Coatings

17 pages, 3279 KiB

Open AccessArticle

Dual Modulation Polarization-Independent Terahertz BIC Metasurface for Multi-Wavelength Sensing

by Yanru Ren, Jingwei Lv, Chao Liu, Debao Wang, Renfeng Li, Liangliang Li, Xili Lu, Qiang Liu, Jianxin Wang, Wei Liu and Paul K. Chu

Coatings 2025, 15(3), 363; https://doi.org/10.3390/coatings15030363 - 20 Mar 2025

Viewed by 384

Abstract

The use of bound states in the continuum (BICs) has emerged as an effective tool to trap light at the nanoscale and has many potential applications in photonics. Breaking the structural symmetry is regarded as an effective way to excite quasi-BICs (QBICs) and [...] Read more.

The use of bound states in the continuum (BICs) has emerged as an effective tool to trap light at the nanoscale and has many potential applications in photonics. Breaking the structural symmetry is regarded as an effective way to excite quasi-BICs (QBICs) and generate high-Q resonances. However, this approach may impact the resonance polarization sensitivity, consequently limiting its practicality in multi-wavelength polarization-dependent applications. Furthermore, the introduction of different types of structural perturbations into the design to form BICs has yet to be explored in depth. In this study, we present an optical sensor consisting of an L-shaped metasurface that supports three quasi-BIC modes in the terahertz band, where specific displacements, collective perturbations, or both occur. Furthermore, we analyze the field distributions in detail and combine them with multipolar decomposition to reveal the underlying mechanisms of the different resonant modes. Multiple asymmetric perturbations are found to affect the sensitivity of the metasurface in refractive index sensing, thus allowing for a comparison of different resonant modes. The quasi-BIC mode can attain a Q-factor of 1067.6, a sensitivity (S) of 300 GHz/RIU, and a figure of merit (FOM) of 5367.8 RIU⁻¹ for vertical light incidence. These three quasi-BIC modes are polarization-independent, and their properties are maintained even for circularly polarized light. The results reveal a novel design strategy for metasurface-based sensors with promising application potential in biosensing, filtering, and lasers. Full article

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29 pages, 10331 KiB

Open AccessArticle

Using Preexisting Surface Cracks to Prevent Thermal Fatigue Failure and Crack Delamination in FGM Thermal Barrier Coatings

by Kai-Chien Lo, Jenn-Kun Kuo, Pei-Hsing Huang and Chang-Yu Hsiao

Coatings 2025, 15(3), 362; https://doi.org/10.3390/coatings15030362 - 20 Mar 2025

Viewed by 279

Abstract

Thermal shock testing has long been employed to assess thermal barrier coatings (TBCs), with crack formation and propagation on TBC surfaces serving as important indicators of fracture toughness. In this study, the influence of preexisting cracks within TBC coatings was investigated. These cracks [...] Read more.

Thermal shock testing has long been employed to assess thermal barrier coatings (TBCs), with crack formation and propagation on TBC surfaces serving as important indicators of fracture toughness. In this study, the influence of preexisting cracks within TBC coatings was investigated. These cracks can help alleviate stress concentrations at the interface and within the thermally grown oxide (TGO) layers of the TBC model. In other words, surface crack propagation may eventually intersect the interface, leading to delamination and spallation. This research focused on modifying the volume fraction of functionally graded materials (FGMs) and optimizing preexisting surface cracks in TBCs to extend their lifespan before delamination occurs. The accuracy of the J-integral and displacement correlation technique (DCT) methods was evaluated for use in thermal shock testing simulations. The results showed that both the stress intensity factor (SIF) and interface tensile stress of preexisting cracks were significantly reduced when the volume fraction was set at N = 3. Furthermore, the SIF values demonstrated strong agreement with calculations using the J-integral and DCT methods. The SIF for preexisting cracks dropped to below 62.42% of the fracture toughness when the crack length was approximately 50% of the TBC coating thickness in FGM structures, with a crack density of 10 cracks per inch (CPI). Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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32 pages, 2445 KiB

Open AccessReview

Toxicity, Irritation, and Allergy of Metal Implants: Historical Perspective and Modern Solutions

by Grzegorz Szczęsny, Mateusz Kopec and Zbigniew L. Kowalewski

Coatings 2025, 15(3), 361; https://doi.org/10.3390/coatings15030361 - 20 Mar 2025

Viewed by 636

Abstract

The widespread adoption of metal implants in orthopaedics and dentistry has revolutionized medical treatments, but concerns remain regarding their biocompatibility, toxicity, and immunogenicity. This study conducts a comprehensive literature review of traditional biomaterials used in orthopaedic surgery and traumatology, with a particular focus [...] Read more.

The widespread adoption of metal implants in orthopaedics and dentistry has revolutionized medical treatments, but concerns remain regarding their biocompatibility, toxicity, and immunogenicity. This study conducts a comprehensive literature review of traditional biomaterials used in orthopaedic surgery and traumatology, with a particular focus on their historical development and biological interactions. Research articles were gathered from PubMed and Web of Science databases using keyword combinations such as “toxicity, irritation, allergy, biomaterials, corrosion, implants, orthopaedic surgery, biocompatible materials, steel, alloys, material properties, applications, implantology, and surface modification”. An initial pool of 400 articles was screened by independent reviewers based on predefined inclusion and exclusion criteria, resulting in 160 relevant articles covering research from 1950 to 2025. This paper explores the electrochemical processes of metals like iron, titanium, aluminium, cobalt, molybdenum, nickel, and chromium post-implantation, which cause ion release and wear debris formation. These metal ions interact with biological molecules, triggering localized irritation, inflammatory responses, and immune-mediated hypersensitivity. Unlike existing reviews, this paper highlights how metal–protein interactions can form antigenic complexes, contributing to delayed hypersensitivity and complications such as peri-implant osteolysis and implant failure. While titanium is traditionally considered bioinert, emerging evidence suggests that under certain conditions, even inert metals can induce adverse biological effects. Furthermore, this review emphasizes the role of oxidative stress, illustrating how metal ion release and systemic toxicity contribute to long-term health risks. It also uncovers the underappreciated genotoxic and cytotoxic effects of metal ions on cellular metabolism, shedding light on potential long-term repercussions. By integrating a rigorous methodological approach with an in-depth exploration of metal-induced biological responses, this paper offers a more nuanced perspective on the complex interplay between metal implants and human biology, advancing the discourse on implant safety and material innovation. Full article

(This article belongs to the Collection Review Papers Collection for Bioactive Coatings)

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20 pages, 16430 KiB

Open AccessArticle

Study on the Properties of Plastic Fillers in Carbon Dioxide Capture System Under High Temperature and High Pressure

by Kun Fang, Xuehua Fan, Jie Chen, Lei Dong, Jiahui Hu, Yiying Liu, Shengyuan Liu, Jianbo Sun, Xiangyu Zheng and Guojian Liu

Coatings 2025, 15(3), 360; https://doi.org/10.3390/coatings15030360 - 20 Mar 2025

Viewed by 243

Abstract

In the CO₂-amine solution system, metal packings in purification devices face corrosion risks, while plastic packings have garnered attention due to their lightweight nature, ease of processing, and excellent corrosion resistance. Since different plastic packings have varying applicable temperature ranges, exceeding [...] Read more.

