Coatings

14 pages, 3342 KiB

Open AccessArticle

Kinetic Modelling of Powder-Pack Boronized 4Cr5MoSiV1 Steel by Two Distinct Approaches

by Katia Benyakoub, Mourad Keddam, Brahim Boumaali and Michał Kulka

Coatings 2023, 13(6), 1132; https://doi.org/10.3390/coatings13061132 - 20 Jun 2023

Cited by 2 | Viewed by 993

This work attempts to model the powder-pack boronizing kinetics of 4Cr5MoSiV1 steel in the interval of 1133 and 1253 K in order to predict the layers’ thicknesses. The first approach is referred to as the bilayer model and relies on the conservation principle [...] Read more.

This work attempts to model the powder-pack boronizing kinetics of 4Cr5MoSiV1 steel in the interval of 1133 and 1253 K in order to predict the layers’ thicknesses. The first approach is referred to as the bilayer model and relies on the conservation principle of mass balance equations at the two phase fronts accounting for the linearity of boron distribution across each boride phase. The second approach deals with the application of dimensional analysis to simulate the boronizing kinetics of 4Cr5MoSiV1 steel. Using the bilayer model and the classical parabolic law, the boron activation energies in FeB and Fe₂B were evaluated and discussed in light of the literature data. The estimated boron activation energies from the bilayer model were respectively equal to 164.92 and 153.39 kJ mol⁻¹. These values were very comparable to those calculated from the classical parabolic law. Finally, it was proven that the dimensional analysis was able to simulate the layers’ thicknesses for the selected processing parameters. Full article

(This article belongs to the Special Issue Surface Treatment on Metals and Their Alloys)

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17 pages, 9839 KiB

Open AccessFeature PaperArticle

Steel Surface Doped with Nb via Modulated Electron-Beam Irradiation: Structure and Properties

by Maxim Sergeevich Vorobyov, Elizaveta Alekseevna Petrikova, Vladislav Igorevich Shin, Pavel Vladimirovich Moskvin, Yurii Fedorovich Ivanov, Nikolay Nikolaevich Koval, Tamara Vasil`evna Koval, Nikita Andreevich Prokopenko, Ruslan Aleksandrovich Kartavtsov and Dmitry Alekseevich Shpanov

Coatings 2023, 13(6), 1131; https://doi.org/10.3390/coatings13061131 - 20 Jun 2023

Cited by 1 | Viewed by 862

Abstract

A niobium film on an AISI 5135 steel substrate was exposed to submillisecond pulsed electron-beam irradiation with controlled energy modulation within a pulse to increase the film–substrate adhesion. This modulated irradiation made it possible to dope the steel-surface layer with Nb through film [...] Read more.

A niobium film on an AISI 5135 steel substrate was exposed to submillisecond pulsed electron-beam irradiation with controlled energy modulation within a pulse to increase the film–substrate adhesion. This modulated irradiation made it possible to dope the steel-surface layer with Nb through film dissolution in the layer, for which optimum irradiation conditions were chosen from experiments and a mathematical simulation. The irradiated system was tested for surface hardness and wear, and its surface structure and elemental composition were analyzed. The results demonstrate that the microhardness of the irradiated system is much higher and that its wear rate is much lower compared to the initial state. Full article

(This article belongs to the Special Issue Mechanical, Corrosive and Tribological Degradation of Metal Coatings and Modified Metallic Surfaces)

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12 pages, 5106 KiB

Open AccessArticle

Generation of Hybrid Lead Halide CH₃NH₃PbI_3-xCl_x Perovskite Crystals via Convective Self-Assembly

by Ioan Petrovai, Otto Todor-Boer, Adriana Vulpoi, Leontin David and Ioan Botiz

Coatings 2023, 13(6), 1130; https://doi.org/10.3390/coatings13061130 - 20 Jun 2023

Cited by 1 | Viewed by 1115

Abstract

In this study, we have employed a film deposition technique based on convective forces acting at the triple air–solution–substrate contact line to tune the rate of solvent evaporation and, thus, to exert control over the morphology of the resulting mixed lead halide perovskite [...] Read more.

In this study, we have employed a film deposition technique based on convective forces acting at the triple air–solution–substrate contact line to tune the rate of solvent evaporation and, thus, to exert control over the morphology of the resulting mixed lead halide perovskite CH₃NH₃PbI_3-xCl_x films. By varying the speed of film deposition while processing at two different temperatures, perovskite crystals of various shapes and dimensions were generated upon the crystallization of the initial perovskite precursor ink. More precisely, longer than half a millimeter 3D needle-like perovskite crystals exhibiting sharp edges co-existing with large cross-like 3D perovskite crystals could only be obtained upon the slow deposition of films at a low sample processing temperature of 17 °C, i.e., under conditions of low solvent evaporation rate. On the contrary, the utilization of higher film deposition speeds and/or processing temperatures led to smaller 3D needle-like or quasi-2D rectangular perovskite crystals that often appeared interconnected and coalesced. Moreover, as it was revealed by the photoluminescence measurements, the emission intensity of perovskite crystals was larger and dominated by a shorter wavelength peak, as compared to the uncrystallized material that emitted much less light, but at a longer wavelength. Full article

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11 pages, 2749 KiB

Open AccessArticle

Sustainable Dyeing and Finishing of Cotton Fabrics with Layer-by-Layer Technique

by Şule Sultan Uğur

Coatings 2023, 13(6), 1129; https://doi.org/10.3390/coatings13061129 - 20 Jun 2023

Cited by 2 | Viewed by 1586

Abstract

Large amounts of water, synthetic dyestuffs and chemicals are used in the wet processes of textile finishing, and at the end of these processes, liquors containing chemical substances create a waste load. For this reason, it is of great importance to develop new [...] Read more.

Large amounts of water, synthetic dyestuffs and chemicals are used in the wet processes of textile finishing, and at the end of these processes, liquors containing chemical substances create a waste load. For this reason, it is of great importance to develop new wet-finishing processes that use less water, dyestuffs and chemicals. For this purpose, the layer-by-layer deposition method (LbL) was used in this research as an environmentally friendly, sustainable method that can be used in wet-finishing processes to minimize chemical, water and energy consumption. The dyeing and functional finishing of cotton fabrics were carried out in one process by the LbL method. Cotton fabrics were pre-treated with a commercial cationic dye fixation agent and cationic charges were produced on the fabric surfaces. Reactive and direct dyestuff groups were used in the dyeing process of cotton fabrics and fluorocarbon was used in the functional finishing process. Eight and 12 dye/fluorocarbon layered structures were obtained by LbL deposition using a laboratory-type padder. Cotton fabrics were dyed and finished with the same dyes and fluorocarbon via the padding method and both samples were compared. The washing, rubbing and light color fastness properties, color strength and color difference of the dyed samples were tested. Tensile strength, air permeability, SEM graphs, contact angle, water and oil repellency analyses were performed for the treated fabrics. Full article

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13 pages, 5552 KiB

Open AccessArticle

Photoconductive Response to Pulsed UV Light of CsPbCl₃ Flexible Thin Films Grown by Magnetron Sputtering

by Mara Bruzzi, Naomi Falsini, Nicola Calisi, Paolo Scardi and Anna Vinattieri

Coatings 2023, 13(6), 1128; https://doi.org/10.3390/coatings13061128 - 20 Jun 2023

Cited by 1 | Viewed by 986

Abstract

CsPbCl₃ perovskite is attracting increasing interest in ultraviolet (UV) detection due to its optical band gap and superior intrinsic optoelectronic properties. In this study, a novel one-step magnetron sputtering technique was applied for fabricating CsPbCl₃ polycrystalline films on flexible plastic substrates [...] Read more.

