath. Results show that the specific resistance to filtration (SRF) of the bioleached excess sludge decreased from (1.45~6.68) × 10¹² m/kg to (1.21~14.30) × 10¹¹ m/kg and the sedimentation rate increased from 69.00~73.00% to 81.70~85.50%. The SRF decreased from 1.45 × 10¹² m/kg to 1.21 × 10¹¹ m/kg and the sedimentation rate increased from 69.00% to 85.00%, which both reached the highest level when the initial pH of the excess sludge was 5 and the bioleaching duration was 48 h. At this time, the rates of pH reduction and oxidative redox potential (ORP) reached the highest values (69.67% and 515 mV, respectively). Illumina HiSeq PE250 sequencing results show that the dominate microbial community members were Thiomonas (relative abundance 4.59~5.44%), which oxidize sulfur and ferrous iron, and Halothiobacillus (2.56~3.41%), which oxidizes sulfur. Thus, the acidic environment can promote microbial acidification and oxidation, which can help sludge dewatering. The presence of dominant sulfur oxidation bacteria is the essential reason for the deep dehydration of the bioleached sludge. Full article

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15 pages, 1340 KiB

Open AccessReview

A Review of Polysaccharide-Zinc Oxide Nanocomposites as Safe Coating for Fruits Preservation

by Daru Seto Bagus Anugrah, Hugo Alexander, Rianita Pramitasari, Dwi Hudiyanti and Christyowati Primi Sagita

Coatings 2020, 10(10), 988; https://doi.org/10.3390/coatings10100988 - 16 Oct 2020

Cited by 27 | Viewed by 5193

Abstract

Safe coating formulated from biopolymer can be an alternative for better packaging for fruits. Among biopolymers used for safe coating, polysaccharides attracted more attention due to its biocompatibility and edibility. However, polysaccharide-based materials have weaknesses such as low water barrier and mechanical properties [...] Read more.

Safe coating formulated from biopolymer can be an alternative for better packaging for fruits. Among biopolymers used for safe coating, polysaccharides attracted more attention due to its biocompatibility and edibility. However, polysaccharide-based materials have weaknesses such as low water barrier and mechanical properties which result in lower capability on preserving the coated fruits. Hence, the incorporation of nanoparticles (NPs) such as zinc oxide (ZnO) is expected to increase the ability of polysaccharide-based coating for the enhancement of fruit shelf life. In this review paper, the basic information and the latest updates on the incorporation of ZnO NPs into the polysaccharide-based safe coating for fruit are presented. Various research has investigated polysaccharide-ZnO nanocomposite safe coating to prolong the shelf life of fruits. The polysaccharides used include chitosan, alginate, carrageenan, cellulose, and pectin. Overall, polysaccharide-ZnO nanocomposites can improve the shelf life of fruits by reducing weight loss, maintaining firmness, reducing the ripening process, reducing respiration, reducing the oxidation process, and inhibiting microbial growth. Finally, the challenges and potential of ZnO NPs as an active agent in the safe coating application are also discussed. Full article

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

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13 pages, 7321 KiB

Open AccessArticle

Microstructure Evolution and Mechanical Behavior of Mo–Si–N Films

by Yu-Cheng Liu, Bing-Hao Liang, Chi-Ruei Huang and Fan-Bean Wu

Coatings 2020, 10(10), 987; https://doi.org/10.3390/coatings10100987 - 16 Oct 2020

Cited by 6 | Viewed by 2607

Abstract

The molybdenum silicon nitride (Mo–Si–N) films were deposited by a radio frequency (RF) magnetron reactive dual-gun co-sputtering technique with process control on input power and gas ratio. Composition variation, microstructure evolution, and related mechanical and tribological behavior of the Mo–Si–N coatings were investigated. [...] Read more.

