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Coatings
Volume 8
Issue 11
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Coatings, Volume 8, Issue 11 (November 2018) – 41 articles

Cover Story (view full-size image): This study aims to proceed to a review regarding the improvements already studied in order to optimize the sputtering PVD process, trying to relate these improvements with the industrial requirements as a function of product development and market demand. View this paper.
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13 pages, 4891 KiB  
Article
Abrasion Resistance of Superhydrophobic Coatings on Aluminum Using PDMS/SiO2
by Divine Sebastian, Chun-Wei Yao and Ian Lian
Coatings 2018, 8(11), 414; https://doi.org/10.3390/coatings8110414 - 21 Nov 2018
Cited by 33 | Viewed by 8540
Abstract
Superhydrophobic coatings have shown tremendous improvement in the usability of metals such as aluminum. These coatings are capable of adding attractive features such as self-cleaning, anti-corrosion, and anti-biofouling to the array of diverse features that aluminum possesses, including lightweight and high ductility. For [...] Read more.
Superhydrophobic coatings have shown tremendous improvement in the usability of metals such as aluminum. These coatings are capable of adding attractive features such as self-cleaning, anti-corrosion, and anti-biofouling to the array of diverse features that aluminum possesses, including lightweight and high ductility. For superhydrophobic surfaces, having considerable abrasion resistance is as important as achieving a high contact angle. In this work, two types of coatings have been prepared, each composed of functionalized silica nanoparticles along with polydimethylsiloxane (PDMS) dispersed in ethanol, and their superhydrophobicity and abrasion characteristics have been investigated. The same silica nanoparticles are present in each coating, but each has a different proportion of the PDMS base to its curing agent. The surface morphology of the coatings was studied with the aid of a scanning electron microscope (SEM) and an atomic force microscope (AFM). The surface chemical composition was characterized using an energy dispersive X-ray spectroscope (EDX). The prepared coatings were analyzed for their degree of superhydrophobicity, abrasion resistance and adhesion characteristics. In addition, atomic force microscopy was used to understand the adhesion characteristics of the coatings. Full article
(This article belongs to the Collection Surface and Interface Science and Engineering for the Society of the Future)
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13 pages, 4307 KiB  
Article
Growth of Atomic Layer Deposited Ruthenium and Its Optical Properties at Short Wavelengths Using Ru(EtCp)2 and Oxygen
by Robert Müller, Lilit Ghazaryan, Paul Schenk, Sabrina Wolleb, Vivek Beladiya, Felix Otto, Norbert Kaiser, Andreas Tünnermann, Torsten Fritz and Adriana Szeghalmi
Coatings 2018, 8(11), 413; https://doi.org/10.3390/coatings8110413 - 20 Nov 2018
Cited by 13 | Viewed by 7275
Abstract
High-density ruthenium (Ru) thin films were deposited using Ru(EtCp)2 (bis(ethylcyclopentadienyl)ruthenium) and oxygen by thermal atomic layer deposition (ALD) and compared to magnetron sputtered (MS) Ru coatings. The ALD Ru film growth and surface roughness show a significant temperature dependence. At temperatures below [...] Read more.
High-density ruthenium (Ru) thin films were deposited using Ru(EtCp)2 (bis(ethylcyclopentadienyl)ruthenium) and oxygen by thermal atomic layer deposition (ALD) and compared to magnetron sputtered (MS) Ru coatings. The ALD Ru film growth and surface roughness show a significant temperature dependence. At temperatures below 200 °C, no deposition was observed on silicon and fused silica substrates. With increasing deposition temperature, the nucleation of Ru starts and leads eventually to fully closed, polycrystalline coatings. The formation of blisters starts at temperatures above 275 °C because of poor adhesion properties, which results in a high surface roughness. The optimum deposition temperature is 250 °C in our tool and leads to rather smooth film surfaces, with roughness values of approximately 3 nm. The ALD Ru thin films have similar morphology compared with MS coatings, e.g., hexagonal polycrystalline structure and high density. Discrepancies of the optical properties can be explained by the higher roughness of ALD films compared to MS coatings. To use ALD Ru for optical applications at short wavelengths (λ = 2–50 nm), further improvement of their film quality is required. Full article
(This article belongs to the Special Issue Atomic Layer Deposition)
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16 pages, 8205 KiB  
Article
Comparison of the Physicochemical Properties of TiO2 Thin Films Obtained by Magnetron Sputtering with Continuous and Pulsed Gas Flow
by Artur Wiatrowski, Michał Mazur, Agata Obstarczyk, Damian Wojcieszak, Danuta Kaczmarek, Jerzy Morgiel and Des Gibson
Coatings 2018, 8(11), 412; https://doi.org/10.3390/coatings8110412 - 20 Nov 2018
Cited by 63 | Viewed by 6615
Abstract
In this paper, a comparison of TiO2 thin films prepared by magnetron sputtering with a continuous and pulsed gas flow was presented. Structural, surface, optical, and mechanical properties of deposited titanium dioxide coatings were analyzed with the use of a wide range [...] Read more.
In this paper, a comparison of TiO2 thin films prepared by magnetron sputtering with a continuous and pulsed gas flow was presented. Structural, surface, optical, and mechanical properties of deposited titanium dioxide coatings were analyzed with the use of a wide range of measurement techniques. It was found that thin films deposited with a gas impulse had a nanocrystalline rutile structure instead of fibrous-like anatase obtained with a continuous gas flow. TiO2 thin films deposited with both techniques were transparent in the visible wavelength range, however, a much higher refractive index and packing density were observed for coatings deposited by the pulsed gas technique. The application of a gas impulse improved the hardness and scratch resistance of the prepared TiO2 thin films. Full article
(This article belongs to the Special Issue Applications of Optical Thin Film Coatings)
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13 pages, 4207 KiB  
Article
Preparation and Properties of High Hardness Ultraviolet Curable Polyethylene Terephthalates Surface Coatings Modified with Octavinyl-Polyhedral Oligomeric Silsesquioxane
by Tianmiao Kang, Liuyan Tang and Jinqing Qu
Coatings 2018, 8(11), 411; https://doi.org/10.3390/coatings8110411 - 20 Nov 2018
Cited by 8 | Viewed by 4518
Abstract
Using organic coatings helps to protect PET (polyethylene terephthalates) surfaces, improve surface hardness, scratch resistance, and solvent resistance, prolong the service life of PET film, and to expand their scope of applications. There were some disadvantages, including poor flexibility and impact resistance in [...] Read more.
