Research

12 pages, 6512 KiB

Open AccessArticle

Biodegradable Conductive Layers Based on a Biopolymer Polyhydroxybutyrate/Polyhydroxyvalerate and Graphene Nanoplatelets Deposited by Spray-Coating Technique

by Sandra Lepak-Kuc, Katarzyna Wójkowska, Dorota Biernacka, Aleksandra Kądziela, Tomasz Tadeusz Murawski, Daniel Janczak and Małgorzata Jakubowska

Coatings 2023, 13(10), 1791; https://doi.org/10.3390/coatings13101791 - 19 Oct 2023

Viewed by 1001

Abstract

In light of the growing concern for environmental protection and the alarming amount of waste produced due to hygiene regulations, this study suggests a biodegradable and eco-friendly solution that could make a significant contribution to the preservation of our planet. The developed solution [...] Read more.

In light of the growing concern for environmental protection and the alarming amount of waste produced due to hygiene regulations, this study suggests a biodegradable and eco-friendly solution that could make a significant contribution to the preservation of our planet. The developed solution was based on a polyhydroxybutyrate/polyhydroxyvalerate biopolymer, which has been tested regarding its physicochemical parameters and possible use in printed electrically conductive structures. Graphene nanoplatelets have been used as the conductive functional phase, due to literature reports of their potential use in biomedical applications and due to the potential of providing cytocompatibility in electrical structures by carbon nanomaterials. Prepared composites have been spray-coated onto PET film and paper substrates and then subjected to electrical, adhesion and optical measurements. In order to establish the conductivity of the developed composite, its resistance, layer thickness and surface topography were measured. Optical parameters have been specified using scanning electron microscopy (SEM) imaging and spectrophotometry. The conducted research opens a wide path for the use of the polyhydroxybutyrate/polyhydroxyvalerate biopolymer with graphene nanoplatelets in biomedical applications, ensuring good conductivity, biocompatibility and stability. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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13 pages, 4933 KiB

Open AccessArticle

Tribological and Grinding Properties of Spherical Diamond Grown on a Rough Discontinuous Surface

by Xiangyong Zeng, Shaoxin Meng, Jianben Liu and Naichao Chen

Coatings 2023, 13(10), 1735; https://doi.org/10.3390/coatings13101735 - 05 Oct 2023

Viewed by 876

Abstract

Spherical diamond particles have great potential as additive materials for improving lubricity of lubricants, and yet the complicated preparation process is difficult to meet the current industrial demand. Therefore, a novel method was proposed to deposit mass spherical diamond on the discontinuous silicon [...] Read more.

Spherical diamond particles have great potential as additive materials for improving lubricity of lubricants, and yet the complicated preparation process is difficult to meet the current industrial demand. Therefore, a novel method was proposed to deposit mass spherical diamond on the discontinuous silicon nitride (Si₃N₄) powder substrate by the hot filament chemical vapor deposition method. The results revealed that the substrate was covered by the spherical diamond grains with a diameter of about 20 μm. Thereafter, they were used as lubricant additives to examine the tribological and grinding properties. Therein, the Si₃N₄ surface had a remarkable reduction in surface roughness by a factor of 124.62% as compared to that without spherical diamond powder, while GCr15 alloy had a 31.17% increase under the same condition. Hence, our method provides a promising way to deposit the mass spherical diamond powder that might become a great abrasive material for machining the ceramic. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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12 pages, 3760 KiB

Open AccessArticle

Washing and Abrasion Resistance of Textile Electrodes for ECG Measurements

by Dajana Doci, Melisa Ademi, Khorolsuren Tuvshinbayar, Niclas Richter, Guido Ehrmann, Tatjana Spahiu and Andrea Ehrmann

Coatings 2023, 13(9), 1624; https://doi.org/10.3390/coatings13091624 - 16 Sep 2023

Viewed by 837

Abstract

Electrocardiogram (ECG) signals are often measured for medical purposes and in sports. While common Ag/AgCl glued gel electrodes enable good electrode skin contact, even during movements, they are not comfortable and can irritate the skin during long-term measurements. A possible alternative is textile [...] Read more.

