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Coatings, Volume 8, Issue 1 (January 2018)

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Editorial

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Open AccessEditorial Acknowledgement to Reviewers of Coatings in 2017
Coatings 2018, 8(1), 28; doi:10.3390/coatings8010028
Received: 9 January 2018 / Revised: 9 January 2018 / Accepted: 9 January 2018 / Published: 9 January 2018
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Abstract
Peer review is an essential part in the publication process, ensuring that Coatings maintains high quality standards for its published papers.[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle Preparation and Isothermal Oxidation Behavior of Zr-Doped, Pt-Modified Aluminide Coating Prepared by a Hybrid Process
Coatings 2018, 8(1), 1; doi:10.3390/coatings8010001
Received: 16 November 2017 / Revised: 17 December 2017 / Accepted: 18 December 2017 / Published: 21 December 2017
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Abstract
To take advantage of the synergistic effects of Pt and Zr, a kind of Zr-doped, Pt-modified aluminide coating has been prepared by a hybrid process, first electroplating a Pt layer and then co-depositing Zr and Al elements by an above-the-pack process. The microstructure
[...] Read more.
To take advantage of the synergistic effects of Pt and Zr, a kind of Zr-doped, Pt-modified aluminide coating has been prepared by a hybrid process, first electroplating a Pt layer and then co-depositing Zr and Al elements by an above-the-pack process. The microstructure and isothermal oxidation behavior of the coating has been studied, using a Pt-modified aluminide coating as a reference. Results showed that the Zr-doped, Pt-modified aluminide coating was primarily composed of β-(Ni,Pt)Al phase, with small amounts of PtAl2- and Zr-rich phases dispersed in it. The addition of Zr diminished voids on the coating surface since Zr could hinder the growth of β-NiAl grains. It also helped to increase the spalling resistance of the oxide scale and reduce the oxidation rate, which made the Zr-doped, Pt-modified aluminide coating possess better oxidation resistance than the reference Pt-modified aluminide coating at the temperature of 1100 °C. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Photovoltaic Effect in Graphene/MoS2/Si Van der Waals Heterostructures
Coatings 2018, 8(1), 2; doi:10.3390/coatings8010002
Received: 16 October 2017 / Revised: 7 December 2017 / Accepted: 19 December 2017 / Published: 21 December 2017
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Abstract
This paper presents a study on the photovoltaic effect of a graphene/MoS2/Si double heterostructure, grown by rapid chemical vapor deposition. It was found that the double junctions of the graphene/MoS2 Schottky junction and the MoS2/Si heterostructure played important
[...] Read more.
This paper presents a study on the photovoltaic effect of a graphene/MoS2/Si double heterostructure, grown by rapid chemical vapor deposition. It was found that the double junctions of the graphene/MoS2 Schottky junction and the MoS2/Si heterostructure played important roles in enhancing the device’s performance. They allowed more electron-hole pairs to be efficiently generated, separated, and collected in the graphene/MoS2/Si double interface. The device demonstrated an open circuit voltage of 0.51 V and an energy conversion efficiency of 2.58% under an optical illumination of 500 mW/cm2. The photovoltaic effect of the device was partly attributed to the strong light absorption and photoresponse of the few-layer MoS2 film, and partly ascribed to the high carrier-collection-rate of the double van der Waals heterostructures (vdWHs) in the device. Full article
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Open AccessArticle Influence of N2/Ar Flow Ratio on Microstructure and Properties of the AlCrSiN Coatings Deposited by High-Power Impulse Magnetron Sputtering
Coatings 2018, 8(1), 3; doi:10.3390/coatings8010003
Received: 9 November 2017 / Revised: 12 December 2017 / Accepted: 18 December 2017 / Published: 21 December 2017
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Abstract
The cutting properties of tools can be greatly improved by AlCrSiN coatings. The AlCrSiN coatings with nitrogen content in the range of 28.2–56.3 at.% were prepared by varying the N2/Ar flow ratio from 1/4 to 1/1. The influence of N2
[...] Read more.
The cutting properties of tools can be greatly improved by AlCrSiN coatings. The AlCrSiN coatings with nitrogen content in the range of 28.2–56.3 at.% were prepared by varying the N2/Ar flow ratio from 1/4 to 1/1. The influence of N2/Ar flow ratio on composition, microstructure, and mechanical properties, as well as the tribological properties, of the coatings was investigated. With increasing N content, the coating microstructure gradually evolved from single fcc-(Cr,Al)N (200) phase to the mixture of fcc-(Cr,Al)N and hcp-(Cr,Al)N phase, which corresponds to an increased crystallinity within the coatings. The coating presents the highest hardness and best wear resistance for an N2/Ar flow ratio of 1/1, but the film adhesive strength and inner stress decreased obviously with increasing N2/Ar flow ratio, which was attributed to the rapid reduction of particle kinetic energy induced by the obstruction of neutral nitride particles between target and substrates. The highest H3/E*2 value exhibited the lowest wear rate, at 0.81 × 10−14 m3/(N·m), indicating that it had the best resistance to plastic deformation. The main wear mechanisms of the as-deposited coatings were abrasive wear and adhesive wear. The increasing crystallinity of the interior coatings resulted in higher hardness and better tribological behavior with an increase in N2/Ar flow ratio. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle The Electronic and Elastic Properties of Si Atom Doping in TiN: A First-Principles Calculation
Coatings 2018, 8(1), 4; doi:10.3390/coatings8010004
Received: 28 August 2017 / Revised: 5 December 2017 / Accepted: 8 December 2017 / Published: 21 December 2017
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Abstract
The elastic properties and electronic structure of interfaces in Ti–Si–N nanocomposite films were calculated using first principles based on density functional theory (DFT). The results showed that the mechanical moduli of the single-substitution interface (1Si–6N) were higher than those of the double-substitution interface
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The elastic properties and electronic structure of interfaces in Ti–Si–N nanocomposite films were calculated using first principles based on density functional theory (DFT). The results showed that the mechanical moduli of the single-substitution interface (1Si–6N) were higher than those of the double-substitution interface and interstitial interface (1Si–4Ti4N). The single-substitution interface (1Si–6N) was revealed to be characterized as the more elastically isotropic structure in different directions, whereas the Young’s moduli significantly varied in different directions in the interstitial interface (1Si–4Ti4N). The electronic structures of interfaces indicated that the structures were conductors with intersecting bands. Strongly delocalized d states of titanium and silicon ions were spread over a wide region of about 10–12 eV and were strongly hybridized with the nitrogen 2p states. The overall appearance of the calculated cross-sections of the electron density difference changed drastically. Full article
(This article belongs to the Special Issue Advanced Ceramic Coatings and Interfaces)
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Open AccessArticle Electrodeposition of Copper/Carbonous Nanomaterial Composite Coatings for Heat-Dissipation Materials
Coatings 2018, 8(1), 5; doi:10.3390/coatings8010005
Received: 24 November 2017 / Revised: 8 December 2017 / Accepted: 19 December 2017 / Published: 21 December 2017
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Abstract
Carbonous nanomaterials are promising additives for composite coatings for heat-dissipation materials because of their excellent thermal conductivity. Here, copper/carbonous nanomaterial composite coatings were prepared using nanodiamond (ND) as the carbonous nanomaterial. The copper/ND composite coatings were electrically deposited onto copper substrates from a
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Carbonous nanomaterials are promising additives for composite coatings for heat-dissipation materials because of their excellent thermal conductivity. Here, copper/carbonous nanomaterial composite coatings were prepared using nanodiamond (ND) as the carbonous nanomaterial. The copper/ND composite coatings were electrically deposited onto copper substrates from a continuously stirred copper sulfate coating bath containing NDs. NDs were dispersed by ultrasonic treatment, and the initial bath pH was adjusted by adding sodium hydroxide solution or sulfuric acid solution before electrodeposition. The effects of various coating conditions—the initial ND concentration, initial bath pH, stirring speed, electrical current density, and the amount of electricity—on the ND content of the coatings were investigated. Furthermore, the surface of the NDs was modified by hydrothermal treatment to improve ND incorporation. A higher initial ND concentration and a higher stirring speed increased the ND content of the coatings, whereas a higher initial bath pH and a greater amount of electricity decreased it. The electrical current density showed a minimum ND content at approximately 5 A/dm2. Hydrothermal treatment, which introduced carboxyl groups onto the ND surface, improved the ND content of the coatings. A copper/ND composite coating with a maximum of 3.85 wt % ND was obtained. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Effects of Laser Processing Parameters on Texturized Layer Development and Surface Features of Ti6Al4V Alloy Samples
Coatings 2018, 8(1), 6; doi:10.3390/coatings8010006
Received: 30 November 2017 / Revised: 14 December 2017 / Accepted: 20 December 2017 / Published: 22 December 2017
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Abstract
Surface engineering is widely used in different areas, such as the aerospace industry or the biomechanical and medical fields. Specifically, laser surface modification techniques may obtain specific surface finishes for special applications. In texturing laser procedures, the control of processing parameters has a
[...] Read more.
