Coatings

11 pages, 7405 KiB

Open AccessArticle

High-Temperature Oxidation Resistance and Tribological Properties of Al₂O₃/ta-C Coating

by Asad Alamgir, Andrei Bogatov, Taivo Jõgiaas, Mart Viljus, Taavi Raadik, Jakob Kübarsepp, Fjodor Sergejev, Andreas Lümkemann, Jan Kluson and Vitali Podgursky

Coatings 2022, 12(4), 547; https://doi.org/10.3390/coatings12040547 - 18 Apr 2022

Cited by 5 | Viewed by 2863

Abstract

The focus is on the oxidation resistance and tribological performance of ta-C and Al₂O₃/ta-C coatings. The wear tests were carried out on the ball on disc tribometer at room (25 °C) and high (400, 450 and 500 °C) temperatures [...] Read more.

The focus is on the oxidation resistance and tribological performance of ta-C and Al₂O₃/ta-C coatings. The wear tests were carried out on the ball on disc tribometer at room (25 °C) and high (400, 450 and 500 °C) temperatures in ambient air with Si₃N₄ balls as counterbodies. Scanning electron microscopy and Raman spectroscopy were used to analyze the surface morphology and chemical bonding, respectively. The Al₂O₃/ta-C coating exhibited better oxidation resistance and tribological performance at elevated temperatures than the ta-C coating. The Raman analysis revealed that a thin alumina layer suppresses structural changes in the ta-C coating at elevated temperatures, thus preserving the sp³ content. Full article

(This article belongs to the Special Issue Tribological Studies on Diamond, DLC and Ta-C Coatings)

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13 pages, 4727 KiB

Open AccessArticle

Structural Determination of Pectins by Spectroscopy Methods

by Agata Kozioł, Kamila Środa-Pomianek, Agata Górniak, Agnieszka Wikiera, Konrad Cyprych and Magdalena Malik

Coatings 2022, 12(4), 546; https://doi.org/10.3390/coatings12040546 - 18 Apr 2022

Cited by 44 | Viewed by 5361

Abstract

Plant polysaccharides include pectins, which are responsible for an important role in plant physiology and are part of the plant cell wall. These compounds are known as gelling and stabilizing agents, which are widely used in the food industry. The scientific literature lacks [...] Read more.

Plant polysaccharides include pectins, which are responsible for an important role in plant physiology and are part of the plant cell wall. These compounds are known as gelling and stabilizing agents, which are widely used in the food industry. The scientific literature lacks precise information on the spectroscopy of apple pectin and citrus pectin. Therefore, the aim of this work was to test and compare the physicochemical properties of these compounds. The curves of FT-IR, NMR, ESI-MS, and thermogravimetric analysis (TGA) of pectin samples were measured and discussed. The analysis of the spectroscopic results confirms that the isolated pectins using various enzymes (xylanase and cellulase) have a structure similar to the commercially available pectin (PectaSol-C), with a noticeable change in morphology. These characteristics are helpful for further basic research and application. Full article

(This article belongs to the Special Issue Novel Approaches on the Coatings Materials: Biomedical and Industrial Applications)

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12 pages, 3994 KiB

Open AccessFeature PaperArticle

WO₃ Films Grown by Spray Pyrolysis for Smart Windows Applications

by Kyriakos Mouratis, Ioan Valentin Tudose, Cosmin Romanitan, Cristina Pachiu, Marian Popescu, Georgios Simistiras, Stelios Couris, Mirela Petruta Suchea and Emmanuel Koudoumas

Coatings 2022, 12(4), 545; https://doi.org/10.3390/coatings12040545 - 18 Apr 2022

Cited by 10 | Viewed by 3170

Abstract

WO₃ nanostructured thin films were grown using spray deposition on FTO coated glass. The effect of the precursor concentration and the solution quantity, which determines the deposition time, on the electrochemical, electrochromic and optical properties of the WO₃ films was investigated. [...] Read more.

WO₃ nanostructured thin films were grown using spray deposition on FTO coated glass. The effect of the precursor concentration and the solution quantity, which determines the deposition time, on the electrochemical, electrochromic and optical properties of the WO₃ films was investigated. The films were found to exhibit a good electrochromic activity with a reasonably good durability of charge exchange and optical modulation under harsh electrochemical cycling in Li-ion-conducting electrolyte. Associated compositional and structural characteristics were probed by several techniques, indicating that the observed improved durability may be due to the unique WO₃ thin films’ structuring, the surface of the films consisting of wall-like structures combined with bubble-like islands on a polycrystalline WO₃ granular background, that requires further study in greater detail. Full article

(This article belongs to the Special Issue New Trends in Functional Materials and Devices)

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16 pages, 9194 KiB

Open AccessArticle

Deposition Behavior and Microstructure of Cold-Sprayed Ni-Coated Al Particles

by Xiao Chen, Hongkai Zhou, Zhimin Pi and Zhiwu Huang

Coatings 2022, 12(4), 544; https://doi.org/10.3390/coatings12040544 - 18 Apr 2022

Viewed by 1846

Abstract

Cold spraying is a novel technology for preparing solid-state coatings. Single Ni-coated Al particles were deposited onto different substrates by cold spraying at different accelerating gas temperatures, as well as preparing for the coatings. The influence of the accelerating gas temperature and substrate [...] Read more.

Cold spraying is a novel technology for preparing solid-state coatings. Single Ni-coated Al particles were deposited onto different substrates by cold spraying at different accelerating gas temperatures, as well as preparing for the coatings. The influence of the accelerating gas temperature and substrate microhardness on the particle deposition deformation, microstructure, and microhardness of Ni-coated Al coatings were investigated. The results show that the embedding depth of Ni-coated Al particles into the Al substrate increased with increasing the accelerating gas temperature. However, the cold-sprayed Ni-coated Al particles did not embed into the Q235 steel substrate, and the degree of plastic deformation of the Ni-coated Al particles increased with increasing the accelerating gas temperature. Moreover, the morphology of the Ni-coated Al splat deposited onto the Q235 steel substrate at an accelerating gas temperature of 400 °C presented a flattened morphology, which was different from the nearly spherical or ellipsoidal morphology of the Ni-coated Al feedstock. Ni-coated Al coatings exhibited the same phase compositions as the feedstock powders, and the Ni and Al phases in the coatings incurred a certain plastic deformation. Compared with the Q235 steel substrate, an Al substrate with a lower microhardness is beneficial for forming the first layer coating, as well as for the formation of an intermixing structure between the Ni-coated Al coating and Al substrate. The porosity of Ni-coated Al coatings decreased and the thickness increased when increasing the gas temperature; in particular, the coating deposited onto Al substrate had the lowest porosity and the largest thickness at an accelerating gas temperature of 400 °C. Meanwhile, the microhardness of the coating deposited onto the Al substrate was higher than that deposited onto the Q235 steel substrate under the same cold spraying conditions. Full article

(This article belongs to the Special Issue Cold Gas Spray Coatings: Fundamentals and Applications)

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13 pages, 2054 KiB

Open AccessArticle

Calcium Phosphate Cement Promotes Odontoblastic Differentiation of Dental Pulp Cells In Vitro and In Vivo

by Haiyan Huang, Linjuan Luo, Lefeng Li, Yun Guan, Yanhong Yan, Zhen Jiang and Beizhan Jiang

Coatings 2022, 12(4), 543; https://doi.org/10.3390/coatings12040543 - 18 Apr 2022

Cited by 2 | Viewed by 2935

Abstract

In the case of pulp injury, odontoblastic differentiation of dental pulp cells (DPCs) at the site of the exposed pulp is necessary for a successful direct pulp capping treatment. Calcium phosphate cement (CPC), a kind of hydroxyapatite-like bone cement, exhibits therapeutic potential in [...] Read more.

