Coatings

20 pages, 9019 KiB

Open AccessArticle

Enhancing UV Radiation Resilience of DLC-Coated Stainless Steel with TiO₂: A Dual-Layer Approach

by Paulo Fabrício Macário, Carolina Hahn da Silveira, Angela Aparecida Moraes Vieira, André Ricardo Marcondes, Francisco das Chagas Marques, Guilhermino José Macêdo Fechine and Lúcia Vieira

Coatings 2024, 14(6), 777; https://doi.org/10.3390/coatings14060777 - 20 Jun 2024

Viewed by 302

Abstract

This study presents an innovative dual-layer coating approach integrating titanium dioxide (TiO₂) onto diamond-like carbon (DLC)-coated 316L stainless steel. The combination of PECVD-deposited DLC and ALD-deposited TiO₂ aims to preserve the inherent tribological properties of DLC while mitigating UV-induced degradation. [...] Read more.

This study presents an innovative dual-layer coating approach integrating titanium dioxide (TiO₂) onto diamond-like carbon (DLC)-coated 316L stainless steel. The combination of PECVD-deposited DLC and ALD-deposited TiO₂ aims to preserve the inherent tribological properties of DLC while mitigating UV-induced degradation. By leveraging the ability of TiO₂ to absorb, reflect, and scatter UV light, this dual-layer strategy significantly enhances the durability of DLC coatings in radiation-prone environments. The effects of accelerated aging through UV exposure on DLC and DLC/TiO₂ films were evaluated using an Accelerated Weathering Tester. Comprehensive analyses were conducted to assess the structural and mechanical properties before and after UV exposure, including Raman spectroscopy, profilometry, SEM, EDS, nanoindentation, and tribometry. The results demonstrate that the TiO₂ layer effectively mitigates UV-induced damage, preserving the DLC film’s integrity and tribological performance even after 408 h of UV aging. Specifically, the DLC/TiO₂ coatings maintained lower roughness, higher hardness, and better adhesion than DLC-only coatings under identical conditions. This research significantly advances protective coating technology by enhancing the durability and performance of DLC films, particularly in aerospace and other demanding industries where exposure to UV radiation is a critical concern. Full article

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

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11 pages, 2765 KiB

Open AccessArticle

Effect of Tempering Temperature on Microstructure and Intergranular Corrosion Property of 2205 Duplex Stainless Steel

by Xianfu Luo, Kun Fang, Wenli Zhang, Jinmin Zhang, Xiao Yang, Xiaoyong Liu, Xiaoqin Zha and Xinyao Zhang

Coatings 2024, 14(6), 776; https://doi.org/10.3390/coatings14060776 - 20 Jun 2024

Viewed by 391

Abstract

The effect of tempering temperature on the microstructure and intergranular corrosion property of 2205 duplex stainless steel (DSS2205) was determined using a boiling acid intergranular corrosion test (boiling 65% nitric acid and 50% sulfuric acid–ferric sulfate), an optical microscope, a transmission electron microscope, [...] Read more.

The effect of tempering temperature on the microstructure and intergranular corrosion property of 2205 duplex stainless steel (DSS2205) was determined using a boiling acid intergranular corrosion test (boiling 65% nitric acid and 50% sulfuric acid–ferric sulfate), an optical microscope, a transmission electron microscope, and a double-loop electrochemical potentiokinetic reactivation (DL-EPR) test. The results show that the ferrite content of the DSS2205 is about 50% in a specimen close to a solid solution state (1050 °C for 1 h, then water-quenched) when tempered at 675 °C–725 °C for 1 h. As the tempering temperature rises to 750 °C–800 °C for 1 h, the ferrite content drops gradually from 49% to 35%. M₂₃C₆, FeCr (σ phase), and Cr₂N phases are precipitated when the specimen is tempered at 675°C–800 °C for 1 h. When the tempering temperature rises to 750 °C–800 °C for 1 h, the content and size of σ phase increase significantly. In the boiling acid intergranular corrosion test, when the specimen is tempered at 675 °C–725 °C for 1 h, the corrosion rate is higher than when it is tempered at 750 °C–800 °C for 1 h. In the DL-EPR test, when the specimen is tempered at 675 °C–800 °C for 1 h, the intergranular corrosion sensitivity rises gradually. External polarization is added during the DL-EPR test, and the test principle is different from that of the boiling acid intergranular corrosion test, resulting in a different sensitivity to intergranular corrosion compared to boiling acid intergranular corrosion. Full article

(This article belongs to the Special Issue Micro- and Nano- Mechanical Testing of Coatings and Surfaces)

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13 pages, 3564 KiB

Open AccessArticle

Characterisation of TiCN Coatings for Biomedical Applications

by Monika Madej and Katarzyna Piotrowska

Coatings 2024, 14(6), 775; https://doi.org/10.3390/coatings14060775 - 20 Jun 2024

Viewed by 295

Abstract

This study aims to characterise TiCN coatings deposited on Ti6Al4V by physical vapour deposition. Findings on surface morphology, geometric structure, adhesion, instrumental hardness, and tribology are presented. Microscopic examination revealed a uniform coating with a thickness of about 1.5 µm and roughness (Sq) [...] Read more.

This study aims to characterise TiCN coatings deposited on Ti6Al4V by physical vapour deposition. Findings on surface morphology, geometric structure, adhesion, instrumental hardness, and tribology are presented. Microscopic examination revealed a uniform coating with a thickness of about 1.5 µm and roughness (Sq) equal to 0.13 µm. Mechanical tests showed that the coating deposition increased the hardness of the Ti6Al4V alloy by about 75%. The artificial saliva solution used in the tribological tests reduced the coefficient of friction and the volumetric wear of the tested friction pairs. Microscopic observations of wear tracks after tribological tests allowed for the identification of wear mechanisms: micro-cutting/ploughing wear dominated in both the Ti6Al4V alloy and TiCN coating samples, but wear was much less pronounced overall with the TiCN coating. The study results demonstrate that the deposition of a TiCN coating simultaneously imparts low-friction and anti-wear properties to the surface of titanium alloys. Full article

(This article belongs to the Special Issue Bioactive Coatings on Elements Used in the Oral Cavity Environment)

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12 pages, 2135 KiB

Open AccessCommunication

Navigating the Labyrinth of Polymer Sustainability in the Context of Carbon Footprint

by Jomin Thomas, Renuka Subhash Patil, Mahesh Patil and Jacob John

Coatings 2024, 14(6), 774; https://doi.org/10.3390/coatings14060774 - 20 Jun 2024

Viewed by 322

Abstract

The ubiquitous nature of polymers has led to a widespread demand for sustainable polymers in numerous industrial applications. However, a lack of well laid out guidelines, product development pathways and certifications has resulted in a lot of commotions and confusions within the polymer [...] Read more.

