Coatings

13 pages, 2453 KiB

Open AccessArticle

ANN Laser Hardening Quality Modeling Using Geometrical and Punctual Characterizing Approaches

by Ilyes Maamri, Noureddine Barka and Abderrazak El Ouafi

Coatings 2018, 8(6), 226; https://doi.org/10.3390/coatings8060226 - 20 Jun 2018

Cited by 3 | Viewed by 3862

Maximum hardness and hardened depth are the responses of interest in relation to the laser hardening process. These values define heat treatment quality and have a direct impact on mechanical performance. This paper aims to develop models capable of predicting the shape of [...] Read more.

Maximum hardness and hardened depth are the responses of interest in relation to the laser hardening process. These values define heat treatment quality and have a direct impact on mechanical performance. This paper aims to develop models capable of predicting the shape of the hardness profile depending on laser process parameters for controlling laser hardening quality (LHQ), or rather the response values. An experimental study was conducted to highlight hardened profile sensitivity to process input parameters such as laser power (P_L), beam scanning speed (V_S) and initial hardness in the core (H_C). LHQ modeling was conducted by modeling attributes extracted from the hardness profile curve using two effective techniques based on the punctual and geometrical approaches. The process parameters with the most influence on the responses were laser power, beam scanning speed and initial hardness in the core. The obtained results demonstrate that the geometrical approach is more accurate and credible than the punctual approach according to performance assessment criteria. Full article

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

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16 pages, 8370 KiB

Open AccessArticle

Interdiffusion at Room Temperature in Cu-Ni(Fe) Nanolaminates

by Alan F. Jankowski

Coatings 2018, 8(6), 225; https://doi.org/10.3390/coatings8060225 - 20 Jun 2018

Cited by 1 | Viewed by 3535

Abstract

The decomposition of a one-dimensional composition wave in Cu-Ni(Fe) nanolaminate structures is quantified using X-ray diffraction to assess kinetics of the interdiffusion process for samples aged at room temperature for 30 years. Definitive evidence for growth to the composition modulation within the chemical [...] Read more.

The decomposition of a one-dimensional composition wave in Cu-Ni(Fe) nanolaminate structures is quantified using X-ray diffraction to assess kinetics of the interdiffusion process for samples aged at room temperature for 30 years. Definitive evidence for growth to the composition modulation within the chemical spinodal is found through measurement of a negative interdiffusivity for each of sixteen different nanolaminate samples over a composition wavelength range of 2.1–10.6 nm. A diffusivity value Ď of 1.77 × 10⁻²⁴ cm²·s⁻¹ is determined for the Cu-Ni(Fe) alloy system, perhaps the first such measurement at a ratio of melt temperature to test temperature that is greater than 5. The anomalously high diffusivity value with respect to bulk diffusion is attributed to the nanolaminate structure that features paths for short-circuit diffusion through interlayer grain boundaries. Full article

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12 pages, 5398 KiB

Open AccessArticle

The Potential of Functionalized Ceramic Particles in Coatings for Improved Scratch Resistance

by Caterina Lesaint Rusu, Malin Brodin, Tor Inge Hausvik, Leif Kåre Hindersland, Gary Chinga-Carrasco, Mari-Ann Einarsrud and Hilde Lea Lein

Coatings 2018, 8(6), 224; https://doi.org/10.3390/coatings8060224 - 19 Jun 2018

Cited by 5 | Viewed by 5996

Abstract

The top layer of a typical high pressure floor laminate (HPL) consists of a melamine formaldehyde (MF) impregnated special wear layer (overlay) with alumina particles. This top layer plays a crucial role in determining the mechanical properties of the laminate. For HPLs, scratch [...] Read more.

The top layer of a typical high pressure floor laminate (HPL) consists of a melamine formaldehyde (MF) impregnated special wear layer (overlay) with alumina particles. This top layer plays a crucial role in determining the mechanical properties of the laminate. For HPLs, scratch resistance and scratch visibility are particularly important properties. This study aimed to improve the mechanical properties, particularly the scratch resistance, by adjusting the composition of the overlay. Laminates containing alumina particles were prepared and tested. These alumina particles were additionally functionalized with a silane coupling agent to ensure better adhesion between the particles and the resin. The functionalized particles led to enhanced scratch resistance of the laminates as well as improved dispersion of the particles within the resin. Micro scratch testing revealed that by using functionalized particles, the scratch surface damage was reduced and the recovery characteristics of the surface layer were improved. Higher scratch resistance and scratch hardness were thus obtained, along with a reduced scratch visibility. Full article

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

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9 pages, 2645 KiB

Open AccessArticle

Tribooxidation as a Way to Improve the Wear Resistance of Cutting Tools

by Dmitry Wainstein and Anatoly Kovalev

Coatings 2018, 8(6), 223; https://doi.org/10.3390/coatings8060223 - 18 Jun 2018

Cited by 15 | Viewed by 3753

Abstract

This paper generalizes the results of our research, which was aimed at the development of adaptive cutting tool coatings for high speed dry cutting, from the inception of the idea to complex multilayer coatings for processing tough metals. Typically, the streams of external [...] Read more.

This paper generalizes the results of our research, which was aimed at the development of adaptive cutting tool coatings for high speed dry cutting, from the inception of the idea to complex multilayer coatings for processing tough metals. Typically, the streams of external energy and matter during high speed cutting are causing damage to the tool materials and to the hard, protective coatings through multiple mechanical and chemical processes including oxidation, however these oxidation processes could be used to improve the tools’ lifetime. The structure and the phase transformations on the wear surface in the nanostructured single layer and nanolaminated multilayer PVD coatings were investigated by a set of electron spectroscopy methods. The dynamics of the secondary phase formation on the various stages of tool life is demonstrated. The obtained results show that the enhancement of non-equilibrium processes during friction leads to a dominating formation of protective triboceramics on a base of sapphire-like, tungsten, and niobium polyvalent oxides with a structure which decisively improves the wear performance. The mechanisms of the formation of non-equilibrium protective oxides at high speed dry cutting and the non-equilibrium thermodynamics approaches for the tribooxidation description are discussed. Polyvalent metals and multilayer coatings provide a wider set of protective oxide nanofilms. Full article

(This article belongs to the Special Issue Surface Engineering and Nanofilms)

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12 pages, 4428 KiB

Open AccessArticle

Stainless Steel Surface Coating with Nanocrystalline Ag Film by Plasma Electrolysis Technology

by Ah-Der Lin, Chi-Liang Kung, You-Qing Cao, Chao-Ming Hsu and Cheng-Yi Chen

Coatings 2018, 8(6), 222; https://doi.org/10.3390/coatings8060222 - 17 Jun 2018

Cited by 7 | Viewed by 4449

Abstract

This paper describes the use of a plasma electrolysis technique to apply a nanosilver coating to the surface of stainless steel to achieve hydrophobic properties. We propose an experimental reaction system, which includes stainless steel 316 as the two electrodes and an aqueous [...] Read more.

