Coatings

2 pages, 172 KiB

Open AccessEditorial

Special Issue: Plasma Electrolytic Oxidation (PEO) Coatings

by Marta Mohedano and Beatriz Mingo

Coatings 2021, 11(1), 111; https://doi.org/10.3390/coatings11010111 - 19 Jan 2021

Cited by 1 | Viewed by 2178

The demand of modern technological society for light structural materials (Al, Ti, Mg) emphasizes a combination of good corrosion resistance with wear properties and functionalized surfaces [...] Full article

(This article belongs to the Special Issue Plasma Electrolytic Oxidation (PEO) Coatings)

62 pages, 5566 KiB

Open AccessReview

Electrodeposited Hydroxyapatite-Based Biocoatings: Recent Progress and Future Challenges

by Mir Saman Safavi, Frank C. Walsh, Maria A. Surmeneva, Roman A. Surmenev and Jafar Khalil-Allafi

Coatings 2021, 11(1), 110; https://doi.org/10.3390/coatings11010110 - 19 Jan 2021

Cited by 79 | Viewed by 5730

Abstract

Hydroxyapatite has become an important coating material for bioimplants, following the introduction of synthetic HAp in the 1950s. The HAp coatings require controlled surface roughness/porosity, adequate corrosion resistance and need to show favorable tribological behavior. The deposition rate must be sufficiently fast and [...] Read more.

Hydroxyapatite has become an important coating material for bioimplants, following the introduction of synthetic HAp in the 1950s. The HAp coatings require controlled surface roughness/porosity, adequate corrosion resistance and need to show favorable tribological behavior. The deposition rate must be sufficiently fast and the coating technique needs to be applied at different scales on substrates having a diverse structure, composition, size, and shape. A detailed overview of dry and wet coating methods is given. The benefits of electrodeposition include controlled thickness and morphology, ability to coat a wide range of component size/shape and ease of industrial processing. Pulsed current and potential techniques have provided denser and more uniform coatings on different metallic materials/implants. The mechanism of HAp electrodeposition is considered and the effect of operational variables on deposit properties is highlighted. The most recent progress in the field is critically reviewed. Developments in mineral substituted and included particle, composite HAp coatings, including those reinforced by metallic, ceramic and polymeric particles; carbon nanotubes, modified graphenes, chitosan, and heparin, are considered in detail. Technical challenges which deserve further research are identified and a forward look in the field of the electrodeposited HAp coatings is taken. Full article

(This article belongs to the Special Issue Recent Progress in Bioactive Surfaces and Thin Films)

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28 pages, 7095 KiB

Open AccessArticle

Electron Transfer through a Natural Oxide Layer on Real Metal Surfaces Occurring during Sliding with Polytetrafluoroethylene: Dependence on Heat of Formation of Metal Oxides

by Yoshihiro Momose

Coatings 2021, 11(1), 109; https://doi.org/10.3390/coatings11010109 - 19 Jan 2021

Cited by 4 | Viewed by 2511

Abstract

Electron emission (EE) from real metal surfaces occurring during sliding contact with a polytetrafluoroethylene (PTFE) rider has been investigated using the thermodynamic data of metal oxides and the X-ray photoelectron spectroscopy (XPS) intensity ratio of oxygen/metal on the surfaces. EE was termed triboelectron [...] Read more.

Electron emission (EE) from real metal surfaces occurring during sliding contact with a polytetrafluoroethylene (PTFE) rider has been investigated using the thermodynamic data of metal oxides and the X-ray photoelectron spectroscopy (XPS) intensity ratio of oxygen/metal on the surfaces. EE was termed triboelectron emission (TriboEE). Rolled metal sheets of 18 types were used. The metal‒oxygen bond energy calculated from the heat of the formation of metal oxide, (D(M–O)), was shown to be a key factor in dividing the EE into two routes, the so-called Schottky effect and the tunnel effect, due to the surface oxide layer. The metals in periodic groups 4 (Ti and Zr), 5 (V, Nb, and Ta), and 6 (Mo and W) maintained higher values of D(M–O), while, moving down the groups, the TriboEE intensity increased, being ascribed to the former route. In groups 10 (Ni, Pd, and Pt) and 11 (Cu, Ag, and Au), the D(M–O) values decreased moving down the groups, but the TriboEE intensity increased significantly, which can be attributed to the latter route. Furthermore, with the increase in the electrical conductivity of metals, the TriboEE intensity became remarkably high, while the D(M–O) value fell rapidly and became almost constant. The XPS results showed that the dependence of the D(M–O) and XPS metal core intensity on the O1s intensity and the XPS intensity ratio of the O1s/metal core was different between groups 10 and 11 and groups 4, 5, and 6. It was concluded that, under the electric field caused on the real metal surface by the friction with PTFE, the electron from metals with small D(M–O) values predominantly tunnels the surface oxide layer as a surface barrier, while with large D(M–O) values, the electron passes over the top of the barrier. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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12 pages, 2895 KiB

Open AccessArticle

Investigation of Thick-Film-Paste Rheology and Film Material for Pattern Transfer Printing (PTP) Technology

by Adrian Adrian, Dominik Rudolph, Jan Lossen and Norbert Willenbacher

Coatings 2021, 11(1), 108; https://doi.org/10.3390/coatings11010108 - 19 Jan 2021

Cited by 1 | Viewed by 3067

Abstract

Steady cost pressure in silicon solar cell production leads to a continuous reduction of silver consumption per cell. Pattern Transfer Printing (PTP) technology enables to reduce silver consumption by depositing smaller front electrodes on solar cells. Here, we aim at a better understanding [...] Read more.

Steady cost pressure in silicon solar cell production leads to a continuous reduction of silver consumption per cell. Pattern Transfer Printing (PTP) technology enables to reduce silver consumption by depositing smaller front electrodes on solar cells. Here, we aim at a better understanding of the laser deposition process. The aspect ratio of printed lines improved with increasing paste yield stress but was lower than the theoretical aspect ratio for a given trench geometry, suggesting that line spreading was caused by the pressure that was due to the vaporization of volatile paste components and a yield stress reduction that was due to local paste heating. A low laser power threshold, mandatory to fabricate narrow electrodes with a high aspect ratio and low amount of debris, could be achieved using pastes with low boiling temperature of volatile components and poor wetting between paste and film. The material with the lowest light transmission exhibited the lowest laser power threshold. We attribute this to the weaker adhesion to the paste and a better alignment with the laser focal plane. Our results provide valuable guidelines for paste and film material design aimed at narrower electrodes, with a higher aspect ratio to be obtained at an even lower laser power threshold in PTP-based solar cell metallization. Full article

(This article belongs to the Special Issue Thin and Thick Films: Deposition, Characterization and Applications)

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14 pages, 3879 KiB

Open AccessFeature PaperArticle

Cytotoxicity and Genotoxicity of Metal Oxide Nanoparticles in Human Pluripotent Stem Cell-Derived Fibroblasts

by Harish K Handral, C. Ashajyothi, Gopu Sriram, Chandrakanth R. Kelmani, Nileshkumar Dubey and Tong Cao

Coatings 2021, 11(1), 107; https://doi.org/10.3390/coatings11010107 - 19 Jan 2021

Cited by 5 | Viewed by 2769

Abstract

Advances in the use of nanoparticles (NPs) has created promising progress in biotechnology and consumer-care based industry. This has created an increasing need for testing their safety and toxicity profiles. Hence, efforts to understand the cellular responses towards nanomaterials are needed. However, current [...] Read more.

