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Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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12 pages, 11049 KiB  
Article
High-Temperature Heat Treatment of Plasma Sprayed Ti–Si–C–Mo Coatings
by Jining He, Jialin Liu, Hongjian Zhao, Yanfang Qin and Jiawei Fan
Coatings 2024, 14(1), 109; https://doi.org/10.3390/coatings14010109 - 15 Jan 2024
Viewed by 949
Abstract
In this work, the effect of 800 °C and 1100 °C post-heat treatment on the plasma spraying of Ti–Si–C–xMo (x = 1.0, 1.5) composite coatings was investigated. The composite coatings were composed of TiC, Ti3SiC2, Ti5Si3 [...] Read more.
In this work, the effect of 800 °C and 1100 °C post-heat treatment on the plasma spraying of Ti–Si–C–xMo (x = 1.0, 1.5) composite coatings was investigated. The composite coatings were composed of TiC, Ti3SiC2, Ti5Si3 and Mo5Si3 reacted phases. After heat treatment, the Ti3SiC2 and Mo5Si3 phases increased. The coating microhardness decreased by 16% and 18% for Ti–Si–C–1.0Mo and Ti–Si–C–1.5Mo coatings, respectively, after heat treatment at 1100 °C. Fracture toughness increased by 16% for the Ti–Si–C–1.5Mo coating after heat treatment at 1100 °C, which was mainly due to the heat treatment promoting Ti3SiC2 formation, healing micro-cracks, reducing the internal stress and making the microstructure dense. The coating friction coefficient before and after heat -treatment was between 0.4 and 0.6. After heat treatment, the wear amount of the coating was first reduced and then increased, and the minimum wear loss occurred after heat treatment at 800 °C. The wear mechanism was mixed abrasive wear, adhesive wear and tribo-oxidation wear. Full article
(This article belongs to the Special Issue Advanced Materials and Surface Protection)
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14 pages, 12915 KiB  
Article
Decoration of a Glass Surface with AgNPs Using Thio-Derivates for Environmental Applications
by Cornelia-Ioana Ilie, Angela Spoială, Ludmila Motelica, Liliana Marinescu, Georgiana Dolete, Doina-Roxana Trușcă, Ovidiu-Cristian Oprea, Denisa Ficai and Anton Ficai
Coatings 2024, 14(1), 96; https://doi.org/10.3390/coatings14010096 - 11 Jan 2024
Viewed by 1398
Abstract
The aim of this study is to decorate a glass surface with silver nanoparticles (AgNPs) and further prove its efficiency in the removal of some thio-derivatives—potential pollutants from water. Therefore, grafting the surface of glass-based platforms with AgNPs will strongly influence their interaction [...] Read more.
The aim of this study is to decorate a glass surface with silver nanoparticles (AgNPs) and further prove its efficiency in the removal of some thio-derivatives—potential pollutants from water. Therefore, grafting the surface of glass-based platforms with AgNPs will strongly influence their interaction with other substances or molecules. The most commonly used molecules for glass-based platform functionalization/modification are organosilanes. In this case, the main interest is in thioalkyl organosilanes because, after silanization, the thio (-SH) functional groups that have a high affinity for AgNPs can intermediate their binding on the surface. By decorating the glass platforms with AgNPs, these surfaces become active for the adsorption of dyes from wastewater. Certainly, in this case, the dyes must bear -SH groups to ensure a high affinity for these surfaces. Therefore, the desired purpose of this study was to develop glass-based platforms decorated with AgNPs able to bind model molecules—dyes from aqueous media (dithizone—DIT and thioindigo—TIO), with these platforms being potentially used for environmental applications. Full article
(This article belongs to the Collection Feature Paper Collection in 'Surface Coatings for Biomedicine and Bioengineering')
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43 pages, 7178 KiB  
Review
Coatings and Surface Modification of Alloys for Tribo-Corrosion Applications
by Robert J. K. Wood and Ping Lu
Coatings 2024, 14(1), 99; https://doi.org/10.3390/coatings14010099 - 11 Jan 2024
Cited by 5 | Viewed by 2536
Abstract
This review of the tribocorrosion of coatings and surface modifications covers nearly 195 papers and reviews that have been published in the past 15 years, as compared to only 37 works published up to 2007, which were the subject of a previous review [...] Read more.
This review of the tribocorrosion of coatings and surface modifications covers nearly 195 papers and reviews that have been published in the past 15 years, as compared to only 37 works published up to 2007, which were the subject of a previous review published in 2007. It shows that the research into the subject area is vibrant and growing, to cover emerging deposition, surface modification and testing techniques as well as environmental influences and modelling developments. This growth reflects the need for machines to operate in harsh environments coupled with requirements for increased service life, lower running costs and improved safety factors. Research has also reacted to the need for multifunctional coating surfaces as well as functionally graded systems with regard to depth. The review covers a range of coating types designed for a wide range of potential applications. The emerging technologies are seen to be molten-, solution-, PVD- and PEO-based coatings, with CVD coatings being a less popular solution. There is a growing research interest in duplex surface engineering and coating systems. Surface performance shows a strong playoff between wear, friction and corrosion rates, often with antagonistic relationships and complicated interactions between multiple mechanisms at different scale lengths within tribocorrosion contacts. The tribologically induced stresses are seen to drive damage propagation and accelerate corrosion either within the coating or at the coating coating–substrate interface. This places a focus on coating defect density. The environment (such as pH, DO2, CO2, salinity and temperature) is also shown to have a strong influence on tribocorrosion performance. Coating and surface modification solutions being developed for tribocorrosion applications include a whole range of electrodeposited coatings, hard and tough coatings and high-impedance coatings such as doped diamond-like carbon. Hybrid and multilayered coatings are also being used to control damage penetration into the coating (to increase toughness) and to manage stresses. A particular focus involves the combination of various treatment techniques. The review also shows the importance of the microstructure, the active phases that are dissolved and the critical role of surface films and their composition (oxide or passive) in tribocorrosion performance which, although discovered for bulk materials, is equally applicable to coating performance. New techniques show methods for revealing the response of surfaces to tribocorrosion (i.e., scanning electrochemical microscopy). Modelling tribocorrosion has yet to embrace the full range of coatings and the fact that some coatings/environments result in reduced wear and thus are antagonistic rather than synergistic. The actual synergistic/antagonistic mechanisms are not well understood, making them difficult to model. Full article
(This article belongs to the Special Issue Role of Coatings on Corrosion, Wear and Erosion Behavior)
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30 pages, 1508 KiB  
Systematic Review
Antimicrobial Activity of Photocatalytic Coatings on Surfaces: A Systematic Review and Meta-Analysis
by Francesca Ubaldi, Federica Valeriani, Veronica Volpini, Giusy Lofrano and Vincenzo Romano Spica
Coatings 2024, 14(1), 92; https://doi.org/10.3390/coatings14010092 - 10 Jan 2024
Cited by 3 | Viewed by 1901
Abstract
Photocatalytic technologies represent an innovative method to reduce microbial load on surfaces, even considering recent public health emergencies involving coronaviruses and other microorganisms, whose presence has been detected on surfaces. In this review paper, the antimicrobial efficacy of various photocatalysts applied by different [...] Read more.
Photocatalytic technologies represent an innovative method to reduce microbial load on surfaces, even considering recent public health emergencies involving coronaviruses and other microorganisms, whose presence has been detected on surfaces. In this review paper, the antimicrobial efficacy of various photocatalysts applied by different coating methods on different surfaces has been compared and critically discussed. Publications reviewing the use of photocatalytic coatings on surfaces for antimicrobial effectiveness have been examined. Clear search parameters were employed to analyze the PubMed, Scopus, and WOS databases, resulting in 45 papers published between 2006 to 2023 that met the inclusion criteria. The paper assessed various types of photocatalytic coatings that targeted different microbial objectives. Based on the pooled data analysis, the TiO2 coating exhibited a substantial effect in decreasing bacteria strains, both Gram-positive and -negative (99.4%). Although the diversity of these technologies poses significant obstacles to obtaining a comprehensive final assessment of their effectiveness and feasibility for surface application, subgroup analysis indicated significant variations in the removal efficiency of Gram-positive strains based on different surface types (p = 0.005) and time of exposure (p = 0.05). Photocatalytic coatings provide a promising approach to combating the spread of microorganisms on surfaces. Further “in-field” investigations are necessary in the foreseeable future to explore and optimize this novel and exciting health technology. Full article
(This article belongs to the Special Issue Nanostructured Materials and Interfaces: Biomedical and Healthcare Applications)
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0 pages, 9818 KiB  
Article
Tensile Properties of Aircraft Coating Systems and Applied Strain Modeling
by Attilio Arcari, Rachel M. Anderson, Carlos M. Hangarter, Erick B. Iezzi and Steven A. Policastro
Coatings 2024, 14(1), 91; https://doi.org/10.3390/coatings14010091 - 10 Jan 2024
Viewed by 1062
Abstract
In this work, we develop a structural model for the fracturing of an aircraft coating system applied to a complex airframe structure that includes aluminum panels and stainless-steel fasteners. The mechanical properties of the coating system, which consisted of an MIL-PRF-85582E, Type II, [...] Read more.
In this work, we develop a structural model for the fracturing of an aircraft coating system applied to a complex airframe structure that includes aluminum panels and stainless-steel fasteners. The mechanical properties of the coating system, which consisted of an MIL-PRF-85582E, Type II, Class C1, two-part epoxy primer and an MIL-PRF-85285 Rev E, Type IV, Class H, two-part polyurethane topcoat, were measured before and after 8 months of atmospheric exposure. The loads applied to the coating occurred from local deformations of the fastener-panel system in response to flight stresses. Two types of flight stresses, compression dominated and tension dominated, were modeled. The degradation of the mechanical properties of the coating after atmospheric exposure increases the severity of cracking of the coating at a critical fastener–skin interface. Full article
(This article belongs to the Special Issue Research Progress on Coatings Degradation and Atmospheric Corrosion of Metal Surfaces)
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14 pages, 7220 KiB  
Article
A One-Step Novel Method to Fabricate Multigrade Ti6Al4V/TiN Composites Using Laser Powder Bed Fusion
by Carmen Sánchez de Rojas Candela, Ainhoa Riquelme, Pilar Rodrigo, Victoria Bonache, Javier Bedmar, Belén Torres and Joaquín Rams
Coatings 2024, 14(1), 90; https://doi.org/10.3390/coatings14010090 - 9 Jan 2024
Viewed by 1238
Abstract
Ti6Al4V is the most used alloy for implants because of its excellent biocompatibility; however, its low wear resistance limits its use in the biomedical industry. The additive manufacturing (AM) of Ti6Al4V is a well-established technique that is being used in many fields. However, [...] Read more.
Ti6Al4V is the most used alloy for implants because of its excellent biocompatibility; however, its low wear resistance limits its use in the biomedical industry. The additive manufacturing (AM) of Ti6Al4V is a well-established technique that is being used in many fields. However, the AM of Ti6Al4V composites is currently under investigation, and its manufacture using laser powder bed fusion (L-PBF) would result in a great benefit for many industries. The one-step novel concept proposed uses a gas-controlled L-PBF system that enables the AM of layers with different compositions. Six millimeter-edged cubes of Ti6Al4V were manufactured in an Ar atmosphere and coated with in situ Ti6Al4V/TiN layers by using an Ar–N2 mixture given the direct reaction between titanium and nitrogen. Unreinforced Ti6Al4V presented a martensitic microstructure, and TiN reinforcement dendrites and a minor Ti2N phase were gradually introduced into an α + β basketweave titanium matrix. The composites’ microhardness, nanohardness, and elastic modulus were 2, 3, and 1.5 times higher, respectively, than those of the Ti6Al4V. Porosity levels (caused by a lack of fusion, trapping gases, and interdendritic porosity), ranged from 7 to 12% (most measured 20–40 µm) and increased with the reinforcement content (15 to 25%). A scaled-up, proof-of-concept design of a hip implant stem was 3D printed using this nitriding method. Since the neck of the stem (top part) is more susceptible to the fracture and fretting corrosion process, the resulting graded material part consisted of unreinforced Ti6Al4V at the bottom and Ti6Al4V/TiN at the top. This change was controlled by gradually adding nitrogen to the atmosphere; moreover, it was found that the more nitrogen in the chamber, the more TiN reinforcement formed in the part. A microhardness of ~450 HV0.1 was measured at the bottom and gradually increased to ~900 HV0.1, with the increment corresponding to the in situ TiN reinforcement amount. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)
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14 pages, 3660 KiB  
Article
Investigation of Polyelectrolyte Multilayers Deposited on Biodegradable Corona-Charged Substrates Used as Drug Delivery Systems
by Asya Viraneva, Maria Marudova, Sofia Milenkova, Aleksandar Grigorov and Temenuzhka Yovcheva
Coatings 2024, 14(1), 85; https://doi.org/10.3390/coatings14010085 - 7 Jan 2024
Cited by 1 | Viewed by 1305
Abstract
Polyelectrolyte multilayers (PEMs) deposited on porous composite polylactic acid/poly(ε-caprolactone) (PDLA/PEC) substrates were studied. The substrates were previously charged in a corona discharge. Time dependences of the normalized surface potential for positively and negatively charged electrets were investigated. The morphology of the obtained porous [...] Read more.