In the case of pulp injury, odontoblastic differentiation of dental pulp cells (DPCs) at the site of the exposed pulp is necessary for a successful direct pulp capping treatment. Calcium phosphate cement (CPC), a kind of hydroxyapatite-like bone cement, exhibits therapeutic potential in osteogenesis by regulating cell cycle progression and promoting osteoblastic differentiation. Based on the similar biological process of osteo/odontoblastic differentiation, the present study evaluated the effects of CPC on odontoblastic differentiation of DPCs in vitro and in vivo, respectively. The morphology of CPC was observed by scanning electron microscopy. Colony-forming units were used to assess the antibacterial activity. The effects of CPC on cell proliferation and odontoblastic differentiation of human dental pulp cells (hDPCs) were also measured. Histological staining was performed to observe the reparative dentin formation in rat molars. In vitro, results of antibacterial studies showed that CPC significantly inhibited the growth of Streptococcus mutans. The appropriate concentration of CPC extract showed low cytotoxicity on hDPCs. Furthermore, CPC extract also promoted odontoblastic differentiation and mineralization compared with the control group, as shown by a dynamic increase in the expression of odontogenic marker genes and the increased number of mineralized nodules at 21 days. The pulpotomy models with CPC facilitated the formation of dentin bridge with the highly expressed dentin matrix protein 1 (DMP1) in odontoblast-like cells. In conclusion, the favorable biocompatibility, antibacterial property and bio-inductivity of CPC suggest that CPC can be used as a promising direct pulp capping material. Full article

(This article belongs to the Special Issue Antibacterial Coating in Biomedical Applications)

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8 pages, 3418 KiB

Open AccessEditor’s ChoiceArticle

Strain Engineering of Domain Coexistence in Epitaxial Lead-Titanite Thin Films

by Yanzhe Dong, Xiaoyan Lu, Jinhui Fan, Si-Young Choi and Hui Li

Coatings 2022, 12(4), 542; https://doi.org/10.3390/coatings12040542 - 18 Apr 2022

Cited by 3 | Viewed by 2491

Abstract

Phase and domain structures in ferroelectric materials play a vital role in determining their dielectric and piezoelectric properties. Ferroelectric thin films with coexisting multiple domains or phases often have fascinating high sensitivity and ultrahigh physical properties. However, the control of the coexisting multiple [...] Read more.

Phase and domain structures in ferroelectric materials play a vital role in determining their dielectric and piezoelectric properties. Ferroelectric thin films with coexisting multiple domains or phases often have fascinating high sensitivity and ultrahigh physical properties. However, the control of the coexisting multiple domains is still challenging, thus necessitating the theoretical prediction. Here, we studied the phase coexistence and the domain morphology of PbTiO₃ epitaxial films by using a Landau–Devonshire phenomenological model and canonic statistical method. Results show that PbTiO₃ films can exist in multiple domain structures that can be diversified by the substrates with different misfit strains. Experimental results for PbTiO₃ epitaxial films on different substrates are in good accordance with the theoretical prediction, which shows an alternative way for further manipulation of the ferroelectric domain structures. Full article

(This article belongs to the Special Issue Ferroelectric Thin Films and Composites)

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15 pages, 6208 KiB

Open AccessArticle

The Ferrite Layer on the Surface of Carbon Steel Obtained by Precisely Designed Cooling Rate Heat Treatment and Its Microstructure Analysis

by Weijiang Yang, Yining Zhou, Yunzan Ma, Kejia Liu, Lianbo Wang and Kun Chen

Coatings 2022, 12(4), 541; https://doi.org/10.3390/coatings12040541 - 18 Apr 2022

Cited by 2 | Viewed by 3089

Abstract

This paper presents obtaining a single-phase ferrite layer with low content of carbon (the average thickness is about 156–246 µm) on the surface of 0.45% carbon steel by precisely designing the cooling rate during heat treatment, and its mechanical properties show a graded [...] Read more.

This paper presents obtaining a single-phase ferrite layer with low content of carbon (the average thickness is about 156–246 µm) on the surface of 0.45% carbon steel by precisely designing the cooling rate during heat treatment, and its mechanical properties show a graded change in the cross-section. It may be achieved by preparing gradient/multilayer materials with more commonly utilized structures or a specific performance. Combining with phase identification by employing electron backscatter diffraction (EBSD) of the layer in this study is BCC ferritic phases. Based on the examination of Continuous Cooling Transformation (CCT) curves, the following conclusions are given. Under the cooling process with gradient temperature, a ferrite layer first forms on the outer lower temperature surface of the 0.45% carbon steel and subsequently develops by pushing the surplus carbon to the inner higher temperature austenite region. It is corroborated by the experimental findings of carbon contents dispersion acquired by electron probe microanalyzer (EPMA). Finally, the experimental findings of grain orientations and size distribution defined by electron backscatter diffraction (EBSD) are given as requirements for microscopic interpretation of the combination of excellent strength and bending capabilities of materials. Furthermore, the experimental findings of oxidation precisely specified the cooling rate during heat treatment of Cu coating samples, which are defined as criteria for identifying the production mechanism of the surface ferrite layer. It provides a theoretical explanation and direct experimental proof for creating the ferrite layer on the surface. Full article

(This article belongs to the Section Thin Films)

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14 pages, 3497 KiB

Open AccessArticle

Large Two-Magnon Raman Hysteresis Observed in a Magnetically Uncompensated Hematite Coating across the Morin Transition

by Jesús López-Sánchez, Adolfo del Campo, Sara Román-Sánchez, Óscar Rodríguez de la Fuente, Noemí Carmona and Aída Serrano

Coatings 2022, 12(4), 540; https://doi.org/10.3390/coatings12040540 - 17 Apr 2022

Cited by 6 | Viewed by 2983

Abstract

A temperature-dependent Raman experiment between 80 and 600 K was performed in a nanoparticulated coating of single-phase hematite grown on a silica substrate. In that range, a thermal Raman shift hysteresis was identified in the vibrational modes that accompanies the Morin transition, observing [...] Read more.