In the CO₂-amine solution system, metal packings in purification devices face corrosion risks, while plastic packings have garnered attention due to their lightweight nature, ease of processing, and excellent corrosion resistance. Since different plastic packings have varying applicable temperature ranges, exceeding their tolerance limits can significantly reduce their corrosion resistance. Therefore, selecting suitable plastic packings at different temperatures is crucial for ensuring safety. This study selected four plastic materials–PVC-C, PP, FEP, and PEEK–and systematically tested their performance indicators, such as volume, mass, strength, elongation, and thermal stability, in a CO₂-amine solution system at experimental temperatures ranging from 60 to 130 °C. The experimental results show that PEEK outperformed the other three materials within the 60–130 °C range, making it suitable as a packing material for purification devices in high-temperature environments. Although FEP demonstrated good performance under the same conditions, its tendency to deform may limit its applicability. PP and PVC-C exhibited poor performance at high temperatures, with PVC-C particularly failing above 100 °C, rendering it unsuitable for high-temperature applications. This research provides important insights for the future selection of packing materials in CO₂-amine solution systems for purification devices. Full article

(This article belongs to the Special Issue Investigation on Structure and Corrosion Resistance of Steels/Alloys, 2nd Edition)

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30 pages, 8153 KiB

Open AccessArticle

Anticorrosive Effect of New Polymer Composite Coatings on Carbon Steel in Aggressive Environments by Electrochemical Procedures

by Florina Branzoi, Adriana Băran, Marius Alexandru Mihai and Alexandru Praschiv

Coatings 2025, 15(3), 359; https://doi.org/10.3390/coatings15030359 - 20 Mar 2025

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Abstract

In this investigation, electrochemical deposition procedures were reported to synthesize a novel composite polymer, 3-methylpyrrole-dodecyl sulfate sodium/3,4-ethylenedioxythiophene (3MPY-SDS/EDOT) coatings, on OL 37 samples for anticorrosion protection. The anionic surfactant dodecyl sulfate sodium used in deposition can have a relevant action on the protective [...] Read more.

In this investigation, electrochemical deposition procedures were reported to synthesize a novel composite polymer, 3-methylpyrrole-dodecyl sulfate sodium/3,4-ethylenedioxythiophene (3MPY-SDS/EDOT) coatings, on OL 37 samples for anticorrosion protection. The anionic surfactant dodecyl sulfate sodium used in deposition can have a relevant action on the protective capacity. These coatings were considered by cyclic voltammetry (CV), Fourier transform infrared (FT-IR) spectroscopy, and scanning electron microscopy (SEM) methods. The protective attributes of OL 37 coated with P3MPY-SDS/PEDOT have been examined by potentiostatic and potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) procedures in 0.5 M H₂SO₄. The corrosion rate of the P3MPY-SDS/PEDOT-coated OL 37 sample was found to be approximately nine times lower than that of the uncoated sample. The protective layers of these composites demonstrate an effectiveness of over 90%. The optimal efficiency is obtained by electrochemical deposition of P3MPY-SDS/PEDOT, performed at applied potentials of 1.0 V, 1.2 V, and 1.4 V, with current densities of 3 mA/cm² and 5 mA/cm² and a molar ratio of 5:3 at 20 min. The influence of electrochemical polymerization parameters—applied potential, current density, scan rate, cycle number, and monomer ratio—on the protective behavior of P3MPY-SDS/PEDOT layers was analyzed, identifying optimal synthesis conditions. Corrosion examinations confirmed that P3MPY-SDS/PEDOT coatings provide effective protection for OL 37 in a corrosive environment. Full article

(This article belongs to the Special Issue New Developments of Protective Coatings, Organic Polymers, and Surface Analysis: 2nd Edition)

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20 pages, 10586 KiB

Open AccessArticle

Micromechanical Properties and Tribological Performance of Mo, Cr, and Ta Coatings Obtained by Cathodic Arc-Deposition

by Vadim Zakiev, Volodymyr Nadtoka, Islam Zakiev, Bohdan Mordyuk, Oleksandr Yakushenko, Igor Trofimov, Mykola Skoryk and Sviatoslav Yutskevych

Coatings 2025, 15(3), 358; https://doi.org/10.3390/coatings15030358 - 19 Mar 2025

Viewed by 206

Abstract

The aim of the study is a comparative analysis of micromechanical and microtribological properties of the cathodic arc-deposited Mo, Cr, and Ta coatings using nanoindentation and scratch test techniques as well as a microtribological dry sliding test with wear tracks post-examination and worn [...] Read more.

The aim of the study is a comparative analysis of micromechanical and microtribological properties of the cathodic arc-deposited Mo, Cr, and Ta coatings using nanoindentation and scratch test techniques as well as a microtribological dry sliding test with wear tracks post-examination and worn volume determination using interference profilometry. A new scratch test technique based on the statistical processing of registered sclerograms during a multi-pass scratch test well adopted for the scratch resistance assessment of rough surfaces is suggested. New approaches to microtribological testing based on the indentation tester equipped with an additional precision rotational stage are proposed, which could fill the gap between macro- and nano-scale. X-ray diffraction analysis reveals the structure of the studied coatings and phase compositions of the coating-substrate interface. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings, 2nd Edition)

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16 pages, 8331 KiB

Open AccessArticle

Effect of Gun Geometry on MCrAlX Coating Microstructure and In-Flight Oxidation Deposited by Low-Temperature High-Velocity Air Fuel

by Murilo Sergio Lamana, Aravind Kumar Thoutam, Bruno C. N. M. de Castilho, Fadhel Ben Ettouil, Ritvij Chandrakar, Stephanie Bessette, Nicolas Brodusch, Raynald Gauvin, Ali Dolatabadi and Christian Moreau

Coatings 2025, 15(3), 357; https://doi.org/10.3390/coatings15030357 - 19 Mar 2025

Viewed by 225

Abstract

Aircraft gas turbine blades operate in aggressive, generally oxidizing, atmospheres. A solution to mitigate the degradation and improve the performance of such components is the deposition of thermal barrier coatings systems (TBCs). High-velocity air fuel (HVAF) is a very efficient process for coating [...] Read more.

Aircraft gas turbine blades operate in aggressive, generally oxidizing, atmospheres. A solution to mitigate the degradation and improve the performance of such components is the deposition of thermal barrier coatings systems (TBCs). High-velocity air fuel (HVAF) is a very efficient process for coating deposition in TBC systems, particularly for bond coats in aerospace applications. However, its low-temperature variant has received little attention in the literature and could be a promising alternative to limit oxidation during spraying when compared to conventional methods. This study has the main objective of analyzing how the geometry of the low-temperature HVAF gun influences the microstructure and the in-flight oxidation of MCrAlX coatings. To that end, a low-temperature HVAF torch is used to deposit MCrAlX coatings on a steel substrate with different nozzle lengths. In-flight particle diagnosis is used to measure the MCrAlX particle velocity, and to correlate to the nozzle geometry and to analyze its influence on the final coating. The microstructure of the coatings is assessed by scanning electron microscopy (SEM) and the material oxidation is analyzed and measured on a field emission scanning transmission electron microscope (FE-STEM) equipped with focused ion beam (FIB) and by Energy Dispersive Spectroscopy (EDS). Full article

(This article belongs to the Special Issue Advances in Protective Coatings: Materials, Fabrication, Corrosion and Applications)

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27 pages, 35081 KiB

Open AccessArticle

Carbon Felt/Nickel Oxide/Polyaniline Nanocomposite as a Bifunctional Anode for Simultaneous Power Generation and Energy Storage in a Dual-Chamber MFC

by Yuyang Wang, Zhijie Wang, Dongming Zhang, Xiangquan Kong, Yu Song, Su Ma, Ying Duan, Andrii Vyshnikin and Vitalii Palchykov

Coatings 2025, 15(3), 356; https://doi.org/10.3390/coatings15030356 - 19 Mar 2025

Viewed by 197

Abstract

Microbial fuel cell (MFC) technology has become a novel and attractive method for generating renewable energy during wastewater treatment. In this study, researchers combined carbon felt (CF), metal oxide (NiO), and polyaniline (PANI) to prepare CF/NiO/PANI multilayer capacitive bioelectrodes. The MFC equipped with [...] Read more.