CsPbCl₃ perovskite is attracting increasing interest in ultraviolet (UV) detection due to its optical band gap and superior intrinsic optoelectronic properties. In this study, a novel one-step magnetron sputtering technique was applied for fabricating CsPbCl₃ polycrystalline films on flexible plastic substrates with interdigitated contacts. The photoconductive response of 500 nm and 1 µm thick films to pulsed ultraviolet (UV) light in the 0.1–100 Hz frequency range and intensity of 10–500 W/m² was tested at room temperature. The experimental results demonstrated the good performances of the CsPbCl₃ films in terms of signal stability, fast response to transient signal, detectivity, light dynamic range, and dark current noise for the photodetection of pulsed UV light. Full article

(This article belongs to the Special Issue Optical and Electrical Properties and Applications of Semiconductors)

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18 pages, 4478 KiB

Open AccessArticle

Advanced Electrochemical Degradation of Organic Pollutants from Water Using Sb-Doped SnO₂/Ti Anode and Assisted by Granular Activated Carbon

by Anamaria Baciu, Corina Orha, Radu Nicolae, Mircea Nicolaescu, Sorina Ilies and Florica Manea

Coatings 2023, 13(6), 1127; https://doi.org/10.3390/coatings13061127 - 19 Jun 2023

Cited by 2 | Viewed by 1087

Abstract

In this paper, mesoporous electrodes consisting of Sb-doped SnO₂ deposited onto Ti plates that had undergone controlled corrosion under acidic medium were synthesized via a spin-coating method and morpho-structurally characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrodes were [...] Read more.

In this paper, mesoporous electrodes consisting of Sb-doped SnO₂ deposited onto Ti plates that had undergone controlled corrosion under acidic medium were synthesized via a spin-coating method and morpho-structurally characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrodes were electrochemically tested to examine their degradation/mineralization through electrooxidation (EO) of doxorubicin (DOX) as a single component and multi-component, together with capecitabine (CCB) from the cytostatic class and humic acid (HA) from the natural organic matter (NOM) class in the absence/the presence of activated carbon (AC) as a particulate electrode. The best mineralization efficiency of 67% was achieved for DOX mineralization using Sb-doped SnO₂ deposited onto a Ti plate that had undergone controlled corrosion with oxalic acid during the electrooxidation process. The presence of AC within the electrolysis process generated a synergistic effect of 52.75% for total organic carbon (TOC) parameter removal, which is in accordance with and significantly better than the results reported in the literature. The aspects related to the complex mechanism of DOX degradation and mineralization are discussed. The superiority of AC assisted electrooxidation, as electrochemical filtering (EF), was proved, considering simultaneous degradation and mineralization of mixture of doxorubicin, capecitabine and humic acid. Full article

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15 pages, 3835 KiB

Open AccessArticle

Preparation of Nitrogen-Doped ZnFe₂O₄-Modified Carbon Composite and Its Collaborative Energy Storage Mechanism

by Li Wang, Baobao Li, Hongyu Bai, Hong Ding, Na Xu, Chaofan Yin, Jingjing Xiong, Zhiwei Yang, Xianfa Rao and Binbin Dong

Coatings 2023, 13(6), 1126; https://doi.org/10.3390/coatings13061126 - 19 Jun 2023

Viewed by 988

Abstract

The pyrolytic carbon of polymer adsorbent resin (SAP) is used as a waste carbon source, which can be used as a porous carbon network via pyrolysis to remove surface sodium carbonate and other substances. In this paper, a ZnFe₂O₄/nitrogen-doped [...] Read more.

The pyrolytic carbon of polymer adsorbent resin (SAP) is used as a waste carbon source, which can be used as a porous carbon network via pyrolysis to remove surface sodium carbonate and other substances. In this paper, a ZnFe₂O₄/nitrogen-doped porous carbon composite was prepared using the template method. Through the high-temperature carbonization of a polymer and crystallization of inorganic elements, the morphology of the composite showed uniform load characteristics. This well-defined structure and morphology facilitate the transport of Li⁺, enhance the effective contact area with the electrolyte, and provide a wealth of active sites. For the SAP-Fe/Zn anode, at a high current density of 0.1 A g⁻¹, the reversible capacity of the anode reached 753 mAh g⁻¹ after 200 cycles, showing excellent magnification performance. The final modified SAP-Fe/Zn&NC electrode had a reversible capacity of 205.6 mAh g⁻¹ after 1000 cycles at the high current density of 2 A g⁻¹, and the cycle retention rate was as high as 80.7%. The enhanced electrochemical performance can be attributed to the abundant active sites and shortened diffusion pathway of the composite. This ensures adequate conversion reactions during the Li-litization process between Zn, Fe, and Li⁺, alleviates volume expansion, and prevents comminution/aggregation during long cycles at high current densities. Full article

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16 pages, 6595 KiB

Open AccessArticle

Study on Dyeing Properties and Color Characteristics of Wool Fabrics Dyed with Geranium caespitosum L. Extract—A New Natural Yellow Dye

by Zhijun Zhao, Chunxiao Yan, Fei Xu and Jianhong Liu

Coatings 2023, 13(6), 1125; https://doi.org/10.3390/coatings13061125 - 19 Jun 2023

Cited by 3 | Viewed by 1539

Abstract

Natural dyes play an important role in sustainable dyeing processes. However, natural yellow dyes with good performance are rare. Traditional natural yellow dyes have issues, such as a narrow color range and poor light fastness. In this paper, a new natural yellow dye [...] Read more.

Natural dyes play an important role in sustainable dyeing processes. However, natural yellow dyes with good performance are rare. Traditional natural yellow dyes have issues, such as a narrow color range and poor light fastness. In this paper, a new natural yellow dye was extracted from a low-cost herb Geranium caespitosum L. (G. caespitosum). In addition, the dye composition was analyzed using UV-visible spectroscopy. The dyeing process of G. caespitosum dye on wool fabrics was optimized using single-factor experiments. Standard fastness tests were conducted to evaluate the sunlight, washing, and rubbing fastness of the dyed fabrics. The color characteristics and color gamut range of the dyed fabrics were evaluated. The obtained colors were compared and assessed with Pantone Matching Systems and Chinese traditional colors. The results showed that phenolic acids and flavonoids were present in the G. caespitosum dye solution as yellow dye compounds. The best dyeing process for wool fabrics was meta-mordanting. The dyed fabrics were bright yellow at 60 °C and golden yellow at 90 °C. All the obtained colors were in the yellow-red range. According to the ISO color fastness standards, wool fabrics dyed with G. caespitosum dye had good color fastness ratings, particularly sunlight fastness. Therefore, G. caespitosum dye is a promising natural yellow dye that can be used for wool fabric dyeing. It has advantages over other known natural yellow dyes and has certain application value. Full article

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14 pages, 4556 KiB

Open AccessArticle

CoNi₂O₄ Coated on Activated Carbon Wheat Husk (ACWH) as a Novel Nano-Electrocatalyst for Methanol and Ethanol Electro-Oxidation

by Fatemeh Jamali, Majid Seifi and Mohammad Bagher Askari

Coatings 2023, 13(6), 1124; https://doi.org/10.3390/coatings13061124 - 19 Jun 2023

Viewed by 1161

Abstract

In this paper, for the first time, a CoNi₂O₄ nanocatalyst coated on the surface of activated carbon wheat husk (ACWH) was synthesized in the form of CoNi₂O₄/ACWH through a hydrothermal process. The electrocatalytic activity of this [...] Read more.