Polyelectrolyte multilayers (PEMs) deposited on porous composite polylactic acid/poly(ε-caprolactone) (PDLA/PEC) substrates were studied. The substrates were previously charged in a corona discharge. Time dependences of the normalized surface potential for positively and negatively charged electrets were investigated. The morphology of the obtained porous substrates was examined by means of scanning electron microscopy (SEM). The chitosan and the casein polyelectrolytes were deposited on the substrates using the layer-by-layer (LbL) technique. The drug loading efficiency and the release kinetics were determined spectrophotometrically. Full article
(This article belongs to the Section Surface Characterization, Deposition and Modification)
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23 pages, 7194 KiB  
Article
Functionalization of Plasma Electrolytic Oxidation/Sol–Gel Coatings on AZ31 with Organic Corrosion Inhibitors
by Borja Pillado, Endzhe Matykina, Marie-Georges Olivier, Marta Mohedano and Raúl Arrabal
Coatings 2024, 14(1), 84; https://doi.org/10.3390/coatings14010084 - 7 Jan 2024
Cited by 2 | Viewed by 1376
Abstract
In this investigation, the sol–gel method is employed along with a corrosion inhibitor to seal a plasma electrolytic oxidation (PEO) coating, aiming to improve the long-term corrosion resistance of the AZ31 Mg alloy. Following an initial screening of corrosion inhibitors, 8-hydroxyquinoline (8HQ) is [...] Read more.
In this investigation, the sol–gel method is employed along with a corrosion inhibitor to seal a plasma electrolytic oxidation (PEO) coating, aiming to improve the long-term corrosion resistance of the AZ31 Mg alloy. Following an initial screening of corrosion inhibitors, 8-hydroxyquinoline (8HQ) is incorporated into the hybrid PEO/sol–gel system using two methods: (i) post-treatment of the PEO layer through immersion in an inhibitor-containing solution; (ii) loading the inhibitor into the sol–gel precursor. The characterization includes scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and water drop contact angle measurements. The rheological properties of the inhibitor-loaded sol–gel precursors are assessed by measuring flow curves. The corrosion processes are evaluated in a saline solution through electrochemical impedance spectroscopy (EIS) and immersion tests with unscratched and scratched specimens, respectively. The results demonstrate the successful incorporation of the inhibitor for both loading strategies. Regardless of the loading approach, systems containing 8HQ exhibit the most favourable long-term corrosion resistance. Full article
(This article belongs to the Special Issue Plasma Electrolytic Oxidation (PEO) Coatings, 2nd Edition)
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17 pages, 5240 KiB  
Article
Tailoring the Silicon Cementation Applied to P265GH Grade Steel
by Mihai Branzei, Mihai Ovidiu Cojocaru, Mircea Dan Morariu and Leontin Nicolae Druga
Coatings 2024, 14(1), 74; https://doi.org/10.3390/coatings14010074 - 4 Jan 2024
Viewed by 983
Abstract
Increasing the serviceability of industrial components intended for the petrochemical industry is possible through their superficial saturation with silicon (silicon cementation). Obtaining a silicon-rich surface coating results in a considerable increase in corrosion resistance, refractoriness, and wear resistance. One of the most economically [...] Read more.
Increasing the serviceability of industrial components intended for the petrochemical industry is possible through their superficial saturation with silicon (silicon cementation). Obtaining a silicon-rich surface coating results in a considerable increase in corrosion resistance, refractoriness, and wear resistance. One of the most economically convenient options for silicon cementation is pack siliconizing in powdery solid media. This paper presents the possibility of pack siliconizing that contains ferrosilicon (FeSi75C) and a thermite mixture (SiO2 + Al) as active, silicon-providing components, in P265GH grade steel, which is frequently used in the petrochemical industry. The aim of the study was to determine the most suitable active component of the two that were analyzed and at the same time identify the processing conditions in which the siliconized coating has the greatest thickness, is free of porosity, and is in direct contact with the support. The use of experimental programming methods allowed the optimization of the operation to obtain the optimal solution. It was concluded that the thermite mixture is not compatible with pack siliconizing because it results in a superficial saturation predominantly composed of aluminum. When ferrosilicon is used as the active component, it determines the particularly intense formation kinetics of the non-porous siliconized coating with its maximum thickness being reached at high processing temperature values (over 1100 °C) with a proportion of 60% FeSi75 and, simultaneously, with the lowest possible proportion of ammonium chloride (max. 3%), which is the surface activation/cleaning component. Full article
(This article belongs to the Special Issue Advanced Coatings with Noble and Refractory Alloy Metals in Extreme Environments)
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13 pages, 19782 KiB  
Article
Effects of Heat Treatment and Erosion Particle Size on Erosion Resistance of a Hypereutectic High-Chromium Cast Iron
by Alessio Suman and Annalisa Fortini
Coatings 2024, 14(1), 66; https://doi.org/10.3390/coatings14010066 - 3 Jan 2024
Viewed by 1150
Abstract
This research addresses the erosive resistance of a hypereutectic high-chromium cast iron subjected to solid particle erosion. The study stems from a specific application of high-chromium cast iron, i.e., the critical surfaces of large industrial fans operating in a cement clinker grinding plant [...] Read more.
This research addresses the erosive resistance of a hypereutectic high-chromium cast iron subjected to solid particle erosion. The study stems from a specific application of high-chromium cast iron, i.e., the critical surfaces of large industrial fans operating in a cement clinker grinding plant where such damage is a limiting factor for the components’ lifespan. A dedicated experimental investigation on the impact of substrate microstructure and erodent particle size on erosion resistance was set. The experimental campaign, conducted on a dedicated test bench per the ASTM G76 standard, comprised the analysis of the as-received, tempered, and destabilized conditions for the cast iron. From a preliminary image analysis of the microstructural features, two diameters of the erodent powder for the erosion tests were defined. The observed erosion rate decreased with the increase in the mean particle diameter of the erodent, indicating more severe erosive conditions for smaller particles. From the analysis of the worn surfaces, it was possible to highlight the involved mechanisms concerning the considered test combinations. For the as-received condition, the erosion rate with the larger mean particle diameter of the erodent decreased three times compared to the smaller one. For the heat-treated conditions, the erosion rate was halved with the larger mean particle diameter of the erodent. The proposed analysis, intended to acquire more insight into the limiting factor for the components’ lifespan for erosive wear damage, proved that erosion resistance is not dependent on the material’s hardness. The contribution of the mean particle diameter of the erodent is predominant compared to the substrate conditions. Full article
(This article belongs to the Special Issue Wear-Resistance and Corrosion-Resistance Coatings)
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18 pages, 4613 KiB  
Article
Machine Learning Modeling and Run-to-Run Control of an Area-Selective Atomic Layer Deposition Spatial Reactor
by Matthew Tom, Henrik Wang, Feiyang Ou, Gerassimos Orkoulas and Panagiotis D. Christofides
Coatings 2024, 14(1), 38; https://doi.org/10.3390/coatings14010038 - 27 Dec 2023
Viewed by 1268
Abstract
Semiconducting materials require stringent design specifications that make their fabrication more difficult and prone to flaws that are costly and damaging to their computing and electrical properties. Area-selective atomic layer deposition is a process that addresses concerns associated with design imperfections but requires [...] Read more.
Semiconducting materials require stringent design specifications that make their fabrication more difficult and prone to flaws that are costly and damaging to their computing and electrical properties. Area-selective atomic layer deposition is a process that addresses concerns associated with design imperfections but requires substantial monitoring to ensure that process regulation is maintained. This work proposes a run-to-run controller with an exponentially weighted moving average method for an area-selective atomic layer deposition rotary reactor by adjusting the rotation speed of the substrate to control the growth per cycle of the wafer, which is calculated through a multiscale model with machine learning integration for pressure field generation and kinetic Monte Carlo simulations to increase computational efficiency. Results indicate that the run-to-run controller was able to bring the process to the setpoint when subjected to moderate pressure and kinetic shift disturbances. Full article
(This article belongs to the Special Issue Recent Advances in Chemical Vapor Deposition)
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17 pages, 8339 KiB  
Article
Preparation and Characterization of Polymer-Based Electrospun Nanofibers for Flexible Electronic Applications
by Gopiraman Mayakrishnan, Ramkumar Vanaraj, Takayasu Kitauchi, Rajakumar Kanthapazham, Seong Cheol Kim and Ick Soo Kim
Coatings 2024, 14(1), 35; https://doi.org/10.3390/coatings14010035 - 27 Dec 2023
Cited by 1 | Viewed by 1226
Abstract
This study was undertaken to synthesize and characterize PVDF/CB (polyvinylidene fluoride/carbon block) nanofiber composites for flexible, wearable electronic applications. Nanofibers were produced by electrospinning method and used to produce thin films. Fiber surface morphologies were investigated by FE-SEM and HR-TEM, crystalline structures by [...] Read more.
This study was undertaken to synthesize and characterize PVDF/CB (polyvinylidene fluoride/carbon block) nanofiber composites for flexible, wearable electronic applications. Nanofibers were produced by electrospinning method and used to produce thin films. Fiber surface morphologies were investigated by FE-SEM and HR-TEM, crystalline structures by FT-IR and P-XRD, and thermal characteristics by TGA and DSC. The prepared materials are thermally stable up to 390 °C. Mechanical properties were ascertained using tensile characteristics, and results showed that the addition of carbon black (CB) powder to PVDF polymer solution decreased Young’s modulus values and reduced the dielectric constant of PVDF nanofiber films. The obtained dielectric constants of nanofibers loaded with various concentrations of CB were found from 1.4 to 2.0. Flexible electronics materials are essential for the production of wearable electronics and various biomedical engineering applications. The PVDF/CB nanofibers containing 1% showed maximum Young’s moduli of 101.29 ± 15.94. Nanofiber thin films offer various advantages, including simplicity of manufacture, low power consumption, flexibility, and exceptional stability, all of which are crucial for flexible, wearable device applications. Full article
(This article belongs to the Special Issue Advanced Materials for Electrocatalysis and Energy Storage)
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25 pages, 3792 KiB  
Review
Structural Damage Detection Based on Static and Dynamic Flexibility: A Review and Comparative Study
by Xi Peng, Qiuwei Yang, Fengjiang Qin and Binxiang Sun
Coatings 2024, 14(1), 31; https://doi.org/10.3390/coatings14010031 - 26 Dec 2023
Cited by 1 | Viewed by 1172
Abstract
Material damage in structures must be detected in a timely manner to prevent engineering accidents. Damage detection based on structural flexibility has attracted widespread attention in recent years due to its simplicity and practicality. This article provides a detailed overview of damage detection [...] Read more.