Advances in the use of nanoparticles (NPs) has created promising progress in biotechnology and consumer-care based industry. This has created an increasing need for testing their safety and toxicity profiles. Hence, efforts to understand the cellular responses towards nanomaterials are needed. However, current methods using animal and cancer-derived cell lines raise questions on physiological relevance. In this aspect, in the current study, we investigated the use of pluripotent human embryonic stem cell- (hESCs) derived fibroblasts (hESC-Fib) as a closer representative of the in vivo response as well as to encourage the 3Rs (replacement, reduction and refinement) concept for evaluating the cytotoxic and genotoxic effects of zinc oxide (ZnO), titanium dioxide (TiO₂) and silicon-dioxide (SiO₂) NPs. Cytotoxicity assays demonstrated that the adverse effects of respective NPs were observed in hESC-Fib beyond concentrations of 200 µg/mL (SiO₂ NPs), 30 µg/mL (TiO₂ NPs) and 20 µg/mL (ZnO NPs). Flow cytometry results correlated with increased apoptosis upon increase in NP concentration. Subsequently, scratch wound assays showed ZnO (10 µg/mL) and TiO₂ (20 µg/mL) NPs inhibit the rate of wound coverage. DNA damage assays confirmed TiO₂ and ZnO NPs are genotoxic. In summary, hESC-Fib could be used as an alternative platform to understand toxicity profiles of metal oxide NPs. Full article

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

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25 pages, 2466 KiB

Open AccessReview

In Vivo Assessment of Synthetic and Biological-Derived Calcium Phosphate-Based Coatings Fabricated by Pulsed Laser Deposition: A Review

by Liviu Duta

Coatings 2021, 11(1), 99; https://doi.org/10.3390/coatings11010099 - 18 Jan 2021

Cited by 18 | Viewed by 2848

Abstract

The aim of this review is to present the state-of-the art achievements reported in the last two decades in the field of pulsed laser deposition (PLD) of biocompatible calcium phosphate (CaP)-based coatings for medical implants, with an emphasis on their in vivo biological [...] Read more.

The aim of this review is to present the state-of-the art achievements reported in the last two decades in the field of pulsed laser deposition (PLD) of biocompatible calcium phosphate (CaP)-based coatings for medical implants, with an emphasis on their in vivo biological performances. There are studies in the dedicated literature on the in vivo testing of CaP-based coatings (especially hydroxyapatite, HA) synthesized by many physical vapor deposition methods, but only a few of them addressed the PLD technique. Therefore, a brief description of the PLD technique, along with some information on the currently used substrates for the synthesis of CaP-based structures, and a short presentation of the advantages of using various animal and human implant models will be provided. For an in-depth in vivo assessment of both synthetic and biological-derived CaP-based PLD coatings, a special attention will be dedicated to the results obtained by standardized and micro-radiographies, (micro) computed tomography and histomorphometry, tomodensitometry, histology, scanning and transmission electron microscopies, and mechanical testing. One main specific result of the in vivo analyzed studies is related to the demonstrated superior osseointegration characteristics of the metallic (generally Ti) implants functionalized with CaP-based coatings when compared to simple (control) Ti ones, which are considered as the “gold standard” for implantological applications. Thus, all such important in vivo outcomes were gathered, compiled and thoroughly discussed both to clearly understand the current status of this research domain, and to be able to advance perspectives of these synthetic and biological-derived CaP coatings for future clinical applications. Full article

(This article belongs to the Special Issue Current Research in Pulsed Laser Deposition)

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12 pages, 1520 KiB

Open AccessArticle

Ion Release from Dental Implants, Prosthetic Abutments and Crowns under Physiological and Acidic Conditions

by María Arregui, Florian Latour, Francisco Javier Gil, Román A. Pérez, Luis Giner-Tarrida and Luis M. Delgado

Coatings 2021, 11(1), 98; https://doi.org/10.3390/coatings11010098 - 18 Jan 2021

Cited by 10 | Viewed by 2655

Abstract

Ion release from dental implants and prosthetic restoration can affect osteointegration and implant viability over a long period of time. Therefore, the aim of this study was to study the ion release from implants and crowns, with and without intermediate anodized abutments, in [...] Read more.

Ion release from dental implants and prosthetic restoration can affect osteointegration and implant viability over a long period of time. Therefore, the aim of this study was to study the ion release from implants and crowns, with and without intermediate anodized abutments, in two different media, simulating clinical conditions. The implants, intermediate prosthetic abutments and Cr–Co crowns were divided into two groups depending on the media: Hanks’ solution and 1% lactic acid, simulating body fluids and microbiologically conditioned fluids, respectively. The study followed the ISO 10271:2011 and 10993-15:2000 standards modified to simulate the replacement of fluids in the oral environment. The ions’ release was measured by inductively coupled plasma mass spectroscopy (ICP-EOS), and only aluminum, chromium, cobalt, titanium and vanadium were identified. Ion concentration was higher in lactic acid than in Hanks’ solution at all time points (p < 0.05). Only vanadium showed a very low ion release in lactic acid, with no statistically significant differences from the ion release in Hanks’ solution (p = 0.524). Both anodized abutments and the immersion medium influenced the release of ions and affected the corrosion of these structures. The presence of an intermediate anodized abutment also affected ion release, as the level of ions was lower in groups with this component. Full article

(This article belongs to the Special Issue Bioactive Surfaces and Coatings for Bone Regeneration)

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23 pages, 5148 KiB

Open AccessArticle

Spilanthes acmella Leaves Extract for Corrosion Inhibition in Acid Medium

by Akbar Ali Samsath Begum, Raja Mohamed Abdul Vahith, Vijay Kotra, Mohammed Rafi Shaik, Abdelatty Abdelgawad, Emad Mahrous Awwad and Mujeeb Khan

Coatings 2021, 11(1), 106; https://doi.org/10.3390/coatings11010106 - 18 Jan 2021

Cited by 21 | Viewed by 3107

Abstract

In the present study, the corrosion inhibition effect of Spilanthes acmella aqueous leaves extract (SA-LE) on mild steel was investigated in 1.0 M HCl solution at different temperature using weight loss, Tafel polarization, linear polarization resistance (LPR), and electrochemical impedance (EIS) measurements. Adsorption [...] Read more.

