Coatings

9 pages, 956 KiB

Open AccessEditor’s ChoiceArticle

Atomic Layer Deposition of Y₂O₃ Thin Films Using Y(MeCp)₂(iPr-nPrAMD) Precursor and H₂O, and Their Erosion Resistance in CF₄-Based Plasma

by Seong Lee, Hyunchang Kim and Sehun Kwon

Coatings 2025, 15(1), 22; https://doi.org/10.3390/coatings15010022 - 30 Dec 2024

Cited by 2 | Viewed by 1409

Abstract

Atomic layer deposition (ALD) of Y₂O₃ thin films was investigated using Y(MeCp)₂(iPr-nPrAMD) precursor and H₂O reactant. The self-limiting reaction mechanism of ALD-Y₂O₃ thin films was confirmed at a growth temperature of 260 °C. [...] Read more.

Atomic layer deposition (ALD) of Y₂O₃ thin films was investigated using Y(MeCp)₂(iPr-nPrAMD) precursor and H₂O reactant. The self-limiting reaction mechanism of ALD-Y₂O₃ thin films was confirmed at a growth temperature of 260 °C. And, the saturated growth rate was confirmed to be ~0.11 nm/cycle. Also, it was demonstrated that a wide ALD temperature window from 150 °C to 290 °C maintains a consistent growth rate. ALD-Y₂O₃ thin films were found to have a typical cubic polycrystalline structure, independent of growth temperature, which can be attributed to their stoichiometric composition of Y₂O₃, negligible carbon impurity, and high film density, analogous to the Y₂O₃ bulk. Even at a low growth temperature of 150 °C, ALD-Y₂O₃ exhibited a markedly lower plasma etching rate (~0.77 nm/min) than that (~4.6 nm/min) of ALD-Al₂O₃ when using RIE at a plasma power of 400 W with a mixed gas of Ar/CF₄/O₂. Furthermore, the growth temperature of Y₂O₃ thin films had minimal impact on the etching rate. Full article

(This article belongs to the Special Issue Anti-Corrosion and Anti-Wear Coatings: Fundamentals, Technologies, and Applications)

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20 pages, 17374 KiB

Open AccessEditor’s ChoiceArticle

Tribological Behavior of Gas-Nitrided 42CrMo4 Steel at Elevated Temperatures

by Dominika Panfil-Pryka, Michal Kulka, Mateusz Kotkowiak, Jerzy Michalski and Karol Grochalski

Coatings 2025, 15(1), 18; https://doi.org/10.3390/coatings15010018 - 28 Dec 2024

Viewed by 1154

Abstract

Nitriding is a well-known thermochemical treatment improving the surface hardness and the wear resistance of steel. The phase composition and growth kinetics of the nitrided layer can be controlled using a gas nitriding with changeable nitriding potential. In this work, such a gas [...] Read more.

Nitriding is a well-known thermochemical treatment improving the surface hardness and the wear resistance of steel. The phase composition and growth kinetics of the nitrided layer can be controlled using a gas nitriding with changeable nitriding potential. In this work, such a gas nitriding was used to produce, on 42CrMo4 steel, the two nitrided layers differing in the thickness of compound zone and diffusion zone. The microstructure and nanohardness of these layers were studied. For the first time, the tribological behavior of gas nitrided layers at elevated temperatures (from 23 to 400 °C) was investigated. The compound zone consisted of ε + (ε + γ’) iron nitrides and, in the diffusion zone, the nitric sorbite with γ’ precipitates was observed. The highest nanohardness was measured in the ε + γ’ zone. The lowest values of friction coefficients were obtained if the contact surface of the friction pair entered the ε + γ’ zone. After the wear process, at a final temperature of 400 °C, worn surfaces showed only intensive abrasive wear, evidenced by shallow grooves. The increased oxygen content at the edges of wear tracks indicated possible oxidative wear. Full article

(This article belongs to the Special Issue Wear-Resistance and Corrosion-Resistance Coatings)

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18 pages, 1365 KiB

Open AccessEditor’s ChoiceArticle

Increasing the Resistance of Steel and Austenitic Stainless Steels Against Pitting Corrosion by a γ-Irradiated Self-Assembled Amphiphilic Molecular Layer

by Éva Kocsisné Pfeifer, Zoltán May, Miklós Péter Mohai, János Mink, István Gábor Gyurika and Judit Telegdi

Coatings 2024, 14(12), 1601; https://doi.org/10.3390/coatings14121601 - 21 Dec 2024

Viewed by 925

Abstract

This study, based on our previous research, aims to quantitatively determine the enhanced protection of austenitic stainless steels against pitting corrosion in NaCl solution by self-assembled molecular (SAM) layers, in their original form and after γ-irradiation. This study focuses on four stainless steels [...] Read more.

This study, based on our previous research, aims to quantitatively determine the enhanced protection of austenitic stainless steels against pitting corrosion in NaCl solution by self-assembled molecular (SAM) layers, in their original form and after γ-irradiation. This study focuses on four stainless steels of varying compositions, covered by self-assembled undecenyl phosphonic acid layers. The metal dissolution in corrosion experiments was measured by a special, highly sensitive analytical technique using the inductively coupled plasma–optical emission spectrometry (ICP-OES). The comparison of the dissolved metal ion concentrations measured in the presence of different metals with and without nanocoatings allowed the evaluation of the anticorrosion effectiveness of nanofilms as well as the importance of the alloying elements. The ICP-OES results demonstrated that the quality of layers have a significant impact on anticorrosion efficacy. The γ-irradiated self-assembled layers were the most effective in controlling the dissolution of stainless steels. The mechanisms of the inhibition in the presence of these nanolayers were elucidated by infrared spectroscopy. First of all, it revealed the differences in the adsorption of the undecenyl phosphonic acid self-assembled layer, both with and without γ-irradiation. The other important observation that confirmed the increased anticorrosion efficiency after γ-irradiation proved the formation of a more compact, polymer-like layer over the metal surface. The increased anticorrosion efficacy, defined as the enhancement in Pitting Resistance Equivalent Numbers (PRENs) in the presence of self-assembled layers (either pre- or post-γ-irradiation), can be documented. Full article

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

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17 pages, 13353 KiB

Open AccessEditor’s ChoiceArticle

Microstructural, Nanomechanical, and Tribological Properties of Thin Dense Chromium Coatings

by E. Broitman, A. Jahagirdar, E. Rahimi, R. Meeuwenoord and J. M. C. Mol

Coatings 2024, 14(12), 1597; https://doi.org/10.3390/coatings14121597 - 20 Dec 2024

Cited by 2 | Viewed by 1194

Abstract

Nowadays, Thin Dense Chromium (TDC) coatings are being industrially used in rolling bearings applications due to their claimed advantages such as high hardness, low wear, and good corrosion resistance. However, despite their broad commercial use, very little has been published in the open [...] Read more.

Nowadays, Thin Dense Chromium (TDC) coatings are being industrially used in rolling bearings applications due to their claimed advantages such as high hardness, low wear, and good corrosion resistance. However, despite their broad commercial use, very little has been published in the open scientific literature regarding their microstructure, nanomechanical, and tribological properties. In this paper, TDC coatings with a thickness of about 5 µm were deposited by a customized electrochemical process on ASTM 52100 bearing steel substrates. Surface microstructure and chemical composition analysis of the TDC coatings was carried out by scanning electron microscopy and atomic force microscopy. The results revealed a coating with a dense, nodular, and polycrystalline microstructure. Unlike standard electrodeposited “Hard Chromium” coatings, TDC coatings show no presence of micro/nano-cracks, likely contributing to their superior corrosion resistance. The nanomechanical behavior, studied by nanoindentation as a function of penetration depths, exhibits a pronounced size effect near the coating surface that can be linked to the nodular microstructure. A hard surface with hardness H_IT 14.9 ± 0.5 GPa and reduced elastic modulus E_r = 216.8 ± 3.9 GPa was observed. Tribological characterization under the presence of lubricants was performed by two single-contact tribometers using coated and uncoated steel balls against flat steel substrates. An in-house fretting wear rig was used to measure the lubricated friction coefficient in pure sliding conditions, whilst the friction performance in rolling/sliding lubricated conditions was evaluated using a WAM test rig. In pure sliding, TDC/TDC contacts show ~13% lower friction than for steel. Under rolling/sliding conditions with 5% sliding, the traction coefficient of TDC/TDC coating contact was at least 20% lower than that for steel/steel contact. The tribological results obtained in various contact conditions demonstrate the benefits of applying TDC coatings to reduce bearing friction. Full article

(This article belongs to the Special Issue Advanced Tribological Coatings: Fabrication and Application)

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11 pages, 3079 KiB

Open AccessEditor’s ChoiceArticle

Controlled Aggregation of Cobalt and Platinum Atoms via Plasma Treatment for Exceptional Hydrogen Evolution Reaction Activity

by Guoqing Zhang, Jiankun Li, Yixing Wang, Linfeng Lei and Linzhou Zhuang

Coatings 2024, 14(12), 1569; https://doi.org/10.3390/coatings14121569 - 15 Dec 2024

Cited by 1 | Viewed by 997

Abstract

Designing and developing highly active, stable, and cost-effective hydrogen evolution reaction (HER) catalysts is crucial in the field of water electrolysis. In this study, we utilize N-doped porous carbon (CoNC) derived from zeolite imidazole metal–organic frameworks (ZIF-67) as support and prepare CoNC-Pt-IM-P via [...] Read more.

Designing and developing highly active, stable, and cost-effective hydrogen evolution reaction (HER) catalysts is crucial in the field of water electrolysis. In this study, we utilize N-doped porous carbon (CoNC) derived from zeolite imidazole metal–organic frameworks (ZIF-67) as support and prepare CoNC-Pt-IM-P via chemical impregnation (CoNC-Pt-IM) and plasma treatment. Systematic analyses reveal that calcined CoNC with pyridinic nitrogen could serve as a robust support to strongly anchor PtCo nanoclusters, while argon plasma treatment could lead to a noticeable aggregation of Co and Pt atoms so as to alter the electronic environment and enhance intrinsic HER catalytic activity. CoNC-Pt-IM-P could exhibit outstanding catalytic activity toward HER, achieving an exceptionally low overpotential of 31 mV at the current density of −10 mA cm⁻² and a Tafel slope of 36 mV dec⁻¹. At an overpotential of 50 mV, its mass activity reaches 4.90 A mg_Pt⁻¹, representing enhancements of 1.5 times compared to CoNC-Pt-IM and 12.3 times compared to commercial 20 wt% Pt/C. Furthermore, it could operate stably for over 110 h at a current density of −10 mA cm⁻², demonstrating its exceptional durability. This work uses plasma treatment to achieve the controllable aggregation of Co and Pt atoms to enhance their catalytic activity, which has the advantage of avoiding excessive particle aggregation compared to the commonly used method of high-temperature calcination. Full article

(This article belongs to the Special Issue Coatings as Key Materials in Catalytic Applications)

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20 pages, 20891 KiB

Open AccessEditor’s ChoiceArticle

Efficient Photocatalytic Reduction of Hexavalent Chromium by NiCo₂S₄/BiOBr Heterogeneous Photocatalysts

by Shumeng Qin, Ruofan Xu, Qiu Jin, Sen Wang, Yi Ren, Yulin Huang, Ziye Zheng, Lihui Xiao, Dong Zhai, Shuguang Wang and Zuoli He

Coatings 2024, 14(12), 1492; https://doi.org/10.3390/coatings14121492 - 27 Nov 2024

Cited by 3 | Viewed by 1102

Abstract

For typical Cr(VI)-containing industrial wastewater, more efficient water treatment technologies need to be used to ensure that Cr(VI) concentrations are reduced to safe levels before discharge. Photocatalytic technology is highly efficient, environmentally friendly, and has been extensively used to address this demand. Herein, [...] Read more.

