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Coatings, Volume 14, Issue 2 (February 2024) – 92 articles

Cover Story (view full-size image): During the early stages of growth of nanodiamond crystals (NCDs) inside a linear antenna microwave plasma CVD reactor, the substrate temperature rises over time via plasma heating. The NCD film remains discontinuous on the DND-seeded substrates and can only fully coalesce once the temperature becomes stable around 263 °C after 2 hours of CVD, even at low 1100W MW power. Substrate-to-stage distance, addition of CO2, CH4 percentages in the gas recipe, type of substrates, and pulse mode of MW input power were other factors which determined the early stages of NCD growth. View this paper
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17 pages, 7095 KiB  
Review
Sulfonated Molecules and Their Latest Applications in the Field of Biomaterials: A Review
by Ambreen Akram, Mujahid Iqbal, Aqeela Yasin, Kun Zhang and Jingan Li
Coatings 2024, 14(2), 243; https://doi.org/10.3390/coatings14020243 - 19 Feb 2024
Viewed by 899
Abstract
This review provides an overview of the latest applications of sulfonated molecules in biomaterials. Sulfonation, a chemical modification process introducing sulfonic acid groups, enhances biomaterial properties. This review explores the effect of sulfonation and recent innovations in biomaterial applications. It covers hydrogels, scaffolds, [...] Read more.
This review provides an overview of the latest applications of sulfonated molecules in biomaterials. Sulfonation, a chemical modification process introducing sulfonic acid groups, enhances biomaterial properties. This review explores the effect of sulfonation and recent innovations in biomaterial applications. It covers hydrogels, scaffolds, and nanoparticles, emphasizing sulfonation’s unique advantages. The impact on cellular responses, including adhesion, proliferation, and differentiation, is discussed. This review also addresses sulfonated biomaterials’ role in regenerative medicine, drug delivery, and tissue engineering challenges. It also provides a small overview of the sources and features of marine-derived sulfonated molecules, emphasizing their potential roles in advancing scientific research. As a novel aspect, an unconventional complex, “traditional Chinese medicine” and its sulfonation method have come to the forefront after a thousand years of history. This article concludes with a reflection on current research and future avenues, highlighting sulfonation’s transformative potential in biomedicine. Full article
(This article belongs to the Special Issue Advanced Alloy Degradation and Implants)
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14 pages, 7634 KiB  
Article
The Icing Characteristics of a 1.5 MW Wind Turbine Blade and Its Influence on the Blade Mechanical Properties
by Yexue Han, Zhen Lei, Yuxiao Dong, Qinghui Wang, Hailin Li and Fang Feng
Coatings 2024, 14(2), 242; https://doi.org/10.3390/coatings14020242 - 19 Feb 2024
Viewed by 701
Abstract
Ice accumulation significantly impacts the mechanical properties of wind turbine blades, affecting power output and reducing unit lifespan. This study explores the icing characteristics and their effects on a 1.5 megawatt (MW) wind turbine blade’s mechanical properties under various conditions, including wind speeds [...] Read more.
Ice accumulation significantly impacts the mechanical properties of wind turbine blades, affecting power output and reducing unit lifespan. This study explores the icing characteristics and their effects on a 1.5 megawatt (MW) wind turbine blade’s mechanical properties under various conditions, including wind speeds of 5 m per second (m/s) and 10 m per second, temperatures of −5 degrees centigrade (°C) and −10 degrees centigrade, and different liquid water contents, by using icing wind tunnel tests and structural statics analysis. The research reveals that ice predominantly forms in an irregular pattern on the leading edge of the blade. It is easy to produce corner ice and ice skating when the icing temperature and wind speed are higher, and the icing surface is rougher. When the other conditions remain unchanged, the decrease in temperature, an increase in wind speed, or a rise in liquid water content all lead to an increase in the average thickness of icing and the volume of icing at the leading edge, with the effect of the wind speed on the two being 147.8% and 147.9%, the effect of the liquid water content on the two being 39.9% and 53.5%, and the effect of the temperature on the two being 24.6% and 13.2%. The study finds that the blade tip experiences the maximum displacement in both iced and non-iced states, although the positions of peak equivalent stress and strain vary. The above study will also provide references for the design of new wind turbine blades and the anti-icing maintenance of wind turbine generator sets. Full article
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18 pages, 5478 KiB  
Article
Enhanced Biocidal Activity of Heterophase Zinc Oxide/Silver Nanoparticles Contained within Painted Surfaces
by Olga Bakina, Elizaveta Pikuschak, Anna Prokopchuk, Elena Evplonova, Tatiana Plaksina, Alexandra Avgustinovich, Liudmila Spirina, Alexander Vorozhtsov, Nikolay Yakovlev and Marat Lerner
Coatings 2024, 14(2), 241; https://doi.org/10.3390/coatings14020241 - 19 Feb 2024
Viewed by 846
Abstract
Today, one of the biggest challenges is infections in the painted walls of hospitals. Acrylic-based paints are a target of antibiotic-resistant microorganisms since they contain cellulosic compounds as thickeners. The aim of this study was to synthesize and investigate the biocidal activity and [...] Read more.
Today, one of the biggest challenges is infections in the painted walls of hospitals. Acrylic-based paints are a target of antibiotic-resistant microorganisms since they contain cellulosic compounds as thickeners. The aim of this study was to synthesize and investigate the biocidal activity and toxicity of heterophase ZnO-Ag nanoparticles fixed in water-based acrylic paint layers in reference to a nontreated water-based paint. The ZnO-Ag nanoparticles with average particle sizes of about 80 nm were simply obtained by electrical explosion of two twisted wires in an oxygen-containing atmosphere. The nanoparticles and modified paint were characterized using SEM, TEM, XPS, and XRD techniques. The antimicrobial activity of the nanoparticles and modified paint layers was tested against P. aeruginosa, S. aureus, MRSA, E. coli bacteria, and C. albicans using ISO 22196. The antiviral activity against smallpox virus was tested according to ISO 21702. Flow cytometry tests were used to investigate the toxicity of the modified paint coating. As-synthesized nanoparticles had “Janus-like” morphology, with a clear interface inside the nanoparticle. Nanoparticles had enhanced antibacterial activity, which is based on the nanoparticle photocatalytic activity in water decomposition and reactive oxygen species generation. The paint coating with a ZnO-Ag nanoparticle mass ratio of 1.0 wt.% displayed significant antibacterial activity (more than a 99% reduction) and 100% antifungal activity. In addition, this coating inactivates >99% of the virus after 2 h of contact relative to a nontreated control paint. The paint coating showed low toxicity against the sensitive 3T3 fibroblast cell line. More than 90% cell viability was observed after 24 h of incubation with the sample extract. Therefore, heterophase ZnO-Ag nanoparticles have high biocidal activity and low toxicity use and can be applied to other commercial water-based paints to improve their performance against pathogens. Full article
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17 pages, 18245 KiB  
Article
Corrosion Behavior of Aluminum Alloys in Different Alkaline Environments: Effect of Alloying Elements and Anodization Treatments
by Riccardo Fabris, Giulia Masi and Maria Chiara Bignozzi
Coatings 2024, 14(2), 240; https://doi.org/10.3390/coatings14020240 - 19 Feb 2024
Viewed by 1094
Abstract
Aluminum alloys are extensively used to manufacture mechanical components. However, when exposed to alkaline environments, like lubricants, refrigerants, or detergents, they can be corroded, reducing their durability. For this reason, the aim of this study is to investigate the influence of aggressive alkaline [...] Read more.
