Coatings

72 pages, 77791 KiB

Open AccessArticle

The Origin of Ko-Kutani Porcelain: New Discoveries and a Reassessment

by Riccardo Montanari, Hiroharu Murase, Maria Francesca Alberghina, Salvatore Schiavone and Claudia Pelosi

Coatings 2024, 14(9), 1146; https://doi.org/10.3390/coatings14091146 - 5 Sep 2024

Abstract

The origin of Ko-Kutani porcelain and its decoration style have been debated for over a century. Despite the well-established theory that identified the wares as the result of porcelain production in Kaga (present-day Ishikawa Prefecture) in the 17th century, there still is no [...] Read more.

The origin of Ko-Kutani porcelain and its decoration style have been debated for over a century. Despite the well-established theory that identified the wares as the result of porcelain production in Kaga (present-day Ishikawa Prefecture) in the 17th century, there still is no general agreement as to where they were first incepted and fired. In recent years, curatorial traditional criteria have formed the basis upon which a new theory has been gaining popularity in Japan, identifying Arita (present-day Saga Prefecture) as their actual place of birth. Such a new theory, however, has proven insufficient to cast new light on many of the unexplained facts that characterize the history of the wares. Furthermore, scientific evidence has been lacking, as no systematic analyses of the porcelains were carried out until the present work. In order to define univocally the dynamics behind this period of Japanese history, the most important and complete Ko-Kutani collection extant in Japan today (Ishikawa Prefectural Museum of Art) was analyzed by portable X-ray fluorescence (pXRF). The scientific investigation was also extended to the very scarce shards excavated at the Kaga kiln site and Nonomura Ninsei’s masterpieces. For the first time ever, the results herein presented clarify the missing points crucial to reaching a definitive conclusion. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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13 pages, 6237 KiB

Open AccessArticle

Influence of Spraying Process Parameters on the Characteristics of Steel Coatings Produced by Arc Spraying Method

by Bauyrzhan Rakhadilov, Nurtoleu Magazov, Dauir Kakimzhanov, Akbota Apsezhanova, Yermakhan Molbossynov and Aidar Kengesbekov

Coatings 2024, 14(9), 1145; https://doi.org/10.3390/coatings14091145 - 5 Sep 2024

Abstract

Arc spraying is one of the most effective and cost-efficient thermal spraying technologies for creating high-quality protective coatings. This paper examines the influence of arc spraying process parameters on the properties of steel coatings. The parameters varied in this study included gas pressure, [...] Read more.

Arc spraying is one of the most effective and cost-efficient thermal spraying technologies for creating high-quality protective coatings. This paper examines the influence of arc spraying process parameters on the properties of steel coatings. The parameters varied in this study included gas pressure, wire feed rate, and the distance from the spray gun to the substrate (standoff distance). Experimental evaluations focused on surface roughness, thickness, porosity, structure, and hardness of the coatings. The techniques used for these evaluations included profilometry for roughness measurement, scanning electron microscopy (SEM) for structural analysis, Vickers hardness testing, and optical microscopy. The results demonstrate a significant influence of arc spraying parameters on the characteristics of the resulting coatings. The analysis revealed that the coatings produced under different modes exhibit a layered structure and vary in thickness. A detailed examination of the coating structure identified defects such as unmelted particles, voids, and delamination in the interface zone. The study of coating thickness and porosity showed that increasing the wire feed rate and decreasing the standoff distance leads to the formation of thicker and denser coatings. Specifically, increasing the wire feed rate from 2 to 12 cm/s resulted in a decrease in porosity from 12.59% to 4.33% and an increase in coating thickness to 699 μm. The surface analysis highlighted the importance of a comprehensive approach to selecting the optimal roughness. While increasing the wire feed rate up to 12 cm/s can increase the Ra roughness parameter, gas pressure also significantly influences this parameter, reducing roughness from Ra = 18.63 μm at 6 MPa to Ra = 15.95 μm at 8 MPa. Additionally, it was found that varying the arc spraying parameters affects the hardness of the coatings, with all modes resulting in hardness values higher than that of the substrate. Therefore, optimizing these parameters enables the achievement of the best combination of mechanical and structural properties in the coatings. These findings can be valuable for further improvement of arc spraying technologies and the expansion of their application across various industries. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)

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14 pages, 6613 KiB

Open AccessArticle

Erosion Performance of TiN/Ti Coatings under Different Nitrogen Flow Rates

by Yuxin Ren, Zhaolu Zhang, Guangyu He, Yan Chai, Yanli Zhang and Zilei Zhang

Coatings 2024, 14(9), 1144; https://doi.org/10.3390/coatings14091144 - 5 Sep 2024

Abstract

This study employed magnetic filtered cathodic vacuum arc deposition to fabricate TiN/Ti multilayer coatings, examining the impact of nitrogen flow rates—4, 8, 12, and 16 sccm—on their performance, with an emphasis on gradient flow rates from 4 to 12 sccm. The coatings’ phase [...] Read more.

This study employed magnetic filtered cathodic vacuum arc deposition to fabricate TiN/Ti multilayer coatings, examining the impact of nitrogen flow rates—4, 8, 12, and 16 sccm—on their performance, with an emphasis on gradient flow rates from 4 to 12 sccm. The coatings’ phase composition shifted from TiN_0.26 to a Ti₂N and TiN composite, optimizing the microstructure and significantly increasing the hardness to 24.37 GPa and the elastic modulus to 219.84 GPa at the 16 sccm rate. The surface roughness reduction further improved erosion resistance. Coatings made under gradient flow exhibited reduced mass loss and an erosion rate of 0.07 mg·g⁻¹, outperforming single flow rates. Erosion failure analysis highlighted that while 12 sccm coatings failed due to extensive crack interconnection, 16 sccm coatings showed spalling from crack expansion. Gradient flow coatings, despite the presence of a crack, demonstrated a more confined damage area and enhanced erosion resistance, indicating the benefits of varied nitrogen flow rates in coating optimization. Full article

(This article belongs to the Special Issue Tribomechanical and Corrosion Tests for Advanced Surface Characterization)

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15 pages, 1389 KiB

Open AccessArticle

Impact of Harvesting Stages and Postharvest Treatments on the Quality and Storability of Tomato Fruits (Solanum lycopersicum L.) cv. Sangaw

by Bzhwean Anwar Mouhamed and Sidiq Aziz Sidiq Kasnazany

Coatings 2024, 14(9), 1143; https://doi.org/10.3390/coatings14091143 - 5 Sep 2024

Abstract

The objective of this study was to evaluate the impact of harvesting stages (turning-color fruit and light red color) and postharvest treatments (distilled water, hot water at 35 °C, 10% Aloe vera, 2% CaCl₂, 5% Mint, and 5% Catnip) for [...] Read more.