For typical Cr(VI)-containing industrial wastewater, more efficient water treatment technologies need to be used to ensure that Cr(VI) concentrations are reduced to safe levels before discharge. Photocatalytic technology is highly efficient, environmentally friendly, and has been extensively used to address this demand. Herein, heterogeneous NiCo₂S₄/BiOBr photocatalysts with different ratios were prepared using a solvothermal method. When compared with pure NiCo₂S₄ and BiOBr, the NiCo₂S₄/BiOBr-30 had significantly increased adsorption capacity and visible-light-driven photocatalytic reduction activity for Cr(VI) removal. The improved adsorption performance of the NiCo₂S₄/BiOBr-30 was mainly due to its increased specific surface area, and the enhanced photocatalytic performance of the NiCo₂S₄/BiOBr-30 could be attributed to the improved separation and transfer of photogenerated carriers at the interface. Lastly, a possible enhanced photocatalytic Cr(VI) reduction mechanism of the NiCo₂S₄/BiOBr heterostructure was developed. Full article

(This article belongs to the Special Issue Advanced Materials and Coatings for Photocatalytic Applications)

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19 pages, 6285 KiB

Open AccessEditor’s ChoiceArticle

Improving Prediction Model for Colorimetric Changes Due to Coating Processes with Oil-Based and UV Coatings

by Igor Zjakić, Eduard Galić, Ivana Ljevak and Mile Matijević

Coatings 2024, 14(12), 1488; https://doi.org/10.3390/coatings14121488 - 26 Nov 2024

Cited by 1 | Viewed by 967

Abstract

The measurability and predictability of the printing process are influenced by the impact of various coating methods. Besides enhancing and protecting the printed product, these methods can alter the colorimetric properties of spot colors across different wavelengths. Prediction models based on ink trapping [...] Read more.

The measurability and predictability of the printing process are influenced by the impact of various coating methods. Besides enhancing and protecting the printed product, these methods can alter the colorimetric properties of spot colors across different wavelengths. Prediction models based on ink trapping formulas were analyzed, particularly those from Deshpande, Green, and Hoffstadt, designed to forecast colorimetric values in overprinted spot color scenarios. This study examined the influence of coating methods on the colorimetric properties of spot colors and evaluated the applicability of the prediction model for these conditions. Spectrophotometric and densitometric methods, combined with mathematical analysis, were used to quantify the degree of color change induced by different coatings. The findings clearly indicate the extent of colorimetric changes in spot colors resulting from various coating applications. They also highlight the potential, albeit limited, application of this model in predicting color changes for improved process repeatability and predictability. While the prediction method analyzed in this study proved inadequate for coating-over-spot-color scenarios, it remains useful for predicting colorimetric shifts in spot-on-spot-color overprinting. The model demonstrated that it is not entirely accurate, as some coatings show ∆E₀₀ deviations of up to 10. To improve the model’s applicability, a varnishing coefficient, V, should be introduced, which can reduce ∆E₀₀ variation for each color and substrate. The research showed that a coefficient range from 0.8 to 1.2 yields acceptable results, bringing ∆E₀₀ below 2, thus making the model suitable for coating processes with oil-based and UV coatings. Full article

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

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16 pages, 5245 KiB

Open AccessEditor’s ChoiceArticle

Ball-on-Disk Wear Maps for Bearing Steel–Hard Anodized EN AW-6082 Aluminum Alloy Tribocouple in Dry Sliding Conditions

by Enrico Baroni, Annalisa Fortini, Lorenzo Meo, Chiara Soffritti, Mattia Merlin and Gian Luca Garagnani

Coatings 2024, 14(11), 1469; https://doi.org/10.3390/coatings14111469 - 19 Nov 2024

Cited by 1 | Viewed by 1262

Abstract

In recent years, Golden Hard Anodizing (G.H.A.^®) has been developed as a variant of the traditional hard anodizing process with the addition of Ag⁺ ions in the nanoporous structure. The tribological properties of this innovative surface treatment are still not [...] Read more.

In recent years, Golden Hard Anodizing (G.H.A.^®) has been developed as a variant of the traditional hard anodizing process with the addition of Ag⁺ ions in the nanoporous structure. The tribological properties of this innovative surface treatment are still not well understood. In this study, ball-on-disk tests were conducted in dry sliding conditions using 100Cr6 (AISI 52100) bearing steel balls as a counterbody and GHA^®-anodized EN AW-6082 aluminum alloy disks. The novelty of this work lies in the mapping of the wear properties of the tribocouple under different test conditions for a better comparison of the results. Three different normal loads (equal to 5, 10, and 15 N) and three different reciprocating frequencies (equal to 2, 3, and 4 Hz) were selected to investigate a spectrum of operating conditions for polished and unpolished G.H.A.^®-anodized EN AW-6082 aluminum alloy. Quantitative wear maps were built based on the resulting wear rate values to define the critical operating limits of the considered tribocouple. The results suggest that the coefficient of friction (COF) was independent of test conditions, while different wear maps were found for polished and non-polished surfaces. Polishing before anodizing permitted the acquisition of lower wear for the anodized disks and the steel balls. Full article

(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings, 2nd Edition)

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13 pages, 6719 KiB

Open AccessEditor’s ChoiceArticle

Fatigue Crack Growth Behavior of Additively Manufactured Ti Metal Matrix Composite with TiB Particles

by Thevika Balakumar, Afsaneh Edrisy and Reza A. Riahi

Coatings 2024, 14(11), 1447; https://doi.org/10.3390/coatings14111447 - 13 Nov 2024

Viewed by 1222

Abstract

Fatigue crack growth behavior of additively manufactured Ti metal matrix composite with TiB particles at room temperature was studied using a compact tension specimen and at the stress ratio of 0.1 (R = 0.1). The composite studied in this work was manufactured with [...] Read more.

Fatigue crack growth behavior of additively manufactured Ti metal matrix composite with TiB particles at room temperature was studied using a compact tension specimen and at the stress ratio of 0.1 (R = 0.1). The composite studied in this work was manufactured with a unique additive technique called plasma transferred arc solid free-form fabrication, which was designed to manufacture low-cost near-net-shaped components for aerospace and automotive industries. The fatigue crack growth rate experiments were carried perpendicular and parallel to the additive material build, aiming to find any fatigue anisotropies at room temperature. The findings reveal that additively manufactured Ti-TiB composite shows isotropic fatigue properties with respect to fatigue crack growth. Furthermore, the fatigue crack growth mechanisms in this additive composite material were identified as void nucleation/coalescence and the bypassing of particles and matrix, depending on the interparticle distance. Full article

(This article belongs to the Special Issue Latest Insights in Metal Fatigue, Failure, and Fracture)

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17 pages, 7142 KiB

Open AccessEditor’s ChoiceArticle

Wear and Corrosion Resistance of ZrN Coatings Deposited on Ti6Al4V Alloy for Biomedical Applications

by Stanislava Rabadzhiyska, Dimitar Dechev, Nikolay Ivanov, Tatyana Ivanova, Velichka Strijkova, Vesela Katrova, Velko Rupetsov, Nina Dimcheva and Stefan Valkov

Coatings 2024, 14(11), 1434; https://doi.org/10.3390/coatings14111434 - 11 Nov 2024

Cited by 7 | Viewed by 1650

Abstract

Zirconium nitrides films were synthesized on Ti6Al4V substrates at a bias voltage of −50 V, −80 V, −110 V and −150 V by the direct current (DC) reactive magnetron sputtering technique. The as-deposited coatings were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) [...] Read more.

Zirconium nitrides films were synthesized on Ti6Al4V substrates at a bias voltage of −50 V, −80 V, −110 V and −150 V by the direct current (DC) reactive magnetron sputtering technique. The as-deposited coatings were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The wear and corrosion resistance of the obtained ZrN coatings were evaluated to determine the possibility for their implementation in modern biomedical applications. It was found that the intensity of the diffraction peak of the Zr-N phase corresponding to the (1 1 1) crystallographic plane rose as the bias voltage increased, while the ZrN coatings’ thickness reduced from 1.21 µm to 250 nm. The ZrN films’ surface roughness rose up to 75 nm at −150 V. Wear tests showed an increase in the wear rate and wear intensity as the bias voltage increased. Corrosion studies of the ZrN coatings were carried out by three electrochemical methods: open circuit potential (OCP), cyclic voltammetry (polarization measurements) and electrochemical impedance spectroscopy (EIS). All electrochemical measurements confirmed that the highest protection to corrosion is the ZrN coating, which was deposited on the Ti6Al4V substrate at a bias voltage of −150 V. Full article

(This article belongs to the Special Issue Anti-corrosion Coatings of Metals and Alloys—New Perspectives)

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5 pages, 178 KiB

Open AccessEditor’s ChoiceEditorial

Innovations in Active Food Packaging During the Pandemic and into the ‘New Normal’

by Maria-Ioana Socaciu, Dan Cristian Vodnar and Cristina Anamaria Semeniuc

Coatings 2024, 14(11), 1419; https://doi.org/10.3390/coatings14111419 - 8 Nov 2024

Viewed by 1344

Abstract

COVID-19 significantly impacted global socioeconomic conditions and food security [...] Full article

(This article belongs to the Special Issue Innovations in Active Food Packaging during the Pandemic and into the 'New Normal')

18 pages, 4583 KiB

Open AccessEditor’s ChoiceReview

Ni Catalysts for Thermochemical CO₂ Methanation: A Review

by Jungpil Kim

Coatings 2024, 14(10), 1322; https://doi.org/10.3390/coatings14101322 - 16 Oct 2024

Cited by 8 | Viewed by 4721

Abstract

This review underscores the pivotal role that nickel-based catalysts play in advancing CO₂ methanation technologies, which are integral to achieving carbon neutrality. This study meticulously examines various aspects of catalyst design, including the significance of support materials and co-catalysts in enhancing catalytic [...] Read more.

This review underscores the pivotal role that nickel-based catalysts play in advancing CO₂ methanation technologies, which are integral to achieving carbon neutrality. This study meticulously examines various aspects of catalyst design, including the significance of support materials and co-catalysts in enhancing catalytic activity and selectivity. This discussion reveals that while nickel catalysts offer a cost-effective solution due to their availability and high performance, challenges such as sintering and carbon deposition at high temperatures remain. These issues necessitate the development of catalysts with superior thermal stability or those capable of maintaining high activity at lower temperatures. This review also highlights the innovative use of three-dimensional fiber deposition technology in fabricating catalysts, which has shown promising results in improving reaction efficiency and stability over prolonged operation. Moving forward, this research emphasizes the importance of optimizing catalyst structure and fabrication techniques to overcome existing limitations. The ongoing development in this field holds great promise for the industrial application of CO₂ methanation, contributing significantly to global efforts in reducing greenhouse gas emissions and promoting sustainable energy use. Full article

(This article belongs to the Special Issue Advanced Research on Energy Storage Materials and Devices)

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17 pages, 9928 KiB

Open AccessEditor’s ChoiceArticle

Anti-Corrosion and Wave-Absorbing Properties of Epoxy-Based Coatings on Q235 Steel

by Rehan Zhang, Kai Yang, Bo Dang, Mengling Zhan, Pingze Zhang and Shuqin Li

Coatings 2024, 14(10), 1315; https://doi.org/10.3390/coatings14101315 - 15 Oct 2024

Cited by 3 | Viewed by 1807

Abstract

Carbon nanotube/epoxy resin (CNE) coatings and carbon nanotube/carboxy iron powder/epoxy resin (CIE) coatings were applied on the surface of Q235 steel, and their corrosion, absorption properties and other characteristics were measured in this work. The results indicate that the average thickness of a [...] Read more.

Carbon nanotube/epoxy resin (CNE) coatings and carbon nanotube/carboxy iron powder/epoxy resin (CIE) coatings were applied on the surface of Q235 steel, and their corrosion, absorption properties and other characteristics were measured in this work. The results indicate that the average thickness of a single application was approximately 400 μm, and the surface of the CNE coating was still smooth and intact after a 3000 h copper ion accelerated salt spray test without bubbles, falling off or other corrosion phenomena. The same was true for 28 days of full immersion in solutions of 10% hydrochloric acid (HCl) and 10% sodium hydroxide (NaOH) of the coating. The electrochemical testing exhibited the corrosion current of the CNE coating as being markedly lower than that of Q235 steel, with a protection efficiency of 81.68% for the Q235 steel. The CNE-0.6 coating had the maximum corrosion voltage (−0.390 V), and the CNE-0.3 coating had the minimum corrosion current of 2.07 × 10⁻⁶ A·cm². The adhesion between the coating and Q235 could reach level 0, and the tensile strength of the coating was up to 18.75 MPa. The coating was observed to remain intact and free from detachment upon undergoing a drop test from a height of 50 cm. In addition, the CIE-0.6 coating exhibited an effective absorption band of 9.1 GHz, covering the range from 8.2 to 13.7 GHz, and it achieved a maximum reflection loss of −15.1 dB at a frequency of 8.6 GHz. Full article

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

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15 pages, 2271 KiB

Open AccessEditor’s ChoiceArticle

Preparation and Characterization of PLA-Based Films Fabricated with Different Citrus Species Peel Powder

by Antonios S. Koutoulis, Andreas E. Giannakas, Dimitrios G. Lazaridis, Apostolos-Panagiotis Kitsios, Vassilios K. Karabagias, Aris E. Giannakas, Athanasios Ladavos and Ioannis K. Karabagias

Coatings 2024, 14(10), 1311; https://doi.org/10.3390/coatings14101311 - 14 Oct 2024

Cited by 5 | Viewed by 2045

Abstract

The present study aimed to investigate whether different citrus peel powders (orange, mandarin, and lemon) could be incorporated into polylactic acid (PLA), for the preparation and characterization of biodegradable films made of this fruit waste. In particular, films were prepared by the solvent [...] Read more.