Using organic coatings helps to protect PET (polyethylene terephthalates) surfaces, improve surface hardness, scratch resistance, and solvent resistance, prolong the service life of PET film, and to expand their scope of applications. There were some disadvantages, including poor flexibility and impact resistance in high-hardness coatings; organic coatings should also be modified to improve the toughness. Herein, a UV (ultraviolet curing) curable high-hardness organic coating used in PET surface protection was prepared and modified with inorganic nanoparticles, such as OVPOSS (octavinyl-polyhedral oligomeric silsesquioxane). The effects of the categories of nanoparticles on the coating performance were studied. UV-Vis spectra (ultraviolet visible light spectra), FT-IR (Fourier transform infrared spectrometer), TGA (thermogravimetric analysis), DMA (dynamic-mechanical), SEM (field emission scanning electron microscope), and AFM (atomic force microscope) were used to characterize the properties of the coatings. The results showed that the addition of eight-vinyl POSS to the organic coating significantly increased its glass transition temperature (Tg) from 100 to 120 °C, improved its storage modulus from 167.6 to 258.9 MPa, and raised its impact resistance and flexibility. The SEM and AFM images displayed that the eight-vinyl POSS particles were dispersed homogeneously in the coating, arranged in an ordered network, and had good compatibility with organic components. The film displayed excellent properties, including 4 H of the pencil hardness, 100 g cm of impact resistance, excellent flexibility, and 90% of light transmittance, with the addition of 0.3 wt % OVPOSS. TGA analysis revealed that the coating had good thermal stability, with 5% weight loss temperature up to 335 °C. Full article
(This article belongs to the Special Issue Light-Curable Coatings)
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21 pages, 2140 KiB  
Review
Numerical Simulation Applied to PVD Reactors: An Overview
by Gustavo Pinto, Francisco Silva, Jacobo Porteiro, José Míguez and Andresa Baptista
Coatings 2018, 8(11), 410; https://doi.org/10.3390/coatings8110410 - 19 Nov 2018
Cited by 13 | Viewed by 7771
Abstract
The technological evolution in the last century also required an evolution of materials and coatings. Therefore, it was necessary to make mechanical components subject to heavy wear more reliable, improving their mechanical strength and durability. Surfaces can contribute decisively to extending the lifespan [...] Read more.
The technological evolution in the last century also required an evolution of materials and coatings. Therefore, it was necessary to make mechanical components subject to heavy wear more reliable, improving their mechanical strength and durability. Surfaces can contribute decisively to extending the lifespan of mechanical components. Chemical vapor deposition (CVD) and physical vapor deposition (PVD) technologies have emerged to meet the new requirements that have enabled a remarkable improvement in the morphology, composition and structure of films as well as an improved adhesion to the substrate allowing a greater number of diversified applications. Thin films deposition using PVD coatings has been contributing to tribological improvement, protecting their surfaces from wear and corrosion, as well as enhancing their appearance. This process can be an advantage over other processes due to their excellent properties and environmental friendly behavior, which gives rise to a large number of studies in mathematical modelling and numerical simulation, like finite element method (FEM) and computational fluid dynamics (CFD). This review intends to contribute to a better PVD process knowledge, in the fluids and heat area, using CFD simulation methods focusing on the process energy efficiency improvement regarding the industrial context with the sputtering technique. Full article
(This article belongs to the Special Issue Advances in Coatings Vacuum Deposition Systems)
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14 pages, 2670 KiB  
Article
Universality of Droplet Impingement: Low-to-High Viscosities and Surface Tensions
by Yukihiro Yonemoto and Tomoaki Kunugi
Coatings 2018, 8(11), 409; https://doi.org/10.3390/coatings8110409 - 19 Nov 2018
Cited by 9 | Viewed by 6220
Abstract
When a droplet impinges on a solid surface, its kinetic energy is mainly converted to capillary energy and viscous dissipation energy, the ratio of which depends on the wettability of the target surface and the liquid properties. Currently, there is no experimental or [...] Read more.
When a droplet impinges on a solid surface, its kinetic energy is mainly converted to capillary energy and viscous dissipation energy, the ratio of which depends on the wettability of the target surface and the liquid properties. Currently, there is no experimental or theoretical evidence that suggests which types of liquids exhibit the capillary energy-dominated impingement behavior. In this paper, we reported the droplet impingement behavior for a wide range of liquid viscosities, surface tensions and target surface wettabilities. Then, we showed that a recently developed energy balance equation for the droplet impingement behavior can be universally employed for predicting the maximum spreading contact area diameter of a droplet for Newtonian liquids in deposition process by modelling the droplet surface deformation. Subsequently, applicability limitations of recent existing models are discussed. The newly developed model demonstrated that the capillary energy-dominated impingement behavior can be observed at considerably low viscosities of liquid droplets such as that of the superfluid of liquid helium. Full article
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12 pages, 2740 KiB  
Article
Tuning Nucleation Sites to Enable Monolayer Perovskite Films for Highly Efficient Perovskite Solar Cells
by Yan Li, Xiaolei Li, Qianqian Chu, Hui Dong, Jiantao Yao, Yong Zhou and Guanjun Yang
Coatings 2018, 8(11), 408; https://doi.org/10.3390/coatings8110408 - 18 Nov 2018
Cited by 10 | Viewed by 5670
Abstract
The nucleation site plays a critical role in achieving the full coverage of perovskite film at both the macroscopic and microscopic scales, and it is systematically investigated for the first time in this study. The results show that under natural conditions, the incomplete [...] Read more.
The nucleation site plays a critical role in achieving the full coverage of perovskite film at both the macroscopic and microscopic scales, and it is systematically investigated for the first time in this study. The results show that under natural conditions, the incomplete coverage of perovskite film is due to both heterogeneous nucleation and homogeneous nucleation. The established concentration field and temperature field in the precursor solution show that there are two preferential nucleation sites, i.e., the upper surface of the precursor solution (homogeneous nucleation) and the surface of the substrate (heterogeneous nucleation). The nucleation sites are tuned by decreasing the drying pressure from the atmosphere to 3000 Pa, and then to 100 Pa, and then the microstructures of the perovskite films change from an incomplete coverage state to a monolayer full coverage state, and then to a bilayer full coverage state. At last, when the full coverage perovskite films are assembled into perovskite solar cells, the photovoltaic performance of the monolayer perovskite solar cells is slightly greater than that of the bilayer perovskite solar cells. The electrochemical characterization shows that there is more restrained internal recombination of the monolayer perovskite solar cells compared with bilayer perovskite solar cells. Full article
(This article belongs to the Special Issue From Metallic Coatings to Additive Manufacturing)
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15 pages, 3726 KiB  
Article
Mass Transport with Asymmetric Peristaltic Propulsion Coated with Synovial Fluid
by Arshad Riaz, Hanan A. Al-Olayan, Ahmad Zeeshan, Abdul Razaq and Muhammad Mubashir Bhatti
Coatings 2018, 8(11), 407; https://doi.org/10.3390/coatings8110407 - 16 Nov 2018
Cited by 15 | Viewed by 3289
Abstract
This article aims to model two-dimensional, incompressible asymmetric peristaltic propulsion coated with Synovial fluid (“non-Newtonian model”) with mass transport. Due to the coating of the same base-fluid at the surface of the channel, the boundaries become non-porous and exert no slip on the [...] Read more.
