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Coatings, Volume 8, Issue 2 (February 2018)

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Cover Story (view full-size image) In principle, coatings cannot be adopted to modify the damping behaviour of mechanical components [...] Read more.
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Open AccessFeature PaperArticle X-ray Microanalysis of Precious Metal Thin Films: Thickness and Composition Determination
Received: 4 December 2017 / Revised: 9 February 2018 / Accepted: 12 February 2018 / Published: 24 February 2018
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Abstract
Measuring the thickness and the composition of precious metal thin films is a challenging task. Currently, the available techniques for thickness measurements are either destructive or need heavy assumptions on the nature of the sample, relying on information that are not always available
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Measuring the thickness and the composition of precious metal thin films is a challenging task. Currently, the available techniques for thickness measurements are either destructive or need heavy assumptions on the nature of the sample, relying on information that are not always available with sufficient accuracy. In this paper we propose a new methodology based on X-ray microanalysis that can complement, with better lateral resolution, the use of X-ray Fluorescence, the most widely employed technique for measuring the thickness of electrodeposited coatings. The proposed method employs a combination of energy dispersive microanalysis spectra acquisition and Monte Carlo simulation. The effectiveness of the technique has been demonstrated by the measure of the thickness and the composition of a thin 24 kt gold electroplated film that contained small amount of nickel. Results have been validated by comparing data with those obtained by X-ray fluorescence and the scanning electron microscopy of metallographic cross-sections. Full article
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Open AccessArticle Improving the Tribological Properties of Spark-Anodized Titanium by Magnetron Sputtered Diamond-Like Carbon
Received: 29 November 2017 / Revised: 8 February 2018 / Accepted: 23 February 2018 / Published: 24 February 2018
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Abstract
Spark-anodization of titanium can produce adherent and wear-resistant TiO2 film on the surface, but the spark-anodized titanium has lots of surface micro-pores, resulting in an unstable and high friction coefficient against many counterparts. In this study, the diamond-like carbon (DLC) was introduced
[...] Read more.
Spark-anodization of titanium can produce adherent and wear-resistant TiO2 film on the surface, but the spark-anodized titanium has lots of surface micro-pores, resulting in an unstable and high friction coefficient against many counterparts. In this study, the diamond-like carbon (DLC) was introduced into the micro-pores of spark-anodized titanium by the magnetron sputtering technique and a TiO2/DLC composite coating was fabricated. The microstructure and tribological properties of TiO2/DLC composite coating were investigated and compared with the anodic TiO2 mono-film and DLC mono-film. Results show that the DLC deposition significantly decreased the surface roughness and porosity of spark-anodized titanium. The fabricated TiO2/DLC composite coating exhibited a more stable and much lower friction coefficient than anodic TiO2 mono-film. Although the friction coefficient of the composite coating and the DLC mono-film was similar under both light load and heavy load conditions, the wear life of the composite coating was about 43% longer than that of DLC mono-film under heavy load condition. The wear rate of titanium with protective composite coating was much lower than that of titanium with DLC mono-film. The superior low friction coefficient and wear rate of the TiO2/DLC composite coating make it a good candidate as protective coating on titanium alloys. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Exploration of Growth Window for Phase-Pure Cubic Boron Nitride Films Prepared in a Pure N2 Plasma
Received: 22 December 2017 / Revised: 21 February 2018 / Accepted: 23 February 2018 / Published: 24 February 2018
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Abstract
Cubic boron nitride (c-BN) films were prepared via radio frequency (RF) magnetron sputtering from a hexagonal boron nitride (h-BN) target in a pure N2 plasma. The composition and microstructure morphology of the BN films with different deposition times under pure N2
[...] Read more.