The present study aimed to investigate whether different citrus peel powders (orange, mandarin, and lemon) could be incorporated into polylactic acid (PLA), for the preparation and characterization of biodegradable films made of this fruit waste. In particular, films were prepared by the solvent casting method and tested in terms of physicochemical and biochemical parameters, along with mechanical properties. Furthermore, the citrus peel powders were tested for their physicochemical and biochemical properties after ethanolic extraction. The results showed that the addition of citrus powders into PLA proved to be efficient compared to the control films (PLA). The citrus peel-based films showed high antioxidant capacity (38.37%–32.54%), a considerable total phenolic content (17.2–12.58 mg GAE/L), good lightness (L*: 42.83–41.93), elastic Young’s modulus (257.95–175.38 MPa), oxygen transmission rate (976.5 mL m⁻² day⁻¹–1218 mL m⁻² day⁻¹), elongation at break (183.06%–135.95%), and tensile strength (6.15–4.56 MPa), which were affected significantly (p < 0.05) by the botanical origin of citrus peel. Concerning the citrus peel extracts, the highest values in antioxidant capacity (52.56%), total phenolic content (724.8 mg GAE/L), and titratable acidity (714.67 mg of citric acid/L) were recorded in the extract of lemon peel powders. The corresponding values for orange peel powder extracts were 39.43%, 563.8 mg GAE/L, and 576 mg of citric acid/L, while those for mandarin were 33.01%, 558.46 mg GAE/L, and 54.67 mg of citric acid/L. The application of multivariate analysis of variance and linear discriminant analysis on the mechanical properties, physicochemical, and biochemical data resulted in the differentiation of pure PLA and PLA-based films fabricated with citrus peel powder. From the above findings, it is concluded that citrus peel powders are sources of phytochemicals and can be used for the preparation of PLA-based films for potential applications in food preservation. Full article

(This article belongs to the Special Issue Trends in Sustainable Food Packaging and Coatings)

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24 pages, 1442 KiB

Open AccessEditor’s ChoiceReview

Thermochromic Polymers in Food Packaging: A Comprehensive Systematic Review and Patent Landscape Analysis

by Colette Breheny, Kieran Donlon, Alan Harrington, Declan Mary Colbert, Gilberto S. N. Bezerra and Luke M. Geever

Coatings 2024, 14(10), 1252; https://doi.org/10.3390/coatings14101252 - 1 Oct 2024

Cited by 6 | Viewed by 4151

Abstract

This study addresses the gap in research on the application of thermochromic polymers (TPs) in food packaging and their potential for real-time temperature monitoring, aiding in the assessment of food quality and shelf-life. TPs exhibit a visible color change in response to temperature [...] Read more.

This study addresses the gap in research on the application of thermochromic polymers (TPs) in food packaging and their potential for real-time temperature monitoring, aiding in the assessment of food quality and shelf-life. TPs exhibit a visible color change in response to temperature variations. A comprehensive systematic review (SR) across multiple engineering peer-review databases using predefined terms was conducted. Additionally, international patent databases were investigated using the same predefined terms. Independent experts reviewed the methodology to identify and address potential biases. A total of 288 eligible articles and 922 patents were identified. After a duplicate selection and extraction process according to the inclusion criteria, four related full-text publications were selected from the initial 288 articles, and five relevant patents were selected from the 922 patents. The qualitative review suggests that TPs hold significant promise as food packaging materials due to their unique physical properties. The study concludes that TPs offer valuable properties for the food packaging industry, meriting further investigation to exploit their benefits fully. Full article

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

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15 pages, 4976 KiB

Open AccessEditor’s ChoicePerspective

Low-Carbon Embodied, Self-Cleaning, and Air-Purifying Building Envelope Components Using TiO₂ Photocatalysis, 3D Printing, and Recycling

by Aníbal Maury-Ramírez, Mario Rinke and Johan Blom

Coatings 2024, 14(9), 1228; https://doi.org/10.3390/coatings14091228 - 23 Sep 2024

Cited by 2 | Viewed by 4277

Abstract

This perspective article describes the past, present, and future directions on TiO₂ photocatalysis, 3D concrete printing, and recycling for developing innovative building envelope components from façade skins. Using a methodology consisting of three phases, first the historical evolution of TiO₂ photocatalysis, [...] Read more.

This perspective article describes the past, present, and future directions on TiO₂ photocatalysis, 3D concrete printing, and recycling for developing innovative building envelope components from façade skins. Using a methodology consisting of three phases, first the historical evolution of TiO₂ photocatalysis, 3D concrete printing, and recycling policies was investigated. Second, the rationale and positioning with regard to the state of the art were developed. Third, the cementitious mix design assessment for 3D printing of the building envelope components, evaluation of the photocatalytic activity, evaluation of the self-cleaning and air-purifying properties, and environmental and health assessment of the building envelope components were identified and discussed as major issues in developing innovative building envelope components that have the potential to mitigate urban air pollution, reduce building maintenance activities, and reduce building embedded carbon while, for example, recycling significant amounts of construction and demolition waste. Full article

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

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13 pages, 8918 KiB

Open AccessEditor’s ChoiceArticle

Effect of SiC Contents on Wear Resistance Performance of Electro-Codeposited Ni-SiC Composite Coatings

by Shaoqing Wang, Faqin Xie and Xiangqing Wu

Coatings 2024, 14(9), 1224; https://doi.org/10.3390/coatings14091224 - 23 Sep 2024

Cited by 3 | Viewed by 1260

Abstract

This paper focuses on the wear resistance performance of Ni-SiC composite coatings with various contents of SiC particles. The coatings were characterized via a scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM), and the wear behaviors of different coatings [...] Read more.

This paper focuses on the wear resistance performance of Ni-SiC composite coatings with various contents of SiC particles. The coatings were characterized via a scanning electron microscope (SEM), X-ray diffractometer (XRD), and transmission electron microscopy (TEM), and the wear behaviors of different coatings were tested. The results show that SiC particle incorporation results in a nanocrystalline metal matrix and nanotwins in nickel nanograins. The microhardness and wear resistance Ni-SiC composite coatings increased with the increasing SiC content. Microhardness was improved due to the grain-refinement strengthening effect and the presence of a nanotwin structure. The dominant wear mechanism was described in two stages: the first stage involves the interaction of SiC particles/the counter ball, and the second stage involves the formation of the oxide film its breaking up into wear debris. A higher SiC content increased the duration of the first stage and slowed down the rate of breaking up into debris, thereby decreasing the wear rate. Full article

(This article belongs to the Section Tribology)

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23 pages, 6574 KiB

Open AccessEditor’s ChoiceReview

Polymer Capacitor Films with Nanoscale Coatings for Dielectric Energy Storage: A Review

by Liang Cao, Rui Xi, Chen Zhou, Gaohui He, Feng Yang, Lingna Xu and He Li

Coatings 2024, 14(9), 1193; https://doi.org/10.3390/coatings14091193 - 15 Sep 2024

Cited by 2 | Viewed by 3330

Abstract

Enhancing the energy storage properties of dielectric polymer capacitor films through composite materials has gained widespread recognition. Among the various strategies for improving dielectric materials, nanoscale coatings that create structurally controlled multiphase polymeric films have shown great promise. This approach has garnered considerable [...] Read more.

Enhancing the energy storage properties of dielectric polymer capacitor films through composite materials has gained widespread recognition. Among the various strategies for improving dielectric materials, nanoscale coatings that create structurally controlled multiphase polymeric films have shown great promise. This approach has garnered considerable attention in recent years due to its effectiveness. This review examines surface-coated polymer composites used for dielectric energy storage, discussing their dielectric properties, behaviors, and the underlying physical mechanisms involved in energy storage. The review thoroughly examines the fabrication methods for nanoscale coatings and the selection of coating materials. It also explores the latest advancements in the rational design and control of interfaces in organic–inorganic, organic–organic, and heterogeneous multiphase structures. Additionally, the review delves into the structure–property relationships between different interfacial phases and various interface structures, analyzing how nanoscale coatings the impact dielectric constant, breakdown strength, conduction and charge transport mechanisms, energy density and efficiency, thermal stability, and electrothermal durability of polymeric capacitor films. Moreover, the review summarizes relevant simulation methods and offers computational insights. The potential practical applications and characteristics of such nanoscale coating techniques are discussed, along with the existing challenges and practical limitations. Finally, the review concludes with a summary and outlook, highlighting potential research directions in this rapidly evolving field. Full article

(This article belongs to the Special Issue Trends and Advances in Thin Films and Coatings for High-Efficiency Organic Solar Cells)

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16 pages, 13078 KiB

Open AccessEditor’s ChoiceArticle

Metallization of Carbon Fiber-Reinforced Plastics (CFRP): Influence of Plasma Pretreatment on Mechanical Properties and Splat Formation of Atmospheric Plasma-Sprayed Aluminum Coatings

by Christian Semmler, Willi Schwan and Andreas Killinger

Coatings 2024, 14(9), 1169; https://doi.org/10.3390/coatings14091169 - 11 Sep 2024

Cited by 1 | Viewed by 1725

Abstract

Carbon fiber-reinforced plastics (CFRPs) have broad applications as lightweight structural materials due to their remarkable strength-to-weight ratio. Aluminum is often used as a bond coating to ensure adhesion between CFRPs and further coatings with a higher melting temperature. However, challenges persist in optimizing [...] Read more.

Carbon fiber-reinforced plastics (CFRPs) have broad applications as lightweight structural materials due to their remarkable strength-to-weight ratio. Aluminum is often used as a bond coating to ensure adhesion between CFRPs and further coatings with a higher melting temperature. However, challenges persist in optimizing their surface properties and adhesion attributes for diverse applications. This investigation explores the impact of sandblasting and plasma pretreatment on CFRP surfaces and their influence on plasma-sprayed aluminum coatings. Two distinct CFRP substrates, distinguished by their cyanate ester and epoxy resin matrices, and two different aluminum powder feedstocks were employed. Plasma pretreatment induced micro-surface roughening in the range of 0.5 µm and significantly reduced the contact angles on polished specimens. Notably, on sandblasted specimens, plasma-activated surfaces displayed improved wetting behavior, which is attributed to the removal of polymeric fragments and augmented fiber exposure. Aluminum splats show a better interaction with carbon fibers compared to a polymeric matrix material. The impact of plasma activation on the coating adhesion proved relatively limited. All samples with plasma activation had deposition efficiencies that increased by 12.5% to 34.4%. These findings were supported by SEM single-splat analysis and contribute to a deeper comprehension of surface modification strategies tailored to CFRPs. Full article

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

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25 pages, 3225 KiB

Open AccessEditor’s ChoiceReview

Electrophoretic Deposition of Bioactive Glass Coatings for Bone Implant Applications: A Review

by Richard Drevet, Joël Fauré and Hicham Benhayoune

Coatings 2024, 14(9), 1084; https://doi.org/10.3390/coatings14091084 - 23 Aug 2024

Cited by 8 | Viewed by 3763

Abstract

This literature review deals with the electrophoretic deposition of bioactive glass coatings on metallic substrates to produce bone implants. Biocompatible metallic materials, such as titanium alloys or stainless steels, are commonly used to replace hard tissue functions because their mechanical properties are appropriate [...] Read more.