Surface engineering is widely used in different areas, such as the aerospace industry or the biomechanical and medical fields. Specifically, laser surface modification techniques may obtain specific surface finishes for special applications. In texturing laser procedures, the control of processing parameters has a great influence on the geometry and characteristics of the treated area. When these processes are carried out on titanium alloys, thin oxide layers are usually developed on the irradiated surface, formed through the thermochemical combination of vaporized material with atmospheric oxygen in the air. In thermal oxidation treatments of Ti6Al4V, the highest concentration of oxides is mainly composed by rutile (TiO2), producing surface property modifications such as hardness, among others. In this research, a thermochemical oxidation of Ti6Al4V alloy has been performed through laser texturing, using laser scanning speed (Vs) and pulse rate (f) as process control variables, and its influence on the beam absorption capacity of the modified layer have been analyzed. Combined evaluations of microgeometrical features and mechanical properties, such as hardness, verified that, by means of laser texturing treatments, the ability to generate specific topographies and increase the initial hardness of the alloy is obtained. The most advantageous results for the increase of hardness by thermochemical oxidation have been detected in low scan speeds of laser beam treatments, resulting in an increase of approximately 270% using a scanning speed of 10 mm/s. On the other hand, a dependence between roughness values, in terms of Ra and Rz, and the energy density of pulse (Ed) has been observed, showing higher values of roughness for a 17.68 J/cm2 energy density of pulse. Full article
(This article belongs to the Special Issue Manufacturing and Surface Engineering)
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Open AccessArticle Tuning the Friction of Silicon Surfaces Using Nanopatterns at the Nanoscale
Coatings 2018, 8(1), 7; doi:10.3390/coatings8010007
Received: 23 November 2017 / Accepted: 23 November 2017 / Published: 22 December 2017
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Abstract
Friction and wear become significant at small scale lengths, particularly in MEMS/NEMS. Nanopatterns are regarded as a potential approach to solve these problems. In this paper, we investigated the friction behavior of nanopatterned silicon surfaces with a periodical rectangular groove array in dry
[...] Read more.
Friction and wear become significant at small scale lengths, particularly in MEMS/NEMS. Nanopatterns are regarded as a potential approach to solve these problems. In this paper, we investigated the friction behavior of nanopatterned silicon surfaces with a periodical rectangular groove array in dry and wear-less single-asperity contact at the nanoscale using molecular dynamics simulations. The synchronous and periodic oscillations of the normal load and friction force with the sliding distance were determined at frequencies defined by the nanopattern period. The linear load dependence of the friction force is always observed for the nanopatterned surface and is independent of the nanopattern geometry. We show that the linear friction law is a formal Amontons’ friction law, while the significant linear dependence of the friction force-versus-real contact area and real contact area-versus-normal load captures the general features of the nanoscale friction for the nanopatterned surface. Interestingly, the nanopattern increases the friction force at the nanoscale, and the desired friction reduction is also observed. The enlargement and reduction of the friction critically depended on the nanopattern period rather than the area ratio. Our simulation results reveal that the nanopattern can modulate the friction behavior at the nanoscale from the friction signal to the friction law and to the value of the friction force. Thus, elaborate nanopatterning is an effective strategy for tuning the friction behavior at the nanoscale. Full article
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Open AccessArticle Polymeric Antimicrobial Coatings Based on Quaternary Ammonium Compounds
Coatings 2018, 8(1), 8; doi:10.3390/coatings8010008
Received: 23 November 2017 / Revised: 19 December 2017 / Accepted: 20 December 2017 / Published: 23 December 2017
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Abstract
Biocidal coatings that are based on quaternized ammonium copolymers were developed after blending and crosslinking and studied as a function of the ratio of reactive groups and the type of biocidal groups, after curing at room temperature or 120 °C. For this purpose,
[...] Read more.
Biocidal coatings that are based on quaternized ammonium copolymers were developed after blending and crosslinking and studied as a function of the ratio of reactive groups and the type of biocidal groups, after curing at room temperature or 120 °C. For this purpose, two series of copolymers with complementary reactive groups, poly(4-vinylbenzyl chloride-co-acrylic acid), P(VBC-co-AAx), and poly(sodium 4-styrenesulfonate-co-glycidyl methacrylate), P(SSNa-co-GMAx), were synthesized via free radical copolymerization and further modified resulting in covalently bound (4-vinylbenzyl dimethylhexadecylammonium chloride, VBCHAM) and electrostatically attached (hexadecyltrimethylammonium 4-styrene sulfonate, SSAmC16) units. The crosslinking reaction between the carboxylic group of acrylic acid (AA) and the epoxide group of glycidyl methacrylate (GMA) of these copolymers led to the stabilization of the coatings through reactive blending. The so developed coatings were cured at room temperature and 120 °C, and then immersed in ultra-pure water and aqueous NaCl solutions at various concentrations for a time period up to three months. Visual inspection of the integrity of the materials coated onto glass slides, gravimetry, scanning electron microscopy (SEM) characterization, as well as the determination of total organic carbon (TOC) and total nitrogen (TN) of the solutions, were used to investigate the parameters affecting the release of the materials from the coatings based on these systems. The results revealed that curing temperature, complementary reactive groups’ content, and type of antimicrobial species control the release levels and the nature of releasable species of these environmentally-friendly antimicrobial coatings. Full article
(This article belongs to the Special Issue Advances in Antimicrobial Coatings)
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Open AccessArticle Synergistic Effect of Addition of Fillers on Properties of Interior Waterborne UV-Curing Wood Coatings
Coatings 2018, 8(1), 9; doi:10.3390/coatings8010009
Received: 9 November 2017 / Revised: 18 December 2017 / Accepted: 20 December 2017 / Published: 23 December 2017
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Abstract
A waterborne ultraviolet (UV)-curing coating was prepared on the surface of wood materials with modification of talcum powder and calcium carbonate (CaCO3). When the waterborne UV-curing coatings on the surface of wood materials (WUVCW) was radiated for 1 min by UV
[...] Read more.
A waterborne ultraviolet (UV)-curing coating was prepared on the surface of wood materials with modification of talcum powder and calcium carbonate (CaCO3). When the waterborne UV-curing coatings on the surface of wood materials (WUVCW) was radiated for 1 min by UV (λ = 365 nm) and dried at 40 °C for 10 min, it showed good hardness, adhesion, and impact strength, with controlling the talcum content of 2.0% and CaCO3 content of 1.0%, respectively. When the content of talcum powder was higher than 2%, the mechanical properties and gloss of the WUVCW decreased, and when the talcum powder of WUVCW increase to more than 5%, a matte surface appeared after curing. When CaCO3 and talcum powder were present at the same time, the mechanical properties of WUVCW were better than those of only CaCO3 or talcum powder. Full article
(This article belongs to the Special Issue Wood Coatings)
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Open AccessArticle Effects of Negative Bias Voltage and Ratio of Nitrogen and Argon on the Structure and Properties of NbN Coatings Deposited by HiPIMS Deposition System
Coatings 2018, 8(1), 10; doi:10.3390/coatings8010010
Received: 9 November 2017 / Revised: 18 December 2017 / Accepted: 22 December 2017 / Published: 24 December 2017
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Abstract
The NbNx>1 coatings were deposited on Si wafer and SUS 304 stainless steel substrates by a high power impulse magnetron sputtering (HiPIMS) system at various bias voltages and the ratios of nitrogen and argon (N2/Ar). By virtue of electron
[...] Read more.
The NbNx>1 coatings were deposited on Si wafer and SUS 304 stainless steel substrates by a high power impulse magnetron sputtering (HiPIMS) system at various bias voltages and the ratios of nitrogen and argon (N2/Ar). By virtue of electron probe microanalysis (EPMA), X-ray diffraction pattern (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and nano indentation test, the relationships between deposition parameters and coatings properties were examined in detail. These coatings show a strong preferred orientation of (200) plane at free bias voltage. With increasing bias voltage, the intensity of (200) plane peak became weaker and the full width at half maximum of peaks ((200) and (111) peaks) became broader, implying the crystalline grain size were decreased. The (200) plane almost is disappeared at −150 V bias voltage and the phase transition maintains the same change tendency with the increase of N2/Ar gas ratio. The coating microstructure gradually evolved from coarse columnar to dense columnar, and then to compact featureless structure with increase of the bias voltage, corresponding to the decreased surface roughness. The columnar structure of coatings is unrelated to N2/Ar gas ratio and the thickness is minimum at high N2/Ar ratio, which is attributed to the poor sputtering capability of nitrogen compared with argon instead of target poisonous effect. The higher hardness (H) and elastic recovery value are obtained for NbNx>1 (H = 31.3 GPa and We = 69.2%) at −150 V bias voltage, suggesting considerable influence of bias voltage on hardness than that of the N2/Ar gas ratio. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Plastic Deformation Induced by Nanoindentation Test Applied on ZrN/Si3N4 Multilayer Coatings
Coatings 2018, 8(1), 11; doi:10.3390/coatings8010011
Received: 20 November 2017 / Revised: 22 December 2017 / Accepted: 25 December 2017 / Published: 27 December 2017
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Abstract
ZrN/Si3N4 multilayer coating that alternates with either nanocrystalline ZrN or amorphous Si3N4 interlayers was fabricated by reactively magnetron sputtering in an Ar-N2 mixture atmosphere. The thicknesses of the nanocrystalline ZrN and the amorphous Si3N
[...] Read more.