A temperature-dependent Raman experiment between 80 and 600 K was performed in a nanoparticulated coating of single-phase hematite grown on a silica substrate. In that range, a thermal Raman shift hysteresis was identified in the vibrational modes that accompanies the Morin transition, observing large effects in the two-magnon Raman frequency position and in its relative intensity. Interestingly, no decrease in coercivity occurs when the hematite crosses the Morin transition below 230 K. The spin-flop processes produced in the coating leads to a strong decompensation of the surface spins, generating a ferromagnetic component over the whole temperature range studied. Such unusual effects might be promoted by a certain degree of structural disorder and the stresses produced by the nanoparticulation growth approach of the hematite coating. As a result, a high stability of the two-magnon excitation is obtained over a wide temperature range and considerable advances are made for the development of spintronic devices based on semiconductor antiferromagnetic materials. Full article

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

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24 pages, 5725 KiB

Open AccessReview

Electrodeposition of Calcium Phosphate Coatings on Metallic Substrates for Bone Implant Applications: A Review

by Richard Drevet and Hicham Benhayoune

Coatings 2022, 12(4), 539; https://doi.org/10.3390/coatings12040539 - 17 Apr 2022

Cited by 27 | Viewed by 6664

Abstract

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms [...] Read more.

This review summaries more than three decades of scientific knowledge on electrodeposition of calcium phosphate coatings. This low-temperature process aims to make the surface of metallic bone implants bioactive within a physiological environment. The first part of the review describes the reaction mechanisms that lead to the synthesis of a bioactive coating. Electrodeposition occurs in three consecutive steps that involve electrochemical reactions, pH modification, and precipitation of the calcium phosphate coating. However, the process also produces undesired dihydrogen bubbles during the deposition because of the reduction of water, the solvent of the electrolyte solution. To prevent the production of large amounts of dihydrogen bubbles, the current density value is limited during deposition. To circumvent this issue, the use of pulsed current has been proposed in recent years to replace the traditional direct current. Thanks to breaking times, dihydrogen bubbles can regularly escape from the surface of the implant, and the deposition of the calcium phosphate coating is less disturbed by the accumulation of bubbles. In addition, the pulsed current has a positive impact on the chemical composition, morphology, roughness, and mechanical properties of the electrodeposited calcium phosphate coating. Finally, the review describes one of the most interesting properties of electrodeposition, i.e., the possibility of adding ionic substituents to the calcium phosphate crystal lattice to improve the biological performance of the bone implant. Several cations and anions are reviewed from the scientific literature with a description of their biological impact on the physiological environment. Full article

(This article belongs to the Special Issue Calcium Phosphate and Bioglass Materials for Bone Implant Applications)

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12 pages, 3367 KiB

Open AccessArticle

Mechanical Properties of Tensile Cracking in Indium Tin Oxide Films on Polycarbonate Substrates

by Jiali Zhou, Xuan Zhang, Xiaofeng Zhang, Wenqiao Zhang, Jiuyong Li, Yuandong Chen, Hongyan Liu and Yue Yan

Coatings 2022, 12(4), 538; https://doi.org/10.3390/coatings12040538 - 17 Apr 2022

Cited by 17 | Viewed by 3321

Abstract

The electro-mechanical behaviors of transparent conductive oxide film on polymer substrate are of great concern because they would greatly affect the stability and lifespan of the corresponding devices. In this paper, indium tin oxide (ITO) films with different thicknesses were deposited on a [...] Read more.

The electro-mechanical behaviors of transparent conductive oxide film on polymer substrate are of great concern because they would greatly affect the stability and lifespan of the corresponding devices. In this paper, indium tin oxide (ITO) films with different thicknesses were deposited on a polycarbonate (PC) sheet; meanwhile, in situ electrical resistance, in situ scanning electron microscopy and profilometry were employed to record the electrical resistance, morphologies and residual stress in order to investigate the fracture behavior and electrical-mechanical properties of ITO films under uniaxial tension loading. The electrical resistance changes, crack initiation, crack propagation and crack density evolution of ITO films were systematically characterized by in situ tests. Three fracture stages of ITO films were summarized: Ⅰ crack initiation, Ⅱ crack propagation, Ⅲ crack saturation and delamination. The crack initiation and electrical failure in a thinner ITO film occurred at relatively higher applied tensile strain; namely, the ductility of the film decreased as the film thickness increased. Residual compressive stress was recorded in the ITO films deposited on PC at room temperature and increased as the film thickness increased. Intrinsic crack initiation strain (CIS*) showed an opposite thickness dependence to residual strain (ε_r); the increase in residual compressive strain was counteracted by the decrease of intrinsic cohesion, leading to an overall decrease in effective crack initiation strain (CIS) when the film thickness increased. In addition, integrated with a formulated mechanics model and the analysis of the three fracture stages under tension, the fracture toughness and interfacial shear strength were quantitatively determined. As the film thickness increased (in the range of 50~500 nm), the fracture toughness decreased and the films were more prone to crack, whereas the interfacial shear strength increased and the films were less likely to delaminate. Full article

(This article belongs to the Topic Inorganic Thin Film Materials)

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10 pages, 4799 KiB

Open AccessArticle

Eco-Friendly In Situ ZnO Synthesis on PET Fabric Using Oxygen Plasma and Plant Waste

by Anja Verbič, Katja Brenčič, Gregor Primc, Miran Mozetič and Marija Gorjanc

Coatings 2022, 12(4), 537; https://doi.org/10.3390/coatings12040537 - 16 Apr 2022

Cited by 3 | Viewed by 2134

Abstract

This study presents an eco-friendly protocol for the hydrophilization of polyethylene terephthalate (PET) fabric and the in situ synthesis of ZnO particles. The alkaline medium and reducing agent for ZnO synthesis were prepared as aqueous extracts from wood ash and pomegranate peel, respectively. [...] Read more.

This study presents an eco-friendly protocol for the hydrophilization of polyethylene terephthalate (PET) fabric and the in situ synthesis of ZnO particles. The alkaline medium and reducing agent for ZnO synthesis were prepared as aqueous extracts from wood ash and pomegranate peel, respectively. Due to the hydrophobic nature of the PET fabric, oxygen plasma treatment was included in the process. The influence of plasma treatment in different synthesis steps on the formation of ZnO and consequently on the morphological, colour and ultraviolet (UV) protective properties of the samples was discussed. The study showed that incorporating oxygen plasma treatment before immersing the samples in each solution for the ZnO in situ synthesis (natural alkaline medium of wood ash, zinc salt and natural reducing agent from pomegranate peel) produced PET fabric with the most uniform ZnO layer without visible cracks and the highest UV-blocking ability with a UV protection factor (UPF) of 300+. The colour measurements showed that increasing the number of plasma treatments leads to higher colour strength of the samples. Herein, a novel protocol for the production of protective PET fabrics is presented, which is also an example of a completely environmentally benign textile functionalization process. Full article

(This article belongs to the Special Issue Surface Treatment of Textiles Vol. 2)

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15 pages, 2270 KiB

Open AccessArticle

The Theoretical Basis of Face Contact Pressure Design of the Zero-Leakage Mechanical Seal

by Wei Zheng, Jianjun Sun, Chenbo Ma and Qiuping Yu

Coatings 2022, 12(4), 536; https://doi.org/10.3390/coatings12040536 - 16 Apr 2022

Cited by 5 | Viewed by 3325

Abstract

The value of face contact pressure has an important influence on the wear life and leakage rate of the mechanical seal. For a long time, people have chosen face contact pressure based on experience and lack of theoretical support, which greatly reduces the [...] Read more.