Electrocardiogram (ECG) signals are often measured for medical purposes and in sports. While common Ag/AgCl glued gel electrodes enable good electrode skin contact, even during movements, they are not comfortable and can irritate the skin during long-term measurements. A possible alternative is textile electrodes, which have been investigated extensively during the last years. These electrodes, however, are usually not able to provide reliable, constant skin contact, resulting in reduced signal quality. Another important problem is the modification of the electrode surface due to washing or abrasion, which may impede the long-term use of such textile electrodes. Here, we report a study of washing and abrasion resistance of different ECG electrodes based on an isolating woven fabric with conductive embroidery and two conductive coatings, showing unexpectedly high abrasion resistance of the silver-coated yarn and optimum ECG signal quality for an additional coating with a conductive silicone rubber. Sheet resistances of the as-prepared electrodes were in the range of 20–30 Ω, which was increased to the range of 25–40 Ω after five washing cycles and up to approximately 50 Ω after Martindale abrasion tests. ECG measurements during different movements revealed reduced motion artifacts for the electrodes with conductive silicone rubber as compared to glued electrodes, suggesting that electronic filtering of such noise may even be easier for textile electrodes than for commercial electrodes. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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18 pages, 8186 KiB

Open AccessArticle

Effect of Interface Curvature on Local Growth Behavior and Stress of Thermal Barrier Coatings

by Lulu Wang, Jun Yu, Tao Zhang, Zhe Wang and Kunying Ding

Coatings 2023, 13(9), 1618; https://doi.org/10.3390/coatings13091618 - 15 Sep 2023

Viewed by 685

Abstract

It is well known that coating spalling often occurs between the top ceramic coating (TC) and the metal bonding coating (BC) during the working process where the thermal mismatch stress between the layers plays a key role. Dynamic changes in the thermally grown [...] Read more.

It is well known that coating spalling often occurs between the top ceramic coating (TC) and the metal bonding coating (BC) during the working process where the thermal mismatch stress between the layers plays a key role. Dynamic changes in the thermally grown oxide (TGO) between the facing and bonding layers during thermal cycling increase the thermal mismatch at the interface. The effect of oxide thickening on localized mismatch stresses under thermal cycling with different interfacial curvatures is quantitatively investigated using numerical methods in this paper. A dynamic growth model of the oxide was developed based on the consideration of the composition and morphology of the thermally grown oxide. The results show that TGO growth behavior, local stress evolution, crack initiation location, and crack propagation length are influenced by the interface curvature at the same aspect ratio. The interface between the oxide layer and the bonding layer gradually developed significant tensile to dangerous stresses during thermal cycling. These tensile stresses are predominantly distributed at the crest during the early stages of thermal exposure and gradually transferred to the near-peak (the region near the peak) and ramp regions (the region in between the peak and the valley) as the oxidation process progressed. The crack initiation and propagation phenomenon can be observed at various regions during thermal exposure. Increasing interface curvature leads to an earlier dangerous stress moment in the ramp area due to higher maximum tensile stress. Therefore, the small changes in the interface curvature severely affected the location and time of crack initiation and the crack length. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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15 pages, 10513 KiB

Open AccessArticle

Characterization and Electrochemical Investigation of Heterogeneous Sb-Cu Coatings

by Vasil Kostov and Boriana Tzaneva

Coatings 2023, 13(9), 1540; https://doi.org/10.3390/coatings13091540 - 02 Sep 2023

Viewed by 806

Abstract

In recent years, Cu-Sb-based alloys have been considered promising materials for various green applications; for instance, they can serve as catalysts for CO₂ reduction, anodic material for metal-ion batteries, and a light-absorbing layer in solar cell. Our research is focused on the [...] Read more.

In recent years, Cu-Sb-based alloys have been considered promising materials for various green applications; for instance, they can serve as catalysts for CO₂ reduction, anodic material for metal-ion batteries, and a light-absorbing layer in solar cell. Our research is focused on the electrodeposition of antimony-copper alloy layers with copper content between 18–30 wt.%. The layers were observed by scanning, atomic force and transmission electron spectroscopies. Their phase structure, roughness, and hardness were also determined. The electrochemical properties were investigated by using electrochemical impedance spectroscopy and potentiodynamic polarization tests in 0.5 M sulfuric acid. Decreasing the copper content leads to an increase in chemical and morphological heterogeneity and an increase in the roughness from 1.74 to 2.94 μm due to the separation of antimony crystal clusters protruding above the surface but does not significantly affect the hardness and electrochemical behavior of the layers. Copper is recorded only in the form of the Cu₂Sb phase. The corrosion current density and potentials of the layers are close to those of pure antimony (about 20 µA cm⁻² and about −30 mV vs. Ag/AgCl). The highly porous structure obtained after anodic polarization seems suitable for catalytic purposes. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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15 pages, 55990 KiB