Microbial fuel cell (MFC) technology has become a novel and attractive method for generating renewable energy during wastewater treatment. In this study, researchers combined carbon felt (CF), metal oxide (NiO), and polyaniline (PANI) to prepare CF/NiO/PANI multilayer capacitive bioelectrodes. The MFC equipped with a CF/NiO/PANI bioanode has a peak power density of 1988.31 ± 50.96 mW/m², which is 3.8 times higher than that of the MFC with a bare CF electrode, having a peak power density of 518.29 ± 27.07 mW/m². Charge–discharge cycle tests show that the storage charge capacity of the CF/NiO/PANI bioanode is 3304.64 C/m², which is 10.5 times greater than that of the bare CF anode. The electrochemical, morphological, and chemical properties of the prepared anodes are characterized using techniques such as SEM, EDS, FTIR, XPS, and XRD. Notably, high-throughput sequencing reveals that electrogenic bacteria account for 79.2% of the total microbial population on the CF/NiO/PANI multilayer capacitive bioelectrode. The synergistic effects of the composite materials result in the formation of a richer biofilm on the electrode surface, providing more active sites and enhancing capacitive characteristics. This innovative approach significantly improves the output power and peak current of MFCs, while also endowing the electrode with dual functions of simultaneous power generation and energy storage. Full article

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19 pages, 7384 KiB

Open AccessArticle

The Role of HVAF Nozzle Design and Process Parameters on In-Flight Particle Oxidation and Microstructure of NiCoCrAlY Coatings

by Aravind Kumar Thoutam, Murilo Sergio Lamana, Bruno C. N. M. de Castilho, Fadhel Ben Ettouil, Ritvij Chandrakar, Stephanie Bessette, Nicolas Brodusch, Raynald Gauvin, Ali Dolatabadi and Christian Moreau

Coatings 2025, 15(3), 355; https://doi.org/10.3390/coatings15030355 - 19 Mar 2025

Viewed by 195

Abstract

Increasing demand to deposit dense and oxidation-resistant bond coats requires reliable and efficient deposition techniques. High-Velocity Air-Fuel (HVAF), among other thermal spray processes, is showcasing consistent potential to optimize spraying techniques and deposition strategies for depositing NiCoCrAlY coatings. NiCoCrAlY coatings are sensitive to [...] Read more.

Increasing demand to deposit dense and oxidation-resistant bond coats requires reliable and efficient deposition techniques. High-Velocity Air-Fuel (HVAF), among other thermal spray processes, is showcasing consistent potential to optimize spraying techniques and deposition strategies for depositing NiCoCrAlY coatings. NiCoCrAlY coatings are sensitive to high-temperature oxidation, and preserving the aluminum reservoir in the bond coats is of the highest priority to potentially resist oxidation during thermal cycling. Contrary to the existing literature on comparing carbide-based HVAF deposition with other processes, this work investigates the specific role of nozzle configurations. It primarily focuses on in-flight particle characteristics using diagnostic tools and the corresponding inflight particle oxidation of NiCoCrAlY feedstock. This work details individual splat and coating characteristics, revealing the significant influence of nozzle configurations. A comprehensive understanding of process–material–microstructure correlations was established using a commercially available NiCoCrAlY coating system. Comprehensive discussions on nozzle configurations over various feedstock powder characteristics were carried out in this work. Advanced characterization techniques were employed to assess the in-flight particle oxidation and coating microstructure using focused ion beam (FIB), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Full article

(This article belongs to the Special Issue Advances in Protective Coatings: Materials, Fabrication, Corrosion and Applications)

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13 pages, 5166 KiB

Open AccessArticle

Multifunctional Aramid Nanofiber/MXene/Aramid Fiber Composite Fabric with Outstanding EMI Shielding Performance

by Qianyi Wang, Ying Wang, Changmei Sun, Ying Zhang, Rongjun Qu and Yunxia Shen

Coatings 2025, 15(3), 354; https://doi.org/10.3390/coatings15030354 - 19 Mar 2025

Viewed by 239

Abstract

Developing aramid fiber (AF) with electromagnetic interference (EMI) shielding properties is of significant importance for expanding their applications in the military, aerospace, and industrial sectors. Current research on the EMI shielding properties of AF often encounters challenges such as structural damage to the [...] Read more.

Developing aramid fiber (AF) with electromagnetic interference (EMI) shielding properties is of significant importance for expanding their applications in the military, aerospace, and industrial sectors. Current research on the EMI shielding properties of AF often encounters challenges such as structural damage to the fibers and inadequate shielding performance. In this study, we used vacuum-assisted filtration technology to sequentially deposit aramid nanofiber (ANF) and MXene onto the surface of AF fabric, thus preparing ANF/MXene/AF composite fabric. MXene, with its large specific surface area and excellent electrical conductivity, was used in conjunction with ANF, which acts as an intermediate layer to effectively filter MXene and improve the interfacial adhesion between the MXene and AF. The results showed that, under the combined effects of reflection and absorption, the A20M40 sample achieved an average EMI SE of 78.1 dB in the X-band, meeting the EMI shielding requirements for both civilian and military applications. Additionally, the ANF/MXene/AF composite fabric exhibited excellent electrothermal conversion performance (surface temperature reached 120 °C within 32 s under 5 V) and photothermal performance (surface temperature reached 85 °C after 145 s of exposure to 1500 W/m² light intensity). Furthermore, the flame-retardant performance of the ANF/MXene/AF composite fabric was significantly enhanced compared to the pure AF fabric due to the physical barrier effect of MXene. Full article

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15 pages, 5202 KiB

Open AccessArticle

Characterization of AlCrN Coated on Tungsten Carbide Substrate by a Continuous Plasma Nitriding-HiPIMS Hybrid Process

by Fu-Sen Yang, Yu-Lin Kuo, Jian-Fu Tang, Ting-Wei Liu and Chi-Lung Chang

Coatings 2025, 15(3), 353; https://doi.org/10.3390/coatings15030353 - 19 Mar 2025

Viewed by 226

Abstract

Plasma nitriding (PN) is often used to enhance the mechanical properties (surface hardness, wear and corrosion resistance) of bulk alloys. High-quality AlCrN hard coatings were obtained using high-power pulsed magnetron sputtering (HiPIMS) technology. This study proposes a combination of two surface treatment methods [...] Read more.

Plasma nitriding (PN) is often used to enhance the mechanical properties (surface hardness, wear and corrosion resistance) of bulk alloys. High-quality AlCrN hard coatings were obtained using high-power pulsed magnetron sputtering (HiPIMS) technology. This study proposes a combination of two surface treatment methods (plasma nitriding and hard coating deposition) in a continuous plasma process to optimize the application and service life of cutting tools. The main feature of this study is to verify the mechanical properties and adhesion strength of nitride tungsten carbide (WC-Co) bulk at a lower temperature (∼300 °C) and shorter time (0.5 to 1.5 h) of PN treatment. After 1.5 h of PN treatment on the WC-Co substrate without subsequent coating, the ultra-thin WN_x diffusion interlayer (thickness ∼11.5 nm) on the subsurface was directly observed via TEM analysis, and the types of chemical bonding were confirmed by XPS analysis. Vickers analysis indicated that the surface hardness of the nitrided WC-Co substrate was enhanced by PN treatment from 1534 to 2034 Hv. The AlCrN coating deposited on the nitrided WC-Co substrate significantly enhances the surface mechanical properties, including adhesion strength (increasing from 70 to 150 N), hardness (rising from 2257 to 2568 HV), and wear resistance (with the wear rate decreasing from 14.5 to 3.4 × 10⁻⁸ mm³/Nm). Composite surface technology has a high commercial application value because it enhances the value of products under the existing equipment of manufacturers. Full article

(This article belongs to the Special Issue Advances in Novel Coatings)

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18 pages, 8547 KiB

Open AccessArticle

PDINN as an Efficient and Environmentally Friendly Corrosion Inhibitor for Mild Steel in HCl: A Comprehensive Investigation

by Jiakai Kuang, Shaopeng Fu, Jiaqi Song, Lanlan Ma, Xueqi Liu, Zezhou Liang, Jianfeng Li and Jinpeng Dai

Coatings 2025, 15(3), 352; https://doi.org/10.3390/coatings15030352 - 19 Mar 2025

Viewed by 215

Abstract

The screening of environmentally friendly, efficient and high-temperature-resistant organic corrosion inhibitors represents a significant means of reducing metal losses in industrial production. In this study, we investigated using aliphatic amine-functionalized perylene-diimide (PDINN) to inhibit Q235 steel in 1 M HCl media. The results [...] Read more.