The value of face contact pressure has an important influence on the wear life and leakage rate of the mechanical seal. For a long time, people have chosen face contact pressure based on experience and lack of theoretical support, which greatly reduces the effectiveness of the mechanical seal. Based on the percolation theory, the critical porosity of zero-leakage at the wetting and non-wetting sealing interface working in liquid medium is first discussed. The influence of end-face frictional heat on end-face friction and wear is then investigated. The design criteria for the face contact pressure of mechanical seals with zero-leakage and long-life operation are established. Afterwards, the face contact pressure range of the mechanical seal working in conventional different liquid medium is calculated, and the influence of different working conditions on the face contact pressure range change is analyzed. Existing studies have shown that mechanical seals can achieve zero-leakage and long-life operation. Under the rotating and stationary rings’ physical parameters and given working conditions, the face contact pressure range of the sealing medium water and propane propylene is 0.477~1.132 MPa. The diesel sealing medium has a larger face contact pressure range than that of water and propane propylene, which can reach 0.477~2.183 MPa. The working condition speed, medium temperature, and medium pressure have an influence on the face contact pressure range, while the influence of the working condition speed is the most significant. Full article

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14 pages, 3894 KiB

Open AccessArticle

Microstructure and Properties of Hydroxyapatite Coatings Made by Aerosol Cold Spraying–Sintering Technology

by Grzegorz Kubicki, Volf Leshchynsky, Ahmed Elseddawy, Maria Wiśniewska, Roman G. Maev, Jarosław Jakubowicz and Joanna Sulej-Chojnacka

Coatings 2022, 12(4), 535; https://doi.org/10.3390/coatings12040535 - 15 Apr 2022

Cited by 6 | Viewed by 2839

Abstract

Hydroxyapatite is a widely used material used for the bioactivation of an implant’s surface. A promising hydroxyapatite coating approach is the kinetic deposition of powder particles. The possibility of solid-state deposition improvement through the merging of Aerosol Deposition and Low Pressure Cold Spraying [...] Read more.

Hydroxyapatite is a widely used material used for the bioactivation of an implant’s surface. A promising hydroxyapatite coating approach is the kinetic deposition of powder particles. The possibility of solid-state deposition improvement through the merging of Aerosol Deposition and Low Pressure Cold Spraying techniques is a promising prospect for improving the deposition efficiency and the quality of coatings. The objective of the paper is to study the possibilities of hydroxyapatite coating structure modification through changes in the coating process and post-heat treatment. The novel Aerosol Cold Spraying system joining Low Pressure Cold Spraying and Aerosol Deposition was used for the deposition of coatings. The coating’s post-processing was conducted using two techniques: Spark Plasma Sintering and Pressureless Sintering. The coating’s structure was examined using scanning, transmission, and light microscopy, and X-ray diffraction. Substrate–coating bond strength was assessed using a tensile test. Homogenous buildup using Aerosol Cold Spraying of hydroxyapatite was achieved. Various pores and microcracks were visible in the sprayed coatings. The deposition process and the thermal post-processing did not lead to significant degradation of the hydroxyapatite phase. As a result of the Spark Plasma Sintering and Pressureless Sintering at 800 °C, an increase in tensile adhesion bond strength and crystal size was obtained. Full article

(This article belongs to the Special Issue Advances in Cold Spraying for Thin Film Preparation)

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7 pages, 4613 KiB

Open AccessArticle

Effects of the Substitution of 20% Nd for La or Doping with 20% C on the Magnetic Properties and Magnetocaloric Effect in LaFe_11.5Si_1.5 Compound

by Dengkui Zhang, Zhisheng Wu, Yan Li and Ruirui Wang

Coatings 2022, 12(4), 534; https://doi.org/10.3390/coatings12040534 - 15 Apr 2022

Cited by 2 | Viewed by 1588

Abstract

The effects of element substitution and element doping on the magnetic properties and magnetocaloric effect of the LaFe_11.5Si_1.5 compound were investigated. The crystals of the LaFe_11.5Si_1.5, La_0.8Nd_0.2Fe_11.5Si_1.5, and [...] Read more.

The effects of element substitution and element doping on the magnetic properties and magnetocaloric effect of the LaFe_11.5Si_1.5 compound were investigated. The crystals of the LaFe_11.5Si_1.5, La_0.8Nd_0.2Fe_11.5Si_1.5, and LaFe_11.5Si_1.5C_0.2 compounds all showed cubic NaZn₁₃-type structures, but the lattice of the La_0.8Nd_0.2Fe_11.5Si_1.5 shrank and the lattice of the LaFe_11.5Si_1.5C_0.2 expanded. All three compounds had the characteristic of first-order magnetic transition due to the obvious itinerant-electron metamagnetic (IEM) transition occurring above Curie temperature (T_C). For the LaFe_11.5Si_1.5, La_0.8Nd_0.2Fe_11.5Si_1.5, and LaFe_11.5Si_1.5C_0.2 compounds, the T_C were approximately 194 K, 188 K, and 232 K, respectively. Meanwhile, the maximum magnetic entropy changes (−ΔS_M) under a magnetic field change of 0–3 T were approximately 18.7 J/kg·K, 22.8 J/kg·K, and 16.4 J/kg·K, respectively. The T_C was mainly affected by the lattice constant. Furthermore, the −ΔS_M was mainly affected by the latent heat of the first-order magnetic transition. Full article

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14 pages, 2969 KiB

Open AccessArticle

Gloss Level of HDF Finished with Different Numbers of Layers and Hardened with UV Hg-Ga Lamps of Selected Power

by Milena Henke, Barbara Lis and Tomasz Krystofiak

Coatings 2022, 12(4), 533; https://doi.org/10.3390/coatings12040533 - 15 Apr 2022

Cited by 6 | Viewed by 2689

Abstract

A key feature of varnish coatings on furniture surfaces is their optical properties, which often determine customers’ purchase choices. Furniture may be produced using various boards, which are much cheaper than wood-based materials. For their finishing, among others, UV-cured varnish products are used. [...] Read more.

A key feature of varnish coatings on furniture surfaces is their optical properties, which often determine customers’ purchase choices. Furniture may be produced using various boards, which are much cheaper than wood-based materials. For their finishing, among others, UV-cured varnish products are used. The aim of this study was to determine the effect of different types of HDF boards, the amount of basecoat and topcoat applied, the number of layers, and the different lamp powers used for hardening on the gloss of coatings obtained using UV technology. The gloss was tested with a photoelectric apparatus. An auxiliary parameter in the assessment of the gloss of the coatings was the surface roughness, which was measured with the Mitutoyo SJ-210 Analysis of variance (ANOVA) was used to obtain the results. Statistical considerations showed that the amount of topcoat applied, the power of the lamps, and the interactions between them had the greatest impact on gloss, followed by the number of layers. In general, the gloss of the coating decreased with a decrease in lamp power in the range of 120–60 W/cm and with an increase in the amount of topcoat applied. Full article

(This article belongs to the Special Issue UV Lacquer Systems for Wood and Wood Based Materials)

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14 pages, 1664 KiB

Open AccessArticle

Hypothetical Mechanism of Skin Argyria

by Vasily Burmistrov, Alexander Burmistrov, Galina Odegova, Alexey Pestryakov, Roberto Luna-Vázquez-Gómez and Nina Bogdanchikova

Coatings 2022, 12(4), 532; https://doi.org/10.3390/coatings12040532 - 15 Apr 2022

Cited by 3 | Viewed by 6339

Abstract

Introduction. Argyria is an acquired skin condition that appears after the exposure or consumption of silver, leading to blue or grey coloration of the skin and mucosa. The aim of the present work was to draw researchers’ attention to two aspects of the [...] Read more.