Open AccessArticle

Microstructure and Wear Resistance of High-Chromium Cast Iron with Multicomponent Carbide Coating via Laser Cladding

by Chao Chen, Junfa Wang, Yiyuan Ge, Minghui Zhuang and Zheng Ma

Coatings 2023, 13(8), 1474; https://doi.org/10.3390/coatings13081474 - 21 Aug 2023

Cited by 3 | Viewed by 936

Abstract

High-chromium cast iron (HCCI) coatings with multicomponent carbides were prepared on low-alloy steel substrates using a laser cladding technique in this work. The microstructure and wear resistance of the coatings were characterized via optical microscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, [...] Read more.

High-chromium cast iron (HCCI) coatings with multicomponent carbides were prepared on low-alloy steel substrates using a laser cladding technique in this work. The microstructure and wear resistance of the coatings were characterized via optical microscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction and block-on-ring wear testing. Multicomponent carbides (Ti, Nb, Mo, W, V)C with an FCC structure and multicomponent compounds (Nb, Mo, W, V) (B,C) with an FCC structure were found in the microstructures of coatings after multielement doping. In addition, (Cr, Mo, W, V)₂₃C₆ compounds could be obtained by heat treatment. These multicomponent compounds were beneficial for obtaining coatings with an excellent hardness (60 HRC) and high wear resistance. This multielement doping method provides an effective modified method for preparing high-wear-resistance laser cladding coatings. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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13 pages, 5404 KiB

Open AccessArticle

Determining the Annealing Temperature Dependency of Wetting and Mechanical Features on Fe₃Si Films

by Nattakorn Borwornpornmetee, Chawapon Achirawongwat, Thawichai Traiprom, Bunpot Saekow, Supanit Porntheeraphat, Boonchoat Paosawatyanyong, Tsuyoshi Yoshitake and Nathaporn Promros

Coatings 2023, 13(8), 1328; https://doi.org/10.3390/coatings13081328 - 28 Jul 2023

Viewed by 761

Abstract

The impact of thermal annealing under temperature alteration on the wetting and mechanical attributes of Fe₃Si films built through facing target sputtering (FTS) is an essential topic for study in order to identify their characteristics under varying temperatures. Consequently, we introduced [...] Read more.

The impact of thermal annealing under temperature alteration on the wetting and mechanical attributes of Fe₃Si films built through facing target sputtering (FTS) is an essential topic for study in order to identify their characteristics under varying temperatures. Consequently, we introduced a thermal annealing process in a vacuum for two hours under varying temperatures of 300, 600, and 900 °C to our Fe₃Si films created via FTS. The primary purpose of this current research is to examine the effect of the thermal annealing technique under temperature alteration on the wetting and mechanical traits of Fe₃Si films. In this research, Fe₃Si films were built onto the Si wafer by FTS and divided for use in thermal annealing under temperature alteration. The structural, morphological, wetting, and mechanical traits of the Fe₃Si films under thermal annealing are provided in the present work. Based on our information, this work represents an original study on the change in wetting and mechanical traits of Fe₃Si films through thermal annealing under temperature alteration. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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15 pages, 11924 KiB

Open AccessArticle

Effect of Substrate Bias Voltage on Microstructure and Mechanical Properties of Cr-Nb-Ti-Zr-N-O Ceramic Thin Films Produced by Reactive Sputtering

by Sayed Alireza Ataie, S. Mahmoudi Qashqay, Mohammad Reza Zamani-Meymian and Fabio Ferreira

Coatings 2023, 13(7), 1141; https://doi.org/10.3390/coatings13071141 - 24 Jun 2023

Cited by 1 | Viewed by 1223

Abstract

Hard coatings are applied in various applications to protect substrates from wear and corrosion. In the present study, multi-element ceramic films are deposited by reactive sputtering. The level of substrate bias voltage (−50, −125 and −200 V) is changed to investigate the structural [...] Read more.

