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Coatings, Volume 7, Issue 6 (June 2017)

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Cover Story A novel graphene-coated Ni electrode was developed to improve corrosion resistance of Ni [...] Read more.
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Research

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Open AccessArticle Development of a TiC/Cr23C6 Composite Coating on a 304 Stainless Steel Substrate through a Tungsten Inert Gas Process
Coatings 2017, 7(6), 80; doi:10.3390/coatings7060080
Received: 14 February 2017 / Revised: 10 May 2017 / Accepted: 11 May 2017 / Published: 14 June 2017
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Abstract
The aim of this study was to develop a composite coating on 304 stainless steel employing a TIG (tungsten inert gas) process. Ti wire cored with graphite powder was used as the means of coating material. The process parameters were controlled to develop
[...] Read more.
The aim of this study was to develop a composite coating on 304 stainless steel employing a TIG (tungsten inert gas) process. Ti wire cored with graphite powder was used as the means of coating material. The process parameters were controlled to develop a coating with optimum characteristics (i.e., hardness and wear resistance). The microstructure of the coating was analyzed with SEM and XRD. It was found that both the hardness and the wear resistance increase as the current increases, while both of these properties decrease as travelling speed increases. It was found that the coated samples with composite layers were harder than the substrate and can range up to 1100 HV, almost 4.5 times higher than the hardness of 304 stainless steel. Likewise, the wear resistance of the coating was observed to be 4.5 times higher than that of the substrate. The high performance of the coating, as revealed by microstructural analysis, was due to the formation of TiC and Cr23C6.The optimum conditions for producing the coating are thus proposed to include a 120 A current and a 3.17 mm/s travel speed. Full article
(This article belongs to the Special Issue Advanced Ceramic Coatings and Interfaces)
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Open AccessArticle Maximum Deformation Ratio of Droplets of Water-Based Paint Impact on a Flat Surface
Coatings 2017, 7(6), 81; doi:10.3390/coatings7060081
Received: 3 April 2017 / Revised: 8 May 2017 / Accepted: 8 June 2017 / Published: 19 June 2017
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Abstract
In this research, the maximum deformation ratio of water-based paint droplets impacting and spreading onto a flat solid surface was investigated numerically based on the Navier–Stokes equation coupled with the level set method. The effects of droplet size, impact velocity, and equilibrium contact
[...] Read more.
In this research, the maximum deformation ratio of water-based paint droplets impacting and spreading onto a flat solid surface was investigated numerically based on the Navier–Stokes equation coupled with the level set method. The effects of droplet size, impact velocity, and equilibrium contact angle are taken into account. The maximum deformation ratio increases as droplet size and impact velocity increase, and can scale as We1/4, where We is the Weber number, for the case of the effect of the droplet size. Finally, the effect of equilibrium contact angle is investigated, and the result shows that spreading radius decreases with the increase in equilibrium contact angle, whereas the height increases. When the dimensionless time t* < 0.3, there is a linear relationship between the dimensionless spreading radius and the dimensionless time to the 1/2 power. For the case of 80° ≤ θe ≤ 120°, where θe is the equilibrium contact angle, the simulation result of the maximum deformation ratio follows the fitting result. The research on the maximum deformation ratio of water-based paint is useful for water-based paint applications in the automobile industry, as well as in the biomedical industry and the real estate industry. Please check all the part in the whole passage that highlighted in blue whether retains meaning before. Full article
(This article belongs to the Special Issue Mechanical Behavior of Coatings and Engineered Surfaces)
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Open AccessArticle Ammonia Generation via a Graphene-Coated Nickel Catalyst
Coatings 2017, 7(6), 72; doi:10.3390/coatings7060072
Received: 25 March 2017 / Revised: 7 May 2017 / Accepted: 16 May 2017 / Published: 27 May 2017
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Abstract
A novel graphene-coated Ni electrode was developed in this investigation to improve corrosion resistance while unexpectedly enhancing the ammonia generation rate in the electrochemically induced urea to ammonia (eU2A) process, which is an electrochemical onsite ammonia generation method. The development of the electrode
[...] Read more.