The ubiquitous nature of polymers has led to a widespread demand for sustainable polymers in numerous industrial applications. However, a lack of well laid out guidelines, product development pathways and certifications has resulted in a lot of commotions and confusions within the polymer value chain. Herein, a meticulous review is conducted on the topic of polymer sustainability shedding light on the standards, product declarations, biobased-biomass concepts, product carbon footprint, etc. It is critical that companies significantly contribute to such sustainability efforts in lieu of market readiness and competitive advantages. Any discussion within the sustainability horizon references a couple of terms/abbreviations/concepts. In this article, such key terminologies and concepts related to polymer sustainability are reviewed with a holistic outlook on the widespread approaches within the polymer sustainability horizon. In the polymer raw material manufacturers, the mass balance approach has gained more momentum with International Sustainability and Carbon Certification (ISCC). Product carbon footprint, life cycle analysis and third-party certifications were noted as the three key factors of sustainability engagement, with polymer manufactures placing sustainability commitments and targets for carbon emissions control. It is foreseen that a collaborative network between academic research, raw material manufacturers and the upstream companies and consumers will drive the sustainable polymer products market. Full article

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

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21 pages, 21058 KiB

Open AccessArticle

Tribocatalytic Reaction Enabled by TiO₂ Nanoparticle for MoDTC-Derived Tribofilm Formation at ta-C/Steel Contact

by Daiki Matsukawa, Jae-Hyeok Park, Woo-Young Lee, Takayuki Tokoroyama, Jae-Il Kim, Ryoichi Ichino and Noritsugu Umehara

Coatings 2024, 14(6), 773; https://doi.org/10.3390/coatings14060773 - 19 Jun 2024

Viewed by 375

Abstract

Tribochemically produced triboproducts are becoming increasingly important in tribosystems and serve to improve system performance by preventing friction or wear. Diamond-like carbon (DLC) is chemically stable, which features a trade-off with tribological pros and cons. Chemically stable DLC is thermally stable and suppresses [...] Read more.

Tribochemically produced triboproducts are becoming increasingly important in tribosystems and serve to improve system performance by preventing friction or wear. Diamond-like carbon (DLC) is chemically stable, which features a trade-off with tribological pros and cons. Chemically stable DLC is thermally stable and suppresses surface damage in a high-temperature operating environment; however, it causes a detrimental effect that hinders the formation of a competent tribofilm. In this study, we dispersed highly reactive TiO₂ nanoparticles (TDONPs) in molybdenum dithiocarbamate (MoDTC)-containing lubricant for adhering triboproducts on the DLC surface. In addition, TDONPs contributed to the decomposition of triboproducts by promoting the decomposition of MoDTC through its catalytic role. Rutile TDONPs were more helpful in reducing friction than anatase TDONPs and improved the friction performance by up to ~100%. Full article

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

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15 pages, 3666 KiB

Open AccessArticle

Photoresponsive Electrospun Polycaprolactone Nanofibrous Structure Embedding Dithienylethene Molecules

by Mahad Barre Aden, François Rault and Fabien Salaün

Coatings 2024, 14(6), 772; https://doi.org/10.3390/coatings14060772 - 19 Jun 2024

Viewed by 279

Abstract

Photochromic polycaprolactone (PCL) nanofibers were prepared through electrospinning. Various factors, including the solvent system, the concentration of PCL, the viscosity of the solution, and the electrical conductivity, influence the morphology of PCL nanofibers. A binary solvent system can dissolve PCL, control fiber structure [...] Read more.

Photochromic polycaprolactone (PCL) nanofibers were prepared through electrospinning. Various factors, including the solvent system, the concentration of PCL, the viscosity of the solution, and the electrical conductivity, influence the morphology of PCL nanofibers. A binary solvent system can dissolve PCL, control fiber structure and morphology, and allow solvent evaporation. The photochromic properties of electrospun membranes based on PCL and diethienylethene (DTE) were assessed using the CM-3610a spectrophotometer. The study showed that incorporating DTE into the membrane enables photochromic performance, with the photochromic reaction being reversible. The analysis of the color-change kinetics showed that the mechanism of photo cycling during colorization was linked to the amplitude of the fast and slow mechanisms, which depended on the formulation tested. The study showed that the photoreversion of the membrane under visible illumination occurs according to first-order kinetics. This work presented the design and manufacturing of photochromic membranes through electrospinning, which offers rapid color change rates, adjustable color fade times, superior reversibility, and reproducibility over at least 10 cycles. The thermochromic properties are proportional to the DTE concentration used, making it possible to obtain color variations with a delta E of 13 and 38 for concentrations ranging from 0.95 to 11.4 wt.%. Full article

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

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13 pages, 8128 KiB

Open AccessArticle

Enhancing Tribological Performance of Micro-Arc Oxidation Coatings on 6061 Aluminum Alloy with h-BN Incorporation

by Xia Zhao, Jingfu Song, Jingyi Lin, Guoqing Wang and Gai Zhao

Coatings 2024, 14(6), 771; https://doi.org/10.3390/coatings14060771 - 19 Jun 2024

Viewed by 270

Abstract

Micro-arc oxidation (MAO) coatings of aluminum alloy have great potential applications due to their high hardness and wear resistance. However, the micro-pores and defects formed in the discharge channels during the MAO process limit its application in the corrosion field. This study delves [...] Read more.

Micro-arc oxidation (MAO) coatings of aluminum alloy have great potential applications due to their high hardness and wear resistance. However, the micro-pores and defects formed in the discharge channels during the MAO process limit its application in the corrosion field. This study delves into the impact of h-BN nanoparticles into MAO coatings on their structure, corrosion resistance, phase composition, and tribological properties. The results show that the incorporation of h-BN particles reduces the porosity and surface roughness of the coating while enhancing its hardness and wear resistance. The best corrosion resistance is obtained at a concentration of 2 g/L h-BN. An analysis of worn surface morphology, corrosion resistance, and friction coefficient change was conducted to evaluate the performance of this coating. This method provides a new approach to enhance the surface hardness and wear resistance of aluminum alloys, which is significant for expanding the application of aluminum alloys in corrosion environments. Full article

(This article belongs to the Special Issue Tribological Behavior and Mechanical Performance of Coatings and Materials)

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13 pages, 12260 KiB

Open AccessArticle

Failure Causes Analysis of Circumferential Cracking on Gathering Pipeline in M Oil and Gas Field

by Xuehui Zhao, Zicheng Zhang, Zhiwu He, Yan Han and Juntao Yuan

Coatings 2024, 14(6), 770; https://doi.org/10.3390/coatings14060770 - 18 Jun 2024

Viewed by 242

Abstract

The gathering and transportation pipeline experienced corrosion cracking failure after 2 years of operation. This paper conducted an analysis on the reasons for the pipeline failure by integrating background information on its usage, as well as observations, analyses, and detection of the morphology [...] Read more.

The gathering and transportation pipeline experienced corrosion cracking failure after 2 years of operation. This paper conducted an analysis on the reasons for the pipeline failure by integrating background information on its usage, as well as observations, analyses, and detection of the morphology of failure samples. The results indicated that the fracture originated from the inner wall of the pipeline and extended to the outer wall along the wall thickness until complete fracture occurred. Based on microstructure analysis of the fracture and original microcracks at the top of the pipeline, it was determined that the fracture was a multi-source brittle fracture, spreading in both inter-granular and trans-granular forms with obvious radial quasi-cleavage fractures accompanied by secondary cracks. EDS analysis revealed that the element S was present in all zones related to fracture initiation, spreading, and transient zones. XRD analysis showed that corrosion products on the fracture surface were mainly composed of FeS, indicating the presence of H₂S in the service environment leading to sulfide stress corrosion cracking characteristics in line with pipeline failure. It is recommended to confirm the source of H₂S in the service medium and test residual stress within the same pipeline for potential risk assessment regarding cracking in other areas. Full article

(This article belongs to the Special Issue Corrosion/Wear Mechanisms and Protective Methods)

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12 pages, 3438 KiB

Open AccessArticle

Size Effect of Graphite Nanosheet-Induced Anti-Corrosion of Hydrophobic Epoxy Coatings

by Kuilin Lv, Yiwang Bao, Huachao Ma, Xiaogen Liu, Ying Zhu and Detian Wan

Coatings 2024, 14(6), 769; https://doi.org/10.3390/coatings14060769 - 18 Jun 2024

Viewed by 410

Abstract

In order to broaden the selectivity of graphite nanosheet additives on epoxy resin-based coatings and verify the size effect, this work aims to dope graphite nanosheets of different sizes into the three-dimensional structure produced by cross-linking and curing epoxy resin and polyamide resin. [...] Read more.

