Coatings

17 pages, 7379 KiB

Open AccessArticle

Cracking Resistance of Selected PVD Hard Coatings

by Peter Panjan, Aleksandar Miletić, Aljaž Drnovšek, Pal Terek, Miha Čekada, Lazar Kovačević and Matjaž Panjan

Coatings 2024, 14(11), 1452; https://doi.org/10.3390/coatings14111452 - 14 Nov 2024

Abstract

In this study, we used the depth-sensing indentation technique to determine the cracking resistance of different PVD hard coatings deposited on tool steel substrates. By comparison, with the load–displacement curves, measured at the sites of carbide inclusion and a tempered martensite matrix in [...] Read more.

In this study, we used the depth-sensing indentation technique to determine the cracking resistance of different PVD hard coatings deposited on tool steel substrates. By comparison, with the load–displacement curves, measured at the sites of carbide inclusion and a tempered martensite matrix in the D2 tool steel substrate surface, we observed different fracture mechanisms on TiAlN hard coating prepared by sputtering. Additional information about the deformation and fracture phenomena was obtained from the SEM images of FIB cross-sections of both types of indents. We found that the main deformation mechanism in the coating is the shear sliding along the columnar boundaries, which causes the formation of steps on the substrate surface under individual columns. Using nanoindentation test, we also analyzed the cracking resistance of a set of nl-(Cr,Al)N nanolayer coatings with different Cr/Al atomic ratios, which were sputter deposited in a single batch. From the indentation curves, we determined the loads (F_c) at which the first pop-in appears and compared them with the plasticity index H³/E². A good correlation of both parameters was found. We also compared the indentation curves of the TiAlN coating, which were prepared by cathodic arc evaporation using 1-fold, 2-fold and 3-fold rotation of the substrates. Additionally, on the same set of samples, the fracture toughness measurements were performed by micro-cantilever deflection test. The impact of growth defects on the cracking resistance of the hard coatings was also confirmed. Full article

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

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21 pages, 5832 KiB

Open AccessReview

A Review of the Preparation, Modification, and Applications of Polyetheretherketone Coating

by Yufei Chen, Hongjun Ni, Jae-Jun Park and Shuaishuai Lv

Coatings 2024, 14(11), 1451; https://doi.org/10.3390/coatings14111451 - 14 Nov 2024

Abstract

The progress of research on the preparation of polyetheretherketone (PEEK) coatings is systematically described with emphasis on the three coating preparation methods of thermal spraying, electrophoretic deposition, and melt extrusion coating, and the advantages and disadvantages of these methods and their main applications [...] Read more.

The progress of research on the preparation of polyetheretherketone (PEEK) coatings is systematically described with emphasis on the three coating preparation methods of thermal spraying, electrophoretic deposition, and melt extrusion coating, and the advantages and disadvantages of these methods and their main applications are reviewed. At the same time, research into the modification of PEEK coatings is also introduced, including modification using inorganic materials and chemical modification. Finally, the application of PEEK coatings is introduced, and its future development directions are prospected. Full article

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11 pages, 2737 KiB

Open AccessArticle

Verification of Optimal X-Ray Shielding Properties Based on Material Composition and Coating Design of Shielding Materials

by Seon-Chil Kim, Jae-Han Yun, Hong-Sik Byun and Jian Hou

Coatings 2024, 14(11), 1450; https://doi.org/10.3390/coatings14111450 - 14 Nov 2024

Abstract

Health care workers performing radiography on patients in hospitals typically wear aprons for radiation protection. Protective properties are achieved through a combination of shielding materials and polymers. Various shielding materials are mixed with polymers to prepare composite materials. Numerous methods have been devised [...] Read more.