ZrN/Si3N4 multilayer coating that alternates with either nanocrystalline ZrN or amorphous Si3N4 interlayers was fabricated by reactively magnetron sputtering in an Ar-N2 mixture atmosphere. The thicknesses of the nanocrystalline ZrN and the amorphous Si3N4 interlayers are ~12.5 and 2.5 nm, respectively. The ZrN/Si3N4 coating exhibits a promoted hardness of 28.6 ± 1.2 GPa when compared to the binary ZrN. Microstructure evolution just underneath the nanoindentation impression of the ZrN/Si3N4 multilayer coating has been investigated. The result indicates that both ZrN nanograin rotations and plastic flow of the Si3N4 interlayers contribute to the permanent deformation of the multilayer coating induced by the nanoindentation. In addition, the introduction of the a-Si3N4 interlayers hinders both the initiation and propagation of microcracks when the multilayer coating was applied to the scratch test. The propagation deflection of the microcracks was observed attributed to the heterogenous interface, which produces the hardness promotion of the multilayer coating eventually. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Titanium Aluminium Nitride and Titanium Boride Multilayer Coatings Designed to Combat Tool Wear
Coatings 2018, 8(1), 12; doi:10.3390/coatings8010012
Received: 17 November 2017 / Revised: 13 December 2017 / Accepted: 21 December 2017 / Published: 28 December 2017
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Abstract
The lifetimes and the premature wear of machining tools impact on manufacturing efficiencies and productivities. A significant proportion of machining tool damage can be attributed to component wear. Here, titanium aluminium nitride (TiAlN) multi-layered with titanium diboride (TiB2) prepared by PVD
[...] Read more.
The lifetimes and the premature wear of machining tools impact on manufacturing efficiencies and productivities. A significant proportion of machining tool damage can be attributed to component wear. Here, titanium aluminium nitride (TiAlN) multi-layered with titanium diboride (TiB2) prepared by PVD (Physical Vapour Deposition) sputtering onto H-13 substrates are studied as potential wear-resistant coatings for forging die applications. The TiB2 content has been altered and two-sets of coating systems with a bilayer thickness either less than or greater than 1 μm are investigated by tribological and microstructural analysis. XRD analysis of the multilayers reveals the coatings to be predominately dominated by the TiAlN (200) peak, with additional peaks of TiN (200) and Ti (101) at a TiB2 content of 9%. Progressive loads increasing to 100 N enabled the friction coefficients and the coating failure at a critical load to be determined. Friction coefficients of around 0.2 have been measured in a coating containing 9% TiB2 at critical loads of approximately 70 N. Bi-directional wear tests reveal that bilayers with thicknesses greater than 1 μm have frictional coefficients that are approximately 50% lower than those where the bilayer is less than 1 μm. This is due to the greater ability of thicker bilayers to uniformly distribute the stress within the layers. There are two observed frictional coefficient regimes corresponding to a lower and higher rate of material loss. At the lower regime, with TiB2 contents below 20%, material loss occurs mainly via delamination between the layers, whilst at compositions above this, material loss occurs via a break-up of material into finer particles that in combination with the higher loads results in greater material loss. The measured wear scar volumes for the TiAlN/TiB2 multilayer coatings are approximately three times lower than those measured on the substrate, thus validating the increased wear resistance offered by these composite coatings. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle Dicalcium Phosphate Coated with Graphene Synergistically Increases Osteogenic Differentiation In Vitro
Coatings 2018, 8(1), 13; doi:10.3390/coatings8010013
Received: 8 November 2017 / Revised: 16 December 2017 / Accepted: 26 December 2017 / Published: 28 December 2017
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Abstract
In recent years, graphene and its derivatives have attracted much interest in various fields, including biomedical applications. In particular, increasing attention has been paid to the effects of reduced graphene oxide (rGO) on cellular behaviors. On the other hand, dicalcium phosphate (DCP) has
[...] Read more.
In recent years, graphene and its derivatives have attracted much interest in various fields, including biomedical applications. In particular, increasing attention has been paid to the effects of reduced graphene oxide (rGO) on cellular behaviors. On the other hand, dicalcium phosphate (DCP) has been widely used in dental and pharmaceutical fields. In this study, DCP composites coated with rGO (DCP-rGO composites) were prepared at various concentration ratios (DCP to rGO concentration ratios of 5:2.5, 5:5, and 5:10 μg/mL, respectively), and their physicochemical properties were characterized. In addition, the effects of DCP-rGO hybrid composites on MC3T3-E1 preosteoblasts were investigated. It was found that the DCP-rGO composites had an irregular granule-like structure with a diameter in the range order of the micrometer, and were found to be partially covered and interconnected with a network of rGO. The zeta potential analysis showed that although both DCP microparticles and rGO sheets had negative surface charge, the DCP-rGO composites could be successfully formed by the unique structural properties of rGO. In addition, it was demonstrated that the DCP-rGO composites significantly increased alkaline phosphatase activity and extracellular calcium deposition, indicating that the DCP-rGO hybrid composites can accelerate the osteogenic differentiation by the synergistic effects of rGO and DCP. Therefore, in conclusion, it is suggested that the DCP-rGO hybrid composites can be potent factors in accelerating the bone tissue regeneration. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Composition and Structure Evolution of Bi2O3 Coatings as Efficient Photocatalysts
Coatings 2018, 8(1), 14; doi:10.3390/coatings8010014
Received: 20 November 2017 / Revised: 27 December 2017 / Accepted: 27 December 2017 / Published: 29 December 2017
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Abstract
To overcome the recovery disadvantages of Bi2O3 photocatalyst in the form of powder, Bi2O3 photocatalyst coatings were developed via a ball milling, followed by the calcination method. The composition and structure evolution rules of the as-synthesized samples
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To overcome the recovery disadvantages of Bi2O3 photocatalyst in the form of powder, Bi2O3 photocatalyst coatings were developed via a ball milling, followed by the calcination method. The composition and structure evolution rules of the as-synthesized samples were analyzed based on XRD (X-ray powder diffraction) patterns and SEM (scanning electron microscope) observations. XPS (X-ray photoelectron spectroscopy) and UV-Vis (Ultraviolet-visible) spectra were also employed to characterize the samples. The results showed that monoclinic Bi2O3 coatings were obtained after sintering Bi coatings at 673 or 773 K for 2 h, while calcination at a higher temperature and for a longer time resulted in monoclinic and triclinic mixed-phase Bi2O3 coatings. Bi2O3 coatings with a radial growth structure assembled by nanosheets could be realized at a lower temperature lasting for a longer time, while sintering at a higher temperature with relatively short oxidation time led to tangential growth structure. Photodegradation of malachite green solution under simulated solar irradiation for 180 min showed that the largest degradation efficiency of 91.49% was achieved over the photocatalyst coatings calcined at 873 K for 5 h. Additionally, the degradation efficiency was maintained above 80% even after three cycles. Full article
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Open AccessArticle Computer Simulation of Temperature Parameter for Diamond Formation by Using Hot-Filament Chemical Vapor Deposition
Coatings 2018, 8(1), 15; doi:10.3390/coatings8010015
Received: 15 November 2017 / Revised: 12 December 2017 / Accepted: 28 December 2017 / Published: 29 December 2017
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Abstract
To optimize the deposition parameters of diamond films, the temperature, pressure, and distance between the filament and the susceptor need to be considered. However, it is difficult to precisely measure and predict the filament and susceptor temperature in relation to the applied power
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To optimize the deposition parameters of diamond films, the temperature, pressure, and distance between the filament and the susceptor need to be considered. However, it is difficult to precisely measure and predict the filament and susceptor temperature in relation to the applied power in a hot filament chemical vapor deposition (HF-CVD) system. In this study, the temperature distribution inside the system was numerically calculated for the applied powers of 12, 14, 16, and 18 kW. The applied power needed to achieve the appropriate temperature at a constant pressure and other conditions was deduced, and applied to actual experimental depositions. The numerical simulation was conducted using the commercial computational fluent dynamics software ANSYS-FLUENT. To account for radiative heat-transfer in the HF-CVD reactor, the discrete ordinate (DO) model was used. The temperatures of the filament surface and the susceptor at different power levels were predicted to be 2512–2802 K and 1076–1198 K, respectively. Based on the numerical calculations, experiments were performed. The simulated temperatures for the filament surface were in good agreement with the experimental temperatures measured using a two-color pyrometer. The results showed that the highest deposition rate and the lowest deposition of non-diamond was obtained at a power of 16 kW. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Surface Free Energy Utilization to Evaluate Wettability of Hydrocolloid Suspension on Different Vegetable Epicarps
Coatings 2018, 8(1), 16; doi:10.3390/coatings8010016
Received: 26 September 2017 / Revised: 19 December 2017 / Accepted: 21 December 2017 / Published: 30 December 2017
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Abstract
Surface free energy is an essential physicochemical property of a solid and it greatly influences the interactions between vegetable epicarps and coating suspensions. Wettability is the property of a solid surface to reduce the surface tension of a liquid in contact with it