In the present study, the corrosion inhibition effect of Spilanthes acmella aqueous leaves extract (SA-LE) on mild steel was investigated in 1.0 M HCl solution at different temperature using weight loss, Tafel polarization, linear polarization resistance (LPR), and electrochemical impedance (EIS) measurements. Adsorption of inhibitor on the surface of the mild steel obeyed both Langmuir and Temkin adsorption isotherms. The thermodynamic and kinetic parameters were also calculated to determine the mechanism of corrosion inhibition. The inhibition efficiency was found to increase with an increase in the inhibitor concentration i.e., Spilanthes acmella aqueous leaves extract, however, the inhibition efficiency decreased with an increase in the temperature. The phytochemical constituents with functional groups including electronegative hetero atoms such as N, O, and S in the extract adsorbed on the metal surface are found responsible for the effective performance of the inhibitor, which was confirmed by Fourier-transform infrared spectroscopy (FT-IR) and ultraviolet–visible spectroscopic (UV-Vis) studies. Protective film formation against corrosion was confirmed by scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle studies. The result shows that the leaves extract acts as corrosion inhibitor and is able to promote surface protection by blocking active sites on the metal. Full article

(This article belongs to the Special Issue Solution Processed Coatings and Characterizations for Multiple Applications)

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11 pages, 5719 KiB

Open AccessArticle

Surface Analysis of Chamber Coating Materials Exposed to CF₄/O₂ Plasma

by Seung Hyun Park, Kyung Eon Kim and Sang Jeen Hong

Coatings 2021, 11(1), 105; https://doi.org/10.3390/coatings11010105 - 18 Jan 2021

Cited by 12 | Viewed by 4668

Abstract

Coating the inner surfaces of high-powered plasma processing equipment has become crucial for reducing maintenance costs, process drift, and contaminants. The conventionally preferred alumina (Al₂O₃) coating has been replaced with yttria (Y₂O₃) due to the [...] Read more.

Coating the inner surfaces of high-powered plasma processing equipment has become crucial for reducing maintenance costs, process drift, and contaminants. The conventionally preferred alumina (Al₂O₃) coating has been replaced with yttria (Y₂O₃) due to the long-standing endurance achieved by fluorine-based etching; however, the continuous increase in radio frequency (RF) power necessitates the use of alternative coating materials to reduce process shift in a series of high-powered semiconductor manufacturing environments. In this study, we investigated the fluorine-based etching resistance of atmospheric pressure-sprayed alumina, yttria, yttrium aluminum garnet (YAG), and yttrium oxyfluoride (YOF). The prepared ceramic-coated samples were directly exposed to silicon oxide etching, and the surfaces of the plasma-exposed samples were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. We found that an ideal coating material must demonstrate high plasma-induced structure distortion by the fluorine atom from the radical. For endurance to fluorine-based plasma exposure, the bonding structure with fluoride was shown to be more effective than oxide-based ceramics. Thus, fluoride-based ceramic materials can be promising candidates for chamber coating materials. Full article

(This article belongs to the Section Ceramic Coatings and Engineering Technology)

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23 pages, 7807 KiB

Open AccessArticle

Study on Eccentric Uncoupled Blasting Effect of Cutting Seam Pipe

by Wei Wang, Jiaqi Zhang and Ao Liu

Coatings 2021, 11(1), 104; https://doi.org/10.3390/coatings11010104 - 18 Jan 2021

Cited by 3 | Viewed by 1681

Abstract

In order to study the blasting effect and the damage to the rock mass when the cutting seam cartridge is eccentrically and uncoupled. The ANSYS/LS-DYNA^® nonlinear dynamic platform was used to simulate the blasting effect of five eccentric uncoupled coefficients on the [...] Read more.

In order to study the blasting effect and the damage to the rock mass when the cutting seam cartridge is eccentrically and uncoupled. The ANSYS/LS-DYNA^® nonlinear dynamic platform was used to simulate the blasting effect of five eccentric uncoupled coefficients on the cutting seam cartridge, and the crack growth process under the condition of complete eccentricity was simulated. By comparing and analyzing the stress of measuring points in the direction of cutting seam, vertical cutting seam direction, and circumferential cutting seam pipe under different working conditions. It is concluded that the effect of detonation products is affected by the wrapping property of the cutting seam pipe and the eccentric uncoupled coefficient. With the increase of the eccentric uncoupled coefficient, the load distribution presents obvious non-uniformity. The pressure on the uncoupled side of the blasthole is smaller than that on the coupled side, and the peak time of the uncoupled side also lags behind that on the coupled side. When the eccentric uncoupled coefficient is 1, the peak pressure on the coupled side is 5.78 times that of the uncoupled side, and the explosive stress field is biased toward the coupled side. The existence of the cutting seam pipe causes stress concentration at the opening, which enhances the guiding effect of the initial crack, and the stress in the non-cutting seam direction is buffered. Therefore, the eccentric arrangement of the cutting seam pipe determines the formation of the initial crack and the subsequent blasting effect. When the cutting seam cartridge is arranged eccentrically and uncoupled, it will cause under-excavation at the connection direction of blasthole, which will cause less disturbance to the rock mass on the uncoupled side. If the retaining side rock mass is on the coupled side in actual blasting, the eccentric uncoupled arrangement will cause greater over-excavation and damage. Therefore, it is necessary to avoid this situation as far as possible and provide better guidance for the actual construction. Full article

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13 pages, 4187 KiB

Open AccessArticle

Study on Friction and Wear Properties of Zr–Cu–Ni–Al Crystalline Powder Cladding and Amorphous Composite Powder Cladding by Laser

by Yugan Chen, Pingjun Tao, Weijian Zhang, Chaohan Zhang and Kunsen Zhu

Coatings 2021, 11(1), 103; https://doi.org/10.3390/coatings11010103 - 18 Jan 2021

Cited by 4 | Viewed by 1851

Abstract

In order to improve the friction and wear performance and surface hardness of AISI 1045 steel and expand its application range, this paper carried out the research on friction and wear performance and surface hardness of Zr₆₅Al_7.5Ni₁₀Cu [...] Read more.

In order to improve the friction and wear performance and surface hardness of AISI 1045 steel and expand its application range, this paper carried out the research on friction and wear performance and surface hardness of Zr₆₅Al_7.5Ni₁₀Cu_17.5 crystalline powder (CP) and amorphous powder (AP) after laser cladding on AISI 1045 steel surface. The results show that both CP and amorphous powder (AP) formed a cladding layer on the surface of AISI 1045 steel under laser irradiation. The thickness of the cladding layer is about 400 μm, and the thickness of the AP cladding layer is slightly larger than that of the CP cladding layer. The results show that there are many holes in the AP cladding layer, and holes can be observed at the junction with the matrix; while the CP cladding layer is well combined with the matrix and no holes are observed. The friction performance of CP cladding layer is better than that of AP cladding layer. In the wear marks of the AP cladding layer, there are bonding areas, while the wear marks of the CP cladding layer have a furrow-like morphology, and part of the matrix is exposed. The surface microhardness and average microhardness of AP cladding layer are 49% and 94% higher than that of CP cladding layer, respectively. Hardness modification has obvious advantages. The reasons for porosity, large friction coefficient and low stability of the friction experiment of the AP cladding layer are analyzed and discussed. The ideas and methods for improving the laser irradiation to achieve both high wear resistance and high strength of the AP cladding layer are proposed. Full article

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

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17 pages, 7994 KiB

Open AccessArticle

Analysis of Surface Properties of Ag and Ti Ion-Treated Medical Textiles by Metal Vapor Vacuum Arc Ion Implantation

by Ali Akpek

Coatings 2021, 11(1), 102; https://doi.org/10.3390/coatings11010102 - 18 Jan 2021

Cited by 6 | Viewed by 2516

Abstract

The study focuses on the effects of Ag (silver) and Ti (titanium) ions on textiles by MEVVA (metal vapor vacuum arc) ion implantation. In order to comprehend this, the research was executed in three parts. In the first part, the antibacterial efficiencies of [...] Read more.