Material damage in structures must be detected in a timely manner to prevent engineering accidents. Damage detection based on structural flexibility has attracted widespread attention in recent years due to its simplicity and practicality. This article provides a detailed overview of damage detection methods based on structural flexibility. Depending on the calculation method and data used, flexibility-based methods can be divided into the following categories: flexibility difference, flexibility derivative index, flexibility sensitivity, flexibility decomposition, static flexibility, and combinations of flexibility with other methods. The basic principles and main calculation formulas of various flexibility methods are explained, and their advantages and disadvantages are analyzed. For the method using flexibility difference, the advantage is that the calculation is very simple and does not require the construction of a finite element model of the structure. The disadvantage is that it requires the measurement of modal data of the intact structure, and this method cannot quantitatively assess the degree of damage. For the method using the flexibility derivative index, the advantage is that it only requires the modal data of the damaged structure to locate the damage, but this method is particularly sensitive to noise in the data and is prone to misjudgment. For methods based on flexibility sensitivity and flexibility decomposition, the advantage is that they can simultaneously obtain the location and degree of damage in the structure, but the disadvantage is that they require the establishment of accurate finite element models in advance. Static flexibility methods can compensate for the shortcomings of dynamic flexibility methods, but they usually affect the normal use of the structure during static testing. Combining flexibility-based methods with advanced intelligent algorithms and other methods can further improve their accuracy and efficiency in identifying structural damage. Finally, this article discusses the challenges that have not yet been solved among damage detection methods based on structural flexibility. Full article
(This article belongs to the Special Issue Development and Characterization of New Construction Materials and Coatings)
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9 pages, 2574 KiB  
Article
Atomic Layer Deposition for Tailoring Tamm Plasmon-Polariton with Ultra-High Accuracy
by Mantas Drazdys, Ernesta Bužavaitė-Vertelienė, Darija Astrauskytė and Zigmas Balevičius
Coatings 2024, 14(1), 33; https://doi.org/10.3390/coatings14010033 - 26 Dec 2023
Viewed by 1252
Abstract
In this study, we demonstrate the potential capability to control Tamm plasmon-polaritons (TPP) by applying atomic layer deposition (ALD) as a highly precise technique for plasmonic applications. Applications in plasmonics usually require tens of nanometers or less thick layers; thus, ALD is a [...] Read more.
In this study, we demonstrate the potential capability to control Tamm plasmon-polaritons (TPP) by applying atomic layer deposition (ALD) as a highly precise technique for plasmonic applications. Applications in plasmonics usually require tens of nanometers or less thick layers; thus, ALD is a very suitable technique with monolayer-by-monolayer growth of angstrom resolution. Spectroscopic ellipsometry and polarized reflection intensity identified the TPP resonances in the photonic band gap (PBG) formed by periodically alternating silicon oxide and tantalum oxide layers. The sub-nanometer control of the Al2O3 layer by ALD allows precise tailoring of TPP resonances within a few nanometers of spectral shift. The employing of the ALD method for the fabrication of thin layers with sub-nanometer thickness accuracy in more complex structures proves to be a versatile platform for practical applications where tunable plasmonic resonances of high quality are required. Full article
(This article belongs to the Special Issue Fabrication of Plasmonic Thin Films, Their Characterization and Applications)
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14 pages, 3501 KiB  
Article
Physicomechanical Properties of Gypsum with Mineral Additions at Elevated Temperatures
by Junjie Wang and Engui Liu
Coatings 2023, 13(12), 2091; https://doi.org/10.3390/coatings13122091 - 15 Dec 2023
Viewed by 1742
Abstract
Gypsum, from either nature or industrial by-products, can be a lower-cost and cleaner alternative binder to Portland cement used in construction projects, such as affordable housing in developing countries. Although various building products have successfully used gypsum as the binder, some drawbacks of [...] Read more.
Gypsum, from either nature or industrial by-products, can be a lower-cost and cleaner alternative binder to Portland cement used in construction projects, such as affordable housing in developing countries. Although various building products have successfully used gypsum as the binder, some drawbacks of this material have still been claimed, for example, in the aspects of mechanical strength and some other physical properties. Using mineral additions to gypsum seems to be a possible solution to create composite gypsum with improved properties. This work has investigated the possibility of two common minerals (silica flour and talc powder) in modifying composite gypsum’s physical and mechanical performance at elevated temperatures (100–1100 °C), including hydration, strength, thermal conduction and stability, and microstructure. The results suggest that 10% gypsum replacement by silica flour or talc powder modifies gypsum’s physical and mechanical properties, with silica flour performing better than talc powder. The performance of composite gypsum at elevated temperatures depends on the treatment temperature and reflects the combined effects of gypsum phase change and the filler effects of silica flour or talc powder. Thermal treatment at ≤200 °C increased the thermal resistance of all gypsum boards but decreased their compressive strength. Thermal treatment at ≥300 °C significantly increased the compressive strength of gypsum with silica flour and talc powder but induced intensive microcracks and thus failed the thermal insulation. This investigation indicates that silica flour can potentially raise the mechanical performance of gypsum. At the same time, talc powder can hold water and lubricate, which may help with the continuous hydration of gypsum phases and the rheology of its mixtures. Full article
(This article belongs to the Special Issue Effective Coating Barriers for Protection of Reinforced Concrete)
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17 pages, 7792 KiB  
Article
The Effect of Plasma Spray Parameters on the Quality of Al-Ni Coatings
by Shenglian Wang, Shuang Chen, Ming Liu, Qinghua Huang, Zimo Liu, Xin Li and Shaofeng Xu
Coatings 2023, 13(12), 2063; https://doi.org/10.3390/coatings13122063 - 9 Dec 2023
Cited by 2 | Viewed by 1593
Abstract
The plasma spray method is widely utilized for enhancing wear, surface fatigue, and corrosion properties through coating. The mechanical and surface characteristics of the resulting coating are contingent upon various spraying parameters, including arc current, working current, spraying distance, and plasma gun traversing [...] Read more.
The plasma spray method is widely utilized for enhancing wear, surface fatigue, and corrosion properties through coating. The mechanical and surface characteristics of the resulting coating are contingent upon various spraying parameters, including arc current, working current, spraying distance, and plasma gun traversing speed. This study investigates the impact of these manufacturing parameters on the porosity, hardness, and bond strength of a coating produced from an Al-Ni alloy applied to a Q235 steel substrate. An extensive experimental program was conducted to analyze the influence of these parameters on the coating properties. Consequently, a preferred combination of parameters, identified through a comprehensive evaluation method, yielded greater performance benefits compared to the orthogonal experimental groups. Full article
(This article belongs to the Special Issue Application of Advanced Plasma Technology in Coatings, Films and Etching)
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27 pages, 4410 KiB  
Review
Protecting Street Art from Outdoor Environmental Threats: What Are the Challenges?
by Laura Pagnin, Nicolò Guarnieri, Francesca Caterina Izzo, Sara Goidanich and Lucia Toniolo
Coatings 2023, 13(12), 2044; https://doi.org/10.3390/coatings13122044 - 5 Dec 2023
Cited by 1 | Viewed by 1926
Abstract
Street Art is an artistic expression in constant development, whose interest has grown in recent years among society, public administrations, conservators, and heritage scientists. This growing awareness has given rise to a series of debates between professionals with the intent to expand the [...] Read more.
Street Art is an artistic expression in constant development, whose interest has grown in recent years among society, public administrations, conservators, and heritage scientists. This growing awareness has given rise to a series of debates between professionals with the intent to expand the knowledge relating to conservation practices and possible protection solutions. Additionally, the paint materials used by contemporary artists are in constant development; therefore, difficulty has emerged in the identification of their degradation processes when exposed to environmental conditions and in the consequent selection of a specific protection system. This review presents an overview of the recent literature and experiences in the field of knowledge and preservation of Street Art, focusing on the type and nature of paint formulations, the main deterioration processes of painted artworks in outdoor conditions, and the most recent advances in materials and methods for the conservation and protection of Street Art. This review aims to emphasise how the approach to the challenge of preservation of Street Art is complex, aspiring to the need for optimised diagnostic protocols for the development of innovative and effective protective coatings. This paper is a starting point to provide suggestions and indications for the development of further research projects within the framework of preservation and protection of contemporary muralism. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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16 pages, 5968 KiB  
Article
Self-Healing UV-Curable Urethane (Meth)acrylates with Various Soft Segment Chemistry
by Paulina Bednarczyk, Paula Ossowicz-Rupniewska, Joanna Klebeko, Joanna Rokicka, Yongping Bai and Zbigniew Czech
Coatings 2023, 13(12), 2045; https://doi.org/10.3390/coatings13122045 - 5 Dec 2023
Cited by 1 | Viewed by 1584
Abstract
This study explores the synthesis and evaluation of UV-curable urethane (meth)acrylates (UA) incorporating a Diels–Alder adduct (HODA), diisocyanate, poly(ethylene glycol), and hydroxy (meth)acrylate. Six UAs, distinguished by the soft segment of polymer chains, underwent comprehensive characterization using FTIR and NMR spectroscopy. Real-time monitoring [...] Read more.
This study explores the synthesis and evaluation of UV-curable urethane (meth)acrylates (UA) incorporating a Diels–Alder adduct (HODA), diisocyanate, poly(ethylene glycol), and hydroxy (meth)acrylate. Six UAs, distinguished by the soft segment of polymer chains, underwent comprehensive characterization using FTIR and NMR spectroscopy. Real-time monitoring of the UV-curing process and analysis of self-healing properties were performed. The research investigates the influence of various molecular weights of PEGs on the self-healing process, revealing dependencies on photopolymerization kinetics, microstructure, thermal properties, and thermoreversibility of urethane (meth)acrylates. This work provides valuable insights into the development of UV-curable coatings with tailored properties for potential applications in advanced materials. Full article
(This article belongs to the Special Issue Advanced Polymeric Materials and Coatings: Synthesis, Properties and Applications)
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62 pages, 10199 KiB  
Review
Electrochemical Detection of Hormones Using Nanostructured Electrodes
by Naila Haroon and Keith J. Stine
Coatings 2023, 13(12), 2040; https://doi.org/10.3390/coatings13122040 - 4 Dec 2023
Cited by 10 | Viewed by 3483
Abstract
Hormones regulate several physiological processes in living organisms, and their detection requires accuracy and sensitivity. Recent advances in nanostructured electrodes for the electrochemical detection of hormones are described. Nanostructured electrodes’ high surface area, electrocatalytic activity, and sensitivity make them a strong hormone detection [...] Read more.
Hormones regulate several physiological processes in living organisms, and their detection requires accuracy and sensitivity. Recent advances in nanostructured electrodes for the electrochemical detection of hormones are described. Nanostructured electrodes’ high surface area, electrocatalytic activity, and sensitivity make them a strong hormone detection platform. This paper covers nanostructured electrode design and production using MOFs, zeolites, carbon nanotubes, metal nanoparticles, and 2D materials such as TMDs, Mxenes, graphene, and conducting polymers onto electrodes surfaces that have been used to confer distinct characteristics for the purpose of electrochemical hormone detection. The use of aptamers for hormone recognition is producing especially promising results, as is the use of carbon-based nanomaterials in composite electrodes. These materials are optimized for hormone detection, allowing trace-level quantification. Various electrochemical techniques such as SWV, CV, DPV, EIS, and amperometry are reviewed in depth for hormone detection, showing the ability for quick, selective, and quantitative evaluation. We also discuss hormone immobilization on nanostructured electrodes to improve detection stability and specificity. We focus on real-time monitoring and tailored healthcare with nanostructured electrode-based hormone detection in clinical diagnostics, wearable devices, and point-of-care testing. These nanostructured electrode-based assays are useful for endocrinology research and hormone-related disease diagnostics due to their sensitivity, selectivity, and repeatability. We conclude with nanotechnology–microfluidics integration and tiny portable hormone-detection devices. Nanostructured electrodes can improve hormone regulation and healthcare by facilitating early disease diagnosis and customized therapy. Full article
(This article belongs to the Special Issue Advances in the Preparation and Characterization Techniques for Developing Coating Materials and Applications)
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22 pages, 5029 KiB  
Article
Novel Method for Assessing the Protection Lifetime of Building Coatings against Fungi
by Justyna Szulc, Michał Komar, Iwona Kata, Krzysztof Szafran and Beata Gutarowska
Coatings 2023, 13(12), 2026; https://doi.org/10.3390/coatings13122026 - 30 Nov 2023
Cited by 4 | Viewed by 1401
Abstract
The aim of this study was to develop a novel method for evaluating the service life of building coatings. In Stage 1, we assessed existing methods for determining the degree of fungal overgrowth on building materials (visual assessment, culture method, luminometric ATP (adenosine-5’-triphosphate) [...] Read more.