In order to broaden the selectivity of graphite nanosheet additives on epoxy resin-based coatings and verify the size effect, this work aims to dope graphite nanosheets of different sizes into the three-dimensional structure produced by cross-linking and curing epoxy resin and polyamide resin. In addition, a micro-nano level secondary structure and a surface with special roughness are constructed to obtain the composite epoxy hydrophobic coating. The influence of the size effect of graphite nanosheets on the hydrophobic performance and corrosion resistance of the coating is summarized as well. Among them, the optimized doping size (2.2 μm) of graphite nanosheets in the epoxy coating showed the largest impedance arc of 2.58 × 10⁸ Ω cm², which could form an excellent nano-network covering the micropores to impede the diffusion of corrosive medium. Through simulation calculation analysis, we also found that the edge site of graphene is more effective in capturing H₂O and O₂; therefore, a smaller size of graphene with a large edge can be more favorable. This work will be used as a reference for the industrial application of graphite anti-corrosive coating. Full article

(This article belongs to the Special Issue Preparation and Applications of Functional Inorganic Coatings, Glass, Ceramics)

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16 pages, 19888 KiB

Open AccessArticle

A Deep Learning Image Corrosion Classification Method for Marine Vessels Using an Eigen Tree Hierarchy Module

by Georgios Chliveros, Iason Tzanetatos and Stylianos V. Kontomaris

Coatings 2024, 14(6), 768; https://doi.org/10.3390/coatings14060768 - 18 Jun 2024

Viewed by 382

Abstract

This paper involves the automation of a visual characterisation technique for corrosion in marine vessels, as it appears in the hull preventive coatings of marine vessels and their surfaces. We propose a module that maximizes the utilisation of features learned by a deep [...] Read more.

This paper involves the automation of a visual characterisation technique for corrosion in marine vessels, as it appears in the hull preventive coatings of marine vessels and their surfaces. We propose a module that maximizes the utilisation of features learned by a deep convolutional neural network to identify areas of corrosion and segment pixels in regions of inspection interest for corrosion detection. Our segmentation module is based on Eigen tree decomposition and information-based decision criteria in order to produce specific corroded spots—regions of interest. To assess performance and compare it with our method, we utilize several state-of-the-art deep learning architectures.The results indicate that our method achieves higher accuracy and precision while maintaining the significance score across the entire dataset. To the best of our knowledge, this is the first Eigen tree-based module in the literature in the context of trained neural network predictors for classifying corrosion in marine vessel images. Full article

(This article belongs to the Special Issue Effects of Surface Layer Modification on Fatigue, Corrosion and Wear Behavior of Metallic Materials)

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17 pages, 3996 KiB

Open AccessArticle

Study of Ceramic Hollow Buoyant Balls Prepared Based on Slip Mold Casting and Brazing Process

by Yu Lei, Jian Zhou, Guizhen Liu, Lin Wang and Zhongjun Ding

Coatings 2024, 14(6), 767; https://doi.org/10.3390/coatings14060767 - 17 Jun 2024

Viewed by 390

Abstract

In the domain of deep-sea buoyancy material applications, hollow ceramic spheres, known for their high strength and low mass-to-drainage ratio, contribute to increased buoyancy and payload capacity enhancement for deep submersibles, constituting buoyancy materials of exceptional overall performance. This study entails the brazing [...] Read more.

In the domain of deep-sea buoyancy material applications, hollow ceramic spheres, known for their high strength and low mass-to-drainage ratio, contribute to increased buoyancy and payload capacity enhancement for deep submersibles, constituting buoyancy materials of exceptional overall performance. This study entails the brazing of two ceramic hemispherical shells, obtained through slurry molding, to form a ceramic float. This process, which integrates slurry molding and ceramic brazing, facilitates buoyancy provision. Further refinement involves welding a ceramic connector onto the ceramic shell, incorporating a top opening to create a ceramic float equipped with an observation window seat. The ceramic float maintains uniform wall thickness, while the observation window facilitates external environmental observation in deep-sea research. Two pressure-resistant spherical shells, produced using this process, underwent testing, revealing the wall thickness of the prepared alumina ceramic hollow spheres to be 1.00 mm, with a mass-to-drainage ratio of 0.47 g/cm³ and a buoyancy coefficient of 53%. The resultant ceramic hollow floating ball can withstand hydrostatic pressure of 120 MPa, while the pressure-resistant ball shell with an observation window seat can endure hydrostatic pressure of 100 MPa, ensuring safe operation at depths of 5000–6000 m. This process provides a production method for subsequent large-scale ceramic float manufacturing for the transportation of objects or personnel. Full article

(This article belongs to the Special Issue Laser-Assisted Processes and Thermal Treatments of Materials)

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14 pages, 18506 KiB

Open AccessArticle

Influence of Current Duty Cycle and Voltage of Micro-Arc Oxidation on the Microstructure and Composition of Calcium Phosphate Coating

by Axaule Mamaeva, Aidar Kenzhegulov, Aleksander Panichkin, Rinat Abdulvaliyev, Dametken Fischer, Nauryzbek Bakhytuly and Nazgul Toiynbaeva

Coatings 2024, 14(6), 766; https://doi.org/10.3390/coatings14060766 - 17 Jun 2024

Viewed by 352

Abstract

The micro-arc oxidation (MAO) technique was employed to produce calcium phosphate coatings on titanium surfaces using an electrolyte composed of hydroxyapatite and calcium carbonate in an aqueous solution of orthophosphoric acid. The coatings’ morphology and composition were regulated by adjusting electrical parameters, specifically [...] Read more.

The micro-arc oxidation (MAO) technique was employed to produce calcium phosphate coatings on titanium surfaces using an electrolyte composed of hydroxyapatite and calcium carbonate in an aqueous solution of orthophosphoric acid. The coatings’ morphology and composition were regulated by adjusting electrical parameters, specifically the duty cycle and voltage. This study examined the effects of the duty cycle and voltage during the MAO process on the microstructure and composition of calcium phosphate coatings on VT1–0 titanium substrates. Scanning electron microscopy (SEM) was utilized to analyze the microstructure and thickness of the coatings, while X-ray diffraction (XRD) was employed to determine their phase composition. The findings reveal that the surface morphology of the calcium phosphate coatings transitions from a porous, sponge-like structure to flower-like formations as the duty cycle and voltage increase. A linear increase in the voltage within the applied duty cycles led to a rise in the size of the forming particles of amorphous/crystalline structures containing phases of monetite (CaPO₃(OH)), monocalcium phosphate monohydrate (Ca(H₂PO₄)₂·H₂O), and calcium pyrophosphate (γ–Ca₂P₂O₇). Full article

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

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16 pages, 5276 KiB

Open AccessArticle

A New Method for Determining Necking of Sheet Metal Based on Main Strain Topography

by Liqiu Shi, Yingjie Yang, Bo Hou, Weifang Gu, Haitao Zhao, Yan Feng and Zhouming Hang

Coatings 2024, 14(6), 765; https://doi.org/10.3390/coatings14060765 - 17 Jun 2024

Viewed by 358

Abstract

There are various methods to evaluate the forming limit of a sheet, and these criteria can be classified as position-dependent, time-dependent, and position-time dependent according to the basis of judgment. However, these criteria have a single function and can only find the forming [...] Read more.

