Coatings

13 pages, 61489 KiB

Open AccessEditor’s ChoiceArticle

Effects of Laser Microtexturing on the Wetting Behavior of Ti6Al4V Alloy

by Juan Manuel Vazquez-Martinez, Jorge Salguero Gomez, Pedro Francisco Mayuet Ares, Severo Raul Fernandez-Vidal and Moises Batista Ponce

Coatings 2018, 8(4), 145; https://doi.org/10.3390/coatings8040145 - 17 Apr 2018

Cited by 20 | Viewed by 5352

Abstract

Surface modification procedures by laser techniques allow the generation of specific topographies and microstructures that enable the adaptation of the external layers of materials for specific applications. In laser texturing processes, it is possible to maintain control over the microgeometry and dimensions of [...] Read more.

Surface modification procedures by laser techniques allow the generation of specific topographies and microstructures that enable the adaptation of the external layers of materials for specific applications. In laser texturing processes, it is possible to maintain control over the microgeometry and dimensions of the surface pattern through varying the processing parameters. One of the main areas of interest in the field of surface modification treatments is the ability to generate topographies that are associated with specific surface finishes, in terms of roughness, that can improve the manufactured part’s functional capabilities. In this aspect, several types of phenomena have been detected, such as the friction and sliding wear behavior or wetting capacity, which maintain a high dependence on surface roughness. In this research, surface texturing treatments have been developed by laser techniques through using the scanning speed of the beam (V_s) as a control parameter in order to generate samples that have topographies with different natures. Through assessments of surface finish using specialized techniques, the dimensional and geometrical features of the texturized tracks have been characterized, analyzing their influence on the wetting behavior of the irradiated layer. In this way, more defined texturing grooves has been developed by increasing the V_s, which also improves the hydrophobic characteristics of the treated surface. However, due to the lack of uniformity in the solidification process of the irradiated area, some deviations from the expected trends and singular points can be observed. Using the contact angle method to evaluate the wetting behavior of the applied treatments found increases in the contact angle values for high texturing speeds, finding a maximum value of 65.59° for V_s = 200 mm/s. Full article

(This article belongs to the Special Issue Laser Surface Treatment)

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14 pages, 3206 KiB

Open AccessEditor’s ChoiceReview

2D Materials-Coated Plasmonic Structures for SERS Applications

by Ming Xia

Coatings 2018, 8(4), 137; https://doi.org/10.3390/coatings8040137 - 12 Apr 2018

Cited by 30 | Viewed by 9249

Abstract

Two-dimensional (2D) materials, such as graphene and hexagonal boron nitride, are new kinds of materials that can serve as substrates for surface enhanced Raman spectroscopy (SERS). When combined with traditional metallic plasmonic structures, the hybrid 2D materials/metal SERS platform brings extra benefits, including [...] Read more.

Two-dimensional (2D) materials, such as graphene and hexagonal boron nitride, are new kinds of materials that can serve as substrates for surface enhanced Raman spectroscopy (SERS). When combined with traditional metallic plasmonic structures, the hybrid 2D materials/metal SERS platform brings extra benefits, including higher SERS enhancement factors, oxidation protection of the metal surface, and protection of molecules from photo-induced damages. This review paper gives an overview of recent progress in the 2D materials-coated plasmonic structure in SERS application, focusing on the fabrication of the hybrid 2D materials/metal SERS platform and its applications for Raman enhancement. Full article

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

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10 pages, 2160 KiB

Open AccessEditor’s ChoiceArticle

Application of Industrial XRF Coating Thickness Analyzer for Phosphate Coating Thickness on Steel

by Aleksandr Sokolov, Jelena Hasikova, Aleksej Pecerskis, Vladimir Gostilo, Ki Yong Lee, Hoobok Jung and Jung Hyun Lim

Coatings 2018, 8(4), 126; https://doi.org/10.3390/coatings8040126 - 30 Mar 2018

Cited by 3 | Viewed by 9193

Abstract

The results of industrial application of an online X-ray fluorescence coating thickness analyzer for measuring the thickness of phosphate coatings on moving steel strips are considered in the article. The target range of coating thickness to be measured is from tens to hundreds [...] Read more.

The results of industrial application of an online X-ray fluorescence coating thickness analyzer for measuring the thickness of phosphate coatings on moving steel strips are considered in the article. The target range of coating thickness to be measured is from tens to hundreds of mg/m² in a measurement time of 10 s. The measurement accuracy observed during long-duration factory acceptance test was 10–15%. The coating thickness analyzer consists of two XRF gauges, mounted above and below the steel strip and capable of moving across the moving strip system for their suspension and relocation and electronic control unit. Fully automated software was developed to automatically and continuously (24/7) control both gauges, scanning both sides of the steel strip, and develop and test methods for measuring new coatings. It allows performing offline storage and retrieval of the measurement results, remotely controlling the analyzer components and measurement modes from a control room. The developed XRF coating thickness analyzer can also be used for real-time measurement of other types of coatings, both metallic and non-metallic. Full article

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

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12 pages, 23425 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Selected Properties of Shellac Varnish for Restoration and Polyurethane Varnish for Reconstruction of Historical Artefacts

by Kristýna Šimůnková, Miloš Pánek and Aleš Zeidler

Coatings 2018, 8(4), 119; https://doi.org/10.3390/coatings8040119 - 24 Mar 2018

Cited by 14 | Viewed by 7086

Abstract

At present, many historical artefacts and furniture are only reconstructed and not restored. They are preserved in terms of material reparation, but their historical value decreases significantly. This work is focused on the comparison of the resistance of high-gloss polyurethane varnish with traditional [...] Read more.