This literature review deals with the electrophoretic deposition of bioactive glass coatings on metallic substrates to produce bone implants. Biocompatible metallic materials, such as titanium alloys or stainless steels, are commonly used to replace hard tissue functions because their mechanical properties are appropriate for load-bearing applications. However, metallic materials barely react in the body. They need a bioactive surface coating to trigger beneficial biological and chemical reactions in the physiological environment. Bioactive coatings aim to improve bone bonding, shorten the healing process after implantation, and extend the lifespan of the implant. Bioactive glasses, such as 45S5, 58S, S53P4, 13-93, or 70S30C, are amorphous materials made of a mixture of oxides that are accepted by the human body. They are used as coatings to improve the surface reactivity of metallic bone implants. Their high bioactivity in the physiological environment induces the formation of strong chemical bonding at the interface between the metallic implant and the surrounding bone tissue. Electrophoretic deposition is one of the most effective solutions to deposit uniform bioactive glass coatings at low temperatures. This article begins with a review of the different compositions of bioactive glasses described in the scientific literature for their ability to support hard tissue repair. The second part details the different stages of the bioactivity process occurring at the surface of bioactive glasses immersed in a physiological environment. Then, the mechanisms involved in the electrophoretic deposition of bioactive glass coatings on metallic bone implants are described. The last part of the article details the current developments in the process of improving the properties of bioactive glass coatings by adding biocompatible elements to the glassy structure. Full article

(This article belongs to the Special Issue Advanced Biomaterials and Coatings)

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14 pages, 4991 KiB

Open AccessEditor’s ChoiceArticle

The Evolution of Surfaces on Medium-Carbon Steel for Fatigue Life Estimations

by Phanuphak Seensattayawong and Eberhard Kerscher

Coatings 2024, 14(8), 1077; https://doi.org/10.3390/coatings14081077 - 22 Aug 2024

Cited by 1 | Viewed by 1402

Abstract

Early in fatigue life, fatigue cracks are often initiated at persistent slip bands (PSBs), which play the main role in surface evolution when the components are subjected to cyclic loading. Therefore, this paper aims to study the behavior of the surface development of [...] Read more.

Early in fatigue life, fatigue cracks are often initiated at persistent slip bands (PSBs), which play the main role in surface evolution when the components are subjected to cyclic loading. Therefore, this paper aims to study the behavior of the surface development of medium-carbon steel, specifically 42CrMo4 (SAE 4140). Tests were conducted using tension–compression fatigue testing with stress amplitudes set at 30%, 40%, and 50% of the ultimate tensile strength (UTS); a load ratio of R = −1; and a frequency of f = 10 Hz. The ultimate number of test cycles was 2 × 10⁵. The fatigue test specimens with as-machined surface quality (Ra < 100 nm) were tested on a servo-hydraulic push–pull testing machine, and the tests were interrupted a few times to bring the specimens out for surface measuring with a confocal microscope. The linear roughness values of the arithmetic mean deviation (Ra), maximum height (Rz), maximum profile peak height (Rp), and maximum profile valley depth (Rv) were investigated and further used to determine the roughness evolution during cyclic loading (REC) by analyzing the inclinations of the fitting curves of roughness and number-of-cycles diagrams. REC could then be used to estimate and classify the fatigue lifetime. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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15 pages, 5469 KiB

Open AccessEditor’s ChoiceArticle

High-Temperature Hot Corrosion Resistance of CrAl/NiCoCrAlY/AlSiY Gradient Composite Coating on TiAl Alloy

by Yuanyuan Sun, Qiang Miao, Shijie Sun, Wenping Liang, Zheng Ding, Jiangqi Niu, Feilong Jia, Jianyan Xu and Jiumei Gao

Coatings 2024, 14(8), 1067; https://doi.org/10.3390/coatings14081067 - 20 Aug 2024

Cited by 5 | Viewed by 1682

Abstract

TiAl alloys are used in high-temperature components such as the turbine blades of aeroengines because of their excellent properties. However, TiAl alloys are prone to thermal corrosion when in near-ocean service. In order to solve this problem, a hot-corrosion-resistant CrAl/NiCoCrAlY/AlSiY gradient composite coating [...] Read more.

TiAl alloys are used in high-temperature components such as the turbine blades of aeroengines because of their excellent properties. However, TiAl alloys are prone to thermal corrosion when in near-ocean service. In order to solve this problem, a hot-corrosion-resistant CrAl/NiCoCrAlY/AlSiY gradient composite coating was prepared on the surface of the TiAl alloy. The phase composition and morphology of the coating were analyzed. Hot corrosion tests of the traditional NiCoCrAlY coating and CrAl/NiCoCrAlY/AlSiY gradient composite coating on a TiAl substrate were performed. The samples were coated with 75%Na₂SO₄ + 25%NaCl salt film and treated at 950 °C for 100 h, and the corrosion products were analyzed. The results indicate that compared with the TiAl substrate and traditional NiCoCrAlY-coated samples, the composite coating showed better hot corrosion resistance, only slightly cracking, and no corrosion loss occurred. This is mainly because the continuous Al₂O₃ layer can effectively resist the damage caused by the melting reaction in salt, and the Cr-rich layer can not only slow the mutual diffusion of elements but also generate a good corrosion resistance chromium oxide protective layer under serious corrosion. Moreover, the corrosion mechanism of the TiAl substrate, traditional NiCoCrAlY coating, and experimental composite coating was analyzed in detail. Full article

(This article belongs to the Special Issue High-Temperature Corrosion and Oxidation of Metals and Alloys)

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14 pages, 4242 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Vanadate-Exchanged Electrodeposited Zn-Al Layered Double Hydroxide (LDH) Coating on a ZX21 Mg Alloy to Improve the Corrosion Resistance

by Wei-Lun Hsiao and Peng-Wei Chu

Coatings 2024, 14(8), 1047; https://doi.org/10.3390/coatings14081047 - 16 Aug 2024

Cited by 2 | Viewed by 1740

Abstract

This study presents a vanadate-exchanged Zn-Al layered double hydroxide (LDH) coating on a ZX21 Mg alloy (Mg-2.15 wt%Zn-0.97 wt%Ca) by electrodeposition and immersion anion-exchange post-treatment. With the prepared vanadate-exchanged electrodeposited Zn-Al LDH coating, the corrosion resistance of the ZX21 Mg alloy improves with [...] Read more.

This study presents a vanadate-exchanged Zn-Al layered double hydroxide (LDH) coating on a ZX21 Mg alloy (Mg-2.15 wt%Zn-0.97 wt%Ca) by electrodeposition and immersion anion-exchange post-treatment. With the prepared vanadate-exchanged electrodeposited Zn-Al LDH coating, the corrosion resistance of the ZX21 Mg alloy improves with a decrease in the corrosion current density from 62.4 μA/cm² to 3.32 μA/cm². The fabricated vanadate-exchanged electrodeposited Zn-Al LDH coating contains complex anions in the interlayers, including mainly nitrate (NO₃⁻), carbonate (CO₃²⁻), and different vanadates. The coating not only serves as a physical barrier on the ZX21 Mg alloy but also absorbs chloride ions in the environment through anion exchange and inhibits corrosion with the reduction of the interlayer vanadates. Furthermore, the vanadates can also be released into the damaged area of the coating. Full article

(This article belongs to the Special Issue Advances in Corrosion-Resistant Coatings, 2nd Edition)

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15 pages, 4336 KiB

Open AccessEditor’s ChoiceArticle

Microstructure and Wear Performance of TaC and Ta/TaC Coatings on 30CrNi2MoVA Steel

by Kai Yang, Xuming Lv, Bo Dang, Zhuoyan Lai, Xiaohu Chen, Dongbo Wei, Shuqin Li and Pingze Zhang

Coatings 2024, 14(8), 1039; https://doi.org/10.3390/coatings14081039 - 15 Aug 2024

Cited by 2 | Viewed by 1711

Abstract

To enhance the wear resistance of artillery barrels in harsh environments, TaC and Ta/TaC coatings were prepared on 30CrNi2MoVA steel using double-glow plasma surface metallurgy technology. These coatings, of which their surfaces consisted of almost pure TaC phases, showed defect-free interfaces with the [...] Read more.

To enhance the wear resistance of artillery barrels in harsh environments, TaC and Ta/TaC coatings were prepared on 30CrNi2MoVA steel using double-glow plasma surface metallurgy technology. These coatings, of which their surfaces consisted of almost pure TaC phases, showed defect-free interfaces with the substrate. The Ta/TaC coating demonstrated excellent integration, forming a nearly homogeneous structure. The coatings exhibited a gradient cross-sectional hardness, affecting a depth of approximately 20 μm. The Ta transition layer significantly enhanced the microhardness and adhesive strength of the TaC coating, with about 16.7% and 68.5% increases in the Ta/TaC coating, respectively. Both coatings markedly improved the wear resistance, showing slight wear at room temperature and minor oxidative wear at high temperatures. The Ta/TaC coating had more stable friction coefficient curves and a lower specific wear rate, with an 11.4% wear rate of the substrate at 500 °C. Thermal mismatch and stress concentration under wear loads caused extensive cracks and edge chipping in the TaC coating. In contrast, the good compatibility between the Ta transition layer and the TaC layer allowed for cooperative deformation with the substrate, creating a plastic deformation zone that reduced internal stresses and stress concentration, maintaining the intact structure. This study provides insights into applying Ta/TaC coatings for artillery barrel protection and broadens the possible application scenarios of the preparation technology. Full article

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

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17 pages, 7764 KiB

Open AccessEditor’s ChoiceArticle

An Innovative Wood Fire-Retardant Coating Based on Biocompatible Nanocellulose Surfactant and Expandable Graphite

by Tereza Jurczyková, Elena Kmeťová, František Kačík, Martin Lexa and Jakub Ťoupal

Coatings 2024, 14(8), 1036; https://doi.org/10.3390/coatings14081036 - 15 Aug 2024

Cited by 2 | Viewed by 1886

Abstract

Nanocellulose (CNC) seems to be a promising surfactant, which, together with expandable graphite (EG), forms the essence of an effective natural-based fire-retardant wood coating. In our research, the most suitable composition of the mixture was tested concerning good solubility, dispersion, and consistency. Favorable [...] Read more.

Nanocellulose (CNC) seems to be a promising surfactant, which, together with expandable graphite (EG), forms the essence of an effective natural-based fire-retardant wood coating. In our research, the most suitable composition of the mixture was tested concerning good solubility, dispersion, and consistency. Favorable results were achieved with the formulation composed of a 4% CNC alkaline solution with 80 wt.% of the selected EG. Subsequently, six different types of EG were used to prepare these wood fire-retardant coatings. The effectiveness of treatments was verified using a test with a radiant heat source, where the test samples’ relative weight loss, relative burning rate, and surface temperature during 600 s were evaluated. All prepared formulations can be characterized as more or less equally effective. However, the best results were obtained with the EG of GG 200–100 N, where the mass loss of the sample was 8.10 ± 1.24%. Very good results were also achieved by graphite 25 E + 180 HPH (8.70 ± 0.89%), which is similar to the previous one, even according to the microscopic assessment of the coating as well as the expanded layer. The graphite type 25 K + 180 (8.86 ± 0.65%) shows the expanded layer’s best adhesion, coating uniformity, and ease of application. The results of this work confirmed that the CNC coating itself has significant retardation effects. Full article

(This article belongs to the Special Issue New Challenges in Wood Adhesives and Coatings, 2nd Edition)

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17 pages, 21836 KiB

Open AccessEditor’s ChoiceArticle

Effect of Two Types of Pomelo Peel Flavonoid Microcapsules on the Performance of Water-Based Coatings on the Surface of Fiberboard

by Jinzhe Deng, Tingting Ding and Xiaoxing Yan

Coatings 2024, 14(8), 1032; https://doi.org/10.3390/coatings14081032 - 14 Aug 2024

Cited by 3 | Viewed by 1854

Abstract

In order to achieve antibacterial properties in water-based coatings, two types of antibacterial pomelo peel flavonoid microcapsules were added to water-based coatings and decorated on the surface of fiberboard. The surface coatings of the substrates were tested and analyzed. The antibacterial rate of [...] Read more.