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Surface free energy is an essential physicochemical property of a solid and it greatly influences the interactions between vegetable epicarps and coating suspensions. Wettability is the property of a solid surface to reduce the surface tension of a liquid in contact with it such that it spreads over the surface and wets it, resulting from intermolecular interactions when the two are brought together. The degree of wetting (wettability) is determined by an energy balance between adhesive and cohesive work. The spreading coefficient (Scf/food) is the difference between the work of adhesion and the work of cohesion. Surface wettability is measured by the contact angle, which is formed when a droplet of a liquid is placed on a surface. The objective of this work was to determine the effect of hydroxypropyl methylcellulose (HPMC), κ-carrageenan, glycerol, and cellulose nanofiber (CNF) concentrations on the wettability of edible coatings on banana and eggplant epicarps. Coating suspension wettability on both epicarps were evaluated by contact angle measurements. For the (Scf/food) values obtained, it can be concluded that the surfaces were partially wet by the suspensions. Scf/food on banana surface was influenced mainly by κ-carrageenan concentration, HPMC-glycerol, κ-carrageenan-CNF, and glycerol-CNF interactions. Thus, increasing κ-carrageenan concentrations within the working range led to a 17.7% decrease in Scf/banana values. Furthermore, a HPMC concentration of 3 g/100 g produced a 10.4% increase of the Scf/banana values. Finally, Scf/fruit values for banana epicarps were higher (~10%) than those obtained for eggplant epicarp, indicating that suspensions wetted more the banana than the eggplant surface. Full article
(This article belongs to the Special Issue Edible Films and Coatings)
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Open AccessArticle Effects of Immobilizations of rhBMP-2 and/or rhPDGF-BB on Titanium Implant Surfaces on Osseointegration and Bone Regeneration
Coatings 2018, 8(1), 17; doi:10.3390/coatings8010017
Received: 23 November 2017 / Revised: 28 December 2017 / Accepted: 30 December 2017 / Published: 31 December 2017
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Abstract
The aim of this study was to examine the effects of immobilizing rhPDGF-BB plus rhBMP-2 on heparinized-Ti implants on in vivo osseointegration and vertical bone regeneration at alveolar ridges. Successful immobilizations of rhPDGF-BB and/or rhBMP-2 onto heparinized-Ti (Hepa/Ti) were confirmed by in vitro
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The aim of this study was to examine the effects of immobilizing rhPDGF-BB plus rhBMP-2 on heparinized-Ti implants on in vivo osseointegration and vertical bone regeneration at alveolar ridges. Successful immobilizations of rhPDGF-BB and/or rhBMP-2 onto heparinized-Ti (Hepa/Ti) were confirmed by in vitro analysis, and both growth factors were found to be sustained release. To evaluate bone regeneration, rhPDGF-BB, and/or rhBMP-2-immobilized Hepa/Ti implants were inserted into beagle dogs; implant stability quotients (ISQ), bone mineral densities, bone volumes, osseointegration, and bone formation were assessed by micro CT and histometrically. In vivo study showed that the osseointegration and bone formation were greater in the rhPDGF-BB/rhBMP-2-immobilized Hepa/Ti group than in the rhPDGF-BB-immobilized Hepa/Ti group. The rhPDGF-BB/rhBMP-2 immobilized Hepa/Ti group also showed better implant stability and greater bone volume around defect areas and intra-thread bone density (ITBD) than the rhBMP-2-immobilized Hepa/Ti group. However, no significant differences were observed between these two groups. Through these results, we conclude rhBMP-2 immobilized, heparin-grafted implants appear to offer a suitable delivery system that enhances new bone formation in defect areas around implants. However, we failed to observe the synergetic effects for the rhBMP-2 and rhPDGF-BB combination. Full article
(This article belongs to the Special Issue Surface Engineering of Biomaterials)
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Open AccessArticle Effect of TiN/C Microstructure Composite Layer on the Adhesion of FDLC Film onto Silicon Substrate
Coatings 2018, 8(1), 18; doi:10.3390/coatings8010018
Received: 2 November 2017 / Revised: 25 December 2017 / Accepted: 30 December 2017 / Published: 3 January 2018
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Abstract
Deposition techniques of direct current and radio-frequency magnetron sputtering were used to separately prepare TiN/C microstructural composite layer and fluorinated diamond-like carbon (FDLC) film on monocrystalline silicon. The aim was to investigate the effects of microstructural composite layers on the adhesion property of
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Deposition techniques of direct current and radio-frequency magnetron sputtering were used to separately prepare TiN/C microstructural composite layer and fluorinated diamond-like carbon (FDLC) film on monocrystalline silicon. The aim was to investigate the effects of microstructural composite layers on the adhesion property of FDLC film. The results indicated that the TiN/C microstructural composite layer can distinguish from the substrate and the FDLC film. After adding the composite layers, the film–substrate binding force significantly increased. When the composite film were prepared at a partial pressure of 0.25, the binding force reached 30.5 N, which was greater than the value of 22.6 N for the sample without composite layers. TiN/C in the composite layers intensified the integration with silicon substrate because the C–C bond acted as a bridge linking the FDLC film to the silicon substrate. Furthermore, the bulges on the surface of the composite layers strengthened the physical bonding of the film with silicon substrates. Full article
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Open AccessArticle Influence of Oxygen Contents on the Microstructure, High Temperature Oxidation and Corrosion Resistance Properties of Cr–Si–O–N Coatings
Coatings 2018, 8(1), 19; doi:10.3390/coatings8010019
Received: 8 November 2017 / Revised: 19 December 2017 / Accepted: 25 December 2017 / Published: 3 January 2018
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Abstract
Cr–Si–O–N coatings with different oxygen contents were deposited by multi-arc ion plating, where various O2/(N2 + O2) reactive gas rates were adopted. The XRD and XPS results showed that the CrN crystals disappeared with the increasing of the
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Cr–Si–O–N coatings with different oxygen contents were deposited by multi-arc ion plating, where various O2/(N2 + O2) reactive gas rates were adopted. The XRD and XPS results showed that the CrN crystals disappeared with the increasing of the oxygen flux ratio to 10 at.%. The microhardness of all the Cr–Si–O–N coatings was approximately 2000 Hv0.05, which were dramatically plummeted compared to that of the Cr–Si–N coatings (≈3300 Hv0.05). The Cr–Si–O–N coatings were annealed under 800 °C and 1200 °C in the air atmosphere for 2 h to study the high-temperature oxidation resistance of the coatings. Meanwhile, Cr–Si–O–N coatings with different O2/(N2 + O2) rates were also used to carry out the corrosion resistance testing using the electrochemical working station in 3.5% NaCl solution under free air condition at room temperature. The results indicated that the coatings containing oxygen were more vulnerable to the high-temperature destruction and more easily corroded in the NaCl electrolyte. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Damping Properties of Arc Ion Plating NiCrAlY Coating with Vacuum Annealing
Coatings 2018, 8(1), 20; doi:10.3390/coatings8010020
Received: 5 December 2017 / Revised: 26 December 2017 / Accepted: 28 December 2017 / Published: 3 January 2018
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Abstract
NiCrAlY coating was prepared on a stainless steel substrate by an arc ion plating machine and the annealing experiments were carried out at different temperatures using a tube furnace. The effects of annealing temperatures on the morphology, structure, chemical composition and phase structure
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NiCrAlY coating was prepared on a stainless steel substrate by an arc ion plating machine and the annealing experiments were carried out at different temperatures using a tube furnace. The effects of annealing temperatures on the morphology, structure, chemical composition and phase structure of the coating were characterized by SEM, EDS and XRD, respectively. The change of microstructure is discussed. Dynamic mechanical analyzer results determined the suitable annealing temperature for the best damping performance. The effect of annealing temperature on the microstructure and damping properties of NiCrAlY coating are also discussed. The relationship between annealing temperature and damping properties are explained by microstrcuture, grain size and phase structure. Full article
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Open AccessArticle CuO and CuO/Graphene Nanostructured Thin Films as Counter Electrodes for Pt-Free Dye-Sensitized Solar Cells
Coatings 2018, 8(1), 21; doi:10.3390/coatings8010021
Received: 20 November 2017 / Revised: 24 December 2017 / Accepted: 30 December 2017 / Published: 3 January 2018
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Abstract
Copper oxide (CuO) and CuO/graphene nanostructured thin films were used as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). CuO and CuO/graphene pastes were prepared and coated on fluorine-doped tin oxide (FTO) glass substrates using a doctor-blade coating method. The substrates were then
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Copper oxide (CuO) and CuO/graphene nanostructured thin films were used as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs). CuO and CuO/graphene pastes were prepared and coated on fluorine-doped tin oxide (FTO) glass substrates using a doctor-blade coating method. The substrates were then sintered at 350 °C for 30 min to form CuO and CuO/graphene nanostructures. The material properties of the CuO and CuO/graphene CEs were analyzed using a scanning electron microscope, transmission electron microscope, energy-dispersive spectrometer, thermogravimetric analysis instrument, X-ray diffractometer, Raman spectroscopy, X-ray photoelectron spectrometer, ultraviolet-visible spectrophotometer, and cyclic voltammetry instrument. The CuO and CuO/graphene CEs were used to fabricate DSSCs, and the device characteristics were analyzed using current density–voltage, incident photo-to-current conversion efficiency, and electrochemical impedance spectroscopy measurements. The results showed that when CuO and CuO/graphene were used as the CEs, the device conversion efficiencies were 2.73% and 3.40%, respectively. CuO is a favorable replacement for expensive platinum (Pt) because it features a simple fabrication process and is inexpensive and abundant. Furthermore, graphene, which exhibits high carrier mobility, may be added to enhance the electrical and catalytic abilities of CuO/graphene CEs. This is the first study to examine the use of CuO and CuO/graphene for developing Pt-free CEs in DSSCs. Full article
(This article belongs to the Special Issue Functional Oxide and Oxynitride Coatings)
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Open AccessArticle Combination of Electrodeposition and Transfer Processes for Flexible Thin-Film Thermoelectric Generators
Coatings 2018, 8(1), 22; doi:10.3390/coatings8010022
Received: 19 October 2017 / Revised: 17 December 2017 / Accepted: 21 December 2017 / Published: 3 January 2018
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Abstract
To reduce consumption for ambient assisted living (AAL) applications, we propose the design and fabrication of flexible thin-film thermoelectric generators at a low manufacturing cost. The generators were fabricated using a combination of electrodeposition and transfer processes. N-type Bi2Te3 films