In this paper, for the first time, a CoNi₂O₄ nanocatalyst coated on the surface of activated carbon wheat husk (ACWH) was synthesized in the form of CoNi₂O₄/ACWH through a hydrothermal process. The electrocatalytic activity of this catalyst was evaluated using methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) processes for use in anodes of alcohol fuel cells. Adding ACWH, as a cheap carbon biomass with an excellent active surface area, improves the performance of the catalyst in the oxidation of alcohols. The current density of CoNi₂O₄/ACWH in the MOR process is 160 mA/cm² at an optimal methanol concentration of 2 M; this oxidation current density in the EOR process and at a concentration of 1.5 M ethanol is 150 mA/cm². The stability of CoNi₂O₄/ACWH in MOR and EOR processes, after 1000 consecutive CV cycles, is 98.6% and 94.6%, respectively. Full article

(This article belongs to the Special Issue Advanced Functional Nanostructured Films and Coatings for Energy Applications)

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14 pages, 4709 KiB

Open AccessArticle

Enhancement of Photoelectric Performance Based on Ultrathin Wide Spectrum Solar Absorption in Cruciform Microstructure Germanium Solar Cells

by Ziyou Zhou, Wenfeng Liu, Hailong Huang, Xiaolong Ding and Xintian Li

Coatings 2023, 13(6), 1123; https://doi.org/10.3390/coatings13061123 - 19 Jun 2023

Cited by 4 | Viewed by 1217

Abstract

In this paper, the solar absorption level of PEDOT:PSS/Ge organic and inorganic hybrid solar cells (HSCs) with different parameters of cruciform microstructure (CM) is studied, using the finite-difference time domain (FDTD) method. The light absorption in HSCs with CM is above 90% in [...] Read more.

In this paper, the solar absorption level of PEDOT:PSS/Ge organic and inorganic hybrid solar cells (HSCs) with different parameters of cruciform microstructure (CM) is studied, using the finite-difference time domain (FDTD) method. The light absorption in HSCs with CM is above 90% in the range of 300 nm to 1300 nm. Under the AM1.5 solar spectrum, the average absorptivity of solar energy is also at a very high level. At the same time, we use DEVICE software to calculate the electrical properties, such as the open-circuit voltage (V_oc), short-circuit current density (J_sc), and maximum power density (P_max). The electrical simulation results show that the P_max of HSCs with CM improves to 72.16% from the planar HSCs. Besides, in order to study the mechanism of solar energy absorption in HSCs containing CM, the logarithmic plots of electric field intensity of HSCs with CM and planar HSCs, are analyzed at different wavelengths. The work shows that the CM shows an excellent light-trapping effect, which reduces the surface reflectivity of HSCs, and greatly improves the photoelectric conversion efficiency of Ge solar cells. Full article

(This article belongs to the Special Issue Micro-Nano Optics and Its Applications)

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22 pages, 7769 KiB

Open AccessReview

Nano–Bio Interface of Molybdenum Disulfide for Biological Applications

by Rongrong Wu, Mingdong Dong and Lei Liu

Coatings 2023, 13(6), 1122; https://doi.org/10.3390/coatings13061122 - 18 Jun 2023

Cited by 2 | Viewed by 1637

Abstract

The unique nano–bio interfacial phenomena play a crucial role in the biosafety and bioapplications of nanomaterials. As a representative two-dimensional (2D) nanomaterial, molybdenum disulfide (MoS₂) has shown great potential in biological applications due to its low toxicity and fascinating physicochemical properties. [...] Read more.

The unique nano–bio interfacial phenomena play a crucial role in the biosafety and bioapplications of nanomaterials. As a representative two-dimensional (2D) nanomaterial, molybdenum disulfide (MoS₂) has shown great potential in biological applications due to its low toxicity and fascinating physicochemical properties. This review aims to highlight the nano–bio interface of MoS₂ nanomaterials with the major biomolecules and the implications of their biosafety and novel bioapplications. First, the nano–bio interactions of MoS₂ with amino acids, peptides, proteins, lipid membranes, and nucleic acids, as well as the associated applications in protein detection, DNA sequencing, antimicrobial activities, and wound-healing are introduced. Furthermore, to facilitate broader biomedical applications, we extensively evaluated the toxicity of MoS₂ and discussed the strategies for functionalization through interactions among MoS₂ and the variety of macromolecules to enhance the biocompatibility. Overall, understanding the nano–bio interface interaction of two-dimensional nanomaterials is significant for understanding their biocompatibility and biosafety, and further provide guidance for better biological applications in the future. Full article

(This article belongs to the Special Issue Advances in Antibacterial Coatings: From Materials to Applications)

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17 pages, 3001 KiB

Open AccessEditor’s ChoiceArticle

Corrosion Performance of Ti6Al7Nb Alloy in Simulated Body Fluid for Implant Application Characterized Using Macro- and Microelectrochemical Techniques

by Andrea Abreu-García, Ricardo M. Souto and Javier Izquierdo

Coatings 2023, 13(6), 1121; https://doi.org/10.3390/coatings13061121 - 18 Jun 2023

Cited by 1 | Viewed by 974

Abstract

In this paper, the applicability of Ti6Al7Nb as a more biocompatible alternative for bone and dental implants than Ti6Al4V and pure titanium in terms of corrosion resistance and electrochemical inertness is investigated. The chemical inertness and corrosion resistance of the Ti6Al7Nb biomaterial were [...] Read more.

In this paper, the applicability of Ti6Al7Nb as a more biocompatible alternative for bone and dental implants than Ti6Al4V and pure titanium in terms of corrosion resistance and electrochemical inertness is investigated. The chemical inertness and corrosion resistance of the Ti6Al7Nb biomaterial were characterized by a multi-scale electrochemical approach during immersion in simulated physiological environments at 37 °C comparing its behavior to that of c.p. Ti, Ti6Al4V, and stainless steel. The establishment of a passive regime for Ti6Al7Nb results from the formation of a thin layer of metal oxide on the surface of the material which prevents the action of aggressive species in the physiological medium from direct reaction with the bulk of the alloy. Conventional electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) provide quantified information on the surface film resistance and its stability domain that encompasses the potential range experienced in the human body; unfortunately, these methods only provide an average estimate of the exposed surface because they lack spatial resolution. Although local physiological environments of the human body are usually simulated using different artificial physiological solutions, and changes in the electrochemical response of a metallic material are observed in each case, similar corrosion resistances have been obtained for Ti6Al7Nb in Hank’s and Ringer’s solutions after one week of immersion (with a corrosion resistance of the order of MΩ cm²). Additionally, scanning electrochemical microscopy (SECM) provides in situ chemical images of reactive metal and passive dielectric surfaces to assess localized corrosion phenomena. In this way, it was observed that Ti6Al7Nb exhibits a high corrosion resistance consistent with a fairly stable passive regime that prevents the electron transfer reactions necessary to sustain the metal dissolution of the bulk biomaterial. Our results support the proposition of this alloy as an efficient alternative to Ti6Al4V for biomaterial applications. Full article

(This article belongs to the Special Issue Biodegradation and Bioprotection of Metals and Alloys)

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18 pages, 4515 KiB

Open AccessReview

Progress in the Graphene Oxide-Based Composite Coatings for Anticorrosion of Metal Materials

by Shuo Tang, Bing Lei, Zhiyuan Feng, Honglei Guo, Ping Zhang and Guozhe Meng

Coatings 2023, 13(6), 1120; https://doi.org/10.3390/coatings13061120 - 18 Jun 2023

Cited by 3 | Viewed by 1899

Abstract

Graphene oxide (GO), derived from the two-dimensional nanosheet graphene, has received unprecedented attention in the field of metal corrosion protection owing to its excellent barrier performance and various active functional groups. In this review, the protection mechanism “labyrinth effect” of composite coatings against [...] Read more.