Health care workers performing radiography on patients in hospitals typically wear aprons for radiation protection. Protective properties are achieved through a combination of shielding materials and polymers. Various shielding materials are mixed with polymers to prepare composite materials. Numerous methods have been devised to design and alter the composition of these materials to improve the shielding performance of aprons. In this study, the shielding performance was analyzed based on the arrangement of shielding materials, the composition of materials (mixed or single), and the fabrication design of the shielding sheets. Various shielding sheets were created using different arrangements of tungsten oxide, bismuth oxide, and barium sulfate, and their shielding efficacy was compared. The atomic number and density of the shielding material directly affect the shielding property. The effectiveness of the composite sheet increased by more than 5% when positioned close to the X-ray tube. Sheets fabricated from materials separated by type, rather than mixed, exhibited a greater X-ray shielding effectiveness because of their layered structure. Therefore, structural design considerations such as linings, outer layers, and inner layers of protective sheets should be considered for effective shielding in medical institutions. Full article

(This article belongs to the Special Issue Functional Polymer Coatings and Films: Synthesis, Properties and Applications)

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13 pages, 7529 KiB

Open AccessArticle

Ammonia Plasma Surface Treatment for Enhanced Cu–Cu Bonding Reliability for Advanced Packaging Interconnection

by Ho Jeong Jeon and Sang Jeen Hong

Coatings 2024, 14(11), 1449; https://doi.org/10.3390/coatings14111449 - 14 Nov 2024

Abstract

With the emergence of 3D stacked semiconductor products, such as high-bandwidth memory, bonding-interface reliability cannot be overemphasized. The condition of the surface interface before bonding is important and can substantially affect product reliability. Plasma technology can be used to control the state of [...] Read more.

With the emergence of 3D stacked semiconductor products, such as high-bandwidth memory, bonding-interface reliability cannot be overemphasized. The condition of the surface interface before bonding is important and can substantially affect product reliability. Plasma technology can be used to control the state of a bonding interface, but various factors of interest, such as surface roughness, chemical bonding state, and surface cleanliness, may depend on the type of gaseous plasma. These factors may increase voids at the interface, which can jeopardize the product reliability. In this study, NH₃ plasma surface treatment is investigated and compared with the conventionally preferred surface treatment under Ar plasma. Under the latter method, specific anomalies occurred and led to void formation at the interface during bonding. By contrast, NH₃ plasma treatment maintained higher uniformity, higher overall surface conditions, and a smooth reduction process. Furthermore, the formation of a nitride passivation layer effectively inhibited the oxidation of the metal surface, and the flat surface resulted in the decrease in voids compared with the Ar plasma treatment after the copper–copper bonding. From the experimental analysis, we achieved a 12% reduction in resistance in the samples treated with NH₃ plasma treatment due to the suppression of surface oxidation. However, it is unfortunate that the shear strength in the experimental samples treated with NH₃ plasma treatment needs to be further improved. Full article

(This article belongs to the Special Issue Application of Advanced Plasma Technology in Coatings, Films and Etching)

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Graphical abstract

8 pages, 3741 KiB

Open AccessArticle

Etching Processing of InGaAs/InAlAs Quantum Cascade Laser

by Qi Wu, Yana Zhu, Dongxin Xu, Zaijin Li, Yi Qu, Zhongliang Qiao, Guojun Liu, Zhibin Zhao, Lina Zeng, Hao Chen and Lin Li

Coatings 2024, 14(11), 1448; https://doi.org/10.3390/coatings14111448 - 13 Nov 2024

Abstract

The 3–5 μm mid-infrared band is the atmospheric window band, where there are absorption peaks of many molecules. It plays an important role in trace gas detection, directional infrared countermeasures, biomedicine, and free-space optical communications. The wet etching process of the designed InGaAs/InAlAs [...] Read more.

The 3–5 μm mid-infrared band is the atmospheric window band, where there are absorption peaks of many molecules. It plays an important role in trace gas detection, directional infrared countermeasures, biomedicine, and free-space optical communications. The wet etching process of the designed InGaAs/InAlAs quantum cascade laser with superlattice structure was explored to provide a good experimental basis for the research and development of lasers. The HBr:HNO₃:H₂O series of etching solutions were selected for corrosion experiments, and the surface morphology was observed by scanning electron microscopy (SEM) and metallographic microscopy to obtain the corrosion rate of the etching solution. The experimental results show that the etching liquid ratio is HBr:HNO₃:H₂O = 1:1:10, and the etching rate is 0.6 μm/min. A quantum cascade laser that works continuously at room temperature was prepared, with an injection strip width of 7 μm, a cavity length of 4mm, and an operating temperature of 20 °C. The device works in continuous mode (CW), with a maximum continuous output power of about 186 mW, a threshold current of about 0.4 A, a threshold current density of about 1.428 kA/cm², a device center wavelength of about 4424 nm, a side mode suppression ratio of 28 dB, and a spectrum full width at half maximum of 2 nm. Full article