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To reduce consumption for ambient assisted living (AAL) applications, we propose the design and fabrication of flexible thin-film thermoelectric generators at a low manufacturing cost. The generators were fabricated using a combination of electrodeposition and transfer processes. N-type Bi2Te3 films and p-type Sb2Te3 films were formed on a stainless-steel substrate employing potentiostatic electrodeposition using a nitric acid-based bath, followed by a transfer process. Three types of flexible thin-film thermoelectric generators were fabricated. The open circuit voltage (Voc) and maximum output power (Pmax) were measured by applying a temperature difference between the ends of the generator. The thin-film generators obtained using thermoplastic sheets with epoxy resin exhibited a Voc that was tens of millivolts. In particular, the contact resistance of the thin-film generator decreased when silver paste was inserted at the junctions between the n- and p-type films. The most flexible thin-film generator fabricated in this study exhibited a Pmax of 10.4 nW at a temperature difference of 60 K. The current performance of the generators was too low, but we innovated a combination process to prepare them. It is expected to increase the performance by further decreasing the micro-cracks and contact resistance in the generators. Full article
(This article belongs to the Special Issue Advances in Flexible Films and Coatings)
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Open AccessArticle Formation of Anticorrosive Film for Suppressing Pitting Corrosion on Al-Mg-Si Alloy by Steam Coating
Coatings 2018, 8(1), 23; doi:10.3390/coatings8010023
Received: 28 November 2017 / Revised: 23 December 2017 / Accepted: 29 December 2017 / Published: 4 January 2018
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Abstract
Al alloys offer excellent physical and mechanical properties, such as a low density, high specific strength, and good ductility. However, their low corrosion resistance has restricted their application in corrosive environments. There is a need, therefore, for a novel coating technology that is
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Al alloys offer excellent physical and mechanical properties, such as a low density, high specific strength, and good ductility. However, their low corrosion resistance has restricted their application in corrosive environments. There is a need, therefore, for a novel coating technology that is capable of improving the corrosion resistance of Al alloys. In the present study, we examined a steam-based method of forming a corrosion-resistant film on Al alloys. Al-Mg-Si alloy was used as the substrate. The cleaned substrates were set in an autoclave with ultrapure water as the steam source and processed using different temperatures and holding times, resulting in the formation of anticorrosive films on the alloy. FE-SEM images of the film surfaces showed that plate-like nanocrystals were densely formed over the entire surface. XRD patterns indicated that the film was composed mainly of AlOOH crystals. The potentiodynamic polarization curves revealed that the corrosion current density of the film-coated substrates significantly decreased, and that the pitting corrosion was completely suppressed, indicating that the corrosion resistance of the Al-Mg-Si alloy was improved by the film formed by means of steam coating. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Influence of Nitrogen Partial Pressure on Microstructure and Tribological Properties of Mo-Cu-V-N Composite Coatings with High Cu Content
Coatings 2018, 8(1), 24; doi:10.3390/coatings8010024
Received: 19 November 2017 / Revised: 25 December 2017 / Accepted: 27 December 2017 / Published: 4 January 2018
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Abstract
In this study, Mo-Cu-V-N composite coatings with high Cu content of ~18 at.% were deposited on 316L stainless steel and YT14 cemented carbide substrates by high power impulse magnetron sputtering in Ar–N2 gas mixtures. The influence of N2 partial pressure was
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In this study, Mo-Cu-V-N composite coatings with high Cu content of ~18 at.% were deposited on 316L stainless steel and YT14 cemented carbide substrates by high power impulse magnetron sputtering in Ar–N2 gas mixtures. The influence of N2 partial pressure was investigated with respect to the microstructure and tribological properties of the coatings. The results indicated that the Mo-Cu-V-N composite coatings exhibited FCC B1-MoN phase with a strong (200) preferred orientation, and Cu phase was found to exist as metallic species. As the N2 partial pressure increased from 0.11 to 0.35 Pa, the peak intensity of (200) plane decreased gradually and simultaneous peak broadening was observed, which was typical for grain refinement. With increasing the N2 partial pressure, the columnar microstructure became much coarser, which led to the decrease of residual stress and hardness. The Mo-Cu-V-N composite coatings with high Cu content exhibited a relatively low wear rate of 10−8 mm3/N·m at 25 °C, which was believed to be attributed to the mixed lubricious oxides of MoO2, CuO and V2O5 formed during tribo-oxidation, which cannot be formed in the coatings with low Cu content. When the wear temperature was increased up to 400 °C, the wear rate increased sharply up to 10−6 mm3/N·m despite the formation of lubricious oxides of MoO3/CuMoO4 and V2O5. This could be due to the loss of nitrogen and pronounced oxidation at high temperatures, which led the wear mechanism to be transformed from mild oxidation wear to severe oxidation wear. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Flexible n-Type Tungsten Carbide/Polylactic Acid Thermoelectric Composites Fabricated by Additive Manufacturing
Coatings 2018, 8(1), 25; doi:10.3390/coatings8010025
Received: 14 October 2017 / Revised: 6 November 2017 / Accepted: 13 November 2017 / Published: 4 January 2018
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Abstract
Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices.
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Flexible n-type tungsten carbide/polylactic acid (WC/PLA) composites were fabricated by additive manufacturing and their thermoelectric properties were investigated. The preparation of an n-type polymer-based thermoelectric composite with good stability in air atmosphere via additive manufacturing holds promise for application in flexible thermoelectric devices. For WC/PLA volume ratios varying from ~33% to 60%, the electrical conductivity of the composites increased from 10.6 to 42.2 S/cm, while the Seebeck coefficients were in the range −11 to −12.3 μV/K. The thermal conductivities of the composites varied from ~0.2 to ~0.28 W·m−1·K−1 at ~300 K. Full article
(This article belongs to the Special Issue Novel Thin Film Materials for Thermoelectric Applications)
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Open AccessArticle Solution-Processed Efficient Nanocrystal Solar Cells Based on CdTe and CdS Nanocrystals
Coatings 2018, 8(1), 26; doi:10.3390/coatings8010026
Received: 15 November 2017 / Revised: 4 January 2018 / Accepted: 4 January 2018 / Published: 5 January 2018
Cited by 1 | PDF Full-text (3426 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Solution-processed CdTe nanocrystals solar cells have attracted much attention due to their low cost, low material consumption, and potential for roll-to-roll production. Among all kinds of semiconductor materials, CdS exhibits the lowest lattice mismatch with CdTe, which permits high junction quality and high
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Solution-processed CdTe nanocrystals solar cells have attracted much attention due to their low cost, low material consumption, and potential for roll-to-roll production. Among all kinds of semiconductor materials, CdS exhibits the lowest lattice mismatch with CdTe, which permits high junction quality and high device performance. In this study, high quality CdS nanocrystals were prepared by a non-injection technique with tetraethylthiuram disufide and 2,2′-dithiobisbenzothiazole as the stabilizers. Based on the CdTe and CdS nanocrystals, devices with the architecture of ITO/ZnO/CdS/CdTe/MoOx/Au were fabricated successfully by a solution process under ambient condition. The effects of annealing conditions, film thickness, and detailed device structure on the CdTe/CdS nanocrystal solar cells were investigated and discussed in detail. We demonstrate that high junction quality can be obtained by using CdS nanocrystal thin film compared to traditional CdS film via chemical bath deposition (CBD). The best device had short circuit current density (Jsc), open circuit voltage (Voc) and fill factor (FF) of 17.26 mA/cm2, 0.56 V, and 52.84%, respectively, resulting in a power conversion efficiency (PCE) of 5.14%, which is significantly higher than that reported using CBD CdS as the window layer. This work provides important suggestions for the further improvement of efficiency in CdTe nanocrystal solar cells. Full article
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Open AccessArticle Bioactive and Antibacterial Coatings Based on Zein/Bioactive Glass Composites by Electrophoretic Deposition
Coatings 2018, 8(1), 27; doi:10.3390/coatings8010027
Received: 10 August 2017 / Revised: 26 November 2017 / Accepted: 15 December 2017 / Published: 8 January 2018
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Abstract
This study investigated the electrophoretic deposition (EPD) of the natural polymer zein combined with bioactive glass (BG) particles. Through the deposition of various BG compositions, namely 45S5 BG and Cu-doped BG, this work sought to demonstrate the ability of the films to potentiate
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This study investigated the electrophoretic deposition (EPD) of the natural polymer zein combined with bioactive glass (BG) particles. Through the deposition of various BG compositions, namely 45S5 BG and Cu-doped BG, this work sought to demonstrate the ability of the films to potentiate the formation of hydroxyapatite (HA) in contact with simulated body fluid (SBF). Following incubation in SBF, the physical and chemical surface properties of the EPD films were evaluated using different characterization techniques. The formation of HA at the surface of the coatings following immersion in SBF was confirmed using Fourier transform infrared spectroscopy (FTIR). The results demonstrated HA formation in all coatings after seven days of immersion in SBF. Coating morphology and degradation of the zein films were characterized using environmental scanning electron microscopy (ESEM). The results confirmed EPD as a very convenient room temperature technique for production of ion releasing, bioactive, and antibacterial coatings for potential application in orthopedics. Full article
(This article belongs to the Special Issue Electrophoretic Deposition)
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Open AccessArticle Anti-Corrosive and Scale Inhibiting Polymer-Based Functional Coating with Internal and External Regulation of TiO2 Whiskers
Coatings 2018, 8(1), 29; doi:10.3390/coatings8010029
Received: 21 November 2017 / Revised: 12 December 2017 / Accepted: 2 January 2018 / Published: 9 January 2018
PDF Full-text (7991 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A novel multi-functional carrier of mesoporous titanium dioxide whiskers (TiO2(w)) modified by ethylenediamine tetra (methylene phosphonic acid) (EDTMPA) and imidazoline was devised in epoxy coating to improve the anti-corrosion and scale inhibition properties of metal surface. Rigorous characterization using analytical techniques
[...] Read more.