The screening of environmentally friendly, efficient and high-temperature-resistant organic corrosion inhibitors represents a significant means of reducing metal losses in industrial production. In this study, we investigated using aliphatic amine-functionalized perylene-diimide (PDINN) to inhibit Q235 steel in 1 M HCl media. The results show that PDINN significantly inhibits corrosion of Q235 steel in 1 M HCl. It is of greater significance that PDINN’s inhibition is unresponsive to temperature fluctuations in the corrosive environment, maintaining an efficiency of 86.5% at an ambient temperature of 328 K. DFT and MD analyses indicate that the exceptional inhibitory capacity of PDINN is closely associated with the extensive conjugated structure within the molecule, where it is firmly adsorbed on the Fe (110) via π-electrons. Full article

(This article belongs to the Special Issue Advanced Coating and Surface Engineering for Tribology and Corrosion Resistance)

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19 pages, 3822 KiB

Open AccessArticle

A CNC-Modified PAN Separator Improving the Cycle Stability of Lithium-Ion Batteries

by Anqi Zhou, Kailong Guo, Xuenuan Li, Xinyu Song, Xianming Liu, Weile Ding, Bin Guo, Donglei Guo, Guilong Liu, Naiteng Wu and Aimiao Qin

Coatings 2025, 15(3), 351; https://doi.org/10.3390/coatings15030351 - 19 Mar 2025

Viewed by 326

Abstract

In this paper, a composite separator for lithium-ion batteries was successfully prepared by electrostatic spinning, based on polyacrylonitrile (PAN) and 5% cellulose nanocrystals (CNCs) derived from sisal fiber. Its physical and electrochemical properties as well as the enhanced mechanism were investigated. The obtained [...] Read more.

In this paper, a composite separator for lithium-ion batteries was successfully prepared by electrostatic spinning, based on polyacrylonitrile (PAN) and 5% cellulose nanocrystals (CNCs) derived from sisal fiber. Its physical and electrochemical properties as well as the enhanced mechanism were investigated. The obtained 5%CNCs/PAN separator offers an excellent thermal stability, ultra-high electrolyte uptake (486 ± 30%), high ionic conductivity (2.82 mS cm⁻¹ at 25 °C) and a wide electrochemical window (5.3 V). In addition, a lithium-ion battery assembled with the 5%CNCs/PAN separator can work stably for 1000 h at 5 mA cm⁻². The CNCs in the electrolyte enable the immobilization of PF₆⁻, thereby inhibiting the migration of anions and increasing its Li⁺ transfer number (t_Li⁺) to 0.75, which is 65.3% higher than that of a pure PAN separator. The battery with the 5%CNCs/PAN separator retains 97.4% of its initial reversible capacity after 100 cycles, which is much higher than that of a pure PAN separator, with a value of 62.9%. These results suggest the potential utility of 5%CNCs/PAN separators as high-performance separators required in lithium-ion batteries. Full article

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15 pages, 1766 KiB

Open AccessArticle

Development of Renewable Polyester Resins for Coil Coatings Based on 2,5-Furandicarboxylic Acid

by Nataša Čuk, Danaja Štular, Martin Ocepek, Jaka Langerholc and Peter Venturini

Coatings 2025, 15(3), 350; https://doi.org/10.3390/coatings15030350 - 18 Mar 2025

Viewed by 346

Abstract

In this work, the development of FDCA-based polyester resins for coil coatings in industrial environment is presented. The goal of our research was to prepare industrial coatings made from renewable materials with the same performance as the standard coating. Resins with 1%–41% of [...] Read more.

In this work, the development of FDCA-based polyester resins for coil coatings in industrial environment is presented. The goal of our research was to prepare industrial coatings made from renewable materials with the same performance as the standard coating. Resins with 1%–41% of FDCA on polymer were synthesized and then used in a formulation for primer. Resins were characterized by the determination of non-volatile matter, acid value, hydroxyl value, glass transition temperature, and measurement of viscosity, color and molecular weight. Coatings were characterized by the determination of viscosity, density, non-volatile matter, adhesion, T-test, MEK test, reverse impact, and pencil hardness, as well as the measurement of gloss. FTIR measurements confirmed successful incorporation of FDCA into the polymer. The results showed that resins with up to 31% of FDCA on polymer can be used to prepare coil coating where the properties of resins comply with the requirements and are comparable to the properties of standard resin. Resins had non-volatile matter between 59.0 and 60.1%, an acid value up to 4.6 mg KOH/g, a hydroxyl value of 22.0–24.9 mg KOH/g and viscosity at 23 °C between 6100 and 7500 mPa.s. Nevertheless, with the increase in FDCA in the formulation, discoloration of the resin occurred and incompatibility with the solvents was observed, while up to 10 °C lower glass transition temperatures and up to 28% lower molecular weights of the resins were determined. For coatings prepared from FDCA-based resins, the properties improved or were comparable to the properties of coating prepared from standard resin. Adhesion improved with higher content of FDCA in the resin from 2 Gt to 0 Gt, while all coatings had gloss at 60° of 39%–41%, a reverse impact of 10 J and a pencil hardness of H/2H. T-bend test results varied between 2 T and 0.5 T and the results of the MEK test showed resistance > 100 DR. Full article

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19 pages, 4401 KiB

Open AccessArticle

A Unified Framework for Asphalt Pavement Distress Evaluations Based on an Extreme Gradient Boosting Approach

by Bing Liu, Danial Javed, Jianghai Hu, Wei Li and Leilei Chen

Coatings 2025, 15(3), 349; https://doi.org/10.3390/coatings15030349 - 18 Mar 2025

Viewed by 268

Abstract

Flexible pavements are susceptible to distress when subjected to long-term vehicle loads and environmental factors, thereby reqsuiring appropriate maintenance. To overcome the hectic field data collection and traffic congestion problems, this paper presents an intelligent prediction system framework utilizing Extreme Gradient Boosting (XGboost) [...] Read more.

Flexible pavements are susceptible to distress when subjected to long-term vehicle loads and environmental factors, thereby reqsuiring appropriate maintenance. To overcome the hectic field data collection and traffic congestion problems, this paper presents an intelligent prediction system framework utilizing Extreme Gradient Boosting (XGboost) to predict two relevant functional indices: rutting deformation and cracks damage. The model framework considers multiple essential factors, such as traffic load, material characteristics, and climate data conditions, to predict rutting behavior and employs image data to classify cracks behavior. The Extreme Gradient Boosting (XGboost) algorithm exhibited good performance, achieving an R² value of 0.9 for rutting behavior and an accuracy of 0.91, precision of 0.92, recall of 0.9, and F1-score of 0.91 for cracks. Moreover, a comparative assessment of the framework model with prominent AI methodologies reveals that the XGboost model outperforms support vector machine (SVM), decision tree (DT), random forest (RF), and K-Nearest Neighbor (KNN) methods in terms of quality of the result. For rutting behavior, a SHAP (Shapley Additive Explanations) analysis was performed on the XGboost model to interpret results and analyze the importance of individual features. The analysis revealed that parameters related to load and environmental conditions significantly influence the model’s predictions. Finally, the proposed model provides more precise estimates of pavement performance, which can assist in optimizing budget allocations for road authorities and providing dependable guidance for pavement maintenance. Full article

(This article belongs to the Special Issue Surface and Interface Characteristics of Pavements: New Perspectives and Applications)

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19 pages, 6004 KiB

Open AccessArticle

Investigating the Microstructural Behavior and Energy Absorption of Pure Copper Lattice Structures Fabricated by Selective Electron Beam Melting

by Xin Yang, Zhaoyang Zhang, Fan Song, Xiaodong Xie, Huan Qi and Chao Ding

Coatings 2025, 15(3), 348; https://doi.org/10.3390/coatings15030348 - 18 Mar 2025

Viewed by 276

Abstract

Pure copper’s exceptional thermal and electrical properties, along with its processability, make it indispensable in aerospace, automotive, and electrical industries, particularly in heat exchangers and radiators. Lattice structures, with high specific surface areas, low weight, and high strength, are ideal for lightweight yet [...] Read more.