Hard coatings are applied in various applications to protect substrates from wear and corrosion. In the present study, multi-element ceramic films are deposited by reactive sputtering. The level of substrate bias voltage (−50, −125 and −200 V) is changed to investigate the structural and mechanical properties of Cr-Nb-Ti-Zr-N thin films. Chemical analysis (using EDS, XRD and Raman spectroscopy) reveals that these thin films (with a high amount of oxygen) are composed of a nanocomposite phase structure (amorphous and nano-crystalline phases). CrO₂ and Nb_xN crystalline phases exist in an amorphous matrix in the coatings. By increasing the substrate voltage (from −50 to −200 V), the nitrogen content (from 30 to 40 at. %) increases, and Cr_xN crystalline phases are generated in S125 and S200. Morphological, topological and image analysis (employing FESEM and AFM) data show that the intermediate level of substrate bias voltage (sample S125) can produce a uniform surface with minimum defect density (15%). In addition, S125 has the minimum level of roughness (16.6 nm), skewness (0.2) and kurtosis (2.8). Therefore, the hardness, toughness and wear resistance (extracted from indentation and scratch tests) of this sample is maximum (H is 24.5 GPa and H/E is 0.107), while sample S50 shows complete fracture and delamination. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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16 pages, 7740 KiB

Open AccessArticle

Tribological Behavior of Doped DLC Coatings in the Presence of Ionic Liquid Additive under Different Lubrication Regimes

by Mohammadamin Sadeghi, Takeru Omiya, Filipe Fernandes, Luís Vilhena, Amilcar Ramalho and Fábio Ferreira

Coatings 2023, 13(5), 891; https://doi.org/10.3390/coatings13050891 - 09 May 2023

Cited by 5 | Viewed by 1707

Abstract

Diamond-like carbon (DLC) coatings are widely used in industries that require high durability and wear resistance, and low friction. The unique characteristics of DLC coatings allow for the possibility of creating adsorption sites for lubricant additives through the doping process. In this study, [...] Read more.

Diamond-like carbon (DLC) coatings are widely used in industries that require high durability and wear resistance, and low friction. The unique characteristics of DLC coatings allow for the possibility of creating adsorption sites for lubricant additives through the doping process. In this study, the combined use of europium-doped diamond-like carbon (Eu-DLC), gadolinium-doped diamond-like carbon (Gd-DLC), and pure DLC coatings and an ionic liquid (IL) additive, namely, trihexyltetradecylphosphonium bis (2-ethylhexyl) phosphate [

P_{66614}

] [DEHP], with a 1 wt.% concentration in polyalphaolefin (PAO) 8 as a base lubricant was investigated. Higher hardness, higher thin-film adhesion, a higher ratio of hardness to elastic modulus, and a higher plastic deformation resistance factor were achieved with the Gd-DLC coating. The CoF of the Gd-DLC coating paired with the IL was superior compared to the other pairs in all lubrication regimes, and the pure DLC coating had a better performance than the Eu-DLC coating. The wear could not be quantified due to the low wear on the surface of the DLC coatings. The friction reduction demonstrates that tribological systems combining Gd-DLC thin films with an IL can be a potential candidate for future research and development efforts to reduce friction and increase the efficiency of moving parts in internal combustion engines, for instance. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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19 pages, 12167 KiB

Open AccessArticle

Numerical and Experimental Investigation Gas-Particle Two Phase Flow in Cold Spraying Nanostructured HA/Ti Composite Particle

by Xiao Chen, Zhijun Xi, Hao Liu, Xixi Duan, Qinqin Gao and Chengdi Li

Coatings 2023, 13(5), 818; https://doi.org/10.3390/coatings13050818 - 23 Apr 2023

Viewed by 835

Abstract

HA composite coatings added reinforcement phases could improve the mechanical properties and bonding strength of the coatings. Cold spraying is a feasible surface technology for preparing HA composite coatings. In order to investigate the influence of cold spraying parameters on the deposition behavior [...] Read more.