There are various methods to evaluate the forming limit of a sheet, and these criteria can be classified as position-dependent, time-dependent, and position-time dependent according to the basis of judgment. However, these criteria have a single function and can only find the forming limit of the sheet and cannot determine the strain distribution, strain change, or fracture location during the sheet forming process. This paper introduces a time–location-dependent method, i.e., the spatial strain rate method, which is used to detect the onset of necking of a sheet. The spatial strain rate is directly based on the strain and can not only find the forming limit of the sheet but also depict the strain distribution and strain variation during the two phases of the experimental process—distributed instability and concentrated instability—as well as predict the location of sheet fracture. The spatial strain rate of AA5083 aluminum alloy of different widths was analyzed and verified in detail via Nakazima experiments using digital image correlation techniques and compared with the guidelines published in the literature in recent years. Full article

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

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19 pages, 2237 KiB

Open AccessArticle

Effect of Chain Orientation on Coupling of Optical and Mechanical Anisotropies of Polymer Films

by Aref Samadi-Dooki, Mark A. Lamontia, Juan David Londoño, Curtis Williamson, Heidi E. Burch, Mobin Yahyazadehfar, Leopoldo A. Carbajal and Kostantinos Kourtakis

Coatings 2024, 14(6), 764; https://doi.org/10.3390/coatings14060764 - 16 Jun 2024

Viewed by 527

Abstract

Polymer films have broad applications in different industries with specific requirements for their optical and mechanical properties. In mass production, processing conditions during film formation that apply forces and motions in various directions to the film tend to manifest preferred molecular chain orientation [...] Read more.

Polymer films have broad applications in different industries with specific requirements for their optical and mechanical properties. In mass production, processing conditions during film formation that apply forces and motions in various directions to the film tend to manifest preferred molecular chain orientation in the film microstructure, which unavoidably produces optical and mechanical anisotropies. In this paper, we investigate the effect of such macromolecular orientations on the optical and mechanical anisotropies of several polymer films, including polystyrene, poly(methyl methacrylate), poly(ethylene terephthalate), poly(ethylene naphthalate), poly(ether ether ketone), poly(ether sulfones), poly(ethylene chlorotrifluoroethylene), poly(phenylsulfone), and polycarbonate, at temperatures well below their respective glass transitions (T_g). The film mechanical responses, including elasticity, yielding, and post-yield behaviors, were obtained for the in- and out-of-plane directions utilizing tensile and nanoindentation testing methods, respectively. In addition, the net chain orientation within the films was evaluated by birefringence through analyzing the film optical refractive indices, which were verified and complemented by wide-angle X-ray scattering (WAXS) measurements. The results reveal a considerable quantitative correlation between the birefringence and the degree of elastic anisotropy and a qualitative correlation between the chain orientation and the film post-yield tensile instability (necking). These observations corroborate the interrelationship between the microstructure of polymer films and their optical and mechanical properties. In addition, they emphasize that process conditions can be selected to tune the optical and mechanical anisotropies to best serve the material performance in specific devices. We also propose an empirical equation to approximate the out-of-plane film stiffness based upon the optical and in-plane mechanical properties. Full article

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18 pages, 15930 KiB

Open AccessArticle

Study on the Effects of GO on the Microstructure and Wear Resistance of CuCrZr Plasma Cladding Coatings

by Yang Wang, Hongjun Xiang, Zhiming Qiao, Jianwei Zhen, Qing-Ao Lv, Xichao Yuan, Chunyan Liang and Genrong Cao

Coatings 2024, 14(6), 763; https://doi.org/10.3390/coatings14060763 - 16 Jun 2024

Viewed by 373

Abstract

This study investigates the enhancement of wear resistance in CuCrZr rails through the plasma cladding of CuCrZr-GO coatings with a varying graphene oxide (GO) content. The microstructure, phase composition, and mechanical properties of CuCrZr coatings containing 0%, 0.2%, 0.4%, 0.6%, and 0.8% GO [...] Read more.

This study investigates the enhancement of wear resistance in CuCrZr rails through the plasma cladding of CuCrZr-GO coatings with a varying graphene oxide (GO) content. The microstructure, phase composition, and mechanical properties of CuCrZr coatings containing 0%, 0.2%, 0.4%, 0.6%, and 0.8% GO were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), ESD surface scanning, friction and wear tests, and hardness analysis. The findings indicated that increasing the GO content from 0% to 0.6% results in a transition in the coating microstructure from columnar to equiaxed crystals, leading to an improved density. However, at 0.8% GO, numerous porosity defects were observed. The coating containing 0.6% graphene oxide (GO) exhibited a superior performance, with a hardness of 75, a friction coefficient of approximately 0.7, and a wear mass of 2.84 mg under a 10 N load. In comparison to the CuCrZr coating lacking GO, the hardness showed an increase of around 4.8%, the friction coefficient decreased by approximately 5.1%, and the wear mass diminished by 59.4%. These findings hold significant implications for extending the operational lifespan of electromagnetic railguns. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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14 pages, 5267 KiB

Open AccessArticle

Improving Trace Detection of Methylene Blue by Designing Nanowire Array on Boron-Doped Diamond as Electrochemical Electrode

by Sihan He, Kun Lin, Shaoheng Cheng, Nan Gao, Junsong Liu and Hongdong Li

Coatings 2024, 14(6), 762; https://doi.org/10.3390/coatings14060762 - 16 Jun 2024

Viewed by 449

Abstract

In this study, a boron-doped diamond nanowire array (BDD-NWA)-based electrode is prepared by using a microwave plasma chemical vapor deposition system and treated with inductively coupled plasma reactive ion etching. The BDD-NWA electrode is used for trace detection of methylene blue, which has [...] Read more.

In this study, a boron-doped diamond nanowire array (BDD-NWA)-based electrode is prepared by using a microwave plasma chemical vapor deposition system and treated with inductively coupled plasma reactive ion etching. The BDD-NWA electrode is used for trace detection of methylene blue, which has a wide linear range of 0.04–10 μM and a low detection limit of 0.72 nM. Both the superhydrophilicity (contact angle ~0°) and the dense nanowire array’s structure after the etching process improve the sensitivity of the electrochemical detection compared to the pristine BDD. In addition, the electrode shows great repeatability (peak current fluctuation range of −3.3% to 2.9% for five detection/cleaning cycles) and stability (peak current fluctuation range of −5.3% to 6.3% after boiling) due to the unique properties of diamonds (mechanical and chemical stability). Moreover, the BDD-NWA electrode achieves satisfactory recoveries (93.8%–107.5%) and real-time monitoring in tap water. Full article

(This article belongs to the Special Issue Advances in Diamond Materials and Films)

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12 pages, 3569 KiB

Open AccessReview

PbS Colloidal Quantum Dots: Ligand Exchange in Solution

by Chuanxi Zhang, Dong Han and Xiaoyu Zhang

Coatings 2024, 14(6), 761; https://doi.org/10.3390/coatings14060761 - 16 Jun 2024

Viewed by 531

Abstract

PbS colloidal quantum dots (CQDs) have the advantages of adjustable band gap, large exciton Bohr radius, controllable size, easy synthesis, and potential multi-exciton effect, making them attractive for photodetectors and solar cells. However, the long ligand chain wrapped on PbS CQDs limits carrier [...] Read more.