(This article belongs to the Special Issue Advancements in Lasers: Applications and Future Trends)

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13 pages, 6727 KiB

Open AccessArticle

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

by Thevika Balakumar, Afsaneh Edrisy and Reza A. Riahi

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

Abstract

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

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

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

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20 pages, 19859 KiB

Open AccessArticle

The Influence of the Plasma Electrolytic Oxidation Parameters of the Mg-AZ31B Alloy on the Micromechanical and Sclerometric Properties of Oxide Coatings

by Mateusz Niedźwiedź, Marek Bara, Joanna Korzekwa, Adrian Barylski and Sławomir Kaptacz

Coatings 2024, 14(11), 1446; https://doi.org/10.3390/coatings14111446 - 13 Nov 2024

Abstract

This manuscript presents the influence of manufacturing process parameters (peak current density, frequency, process time) on the micromechanical and sclerometric properties of oxide coatings. These parameters were selected based on Hartley’s experimental design, considering three variables at three levels. The coatings were produced [...] Read more.

This manuscript presents the influence of manufacturing process parameters (peak current density, frequency, process time) on the micromechanical and sclerometric properties of oxide coatings. These parameters were selected based on Hartley’s experimental design, considering three variables at three levels. The coatings were produced on the AZ31B magnesium alloy using the plasma electrolytic oxidation (PEO) method. A trapezoidal voltage waveform and an alkaline, two-component electrolyte were used during the process. The micromechanical and sclerometric properties were assessed by measuring the hardness (H_IT) and Young’s modulus (E_IT) and determining three critical loads: Lc1 (the critical load at which the first coating damage occurred—Hertz tensile cracks within the scratch), Lc2 (the critical load causing the first cohesive damage to the coating), and Lc3 (the load at which the coating was completely destroyed). Scratch tests were supplemented with profilographometric measurements, which were used to generate isometric images. To identify the relationship between micromechanical and sclerometric properties and the manufacturing parameters, statistical analysis was performed. Research has demonstrated that the plasma electrolytic oxidation (PEO) process improves the micromechanical and adhesive properties of oxide coatings on the AZ31B magnesium alloy. The key process parameters, including peak current density, frequency, and duration, are crucial in determining these enhanced properties. Full article

(This article belongs to the Special Issue Application of Advanced Plasma Technology in Coatings, Films and Etching)

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18 pages, 8193 KiB

Open AccessArticle

Influence of Chitosan/Lycopene on Myoglobin and Meat Quality of Beef During Storage

by Yan Hu, Meijuan Xu, Xueqin Gao and Zhenhui Zhang

Coatings 2024, 14(11), 1445; https://doi.org/10.3390/coatings14111445 - 13 Nov 2024

Abstract

Myoglobin (Mb) is easily oxidized, which causes the discoloration of meat. In addition, various microorganisms are responsible for meat spoilage. Chitosan and lycopene can be used to protect the color and extend the shelf life of meat. In this study, a series of [...] Read more.