Graphene oxide (GO), derived from the two-dimensional nanosheet graphene, has received unprecedented attention in the field of metal corrosion protection owing to its excellent barrier performance and various active functional groups. In this review, the protection mechanism “labyrinth effect” of composite coatings against metal corrosion was demonstrated systematically. The origination, structure and properties of GO were also analyzed. Their poor dispersion in polymer and tendency to aggregate as nanofillers in composite coatings are the main limitations during application of the coating fillers. In addition, a comprehensive overview on the perspectives of the surface modification of GO and the multi-functionalization of the composite coatings based on GO were given in particular. Green modification methods, reasonable arrangement of GO sheets in composites and development of multi-functional coatings remain challenges in current studies and should be a focus in the future development of GO-based anticorrosive coatings. This review is of value to researchers interested in the design and application of GO in corrosion protection coatings. Full article

(This article belongs to the Special Issue Advanced Corrosion Protection through Coatings and Surface Rebuilding)

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14 pages, 4848 KiB

Open AccessArticle

CeO₂ Protective Material against CMAS Attack for Thermal–Environmental Barrier Coating Applications

by Lei Guo, Yuanpeng Wang, Mingguang Liu, Yuan Gao and Fuxing Ye

Coatings 2023, 13(6), 1119; https://doi.org/10.3390/coatings13061119 - 18 Jun 2023

Cited by 2 | Viewed by 1242

Abstract

Calcium–magnesium–alumina–silicate (CMAS) attack is a crucial issue for thermal–environmental barrier coatings (T/EBCs) with the ever-increasing operating temperature of turbine engines. In this study, CeO₂ has been demonstrated as a promising protective material for T/EBCs against CMAS attack. At 1300 °C, CeO₂ [...] Read more.

Calcium–magnesium–alumina–silicate (CMAS) attack is a crucial issue for thermal–environmental barrier coatings (T/EBCs) with the ever-increasing operating temperature of turbine engines. In this study, CeO₂ has been demonstrated as a promising protective material for T/EBCs against CMAS attack. At 1300 °C, CeO₂ powder kept excellent phase and structural stability in molten CMAS; there were some CMAS constituents dissolved into the CeO₂ lattice to form a solid solution. With higher CeO₂ contents and longer duration time, more CeO₂ solid solution particles were formed, which acted as the nucleating agent for CMAS crystallization. As a result, apatite, anorthite and wollastonite crystalline products were easily generated. At 1300 °C for 10 h, CeO₂ pellets covered with CMAS powder had limited degradation, which was attributed to the rapid crystallization of molten CMAS due to the excellent nucleating agent effect of the precipitated CeO₂ solid solution. Full article

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

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10 pages, 1932 KiB

Open AccessArticle

Robust Superhydrophilic/Underwater Superoleophobic Surface with Anti-Abrasion and Anti-Corrosion Performances Based on Laser Ablation

by Duoxun Fang, Adham Al-akhali, Molin Cao, Jiahao Liu and Zhengqiang Tang

Coatings 2023, 13(6), 1118; https://doi.org/10.3390/coatings13061118 - 17 Jun 2023

Viewed by 1527

Abstract

Preparing underwater superoleophobic surface is an effective method to solve the problems of oil adhesion on the underwater surfaces and oil spill in water. However, the underwater superoleophobic surfaces at present are not reliable in practical application due to their poor stability under [...] Read more.

Preparing underwater superoleophobic surface is an effective method to solve the problems of oil adhesion on the underwater surfaces and oil spill in water. However, the underwater superoleophobic surfaces at present are not reliable in practical application due to their poor stability under corrosion and abrasion. Herein, we proposed a facile method to fabricate a robust superhydrophilic/underwater superoleophobic surface. The surface is combined with micro honeycomb frame structure and nanostructure, which was fabricated by laser ablation. The surface with the honeycomb pattern shows strong hydrophilicity with a water contact angle of 0° and stable underwater oil repellency with an underwater oil contact angle of 164.9°. Furthermore, it can maintain its excellent underwater superoleophobic performance after 120 cycles of abrasion and corrosion of 6 h at pH = 1–14. Full article

(This article belongs to the Special Issue Recent Advances in Functional Surfaces and Interfaces)

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26 pages, 3359 KiB

Open AccessReview

Crack Formation Mechanisms and Control Methods of Laser Cladding Coatings: A Review

by Mingke Li, Kepeng Huang and Xuemei Yi

Coatings 2023, 13(6), 1117; https://doi.org/10.3390/coatings13061117 - 17 Jun 2023

Cited by 8 | Viewed by 2823

Abstract

Laser cladding, a novel surface treatment technology, utilizes a high-energy laser beam to melt diverse alloy compositions and form a specialized alloy-cladding layer on the surface of the substrate to enhance its property. However, it can generate substantial residual stresses during the rapid [...] Read more.

Laser cladding, a novel surface treatment technology, utilizes a high-energy laser beam to melt diverse alloy compositions and form a specialized alloy-cladding layer on the surface of the substrate to enhance its property. However, it can generate substantial residual stresses during the rapid cooling and heating stages, due to inadequate selection of cladding process parameters and disparities in thermophysical properties between the clad layer and substrate material, leading to the formation of various types of cracks. These cracks can significantly impact the quality and performance of the coating. This paper presents a comprehensive review of crack types and their causes in laser cladding coatings, and identifies that three primary sources of residual stresses, thermal stress, organizational stress, and restraint stress, are the fundamental causes of crack formation. The study proposes several strategies to control coating cracks, including optimizing the coating layer material, refining the coating process parameters, incorporating heat treatment, applying auxiliary fields, and utilizing numerical simulations to predict crack initiation and propagation. Additionally, the paper summarizes crack control methods for emerging structural materials and novel preparation processes. Lastly, the paper analyzes the prospects, technical approaches, and key research directions for effectively controlling cracks in laser cladding coatings. Full article

(This article belongs to the Special Issue Application of Laser Processing Technology in Automobile Manufacturing)

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15 pages, 5905 KiB

Open AccessArticle

Effects of the Ratio of Nano-Cu to Hydroxylated MWCNTs on Anticorrosion and Surface Conductivity of Cu/MWCNT Epoxy Coatings on a Steel Substrate

by Yixun Yu, Mengmeng Liang and Yunfeng Pan

Coatings 2023, 13(6), 1116; https://doi.org/10.3390/coatings13061116 - 17 Jun 2023

Viewed by 877

Abstract

Epoxy coatings provide an economical and practical solution for combating steel corrosion. However, epoxy coatings have poor conductivity, resulting in the accumulation of electrostatic charges. The surface conductivity and anticorrosion properties of epoxy coatings can be improved by adding nano-Cu and hydroxylated multi-walled [...] Read more.