The aim of this study was to develop a novel method for evaluating the service life of building coatings. In Stage 1, we assessed existing methods for determining the degree of fungal overgrowth on building materials (visual assessment, culture method, luminometric ATP (adenosine-5’-triphosphate) measurement, and spectrophotometric assessment of colour changes). Laboratory tests were carried out for 19 types of facade coating (mineral and silicone with/without primer, silicone paint, biocides) and 7 fungal strains (moulds Alternaria alternata, Aspergillus niger, Aureobasidium melanogenum, Cladosporium cladosporioides, Fusarium sp., Penicillium citrinum, and the yeast Rhodotorula mucilaginosa). The number of fungi on the facade coatings after 28 days of incubation was 1.7 × 105–4.6 × 105 CFUs (colony-forming units)/sample. The ATP content was 12 RLUs–30333 RLUs (relative light units). Colour change was ΔE > 5 depending on the coating type and fungal strain. A high or very high correlation was found between the ATP concentration (RLUs), colour change (ΔE), and the results of the culture method (CFUs/sample). In Stage 2, a new methodology for evaluating the protection lifetime of building coatings against fungi was developed, taking into account environmental conditions (impact of ultraviolet radiation, precipitation, presence of organic matter on the surface, quantitative and qualitative composition of bioaerosol). The developed method consists of one research cycle conducted in the laboratory, corresponding to one year under natural conditions. Preliminary verification showed the model to be compatible with long-term observations (3 years) of fungal growth on the facade coatings under real environmental conditions. The novel method could be used to design biodeterioration control and protection strategies for both new and cultural heritage buildings. Full article
(This article belongs to the Special Issue Biological Colonization of Cultural Heritage. Emerging Trends in the Protection of Cultural Properties—Novel Control Strategies and Preventive Approaches)
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17 pages, 6534 KiB  
Article
The Effect of CO2 Laser Engraving on the Surface Structure and Properties of Spruce Wood
by Jozef Kúdela, Michal Andrejko and Ivan Kubovský
Coatings 2023, 13(12), 2006; https://doi.org/10.3390/coatings13122006 - 26 Nov 2023
Cited by 2 | Viewed by 1166
Abstract
This work appraises the influence of CO2 laser irradiation on mass loss, morphology, chemical changes and discolouration of spruce wood surfaces. The amount of energy applied to the surface was expressed as the total irradiation dose, which was demonstrated to have a [...] Read more.
This work appraises the influence of CO2 laser irradiation on mass loss, morphology, chemical changes and discolouration of spruce wood surfaces. The amount of energy applied to the surface was expressed as the total irradiation dose, which was demonstrated to have a strong impact on increasing wood weight loss. Along with increasing mass loss, surface roughness also increased, resulting from the differences in density between the early wood and late wood. The evaluated roughness parameters increased linearly with increasing irradiation dose and mass loss. At the maximum irradiation dose, the Ra parameter value parallel to the fibre direction showed a 6-fold increase; perpendicular to the grain, the increase was as much as 33.5-fold. Similar differences were also observed for the parameter Rz. At the lowest laser power and the lowest raster density, the engraved spruce wood surface exhibited some evidence of discolouration (ΔE* ≅ 9). An additional increase in the amount of supplied energy clearly resulted in a novel surface colour compared to the original (ΔE* = 12). The chemical analysis of the wood surface revealed that the discolouration was mainly caused by heat-induced cleavage of C=O groups in the lignin and hemicellulose structures. Part of these structures (so-called chromophores) are responsible for the natural colour of the wood as well as for colour changes caused by engraving. The detected dependences of the wood mass loss and colour values on the total radiation dose are the basis for achieving targeted modifications of spruce wood surfaces using a laser beam. Full article
(This article belongs to the Special Issue Advances in Surface Modification and Coatings of Wood and Wood Composites)
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15 pages, 6706 KiB  
Article
Effect of the Solvent Type on the Colloidal Stability and the Degree of Condensation of Silica Sols Stabilized by Amphiphilic Urethane Acrylate and the Properties of Their Coating Films
by Hong Nhung Le, Choonho Lee, Woochul Jung and Juyoung Kim
Coatings 2023, 13(12), 1997; https://doi.org/10.3390/coatings13121997 - 24 Nov 2023
Cited by 1 | Viewed by 1765
Abstract
The colloidal stability of silica O-I hybrid sols that have a high degree of condensation could result in the formation of a hard coating film on a substrate, which could depend on the properties of solvents used in the sol-gel reaction. In this [...] Read more.
The colloidal stability of silica O-I hybrid sols that have a high degree of condensation could result in the formation of a hard coating film on a substrate, which could depend on the properties of solvents used in the sol-gel reaction. In this study, the effect of the solvent type on the colloidal stability and degree of condensation of the silica sols was investigated by preparing various silica O-I hybrid sols using different solvent mixtures composed of various aprotic and protic solvents in the presence of amphiphilic urethane acrylate. Silica sols prepared using the appropriate aprotic-protic solvent mixture showed a higher degree of condensation and long-term colloidal stability, which was confirmed using 29Si-NMR and DLS. Furthermore, the coating film formed from these silica sols showed a remarkable hardness of 0.97 GPa, with a thickness of 4.76 µm confirmed using nanoindentation measurements. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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16 pages, 4798 KiB  
Article
Calcium Hydroxyapatite Coatings: Low-Temperature Synthesis and Investigation of Antibacterial Properties
by Laura Lukaviciute, Justina Karciauskaite, Inga Grigoraviciute, Dovile Vasiliauskiene, Denis Sokol and Aivaras Kareiva
Coatings 2023, 13(12), 1991; https://doi.org/10.3390/coatings13121991 - 23 Nov 2023
Cited by 4 | Viewed by 1417
Abstract
In the present work, the low-temperature synthesis of substituted calcium hydroxyapatite (Ca10(PO4)6(OH)2, HAP) with copper and zinc ions on titanium substrates was performed. Initially, CaCO3 coatings were synthesised on titanium substrate using the sol-gel [...] Read more.
In the present work, the low-temperature synthesis of substituted calcium hydroxyapatite (Ca10(PO4)6(OH)2, HAP) with copper and zinc ions on titanium substrates was performed. Initially, CaCO3 coatings were synthesised on titanium substrate using the sol-gel method at 550 °C in a CO2 atmosphere. Crystalline calcium hydroxyapatite was then synthesised from these CaCO3 coatings through the dissolution-precipitation method at low temperature (80 °C). X-ray diffraction (XRD) analysis, FTIR and Raman spectroscopies, and scanning electron microscopy (SEM) were employed to evaluate the phase composition, surface functional groups, crystallinity, and morphology of the coatings. The results showed the formation of hexagonal HAP particles with a size of 20 nm at low temperature, exhibiting high homogeneity in particle size distribution. In the calcium hydroxyapatite, some of the Ca2+ ions were replaced by Cu2+ ions. Heating the mixture of Ca(NO3)2 and Cu(NO3)2 solutions at 550 °C in a CO2 atmosphere led to the formation of copper hydroxide carbonate (malachite, Cu2(OH)2CO3) along with CaCO3. The reaction between the sol-gel precursor obtained and Na2HPO4 resulted in the formation of copper-substituted hydroxyapatite (Cu-HAP). Different synthesis methods were tested with Zn2+ ions, and on the surface of the coating, Zn(OH)(NO3)(H2O), Zn3(OH)4(NO3)2, and unreacted CaCO3 were formed. Antibacterial properties of the coatings were tested using the inhibition zone method. No inhibition zones were observed for HAP. However, in the Cu and Zn containing coatings, inhibition zones were observed in the presence of a colony of B. subtilis bacteria. However, no inhibition zones were detected in the presence of E. coli bacteria. Full article
(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications)
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28 pages, 11599 KiB  
Review
A Review on Geothermal Heat Exchangers: Challenges, Coating Methods, and Coating Materials
by Arunima Bhuvanendran Nair Jayakumari, Nigar Gul Malik, Garima Mittal, David Martelo, Namrata Kale and Shiladitya Paul
Coatings 2023, 13(12), 1988; https://doi.org/10.3390/coatings13121988 - 23 Nov 2023
Cited by 1 | Viewed by 2384
Abstract
Geothermal energy is likely to be a significant contributor in achieving sustainable energy goals and net-zero emissions targets. Within geothermal power plants, heat exchangers play a critical role in harnessing this renewable energy source. However, these heat exchangers encounter significant challenges when exposed [...] Read more.
Geothermal energy is likely to be a significant contributor in achieving sustainable energy goals and net-zero emissions targets. Within geothermal power plants, heat exchangers play a critical role in harnessing this renewable energy source. However, these heat exchangers encounter significant challenges when exposed to geothermal fluids, including erosion, corrosion, and scaling, which adversely affects their performance and longevity. The current review focuses on surface engineering techniques, particularly coatings, as a highly effective and economically viable solution to address these challenges in geothermal heat exchangers. The review begins by providing an overview of geothermal energy, its significance in the context of sustainability and the important role played by heat exchangers in geothermal power generation, followed by the challenges and their impact on heat exchangers. The subsequent section focuses on surface engineering by coatings and its types employed to enhance the performance of heat exchangers. In the final part, the reader is presented with an overview of the challenges associated with the application of coatings in geothermal heat exchangers and potential future directions in this field. This review offers a detailed understanding of the critical role coatings play in improving the efficiency and service life of heat exchangers in geothermal power plants. Full article
(This article belongs to the Special Issue Recent Research in Coatings for Harsh Environments)
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20 pages, 26455 KiB  
Article
Comparison of Various Conversion Layers for Improved Friction Performance of Railway Wheel-End Bearings
by Esteban Broitman, Arnaud Ruellan, Ralph Meeuwenoord, Daan Nijboer and Victor Brizmer
Coatings 2023, 13(12), 1980; https://doi.org/10.3390/coatings13121980 - 21 Nov 2023
Viewed by 1298
Abstract
With a growing global railway market which needs to reduce its energy consumption and emissions, railway wheel-end bearing units are being optimized to further reduce power losses with no compromise on reliability. One of the different solutions being evaluated is the selection of [...] Read more.
With a growing global railway market which needs to reduce its energy consumption and emissions, railway wheel-end bearing units are being optimized to further reduce power losses with no compromise on reliability. One of the different solutions being evaluated is the selection of the optimum surface engineering. Inner and outer rings of railway bearing units are currently coated with a zinc-calcium phosphate conversion coating designed for anti-corrosion, anti-fretting, and mounting properties. In this study, different conversion layers, like zinc-calcium phosphate, manganese-phosphate and tribological black oxide, have been compared in terms of friction performance using a single-contact tribometer and a grease-lubricated bearing friction test rig. Results demonstrate that an optimum tribological black oxide conversion layer can reduce the bearing torque by up to 30% in both low and intermediate speeds relevant to intercity trains. Full article
(This article belongs to the Special Issue Surface Engineering, Coatings and Tribology)
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24 pages, 3488 KiB  
Review
Strategies to Enhance Biomedical Device Performance and Safety: A Comprehensive Review
by Julia Sánchez-Bodón, Maria Diaz-Galbarriatu, Leyre Pérez-Álvarez, Isabel Moreno-Benítez and José Luis Vilas-Vilela
Coatings 2023, 13(12), 1981; https://doi.org/10.3390/coatings13121981 - 21 Nov 2023
Cited by 5 | Viewed by 1906
Abstract
This paper reviews different approaches to obtain biomaterials with tailored functionalities and explains their significant characteristics that influence their bioactivity. The main goal of this discussion underscores the significance of surface properties in materials, with a particular emphasis on their role in facilitating [...] Read more.