A novel multi-functional carrier of mesoporous titanium dioxide whiskers (TiO2(w)) modified by ethylenediamine tetra (methylene phosphonic acid) (EDTMPA) and imidazoline was devised in epoxy coating to improve the anti-corrosion and scale inhibition properties of metal surface. Rigorous characterization using analytical techniques showed that a mesoporous structure was developed on the TiO2(w). EDTMPA and imidazoline were successfully grafted on the outer and inner surfaces of mesoporous TiO2(w) to synthesize iETiO2(w). The results demonstrated that the corrosion resistance of the final iETiO2(w) epoxy coating is 40 times higher than that of the conventional unmodified OTiO2(w) epoxy coating. The enhanced corrosion resistance of the iETiO2(w) functional coating is due to the chelation of the scaling cations by EDTMPA and electron sharing between imidazoline and Fe. Scale formation on the iETiO2(w) coating is 35 times lower than that on the unmodified OTiO2(w) epoxy coating. In addition, EDTMPA and imidazoline act synergistically in promoting the barrier property of mesoporous TiO2(w) in epoxy coating. It is believed that this novel, simple, and inexpensive route for fabricating functional surface protective coatings on various metallic materials will have a wide range of practical applications. Full article
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Open AccessArticle Formation of Phases and Porous System in the Product of Hydrothermal Treatment of χ-Al2O3
Coatings 2018, 8(1), 30; doi:10.3390/coatings8010030
Received: 7 November 2017 / Revised: 26 December 2017 / Accepted: 9 January 2018 / Published: 11 January 2018
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Abstract
The presence of χ-Al2O3 resulting from thermal decomposition gibbsite as part of alumina catalysts is unfavorable because of its acid characteristics. One of the available techniques of χ-Al2O3 removal is crystallization under hydrothermal conditions into boehmite, which
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The presence of χ-Al2O3 resulting from thermal decomposition gibbsite as part of alumina catalysts is unfavorable because of its acid characteristics. One of the available techniques of χ-Al2O3 removal is crystallization under hydrothermal conditions into boehmite, which is a main precursor of active γ-Al2O3. The influence of products of the hydrothermal treatment of χ-Al2O3 obtaining in result of thermal decomposition gibbsite under T = 150–200 °C, P = 0.5–1.5 MPa and pH = 4.0–9.2 were studied. The hydrothermal treatment products in these conditions are gibbsite and boehmite phases which are formed coincidently by parallel ways. In the alkaline medium at pH = 8.0–9.2 three-dimensional parallelepiped boehmite crystals with the edge length > 200 nm are formed, at pH = 4.0 two-dimensional rhombic-shaped plates with thickness 20–100 nm and with the edge length ~ 80–500 nm are formed. Crystallization of coarse boehmite particles promotes the formation of large and closed mesoporous. Full article
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Open AccessArticle The Preparation and Properties of Fluoroacrylate-Modified Polysiloxane as a Fabric Coating Agent
Coatings 2018, 8(1), 31; doi:10.3390/coatings8010031
Received: 11 December 2017 / Revised: 6 January 2018 / Accepted: 9 January 2018 / Published: 11 January 2018
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Abstract
Polysiloxanes, which can add high softness and lubricity to treated textiles, have been proposed as softening post-finishing agents for fabric. However, the hydrophobicity of the finished fabric is not satisfactory. In this work, long-chain fluoroalkyl acrylate was used to modify the polysiloxane, aimed
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Polysiloxanes, which can add high softness and lubricity to treated textiles, have been proposed as softening post-finishing agents for fabric. However, the hydrophobicity of the finished fabric is not satisfactory. In this work, long-chain fluoroalkyl acrylate was used to modify the polysiloxane, aimed at improving hydrophobicity of the finished fabric and retaining its softness simultaneously. Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectra (1H/13C NMR), and thermogravimetric analysis (TGA) were used to characterize the chemical structure and thermal stability of the as-prepared polymer. The modified polysiloxane was tested as a finishing agent. Its film morphologies on the fabric surface and on a silicon wafer were determined. Chemical compositions and performance properties of the finished fabric were investigated. By bonding long-chain fluoroalkyl, the modified polysiloxane presented good thermal stability. Due to the combined effect of the low surface free energy of the perfluorinated side chains and the relatively high surface roughness of the cotton fibers, the treated fabric had favorable hydrophobicity with a WCA of 144.7° on its surface. In addition, their softness was increased, but the color remained unchanged. Full article
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Open AccessArticle Effect of Tip Shape of Frictional Stir Burnishing Tool on Processed Layer’s Hardness, Residual Stress and Surface Roughness
Coatings 2018, 8(1), 32; doi:10.3390/coatings8010032
Received: 30 November 2017 / Revised: 3 January 2018 / Accepted: 9 January 2018 / Published: 11 January 2018
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Abstract
Friction stir burnishing (FSB) is a surface-enhancement method used after machining, without the need for an additional device. The FSB process is applied on a machine that uses rotation tools (e.g., machining center or multi-tasking machine). Therefore, the FSB process can be applied
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Friction stir burnishing (FSB) is a surface-enhancement method used after machining, without the need for an additional device. The FSB process is applied on a machine that uses rotation tools (e.g., machining center or multi-tasking machine). Therefore, the FSB process can be applied immediately after the cutting process using the same machine tool. Here, we apply the FSB to the shaft materials of 0.45% C steel using a multi-tasking machine. In the FSB process, the burnishing tool rotates at a high-revolution speed. The thin surface layer is rubbed and stirred as the temperature is increased and decreased. With the FSB process, high hardness or compressive residual stress can be obtained on the surface layer. However, when we applied the FSB process using a 3 mm diameter sphere tip shape tool, the surface roughness increased substantially (Ra = 20 µm). We therefore used four types of tip shape tools to examine the effect of burnishing tool tip radius on surface roughness, hardness, residual stress in the FSB process. Results indicated that the surface roughness was lowest (Ra = 10 µm) when the tip radius tool diameter was large (30 mm). Full article
(This article belongs to the Special Issue Manufacturing and Surface Engineering)
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Open AccessArticle Corrosion Inhibition Properties of Waterborne Polyurethane/Cerium Nitrate Coatings on Mild Steel
Coatings 2018, 8(1), 34; doi:10.3390/coatings8010034
Received: 26 September 2017 / Revised: 2 January 2018 / Accepted: 10 January 2018 / Published: 15 January 2018
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Abstract
Waterborne polyurethane (WBPU)/cerium nitrate (Ce(NO3)3) dispersions were synthesized with different defined Ce(NO3)3 content. All pristine dispersions were stable with different poly(tetramethylene oxide) glycol (PTMG) number average molecular weights (Mn) of 650, 1000, and 2000. The interaction
[...] Read more.
Waterborne polyurethane (WBPU)/cerium nitrate (Ce(NO3)3) dispersions were synthesized with different defined Ce(NO3)3 content. All pristine dispersions were stable with different poly(tetramethylene oxide) glycol (PTMG) number average molecular weights (Mn) of 650, 1000, and 2000. The interaction between the carboxyl acid salt group and Ce(NO3)3 was analyzed by Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. Coating hydrophilicity, water swelling (%), water contact angle, leaching, and corrosion protection efficiency were all affected when using different Ce(NO3)3 content and PTMG molecular weights. The maximal corrosion protection of the WBPU coating was recorded using a higher molecular weight of PTMG with 0.016 mole Ce(NO3)3 content. Full article
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Open AccessArticle Surface Coatings of TiO2 Nanoparticles onto the Designed Fabrics for Enhanced Self-Cleaning Properties
Coatings 2018, 8(1), 35; doi:10.3390/coatings8010035
Received: 2 November 2017 / Revised: 22 December 2017 / Accepted: 29 December 2017 / Published: 15 January 2018
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Abstract
Herein, the hydrophobic and self-cleaning properties of three different fabric surfaces have been evaluated after applying titanium dioxide (TiO2) nanofinishes. The nanoparticles were prepared by sol-gel techniques and were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and dynamic
[...] Read more.
