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Coatings, Volume 11, Issue 12 (December 2021) – 136 articles

Cover Story (view full-size image): As the population ageing phenomenon intensifies, the demands for orthopedic and dental implants increase rapidly. Meanwhile, more requirements for these implants were put forward. Ti alloys present charming comprehensive properties that make them the ideal choice in orthopedic and dental applications. To mimick the structure and the elastic modulus of human bone, β-Ti alloys with different porous structures were developed by surface modified technologies. The incorporation of functional particles on β-Ti surface endowed the bacterial activity and bone regeneration to overcome infection. The successful development of β-Ti alloys is beneficial for clinical surgery in the orthopedic and dental fields. View this paper.
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Article
Effect of Conventional and Electronic Cigarettes Smoking on the Color Stability and Translucency of Tooth Colored Restorative Materials: An In Vitro Analysis
Coatings 2021, 11(12), 1568; https://doi.org/10.3390/coatings11121568 - 20 Dec 2021
Cited by 2 | Viewed by 967
Abstract
This in vitro study compared the effects of conventional and electronic cigarettes on the aesthetics (color stability and translucency) of two types of composite resins: micro and nano-hybrid. Methods: A total of 120 specimens from two different composite materials Filtek Z250 XT (Nano-hybrid, [...] Read more.
This in vitro study compared the effects of conventional and electronic cigarettes on the aesthetics (color stability and translucency) of two types of composite resins: micro and nano-hybrid. Methods: A total of 120 specimens from two different composite materials Filtek Z250 XT (Nano-hybrid, 3M) and Filtek Z250 (Micro-hybrid, 3M) were divided into four groups (n = 30); shade A2 was used. The samples were exposed to conventional and electronic cigarette smoke via a custom made chamber device. The color values and measurements were recorded using a spectrophotometer before and after the exposure. The color and translucency were evaluated using the three-dimensional CIE Lab. Results: There was a significant change in the color (ΔE) and the translucency parameter (TP) in all of the specimens exposed to electronic cigarettes and conventional cigarettes. The results showed that the highest ΔE mean is for the nano-hybrid composite exposed to conventional cigarettes with 1.74 ΔE while the same material is 0.64 under the electronic cigarettes and the difference is significant with (p < 0.05). The micro-hybrid composite data showed less changes in color under both exposures with 0.85 ΔE mean under the conventional cigarette smoke and 0.48 under the electronic cigarette smoke with (p < 0.004). Conclusions: The conventional cigarette smoke has more effect on the color stability of the composite resins than electronic cigarettes. From a clinical point of view, the effect of smoke exposure on the tested specimens’ color, for the time duration to which the specimens were exposed, were moderate (ΔE < 2). The micro-hybrid composites showed better color stability as compared to the nano-hybrid composites. Full article
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Article
Tribo-Behavior and Corrosion Properties of Welded 304L and 316L Stainless Steel
Coatings 2021, 11(12), 1567; https://doi.org/10.3390/coatings11121567 - 20 Dec 2021
Cited by 1 | Viewed by 860
Abstract
The present study investigates the electrochemical corrosion response and tribo-behavior of 304L and 316L stainless steel welded by gas metal arc welding (GMAW), which offered a high deposition rate. During this research, the metallurgically prepared welded samples were subjected to a tribological test [...] Read more.
The present study investigates the electrochemical corrosion response and tribo-behavior of 304L and 316L stainless steel welded by gas metal arc welding (GMAW), which offered a high deposition rate. During this research, the metallurgically prepared welded samples were subjected to a tribological test and a corrosion test. The wear results were favorable for 316L steel, and it showed a lower coefficient of friction than the 304L specimen. These samples also underwent characterization studies, such as X-ray diffractometry (XRD) and scanning electron microscopy (SEM), to identify the different phases obtained on the cooling of the weld pool. Finally, both specimens were compared against their mechanical properties. Owing to the above properties, the 316L sample showed lasting durability, as compared to the 304L steel. The primary compositional difference is the higher presence of molybdenum and chromium in the 316L steel, compared to the 304L stainless steel. Full article
(This article belongs to the Special Issue Environmental Corrosion of Metals and Its Prevention)
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Article
Comparative Study of Structures and Properties of Detonation Coatings with α-Al2O3 and γ-Al2O3 Main Phases
Coatings 2021, 11(12), 1566; https://doi.org/10.3390/coatings11121566 - 20 Dec 2021
Viewed by 918
Abstract
This study is aimed at obtaining a coating of aluminum oxide containing α-Al2O3 as the main phase by detonation spraying, as well as a comparative study of the structural, tribological and mechanical properties of coatings with the main phases of [...] Read more.
This study is aimed at obtaining a coating of aluminum oxide containing α-Al2O3 as the main phase by detonation spraying, as well as a comparative study of the structural, tribological and mechanical properties of coatings with the main phases of α-Al2O3 and γ-Al2O3. It was experimentally revealed for the first time that the use of propane as a combustible gas and the optimization of the technological regime of detonation spraying leads to the formation of an aluminum oxide coating containing α-Al2O3 as the main phase. Tribological tests have shown that the coating with the main phase of α-Al2O3 has a low value of wear volume and coefficient of friction in comparison with the coating with the main phase of γ-Al2O3. It was also determined that the microhardness of the coating with the main phase of α-Al2O3 is 25% higher than that of the coatings with the main phase of γ-Al2O3. Erosion resistance tests have shown (evaluated by weight loss) that the coating with α-Al2O3 phase is erosion-resistant compared to the coating with γ-Al2O3 (seen by erosion craters). However, the coating with the main phase of γ-Al2O3 has a high value of adhesion strength, which is 2 times higher than that of the coating with the main phase of α-Al2O3. As the destruction of coatings by the primary phase, α-Al2O3 began at low loads than the coating with the main phase γ-Al2O3. The results obtained provide the prerequisites for the creation of wear-resistant, hard and durable layered coatings, in which the lower layer has the main phase of γ-Al2O3, and the upper layer has the main phase of α-Al2O3. Full article
(This article belongs to the Special Issue New Advances in Thermal Spraying)
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Article
Effect of Charge Voltage on the Microstructural, Mechanical, and Tribological Properties of Mo–Cu–V–N Nanocomposite Coatings
Coatings 2021, 11(12), 1565; https://doi.org/10.3390/coatings11121565 - 20 Dec 2021
Cited by 1 | Viewed by 963
Abstract
As an important high-power impulse magnetron sputtering (HIPIMS) parameter, charge voltage has a significant influence on the microstructure and properties of hard coatings. In this work, the Mo–Cu–V–N coatings were prepared at various charge voltages using HIPIMS technique to study their mechanical and [...] Read more.