This paper reviews different approaches to obtain biomaterials with tailored functionalities and explains their significant characteristics that influence their bioactivity. The main goal of this discussion underscores the significance of surface properties in materials, with a particular emphasis on their role in facilitating cell adhesion in order to obtain good biocompatibility and biointegration, while preventing adverse effects, such as bacterial contamination and inflammation processes. Consequently, it is essential to design strategies and interventions that avoid bacterial infections, reducing inflammation and enhancing compatibility systems. Within this review, we elucidate the most prevalent techniques employed for surface modification, notably emphasizing surface chemical composition and coatings. In the case of surface chemical composition, we delve into four commonly applied approaches: hydrolysis, aminolysis, oxidation, and plasma treatment. On the other hand, coatings can be categorized based on their material composition, encompassing ceramic-based and polymer-based coatings. Both types of coatings have demonstrated efficacy in preventing bacterial contamination, promoting cell adhesion and improving biological properties of the surface. Furthermore, the addition of biological agents such as drugs, proteins, peptides, metallic ions plays a pivotal role in manifesting the prevention of bacterial infection, inflammatory responses, and coagulation mechanism. Full article
(This article belongs to the Special Issue Advanced Coatings for Biomedical Applications)
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18 pages, 4423 KiB  
Article
Effect of Electrodeposited Gold Coatings on Micro-Gaps, Surface Profile and Bacterial Leakage of Cast UCLA Abutments Attached to External Hexagon Dental Implants
by Terry R. Walton
Coatings 2023, 13(12), 1976; https://doi.org/10.3390/coatings13121976 - 21 Nov 2023
Viewed by 1072
Abstract
Purpose: The objective of the study was to qualitatively assess the micro-gap dimensions, connecting fitting surface profile, and bacterial leakage of cast high-gold-alloy UCLA abutments, with or without electrodeposited gold coatings attached to external hexagon implants. Materials and methods: Sixteen plastic [...] Read more.
Purpose: The objective of the study was to qualitatively assess the micro-gap dimensions, connecting fitting surface profile, and bacterial leakage of cast high-gold-alloy UCLA abutments, with or without electrodeposited gold coatings attached to external hexagon implants. Materials and methods: Sixteen plastic UCLAs (PUCLAs) were cast with a high-gold-content alloy. Eight were electrolytically gold plated. Five machined cast-to-UCLA (GUCLA) control abutments were cast with the same alloy. All abutments were attached to external hexagon implants, giving 21 implant-abutment combinations (IACs). External perimeter micro-gaps measured with SEM under shadow eliminating silhouette illumination and 2000× magnification were averaged over three regions. The IACs were examined for E. coli leakage following an initial sterility test. Disassembled combinations were examined with SEM, and surface profiles were qualitatively assessed. Results: External micro-gap measurements did not reflect the variable connecting surface profiles, but average values < 5.0 μm were observed for all IACs measured under the shadow eliminating silhouette illumination for both cast and pre-machined external hexagon abutments with and without Au plating. E. coli transfer was observed in 3 of 5 PUCLA-plated and 2 of 5 PUCLA-non-plated IACs. No transfer occurred in the 3 GUCLA-non-plated or 2 GUCLA-plated control IACs. Abutment connecting surfaces, both Au-plated and not Au-plated, showed plastic deformation (smearing) in variable mosaic patterns across the micro-gap. Conclusions: Micro-gap dimensions < 5μm were obtained with both the high noble metal cast and pre-machined control external hexagon abutments with and without Au electrodeposited on the abutment connecting surface. Regions of intimate contact due to plastic deformation (smearing) of these surfaces were observed. A continuous smeared region around the circumference of the surfaces can provide an effective barrier to the egress of E. coli bacteria from the internal regions of the implant under static loading. The sample size was insufficient to determine if the gold coating resulted in a superior bacterial barrier. Full article
(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications)
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13 pages, 1358 KiB  
Article
Paper Coatings Based on Polyvinyl Alcohol and Cellulose Nanocrystals Using Various Coating Techniques and Determination of Their Barrier Properties
by Alicja Tarnowiecka-Kuca, Roos Peeters, Bram Bamps, Magdalena Stobińska, Paulina Kamola, Artur Wierzchowski, Artur Bartkowiak and Małgorzata Mizielińska
Coatings 2023, 13(11), 1975; https://doi.org/10.3390/coatings13111975 - 20 Nov 2023
Viewed by 1664
Abstract
The goal of this work was to improve the barrier properties of selected papers against water, grease and oil or gases (water vapor and oxygen) by covering them with biodegradable commercial coating carriers based on cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVOH). The [...] Read more.
The goal of this work was to improve the barrier properties of selected papers against water, grease and oil or gases (water vapor and oxygen) by covering them with biodegradable commercial coating carriers based on cellulose nanocrystals (CNCs) and polyvinyl alcohol (PVOH). The aim was also to obtain cellulose recyclable packaging materials with improved barrier characteristics. The properties of paper coatings based on CNCs and PVOH were characterized. Various paper coating techniques (flexographic printing, rotogravure printing and blade printing) were evaluated with respect to the final properties of the surface-modified paper with different starting grammages (40 g/m2, 70 g/m2, 100 g/m2). Functional properties, such as the barrier against oxygen, water vapor, water and grease; mechanical properties; and seal characterization of coated paper were examined. The results of this study demonstrated that the covering of the paper may improve the water, grease and oil barrier and that the best results were obtained for Gerstar 70 g/m2 coated with J12 coatings using the flexographic technique. Full article
(This article belongs to the Special Issue Advanced Coatings and Films for Food Packing and Storage)
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30 pages, 7307 KiB  
Article
Preparation and Testing of Anti-Corrosion Properties of New Pigments Containing Structural Units of Melamine and Magnesium Cations (Mg2+)
by Miroslav Kohl, Fouzy Alafid, Karolína Boštíková, Anna Krejčová, Stanislav Slang, Dominik Řezníček, Radim Hrdina and Andréa Kalendová
Coatings 2023, 13(11), 1968; https://doi.org/10.3390/coatings13111968 - 19 Nov 2023
Viewed by 1459
Abstract
This paper deals with the properties and testing of newly prepared organic pigments based on melamine cyanurate containing magnesium or zinc cations depending on their composition and anticorrosive properties in model coatings. Organic pigments based on melamine cyanurate with Mg2+ in the [...] Read more.
This paper deals with the properties and testing of newly prepared organic pigments based on melamine cyanurate containing magnesium or zinc cations depending on their composition and anticorrosive properties in model coatings. Organic pigments based on melamine cyanurate with Mg2+ in the form of a complex differing in the ratio of melamine and cyanurate units were prepared. Furthermore, a pigment based on melamine citrate with magnesium cation Mg2+, a pigment based on melamine citrate with magnesium cation, and a pigment based on melamine cyanurate with zinc cation were prepared. The properties of Mg-containing organic pigments were also compared with those of selected magnesium-containing inorganic oxide-type pigments. The above-synthesized pigments were characterized by inductively coupled plasma-optical emission spectroscopy, elemental analysis, scanning electron microscopy, and X-ray diffraction. In addition, the basic parameters that are indicative of the applicability of the pigments in the binders of anti-corrosion coatings were determined. The anti-corrosive properties of the tested pigments were verified after application to the epoxy-ester resin-based paint binder in three different concentrations: at pigment volume concentrations of 0.10%, 0.25%, and 0.50%. The anticorrosive effectiveness of pigmented organic coatings was verified by cyclic corrosion tests in a salt electrolyte fog (NaCl + (NH4)2SO4) in an atmosphere containing SO2 and by the electrochemical technique of linear polarization. Finally, the effect of the structure of the pigments on the mechanical resistance of the organic coatings was investigated. The results obtained showed that the new organic pigments exhibit anticorrosive properties, and at the same time, differences in performance were found depending on the structure of the pigments tested. Specifically, the results of cyclic corrosion tests and the electrochemical technique of linear polarization clearly demonstrated that synthesized pigments of the organic type based on melamine cyanurate containing magnesium or zinc cations ensure the anti-corrosion efficiency of the tested organic coatings. The highest anti-corrosion efficiency was achieved by the system pigmented with synthesized melamine cyanurate with magnesium cation (C12H16MgN18O6), whose anti-corrosion efficiency was comparable to the anti-corrosion efficiency of the tested inorganic pigment MgFe2O4, which was prepared by high-temperature solid-phase synthesis. In addition, these organic coatings achieved high mechanical resistance after being tested using the most used standardized mechanical tests. 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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16 pages, 4831 KiB  
Article
Fabrication of Piezoelectric ZnO Nanowires on Laser Textured Copper Substrate to Enhance Catalytic Properties
by Hongbin Wang, Rui Zhou, Huangping Yan and Hongjun Liu
Coatings 2023, 13(11), 1963; https://doi.org/10.3390/coatings13111963 - 17 Nov 2023
Viewed by 1350
Abstract
In this work, 3D periodic “grid-type” CuO/Cu2O layers were fabricated on a copper sheet using laser processing techniques, and the laser processing parameters were optimized for favorable ZnO nanowire growth. It was found that ZnO nanowires could be successfully prepared to [...] Read more.
In this work, 3D periodic “grid-type” CuO/Cu2O layers were fabricated on a copper sheet using laser processing techniques, and the laser processing parameters were optimized for favorable ZnO nanowire growth. It was found that ZnO nanowires could be successfully prepared to form a CuO-Cu2O-ZnO heterojunction structure without an extra catalyst or seed layer coating, which could be attributed to the copper oxide active sites induced via laser texturing. ZnO nanowires on laser textured “grid-type” copper substrates demonstrated an effective piezocatalytic performance with different morphologies and the generation of abundant reactive oxygen species in the CuO-Cu2O-ZnO catalytic system, providing a fundamental mechanism for the degradation of organic dye in water. This simple and low-cost method could provide a useful guide for the large-scale efficient and versatile synthesis of immobilized piezoelectric catalysts. Full article
(This article belongs to the Special Issue Fabrication of Metallic Micro-/Nano-Composite Materials for Environmental Applications)
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15 pages, 6870 KiB  
Article
Microstructure and Tribological Performance of HVAF-Sprayed Ti-6Al-4V Coatings
by Tunji A. Owoseni, Irene Ciudad de Lara, Sribalaji Mathiyalagan, Stefan Björklund and Shrikant Joshi
Coatings 2023, 13(11), 1952; https://doi.org/10.3390/coatings13111952 - 15 Nov 2023
Cited by 3 | Viewed by 1852
Abstract
Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must [...] Read more.
Ti-6Al-4V is a widely used titanium alloy in aviation and bio/chemical applications for its attractive mechanical and corrosion resistance properties. The use of Ti-6Al-4V as a coating for repair purposes through thermal spray techniques provides a unique productivity opportunity. A repair coating must be dense to provide the required in-service functionalities, such as resistance to wear. The High Velocity Air Fuel (HVAF) thermal spray technique deposits dense coatings with reduced concern for oxide inclusions. This work presents an investigation of the microstructure, dry sliding, and solid particle erosive wear performance of four different coatings engineered through the configuration of the nozzle of an HVAF spray gun, based on the length of the nozzle and the size of the nozzle exit. A long nozzle length and wide nozzle exit mean increased inflight dwell time and reduced average inflight temperature for the sprayed particles, respectively—a reversed configuration means the opposite. The tested coatings showed a porosity of less than 2%. The sliding and erosion wear performance of the densest of the coatings compares to that of the bulk material tested under the same conditions. Electron microscopy was used to investigate the driving mechanisms for the performance of the respective coatings. The implications of the results are discussed for the potential adoption of HVAF-sprayed coatings in metal component repair. Full article
(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)
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24 pages, 17023 KiB  
Article
Development of a Hydrophobic Polymer Coating in Polyurethane Organic–Mineral Base Containing Waste from Fibreglass Production
by Karolína Hudec Jakubíková, Jakub Hodul, Radek Hermann and Rostislav Drochytka
Coatings 2023, 13(11), 1934; https://doi.org/10.3390/coatings13111934 - 12 Nov 2023
Cited by 4 | Viewed by 2277
Abstract
In this study, the suitability of waste from glass fibre production as a secondary filler for a polymeric durable hydrophobic coating, based on an innovative polyurethane organic–mineral base, was experimentally verified. The main aim of this work was to develop a basic formulation [...] Read more.