Cubic boron nitride (c-BN) films were prepared via radio frequency (RF) magnetron sputtering from a hexagonal boron nitride (h-BN) target in a pure N2 plasma. The composition and microstructure morphology of the BN films with different deposition times under pure N2 plasma or mixed Ar/N2 plasma were investigated with respect to the nucleation and growth processes. The pure-phase c-BN growth window was obtained using pure N2 gas. The effects of pure N2 gas on the growth mechanism, structural morphology, and internal compressive stress of the as-synthesized c-BN films were studied. Using pure N2 gas instead of additional Ar resulted in improved microstructure quality and much reduced compressive stress, suggesting a fundamental strategy for achieving high-quality c-BN films. Full article
(This article belongs to the Special Issue Carbon-Related Coatings)
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Open AccessArticle Tunnel Oxides Formed by Field-Induced Anodisation for Passivated Contacts of Silicon Solar Cells
Received: 5 January 2018 / Revised: 15 February 2018 / Accepted: 19 February 2018 / Published: 23 February 2018
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Abstract
Tunnel silicon oxides form a critical component for passivated contacts for silicon solar cells. They need to be sufficiently thin to allow carriers to tunnel through and to be uniform both in thickness and stoichiometry across the silicon wafer surface, to ensure uniform
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Tunnel silicon oxides form a critical component for passivated contacts for silicon solar cells. They need to be sufficiently thin to allow carriers to tunnel through and to be uniform both in thickness and stoichiometry across the silicon wafer surface, to ensure uniform and low recombination velocities if high conversion efficiencies are to be achieved. This paper reports on the formation of ultra-thin silicon oxide layers by field-induced anodisation (FIA), a process that ensures uniform oxide thickness by passing the anodisation current perpendicularly through the wafer to the silicon surface that is anodised. Spectroscopical analyses show that the FIA oxides contain a lower fraction of Si-rich sub-oxides compared to wet-chemical oxides, resulting in lower recombination velocities at the silicon and oxide interface. This property along with its low temperature formation highlights the potential for FIA to be used to form low-cost tunnel oxide layers for passivated contacts of silicon solar cells. Full article
(This article belongs to the Special Issue Advanced Surface Passivation Processes for Solar Cells)
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Open AccessArticle The Effect of Xanthan Gum and Flaxseed Mucilage as Edible Coatings in Cheddar Cheese during Ripening
Received: 26 December 2017 / Revised: 6 February 2018 / Accepted: 13 February 2018 / Published: 23 February 2018
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Abstract
The object of this study was to investigate the possibility of using xanthan gum and flaxseed mucilage as edible coatings for Cheddar cheese during ripening for 90 days. Five samples of Cheddar cheese blocks were coated with different coating materials in triplicate as
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The object of this study was to investigate the possibility of using xanthan gum and flaxseed mucilage as edible coatings for Cheddar cheese during ripening for 90 days. Five samples of Cheddar cheese blocks were coated with different coating materials in triplicate as follows: Coated with polyvinyl acetate as control (C), coated with 0.5% xanthan gum (XG), coated with 0.75% flaxseed mucilage (FM1), coated with 1% flaxseed mucilage (FM2), and coated with 1.25% flaxseed mucilage (FM3). All samples were kept at 8 ± 2 °C in a cold room for 90 days. The statistical analysis of the results showed that the moisture content of the samples decreased and the protein content increased during the ripening period (P < 0.01). The pH, acidity, fat in dry matter, and TCA-SN/TN of samples were significantly affected by xanthan gum and flaxseed mucilage treatment (P < 0.01). The free fatty acid composition of samples was significantly affected by edible coatings. Edible coatings affected the growth of non-starter lactic acid bacteria and the total mesophilic aerobic bacteria in a non-significant manner (P > 0.01). The growth of starter bacteria was significantly altered under the effect of edible coating materials (P < 0.05). Tyrosine and tryptophan contents as an index of proteolysis, lipolysis, and sensory evaluation of samples were not significantly different. Full article
(This article belongs to the Special Issue Edible Films and Coatings)
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Open AccessArticle Alkoxylated β-Naphthol as an Additive for Tin Plating from Chloride and Methane Sulfonic Acid Electrolytes
Received: 7 December 2017 / Revised: 16 February 2018 / Accepted: 19 February 2018 / Published: 21 February 2018
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Abstract
β-naphthol was one of the first additives introduced for smooth and homogeneous tin electrodeposition. Although it can be oxidized under the plating conditions, forming either 1,2-napthoquinone or polymeric materials based on naphthioxides, it is still in use. In this work, an investigation of
[...] Read more.