A novel graphene-coated Ni electrode was developed in this investigation to improve corrosion resistance while unexpectedly enhancing the ammonia generation rate in the electrochemically induced urea to ammonia (eU2A) process, which is an electrochemical onsite ammonia generation method. The development of the electrode is crucial for the eU2A reactions since in the ammonia generation process, the concentration of ammonia is inevitably high on the surface of the electrode, leading to severe corrosion of the electrode and the loss of generated ammonia as well. In this paper, the graphene was derived from raw coal by using the chemical vapor deposition method and self-lifted onto a Ni electrode to form a protective layer for corrosion prevention. Transmission electron microscopy showed the synthesized graphene had few-layers and Raman spectroscopy indicated that the coating of graphene was stable during the eU2A reaction. As a result, the ammonia corrosion of the Ni electrode was dramatically reduced by ~20 times with the graphene coating method. More importantly, a higher ammonia generation rate (~2 times) was achieved using the graphene-coated Ni working electrode compared to a bare Ni electrode in the eU2A process. Full article
(This article belongs to the Special Issue Thin Films and Patterned Structures by Electrochemical Methods)
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Open AccessArticle Aluminizing via Ionic Liquid Electrodeposition and Pack Cementation: A Comparative Study with Inconel 738 and a CoNiCrAlY
Coatings 2017, 7(6), 83; doi:10.3390/coatings7060083
Received: 1 May 2017 / Revised: 6 June 2017 / Accepted: 15 June 2017 / Published: 19 June 2017
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Abstract
A novel aluminizing process based upon room temperature Al-electrodeposition from Ionic Liquids followed by diffusion heat treatment was applied on bare- and CoNiCrAlY-coated Inconel 738 (IN738). The aluminized samples were tested by isothermal oxidation at 1000 °C in air. The microstructural and chemical
[...] Read more.
A novel aluminizing process based upon room temperature Al-electrodeposition from Ionic Liquids followed by diffusion heat treatment was applied on bare- and CoNiCrAlY-coated Inconel 738 (IN738). The aluminized samples were tested by isothermal oxidation at 1000 °C in air. The microstructural and chemical evolution of the samples were determined as function of oxidation time and compared with the currently applied coatings obtained via pack cementation. The newly proposed method is suitable for the CoNiCrAlY coating, but not for the bare IN738. In the latter, the formed Al-enriched layer is much thinner and the anticorrosion properties resulted in being reduced. This is probably due to the presence of precipitates, which slow down the aluminum inward diffusion impairing the formation of a well-developed interdiffusion zone (IDZ). Traces of the electrolyte, embedded during the Al-electrodeposition process, can be seen as the origin of these precipitates. Full article
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Open AccessArticle Combustion Synthesis of UHTC Composites from Ti–B4C Solid State Reaction with Addition of VIb Transition Metals
Coatings 2017, 7(6), 73; doi:10.3390/coatings7060073
Received: 10 May 2017 / Revised: 24 May 2017 / Accepted: 27 May 2017 / Published: 1 June 2017
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Abstract
UHTC composites were prepared by self-propagating high-temperature synthesis (SHS) from the Ti–B4C reaction system with addition of Cr, Mo, and W. The starting sample composition was formulated as (3−x)Ti + B4C + xMe with x =
[...] Read more.
UHTC composites were prepared by self-propagating high-temperature synthesis (SHS) from the Ti–B4C reaction system with addition of Cr, Mo, and W. The starting sample composition was formulated as (3−x)Ti + B4C + xMe with x = 0.1–1.0 and Me = Cr, Mo, or W. For all samples conducted in this study, self-sustaining combustion was well established and propagated with a distinct reaction front. With no addition of Cr, Mo, or W, solid state combustion of the 3Ti + B4C sample featuring a combustion front temperature (Tc) of 1766 °C and a combustion wave velocity (Vf) of 16.5 mm/s was highly exothermic and produced an in situ composite of 2TiB2 + TiC. When Cr, Mo, or W was adopted to replace a portion of Ti, the reaction exothermicity was lowered, and hence, a significant decrease in Tc (from 1720 to 1390 °C) and Vf (from 16.1 to 3.9 mm/s) was observed. With addition of Cr, Mo, and W, the final products were CrB-, MoB-, and WB-added TiB2–TiC composites. The absence of CrB2, MoB2, and WB2 was attributed partly to the loss of boron from thermal decomposition of B4C and partly to lack of sufficient reaction time inherent to the SHS process. Full article
(This article belongs to the Special Issue Ultrahigh Temperature Ceramic Coatings and Composites)
Open AccessArticle Fabrication of Luminescent Antireflective Coatings with CaMoO4:Eu3+/Ag Composite Structure
Coatings 2017, 7(6), 74; doi:10.3390/coatings7060074
Received: 10 April 2017 / Revised: 12 May 2017 / Accepted: 31 May 2017 / Published: 2 June 2017
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Abstract
Highly transparent and luminescent CaMoO4:Eu3+/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an
[...] Read more.