In this study, the suitability of waste from glass fibre production as a secondary filler for a polymeric durable hydrophobic coating, based on an innovative polyurethane organic–mineral base, was experimentally verified. The main aim of this work was to develop a basic formulation for a polymeric hydrophobic coating designed primarily for usage in aggressive environments. For this purpose, a total of four formulations were tested with different weight percentages of waste glass fibre, i.e., from 30 to 60%. The basic properties in the fresh state, such as the coating workability and kinematic and dynamic viscosity, were verified, and an application test was performed. The formulations were also verified after the polymerisation of the coating. Adhesion on a concrete substrate and the tensile properties and hardness of the coating were tested. Chemical resistance to liquid aggressive media and the microstructure of the coating after exposure to SO2 were also tested, as these are critical properties. All the formulations showed better workability than the reference coating without a filler, and the formulation with the highest filling (60%) appeared to be optimal. The maximum adhesion on the concrete substrate (11.9 MPa) and tensile strength (21.6 MPa) were recorded for the formulation with 60% waste fibreglass. It can be concluded that with an increase in the waste glass content, there was a significant improvement in the properties of the coatings. Additionally, the waste fibreglass did not have a significant negative impact on chemical resistance. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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24 pages, 4524 KiB  
Review
Progress in Marine Antifouling Coatings: Current Status and Prospects
by Liang Li, Heting Hong, Jingyi Cao and Yange Yang
Coatings 2023, 13(11), 1893; https://doi.org/10.3390/coatings13111893 - 3 Nov 2023
Cited by 4 | Viewed by 4963
Abstract
The shipping industry is vital to global trade. Unfortunately, this industry is negatively impacted on a large scale by biofouling, a process whereby unwanted organisms accumulate on submerged surfaces, massively affecting traveling speed and fuel consumption. Fortunately, antifouling coatings have been developed to [...] Read more.
The shipping industry is vital to global trade. Unfortunately, this industry is negatively impacted on a large scale by biofouling, a process whereby unwanted organisms accumulate on submerged surfaces, massively affecting traveling speed and fuel consumption. Fortunately, antifouling coatings have been developed to combat this problem. This review summarizes the process of biofouling and briefly discusses the history of antifouling coating development. Moreover, eight major antifouling coatings are reviewed, including bionic microstructure, self-polishing, fouling and desorption, zwitterionic polymer, self-assembled thin-layer, liquid-smooth surface, conductive, and photocatalytic antifouling coatings. The technical principles, innovation, and advancement of each coating are expounded, and the relevant research progress is discussed. Finally, the remaining issues and challenges in antifouling coatings are discussed, along with their prospects. Full article
(This article belongs to the Special Issue Microstructure and Corrosion Behavior of Metallic Materials)
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19 pages, 4541 KiB  
Article
Composite of Poly(Vinyl Chloride) Plastisol and Wood Flour as a Potential Coating Material
by Przemysław Siekierka, Edwin Makarewicz, Sławomir Wilczewski, Krzysztof Lewandowski, Katarzyna Skórczewska, Jacek Mirowski and Magdalena Osial
Coatings 2023, 13(11), 1892; https://doi.org/10.3390/coatings13111892 - 3 Nov 2023
Cited by 2 | Viewed by 1213
Abstract
This paper presents the results of a study of the properties of a new composite material made from poly(vinyl chloride) plastisol (PVC) and conifer-derived wood flour. The material can be used for thermal insulation, floor coverings with high resistance to mechanical trauma, and [...] Read more.
This paper presents the results of a study of the properties of a new composite material made from poly(vinyl chloride) plastisol (PVC) and conifer-derived wood flour. The material can be used for thermal insulation, floor coverings with high resistance to mechanical trauma, and protective coatings. The plastisol was made from emulsion poly(vinyl chloride), the plasticiser was bis(2-ethylhexyl) adipate, and the stabiliser was octyltin mercapeptide. Two types of flour were used: fine-grained and coarse-grained. Its properties, such as bulk density, oil number, and plasticiser number, were determined. The polymer-wood composite contained 20 or 30 wt.% wood flour in PVC. Plastisol was obtained by repeated mixing, mashing, and venting under vacuum. The produced composite material was gelated at temperatures of 130, 150, and 170 °C. The gelation process of the composites was studied in a Brabender apparatus. Samples in the form of polymer films were used to study density, hardness, thermal stability, and mechanical and thermomechanical properties. The structure of the composites was observed by scanning electron microscopy (SEM). A summary of all test results showed that composite films made from PVC plastisol with 20 wt.% of fine wood flour gelled at 150 °C had the most favourable physical, mechanical, and thermal properties. 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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19 pages, 7395 KiB  
Article
Simple UV-Grafting of PolyAcrylic and PolyMethacrylic Acid on Silicone Breast Implant Surfaces: Chemical and Mechanical Characterizations
by Anna Wozniak, Vincent Humblot, Romain Vayron, Rémi Delille and Céline Falentin-Daudré
Coatings 2023, 13(11), 1888; https://doi.org/10.3390/coatings13111888 - 2 Nov 2023
Viewed by 1180
Abstract
Poly(dimethyl siloxane) (PDMS) is one of the most widely used materials in the biomedical field. Despite its numerous advantages, its hydrophobic character promotes bacterial adhesion and biofilm formation. For breast implants, biocompatibility is challenged due to the biofilm formed around the implant that [...] Read more.
Poly(dimethyl siloxane) (PDMS) is one of the most widely used materials in the biomedical field. Despite its numerous advantages, its hydrophobic character promotes bacterial adhesion and biofilm formation. For breast implants, biocompatibility is challenged due to the biofilm formed around the implant that can degenerate to severe capsular contracture over time. Thus, the laboratory has set up strategies to prevent bacterial contamination by grafting covalently hydrophilic bioactive polymers on the surface of implants. In this study, poly(methacrylic acid) (PMAc) and poly(acrylic acid) (PAAc) were chosen as non-toxic and biocompatible bioactive polymers known for reducing bacteria adhesion. These polymers are also good candidates to lend reactivity on the surface for further functionalization. X-ray photoelectron Spectroscopy (XPS) and Fourier-Transform Infrared spectroscopy (FTIR) analysis have highlighted the covalent grafting of these polymers. Apparent water contact angle measurements have shown the change in hydrophilicity on the surface, and a colorimetric assay allowed us to assess the grafting rate of PMAc and PAAc. Tensile strength assays were performed to ensure that the functionalization process does not significantly alter the material’s mechanical properties. Analyses of the surface aspect and roughness by Scanning Electron Microscope (SEM) and optical profilometer allow us to formulate hypotheses to approach the understanding of the behavior of the polymer once grafted. Full article
(This article belongs to the Special Issue Surface Properties of Implants and Biomedical Devices)
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28 pages, 5396 KiB  
Review
Preparation and Applications of Superhydrophobic Coatings on Aluminum Alloy Surface for Anti-Corrosion and Anti-Fouling: A Mini Review
by Qianyi Zhu, Xiaoqing Du, Yudie Liu, Xuming Fang, Dongchu Chen and Zhao Zhang
Coatings 2023, 13(11), 1881; https://doi.org/10.3390/coatings13111881 - 1 Nov 2023
Viewed by 2623
Abstract
Aluminum alloy is widely used in many fields for its excellent performance. However, in practical application, aluminum alloy is easy to become corroded and be invalidated, owing to the influence of environmental factors. Some pollutants or corrosive media on its surface adhesion will [...] Read more.
Aluminum alloy is widely used in many fields for its excellent performance. However, in practical application, aluminum alloy is easy to become corroded and be invalidated, owing to the influence of environmental factors. Some pollutants or corrosive media on its surface adhesion will further deepen the failure rate of aluminum alloy, resulting in a large amount of workforce waste, waste of material and financial resources, and energy consumption. So the anti-corrosion and anti-fouling treatment of aluminum alloy surfaces to expand their practical application range and reduce energy loss are of great significance. In this paper, we first summarize the types of anti-corrosion and anti-fouling coatings on aluminum alloy surfaces. We found that superhydrophobic coating has attracted widespread attention recently because of its surface’s non-wetting and low surface energy characteristics. The superhydrophobic coating refers to a coating with a water contact angle on its surface greater than 150° and a sliding angle of less than 10°. Preparing superhydrophobic coatings on the surface of aluminum alloy can improve the corrosion resistance and anti-pollutant adhesion ability at the same time. Therefore, in the following part of the review, the preparation methods of superhydrophobic coatings on aluminum alloy surfaces for anti-corrosion and anti-fouling and the significant problems encountered in the practical application of the superhydrophobic coating on aluminum alloy surfaces, such as poor anti-corrosion durability and poor mechanical stability, and the existing methods to solve these critical problems, are summarized and discussed in detail. Finally, we put forward some new solutions to solve these vital issues. Full article
(This article belongs to the Special Issue Smart Coatings)
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15 pages, 9982 KiB  
Article
Correlation between Microstructural Properties and Electric Parameters of Micro-Arc Oxidation Coatings on 5052 Aluminum Alloys with Improving Wear and Corrosion Resistance
by Jhu-Lin You, Chin-Jou Chang and Shun-Yi Jian
Coatings 2023, 13(11), 1874; https://doi.org/10.3390/coatings13111874 - 31 Oct 2023
Cited by 1 | Viewed by 1184
Abstract
Aluminum (Al) alloys are lightweight and machinable and have been widely used in industrial applications, particularly the formation of complex mechanical parts. However, the 5052 Al alloy frequently encounters problems like corrosion and wear during its service life, significantly impacting the equipment’s longevity. [...] Read more.
Aluminum (Al) alloys are lightweight and machinable and have been widely used in industrial applications, particularly the formation of complex mechanical parts. However, the 5052 Al alloy frequently encounters problems like corrosion and wear during its service life, significantly impacting the equipment’s longevity. This study investigated the effects of pulse voltage (320 to 400 V) and frequency (50 to 200 Hz) on the growth and surface morphology of 5052 Al alloy films formed through micro-arc oxidation (MAO) to improve their corrosion and wear resistance while maintaining a surface roughness of less than 1 μm. The results indicate that higher operating voltages and frequencies correlated with increased thickness in the resulting ceramic oxide films formed using MAO. In addition, as the pulse frequency increased, the distribution of the holes became more uniform across the surface. We examined the surface and cross-sectional morphology, as well as the thickness of the MAO coatings, through scanning electron microscopy (SEM). The corrosion and wear resistance of the MAO coatings formed under different electrical parameters were analyzed using electrochemical corrosion tests and scratch tests. The MAO coatings produced at 400 V and 200 Hz were the thickest, at approximately 4.8 μm, and demonstrated superior corrosion and wear resistance. These coatings demonstrate significantly reduced wear width, highlighting their exceptional resistance to corrosion and wear. Hole cracking occurred only above the top layer of the coating and not beneath the mid-layer, which protected the substrate from damage due to the direct passage of Cl ions through the holes. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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22 pages, 6463 KiB  
Article
Effect of Zinc Content on Powder Characteristics, Porosity, Microstructure, and Corrosion Behavior of SLM-Printed Mg-xZn-0.2Mn Alloys for Biomedical Applications
by Weijie Xie, Chen-Liang Wu, Hau-Chung Man and Chi-Wai Chan
Coatings 2023, 13(11), 1876; https://doi.org/10.3390/coatings13111876 - 31 Oct 2023
Viewed by 1378
Abstract
This study investigated the effects of Zinc (Zn) content, specifically in the range of 1 wt.% to 7 wt.%, on the powder characteristics, porosity, microstructure, and corrosion behavior of Mg-xZn-0.2Mn alloys produced using selective laser melting (SLM). To evaluate the porosity of the [...] Read more.
This study investigated the effects of Zinc (Zn) content, specifically in the range of 1 wt.% to 7 wt.%, on the powder characteristics, porosity, microstructure, and corrosion behavior of Mg-xZn-0.2Mn alloys produced using selective laser melting (SLM). To evaluate the porosity of the printed parts and various powder attributes, such as size, circularity, void spaces between powders, and inherent imperfections, scanning electron microscopy (SEM) and optical microscopy (OM) were employed. The alloy microstructure, composition, and phase were examined using energy dispersive X-ray (SEM-EDX) and X-ray Diffraction (XRD). The corrosion resistance and degradation behavior were assessed through electrochemical corrosion tests and immersion tests in Hanks’ solution at 37.5 °C, respectively. Finally, OM and SEM-EDX were used to characterize the corrosion products. The findings of this study indicated that the powder size increased with Zn content, maintaining a 0.8 circularity. Powder defects were minimal, with occasional satellite particles. For the SLM-printed samples, it was evident that porosity characteristics could be influenced by Zn content. As Zn content increased, the pore fraction rose from 1.0% to 5.3%, and the pore size grew from 2.2 μm to 3.0 μm. All printed samples consisted of an α-Mg matrix. Additionally, a higher Zn content resulted in more distinct grain boundaries. Corrosion resistance decreased with Zn, leading to more pronounced localized corrosion after immersion in Hanks’ solution. Ca-P was found as white corrosion products on all samples. Full article
(This article belongs to the Special Issue Laser Surface Engineering and Additive Manufacturing)
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22 pages, 6618 KiB  
Article
AgNWs–Silane Coatings for the Functionalization of Aramid Woven Fabrics
by Alicja Nejman, Anna Baranowska-Korczyc, Grzegorz Celichowski and Małgorzata Cieślak
Coatings 2023, 13(11), 1852; https://doi.org/10.3390/coatings13111852 - 27 Oct 2023
Viewed by 1324
Abstract
Aramid woven fabrics are widely used to provide protection in extreme conditions, especially in high temperatures. Multifunctional aramid fabrics with no deteriorated thermal resistance and antibacterial properties are needed for high-risk professions. In this study, silver nanowires (AgNWs) and silanes (S) were used [...] Read more.
