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Coatings, Volume 13, Issue 12 (December 2023) – 126 articles

Cover Story (view full-size image): Biomedical implants have significantly revolutionized modern medicine, improving the quality of life of countless patients; however, their integration with the human body remains a challenge, carrying an inherent risk of infection and increased susceptibility to inflammation. Indeed, implant-related infections and the lack of biointegration represent the most prevalent and severe complications associated with the use of biomaterials. Several critical advancements and innovative strategies have significantly enhanced the performance and safety of biomedical devices. These include polymer- and ceramic-based coatings, surface chemical functionalization, or even the use of drugs such as antibiotics, anti-inflammatories, or anticoagulants for subsequent immobilization or release. View this paper
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17 pages, 7995 KiB  
Article
High-Power Impulse Magnetron Sputter-Deposited Chromium-Based Coatings for Corrosion Protection
Coatings 2023, 13(12), 2101; https://doi.org/10.3390/coatings13122101 - 18 Dec 2023
Cited by 1 | Viewed by 658
Abstract
The use of high-power impulse magnetron sputtering (HIPIMS) to deposit chromium-based thin films on brass substrates for the purpose of corrosion-protective coating was investigated. By varying the process parameters (pulse frequency, pulse width and N2 flow rate) and structure design, including single-layer [...] Read more.
The use of high-power impulse magnetron sputtering (HIPIMS) to deposit chromium-based thin films on brass substrates for the purpose of corrosion-protective coating was investigated. By varying the process parameters (pulse frequency, pulse width and N2 flow rate) and structure design, including single-layer and multilayer structures, the obtained results revealed that the Cr-N films deposited through the use of HIPIMS exhibited higher film density and corrosion resistance compared to traditional direct-current magnetron sputtering. Based on the results of a field test using copper-accelerated acetic acid solution, the Cr-N film with a multilayered structure can further extend the time to corrosion onset. This is because the bottom layer in the multilayer structure can block structural defects in the layer above it, effectively reducing the penetration of corrosive agents into the substrate. The high bias voltage, coupled with increased temperature during deposition, led to a dezincification effect, resulting in the reduced adhesion of the film to the substrate and decreased overall corrosion resistance. Full article
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17 pages, 10995 KiB  
Article
Physical and Chemical Properties of High-Temperature Silicone-Based Polymer Coatings Applied on Different Surface Roughnesses
Coatings 2023, 13(12), 2100; https://doi.org/10.3390/coatings13122100 - 18 Dec 2023
Viewed by 711
Abstract
High-temperature coatings play a crucial role in protecting surfaces exposed to extreme temperatures, corrosion, and other harsh environments. This paper focuses on the physical and chemical properties of solvent-borne and water-borne high-temperature silicone-based polymer coatings applied on two types of surface roughness of [...] Read more.
High-temperature coatings play a crucial role in protecting surfaces exposed to extreme temperatures, corrosion, and other harsh environments. This paper focuses on the physical and chemical properties of solvent-borne and water-borne high-temperature silicone-based polymer coatings applied on two types of surface roughness of carbon steel plates. The corrosion protection performance of the coatings was characterized using a salt spray chamber, humidity chamber, electrochemical impedance spectroscopy (EIS) measurements, and differential scanning calorimetry (DSC). The physical properties of high-temperature coatings were determined using the Shore D hardness method and cross-cut adhesion tests. This study investigates the effects of different surface preparation methods on coating adhesion, which is considered to be a crucial property of organic coatings for corrosion protection durability. The thermal stability of the coating was tested using furnace cyclic testing. The results show that high-temperature coatings in general exhibit excellent thermal stability, high adhesion strength, and good resistance to warm and humid environments, except in the conditions of a salty atmosphere. This study reveals that coating performance is affected by the composition and surface preparation method. This study can be useful for coating manufacturers and researchers interested in understanding the physical and chemical properties of high-temperature coatings and their applications in various environments. Full article
(This article belongs to the Special Issue Investigation on Corrosion Behaviour of Metallic Materials)
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16 pages, 7601 KiB  
Article
(Ti, Nb)(C, B)/IN625 In-Situ Reactive Coating Prepared by Ultra-High-Speed Laser Cladding: Interfacial Characterization, Residual Stress and Surface Wear Mechanisms
Coatings 2023, 13(12), 2099; https://doi.org/10.3390/coatings13122099 - 18 Dec 2023
Viewed by 761
Abstract
In this study, homogeneous (Ti, Nb)(C, B)/IN625 composite coatings with almost defect-free microstructures were successfully prepared on a 42CrMo steel substrate by coupling ultra-high-speed laser cladding (USLC) with the direct reaction synthesis (DRS) technique to introduce the in-situ exothermic reaction into the cladding [...] Read more.