This article aims to model two-dimensional, incompressible asymmetric peristaltic propulsion coated with Synovial fluid (“non-Newtonian model”) with mass transport. Due to the coating of the same base-fluid at the surface of the channel, the boundaries become non-porous and exert no slip on the fluid particles. Two illustrative models for the viscosity, namely, shear-thinning (Model 1) and shear-thickening (Model 2), are considered, which reveal the presence and integrity of coating. The perturbation method has been applied to linearize the complicated differential equations. Model 1 predicted higher viscosity values and more significant non-Newtonian behavior than Model 2. It is also observed that the shear-thinning model behaved in quite the opposite manner for the shear thickening model. The converse behavior of Models 1 and 2 occurs due to a curvature of the flow domain. Moreover, Model 1 is not able to capture the correct exponential viscosity dependence on concentration for the whole range of shear rates. On the other hand, the second model shows a strong relationship with accurate power. Solutions are attained for velocity field, concentration profile, and pressure gradient. The novelty of all the essential parameters is analyzed through graphical results. Furthermore, streamlines are also drawn to determine the trapping mechanism. The present analysis is beneficial in the study of intrauterine fluid dynamics; furthermore, it is applicable in vivo diagnostic; drug delivery; food diagnostics; protein chips; and cell chips and packaging, i.e., smart sensors. Full article
(This article belongs to the Special Issue Recent Trends in Coatings and Thin Film–Modeling and Application)
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17 pages, 4553 KiB  
Article
Rheology and Screen-Printing Performance of Model Silver Pastes for Metallization of Si-Solar Cells
by Ceren Yüce, Markus König and Norbert Willenbacher
Coatings 2018, 8(11), 406; https://doi.org/10.3390/coatings8110406 - 15 Nov 2018
Cited by 27 | Viewed by 7699
Abstract
Further strong growth of solar energy conversion based on PV (photovoltaic) technology requires constant improvement to increase solar cell efficiency. The challenge in front-side metallization of Si-solar cells is to print uniform fine lines with a high aspect ratio to achieve higher efficiencies [...] Read more.
Further strong growth of solar energy conversion based on PV (photovoltaic) technology requires constant improvement to increase solar cell efficiency. The challenge in front-side metallization of Si-solar cells is to print uniform fine lines with a high aspect ratio to achieve higher efficiencies simultaneously with a reduced consumption of raw materials. An in-depth understanding of the relationship between paste composition, rheology and screen-printed line morphology is essential. Three model pastes with similar silver content and corresponding vehicles differing in their thixotropic agent content were investigated. Rheological properties (yield stress, viscosity, wall slip velocity, structural recovery, and fracture strain) were determined using steady and oscillatory shear, as well as elongational flow rheometry. Pastes were screen-printed at various speeds through a layout screen including line widths between 20 and 55 µm. Dried fingers were analyzed with respect to line width, aspect ratio (AR) and cross-sectional area. Our investigations reveal that minor changes of thixotropic agent result in substantial variations of the paste’s flow properties. However, this only weakly affects the line morphology. Irrespective of printing speed or finger opening, AR is slightly increasing; i.e., the screen-printing process is robust against changes in paste rheology. Full article
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16 pages, 2929 KiB  
Review
Advances in Automotive Conversion Coatings during Pretreatment of the Body Structure: A Review
by Mark Doerre, Larry Hibbitts, Gabriela Patrick and Nelson K. Akafuah
Coatings 2018, 8(11), 405; https://doi.org/10.3390/coatings8110405 - 15 Nov 2018
Cited by 56 | Viewed by 18796
Abstract
Automotive conversion coatings consist of layers of materials that are chemically applied to the body structures of vehicles before painting to improve corrosion protection and paint adhesion. These coatings are a consequence of surface-based chemical reactions and are sandwiched between paint layers and [...] Read more.
Automotive conversion coatings consist of layers of materials that are chemically applied to the body structures of vehicles before painting to improve corrosion protection and paint adhesion. These coatings are a consequence of surface-based chemical reactions and are sandwiched between paint layers and the base metal; the chemical reactions involved distinctly classify conversion coatings from other coating technologies. Although the tri-cationic conversion coating bath chemistry that was developed around the end of the 20th century remains persistent, environmental, health, and cost issues favor a new generation of greener methods and materials such as zirconium. Environmental forces driving lightweight material selection during automobile body design are possibly more influential for transitioning to zirconium than the concerns regarding the body coating process. The chemistry involved in some conversion coatings processing has been known for over 100 years. However, recent advances in chemical processing, changes in the components used for vehicle body structures, environmental considerations and costs have prompted the automobile industry to embrace new conversion coatings technologies. These are discussed herein along with a historical perspective that has led to the use of current conversion coatings technologies. In addition, future directions for automobile body conversion coatings are discussed that may affect conversion coatings in the age of multi-material body structures. Full article
(This article belongs to the Collection Surface and Interface Science and Engineering for the Society of the Future)
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12 pages, 2193 KiB  
Article
Self-Healing Coatings Based on Linseed-Oil-Loaded Microcapsules for Protection of Cementitious Materials
by Dong-Min Kim, In-Ho Song, Ju-Young Choi, Seung-Won Jin, Kyeong-Nam Nam and Chan-Moon Chung
Coatings 2018, 8(11), 404; https://doi.org/10.3390/coatings8110404 - 15 Nov 2018
Cited by 30 | Viewed by 6251
Abstract
Linseed oil undergoes an oxidative drying reaction upon exposure to air, resulting in a soft film. The reaction conversion after 48 h reached 88% and 59% when it reacted at room temperature and −20 °C, respectively. Linseed-oil-loaded microcapsules were prepared using a urea-formaldehyde [...] Read more.
Linseed oil undergoes an oxidative drying reaction upon exposure to air, resulting in a soft film. The reaction conversion after 48 h reached 88% and 59% when it reacted at room temperature and −20 °C, respectively. Linseed-oil-loaded microcapsules were prepared using a urea-formaldehyde polymer as the shell wall material. The microcapsules were integrated into a commercially available protective coating formulation to prepare self-healing coating formulations with different capsule loadings. The coating formulations were applied on mortar specimens to prepare self-healing coatings. The effect of capsule loading on adhesion strength of the self-healing coating was studied. The self-healing function of the coating was investigated by SEM, a water sorptivity test and an accelerated carbonation test. Successful self-healing was demonstrated for both scratch and crack damage in the coatings. Low-temperature self-healing was demonstrated with a saline solution sorptivity test conducted at −20 °C. The linseed-oil-based microcapsule-type self-healing coating system is a promising candidate as a protective coating for cementitious materials. Full article
(This article belongs to the Special Issue Progress in Self-Healing Coatings)
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18 pages, 3448 KiB  
Article
Electrostatic Supercapacitors by Atomic Layer Deposition on Nanoporous Anodic Alumina Templates for Environmentally Sustainable Energy Storage
by Luis Javier Fernández-Menéndez, Ana Silvia González, Víctor Vega and Víctor Manuel De la Prida
Coatings 2018, 8(11), 403; https://doi.org/10.3390/coatings8110403 - 14 Nov 2018
Cited by 9 | Viewed by 4503
Abstract
In this work, the entire manufacturing process of electrostatic supercapacitors using the atomic layer deposition (ALD) technique combined with the employment of nanoporous anodic alumina templates as starting substrates is reported. The structure of a usual electrostatic capacitor, which comprises a top conductor [...] Read more.