The objective of this study was to evaluate the impact of harvesting stages (turning-color fruit and light red color) and postharvest treatments (distilled water, hot water at 35 °C, 10% Aloe vera, 2% CaCl₂, 5% Mint, and 5% Catnip) for 5 min on the quality and storability of tomato fruits cv. Sangaw stored at 10 ± 1 °C and a relative humidity of 90%–95% for 20 days. Fruit harvested at the turning-color fruit stage presented significantly lower weight loss, greater firmness, and higher amounts of vitamin C, total phenol, and calcium (3.22%, 1118.31 g mm/s, 15.83 mg 100 g⁻¹, 95.49 mg 100 mL⁻¹ FW, and 0.14%, respectively). However, the tomatoes harvested from the light red color fruit stage presented the highest contents of total soluble sugars, total sugars, and lycopene (4.36%, 3.99%, and 41.49 mg kg⁻¹, respectively). Notably, the postharvest treatment of tomato fruits with 2% CaCl₂ significantly decreased weight loss and resulted in greater firmness, pH, total sugar, total phenol, and calcium contents (3.90%, 1212.39 g mm/s, 4.83, 3.85%, 95.60 mg 100 mL⁻¹ FW, and 0.18%, respectively) than the control. Hence, coating with 10% Aloe vera resulted in the highest amount of total soluble solids and the highest amount of vitamin C. Tomato picked at the turning-color fruit stage and immersed in 5% Mint significantly lowered the loss of fruit weight, increased the total titratable acidity, and had the lowest content of lycopene. Additionally, the fruits harvested at the same stage and immersed in 2% CaCl₂ retained greater firmness, total phenol content, and calcium content. On the other hand, fruits harvested in the light red stage and dipped in 5% Mint presented the highest total soluble sugars and total sugar contents. Finally, the harvested tomato fruits coated with 10% Aloe vera retained a relatively high level of vitamin C, indicating the storage life and quality of the tomato fruits. Full article

(This article belongs to the Special Issue Advanced Coatings and Films for Food Packing and Storage, 2nd Edition)

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11 pages, 3585 KiB

Open AccessArticle

Synthesis and Spectroscopic Properties of Sm³⁺-Activated Li₆Y(BO₃)₃ Phosphor for Light-Emitting Diode Applications

by Jin Zhao, Yongchun Zhang, Jingwen Lu, Yiming Li and Yong Pan

Coatings 2024, 14(9), 1142; https://doi.org/10.3390/coatings14091142 - 5 Sep 2024

Abstract

A series of orange-red emitting Li₆Y(BO₃)₃: Sm³⁺ (LYBO: Sm³⁺) phosphors were produced via the high temperature solid-state method. The structure, morphology, element distribution and photoluminescent behavior of these phosphors were thoroughly examined. XRD analysis [...] Read more.

A series of orange-red emitting Li₆Y(BO₃)₃: Sm³⁺ (LYBO: Sm³⁺) phosphors were produced via the high temperature solid-state method. The structure, morphology, element distribution and photoluminescent behavior of these phosphors were thoroughly examined. XRD analysis confirmed that all samples exhibited a pure phase. Under 404 nm excitation, the emission spectra included four distinct transitions of Sm³⁺, attributed to ⁴G_5/2→⁶H_5/2 (565 nm), ⁴G_5/2→⁶H_7/2 (613 nm), ⁴G_5/2→⁶H_9/2 (647 nm) and ⁴G_5/2→⁶H_11/2 (708 nm). The ideal doping level for LYBO: xSm³⁺ is x = 0.05, and the concentration quenching primarily stems from electric dipole–dipole interactions among the ions. As the amount of Sm³⁺ dopant was increased, the fluorescence lifetime decreased. The CIE indicates that LYBO: 0.05Sm³⁺ is located in the orange-red region, exhibiting a high color purity (99%) and low color temperature (1711 K). The phosphor demonstrated excellent thermal stability and its activation energy was 0.3238 eV. In summary, LYBO: Sm³⁺ is a potential orange-red phosphor that can be coated onto near-ultraviolet chips suitable for W-LEDs. Full article

(This article belongs to the Special Issue Studying the Optoelectronic Applications of Coating Materials for Perovskite Crystals)

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15 pages, 4340 KiB

Open AccessReview

Application of Metals and Their Compounds/Black Phosphorus-Based Nanomaterials in the Direction of Photocatalytic Hydrogen Evolution

by Weiwei Zhang, Bin Yao, Haotian Yang, Xueru Li, Lina Qiu and Shaoping Li

Coatings 2024, 14(9), 1141; https://doi.org/10.3390/coatings14091141 - 5 Sep 2024

Viewed by 85

Abstract

Black phosphorous (BP) is a novel composite material. Its carrier mobility can reach more than 1000 cm²·V⁻¹·s⁻¹ and has a direct bandgap adjustable from 0.3 to 1.5 eV with thickness, so its photovoltaic performance is good. These properties [...] Read more.

Black phosphorous (BP) is a novel composite material. Its carrier mobility can reach more than 1000 cm²·V⁻¹·s⁻¹ and has a direct bandgap adjustable from 0.3 to 1.5 eV with thickness, so its photovoltaic performance is good. These properties show great potential for applications in many fields, such as energy storage, sensors, biomedicine, and environmental treatment. With the deepening of research, it is found that the instability of BP under natural environmental conditions and the limitations of its preparation limit its development, while combining with other materials can further optimize its performance, which not only improves the mechanical properties of the material but also gives it new functions. Based on this, this paper summarizes the preparation and optical properties of highly stable metals and their compounds/BP-based nanomaterials in recent years, highlights the progress of their application in photocatalytic hydrogen evolution, and gives an outlook on the challenges and opportunities for the future development of BP in photocatalysis. Full article

(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)

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21 pages, 3661 KiB

Open AccessArticle

A Mathematical Model for Predicting the Ultra-Early-Age Strength of Concrete

by Hongfei Cao, Bing Xiao, Fengjiang Qin and Qiuwei Yang

Coatings 2024, 14(9), 1140; https://doi.org/10.3390/coatings14091140 - 5 Sep 2024

Viewed by 90

Abstract

To accurately quantify the time-varying pattern of concrete’s compressive strength, selecting an appropriate curve model is of paramount importance. Currently, widely adopted models such as polynomial, hyperbolic, and exponential models all possess limitations, particularly in terms of low fitting accuracy during the ultra-early-age [...] Read more.