Myoglobin (Mb) is easily oxidized, which causes the discoloration of meat. In addition, various microorganisms are responsible for meat spoilage. Chitosan and lycopene can be used to protect the color and extend the shelf life of meat. In this study, a series of coatings with different ratios (1:0, 3:1, 1:1, 1:3, 0:1) of chitosan to lycopene were prepared. Beef was treated with different coatings. The changes in color, relative content of different Mb forms, thiobarbituric acid-reactive substances (TBARS), sulfhydryl content, carbonyl content, microbial count, cooking loss, and sensory evaluation during storage were investigated. The results showed that after 8 days, compared to the control, the relative content of oxymyoglobin (OxyMb), the lightness (L*) value, the redness (a*) value, and the composite index (CI) value of beef treated with chitosan/lycopene of 1:3 (w:w, the concentration of lycopene was 0.75% (w:v)) increased by 6.34%, 34.73%, 67.25%, and 116.27%, respectively. Meanwhile, the relative content of metmyoglobin (MetMb) and the yellowness (b*) value decreased by 11.67% and 23.21%, respectively. Additionally, beef treated with chitosan/lycopene of 1:3 also performed well in protein oxidation, fat oxidation, microbial count, and cooking loss. Generally, the beef treated with chitosan/lycopene of 1:3 showed the best comprehensive quality. The coating was suitable for application in beef. These results are promising for food preservation. Full article

(This article belongs to the Special Issue Advanced Coatings and Films for Food Packing and Storage, 2nd Edition)

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20 pages, 4309 KiB

Open AccessArticle

Flow Field of Supersonic Oxygen Jet Generated by Various Wear Lengths at the Laval Nozzle Exit

by Fuhai Liu, Songchao Lu, Sibao Zeng, Rong Zhu, Guangsheng Wei and Kai Dong

Coatings 2024, 14(11), 1444; https://doi.org/10.3390/coatings14111444 - 13 Nov 2024

Abstract

As a main apparatus, the oxygen lance is used to deliver the oxygen element and transfer kinetic energy into the molten bath in the steelmaking process. However, the Laval nozzle exit would be gradually worn out during the service life, which suppresses the [...] Read more.

As a main apparatus, the oxygen lance is used to deliver the oxygen element and transfer kinetic energy into the molten bath in the steelmaking process. However, the Laval nozzle exit would be gradually worn out during the service life, which suppresses the performance of the oxygen lance. This paper investigated three different wear length (L_w) conditions at the exit of the Laval nozzle through numerical simulations and high-temperature experiments with various oxygen flow rates. The result showed that the entrainment of the ambient gas was the key factor of the wear phenomenon for the Laval nozzle exit. The maximum total temperature of the gas phase at the Laval nozzle exit formed by the L_w of 0 mm, 2 mm, and 4 mm were 300 K, 959 K, and 1700 K, respectively. Thus, by increasing the L_w value, the total temperature of the gas phase was rapidly improved at the exit of the Laval nozzle, which further accelerated the wear phenomenon at the exit of the Laval nozzle. Besides, axial velocities at the end of the potential core formed by the L_w of 0 mm, 2 mm, and 4 mm were 483.7 m/s, 480.0 m/s, and 478.7 m/s, respectively. As a result, the wear phenomenon reduced the impaction ability of the oxygen jet, which suppressed the impaction depth and radius, resulting in a smaller droplet generation rate. Full article

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

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11 pages, 5038 KiB

Open AccessArticle

Experimental Study on the Pelleting and Coating Performance of Red Clover Seeds

by Jing Xue, Xuejie Ma, Zhanfeng Hou, Mengjun Guo and Xiaoming Zhang

Coatings 2024, 14(11), 1443; https://doi.org/10.3390/coatings14111443 - 13 Nov 2024

Abstract

This study aimed to optimize the pelleting and coating process for red clover seeds, addressing the issue of low pelleting success rates. Through theoretical analysis and experimental research, coating pan fill rate, powder supply quantity, and pelleting time were identified as key factors [...] Read more.