In this work, the entire manufacturing process of electrostatic supercapacitors using the atomic layer deposition (ALD) technique combined with the employment of nanoporous anodic alumina templates as starting substrates is reported. The structure of a usual electrostatic capacitor, which comprises a top conductor electrode/the insulating dielectric layer/and bottom conductor electrode (C/D/C), has been reduced to nanoscale size by depositing layer by layer the required materials over patterned nanoporous anodic alumina membranes (NAAMs) by employing the ALD technique. A thin layer of aluminum-doped zinc oxide, with 3 nm in thickness, is used as both the top and bottom electrodes’ material. Two dielectric materials were tested; on the one hand, a triple-layer made by a successive combination of 3 nm each layers of silicon dioxide/titanium dioxide/silicon dioxide and on the other hand, a simple layer of alumina, both with 9 nm in total thickness. The electrical properties of these capacitors are studied, such as the impedance and capacitance dependences on the AC frequency regime (up to 10 MHz) or capacitance (180 nF/cm2) on the DC regime. High breakdown voltage values of 60 V along with low leakage currents (0.4 μA/cm2) are also measured from DC charge/discharge RC circuits to determine the main features of the capacitors behavior integrated in a real circuit. Full article
(This article belongs to the Special Issue Atomic Layer Deposition)
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22 pages, 6962 KiB  
Review
Sputtering Physical Vapour Deposition (PVD) Coatings: A Critical Review on Process Improvement and Market Trend Demands
by Andresa Baptista, Francisco Silva, Jacobo Porteiro, José Míguez and Gustavo Pinto
Coatings 2018, 8(11), 402; https://doi.org/10.3390/coatings8110402 - 14 Nov 2018
Cited by 318 | Viewed by 41727
Abstract
Physical vapour deposition (PVD) is a well-known technology that is widely used for the deposition of thin films regarding many demands, namely tribological behaviour improvement, optical enhancement, visual/esthetic upgrading, and many other fields, with a wide range of applications already being perfectly established. [...] Read more.
Physical vapour deposition (PVD) is a well-known technology that is widely used for the deposition of thin films regarding many demands, namely tribological behaviour improvement, optical enhancement, visual/esthetic upgrading, and many other fields, with a wide range of applications already being perfectly established. Machining tools are, probably, one of the most common applications of this deposition technique, sometimes used together with chemical vapour deposition (CVD) in order to increase their lifespan, decreasing friction, and improving thermal properties. However, the CVD process is carried out at higher temperatures, inducing higher stresses in the coatings and substrate, being used essentially only when the required coating needs to be deposited using this process. In order to improve this technique, several studies have been carried out optimizing the PVD technique by increasing plasma ionization, decreasing dark areas (zones where there is no deposition into the reactor), improving targets use, enhancing atomic bombardment efficiency, or even increasing the deposition rate and optimizing the selection of gases. These studies reveal a huge potential in changing parameters to improve thin film quality, increasing as well the adhesion to the substrate. However, the process of improving energy efficiency regarding the industrial context has not been studied as deeply as required. This study aims to proceed to a review regarding the improvements already studied in order to optimize the sputtering PVD process, trying to relate these improvements with the industrial requirements as a function of product development and market demand. Full article
(This article belongs to the Special Issue Advances in Coatings Vacuum Deposition Systems)
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10 pages, 21226 KiB  
Article
A Low-Temperature Alumina/Copper Diffusion Bonding Process using La-Doped Titanium Interlayers
by Cherng-Yuh Su, Jia-Liang Huang, Po-Chun Chen, Hsin-Jung Yu, Dai-Liang Ma and Bang-Ying Yu
Coatings 2018, 8(11), 401; https://doi.org/10.3390/coatings8110401 - 14 Nov 2018
Cited by 3 | Viewed by 4348
Abstract
Ceramic-to-metal heterojunctions have been established to improve high-temperature stability for applications in aerospace and harsh environments. In this work, we employed low-temperature diffusion bonding to realize an alumina/Cu heterogeneous joint. Using a thin layer of lanthanum-doped titanium (La-doped Ti) to metallize the alumina [...] Read more.
Ceramic-to-metal heterojunctions have been established to improve high-temperature stability for applications in aerospace and harsh environments. In this work, we employed low-temperature diffusion bonding to realize an alumina/Cu heterogeneous joint. Using a thin layer of lanthanum-doped titanium (La-doped Ti) to metallize the alumina surface, we achieved the bonding at a temperature range of 250–350 °C. We produced a uniform, thermally stable, and high-strength alumina/Cu joint after a hot-press process in vacuum. Signals from X-ray diffraction (XRD) suggested the successful diffusion of Ti and La into the alumina substrate, as Ti can easily substitute Al in alumina, and La has a better oxygen affinity than that of Al. The transmission electron microscopy and XRD results also showed the existence of CuxTiyO phases without CuxTiy or LaOx. In addition, the bonding strength of alumina/copper hot-pressed at 250, 300, and 350 °C were 7.5, 9.8 and 15.0 MPa, respectively. The process developed in this study successfully lowered the bonding temperature for the alumina/copper joint. Full article
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15 pages, 7518 KiB  
Article
Corrosion Damage Mechanism of TiN/ZrN Nanoscale Multilayer Anti-Erosion Coating
by Mingrui Geng, Guangyu He, Zhiping Sun, Jiao Chen, Zhufang Yang and Yuqin Li
Coatings 2018, 8(11), 400; https://doi.org/10.3390/coatings8110400 - 13 Nov 2018
Cited by 19 | Viewed by 5579
Abstract
TiN/ZrN multilayers can effectively improve the erosion resistance of metals, particularly titanium alloys employed in aero engines. To explore the corrosion damage mechanism of TiN/ZrN nanoscale multilayers (nanolaminate), a novel [TiN/ZrN]100 nanolaminate coating was deposited on Ti-6Al-4V alloys by multi-arc ion plating [...] Read more.