β-naphthol was one of the first additives introduced for smooth and homogeneous tin electrodeposition. Although it can be oxidized under the plating conditions, forming either 1,2-napthoquinone or polymeric materials based on naphthioxides, it is still in use. In this work, an investigation of its more stable form, alkoxylated β-naphthol (ABN), on tin plating is undertaken. For this purpose, chloride based (pH ~5) and methane sulfonic acid (MSA, pH ~0.5) electrolytes, including ABN, were prepared. Reaction kinetics were studied by polarization, Tafel measurements, and cyclic voltammetry. Tin electrodeposits were obtained on flat brass substrates. Surface morphology and preferred crystal orientation were studied by Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). In both studied electrolytes ABN acts as an inhibitor but in the case of the chloride electrolyte it is more pronounced. In the MSA electrolyte this effect was overlaid by the presence of tin-citrate complexes. In the chloride-based electrolyte, ABN has a grain refining effect, while in the MSA electrolyte an increase of ABN concentration leads to a slight enlargement of the average grain size. X-ray analysis shows a constant decrease of the (101) intensity with increasing concentration of ABN for the sample deposited from both baths. Full article
(This article belongs to the Special Issue Thin Films and Patterned Structures by Electrochemical Methods)
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Open AccessArticle Chemical Vapor Transport Deposition of Molybdenum Disulfide Layers Using H2O Vapor as the Transport Agent
Received: 8 January 2018 / Revised: 11 February 2018 / Accepted: 14 February 2018 / Published: 21 February 2018
Cited by 1 | PDF Full-text (2862 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Molybdenum disulfide (MoS2) layers show excellent optical and electrical properties and have many potential applications. However, the growth of high-quality MoS2 layers is a major bottleneck in the development of MoS2-based devices. In this paper, we report a
[...] Read more.
Molybdenum disulfide (MoS2) layers show excellent optical and electrical properties and have many potential applications. However, the growth of high-quality MoS2 layers is a major bottleneck in the development of MoS2-based devices. In this paper, we report a chemical vapor transport deposition method to investigate the growth behavior of monolayer/multi-layer MoS2 using water (H2O) as the transport agent. It was shown that the introduction of H2O vapor promoted the growth of MoS2 by increasing the nucleation density and continuous monolayer growth. Moreover, the growth mechanism is discussed. Full article
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Open AccessCommunication A Note on the Dyeing of Wool Fabrics Using Natural Dyes Extracted from Rotten Wood-Inhabiting Fungi
Received: 14 December 2017 / Revised: 7 February 2018 / Accepted: 14 February 2018 / Published: 19 February 2018
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Abstract
Fungal isolates obtained from rotten wood samples were identified and selected by their ability to produce fungal dyes in liquid media. Fungal isolates produced natural extracellular dyes with colors ranging from red to orange, yellow and purple. Dyes from two of these fungi,
[...] Read more.
Fungal isolates obtained from rotten wood samples were identified and selected by their ability to produce fungal dyes in liquid media. Fungal isolates produced natural extracellular dyes with colors ranging from red to orange, yellow and purple. Dyes from two of these fungi, Talaromyces australis (red) and Penicillium murcianum (yellow), were extracted and used to dye wool samples in a Data Color Ahiba IR Pro-Trade (model Top Speed II) machine. The protein nature of wool interacted well with the fungal dyes producing colors suitable for textile applications when used to a concentration of 0.1 g·L−1. Results on color fastness when washing confirmed the affinity of the dyes with wool as the dyed samples kept their color in acceptable ranges after washing, without the implementation of mordanting pretreatments or the use of fixing agents. Full article
(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)
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Open AccessReview Design of Nanostructured Functional Coatings by Using Wet-Chemistry Methods
Received: 22 December 2017 / Revised: 10 February 2018 / Accepted: 11 February 2018 / Published: 14 February 2018
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Abstract
This review reports the implementation of novel nanostructured functional coatings by using different surface engineering techniques based on wet chemistry. In the first section, the theoretical fundaments of three techniques such as sol-gel process, layer-by-layer (LbL) assembly and electrospinning will be briefly described.
[...] Read more.
This review reports the implementation of novel nanostructured functional coatings by using different surface engineering techniques based on wet chemistry. In the first section, the theoretical fundaments of three techniques such as sol-gel process, layer-by-layer (LbL) assembly and electrospinning will be briefly described. In the second section, selected applications in different potential fields will be presented gathering relevant properties such as superhydrophobicity, biocide behavior or applications in the field of optical fiber sensors. Full article
(This article belongs to the Special Issue Nanostructured Functional Coatings)
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Open AccessArticle The Fracture of Plasma-Treated Polyurethane Surface under Fatigue Loading
Received: 6 January 2018 / Revised: 9 February 2018 / Accepted: 11 February 2018 / Published: 14 February 2018
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Abstract
Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading.
[...] Read more.