This paper describes the use of a plasma electrolysis technique to apply a nanosilver coating to the surface of stainless steel to achieve hydrophobic properties. We propose an experimental reaction system, which includes stainless steel 316 as the two electrodes and an aqueous solution of potassium nitrate (KNO₃), silver nitrate (AgNO₃), and ammonium hydroxide (NH₄OH) as the electrolyte. Better results with a stainless steel surface coated by nanocrystalline Ag film are obtained using optimal parameters chosen through one-factor-at-a-time experiments. The main parameters consist of electrode distance, KNO₃ concentration, and AgNO₃ concentration. The experiment focuses on analyzing the impact of the plasma electrolysis technique on processing time. Variations in KNO₃ concentration show that 3 wt.% yields the worst result because it causes an uneven surface, whereas 5 wt.% gives excellent results because it creates an even, porous surface and the highest contact angle. An AgNO₃ concentration of 0.03 wt.% yields the best contact angle. With the same processing time, silver sediment increases as the KNO₃ concentration increases. With respect to variation in electrode distance, we find that when the distance is set at 20 mm, the contact angle exceeds 100° and results in hydrophobic properties on the specimen surface, while other distances yield a contact angle below 80°, resulting in hydrophilic surfaces. The SEM (scanning electron microscope) results show that the surface of the specimen is full of crater-like cavities that directly affect the contact angle. In this experiment, the contact angle yielding optimum hydrophobic properties is 134° ± 10°. Finally, using distribution patterns obtained by elemental analysis, the experimental results lead to an evenly distributed silver coating on the surface of specimens subjected to plasma electrolysis treatment. The study confirms that plasma electrolysis can be used to coat nanosilver onto stainless steel 316. Full article

(This article belongs to the Special Issue Selected Papers from IEEE ICASI 2018)

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17 pages, 6396 KiB

Open AccessArticle

Surface Treatment of Bacterial Cellulose in Mild, Eco-Friendly Conditions

by Adriana Nicoleta Frone, Denis Mihaela Panaitescu, Ioana Chiulan, Cristian Andi Nicolae, Angela Casarica, Augusta Raluca Gabor, Roxana Trusca, Celina Maria Damian, Violeta Purcar, Elvira Alexandrescu and Paul Octavian Stanescu

Coatings 2018, 8(6), 221; https://doi.org/10.3390/coatings8060221 - 14 Jun 2018

Cited by 28 | Viewed by 6279

Abstract

Bacterial cellulose (BC) with increased hydrophobicity is required for several applications including packaging. Surface functionalization of BC may provide good resistance to moisture, increased barrier properties or improved compatibility to polymer matrices. For this purpose, chemical grafting of BC in mild, eco-friendly conditions [...] Read more.

Bacterial cellulose (BC) with increased hydrophobicity is required for several applications including packaging. Surface functionalization of BC may provide good resistance to moisture, increased barrier properties or improved compatibility to polymer matrices. For this purpose, chemical grafting of BC in mild, eco-friendly conditions was carried out using different agents. BC membranes were surface functionalized with vinyl-triethoxy silane (VS) or 3-aminopropyl triethoxysilane (APS), by acylation and acrylation. The efficiency of the surface treatments was highlighted by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, by contact angle measurements and by dynamic mechanical analysis. The morphological investigation by atomic force microscopy and scanning electron microscopy revealed an increased compactness for surface functionalized BC, which correlated well with the different increase of the contact angle. BC treated with APS and VS showed more than a twofold increase in contact angle value. Similarly, the crystallinity degree was reduced to 69.6% and 72.9% after APS and VS treatments as compared with 84.1% for untreated BC, confirming the grafting reaction and the decrease in hydrogen bonding. All the applied treatments delayed the degradation of BC. However, the highest increase in thermal stability was observed for silanes treated membranes. Effective, eco-friendly methods for improving the surface hydrophobicity of bacterial cellulose for food packaging were proposed in this study. Full article

(This article belongs to the Special Issue Surface Modification of Cellulose Fibres)

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19 pages, 2272 KiB

Open AccessEditor’s ChoiceArticle

Chromium Carbide Growth by Direct Liquid Injection Chemical Vapor Deposition in Long and Narrow Tubes, Experiments, Modeling and Simulation

by Alexandre Michau, Francis Maury, Frederic Schuster, Ioana Nuta, Yoan Gazal, Rapahel Boichot and Michel Pons

Coatings 2018, 8(6), 220; https://doi.org/10.3390/coatings8060220 - 13 Jun 2018

Cited by 22 | Viewed by 6363

Abstract

Chromium carbide layers were deposited using liquid-injection metal-organic chemical vapor deposition inside long (0.3 to 1 m) and narrow (8 to 24 mm in diameter) metallic tubes. The deposition was carried out using a molecular single-source, bis(benzene)chromium (BBC), as representative of the bis(arene)metal [...] Read more.

Chromium carbide layers were deposited using liquid-injection metal-organic chemical vapor deposition inside long (0.3 to 1 m) and narrow (8 to 24 mm in diameter) metallic tubes. The deposition was carried out using a molecular single-source, bis(benzene)chromium (BBC), as representative of the bis(arene)metal family diluted in toluene and injected with N₂ as carrier gas. A multicomponent mass transport model for the simulation of the coupled fluid flow, heat transfer and chemistry was built. The kinetic mechanism of the growth of CrC_x films was developed with the help of large-scale experiments to study the depletion of the precursors along the inner wall of the tube. The model fits well in the 400–550 °C temperature range and in the 1.3 × 10² to 7 × 10³ Pa pressure range. The pressure is shown to have a pronounced effect on the deposition rate and thickness uniformity of the resulting coating. Below 525 °C the structure, composition and morphology of the films are not affected by changes of total pressure or deposition temperature. The coatings are amorphous and their Cr:C ratio is about 2:1, i.e., intermediate between Cr₇C₃ and Cr₃C₂. The model was applied to the design of a long reactor (1 m), with a double injection successively and alternatively undertaken at each end to ensure the best uniformity with sufficient thickness. This innovative concept can be used to optimize industrial deposition processes inside long and narrow tubes and channels. Full article

(This article belongs to the Special Issue Chemical Vapor Deposition 2018)

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17 pages, 3585 KiB

Open AccessArticle

Thermo-Mechanical Finite Element Modeling of the Laser Treatment of Titanium Cold-Sprayed Coatings

by Felice Rubino, Antonello Astarita and Pierpaolo Carlone

Coatings 2018, 8(6), 219; https://doi.org/10.3390/coatings8060219 - 12 Jun 2018

Cited by 15 | Viewed by 4478

Abstract

This paper implements a thermo-mechanical model to simulate the laser treatment effects on a cold-sprayed titanium coating and aluminum substrate. The thermo-mechanical finite element model considers the transient temperature field due to the laser source and applied boundary conditions, using them as input [...] Read more.