Aluminum alloys are extensively used to manufacture mechanical components. However, when exposed to alkaline environments, like lubricants, refrigerants, or detergents, they can be corroded, reducing their durability. For this reason, the aim of this study is to investigate the influence of aggressive alkaline solutions (i.e., pH and presence of chlorides) on the corrosion resistance of three aluminum alloys (AA 5083-H111, AA 6082-T6, and AA 7075-T6) with and without anodizing treatments. Open circuit potential (EOCP) and anodic polarization measurements were carried out and typical corrosion parameters such as corrosion current density (icor) and corrosion rate (CR) were determined. Morphology of the corrosion attack and samples microstructure were investigated by scanning electron microscope. Results show that corrosion behavior of the three investigated alloys is influenced by (i) the aggressiveness of the testing environments; (ii) the thickness of the anodizing treatment; (iii) the alloy chemical composition; (iv) the distribution of intermetallic phases in the aluminum matrix. Moreover, three galvanic series have been built also testing other metallic alloys commonly used in mechanical applications, i.e., carbon steel (C40), stainless-steel (AISI 304), and Cu-based alloys (Cu-Ni alloy and CW 617 N, respectively). Results clearly indicate that galvanic series play a fundamental role when it is necessary to select an alloy for a specific environment, highlighting the thermodynamic conditions for corrosion occurrence. On the other hand, kinetic measurements and microstructural studies carried out on the three aluminum alloys stress the importance of the surface treatments and relevant thickness as well as the effect of metal exposure. Future work will involve the study of other surface treatments on aluminum alloys and the evaluation of their corrosion behavior in acidic environments. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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16 pages, 8498 KiB  
Article
Micron-Smooth, Robust Hydrophobic Coating for Photovoltaic Panel Surfaces in Arid and Dusty Areas
by Rongrong Guo, Yuanhao Wang, Hao Lu, Shifeng Wang, Bohan Wang and Qiyu Zhang
Coatings 2024, 14(2), 239; https://doi.org/10.3390/coatings14020239 - 18 Feb 2024
Viewed by 888
Abstract
Photovoltaic (PV) power generation is a clean energy source, and the accumulation of ash on the surface of PV panels can lead to power loss. For polycrystalline PV panels, self-cleaning film is an economical and excellent solution. However, the main reasons why self-cleaning [...] Read more.
Photovoltaic (PV) power generation is a clean energy source, and the accumulation of ash on the surface of PV panels can lead to power loss. For polycrystalline PV panels, self-cleaning film is an economical and excellent solution. However, the main reasons why self-cleaning coatings are currently difficult to use on a large scale are poor durability and low transparency. It is a challenge to improve the durability and transparency of self-cleaning thin films for PV panel surface against ash accumulation. Therefore, in this paper, a resin composite film containing modified silica components was designed and synthesized, mainly by the organic/inorganic composite method. A transparent hydrophobic coating with nano-micro planar structures was constructed, which primarily relies on the hydrophobic properties of the compound itself to build the hydrophobic oleophobic coating. The layer has a micrometer-scale smooth surface structure and high transparency, with a 0.69% increase in light transmittance compared with uncoated glass, and the durability is good. It is mainly applied to the surface of photovoltaic devices, which can alleviate the dust accumulation problem of photovoltaic panels in arid, high-temperature, and dusty areas and reduce the maintenance cost of them. Full article
(This article belongs to the Special Issue Recent Advances in Hydrophobic Surface and Materials)
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11 pages, 23726 KiB  
Article
Microstructure, Wear Resistance and Corrosion Resistance of CrN Coating with Platinum-Iridium Co-Doping
by Di Yang, Feng Yan, Weilun Zhang and Zhiwen Xie
Coatings 2024, 14(2), 238; https://doi.org/10.3390/coatings14020238 - 18 Feb 2024
Cited by 1 | Viewed by 825
Abstract
A novel Pt-Ir co-doping strategy was devised to enhance the corrosion resistance of CrN coating. The deposited CrN coating exhibits a coherent growth pattern, resulting in significant mechanical strength and large grain sizes. However, during the corrosion process, corrosive fluids infiltrate through growth [...] Read more.
A novel Pt-Ir co-doping strategy was devised to enhance the corrosion resistance of CrN coating. The deposited CrN coating exhibits a coherent growth pattern, resulting in significant mechanical strength and large grain sizes. However, during the corrosion process, corrosive fluids infiltrate through growth defects, leading to inadequate corrosion resistance of the coating. By incorporating Pt-Ir atoms as dopants, coherent grain growth is effectively hindered, yielding a uniformly smooth surface. Simultaneously, localized non-coherent lattice growth occurs due to co-doping in the coatings, impacting the mechanical properties of CrN-PtIr coatings and causing multidirectional fracture. Nevertheless, this dense coating surface impedes the penetration of corrosive fluids and enhances the corrosion resistance of the coating to some extent. Full article
(This article belongs to the Special Issue Advances in Corrosion Resistant Coatings)
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12 pages, 2472 KiB  
Article
Promising Antifungal Activity of Cedrela fissilis Wood Extractives as Natural Biocides against Xylophagous Fungi for Wood Artwork of Cultural Heritage
by Camila Sofía Vovchuk, Tomás González Garello, Valeria Pilar Careaga and Alejandra Teresa Fazio
Coatings 2024, 14(2), 237; https://doi.org/10.3390/coatings14020237 - 18 Feb 2024
Cited by 1 | Viewed by 729
Abstract
Xylophagous fungi are able to thrive inside wood because they produce enzymes that can degrade it and cause significant damage. Due to this process, in the case of wood that forms part of the structure of a building or furniture, xylophagous fungi pose [...] Read more.
Xylophagous fungi are able to thrive inside wood because they produce enzymes that can degrade it and cause significant damage. Due to this process, in the case of wood that forms part of the structure of a building or furniture, xylophagous fungi pose a serious problem that needs to be addressed, as they can compromise the integrity and durability of the wood. The aim of this work was to obtain extractives from Cedrela fissilis wood in order to conduct a preliminary evaluation of their antifungal activity against xylophagous fungi Trametes trogii (white rot), Pycnoporus sanguineus (white rot), and Chaetomium globosum (soft rot). The antifungal activity of the extractives was evaluated against these xylophagous fungi through tests of growth fungal colonies with the extractives in Petri dishes. All the evaluated extractives showed antifungal activity against all the fungi tested, demonstrating their potential use as natural biocides for wood artwork of Cultural Heritage. Full article
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9 pages, 2474 KiB  
Article
Polarization-Angle-Insensitive Dual-Band Perfect Metamaterial Absorbers in the Visible Region: A Theoretical Study
by Zhihui Xiong, Zhixi Li, Guangqiang He, Kecheng Su, Yien Huang and Guowei Deng
Coatings 2024, 14(2), 236; https://doi.org/10.3390/coatings14020236 - 18 Feb 2024
Viewed by 541
Abstract
Metamaterial absorbers have been studied extensively due to their potential applications in the field of photonics. In this paper, we propose a simulation study of a polarization-angle-insensitive dual-band perfect metamaterial absorber with absorption peaks at 654 and 781 nm, respectively. By adjusting the [...] Read more.