In this study, homogeneous (Ti, Nb)(C, B)/IN625 composite coatings with almost defect-free microstructures were successfully prepared on a 42CrMo steel substrate by coupling ultra-high-speed laser cladding (USLC) with the direct reaction synthesis (DRS) technique to introduce the in-situ exothermic reaction into the cladding materials; these were comparatively analyzed with the pure IN625 coating prepared only by USLC. Our results showed that the interface of the composite coating/substrate was greatly affected by about 670 kJ Joule heat released from the in-situ reaction happening during the cladding process, which was sufficient to remelt the as-deposited materials and significantly increased the coating/substrate interface width to around 24 μm, six times the interface width of pure IN625 coating. Furthermore, the residual stress inside the coating and across the interfacial region was also reduced, alleviating the interface stress mismatch. However, the surface hardness of (Ti, Nb)(C, B)/IN625 composite coating was found to be lower than that of the IN625 coating, and the average wear weight loss was only 10% of that of the IN625 coating, attributable to the in-situ authigenic TiCB, TiC, NbMo3B4 and NbMo2B2 phases providing load transfer from the hard phases to the IN625 composite matrix to achieve abrasion reduction and wear resistance. It was also found that the formation of nano-equiaxial ultrafine grains in the depth range of 250 nm below the wear surface was facilitated by the coupling of the three fields of plastic rheology-heat-force, which dynamically strengthened the wear surface. Based on these findings, it is suggested to promote the strategy of combing USLC and DRS techniques to achieve an additional ability to enhance the coating microstructure and reduce residual stress, to achieve better tribological performance. Full article
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12 pages, 10954 KiB  
Article
Adhesion Strength and Anti-Corrosion Performance of Ceramic Coating on Laser-Textured Aluminum Alloy
Coatings 2023, 13(12), 2098; https://doi.org/10.3390/coatings13122098 - 17 Dec 2023
Viewed by 731
Abstract
Laser surface texturing and micro-arc oxidation provide excellent approaches to enhance the adhesion strength and anti-corrosion performance of adhesive bonding interfaces in aluminum alloys, which can be applied in the field of automotive light weighting. Herein, micro-arc oxidation coatings were fabricated on the [...] Read more.
Laser surface texturing and micro-arc oxidation provide excellent approaches to enhance the adhesion strength and anti-corrosion performance of adhesive bonding interfaces in aluminum alloys, which can be applied in the field of automotive light weighting. Herein, micro-arc oxidation coatings were fabricated on the laser-textured aluminum surface under the voltage of 500 V for various treatment times (5 min, 15 min, 30 min, 60 min). The anti-corrosion performance of ceramic coatings on the laser-textured surface was analyzed using electrochemical measurements. The results of electrochemical measurement indicate that the coating on the sample surface presents two time constants corresponding to a dual-layer structure. The sample grown under 500 V for 60 min exhibits excellent protective performance with a value of 1.3 × 107 ohm·cm2. The adhesion strength of laser-textured ceramic coating is improved compared with the as-received substrate. The sample treated with 500 V for 30 min exhibits the highest bonding strength with a value of 52 MPa. The wider pores and bulges for the sample grown in 60 min would introduce microcracks and consequently reduce the adhesion strength. Full article
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8 pages, 2978 KiB  
Communication
Effect of Film Thickness on Microstructural and Magnetic Properties of Lithium Ferrite Films Prepared on Strontium Titanate (001) Substrates
Coatings 2023, 13(12), 2097; https://doi.org/10.3390/coatings13122097 - 17 Dec 2023
Viewed by 651
Abstract
Epitaxial lithium ferrite (LiFe5O8) films with different thicknesses were successfully fabricated on strontium titanate (SrTiO3) (001) substrates using the magnetron sputtering deposition technique. The microstructural and magnetic properties of the films were characterized by an advanced transmission [...] Read more.