Pure copper’s exceptional thermal and electrical properties, along with its processability, make it indispensable in aerospace, automotive, and electrical industries, particularly in heat exchangers and radiators. Lattice structures, with high specific surface areas, low weight, and high strength, are ideal for lightweight yet strong components. While traditional methods struggle with complex lattice geometries, selective electron beam melting (SEBM) enables the fabrication of intricate pure copper lattices with high energy efficiency in a vacuum environment. This study used SEBM to fabricate OCTET pure copper lattices with relative densities of 21.16%–73.77%. The macrostructure matched the design, achieving a maximum energy absorption capacity of 15.00 MJ/m³. At 40.04% relative density, compressive response shifted from shock to compression hardening, with densification strains ranging from 23.96% to 51.68%. Microdefects such as corrugation, size differences, and internal holes influenced mechanical properties and energy absorption. Post-polishing reduced surface roughness from 14.12 μm to 2.70 μm without affecting specific energy absorption. Increasing strut diameter reduced the microdefects’ impact on lattice strength, enhancing performance and reliability. Full article

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20 pages, 3945 KiB

Open AccessArticle

Nondestructive Evaluation of Aging Failure in Insulation Coatings by Ultrasonic Guided Wave Based on Signal Processing and Machine Learning

by Mengmeng Qiu and Xin Ge

Coatings 2025, 15(3), 347; https://doi.org/10.3390/coatings15030347 - 18 Mar 2025

Viewed by 312

Abstract

In the field of nondestructive evaluation (NDE) using ultrasonic guided waves, accurately assessing the aging failure of insulation coatings remains a challenging and prominent research topic. While the application of ultrasonic guided waves in material testing has been extensively explored in the existing [...] Read more.

In the field of nondestructive evaluation (NDE) using ultrasonic guided waves, accurately assessing the aging failure of insulation coatings remains a challenging and prominent research topic. While the application of ultrasonic guided waves in material testing has been extensively explored in the existing literature, there is still a significant gap in quantitatively evaluating the aging failure of insulation coatings. This study innovatively proposes an NDE method for assessing insulation coating aging failure by integrating signal processing and machine learning technologies, thereby effectively addressing both theoretical and practical gaps in this domain. The proposed method not only enhances the accuracy of detecting insulation coating aging failure but also introduces new approaches to non-destructive testing technology in related fields. To achieve this, an accelerated aging experiment was conducted to construct a cable database encompassing various degrees of damage. The effects of aging time, temperature, mechanical stress, and preset defects on coating degradation were systematically investigated. Experimental results indicate that aging time exhibits a three-stage nonlinear evolution pattern, with 50 days marking the critical inflection point for damage accumulation. Temperature significantly influences coating damage, with 130 °C identified as the critical threshold for performance mutation. Aging at 160 °C for 100 days conforms to the time-temperature superposition principle. Additionally, mechanical stress concentration accelerates coating failure when the bending angle is ≥90°. Among preset defects, cut defects were most destructive, increasing crack density by 5.8 times compared to defect-free samples and reducing cable life to 40% of its original value. This study employs Hilbert–Huang Transform (HHT) for noise reduction in ultrasonic guided wave signals. Compared to Fast Fourier Transform (FFT), HHT demonstrates superior performance in feature extraction from ultrasonic guided wave signals. By combining HHT with machine learning techniques, we developed a hybrid prediction model—HHT-LightGBM-PSO-SVM. The model achieved prediction accuracies of 94.05% on the training set and 88.36% on the test set, significantly outperforming models constructed with unclassified data. The LightGBM classification model exhibited the highest classification accuracy and AUC value (0.94), highlighting its effectiveness in predicting coating aging damage. This research not only improves the accuracy of detecting insulation coating aging failure but also provides a novel technical means for aviation cable health monitoring. Furthermore, it offers theoretical support and practical references for nondestructive testing and life prediction of complex systems. Future studies will focus on optimizing model parameters, incorporating additional environmental factors such as humidity and vibration to enhance prediction accuracy, and exploring lightweight algorithms for real-time monitoring. Full article

(This article belongs to the Special Issue Microstructure, Friction and Wear, Hardness Properties and Numerical Simulation of Coatings)

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19 pages, 7292 KiB

Open AccessArticle

Mechanism and Pathway of Atrazine Degradation by Peroxymonosulfate Activated by CoNiFe-Layered Double Hydroxide

by Zhanmei Zhang, Xinyue Li, Yang Deng, Yi Zhang, Yunxuan Huang and Huaili Zheng

Coatings 2025, 15(3), 346; https://doi.org/10.3390/coatings15030346 - 18 Mar 2025

Viewed by 242

Abstract

Advanced oxidation processes (AOPs) based on activated persulfate (PS) are gradually being employed in the treatment of novel pollutants. In this study, an efficient and reliable CoNiFe-layered double hydroxide (LDH) was prepared by a hydrothermal method, which could effectively activate peroxomonosulfate (PMS) and [...] Read more.

Advanced oxidation processes (AOPs) based on activated persulfate (PS) are gradually being employed in the treatment of novel pollutants. In this study, an efficient and reliable CoNiFe-layered double hydroxide (LDH) was prepared by a hydrothermal method, which could effectively activate peroxomonosulfate (PMS) and cause free sulfate radical (SO₄^•−) oxidation to decompose atrazine (ATZ). The degradation rate of ATZ was greater than 99% within 60 min at pH 7 when the initial concentration of ATZ was 10 mg·L⁻¹, and the dosages of PMS and activator were 0.6 mM and 80 mg·L⁻¹. The analysis of ATZ degradation confirmed the reusability of the activator and its strong structural stability. The generation of four free radicals was analyzed and confirmed, and the influence on the degradation reaction was SO₄^•− > O₂^•− > ¹O₂ > •OH. The analytical results showed that the metal ions reacted with HSO₅⁻ in PMS to cause an oxidation–reduction cycle change in the valence state of the metal ions and generated the primary factor affecting the degradation reaction—SO₄^•−. Nine degradation intermediates with reduced toxicity were detected and possible ATZ degradation pathways were deduced, thus confirming the activation mechanism of CoNiFe-LDH. Full article

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29 pages, 3266 KiB

Open AccessReview

Pitfalls and Challenges in Specific Absorption Rate Evaluation for Functionalized and Coated Magnetic Nanoparticles Used in Magnetic Fluid Hyperthermia

by Nicusor Iacob

Coatings 2025, 15(3), 345; https://doi.org/10.3390/coatings15030345 - 17 Mar 2025

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Abstract

In recent decades, magnetic hyperthermia (MH) has gained considerable scientific interest in cancer treatment due to its ability to heat tumor tissues deeply localized inside the body. Functionalizing magnetic nanoparticles (MNPs) with vector molecules via specific organic molecules that coat the particle surface [...] Read more.