As an important high-power impulse magnetron sputtering (HIPIMS) parameter, charge voltage has a significant influence on the microstructure and properties of hard coatings. In this work, the Mo–Cu–V–N coatings were prepared at various charge voltages using HIPIMS technique to study their mechanical and tribological properties. The microstructure was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The mechanical and tribological properties were investigated by nano-indentation and ball-on-disc tribometer. The results revealed that all the coatings showed a solid-solution phase of B1-MoVN, the V atoms dissolved into face-centered cubic (FCC) B1-MoN lattice by partial substitution of Mo, and formed a solid-solution phase. Even at a high Cu content (~8.8 at. %), the Cu atoms existed as an amorphous phase. When the charge voltage increased, more energy was put into discharge, and the microstructure changed from coarse structure into dense columnar structure, resulting in the highest hardness of 28.2 GPa at 700 V. An excellent wear performance with low friction coefficient of 0.32 and wear rate of 6.3 × 10−17 m3/N·m was achieved at 750 V, and the wear mechanism was dominated by mild abrasive and tribo-oxidation wear. Full article
(This article belongs to the Topic Inorganic Thin Film Materials)
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Article
Ultra-Sensitive Biosensor with Simultaneous Detection (of Cancer and Diabetes) and Analysis of Deformation Effects on Dielectric Rods in Optical Microstructure
Coatings 2021, 11(12), 1564; https://doi.org/10.3390/coatings11121564 - 20 Dec 2021
Cited by 17 | Viewed by 1152
Abstract
This study proposes a refractive index sensor for the simultaneous detection of cancer and diabetes based on photonic crystals (PhC). The proposed PhC composed of silicon rods in the air bed arranged in a hexagonal lattice forms the fundamental structure. Two tubes are [...] Read more.
This study proposes a refractive index sensor for the simultaneous detection of cancer and diabetes based on photonic crystals (PhC). The proposed PhC composed of silicon rods in the air bed arranged in a hexagonal lattice forms the fundamental structure. Two tubes are used to place the cancerous or diabetic samples for measurement. The sensor’s transmission characteristics are simulated and analyzed by solving Maxwell’s electromagnetic equations using the finite-difference time-domain approach for samples being studied. Therefore, diabetes and cancer are detected according to the changes in the refractive index of the samples using the laser source centered at 1550 nm. Considering the findings, the sensor’s geometry changes to adjust the suggested sensitivity and quality factor of structure. According to the results, transmission power ranges between 91 and 100% based on the sample. Moreover, sensitivity ranges from 1294 to 3080 nm/RIU and the maximum Figure of Mertie is nearly FOM = 1550.11 ± 150.11 RIU−1 with the detection in range 31 × 10−6 RIU. In addition, the small area (61.56 μm2) of biosensor results in its appropriateness for different uses in compact photonic integrated circuits. Next, we changed the shape of the dielectric rods and investigated their effects on the sensitivity parameter. The sensitivity and figure of merit after changes in the shape of dielectric rods and nanocavities are at best S = 20,393 nm/RIU and FOM = 9104.017 ± 606.93 RIU−1, receptively. In addition, the resolution detection range is 203.93 × 10−6 RIU. Full article
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Article
Electrodeposition of Cu-Ag Alloy Films at n-Si(001) and Polycrystalline Ru Substrates
Coatings 2021, 11(12), 1563; https://doi.org/10.3390/coatings11121563 - 20 Dec 2021
Cited by 2 | Viewed by 845
Abstract
Electrodeposition of Cu-Ag films from acidic sulfate bath was conducted at n-Si(001) and polycrystalline Ru substrates. Significant nucleation overpotential of 0.4 V is observed with the Cu-Ag bath at n-Si(001) substrate, whereas the electrodeposition of Cu-Ag at Ru substrate is influenced by Ru [...] Read more.
Electrodeposition of Cu-Ag films from acidic sulfate bath was conducted at n-Si(001) and polycrystalline Ru substrates. Significant nucleation overpotential of 0.4 V is observed with the Cu-Ag bath at n-Si(001) substrate, whereas the electrodeposition of Cu-Ag at Ru substrate is influenced by Ru oxides at the surface. Incomplete coverage of Si substrate by Cu-Ag deposit was observed from the deposition systems without Ag(I), or with 0.1 mM Ag(I), comparing with the compact Cu-Ag film obtained with the deposition bath containing 0.01 mM Ag(I). Layered and faceted Cu-Ag deposit was observed at small Cu deposition overpotential with the Ru substrate. Phase composition of the Cu-Ag deposits at n-Si(001) substrate from electrolyte with various Ag(I) concentrations is examined by XRD. Limited solubility of Ag (0.4 at.%) was observed in fcc-Cu until phase separation occurs. The classical model for nucleation kinetics in electrodeposition was used to examine the potentiostatic transients of the Cu-Ag electrodeposition at n-Si(001) substrate. Full article
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Article
Defect Analysis of 316 L Stainless Steel Prepared by LPBF Additive Manufacturing Processes
Coatings 2021, 11(12), 1562; https://doi.org/10.3390/coatings11121562 - 19 Dec 2021
Viewed by 983
Abstract
The 316 L stainless-steel samples were prepared by laser powder bed fusion (LPBF). The effects of processing parameters on the density and defects of 316 L stainless steel were studied through an orthogonal experiment. The density of the samples was measured by the [...] Read more.
The 316 L stainless-steel samples were prepared by laser powder bed fusion (LPBF). The effects of processing parameters on the density and defects of 316 L stainless steel were studied through an orthogonal experiment. The density of the samples was measured by the Archimedes method, optical microscopy (OM) and X-ray Computed Tomography (XCT). The microstructures and defects under different LPBF parameters were studied by OM and SEM. The results show that the energy density has a significant effect on the defect and density of the structure. When the energy density is lower than 35.19 J/mm3, the density increases significantly with the increase of energy density. However, when the energy density is larger than this value, the density remains relatively stable. The process parameter with the greatest influence on energy density is the hatch distance D, followed by laser power P, scanning speed V and rotation angle θ. In this paper, the optimum parameters consist of P = 260 W, V = 1700 mm, D = 0.05 mm and θ = 67°, in which the density is as high as 98.5%. In addition, the possibility and accuracy of the XCT method in detecting the discontinuity and porosity of 316 L stainless steel were discussed. The results show that XCT can provide the whole size and variation trend of pores in the different producing direction of LPBF. Full article
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Article
Fabrication of Novel Chitosan–Hydroxyapatite Nanostructured Thin Films for Biomedical Applications
Coatings 2021, 11(12), 1561; https://doi.org/10.3390/coatings11121561 - 19 Dec 2021
Cited by 4 | Viewed by 891
Abstract
In this study, we develop chitosan–hydroxyapatite (CS–HAp) composite layers that were deposited on Si substrates in radio frequency (RF) magnetron sputtering discharge in argon gas. The composition and structure of CS–HAp composite layers were investigated by analytical techniques, such as Fourier transform infrared [...] Read more.