Introduction. Argyria is an acquired skin condition that appears after the exposure or consumption of silver, leading to blue or grey coloration of the skin and mucosa. The aim of the present work was to draw researchers’ attention to two aspects of the argyria that until now have not received enough consideration. They are: (1) the process of delivering silver compound from the gastrointestinal tract to the skin and (2) the possibility for silver chloride to participate in this process along with the silver proteinates. Methodology. Illustrative experiments included the observation of color change (visual and using UV-Vis spectrometry) under different light exposure conditions of silver chloride sol in a sweat-simulating solution, in vials and under pig skin (in direct contact). Results and Discussion. A hypothetical mechanism based on a perspiration system for delivering the silver compounds from the gastrointestinal tract to the skin for argyria was proposed. It was also proposed not to completely exclude the partial participation of silver chloride along with the silver proteinates in this process. Full article

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15 pages, 3568 KiB

Open AccessArticle

Design, Simulation and Performance Research of New Biomaterial Mg₃₀Zn₃₀Sn₃₀Sr₅Bi₅

by Beiyi Ma, Dongying Ju and Qian Liu

Coatings 2022, 12(4), 531; https://doi.org/10.3390/coatings12040531 - 14 Apr 2022

Cited by 4 | Viewed by 2327

Abstract

This study focused on the design and the preparation method of a new biomaterial, Mg₃₀Zn₃₀Sn₃₀Sr₅Bi₅ (at%) alloy, and its simulation and property analyses. Based on the comprehensive consideration of the preparation of high-entropy alloys, [...] Read more.

This study focused on the design and the preparation method of a new biomaterial, Mg₃₀Zn₃₀Sn₃₀Sr₅Bi₅ (at%) alloy, and its simulation and property analyses. Based on the comprehensive consideration of the preparation of high-entropy alloys, the selection of biomaterial elements, and the existing research results of common Mg-based materials, the atomic percentage of various elements, that is, Mg:Zn:Sn:Sr:Bi = 30:30:30:5:5, was determined. Using the theoretical methods of thermodynamic performance analysis and solidification performance analysis, the proposed composition was simulated and analyzed. The analysis results showed that the mechanical properties of the new material can meet the design requirements, and it can be prepared in physical form. XRD, SEM, PSD, compression tests, and other experimental tests were conducted on the material, and the alloy composition and distribution law showed various characteristics, which conformed to the “chaotic” characteristics of high-entropy alloys. The elastic modulus of the material was 17.98 GPa, which is within the 0–20 GPa elastic modulus range of human bone. This means that it can avoid the occurrence of stress shielding problems more effectively during the material implantation process. Full article

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19 pages, 7671 KiB

Open AccessArticle

A Multi-Analytical Investigation of Roman Frescoes from Rapoltu Mare (Romania)

by Rodica-Mariana Ion, Marius Gheorghe Barbu, Andrei Gonciar, Gabriel Vasilievici, Anca Irina Gheboianu, Sofia Slamnoiu-Teodorescu, Madalina Elena David, Lorena Iancu and Ramona Marina Grigorescu

Coatings 2022, 12(4), 530; https://doi.org/10.3390/coatings12040530 - 14 Apr 2022

Cited by 7 | Viewed by 2898

Abstract

(1) Background: Due to the precarious situation of many monuments or archeological sites, analytical investigations are necessary to obtain information about the used materials, as well as to identify the most appropriate solutions for their conservation/restoration. This paper addresses the characterization of mural [...] Read more.

(1) Background: Due to the precarious situation of many monuments or archeological sites, analytical investigations are necessary to obtain information about the used materials, as well as to identify the most appropriate solutions for their conservation/restoration. This paper addresses the characterization of mural painting fragments collected during the excavation in 2018 in Rapoltu Mare (La vie), Deva. (2) Methods: Specific analytical techniques were used, as follows: X-ray diffractometry (XRD), wavelength dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), zoom microscopy and scanning electron microscopy (SEM), spectroscopic techniques (UV–Vis, FTIR, Raman), porosity and thermal analysis, all of which provide information about the structure, chemical composition, morphology and topography of pigments and their deterioration as well. (3) Results: Up to seven different pigments were identified: Egyptian blue, carbon, calcite, gypsum, hematite, goethite and green earth. Egyptian Blue is identified in all the other color areas, except the white area: in the green zone (as degradation product with beeswax) and in the red zone (in mixture with ochre) too. In addition, carbon and beeswax were highlighted as toner and binder for pigments, respectively. In the presence of the organic beeswax binding environment, the Egyptian blue pigment particles darkened or turned yellow significantly, changing the blue to a greenish color. It is also possible to identify wollastonite (CaSiO₃) in the blue pigment, which indicates that the temperature used in the manufacturing of Egyptian blue was higher than 950 °C from thermal analysis. The presence of apatite, hematite and gypsum deposits in the Hunedoara region certifies that these pigments could have been of local origin, as demonstrated by the presence of analytically identified elements (Fe, P, S, Ca). (4) Conclusions: The analytical techniques used for such investigations have highlighted the main pigments used in Roman times for various Roman murals. Full article

(This article belongs to the Special Issue Syntheses, Properties, and Applications of Organic Dyes and Pigments)

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14 pages, 5323 KiB

Open AccessArticle

Facile Route to Achieve Self-Supported Cu(OH)₂/Ni₃S₂ Composite Electrode on Copper Foam for Enhanced Capacitive Energy Storage Performance

by Sa Lv, Peiyu Geng, Yaodan Chi, Huan Wang, Xuefeng Chu, Gongda Chen, Wenshi Shang, Chao Wang, Jia Yang, Zhifei Cheng and Xiaotian Yang

Coatings 2022, 12(4), 529; https://doi.org/10.3390/coatings12040529 - 14 Apr 2022

Cited by 1 | Viewed by 2174

Abstract

Herein, a Cu(OH)₂/Ni₃S₂ composite was successfully prepared through facile two-step electrodeposition. As the electrode substrate and the only copper source, the copper foam underwent surface oxidation by galvanostatic deposition technology to form Cu(OH)₂, and the subsequent [...] Read more.