Plasma treatment of soft polymers is a promising technique to improve biomedical properties of the materials. The response to the deformation of such materials is not yet clear. Soft elastic polyurethane treated with plasma immersion ion implantation is subjected to fatigue uniaxial loading. The influence of the strain amplitude and the plasma treatment regime on damage character is discussed. Surface defects are studied in unloaded and stretched states of the material. As a result of fatigue loading, transverse cracks (with closed overlapping edges as well as with open edges deeply propagating into the polymer) and longitudinal folds which are break and bend inward, appear on the surface. Hard edges of cracks cut the soft polymer which is squeezed from the bulk to the surface. The observed damages are related to the high stiffness of the modified surface and its transition to the polymer substrate. Full article
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Open AccessArticle Study on the Properties of 1319 nm Ultra-High Reflector Deposited by Electron Beam Evaporation Assisted by an Energetic RF Ion Source
Received: 24 December 2017 / Revised: 3 February 2018 / Accepted: 6 February 2018 / Published: 14 February 2018
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Abstract
Ultra-high reflectors, working as a critical optical component, has been widely applied as a cavity mirror in fine optical systems such as laser gyro, F-P interferometer, etc. For decades, ion beam sputtering (IBS) technology, which can deposit ultra-low loss and dense layers, has
[...] Read more.
Ultra-high reflectors, working as a critical optical component, has been widely applied as a cavity mirror in fine optical systems such as laser gyro, F-P interferometer, etc. For decades, ion beam sputtering (IBS) technology, which can deposit ultra-low loss and dense layers, has been commonly believed to be the only and irreplaceable method to fabricate ultra-high reflectors. Thus, reports on other methods are rare and a reflectivity above 99.99% obtained by evaporation technology (including ion assisted evaporation) has not been seen yet. In the present study, an energetic radio frequency (RF) ion source was introduced during the electron beam evaporation process, which improved the layer quality dramatically. An ultra-high reflector at 1319 nm with reflectivity of 99.992% (measured by cavity-ring down method) was successfully deposited on a φ100 mm × 25 mm single crystal silicon substrate whose surface roughness was approximately 0.420 nm. The surface figure of the reflector was accurately controlled superior to 1/6λ (λ = 632.8 nm). The measured absorption was approximately 3–5 ppm and the calculated scatter based on surface roughness measurement was approximately 6.64 ppm. Total loss of the reflector was systematically discussed. This study showed that it is possible to apply electron beam evaporation in ultra-high reflector manufacture and the method is capable of depositing reflectors with an aperture larger than φ600 mm which is the maximum capacity of current IBS technology. Full article
(This article belongs to the Special Issue Applications of Optical Thin Film Coatings)
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Open AccessArticle Damping Oriented Design of Thin-Walled Mechanical Components by Means of Multi-Layer Coating Technology
Received: 29 December 2017 / Revised: 31 January 2018 / Accepted: 9 February 2018 / Published: 13 February 2018
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Abstract
The damping behaviour of multi-layer composite mechanical components, shown by recent research and application papers, is analyzed. A local dissipation mechanism, acting at the interface between any two different layers of the composite component, is taken into account, and a beam model, to
[...] Read more.
The damping behaviour of multi-layer composite mechanical components, shown by recent research and application papers, is analyzed. A local dissipation mechanism, acting at the interface between any two different layers of the composite component, is taken into account, and a beam model, to be used for validating the known experimental results, is proposed. Multi-layer prismatic beams, consisting of a metal substrate and of some thin coated layers exhibiting variable stiffness and adherence properties, are considered in order to make it possible to study and validate this assumption. A dynamical model, based on a simple beam geometry but taking into account the previously introduced local dissipation mechanism and distributed visco-elastic constraints, is proposed. Some different application examples of specific multi-layer beams are considered, and some numerical examples concerning the beam free and forced response are described. The influence of the multilayer system parameters on the damping behaviour of the free and forced response of the composite beam is investigated by means of the definition of some damping estimators. Some effective multi-coating configurations, giving a relevant increase of the damping estimators of the coated structure with respect to the same uncoated structure, are obtained from the model simulation, and the results are critically discussed. Full article
(This article belongs to the Special Issue Manufacturing and Surface Engineering)
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Open AccessArticle Effect of Hexagonal Phase Content on Wear Behaviour of AlTiN Arc PVD Coatings
Received: 30 January 2018 / Revised: 6 February 2018 / Accepted: 9 February 2018 / Published: 13 February 2018
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Abstract
In this study, the effect of increasing aluminum content and magnetic steering field strength on the structure and wear behavior of arc PVD AlTiN coatings is discussed. Deposition was done by means of an industrial-scale PVD unit for tool coating. The aluminium content
[...] Read more.
