Coatings

10123 KiB

Open AccessArticle

The Dispersion Tolerance of Micro/Nano Particle in Polydimethylsiloxane and Its Influence on the Properties of Fouling Release Coatings Based on Polydimethylsiloxane

by Miao Ba, Zhanping Zhang and Yuhong Qi

Coatings 2017, 7(7), 107; https://doi.org/10.3390/coatings7070107 - 21 Jul 2017

Cited by 21 | Viewed by 5741

Abstract

Particles can be used to improve the mechanical properties of fouling release coatings based on polydimethylsiloxane (PDMS). In this study, coatings were prepared by high speed stirring using seven types of particles, with different particle size from nanometer to micrometer. The influence of [...] Read more.

Particles can be used to improve the mechanical properties of fouling release coatings based on polydimethylsiloxane (PDMS). In this study, coatings were prepared by high speed stirring using seven types of particles, with different particle size from nanometer to micrometer. The influence of specific surface area of the particles on the dispersion tolerance was investigated. The results showed that the dispersion tolerance of particles in PDMS decreased with the increase in specific surface area of the particle, and for nano particles, the factor most affecting the dispersion tolerance was the specific surface area of agglomerate particle. Subsequently, the surface properties, mechanical properties, and biofilm adhesion assay of coatings were investigated. Results indicated that surface roughness increased with the increase of dispersion tolerance. Surface roughness of samples improved the hydrophobicity of samples, yet the polar chemical group of nano silica and fumed silica reduced the hydrophobicity of samples. Further, particles could enhance the mechanical properties of coating, especially nano particles. Compared to the coating without particle, biofilm adhesion performance of coating with particles decreased, which was determined by the increase of the elastic modulus and surface roughness of coatings. Full article

(This article belongs to the Special Issue Novel Marine Antifouling Coatings)

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24128 KiB

Open AccessArticle

Particle Characterisation and Depletion of Li₂CO₃ Inhibitor in a Polyurethane Coating

by Anthony Hughes, James Laird, Chris Ryan, Peter Visser, Herman Terryn and Arjan Mol

Coatings 2017, 7(7), 106; https://doi.org/10.3390/coatings7070106 - 21 Jul 2017

Cited by 14 | Viewed by 5359

Abstract

The distribution and chemical composition of inorganic components of a corrosion-inhibiting primer based on polyurethane is determined using a range of characterisation techniques. The primer consists of a Li₂CO₃ inhibitor phase, along with other inorganic phases including TiO₂, [...] Read more.

The distribution and chemical composition of inorganic components of a corrosion-inhibiting primer based on polyurethane is determined using a range of characterisation techniques. The primer consists of a Li₂CO₃ inhibitor phase, along with other inorganic phases including TiO₂, BaSO₄ and Mg-(hydr)oxide. The characterisation techniques included particle induced X-ray and γ-ray emission spectroscopies (PIXE and PIGE, respectively) on a nuclear microprobe, as well as SEM/EDS hyperspectral mapping. Of the techniques used, only PIGE was able to directly map the Li distribution, although the distribution of Li₂CO₃ particles could be inferred from SEM through using backscatter contrast and EDS. Characterisation was also performed on a primer coating that had undergone leaching in a neutral salt spray test for 500 h. Overall, it was found that Li₂CO₃ leaching resulted in a uniform depletion zone near the surface, but also much deeper local depletion, which is thought to be due to the dissolution of clusters of Li₂CO₃ particles that were connected to the external surface/electrolyte interface. Full article

(This article belongs to the Special Issue New Generation Coatings for Metals)

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25690 KiB

Open AccessArticle

Preparation of Hydroxyapatite/Tannic Acid Coating to Enhance the Corrosion Resistance and Cytocompatibility of AZ31 Magnesium Alloys

by Bowu Zhu, Shimeng Wang, Lei Wang, Yang Yang, Jun Liang and Baocheng Cao

Coatings 2017, 7(7), 105; https://doi.org/10.3390/coatings7070105 - 20 Jul 2017

Cited by 40 | Viewed by 7493

Abstract

Hydroxyapatite/tannic acid coating (HA/TA) were prepared on AZ31 magnesium alloys (AZ31) via chemical conversion and biomimetic methods. The characterization and properties of the coating were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), corrosion testing, MC3T3-E1 cell [...] Read more.

Hydroxyapatite/tannic acid coating (HA/TA) were prepared on AZ31 magnesium alloys (AZ31) via chemical conversion and biomimetic methods. The characterization and properties of the coating were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), corrosion testing, MC3T3-E1 cell proliferation assay, and MC3T3-E1 cell morphology observation. The results showed that tannic acid as an inducer increased the number of nucleation centers of hydroxyapatite and rendered the morphology more uniform. Compared to bare AZ31 magnesium (Mg) alloys (E_corr = −1.462 ± 0.006 V, I_corr = (4.8978 ± 0.2455) × 10⁻⁶ A/cm²), the corrosion current density of the HA/TA-coated magnesium alloys ((5.6494 ± 0.3187) × 10⁻⁸ A/cm²) decreased two orders of magnitude, and the corrosion potential of the HA/TA-coated Mg alloys (E_corr = −1.304 ± 0.006 V) increased by about 158 mV. This indicated that the HA/TA coating was effectively protecting the AZ31 against corrosion in simulated body fluid (SBF). Cell proliferation assays and cell morphology observations results showed that the HA/TA coating was not toxic to the MC3T3-E1 cells. Full article