The study focuses on the effects of Ag (silver) and Ti (titanium) ions on textiles by MEVVA (metal vapor vacuum arc) ion implantation. In order to comprehend this, the research was executed in three parts. In the first part, the antibacterial efficiencies of Ag and TiO₂ were investigated in detail since the antibacterial capabilities of Ag and TiO₂ are well known. A group of polyester- and cotton-based medical textiles were modified by Ag and TiO₂ ions, with doses ranging from 5 × 10¹⁵ to 5 × 10¹⁶ ion/cm². To determine the adhesion capabilities of the implanted ions on surfaces, after the first round of antibacterial tests, these medical textiles were washed 30 times, and then antibacterial tests were performed for the second time. The results were also compared with nanoparticle-treated medical textiles. In the second part, the corrosion and friction capabilities of Ag and Ti ion-implanted polyester textiles, with a dose of 5 × 10¹⁵ ion/cm², were investigated. Finally, the UV protection capabilities of Ag and Ti ion-implanted polyester textiles, with a dose of 5 × 10¹⁵ ion/cm², were investigated. The experiments showed that even after 30 washes, the TiO₂ ion-implanted polyester textile had almost 85% antibacterial efficiency. In addition, Ti ion implantation reduced the friction coefficiency of a polyester textile by almost 50% when compared with an untreated textile. Finally, the Ag-ion-implanted polyester textile provided a UV protection factor of 30, which is classified as very good protection. Full article

(This article belongs to the Special Issue Surface Treatment of Textiles)

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12 pages, 3877 KiB

Open AccessArticle

Microstructure and Corrosion Properties of La₂Zr₂O₇/NiCoAlY Thermal Barrier Coatings Deposited on Inconel 718 Superalloy by Laser Cladding

by Kaijin Huang, Wei Li, Kai Pan, Xin Lin and Aihua Wang

Coatings 2021, 11(1), 101; https://doi.org/10.3390/coatings11010101 - 18 Jan 2021

Cited by 6 | Viewed by 2337

Abstract

In order to improve the seawater corrosion resistance of Inconel 718 superalloy, a La₂Zr₂O₇/NiCoCrAlY thermal barrier coating corrosion resistant to 3.5 wt.% NaCl aqueous solution was prepared by laser cladding on Inconel 718 superalloy. X-ray diffraction (XRD), [...] Read more.

In order to improve the seawater corrosion resistance of Inconel 718 superalloy, a La₂Zr₂O₇/NiCoCrAlY thermal barrier coating corrosion resistant to 3.5 wt.% NaCl aqueous solution was prepared by laser cladding on Inconel 718 superalloy. X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and electrochemical techniques were used to study the microstructure and the corrosion performance of the coating in 3.5 wt.% NaCl solution. The results show that the thermal barrier coating is mainly composed of primary La₂Zr₂O₇ phase and γ + laves/δ phase eutectic structure. The corrosion potential and corrosion current of the coating in 3.5 wt.% NaCl solution are higher and lower than that of the Inconel 718 substrate, respectively, indicating that the corrosion performance of the coating is better than that of the Inconel 718 substrate. The presence of La₂Zr₂O₇ phase in the thermal barrier coating is the main reason for its corrosion resistance to 3.5 wt.% NaCl solution. Full article

(This article belongs to the Special Issue Coatings for High Temperature Applications)

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14 pages, 6169 KiB

Open AccessArticle

Electrodeposition and Characterization of Lanthanide Elements on Carbon Sheets

by Min Hee Joo, So Jeong Park, Sung-Min Hong, Choong Kyun Rhee, Dongsoo Kim and Youngku Sohn

Coatings 2021, 11(1), 100; https://doi.org/10.3390/coatings11010100 - 18 Jan 2021

Cited by 14 | Viewed by 2649

Abstract

Electrochemical coating and recovery by electrodeposition have been invaluably employed for facial thin film fabrication and the recycling of used materials. Herein, we have established a full data set of lanthanide (Ln: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, [...] Read more.

Electrochemical coating and recovery by electrodeposition have been invaluably employed for facial thin film fabrication and the recycling of used materials. Herein, we have established a full data set of lanthanide (Ln: La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb) elements electrodeposited on carbon sheets. Cyclic voltammetry was performed for 10 mM Ln(III) ions in a 0.1 M NaClO₄ electrolyte over a carbon sheet between +0.5 V and −1.7 V (vs. Ag/AgCl). Amperometry was performed at a given potential to electrodeposit the Ln element on the carbon sheet. Their physicochemical properties were fully investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The newly established full data set for Ln(III) ions over carbon electrodes provides useful fundamental information for the development of coating and recovery methods of Ln elements. Full article

(This article belongs to the Special Issue Electrodeposition of Thin Films for Energy Applications)

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17 pages, 4262 KiB

Open AccessArticle

Characterization of Carboxymethyl Cellulose Films Incorporated with Chinese Fir Essential Oil and Their Application to Quality Improvement of Shine Muscat Grape

by Luyu Mei, Liuxin Shi, Xiuli Song, Su Liu, Qiang Cheng, Kai Zhu and Rongxia Zhuge

Coatings 2021, 11(1), 97; https://doi.org/10.3390/coatings11010097 - 17 Jan 2021

Cited by 11 | Viewed by 2947

Abstract

In this study, carboxymethyl cellulose (CMC) films containing 1%, 2%, and 3% Chinese fir essential oil (CFEO) were prepared. The mechanical, optical, physical, microstructural, thermal stability and antimicrobial properties of the films were studied. A traditional steam distillation method was applied for CFEO [...] Read more.

In this study, carboxymethyl cellulose (CMC) films containing 1%, 2%, and 3% Chinese fir essential oil (CFEO) were prepared. The mechanical, optical, physical, microstructural, thermal stability and antimicrobial properties of the films were studied. A traditional steam distillation method was applied for CFEO extraction, in which 35 volatile components were identified. The research results showed that the CMC film mixed with 1% CFEO had the highest tensile strength (TS) and elongation at break (EB), whereas the flexibility was decreased under higher concentrations of CFEO. However, the film’s degree of transparency under controlled humidity did not decrease with an increase in CFEO concentration; thus, the sensory evaluation was not adversely effect. Furthermore, the thickness and the water solubility (WS) of film increased after the addition of CFEO. The thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) results indicated that the thermal stability of the CMC-CFEO films improved. Moreover, the composite films showed excellent inhibitory effects toward Gram-positive bacterias and Penicillium citrinum. The treatments of grapes with CMC + 1% CFEO resulted in the best properties during storage. CMC-CFEO film can be a candidate for food packaging due to its excellent performances. Full article

(This article belongs to the Special Issue Edible Films and Coatings with Tailored Features for Improvement of Food Quality)

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26 pages, 10896 KiB

Open AccessFeature PaperReview

What Can Electric Noise Spectroscopy Tell Us on the Physics of Perovskites?

by Carlo Barone and Sergio Pagano

Coatings 2021, 11(1), 96; https://doi.org/10.3390/coatings11010096 - 17 Jan 2021

Cited by 12 | Viewed by 2762

Abstract

Electric noise spectroscopy is a non-destructive and a very sensitive method for studying the dynamic behaviors of the charge carriers and the kinetic processes in several condensed matter systems, with no limitation on operating temperatures. This technique has been extensively used to investigate [...] Read more.