In this study, the effect of increasing aluminum content and magnetic steering field strength on the structure and wear behavior of arc PVD AlTiN coatings is discussed. Deposition was done by means of an industrial-scale PVD unit for tool coating. The aluminium content in the AlTi source material was increased from 67 to 73 at.%. We applied two settings of the magnetic field that steers the arc across the cathode surface thereby evaporating the AlTi alloy differently. The resulting coating thickness ranged from 3.5 to about 7 µm. Cemented tungsten carbide was used as substrate material. Coating properties like hardness, adhesion, and crystal phases were analyzed by indentation and X-ray diffraction, respectively. The wear behaviour of the different AlTiN hard coatings were investigated in two ways. In a first idealized test, cyclic impacting was done applying a constant force. The resulting wear pattern was quantified by an Alicona multi-focus microscope. A second wear test was done by metal cutting under realistic conditions. Fly milling of ductile cast iron (EN-GJS-700) was performed with regular interruptions in order to measure the increasing wear mark. As expected, aluminium contents above 67 at.% (in the metal fraction of the coating) lead to a decreased wear resistance as the soft hexagonal phase exceeds values of a few vol.%. However, it was found that the formation of the hexagonal phase can be effectively influenced and delayed by increasing the magnetic steering field at the cathode. The wear behavior observed in cyclic impact testing corresponds well to results obtained with the more complex loading situation encountered in milling. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle Arc-Sprayed Fe-Based Coatings from Cored Wires for Wear and Corrosion Protection in Power Engineering
Received: 17 October 2017 / Revised: 20 January 2018 / Accepted: 29 January 2018 / Published: 13 February 2018
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Abstract
High wear and corrosion of parts lead to an increase in operating costs at thermal power plants. The present paper shows a possible solution to this problem through the arc spraying of protective coatings. Cored wires of the base alloying system Fe-Cr-C were
[...] Read more.
High wear and corrosion of parts lead to an increase in operating costs at thermal power plants. The present paper shows a possible solution to this problem through the arc spraying of protective coatings. Cored wires of the base alloying system Fe-Cr-C were used as a feedstock. Rise of wear- and heat-resistance of the coatings was achieved by additional alloying with Al, B, Ti, and Y. The wear and heat resistance of the coatings were tested via a two-body wear test accompanied by microhardness measurement and the gravimetric method, respectively. A high-temperature corrosion test was performed at 550 °C under KCl salt deposition. The porosity and adhesion strengths of the coatings were also evaluated. The microstructure was investigated with a scanning electron microscope (SEM) unit equipped with an energy dispersive X-ray (EDX) microanalyzer, and the phase composition was assessed by X-ray diffractometry. The test results showed the positive influence of additional alloying with Y on the coating properties. A comparison with commercial boiler materials showed that the coatings have the same level of heat resistance as austenite steels and are an order of magnitude higher than that of pearlite and martensite-ferrite steels. The coatings can be applied to wear- and heat-resistant applications at 20–700 °C. Full article
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Open AccessArticle Corrosion Resistance and Durability of Superhydrophobic Copper Surface in Corrosive NaCl Aqueous Solution
Received: 20 December 2017 / Revised: 8 February 2018 / Accepted: 9 February 2018 / Published: 11 February 2018
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Abstract
Artificial superhydrophobic copper surfaces play an important role in modern applications such as self-cleaning and dropwise condensation; however, corrosion resistance and durability often present as major concerns in such applications. In this study, the anti-corrosion properties and mechanical durability of superhydrophobic copper surface
[...] Read more.
Artificial superhydrophobic copper surfaces play an important role in modern applications such as self-cleaning and dropwise condensation; however, corrosion resistance and durability often present as major concerns in such applications. In this study, the anti-corrosion properties and mechanical durability of superhydrophobic copper surface have been investigated. The superhydrophobic copper surfaces were achieved with wet chemical etching and an immersion method to reduce the complexity of the fabrication process. The surface structures and materials were characterized using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectrometer (FTIR). The corrosion resistance and mechanical properties of the superhydrophobic copper surface were characterized after immersing surfaces in a 3.5 wt % NaCl solution. The chemical stability of the superhydrophobic copper surface in the NaCl solution for a short period of time was also evaluated. An abrasion test and an ultrasound oscillation were conducted to confirm that the copper surface contained durable superhydrophobic properties. In addition, an atomic force microscope was employed to study the surface mechanical property in the corrosion conditions. The present study shows that the resulting superhydrophobic copper surface exhibit enhanced corrosion resistance and durability. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings)
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