This paper implements a thermo-mechanical model to simulate the laser treatment effects on a cold-sprayed titanium coating and aluminum substrate. The thermo-mechanical finite element model considers the transient temperature field due to the laser source and applied boundary conditions, using them as input loads for the subsequent stress-strain analysis. Numerical outcomes highlighted the relevance of thermal gradients and the presence of thermally-induced stress-strain fields responsible for promoting damage in the coating. Full article

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

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10 pages, 4219 KiB

Open AccessArticle

Oxidation Behavior of MoSi₂-Coated TZM Alloys during Isothermal Exposure at High Temperatures

by Kwangsu Choi, Young Joo Kim, Min Kyu Kim, Sangyeob Lee, Seong Lee and Joon Sik Park

Coatings 2018, 8(6), 218; https://doi.org/10.3390/coatings8060218 - 11 Jun 2018

Cited by 14 | Viewed by 4362

Abstract

Coating properties and oxidation behaviors of Si pack cementation-coated TZM (Mo-0.5Ti-0.1Zr-0.02C) alloys were investigated in order to understand the stability of the coating layer at high temperatures up to 1350 °C in an ambient atmosphere. After the pack cementation coatings, MoSi₂ and [...] Read more.

Coating properties and oxidation behaviors of Si pack cementation-coated TZM (Mo-0.5Ti-0.1Zr-0.02C) alloys were investigated in order to understand the stability of the coating layer at high temperatures up to 1350 °C in an ambient atmosphere. After the pack cementation coatings, MoSi₂ and Mo₅Si₃ layers were formed. When MoSi₂-coated TZM alloys were oxidized in air at high temperatures, the Si in the outer MoSi₂ layer diffused and formed SiO₂. Also, due to the diffusion of Si, the MoSi₂ layer was transformed into a columnar shaped Mo₅Si₃ phase. During isothermal oxidation, the Mo₅Si₃ phase was formed both within the coated MoSi₂ layer and between the MoSi₂ and the substrate. The coating properties and the oxidation behavior of the Si pack-coated TZM alloys were discussed along with the identification of growth kinetics. Full article

(This article belongs to the Special Issue Coatings for Harsh Environments)

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13 pages, 2051 KiB

Open AccessArticle

On the Activity Enhancing Role of Iron Oxide for Noble Metal Oxidation Catalysts: A CVD-Based Study with Differently Structured Combinations of Pt and FeO_x Coatings on Al₂O₃

by Laila Pasin, Jörg Meyer, Elisabeth Eiche and Gerhard Kasper

Coatings 2018, 8(6), 217; https://doi.org/10.3390/coatings8060217 - 11 Jun 2018

Cited by 3 | Viewed by 4279 | Correction

Abstract

With regard to the catalysis of oxidation reactions by noble metals, the addition of FeO_x to an Al₂O₃-supported Pt catalyst is known to be energetically more favorable compared to only Pt. In this work, different process routes for [...] Read more.

With regard to the catalysis of oxidation reactions by noble metals, the addition of FeO_x to an Al₂O₃-supported Pt catalyst is known to be energetically more favorable compared to only Pt. In this work, different process routes for the preparation of such Fe-promoted Pt/Al₂O₃ catalysts via atmospheric chemical vapor deposition (CVD) in a fluidized bed were explored. Specifically, the question of whether it would be advantageous to deposit the Fe before, along with, or after the Pt was addressed, and new information was obtained about the optimum FeO_x–Pt interface and mixing ratio. Vapors of Trimethyl(methylcyclopentadienyl)platinum(IV) and/or Ethyl-ferrocene were injected into the bed from the top, permitting a quasi-lossless precursor operation and a very good control of the deposited metal, and hence of the catalyst structure. Samples could be extracted from the top while CVD was ongoing to obtain time-resolved data. The catalytic activity was determined through CO oxidation. The Fe-Pt mixing ratio was then varied for the most active deposition sequence, in order to identify an activity optimum generated by the minimum amount of Pt catalyst. When compared to pure Pt/Al₂O₃, the optimum catalyst consistently showed superior performance even after thermal stress. Full article

(This article belongs to the Special Issue Chemical Vapor Deposition 2018)

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11 pages, 2745 KiB

Open AccessArticle

Improvement of Corrosion Resistance for Gray Cast Iron in Palm Biodiesel Application Using Thermoreactive Diffusion Niobium Carbide (NbC) Coating

by Ariel Amaya, Oscar Piamba and Jhon Olaya

Coatings 2018, 8(6), 216; https://doi.org/10.3390/coatings8060216 - 07 Jun 2018

Cited by 18 | Viewed by 5031

Abstract

Biodiesel is a renewable fuel consisting of alkyl esters, which show a higher corrosive behavior when compared with a diesel fuel. The corrosive processes by biodiesel affects the processing infrastructure of this biofuel and mechanical parts of automotives. Valves, engine blocks, and cylinder [...] Read more.

Biodiesel is a renewable fuel consisting of alkyl esters, which show a higher corrosive behavior when compared with a diesel fuel. The corrosive processes by biodiesel affects the processing infrastructure of this biofuel and mechanical parts of automotives. Valves, engine blocks, and cylinder liners are gray cast iron components affected by biodiesel corrosion. The corrosion resistance of niobium carbide (NbC) coatings deposited using thermoreactive diffusion (TRD) on gray cast iron in continuous contact with diesel fuel and palm biodiesel was studied. Both coated and uncoated samples were subjected to immersion tests, cyclic oxidation at 473 K, and an electrochemical impedance spectroscopy (EIS) test. The coatings were characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Both the rate of corrosion by immersion and the resistance to polarization via EIS showed the favorable behavior of niobium carbide coatings against the corrosion of palm biodiesel. The corrosion rate on samples coated with niobium carbide was three times lower than that of the gray casting samples. These results allow the conclusion that niobium carbide coatings could be a viable alternative to lessening the corrosive effects of palm biodiesel in the applications where gray cast iron is used in continuous contact with biofuel. Full article

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14 pages, 5177 KiB

Open AccessArticle

Surface Modification of Esophageal Stent Materials by a Drug-Eluting Layer for Better Anti-Restenosis Function

by Yuxin Bai, Kun Zhang, Ru Xu, Hongtao Liu, Fangxia Guan, Huiwen Luo, Ye Chen and Jingan Li

Coatings 2018, 8(6), 215; https://doi.org/10.3390/coatings8060215 - 06 Jun 2018

Cited by 14 | Viewed by 4878

Abstract

It is generally accepted that stent implantation is the mainstream therapy in clinics for esophageal cancer in the later period. However, the restenosis caused by tumor cells, epithelial cells, and fibroblasts seriously interferes with the stent medical application and limits its long-term services. [...] Read more.