Metamaterial absorbers have been studied extensively due to their potential applications in the field of photonics. In this paper, we propose a simulation study of a polarization-angle-insensitive dual-band perfect metamaterial absorber with absorption peaks at 654 and 781 nm, respectively. By adjusting the structure parameters, dielectric thickness, and refractive index, the obtained absorber has high scalability in the visible wavelength region. To further understand the performance of the cross-structure absorber, analysis of its electric and magnetic field distribution shows that it produces two resonance modes leading to different absorption properties. In addition, the position and intensity of the absorption peaks were found to be unchanged with increasing incident polarization angle, indicating that the absorber is insensitive to the polarization of the incident light. The absorber has great flexibility and has good application potential in sensing and detection. Full article
(This article belongs to the Special Issue Optoelectronic Thin Films)
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10 pages, 5999 KiB  
Article
NIR to LWIR Dichroic Beamsplitter Designed and Manufactured for Space Optical Remote Sensor
by Lin Jiang, Yang Qin, Tianyan Yu, Weibo Duan and Dingquan Liu
Coatings 2024, 14(2), 235; https://doi.org/10.3390/coatings14020235 - 18 Feb 2024
Viewed by 722
Abstract
The infrared dichroic beamsplitter plays an important role in infrared multi-band imaging systems, especially for infrared remote sensing. This paper presents the design and preparation of a dichroic beamsplitter that is capable of reflecting near infrared (NIR) and shortwave infrared (SWIR), and transmitting [...] Read more.
The infrared dichroic beamsplitter plays an important role in infrared multi-band imaging systems, especially for infrared remote sensing. This paper presents the design and preparation of a dichroic beamsplitter that is capable of reflecting near infrared (NIR) and shortwave infrared (SWIR), and transmitting medium wave infrared (MWIR) as well as longwave infrared (LWIR). A single crystal germanium (Ge) sheet is used as the substrate of the dichroic beamsplitter, while Ge, zinc sulfide (ZnS) and ytterbium trifluoride (YbF3) are selected as coating materials. The average reflectance of the dichroic beamsplitter is more than 95% in bands 1.28 to 1.38 μm, 1.58 to 1.83 μm, and 1.95 to 2.32 μm, and the average transmittance is more than 92% in bands 3.7 to 6.2 μm and 7.5 to 12.5 μm at an incident angle of 45°. The dichroic beamsplitter has been successfully applied in the optical system of infrared remote sensing. It provides a technical approach for other optical systems to separate the optical spectrum from NIR to LWIR. Full article
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19 pages, 6070 KiB  
Article
Hybrid Organic–Inorganic Biomaterials as Drug Delivery Systems: A Molecular Dynamics Study of Quercetin Adsorption on Amorphous Silica Surfaces
by Giuseppina Raffaini, Pasqualina Pirozzi, Michelina Catauro and Antonio D’Angelo
Coatings 2024, 14(2), 234; https://doi.org/10.3390/coatings14020234 - 17 Feb 2024
Viewed by 1064
Abstract
Many important drugs in pharmaceutical applications are poorly soluble. Solubilization, which is diffusion through biological barriers, and the control of local administration are crucial steps for bioavailability and to avoid cytotoxic effects. Hybrid organic/inorganic biomaterials can incorporate drugs for in situ release after [...] Read more.
Many important drugs in pharmaceutical applications are poorly soluble. Solubilization, which is diffusion through biological barriers, and the control of local administration are crucial steps for bioavailability and to avoid cytotoxic effects. Hybrid organic/inorganic biomaterials can incorporate drugs for in situ release after implantation. Molecular Mechanics (MM) and Molecular Dynamics (MD) simulations are useful tools for investigating intermolecular interactions between drug and biomaterial surfaces at the atomistic level for these applications. This work studies quercetin, a flavonoid drug important for its anti-inflammatory, antioxidant, and anticancer properties, and the amorphous SiO2 surface using a simulation protocol proposed in previous work related to ketoprofen drugs. After adsorption on the amorphous silica surface, the adsorption process of quercetin drug molecules at two different drug concentrations near a hydrated and then dried silica surface is investigated. Interestingly, these theoretical results are compared with experimental data obtained via Fourier Transform Infrared Spectroscopy (FT–IR) spectra related to quercetin molecules homogenously entrapped in a silica matrix obtained via the Sol–Gel method. Favorable H– bonds and some π–π interactions among drug molecules are crucial surface interactions for the new generation of biocompatible materials capable of incorporating anti-inflammatory agents for release into the human body. Full article
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17 pages, 3174 KiB  
Article
Reliability Evaluation of a Dynamic-Pressure Mechanical Seal Based on Liquid Film Vaporization Phase Transition
by Guangyao Bei, Xiaodong Xu, Chenbo Ma, Jianjun Sun, Yuyan Zhang and Qiuping Yu
Coatings 2024, 14(2), 233; https://doi.org/10.3390/coatings14020233 - 17 Feb 2024
Viewed by 667
Abstract
Aiming at the problem of researching the reliability of dynamic-pressure mechanical seals, this paper proposes a reliability evaluation method for dynamic-pressure mechanical seals based on the Monte Carlo method. Based on the influence of the mass transfer coefficient on vaporization phase transition, a [...] Read more.
Aiming at the problem of researching the reliability of dynamic-pressure mechanical seals, this paper proposes a reliability evaluation method for dynamic-pressure mechanical seals based on the Monte Carlo method. Based on the influence of the mass transfer coefficient on vaporization phase transition, a liquid film vaporization model of a hydrodynamic mechanical seal’s end face is established, and the working condition parameters and groove structure parameters are designed using the experimental design method. The vaporization characteristics of the liquid film under various parameters are analyzed, and the functional functions of the vaporization characteristics are obtained by fitting. Combined with the maximum vapor phase volume fraction when the dynamic-pressure mechanical seal changes from the liquid miscible phase to the vapor miscible phase, the limit state equation of the vapor phase volume fraction is obtained. Finally, based on the Monte Carlo simulation method, the sealing reliability under specific groove structure parameters is calculated. Our research shows that this method has practicability and effectiveness for the reliability evaluation of mechanical seals with different working conditions and different groove structures. Full article
(This article belongs to the Section Thin Films)
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24 pages, 9847 KiB  
Article
Repairing Performance of Polymer-Modified Cement-Based Thin Spray-On Liners on Pre-Cracked Rock-like Specimens
by Jinlong Teng, Xiaotong Yu, Ping Wang, Guoming Liu, Lingnan Cui and Xiangfei Cui
Coatings 2024, 14(2), 232; https://doi.org/10.3390/coatings14020232 - 17 Feb 2024
Viewed by 715
Abstract
With the development of coal mining and the increase in excavation depth, the stress on roadway surrounding rock is also increasing. This creates conditions for crack development in the roadway, so it is urgent to develop rock repair materials with excellent performance. The [...] Read more.