PbS colloidal quantum dots (CQDs) have the advantages of adjustable band gap, large exciton Bohr radius, controllable size, easy synthesis, and potential multi-exciton effect, making them attractive for photodetectors and solar cells. However, the long ligand chain wrapped on PbS CQDs limits carrier transport, and defect states of as-synthesized CQDs increase non-radiative recombination, negatively affecting photovoltaic performance. Surface properties determine the characteristics of CQDs, so ligand exchange processes are crucial. Because solution phase ligand exchange reduces labor and time requirements, it is more advantageous than solid phase ligand exchange. This review discusses the solution phase ligand exchange process of PbS CQDs, emphasizing the impact of surface ligands on conformation and conductivity. Full article

(This article belongs to the Special Issue Advances in Nanostructured Thin Films and Coatings, 2nd Edition)

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16 pages, 11647 KiB

Open AccessArticle

The Microstructures and Wear Resistance of CoCrFeNi₂Mo_x High-Entropy Alloy Coatings

by Hui Liang, Jinxin Hou, Jianhong Liu, Hongtai Xu, Yaning Li, Li Jiang and Zhiqiang Cao

Coatings 2024, 14(6), 760; https://doi.org/10.3390/coatings14060760 - 15 Jun 2024

Viewed by 301

Abstract

The CoCrFeNi₂Mo_x (x = 0, 0.4, 0.5, 1.0, x values in atomic ratio) high-entropy alloy coatings were designed and prepared on the Ti-6Al-4V substrate by laser cladding technology, their microstructures, and dry sliding wear resistance were studied in detail. When [...] Read more.

The CoCrFeNi₂Mo_x (x = 0, 0.4, 0.5, 1.0, x values in atomic ratio) high-entropy alloy coatings were designed and prepared on the Ti-6Al-4V substrate by laser cladding technology, their microstructures, and dry sliding wear resistance were studied in detail. When x < 0.4, the coatings were mainly composed of BCC solid solution phase, (Ni, Co)Ti₂ phase, and α-Ti phase. When x ≥ 0.4, the new σ phase appeared in the coatings. As the Mo content increases from 0 to 1.0, the hardness showed a trend of first increasing and then decreasing, especially when x = 0.5, the coating hardness reached its maximum (882 HV), which was 2.65 times the hardness of the Ti-6Al-4V substrate. The CoCrFeNi₂Mo_x high-entropy alloy coatings significantly improved the wear resistance of Ti-6Al-4V substrate, and with the increase in Mo content, the friction coefficient, widths/depths of worn tracks and wear rates of the coatings showed a trend of first decreasing and then increasing. In particular, when x = 0.5, the CoCrFeNi₂Mo_0.5 high-entropy alloy coating has the lowest friction coefficient (0.63), widths/depths of worn tracks (width: 803.690 μm; depth: 20.630 μm) and wear rate (5.136 × 10⁻⁵ mm³/(N·m)), which is one order of magnitude smaller than that of the substrate (3.694 × 10⁻⁴ mm³/(N·m)), demonstrating the best wear resistance. This is mainly because the appropriate proportion of hard α-Ti and σ phases effectively played a supporting role in resisting wear, while the relatively soft and dispersed BCC and (Ni, Co)Ti₂ phases could effectively prevent the occurrence of brittle fracture during wear test process. Full article

(This article belongs to the Special Issue Microstructure, Wear Resistance and Corrosion Resistance of High-Entropy Alloy Coatings)

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11 pages, 4131 KiB

Open AccessArticle

Investigation of the Bonding Mechanism of Al Powder Particles through Pulse Current Sintering Technology

by Zhou Lv and Ruifeng Liu

Coatings 2024, 14(6), 759; https://doi.org/10.3390/coatings14060759 - 15 Jun 2024

Viewed by 310

Abstract

Compared with traditional powder metallurgy, pulse current sintering is an advanced powder-forming technology, but its bonding mechanism is still an open topic for debate. In this paper, pulse current sintering is used as the connection technology and millimeter-sized Al particles are used as [...] Read more.

Compared with traditional powder metallurgy, pulse current sintering is an advanced powder-forming technology, but its bonding mechanism is still an open topic for debate. In this paper, pulse current sintering is used as the connection technology and millimeter-sized Al particles are used as the research object. In the whole sintering process, no pressure was loaded; the function of the pulse current was the only source of heat with which to achieve the bonding of Al particles. The bonding mechanism of pulse current sintering was investigated from the perspective of material connection behavior. The results show that the pulse current density of the particle surface reaches 3.48 × 10⁵ A/m² instantly, while the current density of the particle center is only 8187 A/m² at the initial stage, which is the main difference between pulse current sintering and traditional powder metallurgy sintering. With the densification process, the current density and temperature distribution in the contact region as well as the center of Al particles contact region tend to be more consistent. Finally, dense interfacial bonding was obtained, and the contact region of Al particles also demonstrated a high hardness value of 0.6385 GPa and yield strength value of 212.83 MPa. The whole process can be considered as a comprehensive action of melting (evaporation), diffusion, and plastic deformation. Based on the above results, a new technology, named high-frequency pulse current sintering, was proposed. Full article

(This article belongs to the Special Issue Trends in Spark Plasma Sintering of Advanced Materials)

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14 pages, 4206 KiB

Open AccessArticle

Water-Borne Photo-Thermal Superhydrophobic Coating for Anti-Icing, Self-Cleaning and Oil–Water Separation

by Jinsong Huang, Shengqi Lu, Yan Hu, Liming Liu and Hui You

Coatings 2024, 14(6), 758; https://doi.org/10.3390/coatings14060758 - 14 Jun 2024

Viewed by 423

Abstract

Superhydrophobic coatings with photo-thermal effects have advantages in anti-/de-icing and self-cleaning. Here, an eco-friendly and low-cost fabrication of superhydrophobic coating was proposed by spraying a water-borne suspension including carbon black and paraffin wax onto substrate-independent surfaces. The a water-borne suspension coated on stain [...] Read more.