Herein, the hydrophobic and self-cleaning properties of three different fabric surfaces have been evaluated after applying titanium dioxide (TiO2) nanofinishes. The nanoparticles were prepared by sol-gel techniques and were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and dynamic light scattering (DLS) methods. The ultra-refined particles were applied over three different fabric substrates having similar weave of Z-twill (3/1). The yarns of 100% polyester, blend of viscose with mod-acrylic and high performance polyethylene containing 16 yarn count (Ne) and 31.496 and 15.748 ends/cm and picks/cm, respectively, were used for required fabric preparation. The different fabric structures were applied with self-cleaning finish of TiO2 nanoparticles prepared in our laboratory and the results were compared with commercially available finish Rucoguard AFR. The static contact angles, UV-protection factor, air permeability and hydrophobic activity of nanofinished fabric helped in evaluating their breathability and self-cleaning properties. Full article
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Open AccessArticle Effect of Al-B2O3-TiO2 Exothermic System on Performances of Fly Ash Glass/Ceramic Composite Coating
Coatings 2018, 8(1), 36; doi:10.3390/coatings8010036
Received: 3 December 2017 / Revised: 21 December 2017 / Accepted: 28 December 2017 / Published: 16 January 2018
PDF Full-text (3378 KB) | HTML Full-text | XML Full-text
Abstract
Glass/ceramic composite coatings were prepared on 40Cr steel matrix by thermo-chemical reaction with fly ash and a small amount of SiO2, Al2O3, MgO, and albite as main raw materials. On this basis, adding 10% Al-TiO2-B
[...] Read more.
Glass/ceramic composite coatings were prepared on 40Cr steel matrix by thermo-chemical reaction with fly ash and a small amount of SiO2, Al2O3, MgO, and albite as main raw materials. On this basis, adding 10% Al-TiO2-B2O3 exothermic system, the morphology, phase, thermal shock resistance, and corrosion resistance of the coating were tested, and the influence of exothermic system on the structure and properties of the composite coating was studied. The experimental results show that the addition of exothermic system can promote the formation of NaB15, TiB2, Na2B4O7, Ca2Al2SiO7, and other new phases by thermo-chemical reaction; when compared to the composite coating without addition of exothermic system, combined with a good interface, higher compactness, and lower porosity. The highest micro hardness can be reached 725HV0.1. The number of thermal shock from 700 °C to room temperature can reach more than 50 times; acid, salt, oil immersion corrosion test, composite coating with exothermic system relative to the matrix increased by 27.40 times, 3.97 times, and 1.88 times, respectively. The overall performance is better than that of the composite coating without exothermic system. Full article
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Open AccessArticle Synthesis, Characterization, and Application of Novel Ni-P-Carbon Nitride Nanocomposites
Coatings 2018, 8(1), 37; doi:10.3390/coatings8010037
Received: 28 November 2017 / Revised: 10 January 2018 / Accepted: 15 January 2018 / Published: 17 January 2018
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Abstract
Dispersion of 2D carbon nitride (C3N4) nanosheets into a nickel phosphorous (NiP) matrix was successfully achieved by ultrasonication during the electroless plating of NiP from an acidic bath. The morphology and thickness, elemental analysis, phases, roughness, and wettability for
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Dispersion of 2D carbon nitride (C3N4) nanosheets into a nickel phosphorous (NiP) matrix was successfully achieved by ultrasonication during the electroless plating of NiP from an acidic bath. The morphology and thickness, elemental analysis, phases, roughness, and wettability for as-plated and heat-treated nanocomposite were determined by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, atomic force microscopy, and contact angle measurements, respectively. C3N4 showed a homogeneous distribution morphology in the nanocomposite that changed from amorphous in case of the NiP to a mixed crystalline-amorphous structure in the NiP-C3N4 nanocomposite. The microhardness and corrosion resistance of the as-plated nanocomposite and the heat-treated nanocomposite coating were significantly enhanced compared to the Ni-P. The nanocomposite showed a superior corrosion protection efficiency of ~95%, as observed from the electrochemical impedance spectroscopy (EIS) measurements. On the other hand, the microhardness of the nanocomposite was significantly increased from 780 to reach 1175 HV200 for NiP and NiP-C3N4, respectively. Full article
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Open AccessArticle Cutting Performance of Low Stress Thick TiAlN PVD Coatings during Machining of Compacted Graphite Cast Iron (CGI)
Coatings 2018, 8(1), 38; doi:10.3390/coatings8010038
Received: 18 December 2017 / Revised: 6 January 2018 / Accepted: 13 January 2018 / Published: 18 January 2018
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Abstract
A new family of physical vapor deposited (PVD) coatings is presented in this paper. These coatings are deposited by a superfine cathode (SFC) using the arc method. They combine a smooth surface, high hardness, and low residual stresses. This allows the production of
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A new family of physical vapor deposited (PVD) coatings is presented in this paper. These coatings are deposited by a superfine cathode (SFC) using the arc method. They combine a smooth surface, high hardness, and low residual stresses. This allows the production of PVD coatings as thick as 15 µm. In some applications, in particular for machining of such hard to cut material as compacted graphite iron (CGI), such coatings have shown better tool life compared to the conventional PVD coatings that have a lower thickness in the range of up to 5 μm. Finite element modeling of the temperature/stress profiles was done for the SFC coatings to present the temperature/stress profiles during cutting. Comprehensive characterization of the coatings was performed using XRD, TEM, SEM/EDS studies, nano-hardness, nano-impact measurements, and residual stress measurements. Application of the coating with this set of characteristics reduces the intensity of buildup edge formation during turning of CGI, leading to longer tool life. Optimization of the TiAlN-based coatings composition (Ti/Al ratio), architecture (mono vs. multilayer), and thickness were performed. Application of the optimized coating resulted in a 40–60% improvement in the cutting tool life under finishing turning of CGI. Full article
(This article belongs to the Special Issue Coatings for Cutting Tools)
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Open AccessArticle Improved Corrosion Resistance of 5XXX Aluminum Alloy by Homogenization Heat Treatment
Coatings 2018, 8(1), 39; doi:10.3390/coatings8010039
Received: 30 November 2017 / Revised: 28 December 2017 / Accepted: 15 January 2018 / Published: 18 January 2018
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Abstract
The corrosion resistance of homogenized Al-Mg (6.5%) alloy—adding Si, Zn, Mn, and Fe (0.2%) to improve various properties—was observed. Differential scanning calorimetry (DSC) and a JMatPro simulation revealed that the optimal homogenization temperature was 450 °C. The homogenization was carried out at 450
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The corrosion resistance of homogenized Al-Mg (6.5%) alloy—adding Si, Zn, Mn, and Fe (0.2%) to improve various properties—was observed. Differential scanning calorimetry (DSC) and a JMatPro simulation revealed that the optimal homogenization temperature was 450 °C. The homogenization was carried out at 450 °C for 3, 6, 12, 18, 24, and 30 h in order to view the corrosion resistance change. Corrosion resistance was analyzed by a polarization test in 3.5 wt % NaCl solution. The corrosion resistance improved with increasing homogenization time up to 24 h, but there was no change with longer time periods. To observe the reason for the change in corrosion resistance, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), and transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM-EDS) analyses were performed. Precipitates containing Mg, such as Al3Mg2 and Mg32(Al, Zn)49, decreased at the grain boundary. After homogenization, the amount of Mg measured by SEM-EDS at the grain boundary decreased from 36% to 8%, while Si increased. Generally, the potential difference between the grain boundary and the grains leads to intergranular corrosion. Reduction of Mg, whose standard electrode potential is lower than that of Al, and an increase of Si, which is present in higher concentration than Al at the grain boundaries, improved the corrosion resistance of 5XXX Al alloy by reducing the intergranular corrosion. Full article
(This article belongs to the Special Issue Hybrid Surface Coatings & Process (Selected Papers from HyMaP 2017))
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Open AccessArticle Antimicrobial Double-Layer Coating Prepared from Pure or Doped-Titanium Dioxide and Binders
Coatings 2018, 8(1), 41; doi:10.3390/coatings8010041
Received: 27 October 2017 / Revised: 26 December 2017 / Accepted: 17 January 2018 / Published: 20 January 2018
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Abstract
Fruit and vegetable containers with microbe-free surfaces can be made by coating with titanium dioxide (TiO2) particles or nonmetal (C, N, B, F) doped-TiO2 particles, using wear resistant polymers, such as zein, and paint, as the binders and to form
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Fruit and vegetable containers with microbe-free surfaces can be made by coating with titanium dioxide (TiO2) particles or nonmetal (C, N, B, F) doped-TiO2 particles, using wear resistant polymers, such as zein, and paint, as the binders and to form a continuous binding phase. The doped-TiO2 powders absorb visible light radiation, and thus possess a higher antibacterial effect than non-modified TiO2 particles in environmental conditions. The study also presents a double-layer coating to use less TiO2 particles in coating, while achieving higher antimicrobial activity. Containers with microbe-free surfaces can stop cross-contamination from infected workers or spoiled/decayed/contaminated fruits or vegetables, and thus are expected to be able to reduce the risk from microbiological contamination of fruits and vegetables during harvest in fields, and postharvest storage or transportation. Full article
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Open AccessArticle Oxidation Characteristics and Electrical Properties of Doped Mn-Co Spinel Reaction Layer for Solid Oxide Fuel Cell Metal Interconnects
Coatings 2018, 8(1), 42; doi:10.3390/coatings8010042
Received: 7 December 2017 / Revised: 16 January 2018 / Accepted: 16 January 2018 / Published: 22 January 2018