Epitaxial lithium ferrite (LiFe5O8) films with different thicknesses were successfully fabricated on strontium titanate (SrTiO3) (001) substrates using the magnetron sputtering deposition technique. The microstructural and magnetic properties of the films were characterized by an advanced transmission electron microscope and a magnetic measurement device. It was found that the formation of structural defects can be influenced by the thickness of the film. In addition to misfit dislocations, orientation domains form in thinner films and twin boundaries appear in thicker films, respectively, contributing to the misfit strain relaxation in the heterosystem. The magnetic measurement showed that the thinner films have enhanced magnetization and a relatively lower coercive field compared with the thicker films containing antiferromagnetic twin boundaries. Our results provide a way of tuning the microstructure and magnetic properties of lithium ferrite films by changing the film thickness. Full article
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20 pages, 20489 KiB  
Article
Microstructural, Mechanical and Oxidation Resistance of Nanolayer Sputter-Deposited CrAlN Hard Coatings
Coatings 2023, 13(12), 2096; https://doi.org/10.3390/coatings13122096 - 17 Dec 2023
Viewed by 666
Abstract
In the present study, (Cr,Al)N nanolayer coatings with different Al/Cr atomic ratios were deposited by magnetron sputtering on different substrate materials (H11 and D2 tool steel, alumina). To prepare the (Cr,Al)N coatings with different Al/Cr atomic ratios in the same batch, we used [...] Read more.
In the present study, (Cr,Al)N nanolayer coatings with different Al/Cr atomic ratios were deposited by magnetron sputtering on different substrate materials (H11 and D2 tool steel, alumina). To prepare the (Cr,Al)N coatings with different Al/Cr atomic ratios in the same batch, we used two targets composed of two triangle-like segments together with two standard Al and Cr targets. This approach enabled us to study the evolution of structural and mechanical properties in dependence on composition. The elemental composition of the coatings was determined by energy-dispersive X-ray analysis (EDS). The phase composition of the (Cr,Al)N coatings was determined utilizing X-ray diffraction (XRD), while scanning electron microscopy (SEM) was employed to assess their morphology and microstructure. The coating surface topography was analyzed by atomic force microscopy (AFM). In order to evaluate the effect of the Al/Cr atomic ratio on the oxidation behavior, the (Cr,Al)N coatings were oxidized in ambient atmospheres at temperatures between 700 and 850 °C and subsequently analyzed by means of cross-sectional SEM and transmission electron microscopy (TEM). The oxidation rate, determined by weight gain over time, was utilized to quantify the oxidation process. The oxidation tests showed that the Al-rich (Cr,Al)N nanolayer coatings exhibit a considerably better oxidation resistance than the Cr-rich ones. We found that the oxide scale formed on the Al-rich coating is composed of double layers: a Cr-oxide top layer and an inner (Cr,Al) mixed oxide layer. In contrast, the oxide scale of the Cr-rich coating mainly consists of the Cr2O3 layer. In particular, we focused on the oxidation process occurring at the locations of growth defects. We noticed that the first oxidation products on the coated substrate occurred at a temperature that was much lower than the temperature for the (Cr,Al)N coating oxidation initiation. These products (iron oxides) formed only at the sites of those growth defects that extended through the entire coating thickness. Full article
(This article belongs to the Special Issue The State-of-the-Art in PVD Hard Coatings and Their Applications)
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19 pages, 5313 KiB  
Review
A Review of the Developments of the Characteristics and Mechanisms of Airless Spraying on Complex Surfaces
Coatings 2023, 13(12), 2095; https://doi.org/10.3390/coatings13122095 - 17 Dec 2023
Viewed by 770
Abstract
The special surface appearance of complex surfaces restricts the coating film quality of spraying. The study of the atomization and film formation characteristics of typical complex surfaces, as well as the spraying mechanism, is essential for planning the spraying robotic trajectory and improving [...] Read more.
The special surface appearance of complex surfaces restricts the coating film quality of spraying. The study of the atomization and film formation characteristics of typical complex surfaces, as well as the spraying mechanism, is essential for planning the spraying robotic trajectory and improving the spraying efficiency. In this paper, modeling and characteristics of the atomization and film formation process, based on CFD numerical simulations in previous studies, are systematically reviewed, focusing especially on airless spraying. In addition, the advantages and disadvantages of the existing research from the perspective of numerical models and methods are discussed. Finally, a further research direction for spraying on complex surface is prospected. Overall, a comprehensive and up-to-date review of spray atomization and film formation characteristics is considered valuable to practitioners and researchers in these fields, and will facilitate the further application of robotic spraying in the mechanical, automotive, marine, aerospace, petrochemical and other industries. Full article
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0 pages, 1611 KiB  
Article
Chemisorption and Surface Reaction of Hafnium Precursors on the Hydroxylated Si(100) Surface
Coatings 2023, 13(12), 2094; https://doi.org/10.3390/coatings13122094 - 16 Dec 2023
Viewed by 718
Abstract
Hafnium oxide (HfO2) is widely recognized as one of the most promising high-k dielectric materials due to its remarkable properties such as high permittivity, wide band gap, and excellent thermal and chemical stability. The atomic layer deposition (ALD) of HfO [...] Read more.