It is generally accepted that stent implantation is the mainstream therapy in clinics for esophageal cancer in the later period. However, the restenosis caused by tumor cells, epithelial cells, and fibroblasts seriously interferes with the stent medical application and limits its long-term services. To address this conundrum, a series of drug-eluting stents were invented and verified to be feasible in the early stage after implantation, but the limited drug loading and good cell compatibility of the stent materials may lead to more serious restenosis and further endanger the patient’s life. In previous work, we modified the esophageal stent material 317L stainless steel (317L SS) surface with a poly-dopamine/poly-ethylenimine layer (PDA/PEI), which had strong anti-tumor functions. In this contribution, we employed a usual drug in clinic, 5-fluorouracil (5-Fu), with series of density onto the PDA/PEI modified 317L SS to investigate the influence of 5-Fu immobilization on the anti-restenosis function. The surface characterization including 5-Fu quantity, atomic force microscopy (AFM). Water contact angle measurement indicated successful preparation of the PDA/PEI/5-Fu layers. The spectrophotometric characterization revealed that the immobilized 5-Fu rapidly released over 24 h. However, the Eca109, Het-1A, and L929 cells culture results suggested that the released 5-Fu made a significant contribution to improving the apoptosis and necrosis of these pathological cells, and the PDA/PEI/5-Fu layers maintain the consistent anti-restenosis function on their surfaces with the PDA/PEI layer after 24 h. All the results demonstrated the PDA/PEI/5-Fu layers’ excellent ability to suppress esophageal tumor cells, epithelial cells, and fibroblasts, suggesting a potential application on the surface modification of esophageal stents for better anti-restenosis function. 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, 9107 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Flake Boron Nitride Prepared from the Low Temperature Combustion Synthesized Precursor and Its Application for Dye Adsorption

by Jinglong Qu, Qun Li, Chang Luo, Jin Cheng and Xinmei Hou

Coatings 2018, 8(6), 214; https://doi.org/10.3390/coatings8060214 - 04 Jun 2018

Cited by 61 | Viewed by 5873

Abstract

Flake boron nitride (BN) in large yield was successfully synthesized at low temperature from the combustion synthesized precursor. The precursor was prepared by a low-temperature (350 °C) combustion synthesis (LCS) method using nitric acid (HNO₃), urea (CO(NH₂)₂), [...] Read more.

Flake boron nitride (BN) in large yield was successfully synthesized at low temperature from the combustion synthesized precursor. The precursor was prepared by a low-temperature (350 °C) combustion synthesis (LCS) method using nitric acid (HNO₃), urea (CO(NH₂)₂), boric acid (H₃BO₃), and glucose (C₆H₁₂O₆·H₂O) as starting materials. The precursor consists of B₂O₃ and amorphous carbon and the morphology is composed of blocks with average diameters of about 10 μm by statistical methods using SEM at different fields. Then BN was synthesized at 900 °C in NH₃ at a heating rate of 5 °C min⁻¹. The as-prepared BN possesses a flake morphology and high specific surface area up to 936 m² g⁻¹. It also has high density structural defects and abundant –NH₂/–OH groups. The surface groups improve its water wettability and electronegativity, which contributes to the rapid and selective adsorption performance, especially towards the cationic dyes. When 4 mg of the sample was added into a 100 mL RhB solution with an initial concentration of 5 mg L⁻¹, 95% of the RhB was removed within 1 min and the adsorption capacity is 125 mg g⁻¹. Importantly, the sample can be regenerated by heating at 400 °C in air. Full article

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11 pages, 5143 KiB

Open AccessArticle

Superconducting Niobium Coatings Deposited on Spherical Substrates in Molten Salts

by Anton Dubrovskiy, Maksim Okunev, Olga Makarova and Sergey Kuznetsov

Coatings 2018, 8(6), 213; https://doi.org/10.3390/coatings8060213 - 04 Jun 2018

Cited by 14 | Viewed by 3846

Abstract

The interaction of substrates from ceramics, beryllium, and carbopyroceram with the electrolyte for the electrodeposition of niobium coatings was investigated. The corrosion resistance of spherical ceramic and beryllium samples with the protective molybdenum films obtained by magnetron sputtering was studied. The exfoliation of [...] Read more.

The interaction of substrates from ceramics, beryllium, and carbopyroceram with the electrolyte for the electrodeposition of niobium coatings was investigated. The corrosion resistance of spherical ceramic and beryllium samples with the protective molybdenum films obtained by magnetron sputtering was studied. The exfoliation of molybdenum film from ceramics and beryllium samples was observed after the experiments due to the interaction of substrates with the melt. It was found that the carbopyroceram did not corrode in the niobium containing melt and this material was chosen as the substrate for the electrodeposition of superconducting niobium coatings. The influence of the oxide ions on the electrochemical behavior of niobium complexes in the NaCl–KCl–NaF–K₂NbF₇ melt was studied. A special form of the cathode was constructed for the electrodeposition of niobium coatings on spherically shaped substrates. Electrodeposition of the niobium coatings on spheres 10 mm in diameter manufactured from carbopyroceram was carried out at 750 °C with the cathodic current density of 5 × 10⁻³–2 × 10⁻² A·cm⁻² and the electrolysis time of 8–12 h. Influence of the cathodic current density on the microstructure of niobium coatings was studied. The roughness, nonsphericity, and superconductive properties of niobium coatings were determined. Full article

(This article belongs to the Special Issue Thin Films and Patterned Structures by Electrochemical Methods)

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15 pages, 5107 KiB

Open AccessArticle

Conductive Characteristics of Indium Tin Oxide Thin Film on Polymeric Substrate under Long-Term Static Deformation

by Dinh-Phuc Tran, Hung-I Lu and Chih-Kuang Lin

Coatings 2018, 8(6), 212; https://doi.org/10.3390/coatings8060212 - 01 Jun 2018

Cited by 40 | Viewed by 7677

Abstract

The objective of this study is to investigate the effect of long-term static bending on the conductive characteristics of indium tin oxide (ITO) thin film in flexible optoelectronics. Two types of substrate are considered, namely ITO on polyethylene naphthalate (ITO/PEN) and ITO on [...] Read more.