In this study, we develop chitosan–hydroxyapatite (CS–HAp) composite layers that were deposited on Si substrates in radio frequency (RF) magnetron sputtering discharge in argon gas. The composition and structure of CS–HAp composite layers were investigated by analytical techniques, such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), metallographic microscopy (MM), and atomic force microscopy (AFM). On the other hand, in the present study the second order derivative of FT-IR–ATR spectra, for compositional analyses of CS–HAp, were used. The SEM, MM, and AFM data have shown the formation of CS–HAp composite layers. The surface of CS–HAp composite layers showed uniform growth (at an Ar gas working pressure of p = 2 × 10−3 mbar). The surface of the CS–HAp composites coatings became more nanostructured, becoming granular as the gas pressure increased from 5 × 10−3 to 1.2 × 10−2 mbar. However, our studies revealed that the surface morphology of the CS–HAp composite layers varies with the Ar gas working pressure. At the same time, optical properties are slightly influenced by Ar pressure. Their unique physicochemical properties make them suitable for various applications in the biomedical field, if we consider the already proven antimicrobial properties of chitosan. The antifungal properties and the capacity of the CS–HAp composite layers to inhibit the development of fungal biofilms were also demonstrated using the Candida albicans ATCC 10231 (C. albicans) fungal strain. Full article
(This article belongs to the Special Issue Biomaterials and Antimicrobial Coatings)
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Article
The Effect of Incorporating Ceramic Particles with Different Morphologies on the Microstructure, Mechanical and Tribological Behavior of Hybrid TaC_ BN/AA2024 Nanocomposites
Coatings 2021, 11(12), 1560; https://doi.org/10.3390/coatings11121560 - 18 Dec 2021
Viewed by 902
Abstract
Improving the mechanical durability and wear resistance of aluminum alloys is a research challenge that can be solved by their reinforcement with ceramics. This article is concerned with the improvement of the mechanical properties and wear resistance of the AA2024 aluminum alloy surface. [...] Read more.
Improving the mechanical durability and wear resistance of aluminum alloys is a research challenge that can be solved by their reinforcement with ceramics. This article is concerned with the improvement of the mechanical properties and wear resistance of the AA2024 aluminum alloy surface. Surface composites were prepared by incorporating a hybrid of heavy particles (tantalum carbide (TaC), light nanoparticles, and boron nitride (BN)) into the AA2024 alloy using the friction stir process (FSP) approach. Three pattern holes were milled in the base metal to produce the composites with different volume fractions of the reinforcements. The effects of the FSP and the reinforcements on the microstructure, mechanical properties, and wear resistance are investigated. In addition to the FSP, the reinforced particles contributed to greater grain refinement. The rolled elongated grains became equiaxed ultrafine grains reaching 6 ± 1 µm. The refinement and acceptable distribution in the reinforcements significantly improved the hardness and wear resistance of the produced composites. Overall, the hardness was increased by 60% and the wear resistance increased by 40 times compared to the base alloy. Full article
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Article
The Study on Feasibility and Welding Characteristics of GMAW Surfacing Remanufacturing of H13 Steel Cutter Ring of TBM Hob
Coatings 2021, 11(12), 1559; https://doi.org/10.3390/coatings11121559 - 18 Dec 2021
Viewed by 750
Abstract
As H13 steel is a common material for cutters of Tunnel Boring Machine (TBM), the research on surfacing remanufacturing performance is of great value. In this paper, the phase composition of the surfacing layer of H13 steel after gas metal arc welding (GMAW) [...] Read more.
As H13 steel is a common material for cutters of Tunnel Boring Machine (TBM), the research on surfacing remanufacturing performance is of great value. In this paper, the phase composition of the surfacing layer of H13 steel after gas metal arc welding (GMAW) was analyzed by exploring the precipitation of hard phase in the molten pool, and the microstructure evolution of the surfacing layer was revealed. Then, we carried out simulation modeling analysis on H13 steel surfacing remanufacturing. Results show that: (1) the surfacing layer is combined with the base metal by physical metallurgy without obvious defects such as pores, inclusions and cracks in the surfacing layer; (2) the hardness of the surfacing layer is 60 HRC, which is about 1.5 times of that of the base metal; (3) the stress is mainly concentrated in the arc starting and ending points, followed by the external constraints on both sides of the surfacing layer; (4) the deformation of surfacing layer is slight, which does not affect the forming quality of base metal, while the deformation of base metal is relatively severe. This paper verifies the feasibility of H13 steel remanufacturing from experimental and simulation, providing theoretical basis for future engineering practice. Full article
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Article
Influence of Waste Fly Ash on the Rheological Properties of Fresh Cement Paste and the Following Electrical Performances and Mechanical Strengths of Hardened Specimens
Coatings 2021, 11(12), 1558; https://doi.org/10.3390/coatings11121558 - 18 Dec 2021
Cited by 3 | Viewed by 739
Abstract
Waste fly ash (WFA) is a kind of solid waste without reasonable disposition. The WFA with active substance can promote the cement hydration, therefore, WFA may enhance the mechanical strengths of cement-based materials. In this paper, the rheological properties (slump flow and plastic [...] Read more.
Waste fly ash (WFA) is a kind of solid waste without reasonable disposition. The WFA with active substance can promote the cement hydration, therefore, WFA may enhance the mechanical strengths of cement-based materials. In this paper, the rheological properties (slump flow and plastic viscosity) of fresh cement paste with WFA ranging from 0% to 25% by mass ratio of cement were studied. The alternating current (AC) electrical resistance and direct current (DC) resistance time curves were determined. The AC impedance spectroscopy curves of the specimens cured for 1 day and 28 days were obtained. Finally, the mechanical strengths of hardened cement paste cured for 1 day, 3 days, 7 days, and 28 days were tested. The results showed that the slump flow was decreased and the plastic viscosity was increased by the addition of WFA and the increasing curing time. The AC electrical resistance increased in the form of the quadratic function with the cuing age. Meanwhile, the addition of WFA demonstrated an enhancing effect on the electrical conduction of cement paste. The variation rate of DC electrical resistance during the testing time increased with the increasing dosages of WFA and the curing age. The mechanical strengths increased with the addition of curing time and the content of WFA. The increasing rate of mechanical strengths increased with the addition of WFA (0~15%) and decreased with curing time. However, when the dosage of WFA increased from 15% to 25%, the increasing rate decreased. Full article
(This article belongs to the Special Issue State-of-the-Art on Coatings Research in Asia)
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Article
The Effect of Adding Sodium Carbonate on the Electrical Conductivity of Aluminum Paste
Coatings 2021, 11(12), 1557; https://doi.org/10.3390/coatings11121557 - 18 Dec 2021
Viewed by 631
Abstract
Base metal pastes have been widely used in the preparation of ZnO varistor electrodes, and it is important to accurately grasp the relevant mechanisms affecting the conductivity of aluminum electrodes. In this paper, the effect of adding sodium carbonate on the conductive property [...] Read more.