The molybdenum silicon nitride (Mo–Si–N) films were deposited by a radio frequency (RF) magnetron reactive dual-gun co-sputtering technique with process control on input power and gas ratio. Composition variation, microstructure evolution, and related mechanical and tribological behavior of the Mo–Si–N coatings were investigated. The N₂/(Ar + N₂) flow ratios were controlled at 10/20 and 5/20 levels with the tuning of input power on the Si target at 0, 100, and 150 W. As the silicon contents increased from 0 to 33.7 at.%, the film microstructure evolved from a crystalline structure with Mo₂N and MoN phases to an amorphous feature with the Si₃N₄ phase. The analysis of selected area electron diffraction patterns in TEM also indicated an amorphous feature of the Mo–Si–N films when Si content reached 20 at.% and beyond. The hardness and Young’s modulus changed from 16.5 to 26.9 and 208 to 273 GPa according to their microstructure features. The highest hardness and modulus were attributed to nanocrystalline Mo₂N and MoN with Si solid-solution. The crystalline Mo–Si–N films showed a smooth tribological track and less wear failure was found. In contrast, the wear track with severe failures were observed for Mo–N and amorphous Mo–Si–N coatings due to their lower hardness. The ratios of H/E and H³/E² were intensively discussed and correlated to the wear behavior of the Mo–Si–N coatings. Full article

(This article belongs to the Special Issue Multicomponent and Nanocomposite Hard Coatings: Coating Technologies, Properties and Applications)

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10 pages, 3958 KiB

Open AccessArticle

Highly Hydrophobic and Self-Cleaning Heat-Treated Larix spp. Prepared by TiO₂ and ZnO Particles onto Wood Surface

by Dong Xing, Yan Zhang, Jianpeng Hu and Lihong Yao

Coatings 2020, 10(10), 986; https://doi.org/10.3390/coatings10100986 - 16 Oct 2020

Cited by 8 | Viewed by 2354

Abstract

The deposition of TiO₂/ZnO on heat-treated wood was prepared by a hydrothermal reaction and sol-gel method. Highly hydrophobic wood was successfully prepared with low surface free energy. The surface-modified wood samples were characterized by 3D-laser shape measurement microscopy, scanning electron microscopy, [...] Read more.

The deposition of TiO₂/ZnO on heat-treated wood was prepared by a hydrothermal reaction and sol-gel method. Highly hydrophobic wood was successfully prepared with low surface free energy. The surface-modified wood samples were characterized by 3D-laser shape measurement microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy for the microstructure and chemical composition investigation. The deposited TiO₂ or ZnO markedly made the wood surface brighter, which was demonstrated by visual observation and spectrophotometer. The TiO₂/ZnO particles were successfully loaded onto the surface of the wood, proven by SEM-EDS and FTIR analyses. The contact angle of TiO₂ and ZnO-modified wood reached 123.9° and 134.1° respectively, which is obviously higher than that of the control at 88.9°. The hydrophobic properties of the TiO₂/ZnO modified wood samples were directly related to the shapes of clusters and spheres of particles, which increased the roughness of the wood surface. This study shows the hydrophobic properties of the TiO₂/ZnO-modified wood and provides the color and roughness changes for the painting process of heat-treated wood. Full article

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7 pages, 1385 KiB

Open AccessCommunication

Photoluminescence of Layered Semiconductor Materials for Emission-Color Conversion of Blue Micro Light-Emitting Diode (µLED)

by Yuma Tsuboi, Noriyuki Urakami and Yoshio Hashimoto

Coatings 2020, 10(10), 985; https://doi.org/10.3390/coatings10100985 - 15 Oct 2020

Cited by 2 | Viewed by 2095

Abstract

A micro light-emitting diode (μLED) is a key device for the future of advanced information. Owing to expand its application widely, the concept of the emission-color conversion using layered semiconductors as a color converter is proposed. In addition, it is demonstrated that layered [...] Read more.

A micro light-emitting diode (μLED) is a key device for the future of advanced information. Owing to expand its application widely, the concept of the emission-color conversion using layered semiconductors as a color converter is proposed. In addition, it is demonstrated that layered semiconductors were transferred directly onto μLED chips, and the emission-color conversion is realized. The layered GaS_1−xSe_x alloy, whose energy bandgap can be controlled by tuning the S and Se compositions, was selected as a color converter. The photoluminescence (PL) measurements using a blue LED as an excitation source revealed that GaS_0.65Se_0.35 and GaSe can show green and red luminescence with center energies of 2.34 and 1.94 eV, respectively. The emission color of gallium nitride (GaN)-based blue μLEDs covered with GaS_0.65Se_0.35 and GaSe thin films were clearly converted to green and red, respectively. Furthermore, the emission color could be controlled by changing the film thickness. Thus, these results suggest the possibility of emission-color conversion of blue μLED chips utilizing layered materials. Full article