(This article belongs to the Special Issue Advanced Biomimetic Calcium Phosphate Coatings)

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3503 KiB

Open AccessArticle

Enhancing Dark Shade Pigment Dyeing of Cotton Fabric Using Plasma Treatment

by Chi-Wai Kan and Wai-Shan Man

Coatings 2017, 7(7), 104; https://doi.org/10.3390/coatings7070104 - 19 Jul 2017

Cited by 12 | Viewed by 5440

Abstract

This study is intended to investigate the effect of atmospheric pressure plasma treatment on dark shade pigment dyeing of cotton fabric. Experimental results reveal that plasma-treated cotton fabric can attain better color yield, levelness, and crocking fastness in dark shade pigment dyeing, compared [...] Read more.

This study is intended to investigate the effect of atmospheric pressure plasma treatment on dark shade pigment dyeing of cotton fabric. Experimental results reveal that plasma-treated cotton fabric can attain better color yield, levelness, and crocking fastness in dark shade pigment dyeing, compared with normal cotton fabric (not plasma treated). SEM analysis indicates that cracks and grooves were formed on the cotton fiber surface where the pigment and the binder can get deposited and improve the color yield, levelness, and crocking fastness. It was also noticed that pigment was aggregated when deposited on the fiber surface which could affect the final color properties. Full article

(This article belongs to the Special Issue Plasma Etching and Deposition)

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9086 KiB

Open AccessArticle

Reduced-Order Modeling for and Vibration Characteristics Analysis of a Hard-Coated Mistuned Blisk

by Feng Gao and Wei Sun

Coatings 2017, 7(7), 103; https://doi.org/10.3390/coatings7070103 - 18 Jul 2017

Cited by 10 | Viewed by 4868

Abstract

This paper develops a damping strategy for the vibration reduction of a mistuned bladed disk (blisk) by depositing hard coating on its blades, and systematically investigates the vibration characteristics of the hard-coated mistuned (HCM) blisk. By using an improved fixed-interface component modal synthesis [...] Read more.

This paper develops a damping strategy for the vibration reduction of a mistuned bladed disk (blisk) by depositing hard coating on its blades, and systematically investigates the vibration characteristics of the hard-coated mistuned (HCM) blisk. By using an improved fixed-interface component modal synthesis method (fixed-ICMSM), a reduced-order model (ROM) of the HCM blisk is established. Then, based on the proposed ROM, solutions of eigenvalue equations are carried out to obtain the natural frequencies and mode shapes. Further, modal loss factors and a damping matrix of the HCM blisk are achieved by taking advantage of the modal strain energy method and the proportional damping model, respectively. Moreover, the frequency response function of the HCM blisk, which can exhibit dynamic behaviors, was deduced. Finally, a mistuned blisk with a deposited NiCoCrAlY + YSZ hard coating on both sides of the blades is chosen as a study case to conduct a finite element analysis, and the results are compared with those obtained from the experimental test in terms of natural frequencies and mode shapes. The variation of the natural frequencies, the modal loss factors, and the frequency response function generated by the NiCoCrAlY + YSZ hard coating are studied, and the influence of coating area on damping capacity is further discussed. Full article

(This article belongs to the Special Issue Modelling and Simulation of Coating)

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4056 KiB

Open AccessArticle

Ti-SLActive and TiZr-SLActive Dental Implant Surfaces Promote Fast Osteoblast Differentiation

by Milena R. Kaluđerović, Tamara Krajnović, Danijela Maksimović-Ivanić, Hans-Ludwig Graf and Sanja Mijatović

Coatings 2017, 7(7), 102; https://doi.org/10.3390/coatings7070102 - 15 Jul 2017

Cited by 9 | Viewed by 5809

Abstract

A primary goal in modern surface modification technology of dental implants is to achieve biocompatible surfaces with rapid but controlled healing which also allow health and longevity of implants. In order to realize all, understanding of osseointegration phenomena is crucial. Although Ti-SLA, Ti-SLActive [...] Read more.

A primary goal in modern surface modification technology of dental implants is to achieve biocompatible surfaces with rapid but controlled healing which also allow health and longevity of implants. In order to realize all, understanding of osseointegration phenomena is crucial. Although Ti-SLA, Ti-SLActive and TiZr-SLActive surfaces have been successfully used in clinical implantology and were shown to notably reduce the primary healing time, available in vitro studies are sparse and do not concern or explore the mechanism(s) involved in human osteoblast behavior on these surfaces. Ti-SLA, Ti-SLActive, TiZr-SLActive, Ti cp, Ticer and Cercon surfaces were used. Osteoblast proliferation, cell cluster formation, morphological changes, induction of autophagy, nitric oxide (NO), reactive oxygen species/reactive nitrogen species (ROS/RNS) formation, osteocalcin (OC), bone sialoprotein (BSP) and collagen type I (Col-1) affected by various surfaces were analyzed. These surfaces induced formation of mature osteoblasts caused by elevated oxidative stress (ROS) followed by overexpression of osteoblast maturation key molecule (NO), with different intensity however. These mature osteoblasts induced upregulation of OC, BSP and Col-1, activating PI3/Akt signalling pathway resulting in autophagy, known as an important process in differentiation of osteoblast cells. Additional distinctive subpopulation identified on Ticer, Ti-SLA (after 5 days), Ti-SLActive and TiZr-SLActive surfaces (after 2 days) were forming cell clusters, essential for bone noduli formation and mineralisation. The results suggest that Ti- and TiZr-SLActive possess advanced properties in comparison with Ticer and Ti-SLA manifested as accelerated osteoblast differentiation. These effects could explain already known fast osseointegration of these surfaces in vivo. Full article