This study aimed to optimize the pelleting and coating process for red clover seeds, addressing the issue of low pelleting success rates. Through theoretical analysis and experimental research, coating pan fill rate, powder supply quantity, and pelleting time were identified as key factors influencing the pelleting success rate. Single-factor experiments were conducted to investigate the effects of these parameters on the quality of red clover seed pelleting and coating. Based on these results, orthogonal trials were carried out, and response surface analysis was employed to reveal the influence patterns and interactions of each factor. The research results indicate that the factors affecting the pelleting success rate, ranked in order of importance, are coating pan fill rate, pelleting time, and powder supply quantity. Through mathematical model optimization, the optimal combination of process parameters was determined to be coating pan fill rate of 35.9%, powder supply quantity of 160.2 g, and pelleting time of 6.9 s. Under these conditions, a pelleting success rate of 94.3% was achieved in validation experiments. This study provides a theoretical foundation and practical guidance for optimizing the pelleting and coating process of red clover seeds, which is significant for improving seed coating quality and promoting red clover cultivation. Full article

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9 pages, 6360 KiB

Open AccessArticle

The Study of the Etching Resistance of YOF Coating Deposited by Atmospheric Plasma Spraying in HBr/O₂ Plasma

by Zaifeng Tang, Bing Wang, Kaiqu Ang, Xiaojun Jiang, Yuwei Wang, Jin Xu, Hua Meng, Hongli Chen, Ying Shi and Linjun Wang

Coatings 2024, 14(11), 1442; https://doi.org/10.3390/coatings14111442 - 13 Nov 2024

Abstract

Yttrium oxyfluoride (YOF) coatings with different oxygen content were prepared using atmospheric plasma spraying (APS) technology. The etching resistance of the coatings in HBr/O₂ plasma was investigated. Shifts in diffraction peaks of the X-ray diffraction, along with XPS analysis conducted before and [...] Read more.

Yttrium oxyfluoride (YOF) coatings with different oxygen content were prepared using atmospheric plasma spraying (APS) technology. The etching resistance of the coatings in HBr/O₂ plasma was investigated. Shifts in diffraction peaks of the X-ray diffraction, along with XPS analysis conducted before and after etching, demonstrated that Br ions could replace O and F ions and fill the oxygen vacancies after exposure to HBr/O₂ plasma, which is supported by the first-principles calculations. Br ions formed a protective layer on the surface of the YOF coating, slowing down further etching by Br ions. By adjusting the oxygen mass fraction in YOF powder, the oxygen vacancy concentration and Br ion filling were regulated to enhance etching resistance. YOF coatings with 6% oxygen content exhibited improved etching resistance compared to YOF coatings with 3% and 9% oxygen content. This improvement was primarily due to the increased Br ion concentration. These findings provide a new approach for developing coatings with enhanced etching resistance. Full article

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13 pages, 8022 KiB

Open AccessArticle

On the Effect of Randomly Oriented Grain Growth on the Structure of Aluminum Thin Films Deposited via Magnetron Sputtering

by Vagelis Karoutsos, Nikoletta Florini, Nikolaos C. Diamantopoulos, Christina Balourda, George P. Dimitrakopulos, Nikolaos Bouropoulos and Panagiotis Poulopoulos

Coatings 2024, 14(11), 1441; https://doi.org/10.3390/coatings14111441 - 13 Nov 2024

Abstract

The microstructure of aluminum thin films, including the grain morphology and surface roughness, are key parameters for improving the thermal or electrical properties and optical reflectance of films. The first step in optimizing these parameters is a thorough understanding of the grain growth [...] Read more.

The microstructure of aluminum thin films, including the grain morphology and surface roughness, are key parameters for improving the thermal or electrical properties and optical reflectance of films. The first step in optimizing these parameters is a thorough understanding of the grain growth mechanisms and film structure. To investigate these issues, thin aluminum films with thicknesses ranging from 25 to 280 nm were coated on SiO_x/Si substrates at ambient temperature under high-vacuum conditions and a low argon pressure of 3 × 10⁻³ mbar (0.3 Pa) using the radio frequency magnetron sputtering method. Quantitative analyses of the surface roughness and nanograin characteristics were conducted using atomic force microscopy (AFM), transmission electron microscopy (TEM), and X-ray diffraction. Changes in specular reflectance were measured using ultraviolet–visible and near-infrared spectroscopy. The low roughness values obtained from the AFM images resulted in high film reflectivity, even for thicker films. TEM and AFM results indicate monomodal, randomly oriented grain growth without a distinct columnar or spherical morphology. Using TEM cross-sectional images and the dependence of the grain size on the film thickness, we propose a grain growth mechanism based on the diffusion mobility of aluminum atoms through grain boundaries. Full article