Highly transparent and luminescent CaMoO4:Eu3+/Ag composite films were fabricated on glass substrates as multifunctional antireflective (AR) coatings. The films were deposited through a combination of a sol–gel dip-coating technique and a hot water treatment. With the addition of an aluminum source in coating solutions, the sol–gel-derived films underwent a remarkable microstructural change during the hot water treatment due to the reaction between an amorphous alumina phase and water. This change brought both an antireflective effect (suppression of Fresnel reflection) and luminescence enhancement (suppression of total internal reflection) to the films. The introduction of Ag nanoparticles into the films further increased luminescence intensity without losing the antireflective effect. Full article
(This article belongs to the Special Issue Antireflective Coatings for Glass and Transparent Polymers)
Open AccessArticle Surface Erosion of Low-Current Reed Switches
Coatings 2017, 7(6), 75; doi:10.3390/coatings7060075
Received: 18 April 2017 / Revised: 13 May 2017 / Accepted: 31 May 2017 / Published: 3 June 2017
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Abstract
The erosion model of the surface coatings of reed switches considering different physicochemical processes occurring on the contact surfaces and inside the inter-electrode gap was proposed. According to that, the discrete electron avalanche (ecton) introduced in the explosive electron emission theory
[...] Read more.
The erosion model of the surface coatings of reed switches considering different physicochemical processes occurring on the contact surfaces and inside the inter-electrode gap was proposed. According to that, the discrete electron avalanche (ecton) introduced in the explosive electron emission theory by Mesyats is considered as the main motive force responsible for the surface modification and mass transfer of materials in the course of breaking/shorting of the contacts. By means of SEM imaging and energy dispersive X-ray microanalysis of the contact surfaces after various numbers of switching cycles, the energy threshold of the ecton generation defining the erosion stability of the coatings was found to be proportional to the specific sublimation and ionization energies of coating materials. It has been shown that the total erosion of the coatings on the working surface of the contacts after the commutation test possess the resultant character; i.e., the specificities of erosion occurring after each commutation event are characteristic for the whole of the commutation test. In further development of our model, we suggested that a few monolayers of metals (or alloys) with low ionization potential deposited on the main coatings can improve the erosion stability of contacts. Full article
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Open AccessArticle Alternative Fillers for the Production of Bituminous Mixtures: A Screening Investigation on Waste Powders
Coatings 2017, 7(6), 76; doi:10.3390/coatings7060076
Received: 27 February 2017 / Revised: 11 May 2017 / Accepted: 27 May 2017 / Published: 3 June 2017
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Abstract
There has been a significant increase in the demand for using recycled materials in construction because of the lack and limitation of available natural resources. A number of industrial and domestic waste products are being used in the replacement of traditional materials for
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There has been a significant increase in the demand for using recycled materials in construction because of the lack and limitation of available natural resources. A number of industrial and domestic waste products are being used in the replacement of traditional materials for road construction, and many studies have been carried out in recent years on the use of different recycled materials in substitution of conventional fillers in Asphalt Concretes (AC). The aim of this laboratory research is to analyze the physical characteristics of three different recycled fillers and compare them with those of a traditional limestone filler. The alternative fillers presented in this paper are: a waste bleaching clay that comes from two consecutive stages in the industrial process for decolouring vegetable oils and producing biogas (Ud filler), a dried mud waste from a tungsten mine (MW filler) and a recycled glass powder (Gl filler). Results show significant differences between the fillers, and, in particular, Rigden Voids (RV) seem to have the largest potential influence on the rheology of ACs. Full article
(This article belongs to the Special Issue Low Environmental Impact Coatings for Road Pavements)
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Open AccessArticle Optimization of the Laser Hardening Process by Adapting the Intensity Distribution to Generate a Top-hat Temperature Distribution Using Freeform Optics
Coatings 2017, 7(6), 77; doi:10.3390/coatings7060077
Received: 29 March 2017 / Revised: 22 May 2017 / Accepted: 2 June 2017 / Published: 7 June 2017
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Abstract
Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser
[...] Read more.