The objective of this study is to investigate the effect of long-term static bending on the conductive characteristics of indium tin oxide (ITO) thin film in flexible optoelectronics. Two types of substrate are considered, namely ITO on polyethylene naphthalate (ITO/PEN) and ITO on polyethylene terephthalate (ITO/PET). Electrical properties of the ITO/PEN and ITO/PET sheets are measured in situ under static bending at various radii of curvature. Experimental results indicate that no significant change in electrical resistance of the ITO/PEN and ITO/PET sheets is found for compressive bending after 1000 h at a curvature radius of 10 mm or larger. However, the ITO/PEN and ITO/PET sheets are seriously damaged under a tensile bending of 10 mm radius and 5 mm radius, respectively. The given ITO/PET sheet exhibits a greater resistance to long-term mechanical bending than the ITO/PEN one, which is attributed to the effect of stiffness and thickness of substrate. As the given PET substrate has a lower stiffness and thickness than the PEN one, ITO thin film in the ITO/PET sheet has a smaller stress given a bending radius. Consequently, a smaller extent of change in the electrical conductance of ITO thin film is found in the ITO/PET sheet. Full article

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13 pages, 3242 KiB

Open AccessArticle

Characterization of Ultrasonic-Assisted Electrochemical Deposition of Ni-Co-ZrO₂

by Yiyong Wang, Xinyu Zhou, Zhipeng Liang and Hui Jin

Coatings 2018, 8(6), 211; https://doi.org/10.3390/coatings8060211 - 01 Jun 2018

Cited by 16 | Viewed by 4476

Abstract

In order to evaluate the electrochemical behavior of nano-ZrO₂ particles in the co-deposition process, revealing the electrocrystallization mechanism and electrodeposition parameters of composite coatings, cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) techniques were used to offer a favorable reference [...] Read more.

In order to evaluate the electrochemical behavior of nano-ZrO₂ particles in the co-deposition process, revealing the electrocrystallization mechanism and electrodeposition parameters of composite coatings, cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) techniques were used to offer a favorable reference for electrochemical studies in an acidic amino sulfonate bath, and the kinetic parameters were calculated by fitting the experimental curves. The CV results suggested that the co-deposition of nano-ZrO₂ particles and matrix metal caused the initial deposition potential of Ni²⁺ and Co²⁺ to shift to more positive values (−0.80 V vs SCE) while the nano-ZrO₂ inhibited the reduction of H⁺ and decreased the cathodic polarization in co-deposition. The electrocrystallization of Ni-Co and Ni-Co-ZrO₂ sedimentary layer were governed by the Scharifker–Hill instantaneous nucleation model, and the nucleation rate of composite coatings was higher at potentials ranging from −1.10 to −1.15 V, and nano-ZrO₂ absorbed on an electrode surface promoted the nucleation/growth of Ni²⁺ and Co²⁺. However, nano-ZrO₂ particles hindered the nucleation/growth of Ni²⁺ and Co²⁺ at −1.20 and −1.25 V vs. SCE; the calculated results were consistent with the theoretical analysis of experimental curves. An EIS test indicated that the incorporation of nano-ZrO₂ particles into the matrix did not obviously effect the electric double layer at the electrode/electrolyte interface, but the charged transfer resistance of the composite was decreased in the electrodeposition. Full article

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14 pages, 2375 KiB

Open AccessArticle

Omnidirectional SiO₂ AR Coatings

by Sadaf Bashir Khan, Hui Wu and Zhengjun Zhang

Coatings 2018, 8(6), 210; https://doi.org/10.3390/coatings8060210 - 01 Jun 2018

Cited by 5 | Viewed by 4986

Abstract

It is of great importance to develop antireflective (AR) coatings and techniques because improved optical performance has been progressively prerequisite for wide-ranging applications such as flat panel displays, optoelectronic devices or solar cells. Natural surroundings inspire researchers considerably to impersonate in order to [...] Read more.

It is of great importance to develop antireflective (AR) coatings and techniques because improved optical performance has been progressively prerequisite for wide-ranging applications such as flat panel displays, optoelectronic devices or solar cells. Natural surroundings inspire researchers considerably to impersonate in order to provoke analogous characteristics via artificial approaches, which provide the opportunity for emerging techniques and development in material engineering. Herein, SiO₂ antireflective (AR) coatings comprised of two layers were fabricated using a physical vapour deposition method via glancing angle. The top layer fabricated at an oblique angle of 80° and the bottom layer close to the substrate was deposited at a deposition angle of 0°. The experimental outcomes demonstrate that there is a slight influence on the refractive index of thin films by changing the morphology of nanostructures keeping deposition angles the same. The top layer shows a periodic arrangement of SiO₂ nanostructures while the bottom stratum represents a SiO₂ compact dense layer. The assembled bilayer SiO₂ AR coating retains omnidirectional AR efficiency and tunability at a preferred wavelength range displaying <1% reflectance. Moreover, the fabricated omnidirectional SiO₂ AR coatings have thermal stability up to 300 °C. These SiO₂ AR coatings also possess negative temperature resistivity to withstand different cold storage conditions. Hence, the flexible and environmental adaptive SiO₂ AR coating offers an intriguing route for imminent research in optics. Full article

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

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13 pages, 8246 KiB

Open AccessArticle

Corrosion Resistance of Waterborne Epoxy Coatings by Incorporation of Dopamine Treated Mesoporous-TiO₂ Particles

by Na Wang, Xinlin Diao, Jing Zhang and Ping Kang

Coatings 2018, 8(6), 209; https://doi.org/10.3390/coatings8060209 - 31 May 2018

Cited by 40 | Viewed by 5582

Abstract

In this paper, waterborne epoxy (EP) coatings were modified by the incorporation of synthetic structure (DA/meso-TiO₂) to improve the anticorrosion ability of waterborne epoxy coatings for steel structures. Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption–desorption, X-ray diffraction (XRD) and thermo-gravimetric analyses [...] Read more.

In this paper, waterborne epoxy (EP) coatings were modified by the incorporation of synthetic structure (DA/meso-TiO₂) to improve the anticorrosion ability of waterborne epoxy coatings for steel structures. Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption–desorption, X-ray diffraction (XRD) and thermo-gravimetric analyses (TGA) were used to characterize textural properties of DA/meso-TiO₂. Corrosion performances of mild carbon steel coated samples were tested by salt spray tests and employing electrochemical impedance spectroscopy (EIS). FTIR, XRD, TGA and nitrogen adsorption–desorption attested to dopamine polymerization within the mesopores and on the surface of meso-TiO₂. The results of EIS and salt spray test showed that the specimen coated with 1.0 wt % DA/meso-TiO₂ exhibited optimum corrosion performance among other coating specimens. Full article

(This article belongs to the Collection Advanced Surface Coating of Nanoparticles)

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33 pages, 9416 KiB

Open AccessReview

Recent Progress in Preparation and Anti-Icing Applications of Superhydrophobic Coatings

by Yuebin Lin, Haifeng Chen, Guanyu Wang and Aihui Liu

Coatings 2018, 8(6), 208; https://doi.org/10.3390/coatings8060208 - 31 May 2018

Cited by 128 | Viewed by 11445

Abstract

Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of [...] Read more.