Electric noise spectroscopy is a non-destructive and a very sensitive method for studying the dynamic behaviors of the charge carriers and the kinetic processes in several condensed matter systems, with no limitation on operating temperatures. This technique has been extensively used to investigate several perovskite compounds, manganese oxides (La_1−xSr_xMnO₃, La_0.7Ba_0.3MnO₃, and Pr_0.7Ca_0.3MnO₃), and a double perovskite (Sr₂FeMoO₆), whose properties have recently attracted great attention. In this work are reported the results from a detailed electrical transport and noise characterizations for each of the above cited materials, and they are interpreted in terms of specific physical models, evidencing peculiar properties, such as quantum interference effects and charge density waves. Full article

(This article belongs to the Special Issue Advance in Perovskite Thin Films)

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15 pages, 3948 KiB

Open AccessEditor’s ChoiceArticle

One-Step Methods to Fabricate Durable Superhydrophobic Coatings for Flexible Electronic Sensors

by Xiang Liu, Kai Chen, Dekun Zhang and Zhiguang Guo

Coatings 2021, 11(1), 95; https://doi.org/10.3390/coatings11010095 - 16 Jan 2021

Cited by 3 | Viewed by 3619

Abstract

Inspired by lotus leaves in nature, superhydrophobic surfaces have attracted extensive attention in many fields. However, their complex preparation process, poor durability and high cost seriously restrict their large-scale application in industrial production. Based on the good flexibility and durability of carbon nanofibers, [...] Read more.

Inspired by lotus leaves in nature, superhydrophobic surfaces have attracted extensive attention in many fields. However, their complex preparation process, poor durability and high cost seriously restrict their large-scale application in industrial production. Based on the good flexibility and durability of carbon nanofibers, several simple modifier-free one-step approaches were adopted to fabricate a durable CNF/PVDF/PDMS conductive superhydrophobic coating. The fabricated coating not only possesses good superhydrophobicity to many kinds of liquids, but also has excellent self-cleaning and anti-fouling properties. In addition, the superhydrophobicity of the obtained multifunctional coating is stable even after harsh bending fatigue deformation, long immersion times and high-temperature treatment. Due to its strong adhesion and excellent conductivity, the CNF/PVDF/PDMS coating displays reliable mechanical stability and superior sensitivity. These distinct features make the obtained conductive superhydrophobic coating a good candidate for multifunctional smart sensors, with great application prospects in gesture detectors, waterproof wearable electronics and health monitors. Full article

(This article belongs to the Section Bioactive Coatings and Biointerfaces)

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11 pages, 3172 KiB

Open AccessArticle

Mechanical Characteristics and Adhesion of Glass-Kevlar Hybrid Composites by Applying Different Ratios of Epoxy in Lamination

by Sajid Hussian Siyal, Subhan Ali Jogi, Salman Muhammadi, Zubair Ahmed Laghari, Sadam Ali Khichi, Khalida Naseem, Tahani Saad Algarni, Asma Alothman, Shahid Hussain and Muhammad Sufyan Javed

Coatings 2021, 11(1), 94; https://doi.org/10.3390/coatings11010094 - 15 Jan 2021

Cited by 13 | Viewed by 3667

Abstract

Hybrid composites have great potential for specific strength and specific stiffness, effective in aerospace industries, submarines, and light-weight automotives. The mechanical strength and adhesiveness of hybrid laminates can be enhanced by effective use of matrix materials in different ratios of epoxy resin and [...] Read more.

Hybrid composites have great potential for specific strength and specific stiffness, effective in aerospace industries, submarines, and light-weight automotives. The mechanical strength and adhesiveness of hybrid laminates can be enhanced by effective use of matrix materials in different ratios of epoxy resin and epoxy hardener. Gentle use of resin and hardener in the fabrication of hybrid composites can alter tensile modulus, the bonding strength between matrix and fabric. Spectacular progress has been achieved by the selection of appropriate amounts of resin and hardener in the hybridization of composite laminate. Hybridization was made by Kevlar inorganic/organic fabrics and glass fabrics stacked with epoxy matrix material. To achieve the combination of mechanical properties and bonding strength, transparent epoxy resin and hardener of commercial grades mixed in various ratios are incorporated as matrix material to fabricate laminate. Three different sheets, named A (3:2), B (4:1), and C (2:3), were embedded by the hand layup method to prepare a hybrid composite. Experimental tests, according to ASTM 3039, were performed to determine the tensile mechanical properties. Peel tests, according to ASTM 6862-11, were performed to investigate the interlaminar strength between Kevlar and glass layers. Shore A and Shore C hardness durometers were used to find out the hardness of the specimens at different spots using the ASTM D-2240 standard. Finally, physical testing, such as density and then water absorption, was carried out using the ASTM D-570 standard to check the swelling ratio of the different specimens. The results obtained highlight that the specimen of the glass/Kevlar hybrid embedded in the ratio 3:2 in lamination has the best mechanical properties (tensile strength and hardness) and the lowest swelling ratio, while the material system in the ratio 4:1 shows the best interlaminar properties and adhesion capabilities. Full article

(This article belongs to the Special Issue Synthesis, Chracterization and Applications of Coated Composite Materials for Energy Applications)

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12 pages, 5839 KiB

Open AccessArticle

Evaluation of Antithrombogenic pHPC on CoCr Substrates for Biomedical Applications

by Catrin Bannewitz, Tim Lenz-Habijan, Jonathan Lentz, Marcus Peters, Volker Trösken, Sabine Siebert, Sebastian Weber, Werner Theisen, Hans Henkes and Hermann Monstadt

Coatings 2021, 11(1), 93; https://doi.org/10.3390/coatings11010093 - 15 Jan 2021

Cited by 3 | Viewed by 2309

Abstract

Bare metal endovascular implants pose a significant risk of causing thrombogenic complications. Antithrombogenic surface modifications, such as phenox’s “Hydrophilic Polymer Coating” (pHPC), which was originally developed for NiTi implants, decrease the thrombogenicity of metal surfaces. In this study, the transferability of pHPC onto [...] Read more.