TiN/ZrN multilayers can effectively improve the erosion resistance of metals, particularly titanium alloys employed in aero engines. To explore the corrosion damage mechanism of TiN/ZrN nanoscale multilayers (nanolaminate), a novel [TiN/ZrN]100 nanolaminate coating was deposited on Ti-6Al-4V alloys by multi-arc ion plating method. Salt spray corrosion tests and hot corrosion experiment were carried out to evaluate the corrosion resistance of the coating. The corrosion and damage mechanisms were explored with the help of detailed microstructure, phase composition and element distribution characterizations. The salt spray corrosion tests showed that the [TiN/ZrN]100 nanolaminate coating possessed good corrosion resistance, which protected substrate against the corrosion. The low temperature hot corrosion tests showed that the oxidation occurred on the surface of the coating, which improved the oxidation resistance of the sample. However, the oxidized droplets squeezed the coating, and destroyed the oxidized layers. As a result, the coating was peeled off from the substrate. The research highlights the corrosion resistance of the novel TiN/ZrN nanolaminate coating and offers a support for their application in engine compressor blade. Full article
(This article belongs to the Special Issue From Metallic Coatings to Additive Manufacturing)
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11 pages, 11775 KiB  
Article
Effect of Self-Generated Transfer Layer on the Tribological Properties of PTFE Composites Sliding against Steel
by Ting Xie, Shihao Feng, Yongheng Qi and Ailong Cui
Coatings 2018, 8(11), 399; https://doi.org/10.3390/coatings8110399 - 13 Nov 2018
Cited by 8 | Viewed by 3040
Abstract
Coatings are normally employed to meet some functional requirements. There is a kind of self-generated coating during use, such as the transfer layer during sliding, which may greatly affect the tribological behavior. Although the transfer layer has aroused much attention recently, the formation [...] Read more.
Coatings are normally employed to meet some functional requirements. There is a kind of self-generated coating during use, such as the transfer layer during sliding, which may greatly affect the tribological behavior. Although the transfer layer has aroused much attention recently, the formation of the transfer layer closely depends on the service conditions, which need to be further studied. In this paper, the effects of sliding speed, normal load, and duration of wear test on the transfer layer thickness during friction of Ni/PTFE (Polytetrafluoroethylene) composites were experimentally investigated. The formation mechanism of transfer layer and the relationships between tribological properties and transfer layer thickness were analyzed in detail. It was found that the transfer layer thickness increased with increases of sliding speed and normal load; and after a period of wear test, the transfer layer thickness remained stable. The transfer layer thickness correlates linearly with the friction coefficient and wear volume of the PTFE composites. With the increase of the transfer layer thickness, the friction coefficient decreased, while the wear volume increased, which means that a uniform, thin, and stable transfer layer is beneficial for the reduction of friction and wear of the polymeric composites. Full article
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14 pages, 2572 KiB  
Article
Biofilm Formation of a Polymer Brush Coating with Ionic Liquids Compared to a Polymer Brush Coating with a Non-Ionic Liquid
by Hideyuki Kanematsu, Atsuya Oizumi, Takaya Sato, Toshio Kamijo, Saika Honma, Dana M. Barry, Nobumitsu Hirai, Akiko Ogawa, Takeshi Kogo, Daisuke Kuroda, Katsuhiko Sano, Katsuhiko Tsunashima, Seung-Hyo Lee and Myeong-Hoon Lee
Coatings 2018, 8(11), 398; https://doi.org/10.3390/coatings8110398 - 13 Nov 2018
Cited by 8 | Viewed by 4610
Abstract
N,N-diethyl-N-(2-methancryloylethy)-N-methylammonium bis(trifluoromethylsulfonyl) imide polymer (DEMM-TFSI) brush coated specimens (substrate: glasses) and a liquid ion type of polymer brush coating were investigated for their antifouling effect on biofilms. Biofilms were produced by two kinds of bacteria, E. coli and S. epidermidis. They were [...] Read more.
N,N-diethyl-N-(2-methancryloylethy)-N-methylammonium bis(trifluoromethylsulfonyl) imide polymer (DEMM-TFSI) brush coated specimens (substrate: glasses) and a liquid ion type of polymer brush coating were investigated for their antifouling effect on biofilms. Biofilms were produced by two kinds of bacteria, E. coli and S. epidermidis. They were formed on specimens immersed into wells (of 12-well plates) that were filled with culture liquids and bacteria. The biofilm formation was observed. Also, brush coated specimens and glass substrates were investigated in the same way. DEMM polymer brush coated specimens formed more biofilm than PMMA (polymethyl methacrylate) polymer brush coated specimens and glass substrates. A greater amount of polarized components of biofilms was also observed for DEMM polymer brush coated specimens. The polar characteristics could be attributed to the attraction capability of bacteria and biofilms on DEMM polymer brush coated specimens. When considering the ease of removing biofilms by washing it with water, the ionic liquid type polymer brush (coated specimens) could be used for antifouling applications. If an initial antifouling application is needed, then the polar characteristics could be adjusted (design of the components and concentrations of ionic liquids, etc.) to solve the problem. Full article
(This article belongs to the Special Issue Advanced Coatings for Buildings)
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11 pages, 3405 KiB  
Article
Preparation of Ti–Zr-Based Conversion Coating on 5052 Aluminum Alloy, and Its Corrosion Resistance and Antifouling Performance
by Hehong Zhang, Xiaofeng Zhang, Xuhui Zhao, Yuming Tang and Yu Zuo
Coatings 2018, 8(11), 397; https://doi.org/10.3390/coatings8110397 - 12 Nov 2018
Cited by 21 | Viewed by 6915
Abstract
A chemical conversion coating on 5052 aluminum alloy was prepared by using K2ZrF6 and K2TiF6 as the main salts, KMnO4 as the oxidant and NaF as the accelerant. The surface morphology, structure and composition were analyzed [...] Read more.
A chemical conversion coating on 5052 aluminum alloy was prepared by using K2ZrF6 and K2TiF6 as the main salts, KMnO4 as the oxidant and NaF as the accelerant. The surface morphology, structure and composition were analyzed by SEM, EDS, FT–IR and XPS. The corrosion resistance of the conversion coating was studied by salt water immersion and polarization curve analysis. The influence of fluorosilane (FAS-17) surface modification on its antifouling property was also discussed. The results showed that the prepared conversion coating mainly consisted of AlF3·3H2O, Al2O3, MnO2 and TiO2, and exhibited good corrosion resistance. Its corrosion potential in 3.5 wt % NaCl solution was positively shifted about 590 mV and the corrosion current density was dropped from 1.10 to 0.48 μA cm−2. By sealing treatment in NiF2 solution, its corrosion resistance was further improved yielding a corrosion current density drop of 0.04 μA cm−2. By fluorosilane (FAS-17) surface modification, the conversion coating became hydrophobic due to low-surface-energy groups such as CF2 and CF3, and the contact angle reached 136.8°. Moreover, by FAS-17 modification, the corrosion resistance was enhanced significantly and its corrosion rate decreased by about 25 times. Full article
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11 pages, 3121 KiB  
Article
Toward Superhydrophobic/Superoleophilic Materials for Separation of Oil/Water Mixtures and Water-in-Oil Emulsions Using Phase Inversion Methods
by Chih-Feng Wang, Yi-Jung Tsai, Shiao-Wei Kuo, Kuo-Jung Lee, Chien-Chieh Hu and Juin-Yih Lai
Coatings 2018, 8(11), 396; https://doi.org/10.3390/coatings8110396 - 11 Nov 2018
Cited by 14 | Viewed by 8609
Abstract
In this study, a method that can simultaneously separate oil/water mixtures and water-in-oil emulsions were developed. Various substrates (synthetic polymers and stainless steel meshes) were coated by rough hydrophobic polymer films. The prepared materials possessed superhydrophobicity and superoleophilicity. These superhydrophobic sponges can isolate [...] Read more.