Aircraft icing refers to ice formation and accumulation on the windward surface of aircrafts. It is mainly caused by the striking of unstable supercooled water droplets suspended in clouds onto a solid surface. Aircraft icing poses an increasing threat to the safety of flight due to the damage of aerodynamic shape. This review article provides a comprehensive understanding of the preparation and anti-icing applications of the superhydrophobic coatings applied on the surface of aircrafts. The first section introduces the hazards of aircraft icing and the underlying formation mechanisms of ice on the surface of aircrafts. Although some current anti-icing and de-icing strategies have been confirmed to be effective, they consume higher energy and lead to some fatigue damages to the substrate materials. Considering the icing process, the functional coatings similar to lotus leaf with extreme water repellency and unusual self-cleaning properties have been proposed and are expected to reduce the relied degree on traditional de-icing approaches and even to replace them in near future. The following sections mainly discuss the current research progress on the wetting theories of superhydrophobicity and main methods to prepare superhydrophobic coatings. Furthermore, based on the bouncing capacity of impact droplets, the dynamic water repellency of superhydrophobic coatings is discussed as the third evaluated parameter. It is crucial to anti-icing applications because it describes the ability of droplets to rapidly bounce off before freezing. Subsequently, current studies on the application of anti-icing superhydrophobic coatings including the anti-icing mechanisms and application status are introduced in detail. Finally, some limitations and issues related to the anti-icing applications are proposed to provide a future outlook on investigations of the superhydrophobic anti-icing coatings. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings)

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13 pages, 2665 KiB

Open AccessEditor’s ChoiceArticle

Application of Nanofibrillated Cellulose on BOPP/LDPE Film as Oxygen Barrier and Antimicrobial Coating Based on Cold Plasma Treatment

by Peng Lu, Mengya Guo, Zhijun Xu and Min Wu

Coatings 2018, 8(6), 207; https://doi.org/10.3390/coatings8060207 - 30 May 2018

Cited by 37 | Viewed by 9488

Abstract

The application of nanofibrillated cellulose (NC) films in packaging industry has been hindered by its lack of heat-sealing ability. Incorporation of NC films with the biaxially oriented polypropylene/low density polyethylene (BOPP/LDPE) laminates can take advantage of each material and endow the films with [...] Read more.

The application of nanofibrillated cellulose (NC) films in packaging industry has been hindered by its lack of heat-sealing ability. Incorporation of NC films with the biaxially oriented polypropylene/low density polyethylene (BOPP/LDPE) laminates can take advantage of each material and endow the films with novel functions for food packaging applications. In this study, a coating that consists of NC and nisin was applied onto a cold plasma treated BOPP/LDPE film to fabricate a novel active packaging with an improved oxygen barrier performance and an added antimicrobial effect. The results showed that cold plasma treatment improved the surface hydrophilicity of BOPP/LDPE films for better attachment of the coatings. NC coatings significantly enhanced oxygen barrier property of the BOPP/LDPE film, with an oxygen transmission rate as low as 24.02 cc/m²·day as compared to that of the non-coated one (67.03 cc/m²·day). The addition of nisin in the coating at a concentration of 5 mg/g caused no significant change in barrier properties but imparted the film excellent antimicrobial properties, with a growth inhibition of L. monocytogenes by 94%. All films exhibit satisfying mechanical properties and transparency, and this new film has the potential to be used as antimicrobial and oxygen barrier packaging. Full article

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18 pages, 13951 KiB

Open AccessEditor’s ChoiceArticle

Surface Aging Effect on Tire/Pavement Noise Medium-Term Evolution in a Medium-Size City

by Víctor F. Vázquez, Fernando Terán, Pedro Huertas and Santiago Expósito Paje

Coatings 2018, 8(6), 206; https://doi.org/10.3390/coatings8060206 - 30 May 2018

Cited by 10 | Viewed by 3931

Abstract

This paper presents the geo-referenced acoustical results obtained throughout the close proximity noise (CPX) technique carried out on different urban sections included within the 2017 strategic noise mapping (Directive 2002/49/CE) in Ciudad Real, a Spanish medium-sized city. The employed methodology quantifies the tire/pavement [...] Read more.

This paper presents the geo-referenced acoustical results obtained throughout the close proximity noise (CPX) technique carried out on different urban sections included within the 2017 strategic noise mapping (Directive 2002/49/CE) in Ciudad Real, a Spanish medium-sized city. The employed methodology quantifies the tire/pavement noise generated in the contact between the tire and the surface of the studied sections. Measurements were carried out in different research campaigns between 2008 and 2015 (medium-term evolution). They give valuable information about the pavement-aging effect on its surface characteristics. Throughout these years, the acoustic situation of these sections has worsened mainly due to surface damage and higher mean profile depth (MPD) values, although the performance does not follow the same pattern in every section. The relationships between measured tire/pavement noise and theoretical environmental noise, just due to the geometric spreading of sound energy, is also studied in order to elaborate a simple rolling noise mapping and to assess the environmental noise evolution. Traffic noise plays the main role in the noise registered within the assessed sections, therefore, CPX assessment could be used by local authorities to take decisions regarding urban planning and traffic management, with the aim of reducing noise exposure from traffic. Full article

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8 pages, 1549 KiB

Open AccessArticle

Preparation and Photoluminescence of Tungsten Disulfide Monolayer

by Yanfei Lv, Feng Huang, Luxi Zhang, Jiaxin Weng, Shichao Zhao and Zhenguo Ji

Coatings 2018, 8(6), 205; https://doi.org/10.3390/coatings8060205 - 30 May 2018

Cited by 10 | Viewed by 5586

Abstract

Tungsten disulfide (WS₂) monolayer is a direct band gap semiconductor. The growth of WS₂ monolayer hinders the progress of its investigation. In this paper, we prepared the WS₂ monolayer through chemical vapor transport deposition. This method makes it easier [...] Read more.

Tungsten disulfide (WS₂) monolayer is a direct band gap semiconductor. The growth of WS₂ monolayer hinders the progress of its investigation. In this paper, we prepared the WS₂ monolayer through chemical vapor transport deposition. This method makes it easier for the growth of WS₂ monolayer through the heterogeneous nucleation-and-growth process. The crystal defects introduced by the heterogeneous nucleation could promote the photoluminescence (PL) emission. We observed the strong photoluminescence emission in the WS₂ monolayer, as well as thermal quenching, and the PL energy redshift as the temperature increases. We attribute the thermal quenching to the energy or charge transfer of the excitons. The redshift is related to the dipole moment of WS₂. Full article

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

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9 pages, 1450 KiB

Open AccessFeature PaperArticle

Application of Oxovanadium Complex Stabilized by N,N,N,N-Chelating Ligand in Air-Drying Paints

by Iva Charamzová, Jaromír Vinklárek, Petr Kalenda and Jan Honzíček

Coatings 2018, 8(6), 204; https://doi.org/10.3390/coatings8060204 - 28 May 2018

Cited by 9 | Viewed by 4279

Abstract

New vanadium-based drier, stabilized with macrocyclic chelating ligand, is described. Its drying activity was established on solvent-borne alkyd resins of different oil-length modified by soybean oil. The test coatings were characterized by standardized mechanical tests as well as spectroscopic methods. Time-resolved infrared spectroscopy [...] Read more.