In recent decades, magnetic hyperthermia (MH) has gained considerable scientific interest in cancer treatment due to its ability to heat tumor tissues deeply localized inside the body. Functionalizing magnetic nanoparticles (MNPs) with vector molecules via specific organic molecules that coat the particle surface has enabled targeting particular tissues, thereby increasing the specificity of MH. MH relies on applying radiofrequency (RF) magnetic fields to a magnetic nanoparticle distribution injected in a tumor tissue. The RF field energy is converted into thermal energy through specific relaxation mechanisms and magnetic hysteresis-driven processes. This increases the tumor tissue temperature over the physiological threshold, triggering a series of cellular apoptosis processes. Additionally, the mechanical effects of low-frequency AC fields on anisotropic MNPs have been shown to be highly effective in disrupting the functional cellular components. From the macroscopic perspective, a crucial parameter measuring the efficiency of magnetic nanoparticle systems in MH is the specific absorption rate (SAR). This parameter is experimentally evaluated by different calorimetric and magnetic techniques and methodologies, which have specific drawbacks and may induce significant errors. From a microscopic perspective, MH relies on localized thermal and kinetic effects in the nanoparticle proximity environment. Studying MH at the cellular level has become a focused research topic in the last decade. In the context of these two perspectives, inevitable questions arise: could the thermal and kinetic effects exhibited at the cellular scale be linked by the macroscopic SAR parameter, or should we find new formulas for quantifying them? The present work offers a general perspective of MH, highlighting the experimental pitfalls encountered in SAR evaluation and motivating the necessity of standardizing the devices and protocols involved. It also discusses the challenges that arise in MH performance evaluation at the cellular level. Full article

(This article belongs to the Special Issue Advances of Nanoparticles and Thin Films)

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18 pages, 6472 KiB

Open AccessArticle

Study on the BRDF for the Surfaces of Typical Metal Materials

by Zhiqiang Yang, Shilin Zhang, Yaqing Li, Qiang Xu, Liguo Wang and Lei Gong

Coatings 2025, 15(3), 344; https://doi.org/10.3390/coatings15030344 - 17 Mar 2025

Viewed by 236

Abstract

The surface scattering property is one of the important indicators of the optical properties of metal materials, which is of great significance for the development, processing, and application of optical devices. The bidirectional reflection distribution function (BRDF), as an optical mathematical model, describes [...] Read more.

The surface scattering property is one of the important indicators of the optical properties of metal materials, which is of great significance for the development, processing, and application of optical devices. The bidirectional reflection distribution function (BRDF), as an optical mathematical model, describes the spatial distribution of reflected light energy on the surface of an object and can provide an important basis for the characterization of the optical properties of the surface of an object. In this paper, the white light scattering characteristics of the surfaces of four metallic materials, namely brass, aerospace aluminum, oxygen-free copper, and red copper, are investigated based on the BRDF microfacet metamodel, and the scattered field distributions are explored for different angles of incidence, scattering angles, and azimuthal angles. This study provides a reference for the evaluation of the optical properties of metal material surfaces and provides a theoretical basis and technical support for the design and application of optical devices. Full article

(This article belongs to the Special Issue Surface Science of Degradation and Surface Protection)

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15 pages, 4162 KiB

Open AccessArticle

C9 Petroleum Resin and Polyethylene-Based High-Viscosity Modified Asphalt Binder Proportioning Optimization and Performance Study

by Zining Chen, Wei Wang, Abduhaibir Abdukadir, Junwen Lei, Junyan Yi and Zhongshi Pei

Coatings 2025, 15(3), 343; https://doi.org/10.3390/coatings15030343 - 17 Mar 2025

Viewed by 221

Abstract

This study, based on 90# matrix asphalt binder, investigates the use of SBS, C9 petroleum resin, and polyethylene (PE) as modifiers to prepare high-viscosity modified asphalt binders. Using the uniform design method, the modifier proportions were optimized to meet engineering requirements for high [...] Read more.

This study, based on 90# matrix asphalt binder, investigates the use of SBS, C9 petroleum resin, and polyethylene (PE) as modifiers to prepare high-viscosity modified asphalt binders. Using the uniform design method, the modifier proportions were optimized to meet engineering requirements for high viscosity. The effects of modifier dosages on asphalt binder properties, including penetration, ductility, softening point, and dynamic viscosity, were systematically analyzed, and a multivariate nonlinear regression model was constructed to determine the optimal proportioning. Subsequently, the aging resistance and high-temperature performance of the modified asphalt binders were evaluated through short-term aging tests and rheological property tests. The results show that SBS and PE have a significant positive impact on penetration and softening point, while C9 petroleum resin mainly enhances ductility. The synergistic effect of SBS and PE significantly improves dynamic viscosity. Under the optimal proportioning (SBS 7.5%, C9 petroleum resin 6.0%, PE 5.0%), the high-viscosity modified asphalt binders meet technical standards for key performance indicators. The short-term aging test reveals an elastic recovery ratio exceeding 95%. Rheological performance testing indicates that the modified asphalt binders exhibit excellent rutting resistance and temperature adaptability under high-temperature conditions. Full article

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14 pages, 23162 KiB

Open AccessArticle

Effect of Si Content on Phase Structure, Microstructure, and Corrosion Resistance of FeCrNiAl_0.7Cu_0.3Six High-Entropy Alloys in 3.5% NaCl Solution

by Xiaolong Shi, Hua Liang and Yanzhou Li

Coatings 2025, 15(3), 342; https://doi.org/10.3390/coatings15030342 - 15 Mar 2025

Cited by 1 | Viewed by 512

Abstract

This study examines the microstructure and corrosion resistance of FeCrNiAl_0.7Cu_0.3Si_x (x = 0, 0.1, 0.3, and 0.5) high-entropy alloys (HEAs) in a 3.5% NaCl solution. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical testing [...] Read more.

This study examines the microstructure and corrosion resistance of FeCrNiAl_0.7Cu_0.3Si_x (x = 0, 0.1, 0.3, and 0.5) high-entropy alloys (HEAs) in a 3.5% NaCl solution. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical testing were employed to systematically analyze the alloys’ microstructures and corrosion behavior. The XRD results indicate that the addition of Si affects the phase structure of the alloy. At Si = 0, the alloy exhibits a single BCC phase. By increasing the Si content to 0.1 and 0.3, a BCC₂ phase appears. At Si = 0.5, Si-containing intermetallic compounds form. SEM observations reveal that as the Si content increases, the alloy develops a distinct dendritic structure. Polarization tests in the 3.5% NaCl solution show that the corrosion current density first decreases and then increases with increasing Si content. At Si contents of 0.1, 0.3, and 0.5, the corrosion current densities are 4.275 × 10⁻⁶ A·cm⁻², 4.841 × 10⁻⁷ A·cm⁻², and 2.137 × 10⁻⁶ A·cm⁻², respectively. FeCrNiAl_0.7Cu_0.3S_0.3 HEA exhibits the lowest corrosion current density, indicating a lower corrosion rate. Electrochemical impedance spectroscopy (EIS) tests show that at Si = 0.3, the alloy has the largest capacitive arc radius. The charge-transfer resistance (RCT) for the alloys with the Si contents of 0.1, 0.3, and 0.5 are 2.532 × 10⁵ Ω·cm², 4.088 × 10⁵ Ω·cm², 4.484 × 10⁵ Ω·cm², and 2.083 × 10⁵ Ω·cm², respectively. FeCrNiAl_0.7Cu_0.3Si_0.3 HEA has the highest RCT, which indicates a more stable passivation film and better resistance to chloride ion intrusion. The corrosion morphology observed after polarization testing shows that all alloys exhibit intergranular corrosion characteristics. The Si content alters the distribution of passivation film-forming elements, Cr and Ni. Compared to other alloys, the corrosion morphology of FeCrNiAl_0.7Cu_0.3Si_0.3 HEA is more complete. Combining the polarization, EIS, and corrosion morphology results, it can be concluded that FeCrNiAl_0.7Cu_0.3Si_0.3 HEA exhibits the best corrosion resistance in the 3.5% NaCl solution. Full article

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18 pages, 10064 KiB

Open AccessArticle

Coatings Applied to the Optimization of Portulaca oleracea L. Seed Pellet Formulation Based on Mixture Design

by Jinhua Sun, Fen Liu, Yanqin Xu and Weiming Hu

Coatings 2025, 15(3), 341; https://doi.org/10.3390/coatings15030341 - 15 Mar 2025

Viewed by 639

Abstract

Portulaca oleracea L. is an important herb with the same origin in medicine and food. To achieve the precise sowing of P. oleracea, this study employed a mixed experimental design to optimize the pellet formulation of the seeds. Fillers such as kaolin, [...] Read more.