Base metal pastes have been widely used in the preparation of ZnO varistor electrodes, and it is important to accurately grasp the relevant mechanisms affecting the conductivity of aluminum electrodes. In this paper, the effect of adding sodium carbonate on the conductive property of aluminum paste was assessed, and the microscopic mechanism during aluminum electrode sintering explored. The results show that adding sodium carbonate can reduce the softening point of glass powder and enhance its fluidity. Sodium carbonate, glass, and aluminum oxide film react together; consequently, the aluminum oxide film is partially dissolved by reaction to produce defects, and there is tight contact at the interface between the aluminum powder particles. The sodium ions will displace the aluminum ions in the alumina, conferring the alumina film with a certain ionic conductivity. At the same time, sodium ions are doped into the aluminum lattice, which causes the aluminum lattice to swell. After sintering, the structure of aluminum electrode is compact and its electrical conductivity is significantly improved. This study is a valuable reference for the theoretical research and the potential applications of aluminum paste. Full article
(This article belongs to the Special Issue Functional Coatings for Metallic and Ceramic Materials)
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Article
UV Curable Coatings Based on Urethane Acrylates Containing Eugenol and Evaluation of Their Antimicrobial Activity
Coatings 2021, 11(12), 1556; https://doi.org/10.3390/coatings11121556 - 17 Dec 2021
Viewed by 960
Abstract
This work presents studies on the obtaining of UV-curable coatings with antimicrobial activity. Urethane acrylates (UAs) have excellent physicochemical properties including high reactivity in systems with radical photoinitiators in the presence of UV radiation and good balance between hardness and flexibility in the [...] Read more.
This work presents studies on the obtaining of UV-curable coatings with antimicrobial activity. Urethane acrylates (UAs) have excellent physicochemical properties including high reactivity in systems with radical photoinitiators in the presence of UV radiation and good balance between hardness and flexibility in the formed coatings. At the same time, eugenol is well known as the compound hindering the growth of various microorganisms. Hence, the materials obtained by the modification of UA resins with eugenol can be used to protect various surfaces, especially against microorganisms. This study aimed to examine the influence of the amount of eugenol on the chemical, physical, thermal, and mechanical properties of the obtained UA coatings and find the conditions at which the optimal properties for industrial applications such coatings can be achieved. These materials were successfully obtained. Taking into account that eugenol is a very cheap reactant, and it can be obtained from natural sources by the simple distillation method, the proposed method combined the good points of obtaining protective coatings by UV curing with the utilization of vegetable, renewable reactants (biomass), such as components giving special properties to these materials, in this case, antimicrobial properties. In this study, photoreactive coatings with antimicrobial properties for the following microorganisms: fungi (C. albicans), Gram-positive bacteria (S. epidermidis) as well as Gram-negative bacteria (E. coli), were obtained. The obtained coatings were cured over a short time. They were colorless and characterized by a wide range of properties and applications. Full article
(This article belongs to the Special Issue New Advances in Polyurethane Coatings and Its Application)
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Article
High-Sensitivity Biosensor Based on Glass Resonance PhC Cavities for Detection of Blood Component and Glucose Concentration in Human Urine
Coatings 2021, 11(12), 1555; https://doi.org/10.3390/coatings11121555 - 17 Dec 2021
Cited by 11 | Viewed by 900
Abstract
In this work, a novel structure of an all-optical biosensor based on glass resonance cavities with high detection accuracy and sensitivity in two-dimensional photon crystal is designed and simulated. The free spectral range in which the structure performs well is about FSR = [...] Read more.
In this work, a novel structure of an all-optical biosensor based on glass resonance cavities with high detection accuracy and sensitivity in two-dimensional photon crystal is designed and simulated. The free spectral range in which the structure performs well is about FSR = 630 nm. This sensor measures the concentration of glucose in human urine. Analyses to determine the glucose concentration in urine for a normal range (0~15 mg/dL) and urine despite glucose concentrations of 0.625, 1.25, 2.5, 5 and 10 g/dL in the wavelength range 1.326404~1.326426 μm have been conducted. The detection range is RIU = 0.2 × 10−7. The average bandwidth of the output resonance wavelengths is 0.34 nm in the lowest case. In the worst case, the percentage of optical signal power transmission is 77% with an amplitude of 1.303241 and, in the best case, 100% with an amplitude of 1.326404. The overall dimensions of the biosensor are 102.6 µm2 and the sensitivity is equal to S = 1360.02 nm/RIU and the important parameter of the Figure of Merit (FOM) for the proposed biosensor structure is equal to FOM = 1320.23 RIU−1. Full article
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Article
MHD Hybrid Nanofluid Flow Due to Rotating Disk with Heat Absorption and Thermal Slip Effects: An Application of Intelligent Computing
Coatings 2021, 11(12), 1554; https://doi.org/10.3390/coatings11121554 - 17 Dec 2021
Cited by 7 | Viewed by 747
Abstract
The objective of this study is to explore the flow features and heat transfer properties of an MHD hybrid nanofluid between two parallel plates under the effects of joule heating and heat absorption/generation (MHD-HFRHT) by utilizing the computational strength of Levenberg–Marquardt Supervised Neural [...] Read more.
The objective of this study is to explore the flow features and heat transfer properties of an MHD hybrid nanofluid between two parallel plates under the effects of joule heating and heat absorption/generation (MHD-HFRHT) by utilizing the computational strength of Levenberg–Marquardt Supervised Neural Networks (LM-SNNs). Similarity equations are utilized to reduce the governing PDEs into non-linear ODEs. A reference solution in the form of data sets for MHD-HFRHT flow is obtained by creating different scenarios by varying involved governing parameters such as the Hartman number, rotation parameter, Reynolds number, velocity slip parameter, thermal slip parameter and Prandtl number. These reference data sets for all scenarios are placed for training, validation and testing through LM-SNNs and the obtained results are then compared with reference output to validate the accuracy of the proposed solution methodology. AI-based computational strength with the applicability of LM-SNNs provides an accurate and reliable source for the analysis of the presented fluid-flow system, which has been tested and incorporated for the first time. The stability, performance and convergence of the proposed solution methodology are validated through the numerical and graphical results presented, based on mean square error, error histogram, regression plots and an error-correlation measurement. MSE values of up to the accuracy level of 1 × 10−11 established the worth and reliability of the computational technique. Due to an increase in the Hartmann number, a resistance was observed, resulting in a reduction in the velocity profile. This occurs as the Hartmann number measures the relative implication of drag force that derives from magnetic induction of the velocity of the fluid flow system. However, the Reynolds number accelerates in the velocity profile due to the dominating impact of inertial force. Full article
(This article belongs to the Special Issue Nanofluidics: Interfacial Transport Phenomena)
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Article
Investigations of Microstructures and Erosion–Corrosion Performance of Cast Boron-Bearing Stainless Steel
Coatings 2021, 11(12), 1553; https://doi.org/10.3390/coatings11121553 - 17 Dec 2021
Viewed by 687
Abstract
The microstructures and erosion–corrosion properties of boron-bearing stainless steel were researched by an erosion–corrosion tester, energy dispersive X–ray spectrometry, scanning electron microscope and X-ray diffraction analysis. The microstructures of as-cast, boron-bearing stainless steel contain M7(B,C)3, M2(B,C) borocarbides [...] Read more.