Epoxy coatings provide an economical and practical solution for combating steel corrosion. However, epoxy coatings have poor conductivity, resulting in the accumulation of electrostatic charges. The surface conductivity and anticorrosion properties of epoxy coatings can be improved by adding nano-Cu and hydroxylated multi-walled carbon nanotubes (MWCNTs). This paper investigates the impact of MWCNTs at different concentrations (2.5, 5%) and the ratio of nano-Cu to MWCNTs on the surface conductivity and anticorrosion properties of epoxy coatings on a steel substrate. The findings from the four-probe method of measuring surface resistance indicated that the surface resistivity of steel coated with an epoxy composite of 5% MWCNTs and 65% nano-Cu (Cu65/MWCNT5) was significantly lower, approximately by one order of magnitude, compared to steel coated with a 5% MWCNT (MWCNT5) epoxy coating. When the Cu65/MWCNT5-coated steel was immersed in a 3.5 wt % NaCl solution for 30 days, it was observed that there was a minimal effect on its surface resistivity. The inclusion of a high content of MWCNTs facilitates a more uniform distribution of Cu particles within the epoxy coatings, thereby improving the anticorrosion properties of these coatings on a steel substrate. This was further corroborated by the results of the polarization curves and electrochemical impedance spectroscopy, demonstrating that the Cu65/MWCNT5 epoxy coating on a steel substrate offers exceptional anticorrosion and barrier protection properties. The corrosion rate of steel with a Cu65/MWCNT5 epoxy coating was three orders of magnitude lower than that of steel with a Cu65/MWCNT2.5 epoxy coating, at 4.79 × 10⁻⁷ mm/year. Full article

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14 pages, 3762 KiB

Open AccessArticle

Transparent, High-Strength, and Antimicrobial Polyvinyl Alcohol/Boric Acid/Poly Hexamethylene Guanidine Hydrochloride Films

by Shaotian Zhang, Dafu Wei, Xiang Xu and Yong Guan

Coatings 2023, 13(6), 1115; https://doi.org/10.3390/coatings13061115 - 17 Jun 2023

Cited by 1 | Viewed by 1547

Abstract

It is still crucial to improve the mechanical characteristics of polyvinyl alcohol (PVA) films without resorting to chemical cross-linking. In this study, boric acid (BA) was used to enhance the mechanical characteristics of PVA films while maintaining their excellent transparency and biodegradability. The [...] Read more.

It is still crucial to improve the mechanical characteristics of polyvinyl alcohol (PVA) films without resorting to chemical cross-linking. In this study, boric acid (BA) was used to enhance the mechanical characteristics of PVA films while maintaining their excellent transparency and biodegradability. The hydrogen bond interaction between PVA and BA resulted in a 70% increase in tensile strength (from 48.5 to 82.1 MPa) and a 46% increase in elongation at break (from 150 to 220%). To introduce antibacterial properties, polyhexamethylene guanidine hydrochloride (PHMG) was incorporated into PVA/BA composite films resulting in PVA/BA/PHMG composite films. The PVA/BA/PHMG films exhibited 99.99% bacterial inhibition against Escherichia coli and Staphylococcus aureus with negligible leaching of PHMG. The PVA/BA/PHMG films maintained a tensile strength of 75.3 MPa and an elongation at a break of 208%. These improved mechanical and antimicrobial properties make PVA/BA and PVA/BA/PHMG films promising for applications in food and medicinal packaging. Full article

(This article belongs to the Special Issue Surface Modification Technology of Biomedical Metals)

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13 pages, 4425 KiB

Open AccessArticle

The Design and Preparation of Antibacterial Polymer Brushes with Phthalocyanine Pigments

by Yu Zhou, Kaimin Chen, Li Liu, Shaoguo Wen and Taijiang Gui

Coatings 2023, 13(6), 1114; https://doi.org/10.3390/coatings13061114 - 17 Jun 2023

Cited by 1 | Viewed by 1456

Abstract

Phthalocyanine pigments have many problems in waterborne coating applications because of their low polarity, poor dispersion in water, and easy agglomeration properties. In order to solve these problems, the phthalocyanine pigments were encapsulated with a copolymer of methyl methacrylate (MMA) and butyl acrylate [...] Read more.

Phthalocyanine pigments have many problems in waterborne coating applications because of their low polarity, poor dispersion in water, and easy agglomeration properties. In order to solve these problems, the phthalocyanine pigments were encapsulated with a copolymer of methyl methacrylate (MMA) and butyl acrylate (BA) by a mini-emulsion polymerization method. The pigments are effectively dispersed in water and have good compatibility with the resin. Concerning the bacterial reproduction and growth problem for the waterborne system, the resin-encapsulated phthalocyanine pigments were further grafted with antibacterial polymer poly(N-(2-hydroxyethyl) acrylamide) (PHEAA) on its surface using the photoemulsion polymerization technique. Comprehensive properties, including centrifugal stability and chromaticity change, were studied. The polymer encapsulation improved the centrifugal stability of the pigment. The thermogravimetric results showed that the residual mass of C.I. Pigment Green 7 (52.30%) was higher than that of C.I. Pigment Blue 15:3 (30.06%), and the sublimation fastness of PG7 was higher. The TEM results revealed that the shape of the PG7 after encapsulation and grafting was more regular than that of PB15:3. The L* of the pigment decreased after encapsulation but then increased after further grafting. The phthalocyanine pigment composite latex had good antibacterial properties after the grafting of PHEAA. Full article

(This article belongs to the Special Issue Advanced Polymeric Materials and Coatings: Synthesis, Properties and Applications)

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14 pages, 8927 KiB

Open AccessArticle

Morphological Evolution of La₂NiO₄ Coatings Synthesized by Reactive Magnetron Sputtering (RMS) at High Pressure as Cathode for Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC)

by Xiaolei Ye, Huan Luo, Ming Hou, Pierre Bertrand, Alain Billard and Pascal Briois

Coatings 2023, 13(6), 1113; https://doi.org/10.3390/coatings13061113 - 16 Jun 2023

Cited by 1 | Viewed by 1051

Abstract

This work focuses on the evolution of the morphology and structure of La₂NiO₄ (namely, LNO) coatings deposited by reactive magnetron sputtering (RMS) with subsequent annealing processes. The LNO coatings start to crystallize at 600 °C, and the LNO with K [...] Read more.