In this study, a method that can simultaneously separate oil/water mixtures and water-in-oil emulsions were developed. Various substrates (synthetic polymers and stainless steel meshes) were coated by rough hydrophobic polymer films. The prepared materials possessed superhydrophobicity and superoleophilicity. These superhydrophobic sponges can isolate extensive amounts of oil from water when connected to a related vacuum framework. Moreover, the superhydrophobic meshes (SHM) can separate both surfactant-free and -stabilized water-in-oil emulsions via gravity with high separation efficiency (oil purity: >99.99%) and flux (up to 4760 L m−2 h−1). The extraordinary performance of our materials and their low-energy, efficient, low-cost preparation propose that they have great potential for real-time applications. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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14 pages, 6389 KiB  
Article
Increase in Efficiency of End Milling of Titanium Alloys Due to Tools with Multilayered Composite Nano-Structured Zr-ZrN-(Zr,Al)N and Zr-ZrN-(Zr,Cr,Al)N Coatings
by Alexey Vereschaka, Maksim Oganyan, Yuri Bublikov, Nikolay Sitnikov, Konstantin Deev, Vladimir Pupchin and Boris Mokritskii
Coatings 2018, 8(11), 395; https://doi.org/10.3390/coatings8110395 - 10 Nov 2018
Cited by 10 | Viewed by 3709
Abstract
The study deals with an increase in the tool life parameter for metal-cutting tools and efficiency of end milling for titanium alloys, due to the use of tools with multilayered composite nano-structured Zr–ZrN–(Zr,Al)N and Zr–ZrN–(Zr,Cr,Al)N coatings, deposited through the technology of the filtered [...] Read more.
The study deals with an increase in the tool life parameter for metal-cutting tools and efficiency of end milling for titanium alloys, due to the use of tools with multilayered composite nano-structured Zr–ZrN–(Zr,Al)N and Zr–ZrN–(Zr,Cr,Al)N coatings, deposited through the technology of the filtered cathodic vacuum arc deposition (FCVAD). The studies included the microstructured investigations using SEM, the analysis of chemical composition (Energy-dispersive X-ray spectroscopy, EDXS), the determination of the value of critical failure force (with the use of scratch testing), and the measurement of the microhardness of the coatings under study. The cutting tests were conducted in end milling of titanium alloys at various cutting speeds. The mechanisms of wear and failure for end milling cutters with the coatings under study were studied in milling. The studies determined the advantages of using a tool with the coatings under study compared to an uncoated tool, as well as to tools with the commercial Ti–TiN coating and the nano-structured Ti–TiN–(Ti,Al)N coating. Adding Cr to the composition of the coating can significantly increase the hardness, while the coating retains sufficient ductility and brittle fracture resistance, which allows for a best result when milling titanium alloys. Full article
(This article belongs to the Special Issue Nanocomposite Coatings)
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9 pages, 2536 KiB  
Article
A Rapid Surface-Enhanced Raman Scattering (SERS) Method for Pb2+ Detection Using L-Cysteine-Modified Ag-Coated Au Nanoparticles with Core–Shell Nanostructure
by Zhou Xu, Linwei Zhang, Bo Mei, Jia Tu, Rong Wang, Maolong Chen and Yunhui Cheng
Coatings 2018, 8(11), 394; https://doi.org/10.3390/coatings8110394 - 10 Nov 2018
Cited by 21 | Viewed by 5918
Abstract
A rapid surface-enhanced Raman scattering (SERS) method for Pb2+ detection has been developed based on l-cysteine-modified Ag-coated Au nanoparticles with core-shell nanostructure. Specifically, l-cysteine-functionalized Au@Ag core-shell probes bearing Raman-labeling molecules (4-ATP) are used to detect Pb2+ upon the formation [...] Read more.
A rapid surface-enhanced Raman scattering (SERS) method for Pb2+ detection has been developed based on l-cysteine-modified Ag-coated Au nanoparticles with core-shell nanostructure. Specifically, l-cysteine-functionalized Au@Ag core-shell probes bearing Raman-labeling molecules (4-ATP) are used to detect Pb2+ upon the formation of nanoparticle aggregates. The proposed SERS-based method shows a linear range between 5 pM and 10 nM, with an unprecedented limit of detection (LOD) of 1 pM for Pb2+; this LOD shows the method to be a few orders of magnitude more sensitive than the typical colorimetric approach that is based on the aggregation of noble metal nanoparticles. Real water samples diluted with pure water have been successfully analyzed. This SERS-based assay may provide a general and simple approach for the detection of other metal ions of interest, and so could have wide-ranging applications in many areas. Full article
(This article belongs to the Special Issue Fabrication of Plasmonic Thin Films, Their Characterization and Applications)
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15 pages, 7916 KiB  
Article
Microstructure and Corrosion Resistance of WC-Based Cermet/Fe-Based Amorphous Alloy Composite Coatings
by Liping Xu, Jinbing Song, Xiaofeng Zhang, Changguang Deng, Min Liu and Kesong Zhou
Coatings 2018, 8(11), 393; https://doi.org/10.3390/coatings8110393 - 6 Nov 2018
Cited by 14 | Viewed by 4765
Abstract
There is an urgent need to improve the corrosion resistance of WC-based cermet coatings in different corrosive environments. The main objective of this work was to investigate the microstructure and evaluate the corrosion resistance in neutral, acidic, and alkaline electrolytes of the WC-based [...] Read more.