In order to achieve antibacterial properties in water-based coatings, two types of antibacterial pomelo peel flavonoid microcapsules were added to water-based coatings and decorated on the surface of fiberboard. The surface coatings of the substrates were tested and analyzed. The antibacterial rate of the surface coatings of the two groups of fiberboards gradually increased with the increase in the content of the microcapsules. The color difference of the surface coatings of both groups increased slightly, the glossiness decreased, the gloss loss rate increased greatly, and the reflectivity increased slightly. The adhesion of the surface coatings of the two groups of fiberboards did not change significantly, the roughness gradually increased, the hardness of the melamine-resin-coated pomelo peel flavonoid microcapsules gradually increased, and the impact resistance slightly improved. Compared with the antibacterial results of the coating without substrate at the same content, the antibacterial effect of the fiberboard surface coating was slightly decreased. Overall, the surface coating on the fiberboard with 9.0% chitosan-coated pomelo peel flavonoid microcapsules demonstrated superior performance, superior coating morphology, and enhanced antibacterial properties. The antibacterial rate was 73.7% against Escherichia coli, and the antibacterial rate was 77.4% against Staphylococcus aureus. The color difference was 3.85, the gloss loss rate was 90.0%, and the reflectivity was 20.19%. The hardness was HB, the adhesion was level 1, the impact resistance level was 3, and the roughness was 1.94 μm. This study explored the effect of antibacterial microcapsules on coating performance, providing a technical basis for the application of the antibacterial microcapsules. Full article

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

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12 pages, 27979 KiB

Open AccessEditor’s ChoiceArticle

Extraction of Anthocyanin Dye from Staghorn Sumac Fruit in Various Solvents and Use for Pigment Printing

by Maja Klančnik and Elena Koradin

Coatings 2024, 14(8), 1025; https://doi.org/10.3390/coatings14081025 - 13 Aug 2024

Cited by 3 | Viewed by 2387

Abstract

This study investigates the potential of the dye extracted from the fruits of the alien invasive plant staghorn sumac (lat. Rhus typhina) as a sustainable and environmentally friendly colorant. By using a range of solvents, including distilled water, methanol, ethanol, propanol, acetonitrile, [...] Read more.

This study investigates the potential of the dye extracted from the fruits of the alien invasive plant staghorn sumac (lat. Rhus typhina) as a sustainable and environmentally friendly colorant. By using a range of solvents, including distilled water, methanol, ethanol, propanol, acetonitrile, acetone, and dichloromethane, this study aims to determine the optimum solvent for the extraction of anthocyanin dyes from the fruit of staghorn sumac for the formulation of printing inks and for screen printing on paper and cotton fabric. The colors of the prints made with different dye extracts varied between more or less intense brownish-yellow hues, with the exception of the dye extracts in methanol and ethanol, which gave more brownish-orange hues. All prints showed excellent resistance to rubbing on cotton fabrics as well as to wet ironing. The light fastness of prints made with inks containing dyes extracted from all organic solvents was very good. Good wash fastness of prints on cotton fabrics was only achieved with inks made with dyes extracted in propanol and dichloromethane. The ink made from the dye extracted in propanol proved to be the best choice for printing on cotton fabric due to its uniform, intense, and resilient prints, while the inks made from the dyes extracted in distilled water and ethanol were also a good choice for printing on paper. Full article

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

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25 pages, 11956 KiB

Open AccessEditor’s ChoiceArticle

Innovative Paper Coatings: Regenerative Superhydrophobicity through Self-Structuring Aqueous Wax-Polymer Dispersions

by Cynthia Cordt, Jennifer Daeg, Oliver Elle, Andreas Geissler and Markus Biesalski

Coatings 2024, 14(8), 1028; https://doi.org/10.3390/coatings14081028 - 13 Aug 2024

Cited by 7 | Viewed by 3220

Abstract

For a wide range of applications, paper materials require effective protection against the destructive effect of water, which is most effectively realized by superhydrophobic coatings. In recent years, a considerable amount of scientific research has been carried out in this area, focusing particularly [...] Read more.

For a wide range of applications, paper materials require effective protection against the destructive effect of water, which is most effectively realized by superhydrophobic coatings. In recent years, a considerable amount of scientific research has been carried out in this area, focusing particularly on biogenic resources. With this contribution, we go one step further and examine how biogenic materials can be transferred into aqueous dispersions and coated onto paper via existing technologies. With this paper coating, based on a hydrophobic cellulose derivative in combination with a structurally similar wax, thermally regenerable flower-like surface morphologies are obtained via self-assembly, where the hydrophobic cellulose polymer acts as a structural template for the co-crystallization of the wax component. Such hydrophobic structures in the low micrometer range ensure perfectly water-repellent paper surfaces with contact angles > 150° starting from coating weights of 5 g/m². The dispersion can be successfully applied to a variety of commercially available paper substrates, whereby the effects of different roughness, porosity, and hydrophobicity were investigated. In this context, a certain roughness of the base paper (S_a ~ 1.5–3 µm) was found to be beneficial for achieving the highest possible contact angles. Furthermore, the approach proved to be paper process-compatible, recyclable, and regenerable, whereby the processing temperatures allow the coating properties to be thermally generated in situ. With this work, we demonstrate how biogenic waxes are very well suited for superhydrophobic, regenerative coatings and, importantly, how they can be applied from aqueous coatings, enabling simple transfer into the paper industry. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology, 2nd Edition)

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12 pages, 5330 KiB

Open AccessEditor’s ChoiceArticle

Friction and Wear Behavior of 3D-Printed Inconel 718 Alloy under Dry Sliding Conditions

by Ioannis Karagiannidis, Athanasios Tzanis, Dirk Drees, Lais Lopes, Georgios Chondrakis, Maria Myrto Dardavila, Emmanuel Georgiou and Angelos Koutsomichalis

Coatings 2024, 14(8), 1029; https://doi.org/10.3390/coatings14081029 - 13 Aug 2024

Cited by 1 | Viewed by 2229

Abstract

Tailor-made materials used for advanced applications are nowadays of great research interest in various industrial and technological fields, ranging from aerospace and automotive applications to consumer goods and biomedical components. In the present research, Inconel 718 superalloy specimens were fabricated by the selective [...] Read more.

Tailor-made materials used for advanced applications are nowadays of great research interest in various industrial and technological fields, ranging from aerospace and automotive applications to consumer goods and biomedical components. In the present research, Inconel 718 superalloy specimens were fabricated by the selective laser melting (SLM) technique. Structural characterization of the 3D-printed samples showed that they consisted of γ solid solution along with spherical carbide particles. To explore the applicability of these materials in abrasive tribological applications, reciprocating sliding tests were performed under dry conditions versus an Al₂O₃ counter-body. A 3D representation (triboscopy) of the tangential force during each sliding cycle was carried out in order to obtain better insight on the evolution of friction and to visualize localized tribological phenomena. Quantification of wear was performed with confocal microscopy and the wear mechanisms were analyzed with SEM and EDS techniques. Furthermore, the effect of surface finishing (as-printed and polished) on friction and wear were also investigated, and a comparison with other industrial materials is also included to evaluate the applicability of these alloys. The results indicated that surface finishing had an effect on friction during the run-in stage, whereas in steady-state conditions, no significant differences were observed between the as-printed and polished specimens. In all cases, the main wear mechanisms observed were a mixture of two-body and three-body abrasion, along with oxidative wear (indicated by the formation of an oxide-based tribo-layer). Full article

(This article belongs to the Special Issue Surface Engineering Processes for Reducing Friction and Wear)

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10 pages, 5124 KiB

Open AccessEditor’s ChoiceArticle

Thick Columnar-Structured Thermal Barrier Coatings Using the Suspension Plasma Spray Process

by Dianying Chen and Christopher Dambra

Coatings 2024, 14(8), 996; https://doi.org/10.3390/coatings14080996 - 7 Aug 2024

Cited by 5 | Viewed by 2210

Abstract

Higher operating temperatures for gas turbine engines require highly durable thermal barrier coatings (TBCs) with improved insulation properties. A suspension plasma spray process (SPS) had been developed for the deposition of columnar-structured TBCs. SPS columnar TBCs are normally achieved at a short standoff [...] Read more.

Higher operating temperatures for gas turbine engines require highly durable thermal barrier coatings (TBCs) with improved insulation properties. A suspension plasma spray process (SPS) had been developed for the deposition of columnar-structured TBCs. SPS columnar TBCs are normally achieved at a short standoff distance (50.0 mm–75.0 mm), which is not practical when coating complex-shaped engine hardware since the plasma torch may collide with the components being sprayed. Therefore, it is critical to develop SPS columnar TBCs at longer standoff distances. In this work, a commercially available pressure-based suspension delivery system was used to deliver the suspension to the plasma jet, and a high-enthalpy TriplexPro-210 plasma torch was used for the SPS coating deposition. Suspension injection pressure was optimized to maximize the number of droplets injected into the hot plasma core and achieving the best particle-melting states and deposition efficiency. The highest deposition efficiency of 51% was achieved at 0.34 MPa injection pressure with a suspension flow rate of 31.0 g/min. With the optimized process parameters, 1000 μm thick columnar-structured SPS 8 wt% Y₂O₃-stabilized ZrO₂ (8YSZ) TBCs were successfully developed at a standoff distance of 100.0 mm. The SPS TBCs have a columnar width between 100 μm and 300 μm with a porosity of ~22%. Furnace cycling tests at 1125 °C showed the SPS columnar TBCs had an average life of 1012 cycles, which is ~2.5 times that of reference air-plasma-sprayed dense vertically cracked TBCs with the same coating thickness. The superior durability of the SPS columnar TBCs can be attributed to the high-strain-tolerant microstructure. SEM cross-section characterization indicated the failure of the SPS TBCs occurred at the ceramic top coat and thermally grown oxide (TGO) interface. Full article

(This article belongs to the Special Issue Functional Coatings and Surface Science for Precision Engineering)

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12 pages, 2175 KiB

Open AccessEditor’s ChoiceArticle

Protection against Atmospheric Corrosion of Zinc in Marine Environment Rich in H₂S Using Self-Assembled Monolayers Based on Sargassum fluitans III Extract

by Prescilla Lambert, Mahado Said-Ahmed, Benoit Lescop, Stéphane Rioual and Mounim Lebrini

Coatings 2024, 14(8), 988; https://doi.org/10.3390/coatings14080988 - 5 Aug 2024

Viewed by 1325

Abstract

The self-assembled monolayers (SAMs) process is one of the techniques used for the production of ultra-thin layers. The present work is therefore devoted to the study of the inhibition of zinc corrosion in a marine environment rich in H₂S by SAMs [...] Read more.

The self-assembled monolayers (SAMs) process is one of the techniques used for the production of ultra-thin layers. The present work is therefore devoted to the study of the inhibition of zinc corrosion in a marine environment rich in H₂S by SAMs based on Sargassum fluitans III. The protective effect of crude extracts of Sargassum fluitans on the surface of zinc using the SAMs process was evaluated by gravimetry and impedance on two different sites after three months of exposure. The formation of SAMs was characterized by FTIR, and the corrosion products formed on the surfaces were analyzed by XRD. The results obtained show that SAMs based on Sargassum fluitans III effectively inhibit zinc corrosion. Full article

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

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16 pages, 3022 KiB

Open AccessEditor’s ChoiceArticle

Data-Driven Optimization of Plasma Electrolytic Oxidation (PEO) Coatings with Explainable Artificial Intelligence Insights

by Patricia Fernández-López, Sofia A. Alves, Aleksey Rogov, Aleksey Yerokhin, Iban Quintana, Aitor Duo and Aitor Aguirre-Ortuzar

Coatings 2024, 14(8), 979; https://doi.org/10.3390/coatings14080979 - 3 Aug 2024

Cited by 2 | Viewed by 2416

Abstract

PEO constitutes a promising surface technology for the development of protective and functional ceramic coatings on lightweight alloys. Despite its interesting advantages, including enhanced wear and corrosion resistances and eco-friendliness, the industrial implementation of PEO technology is limited by its relatively high energy [...] Read more.