(This article belongs to the Section Thin Films)

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11 pages, 886 KiB

Open AccessArticle

Energy Loss in Frictional Hertzian Contact Subjected to Two-Dimensional Cyclic Loadings

by Young Ju Ahn

Coatings 2024, 14(11), 1440; https://doi.org/10.3390/coatings14111440 - 13 Nov 2024

Abstract

We investigate the effect of three different harmonically varying loads as a function of the friction coefficient on energy loss in a three-dimensional discrete uncoupled frictional contact problem. Three loading cases include (1) a normal force is constant and a tangential force varies, [...] Read more.

We investigate the effect of three different harmonically varying loads as a function of the friction coefficient on energy loss in a three-dimensional discrete uncoupled frictional contact problem. Three loading cases include (1) a normal force is constant and a tangential force varies, (2) normal and tangential forces both vary, but the loading and unloading curves are identical, and (3) normal and tangential forces both vary, but the loading and unloading curves are different. For a higher coefficient of friction, three loading cases show different characteristics. If a normal force is constant and a tangential force varies, there is always some slip, but dissipation tends asymptotically to zero at large coefficient of friction. If normal and tangential forces both vary, but the loading and unloading curves are identical, there is no slip and no dissipation above a critical coefficient of friction. If the loading and unloading curves are different, dissipation occurs for all values of the coefficient of friction, and we expect that the dissipation is asymptotic to the relaxation damping value as the coefficient of friction approaches infinity. For lowering coefficient of friction, the three loading cases show similar behavior. Dissipation increases and reaches a maximum just before a state where gross slip is possible. Full article

(This article belongs to the Special Issue Advanced Wear-Resistant Materials and Coatings)

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20 pages, 1612 KiB

Open AccessArticle

Determination of Optical and Structural Parameters of Thin Films with Differently Rough Boundaries

by Ivan Ohlídal, Jiří Vohánka, Jan Dvořák, Vilma Buršíková and Petr Klapetek

Coatings 2024, 14(11), 1439; https://doi.org/10.3390/coatings14111439 - 12 Nov 2024

Abstract

The optical characterization of non-absorbing, homogeneous, isotropic polymer-like thin films with correlated, differently rough boundaries is essential in optimizing their performance in various applications. A central aim of this study is to derive the general formulae necessary for the characterization of such films. [...] Read more.

The optical characterization of non-absorbing, homogeneous, isotropic polymer-like thin films with correlated, differently rough boundaries is essential in optimizing their performance in various applications. A central aim of this study is to derive the general formulae necessary for the characterization of such films. The applicability of this theory is illustrated through the characterization of a polymer-like thin film deposited by plasma-enhanced chemical vapor deposition onto a silicon substrate with a randomly rough surface, focusing on the analysis of its rough boundaries over a wide range of spatial frequencies. The method is based on processing experimental data obtained using variable-angle spectroscopic ellipsometry and spectroscopic reflectometry. The transition layer is considered at the lower boundary of the polymer-like thin film. The spectral dependencies of the optical constants of the polymer-like thin film and the transition layer are determined using the Campi–Coriasso dispersion model. The reflectance data are processed using a combination of Rayleigh–Rice theory and scalar diffraction theory in the near-infrared and visible spectral ranges, while scalar diffraction theory is used for the processing of reflectance data within the ultraviolet range. Rayleigh–Rice theory alone is sufficient for the processing of the ellipsometric data across the entire spectral range. We accurately determine the thicknesses of the polymer-like thin film and the transition layer, as well as the roughness parameters of both boundaries, with the root mean square (rms) values cross-validated using atomic force microscopy. Notably, the rms values derived from optical measurements and atomic force microscopy show excellent agreement. These findings confirm the reliability of the optical method for the detailed characterization of thin films with differently rough boundaries, supporting the applicability of the proposed method in high-precision film analysis. Full article