Bare metal endovascular implants pose a significant risk of causing thrombogenic complications. Antithrombogenic surface modifications, such as phenox’s “Hydrophilic Polymer Coating” (pHPC), which was originally developed for NiTi implants, decrease the thrombogenicity of metal surfaces. In this study, the transferability of pHPC onto biomedical CoCr-based alloys is examined. Coated surfaces were characterized via contact-angle measurement and atomic force microscopy. The equivalence of the antithrombogenic effect in contact with whole human blood was demonstrated in vitro for CoCr plates compared to NiTi plates on a platform shaker and for braided devices in a Chandler loop. Platelet adhesion was assessed via scanning electron microscopy and fluorescence microscopy. The coating efficiency of pHPC on CoCr plates was confirmed by a reduction of the contact angle from 84.4° ± 5.1° to 36.2° ± 5.2°. The surface roughness was not affected by the application of pHPC. Platelet adhesion was significantly reduced on pHPC-coated specimens. The platelet covered area was reduced by 85% for coated CoCr plates compared to uncoated samples. Uncoated braided devices were completely covered by platelets, while on the pHPC-coated samples, very few platelets were visible. In conclusion, the antithrombogenic effect of pHPC coating can be successfully applied on CoCr plates as well as stent-like CoCr braids. Full article

(This article belongs to the Special Issue Bioactive Coatings for Implantable Devices)

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14 pages, 4255 KiB

Open AccessArticle

Indium Tin Oxide Thin Film Deposition by Magnetron Sputtering at Room Temperature for the Manufacturing of Efficient Transparent Heaters

by Jago Txintxurreta, Eva G-Berasategui, Rocío Ortiz, Oihane Hernández, Lucía Mendizábal and Javier Barriga

Coatings 2021, 11(1), 92; https://doi.org/10.3390/coatings11010092 - 15 Jan 2021

Cited by 27 | Viewed by 6688

Abstract

Indium tin oxide (ITO) thin films are widely used as transparent electrodes in electronic devices. Many of those electronic devices are heat sensitive, thus their manufacturing process steps should not exceed 100 °C. Manufacturing competitive high-quality ITO films at low temperature at industrial [...] Read more.

Indium tin oxide (ITO) thin films are widely used as transparent electrodes in electronic devices. Many of those electronic devices are heat sensitive, thus their manufacturing process steps should not exceed 100 °C. Manufacturing competitive high-quality ITO films at low temperature at industrial scale is still a challenge. Magnetron sputtering technology is the most suitable technology fulfilling those requirements. However, ITO layer properties and the reproducibility of the process are extremely sensitive to process parameters. Here, morphological, structural, electrical, and optical characterization of the ITO layers deposited at low temperature has been successfully correlated to magnetron sputtering process parameters. It has been demonstrated that the oxygen flow controls and influences layer properties. For oxygen flow between 3–4 sccm, high quality crystalline layers were obtained with excellent optoelectronic properties (resistivity <8 × 10⁻⁴ Ω·cm and visible transmittance >80%). The optimized conditions were applied to successfully manufacture transparent ITO heaters on large area glass and polymeric components. When a low supply voltage (8 V) was applied to transparent heaters (THs), de-icing of the surface was produced in less than 2 min, showing uniform thermal distribution. In addition, both THs (glass and polycarbonate) showed a great stability when exposed to saline solution. Full article

(This article belongs to the Special Issue Micro-Nano Surface Functionalization of Materials and Thin Films for Optical Applications)

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13 pages, 622 KiB

Open AccessArticle

Interactions of Coating and Wood Flooring Surface System Properties

by Matjaž Pavlič, Marko Petrič and Jure Žigon

Coatings 2021, 11(1), 91; https://doi.org/10.3390/coatings11010091 - 15 Jan 2021

Cited by 22 | Viewed by 2945

Abstract

Parquet flooring is one of the most common types of flooring, the surface of which can be covered with various coatings. To avoid possible damage to the parquet during use, it is necessary to test the surfaces before installation according to various non-standard [...] Read more.

Parquet flooring is one of the most common types of flooring, the surface of which can be covered with various coatings. To avoid possible damage to the parquet during use, it is necessary to test the surfaces before installation according to various non-standard and standard protocols. The present study provides an overview of the interactions between the properties of selected waterborne coatings (solids content, hardness, resistance to cracking, tensile strength) and the properties of oak wood flooring surfaces (dry film thickness, coating adhesion, resistance to scratching, impact, abrasion and cold liquids). The tests conducted showed that the performance of the surface systems was highly dependent on the coating formulations, as they were either one- or two-component systems. Although no major differences in surface resistance to cold liquids were found, there was a correlation between coating thickness, hardness and tensile strength. The harder coatings had higher tensile strengths and lower elongations. The coatings with higher tensile strength and better hardness achieved better adhesion properties. The coatings that exhibited ductile behavior showed the worst scratch resistance. A statistically significant relationship was found between the higher resistance of the flooring systems to impact stress and the improved abrasion resistance. The obtained results provide potential end users of surface coatings with valuable information on the quality that can be expected in wood flooring. Full article

(This article belongs to the Special Issue Surface Properties and Surface Treatments of Wood and Wood-Based Composites)

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11 pages, 6609 KiB

Open AccessFeature PaperArticle

Developing New Marine Antifouling Surfaces: Learning from Single-Strain Laboratory Tests

by Sara I. Faria, Luciana C. Gomes, Rita Teixeira-Santos, João Morais, Vítor Vasconcelos and Filipe J. M. Mergulhão

Coatings 2021, 11(1), 90; https://doi.org/10.3390/coatings11010090 - 15 Jan 2021

Cited by 12 | Viewed by 3095

Abstract

The development of antifouling (AF) technology for marine environments is an area of intense research given the severe economic and ecological effects of marine biofouling. Preliminary data from in vitro assays is frequently used to screen the performance of AF coatings. It is [...] Read more.

The development of antifouling (AF) technology for marine environments is an area of intense research given the severe economic and ecological effects of marine biofouling. Preliminary data from in vitro assays is frequently used to screen the performance of AF coatings. It is intuitive that microbial composition plays a major role in surface colonization. The rationale behind this study is to investigate whether using a mixed population for the in vitro tests yields substantially different results than using single strains during initial screening. A polymeric coating was tested against single- and dual-species cultures of two common microfouler organisms for 49 days. A bacterium (Pseudoaltermonas tunicata) and a cyanobacterium (Cyanobium sp. LEGE 10375) were used in this study. Linear regression analysis revealed that Cyanobium sp. biofilms were significantly associated with a higher number of cells, wet weight, thickness, and biovolume compared to dual-species biofilms. P. tunicata alone had a biofilm growth kinetics similar to dual-species biofilms, although the P. tunicata–Cyanobium sp. mixture developed less dense and thinner biofilms compared to both single-species biofilms. Cyanobium sp. LEGE 10375 biofilms provided the worst-case scenario, i.e., the conditions that caused higher biofilm amounts on the surface material under test. Therefore, it is likely that assessing the AF performance of new coatings using the most stringent conditions may yield more robust results than using a mixed population, as competition between microfouler organisms may reduce the biofilm formation capacity of the consortium. Full article

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

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11 pages, 3589 KiB

Open AccessFeature PaperArticle

Phase Transformation and Superstructure Formation in (Ti_0.5, Mg_0.5)N Thin Films through High-Temperature Annealing

by Mohammad Amin Gharavi, Arnaud le Febvrier, Jun Lu, Grzegorz Greczynski, Björn Alling, Rickard Armiento and Per Eklund

Coatings 2021, 11(1), 89; https://doi.org/10.3390/coatings11010089 - 14 Jan 2021

Cited by 2 | Viewed by 2828

Abstract

(Ti_0.5, Mg_0.5)N thin films were synthesized by reactive dc magnetron sputtering from elemental targets onto c-cut sapphire substrates. Characterization by θ–2θ X-ray diffraction and pole figure measurements shows a rock-salt cubic structure with (111)-oriented growth and a twin-domain structure. [...] Read more.