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Abstract
To prevent Cr poisoning of the cathode and to retain high conductivity during solid oxide fuel cell (SOFC) operation, Cu or La doped Co-Mn coatings on a metallic interconnect is deposited and followed by oxidation at 750 °C. Microstructure and composition of coatings
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To prevent Cr poisoning of the cathode and to retain high conductivity during solid oxide fuel cell (SOFC) operation, Cu or La doped Co-Mn coatings on a metallic interconnect is deposited and followed by oxidation at 750 °C. Microstructure and composition of coatings after preparation and oxidation is analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). High energy micro arc alloying process, a low cost technique, is used to prepare Cu or La doped Co-Mn coatings with the metallurgical bond. When coatings oxidized at 750 °C in air for 20 h and 100 h, Co3O4 is the main oxide on the surface of Co-38Mn-2La and Co-40Mn coatings, and (Co,Mn)3O4 spinel continues to grow with extended oxidation time. The outmost scales of Co-33Mn-17Cu are mainly composed of cubic MnCo2O4 spinel with Mn2O3 after oxidation for 20 h and 100 h. The average thickness of oxide coatings is about 60–70 μm after oxidation for 100 h, except that Co-40Mn oxide coatings are a little thicker. Area-specific resistance of Cu/La doped Co-Mn coatings are lower than that of Co-40Mn coating. (Mn,Co)3O4/MnCo2O4 spinel layer is efficient at blocking the outward diffusion of chromium and iron. Full article
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Open AccessArticle Nonpolar Surface Modification Using Fatty Acids and Its Effect on Calcite from Mineral Carbonation of Desulfurized Gypsum
Coatings 2018, 8(1), 43; doi:10.3390/coatings8010043
Received: 28 November 2017 / Revised: 15 January 2018 / Accepted: 19 January 2018 / Published: 22 January 2018
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Abstract
CaCO3 is often used as an additive in many industries. However, additional functions are required to expand its applicability. This entails modification of its physicochemical properties. Accordingly, in this study, a particle surface modification treatment was performed on CaCO3 produced from
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CaCO3 is often used as an additive in many industries. However, additional functions are required to expand its applicability. This entails modification of its physicochemical properties. Accordingly, in this study, a particle surface modification treatment was performed on CaCO3 produced from desulfurized gypsum for a range of industrial applications. In the experiment, fatty acids were used to modify the CaCO3 surface, and the scale of the modification effect was based on the degree of change associated with a polar surface taking on nonpolar surface properties. In the preliminary modification experiment, stearic acid was dissolved in 2-propanol or chloroform, and the extent of the reaction and the active ratio were measured according to the stearic acid concentration. The results showed that the effective active ratio, considering the activity to unit adsorption, was higher in 2-propanol than in chloroform. Consequently, the modification solvent used in the experiment changed the CaCO3 surface from a hydrophilic, polarized form to a hydrophobic, nonpolarized form. These results will also allow the CaCO3 produced to be used as a filler in a range of chemical industries. Full article
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Open AccessArticle Influence of Thickness of Multilayered Nano-Structured Coatings Ti-TiN-(TiCrAl)N and Zr-ZrN-(ZrCrNbAl)N on Tool Life of Metal Cutting Tools at Various Cutting Speeds
Coatings 2018, 8(1), 44; doi:10.3390/coatings8010044
Received: 24 December 2017 / Revised: 14 January 2018 / Accepted: 16 January 2018 / Published: 23 January 2018
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Abstract
This paper considers the influence of thickness of multilayered nano-structured coatings Ti-TiN-(TiCrAl)N and Zr-ZrN-(ZrCrNbAl)N on tool life of metal cutting tools at various cutting speeds (vc = 250, 300, 350 and 400 m·min−1). The paper investigates the basic mechanical
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This paper considers the influence of thickness of multilayered nano-structured coatings Ti-TiN-(TiCrAl)N and Zr-ZrN-(ZrCrNbAl)N on tool life of metal cutting tools at various cutting speeds (vc = 250, 300, 350 and 400 m·min−1). The paper investigates the basic mechanical parameters of coatings and the mechanism of coating failure in scratch testing depending on thickness of coating. Cutting tests were conducted in longitudinal turning of steel C45 with tools with the coatings under study of various thicknesses (3, 5, and 7 µm), with an uncoated tool and with a tool with a “reference” coating of TiAlN. The relationship of “cutting speed vc—tool life T” was built and investigated; and the mechanisms were found to determine the selection of the optimum coating thickness at various cutting speeds. Advantages of cutting tools with these coatings are especially obvious at high cutting speeds (in particular, vc = 400 m·min−1). If at lower cutting speeds, the longest tool life is shown by tools with thicker coatings (of about 7 μm), then with an increase in cutting speed (especially at vc = 400 m·min−1) the longest tool life is shown by tools with thinner coating (of about 3 μm). Full article
(This article belongs to the Special Issue Manufacturing and Surface Engineering)
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Open AccessArticle Performance Investigation of an Exhaust Thermoelectric Generator for Military SUV Application
Coatings 2018, 8(1), 45; doi:10.3390/coatings8010045
Received: 4 December 2017 / Revised: 16 January 2018 / Accepted: 17 January 2018 / Published: 22 January 2018
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Abstract
To analyze the thermoelectric power generation for sports utility vehicle (SUV) application, a novel thermoelectric generator (TEG) based on low-temperature Bi2Te3 thermoelectric modules (TEMs) and a chaos-shaped brass heat exchanger is constructed. The temperature distribution of the TEG is analyzed
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To analyze the thermoelectric power generation for sports utility vehicle (SUV) application, a novel thermoelectric generator (TEG) based on low-temperature Bi2Te3 thermoelectric modules (TEMs) and a chaos-shaped brass heat exchanger is constructed. The temperature distribution of the TEG is analyzed based on an experimental setup, and the temperature uniformity optimization method is performed by chipping peak off and filling valley is taken to validate the improved output power. An automobile exhaust thermoelectric generator (AETEG) using four TEGs connected thermally in parallel and electrically in series is assembled into a prototype military SUV, its temperature distribution, output voltage, output power, system efficiency, inner resistance, and backpressure is analyzed, and several important influencing factors such as vehicle speed, clamping pressure, engine coolant flow rate, and ambient temperature on its output performance are tested. Experimental results demonstrate that higher vehicle speed, larger clamping pressure, faster engine coolant flow rate and lower ambient temperature can enhance the overall output performance, but the ambient temperature and coolant flow rate are less significant. The maximum output power of AETEG is 646.26 W, the corresponding conversion efficiency is 1.03%, and the increased backpressure changes from 1681 Pa to 1807 Pa when the highest vehicle speed is 125 km/h. Full article
(This article belongs to the Special Issue Novel Thin Film Materials for Thermoelectric Applications)
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Open AccessReview Recent Developments Concerning the Dispersion Methods and Mechanisms of Graphene
Coatings 2018, 8(1), 33; doi:10.3390/coatings8010033
Received: 7 December 2017 / Revised: 31 December 2017 / Accepted: 6 January 2018 / Published: 12 January 2018
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Abstract
Graphene, as a reinforcement for composite materials, has become a focus recently. However, the dispersion of graphene in composite materials is a problem that has been difficult to solve for a long time, which makes it difficult to produce and use graphene-reinforced composites
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Graphene, as a reinforcement for composite materials, has become a focus recently. However, the dispersion of graphene in composite materials is a problem that has been difficult to solve for a long time, which makes it difficult to produce and use graphene-reinforced composites on a large scale. Herein, methods to improve the dispersion of graphene and dispersion mechanisms that have been developed in recent years are reviewed, and the advantages and disadvantages of various methods are compared and analyzed. On this basis, the dispersion methods and mechanisms of graphene are prospected, which lays the foundation for graphene application and preparation. Full article
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Open AccessReview Thermal Growth of Graphene: A Review
Coatings 2018, 8(1), 40; doi:10.3390/coatings8010040
Received: 29 November 2017 / Revised: 25 December 2017 / Accepted: 30 December 2017 / Published: 19 January 2018
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Abstract
A common belief proposed by Peierls and Landau that two-dimensional material cannot exist freely in a three-dimensional world has been proved false when graphene was first synthesized in 2004. Graphene, which is the base structure of other carbon materials, has drawn much attention
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A common belief proposed by Peierls and Landau that two-dimensional material cannot exist freely in a three-dimensional world has been proved false when graphene was first synthesized in 2004. Graphene, which is the base structure of other carbon materials, has drawn much attention of scholars and researchers due to its extraordinary electrical, mechanical and thermal properties. Moreover, methods for its synthesis have developed greatly in recent years. This review focuses on the mechanism of the thermal growth method and the different synthesis methods, where epitaxial growth, chemical vapor deposition, plasma-enhanced chemical vapor deposition and combustion are discussed in detail based on this mechanism. Meanwhile, to improve the quality and control the number of graphene layers, the latest research progress in optimizing growth parameters and developmental technologies has been summarized. The strategies for synthesizing high-quality and large-scale graphene are proposed and an outlook on the future synthesis direction is also provided. Full article
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