Herein, a Cu(OH)₂/Ni₃S₂ composite was successfully prepared through facile two-step electrodeposition. As the electrode substrate and the only copper source, the copper foam underwent surface oxidation by galvanostatic deposition technology to form Cu(OH)₂, and the subsequent coverage of Ni₃S₂ was achieved by potentiostatic deposition. The Cu(OH)₂ acts as a skeleton, providing support for Ni₃S₂ growth, thus providing more abundant electrochemical active sites. By virtue of the in situ growth strategy and the synergy of different components, the optimized Cu(OH)₂/Ni₃S₂ electrode illustrates significantly enhanced pseudocapacitance performance, with an areal specific capacitance of 11.43 F cm⁻² at 2 mA cm⁻², good coulombic efficiency of 94.55%, and remarkable cyclic stability (83.33% capacitance retention after 5000 cycles). Full article

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11 pages, 8644 KiB

Open AccessArticle

Photocatalytic Inactivation of Bacillus subtilis Spores by Natural Sphalerite with Persulfate under Visible Light Irradiation

by Yan Liu, Zhenni Liu, Dong Liu and Wanjun Wang

Coatings 2022, 12(4), 528; https://doi.org/10.3390/coatings12040528 - 13 Apr 2022

Cited by 2 | Viewed by 2144

Abstract

Bacterial spores are highly resistant to be inactivated by conventional water disinfection methods. In this study, the inactivation efficiency and mechanisms of Bacillus subtitles (B. subtilis) spores by natural sphalerite (NS) with persulfate (PS) under visible light (Vis) irradiation were investigated [...] Read more.

Bacterial spores are highly resistant to be inactivated by conventional water disinfection methods. In this study, the inactivation efficiency and mechanisms of Bacillus subtitles (B. subtilis) spores by natural sphalerite (NS) with persulfate (PS) under visible light (Vis) irradiation were investigated for the first time. The NS was composed of ZnS doped with trace amounts of metal ions, including As, Fe, Cd, and Mn. The results showed that 7 log of B. subtilis spores could be completely inactivated within 5 h in the Vis/NS/PS photocatalytic system, and the inactivation efficiency was about four and seven times higher than that of the NS/PS system and the Vis/PS system, respectively. The photo-generated electrons are generated by the excitation of NS under the illumination activated PS to form PS radicals (∙SO₄⁻) and hydroxyl radicals (∙OH), which are the main active species for spore inactivation. Mechanism studies further showed that spore inactivation was related to physiological responses, including the increase in intracellular reactive oxygen species, the change of induced antioxidant enzyme activity, and the change of total protein. Furthermore, the dynamic changes of cells during spore inactivation were observed by SEM. These results not only clarify the relationship between the cell physiological stress response and inactivation mechanism of spores, but also reveal the interaction between minerals and PS under Vis, which provides technical methods for the inactivation of bacterial spores in the field of water disinfection. Full article

(This article belongs to the Special Issue Designs, Preparations and Applications of Catalyst Materials)

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15 pages, 6558 KiB

Open AccessArticle

Rheological and Tribological Properties of Lithium Grease and Polyurea Grease with Different Consistencies

by Yanshuang Wang, Pu Zhang, Jianghai Lin and Xudong Gao

Coatings 2022, 12(4), 527; https://doi.org/10.3390/coatings12040527 - 13 Apr 2022

Cited by 20 | Viewed by 3794

Abstract

The rheological properties of lithium grease and polyurea grease at different temperatures and consistencies were determined with a rotary rheometer. The plateau moduli of the greases were calculated, and the mechanism of influence of consistency and temperature on the rheological properties of the [...] Read more.

The rheological properties of lithium grease and polyurea grease at different temperatures and consistencies were determined with a rotary rheometer. The plateau moduli of the greases were calculated, and the mechanism of influence of consistency and temperature on the rheological properties of the greases was explained. The tribological and wear properties of the two greases were measured by high-temperature friction and wear tester. The friction and wear mechanisms are probed by the rheological properties of lubricating grease. The results show that the plateau modulus G_N can be used to assess the structural strength of different greases, but it can only assess the degree of entanglement of the same grease. The higher the consistency of the grease, the larger the apparent viscosity, structural strength, and yield stress. The rheological properties of PAO-polyurea grease are greatly affected by temperature, but its structural strength is better than that of mineral oil-lithium grease. The consistency of mineral oil-lithium grease is expected to affect the friction coefficient and wear through its influence on the grease’s structural strength and film-forming ability. For PAO-polyurea, the consistency in a certain range has little effect on the friction coefficient and wear resistance. Full article

(This article belongs to the Special Issue 10th Anniversary of Coatings: Invited Papers in Tribology Section)

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8 pages, 3091 KiB

Open AccessArticle

Microstructure and Electric Properties of Bi₂O₃-Doped (K_0.5Na_0.5)NbO₃ Lead-Free Ceramics

by Jiaqi Li, Junjun Wang, Fengmin Wu, Hui Ma, Tianyi Ma, Yu Tian, Danqing Liu and Bin Yang

Coatings 2022, 12(4), 526; https://doi.org/10.3390/coatings12040526 - 13 Apr 2022

Cited by 7 | Viewed by 2180

Abstract

In this paper, Bi₂O₃-doped (K_0.5Na_0.5)NbO₃ (x = 0.1, 0.2, 0.3, 0.4) lead-free ceramics are prepared by a conventional solid-state reaction and analyzed by studying the structure, ferroelectric, and piezoelectric properties. It is found that [...] Read more.

In this paper, Bi₂O₃-doped (K_0.5Na_0.5)NbO₃ (x = 0.1, 0.2, 0.3, 0.4) lead-free ceramics are prepared by a conventional solid-state reaction and analyzed by studying the structure, ferroelectric, and piezoelectric properties. It is found that the doping of Bi₂O₃ increases the proportion of the trigonal phase in KNN ceramics, thus enabling the construction of KNN ceramics with an orthogonal–trigonal phase boundary at room temperature. At the same time, doping with Bi₂O₃ can reduce the grain size and improve grain size uniformity of the ceramics. The KNN-0.1%Bi₂O₃ ceramic has the best piezoelectric properties in all composition; the results are as follows: d₃₃ = 121pC/N, k_p = 0.474, k_t = 0.306. Full article

(This article belongs to the Special Issue Ferroelectric Thin Films and Composites)

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11 pages, 7617 KiB

Open AccessArticle

Microstructure and Micro-Hardness of Dissimilar Metal Cladding from a Pipe–Nozzle Mockup for PWR

by Jiazhen Wang, Hongliang Ming, Zhiming Zhang, Jian Chen and Jianqiu Wang

Coatings 2022, 12(4), 525; https://doi.org/10.3390/coatings12040525 - 13 Apr 2022

Cited by 2 | Viewed by 2257

Abstract

In this study, the dissimilar metal cladding from a pressure vessel pipe–nozzle mockup for PWR was studied using an optical microscope, scanning electron microscopy, energy-dispersive X-ray spectrometry, electron back-scattering diffraction, and micro-hardness measurement. The microstructure of the SA508 side is non-uniform along the [...] Read more.