Aramid woven fabrics are widely used to provide protection in extreme conditions, especially in high temperatures. Multifunctional aramid fabrics with no deteriorated thermal resistance and antibacterial properties are needed for high-risk professions. In this study, silver nanowires (AgNWs) and silanes (S) were used for the functionalization of meta- (mAr) and para-aramid (pAr) woven fabrics by mixture (Ag + S) or by the layer-by-layer (Ag/S) method. Antibacterial properties, thermal management, and stability were studied to select the functionalization method which provided the highest thermal performance, comfort, and bioactivity. Both methods decreased the fabric’s surface temperature during heating in the range of 35–40 °C by 3 °C and 2 °C, respectively, for mAr and pAr, in comparison to unmodified fabrics. After Ag + S and Ag/S modifications, the thermal degradation initial temperature increased from 554 °C to 560 °C (TG/DTG) and from 525 °C to 533 °C (DSC) for pAr fabrics, and decreased from 417 °C to 403 °C (TG/DTG) and from 411 °C to 406 °C (DSC) for mAr fabrics. The reduction in Gram− (Klebsiella pneumonia) and Gram+ (Staphylococcus aureus) bacterial growth for all modified samples was above 90%. The bactericidal and bacteriostatic coefficients were slightly higher for Ag/S functionalization. The highest thermal performance and antimicrobial activity were noted for pAr fabric modified using the Ag/S method. Full article
(This article belongs to the Special Issue Antibacterial, High Oxidation Coatings for Environmental Applications)
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16 pages, 17298 KiB  
Article
Epoxy Coatings Doped with (3-Aminopropyl)triethoxysilane-Modified Silica Nanoparticles for Anti-Corrosion Protection of Zinc
by Tamara-Rita Ovari, Timea Toth, Gabriel Katona, Gabriella Stefánia Szabó and Liana Maria Muresan
Coatings 2023, 13(11), 1844; https://doi.org/10.3390/coatings13111844 - 27 Oct 2023
Cited by 2 | Viewed by 2713
Abstract
Epoxy (EP) coatings containing silica (SiO2) and (3-Aminopropyl)triethoxysilane-modified silica (SiO2-APTES) nanoparticles were prepared via the dip-coating technique on a zinc substrate. A detailed study was performed regarding their incorporation into the matrix, followed by the investigation of the newly [...] Read more.
Epoxy (EP) coatings containing silica (SiO2) and (3-Aminopropyl)triethoxysilane-modified silica (SiO2-APTES) nanoparticles were prepared via the dip-coating technique on a zinc substrate. A detailed study was performed regarding their incorporation into the matrix, followed by the investigation of the newly obtained organic–inorganic hybrid coatings’ anti-corrosive properties. The two methods of embedding the nanoparticles were (I) modification of the silica nanoparticles with APTES followed by their introduction into the epoxy resin, and (II) functionalization of the silica nanoparticles in the epoxy gel before the addition of the hardener. It was observed that through the second method, the coating was homogeneous, with no sign of agglomerates. The nanoparticles were subjected to morpho-structural and physical–chemical analysis using Fourier-Transform Infrared Spectroscopy and Transmission Electron Microscopy, while the coatings were examined through Scanning Electron Microscopy and Energy-Dispersive X-Ray Spectroscopy, contact angle measurements and adhesion tests. The anti-corrosive performance of epoxy-coated zinc was analyzed using electrochemical impedance spectroscopy and polarization curves to investigate the impact of silanized SiO2 nanoparticle incorporation. Based on long-term corrosion testing, the epoxy-SiO2-APTES composite coatings showed a higher corrosion resistance than the undoped epoxy layer. 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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15 pages, 1491 KiB  
Article
Effect of Aminopropyltriethoxysilane on the Adhesion of Flexographic Water-Based Ink to Packaging Films
by Joanna Izdebska-Podsiadły and Jolanta Napiórkowska
Coatings 2023, 13(11), 1833; https://doi.org/10.3390/coatings13111833 - 26 Oct 2023
Cited by 1 | Viewed by 1562
Abstract
Plastic films are widely used in packaging, where high-quality printing on their surface is required. When printing on films, particularly with water-based inks, problems arise with proper ink adhesion to the substrate. As part of the ongoing research, formulas of flexographic water-based inks [...] Read more.
Plastic films are widely used in packaging, where high-quality printing on their surface is required. When printing on films, particularly with water-based inks, problems arise with proper ink adhesion to the substrate. As part of the ongoing research, formulas of flexographic water-based inks were developed, where aminopropyltriethoxysilane was used in various amounts as an adhesion promoter, its effect on the adhesion of inks to three types of films commonly used in packaging was determined, and the quality of prints was examined. The research included the tape test, the T-peel test, and the abrasion-resistance test, as well as measurements of the pH of the inks, contact angles, and optical properties of the prints and their gloss. As a result of the study, the type of film was found to be crucial to the effect of aminopropyltriethoxysilane on the adhesion of flexographic water-based ink to the substrate and print quality. An addition of 1.0%–1.5% makes it possible to achieve the best adhesion improvement (bonding strength increased by about 26, 35, and 102% for PE, BOPP, and PET films, respectively) while improving print quality—increasing the optical density of prints and their gloss. However, the use of 1.5% silane in ink has a significant impact on the color of the ink (∆E ranging from 2.2 to 7.8 depending on the film). The amount of the additive used (0.5 to 1.5%) of aminopropyltriethoxysilane in the ink would need to vary depending on the type of film to be printed. Full article
(This article belongs to the Section Functional Polymer Coatings and Films)
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14 pages, 1732 KiB  
Article
Fluorine-Free Plasma Polymers to Obtain Water-Repellent Cotton Fabrics: How to Control Their Durability?
by Syrine Jebali, Jamerson Carneiro de Oliveira, Aissam Airoudj, Asma Riahi, Philippe Fioux, Fabrice Morlet-Savary, Ludovic Josien, Isabelle Ferreira, Vincent Roucoules and Florence Bally-Le Gall
Coatings 2023, 13(11), 1827; https://doi.org/10.3390/coatings13111827 - 25 Oct 2023
Cited by 1 | Viewed by 1381
Abstract
The plasma polymerization of hexamethyldisiloxane (HMDSO) leads to the environmentally friendly fabrication of water-repellent coatings through a vapor-phase surface functionalization process using alternatives to the controversial perfluoroacrylate precursors. However, the durability of these coatings is their Achilles’ heel, which requires an in-depth study [...] Read more.
The plasma polymerization of hexamethyldisiloxane (HMDSO) leads to the environmentally friendly fabrication of water-repellent coatings through a vapor-phase surface functionalization process using alternatives to the controversial perfluoroacrylate precursors. However, the durability of these coatings is their Achilles’ heel, which requires an in-depth study of the relationship between the structure and properties of these thin films in order to propose concrete solutions for the fabrication of fluorine-free water-repellent textiles. In this context, HMDSO plasma polymers have been deposited on cotton fabrics in an original reactor that allows easy tuning of temporal and spatial parameters of the glow discharge. The functionalized fabrics were characterized to gain insights into the chemical composition of the coatings, their morphology and, above all, their adhesion properties. Interestingly, the results after washing tests revealed a significant dependence of the durability of the superhydrophobic property on the elastic modulus of the deposited polymer. The formation of some radicals at the substrate–thin film interface in the early stages of deposition also correlates with some results. These relationships between the operating conditions of the plasma polymerization, the interfacial properties and the performances of the functionalized fabrics, but also the characterization methodology developed in this work, can undoubtedly serve the engineering of water-repellent fluorine-free coatings on fabrics with optimal durability. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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25 pages, 6461 KiB  
Article
The Influence of the Magnetic Field on Ni Thin Film Preparation by Electrodeposition Method and Its Electrocatalytic Activity towards Hydrogen Evolution Reaction
by Safya Elsharkawy, Dawid Kutyła and Piotr Zabinski
Coatings 2023, 13(10), 1816; https://doi.org/10.3390/coatings13101816 - 23 Oct 2023
Cited by 6 | Viewed by 2041
Abstract
Ni thin films were synthesized through the electrodeposition method from three different electrolytes (acetate, borate, and citrate). Furthermore, they were assessed as electrocatalysts for hydrogen evolution reaction (HER) in 1 M NaOH. Herein, various electrodeposition parameters, such as the pH of the electrolytes, [...] Read more.
Ni thin films were synthesized through the electrodeposition method from three different electrolytes (acetate, borate, and citrate). Furthermore, they were assessed as electrocatalysts for hydrogen evolution reaction (HER) in 1 M NaOH. Herein, various electrodeposition parameters, such as the pH of the electrolytes, the deposition potential, and the influence of the magnetic field, were measured. We compared the different morphologies and characteristics depending on the thin film electrodeposition process parameters. Moreover, we studied the material’s wettability changes based on the electrolyte’s composition and the applied external magnetic field. It was found that the deposited Ni thin film from the citrate electrolyte under the influence of the magnetic field in the perpendicular direction to the electrode surface had the best catalytic performance to HER. It possessed an overpotential value of 231 mV and a Tafel slope of 118 mV dec−1. The deposition process was accomplished by using the chronoamperometry technique. Measuring scanning electron microscope and X-ray diffraction were used to characterize the fabricated films’ surface morphologies and crystalline structures. Full article
(This article belongs to the Special Issue Recent Achievements in Coatings Electroplating from Non-aqueous Electrolytes)
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17 pages, 9768 KiB  
Article
Experimental Evaluation of the Properties of Asphalt Binders Modified with Calcium Sulfate Anhydrous Whiskers and Polyester Fibers
by Taotao Fan, Chundi Si and Junfeng Gao
Coatings 2023, 13(10), 1802; https://doi.org/10.3390/coatings13101802 - 20 Oct 2023
Viewed by 1025
Abstract
The use of waste calcium sulfate whiskers in pavement construction is cost-effective and beneficial to the environment. In this paper, modified asphalt binders are prepared by adding calcium sulfate anhydrous whiskers (ACSW, 9 wt.%,11 wt.%, and 13 wt.% by weight of asphalt binder) [...] Read more.
The use of waste calcium sulfate whiskers in pavement construction is cost-effective and beneficial to the environment. In this paper, modified asphalt binders are prepared by adding calcium sulfate anhydrous whiskers (ACSW, 9 wt.%,11 wt.%, and 13 wt.% by weight of asphalt binder) and polyester fibers (4 wt.%,6 wt.%, and 8 wt.% by weight of asphalt binder). The viscosity-temperature, rheological, and low-temperature properties of the modified asphalt binder were evaluated using the Brookfield rotational viscosity test, the dynamic shear rheometer (DSR) test, the bending beam rheometer (BBR) test, and the force ductility test. The results demonstrated that the addition of the ACSW and polyester fiber could improve the anti-deformation and low-temperature properties of the asphalt binders, but reduce their viscosity-temperature properties to some extent. The modified asphalt binder with 11 wt.% ACSW and 8% polyester fiber showed the best anti-deformation property, while the 11 wt.% ACSW and 6 wt.% polyester fiber modified asphalt binder had a better low-temperature performance. The force ductility test was more suitable than the BBR test to characterize the low-temperature properties of the modified asphalt binders. The Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) tests were conducted to study the functional groups and micro-structure of the modified asphalt binders, and the results indicated that no new functional groups were generated and that the interaction between the ACSW, polyester fiber, and asphalt binder was a physical adsorption and interleaving process. Full article
(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)
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10 pages, 7354 KiB  
Article
Tribo-Catalytic Degradation of Methyl Orange Solutions Enhanced by Silicon Single Crystals
by Xiaodong Cui, Zhiyu Guo, Hua Lei, Xuchao Jia, Chenyue Mao, Lujie Ruan, Xiaoyuan Zhou, Zhu Wang, Feng Chen and Wanping Chen
Coatings 2023, 13(10), 1804; https://doi.org/10.3390/coatings13101804 - 20 Oct 2023
Cited by 7 | Viewed by 2387
Abstract
Coating materials on the bottoms of reactors/beakers has emerged as an effective method to regulate tribo-catalytic reactions. In this study, silicon single crystals were coated on the bottoms of glass beakers, in which 30 mg/L methyl orange (MO) solutions suspended with alumina nanoparticles [...] Read more.