With the development of coal mining and the increase in excavation depth, the stress on roadway surrounding rock is also increasing. This creates conditions for crack development in the roadway, so it is urgent to develop rock repair materials with excellent performance. The ability of thin spray-on liner (TSL) to repair rock and concrete opens up the possibility of reusing abandoned roadways. The ability of TSL to support the surrounding rock is also important in preventing the generation of roadway waste. In this paper, styrene–acrylic emulsion (SAE), vinyl acetate–ethylene copolymer emulsion (VAE), and polyvinyl alcohol powder (PVA) were used to prepare three TSLs. Rock-like materials were configured using cement mortar according to similar principles. Three types of TSLs were tested for basic properties such as viscosity and mechanical strength, which provided data to support the explanation of the repair performance of TSLs. Three TSLs were used to repair pre-cracked rock-like specimens (PR). The number of brushing times and the angle of PR’s cracks were regarded as test variables. Changes in the mechanical strength of repaired PRs were tested by compressive and flexural tests. TSL repair performance was evaluated with the help of mechanical strength changes. Results show that polyvinyl alcohol powder modified cement-based thin spray-on liner is most suitable for repairing rock cracks; as the thickness of the brush slurry increases, its repair performance continues to improve. This paper can provide experience and a theoretical basis for the research of other rock repair materials, and it is also instructive for repairing shotcrete in the roadway. Full article
(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)
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17 pages, 3966 KiB  
Article
Splitting Tensile Test of ECC Functional Gradient Concrete with PVA Fiber Admixture
by Yin Xu, Qiang Liu, Xiaoqiang Zhang, Xiaofeng Xu and Peng Liu
Coatings 2024, 14(2), 231; https://doi.org/10.3390/coatings14020231 - 17 Feb 2024
Viewed by 626
Abstract
Engineered cementitious composite (ECC) functional gradient concrete has a promising application future, and its mechanical features are piquing the interest of researchers. The impacts of this strength class of concrete, interface reinforcement technique, ECC thickness (i.e., fiber dosage), and other factors on the [...] Read more.
Engineered cementitious composite (ECC) functional gradient concrete has a promising application future, and its mechanical features are piquing the interest of researchers. The impacts of this strength class of concrete, interface reinforcement technique, ECC thickness (i.e., fiber dosage), and other factors on the splitting tensile strength qualities are explored using an experimental investigation of functional gradient concrete. The splitting tensile tests of 150 mm × 150 mm × 150 mm functional gradient concrete specimens were used to explore the link between concrete strength grade, interface reinforcing technique, and ECC thickness with polyvinyl alcohol (PVA) fiber additive and functional gradient concrete. The test results show that the splitting tensile strength of functional gradient concrete increases as the concrete strength grade increases; different interfacial treatments have a significant effect on the splitting tensile strength of functional gradient concrete; and the effect of ECC thickness change on the splitting tensile strength of functional gradient concrete shows different trends, which research can be used as an experimental reference for functional gradient concrete engineering applications. Full article
(This article belongs to the Special Issue Coatings for Building Applications)
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12 pages, 6661 KiB  
Article
Effect of Aging Time on Microstructure and Properties of Cold-Rolled Ni-W-Co-Ta Medium–Heavy Alloy
by Yong Li, Yi Xiong, Hua-fei Li, Shun Han, Feng-zhang Ren and Chun-xu Wang
Coatings 2024, 14(2), 230; https://doi.org/10.3390/coatings14020230 - 16 Feb 2024
Viewed by 557
Abstract
A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium–heavy alloy with 90% thickness reduction at the aging temperature of 700 °C was performed. The results demonstrate that the volume fraction of the precipitation [...] Read more.
A systematical exploration of the effect of aging time on the microstructure and mechanical properties of cold-rolled Ni-W-Co-Ta medium–heavy alloy with 90% thickness reduction at the aging temperature of 700 °C was performed. The results demonstrate that the volume fraction of the precipitation (Ni4W), which persists under various aging times, increases from 13.7% (2 h) to 28.7% (32 h) with the extension of aging time. Meanwhile, the microstructure after aging treatment is still dominated by dislocation entanglement and dislocation walls, although the degree of lattice distortion and dislocation density attributed to heavy deformation decreases. The maximum tensile strength, yield strength, and microhardness (2286 MPa, 1989 MPa, 766 HV) of the cold-rolled Ni-W-Co-Ta medium–heavy alloy under the 16 h aging treatment at 700 °C are reached, respectively. The ductile–brittle mixed fracture morphology is maintained in the fracture morphology of the medium–heavy alloy before and after aging treatment. Full article
(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)
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16 pages, 11335 KiB  
Article
Axial Compression Bearing Capacity of Bolted Drum-Shaped Spherical Shell Joints: Experimental and Numerical Analysis
by Yajie Yan, Maoqing Liu, Zichun Zhou and Xingpeng Ma
Coatings 2024, 14(2), 229; https://doi.org/10.3390/coatings14020229 - 16 Feb 2024
Viewed by 677
Abstract
Bolted drum-shaped spherical shell joints (BDSSJs) represent a type of joint applicable to space grid structures. These joints merge the benefits of both bolted spherical joints and welded hollow spherical joints, embodying features such as a compact size, favorable centerline alignment with members, [...] Read more.
Bolted drum-shaped spherical shell joints (BDSSJs) represent a type of joint applicable to space grid structures. These joints merge the benefits of both bolted spherical joints and welded hollow spherical joints, embodying features such as a compact size, favorable centerline alignment with members, a high degree of adjustability, and high installation efficiency. Through unidirectional axial compression tests on specimens of BDSSJs, this study examines the stress distribution, force transmission pathways, ultimate bearing capacity, and failure modes of the joint, thereby determining its bearing capacity and presenting a bearing capacity calculation formula for such joints. By establishing a finite element model with parameters identical to the experimental specimens, this study analyzes the force and deformation of BDSSJs under unidirectional compression, identifying the high-stress areas during the compression process of BDSSJs. The findings of this study provide a basis for the practical engineering application of such joints, as well as theoretical support for subsequent dynamic performance into BDSSJs. Full article
(This article belongs to the Special Issue Enhanced Mechanical Properties of Metals by Surface Treatments)
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11 pages, 12013 KiB  
Communication
Interface Modulation of CoNi Alloy Decorated with Few-Layer Reduced Graphene Oxide for High-Efficiency Microwave Absorption
by Hai Xie, Jinmei Li, Yaoming Zhang, Juan Yang, Tingmei Wang and Qihua Wang
Coatings 2024, 14(2), 228; https://doi.org/10.3390/coatings14020228 - 15 Feb 2024
Viewed by 815
Abstract
Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) [...] Read more.