New vanadium-based drier, stabilized with macrocyclic chelating ligand, is described. Its drying activity was established on solvent-borne alkyd resins of different oil-length modified by soybean oil. The test coatings were characterized by standardized mechanical tests as well as spectroscopic methods. Time-resolved infrared spectroscopy was used for determination of kinetic parameters of the autoxidation process while the EPR (electron paramagnetic resonance) spectroscopy enabled confirmation of stability of oxovanadium(IV) species in the cured films. The obtained experimental data revealed promising catalytic activity of the oxovanadium(IV) compound stabilized with N,N,N,N-chelating ligand at low concentration. At 0.03 wt % of metal in dry matter content, it shows short total dry times not exceeding 12 h while commercial cobalt(II) 2-ethylhexanoate is, at the same concentration, considerably lower active with total dry times 15.4 h (alkyd of short oil-length) and >24 h (alkyd of medium oil-length). Full article

(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)

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14 pages, 5302 KiB

Open AccessArticle

Osteogenesis and Antibacterial Activity of Graphene Oxide and Dexamethasone Coatings on Porous Polyetheretherketone via Polydopamine-Assisted Chemistry

by Ling Ouyang, Meiyao Qi, Shengnan Wang, Shan Tu, Bogang Li, Yi Deng and Weizhong Yang

Coatings 2018, 8(6), 203; https://doi.org/10.3390/coatings8060203 - 28 May 2018

Cited by 26 | Viewed by 5989

Abstract

Endowing implants with antibacterial ability and osteogenic ability plays important roles in preventing post-operative bacterial contamination and facilitating integration between implants and osseous tissue, consequently reducing implant failure rates. In this study, we develop a facile and versatile strategy with dopamine as an [...] Read more.

Endowing implants with antibacterial ability and osteogenic ability plays important roles in preventing post-operative bacterial contamination and facilitating integration between implants and osseous tissue, consequently reducing implant failure rates. In this study, we develop a facile and versatile strategy with dopamine as an auxiliary for construction of dexamethasone (Dex)/liposome porous coatings. In detail, the surfaces of sulfonated polyetheretherketone (SP) plates are coated with polydopamine firstly and then modified with graphene oxide (GO) and dexamethasone (Dex)-loaded liposome, which is verified by contact angle, X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR), and Raman spectra. The results of our study suggest that the GO and Dex are successfully coated on the samples’ surfaces. In vitro cell attachment, growth, differentiation, and apatite deposition tests all illustrate that the substrate coated with GO and Dex can significantly accelerate the proliferation and osteogenic differentiation of MC3T3 cells compared with the pristine sulfonated polyetheretherketone (PEEK). Additionally, it exhibits acceptable antibacterial activity against E. coli and S. aureus in vitro. Altogether, our results demonstrate that the modified GO- and Dex-loaded substrates are endowed with impressive biocompatibility and certain antibacterial qualities, making it possible for future application as a perspective implant material. Full article

(This article belongs to the Special Issue Advanced Bioadhesive and Bioabhesive Coatings)

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13 pages, 5861 KiB

Open AccessArticle

Tribocorrosion Properties of PEO Coatings Produced on AZ91 Magnesium Alloy with Silicate- or Phosphate-Based Electrolytes

by Luca Pezzato, Dragos Vranescu, Marco Sinico, Claudio Gennari, Alessio Giorgio Settimi, Pietro Pranovi, Katya Brunelli and Manuele Dabalà

Coatings 2018, 8(6), 202; https://doi.org/10.3390/coatings8060202 - 25 May 2018

Cited by 28 | Viewed by 5009

Abstract

In this work, the tribocorrosion behavior of plasma electrolytic oxidation (PEO)-coated AZ91 samples was studied. In particular, two different coatings were produced and compared. One was obtained with an alkaline electrolyte containing sodium phosphate, whereas the other one was produced with an alkaline [...] Read more.

In this work, the tribocorrosion behavior of plasma electrolytic oxidation (PEO)-coated AZ91 samples was studied. In particular, two different coatings were produced and compared. One was obtained with an alkaline electrolyte containing sodium phosphate, whereas the other one was produced with an alkaline electrolyte containing sodium silicate. The coatings were characterized with SEM-EDS and XRD techniques, and after the tribocorrosion tests, the wear scars were analyzed with SEM-EDS. The tribocorrosion behavior was evaluated measuring the OCP during a pin on disk test performed in an aggressive environment. Moreover, potentiodynamic polarization and electrochemical impedance spectroscopy tests were performed, to evaluate the corrosion resistance of the different samples in the absence of wear phenomena. The behavior of all the PEO-treated specimens was compared with the one of the untreated sample. A remarkable increase in the tribocorrosion performances after the PEO treatments was observed. Moreover, the samples obtained with the electrolyte containing silicates showed higher tribocorrosion performances. Full article

(This article belongs to the Special Issue Advances in Functional Inorganic Coatings)

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11 pages, 26644 KiB

Open AccessArticle

Adhesion Performance of Electrodeposited Ni Films with Different Treating Methods

by Rui Liu, Yanyan Yuan, Hong Wang and Xi Guo

Coatings 2018, 8(6), 201; https://doi.org/10.3390/coatings8060201 - 25 May 2018

Cited by 2 | Viewed by 3953

Abstract

The adhesion strength between thin films has a significant effect on performance of micro-devices. It is introduced that the effects of three pre-treatment methods: acid, pulse reverse current and anodic current, on the adhesion performance of electrodeposited Ni films on Ni substrate. The [...] Read more.