This work focuses on the evolution of the morphology and structure of La₂NiO₄ (namely, LNO) coatings deposited by reactive magnetron sputtering (RMS) with subsequent annealing processes. The LNO coatings start to crystallize at 600 °C, and the LNO with K₂NiF₄ structure was formed at 700 °C. A small amount of La₃Ni₂O₇ appeared in the La₂NiO₄ coatings at 1100 °C. Interestingly, the LNO coatings realize the transformation from dense to different porous morphologies due to the annealing process. The LNO coating with abundant pores was formed after annealing treatment at 1000 °C for 2 h. This porous morphology can be stably maintained after short-term thermal stability experiments at 750 °C for 120 h. The electrochemical impedance spectroscopy (EIS) measurement of the LNO/YSZ/LNO symmetrical half-cells shows that the LNO cathode coating after annealing at 1000 °C for 2 h exhibits lower polarization resistance (R_pol) and activation energy. Full article

(This article belongs to the Special Issue Advanced Multielement Coatings: Deposition, Materials and Applications)

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22 pages, 4824 KiB

Open AccessArticle

Atmospheric Pressure Plasma Polymerization of Carvone: A Promising Approach for Antimicrobial Coatings

by Asad Masood, Naeem Ahmed, Fatima Shahid, M. F. Mohd Razip Wee, Anuttam Patra and Kim S. Siow

Coatings 2023, 13(6), 1112; https://doi.org/10.3390/coatings13061112 - 16 Jun 2023

Cited by 1 | Viewed by 1231

Abstract

Medical devices are often vulnerable to colonization by nosocomial pathogens (bacteria), leading to infections. Traditional sterilization methods may not always be effective, and as a result, alternative options are being explored to prevent microbial contamination. Recently, scientists are emphasizing using plant-derived essential oils [...] Read more.

Medical devices are often vulnerable to colonization by nosocomial pathogens (bacteria), leading to infections. Traditional sterilization methods may not always be effective, and as a result, alternative options are being explored to prevent microbial contamination. Recently, scientists are emphasizing using plant-derived essential oils that possess inherent antibacterial properties to produce antimicrobial coatings using plasma polymerization technology carried out at atmospheric pressure (AP). This approach shows promise compared to other coating strategies that need several processing steps, including a high-vacuum system, and are laborious, such as the immobilization of antimicrobial materials on precoated layers in the low-pressure plasma polymerization approach. The present study demonstrates the potential of AP plasma polymerization for producing thin films with excellent antibacterial properties and surface characteristics. The resulting coatings are stable, smooth, and have high wettability, making them ideal for repelling bacteria. The calculated zeta potential and deposition rate for the films are also favorable. These AP plasma-polymerized thin films created from carvone show a reduction rate of more than 90% for Escherichia coli and Staphylococcus aureus bacteria. Our computational docking studies also reveal strong binding interactions between the original carvone monomer and both bacteria. The study suggests that these AP plasma-produced coatings have great potential as antibacterial coatings for biomedical devices. Full article

(This article belongs to the Special Issue Plasma Surface Modification for Bio-Applications)

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14 pages, 4382 KiB

Open AccessArticle

Mechanical Properties and Creep Behavior of Undoped and Mg-Doped GaN Thin Films Grown by Metal–Organic Chemical Vapor Deposition

by Ali Khalfallah and Zohra Benzarti

Coatings 2023, 13(6), 1111; https://doi.org/10.3390/coatings13061111 - 16 Jun 2023

Viewed by 1100

Abstract

This paper investigates the mechanical properties and creep behavior of undoped and Mg-doped GaN thin films grown on sapphire substrates using metal–organic chemical vapor deposition (MOCVD) with trimethylgallium (TMG) and bis(cyclopentadienyl)magnesium (Cp2Mg) as the precursors for Ga and Mg, respectively. The Mg-doped GaN [...] Read more.

This paper investigates the mechanical properties and creep behavior of undoped and Mg-doped GaN thin films grown on sapphire substrates using metal–organic chemical vapor deposition (MOCVD) with trimethylgallium (TMG) and bis(cyclopentadienyl)magnesium (Cp2Mg) as the precursors for Ga and Mg, respectively. The Mg-doped GaN layer, with a [Mg]/[TMG] ratio of 0.33, was systematically analyzed to compare its mechanical properties and creep behavior to those of the undoped GaN thin film, marking the first investigation into the creep behavior of both GaN and Mg-doped GaN thin films. The results show that the incorporated [Mg]/[TMG] ratio was sufficient for the transition from n-type to p-type conductivity with higher hole concentration around

4.6 \times 10^{17}

cm⁻³. Additionally, it was observed that Mg doping impacted the hardness and Young’s modulus, leading to an approximately 20% increase in these mechanical properties. The creep exponent is also affected due to the introduction of Mg atoms. This, in turn, contributes to an increase in pre-existing dislocation density from 2 × 10⁸ cm⁻² for undoped GaN to 5 × 10⁹ cm⁻² for the Mg-doped GaN layer. The assessment of the creep behavior of GaN and Mg-doped GaN thin films reveals an inherent creep mechanism governed by dislocation glides and climbs, highlighting the significance of Mg doping concentration in GaN thin films and its potential impact on various technological applications. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Thin Films)

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10 pages, 13583 KiB

Open AccessEditor’s ChoiceArticle

Seeking the Oxidation Mechanism of Debris in the Fretting Wear of Titanium Functionalized by Surface Laser Treatments

by María del Carmen Marco de Lucas, Franck Torrent, Gianni-Paolo Pillon, Pascal Berger and Luc Lavisse

Coatings 2023, 13(6), 1110; https://doi.org/10.3390/coatings13061110 - 16 Jun 2023

Viewed by 853

Abstract

Surface laser treatment (SLT) using nanosecond IR lasers has been shown to improve the tribological behaviour of titanium. Here, we studied the fretting wear of SLT-functionalized pure titanium in a mixture of reactive gases O

_{2}

(20 vol.%) + N

_{2}

(80 vol.%). [...] Read more.

Surface laser treatment (SLT) using nanosecond IR lasers has been shown to improve the tribological behaviour of titanium. Here, we studied the fretting wear of SLT-functionalized pure titanium in a mixture of reactive gases O

_{2}

(20 vol.%) + N

_{2}

(80 vol.%). The contact geometry was a ball on a plane and the ball was made of bearing steel. The very small amplitude of relative displacement between reciprocating parts in fretting wear makes the evacuation of wear particles difficult. Moreover, the oxidation mechanism of the debris depends on the accessibility of the surrounding atmosphere to the tribological contact. This work focused in the analysis of debris generation and oxidation mechanisms, and sought to differentiate the role of oxygen forming part of the ambient O

_{2}

+ N

_{2}

gas mixture from oxygen present in the surface layer of the SL-treated titanium. Before the fretting test, the surface of the commercially pure titanium plates was treated with a laser under a mixture of O

_{2}

+ N

_{2}

gases with oxygen enriched in the

^{18}

O isotope. Then, the fretting tests were performed in regular air containing natural oxygen. Micro-Raman spectroscopy and ion beam analysis (IBA) techniques were used to analyse the TiO

_{2}

surface layers and fretting scars. Iron oxide particles were identified by Raman spectroscopy and IBA as the third body in the tribological contact. The spatial distribution of

^{18}

O, Ti,

^{16}

O and Fe in the fretting scars was studied by IBA. The analysis showed that the areas containing high concentrations of Fe displayed also high concentrations of

^{16}

O, but smaller concentrations of

^{18}

O and Ti. Therefore, it was concluded that tribological contact allows the oxidation of iron debris by its reaction with ambient air. Full article

(This article belongs to the Section Laser Coatings)

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21 pages, 7134 KiB

Open AccessArticle

Theoretical and Experimental Studies of 1-Dodecyl-3-phenylquinoxalin-2(1H)-one as a Sustainable Corrosion Inhibitor for Carbon Steel in Acidic Electrolyte

by Fouad Benhiba, Mohcine Missioui, Selma Lamghafri, Rachid Hsissou, Abdelkbir Bellaouchou, Hassan Oudda, Abdellatif Lamhamdi, Ismail Warad, Youssef Ramli and Abdelkader Zarrouk

Coatings 2023, 13(6), 1109; https://doi.org/10.3390/coatings13061109 - 16 Jun 2023

Cited by 2 | Viewed by 1303

Abstract

The anti-corrosion features of 1-dodecyl-3-phenylquinoxalin-2(1H)-one (QO12) for carbon steel CS were evaluated in a 1 M HCl solution using potentiodynamic polarization (PDP), electrochemical impedance (EIS) and UV-visible spectroscopy, and scanning electron microscopy (SEM), as well as quantum-chemical methods. The inhibition performance achieves a [...] Read more.