PEO constitutes a promising surface technology for the development of protective and functional ceramic coatings on lightweight alloys. Despite its interesting advantages, including enhanced wear and corrosion resistances and eco-friendliness, the industrial implementation of PEO technology is limited by its relatively high energy consumption. This study explores the development and optimization of novel PEO processes by means of machine learning (ML) to improve the coating thickness. For this purpose, ML models random forest and XGBoost were employed to predict the thickness of the developed PEO coatings based on the key process variables (frequency, current density, and electrolyte composition). The predictive performance was significantly improved by including the composition of the used electrolyte in the models. Furthermore, Shapley values identified the pulse frequency and the TiO₂ concentration in the electrolyte as the most influential variables, with higher values leading to increased coating thickness. The residual analysis revealed a certain heteroscedasticity, which suggests the need for additional samples with high thickness to improve the accuracy of the model. This study reveals the potential of artificial intelligence (AI)-driven optimization in PEO processes, which could pave the way for more efficient and cost-effective industrial applications. The findings achieved further emphasize the significance of integrating interactions between variables, such as frequency and TiO₂ concentration, into the design of processing operations. Full article

(This article belongs to the Special Issue Functional Films/Coatings Processing Technologies: Deposition and Process)

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18 pages, 12340 KiB

Open AccessEditor’s ChoiceArticle

High-Temperature Mechanical and Tribological Performance of W-DLC Coating with Cr interlayer on X40CrMoV5-1 Hot Work Tool Steel

by Mária Hagarová, Gabriela Baranová, Mária Heželová, Martin Truchlý, Marek Vojtko, Ondrej Petruš and Dávid Csík

Coatings 2024, 14(8), 971; https://doi.org/10.3390/coatings14080971 - 2 Aug 2024

Cited by 3 | Viewed by 1989

Abstract

Diamond-like carbon (DLC) coatings enhance tool wear resistance across various temperatures. The sp³/sp² bond ratio within DLC significantly impacts its properties and thermal stability. Elevated temperatures can alter DLC’s structure, while metallic elements and interlayers like chromium can modify its [...] Read more.

Diamond-like carbon (DLC) coatings enhance tool wear resistance across various temperatures. The sp³/sp² bond ratio within DLC significantly impacts its properties and thermal stability. Elevated temperatures can alter DLC’s structure, while metallic elements and interlayers like chromium can modify its microstructure and performance. To evaluate the potential of W-DLC coatings with a chromium interlayer on 40CrMoV5-1 hot work tool steel under elevated temperatures, mechanical and tribological properties were assessed at room temperature and at temperatures of 100, 200, 300, 400, and 500 °C. Nanoindentation revealed a maximum hardness of 14.1 ± 1.3 GPa for the coating deposited at room temperature, attributed to a high sp³ content confirmed by Raman spectroscopy. Hardness decreased to 9.3 ± 1.0 GPa at 400 °C due to graphitization. The elastic modulus remained relatively constant across all temperatures. Tribological tests indicated a low coefficient of friction (CoF) of 0.15 at room temperature, increasing to 0.35 at 100 °C. The CoF further rose to 0.5 at 200 °C, coinciding with increased graphitization. However, the CoF reduced to 0.45 and 0.35 at 400 °C and 500 °C, respectively, likely due to the formation of a WO₃ tribo-film and the protective effect of the chromium interlayer. Full article

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

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13 pages, 8603 KiB

Open AccessEditor’s ChoiceArticle

Natural Tannin Layers for the Corrosion Protection of Steel in Contact with Water-Based Media

by Rossella Sesia, Silvia Spriano, Marco Sangermano, Massimo Calovi, Stefano Rossi and Sara Ferraris

Coatings 2024, 14(8), 965; https://doi.org/10.3390/coatings14080965 - 2 Aug 2024

Cited by 3 | Viewed by 2848

Abstract

Numerous strategies have been developed for the corrosion protection of steel; however, most of them have a significant environmental impact and employ toxic compounds. Tannins are a green and promising solution for sustainable corrosion protection strategies. In this context, this work was focused [...] Read more.

Numerous strategies have been developed for the corrosion protection of steel; however, most of them have a significant environmental impact and employ toxic compounds. Tannins are a green and promising solution for sustainable corrosion protection strategies. In this context, this work was focused on natural (condensed and hydrolysable) tannin layers as a possible corrosion protection strategy for carbon steel. The impact of the tannins’ dissolution medium (ultrapure water or Phosphate-Buffered Saline), surface pre-treatment (acid pickling or plasma), and deposition technology (dipping or spin coating) on layer homogeneity and adhesion has been evaluated. The effects of these parameters on coating formation, homogeneity, and adhesion have been investigated by means of visual inspections, swabbing, Fourier Transformed Infrared spectroscopy (FTIR), Scanning Electron Microscopy equipped with Energy Dispersive Spectroscopy (SEM-EDS) and tape adhesion tests. Preliminary electrochemical corrosion tests have been performed on the most promising material (carbon steel acid pickled and coated with a hydrolysable tannin solved in water by spin coating) to estimate the protective ability of the developed layers and highlight the main criticisms to be overcome. Full article

(This article belongs to the Special Issue Advanced Anticorrosion Coatings and Coating Testing)

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14 pages, 11328 KiB

Open AccessEditor’s ChoiceArticle

High-Temperature Zn-5Al Hot Dip Galvanizing of Reinforcement Steel

by Anżelina Marek, Veronika Steinerová, Petr Pokorný, Henryk Kania and Franciszek Berger

Coatings 2024, 14(8), 959; https://doi.org/10.3390/coatings14080959 - 1 Aug 2024

Cited by 2 | Viewed by 1970

Abstract

This article presents the results of research on the growth kinetics, microstructure (SEM/EDS/XRD), and corrosion behavior of Zn-5Al coatings obtained using a high-temperature hot dip process on B500B reinforcing steel. The corrosion resistance of the coatings was determined using the neutral salt spray [...] Read more.

This article presents the results of research on the growth kinetics, microstructure (SEM/EDS/XRD), and corrosion behavior of Zn-5Al coatings obtained using a high-temperature hot dip process on B500B reinforcing steel. The corrosion resistance of the coatings was determined using the neutral salt spray (NSS) test (EN ISO 9227). Based on chemical composition tests in micro-areas (EDS) and phase composition tests (XRD), corrosion products formed on the coating surface after exposure to a corrosive environment containing chlorides were identified. In the outer layer of the coating, areas rich in Zn and Al were found, which were solid solutions of Al in Zn (α), while the diffusion layer was formed by a layer of Fe(Al,Zn)₃ intermetallics. The growth kinetics of the coatings indicate the sequential growth of the diffusion layer, controlled by diffusion in the initial phase of growth, and the formation of a periodic layered structure with a longer immersion time. The NSS test showed an improved corrosion resistance of reinforcing bars with Zn-5Al coatings compared to a conventional hot-dip-galvanized zinc coating. The increase in corrosion resistance was caused by the formation of beneficial corrosion products: layered double hydroxides (LDH) based on Zn²⁺ and Al³⁺ cations and Cl⁻ anions and simonkolleite—Zn₅(OH)₈Cl₂·H₂O. Full article

(This article belongs to the Special Issue High-Temperature Corrosion and Oxidation of Metals and Alloys)

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22 pages, 78862 KiB

Open AccessEditor’s ChoiceArticle

Fatigue Behaviour and Life Prediction of YSZ Thermal Barrier Coatings at Elevated Temperature under Cyclic Loads

by Qiannan Tao, Yanrong Wang and Yu Zheng

Coatings 2024, 14(8), 960; https://doi.org/10.3390/coatings14080960 - 1 Aug 2024

Cited by 5 | Viewed by 1991

Abstract

The concentration of interfacial normal stress at the free edges of thermal barrier coatings (TBCs) can result in coating spallation. Fatigue cracking is one of the main reasons for creating free edges under complex loads. It is crucial to investigate the fatigue cracking [...] Read more.

The concentration of interfacial normal stress at the free edges of thermal barrier coatings (TBCs) can result in coating spallation. Fatigue cracking is one of the main reasons for creating free edges under complex loads. It is crucial to investigate the fatigue cracking of coatings under cyclic loads to assess potential coating failure. To address this issue, a novel model was proposed to predict the fatigue life of the YSZ topcoat under stress parallel to the interface. Firstly, this study conducted uniaxial and tensile-torsional fatigue tests at elevated temperatures on specimens with atmospheric plasma-sprayed TBCs. The test results revealed that fatigue cracks appeared in the topcoat under cyclic loads, but these cracks did not propagate into the bondcoat or substrate immediately. The number of cycles before the topcoat cracked was found to be associated with the magnitude of the cyclic load. Secondly, this study analyzed the test conditions using the finite element method. Simulations indicated that the crack direction in the topcoat under complex loading conditions was aligned with the first principal stress direction. Finally, the fatigue life prediction model of the topcoat was established based on experiments and simulations. The predicted results fell within a fourfold scatter band. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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14 pages, 9409 KiB

Open AccessEditor’s ChoiceArticle

The Effects of Nitrogen Content on the Mechanical and Tribological Properties of CrTaWN_x Thin Films

by Li-Chun Chang, Li-Zhu Wang and Yung-I Chen

Coatings 2024, 14(8), 939; https://doi.org/10.3390/coatings14080939 - 26 Jul 2024

Cited by 2 | Viewed by 1171

Abstract

In the study described herein, CrTaWN_x thin films were deposited on Si and 304 stainless-steel (SUS304) substrates through magnetron co-sputtering using CrW and Ta targets. The nitrogen flow ratio (f_N2 = [N₂/(N₂ + Ar)]) was adjusted to [...] Read more.

In the study described herein, CrTaWN_x thin films were deposited on Si and 304 stainless-steel (SUS304) substrates through magnetron co-sputtering using CrW and Ta targets. The nitrogen flow ratio (f_N2 = [N₂/(N₂ + Ar)]) was adjusted to 0.05, 0.2, 0.4, and 0.5 to fabricate CrTaWN_x films with various N contents. The CrTaWN_x films prepared at a low f_N2 of 0.05 exhibited a low stoichiometric ratio x of 0.16 and a nanocrystalline structure. In contrast, the CrTaWN_x films fabricated at an f_N2 of 0.2–0.5 exhibited x values of 0.42–0.62 and formed a face-centered cubic phase. The nanocrystalline (Cr_0.34Ta_0.20W_0.46)N_0.16 film exhibited mechanical properties and wear resistances that were inferior to those of the crystalline CrTaWN_x thin films. A (Cr_0.38Ta_0.15W_0.47)N_0.55 film exhibited a hardness of 25.2 GPa, an elastic modulus of 289 GPa, and a low wear rate of 0.51 × 10⁻⁵ mm³/Nm. Full article

(This article belongs to the Special Issue Thin-Film Synthesis, Characterization and Properties)

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18 pages, 6306 KiB

Open AccessEditor’s ChoiceArticle

Self-Assembled Pd Nanocomposites into a Monolayer for Enhanced Sensing Performance

by Mohammad Navvabpour, Pierre-Michel Adam, Safi Jradi and Suzanna Akil

Coatings 2024, 14(8), 934; https://doi.org/10.3390/coatings14080934 - 25 Jul 2024

Cited by 4 | Viewed by 1287

Abstract

To date, the advanced synthetic approaches for palladium nanoparticle-based catalysts involve multistep, toxic, and high-cost fabrication routes with low catalytic and sensing performance. In this work, we introduce a new one-shot approach to produce highly sensitive Pd nanocomposites using a large-area polymer self-assembly [...] Read more.

To date, the advanced synthetic approaches for palladium nanoparticle-based catalysts involve multistep, toxic, and high-cost fabrication routes with low catalytic and sensing performance. In this work, we introduce a new one-shot approach to produce highly sensitive Pd nanocomposites using a large-area polymer self-assembly strategy. This synthesis method allowed us to control the Pd nanoparticle shape and to tailor their plasmonic band positions in a wide light spectral range from ~350 to ~800 nm. We thus determined the critical synthesis conditions that give rise to a ringlike morphology in a reproducible manner. No need for a reducing agent and preliminary functionalization of the surface supporting the nanoparticles upon synthesis. To the best of our knowledge, few works have demonstrated the good performance of PdNPs in sensing. Here, we have demonstrated a robust SERS response for 4-mercaptopyridine with an enhancement factor of 4.2 × 10⁵. We were able to exceed this high value, which matches the current maximum found in the literature, by decreasing the gap distances between Pd nanorings due to the high density of hotspots and the exacerbation of the coupling effect between PdNPs. These tailored products provide new insights for the use of Pd nanomaterials in photocatalysis applications, according to the well-established catalytic performance of Pd materials obtained in this work. Full article

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

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19 pages, 15991 KiB

Open AccessEditor’s ChoiceArticle

Amorphous Alumina ALD Coatings for the Protection of Limestone Cultural Heritage Objects

by Gillian P. Boyce, Suveena Sreenilayam, Eleonora Balliana, Elisabetta Zendri and Raymond J. Phaneuf

Coatings 2024, 14(8), 931; https://doi.org/10.3390/coatings14080931 - 25 Jul 2024

Cited by 1 | Viewed by 1869

Abstract

From natural erosion to pollution-accelerated decay, stone cultural heritage deteriorates constantly through interactions with the environment. Common protective treatments such as acrylic polymers are generally prone to degradation and loss of performance, and they are often limited in their ability to achieve uniform [...] Read more.