Superhydrophobic coatings with photo-thermal effects have advantages in anti-/de-icing and self-cleaning. Here, an eco-friendly and low-cost fabrication of superhydrophobic coating was proposed by spraying a water-borne suspension including carbon black and paraffin wax onto substrate-independent surfaces. The a water-borne suspension coated on stain steel plate showed a strong water-repellence, delaying the ice freezing time to 665 s, which is much higher than that of bare stain steel plate (210 s) under the same experimental condition. The ice-melting time was measured as 120 s under a solar irradiation of 0.1 W/cm², while the control group had no sign of ice-melting during the same time. As a concept of proof, the self-cleaning, anti-corrosion, and oil–water separation were enabled by spraying the water-borne suspension on various substrates, demonstrating its diverse performances. Hence, the water-borne superhydrophibic coating provides an efficient, safe, and sustainable solution for wettability-related applications. Full article

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

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15 pages, 9195 KiB

Open AccessArticle

Joining and Coating of Plasma Electrolytic Oxidated Aluminum Using a Silica Preceramic Polymer

by Monica Ferraris, Alessandro Benelli, Valentina Casalegno, Pavel Shashkov and Vincenzo Maria Sglavo

Coatings 2024, 14(6), 757; https://doi.org/10.3390/coatings14060757 - 14 Jun 2024

Viewed by 673

Abstract

This study evaluates the effectiveness of a silica preceramic polymer for joining and coating Plasma Electrolytic Oxidated (PEO) aluminum components at temperatures below 200 °C. PEO aluminum slabs were coated and joined with a silica precursor polymer (Durazane1800, Merck, Darmstadt, Germany), both with [...] Read more.

This study evaluates the effectiveness of a silica preceramic polymer for joining and coating Plasma Electrolytic Oxidated (PEO) aluminum components at temperatures below 200 °C. PEO aluminum slabs were coated and joined with a silica precursor polymer (Durazane1800, Merck, Darmstadt, Germany), both with and without the addition of 48 wt% silica nanoparticles, and cured at 180 °C for 4 h in air. Thermogravimetric analysis assessed the curing process and thermal stability, while X-ray diffraction confirmed the polymer’s conversion to amorphous silica after heating at 1200 °C. Resistance to humid environments was tested by soaking coated samples in tap water for a week, with no mass variation observed. Mechanical testing through tensile mode and tensile lap tests showed that adding 48 wt% silica nanoparticles significantly improved joint cohesion and nearly quadrupled mechanical strength. Fracture surfaces were examined using Field Emission Scanning Electron Microscopy, and composition analysis was performed with Energy Dispersion X-ray Spectroscopy. Crack detection was conducted using Computer Tomography with an in situ bending test setup to obtain the mechanical resistance of the PEO coating. The results indicate that the silica preceramic polymer is suitable for joining and coating PEO aluminum components, with silica nanoparticles enhancing mechanical strength and providing excellent thermal stability and resistance to humidity. Full article

(This article belongs to the Special Issue Plasma Electrolytic Oxidation (PEO) Coatings, 2nd Edition)

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13 pages, 7173 KiB

Open AccessArticle

Modeling for the Fabrication Process of a ϕ1185 mm C/C Composite Thermal Insulation Tube in an Isothermal Chemical Vapor Infiltration Reactor

by Jicheng Zhou, Jianyong Zhan, Huiling Liang, Yan Guo, Baoxing Zhao, Linzhao Hao, Tong Zhang and Bingchun Jiang

Coatings 2024, 14(6), 756; https://doi.org/10.3390/coatings14060756 - 14 Jun 2024

Viewed by 385

Abstract

The large-size chemical vapor infiltration (CVI) of the carbon/carbon (C/C) composite thermal insulation tube is a key component for drawing large diameter monocrystalline silicon rods. However, the CVI densification process is complex, and the cost of experiment optimization is extremely high. In this [...] Read more.

The large-size chemical vapor infiltration (CVI) of the carbon/carbon (C/C) composite thermal insulation tube is a key component for drawing large diameter monocrystalline silicon rods. However, the CVI densification process is complex, and the cost of experiment optimization is extremely high. In this article, a multi-physics coupling simulation model was established and validated based on COMSOL Multiphysics v.5.6 software to simulate the fabrication process of an isothermal CVI process for a Φ1185 mm C/C composite thermal insulation tube. The influence of process parameters on densification was explored, and a method of optimization was proposed. Our modeling results revealed that the deposition status in areas of low densification was effectively and significantly enhanced after process optimization. At the monitoring site, the carbon density was no less than 1.08 × 10³ kg·m⁻³, the average density of the composite-material thermal insulation tube improved by 5.7%, and the densification rate increased by 26.5%. This article effectively simulates the CVI process of large-sized C/C composite thermal insulation tubes, providing an important technical reference scheme for the preparation of large-sized C/C composite thermal insulation tubes. Full article

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

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12 pages, 3752 KiB

Open AccessArticle

Effect of Deep Cryogenic Treatment on the Artificial Aging Behavior of 6082 Aluminum Alloy

by Sawei Qiu, Jian Tang, Yiran Tian, Changping Wu, Tuo Ye, Erli Xia and Yuanzhi Wu

Coatings 2024, 14(6), 755; https://doi.org/10.3390/coatings14060755 - 14 Jun 2024

Viewed by 316

Abstract

This study investigates the impact of cryogenic treatment duration on the mechanical properties and microstructural evolution of 6082 aluminum alloy subjected to subsequent artificial aging. Tensile tests were conducted using an electronic universal testing machine, and the microstructure was characterized by employing optical [...] Read more.

This study investigates the impact of cryogenic treatment duration on the mechanical properties and microstructural evolution of 6082 aluminum alloy subjected to subsequent artificial aging. Tensile tests were conducted using an electronic universal testing machine, and the microstructure was characterized by employing optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicate that both the tensile strength and elongation of the alloy first increase and then decrease with the extension of cryogenic treatment duration. The alloy treated with 12 h of cryogenic treatment followed by artificial aging at 180 °C for 8 h achieved a peak strength of 390 MPa. Meanwhile, the alloy treated with 8 h of cryogenic treatment and the same artificial aging process reached a maximum elongation of 13%. All specimens of 6082 aluminum alloy subjected to cryogenic and aging treatments exhibited ductile fracture under room temperature tensile conditions. The size of dimples at the fracture surface first increased and then decreased with increasing cryogenic treatment duration, indicating a transition from deeper to shallower dimples. The cryogenic treatment did not significantly affect the grain size of the alloy, which remained approximately 230 µm on average. Cryogenic treatment facilitated the precipitation of fine, densely distributed precipitates, enhancing the pinning effect of dislocations and thus improving the tensile strength. Additionally, cryogenic treatment increased the dislocation density and promoted the formation of subgrains, while the grain boundary precipitates transitioned from a continuous to a discontinuous distribution, all of which contribute to the enhancement of the plasticity. Full article

(This article belongs to the Special Issue Microstructure, Mechanical and Tribological Properties of Alloys)

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20 pages, 5138 KiB

Open AccessArticle

The Effects of Preharvest Silicon Treatment and Passive MAP on Quality and Shelf Life of White Button Mushrooms in Thermoformed Recycled PET Packaging System

by Tigist T. Shonte, Helen Grogan, Jesus Maria Frias Celayeta, Francesco S. Giordano, Andrew Reynolds, Orla O’Halloran, Lorraine Foley and Shivani Pathania

Coatings 2024, 14(6), 754; https://doi.org/10.3390/coatings14060754 - 14 Jun 2024

Viewed by 370

Abstract

A crop pretreatment with silicon was combined with passive modified atmosphere packaging (PMAP) in a thermoformed recycled PET packaging format as a novel approach to minimize the quality degradation in mushrooms. This study was aimed to evaluate the effects of (a) two preharvest [...] Read more.