At present, many historical artefacts and furniture are only reconstructed and not restored. They are preserved in terms of material reparation, but their historical value decreases significantly. This work is focused on the comparison of the resistance of high-gloss polyurethane varnish with traditional shellac varnish. The varnishes were applied to oak wood and exposed to interior artificial accelerated ageing in Xenotest. Before and after ageing, cold liquid-resistance tests were performed on the tested specimens and gloss, colour, and adhesion were also evaluated. The structures of the surfaces were also analysed using a confocal laser scanning microscope. As expected, polyurethane varnish was much more durable than shellac varnish. Interestingly, shellac varnish was fairly resistant to water at the beginning, but this resistance was greatly reduced after artificial accelerated ageing. This illustrates the importance of sheltering the shellac treated artefacts in stable temperature-humidity conditions with the least possible effect of solar radiation. Full article

(This article belongs to the Special Issue Varnishes and Surface Treatments of Historical Wooden Artworks)

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16 pages, 21124 KiB

Open AccessEditor’s ChoiceArticle

Bacterial Biofilm Characterization and Microscopic Evaluation of the Antibacterial Properties of a Photocatalytic Coating Protecting Building Material

by Thomas Verdier, Alexandra Bertron, Benjamin Erable and Christine Roques

Coatings 2018, 8(3), 93; https://doi.org/10.3390/coatings8030093 - 5 Mar 2018

Cited by 23 | Viewed by 7030

Abstract

Use of photocatalytic paint-like coatings may be a way to protect building materials from microbial colonization. Numerous studies have shown the antimicrobial efficiency of TiO

_{2}

photocatalysis on various microorganisms. However, few have focused on easy-to-apply solutions and on photocatalysis under low irradiance. [...] Read more.

Use of photocatalytic paint-like coatings may be a way to protect building materials from microbial colonization. Numerous studies have shown the antimicrobial efficiency of TiO

_{2}

photocatalysis on various microorganisms. However, few have focused on easy-to-apply solutions and on photocatalysis under low irradiance. This paper focuses on (a) the antibacterial properties of a semi-transparent coating formulated using TiO

_{2}

particles and (b) the microscopic investigations of bacterial biofilm development on TiO

_{2}

-coated building materials under accelerated growth conditions. Results showed significant antibacterial activity after few hours of testing. The efficiency seemed limited by the confinement of the TiO

_{2}

particles inside the coating binder. However, a pre-irradiation with UV light can improve efficiency. In addition, a significant effect against the formation of a bacterial biofilm was also observed. The epifluorescence approach, in which fluorescence is produced by reflect rather than transmitted light, could be applied in further studies of microbial growth on coatings and building materials. Full article

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

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9 pages, 17814 KiB

Open AccessEditor’s ChoiceArticle

New Method to Identify Field Joint Coating Failures Based on MFL In-Line Inspection Signals

by Lianshuang Dai, Ting Wang, Caiyan Deng, Qingshan Feng and Dongpo Wang

Coatings 2018, 8(3), 86; https://doi.org/10.3390/coatings8030086 - 27 Feb 2018

Cited by 5 | Viewed by 7048

Abstract

Above ground indirect detections and random excavations that have applied the past years for buried long distance oil and gas pipelines can only identify some damaged coating locations. Hence, large number of field joint coating (FJC) failures happen unconsciously until they lead to [...] Read more.

Above ground indirect detections and random excavations that have applied the past years for buried long distance oil and gas pipelines can only identify some damaged coating locations. Hence, large number of field joint coating (FJC) failures happen unconsciously until they lead to failures of the pipelines. Based on the analysis of magnetic flux leakage (MFL) in-line inspection (ILI) signals, combined with the statistical results of 414 excavations from two different pipeline sections, a new method to identify the failed FJC is established. Though it can only identify FJC failures when there are signs of corrosion on pipe body, it is much more efficient and cost-saving. The concluded identification rule still needs more validations and improvements to be more applicable and accuracy. Full article

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

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0 pages, 1658 KiB

Open AccessEditor’s ChoiceArticle

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

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

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

Cited by 7 | Viewed by 6398

Abstract

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

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

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

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10 pages, 2751 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

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

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

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

Cited by 16 | Viewed by 6250

Abstract

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

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

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

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17 pages, 4194 KiB

Open AccessEditor’s ChoiceReview

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

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

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

Cited by 50 | Viewed by 10649

Abstract

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

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

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

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16 pages, 5701 KiB

Open AccessEditor’s ChoiceReview

Thermal Growth of Graphene: A Review

by Hai Tan, Deguo Wang and Yanbao Guo

Coatings 2018, 8(1), 40; https://doi.org/10.3390/coatings8010040 - 19 Jan 2018

Cited by 55 | Viewed by 10786

Abstract

A common belief proposed by Peierls and Landau that two-dimensional material cannot exist freely in a three-dimensional world has been proved false when graphene was first synthesized in 2004. Graphene, which is the base structure of other carbon materials, has drawn much attention [...] Read more.