In this study, the dissimilar metal cladding from a pressure vessel pipe–nozzle mockup for PWR was studied using an optical microscope, scanning electron microscopy, energy-dispersive X-ray spectrometry, electron back-scattering diffraction, and micro-hardness measurement. The microstructure of the SA508 side is non-uniform along the fusion boundary, especially at the concave and convex areas. Martensitic layer (type I and type II) boundaries are found at the fusion boundary area. The chemical composition, residual strain, and microstructure across the SA508–309L fusion boundary are very complex and hence result in a complicated micro-hardness distribution. Full article

(This article belongs to the Special Issue Corrosion and Degradation of Materials)

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14 pages, 34137 KiB

Open AccessArticle

Supercritical Fluid-Assisted Fabrication of PDA-Coated Poly (l-lactic Acid)/Curcumin Microparticles for Chemo-Photothermal Therapy of Osteosarcoma

by Zheng Zhao, Shilu Chen, Yao Xiao, Maobin Xie and Wen Yu

Coatings 2022, 12(4), 524; https://doi.org/10.3390/coatings12040524 - 13 Apr 2022

Cited by 4 | Viewed by 2460

Abstract

After traditional osteosarcoma resection, recurrence of tumor is still a major clinical challenge. The combination of chemotherapy and photothermal therapy (PTT) has great potential in improving therapeutic effect. However, the studies using polydopamine (PDA) as photothermal transducing agent to improve the anti-cancer activity [...] Read more.

After traditional osteosarcoma resection, recurrence of tumor is still a major clinical challenge. The combination of chemotherapy and photothermal therapy (PTT) has great potential in improving therapeutic effect. However, the studies using polydopamine (PDA) as photothermal transducing agent to improve the anti-cancer activity of curcumin (CM)-loaded poly (l-lactic acid) (PLLA) microparticles (PLLA/CM) have seldom been investigated. In this study, we reported the synthesis of PDA-coated PLLA/CM microparticles (PDA-PLLA/CM) prepared by PDA coating on the surface of the PLLA/CM microparticles fabricated by solution-enhanced dispersion by supercritical CO₂ (SEDS) for chemo-photothermal therapy of osteosarcoma. The average particle sizes of PLLA/CM and PDA-PLLA/CM microparticles with a spherical shape were (802.6 ± 8.0) nm and (942.5 ± 39.5) nm, respectively. PDA-PLLA/CM microparticles exhibited pH- and near-infrared (NIR)-responsive release behavior to promote CM release in the drug delivery system. Moreover, PDA-PLLA/CM microparticles displayed good photothermal conversion ability and photothermal stability attributed to PDA coating. Additionally, the results of in vitro anti-cancer experiment showed that 500 μg/mL PDA-PLLA/CM microparticles had good anti-cancer effect on MG-63 cells and no obvious toxicity to MC3T3-E1 cells. After incubation with PDA-PLLA/CM microparticles for 2 days, NIR irradiation treatment improved the anti-cancer activity of PDA-PLLA/CM microparticles obviously and reduced the cell viability of osteosarcoma from 47.4% to 20.6%. These results indicated that PDA-PLLA/CM microparticles possessed a synergetic chemo-photothermal therapy for osteosarcoma. Therefore, this study demonstrated that PDA-PLLA/CM microparticles may be an excellent drug delivery platform for chemo-photothermal therapy of tumors. Full article

(This article belongs to the Special Issue Advanced Materials for Highly Biocompatible Hydrogel Systems)

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12 pages, 3569 KiB

Open AccessFeature PaperArticle

Selection of Organic Coating Systems for Corrosion Protection of Industrial Equipment

by Michał Drozda and Andrzej Miszczyk

Coatings 2022, 12(4), 523; https://doi.org/10.3390/coatings12040523 - 13 Apr 2022

Cited by 5 | Viewed by 2767

Abstract

The most important element of corrosion protection in industrial conditions is the protective coating system. However, selecting the right coating can often be a real problem due to the sheer number of coating manufacturers and their products on the market. A quantitative approach [...] Read more.

The most important element of corrosion protection in industrial conditions is the protective coating system. However, selecting the right coating can often be a real problem due to the sheer number of coating manufacturers and their products on the market. A quantitative approach based on the data mining technique used to analyze the obtained multi-site exposure data has been proposed. This was demonstrated by the example of the selection of a coating system to protect an industrial ball mill located in a hall for the enrichment of copper ore at the Polish company KGHM Polska Miedz S.A. A collection of 21 two-layer coating systems from different manufacturers was tested for one year. Multiple areas on the industrial ball mill, subjected to varying degrees of vibrations and abrasion, were painted. In addition, sets of samples that can be detached from the mill housing were mounted, as well as the set exposed in the hall without vibrations. The condition of the coatings after exposure was assessed using impedance spectroscopy. The obtained data from many different exposure areas were analyzed using principal components analysis (PCA). In this way, the most advantageous coating systems for the specific conditions in the hall were indicated. Additionally, on this basis, the contribution of various destructive factors, including vibrations and abrasion, to the protective properties of the tested coatings, was estimated. Full article

(This article belongs to the Special Issue Anti-corrosion Coatings: New Ideas to Make Them More Effective)

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16 pages, 4411 KiB

Open AccessArticle

Long-Term Performance of Recycled Asphalt Pavement with Recycled Engine Oil Bottom Based on Accelerated Loading Test

by Jin Li, Li Zhu, Miaozhang Yu, Shen Zuo, Xinzhuang Cui and Peng Liu

Coatings 2022, 12(4), 522; https://doi.org/10.3390/coatings12040522 - 12 Apr 2022

Cited by 7 | Viewed by 2352

Abstract

The practical performance of recycled asphalt obtained from recycled engine oil bottom (REOB) was evaluated by paving a test road of base asphalt and REOB-recycled asphalt mixture in a laboratory, where accelerated loading tests with 700,000 cycles were conducted. During accelerated loading, pavement [...] Read more.

The practical performance of recycled asphalt obtained from recycled engine oil bottom (REOB) was evaluated by paving a test road of base asphalt and REOB-recycled asphalt mixture in a laboratory, where accelerated loading tests with 700,000 cycles were conducted. During accelerated loading, pavement temperature, layer bottom strain, pavement skid resistance, and rutting were monitored. The performance of pavement core material was tested after loading to analyze the index change of binder and the compaction degree of the mixture. The results show that the long-term anti-rutting ability of REOB-recycled asphalt pavement is approximately 10% higher than that of the base asphalt pavement, although the long-term anti-sliding force and anti-fatigue performance are poor. A developed model of rut with loading time can better predict the development trends of these parameters with loading cycles. The performance test of the pavement material after loading shows that 700,000 cycles can only degrade the performance of the test pavement, not damage it. The recycled asphalt pavement with 7% REOB has basically the same performance as the base asphalt under 700,000 cycles, indicating that REOB-recycled asphalt pavement can ensure basic road performance, while providing economic and environmental advantages. These results provide a reference for the application and form optimization of REOB-recycled asphalt pavement. Full article

(This article belongs to the Special Issue Current Research in Cement and Building Materials)

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11 pages, 4684 KiB

Open AccessArticle

Design, Fabrication and Analysis for Al₂O₃/Ti/Al₂O₃ Colored Solar Selective Absorbers for Building Applications

by Fu-Der Lai and Wen-Yang Li

Coatings 2022, 12(4), 521; https://doi.org/10.3390/coatings12040521 - 12 Apr 2022

Cited by 4 | Viewed by 2006

Abstract

A good solar selective absorber (SSA) used in building applications must have good color brightness rendering, an excellent photo–thermal conversion efficiency (PTCE) and a long life. The optical thin film design plays an important role before the coating of the optical thin films. [...] Read more.