A crop pretreatment with silicon was combined with passive modified atmosphere packaging (PMAP) in a thermoformed recycled PET packaging format as a novel approach to minimize the quality degradation in mushrooms. This study was aimed to evaluate the effects of (a) two preharvest treatments, namely preharvest control (PHTC) and preharvest silicon treatment (PHTS) and (b) four packaging lid formats, namely PMAP1: a single hole of 1.1 mm size, PMAP2: two holes of 0.53 mm size, PMAP3: three holes of 0.53 mm size, and PMAPC: OMNI-PW micro perforated cling film as a control on the quality and shelf life of mushrooms during five days of storage at 4 °C and 99.9% RH. The results of the analysis of variance showed that packaging type, storage days, and the double interaction effects of storage days × packaging type had significant effects (p < 0.0001) on the changes in O₂, CO₂, colour L* and a* values, ΔE, total soluble solids (TSS), and the density of mushrooms. Density, electrolyte leakage (EL), and TSS were significantly affected by the double interaction effects of preharvest treatment × packaging type. Overall, PMAP1, PMAP2, and PMAP3 resulted in lower O₂ + higher CO₂ within packages compared with the conventional control. A preharvest silicon treatment had little overall effect. PMAP 1, 2 and 3 had a significantly lower ΔE (=better quality) after 5 days storage compared to PMAPC which had the highest ΔE (lowest quality) overall. PMAP1 and PMAP2 had the lowest EL values compared to PMAP3 and PMAPC. PMAP1, PMAP2, and PMAP3 all gave better TSS levels and density compared to PMAPC. Notably, this study proved that a perforation-mediated MAP design for mushrooms packaged in a thermoformed recycled PET packaging format maintained improved CO₂, lowered O₂, and reduced EL while maintaining TSS and the density of the mushrooms during the storage period. Full article

(This article belongs to the Special Issue Advances in Modified Atmosphere Packaging and Edible Coatings)

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12 pages, 6136 KiB

Open AccessArticle

Microstructure and Properties of Ti6Al4V Surface Processed by Continuous Wave Laser in Different Atmospheres

by Lei Huang, Lei Li, Yanfei Zhao, Yaoyao Liu, Hongyu Zheng, Zhongchen Du and Jian Liu

Coatings 2024, 14(6), 753; https://doi.org/10.3390/coatings14060753 - 14 Jun 2024

Viewed by 302

Abstract

Titanium alloys are considered lightweight alloys and are widely applied across various industries. However, titanium alloys are prone to wearing out or galvanic corrosion. In this paper, Ti6Al4V alloy was scanned by using a continuous laser in different atmospheres to prepare composite hardening [...] Read more.

Titanium alloys are considered lightweight alloys and are widely applied across various industries. However, titanium alloys are prone to wearing out or galvanic corrosion. In this paper, Ti6Al4V alloy was scanned by using a continuous laser in different atmospheres to prepare composite hardening coatings. The scanning speed was varied to adjust the heat input. When the alloy was irradiated in air, a whole coating composed of TiO₂ and TiN was fabricated. With the increase in scanning speed from 10 mm/s to 20 mm/s, the melting area of the surface decreased from about 1.8 mm to 0 mm, but the thickness of the coatings underwent no significant change. When prepared under compressed oxygen with a speed of 10 mm/s, a coating with a thickness of about 60 μm was prepared. In addition, the layered phenomenon occurred, and an N-enriched layer was formed at the bottom of the coating. The coatings were composed of TiO₂, TiN and Ti. With the increase in the scanning speed, the thickness of the coatings decreased obviously. The testing results show that the hardness of samples Ti-A10 and Ti-O10 increased by around 160% and 140% over that of untreated samples, respectively. The anti-corrosion performance of the samples treated via laser scanning was also improved. Full article

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

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17 pages, 21168 KiB

Open AccessArticle

Microstructure and Tribological Properties of HVOF-Sprayed Nanostructured WC-12Co/Fe₃O₄ Coatings

by Wojciech Żórawski, Anna Góral, Otakar Bokuvka, Medard Makrenek and Martin Vicen

Coatings 2024, 14(6), 752; https://doi.org/10.3390/coatings14060752 - 14 Jun 2024

Viewed by 335

Abstract

Due to wear and improper operation, many machine parts become useless, which is why issues of friction and wear remain constantly relevant across all industrial sectors. This paper presents the results of research on the microstructure and properties of a nanostructural composite coating [...] Read more.

Due to wear and improper operation, many machine parts become useless, which is why issues of friction and wear remain constantly relevant across all industrial sectors. This paper presents the results of research on the microstructure and properties of a nanostructural composite coating containing solid lubricant. The coating was deposited from a mixture of nanostructural WC-12Co powder and nanostructural Fe₃O₄ powder using HVOF spraying. Despite significant differences in grain size and density of both powders, the deposited coating consisted of WC-12Co matrix containing evenly distributed Fe₃O₄. The XRD analysis of the coating confirmed the presence of both components and the presence of W₂C, which resulted from the decarburization of WC due to the high temperature during the spraying process. Furthermore, the microstructure analysis of the coatings confirmed that they contained both nanostructural WC and Fe₃O₄ grains that were present in the feedstock. The coefficients of friction, microhardness, and wear of the nanostructured composite coatings were determined using an experimental binomial program. Based on the ANOVA conducted, it was determined that the most significant impact on the friction coefficient is the Fe₃O₄ content in the sprayed mixture, while the oxygen to propane ratio affects the microhardness. For the wear of nanostructural composite coatings, the most important parameter is the spraying distance. Full article

(This article belongs to the Special Issue The Present Status of Thermally Sprayed Composite Coatings)

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11 pages, 902 KiB

Open AccessArticle

The Effect of Different Coating Agents on the Microhardness, Water Sorption, and Solubility of EQUIA Forte^® HT

by Saleh Y. Alqasabi, Ayman M. Sulimany, Thamer Almohareb, Abdullah S. Alayad and Omar A. Bawazir

Coatings 2024, 14(6), 751; https://doi.org/10.3390/coatings14060751 - 13 Jun 2024

Viewed by 279

Abstract

Objective: This study aimed to assess the effect of four different surface-coating agents on the microhardness, water sorption, and solubility of the highly viscous glass ionomer cement EQUIA Forte^® HT. Materials and methods: A total of 100 cylindrical EQUIA Forte^® HT [...] Read more.