Metal-organic frameworks (MOFs)-derived microwave absorbers with tunable components and microstructures show great potential in microwave absorption. Herein, we report a facile thermal reduction approach for synthesizing CoNi alloy/reduced graphene oxide (CoNi/rGO) composites from bimetallic CoNi-MOFs. By tuning the ratio of graphene oxide (GO) in the precursors, the resulting CoNi/rGO-2 composite demonstrates optimal microwave absorption performance with a minimum reflection loss (RLmin) of −66.2 dB at 7.6 GHz in the C band. Moreover, the CoNi/rGO-2 with 50 wt% filler loading achieves a maximum effective absorption bandwidth (EAB) of 6.8 GHz (10.6–17.4 GHz) at a thickness of 2.5 mm, almost spanning the entire Ku band and a portion of the X band. The outstanding performance of CoNi/rGO-2 is ascribed to the high magnetic loss from the CoNi alloy and the incorporation of rGO, which induces interfacial polarization to enhance the dielectric loss and improve the impedance matching of composite. These favorable findings highlight the considerable potential and superiority of the CoNi/rGO-2 composite as an electromagnetic wave absorption material. This work sets forth a viable strategy for designing high-efficiency alloy/rGO absorbers. Full article
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14 pages, 3627 KiB  
Article
Polypyrrole/α-Fe2O3 Hybrids for Enhanced Electrochemical Sensing Performance towards Uric Acid
by Renjie Wang, Shanshan Liu, Xudong Song, Kai Jiang, Yaohui Hou, Qiaohuan Cheng, Wei Miao, Li Tian, Ying Ren and Sankui Xu
Coatings 2024, 14(2), 227; https://doi.org/10.3390/coatings14020227 - 15 Feb 2024
Viewed by 812
Abstract
Uric acid, a metabolite formed by the oxidation of purines in the human body, plays a crucial role in disease development when its metabolism is altered. Various techniques have been employed for uric acid analysis, with electrochemical sensing emerging as a sensitive, selective, [...] Read more.
Uric acid, a metabolite formed by the oxidation of purines in the human body, plays a crucial role in disease development when its metabolism is altered. Various techniques have been employed for uric acid analysis, with electrochemical sensing emerging as a sensitive, selective, affordable, rapid, and simple approach. In this study, we developed a polymer-based sensor (PPy/α-Fe2O3) for the accurate determination of uric acid levels. The PPy/α-Fe2O3 hybrids were synthesized using an uncomplicated in situ growth technique. Characterization of the samples was performed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical sensing performance towards uric acid was evaluated through cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained results demonstrated that the sensor exhibited excellent sensitivity towards uric acid detection within a wide range of 5–200 μM with a limit of detection (LOD) as low as 1.349 μM. Furthermore, this work elucidated the underlying sensing mechanism and highlighted the pivotal role played by PPy/α-Fe2O3 hybrids in enabling efficient uric acid sensing applications using electrochemical sensors. Full article
(This article belongs to the Special Issue Advances in Electrochemical Sensors and Biosensors)
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24 pages, 5728 KiB  
Article
Study on Rheological Properties and Modification Mechanism of Budun Rock Asphalt/Nano-Silica Composite Modified Asphalt
by Chaojie Li, Zhenxia Li, Tengteng Guo, Yuanzhao Chen, Shangwei Jing, Jing Wang and Lihui Jin
Coatings 2024, 14(2), 226; https://doi.org/10.3390/coatings14020226 - 14 Feb 2024
Viewed by 646
Abstract
To enhance the high and low-temperature performance of asphalt materials and extend the service life of asphalt pavement, two types of external admixtures, Butonite rock asphalt, and nano-silica are added to the asphalt. By conducting dynamic shear rheological tests and bending creep stiffness [...] Read more.
To enhance the high and low-temperature performance of asphalt materials and extend the service life of asphalt pavement, two types of external admixtures, Butonite rock asphalt, and nano-silica are added to the asphalt. By conducting dynamic shear rheological tests and bending creep stiffness tests, the high and low-temperature rheological properties of Budun rock asphalt/nano-silica composite-modified asphalt were evaluated. The distribution of Budun rock asphalt and nano-silica in asphalt was studied using scanning electron microscopy and infrared spectroscopy tests, revealing the synergistic modification mechanism of Budun rock asphalt and nano-silica. The results show that the optimal dosage of Butonite rock asphalt and nano-silica composite-modified asphalt is 25% and 5%, respectively. At this dosage, the rutting factor G*/sinδ of composite-modified asphalt at 82 °C Compared with the matrix asphalt, the frequency main curve of Budun rock asphalt/nano-silica composite-modified asphalt is higher than that of the matrix asphalt and nano-silica-modified asphalt by 4 kPa. The creep modulus S at −18 °C decreases by 117.2 MPa, indicating that the high-temperature performance, low-temperature performance, and temperature sensitivity of Budun rock asphalt/nano-silica composite-modified asphalt are significantly improved compared to the matrix asphalt; The distribution of nano-silica particles in Budun rock asphalt/nano-silica composite-modified asphalt is uniform, and together with Budun rock asphalt, it forms a stable three-dimensional network skeleton structure; Budun rock asphalt/nano-silica composite-modified asphalt has generated new functional groups, and the blending process is mainly based on physical reactions, supplemented by weak chemical reactions. Full article
(This article belongs to the Special Issue Recent Development in Novel Green Asphalt Materials for Pavement)
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13 pages, 22061 KiB  
Article
Water Lubrication of Al-Cu Composites Reinforced by Nickel-Coated Si3N4 Particles
by Yanan Peng, Qinqwen Dai, Wei Huang and Xiaolei Wang
Coatings 2024, 14(2), 225; https://doi.org/10.3390/coatings14020225 - 14 Feb 2024
Viewed by 643
Abstract
Silicon nitride (Si3N4) particle-reinforced aluminum–copper (Al-Cu) alloy matrix composites have been prepared in our previous works and experimental result shows that they can be used as a new kind of water-lubricated materials. However, the wettability between Si3N [...] Read more.
Silicon nitride (Si3N4) particle-reinforced aluminum–copper (Al-Cu) alloy matrix composites have been prepared in our previous works and experimental result shows that they can be used as a new kind of water-lubricated materials. However, the wettability between Si3N4 ceramics and Al-Cu alloys is poor and the manufacturing process is usually carried out at a high temperature of 1100 °C. To overcome this shortcoming, a layer of nickel was deposited on the surface of Si3N4 particles, forming a core-shell structure. Thus, the interface bonding property between Si3N4 and Al-Cu alloy can be improved and the lower sintering temperature can be applied. Si3N4/Al-Cu alloy composites with different proportions of Ni-coated Si3N4 were fabricated by powder matrix metallurgy technology at 800 °C, and the water lubrication properties of the composite were investigated. The experimental results show that with the increase in the particle content (10 wt%–40 wt%), the microhardness of the composites increased first and then decreased, while the porosity increased continuously. A low friction coefficient (0.001–0.005) can be achieved for the composites with the lower particle content (10 wt%–20 wt%). The major wear mechanism changes from the mechanically dominated wear during the running-in process to the tribochemical wear at the low frictional stage. Full article
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14 pages, 5795 KiB  
Article
Laser Processing of Liquid Feedstock Plasma-Sprayed Lithium Titanium Oxide Solid-State-Battery Electrode
by Arman Hasani, Mathis Luya, Nikhil Kamboj, Chinmayee Nayak, Shrikant Joshi, Antti Salminen, Sneha Goel and Ashish Ganvir
Coatings 2024, 14(2), 224; https://doi.org/10.3390/coatings14020224 - 12 Feb 2024
Viewed by 1150
Abstract
The astonishing safety and capacity characteristics of solid-state-batteries are encouraging researchers and companies to work on the manufacturing, development, and characterization of battery materials. In the present work, the effects of laser beam interaction with a liquid feedstock plasma-sprayed ceramic solid-state-battery (SSB) material [...] Read more.