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11 pages, 3979 KiB

Open AccessArticle

Development and Performance of ZnO/MoS₂ Gas Sensors for NO₂ Monitoring and Protection in Library Environments

by Jia Wang, Yuting Xu, Canxin Tian, Yunjiang Yu and Changwei Zou

Coatings 2024, 14(11), 1438; https://doi.org/10.3390/coatings14111438 - 12 Nov 2024

Abstract

The presence of harmful oxidizing gases accelerates the oxidation of cellulose fibers in paper, resulting in reduced strength and fading ink. Therefore, the development of highly sensitive NO₂ gas sensors for monitoring and protecting books holds significant practical value. In this manuscript, [...] Read more.

The presence of harmful oxidizing gases accelerates the oxidation of cellulose fibers in paper, resulting in reduced strength and fading ink. Therefore, the development of highly sensitive NO₂ gas sensors for monitoring and protecting books holds significant practical value. In this manuscript, ZnO/MoS₂ composites were synthesized using sodium molybdate and thiourea as raw materials through a hydrothermal method. The morphology and microstructure were characterized by X-ray diffraction analysis (XRD), energy dispersive spectroscopy (EDS), field emission scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The ZnO/MoS₂ composite exhibited a flower-like structure, with ZnO nanoparticles uniformly attached to the surface of MoS₂, demonstrating advantages such as high specific surface area and good uniformity. The gas sensitivity of the ZnO/MoS₂ nanocomposites reached its peak at 260 °C, with a sensitivity value around 3.5, which represents an improvement compared to pure ZnO, while also enhancing sensitivity. The resistance of the ZnO/MoS₂ gas sensor remained relatively stable in air, exhibiting short response times during transitions between air and NO₂ environments while consistently returning to a stable state. In addition to increasing adsorption capacity and improving light utilization efficiency, the formation of hetero-junctions at the ZnO-MoS₂ interface creates an internal electric field that effectively promotes the rapid separation of photo-generated charge carriers within ZnO, thereby extending carrier lifetime. Full article

(This article belongs to the Special Issue Surface Modified Nanoparticles: For Gas and Chemical Sensors)

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16 pages, 10754 KiB

Open AccessArticle

Unveiling Frequency-Dependent Electromechanical Dynamics in Ferroelectric BaTiO₃ Nanofilm with a Core-Shell Structure

by Mingran Zhang, Rui Ma, Jianqiang Zhou, Yuanxiang Zhang, Jie Wang and Shengbin Weng

Coatings 2024, 14(11), 1437; https://doi.org/10.3390/coatings14111437 - 12 Nov 2024

Abstract

Diverse domain patterns significantly influence the nonlinear electromechanical behaviors of ferroelectric nanomaterials, with polarization switching under strong electric fields being inherently a frequency-dependent phenomenon. Nevertheless, research in this area remains limited. In this study, we present a phase-field investigation of frequency-dependent electromechanical dynamics [...] Read more.

Diverse domain patterns significantly influence the nonlinear electromechanical behaviors of ferroelectric nanomaterials, with polarization switching under strong electric fields being inherently a frequency-dependent phenomenon. Nevertheless, research in this area remains limited. In this study, we present a phase-field investigation of frequency-dependent electromechanical dynamics of a polycrystalline BaTiO₃ nanofilm with a core-shell structure, subjected to applied frequencies ranging from 1 to 80 kHz. Our findings elucidate the microstructural mechanisms underlying the electromechanical behaviors observed in these materials. The effect of the grain size and the strains effect are also taken into account. Hysteresis and butterfly loops exhibit a marked change in shape as the frequency changes. We discuss the underlying domain-switching dynamics as a basis for evaluating such frequency-dependent properties. In addition, we examine the scaling behaviors of the dynamic hysteresis and the influence of grain boundaries on the domain structure. We can also observe from hysteresis loops that the remnant polarization and coercive field significantly diminish when grain sizes decrease from 60 to 5 nm. A smaller grain size of the nanofilm yields a larger percentage of the dielectric grain boundary, which “dilutes” the overall ferroelectricity of the film. A vortex domain structure is more likely to form at low frequency and a small grain size. Full article