(Ti_0.5, Mg_0.5)N thin films were synthesized by reactive dc magnetron sputtering from elemental targets onto c-cut sapphire substrates. Characterization by θ–2θ X-ray diffraction and pole figure measurements shows a rock-salt cubic structure with (111)-oriented growth and a twin-domain structure. The films exhibit an electrical resistivity of 150 mΩ·cm, as measured by four-point-probe, and a Seebeck coefficient of −25 µV/K. It is shown that high temperature (~800 °C) annealing in a nitrogen atmosphere leads to the formation of a cubic LiTiO₂-type superstructure as seen by high-resolution scanning transmission electron microscopy. The corresponding phase formation is possibly influenced by oxygen contamination present in the as-deposited films resulting in a cubic superstructure. Density functional theory calculations utilizing the generalized gradient approximation (GGA) functionals show that the LiTiO₂-type TiMgN₂ structure has a 0.07 eV direct bandgap. Full article

(This article belongs to the Special Issue Magnetron Sputter Deposition of Nitride Thin Films and Nanostructures)

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22 pages, 9769 KiB

Open AccessArticle

Maya Blue Used in Wall Paintings in Mexican Colonial Convents of the XVI Century

by Luisa Straulino-Mainou, Teresa Pi-Puig, Becket Lailson-Tinoco, Karla Castro-Chong, María Fernanda Urbina-Lemus, Pablo Escalante-Gonzalbo, Sergey Sedov and Aban Flores-Morán

Coatings 2021, 11(1), 88; https://doi.org/10.3390/coatings11010088 - 14 Jan 2021

Cited by 2 | Viewed by 3005

Abstract

Maya blue is a well-known pre-Hispanic pigment, composed of palygorskite or sepiolite and indigo blue, which was used by various Mesoamerican cultures for centuries. There has been limited research about its continued use during the Viceroyalty period; therefore, the sixteenth century is the [...] Read more.

Maya blue is a well-known pre-Hispanic pigment, composed of palygorskite or sepiolite and indigo blue, which was used by various Mesoamerican cultures for centuries. There has been limited research about its continued use during the Viceroyalty period; therefore, the sixteenth century is the perfect period through which to study the continuity of pre-Hispanic traditions. The fact that the indigenous people were active participants in the construction and decoration of convents makes their wall paintings a good sampling material. X-ray fluorescence (XRF), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed in samples of blue found in convents across Puebla, Tlaxcala and Morelos in order to identify whether the numerous hues of blue were achieved with Maya blue or with other pigments. We found no copper (Cu) or cobalt (Co) with the XRF, so several pigments, such as azurite, smalt or verdigris, were discarded. With SEM, we discovered that the micromorphology of certain blues was clearly needle-shaped, suggesting the presence of palygorskite or sepiolite. In addition, we found silicon (Si), magnesium (Mg) and aluminum (Al) by using energy-dispersive X-ray spectroscopy (EDS) in all blue samples, which also suggests the presence of these magnesium-rich clay minerals. With the XRD samples, we verified that the blues were produced with these two clay minerals, thus confirming that several wall paintings were manufactured with Maya blue. These findings confirm that this particular manmade pre-Hispanic pigment, Maya blue, was an important pigment prior to the Viceroyal period. Full article

(This article belongs to the Special Issue Conservation Tools, Protocols and Treatments on Painted Surfaces, Metal Leaves and Finishes in Cultural Heritage)

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13 pages, 26391 KiB

Open AccessArticle

Research of Curing Time and Temperature-Dependent Strengths and Fire Resistance of Geopolymer Foam Coated on an Aluminum Plate

by Van Su Le and Petr Louda

Coatings 2021, 11(1), 87; https://doi.org/10.3390/coatings11010087 - 14 Jan 2021

Cited by 12 | Viewed by 2249

Abstract

Geopolymer foam (GF) uses a potassium activator and can be cured at high temperatures, which can improve its mechanical properties. In this study, we attempted to test this hypothesis by comparing the flexural and compressive strength, apparent density and fire resistance of GF. [...] Read more.

Geopolymer foam (GF) uses a potassium activator and can be cured at high temperatures, which can improve its mechanical properties. In this study, we attempted to test this hypothesis by comparing the flexural and compressive strength, apparent density and fire resistance of GF. The composition of the GF used in the experiment included a potassium activator, basalt ground fiber and aluminum powder with a mass ratio to the binder of 0.45, 0.3 and 0.015, respectively. The samples were cured at room temperature and at 50, 70, 85 and 105 °C with a curing time of 2, 4, 6, 12 and 24 h. Then, the samples were kept until being tested on the third, seventh, 14th and 28th day. The results showed that the flexural and compressive strength and apparent density improved and stabilized after seven days at 85 °C. Furthermore, the GF exhibited a substantial increase after three days in its flexural strength by 111% and compressive strength by 122.9% at the optimal temperature of 85 °C for 2 h compared to the values at RT after 28 days. The GF had an apparent density of 0.558–0.623 g/cm³ on the 28th day. As a new alternative to aluminum materials, investigating the fire resistance of sandwich panels (an aluminum plate covered with a GF layer) is important for their safe impregnation. Sandwich panels with thicknesses of 10–20 mm were exposed to a gas fire. The test results showed that the sandwich panels had significantly improved fire resistance compared to unprotected panels. The longest fire resistance times for the aluminum plate coated with 20 mm of GF layer thickness was 7500 s. Thus, the GF coated on the aluminum plate exhibited superior fire resistance and a reduced heat transfer rate compared to uncoated panels. Full article

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21 pages, 10113 KiB

Open AccessFeature PaperArticle

Erosion Performance of Atmospheric Plasma Sprayed Thermal Barrier Coatings with Diverse Porosity Levels

by Satyapal Mahade, Abhilash Venkat, Nicholas Curry, Matthias Leitner and Shrikant Joshi

Coatings 2021, 11(1), 86; https://doi.org/10.3390/coatings11010086 - 14 Jan 2021

Cited by 21 | Viewed by 3586

Abstract

Thermal barrier coatings (TBCs) prolong the durability of gas turbine engine components and enable them to operate at high temperature. Several degradation mechanisms limit the durability of TBCs during their service. Since the atmospheric plasma spray (APS) processed 7–8 wt.% yttria stabilized zirconia [...] Read more.