From natural erosion to pollution-accelerated decay, stone cultural heritage deteriorates constantly through interactions with the environment. Common protective treatments such as acrylic polymers are generally prone to degradation and loss of performance, and they are often limited in their ability to achieve uniform and conformal coverage across a stone’s topographical features. In this work, atomic layer deposition (ALD) was explored to address these issues by growing protective amorphous alumina coatings on compact carbonate (Istria) stone. ALD protective coatings, unlike coatings produced by traditional methods, do not significantly alter morphology by filling open pores or accumulating on the surface in more compact areas. Our morphological and spectroscopic investigations revealed that the ALD alumina films deposited uniformly over the surfaces of Istria stone, without significantly altering the topography or appearance. The protective effects of the ALD coatings were investigated by aqueous acid immersion. The solution pH, along with the Ca²⁺ concentration, was tracked over time for a constant volume of acetic acid solution with an initial pH of 4 with the stone samples immersed. We found that the protective effects of ALD alumina coatings were extremely promising, slowing the average rate of pH evolution significantly. The eventual failure of the ALD coatings during immersion was also investigated, with interesting morphological findings that point to the role of defects in the coatings, suggesting new directions for improving the use of ALD coatings in future research and applications. Full article

(This article belongs to the Special Issue Recent Advances in Chemical Vapor Deposition)

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10 pages, 9460 KiB

Open AccessEditor’s ChoiceArticle

Influence of Oxygen Flow Rate on the Phase Structures and Properties for Copper Oxide Thin Films Deposited by RF Magnetron Sputtering

by Junghwan Park, Young-Guk Son, Chang-Sik Son and Donghyun Hwang

Coatings 2024, 14(8), 930; https://doi.org/10.3390/coatings14080930 - 25 Jul 2024

Cited by 2 | Viewed by 2117

Abstract

This study examines the impact of varying oxygen flow rates on the properties of Cu₂O thin films deposited via radio frequency (RF) magnetron sputtering. X-ray diffraction (XRD) analysis showed a phase transition from cubic Cu₂O to a mixed Cu [...] Read more.

This study examines the impact of varying oxygen flow rates on the properties of Cu₂O thin films deposited via radio frequency (RF) magnetron sputtering. X-ray diffraction (XRD) analysis showed a phase transition from cubic Cu₂O to a mixed Cu₂O and CuO phase, eventually forming a Cu₄O₃ tetragonal structure as oxygen content increased. The surface morphology and cross-sectional structure of Cu₂O thin films observed through field emission scanning electron microscopy (FE-SEM) were found to vary significantly depending on the oxygen flow rate. X-ray photoelectron spectroscopy (XPS) indicated notable variations in the chemical states of copper and oxygen. The Cu 2p spectra revealed peaks around 933 eV and 953 eV for all samples, with the S01 sample (deposited with only argon gas) exhibiting the lowest intensity. The S02 sample showed the highest peak intensity, which then gradually decreased from S03 to S06. The O 1s spectra followed a trend with peak intensity being highest in S02 and decreasing with further oxygen flow rates, indicating the formation of complex oxides such as Cu₄O₃. UV-Vis-NIR spectroscopy results demonstrated a decrease in transmittance and optical band gap energy with increasing oxygen content, suggesting a decline in crystallinity and an increase in defects and impurities. These findings underscore the critical role of precise oxygen flow rate control in tailoring the structural, morphological, compositional, and optical properties of Cu₂O thin films for specific electronic and optical applications. Full article

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

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24 pages, 5687 KiB

Open AccessEditor’s ChoiceArticle

CMAS Corrosion Resistance of Plasma-Sprayed YSZ and Yb₂O₃-Y₂O₃-Co-Stabilized ZrO₂ Coatings under 39–40 KW Spraying Power

by Wenkang Zhang, Wei Liu, Yangguang Liu, Weize Wang, Ting Yang, Kaibin Li, Junhao Wang, Xiaoqin Zhang, Shilong Yang, Pengpeng Liu and Chengcheng Zhang

Coatings 2024, 14(8), 928; https://doi.org/10.3390/coatings14080928 - 24 Jul 2024

Viewed by 1670

Abstract

This study uses atmospheric plasma spraying (APS) technology to prepare thermal barrier coatings (TBCs) with yttrium-stabilized zirconia (YSZ) and Yb₂O₃-Y₂O₃-co-stabilized ZrO₂ (YbYSZ) materials at different spraying powers. It analyzes the differences and changes in [...] Read more.

This study uses atmospheric plasma spraying (APS) technology to prepare thermal barrier coatings (TBCs) with yttrium-stabilized zirconia (YSZ) and Yb₂O₃-Y₂O₃-co-stabilized ZrO₂ (YbYSZ) materials at different spraying powers. It analyzes the differences and changes in the microstructure, thermodynamic properties, and mechanical properties of the TBCs. The CaO-MgO-Al₂O₃-SiO₂ (CMAS) resistance of coatings was tested using thermal cycling-CMAS experiments and isothermal corrosion experiments. Compared to YSZ coatings, YbYSZ coatings have lower thermal conductivity, a higher hardness and elastic modulus, a longer lifetime under thermal cycling-CMAS conditions, and lower penetration and degradation depths. Under thermal cycling-CMAS coupling conditions, the optimal power range for the longest thermal cycling lifetime for both coatings is 39–40 kW. Overall, compared to the YSZ material, the YbYSZ material exhibits superior properties. Full article

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

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22 pages, 6636 KiB

Open AccessEditor’s ChoiceArticle

Chemical and UV Durability of Hydrophobic and Icephobic Surface Layers on Femtosecond Laser Structured Stainless Steel

by Roland Fürbacher, Gabriel Grünsteidl, Andreas Otto and Gerhard Liedl

Coatings 2024, 14(8), 924; https://doi.org/10.3390/coatings14080924 - 23 Jul 2024

Cited by 1 | Viewed by 1635

Abstract

Femtosecond laser processing significantly alters the surface structure and chemical composition, impacting its wetting properties. Post-treatments such as immersion in a hydrocarbon liquid (petrol) or storage in a vacuum can significantly reduce ice adhesion, making the surfaces interesting for anti-ice applications. This study [...] Read more.

Femtosecond laser processing significantly alters the surface structure and chemical composition, impacting its wetting properties. Post-treatments such as immersion in a hydrocarbon liquid (petrol) or storage in a vacuum can significantly reduce ice adhesion, making the surfaces interesting for anti-ice applications. This study investigates their durability against acetone, ethylene glycol, and UV radiation. The laser-structured surfaces were immersed in the respective liquids for up to 48 h. The results indicate limited durability of the superhydrophobic and icephobic layers when submerged in acetone and ethylene glycol, with more favorable results for petrol treatment than vacuum treatment. Similar results were obtained after 100 h of UV exposure, showing a decrease in superhydrophobic properties and an increase in ice adhesion. However, repeated vacuum treatments conducted after the chemical durability tests revealed the potential for partial recovery of the hydrophobic and icephobic properties. XPS analysis was performed throughout the experiments to evaluate changes in surface chemistry resulting from the post-laser treatments and the durability tests. Full article

(This article belongs to the Special Issue Recent Advances in Hydrophobic Surface and Materials)

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12 pages, 3243 KiB

Open AccessEditor’s ChoiceArticle

Effects of Precursors Ratio and Curing Treatment on the Icephobicity of Polydimethylsiloxane

by Marcella Balordi, Alessandro Casali, Paolo Gadia, Paolo Pelagatti, Francesco Pini and Giorgio Santucci de Magistris

Coatings 2024, 14(7), 901; https://doi.org/10.3390/coatings14070901 - 18 Jul 2024

Viewed by 1540

Abstract

Elastomers are intriguing materials for many applications, one of these being icephobic coatings. Elastic modulus and work of adhesion are the key parameters coming into play in ice detachment mechanisms, and can be related to hardness and wettability. Polydimethylsiloxane (PDMS) is widely used [...] Read more.

Elastomers are intriguing materials for many applications, one of these being icephobic coatings. Elastic modulus and work of adhesion are the key parameters coming into play in ice detachment mechanisms, and can be related to hardness and wettability. Polydimethylsiloxane (PDMS) is widely used for anti-ice applications; however, not many works deal with the correlation between cross-linking grade, curing treatments, and icephobicity. This study focuses on PDMS (Sylgard184^®) coatings, encompassing four different pre-polymer to cross-linking agent (A:B) ratios ranging from 5:1 to 30:1, and nine curing treatments. The results indicate that increasing the A:B ratio enhances hydrophobicity, softness, and icephobicity, assessed through shear stress measurements. Curing treatments primarily affect hardness and icephobicity, with longer heat treatments resulting in higher hardness and ice adhesion. All samples exhibit promising performances in lowering shear stress values, up to seven times in respect to the uncoated reference for 30:1 ratio. Additionally, a durability assessment is conducted on samples exposed to stress tests in the climatic chamber. A slight deterioration in hydrophobicity across all samples is observed and, notably, a significant hardness increase, around 13%, is experienced for the 5:1 ratio only. The samples also demonstrate an overall robust icephobicity after stress tests, and, for the 30:1 ratio, an average shear stress value four times lower than the reference is maintained. In this work, we highlight the importance of the fine-tuning of the precursors ratio and thermal treatments on the PDMS properties and durability. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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15 pages, 7208 KiB

Open AccessEditor’s ChoiceArticle

Chemical Bonding of Nanorod Hydroxyapatite to the Surface of Calciumfluoroaluminosilicate Particles for Improving the Histocompatibility of Glass Ionomer Cement

by Sohee Kang, So Jung Park, Sukyoung Kim and Inn-Kyu Kang

Coatings 2024, 14(7), 893; https://doi.org/10.3390/coatings14070893 - 17 Jul 2024

Cited by 2 | Viewed by 1295

Abstract

Glass ionomer cement (GIC) is composed of anionic polyacrylic acid and a silica-based inorganic powder. GIC is used as a filling material in the decayed cavity of the tooth; therefore, compatibility with the tooth tissue is essential. In the present study, we aimed [...] Read more.

Glass ionomer cement (GIC) is composed of anionic polyacrylic acid and a silica-based inorganic powder. GIC is used as a filling material in the decayed cavity of the tooth; therefore, compatibility with the tooth tissue is essential. In the present study, we aimed to improve the histocompatibility of GIC by introducing nano-hydroxyapatite (nHA), a component of teeth, into a silica-based inorganic powder. CFAS-nHA was prepared by chemically bonding nanorod hydroxyapatite (nHA) to the surface of calciumfluoroaluminosilicate (CFAS). The synthesis of CFAS-nHA was confirmed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The prepared CFAS-nHA was mixed with polyacrylic acid and cured to prepare GIC containing nHA (GIC-nHA). Cytocompatibility tests of GIC-nHA and GIC were performed using osteoblasts. Osteoblast activity and bone formation ability were superior after GIC-nHA treatment than after control GIC treatment. This enhanced histocompatibility is believed to be due to the improvement of the biological activity of osteoblasts induced by the HA introduced into the GIC. Therefore, to enhance its compatibility with dental tissues, GIC could be manufactured by chemically bonding nHA to the surface of GI inorganic powder. Full article

(This article belongs to the Special Issue Advanced Biomaterials and Coatings)

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22 pages, 4157 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Indium Tin Oxide (ITO) Thin Films towards Terahertz (THz) Functional Device Applications

by Anup Kumar Sahoo, Wei-Chen Au and Ci-Ling Pan

Coatings 2024, 14(7), 895; https://doi.org/10.3390/coatings14070895 - 17 Jul 2024

Cited by 3 | Viewed by 3803

Abstract

In this study, we explored the manipulation of optical properties in the terahertz (THz) frequency band of radio-frequency (RF) sputtered indium tin oxide (ITO) thin films on highly resistive silicon substrate by rapid thermal annealing (RTA). The optical constants of as-deposited and RTA-processed [...] Read more.