(This article belongs to the Special Issue Dental Implant Surface: Science and Technology)

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6150 KiB

Open AccessArticle

Chemical Vapor Deposition of TaC/SiC on Graphite Tube and Its Ablation and Microstructure Studies

by Suresh Kumar, Samar Mondal, Anil Kumar, Ashok Ranjan and Namburi Eswara Prasad

Coatings 2017, 7(7), 101; https://doi.org/10.3390/coatings7070101 - 13 Jul 2017

Cited by 15 | Viewed by 7270

Abstract

Tantalum carbide (TaC) and silicon carbide (SiC) layers were deposited on a graphite tube using a chemical vapor deposition process. Tantalum chloride (TaCl₅) was synthesized in situ by reacting tantalum chips with chlorine at 550 °C. TaC was deposited by reacting [...] Read more.

Tantalum carbide (TaC) and silicon carbide (SiC) layers were deposited on a graphite tube using a chemical vapor deposition process. Tantalum chloride (TaCl₅) was synthesized in situ by reacting tantalum chips with chlorine at 550 °C. TaC was deposited by reacting TaCl₅ with CH₄ in the presence of H₂ at 1050–1150 °C and 50–100 mbar. SiC was deposited at 1000 °C using methyl-tri-chloro-silane as a precursor at 50 mbar. At 1150 °C; the coating thickness was found to be about 600 μm, while at 1050 °C it was about 400 μm for the cumulative deposition time of 10 h. X-ray diffraction (XRD) and X-ray Photo-Electron Spectroscopy (XPS) studies confirmed the deposition of TaC and SiC and their phases. Ablation studies of the coated specimens were carried out under oxyacetylene flame up to 120 s. The coating was found to be intact without surface cracks and with negligible erosion. The oxide phase of TaC (TaO₂ and Ta₂O₅) and the oxide phase of SiC (SiO₂) were also found on the surface, which may have protected the substrate underneath from further oxidation. Full article

(This article belongs to the Special Issue Ultrahigh Temperature Ceramic Coatings and Composites)

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13750 KiB

Open AccessArticle

Electrodeposition of Vanadium Oxides at Room Temperature as Cathodes in Lithium-Ion Batteries

by Michalis Rasoulis and Dimitra Vernardou

Coatings 2017, 7(7), 100; https://doi.org/10.3390/coatings7070100 - 12 Jul 2017

Cited by 13 | Viewed by 6910

Abstract

Electrodeposition of vanadium pentoxide coatings was performed at room temperature and a short growth period of 15 min based on an alkaline solution of methanol and vanadyl (III) acetyl acetonate. All samples were characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, [...] Read more.

Electrodeposition of vanadium pentoxide coatings was performed at room temperature and a short growth period of 15 min based on an alkaline solution of methanol and vanadyl (III) acetyl acetonate. All samples were characterized by X-ray diffraction, Raman spectroscopy, field-emission scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The current density and electrolyte concentration were found to affect the characteristics of the as-grown coatings presenting enhanced crystallinity and porous structure at the highest values employed in both cases. The as-grown vanadium pentoxide at current density of 1.3 mA·cm⁻² and electrolyte concentration of 0.5 M indicated the easiest charge transfer of Li⁺ across the vanadium pentoxide/electrolyte interface presenting a specific discharge capacity of 417 mAh·g⁻¹, excellent capacitance retention of 95%, and coulombic efficiency of 94% after 1000 continuous Li⁺ intercalation/deintercalation scans. One may then suggest that this route is promising to prepare large area vanadium pentoxide electrodes with excellent stability and efficiency at very mild conditions. Full article

(This article belongs to the Special Issue Thin Film Deposition and Characterization Techniques)

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7173 KiB

Open AccessReview

Progress in Wear Resistant Materials for Total Hip Arthroplasty

by Rohit Khanna, Joo L. Ong, Ebru Oral and Roger J. Narayan

Coatings 2017, 7(7), 99; https://doi.org/10.3390/coatings7070099 - 09 Jul 2017

Cited by 24 | Viewed by 9651

Abstract

Current trends in total hip arthroplasty (THA) are to develop novel artificial hip joints with high wear resistance and mechanical reliability with a potential to last for at least 25–30 years for both young and old active patients. Currently used artificial hip joints [...] Read more.