The astonishing safety and capacity characteristics of solid-state-batteries are encouraging researchers and companies to work on the manufacturing, development, and characterization of battery materials. In the present work, the effects of laser beam interaction with a liquid feedstock plasma-sprayed ceramic solid-state-battery (SSB) material coating were studied. Lithium Titanium Oxide (LTO) in the form of an aqueous suspension consisting of submicron powder particles was plasma-sprayed for the first time using a high-power axial III plasma torch on an aluminum substrate. The plasma-sprayed LTO coating suspension was subsequently post-processed using a fiber laser. The energy input of the laser beam on the surface of the deposited layer was the main variable. By varying the laser power and laser processing speed, the energy input values were varied, with values of 3.8 J/mm2, 9.6 J/mm2, 765.9 J/mm2, and 1914.6 J/mm2, and their effects on some key characteristics such as laser-processed zone dimensions and chemical composition were investigated. The results indicated that changing the laser beam parameter values has appreciable effects on the geometry, surface morphology, and elemental distribution of laser-processed zones; for instance, the highest energy inputs were 33% and 152%, respectively, higher than the lowest energy input. Full article
(This article belongs to the Special Issue Laser Surface Engineering: Technologies and Applications)
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17 pages, 13016 KiB  
Article
Enhanced Osteogenic Activity and Antibacterial Properties of Graphene Oxide-Poly(Lactic Acid) Films for the Repair of Cranial Defects in Rats
by Kai Liu, Wen Lai, Jianyong Wu and Yongjian Lu
Coatings 2024, 14(2), 223; https://doi.org/10.3390/coatings14020223 - 12 Feb 2024
Viewed by 794
Abstract
The failure of bone defect repair caused by bacterial infection is a significant clinical challenge. However, the currently utilized bone graft materials lack antibacterial properties, necessitating the development of bone repair materials with both osteoinductive and antibacterial capabilities. Graphene oxide (GO) has garnered [...] Read more.
The failure of bone defect repair caused by bacterial infection is a significant clinical challenge. However, the currently utilized bone graft materials lack antibacterial properties, necessitating the development of bone repair materials with both osteoinductive and antibacterial capabilities. Graphene oxide (GO) has garnered considerable attention due to its distinctive physical, chemical, and biological characteristics. In this study, we prepared a graphene oxide-poly(lactic acid) (GO-PLA) film with exceptional biological properties. In vitro investigations demonstrated that the GO-PLA film substantially enhanced the adhesion and proliferation capacity of rat bone marrow mesenchymal stem cells (rBMSCs). Furthermore, we observed augmented alkaline phosphatase activity as well as increased expression levels of osteogenic genes in rBMSCs cultured on the GO-PLA film. Additionally, we evaluated the antibacterial activity of our samples using gram-positive Streptococcus mutans (Sm) and gram-negative Actinobacillus actinomycetemcomitans (Aa). Our findings revealed that GO doping significantly inhibited bacterial growth. Moreover, implantation experiments conducted on rat skull defects demonstrated excellent guided bone regeneration performance exhibited by the GO-PLA film. Overall, our results indicate that the GO-PLA film possesses outstanding osteogenic and antibacterial properties, making it a promising biomaterial for bone tissue regeneration. Full article
(This article belongs to the Section Thin Films)
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19 pages, 8906 KiB  
Article
Influence of Processing Parameters on Microstructure and Surface Hardness of Hypereutectic Al-Si-Fe-Mg Alloy via Friction Stir Processing
by Quan Liu, Xiaomi Chen, Kun Liu, Valentino A. M. Cristino, Kin-Ho Lo, Zhengchao Xie, Dawei Guo, Lap-Mou Tam and Chi-Tat Kwok
Coatings 2024, 14(2), 222; https://doi.org/10.3390/coatings14020222 - 12 Feb 2024
Viewed by 825
Abstract
In this study, the effects of friction stir processing (FSP) parameters on the microstructure and hardness of cast Al-Si-Fe-Mg alloy were investigated. Orthogonal arrays were applied in the design of the experiments. The selected parameters for the experiments included rotation speed, transverse speed, [...] Read more.
In this study, the effects of friction stir processing (FSP) parameters on the microstructure and hardness of cast Al-Si-Fe-Mg alloy were investigated. Orthogonal arrays were applied in the design of the experiments. The selected parameters for the experiments included rotation speed, transverse speed, penetration depth, and tilt angle. The microstructure and hardness of the FSPed Al-Si-Fe-Mg were studied using optical and scanning electron microscopy, and microhardness testing, respectively. The quadratic model was proposed to fit the experimental data of hardness. Signal-to-noise ratio (S/N) analysis showed the maximum hardness achieved when rotation speed, transverse speed, penetration depth, and tilt angle were chosen as 1600 rpm, 400 mm/min, 0.1 mm, and 1.5°, respectively. Taguchi’s analysis of variance (ANOVA) was used to determine the significant FSP parameters on hardness, which revealed that rotation speed was the most dominant processing parameter, followed by transverse speed, tilt angle, and penetration depth. Moreover, a quadratic polynomial model was developed to predict and optimize the combination of the parameters, enabling superior mechanical properties. Subsequently, the verification of the microstructure was conducted, demonstrating good agreement between the experimental observation of the microstructure and estimated outcomes. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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10 pages, 3330 KiB  
Article
Microstructure and Dry-Sliding Wear Resistance of CoCrFeNiMoTix High Entropy Alloy Coatings Produced by Laser Cladding
by Hui Liang, Jinxin Hou, Li Jiang and Zhiqiang Cao
Coatings 2024, 14(2), 221; https://doi.org/10.3390/coatings14020221 - 12 Feb 2024
Viewed by 850
Abstract
The new-type CoCrFeNiMoTix high-entropy alloy coatings were successfully devised and prepared on Q235 steel using laser cladding. Influence of Ti content on their microstructure and wear-resistance was studied systematically; the relevant mechanisms were deeply revealed. The CoCrFeNiMoTix coatings consisted of NiTi, [...] Read more.
The new-type CoCrFeNiMoTix high-entropy alloy coatings were successfully devised and prepared on Q235 steel using laser cladding. Influence of Ti content on their microstructure and wear-resistance was studied systematically; the relevant mechanisms were deeply revealed. The CoCrFeNiMoTix coatings consisted of NiTi, FCC, and BCC phases, and with the increasing of Ti content, contents of BCC phase and FCC phase gradually increased and decreased, respectively. The CoCrFeNiMoTi0.75 coating had the highest hardness (950 HV), which was about 6.5 times higher than the substrate (Q235 steel, 150 HV). According to Archard law, metal materials’ wear resistance is generally proportional to hardness; thus, the CoCrFeNiMoTi0.75 high entropy alloy coating with the highest hardness showed the best wear resistance, exhibiting a wear mechanism of slight abrasive wear. Full article
(This article belongs to the Special Issue Advances in Wear-Resistant Coatings)
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13 pages, 5567 KiB  
Article
Albumin–Rutin Nanoparticles: Design, Characterization, and Biophysical Evaluation
by Claudia G. Chilom, Adriana Elena Balan, Teodor Adrian Enache, Daniela Oprea, Monica Enculescu, Monica Florescu and Melinda David
Coatings 2024, 14(2), 220; https://doi.org/10.3390/coatings14020220 - 10 Feb 2024
Viewed by 853
Abstract
The bioavailability of the administered drugs that reach the systemic circulation is the first point in resolving the pathology of patients. Albumin-based nanoparticles represent an increasingly used strategy to deliver cancer drugs into cells that otherwise cannot overcome biological barriers. In this work, [...] Read more.