HA composite coatings added reinforcement phases could improve the mechanical properties and bonding strength of the coatings. Cold spraying is a feasible surface technology for preparing HA composite coatings. In order to investigate the influence of cold spraying parameters on the deposition behavior of a single HA/Ti composite particle, numerical and experimental investigation of gas-particle two-phase flow in cold spraying nanostructured HA/Ti composite particle were investigated in this study. The results show that the influence of different temperatures and pressures on static pressure was not significant. The effects of gas pressure on the static temperature were tiny under the same inlet temperature and different pressure conditions; however, the static temperature in the entire spray gun cavity increased as the inlet temperature increased under the same pressure and different inlet temperature conditions. There is little effect of gas pressure on the axial velocity of gas flow in the spray gun cavity; however, the axial velocity of gas flow increased with the increase in gas temperature. Meanwhile, the axial velocity of gas flow gradually increases throughout the spraying process. At a gas temperature of 573 K and 973 K, the maximum axial velocities of a gas flow at gas pressure of 2.2 MPa were 778 m/s and 942 m/s, respectively. There is little effect of gas pressure on the axial velocity of HA/30 wt.% Ti particles under the same gas temperature. The axial velocity of HA/30 wt.% Ti particles increased with the increase in gas temperature under the same gas pressure condition. The axial velocity of composite particles decreased with the increase in the particle size under the same gas pressure and gas temperature. At a gas temperature of 573 K and 973 K, the minimum axial velocity of HA/30 wt.% Ti particles with a particle size of 30 μm at a gas pressure of 2.2 MPa was 435 m/s and 467 m/s, respectively. A certain deformation of splats occurred after impacting the substrate, and the splats adhered to the surface of the Ti6Al4Vsubstrate, clearly presenting a flat shape with a central hump surrounded by a ringy band. At a gas temperature of 973 K, particles generated more severe deformation with more cracks and ejecta phenomenon. The splats attached to the substrate were increased as the gas temperature increased. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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9 pages, 3262 KiB

Open AccessArticle

Preparation of Nanochitin Films with Oligochitin Graft Chains

by Kazuya Yamamoto, Yu Obama and Jun-ichi Kadokawa

Coatings 2023, 13(1), 47; https://doi.org/10.3390/coatings13010047 - 27 Dec 2022

Viewed by 1754

Abstract

Even nowadays, chitin is mostly unutilized as a biomass resource, although it is abundantly present in nature. To develop an efficient method to use chitin as the component in new functional bio-based materials, in this study, we investigated the preparation of a flexible [...] Read more.

Even nowadays, chitin is mostly unutilized as a biomass resource, although it is abundantly present in nature. To develop an efficient method to use chitin as the component in new functional bio-based materials, in this study, we investigated the preparation of a flexible nanochitin (chitin nanofiber, ChNF) film with oligochitin dihexanoate graft chains. The parent ChNF film was prepared by regeneration of a chitin ion gel with an ionic liquid, 1-allyl-3-methylimidazolium bromide (AMIMBr), using methanol and subsequent filtration. However, the obtained film showed a quite brittle nature, probably because of the high crystallinity of the chitin chains. To reduce the crystallinity, oligochitin dihexanoate, which was provided by partial depolymerization of the parent chitin dihexanoate under acidic conditions, was modified on the partially deacetylated ChNF film by reductive amination. The introduction of the oligochitin dihexanoate graft chains was supported by ¹H NMR and IR measurements. The powder X-ray diffraction (XRD) profile of a film, which was obtained from an aqueous acetic acid suspension of the grafted product, indicated a reduction in chitin crystallinity, which contributes to the disappearance of nanofiber morphology and enhancement of flexibility. The removal of hexanoyl groups from the film was performed by treatment with aqueous NaOH. The IR and XRD measurements of the obtained film suggested the compete dehexanoylation and the reformation of the chitin crystalline structure, respectively. This study provides a method to fabricate new bio-based graft and soft materials entirely comprising chitin moieties. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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15 pages, 6521 KiB

Open AccessArticle

Tailoring the Structural, Optical and Electrical Properties of Zinc Oxide Nanostructures by Zirconium Doping

by Asad ur Rehman Khan, Muhammad Ramzan, Muhammad Imran, Muhammad Zubair, Sana Shahab, Sara J. Ahmed, Fábio Ferreira and Muhammad Faisal Iqbal

Coatings 2023, 13(1), 34; https://doi.org/10.3390/coatings13010034 - 25 Dec 2022

Cited by 3 | Viewed by 1820

Abstract

Owing to its low resistivity, high transmittance, and tunable optical band gap, ZnO is of great interest for optoelectronic applications. Herein, the sol–gel technique was used to synthesize un-doped and zirconium-doped zinc oxide (ZZO) nanostructures with different concentrations of Zirconium (Zr). X-ray diffraction [...] Read more.