Current trends in total hip arthroplasty (THA) are to develop novel artificial hip joints with high wear resistance and mechanical reliability with a potential to last for at least 25–30 years for both young and old active patients. Currently used artificial hip joints are mainly composed of femoral head of monolithic alumina or alumina-zirconia composites articulating against cross-linked polyethylene liner of acetabular cup or Co-Cr alloy in a self-mated configuration. However, the possibility of fracture of ceramics or its composites, PE wear debris-induced osteolysis, and hypersensitivity issue due to metal ion release cannot be eliminated. In some cases, thin ultra-hard diamond-based, TiN coatings on Ti-6A-4V or thin zirconia layer on the Zr-Nb alloy have been fabricated to develop high wear resistant bearing surfaces. However, these coatings showed poor adhesion in tribological testing. To provide high wear resistance and mechanical reliability to femoral head, a new kind of ceramic/metal artificial hip joint hybrid was recently proposed in which 10–15 μm thick dense layer of pure α-alumina was formed onto Ti-6Al-4V alloy by deposition of Al metal layer by cold spraying or cold metal transfer methods with 1–2 μm thick Al₃Ti reaction layer formed at their interface to improve adhesion. An optimal micro-arc oxidation treatment transformed Al to dense α-alumina layer, which showed high Vickers hardness 1900 HV and good adhesion to the substrate. Further tribological and cytotoxicity analyses of these hybrids will determine their efficacy for potential use in THA. Full article

(This article belongs to the Special Issue Surface Chemical Modification)

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4670 KiB

Open AccessArticle

Influence of Process Parameters on High Velocity Oxy-Fuel Sprayed Cr₃C₂-25%NiCr Coatings

by Mingxiang Xie, Yue Lin, Peng Ke, Shuoyu Wang, Shihong Zhang, Zhicheng Zhen and Liangshui Ge

Coatings 2017, 7(7), 98; https://doi.org/10.3390/coatings7070098 - 09 Jul 2017

Cited by 22 | Viewed by 4652

Abstract

In this work, the Cr₃C₂-25% NiCr powder was deposited on stainless steel with different combustion pressures and powder feed rates using HVOF technique. The microstructure, porosity, micro-hardness, indentation fracture toughness, adhesion strength, and wear resistance at 500 °C of [...] Read more.

In this work, the Cr₃C₂-25% NiCr powder was deposited on stainless steel with different combustion pressures and powder feed rates using HVOF technique. The microstructure, porosity, micro-hardness, indentation fracture toughness, adhesion strength, and wear resistance at 500 °C of the coatings were investigated. The results showed that HVOF sprayed Cr₃C₂-25% NiCr coatings possessed low porosity, high micro-hardness, and enough adhesion strength. The powder feed rate had obvious effect on porosity, micro-hardness and indention fracture toughness of the coatings, and the coating sprayed under the powder feed rate of 33.5 g/min possessed the optimal performance. The wear tests illustrated that the HVOF sprayed Cr₃C₂-25NiCr coating possessed good wear resistance at the temperature of 500 °C, in which the coating sprayed at the powder feed rate of 33.5 g/min had the best wear resistance due to its dense structure and enough fracture toughness. Full article

(This article belongs to the Special Issue Thermal Spray Technology)

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1432 KiB

Open AccessArticle

Technological Strategies to Preserve Burrata Cheese Quality

by Cristina Costa, Annalisa Lucera, Amalia Conte, Angelo Vittorio Zambrini and Matteo Alessandro Del Nobile

Coatings 2017, 7(7), 97; https://doi.org/10.3390/coatings7070097 - 09 Jul 2017

Cited by 5 | Viewed by 5046

Abstract

Burrata cheese is a very perishable product due to microbial proliferation and undesirable sensory changes. In this work, a step-by-step optimization approach was used to design proper processing and packaging conditions for burrata in brine. In particular, four different steps were carried out [...] Read more.

Burrata cheese is a very perishable product due to microbial proliferation and undesirable sensory changes. In this work, a step-by-step optimization approach was used to design proper processing and packaging conditions for burrata in brine. In particular, four different steps were carried out to extend its shelf life. Different headspace gas compositions (MAP-1 30:70 CO₂:N₂; MAP-2 50:50 CO₂:N₂ and MAP-3 65:35 CO₂:N₂) were firstly tested. To further promote product preservation, a coating was also optimized. Then, antimicrobial compounds in the filling of the burrata cheese (lysozyme and Na₂-EDTA) and later in the coating (enzymatic complex and silver nanoparticles) were analyzed. To evaluate the quality of the samples, in each step headspace gas composition, microbial population, and pH and sensory attributes were monitored during storage at 8 ± 1 °C. The results highlight that the antimicrobial compounds in the stracciatella, coating with silver nanoparticles, and packaging under MAP-3 represent effective conditions to guarantee product preservation, moving burrata shelf life from three days (control sample) to ten days. Full article

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

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1857 KiB

Open AccessArticle

Polymerization of PEDOT/PSS/Chitosan-Coated Electrodes for Electrochemical Bio-Sensing

by Li Sui, Bingshu Zhang, Jun Wang and Ainan Cai

Coatings 2017, 7(7), 96; https://doi.org/10.3390/coatings7070096 - 06 Jul 2017

Cited by 12 | Viewed by 6241

Abstract

Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly (styrene sulfonate) (PSS) has a variety of chemical and biomedical applications. Additionally, chitosan has been extensively used in industrial and medical fields. However, whether chitosan could be incorporated into conducting polymers of PEDOT/PSS is not clear. In this [...] Read more.

Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly (styrene sulfonate) (PSS) has a variety of chemical and biomedical applications. Additionally, chitosan has been extensively used in industrial and medical fields. However, whether chitosan could be incorporated into conducting polymers of PEDOT/PSS is not clear. In this study, the PEDOT/PSS/chitosan coatings were electrochemically polymerized on the surface of 0.5 mm platinum (Pt) electrodes and the properties of electrochemical cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of the PEDOT/PSS/chitosan-coated electrodes were investigated. Furthermore, PEDOT/PSS/chitosan-coated electrodes used for electrochemical bio-sensing, using dexamethasone (Dex) as a model bio-sensing material, were examined. The results demonstrated that PEDOT/PSS/chitosan-coated electrodes were stable in phosphate-buffered saline (PBS) solution. The electrochemical CV curve areas, reflecting the charge delivery capacity, and the EIS of the PEDOT/PSS/chitosan-coated electrodes were sensitive to Dex, and the good linearity can be obtained between CV curve areas, the EIS and the concentration of Dex. In addition, electrochemical sensitivity of the PEDOT/PSS/chitosan-coated electrodes to Dex was much higher than ultraviolet (UV) spectroscopy detection. All these results revealed that the PEDOT/PSS/chitosan-coated electrodes can be electrochemical polymerized and used for electrochemical bio-sensing. Full article

(This article belongs to the Special Issue Novel Thin Film Materials for Biomedical Application)

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11859 KiB

Open AccessArticle

The Effect of Deposition Parameters on the Growth Rate of Microcrystalline Diamond Powders Synthesized by HFCVD Method

by Tao Zhang and Ye Zou

Coatings 2017, 7(7), 95; https://doi.org/10.3390/coatings7070095 - 06 Jul 2017

Cited by 6 | Viewed by 5157

Abstract

Conventional diamond powders (<10 μm) are generally produced from crushing large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, these powders are served as diamond seeds and regrown by hot filament chemical vapor [...] Read more.

Conventional diamond powders (<10 μm) are generally produced from crushing large-sized diamonds synthesized by high-pressure and high-temperature (HPHT) technique, whereas they have many morphological imperfections. In the present work, these powders are served as diamond seeds and regrown by hot filament chemical vapor deposition (HFCVD). Deposition parameters—such as the carbon concentration, substrate temperature, and bias current—which play a determined role in the homoepitaxial growth rate of micron diamonds, are investigated in their respective usual ranges. As shown in the experimental results, under the preconditions of maintaining the good morphology of crystals and inhibiting polycrystal growth, the growth rate of isolated diamond crystals can be controlled at 0.9 μm/h. Besides, the final improved powders have a wide range of particle sizes, which could fail to meet the requirements for commercial powders without the post-process of sieving. Full article

(This article belongs to the Special Issue Chemical Vapor Deposition)

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3456 KiB

Open AccessArticle

Study on the Preparation of a High-Efficiency Carbon Fiber Dissipating Coating

by Jing Li, Xue Li, Chunlei Fan, Huan Yao, Xuyang Chen and Yeming Liu

Coatings 2017, 7(7), 94; https://doi.org/10.3390/coatings7070094 - 04 Jul 2017

Cited by 35 | Viewed by 4680

Abstract

The working temperature of electronic components directly determines their service life and stability. In order to ensure normal operation of electronic components, cooling the coating is one of the best ways to solve the problem. Based on an acrylic amino-resin system, a dissipating [...] Read more.

The working temperature of electronic components directly determines their service life and stability. In order to ensure normal operation of electronic components, cooling the coating is one of the best ways to solve the problem. Based on an acrylic amino-resin system, a dissipating coating was prepared with carbon fiber (CF) as the main thermal conductive filler. The influence of the CF content on the thermal conductivity was determined by the single factor method. The surface structure was observed by scanning electron microscopy (SEM). The results show: With the increase of the CF mass fraction, both the heat dispersion and heat conduction coefficient of the coating tend to increase at first and then decrease, and the heat dissipation effect is optimum when the CF mass fraction is 12.3 wt %. At this point, the coating shows an excellent comprehensive performance, such as 1st level adhesion, H grade hardness, and thermal conductivity of 1.61 W/m·K. Furthermore, this paper explored the radiating mechanism of coating in which CF produces a coating which forms a heat “channel” for rapid heat conduction. When the optimal value is exceeded, the cooling effect is reduced because of the accumulation and the anisotropy of CF. Full article

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4585 KiB

Open AccessArticle

Investigation on the Cathodic Protection Effect of Low Pressure Cold Sprayed AlZn Coating in Seawater via Numerical Simulation

by Guosheng Huang, Xiaodan Lou, Hongren Wang, Xiangbo Li and Lukuo Xing

Coatings 2017, 7(7), 93; https://doi.org/10.3390/coatings7070093 - 04 Jul 2017

Cited by 9 | Viewed by 6130

Abstract

Cold spray can deposit a composite coating simply by spraying mechanically-mixed Al and Zn powders, while no quantitative data has been reported on the anti-corrosion performance of different composite cold-sprayed coatings. In the present work, the finite element method was used to estimate [...] Read more.