The bioavailability of the administered drugs that reach the systemic circulation is the first point in resolving the pathology of patients. Albumin-based nanoparticles represent an increasingly used strategy to deliver cancer drugs into cells that otherwise cannot overcome biological barriers. In this work, rutin (Ru), a flavonoid with anticancer and antioxidant potential, was incorporated into bovine serum albumin nanoparticles (BSA-Ru NPs), developed using the desolvation method, and the entire system was characterized and evaluated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–Vis absorption spectroscopy. The results showed that BSA and BSA–Ru NPs are uniformly distributed, have relatively large sizes, and have a time stability of more than 60%. Furthermore, the effect of these nanohybrids on the thermal stability of liposomal membranes was evaluated by surface plasmon resonance (SPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The viability evaluation was assessed by the tetrazolium salt (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) (MTS) protocol in the fibroblast L929 line and a high level of biocompatibility, confirmed by SEM results, was found. Full article
(This article belongs to the Special Issue Multilayer Coatings for Nanomaterials: From Synthesis to Applications)
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10 pages, 1932 KiB  
Article
Dependence of Nucleation Field on the Size of Soft Phase in Magnetic Hard–Soft Exchange Coupling Nanocomposites
by Fang Wang, Guoqi Hu, Pengna Zhang, Tangfu Feng, Yajuan Wang, Renbing Sun and Jian Zhang
Coatings 2024, 14(2), 219; https://doi.org/10.3390/coatings14020219 - 10 Feb 2024
Viewed by 655
Abstract
Hard–soft exchange coupling nanocomposites have critical applications in various important materials. The magnetic properties of nanocomposite permanent magnetic films improve with a higher nucleation field (Hns) of the soft magnetic phase. Hns is sensitive to the thickness (ds) [...] Read more.
Hard–soft exchange coupling nanocomposites have critical applications in various important materials. The magnetic properties of nanocomposite permanent magnetic films improve with a higher nucleation field (Hns) of the soft magnetic phase. Hns is sensitive to the thickness (ds) of the soft magnetic layer. Understanding the dependence of Hns and irreversible field (Hirr) on ds, especially at the nanometric scale, is crucial for comprehending the magnetic mechanism and facilitating the design and preparation of high-performance nanocomposite permanent magnets. However, during the high-temperature deposition process, diffusion between hard and soft magnetic phases occurs, leading to the generation of other phases. This makes it challenging to accurately reflect the relationship between Hns and ds. To address this issue, we successfully fabricated high-quality SmCo5/Fe nanocomposite bilayer films with different soft magnetic thicknesses and high textures by controlling the preparation process. We conducted a quantitative analysis of the relationship between Hns and ds within the range of 2–40 nm. Based on the experimental results, we propose a new theoretical simulation formula that enhances the understanding of the characteristics at the interface between the soft magnetic and hard magnetic phases. The theoretical simulation results show that a thin softened hard layer of about 4–6 nm thickness exists at the interfacial region, which concurrently reverses with the soft magnetic phase during the demagnetization process. Our results offer the generality and critical basis for the further study of hard–soft nanocomposite magnetic materials. Full article
(This article belongs to the Special Issue Thin-Film Synthesis, Characterization and Properties)
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19 pages, 10815 KiB  
Article
The Influence of TiO2 Nanoparticles on the Physico–Mechanical and Structural Characteristics of Cementitious Materials
by Carmen T. Florean, Horatiu Vermesan, Gyorgy Thalmaier, Bogdan V. Neamtu, Timea Gabor, Cristina Campian, Andreea Hegyi and Alexandra Csapai
Coatings 2024, 14(2), 218; https://doi.org/10.3390/coatings14020218 - 09 Feb 2024
Viewed by 849
Abstract
The urgent need for sustainable construction that corresponds to the three pillars of sustainable development is obvious and continuously requires innovative solutions. Cementitious composites with TiO2 nanoparticles (NT) addition show potential due to their improved durability, physico–mechanical characteristics, and self-cleaning capacity. This [...] Read more.
The urgent need for sustainable construction that corresponds to the three pillars of sustainable development is obvious and continuously requires innovative solutions. Cementitious composites with TiO2 nanoparticles (NT) addition show potential due to their improved durability, physico–mechanical characteristics, and self-cleaning capacity. This study aimed to evaluate the influence of NT on cementitious composites by comparing those with 2%–5% nanoparticles with a similar control sample without nanoparticles, as well as an analysis of cost growth. The experimental results showed an increase in bulk density of the material (4.7%–7.4%), reduction in large pore sizes by min. 12.5%, together with an increase in cumulative volume and cumulative specific surface area of small pore sizes, indicating densification of the material, also supported by SEM, EDS, and XRD analyses indicating acceleration of cement hydration processes with formation of specific products. The changes at microstructural level support the experimental results obtained at macrostructural level, i.e., modest but existent increases in flexural strength (0.6%–7.9%) and compressive strength (0.2%–2.6%) or more significant improvements in abrasion resistance (8.2%–58%) and reduction in water absorption coefficient (37.5%–81.3%). Following the cost–benefit analysis, it was concluded that, for the example case considered of a pedestrian pavement with a surface area of 100 m2, using 100 mm thick slabs, if these slabs were to be made with two layers, the lower layer made of cementitious composite as a reference and the upper layer with a thickness of 10 mm made of cementitious composite with 3% NT or 4% NT, the increase in cost would be acceptable, representing less than 15% compared to the cost for the exclusive use of cementitious composite without NT. Full article
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34 pages, 17972 KiB  
Review
Plasma Electrolytic Oxidation (PEO) as a Promising Technology for the Development of High-Performance Coatings on Cast Al-Si Alloys: A Review
by Patricia Fernández-López, Sofia A. Alves, Jose T. San-Jose, Eva Gutierrez-Berasategui and Raquel Bayón
Coatings 2024, 14(2), 217; https://doi.org/10.3390/coatings14020217 - 09 Feb 2024
Cited by 1 | Viewed by 1363
Abstract
Cast Al-Si alloys, recognized for their excellent mechanical properties, constitute one of the most widely employed non-ferrous substrates in several sectors, and are particularly relevant in the transport industry. Nevertheless, these alloys also display inherent limitations that significantly restrict their use in several [...] Read more.