Objective: This study aimed to assess the effect of four different surface-coating agents on the microhardness, water sorption, and solubility of the highly viscous glass ionomer cement EQUIA Forte^® HT. Materials and methods: A total of 100 cylindrical EQUIA Forte^® HT samples were examined, with 50 tested for Vickers hardness and the other 50 for water sorption and solubility. For each test, the specimens were divided into five groups (10 specimens/group) according to coating method: Group 1—no coating (control), Group 2—EQUIA Forte^® Coat, Group 3—Single Bond™ Universal Adhesive, Group 4—ExciTE^®F adhesive, and Group 5—petroleum jelly. Data were analyzed using the paired t-test, one-way analysis of variance, and Tukey’s post hoc test for multiple comparisons. Statistical significance was set at p < 0.05. Results: The mean microhardness of the coated groups was significantly higher than that of the uncoated group. Moreover, a significant difference in the microhardness value was detected between the coated groups. Furthermore, EQUIA Forte^® Coat had the highest mean hardness value. The mean water sorption at 7 days showed that EQUIA Forte^® Coat had the lowest values. In terms of water solubility, a statistically significant difference was found between no coating and all groups except EQUIA Forte^®, between Single Bond Universal Adhesive and petroleum jelly, between petroleum jelly and EQUIA Forte Coat, and between EQUIA Forte^® Coat and ExciTE^®F. Conclusions: The study revealed that all coating agents significantly increased the microhardness of EQUIA Forte^® HT, with EQUIA Forte^® Coat showing the highest hardness and the lowest water sorption values. Full article

(This article belongs to the Special Issue Reshaping Dentistry: Coatings and Innovations in Dental Biomaterials)

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20 pages, 9994 KiB

Open AccessArticle

Study on High Temperature Properties of Yttrium-Modified Aluminide Coating on K444 Alloy by Chemical Vapor Deposition

by Hanzhe Yang, Yong Wu, Qingyun Sun, Fu Yang, Chunhuai Xia, Siyao Xia and Jianrong Du

Coatings 2024, 14(6), 750; https://doi.org/10.3390/coatings14060750 - 13 Jun 2024

Viewed by 333

Abstract

This work aims to explore a method of improving the high-temperature oxidation resistance and thermal corrosion resistance of a hollow blade of gas turbine. The yttrium-modified aluminide coating was prepared on the surface of nickel-based superalloy K444 by chemical vapor deposition (CVD). The [...] Read more.

This work aims to explore a method of improving the high-temperature oxidation resistance and thermal corrosion resistance of a hollow blade of gas turbine. The yttrium-modified aluminide coating was prepared on the surface of nickel-based superalloy K444 by chemical vapor deposition (CVD). The microstructure, high temperature oxidation resistance, and thermal corrosion resistance of the modified aluminide coating deposited at 950 °C, 1000 °C, and 1050 °C were compared. The microstructure and morphology of the coatings were observed and analyzed by XRD, SEM, and EDS. The results showed that adding yttrium and changing the deposition temperature had no effect on the double-layer structure (outer layer and diffusion layer) of the coating. Compared with adding yttrium, the deposition temperature had a greater effect on the coating thickness. When the deposition temperature was 1050 °C and the deposition time was 2 h, the thickness of the yttrium-modified aluminide coating increased by 33% compared to that of a single aluminide coating. The high temperature oxidation resistance and thermal corrosion resistance of the three groups of yttrium-modified aluminide coatings are better than that of the single aluminide coating. The resistance to high temperature oxidation and hot corrosion of the yttrium-modified aluminide coating deposited at 1050 °C was better than that of yttrium-modified aluminide coating deposited at 1000 °C, and both were better than that of the modified coating deposited at 950 °C. The higher the deposition temperature, the higher the yttrium content of the coating, the faster the film-forming speed of α-Al₂O₃, and the better the high temperature oxidation resistance and thermal corrosion resistance of the coating. Full article

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

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19 pages, 3640 KiB

Open AccessArticle

Research on the Skidding Resistance and Attenuation Characteristics of Asphalt Pavement Based on Image Recognition-Analysis Strategy

by Ke Zhang, Dianliang Xi, Yu Zhao, Wei Xie, Wei Zhang and Jiantao Gao

Coatings 2024, 14(6), 749; https://doi.org/10.3390/coatings14060749 - 13 Jun 2024

Viewed by 262

Abstract

To accurately evaluate the skidding resistance of asphalt pavements, a texture imaging device was developed to realize the standardized acquisition of pavement images. Based on the gray-level co-occurrence matrix and multifractal theory of texture structure, the influence of segregation degree and gradation type [...] Read more.

To accurately evaluate the skidding resistance of asphalt pavements, a texture imaging device was developed to realize the standardized acquisition of pavement images. Based on the gray-level co-occurrence matrix and multifractal theory of texture structure, the influence of segregation degree and gradation type on the texture properties of asphalt pavement was studied. Meanwhile, a comprehensive evaluation index of skidding resistance was proposed for asphalt pavement. Furthermore, the attenuation characteristics of the anti-skidding performance for asphalt mixture were explored, and the corresponding attenuation model of asphalt pavement was established. The results show that the segregation degree and gradation type significantly affected the texture parameters and anti-skidding performance of asphalt mixture. Specially, with an increase in the segregation degree of coarse aggregate, the parameters of energy, entropy, and multifractal spectrum width gradually increased, whereas the inertial moment gradually decreased. The variation range of the multifractal spectrum difference initially increased and subsequently decreased. For the texture parameters such as energy, entropy, inertial moment, and multifractal spectrum width Δα, the values of the asphalt mixture with larger nominal maximum particle were higher than those of the mixture with smaller nominal maximum particle, whereas the multifractal spectrum difference value showed the opposite law. In addition, the texture parameters of energy, entropy, and multifractal spectrum width exhibited good linear correlation with the texture depth (TD) of asphalt mixtures with various segregation levels and gradation types. The index based on the texture parameters of energy, entropy, and multifractal spectrum width effectively evaluated the skidding resistance of asphalt pavements, which showed the same trend as the TD with the increase of the abrasion number. The achievement provides an effective solution for the evaluation of skidding resistance and attenuation characteristics of asphalt mixtures. Full article

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

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16 pages, 1227 KiB

Open AccessReview

Soft Feel Material Coatings on the Surface of Plastic Products and Their Application Prospects in the Popular Fields: A Review

by Bangzheng Jiang, Yueyang Xu, Lanlan Zhang, Xing Zhou, Hui Zhang, Luqi Liu and Jun Zhao

Coatings 2024, 14(6), 748; https://doi.org/10.3390/coatings14060748 - 13 Jun 2024

Viewed by 327

Abstract

Soft-feel material (mainly polyurethane (PU), silicone rubber (SR), and polyacrylic acid (PAA), etc.) coatings can overcome the drawbacks of common plastic products such as acrylonitrile butadiene styrene copolymer (ABS), polycarbonate (PC), and polypropylene (PP), which have cold, hard, and bright surfaces, achieving warm, [...] Read more.

Soft-feel material (mainly polyurethane (PU), silicone rubber (SR), and polyacrylic acid (PAA), etc.) coatings can overcome the drawbacks of common plastic products such as acrylonitrile butadiene styrene copolymer (ABS), polycarbonate (PC), and polypropylene (PP), which have cold, hard, and bright surfaces, achieving warm, soft, and matte effects, thus greatly improving the quality and price level of the products. Although these coating materials can partially meet the main requirements of the soft feel effect, their comprehensive properties, such as mechanical performance, weather resistance, and foul resistance, still have shortcomings and need to be improved. Besides, there is a lack of in-depth exploration in the literature on the design philosophy and preparation strategies of soft-feel materials. Starting from the mechanism of producing this comfortable feeling and then systematically exploring their application in popular fields with high economic added value, such as mobile phone cases, electronic cigarette cases, cosmetic containers, etc., this article attempts to systematically and meticulously review the research and development progress in the related fields in recent decades and tries to provide an open outlook on their future development directions, e.g., the employment of surface engineering and hybrid materials. This review is expected to provide some rational thinking directions and convenient practical guidance for the rapid and healthy development of soft-feel materials in the research and application fields. Full article

(This article belongs to the Topic Advances in Functional Thin Films)

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