Cold spray can deposit a composite coating simply by spraying mechanically-mixed Al and Zn powders, while no quantitative data has been reported on the anti-corrosion performance of different composite cold-sprayed coatings. In the present work, the finite element method was used to estimate the cathodic protection effect by simulating the potential distribution on a damaged cold-sprayed AlZn coating on Q235 steel. The results indicate that AlZn coating can only provide a limiting cathodic protection for substrate, because it can only polarize a very narrow zone negative to −0.78 V (vs. SCE, saturated calomel electrode). The remaining area of the steel substrate still has a very high residual corrosion rate. Computational methods can be used to predict the corrosion rate of AlZn coating, and the simulation results were validated by the results of a weight loss experiment. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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5844 KiB

Open AccessArticle

Effect of Si₃N₄ Addition on Oxidation Resistance of ZrB₂-SiC Composites

by Manab Mallik, Kalyan Kumar Ray and Rahul Mitra

Coatings 2017, 7(7), 92; https://doi.org/10.3390/coatings7070092 - 30 Jun 2017

Cited by 14 | Viewed by 4666

Abstract

The oxidation behavior of ZrB₂-20 vol % SiC and ZrB₂-20 vol % SiC-5 vol % Si₃N₄ composites prepared by hot-pressing and subjected to isothermal exposure at 1200 or 1300 °C for durations of 24 or 100 [...] Read more.

The oxidation behavior of ZrB₂-20 vol % SiC and ZrB₂-20 vol % SiC-5 vol % Si₃N₄ composites prepared by hot-pressing and subjected to isothermal exposure at 1200 or 1300 °C for durations of 24 or 100 h in air, as well as cyclic exposure at 1300 °C for 24 h, have been investigated. The oxidation resistance of the ZrB₂-20 vol % SiC composite has been found to improve by around 20%–25% with addition of 5 vol % Si₃N₄ during isothermal or cyclic exposures at 1200 or 1300 °C. This improvement in oxidation resistance has been attributed to the formation of higher amounts of SiO₂ and Si₂N₂O, as well as a greater amount of continuity in the oxide scale, because these phases assist in closing the pores and lower the severity of cracking by exhibiting self-healing type behavior. For both the composites, the mass changes are found to be higher during cyclic exposure at 1300 °C by about 2 times compared to that under isothermal conditions. Full article

(This article belongs to the Special Issue Ultrahigh Temperature Ceramic Coatings and Composites)

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7468 KiB

Open AccessArticle

Application of FEM to Estimate Thermo-Mechanical Properties of Plasma Sprayed Composite Coatings

by Rodolphe Bolot, Delphine Aussavy and Ghislain Montavon

Coatings 2017, 7(7), 91; https://doi.org/10.3390/coatings7070091 - 30 Jun 2017

Cited by 14 | Viewed by 5517

Abstract

The presence of defects such as voids, inter-lamellar porosities or cracks causes a decrease in the effective thermal conductivity of plasma-sprayed coatings as well as a decrease in corresponding mechanical properties, such as the Young’s modulus. In general, the effective properties of thermal [...] Read more.

The presence of defects such as voids, inter-lamellar porosities or cracks causes a decrease in the effective thermal conductivity of plasma-sprayed coatings as well as a decrease in corresponding mechanical properties, such as the Young’s modulus. In general, the effective properties of thermal spray coatings are thus very different from that of bulk materials and thus have to be quantified to validate in service performances. A complementary approach allowing us to understand the relationships between the microstructure of a coating and its macro-properties is that of Finite Element Modeling (FEM). The case of composite coatings is more complicated still, due to the presence of different materials. In the present study, thermo-mechanical properties of a plasma-sprayed composite coating were estimated by numerical modeling based on FEM. The method applied uses directly cross-sectional micrographs without simplification, using a one-cell per pixel approach. Characteristics such as the thermal conductivity, the Young’s modulus, the Poisson’s ratio and the dilatation coefficient were considered. The example selected was an AlSi/polyester coating used as an abradable seal in the aerospace industry. Full article

(This article belongs to the Special Issue Modelling and Simulation of Coating)

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7665 KiB

Open AccessArticle

Concrete Damage in Field Conditions and Protective Sealer and Coating Systems

by Md. Safiuddin

Coatings 2017, 7(7), 90; https://doi.org/10.3390/coatings7070090 - 29 Jun 2017

Cited by 55 | Viewed by 14291

Abstract

Concrete structures undergo different forms of damage during their service life. The aim of this study is to identify the most common forms of concrete damage in field conditions. A number of concrete elements and structures were visually inspected and the damage was [...] Read more.

Concrete structures undergo different forms of damage during their service life. The aim of this study is to identify the most common forms of concrete damage in field conditions. A number of concrete elements and structures were visually inspected and the damage was photographed. The damage phenomena covered are delamination, popout, spalling, scaling, drying shrinkage cracking, corrosion-induced cracking, map cracking, rust and salt stains, discoloration, and mold and moss growths. The probable reasons for these damage phenomena are discussed in this study. Moreover, this study highlights how concrete structures can be protected from the aforementioned forms of damage by using sealer and coating systems as surface treatments. Different sealer and coating systems, emphasizing their selection for specific uses, installation on concrete substrate, effects on concrete durability, performance criteria, and performance evaluation methods have been discussed. Furthermore, some recommendations are given to improve the performance of concrete sealer and coating systems for the protection of concrete structures in field conditions. Full article