Laser hardening is a surface hardening process which enables high quality results due to the controllability of the energy input. The hardened area is determined by the heat distribution caused by the intensity profile of the laser beam. However, commonly used top-hat laser beams do not provide an ideal temperature profile. Therefore, in this paper the beam profile, and thus the temperature profile, is optimized using freeform optics. The intensity distribution is modified to generate a top-hat temperature profile on the surface. The results of laser hardening with the optimized distribution are thereupon compared with results using a top-hat intensity distribution. Full article
(This article belongs to the Special Issue Laser Surface Treatment)
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Open AccessArticle Nitrogen Trapping Ability of Hydrogen-Induced Vacancy and the Effect on the Formation of AlN in Aluminum
Coatings 2017, 7(6), 79; doi:10.3390/coatings7060079
Received: 24 April 2017 / Revised: 6 June 2017 / Accepted: 6 June 2017 / Published: 9 June 2017
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Abstract
This paper presents the ternary interaction of N, H, and vacancy point defects and the nitrogen trapping ability of aluminum vacancies induced by hydrogen by means of DFT methods employed in VASP (Vienna Ab initio Simulation Package) and Abinit packages. The obtained vacancy
[...] Read more.
This paper presents the ternary interaction of N, H, and vacancy point defects and the nitrogen trapping ability of aluminum vacancies induced by hydrogen by means of DFT methods employed in VASP (Vienna Ab initio Simulation Package) and Abinit packages. The obtained vacancy formation energy of 0.65 eV is close to experimental values. Although the N–vacancy complex is unstable with the negative binding energy of −0.51 eV, the stability of H–vacancy–N is proved by the positive binding energy of 0.59 eV and the appearance of the orbital hybridization in the density of state (DOS) of atoms connecting to this complex. Moreover, Al vacancies can trap more than 4 N atoms, which prevents the formation of aluminum nitride and subsequently affects not only the hardness of the Al surface but also many practical applications of AlN coating. Full article
(This article belongs to the Special Issue Modelling and Simulation of Coating)
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Review

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Open AccessReview Functionalized Textile Based Therapy for the Treatment of Atopic Dermatitis
Coatings 2017, 7(6), 82; doi:10.3390/coatings7060082
Received: 8 May 2017 / Revised: 9 June 2017 / Accepted: 12 June 2017 / Published: 17 June 2017
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Abstract
Atopic dermatitis (AD) is a common chronic inflammatory skin condition characterized by intense puritus and skin dryness. The pathogenesis for AD has not been fully understood to date. Complementary therapies are very popular as effective treatment for AD among clinical practitioners. This study
[...] Read more.
Atopic dermatitis (AD) is a common chronic inflammatory skin condition characterized by intense puritus and skin dryness. The pathogenesis for AD has not been fully understood to date. Complementary therapies are very popular as effective treatment for AD among clinical practitioners. This study presents a comprehensive review of published works associated with textiles-based complementary therapies for AD treatment such as wet-wrap dressing, functionalized textiles, and the application of hydrogel techniques in the textile industry to provide a better understanding of the development and design of new textiles-based transdermal therapies. Full article
(This article belongs to the Special Issue Fabric Coatings)
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Other

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Open AccessLetter Mn-Promoted Growth and Photoluminescence of Molybdenum Disulphide Monolayer
Coatings 2017, 7(6), 78; doi:10.3390/coatings7060078
Received: 4 May 2017 / Revised: 5 June 2017 / Accepted: 6 June 2017 / Published: 8 June 2017
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Abstract
Molybdenum disulphide (MoS2) monolayer is a two-dimensional semiconductor material with potential applications in nano electronic devices. However, it is still a challenge to reproducibly synthesize single layer MoS2 in high quality. Herein, we report the growth of monolayer of MoS
[...] Read more.
Molybdenum disulphide (MoS2) monolayer is a two-dimensional semiconductor material with potential applications in nano electronic devices. However, it is still a challenge to reproducibly synthesize single layer MoS2 in high quality. Herein, we report the growth of monolayer of MoS2 on the SiO2/Si substrate with manganese heterogeneous nucleation. It was shown that the Mn promotes the growth of monolayer MoS2 via heterogeneous nucleation. The growth temperature range expanded two-fold, the nucleation density increased as well. The monolayer prepared in the presence of Mn exhibits a unique red emission peak at 732 nm at room temperature compared to the sample in the absence of Mn. Full article
(This article belongs to the Special Issue Chemical Vapor Deposition)
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