To accurately quantify the time-varying pattern of concrete’s compressive strength, selecting an appropriate curve model is of paramount importance. Currently, widely adopted models such as polynomial, hyperbolic, and exponential models all possess limitations, particularly in terms of low fitting accuracy during the ultra-early-age stage. This paper innovatively introduces a mathematical model that utilizes a combined curve approach. This model boasts a simplified structure with only two fitting parameters. Compared to traditional models, when utilizing three or more sets of experimental data on compressive strength across different ages, the new model is capable of yielding more precise strength predictions. Due to its minimal reliance on experimental data, the new model exhibits high practicality and convenience in real-world applications. To validate its superiority, a detailed comparison between the new model and existing models was conducted based on several sets of experimental data. The results demonstrate that the new model has significant advantages in terms of mean fitting error and standard deviation, making its predictions the most reliable. For most cases, the standard deviation of the new model is reduced by approximately 30% to 80% compared to the second-best model, underscoring its exceptional stability and consistency. Additionally, the predicted long-term compressive strength values of the new model are closer to the design strength grade of the concrete. This model can also be successfully applied to predict the tensile strength of concrete during its ultra-early age. It has been demonstrated that the combined model proposed in this paper shows promising application prospects in evaluating the time-varying behavior of concrete strength. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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15 pages, 6078 KiB

Open AccessArticle

Wear Behavior of TiN/TiAlSiN Nanocomposite Multilayer Coatings from Ambient Temperature to Medium Temperature

by Hairui Ma, Qiang Miao, Wenping Liang, Shijie Sun, Yan Qi, Feilong Jia and Xiangle Chang

Coatings 2024, 14(9), 1139; https://doi.org/10.3390/coatings14091139 - 4 Sep 2024

Viewed by 197

Abstract

TiN/TiAlSiN nanocomposite multilayer coatings were deposited on a titanium alloy by multi-arc ion plating. The investigation of the wear behavior of TiN/TiAlSiN multilayer coatings against Si₃N₄ was conducted at temperatures of 25 °C, 300 °C, and 500 °C using a [...] Read more.

TiN/TiAlSiN nanocomposite multilayer coatings were deposited on a titanium alloy by multi-arc ion plating. The investigation of the wear behavior of TiN/TiAlSiN multilayer coatings against Si₃N₄ was conducted at temperatures of 25 °C, 300 °C, and 500 °C using a ball-on-disk tribometer. Additionally, to gain a deeper understanding of medium-temperature oxidation products, an oxidation test was performed at 500 °C for 10 h. The microstructure and chemical composition of the coatings were evaluated by X-ray diffraction and scanning electron microscopy. The primary peak in the XRD pattern of the multilayer coating changed from TiN (111) to Ti₃AlN (111) after the oxidation test. The hardness of the TiN/TiAlSiN multilayer coating was 1540 HV_0.1, representing a notable five times improvement compared to the substrate. The critical load in the scratch test was 52.3 N, indicating robust adhesion performance. The wear rate exhibited a sharp increase from 25 °C to 300 °C, compared to the rise from 300 °C to 500 °C. Furthermore, the friction coefficient of the coated sample was more stable than the substrate, with different scratch track morphologies between the samples before and after the oxidation test. Full article

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11 pages, 2854 KiB

Open AccessArticle

Study on the Alloying Elements Competition Mechanism of Ni_x₁Cr_x₂Co_x₃Al₁₅Ti₁₀ Alloys Based on High-Throughput Computation and Numerical Analysis

by Yu Liu, Lijun Wang, Wenjie He and Yunpeng Liu

Coatings 2024, 14(9), 1138; https://doi.org/10.3390/coatings14091138 - 4 Sep 2024

Viewed by 278

Abstract

Previous studies on the physical properties of alloy materials often focus solely on analyzing the impact of individual alloying element content, overlooking the underlying mechanism behind the synergistic action of multiple alloying elements. Therefore, in this study, we propose a combination of high-throughput [...] Read more.

Previous studies on the physical properties of alloy materials often focus solely on analyzing the impact of individual alloying element content, overlooking the underlying mechanism behind the synergistic action of multiple alloying elements. Therefore, in this study, we propose a combination of high-throughput computation and numerical analysis to conduct single-element (SE) analysis and multi-element (ME) analysis on the internal relationships between alloying element content and physical properties for the multi-component Ni_x₁Cr_x₂Co_x₃Al₁₅Ti₁₀ alloys, aiming to elucidate the competition mechanism among the Ni, Cr, and Co elements. The analysis of SE reveals how the physical properties of alloys are affected by the content of each individual alloying element, and the ME analysis further unveils the underlying competitive relationships among multiple alloying elements. The order of competitive intensity for the formation of lattice constant is Cr > Co > Ni, whereas for the formation of elastic constants and elastic moduli it is Ni > Co > Cr. At the same time, there are contradictory conclusions, such as the SE analysis showing that the Ni content is positively correlated with elastic constant

C_{11}

, while the ME analysis demonstrates that the Ni element produces a negative competitive direction. This outcome arises from the omission of considering the combined impacts of various alloying elements in SE analysis. Therefore, the ME analysis can compensate for the limitations of SE analysis, and the integration of these two analytical methods is more conducive to elucidating the competition mechanism among various alloying elements in shaping the physical properties of alloys, which provides a promising avenue for theoretical research. Full article

(This article belongs to the Special Issue Microstructure, Mechanical and Tribological Properties of Alloys)

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21 pages, 4502 KiB

Open AccessArticle

Ultrasound-Assisted Acellular Spinal Cord Scaffold for Spinal Cord Injury Treatment

by Xi Deng, Yun Liu, Zhongsheng Xu and Hong Yin

Coatings 2024, 14(9), 1137; https://doi.org/10.3390/coatings14091137 - 4 Sep 2024

Viewed by 208

Abstract

Spinal cord injury (SCI) treatment remains challenging globally, with limited breakthroughs. Tissue engineering offers promise, particularly using acellular spinal cord scaffolds. This study developed a 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)-crosslinked vascular endothelial growth factor (VEGF)-modified acellular spinal cord scaffold for sustained VEGF release. The [...] Read more.

Spinal cord injury (SCI) treatment remains challenging globally, with limited breakthroughs. Tissue engineering offers promise, particularly using acellular spinal cord scaffolds. This study developed a 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)-crosslinked vascular endothelial growth factor (VEGF)-modified acellular spinal cord scaffold for sustained VEGF release. The results show sustained VEGF release over 20 days without altering the scaffold’s properties. Enhanced stability and mechanical properties were observed without increased cytotoxicity. In a rat SCI model, the system improved motor function, reduced glial scarring, and restored spinal cord morphology and histology, indicating potential for SCI therapy. Full article

(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications, 2nd Edition)

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14 pages, 1720 KiB

Open AccessArticle

The Role of the Manganese Content on the Properties of Mn₃O₄ and Reduced Graphene Oxide Nanocomposites for Supercapacitor Electrodes

by Víctor Fernández-Jiménez, Santiago de Bernardi-Martín, Alejandra García-Gómez, David López-Díaz, M. Jesús Sánchez-Montero, M. Mercedes Velázquez and M. Dolores Merchán

Coatings 2024, 14(9), 1136; https://doi.org/10.3390/coatings14091136 - 4 Sep 2024

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Abstract

Increasing the energy density and power of supercapacitors through hybrids of carbonaceous materials and metal oxides continues to be the subject of numerous research works. The correlation between specific capacitance and the properties of materials used as electrodes attracts great interest. In the [...] Read more.