The microstructures and erosion–corrosion properties of boron-bearing stainless steel were researched by an erosion–corrosion tester, energy dispersive X–ray spectrometry, scanning electron microscope and X-ray diffraction analysis. The microstructures of as-cast, boron-bearing stainless steel contain M7(B,C)3, M2(B,C) borocarbides and the martensite matrix; the matrix has less chromium and more nickel than those in the M2(B,C) and M7(B,C)3. The microstructures in heat-treated, boron-bearing stainless steel consist of M7(B,C)3, M2(B,C) and M23(B,C)6 borocarbides and ferrite, and the Rockwell hardness of heat-treated, boron-bearing stainless steel is lower than that of as-cast steel. For Cr28 white cast iron and boron-bearing stainless steel, the mixing wheel with higher rotating speed leads to a higher erosion–corrosion weight loss, and as the impingement angle increases, the erosion–corrosion weight loss increases first, and then decreases. For any erosion–corrosion experiment conditions, the erosion–corrosion resistance of boron-bearing stainless steel is better than that of Cr28 white cast iron. Full article
(This article belongs to the Special Issue Trends and Advances in Anti-wear Materials)
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Article
Thermal Characterization of Coolant Maxwell Type Nanofluid Flowing in Parabolic Trough Solar Collector (PTSC) Used Inside Solar Powered Ship Application
Coatings 2021, 11(12), 1552; https://doi.org/10.3390/coatings11121552 - 17 Dec 2021
Cited by 23 | Viewed by 1128
Abstract
Parabolic trough solar collectors (PTSCs) are generally utilized to reach high temperatures in solar-thermal applications. The current work investigates entropy production analysis and the influence of nano solid particles on a parabolic trough surface collector (PTSC) installed within a solar powered ship (SPS). [...] Read more.
Parabolic trough solar collectors (PTSCs) are generally utilized to reach high temperatures in solar-thermal applications. The current work investigates entropy production analysis and the influence of nano solid particles on a parabolic trough surface collector (PTSC) installed within a solar powered ship (SPS). For the current investigation, the non-Newtonian Maxwell type, as well as a porous medium and Darcy–Forchheimer effects, were used. The flow in PTSC was produced by a nonlinear stretching surface, and the Cattaneo–Christov approach was used to assess the thermal boundary layer’s heat flux. Similarity transformation approach has been employed to convert partial differential equations into solvable ordinary differential equations allied to boundary conditions. Partial differential and the boundary conditions have been reduced into a group of non-linear ordinary differential equations. A Keller-box scheme applied to solve approximate solutions of the ordinary differential equations. Single-walled carbon nanotubes -engine oil (SWCNT-EO) and Multiwalled carbon nanotubes/engine oil (MWCNT-EO) nanofluids have been utilized as working fluid. According to the findings, the magnetic parameter led to a reduction in the Nusselt number, as well as an increment in skin friction coefficient. Moreover, total entropy variance over the domain enhanced for flow rates through Reynolds number and viscosity fluctuations were monitored by using Brinkman number. Utilizing SWCNT-EO nanofluid increased the thermal efficiency between 1.6–14.9% in comparison to MWCNT-EO. Full article
(This article belongs to the Special Issue Nanofluidics: Interfacial Transport Phenomena)
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Article
Theoretical and Experimental Analysis of Surface Roughness and Adhesion Forces of MEMS Surfaces Using a Novel Method for Making a Compound Sputtering Target
Coatings 2021, 11(12), 1551; https://doi.org/10.3390/coatings11121551 - 17 Dec 2021
Cited by 13 | Viewed by 1100
Abstract
Achieving a compound thin film with uniform thickness and high purity has always been a challenge in the applications concerning micro electro mechanical systems (MEMS). Controlling the adhesion force in micro/nanoscale is also critical. In the present study, a novel method for making [...] Read more.
Achieving a compound thin film with uniform thickness and high purity has always been a challenge in the applications concerning micro electro mechanical systems (MEMS). Controlling the adhesion force in micro/nanoscale is also critical. In the present study, a novel method for making a sputtering compound target is proposed for coating Ag–Au thin films with thicknesses of 120 and 500 nm on silicon substrates. The surface topography and adhesion forces of the samples were obtained using atomic force microscope (AFM). Rabinovich and Rumpf models were utilized to measure the adhesion force and compare the results with the obtained experimental values. It was found that the layer with a thickness of 500 nm has a lower adhesion force than the one with 120 nm thickness. The results further indicated that due to surface asperity radius, the adhesion achieved from the Rabinovich model was closer to the experimental values. This novel method for making a compound sputtering target has led to a lower adhesion force which can be useful for coating microgripper surfaces. Full article
(This article belongs to the Special Issue Novel Approaches to Hybrid Films or Coatings)
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Article
On the Effects of High and Ultra-High Rotational Speeds on the Strength, Corrosion Resistance, and Microstructure during Friction Stir Welding of Al 6061-T6 and 316L SS Alloys
Coatings 2021, 11(12), 1550; https://doi.org/10.3390/coatings11121550 - 17 Dec 2021
Cited by 1 | Viewed by 687
Abstract
In this study, under the conditions of using tools at a high rotational speed (HRS) of 10,000 rpm and an ultra-high rotational speed (ultra-HRS) of 18,000 rpm, the produced welding heat input was utilized to weld two specimens of Al alloy 6061-T6 with [...] Read more.