Owing to its low resistivity, high transmittance, and tunable optical band gap, ZnO is of great interest for optoelectronic applications. Herein, the sol–gel technique was used to synthesize un-doped and zirconium-doped zinc oxide (ZZO) nanostructures with different concentrations of Zirconium (Zr). X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, and photoluminescence (PL) measurements were used to investigate the influence of Zr doping on the structural, optical, and electrical properties of developed nanostructures. XRD and SEM confirmed the increase in crystallite size with increasing concentrations of Zr. Raman analysis indicated the presence of oxygen vacancies in synthesized nanostructures. UV-Vis spectroscopy illustrated the blue shift of band gap and red shift of the absorption edge for ZZO nanostructures with increasing concentrations of Zr. For the measurement of electrical properties, the spin-coating technique was used to deposit un-doped and Zr-doped ZnO layers of ~165 nm thickness. The four-probe-point (4PP) method illustrated that the doping of Zr caused a reduction in electrical resistance. Hall Effect measurements showed a high value, 3.78 × 10²⁰ cm⁻³, of the carrier concentration and a low value, 10.2 cm²/Vs, of the carrier mobility for the Zr-doped layer. The high optical transmittance of ~80%, wide band gap of 3.51 eV, low electrical resistivity of 1.35 × 10⁻³ Ω·cm, and maximum carrier concentration of 3.78 × 10²⁰ cm⁻³ make ZZO nanostructures one of the most promising candidates for the application of transparent conductive oxide (TCO) in optoelectronic devices. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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13 pages, 4082 KiB

Open AccessArticle

Enhanced Pickering Emulsion Stabilization of Cellulose Nanocrystals and Application for Reinforced and Hydrophobic Coatings

by Fan Zhang, Haoran Tao, Yilin Li, Yanbing Wang, Yingying Zhou, Qunna Xu and Jianzhong Ma

Coatings 2022, 12(10), 1594; https://doi.org/10.3390/coatings12101594 - 20 Oct 2022

Cited by 2 | Viewed by 1537

Abstract

For oil-in-water (O/W) Pickering emulsions, a new polymer stabilizer of butyl acrylate (BA) grafted cellulose nanocrystals (BA-g-CNC_S) has been developed. By adjusting the BA concentration, the hydrophilic and hydrophobic surfaces of BA-g-CNCs could be systematically modified based [...] Read more.

For oil-in-water (O/W) Pickering emulsions, a new polymer stabilizer of butyl acrylate (BA) grafted cellulose nanocrystals (BA-g-CNC_S) has been developed. By adjusting the BA concentration, the hydrophilic and hydrophobic surfaces of BA-g-CNCs could be systematically modified based on the controllable interface activity. Specifically, the emulsification stability of the as-prepared stabilizer was examined as a function of BA content, BA-g-CNC_S usage, and oil type. The results showed that the Pickering emulsion stabilized by BA-g-CNC_S had a 98% volume fraction of emulsion with long-term stability. Importantly, BA-g-CNC_S could be a promising choice for polymer stabilizers and could generate high internal phase Pickering emulsions without cross-linking when combined with 13% BA and 1.75% BA-g-CNC_S. Furthermore, it was established that BA-g-CNCs possessed self-emulsifying quality, worked as hydrophobic coatings, and improved the mechanical properties. This was of fundamental interest to polymer stabilizer and functional coatings, allowing for promising applications in coating fields such as fabrics, leather, paper, controlled encapsulation, and the release of actives in material science. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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13 pages, 5161 KiB

Open AccessArticle

Numerical Study on the Regression Method to Eliminate the Influence of Surface Morphology on Indentation Hardness of Thin Films

by Xiaozhen Li, Weixu Zhang, Dingjun Li, Jianpu Zhang and Bin Long

Coatings 2022, 12(10), 1447; https://doi.org/10.3390/coatings12101447 - 30 Sep 2022

Cited by 2 | Viewed by 1105

Abstract

The surface morphology of specimens significantly affects the measurement accuracy of indentation hardness. Surface undulation leads to dispersion in measured hardness and makes it very difficult to obtain an accurate hardness. In the past, mechanical polishing and increasing the indentation depth were widely [...] Read more.