There is an urgent need to improve the corrosion resistance of WC-based cermet coatings in different corrosive environments. The main objective of this work was to investigate the microstructure and evaluate the corrosion resistance in neutral, acidic, and alkaline electrolytes of the WC-based cermet/Fe-based amorphous alloy composite coating. Thus, a composite coating of WC–CoCr/Fe-based amorphous alloy and a single WC–CoCr coating were fabricated using the high-velocity oxygen fuel (HVOF) process. The phase composition, microstructure of the original powders, and as-sprayed coatings were studied. The detailed interface information between different compositions of the composite coating was observed by high-resolution transmission electron microscopy (HRTEM). The corrosion resistance of the coatings was studied comparatively by electrochemical tests in 3.5 wt % NaCl, 1 M HCl and 1 M NaOH solutions, respectively. Results showed that the composited coating had a dense layered structure with a composition of WC, Fe-based amorphous alloy, and small amount of W2C. It was revealed that obvious inter-diffusion exists between the interfaces of tungsten carbide/Co, Cr binder and WC–CoCr/Fe-based amorphous alloy. The electrochemical test results showed that the composite coating displayed better corrosion resistance than single WC–CoCr coating both in 3.5 wt % NaCl solution and in 1 M NaOH solution. Full article
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10 pages, 7427 KiB  
Article
One-Step Potentiostatic Deposition of Micro-Particles on Al Alloy as Superhydrophobic Surface for Enhanced Corrosion Resistance by Reducing Interfacial Interactions
by Tian Shi, Xuewu Li, Qiaoxin Zhang and Ben Li
Coatings 2018, 8(11), 392; https://doi.org/10.3390/coatings8110392 - 5 Nov 2018
Cited by 3 | Viewed by 3426
Abstract
Corrosion failure is a thorny problem that restricts the application of Al alloys. As a new technique for functional realization, hydrophobic preparation offers an efficient approach to solve corrosion problem. This work has developed a facile and low-cost method to endow Al alloy [...] Read more.
Corrosion failure is a thorny problem that restricts the application of Al alloys. As a new technique for functional realization, hydrophobic preparation offers an efficient approach to solve corrosion problem. This work has developed a facile and low-cost method to endow Al alloy with enhanced water-repellent and anticorrosion abilities. The micro-particles have been firstly prepared by one-step deposition process. Furthermore, wetting and electrochemical behaviors of as-prepared structures have been investigated after silicone modification. Results show that the fabricated surface possesses excellent superhydrophobicity with a water contact angle (CA) of 154.7° and a sliding angle (SA) of 6.7°. Meanwhile, the resultant surface is proved with enhanced corrosion resistance by reducing interfacial interactions with seawater, owing to newly-generated solid-air-liquid interfaces. This work sheds positive insights into extending applications of Al alloys, especially in oceaneering fields. Full article
(This article belongs to the Special Issue Advanced Coatings for Corrosion Protection in Extreme Environments)
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13 pages, 3846 KiB  
Review
Mechanisms of the Antibacterial Effects of TiO2–FeOx under Solar or Visible Light: Schottky Barriers versus Surface Plasmon Resonance
by John Kiwi and Sami Rtimi
Coatings 2018, 8(11), 391; https://doi.org/10.3390/coatings8110391 - 4 Nov 2018
Cited by 19 | Viewed by 4978
Abstract
This study reports the significant mechanistic difference between binary-oxide antibacterial films with the same composition but different microstructures. Binary TiO2-FeOx films were found to present a faster bacterial inactivation kinetics under visible light irradiation than each single oxide acting independently. [...] Read more.
This study reports the significant mechanistic difference between binary-oxide antibacterial films with the same composition but different microstructures. Binary TiO2-FeOx films were found to present a faster bacterial inactivation kinetics under visible light irradiation than each single oxide acting independently. The interaction between the film active surface species and the bacteria within the disinfection period was followed by X-ray photoelectron spectroscopy (XPS) and provided the evidence for a redox catalysis taking place during the bacterial inactivation time. The optical and surface properties of the films were evaluated by appropriate surface analytical methods. A differential mechanism is suggested for each specific microstructure inducing bacterial inactivation. The surface FeOx plasmon resonance transferred electrons into the conduction band of TiO2 because of the Schottky barrier after Fermi level equilibration of the two components. An electric field at the interface between TiO2 and FeOx, favors the separation of the photo-generated charges leading to a faster bacterial inactivation by TiO2–FeOx compared to the bacterial inactivation kinetics by each of the single oxides. Full article
(This article belongs to the Special Issue Photocatalytic Thin Films)
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11 pages, 3303 KiB  
Article
Fabrication of Superhydrophobic AA5052 Aluminum Alloy Surface with Improved Corrosion Resistance and Self Cleaning Property
by Qian Zhao, Tiantian Tang and Fang Wang
Coatings 2018, 8(11), 390; https://doi.org/10.3390/coatings8110390 - 31 Oct 2018
Cited by 17 | Viewed by 4722
Abstract
The development of a self-cleaning and corrosion resistant superhydrophobic coating for aluminum alloy surfaces that is durable in aggressive conditions has attracted great interest in materials science. In the present study, a superphydrophobic film was fabricated on an AA5052 aluminum alloy surface by [...] Read more.
The development of a self-cleaning and corrosion resistant superhydrophobic coating for aluminum alloy surfaces that is durable in aggressive conditions has attracted great interest in materials science. In the present study, a superphydrophobic film was fabricated on an AA5052 aluminum alloy surface by the electrodeposition of Ni–Co alloy coating, followed by modification with 6-(N-allyl-1,1,2,2-tetrahydro-perfluorodecyl) amino-1,3,5-triazine-2,4-dithiol monosodium (AF17N). The surface morphology and characteristics of the composite coatings were investigated by means of scanning electron microscopy (SEM), energy dispersive X-ray spectrum (EDS), atomic force microscope (AFM) and contact angle (CA). The corrosion resistance of the coatings was assessed by electrochemical tests. The results showed that the surface exhibited excellent superhydrophobicity and self-cleaning performance with a contact angle maintained at 160° after exposed to the atmosphere for 240 days. Moreover, the superhydrophobic coatings significantly improved the corrosion resistant performance of AA5052 aluminum alloy substrate in 3.5 wt.% NaCl solution. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings for Corrosion and Tribology)
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18 pages, 2752 KiB  
Article
Non-Local Buckling Analysis of Functionally Graded Nanoporous Metal Foam Nanoplates
by Yanqing Wang and Zhiyuan Zhang
Coatings 2018, 8(11), 389; https://doi.org/10.3390/coatings8110389 - 31 Oct 2018
Cited by 19 | Viewed by 3851
Abstract
In this study, the buckling of functionally graded (FG) nanoporous metal foam nanoplates is investigated by combining the refined plate theory with the non-local elasticity theory. The refined plate theory takes into account transverse shear strains which vary quadratically through the thickness without [...] Read more.
In this study, the buckling of functionally graded (FG) nanoporous metal foam nanoplates is investigated by combining the refined plate theory with the non-local elasticity theory. The refined plate theory takes into account transverse shear strains which vary quadratically through the thickness without considering the shear correction factor. Based on Eringen’s non-local differential constitutive relations, the equations of motion are derived from Hamilton’s principle. The analytical solutions for the buckling of FG nanoporous metal foam nanoplates are obtained via Navier’s method. Moreover, the effects of porosity distributions, porosity coefficient, small scale parameter, axial compression ratio, mode number, aspect ratio and length-to-thickness ratio on the buckling loads are discussed. In order to verify the validity of present analysis, the analytical results have been compared with other previous studies. Full article
(This article belongs to the Special Issue Functionally Graded Nanocomposite Surfaces)
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15 pages, 4370 KiB  
Article
A Novel Way of Adhering PET onto Protein (Wheat Gluten) Plastics to Impart Water Resistance
by Oisik Das, Thomas Aditya Loho, Antonio José Capezza, Ibrahim Lemrhari and Mikael S. Hedenqvist
Coatings 2018, 8(11), 388; https://doi.org/10.3390/coatings8110388 - 31 Oct 2018
Cited by 36 | Viewed by 4781
Abstract
This study presents an approach to protect wheat gluten (WG) plastic materials against water/moisture by adhering it with a polyethylene terephthalate (PET) film using a diamine (Jeffamine®) as a coupling agent and a compression molding operation. The laminations were applied using [...] Read more.