Increasing the energy density and power of supercapacitors through hybrids of carbonaceous materials and metal oxides continues to be the subject of numerous research works. The correlation between specific capacitance and the properties of materials used as electrodes attracts great interest. In the present study, we investigated composites (GO/Mn₃O₄) prepared by the hydrothermal method with a variable ratio of GO/Mn₃O₄ and tested them as supercapacitor electrode materials in three- and two-electrode cells. The chemical characterization carried out by X-ray photoelectron spectroscopy and the adsorption techniques used allowed the determination of the surface carbon and oxygen content, as well as its textural properties. In this work, we analyzed the contribution of the double layer and the Faradaic reactions to the value of the final capacitance of the synthesized materials. Beyond empirically obtaining the electrochemical properties, these have been related to the physicochemical characteristics of the hybrids to help design materials with the best performance for supercapacitor electrodes. Full article

(This article belongs to the Special Issue Application of Graphene and Two-Dimensional Materials in Thin Films)

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22 pages, 8022 KiB

Open AccessArticle

Study of a New Novel HVOAF Coating Based on a New Multicomponent Al80Mg10Si5Cu5 Alloy

by Ester Villanueva, Iban Vicario, Carlos Vaquero, Joseba Albizuri, Maria Teresa Guraya, Nerea Burgos and Iñaki Hurtado

Coatings 2024, 14(9), 1135; https://doi.org/10.3390/coatings14091135 - 4 Sep 2024

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Abstract

This paper presents and demonstrates the development of a new lightweight coating for aluminum alloy from a novel multicomponent alloy based on the AlSiMgCu system. The coating was applied using a newly designed approach that combined high velocity oxy-fuel (HVOF) and plasma spraying [...] Read more.

This paper presents and demonstrates the development of a new lightweight coating for aluminum alloy from a novel multicomponent alloy based on the AlSiMgCu system. The coating was applied using a newly designed approach that combined high velocity oxy-fuel (HVOF) and plasma spraying processes. This hybrid technique enables the deposition of coatings with enhanced performance characteristics. The optical microscopy (OM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM + EDS) revealed a strong adhesion and compaction between the multicomponent coating and the A6061 substrate. The new coating improved hardness by 50% and increased electrical conductivity by approximately 3.3 times compared to the as-cast alloy. Corrosion tests showed a lower corrosion rate, comparable to thermally treated A6061 alloy. Tribological tests indicated over 20% reduction in friction and over 50% reduction in wear rate. This suggests that multicomponent aluminum coatings could improve automotive and parts in contact with hydrogen by enhancing hydrogen fragilization resistance, corrosion resistance, electrical conductivity, and wear properties, with further optimization of thermal spraying potentially boosting performance even further. Full article

(This article belongs to the Special Issue Advanced Surface Coatings of Metals: Properties, Techniques and Applications)

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8 pages, 2400 KiB

Open AccessArticle

MnBi₂Te₄ Thin-Film Photodetector with a Millisecond Response Speed and Long-Term Air Stability

by Ming Yang, Haotian Ren, Wenze Deng, Haoliang Chang, Qiqin Li, Hongxi Zhou, Xiaoguang Tu, Mian Zhong, Fei Li and Xinyu Zhu

Coatings 2024, 14(9), 1134; https://doi.org/10.3390/coatings14091134 - 4 Sep 2024

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Abstract

Topological materials with well-defined surfaces and edges have become a prominent research topic. As topological insulators, MnBi₂Te₄ thin films, with their unique surfaces, exhibit exceptional electron transport properties and good applicability in low-noise, high-sensitivity photoelectric detection. This paper reports a [...] Read more.

Topological materials with well-defined surfaces and edges have become a prominent research topic. As topological insulators, MnBi₂Te₄ thin films, with their unique surfaces, exhibit exceptional electron transport properties and good applicability in low-noise, high-sensitivity photoelectric detection. This paper reports a straightforward, efficient, and cost-effective thermal evaporation method for preparing quantum MnBi₂Te₄ thin films, along with an investigation into their photoelectric detection performance. These films can be used to fabricate array devices, with the resulting photodetectors achieving a response current of 97 mA W⁻¹ at room temperature and a response speed of <1 ms. Moreover, they demonstrate stability in the air for >30 d, with the photoelectric performance degrading by <15%. Our research introduces a new application for topological materials in photoelectric detection and establishes a strong foundation for the design and development of high-performance photodetectors in the future. Full article

(This article belongs to the Special Issue Thermoelectric Thin Films for Thermal Energy Harvesting)

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15 pages, 4355 KiB

Open AccessArticle

All-Layer Electrodeposition of a CdTe/Hg_0.1Cd_0.9Te/CdTe Photodetector for Short- and Mid-Wavelength Infrared Detection

by Vianey A. Candelas-Urrea, Carlos Villa-Angulo, Iván O. Hernández-Fuentes, Ricardo Morales-Carbajal and Rafael Villa-Angulo

Coatings 2024, 14(9), 1133; https://doi.org/10.3390/coatings14091133 - 3 Sep 2024

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Abstract

CdS, CdTe, Hg_0.1Cd_0.9Te, CdTe, and Ag films were progressively electrodeposited on ITO-coated soda–lime glass to manufacture a short- and mid-wavelength infrared photodetector. A distinctive feature of the applied electrodeposition method is the use of a non-aqueous solution containing ethylene [...] Read more.

CdS, CdTe, Hg_0.1Cd_0.9Te, CdTe, and Ag films were progressively electrodeposited on ITO-coated soda–lime glass to manufacture a short- and mid-wavelength infrared photodetector. A distinctive feature of the applied electrodeposition method is the use of a non-aqueous solution containing ethylene glycol (EG) as the electrolyte in a traditional three-electrode configuration for every film deposition. Using EG as a supplementary electrolyte and using the same deposition conditions with a potential below 0.75 V for all film coatings reduces their environmental incompatibility and offers a low-cost and low-energy route for fabricating the reported photodetector. The produced photodetector has a sensitivity of up to ≈957 nm with a detectivity (D*) of 2.86 × 10¹² cm Hz^1/2 W⁻¹ and a dark current density (J_dark) of 10⁻⁶ mA cm⁻². Furthermore, the manufactured photodiode exhibits self-powered performance because V_oc and J_sc are self-generated, unlike previously reported photodiodes. The presented all-layer electrodeposition assembly approach can easily be adapted to fabricate sensing devices for different applications. Full article

(This article belongs to the Special Issue Optical Coatings: From Materials to Applications)

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17 pages, 4510 KiB

Open AccessArticle

Study on the Stability of Fe/Al₂O₃ Interface in Metal-Based Cermets Using Thermodynamic Modeling

by Xiangyu Wei, Tengfei Sun, Kuai Zhang and Yungang Li

Coatings 2024, 14(9), 1132; https://doi.org/10.3390/coatings14091132 - 3 Sep 2024

Viewed by 188

Abstract

Iron-based cermet has the advantages of high-temperature resistance, low price, good performance, and so on. At present, most of the studies on cermets are focused on the measurement of macroscopic properties and optical microscopic characterization, while there are few microscopic studies on the [...] Read more.