The surface morphology of specimens significantly affects the measurement accuracy of indentation hardness. Surface undulation leads to dispersion in measured hardness and makes it very difficult to obtain an accurate hardness. In the past, mechanical polishing and increasing the indentation depth were widely performed to decrease the influence of surface morphology. However, both methods have limitations for the hardness measurement of small-scale structures such as thin films or coatings. Thus, obtaining an accurate hardness measurement from one or two simple indentation tests is of great application value. In this study, we introduced a new regression method to eliminate the influence of surface undulation on hardness measurements. We simulated the indentation tests of thin films with undulating surfaces by finite element simulation and then analyzed the regularity of the measured hardness. The numerical simulations validated that the regression method can effectively eliminate the influence of surface undulation and obtain the accurate hardness of materials. This method breaks through the limitations of conventional methods, simplifies the testing workload, and improves measurement accuracy. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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11 pages, 2102 KiB

Open AccessArticle

Physical Vapor Deposition Technology in Personal Protective Equipment Production: Improved Antibacterial and Hydrophobic Character of Textiles

by José Antunes, Karim Matos, Isabel Carvalho, Sandra Carvalho, Fábio Ferreira and Sandra M. A. Cruz

Coatings 2022, 12(10), 1399; https://doi.org/10.3390/coatings12101399 - 25 Sep 2022

Cited by 5 | Viewed by 1926

Abstract

Personal protective equipment (PPE) has been adapted as biological threats have emerged, such as increasingly drug-resistant bacteria and the emergence of new viruses such as COVID-19. PPE must be increasingly resilient to prevent the proliferation of pathogens, but using sustainable raw materials and [...] Read more.

Personal protective equipment (PPE) has been adapted as biological threats have emerged, such as increasingly drug-resistant bacteria and the emergence of new viruses such as COVID-19. PPE must be increasingly resilient to prevent the proliferation of pathogens, but using sustainable raw materials and environmentally friendly technologies. The aim of this study is to show a new way of modifying the surface of various types of fabrics to enable their efficient use as PPE. The Ag/DLC coating was successfully deposited by sputtering onto several types of textiles using different chemical compositions of Ag/DLC (0, 8, 10, and 12Ag). As a crucial parameter, wettability was evaluated, showing that silver addition increases the hydrophobicity character of the coated fabrics, namely in cotton, changing from hydrophilic to hydrophobic. Antibacterial activity and cytotoxicity were evaluated on all coatings, revealing that they are efficient in eliminating the spread of bacteria (Staphylococcus aureus and Klebsiella pneumoniae) and pose no risk to the human body. The results presented here are promising in protecting healthcare workers, with the next steps being to study the efficiency of these coatings against viruses. In addition, this study reveals an opportunity to use sustainable fabrics, such as cotton, with high efficiency in protection against pathogens, instead of synthetic fiber textiles. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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15 pages, 4887 KiB

Open AccessArticle

Interfacial Stresses of Thermal Barrier Coating with Film Cooling Holes Induced by CMAS Infiltration

by Chenchun Chiu, Shaochen Tseng, Chingkong Chao, Xueling Fan and Weihung Cheng

Coatings 2022, 12(3), 326; https://doi.org/10.3390/coatings12030326 - 01 Mar 2022

Cited by 7 | Viewed by 1967

Abstract

To obtain high gas turbine efficiency, a film cooling hole is introduced to prevent the destruction of thermal barrier coating systems (TBCs) due to hot gases. Furthermore, environmental calcium-magnesium-aluminum-silicate (CMAS) particulates plug the film cooling hole and infiltrate the TBCs to form a [...] Read more.

To obtain high gas turbine efficiency, a film cooling hole is introduced to prevent the destruction of thermal barrier coating systems (TBCs) due to hot gases. Furthermore, environmental calcium-magnesium-aluminum-silicate (CMAS) particulates plug the film cooling hole and infiltrate the TBCs to form a CMAS-rich layer, which results in phase transformations and significant modifications in the thermomechanical properties that impact the TBCs during cooling. This study aimed to establish a three-dimensional thermo-fluid-solid coupling TBCs model with film cooling holes and CMAS infiltration to analyze the temperature and residual stress distribution via simulations. For the interfacial stress around the cooling hole at the TC/BC interface, the film cooling holes alleviated the interfacial residual stress by 60% due to the reduction in temperature by 40%. In addition, CMAS infiltration intensified the interfacial residual stress via phase transformation. As a result of the influence of larger penetration depths and expansion rates of phase transformation, a significant increase in residual stress was observed. At the beginning of CMAS infiltration, the interfacial stress would be more dominated by the effect of infiltration depth. In addition, the failure due to interfacial normal and tangential stresses was more likely to be found at the infiltration zone near the cooling hole. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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11 pages, 2991 KiB