(This article belongs to the Special Issue Surface Treatments and Coatings for Structural Steel and Reinforced Concrete)

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7625 KiB

Open AccessArticle

Ultra-Low Reflectivity Anti-Reflection Coating on a Plastic Cover Slip in Liquid for He-Ne Laser Light

by Jin-Cherng Hsu, Heng-Ying Cho, Tsang-Yen Hsieh and Jyh-Liang Wang

Coatings 2017, 7(7), 89; https://doi.org/10.3390/coatings7070089 - 29 Jun 2017

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Abstract

An ultra-low anti-reflection optical coating on both surfaces of a plastic cover slip was studied for use in confocal image measurements. The optical reflectance at a wavelength of 632.8 nm was less than 0.1% when the coated sample was placed in a liquid [...] Read more.

An ultra-low anti-reflection optical coating on both surfaces of a plastic cover slip was studied for use in confocal image measurements. The optical reflectance at a wavelength of 632.8 nm was less than 0.1% when the coated sample was placed in a liquid having a refractive index of 1.34, close to the aqueous solution of the biomaterial. The high- and low-index coating films, Substance-2 (PrTiO₃) and silicon dioxide (SiO₂), were measured by an ellipsometer to determine their optical refraction indices and extinction coefficients. Theoretically, when the two layer thicknesses are designed using the optical admittance diagram of the cover slip to approach the equivalent index of 1.34, a reflectance of 1.6 × 10⁻⁵% in the liquid could be obtained. Experimentally, the reflectance of the sample deposited on the two faces of the cover slip was 4.223 ± 0.145% as measured in the air; and 0.050 ± 0.002% as measured by a He-Ne laser in the liquid. Full article

(This article belongs to the Special Issue Antireflective Coatings for Glass and Transparent Polymers)

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3461 KiB

Open AccessArticle

Barrier Heights of Au on Diamond with Different Terminations Determined by X-ray Photoelectron Spectroscopy

by Fengnan Li, Jingwen Zhang, Xiaoliang Wang, Minghui Zhang and Hongxing Wang

Coatings 2017, 7(7), 88; https://doi.org/10.3390/coatings7070088 - 29 Jun 2017

Cited by 9 | Viewed by 4448

Abstract

Barrier heights of Au on hydrogen-/oxygen-/fluorine-/nitrogen-terminated diamond (H-/O-/F-/N-diamond) have been investigated by X-ray photoelectron spectroscopy. All of the H-/O-/F-/N-diamond surfaces have been formed on different areas of one diamond sample. An Au film with a thickness of 4 nm was evaporated to form [...] Read more.

Barrier heights of Au on hydrogen-/oxygen-/fluorine-/nitrogen-terminated diamond (H-/O-/F-/N-diamond) have been investigated by X-ray photoelectron spectroscopy. All of the H-/O-/F-/N-diamond surfaces have been formed on different areas of one diamond sample. An Au film with a thickness of 4 nm was evaporated to form Au/diamond contacts. Barrier height values for Au on H-/O-/F-/N-diamond contacts were determined to be −0.19, 1.71, 2.29, and 2.39 eV, respectively. Then, the surface of Au/diamond contacts was treated by 1000 eV Ar⁺ bombardment with different duration of time, resulting in a pinned barrier height of 1.83 eV independent of contact structures. In the end, the spatial distribution of the energy band diagram has been calculated by solving Poisson’s equation. Full article

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5630 KiB

Open AccessArticle

Effect of Cold-Spray Conditions Using a Nitrogen Propellant Gas on AISI 316L Stainless Steel-Coating Microstructures

by Shinichiro Adachi and Nobuhiro Ueda

Coatings 2017, 7(7), 87; https://doi.org/10.3390/coatings7070087 - 28 Jun 2017

Cited by 32 | Viewed by 7208

Abstract

Cold-spray techniques have been a significant development for depositing metal coatings in recent years. In cold-spray processes, inexpensive nitrogen gas is widely used as the propellant gas in many industries. However, it is difficult to produce austenitic stainless steel coatings with dense microstructures [...] Read more.

Cold-spray techniques have been a significant development for depositing metal coatings in recent years. In cold-spray processes, inexpensive nitrogen gas is widely used as the propellant gas in many industries. However, it is difficult to produce austenitic stainless steel coatings with dense microstructures with cold-spray techniques when using nitrogen propellant gas because of work hardening. In this study, the effects of cold-spray conditions using a nitrogen propellant gas on AISI 316L stainless steel coatings were examined. It was found that a higher nitrogen propellant gas temperature and pressure produce coatings with dense microstructures. The measured AISI 316L coating hardness values suggest that AISI 316L particles sprayed at temperatures of 700 and 800 °C soften due to the heat, allowing uniform deformation on the substrate and consequently forming dense coating microstructures. In addition, AISI 316L powder with particle diameters of 5–20 µm resulted in a denser coating microstructure than powder with particle diameters of 10–45 and 20–53 µm. Finally, the standoff distance between the nozzle and the substrate also affected the AISI 316L coating microstructures; a standoff distance of 40 mm produced the densest microstructure. Full article

(This article belongs to the Special Issue Thermal Spray Technology)

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5916 KiB

Open AccessArticle

Oxidation Behavior and Mechanism of Al₄SiC₄ in MgO-C-Al₄SiC₄ System

by Huabai Yao, Xinming Xing, Enhui Wang, Bin Li, Junhong Chen, Jialin Sun and Xinmei Hou

Coatings 2017, 7(7), 85; https://doi.org/10.3390/coatings7070085 - 23 Jun 2017

Cited by 14 | Viewed by 4668

Abstract

Al₄SiC₄ powder with high purity was synthesized using the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800 °C in argon. Their oxidation behavior and mechanism in a MgO-C-Al₄SiC₄ system was investigated at 1400–1600 [...] Read more.