Portulaca oleracea L. is an important herb with the same origin in medicine and food. To achieve the precise sowing of P. oleracea, this study employed a mixed experimental design to optimize the pellet formulation of the seeds. Fillers such as kaolin, bentonite, and talcum powder were used, along with binders including polyvinyl alcohol, sodium alginate, and sodium carboxymethyl cellulose. The physical characteristics and germination properties of the pelletized seeds were evaluated to determine the optimal formulation. The results indicated that, after pelletizing, the seeds exhibited a higher seed viability and vigor, germination rate, and germination index. Specifically, the seed singulation rate correlated positively with the kaolin content, the disintegration rate was proportional to the amount of talcum powder added, and the compression resistance was positively correlated with the bentonite ratio. Using response optimization, the optimal formulation of fillers used for pelletizing P. oleracea seeds was identified as 17% talcum powder, 16% kaolin, and 67% bentonite. Single-factor experiments showed that using PVP as a binder at a mass fraction of 10% resulted in improved pelletizing indices. This study not only optimized the pelletizing formulation of P. oleracea seeds based on physical and germination properties, but also expanded the application of pelletizing in the processing of the seeds of traditional Chinese herbs. It holds significant implications for the mechanized production of small, pelletized seeds of traditional Chinese herbs. Full article

(This article belongs to the Section Coatings for Food Technology and System)

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13 pages, 2308 KiB

Open AccessArticle

A Large-Scale Preparation Approach for Daytime Radiative Cooling Using SiO₂ Hollow Microsphere Composite Film

by Changhai Li, Xiaojie Sun, Yuting Yang, Baojian Liu, Haotian Zhang, Rong He, Rongjun Zhang, Yuxiang Zheng, Songyou Wang, Young-Pak Lee and Liangyao Chen

Coatings 2025, 15(3), 340; https://doi.org/10.3390/coatings15030340 - 14 Mar 2025

Viewed by 477

Abstract

Radiative cooling is a passive cooling strategy that dissipates heat externally through the atmospheric window (8–13 μm). This study presents a radiative cooling film with a simple and cost-effective fabrication process. The film was fabricated by mixing SiO₂ hollow microspheres with a [...] Read more.

Radiative cooling is a passive cooling strategy that dissipates heat externally through the atmospheric window (8–13 μm). This study presents a radiative cooling film with a simple and cost-effective fabrication process. The film was fabricated by mixing SiO₂ hollow microspheres with a UV-curable resin, employing a photopolymerization-induced phase separation method. The resulting gradient refractive index structure enhanced thermal radiation emissivity. At an optimal silica-to-resin mass ratio of 1:1.5 and a film thickness of 1.1 mm, the film achieved a solar reflectivity of 85% and an emissivity of 91% within the atmospheric window. Outdoor experiments conducted in both summer and winter demonstrated stable cooling performance. Under a solar irradiance of 796.9 W/m² (summer), the film reduced surface temperature by 10 °C compared to ambient air and 20 °C compared to an uncoated glass substrate, achieving a radiative cooling power of 76.7 W/m². In winter (solar irradiance of 588.8 W/m²), the film maintained a significant cooling effect, though with reduced efficiency due to lower solar exposure. Furthermore, long-term stability tests over six months showed that the film retained high solar reflectivity and infrared emissivity, indicating good durability. Overall, the developed radiative cooling films demonstrate excellent optical properties, structural stability, and cooling efficiency, making it a promising candidate for real-world radiative cooling applications. Further studies on environmental resilience and optimization under diverse climatic conditions are necessary for broader deployment. Full article

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32 pages, 13276 KiB

Open AccessArticle

Corrosion Analysis of Bronze Arrowheads from the Minyue Kingdom Imperial City Ruins

by Lei Zhang, Liang Zheng, Yile Chen, Ruyi Zheng, Lei Huang, Jiali Zhang, Binwen Yan and Zirong Chen

Coatings 2025, 15(3), 339; https://doi.org/10.3390/coatings15030339 - 14 Mar 2025

Viewed by 480

Abstract

This study investigates the material properties, metallurgical processes, and corrosion mechanisms of bronze arrowheads excavated from the Imperial City of the Minyue Kingdom, a UNESCO World Heritage site in Wuyishan, Fujian, China. Using optical microscopy, SEM-EDS, XRF, XRD, and Raman spectroscopy, the researchers [...] Read more.

This study investigates the material properties, metallurgical processes, and corrosion mechanisms of bronze arrowheads excavated from the Imperial City of the Minyue Kingdom, a UNESCO World Heritage site in Wuyishan, Fujian, China. Using optical microscopy, SEM-EDS, XRF, XRD, and Raman spectroscopy, the researchers analyzed the cross-section and corrosion layers of the artifacts. Results show that the arrowheads are Cu-Sn-Pb alloys, with Cu (70.76%), Sn (8.73%), and Pb (8.72%), optimizing hardness, toughness, and casting performance. Corrosion analysis reveals a surface layer rich in Cu₂O, CuO, SnO₂, and Cu₂(OH)₂CO₃, driven by oxidation, carbonation, and sulfidation reactions. The corrosion layer exhibits stratification, porosity, and cracks, indicating the influence of oxygen, carbonate ions, and sulfides in burial environments. This study provides crucial insights into ancient bronze metallurgy and the long-term preservation of cultural relics. Full article

(This article belongs to the Special Issue Functional Coatings for Cultural Heritage Conservation)

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18 pages, 5609 KiB

Open AccessArticle

Construction of High-Load-Bearing Capacity Polyamide-Imide Self-Lubricating Coatings with Various Nanoparticles Through Worn Surface of Cobblestone-like Road

by Wenyong Ye, Mengchuan Niu, Lijie Bian, Chunjian Duan, Chuanping Gao, Pingyu Zhang, Yujuan Zhang and Shengmao Zhang

Coatings 2025, 15(3), 338; https://doi.org/10.3390/coatings15030338 - 14 Mar 2025

Cited by 1 | Viewed by 422

Abstract

Polymer composite coatings exhibit excellent mechanical properties, chemical resistance, and self-lubricating characteristics, providing an effective solution to address the failure of transmission components under harsh operating conditions, including high-speed, high-pressure, and oil-deficient environments, which often lead to excessive friction and limited bearing performance. [...] Read more.

Polymer composite coatings exhibit excellent mechanical properties, chemical resistance, and self-lubricating characteristics, providing an effective solution to address the failure of transmission components under harsh operating conditions, including high-speed, high-pressure, and oil-deficient environments, which often lead to excessive friction and limited bearing performance. This study fabricated three polyamide-imide (PAI) composite coatings modified with monodisperse surface-modified nano-silica (SiO₂) via direct spraying and compared their physicochemical parameters. The tribological performance of the three coatings was evaluated using ring-block high-speed friction and wear tester under continuous loading conditions. The tests were conducted using diesel engine oil CI4-5W40, supplemented with oil-soluble cerium dioxide (CeO₂) nanoparticles as an energy-efficient and restorative additive, as the lubricating medium. The experimental results demonstrated that the PAI composite coating exhibited a load-bearing capacity exceeding 1000 N (66 MPa). The wear mechanism analysis reveals that CeO₂ nanoparticles embedded in the coating surface form a cobblestone-like protective layer. This unique microstructure compensates for the surface pits generated by PAI matrix transfer and minimizes direct contact between the coating and steel ring. Additionally, the synergistic interaction between short carbon fiber (SCF) and the tribofilm contributes to the exceptional tribological properties of the coating, including coefficients of friction as low as 0.04 and wear rates below 0.41 × 10⁻⁸ mm³/N·m. The experimental findings could provide an experimental and theoretical foundation for the application of coatings under conditions involving finished lubricants. Full article

(This article belongs to the Special Issue Tribological Behavior and Mechanical Performance of Coatings and Materials)

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24 pages, 4813 KiB

Open AccessArticle

Metagenomics of the Surface of an Architectural Heritage Site: A Case Study of the Ji Family’s Residence in the Southeast of Shanxi Province, China

by Yanyu Li, Mingyi Zhao, Jinyan Jiang, Yile Chen, Haojie Chen, Liang Zheng, Huanhuan Chen and Yue Wu

Coatings 2025, 15(3), 337; https://doi.org/10.3390/coatings15030337 - 14 Mar 2025

Viewed by 639

Abstract

Microbial corrosion poses a significant threat to architectural heritage worldwide. This study used metagenomics to investigate microbial diversity and taxonomic groups present in the door walls of the Ji family’s residential houses, as well as their biological functions and chemical cycles. Taxonomic annotation [...] Read more.