In this study, under the conditions of using tools at a high rotational speed (HRS) of 10,000 rpm and an ultra-high rotational speed (ultra-HRS) of 18,000 rpm, the produced welding heat input was utilized to weld two specimens of Al alloy 6061-T6 with 1.0 mm thickness and 316L SS with 0.8 mm thickness. The microstructural characteristics, mechanical properties, and electrochemical corrosion properties of the aluminum alloy–steel joints were analyzed. The higher tool offset forms an intermetallic compound layer of less than 1 µm at the Fe-Al interface on the advancing side (AS) at different speeds. This results in a mixed zone structure. The lower tool offset forms intermetallic compounds of only 2 µm. The formation of a composite material based on aluminum alloy in the weld nugget zone improves the hardness value. The intermetallic compounds are Fe3Al and FeAl3, respectively. It was observed that the formation of intermetallic compounds is solely related to the rotational speed, and the iron-rich intermetallic compounds produced under ultra-HRS parameters have higher corrosion resistance. When the tool offset is 0.55 mm, using the HRS parameters, the tensile strength is 220.8 MPa (about 75.9% of that of the base metal). Full article
(This article belongs to the Special Issue Corrosion and Degradation of Materials)
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Article
Impaired Proliferation, Apoptosis, and Angiogenesis of Adipose-Derived Stem Cells Isolated from Rats during the Course of Diabetes
Coatings 2021, 11(12), 1549; https://doi.org/10.3390/coatings11121549 - 17 Dec 2021
Viewed by 654
Abstract
Background: To characterize the impaired of proliferation, apoptosis, and angiogenic activity in ASCs isolated at different stages of the disease course from rats with type 1 diabetes mellitus (T1DM) rats induced by streptozotocin (STZ). Methods: Adipose tissues of the epididymis were harvested at [...] Read more.
Background: To characterize the impaired of proliferation, apoptosis, and angiogenic activity in ASCs isolated at different stages of the disease course from rats with type 1 diabetes mellitus (T1DM) rats induced by streptozotocin (STZ). Methods: Adipose tissues of the epididymis were harvested at 0, 4, 8, 12, and 16 weeks after the induction of T1DM in rats and from normal rats at the same time points and the morphological variations were detected by Oil red O staining. ASCs were collected from adipose tissues. Cell proliferation, apoptosis, vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) expression were assessed. Results: With the prolongation of the disease course, the size and the morphology of adipocytes were distorted, and intracellular lipid droplets became smaller. After 4 weeks, the proliferation of ASCs was decreased, while apoptosis in ASCs was increased. Furthermore, as the disease proceeded, proliferation decreased and apoptosis increased. VEGF and bFGF expression in ASCs from diabetic rats was downregulated at 8 weeks. Conclusion: At 4 weeks after T1DM induction, the proliferation of ASCs decreased and apoptosis increased. The expression of angiogenic factors in ASCs declined at 8 weeks after T1DM induction. The changes in the proliferation, apoptosis, and angiogenic activity are related to the prolongation of disease course. Full article
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Article
Fabrication of a High Water Flux Conductive MWCNTs/PVC Composite Membrane with Effective Electrically Enhanced Antifouling Behavior
Coatings 2021, 11(12), 1548; https://doi.org/10.3390/coatings11121548 - 16 Dec 2021
Viewed by 946
Abstract
Membrane fouling is a major issue that deteriorates the performance of membrane filtration systems. The electrically assisted membrane filtration process is proven to be effective for alleviating membrane fouling. In this study, we synthesized an electrically conductive membrane by incorporating multiwalled carbon nanotubes [...] Read more.
Membrane fouling is a major issue that deteriorates the performance of membrane filtration systems. The electrically assisted membrane filtration process is proven to be effective for alleviating membrane fouling. In this study, we synthesized an electrically conductive membrane by incorporating multiwalled carbon nanotubes (MWCNTs) into polyvinyl chloride (PVC). The synthesized membranes have larger porosity than the PVC membrane (incorporating polyethylene glycol (PEG)), and thus possess much higher water flux under the same testing conditions. The initial and stable water fluxes are 2033 L/(m2·h) and 750 L/(m2·h), respectively, which are much higher than that of the pure PVC membrane. More importantly, the membrane has higher surface charge density and excellent electrical conductivity, but the surface hydrophilicity and toughness decreased with the addition of the MWCNTs. The 25 wt % MWCNTs/PVC composite membrane possesses suitable electrical conductivity of 0.128 S/m. The same membrane shows electro-enhanced antifouling performance during the antifouling test with yeast as a model foulant because the external electric field (−2 V) impulses a strong repulsion force while producing some micro bubbles to repel the foulant; thus, the membrane fouling is suppressed. In the current study, we develop a simple method to fabricate the electrically conductive membrane for application in the electrically assisted membrane filtration process. Full article
(This article belongs to the Special Issue Polymer Films/Membranes: Structure, Properties, and Applications)
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Article
Laser Texturing for Superwetting Titanium Alloy and Investigation of Its Erosion Resistance
Coatings 2021, 11(12), 1547; https://doi.org/10.3390/coatings11121547 - 16 Dec 2021
Cited by 7 | Viewed by 1175
Abstract
Erosion of materials is one of the major causes that lead to the malfunction of equipment and facilities, and surface texturing can be a solution for enhancement of erosion resistance. In this work, superwetting (superhydrophilic/superhydrophobic) titanium (Ti) alloy surface with periodic microstructure was [...] Read more.
Erosion of materials is one of the major causes that lead to the malfunction of equipment and facilities, and surface texturing can be a solution for enhancement of erosion resistance. In this work, superwetting (superhydrophilic/superhydrophobic) titanium (Ti) alloy surface with periodic microstructure was prepared by a facile laser-based surface texturing approach which combines laser surface texturing and low-temperature annealing. The effect of laser-induced surface texture and wettability on the erosion resistance of the laser textured surface was studied. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to analyze the chemical surface microstructure and surface on the untreated and laser textured surfaces. The hardness and contact angle of the untreated surface, superhydrophilic surface and superhydrophobic surface were measured by microhardness tester and contact angle goniometer. Using an in-house built erosion experimental setup, the erosion resistance of the untreated surface, superhydrophilic surface and superhydrophobic surface was investigated. The experimental results demonstrate that micro-bumps are formed after laser surface texturing. In the meantime, the surface hardness for the laser textured surface with a step size of 150 μm is increased by 48% under the load of 1.961 N. Compared with the untreated surface, the erosion resistance is increased by 33.9%, 23.8% and 16.1%, respectively, for the superhydrophobic surface. The SEM results show that the untreated surface has large and deep impact pits, while the superhydrophobic surface only has small and shallow impact pits, indicating that the erosion process resulted in less damage to the substrate. The EDS results shows that superhydrophobicity plays a critical role in protecting the substrate from erosion. It is thus believed that the superhydrophobic surface has pronounced effects for improving the hardness and erosion resistance of Ti alloy. Full article
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Article
Thermal Stability of the Copper and the AZO Layer on Textured Silicon
Coatings 2021, 11(12), 1546; https://doi.org/10.3390/coatings11121546 - 16 Dec 2021
Cited by 1 | Viewed by 858
Abstract
Transparent conductive oxide (TCO) film is the most widely used front electrode in silicon heterojunction (SHJ) solar cells. A copper metallization scheme can be applied to the SHJ process. The abundance of zinc in the earth’s crust makes aluminum-doped zinc oxide (AZO) an [...] Read more.