Al₄SiC₄ powder with high purity was synthesized using the powder mixture of aluminum (Al), silicon (Si), and carbon (C) at 1800 °C in argon. Their oxidation behavior and mechanism in a MgO-C-Al₄SiC₄ system was investigated at 1400–1600 °C. XRD, SEM, and energy dispersive spectrometry (EDS) were adopted to analyze the microstructure and phase evolution. The results showed that the composition of oxidation products was closely related to the atom diffusion velocity and the compound oxide layer was generated on Al₄SiC₄ surface. In addition, the effect of different CO partial pressure on the oxidation of Al₄SiC₄ crystals was also studied by thermodynamic calculation. This work proves the great potential of Al₄SiC₄ in improving the MgO-C materials. Full article

(This article belongs to the Special Issue Ultrahigh Temperature Ceramic Coatings and Composites)

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4962 KiB

Open AccessArticle

Silica-Based Sol-Gel Coating on Magnesium Alloy with Green Inhibitors

by Vinod Upadhyay, Zachary Bergseth, Brett Kelly and Dante Battocchi

Coatings 2017, 7(7), 86; https://doi.org/10.3390/coatings7070086 - 22 Jun 2017

Cited by 19 | Viewed by 6127

Abstract

In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate). The inhibitors were quinaldic acid (QDA), betaine (BET), dopamine hydrochloride (DOP), and diazolidinyl urea (DZU). Thin, uniform, and defect-free [...] Read more.

In this work, the performances of several natural organic inhibitors were investigated in a sol-gel system (applied on the magnesium alloy Mg AZ31B substrate). The inhibitors were quinaldic acid (QDA), betaine (BET), dopamine hydrochloride (DOP), and diazolidinyl urea (DZU). Thin, uniform, and defect-free sol-gel coatings were prepared with and without organic inhibitors, and applied on the Mg AZ31B substrate. SEM and EDX were performed to analyze the coating surface properties, the adhesion to the substrate, and the thickness. Electrochemical measurements, including electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization scan (PDS), were performed on the coated samples to characterize the coatings’ protective properties. Also, hydrogen evolution measurement—an easy method to measure magnesium corrosion—was performed in order to characterize the efficiency of coating protection on the magnesium substrate. Moreover, scanning vibrating electrode technique (SVET) measurements were performed to examine the efficiency of the coatings loaded with inhibitors in preventing and containing corrosion events in defect areas. From the testing results it was observed that the formulated sol-gel coatings provided a good barrier to the substrate, affording some protection even without the presence of inhibitors. Finally, when the inhibitors’ performances were compared, the QDA-doped sol-gel was able to contain the corrosion event at the defect. Full article

(This article belongs to the Special Issue Coatings for Corrosion Mitigation)

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8830 KiB

Open AccessArticle

Corrosion Protection of Steel by Epoxy-Organoclay Nanocomposite Coatings

by Domna Merachtsaki, Panagiotis Xidas, Panagiotis Giannakoudakis, Konstantinos Triantafyllidis and Panagiotis Spathis

Coatings 2017, 7(7), 84; https://doi.org/10.3390/coatings7070084 - 22 Jun 2017

Cited by 16 | Viewed by 6592

Abstract

The purpose of the present work was to study the corrosion behavior of steel coated with epoxy-(organo) clay nanocomposite films. The investigation was carried out using salt spray exposures, optical and scanning electron microscopy examination, open circuit potential, and electrochemical impedance measurements. The [...] Read more.

The purpose of the present work was to study the corrosion behavior of steel coated with epoxy-(organo) clay nanocomposite films. The investigation was carried out using salt spray exposures, optical and scanning electron microscopy examination, open circuit potential, and electrochemical impedance measurements. The mechanical, thermomechanical, and barrier properties of pristine glassy epoxy polymer and epoxy-clay nanocomposites were examined. The degree of intercalation/exfoliation of clay nanoplatelets within the epoxy polymer also was determined. The mechanical, thermomechanical, and barrier properties of all the epoxy-clay nanocomposites were improved compared to those of the pristine epoxy polymer. In addition, both the pristine epoxy and the epoxy nanocomposite coatings protected the steel from corrosion. Furthermore, the protective properties of the nanocomposite coatings were superior compared to those of the pristine epoxy polymer. The protective properties of the nanocomposite coatings varied with the modified clay used. The epoxy-montmorillonite clay modified with primary octadecylammonium ions, Nanomer I.30E, had a better behavior than that modified with quaternary octadecylammonium ions, Nanomer I.28E. Full article

(This article belongs to the Special Issue New Generation Coatings for Metals)

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Coatings, Volume 7, Issue 7 (July 2017) – 24 articles

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