The anti-corrosion features of 1-dodecyl-3-phenylquinoxalin-2(1H)-one (QO12) for carbon steel CS were evaluated in a 1 M HCl solution using potentiodynamic polarization (PDP), electrochemical impedance (EIS) and UV-visible spectroscopy, and scanning electron microscopy (SEM), as well as quantum-chemical methods. The inhibition performance achieves a maximum of 95.33% at 0.001 M. The PDP study revealed that QO12 acts with the character of a mixed-type inhibitor. The EISs mention that the process of corrosion for CS is essentially predominated by the transfer-of-charge mechanism. Moreover, quinoxalinone adsorption follows the Langmuir adsorption isotherm. SEM snapshots show no deterioration after the contribution of QO12 compared to the reference electrolyte. Theoretical calculations suggest that the envisaged inhibitor presents a perfect arrangement capacity through the structure of quinoxalinone. Full article

(This article belongs to the Special Issue Theoretical and Experimental Assessments of Corrosion Inhibitors)

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24 pages, 16561 KiB

Open AccessFeature PaperArticle

Preparation and Performance Characterization of an Active Luminous Coating for Asphalt Pavement Marking

by Kaifeng Wang, Ziyu Lu, Yingxue Zou, Yunsheng Zhu and Junhui Yu

Coatings 2023, 13(6), 1108; https://doi.org/10.3390/coatings13061108 - 16 Jun 2023

Viewed by 1435

Abstract

For improving the night recognition of road markings and enhancing the driving safety of asphalt pavements, single-factor optimization is used to investigate the effects of the component materials, including luminescent power, pigment, filler, and anti-sedimentation agent, on the luminous performance of a coating. [...] Read more.

For improving the night recognition of road markings and enhancing the driving safety of asphalt pavements, single-factor optimization is used to investigate the effects of the component materials, including luminescent power, pigment, filler, and anti-sedimentation agent, on the luminous performance of a coating. Additionally, their composition ratios are optimized using response surface methodology. A phosphorescent marking coating is prepared to investigate the micromorphology, excitation, and emission properties using scanning electron microscopy (SEM) and molecular fluorescence spectroscopy (MFS). The optimum thickness of the coating on an asphalt pavement is investigated, and the durability of the coating on asphalt pavement using a wheel rutting test is evaluated. The results show that the 300 mesh yellow-green luminous powder has the optimal overall performance, with an initial luminescence that exceeds that of orange and sky blue by three times. Initial brightness is mainly influenced by aluminate luminescent powder (ALP), which increases with the dosage. ALP and fumed silica powder (FSP) have a positive effect on brightness after centrifugation, and the effect of FSP dosage is more significant. ALP, rutile titanium dioxide powder (RTDP), and FSP influence the wear value of the coating, and the magnitude of the effect is RTDP > FSP > ALP. The optimal dosages of the main component are 27% ALP, 5% RTDP, and 0.8% FSP. The results of SEM show that the components in the coating are evenly dispersed, and the surface of the coating is rough. The peak excitation wavelength of 420 nm means that the coating has the best excitation effect in UV light, and its emission spectrum in the 440–760 nm wavelength range is well within the sensitive recognition zone of the human eye. The initial brightness gradually reached 4.38 cd/m² when the coating thickness was increased from 482 μm to 546 μm, and the optimal application thickness of the luminous coating was determined to be 500 μm. At high and normal temperatures, the rutting stripping rates of the luminous marking coating are 16.8% and 8.2%, indicating its satisfactory durability. This study provides an experimental basis for the ratio optimization design of a luminous coating for asphalt pavements. Full article

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

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15 pages, 6164 KiB

Open AccessArticle

Cell Response on Laser-Patterned Ti/Zr/Ti and Ti/Cu/Ti Multilayer Systems

by Suzana Petrović, Nevena Božinović, Vladimir Rajić, Danijela Stanisavljević Ninković, Danilo Kisić, Milena J. Stevanović and Emmanuel Stratakis

Coatings 2023, 13(6), 1107; https://doi.org/10.3390/coatings13061107 - 16 Jun 2023

Viewed by 1674

Abstract

Arranged patterns obtained via ultrafast laser processing on the surface of Ti/Cu/Ti/Si and Ti/Zr/Ti/Si thin-film systems are reported. Two differently designed multilayer thin films Ti/Cu/Ti/Si and Ti/Zr/Ti/Si were deposited on silicon using the ion sputtering method. The bioactive surfaces of these systems involve [...] Read more.

Arranged patterns obtained via ultrafast laser processing on the surface of Ti/Cu/Ti/Si and Ti/Zr/Ti/Si thin-film systems are reported. Two differently designed multilayer thin films Ti/Cu/Ti/Si and Ti/Zr/Ti/Si were deposited on silicon using the ion sputtering method. The bioactive surfaces of these systems involve the formation of laser-induced periodic surface structures (LIPSS) in each of the laser-written lines of mesh patterns on 5 × 5 mm areas. The formation of nano- and micro-patterns with an ultra-thin oxide film on the surfaces was used to observe the effects of morphology and proliferation of the MRC-5 cell culture line. To determine whether Ti-based thin films have a toxic effect on living cells, an MTT assay was performed. The relative cytotoxic effect, as a percentage of surviving cells, showed that there was no difference in cell number between the Ti-based thin films and the control cells. There was also no difference in the viability of the MRC-5 cells, except for the Ti/Cu/Ti/Si system, where there was a slight 10% decrease in cell viability. Full article

(This article belongs to the Special Issue Surface Modification of Biomaterials and Biomedical Devices)

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11 pages, 2583 KiB

Open AccessArticle

Flexural Strength and Vickers Microhardness of Graphene-Doped SnO₂ Thin-Film-Coated Polymethylmethacrylate after Thermocycling

by Canan Akay, Gülce Çakmak, Mustafa Borga Donmez, Samir Abou-Ayash, Emre Mumcu, Suat Pat and Burak Yilmaz

Coatings 2023, 13(6), 1106; https://doi.org/10.3390/coatings13061106 - 16 Jun 2023

Viewed by 1205

Abstract

Removable dental prostheses are commonly fabricated using polymethylmethacrylate, a material that does not have favorable mechanical properties and needs reinforcement with particles such as graphene. The aim of this study was to evaluate the flexural strength (FS) and Vickers microhardness of a heat-polymerized [...] Read more.