In this study, we explored the manipulation of optical properties in the terahertz (THz) frequency band of radio-frequency (RF) sputtered indium tin oxide (ITO) thin films on highly resistive silicon substrate by rapid thermal annealing (RTA). The optical constants of as-deposited and RTA-processed ITO films annealed at 400 °C, 600 °C and 800 °C are determined in the frequency range of 0.2 to 1.0 THz. The transmittance can be changed from ~27% for as-deposited to ~10% and ~39% for ITO films heat-treated at different annealing temperatures (T_a’s). Such variations of optical properties in the far infrared for the samples under study are correlated with their mobility and carrier concentration, which are extracted from Drude–Smith modeling of THz conductivity with plasma frequency, scattering time and the c-parameters as fitting parameters. Resistivities of the films are in the range of 10⁻³ to 10⁻⁴ Ω-cm, confirming that annealed ITO films can potentially be used as transparent conducting electrodes for photonic devices operating at THz frequencies. The highest mobility, μ = 47 cm²/V∙s, with carrier concentration, N_c = 1.31 × 10²¹ cm⁻³, was observed for ITO films annealed at T_a = 600 °C. The scattering times of the samples were in the range of 8–21 fs, with c-values of −0.63 to −0.87, indicating strong backscattering of the carriers, mainly by grain boundaries in the polycrystalline film. To better understand the nature of these films, we have also characterized the surface morphology, microscopic structural properties and chemical composition of as-deposited and RTA-processed ITO thin films. For comparison, we have summarized the optical properties of ITO films sputtered onto fused silica substrates, as-deposited and RTA-annealed, in the visible transparency window of 400–800 nm. The optical bandgaps of the ITO thin films were evaluated with a Tauc plot from the absorption spectra. Full article

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

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21 pages, 6113 KiB

Open AccessEditor’s ChoiceArticle

Exploring Heterointerface Characteristics and Charge-Storage Dynamics in ALD-Developed Ultra-Thin TiO₂-In₂O₃/Au Heterojunctions

by Mohammad Karbalaei Akbari, Nasrin Siraj Lopa and Serge Zhuiykov

Coatings 2024, 14(7), 880; https://doi.org/10.3390/coatings14070880 - 14 Jul 2024

Viewed by 1288

Abstract

Directional ionic migration in ultra-thin metal-oxide semiconductors under applied electric fields is a key mechanism for developing various electronic nanodevices. However, understanding charge transfer dynamics is challenging due to rapid ionic migration and uncontrolled charge transfer, which can reduce the functionality of microelectronic [...] Read more.

Directional ionic migration in ultra-thin metal-oxide semiconductors under applied electric fields is a key mechanism for developing various electronic nanodevices. However, understanding charge transfer dynamics is challenging due to rapid ionic migration and uncontrolled charge transfer, which can reduce the functionality of microelectronic devices. This research investigates the supercapacitive-coupled memristive characteristics of ultra-thin heterostructured metal-oxide semiconductor films at TiO₂-In₂O₃/Au Schottky junctions. Using atomic layer deposition (ALD), we nano-engineered In₂O₃/Au-based metal/semiconductor heterointerfaces. TEM studies followed by XPS elemental analysis revealed the chemical and structural characteristics of the heterointerfaces. Subsequent AFM studies of the hybrid heterointerfaces demonstrated supercapacitor-like behavior in nanometer-thick TiO₂-In₂O₃/Au junctions, resembling ultra-thin supercapacitors, pseudocapacitors, and nanobatteries. The highest specific capacitance of 2.6 × 10⁴ F.g⁻¹ was measured in the TiO₂-In₂O₃/Au junctions with an amorphous In₂O₃ electron gate. Additionally, we examined the impact of crystallization, finding that thermal annealing led to the formation of crystalline In₂O₃ films with higher oxygen vacancy content at TiO₂-In₂O₃ heterointerfaces. This crystallization process resulted in the evolution of non-zero I-V hysteresis loops into zero I-V hysteresis loops with supercapacitive-coupled memristive characteristics. This research provides a platform for understanding and designing adjustable ultra-thin Schottky junctions with versatile electronic properties. Full article

(This article belongs to the Special Issue Advanced Films and Coatings Based on Atomic Layer Deposition)

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13 pages, 4598 KiB

Open AccessEditor’s ChoiceArticle

Magnetron Sputtered Low-Platinum Loading Electrode as HER Catalyst for PEM Electrolysis

by Antía Villamayor, Alonso Alba, Laura V. Barrio, Sergio Rojas and Eva Gutierrez-Berasategui

Coatings 2024, 14(7), 868; https://doi.org/10.3390/coatings14070868 - 11 Jul 2024

Cited by 2 | Viewed by 2506

Abstract

The development of cost-effective components for Proton Exchange Membrane (PEM) electrolyzers plays a crucial role in the transformation of renewable energy into hydrogen. To achieve this goal, two main issues should be addressed: reducing the Platinum Group Metal (PGM) content present on the [...] Read more.

The development of cost-effective components for Proton Exchange Membrane (PEM) electrolyzers plays a crucial role in the transformation of renewable energy into hydrogen. To achieve this goal, two main issues should be addressed: reducing the Platinum Group Metal (PGM) content present on the electrodes and finding a large-scale electrode manufacturing method. Magnetron sputtering could solve these hurdles since it allows the production of highly pure thin films in a single-step process and is a well-established industrial and automated technique for thin film deposition. In this work, we have developed an ultra-low 0.1 mg cm⁻² Pt loading electrode using magnetron sputtering gas aggregation method (MSGA), directly depositing the Pt nanoparticles on top of the carbon substrate, followed by a complete evaluation of the electrochemical properties of the sputtered electrode. These ultra-low Pt content electrodes have been thoroughly characterized and tested in a real electrolyzer cell. They demonstrate similar efficiency to commercial electrodes with a Pt content of 0.3 mg/cm², achieving a 67% reduction in Pt loading. Additionally, durability tests indicate that these electrodes offer greater stability compared to their commercial counterparts. Thus, magnetron sputtering has been proven as a promising technology for manufacturing optimum high-performance electrodes at an industrial scale. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Performance Enhancement of Electrode Coatings for Energy Sustainability)

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9 pages, 4872 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Wear Resistance of A390 Aluminum Alloy: A Comprehensive Evaluation of Thermal Sprayed WC, CrC, and Al₂O₃ Coatings

by Jaehui Bang and Eunkyung Lee

Coatings 2024, 14(7), 853; https://doi.org/10.3390/coatings14070853 - 8 Jul 2024

Cited by 5 | Viewed by 1772

Abstract

This study comparatively analyzed the wear characteristics and adhesion properties of 86WC–10Co–4Cr (WC) coatings deposited using the high velocity oxygen fuel process and 75Cr₃C₂–25NiCr (CrC) and Al₂O₃–3TiO₂ (Al₂O₃) coatings deposited [...] Read more.

This study comparatively analyzed the wear characteristics and adhesion properties of 86WC–10Co–4Cr (WC) coatings deposited using the high velocity oxygen fuel process and 75Cr₃C₂–25NiCr (CrC) and Al₂O₃–3TiO₂ (Al₂O₃) coatings deposited using the atmospheric plasma spray process on an A390 aluminum alloy substrate. The adhesion strength and wear test results demonstrated that the WC coating exhibited superior wear resistance. In contrast, the CrC and Al₂O₃ coatings showed lower adhesion properties and unstable frictional variations due to a higher number of defects compared to the WC coating. The WC coating layer, protected by WC particles, exhibited minimal damage and a low wear rate, followed by CrC and Al₂O₃. Ultimately, WC coating is highlighted as the optimal choice to enhance the wear resistance of A390 aluminum alloy. Full article

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

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16 pages, 13325 KiB

Open AccessEditor’s ChoiceArticle

Effect of NO_X and SO_X Contaminants on Corrosion Behaviors of 304L and 316L Stainless Steels in Monoethanolamine Aqueous Amine Solutions

by Eleni Lamprou, Fani Stergioudi, Georgios Skordaris, Nikolaos Michailidis, Evie Nessi, Athanasios I. Papadopoulos and Panagiotis Seferlis

Coatings 2024, 14(7), 842; https://doi.org/10.3390/coatings14070842 - 5 Jul 2024

Cited by 1 | Viewed by 2230

Abstract

This work is devoted to evaluating the corrosion behaviors of SS 304L and SS 316L in monoethanolamine solutions (MEA) containing SO_X and NO_X pollutants, examining both lean and CO₂-loaded conditions at 25 °C and 40 °C. Electrochemical techniques (potentiodynamic [...] Read more.

This work is devoted to evaluating the corrosion behaviors of SS 304L and SS 316L in monoethanolamine solutions (MEA) containing SO_X and NO_X pollutants, examining both lean and CO₂-loaded conditions at 25 °C and 40 °C. Electrochemical techniques (potentiodynamic and cyclic polarization) were used along with Scanning Electron Microscopy, Confocal Microscopy and weight loss measurements. The results reveal that the introduction of SO_X and NO_X pollutants increased the corrosion rate, whereas CO₂ loading primarily reduced the corrosion resistance in the lean MEA solution, while its impact on solutions with SO_X and NO_X was less pronounced. This suggests that SO_X and NO_X play primary roles in the metal’s dissolution. Also, SS 316L demonstrated superior corrosion resistance compared to 304L in nearly all of the cases examined. Elevated temperatures were also found to intensify the corrosion rate, indicating a correlation between the corrosion rate and temperature. A microscopic observation and EDX analysis revealed that corrosion products are characterized by high concentrations of iron (Fe) and oxygen (O) as well as carbon (C). There is also an indication of the possible formation of amine complexes, suggesting a potential for amine degradation. No pitting corrosion was observed in SS 304L and SS 316L across any tested solution. Finally, the immersion results expose a tendency for passivity in all amine solutions and at both temperatures after several days of exposure. Moreover, they confirm the very low corrosion rate calculated from potentiodynamic curves due to minimal weight loss after 24 days of immersion. Full article

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

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12 pages, 3290 KiB

Open AccessEditor’s ChoiceArticle

Anti-Corrosion SiO_x-Doped DLC Coating for Raster Steel Linear Scales

by Algirdas Lazauskas, Viktoras Grigaliūnas, Dalius Jucius, Šarūnas Meškinis, Mindaugas Andrulevičius, Asta Guobienė, Andrius Vasiliauskas and Albinas Kasparaitis

Coatings 2024, 14(7), 818; https://doi.org/10.3390/coatings14070818 - 1 Jul 2024

Cited by 2 | Viewed by 1665

Abstract

In this study, we investigated the efficacy of SiO_x-doped diamond-like carbon (DLC) films for enhancing the corrosion resistance of raster steel linear scales. The research work highlights the significant role of DLC film materials in enhancing corrosion resistance, making them a [...] Read more.

In this study, we investigated the efficacy of SiO_x-doped diamond-like carbon (DLC) films for enhancing the corrosion resistance of raster steel linear scales. The research work highlights the significant role of DLC film materials in enhancing corrosion resistance, making them a promising solution for various industrial applications. The Raman spectroscopy analysis of SiO_x-doped DLC films, synthesized via a direct ion beam technique with HMDSO vapor, revealed prominent D and G bands characteristic of amorphous carbon materials, with a high degree of disorder indicated by an I_D/I_G ratio of 1.85. X-ray diffraction patterns confirmed the amorphous nature of the SiO_x-doped DLC films and the minimal impact of the DLC deposition process on the underlying crystalline structure of steel. UV–Vis-NIR reflectance spectra of SiO_x-doped DLC on stainless steel demonstrated improvements in the blue wavelength region compared to stainless steel with ripples alone, which is beneficial for applications utilizing blue light. Corrosion tests, including immersion in a 5% salt solution and salt spray testing, showed that SiO_x-doped DLC-coated stainless steel exhibited superior corrosion resistance compared to uncoated steel, with no significant signs of corrosion observed after extended exposure. These findings underscore the potential of SiO_x-doped DLC coatings to provide long-term corrosion protection and maintain the structural integrity and surface quality of steel components in harsh environments. Full article

(This article belongs to the Special Issue Recent Developments on Functional Coatings for Industrial Applications, Volume II)

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