Coating materials on the bottoms of reactors/beakers has emerged as an effective method to regulate tribo-catalytic reactions. In this study, silicon single crystals were coated on the bottoms of glass beakers, in which 30 mg/L methyl orange (MO) solutions suspended with alumina nanoparticles were subjected to magnetic stirring using Teflon magnetic rotary disks. With a gentle rotating speed of 400 rpm for the Teflon disks, the MO solutions were changed from yellow to colorless and the characteristic absorption peak of MO at 450 nm in the UV-Vis spectrum disappeared entirely within 120 min. Mass spectrometry tests were further performed to gain insights into the degradation process, which suggested that the degradation was initiated with the cleavage of the nitrogen-nitrogen double bond in ionized MO molecules by the attack of •OH radicals. Through comparison experiments, we established that the observed degradation was related to the friction between alumina and silicon during magnetic stirring, and hydroxyl and superoxide radicals were formed from the friction, according to electron paramagnetic resonance analysis. It is proposed that electron-hole pairs are excited in silicon single crystals through friction with alumina, which diffuse to the surface of the single crystals and result in the degradation. Full article
(This article belongs to the Special Issue Advanced Materials for Electrocatalysis and Energy Storage)
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21 pages, 6279 KiB  
Article
Large Transfer of Nitrogen, Silicon and Titanium through Various Thin Mo–Ti/Si and Ti–Mo/Si Bilayer Films Processed in Expanding Microwave Plasma: Formation of Nitrides and Silicides
by Isabelle Jauberteau, Richard Mayet, Julie Cornette, Pierre Carles, Denis Mangin, Annie Bessaudou, Jean Louis Jauberteau and Armand Passelergue
Coatings 2023, 13(10), 1787; https://doi.org/10.3390/coatings13101787 - 18 Oct 2023
Viewed by 1527
Abstract
Silicides and nitrides of transition metals are expected to play a great role in various applications. They can be both considered as metals and ceramics. Their low resistivity and high melting point make them especially promising for super capacitors technology. Thin bilayer films [...] Read more.
Silicides and nitrides of transition metals are expected to play a great role in various applications. They can be both considered as metals and ceramics. Their low resistivity and high melting point make them especially promising for super capacitors technology. Thin bilayer films of Mo and Ti are evaporated on Si substrates with various thicknesses and location with respect to the Si substrate. They are exposed to expanding plasma using (Ar-31%N2-6%H2) gas mixtures, which promotes the chemical reactions on the surface of the bilayer films. Because of the intensive diffusion of elements such as Si and Ti, which compete with the diffusion of nitrogen into the surface layers, various thin films of nitrides and silicides form, depending on the location of Mo and Ti films relative to Si substrates. Results are analyzed in light of thermodynamic and kinetic considerations and especially the strong reactivity of Ti towards oxygen and silicium compared with Mo. The large diffusion of Si through Mo–Ti/Si bilayer films prevents the formation of nitrides, whereas a film of Mo, only 50 nm thick, prevents the formation of silicides in Ti–Mo/Si bilayer films, which promotes the formation of TiN from TiO2 and nitrogen due to the reducing and nitriding effect of plasma. Full article
(This article belongs to the Special Issue Advanced Processing Technologies of Coatings/Films of Transition Metal Nitrides: Plasma Deposition)
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13 pages, 6852 KiB  
Article
In Vitro Characterization of Doped Bioglass 45S5/HAp Coatings Obtained by CoBlastTM Deposition
by Ana Sofia Pádua, Sílvia Rodrigues Gavinho, Tânia Vieira, Imen Hammami, Jorge Carvalho Silva, João Paulo Borges and Manuel Pedro Fernandes Graça
Coatings 2023, 13(10), 1775; https://doi.org/10.3390/coatings13101775 - 16 Oct 2023
Cited by 3 | Viewed by 2301
Abstract
Bone replacement is one of the major medical procedures in the oral surgery field due to the progressive ageing population and to illness or trauma in younger age groups. The use of implants without biological activity and effective osseointegration increases the chances of [...] Read more.
Bone replacement is one of the major medical procedures in the oral surgery field due to the progressive ageing population and to illness or trauma in younger age groups. The use of implants without biological activity and effective osseointegration increases the chances of implant failure. This work aims to improve the interaction between implants and bone by using Bioglass 45S5 (BG)/hydroxyapatite (HAp) mixtures, including copper-, zinc-, and cerium-doped BG, as well as co-doping by the mentioned metals, as coatings produced by the CoBlastTM technique. All coatings present a uniform coverage of the Ti-6Al-4V substrate. Furthermore, in vitro testing using human osteosarcoma Saos-2 cells indicated that BG/HAp coatings have no cytotoxic effect, and the used of doping agents did not alter cell adhesion, proliferation, or alkaline phosphatase (ALP) expression when compared to undoped coating. These results demonstrate that BG/HAp by CoBlastTM can be a solution to improve implants’ osseointegration. Full article
(This article belongs to the Special Issue Ceramic and Metallic Biomaterials. Application in Medical Sciences)
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18 pages, 77321 KiB  
Article
Barrier and Antimicrobial Properties of Coatings Based on Xylan Derivatives and Chitosan for Food Packaging Papers
by Mirela Roman (Iana-Roman), Petronela Nechita, Mihaela-Aida Vasile and Alina-Mihaela Cantaragiu Ceoromila
Coatings 2023, 13(10), 1761; https://doi.org/10.3390/coatings13101761 - 12 Oct 2023
Cited by 5 | Viewed by 2097
Abstract
This paper analyzes the potential of coatings based on xylan derivatives and chitosan to provide barrier properties and antimicrobial protection for paper food packaging and also to substitute the synthetic materials currently used in the food packaging industry. Colloidal dispersions of xylan derivatives [...] Read more.
This paper analyzes the potential of coatings based on xylan derivatives and chitosan to provide barrier properties and antimicrobial protection for paper food packaging and also to substitute the synthetic materials currently used in the food packaging industry. Colloidal dispersions of xylan derivatives (hydrophobized xylan with alkyl ketene dimers—XyAKD—and acetylated xylan—XyAc) and a chitosan biopolymer (Ch) were applied as coatings in single and two successive layers on a paper substrate using a laboratory automatic film applicator. The assessment of the water and fatty compound barrier properties of coated paper samples showed differences in effectiveness among xylan derivatives and their combination with chitosan. Generally, xylan derivative coatings improved the barrier and antimicrobial features of coated papers compared with native xylan. However, important improvements were obtained by adding to the coating formula a chitosan biopolymer. Thus, the best barrier properties for water, water vapors, oils and greases were obtained for paper coated with the acetylated xylan and chitosan formula in a single layer, where values of 30 g/m2.day for the water vapor transmission rate (WVTR), a 92.8° contact angle (CA) and a KIT rating of 8 were achieved. All coated paper samples exhibited the total inhibition of Bacillus sp. both after 24 and 48 h. Based on the obtained results in this study, one can conclude that the area of application of xylan hemicelluloses could be extended. Their utilization in appropriate chemical structures and combinations as coatings for paper can be a sustainable alternative for the food packaging industry. Full article
(This article belongs to the Special Issue Coatings and Thin Films for Food Packaging Applications)
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20 pages, 11258 KiB  
Article
Thickness, Adhesion and Microscopic Analysis of the Surface Structure of Single-Layer and Multi-Layer Metakaolin-Based Geopolymer Coatings
by Martin Jaskevic, Jan Novotny, Filip Mamon, Jakub Mares and Angelos Markopoulos
Coatings 2023, 13(10), 1731; https://doi.org/10.3390/coatings13101731 - 4 Oct 2023
Cited by 2 | Viewed by 1167
Abstract
This work is focused on creating coating layers made of a metakaolin-based geopolymer suspensions (GP)-formed Al matrix modified using H3PO4 acid with Al(OH)3 in isopropyl alcohol, named GP suspension I, and H3PO4 acid with nano Al [...] Read more.
This work is focused on creating coating layers made of a metakaolin-based geopolymer suspensions (GP)-formed Al matrix modified using H3PO4 acid with Al(OH)3 in isopropyl alcohol, named GP suspension I, and H3PO4 acid with nano Al2O3 in isopropyl alcohol, named GP suspension J. The selected GP suspensions were applied on aluminum and steel underlying substrates as single-layer coatings and multi-layer coatings, where multi-layer coatings included three and five layers that were polymerized by a curing process. Curing was divided into two types with every layer curing process and final layer curing process. For both GP suspensions I and J, the effect of the number of layers and the type of substrate on adhesion was investigated. The prepared samples on underlying substrates were characterized on the microscopy analysis including SEM for high-resolution images and 3D laser confocal microscopy (CLSM) for the 3D visualization of the coatings structure. Microscopy analysis showed structural defects such as porosity, cracks and peeling, which increase with a greater number of applied layers. However, these defects were only evident on a micro scale and did not seem to be fatal for the performance of the surface stability. The EDS mapping of the prepared layer showed inhomogeneity in the distribution of elements caused by the brush application. A grid test and thickness measurement were performed to complete the microscopy analysis. The grid test confirmed a very high adhesion of GP coatings on the aluminum substrate with a rating of one (only in one case was there a rating of two) and a lower adhesion on the steel substrate with the most frequent rating of three (in one case, there were ratings of two and one). The thickness measurement proved a noticeably thicker thickness of the prepared layer on the Fe substrate compared to the Al substrate by 20%–30% in the case of suspension I and by 70%–10% in the case of suspension J. The thickness of the layer also showed a dependence on the method of application and curing, as a thicker layer was always achieved when curing after the final layer of the GP suspension, compared to curing after each applied layer. The resulting single-layer and multi-layer thicknesses ranged from approx. 7 to 30 µm for suspension I and from approx. 3 to 11 µm for suspension J. A non-linear increase in thickness was also evident from the thickness measurement data. Full article
(This article belongs to the Special Issue Polymer Thin Films: From Fundamentals to Applications)
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17 pages, 11001 KiB  
Article
TiO2 Microparticles Incorporation in Coatings Produced by Plasma Electrolytic Oxidation (PEO) on Titanium
by Federica Ceriani, Luca Casanova, Luca Massimini, Andrea Brenna and Marco Ormellese
Coatings 2023, 13(10), 1718; https://doi.org/10.3390/coatings13101718 - 30 Sep 2023
Cited by 2 | Viewed by 2439
Abstract
This research describes the influence of two types of particles, namely rutile and anatase microparticles (average d < 5 µm), on the morphology, structure, and anticorrosive properties of PEO coatings on titanium produced in an alkaline solution based on NaOH and sodium metasilicates. [...] Read more.
This research describes the influence of two types of particles, namely rutile and anatase microparticles (average d < 5 µm), on the morphology, structure, and anticorrosive properties of PEO coatings on titanium produced in an alkaline solution based on NaOH and sodium metasilicates. The paper reports the experimental results relating to the study of the influence of the electrical regime and working frequency of the anodizing treatment on the interaction between the particles, the substrate, and the oxide to determine the optimal conditions that favour the incorporation of the particles and the production of a thick oxide. PEO coatings are characterized by using a scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, and X-ray diffraction (XRD) testing. The electrochemical behaviour is evaluated by free corrosion potential monitoring and electrochemical impedance spectroscopy analysis (EIS) performed in a sulphuric acid solution. The particles are successfully incorporated into the coating under any electrical condition and at any frequency. However, only treatments carried out at 1000 Hz allow the production of coatings that combine a large thickness (up to 50 µm) and improved anticorrosion behaviour. In contrast, oxide layers produced at 20 Hz and in DC show a quite damaged structure, affecting their anticorrosion behaviour and resulting in lower corrosion potential and impedance values. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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