A good solar selective absorber (SSA) used in building applications must have good color brightness rendering, an excellent photo–thermal conversion efficiency (PTCE) and a long life. The optical thin film design plays an important role before the coating of the optical thin films. In this study, for fabricating a good colored SSA (CSSA), the optical properties and color distribution of Al₂O₃/Ti/Al₂O₃ SSA were calculated to obtain the best design. It was found that the color distribution of Al₂O₃/Ti/Al₂O₃ SSA with a PTCE in excess of 90% was wide and included all colors, such as red, orange, yellow, green, blue, purple and white. Five colored Al₂O₃/Ti/Al₂O₃ solar selective absorbers were designed and fabricated and their performances were analyzed. The best PTCE of a fabricated sample and its thermal emittance efficiency were 93.2% and 7.1%, respectively. The peak values of the measured optical reflectance in the visible region for the five fabricated CSSAs were all greater than 10%. Their lifetime could be very long because the temperature difference between thermal stability of more than 450 °C and the working temperature of less than 150 °C was up to 300 °C. After annealing at 550 °C, the Al₂O₃–Ti system formed a compound structure of AlTiO₅. The Al₂O₃/Ti/Al₂O₃ film performances, including the optical properties in the wavelength range of 0.25 to 25 μm, structure, morphology, adhesion, cross-sectional images, AFM image, PTCE, thermal emittance efficiency and thermal stability, were measured and analyzed in detail, and met the characteristic requirements of colored solar absorber films. Full article

(This article belongs to the Special Issue Concentrated Solar Power Plant Absorber Coatings)

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7 pages, 1085 KiB

Open AccessArticle

Optical System Design of a Planar Waveguide Spectrometer

by Shiqun Jin, Zhiming Li, Zhiwei Feng, Lin Gao, Yanduo Li, Long Zhang, Wenjie Shi and Guo Xia

Coatings 2022, 12(4), 520; https://doi.org/10.3390/coatings12040520 - 12 Apr 2022

Viewed by 2192

Abstract

In this paper, an optical design for a hollow planar waveguide spectrometer with Czerny-Turner is proposed. To decrease the propagation loss of the spectrometer, the design strategy of designing the tangential plane and the sagittal plane separately is proposed, corresponding to resolution and [...] Read more.

In this paper, an optical design for a hollow planar waveguide spectrometer with Czerny-Turner is proposed. To decrease the propagation loss of the spectrometer, the design strategy of designing the tangential plane and the sagittal plane separately is proposed, corresponding to resolution and energy, respectively. The Czerny–Turner optical path is designed on the tangential plane, and the sagittal design theory and method are analyzed in detail. The ray tracing results show that the resolution of the spectrometer is better than 4 nm on the tangential plane, while on the sagittal plane, the detector receives the highest energy when the detector pixel height matches the distance between the two mirrors. Full article

(This article belongs to the Special Issue Micro-Nano Optics and Its Applications)

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10 pages, 3687 KiB

Open AccessFeature PaperArticle

Microstructure, Mechanical, and Electrochemical Properties of SiC Particle Reinforced CoCrFeNiCu High-Entropy Alloy Coatings

by Li Xu, Huiling Du, Jia Liu, Danni Feng and Siyu Xia

Coatings 2022, 12(4), 519; https://doi.org/10.3390/coatings12040519 - 11 Apr 2022

Cited by 10 | Viewed by 2455

Abstract

SiC particle reinforced CoCrFeNiCu high-entropy alloy (HEA) coatings (CoCrFeNiCu(SiC)_x, x = 0, 5, 10, 15 wt%) were successfully fabricated on 316L stainless steel via laser cladding technique. The effects of SiC particles on the microstructure, mechanical, and electrochemical properties of CoCrFeNiCu [...] Read more.

SiC particle reinforced CoCrFeNiCu high-entropy alloy (HEA) coatings (CoCrFeNiCu(SiC)_x, x = 0, 5, 10, 15 wt%) were successfully fabricated on 316L stainless steel via laser cladding technique. The effects of SiC particles on the microstructure, mechanical, and electrochemical properties of CoCrFeNiCu HEA were investigated. The results showed that the as-fabricated CoCrFeNiCu(SiC)_x HEA coatings is a FCC structure, and a secondary phase formed of Cr₇C₃ at the grain boundaries. Grain boundary strengthening enhances the mechanical properties of CoCrFeNiCu(SiC)_x HEA coatings. Especially for CoCrFeNiCu(SiC)₁₅ HEA coatings, the microhardness, wear weight, and friction coefficient were 568.4 HV, 0.9 mg, and 0.35, respectively. With the increasing of SiC content, the corrosion resistance of CoCrFeNiCu(SiC)_x HEA coatings was enhanced in 3.5% NaCl solution. The CoCrFeNiCu(SiC)₁₀ coatings showed better performance than others when they were evaluated for corrosion. These results indicated that the CoCrFeNiCu(SiC)_x HEA coatings could significantly enhance the wear, friction, and corrosion resistance properties of the 316L stainless steel. Full article

(This article belongs to the Special Issue Deposition, Characterization and Application of Anti-corrosion and Lubricating Coatings)

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27 pages, 44208 KiB

Open AccessReview

Review of Cr-Free Coatings for the Corrosion Protection of Aluminum Aerospace Alloys

by Fabienne Peltier and Dominique Thierry

Coatings 2022, 12(4), 518; https://doi.org/10.3390/coatings12040518 - 11 Apr 2022

Cited by 45 | Viewed by 7208

Abstract

Aluminum alloys are known to have many advantages (e.g., light weight and low cost) but they are not immune to corrosion. So, it is important to assess their corrosion behavior, in particular under atmospheric conditions. To protect aluminum alloys against corrosion, paints are [...] Read more.

Aluminum alloys are known to have many advantages (e.g., light weight and low cost) but they are not immune to corrosion. So, it is important to assess their corrosion behavior, in particular under atmospheric conditions. To protect aluminum alloys against corrosion, paints are generally applied onto the materials. Corrosion protection in the aerospace industry consists of a conversion or anodized coating, an inhibited primer, and a top-coat. Chromate conversion coating (CCC) and primers containing chromate pigments have been widely used in the aerospace industry over the last decades. However, new environmental regulations have led to major changes for aluminum corrosion protection. By limiting or prohibiting some chemicals, for instance Cr(VI), the European regulation REACH (Regulation on Registration Evaluation, Authorization and Restriction of Chemicals) has induced major changes to some of the finishing processes of aluminum alloys (e.g., chromate conversion, chromic acid anodizing, and chromate sealing). Interesting results have been obtained while seeking replacements for Cr(VI), for example, with the incorporation of cerium, lithium salt, or nanocontainers loaded with corrosion inhibitors in organic coatings. For several years, hybrid sol–gel coatings able to replace the pre-treatment and primer steps have been under development, showing interesting results. New prospects for the future involve the use of photopolymerization to reduce the energy-intensive heat treatment needed in sol–gel technology. It will also be necessary to test these new technologies in service conditions or in accelerated corrosion tests before being able to conclude on the real effectiveness of these coatings. This review summarizes the recent developments in Cr-free coatings for aluminum alloys. Their advantages and drawbacks are also discussed. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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