Iron-based cermet has the advantages of high-temperature resistance, low price, good performance, and so on. At present, most of the studies on cermets are focused on the measurement of macroscopic properties and optical microscopic characterization, while there are few microscopic studies on the interface structure. In this paper, based on density functional theory (DFT), the stability of the Fe/Al₂O₃ interface is studied, and the stability difference and interface formation mechanism of different end combinations are investigated. By calculating the surface energy, adhesion work, interface energy, density of states, charge density, differential charge density, and so on, it was concluded that the stability of the O-terminal interface was greater than that of the Al interface. It has a certain guiding role in the preparation of Fe/Al₂O₃ cermet materials. Full article

(This article belongs to the Special Issue Applications of Ceramic and Cermet Coatings)

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13 pages, 4653 KiB

Open AccessArticle

Research on Process Control of Laser-Based Direct Energy Deposition Based on Real-Time Monitoring of Molten Pool

by Haoda Wang, Jingbin Hao, Mengsen Ding, Xuanyu Zheng, Haifeng Yang and Hao Liu

Coatings 2024, 14(9), 1131; https://doi.org/10.3390/coatings14091131 - 3 Sep 2024

Viewed by 239

Abstract

In the process of laser-based direct energy deposition (DED-LB), the quality of the deposited layer will be affected by the process parameters and the external environment, and there are problems such as poor stability and low accuracy. A molten pool monitoring method based [...] Read more.

In the process of laser-based direct energy deposition (DED-LB), the quality of the deposited layer will be affected by the process parameters and the external environment, and there are problems such as poor stability and low accuracy. A molten pool monitoring method based on coaxial vision is proposed. Firstly, the molten pool image is captured by a coaxial CCD camera, and the geometric features of the molten pool are accurately extracted by image processing techniques such as grayscale, median filtering noise reduction, and K-means clustering combined with threshold segmentation. The molten pool width is accurately extracted by the Canny operator combined with the minimum boundary rectangle method, and it is used as the feedback of weld pool control. The influence of process parameters on the molten pool was further analyzed. The results show that with an increase in laser power, the width and area of the molten pool increase monotonously, but exceeding the material limit will cause distortion. Increasing the scanning speed will reduce the size of the molten pool. By comparing the molten pool under constant power mode and width control mode, it is found that in width control mode, the melt pool width fluctuates less, and the machining accuracy is improved, validating the effectiveness of the real-time control system. Full article

(This article belongs to the Special Issue Advances in High-Entropy Alloy Coatings: Preparation, Properties, and Applications)

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9 pages, 5446 KiB

Open AccessArticle

A Wideband Polarization-Insensitive Bistatic Radar Cross-Section Reduction Design Based on Hybrid Spherical Phase-Chessboard Metasurfaces

by Shun Zhang, Qin Qin and Mengbo Hua

Coatings 2024, 14(9), 1130; https://doi.org/10.3390/coatings14091130 - 3 Sep 2024

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Abstract

A wideband polarization-insensitive bistatic radar cross-section (RCS) reduction design under linear and circular polarization incidence is proposed based on spherical-chessboard metasurfaces. A new metasurface element with wideband characteristics was designed, including a double split-ring structure, single-layer media, and metal board. In the proposed [...] Read more.

A wideband polarization-insensitive bistatic radar cross-section (RCS) reduction design under linear and circular polarization incidence is proposed based on spherical-chessboard metasurfaces. A new metasurface element with wideband characteristics was designed, including a double split-ring structure, single-layer media, and metal board. In the proposed RCS-reduction design, the Pancharatnam–Berry (P-B) phase theory is applied with the designed metasurface element to realize phase distribution mimicking the low-scattering sphere, and thus realizing RCS reduction. In addition, the chessboard configuration is combined with spherical phase distribution to further improve the performance of monostatic and bistatic RCS reduction. Finally, the proposed RCS reduction design can not only realize wideband RCS reduction but also exhibit polarization-insensitive characteristics. It realized 10 dB monostatic and bistatic RCS reduction in a frequency band ranging from 8.5 to 21 GHz (84.8% relative bandwidth) under linear polarization (LP) and circular polarization (CP) incidence. The straightforward and efficient design method of the hybrid spherical chessboard can effectively avoid the complex and time-consuming optimization process in RCS-reduction design. Full article

(This article belongs to the Collection Feature Paper Collection in Surface Characterization, Deposition and Modification)

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16 pages, 2656 KiB

Open AccessArticle

Preparation and Properties of Waterborne Acrylic-Modified Epoxy Phosphate Resin and Its Coating

by Fei Xiao, Tao Yong, Tianlong Cao, Fangyuan Shi, Xuejun Sun and Jin Zhang

Coatings 2024, 14(9), 1129; https://doi.org/10.3390/coatings14091129 - 2 Sep 2024

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Abstract

An acrylic acid-modified epoxy phosphate resin coating was synthesized by a four-step method marked “A-B-C-D”, and it was used as an efficient protective layer for steel structures. The coating exhibited good properties, mainly including water resistance (≥240 h), salt spray resistance (≥300 h), [...] Read more.

An acrylic acid-modified epoxy phosphate resin coating was synthesized by a four-step method marked “A-B-C-D”, and it was used as an efficient protective layer for steel structures. The coating exhibited good properties, mainly including water resistance (≥240 h), salt spray resistance (≥300 h), surface drying time (≤1 h), and adhesion (≥6.5 MPa). Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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18 pages, 5416 KiB

Open AccessArticle

Study of the Impact of Surface Topography on Wear Resistance

by Ben Wang, Wei Zhang and Zhongxun Liu

Coatings 2024, 14(9), 1128; https://doi.org/10.3390/coatings14091128 - 2 Sep 2024

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Abstract

The surface texture parameter is a real reflection of the surface topography, which is closely related to the tribological properties of the surface, and the study of the correlation between the surface texture parameter and wear resistance is of great significance in revealing [...] Read more.

The surface texture parameter is a real reflection of the surface topography, which is closely related to the tribological properties of the surface, and the study of the correlation between the surface texture parameter and wear resistance is of great significance in revealing the tribological influence mechanism of the surface and realising the functional manufacturing of the surface. This paper takes the ball-end milling surface as the research object, establishes the three-dimensional simulation model of the surface topography, and analyses the surface topography and the surface texture parameter change rule. Based on the improved correlation analysis model, the correlation characteristics between the surface texture parameters, and between the surface texture parameters and the relative wear rate of per unit sliding distance K_V, were investigated, and the prediction model of K_V was established based on the surface texture parameters Sku, Sa, Sxp, Sp, and Ssk, and the correctness of the model was verified by experiments. The study in this paper provides a new idea to further reveal the relationship between surface topographical features and wear resistance and to guide the functional manufacturing of surfaces. Full article

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27 pages, 10938 KiB

Open AccessArticle

Niobium Oxide Thin Films Grown on Flexible ITO-Coated PET Substrates

by Alice Marciel, Alexandre Bastos, Luiz Pereira, Suresh Kumar Jakka, Joel Borges, Filipe Vaz, Marco Peres, Katharina Lorenz, Arijeta Bafti, Luka Pavić, Rui Silva and Manuel Graça

Coatings 2024, 14(9), 1127; https://doi.org/10.3390/coatings14091127 - 2 Sep 2024

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Abstract

Niobium oxide thin films were grown on both rigid and flexible substrates using DC magnetron sputtering for electrochromic applications. Three experimental series were conducted, varying the oxygen to argon flow rate ratio and deposition time. In the first series, the oxygen to argon [...] Read more.