(This article belongs to the Special Issue Synthesis, Properties and Application of Thin Films, Nanofilms and Nanocrystals)

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17 pages, 7399 KiB

Open AccessArticle

Micro-Scale Fracture Characteristics of Emulsified Asphalt Cold Recycled Mixture Based on Discrete Element Method

by Yanhai Yang, Yumeng Chen, Baichuan Li and Ye Yang

Coatings 2024, 14(11), 1436; https://doi.org/10.3390/coatings14111436 - 12 Nov 2024

Abstract

Asphalt pavement often experiences structural failure due to repeated vehicle loading. The discrete element method (DEM) model was established based on the semicircle bending test (SCB) to investigate the fracture damage mechanism of emulsified asphalt cold recycled mixture (CRME) under loading. The micro-mechanical [...] Read more.

Asphalt pavement often experiences structural failure due to repeated vehicle loading. The discrete element method (DEM) model was established based on the semicircle bending test (SCB) to investigate the fracture damage mechanism of emulsified asphalt cold recycled mixture (CRME) under loading. The micro-mechanical parameters of CRME were determined through a reliable validation process using the uniaxial compression static creep test. The microscopic fracture characteristics of CRME were investigated through the load-displacement curve, stress distribution, and force chain distribution. The fracture energy was used as the evaluation index to analyze the influence of prefabricated notch length and aggregate gradation on the fracture performance of CRME. The results indicate that the emulsified asphalt mortar-aggregate interface was the critical weak position of the mixture fracture; the failure of the tension chain was the main destructional form of the SCB test. The development of cracks affected the stress concentration phenomenon and stress concentration level of the mixture. Fine-grained mixture exhibited crack resistance. The number and length of cracks were affected by gradation. As the prefabricated notch length increased, the influence gradually diminished. The research results could provide theoretical and data support for the design of CRME. Full article

(This article belongs to the Section Thin Films)

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11 pages, 2628 KiB

Open AccessArticle

Design and Corrosion Resistance Performance of Nano-Multilayer Coatings for the Protection of Breathing Gas Cylinders Used in Diving

by Feng Yuan, Yunjiang Yu, Yuekai Li, Yanxiong Xiang and Changwei Zou

Coatings 2024, 14(11), 1435; https://doi.org/10.3390/coatings14111435 - 12 Nov 2024

Abstract

Seamless gas cylinders for diving exhibit excellent low-temperature impact performance, lightweight characteristics, and good corrosion resistance, making them widely applicable in underwater activities. However, during use, the peeling of paint or corrosion on the surface of these cylinders poses a significant threat to [...] Read more.

Seamless gas cylinders for diving exhibit excellent low-temperature impact performance, lightweight characteristics, and good corrosion resistance, making them widely applicable in underwater activities. However, during use, the peeling of paint or corrosion on the surface of these cylinders poses a significant threat to their safety. In this study, environmentally friendly arc ion plating technology was used to deposit TiBN, CrAlN, and nano-multilayer coatings of CrAlN/TiBN. The surface morphology, tribological properties, and corrosion resistance of these coatings were investigated. The results indicated that both CrAlN and CrAlN/TiBN coatings possess fewer droplets, pinholes, and pits, and the cross-section of the CrAlN/TiBN coating exhibits a denser structure. The preferred orientation for TiBN was identified as TiB₂ (101), while that for CrAlN was Cr(Al)N (200), with the preferred orientation for CrAlN/TiBN being TiB₂ (101). The friction measurements revealed that the lowest coefficient was observed in the CrAlN/TiBN coating (0.489), followed by CrAlN (0.491) and then TiBN (0.642). Electrochemical tests conducted in artificial seawater demonstrated that the self-corrosion potential was highest for the CrAlN/TiBN coating, followed by CrAlN and lastly TiBN. The developed TiBN-based nano-multilayer coatings hold substantial application value in protecting seamless gas cylinders used in diving. 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, 7142 KiB

Open AccessArticle

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

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

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

Abstract

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

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

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

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