Open AccessArticle

Green Synthesis of Carbon-Encapsulated Magnetic Fe₃O₄ Nanoparticles Using Hydrothermal Carbonization from Rattan Holocelluloses

by Linxin Dai, Zhi Jin, Xinge Liu, Long Feng, Jianfeng Ma and Zhe Ling

Coatings 2021, 11(11), 1397; https://doi.org/10.3390/coatings11111397 - 17 Nov 2021

Cited by 1 | Viewed by 1734

Abstract

How to design a simple and scalable procedure for manufacturing multifunctional carbon-based nanoparticles using lignocellulosic biomass directly is a challenging task. Based on the green chemistry concept, we developed a novel one-pot solution-phase reaction to prepare carbon-encapsulated magnetic nano-Fe₃O₄ particles [...] Read more.

How to design a simple and scalable procedure for manufacturing multifunctional carbon-based nanoparticles using lignocellulosic biomass directly is a challenging task. Based on the green chemistry concept, we developed a novel one-pot solution-phase reaction to prepare carbon-encapsulated magnetic nano-Fe₃O₄ particles (Fe₃O₄@C) with a tunable structure and composition through the hydrothermal carbonization (HTC) of Fe²⁺/Fe³⁺ loaded rattan holocelluloses pretreated with ionic liquids (EmimAc and AmimCl). The detailed characterization results indicated that the Fe₃O₄@C synthesized from the holocelluloses pretreated with ionic liquids (ILs) under alkaline conditions tends to have a higher saturation magnetization, probably due to the increased iron ions loading. Moreover, increasing the HTC temperature led to an increased abundance of hydroxyl groups on the surface of the synthesized particles and an elevated saturation magnetization. When EmimAc-treated holocelluloses were used as the carbon precursors, well-encapsulated Fe₃O₄@C nanoparticles were obtained with a maximum saturation magnetization of 42.6 emu/g. This synthetic strategy, coupled with the structure of the iron carbide-based composite and the proposed mechanism, may open a new avenue for the development of carbon-encapsulated iron oxide-based magnetic nanoparticles. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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Open AccessArticle

Understanding the Enhanced Protective Mechanism of CoCrNiAlY–YSZ–LaMgAl₁₁O₁₉ Double-Ceramic Coating with Aluminum Plating

by Junfei Xu, Zhiguo Wang, Shuai Hu, Yongjun Feng, Suying Hu, Yongjun Chen and Zhiwen Xie

Coatings 2021, 11(11), 1312; https://doi.org/10.3390/coatings11111312 - 28 Oct 2021

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Abstract

To understand the enhanced protection mechanism of CoCrNiAlY–YSZ–LaMgAl₁₁O₁₉ double-layer ceramic coating with aluminum plating, a finite element simulation method was used to simulate the distribution of thermal stress in the coating in all directions. The results show that in the [...] Read more.

To understand the enhanced protection mechanism of CoCrNiAlY–YSZ–LaMgAl₁₁O₁₉ double-layer ceramic coating with aluminum plating, a finite element simulation method was used to simulate the distribution of thermal stress in the coating in all directions. The results show that in the air exposure of the un-aluminized coating, high temperature causes a large radial thermal stress on the surface of the LaMgAl₁₁O₁₉ (LMA) layer, and it increases with the increase in temperature, which is the main reason for the initiation of axial cracks. After arc aluminum plating, the aluminum plating layer effectively inhibited the volume shrinkage of the coating through good adhesion to the coating and internal diffusion; the thermal stress of the coating was considerably reduced; and the CoCrNiAlY–YSZ–LMA coating had an effective enhancement and protection effect. However, there was still a certain amount of shear thermal stress inside the LMA layer, the top of the crack, and the bottom of the crack. This thermal stress caused the initiation of radial microcracks in the LMA layer, which also becomes a risk point for the failure of the aluminum coating. Full article

(This article belongs to the Special Issue Trends in Coatings and Surface Technology)

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