Niobium oxide thin films were grown on both rigid and flexible substrates using DC magnetron sputtering for electrochromic applications. Three experimental series were conducted, varying the oxygen to argon flow rate ratio and deposition time. In the first series, the oxygen to argon ratio was adjusted from 0 to 0.32 while maintaining a constant growth time of 30 min. For the second and third series, the oxygen to argon ratios were fixed at 0.40 and 0.56, respectively, with deposition times ranging from 15 to 60 min. A structural transition from crystalline to amorphous was observed at an oxygen to argon flow rate ratio of 0.32. This transition coincided with a change in appearance, from non-transparent with metallic-like electrical conductivity to transparent with dielectric behavior. The transparent niobium oxide films exhibited thicknesses between 51 nm and 198 nm, with a compact, dense, and featureless morphology, as evidenced by both top-view and cross-sectional images. Films deposited on flexible indium tin oxide (ITO)-coated polyethylene terephthalate (PET) substrates displayed a maximum surface roughness (Sq) of 9 nm and a maximum optical transmission of 83% in the visible range. The electrochromic response of niobium oxide thin films on ITO-coated PET substrates demonstrated a maximum coloration efficiency of 30 cm² C⁻¹ and a reversibility of 96%. Mechanical performance was assessed through bending tests. The ITO-coated PET substrate exhibited a critical bending radius of 6.5 mm. Upon the addition of the niobium oxide layer, this decreased to 5 mm. Electrical resistance measurements indicated that the niobium oxide film mitigated rapid mechanical degradation of the underlying ITO electrode beyond the critical bending radius. Full article

(This article belongs to the Special Issue Advances in Deposition and Surface Modification of Oxide Thin Films and Nanocoatings)

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13 pages, 4832 KiB

Open AccessArticle

Enhancing Flame-Retardant Properties of Polyurethane Composites Using N-β-(Aminoethyl)-γ-aminopropyl Trimethoxysilane and Carbon Black Co-Modified Ammonium Polyphosphate

by Lisha Fu, Wanjun Hao, Baoluo Xu, Kexi Zhang, Jianhua Bi, Jingxing Wu and Zhong Wang

Coatings 2024, 14(9), 1126; https://doi.org/10.3390/coatings14091126 - 2 Sep 2024

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Abstract

The search for a straightforward method to obtain efficient, affordable, and long-lasting flame retardants with both desirable flame-retardant and mechanical properties for polyurethane (PU) composites remains a significant challenge. In this study, the surface of ammonium polyphosphate (APP) was modified using N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane [...] Read more.

The search for a straightforward method to obtain efficient, affordable, and long-lasting flame retardants with both desirable flame-retardant and mechanical properties for polyurethane (PU) composites remains a significant challenge. In this study, the surface of ammonium polyphosphate (APP) was modified using N-β-(aminoethyl)-γ-aminopropyl trimethoxysilane (KH792) via an ion-exchange reaction, and the modified APP was coated with nanoscale carbon black (CB) to obtain CBAPP. CBAPP demonstrated good compatibility within the PU matrix and notably increased the tensile strength of the PU composites. Furthermore, CBAPP significantly enhanced the flame-retardant properties of the PU composites. The CBAPP/PU composite with a CBAPP mass fraction of 20% achieved a limiting oxygen index of 41.5% and a UL-94 class of V-0. According to the results of this study, our modification approach can be applied to develop other high-performance flame-retardant polymer-based composites, representing a significant contribution to the field of fire safety materials. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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20 pages, 17195 KiB

Open AccessArticle

Optimization of Black Nickel Coatings’ Electrodeposit onto Steel

by Gabriel Santos, Zohra Benzarti, Diogo Cavaleiro, Luís Figueiredo, Sandra Carvalho and Susana Devesa

Coatings 2024, 14(9), 1125; https://doi.org/10.3390/coatings14091125 - 2 Sep 2024

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Abstract

Coatings can be created using various technologies and serve different roles, including protection, functionality, and decorative purposes. Among these technologies, electrodeposition has emerged as a low-cost, versatile, and straightforward process with remarkable scalability and manufacturability. Nickel, extensively studied in the context of electrodeposition, [...] Read more.

Coatings can be created using various technologies and serve different roles, including protection, functionality, and decorative purposes. Among these technologies, electrodeposition has emerged as a low-cost, versatile, and straightforward process with remarkable scalability and manufacturability. Nickel, extensively studied in the context of electrodeposition, has many applications ranging from decorative to functional. The main objective of the present work is the electrodeposition of double-layer nickel coatings, consisting of a bright nickel pre-coating followed by a black nickel layer with enhanced properties, onto steel substrates. The influence of deposition parameters on colour, morphology, adhesion, roughness, and coefficient of friction was studied. The effects of cetyltrimethylammonium bromide (CTAB) and WS₂ nanoparticles on the coatings’ properties and performance were also investigated. Additionally, the influence of the steel substrate’s pre-treatment, consisting of immersion in an HCl solution, prior to the electrodeposition, to etch the surface and activate it, was evaluated and optimized. The characterization of the pre-coating revealed a homogeneous surface with a medium superficial feature of 2.56 μm. Energy dispersive X-ray spectroscopy (EDS) results showed a high content of Ni, and X-ray diffraction (XRD) confirmed its crystallinity. In contrast, the black films’ characterization revealed their amorphous nature. The BN10 sample, which corresponds to a black nickel layer with a deposition time of 10 min, showed the best results for colour and roughness, presenting the lowest brightness (L*) value (closest to absolute black) and the most homogeneous roughness. EDS analysis confirmed the incorporation of WS₂, but all samples with CTAB exhibited signs of corrosion and cracks, along with higher coefficient of friction (COF) values. Full article

(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)

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20 pages, 17045 KiB

Open AccessArticle

Interlayer Adhesion of Coating System in Analogue and Digital Printing Technologies Formed on Lightweight Honeycomb Furniture Panels

by Maciej Tokarczyk, Barbara Lis and Tomasz Krystofiak

Coatings 2024, 14(9), 1124; https://doi.org/10.3390/coatings14091124 - 2 Sep 2024

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Abstract

This article concerns research into the influence of the energy dose distributed by UV lamps on selected parameters of varnish coatings formed during the varnishing process of lightweight cellular panels. The lightweight cellular board used in the study was made according to an [...] Read more.