A common belief proposed by Peierls and Landau that two-dimensional material cannot exist freely in a three-dimensional world has been proved false when graphene was first synthesized in 2004. Graphene, which is the base structure of other carbon materials, has drawn much attention of scholars and researchers due to its extraordinary electrical, mechanical and thermal properties. Moreover, methods for its synthesis have developed greatly in recent years. This review focuses on the mechanism of the thermal growth method and the different synthesis methods, where epitaxial growth, chemical vapor deposition, plasma-enhanced chemical vapor deposition and combustion are discussed in detail based on this mechanism. Meanwhile, to improve the quality and control the number of graphene layers, the latest research progress in optimizing growth parameters and developmental technologies has been summarized. The strategies for synthesizing high-quality and large-scale graphene are proposed and an outlook on the future synthesis direction is also provided. Full article

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

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12 pages, 30713 KiB

Open AccessEditor’s ChoiceArticle

Cutting Performance of Low Stress Thick TiAlN PVD Coatings during Machining of Compacted Graphite Cast Iron (CGI)

by Kenji Yamamoto, Majid Abdoos, Jose Mario Paiva, Pietro Stolf, Ben Beake, Sushant Rawal, German Fox-Rabinovich and Stephen Veldhuis

Coatings 2018, 8(1), 38; https://doi.org/10.3390/coatings8010038 - 18 Jan 2018

Cited by 26 | Viewed by 8104

Abstract

A new family of physical vapor deposited (PVD) coatings is presented in this paper. These coatings are deposited by a superfine cathode (SFC) using the arc method. They combine a smooth surface, high hardness, and low residual stresses. This allows the production of [...] Read more.

A new family of physical vapor deposited (PVD) coatings is presented in this paper. These coatings are deposited by a superfine cathode (SFC) using the arc method. They combine a smooth surface, high hardness, and low residual stresses. This allows the production of PVD coatings as thick as 15 µm. In some applications, in particular for machining of such hard to cut material as compacted graphite iron (CGI), such coatings have shown better tool life compared to the conventional PVD coatings that have a lower thickness in the range of up to 5 μm. Finite element modeling of the temperature/stress profiles was done for the SFC coatings to present the temperature/stress profiles during cutting. Comprehensive characterization of the coatings was performed using XRD, TEM, SEM/EDS studies, nano-hardness, nano-impact measurements, and residual stress measurements. Application of the coating with this set of characteristics reduces the intensity of buildup edge formation during turning of CGI, leading to longer tool life. Optimization of the TiAlN-based coatings composition (Ti/Al ratio), architecture (mono vs. multilayer), and thickness were performed. Application of the optimized coating resulted in a 40–60% improvement in the cutting tool life under finishing turning of CGI. Full article

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

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12 pages, 3019 KiB

Open AccessEditor’s ChoiceArticle

Corrosion Inhibition Properties of Waterborne Polyurethane/Cerium Nitrate Coatings on Mild Steel

by Mohammad Mizanur Rahman, Md. Hasan Zahir, Md. Bashirul Haq, Dhafer A. Al Shehri and A. Madhan Kumar

Coatings 2018, 8(1), 34; https://doi.org/10.3390/coatings8010034 - 15 Jan 2018

Cited by 26 | Viewed by 7123

Abstract

Waterborne polyurethane (WBPU)/cerium nitrate (Ce(NO₃)₃) dispersions were synthesized with different defined Ce(NO₃)₃ content. All pristine dispersions were stable with different poly(tetramethylene oxide) glycol (PTMG) number average molecular weights (Mn) of 650, 1000, and 2000. The interaction [...] Read more.

Waterborne polyurethane (WBPU)/cerium nitrate (Ce(NO₃)₃) dispersions were synthesized with different defined Ce(NO₃)₃ content. All pristine dispersions were stable with different poly(tetramethylene oxide) glycol (PTMG) number average molecular weights (Mn) of 650, 1000, and 2000. The interaction between the carboxyl acid salt group and Ce(NO₃)₃ was analyzed by Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. Coating hydrophilicity, water swelling (%), water contact angle, leaching, and corrosion protection efficiency were all affected when using different Ce(NO₃)₃ content and PTMG molecular weights. The maximal corrosion protection of the WBPU coating was recorded using a higher molecular weight of PTMG with 0.016 mole Ce(NO₃)₃ content. Full article

(This article belongs to the Special Issue Active Organic and Organic-Inorganic Hybrid Coatings and Thin Films: Challenges, Developments, Perspectives)

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