Removable dental prostheses are commonly fabricated using polymethylmethacrylate, a material that does not have favorable mechanical properties and needs reinforcement with particles such as graphene. The aim of this study was to evaluate the flexural strength (FS) and Vickers microhardness of a heat-polymerized polymethylmethacrylate coated with graphene-doped stannic oxide (SnO₂) thin films using a thermionic vacuum arc method after thermocycling. Forty bar-shaped specimens (65 × 10 × 3 mm) were fabricated using a heat-polymerized denture base resin and divided into four groups according to the graphene-doped SnO₂ thin film surface coating performed: No-coat (uncoated), Coat-15 s (coating duration of 15 s), Coat-20 s (coating duration of 20 s), and Coat-30 s (coating duration of 30 s) (n = 10). The thermionic vacuum arc method was used to coat both surfaces of the specimens of each test group with varying durations, and surface coating was verified using Fourier Transform Infrared Spectroscopy. Specimens were subjected to 10,000 cycles of thermocycling. Atomic force microscopy was used to evaluate the surfaces of all specimens before and after thermocycling. Microhardness values were measured five times and averaged. Then, each specimen was subjected to a three-point bending test, and FS values were calculated. Data were analyzed using one-way analysis of variance and Bonferroni tests (α = 0.05). Differences among test groups were nonsignificant when FS data were considered (p = 0.605). However, significant differences were observed among test groups when Vickers microhardness data were considered (p < 0.001). Coat-30 s had the highest hardness (p ≤ 0.003), while the difference among remaining groups were nonsignificant (p ≥ 0.166). Graphene-doped SnO₂ thin film surface coatings did not significantly affect the FS of tested heat-polymerized denture base resin but increased the Vickers microhardness when the coating duration was 30 s. Full article

(This article belongs to the Special Issue Recent Advances in Thin Films Deposited by Vacuum Methods)

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14 pages, 4667 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Two Types of Polylactic Acid Coating Loaded with Gentamicin Sulphate Deposed on AZ31 Alloy

by Manuela Elena Voicu, Daniela Ionita, George-Octavian Buica, Doina Draganescu, Valentina Anuta, Florentina Monica Raduly and Ioana Demetrescu

Coatings 2023, 13(6), 1105; https://doi.org/10.3390/coatings13061105 - 15 Jun 2023

Cited by 1 | Viewed by 989

Abstract

This paper compares two types of polylactic acid (PLA) coating on AZ31 alloy obtained by dip coating and electrospinning. Both types of coating were loaded with gentamicin sulphate (GS) and the drug-loading efficiency and release were assessed. A higher encapsulation and release efficiency [...] Read more.

This paper compares two types of polylactic acid (PLA) coating on AZ31 alloy obtained by dip coating and electrospinning. Both types of coating were loaded with gentamicin sulphate (GS) and the drug-loading efficiency and release were assessed. A higher encapsulation and release efficiency of GS was seen for dip coating (73% and 49.53%, respectively) compared to nanofiber coating (65% and 12.37%, respectively). Furthermore, the antibacterial effect of the samples with and without GS was assessed using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria, showing that the samples with the drug encapsulated are more resistant to bacteria than the other samples. The electrochemical data reveal a higher stability in the SBF of the surface obtained by dipping than that obtained by electrospinning. The PLA coating shows a porosity of 46% for the sample obtained through dip coating and 32% for nanofibers, which is in accordance with the BET analysis results. Moreover, a higher adhesion strength was obtained for AZ31-PLA-dip (4.99 MPa) than for the AZ31-PLA-nanofibers (1.66 MPa). All samples were structurally, morphologically, and topographically characterized. Full article

(This article belongs to the Special Issue New Strategies and Recent Advances in Investigations of Micro- and Nano-Coatings for Technological and Biomedical Applications)

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13 pages, 21415 KiB

Open AccessArticle

Owens–Wendt Characterization of Femtosecond-Laser-Textured Hydrophobic Aluminum Surfaces

by Oleksiy Myronyuk, Denys Baklan, Aleksej M. Rodin, Egidijus Vanagas and Zuo Yong

Coatings 2023, 13(6), 1104; https://doi.org/10.3390/coatings13061104 - 15 Jun 2023

Cited by 2 | Viewed by 1120

Abstract

The eligibility of applying the Owens–Wendt approach to determining the free surface energy of liquid-repellent aluminum surfaces, with micro- and nanotextures formed by a femtosecond laser, was considered. This approach has been shown to be applicable using two essential parameters that can be [...] Read more.

The eligibility of applying the Owens–Wendt approach to determining the free surface energy of liquid-repellent aluminum surfaces, with micro- and nanotextures formed by a femtosecond laser, was considered. This approach has been shown to be applicable using two essential parameters that can be derived from the graphs. The first is related to the fraction of the contact area between the liquid and the solid surface in the Cassie state. The second is related to the degree of intrinsic polarity of the surface material or the applied organic modifier. The presented interpretation was used to compare the liquid repellency of the obtained textures. A microtexture with a period of 60 μm and a groove width of 45 μm has been shown to be the most liquid repellent. Among the modifiers, 1H,1H,2H,2H-perfluoroctyltriethoxysilane was the most effective, and stearic acid was only slightly inferior, but promising in terms of cost and environmental friendliness. It was shown that spontaneous hydrophobization provided a contact angle with water up to 159°, but the stability of such textures was inferior to the considered modifiers. Full article

(This article belongs to the Special Issue Laser Surface Engineering)

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14 pages, 3548 KiB

Open AccessArticle

The Interplay Effects between Feed-Gas Composition and Bias Plasma Condition during Active-Screen Plasma Nitrocarburizing with a Solid Carbon Source

by Saeed M. Jafarpour, Andrei V. Pipa, Alexander Puth, Anke Dalke, Jürgen Röpcke, Jean-Pierre H. van Helden and Horst Biermann

Coatings 2023, 13(6), 1103; https://doi.org/10.3390/coatings13061103 - 15 Jun 2023

Cited by 2 | Viewed by 879

Abstract

Recent technological development of utilizing an active screen made of solid carbon for plasma-assisted thermochemical diffusion treatments opens up new possibilities for control over the in situ generated treatment environment to guarantee reproducible treatment conditions and material responses. Until now, the investigations of [...] Read more.

Recent technological development of utilizing an active screen made of solid carbon for plasma-assisted thermochemical diffusion treatments opens up new possibilities for control over the in situ generated treatment environment to guarantee reproducible treatment conditions and material responses. Until now, the investigations of active-screen plasma nitrocarburizing (ASPNC) using an active screen manufactured from solid carbon focused on the influence of a single treatment parameter variation on the material response. In this systematic study, experiments were conducted to vary the H₂-N₂ feed-gas composition while varying the bias plasma power. The experiments served to better understand a simultaneous variation in the mentioned parameters on the resulting treatment environment and material response during ASPNC of AISI 316L austenitic stainless steel. Therefore, nitriding and carburizing effects in the expanded austenite layer can be obtained. It is shown that an increased nitriding effect, i.e., nitrogen diffusion depth and content, was achieved in case of biased conditions and for H₂-N₂ feed-gas compositions with higher N₂ amounts. On the contrary, an increased carburizing effect, i.e., carbon diffusion depth and content, was achieved in nonbiased conditions, independent from the H₂-N₂ feed-gas composition. Full article

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

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