This article concerns research into the influence of the energy dose distributed by UV lamps on selected parameters of varnish coatings formed during the varnishing process of lightweight cellular panels. The lightweight cellular board used in the study was made according to an innovative solution. The surface finishing of the boards was carried out using the roller method in combination with digital and analogue printing under industrial conditions. Contact angle measurements of the obtained varnish coatings were carried out, from which the surface free energy was calculated. In addition, interlayer adhesion was assessed by pull-off tests. Irrespective of the radiation dose, higher contact angle values (54.3–89.9°) were recorded for the last two applied layers (base coat 2 and base coat 3) than for the other coatings (39.6–64.1°). For all systems tested, the γs^p component showed lower values (2.25–28.99 mJ/m²) than γs^d (28.66–32.80 mJ/m²). The adhesion test results ranged from 0.5 to 0.9 MPa, although with varying types of delamination. Based on the test results, the most favourable variants from the furniture manufacturer’s point of view were selected that provided the desired level of adhesion, in which cohesive damage located within the substrate (A) predominated. Full article

(This article belongs to the Special Issue Nano/Micro Additive Lamination Fabrication: Novel Circuits Printing on Substrates)

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16 pages, 11227 KiB

Open AccessArticle

Micro-Nano Dual-Scale Coatings Prepared by Suspension Precursor Plasma Spraying for Resisting Molten Silicate Deposit

by Yangguang Liu, Yihao Wang, Weize Wang, Wenkang Zhang, Junhao Wang, Kaibin Li, Hongchen Li, Pengpeng Liu, Shilong Yang and Chengcheng Zhang

Coatings 2024, 14(9), 1123; https://doi.org/10.3390/coatings14091123 - 2 Sep 2024

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Abstract

Yb-doped Y₂O₃ stabilized ZrO₂ (YbYSZ) coatings, developed through solution precursor plasma spraying (SPPS), are engineered to resist calcium–magnesium–alumino–silicate (CMAS) infiltration by leveraging their unique micro-nano structures. This provides superior anti-wetting properties, crucial for preventing CMAS penetration at high temperatures. [...] Read more.

Yb-doped Y₂O₃ stabilized ZrO₂ (YbYSZ) coatings, developed through solution precursor plasma spraying (SPPS), are engineered to resist calcium–magnesium–alumino–silicate (CMAS) infiltration by leveraging their unique micro-nano structures. This provides superior anti-wetting properties, crucial for preventing CMAS penetration at high temperatures. The investigation focused on the structural and compositional changes in YbYSZ-SPPS coatings subjected to prolonged thermal exposure at 1300 °C. Results indicate that while the coatings undergo significant sintering, leading to densification and microstructural evolution, the elemental composition and phase stability remain largely intact after up to 8 h of heat treatment. Despite some reduction in CMAS resistance, the coatings maintained their overall protective performance, demonstrating the potential of SPPS coatings for long-term use in high-temperature environments where CMAS infiltration is a concern. These findings contribute to the development of more durable TBCs for advanced thermal protection applications. Full article

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13 pages, 4795 KiB

Open AccessArticle

Natural Selection on Hydroxyapatite Fiber Orientations for Resisting Damage of Enamel

by Junfu Shen, Haiyan Xin, Xiaopan Li, Yiyun Kong, Siqi Zhu, Yuankai Zhou, Yujie Fan and Jing Xia

Coatings 2024, 14(9), 1122; https://doi.org/10.3390/coatings14091122 - 2 Sep 2024

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Abstract

Teeth have excellent mechanical properties, with high wear resistance and excellent fracture resistance. This is due to their well-organized multilevel hierarchical structure. While a number of studies in the last decades have revealed the relationship between tooth structure and mechanical properties, there is [...] Read more.

Teeth have excellent mechanical properties, with high wear resistance and excellent fracture resistance. This is due to their well-organized multilevel hierarchical structure. While a number of studies in the last decades have revealed the relationship between tooth structure and mechanical properties, there is still no general agreement on how different orientations of hydroxyapatite (HAp) fibers affect the mechanical properties of enamel. With a scanning electron microscope and nanoindenter, the orientations of HAp fibers and their properties were investigated. HAp fibers have two different orientations: parallel and perpendicular to the surface. Fibers oriented parallel to the surface exhibited higher hardness, elastic modulus and wear resistance. Under applied force, fibers oriented perpendicular to the surface suffered deeper shearing in the protein along the long axis, resulting in lower mechanical properties. Teeth resist damaging fractures by combining hard and soft structures. This study may lead to new insights into how nature selects for tooth structure and provide a theoretical basis for the bioinspired design. Full article

(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications, 2nd Edition)

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12 pages, 9726 KiB

Open AccessArticle

In Situ Modulation of Oxygen Vacancy Concentration in Hf_0.5Zr_0.5O_2−x Thin Films and the Mechanism of Its Impact on Ferroelectricity

by Shikai Liu, Xingyu Li, Gang Li, Shaoan Yan, Yingfang Zhu, Yujie Wu, Qin Jiang, Yang Zhan and Minghua Tang

Coatings 2024, 14(9), 1121; https://doi.org/10.3390/coatings14091121 - 2 Sep 2024

Viewed by 282

Abstract

Oxygen vacancies play a crucial role in stabilizing the ferroelectric phase in hafnium (Hf) oxide-based thin films and in shaping the evolution of their ferroelectric properties. In this study, we directly manipulated the oxygen vacancy concentration in Hf_0.5Zr_0.5O₂₋ [...] Read more.

Oxygen vacancies play a crucial role in stabilizing the ferroelectric phase in hafnium (Hf) oxide-based thin films and in shaping the evolution of their ferroelectric properties. In this study, we directly manipulated the oxygen vacancy concentration in Hf_0.5Zr_0.5O_2−x (HZO) ferroelectric thin films in situ using oxygen plasma treatment. We scrutinized the variations in the ferroelectric properties of HZO films across different oxygen vacancy concentrations by integrating the findings from ferroelectric performance tests. Additionally, we elucidated the mechanism underlying the influence of oxygen vacancies on the coercive field and polarization properties of HZO ferroelectric films through the first-principles density functional theory (DFT) calculations. Finally, to study the impact of oxygen vacancies on the practical application of HZO ferroelectric synaptic devices, leveraging the plasticity of the ferroelectric polarization, we constructed a multilayer perceptron (MLP) network. We simulated its recognition accuracy and convergence speed under different oxygen vacancy concentrations in the MNIST recognition task. Full article

(This article belongs to the Special Issue Advances in Deposition and Surface Modification of Oxide Thin Films and Nanocoatings)

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13 pages, 7463 KiB

Open AccessArticle

Rapid Synthesis and Sintering of La₂O₂S and Its Physical, Optical, and Mechanical Properties

by Yuqi Chen, Liang Li, Jin Li and Kun Han

Coatings 2024, 14(9), 1120; https://doi.org/10.3390/coatings14091120 - 2 Sep 2024

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Abstract

Rare-earth oxysulfides are a class of functional ceramic materials with excellent physico-chemical properties and rich functionality. In this study, La₂O₂S powders were prepared from La₂S₃ and La₂O₃ powders at 1000 °C by pressureless [...] Read more.