Transparent conductive oxide (TCO) film is the most widely used front electrode in silicon heterojunction (SHJ) solar cells. A copper metallization scheme can be applied to the SHJ process. The abundance of zinc in the earth’s crust makes aluminum-doped zinc oxide (AZO) an attractive low-cost substitute for indium-based TCOs. No work has focused on the properties of the copper and AZO layers on the textured silicon for solar cells. This work deposited an aluminum-doped zinc oxide layer and copper metal layer on textured (001) silicon by a sputtering to form Cu/AZO/Si stacks. The structures of Cu/AZO/Si are characterized by scanning electron microscope (SEM), scanning transmission electron microscope (STEM), and energy-dispersive X-ray spectrometer (EDS). The results show that the copper thin film detached from AZO in the valley of the textured silicon substrate at a temperature of 400 °C. Additionally, the gap between the copper and AZO layers increases as temperature increases, and the 65 nm thickness AZO layer was found to be preserved up to 800 °C. Full article
(This article belongs to the Special Issue Advances in Thin Film Fabrication by Magnetron Sputtering)
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Article
Biosynthesis and Fabrication of Copper Oxide Thin Films as a P-Type Semiconductor for Solar Cell Applications
Coatings 2021, 11(12), 1545; https://doi.org/10.3390/coatings11121545 - 16 Dec 2021
Cited by 3 | Viewed by 731
Abstract
This study aimed to synthesize copper oxide (CuO) thin films using an eco-friendly green synthetic approach. A sol-gel spin coating technique was employed for the synthesis of the CuO thin film using Allium cepa as a reducing agent. The fabricated CuO thin film [...] Read more.
This study aimed to synthesize copper oxide (CuO) thin films using an eco-friendly green synthetic approach. A sol-gel spin coating technique was employed for the synthesis of the CuO thin film using Allium cepa as a reducing agent. The fabricated CuO thin film was investigated using the Fourier Transform-Infrared (FTIR) spectroscopy, Ultraviolet-visible spectra studies (UV-Vis), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and the Four-Point Probe measurement. The SEM micrographs revealed that the particles were spherically shaped, while the EDX analysis revealed that the CuO thin film was composed of copper and oxygen elements. Furthermore, the XRD analysis confirmed the monoclinic crystalline structure of the CuO thin film, while the FTIR spectroscopy investigated the chemical bonds formed during the production process. Contrarily, the UV-Vis spectroscopy reported a strong absorption of the film at the visible spectra with an estimated optical energy band gap of 1.48 eV. The electrical analysis, however, disclosed that the synthesized thin film portrayed good semiconducting behaviors. Full article
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Article
Detection of Virulence Genes and Biofilm Forming Capacity of Diarrheagenic E. coli Isolated from Different Water Sources
Coatings 2021, 11(12), 1544; https://doi.org/10.3390/coatings11121544 - 16 Dec 2021
Cited by 1 | Viewed by 814
Abstract
Diarrheagenic Escherichia coli (DEC) are associated with frequent incidences of waterborne infections and pose health risk to individuals who contact water for domestic or recreational uses. Detection of DEC pathotypes in drinking water can be used as an indicator of fecal contamination. This [...] Read more.
Diarrheagenic Escherichia coli (DEC) are associated with frequent incidences of waterborne infections and pose health risk to individuals who contact water for domestic or recreational uses. Detection of DEC pathotypes in drinking water can be used as an indicator of fecal contamination. This study aimed to investigate the occurrence of DEC pathotypes and their capacity to form biofilms in drinking water samples collected from different water sources. In this study, PCR analysis was used to determine the occurrence of four clinically significant virulence genes of diarrheagenic E. coli, eaeA (Enteropathogenic E. coli), stx1, stx2 (Enterohemorrhagic E. coli) and sth (Enterotoxigenic E. coli), in drinking water samples (n = 35) by using specific primers and conditions. PCR amplicons were visualized by using agarose gel electrophoresis. A total of 12/35 (34%) samples were detected as positive for at least one of the four DEC virulence genes and 11/12 (91%) E. coli isolates harbored virulence gene while 1/12 (8%) E. coli isolates harbored none. The eaeA and sth genes were the most detected genes (75%), while stx1 and stx2 genes were least detected genes (66%). Biofilm assay confirmed that ETEC pathotypes can cause damage in enteric walls by attaching and effacing to persist diarrheal conditions. This study indicated that drinking water of different sources is contaminated with potential DEC pathotypes and it can be a source of diarrheal diseases. The amplification of four virulence genes associated with DEC pathotypes (EPEC, EHEC and ETEC) in drinking water demonstrates that potentially virulent DEC pathotypes are distributed in water sources and may be a cause of health concern. There is, therefore, an urgent need to monitor DEC pathotypes in drinking water. Full article
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Article
Comparative Investigation on Corrosion Resistance of Stainless Steels Coated with Titanium Nitride, Nitrogen Titanium Carbide and Titanium-Diamond-like Carbon Films
Coatings 2021, 11(12), 1543; https://doi.org/10.3390/coatings11121543 - 15 Dec 2021
Cited by 7 | Viewed by 874
Abstract
In this study, the corrosion resistance of titanium nitride (TiN), nitrogen titanium carbide (TiCN) and titanium-diamond-like carbon (Ti-DLC) films deposited on 316L stainless steel (SS) were compared via differences in the surface and section-cross morphologies, open circuit potential tests, electrochemical impedance spectroscopy and [...] Read more.
In this study, the corrosion resistance of titanium nitride (TiN), nitrogen titanium carbide (TiCN) and titanium-diamond-like carbon (Ti-DLC) films deposited on 316L stainless steel (SS) were compared via differences in the surface and section-cross morphologies, open circuit potential tests, electrochemical impedance spectroscopy and potentiometric tests. The corrosion resistance of the TiCN and Ti-DLC films significantly improved because of the titanium carbide (TiC) crystals that obstruct the corrosive species penetrating the as-deposited film in the electrolyte atmosphere. TiN exhibited the lowest corrosion resistance because of its low thickness and high volume of defects. The Ti-DLC film showed the lowest corrosion current density (approximately 4.577 μA/cm2) and thickness reduction (approximately 0.12 μm) in different electrolytes, particularly those with high Cl and H+ concentrations, proving to be the most suitable corrosion protection material for 316L SS substrates. Full article
(This article belongs to the Special Issue Advances of Ceramic and Alloy Coatings)
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Article
Galvanic Corrosion Behaviour of Different Types of Coatings Used in Safety Systems Manufacturing
Coatings 2021, 11(12), 1542; https://doi.org/10.3390/coatings11121542 - 15 Dec 2021
Cited by 3 | Viewed by 675
Abstract
Worker safety is one of the main aspects to be taken into account in any activity carried out at work. When we talk about the safety of the worker at activities carried out at height, the condition and characteristics of the personal protective [...] Read more.