This study presents an approach to protect wheat gluten (WG) plastic materials against water/moisture by adhering it with a polyethylene terephthalate (PET) film using a diamine (Jeffamine®) as a coupling agent and a compression molding operation. The laminations were applied using two different methods, one where the diamine was mixed with the WG powder and ground together before compression molding the mixture into plates with PET films on both sides. In the other method, the PET was pressed to an already compression molded WG, which had the diamine brushed on the surface of the material. Infrared spectroscopy and nanoindentation data indicated that the diamine did act as a coupling agent to create strong adhesion between the WG and the PET film. Both methods, as expected, yielded highly improved water vapor barrier properties compared to the neat WG. Additionally, these samples remained dimensionally intact. Some unintended side effects associated with the diamine can be alleviated through future optimization studies. Full article
(This article belongs to the Special Issue Functional Coatings for Food Packaging Applications)
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15 pages, 3148 KiB  
Article
Preparation, Structure, and Properties of Surface Modified Graphene/Epoxy Resin Composites for Potential Application in Conductive Ink
by Youliang Cheng, Qingling Zhang, Changqing Fang, Jing Chen, Jian Su, Kaiyan Xu, Liangliang Ai and Donghong Liu
Coatings 2018, 8(11), 387; https://doi.org/10.3390/coatings8110387 - 30 Oct 2018
Cited by 10 | Viewed by 4469
Abstract
The dispersity of graphene (GE) in the matrix has an important influence on the thermal, mechanical, and electrical properties of its derived composites. In this paper, surface modification with a silane coupling agent and a double injection method were used to improve the [...] Read more.
The dispersity of graphene (GE) in the matrix has an important influence on the thermal, mechanical, and electrical properties of its derived composites. In this paper, surface modification with a silane coupling agent and a double injection method were used to improve the dispersity of GE in epoxy resin (EP). The thermal, mechanical, and electrical properties of modified graphene/epoxy resin composites (modified GE/EP) were investigated by the thermogravimetric analysis, a four-probe method, and the tensile and bending strength. The results reveal that these properties of the composites can be improved significantly by using the modified GE as the filler. The surface of the modified GE/EP composite was smooth when the curing temperature was 75 °C. The weight loss of the modified GE/EP composite was lower than that of pure EP. The tensile and bending strength of modified GE/EP-0.07 (0.07 wt % modified GE) reached 74.65 and 106.21 MPa, respectively. In addition, the resistivity of modified GE/EP-0.1 (0.1 wt % modified GE) decreased to 52 Ω·cm, which was lower than that of CB/EP-1 (1 wt % carbon black, 95 Ω·cm) and Ag/EP-50 (50 wt % Ag particles, 102 Ω·cm). It is worth noting that the percolation threshold of the modified GE/EP composites was 0.025 vol % modified GE. These results show that the modified GE/EP composites have a potential application in conductive ink when the modified GE is used as the conductive filler. Full article
(This article belongs to the Special Issue Surface and Interface Science of 2D Materials)
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10 pages, 2143 KiB  
Article
In Silico Screening and Design of Coating Materials for PEMFC Bipolar Plates
by Longjie Liu, Li Yao, Kai Feng, Zhe Luo, Ke Liu, Hong Zhu and Paul. K. Chu
Coatings 2018, 8(11), 386; https://doi.org/10.3390/coatings8110386 - 29 Oct 2018
Cited by 5 | Viewed by 3447
Abstract
Methods used to design coating materials for polymer electrolyte membrane fuel cells (PEMFCs) are unsystematic and time-consuming because current materials research relies on scientific intuition and trial and error experimentation. In this study, a feasible and more efficient scheme of screening and designing [...] Read more.
Methods used to design coating materials for polymer electrolyte membrane fuel cells (PEMFCs) are unsystematic and time-consuming because current materials research relies on scientific intuition and trial and error experimentation. In this study, a feasible and more efficient scheme of screening and designing coating materials is established based on density function theory (DFT) utilizing the fast-growing computing capacity. The scheme consists of four steps: Elements selection by calculation of Pilling–Bedworth ratio and electrical resistivity, corrosion resistance assessment leveraging the Pourbaix diagram approach, running BoltzTrap code to calculate electrical conductivity ( σ / τ ), and interface binding strength evaluation by calculation of separation work. According to the calculation results, TiCo and TiCo3 are proposed to be the two most promising candidates because of relatively better properties required by harsh working environment of PEMFC. The high-throughput screening strategy established in this study makes the ideal of rapidly evaluating hundreds of thousands of possible coating materials candidates into reality and helps to indicate the direction of further synthesis efforts. Full article
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11 pages, 4213 KiB  
Article
Mechanical Properties of Hydrogen Free Diamond-Like Carbon Thin Films Deposited by High Power Impulse Magnetron Sputtering with Ne
by Asim Aijaz, Fabio Ferreira, Joao Oliveira and Tomas Kubart
Coatings 2018, 8(11), 385; https://doi.org/10.3390/coatings8110385 - 29 Oct 2018
Cited by 35 | Viewed by 5868
Abstract
Hydrogen-free diamond-like carbon (DLC) thin films are attractive for a wide range of industrial applications. One of the challenges related to the use of hard DLC lies in the high intrinsic compressive stresses that limit the film adhesion. Here, we report on the [...] Read more.
Hydrogen-free diamond-like carbon (DLC) thin films are attractive for a wide range of industrial applications. One of the challenges related to the use of hard DLC lies in the high intrinsic compressive stresses that limit the film adhesion. Here, we report on the mechanical and tribological properties of DLC films deposited by High Power Impulse Magnetron Sputtering (HiPIMS) with Ne as the process gas. In contrast to standard magnetron sputtering as well as standard Ar-based HiPIMS process, the Ne-HiPIMS lead to dense DLC films with increased mass density (up to 2.65 g/cm3) and a hardness of 23 GPa when deposited on steel with a Cr + CrN adhesion interlayer. Tribological testing by the pin-on-disk method revealed a friction coefficient of 0.22 against steel and a wear rate of 2 × 10−17 m3/Nm. The wear rate is about an order of magnitude lower than that of the films deposited using Ar. The differences in the film properties are attributed to an enhanced C ionization in the Ne-HiPIMS discharge. Full article
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