The adhesion strength between thin films has a significant effect on performance of micro-devices. It is introduced that the effects of three pre-treatment methods: acid, pulse reverse current and anodic current, on the adhesion performance of electrodeposited Ni films on Ni substrate. The adhesion strength, surface and fracture morphology of the Ni films were investigated. The dense oxide films on the Ni substrate were removed effectively by using the anodic dissolution current method in the acidic chloride solutions. Meanwhile, the Ni films treated with specific treatment conditions produced different roughness, which was responsible for the improved adhesion strength. The adhesion strength of the Ni films increased up to 629.8 MPa when substrates were treated with anodic current density of 30 mA/cm² for 10 min, which is nearly two times higher than that of films treated by 5 vol % HCl for 10 min. The results indicate that the anodic current treatment method effectively improves the adhesion strength of Ni films. Full article

(This article belongs to the Special Issue Development and Characterization of Nanostructured Functional Coatings/Films)

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9 pages, 8794 KiB

Open AccessArticle

The Effect of Processing Parameters on the Formation and Properties of Al/Ni Core-Shell Pigments via a Galvanic Displacement Method

by Le Yuan, Min Zhou, Can Wang, Qinyong Zhang, Xiaolong Weng and Longjiang Deng

Coatings 2018, 8(6), 200; https://doi.org/10.3390/coatings8060200 - 24 May 2018

Cited by 3 | Viewed by 3166

Abstract

Al/Ni bimetallic core-shell pigments with flake Al particle as core and metallic Ni as shell were synthesized via a galvanic displacement method and studied with X-ray diffraction, scanning electron micrograph (SEM), specific surface area analysis (BET), thermogravimetry-differential thermalanalysis (TG/DSC), and visible-near infrared-infrared reflectance [...] Read more.

Al/Ni bimetallic core-shell pigments with flake Al particle as core and metallic Ni as shell were synthesized via a galvanic displacement method and studied with X-ray diffraction, scanning electron micrograph (SEM), specific surface area analysis (BET), thermogravimetry-differential thermalanalysis (TG/DSC), and visible-near infrared-infrared reflectance spectroscopy. The influence of reactant ratio (Al:Ni²⁺) and order of addition on phase structure, surface morphology, optical properties, and high temperature oxidation resistance properties were studied systematically. The results show that the local concentration of Ni²⁺ at solid-liquid interfaces can be effectively modulated by adjusting the reactant ratio and order of addition. A high local concentration of Ni²⁺ improves the rate of displacement reaction resulting in more metallic Ni on the surface of the flake Al powders. This increases the relative content of Ni in the shell. The change of displacement reaction rate also leads to a different surface morphology and roughness of the Ni shell. The thick and rough Ni shell has a strong absorption extinction due to the intense light scattering and absorption-this substantially reduces the spectral reflectance of the flake Al core. Infrared reflectance in particular is influenced by light scattering and absorption of the rough surface. In addition, the Ni shell can enhance the high temperature oxidation resistance of the Al core by preventing contact between the metallic Al substrate and oxygen. The oxidation resistance is also associated with the processing parameters of the galvanic displacement reaction. Full article

(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)

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12 pages, 2191 KiB

Open AccessArticle

Effects of sp²/sp³ Ratio and Hydrogen Content on In Vitro Bending and Frictional Performance of DLC-Coated Orthodontic Stainless Steels

by Takeshi Muguruma, Masahiro Iijima, Masahiro Kawaguchi and Itaru Mizoguchi

Coatings 2018, 8(6), 199; https://doi.org/10.3390/coatings8060199 - 24 May 2018

Cited by 22 | Viewed by 5134

Abstract

This study investigated a diamond-like carbon (DLC) coating formed on stainless steels (disk and wire specimens) using a plasma-based ion implantation/deposition method with two different parameters (DLC-1, DLC-2). These specimens were characterized using high-resolution elastic recoil analysis, microscale X-ray photoelectron spectroscopy and nanoindentation [...] Read more.

This study investigated a diamond-like carbon (DLC) coating formed on stainless steels (disk and wire specimens) using a plasma-based ion implantation/deposition method with two different parameters (DLC-1, DLC-2). These specimens were characterized using high-resolution elastic recoil analysis, microscale X-ray photoelectron spectroscopy and nanoindentation testing to determine the hydrogen content, sp²/sp³ ratio and mechanical properties of the coating. Three-point bending and frictional properties were estimated. DLC-1 had a diamond-rich structure at the external surface and a graphite-rich structure at the inner surface, while DLC-2 had a graphite-rich structure at the external surface and a diamond-rich structure at the inner surface. Mean mechanical property values obtained for the external surface were lower than those for the inner surface in both types of DLC-coated specimens. The hydrogen content of DLC-2 was slightly higher versus DLC-1. Both DLC-coated wires produced a significantly higher elastic modulus according to the three-point bending test versus the non-coated wire. DLC-2 produced significantly lower frictional force than the non-coated specimen in the drawing-friction test. The coating of DLC-1 was partially ruptured by the three-point bending and drawing-friction tests. In conclusion, the bending and frictional performance of DLC-coated wire were influenced by the hydrogen content and sp²/sp³ ratio of the coating. Full article

(This article belongs to the Special Issue Surface Engineering of Biomaterials)

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13 pages, 5857 KiB

Open AccessFeature PaperArticle

Anti- and De-Icing Behaviors of Superhydrophobic Fabrics

by Yuyang Liu, Dong Song and Chang-Hwan Choi

Coatings 2018, 8(6), 198; https://doi.org/10.3390/coatings8060198 - 23 May 2018

Cited by 20 | Viewed by 5560

Abstract

This paper reports the application of superhydrophobic coatings on cotton fabrics and their functionalities for anti- and de-icing efficacy. Superhydrophobic cotton fabrics with different water-repellent properties have been achieved by decorating the surface of pristine cotton fibers with ZnO structures of varying sizes [...] Read more.

This paper reports the application of superhydrophobic coatings on cotton fabrics and their functionalities for anti- and de-icing efficacy. Superhydrophobic cotton fabrics with different water-repellent properties have been achieved by decorating the surface of pristine cotton fibers with ZnO structures of varying sizes and shapes through an in situ solution growth process, followed by the treatment of the surface with low-surface-energy coating such as Teflon. The surface morphology of the treated cotton fabrics was characterized using scanning electron microscopy (SEM). The surface wettability of the treated fabrics was evaluated through the measurement of static contact angle (SCA), contact angle hysteresis (CAH), and sliding angle (SA) of a water droplet. The anti- and de-icing behaviors of the treated fabrics were evaluated through both static (sessile droplet) and dynamic (spraying) tests. The results show that the superhydrophobic fabric with a higher SCA and the lower CAH/SA has superior anti- and de-icing behaviors in both the static and dynamic conditions. Compared to hard substrates, the soft, flexible, and porous (air-permeable) superhydrophobic fabrics can lead to broader applicability of textile-based materials for the design and fabrication of anti- and de-icing materials. Furthermore, the multi-scale surface structures of fabrics (fibers, yarns, and weaving constructions) combining with the hierarchical micro-nanostructures of the ZnO coating provides an ideal platform for anti-icing studies. Full article

(This article belongs to the Special Issue Superhydrophobic Coatings)

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Coatings, Volume 8, Issue 6 (June 2018) – 29 articles

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