Rare-earth oxysulfides are a class of functional ceramic materials with excellent physico-chemical properties and rich functionality. In this study, La₂O₂S powders were prepared from La₂S₃ and La₂O₃ powders at 1000 °C by pressureless sintering. La₂O₂S compacts were synthesized from La₂S₃ and La₂O₃ powders at 800–1600 °C by spark plasma sintering. The influences of sintering temperature and time on the preparation of La₂O₂S were studied. XRD results indicated that La₂O₂S ceramics were synthesized successfully and that the lattice constants of La₂O₂S were close to the theoretical values. SEM showed that the microstructure of La₂O₂S compacts was homogeneous. The specific heat of La₂O₂S mainly came from lattice contribution, and its Debye temperature was 237 K. The UV–visible absorption spectra showed different absorption levels in the 240–300 nm range. Raman spectroscopy revealed distinct peaks at different temperatures, indicating changes in the covalence band. The relative density of La₂O₂S ceramics was 92% and lower than theoretical values. Hardness of the synthesized La₂O₂S was greater than that of Gd₂O₂S ceramics. Full article

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16 pages, 3876 KiB

Open AccessArticle

Controlled Compositions in Zn–Ni Coatings by Anode Material Selection for Replacing Cadmium

by Lijia Yi, Shuncai Wang and Robert J. K. Wood

Coatings 2024, 14(9), 1119; https://doi.org/10.3390/coatings14091119 - 2 Sep 2024

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Abstract

Cadmium-based coatings have long been used to protect high-strength steel in aerospace, but due to cadmium’s toxic and carcinogenic nature, its use is increasingly restricted. Zinc–nickel coatings, containing 10–14 wt% Ni, offer superior corrosion resistance compared to pure zinc, making them a promising [...] Read more.

Cadmium-based coatings have long been used to protect high-strength steel in aerospace, but due to cadmium’s toxic and carcinogenic nature, its use is increasingly restricted. Zinc–nickel coatings, containing 10–14 wt% Ni, offer superior corrosion resistance compared to pure zinc, making them a promising alternative. However, Zn–Ni coatings are prone to cracking, which can compromise their protection. This study investigates how different anode materials influence crack formation and coating properties during electrodeposition. Zinc and nickel anodes produced coatings with consistent thicknesses of 13–15 µm, while 1020 steel and stainless steel resulted in thicker coatings of up to 33 µm. Notably, coatings deposited with nickel anodes demonstrated strong adhesion and consistent interface quality. Zinc anodes achieved a high Ni content of about 13.5 wt%, whereas 1020 steel and stainless steel produced lower Ni content, around 7 wt%. Additionally, zinc and nickel anodes led to fewer defects and minimal porosity, in contrast to the higher porosity observed with 1020 steel and stainless steel anodes. Furthermore, zinc anodes maintained stable voltages (~0.5 V), contributing to more uniform coatings. In terms of corrosion resistance, zinc anodes exhibited a lower corrosion rate of 0.44 mm/year compared to 1.54 mm/year for nickel anodes. This study highlights the importance of anode selection in reducing cracking and optimizing Zn–Ni coatings, presenting them as a safer and more effective alternative to cadmium-based coatings. Full article

(This article belongs to the Special Issue Interfacial Electrochemistry of Coatings Produced or Applied in Solution)

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17 pages, 5858 KiB

Open AccessArticle

Effect of Two Types of Chitosan Thermochromic Microcapsules Prepared with Syringaldehyde and Sodium Tripolyphosphate Crosslinking Agents on the Surface Coating Performance of Basswood Board

by Jingyi Hang, Bo Zhang, Hongwei Fan, Xiaoxing Yan and Jun Li

Coatings 2024, 14(9), 1118; https://doi.org/10.3390/coatings14091118 - 2 Sep 2024

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Abstract

In order to investigate the effect of thermochromic microcapsules on the surface coating performance of basswood board, two types of microcapsules prepared with syringaldehyde and sodium tripolyphosphate crosslinking agents were added to a UV primer and coated on the surface of basswood board. [...] Read more.

In order to investigate the effect of thermochromic microcapsules on the surface coating performance of basswood board, two types of microcapsules prepared with syringaldehyde and sodium tripolyphosphate crosslinking agents were added to a UV primer and coated on the surface of basswood board. The color-change effect of the surface coating on basswood board with microcapsules added with syringaldehyde as the crosslinking agent was better than that with microcapsules added with sodium tripolyphosphate as the crosslinking agent, and the color difference varied more significantly with temperature. The effect of the two types of microcapsules on the glossiness of the surface coating on basswood board was relatively weak. The glossiness of the surface coating on basswood board with microcapsules containing syringaldehyde as the crosslinking agent showed an overall increasing trend with the increase in microcapsules, and the change trend was relatively gentle. The glossiness of the surface coating on basswood board with microcapsules containing sodium tripolyphosphate as the crosslinking agent increased first and then decreased as the amount of microcapsules added increased. The addition of microcapsules with syringaldehyde as the crosslinking agent had no significant effect on the reflectance in the visible light band of the surface coating on basswood board. Among the two groups of samples, the hardness increase in the surface coating on basswood board with syringaldehyde as the crosslinking agent was more significant. The adhesion level of the coating on the surface of the basswood board with the two microcapsules did not change. Neither of the microcapsules had a significant effect on the impact resistance of the surface on basswood board. In the comprehensive analysis, the surface coating on basswood board with microcapsules added with syringaldehyde as the crosslinking agent at a content of 4.0% had better comprehensive performance, better surface morphology, better color-change effect, and moderate mechanical properties. The color difference was found to be 21.0 at 25 °C, the reflectivity was found to be 57.06%, the hardness was found to be 3H, the adhesion was found to be five, and the impact resistance was found to be three. Full article

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

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13 pages, 4805 KiB

Open AccessArticle

Fabrication and Properties of Superhydrophobic Colored Stainless Steel Surface for Decoration and Anti-Corrosion

by Changfeng Fan, Xue Wang, Wei Wang, Dechao Meng, Xianghua Zhan, Xiaoli Yin and Yancong Liu

Coatings 2024, 14(9), 1117; https://doi.org/10.3390/coatings14091117 - 2 Sep 2024

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Abstract

A colored superhydrophobic surface on a stainless steel substrate was achieved by means of high temperature oxidation combined with subsequent spraying modification by superhydrophobic nano-silica film. Comprehensive characterizations of the surface were performed in terms of color, morphology, composition, wettability, and corrosion resistance [...] Read more.

A colored superhydrophobic surface on a stainless steel substrate was achieved by means of high temperature oxidation combined with subsequent spraying modification by superhydrophobic nano-silica film. Comprehensive characterizations of the surface were performed in terms of color, morphology, composition, wettability, and corrosion resistance by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), contact angle, potentiodynamic polarization, and electrochemical impedance spectroscopy measurement. At 400 °C, the surface was pale yellow, gradually turning yellow and then red as the temperature increased. At 700 °C and 800 °C, the surface colors were blue and dark brown, respectively. The samples with oxide films demonstrated lower contact angles, specifically 80.5° ± 2.5 at 400 °C, 79.1° ± 2.8 at 500 °C, and 75.6° ± 3.4 at 600 °C. The polarization resistance measured on the oxidized film formed at 600 °C exceeded 7.93 × 10⁴ Ω·cm². After spraying the treatment, these colorful surfaces exhibited superhydrophobicity, they were self-cleaning, and they satisfied anti-corrosion properties. The treatment performs as an excellent barrier and exhibits a high corrosion resistance of 4.68 × 10⁶ Ω·cm². The successful preparation of superhydrophobic colored surfaces offers the possibility of providing stainless steel with both decoration value and self-cleaning function simultaneously by our proposed chromium-free fabrication process. Full article

(This article belongs to the Special Issue Corrosion Resistance of Innovative Composite Coatings Based on Nanoparticles)

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