Microbial corrosion poses a significant threat to architectural heritage worldwide. This study used metagenomics to investigate microbial diversity and taxonomic groups present in the door walls of the Ji family’s residential houses, as well as their biological functions and chemical cycles. Taxonomic annotation revealed the predominant microbial taxa associated with wall corrosion, shedding light on their potential impact on structural integrity. Moreover, analyzing the metabolites and pathways present in these microbial communities allows for a thorough understanding of their functional capabilities. Our results revealed that areas with significant damage (dwelling bad door (DBD) and dwelling bad wall (DBW)) exhibited a higher microbial diversity compared to undamaged areas (dwelling good door (DGD) and dwelling good wall (DGW)), with variations in the occurrence of archaeal and bacterial species. The presence of bacteria was found to be connected with impaired function in DBW, whereas changes in the community patterns of Sphingobium and Sphingomonas, as well as a decrease in Cercospora proportion and an increase in Fusarium proportion, were correlated with damage in DBD. Both the Entner–Doudoroff (ED) route and sulfide oxidation processes were observed in both damaged locations (DBD and DBW). However, significant nitrogen-cycling mechanisms, including dissimilatory nitrate reduction to ammonium, were only found in DBW. Furthermore, DBD specifically detected the shift from methyl mercaptan (MMPA) to methyl mercaptan (MeSH). This research highlights the intricate interplay between microbial communities and the physical deterioration of residential structures, emphasizing the importance of understanding microbial ecology in mitigating such issues. Full article

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12 pages, 4676 KiB

Open AccessArticle

Enhancement of (100) Orientation and Dielectricity in PZT Thin Films Prepared by Radio Frequency Magnetron Sputtering Method

by Xing Wang and Helin Zou

Coatings 2025, 15(3), 336; https://doi.org/10.3390/coatings15030336 - 14 Mar 2025

Viewed by 393

Abstract

PZT thin films with a sol–gel-derived seed layer of Pb_1.2(Zr_0.3, Ti_0.7)O₃ were deposited on Pt/Ti/SiO₂/Si substrates via the magnetron sputtering process. The purpose of this present study was to investigate the influence of sputtering [...] Read more.

PZT thin films with a sol–gel-derived seed layer of Pb_1.2(Zr_0.3, Ti_0.7)O₃ were deposited on Pt/Ti/SiO₂/Si substrates via the magnetron sputtering process. The purpose of this present study was to investigate the influence of sputtering process parameters and heat treatment parameters on the crystal orientation, microstructure, and dielectric behaviors of PZT films. X-ray diffraction (XRD) analysis shows that the (100) orientation degree of the PZT films first increases and then decreases with the increase in oxygen partial pressure during sputtering. The PZT film annealed at a temperature of 550 °C exhibits a pure (100) perovskite phase. There are no significant changes in crystal orientation and the (100) orientation degree with increasing annealing time. An improved surface density, more uniform grains, and clear grain boundaries were detected by scanning electron microscope (SEM) characterization as the annealing time increased to 30 min. Optimal dielectricity was obtained in the film deposited on an O₂/Ar composition of 10/90 with a sputtering pressure of 2 Pa and annealed at 600 °C for 30 min, which presents a permittivity of 852 and a loss factor of 0.026 at a frequency of 1 kHz and a remanent polarization of 18.5 μC/cm². Full article

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19 pages, 13259 KiB

Open AccessArticle

Impact of Surface Tension and Surface Energy on Spray Coating Paper with Polysaccharide-Based Biopolymers

by Anna Mayrhofer and Wolfgang Bauer

Coatings 2025, 15(3), 335; https://doi.org/10.3390/coatings15030335 - 14 Mar 2025

Viewed by 449

Abstract

The demand for sustainable packaging has increased the interest in biopolymer coatings as alternatives to plastic-based barriers on paper and board. Alginate and chitosan offer promising barrier properties by improving gas barrier and grease resistance. However, their high viscosity at low solid contents [...] Read more.

The demand for sustainable packaging has increased the interest in biopolymer coatings as alternatives to plastic-based barriers on paper and board. Alginate and chitosan offer promising barrier properties by improving gas barrier and grease resistance. However, their high viscosity at low solid contents presents challenges for uniform coatings, especially in possible future large-scale applications but also in existing research. This study evaluates spray coating, a non-conventional application method in the paper industry, to apply biopolymer coatings, an approach underexplored in previous studies. The effects of substrate surface energy and biopolymer surface tension on air permeability, grease resistance, and water vapor transmission were evaluated. Contact angle measurements showed that surface energy strongly influences the wetting behavior of these biopolymers, with hydrophilic substrates and lower-surface-energy liquids promoting better droplet spreading. This improved wetting resulted in better barrier performance at low application weights, further enhanced by surfactant addition. At higher application weights, surface energy had less impact on barrier properties. SEM imaging revealed drying defects at increased coat weights, affecting film integrity. These findings demonstrate the potential of spray coating as a scalable method for biopolymer application while highlighting the need for optimized drying conditions to enhance film uniformity and barrier performance. Full article

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16 pages, 3900 KiB

Open AccessArticle

Synthesis of LTA Zeolite from Beach Sand: A Solution for CO₂ Capture

by Clenildo de Longe, Aryandson da Silva, Anne Beatriz Figueira Câmara, Lindiane Bieseki, Luciene Santos de Carvalho, Sibele Berenice Castellã Pergher and Mariele Iara Soares de Mello

Coatings 2025, 15(3), 334; https://doi.org/10.3390/coatings15030334 - 14 Mar 2025

Viewed by 437

Abstract

Emissions caused by polluting gases, such as carbon dioxide, are one of the main contributors to the generation of the greenhouse effect that leads to global warming, responsible for climate change. An alternative to mitigating these emissions is the use of adsorbents capable [...] Read more.

Emissions caused by polluting gases, such as carbon dioxide, are one of the main contributors to the generation of the greenhouse effect that leads to global warming, responsible for climate change. An alternative to mitigating these emissions is the use of adsorbents capable of capturing CO₂. Zeolites are considered one of the most effective adsorbents in gas adsorption and separation technologies due to their high specific area and pore size and, consequently, greater adsorption capacity when compared to other commonly used materials. Despite this, reagents used in syntheses as the source of silica often make obtaining these materials more expensive. Seeking to overcome this limitation, in this work, materials (for CO₂ capture) were developed with a zeolitic structure using a low-cost alternative source of silica from beach sand called MPI silica to make the synthesis process eco-friendly. The crystallization time of the materials was studied, obtaining an LTA zeolite with MPI silica in a period of 1 h (ZAM 1 h), with a relative crystallinity of 74.26%. The materials obtained were characterized using the techniques of X-ray diffraction (XRD), X-ray fluorescence (XRF), absorption spectroscopy in the infrared region with Fourier transform (FTIR), scanning electron microscopy (SEM), and thermal analysis. The evaluation of the experimental adsorption isotherms showed that the zeolite LTA Aerosil^®200 (standard zeolite) and MP had adsorption capacities of 5.25 mmol/g and 4.83 mmol/g of CO₂, respectively. The evaluation of mathematical models indicated that the LTA zeolites fit the Temkin model best and had the same trend, with calculated adsorption capacities of 3.97 mmol/g and 3.75 mmol/g, respectively. Full article

(This article belongs to the Special Issue Advanced Technology in Environmental Remediation and Resource Utilization, 2nd Edition)

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