Cast Al-Si alloys, recognized for their excellent mechanical properties, constitute one of the most widely employed non-ferrous substrates in several sectors, and are particularly relevant in the transport industry. Nevertheless, these alloys also display inherent limitations that significantly restrict their use in several applications. Among these limitations, their low hardness, low wear resistance, or limited anti-corrosion properties, which are often not enough when the component is subjected to more severe environments, are particularly relevant. In this context, surface modification and the development of coatings are essential for the application of cast Al-Si alloys. This review focuses on the development of coatings to overcome the complexities associated with improving the performance of cast Al-Si alloys. Against this background, plasma electrolytic oxidation (PEO), an advanced electrochemical treatment that has revolutionized the surface modification of several metallic alloys in recent years, emerges as a promising approach. Despite the growing recognition of PEO technology, the achievement of high-performance coatings on cast Al-Si is still a challenge nowadays, for which reason this review aims to provide an overview of the PEO treatment applied to these alloys. In particular, the impact of the electrolyte chemical composition on the properties of the coatings obtained on different alloys exposed to harsh environments has been analyzed and discussed. By addressing the existing gaps and challenges, this paper contributes to a better understanding of the intricacies associated with the development of robust PEO coatings on cast Al-Si alloys. Full article
(This article belongs to the Special Issue Plasma Electrolytic Oxidation (PEO) Coatings, 2nd Edition)
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17 pages, 4918 KiB  
Article
The Antibacterial Properties of a Silver Multilayer Coating for the Prevention of Bacterial Biofilm Formation on Orthopedic Implants—An In Vitro Study
by Sanne W. G. van Hoogstraten, Janine Fechter, Rainer Bargon, Julia L. van Agtmaal, Laura C. W. Peeters, Jan Geurts and Jacobus J. C. Arts
Coatings 2024, 14(2), 216; https://doi.org/10.3390/coatings14020216 - 09 Feb 2024
Cited by 1 | Viewed by 967
Abstract
The prevention of biofilm formation on orthopedic implants is essential, as biofilms are the main challenge in the effective treatment of periprosthetic joint infection (PJI). A silver multilayer (SML) coating was developed to prevent biofilm formation on the implant surface. Previous studies have [...] Read more.
The prevention of biofilm formation on orthopedic implants is essential, as biofilms are the main challenge in the effective treatment of periprosthetic joint infection (PJI). A silver multilayer (SML) coating was developed to prevent biofilm formation on the implant surface. Previous studies have already demonstrated its antibacterial properties without cytotoxic effects. However, the coating has not been previously tested when applied to common titanium surfaces used in total joint arthroplasty implants. These surfaces often have increased roughness and porosity in the case of cementless implants, which can alter the antibacterial effect of the coating. In this study, we assessed the antibacterial and anti-biofilm properties of the SML coating on corundum-blasted and plasma-sprayed microporous-coated titanium alloy surfaces, using S. aureus, S. epidermidis, and E. coli. An antibacterial activity test following the principles of ISO 22196, ASTM E2180-18, and JIS Z 2801 standards was performed, as well as a biofilm proliferation assay investigating bacterial adhesion and biofilm formation. The SML coating exhibited strong antibacterial effects for all bacterial strains. After 24 h biofilm culture, a >4-log reduction in CFU was induced by the SML coating for S. epidermidis and E. coli on the corundum-blasted and plasma-sprayed microporous-coated titanium surfaces, respectively, when compared to the uncoated surfaces. The coating showed bactericidal properties against Gram-positive bacteria on the corundum-blasted discs. The SML coating on two common titanium surfaces demonstrates significant potential as an effective strategy in combating PJI across a wide range of orthopedic implants. Full article
(This article belongs to the Special Issue Advances in Antibacterial Coatings: From Materials to Applications)
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17 pages, 6810 KiB  
Article
Deposition of Polymers on Titanium Nitride Electrodes
by Yulia Efremenko, Arwa Laroussi, Akant Sengül, Agnieszka Anna Corley-Wiciak, Inga Anita Fischer and Vladimir M. Mirsky
Coatings 2024, 14(2), 215; https://doi.org/10.3390/coatings14020215 - 08 Feb 2024
Viewed by 963
Abstract
The application of titanium nitride (TiN) as an electrode for electrochemical deposition or characterization requires the removal of an insulating layer from its surface. This process was studied and optimized, and the conditions for the complete removal of this layer through treatment with [...] Read more.
The application of titanium nitride (TiN) as an electrode for electrochemical deposition or characterization requires the removal of an insulating layer from its surface. This process was studied and optimized, and the conditions for the complete removal of this layer through treatment with oxalic acid were formulated. The obtained TiN surfaces were used for the deposition of various conducting and non-conducting polymers. Two different approaches were applied: (i) in situ electrochemical synthesis of the main classes of conducting polymers, including polyaniline, polypyrrole, polythiophene, and selected derivatives thereof, and (ii) electrostatically driven layer-by-layer (LbL) deposition of multilayers of oppositely charged polyelectrolytes. The deposited polymers were characterized by electrochemical methods. The electrochemical properties of the deposited conducting polymers and their deposition on the TiN surface were comparable to those of the metallic electrodes. The films produced via LbL deposition exhibited a pronounced influence of the charge of the last deposited polymer on the redox reaction of ferri/ferrocyanide, validating the charge alteration with each successive polymer layer deposition. The studied deposition technologies can be used for the modification of TiN surfaces required in applications of this material in chemical sensors and other devices. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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19 pages, 9104 KiB  
Article
Silver Containing Antimicrobial Coatings on Innovative Ti-30Nb-5Mo β-Alloy Prepared by Micro-Arc Oxidation for Biomedical Implant Applications
by Giovana Collombaro Cardoso, Katia Barbaro, Pedro Akira Bazaglia Kuroda, Angela De Bonis, Roberto Teghil, Valentina Monteleone, Luca Imperatori, Marco Ortenzi, Iulian Antoniac, Carlos Roberto Grandini and Julietta V. Rau
Coatings 2024, 14(2), 214; https://doi.org/10.3390/coatings14020214 - 07 Feb 2024
Viewed by 1098
Abstract
Micro-arc oxidation (MAO) is a versatile surface-modification method that promotes higher wear and corrosion resistance, osseointegration, and biological activity to titanium alloys’ surfaces. This study aimed to modify the surface of a recently developed metastable β Ti alloy, which exhibits more favorable mechanical [...] Read more.
Micro-arc oxidation (MAO) is a versatile surface-modification method that promotes higher wear and corrosion resistance, osseointegration, and biological activity to titanium alloys’ surfaces. This study aimed to modify the surface of a recently developed metastable β Ti alloy, which exhibits more favorable mechanical properties for implant applications compared to some commercial Ti alloys, by incorporating Ag into the coatings to introduce a bactericidal function to the surface. The Ti-30Nb-5Mo alloy, with lower elastic modulus, was treated by the MAO method using electrolyte solutions containing calcium acetate, magnesium acetate, β-glycerol phosphate, and varied concentrations of silver nitrate (1.5 mM, 2.5 mM, and 3.5 mM). With an increase in the concentration of silver ions in the electrolyte, the galvanostatic period during the MAO process decreased from 1.7 s to 0.5 s. The Ca/P ratio increased from 0.72 up to 1.36. X-ray diffraction showed that the MAO coatings were formed by rutile and anatase TiO2 main phases and calcium phosphates. X-ray photoelectron spectroscopy analysis detected the presence of amorphous Nb2O5, CaCO3, and MgCO3, and metallic and oxide forms of Ag. The increase in Ag in the electrolyte decreased the coating thickness (from 14.2 μm down to 10.0 μm), increased the contact angle (from 37.6° up to 57.4°), and slightly increased roughness (from 0.64 μm up to 0.79 μm). The maximum inhibition of Enterococcus faecalis, Pseudomonas aeruginosa, and Candida albicans strains growth was of 43%, 43%, and 61%, respectively. The Ag did not negatively affect the differentiation of adipose-tissue-derived mesenchymal stem cells. Therefore, the treatment of the surface of the innovative Ti-30Nb-5Mo alloy by the MAO method was effective in producing a noncytotoxic porous coating with bactericidal properties and improved osseointegration capabilities. Full article
(This article belongs to the Section Bioactive Coatings and Biointerfaces)
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