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15 pages, 2701 KiB

Open AccessArticle

X-ray Diffraction Investigation of Stainless Steel—Nitrogen Thin Films Deposited Using Reactive Sputter Deposition

by Faisal I. Alresheedi and James E. Krzanowski

Coatings 2020, 10(10), 984; https://doi.org/10.3390/coatings10100984 - 15 Oct 2020

Cited by 4 | Viewed by 2432

Abstract

An X-ray diffraction investigation was carried out on nitrogen-containing 304 stainless steel thin films deposited by reactive rf magnetron sputtering over a range of substrate temperature and bias levels. The resulting films contained between ~28 and 32 at.% nitrogen. X-ray analysis was carried [...] Read more.

An X-ray diffraction investigation was carried out on nitrogen-containing 304 stainless steel thin films deposited by reactive rf magnetron sputtering over a range of substrate temperature and bias levels. The resulting films contained between ~28 and 32 at.% nitrogen. X-ray analysis was carried out using both the standard Bragg-Brentano method as well as area-detector diffractometry analysis. The extent of the diffraction anomaly ((002) peak shift) was determined using a calculated parameter, denoted R_B, which is based on the (111) and (002) peak positions. The normal value for R_B for FCC-based structures is 0.75 but increases as the (002) peak is anomalously displaced closer to the (111) peak. In this study, the R_B values for the deposited films were found to increase with substrate bias but decrease with substrate temperature (but still always >0.75). Using area detector diffractometry, we were able to measure d₁₁₁/d₀₀₂ values for similarly oriented grains within the films, and using these values calculate c/a ratios based on a tetragonal-structure model. These results allowed prediction of the (002)/(200) peak split for tetragonal structures. Despite predicting a reasonably accessible split (~0.6°–2.9°–2θ), no peak splitting observed, negating the tetragonal-structure hypothesis. Based on the effects of film bias/temperature on R_B values, a defect-based hypothesis is more viable as an explanation for the diffraction anomaly. Full article

(This article belongs to the Special Issue Structure and Phase Transformations in Thin Films)

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11 pages, 6169 KiB

Open AccessArticle

Direct and Indirect Evidence of the Microbially Induced Pitting Corrosion of Steel Structures in Humid Environments

by Jingzhong Zhou, Kuoteng Sun, Songqiang Huang, Xuemin He, Zhaowei Hu and Wenge Li

Coatings 2020, 10(10), 983; https://doi.org/10.3390/coatings10100983 - 15 Oct 2020

Cited by 1 | Viewed by 1775

Abstract

Corrosion is a severe problem for steel structures in humid environments. In particular, humidity usually triggers the surface adhesion of microorganisms, leading to microbiologically induced corrosion. This study aims to explore the effect of bacterial biofilm formation on the pitting corrosion of stainless [...] Read more.

Corrosion is a severe problem for steel structures in humid environments. In particular, humidity usually triggers the surface adhesion of microorganisms, leading to microbiologically induced corrosion. This study aims to explore the effect of bacterial biofilm formation on the pitting corrosion of stainless steel. This research uses electrochemical methods to obtain indirect evidence of the pitting corrosion of steel. In addition, in order to obtain direct evidence of the pitting corrosion of stainless steel, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to characterize the dimensional morphology of the stainless steel after pitting. It was shown that the bacterial adhesion increased with the pH and temperature, which significantly increased the surface roughness of the stainless steel. Electrochemical analysis revealed that the formation of biofilm greatly destroyed the oxide film of 304 SS and accelerated the corrosion of stainless steel by forming an oxygen concentration battery. SEM and AFM analyses showed cracks and dislocations on the surface of stainless steel underneath the attached bacteria, which suggested a direct role of biofilm in corrosion induction. The results presented here show that the bacterial biofilm formation on the steel surfaces significantly accelerated the corrosion and affected the pitting corrosion process of the steel structure. Full article

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