Worker safety is one of the main aspects to be taken into account in any activity carried out at work. When we talk about the safety of the worker at activities carried out at height, the condition and characteristics of the personal protective equipment against falling from a height are one of the main causes of work accidents resulting in serious injuries or death. Carabiners are the main components of the safety system; their role is to connect the other components of the system or to make the connection between the system and the anchor point. Therefore, to be used safely, the carabiners’ material must have high corrosion resistance in different environments. This paper is part of a complex study that aims to improve the corrosion properties of carbon steel used in the manufacture of carabiners. Previous studies have shown that the corrosion resistance of carbon steel in various corrosive environments has been improved by the deposition of different types of phosphate layers, as well as other subsequently deposited layers. The aim of this paper is to study the galvanic corrosion evaluation between different galvanic couples (duralumin-coated samples, aluminium bronze-coated samples, and carbon steel-coated samples) tested in three different corrosive media. Moreover, the study approaches for the first time the galvanic corrosion of systems that can be formed between the materials used in the manufacture of carabiners. Accordingly, it was observed that, overall, the samples coated with a Zn phosphate layer exhibited the best performance in all the corrosive environments (saltwater and fire extinguishing solution). Full article
(This article belongs to the Special Issue Advances in Corrosion Resistant Coatings)
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Article
Ultra-Low-Reflective, Self-Cleaning Surface by Fabrication Dual-Scale Hierarchical Optical Structures on Silicon
Coatings 2021, 11(12), 1541; https://doi.org/10.3390/coatings11121541 - 15 Dec 2021
Cited by 3 | Viewed by 708
Abstract
An integrated functional anti-reflective surface is of great significance for optical and optoelectronic devices. Hence, its preparation has attracted great attention from many researchers. This study combined wet alkaline etching approaches and reactive ion etching (RIE) techniques to create a dual-scale hierarchical anti-reflective [...] Read more.
An integrated functional anti-reflective surface is of great significance for optical and optoelectronic devices. Hence, its preparation has attracted great attention from many researchers. This study combined wet alkaline etching approaches and reactive ion etching (RIE) techniques to create a dual-scale hierarchical anti-reflective surface on silicon substrates. The effect of RIE time on surface morphology and optical performance was investigated using multiple characterization forms. The optimal parameters for the fabrication of dual-scale structures by the composite etching process were explored. The silicon surface with a dual-scale structure indicated excellent anti-reflective properties (minimum reflectivity of 0.9%) in the 300 to 1100 nm wavelength range. In addition, the ultra-low reflection characteristic of the surface remained prominent at incident light angles up to 60°. The simulated spectra using the finite difference time domain (FDTD) method agreed with the experimental results. Superhydrophobicity and self-cleaning were also attractive properties of the surface. The functionally integrated surface enables silicon devices to have broad application prospects in solar cells, light emitting diodes (LEDs), photoelectric detectors, and outdoor equipment. Full article
(This article belongs to the Special Issue Micro-Nano Optics and Its Applications)
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Article
Study on the Influence and Law of Waterproof System Design Factors on the Typical Stress of Bridge Deck Pavement
Coatings 2021, 11(12), 1540; https://doi.org/10.3390/coatings11121540 - 14 Dec 2021
Cited by 2 | Viewed by 781
Abstract
To improve the structural design rationality of cement concrete bridge deck pavement systems and reduce diseases such as interlayer displacement and rutting in the early stage of bridge deck use, this paper studies the influence and law of the coupling effect of various [...] Read more.
To improve the structural design rationality of cement concrete bridge deck pavement systems and reduce diseases such as interlayer displacement and rutting in the early stage of bridge deck use, this paper studies the influence and law of the coupling effect of various factors of the waterproof system on the typical stress of bridge deck pavement and determines the best structure combination for the bridge deck pavement structure. A finite element model was established by using commercial software to simulate the mechanical response of different types of waterproof bonding layer, waterproof leveling layer, and impervious structure layer under different parameters. The simulation results show that when the thickness of the pavement layer was 8 cm, the maximum shear stress of the pavement layer occurred in the middle of the wearing course and the junction between layers. When the pavement layers were continuous, the maximum strain of the waterproof bonding layer with the “rubber asphalt + protective plate” structure in the transverse and longitudinal directions was the largest. When the waterproof leveling layer was cement concrete, the structure bore a large amount of stress and easily produced cracks, resulting in water damage. High-density water-based asphalt concrete with a low permeability coefficient can reduce the interlayer shear stress and effectively ensure the interlayer bonding effect. On this basis, the following bridge deck pavement structure was proposed: waterproof system + multifunctional waterproof layer + load-bearing structure layer + surface functional layer. Full article
(This article belongs to the Collection Pavement Surface Coatings)
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Article
Effects of Nb Addition on Microstructures and Mechanical Properties of Nbx-CoCrFeMnNi High Entropy Alloy Films
Coatings 2021, 11(12), 1539; https://doi.org/10.3390/coatings11121539 - 14 Dec 2021
Viewed by 806
Abstract
In the present work, Nbx-CoCrFeMnNi high entropy alloy films (HEAFs, 0 to 7.2 at.% Nb) were fabricated by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets. The effects of Nb addition on the microstructures and mechanical properties of [...] Read more.
In the present work, Nbx-CoCrFeMnNi high entropy alloy films (HEAFs, 0 to 7.2 at.% Nb) were fabricated by radio frequency (RF) magnetron co-sputtering of CoCrFeMnNi alloy and Nb targets. The effects of Nb addition on the microstructures and mechanical properties of HEAFs were systematically investigated. For Nb-free film (0 at.% Nb), the face-centered cubic (FCC) peaks were identified in the X-ray diffraction (XRD) pattern. The addition of Nb resulted in a broadening of diffraction peaks, a decrease in peak intensity, and the vanishment of high-angle peaks. Transmission electron microscope (TEM) images indicated the formation of nanotwins at low Nb concentrations, and a transition from a single phase FCC solid solution to an amorphous phase was observed with the increasing Nb concentration. The films were strengthened with an increase in Nb concentration. Specifically, the hardness characterized by nanoindentation increased from 6.5 to 8.1 GPa. The compressive yield strength and fracture strength measured from micropillar compression tests were improved from 1.08 GPs and 2.56 GPa to 2.70 GPa and 5.76 GPa, respectively, whereas the fracture strain decreased from >29.4% (no fracture) to 15.8%. Additionally, shear banding was observed in the presence of amorphous phase. Full article
(This article belongs to the Special Issue High Entropy Alloy Films)
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