Thermal barrier coatings (TBCs) prolong the durability of gas turbine engine components and enable them to operate at high temperature. Several degradation mechanisms limit the durability of TBCs during their service. Since the atmospheric plasma spray (APS) processed 7–8 wt.% yttria stabilized zirconia (YSZ) TBCs widely utilized for gas turbine applications are susceptible to erosion damage, this work aims to evaluate the influence of their porosity levels on erosion behavior. Eight different APS TBCs were produced from 3 different spray powders with porosity ranging from 14% to 24%. The as-deposited TBCs were examined by SEM analysis. A licensed software was used to quantify the different microstructural features. Mechanical properties of the as-deposited TBCs were evaluated using micro-indentation technique. The as-deposited TBCs were subjected to erosion tests at different angles of erodent impact and their erosion performance was evaluated. Based on the results, microstructure-mechanical property-erosion performance was correlated. Findings from this work provide new insights into the microstructural features desired for improved erosion performance of APS deposited YSZ TBCs. Full article

(This article belongs to the Special Issue Recent Developments of Thermal Barrier Coatings)

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15 pages, 15364 KiB

Open AccessArticle

Proposed Cool Coatings with High Near-Infrared Reflectance and Heat Insulation for Asphalt Pavement

by Kui Hu, Yujing Chen, Guixiang Chen, Yuzhou Duan and Caihua Yu

Coatings 2021, 11(1), 85; https://doi.org/10.3390/coatings11010085 - 13 Jan 2021

Cited by 1 | Viewed by 3130

Abstract

In summer, black asphalt pavement can absorb a considerable amount of solar radiation, which causes its temperature to rise. Heated asphalt pavement can aggravate the urban heat island (UHI) effect and transfer heat downward, which may cause the problem of permafrost thawing beneath [...] Read more.

In summer, black asphalt pavement can absorb a considerable amount of solar radiation, which causes its temperature to rise. Heated asphalt pavement can aggravate the urban heat island (UHI) effect and transfer heat downward, which may cause the problem of permafrost thawing beneath pavements. The objective of this study was to develop a novel cool coating layer (CCL) with high near-infrared reflectance and heat insulation to make the surface of asphalt pavement cool. A self-developed test device and method was established to evaluate cooling effects. Based on the experimental results, the optimal coating can cool asphalt pavement by 11.21 °C when the radiation striking the sample surface is 650 W/m². This coating, called the composite cool coating layer (CCCL), is composed of the following materials: polyurethane resin, rutile TiO₂ of 18%, hollow glass microspheres of 12%, and copper chromite black spinel of 0.7%. Silicon carbide particles of 1 kg/m² can help the CCCL achieve satisfactory antiskid performance. In conclusion, CCCL can effectively inhibit the absorption of solar radiation and reduce the flow of thermal energy downward without sacrificing skid resistance. Full article

(This article belongs to the Special Issue Road Pavements for Reduction of Climate and Safety Risks)

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16 pages, 2420 KiB

Open AccessArticle

Characterization of Chitosan Films Incorporated with Different Substances of Konjac Glucomannan, Cassava Starch, Maltodextrin and Gelatin, and Application in Mongolian Cheese Packaging

by Sijun Ma, Yuanrong Zheng, Ran Zhou and Ming Ma

Coatings 2021, 11(1), 84; https://doi.org/10.3390/coatings11010084 - 13 Jan 2021

Cited by 19 | Viewed by 4216

Abstract

Four kinds of edible composite films based on chitosan combined with additional substances (konjac glucomannan, cassava starch, maltodextrin and gelatin) and the addition of lysozyme were prepared and used as packaging materials for Mongolian cheese. The prepared composite films were evaluated using scanning [...] Read more.

Four kinds of edible composite films based on chitosan combined with additional substances (konjac glucomannan, cassava starch, maltodextrin and gelatin) and the addition of lysozyme were prepared and used as packaging materials for Mongolian cheese. The prepared composite films were evaluated using scanning electron microscopy and Fourier transform infrared spectroscopy. The physicochemical properties of all chitosan composite films, including thickness, viscosity, opacity, color, moisture content, water vapor permeability, tensile strength and elongation at break, were measured. The results show that Konjac glucomannan–chitosan composite film presented the strongest mechanical property and highest transparency. The cassava starch–chitosan composite film presented the highest water barrier property. The study on the storage characteristics of Mongolian cheese was evaluated at 4 °C. The results show that the cheese packaging by cassava starch–chitosan composite film presented better treatment performance in maintaining the quality, reducing weight loss and delayering microbial growth. Full article

(This article belongs to the Special Issue Recent Advances in Bio-Composite Coatings)

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28 pages, 8602 KiB

Open AccessArticle

Curing of Functionalized Superhydrophobic Inorganic/Epoxy Nanocomposite and Application as Coatings for Steel

by Mohamed H. Wahby, Ayman M. Atta, Yasser M. Moustafa, Abdelrahman O. Ezzat and Ahmed I. Hashem

Coatings 2021, 11(1), 83; https://doi.org/10.3390/coatings11010083 - 13 Jan 2021

Cited by 6 | Viewed by 2116

Abstract

Superhydrophobic epoxy nanocomposites coatings with superior mechanical and adhesion strength are targeted to increase epoxy coating performance and to protect steel corrosion in aggressive environment. The present work prepared hydrophobic organic modified inorganic nanoparticles (NPs) based on magnetite, titanium dioxide and silver capped [...] Read more.

Superhydrophobic epoxy nanocomposites coatings with superior mechanical and adhesion strength are targeted to increase epoxy coating performance and to protect steel corrosion in aggressive environment. The present work prepared hydrophobic organic modified inorganic nanoparticles (NPs) based on magnetite, titanium dioxide and silver capped with epoxide oleic, linoleic and linolenic fatty acids. Their chemical structures, thermal stability, crystalline lattice structure, morphology and particles sizes distribution were determined using different tools. The curing exothermic reactions and thermal mechanical properties of the cured commercial epoxy with polyamine hardener were evaluated in the presence of the modified NPs to investigate their effect on the curing mechanism and crosslinking densities of the cured epoxy networks. The adhesion strength, abrasion resistance, seawater contact angles and seawater salt spray resistances of the cured epoxy coatings were evaluated on the steel surfaces. The obtained results confirm that the increasing weight contents of the modified NPs embedded into epoxy networks via chemical linking affect the adhesion, superhydrophobicity and anticorrosion performances of the cured epoxy coatings on the steel surfaces. Full article

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9 pages, 3243 KiB

Open AccessArticle

Controllable Fabrication of Large-Size Defect-Free Domains of 2D Colloidal Crystal Masks Guided by Statistical Experimental Design

by Xiaofei Sheng, Jing Wang, Yajuan Cheng and Zhe Zhao

Coatings 2021, 11(1), 82; https://doi.org/10.3390/coatings11010082 - 13 Jan 2021

Cited by 1 | Viewed by 1662

Abstract

Large defect-free domains of a hexagonal packed monolayer of silica spheres with the size of 4000 µm² were successfully prepared by dual-speed spin coating. Experimental design and statistical analysis instead of the traditional ‘changing one separate factor at a time’ (COST) approach [...] Read more.

Large defect-free domains of a hexagonal packed monolayer of silica spheres with the size of 4000 µm² were successfully prepared by dual-speed spin coating. Experimental design and statistical analysis instead of the traditional ‘changing one separate factor at a time’ (COST) approach were employed to guide the implementation of the experiments. With its assistance, the hexagonal-close-packed (HCP) percentage was elevated to 84% in this study. Furthermore, almost all the samples with parameters in the selected ranges possessed more than a 60% HCP percentage. In addition, the optimal values for parameters of the suspension concentration, the first rotation speed, and the spinning time to obtain well-ordered silica spheres arrays were also identified as 30 wt.%, 1000 rpm and 20 s, respectively. Full article

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