Hafnium oxide (HfO2) is widely recognized as one of the most promising high-k dielectric materials due to its remarkable properties such as high permittivity, wide band gap, and excellent thermal and chemical stability. The atomic layer deposition (ALD) of HfO2 has attracted significant attention in recent decades since it enables uniform and conformal deposition of HfO2 thin films on various substrates. In this study, we examined the initial surface reactions of a series of homoleptic hafnium precursors on hydroxylated Si(100) surfaces using density functional theory calculations. Our theoretical findings align with previous experimental studies, indicating that hafnium amides exhibit higher reactivity compared to other precursors such as hafnium alkoxides and hafnium halides in surface reactions. Interestingly, we found that the chemisorption and reactivity of hafnium precursors are considerably affected by their thermal stability and size. For alkoxide precursors, which have similar thermal stabilities, the size of alkoxide ligands is an important factor in determining their reactivity. Conversely, the reactivity of hafnium halides, which have ligands of similar sizes, is primarily governed by their thermal stability. These insights are valuable for understanding the surface reaction mechanisms of precursors on hydroxylated Si(100) surfaces and for designing new materials, particularly heteroleptic precursors, in future research. Full article
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13 pages, 14504 KiB  
Article
Microstructure and Texture of Pure Copper under Large Compression Deformation and Different Annealing Times
Coatings 2023, 13(12), 2093; https://doi.org/10.3390/coatings13122093 - 16 Dec 2023
Viewed by 739
Abstract
In this study, the plastic deformation of pure copper under room-temperature compression and different annealing times was examined, and the microstructure and texture evolution were studied via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and microhardness tests. The results showed that when [...] Read more.
In this study, the plastic deformation of pure copper under room-temperature compression and different annealing times was examined, and the microstructure and texture evolution were studied via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and microhardness tests. The results showed that when the deformation degree was 93.75%, the microhardness increased from 76 HV (Vickers hardness) before deformation to 110 HV. After annealing, the hardness decreased with increasing annealing time, and the pure copper grain size could be refined from 150 μm to 6.15 μm. An increase in annealing time did not continue to promote recrystallization, while the effect on grain refinement was weakened. The geometrically necessary dislocation (GND) density decreased from 6.0 × 1014/m2 to 4.83 × 1014/m2 after annealing, which implies that static recrystallization occurs at the cost of dislocation consumption during the annealing process. The compression deformation of pure copper produced a strong deformation weave (<001> orientation), and a portion of the deformation weave within the material was transformed into a recrystallization weave (<111> orientation) after the annealing process. Full article
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11 pages, 7018 KiB  
Article
Decorative Coatings of the Saint Demetrius Basarabov Reliquary’s Wooden Pedestal
Coatings 2023, 13(12), 2092; https://doi.org/10.3390/coatings13122092 - 16 Dec 2023
Viewed by 672
Abstract
This study presents the results and information revealed by in-depth physicochemical investigations carried out on an 18th-century polychrome wooden pedestal of the holy relics of Saint Demetrius Basarabov preserved at the Romanian Patriarchy of Bucharest. The preliminary stylistic observations and examinations on its [...] Read more.
This study presents the results and information revealed by in-depth physicochemical investigations carried out on an 18th-century polychrome wooden pedestal of the holy relics of Saint Demetrius Basarabov preserved at the Romanian Patriarchy of Bucharest. The preliminary stylistic observations and examinations on its present state of conservation were followed by optical microscopy, X-ray fluorescence (XRF) spectrometry, and attenuated total reflectance Fourier-transform infrared spectroscopy (FTIR-ATR) analysis performed in order to adopt an appropriate restoration treatment for bringing the artifact, as close as possible, to its original appearance as well as for dating/attributing the artifact and assessing its state of conservation. It was revealed that several interventions were subsequently undertaken on the original gilded surface consisting of a gypsum support layer with an iron oxide layer of bolus on which a silver foil or a gold foil and a natural resin on top of it as a protective layer were applied. The regilding and later restoration interventions consisted in applying, over the original, layers of a copper–zinc alloy foil (Dutch metal as an imitation of gold) with a resin layer of vernis over it. The final decision on the restoration intervention was taken based on the scientific analysis outcome. This work attempts also to highlight the importance of the interdisciplinary collaboration between researchers, conservation scientists, restorers/conservators, and curators for the preservation and valorization of the historical religious Romanian heritage artifacts, largely unknown worldwide. Full article
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14 pages, 3501 KiB  
Article
Physicomechanical Properties of Gypsum with Mineral Additions at Elevated Temperatures
Coatings 2023, 13(12), 2091; https://doi.org/10.3390/coatings13122091 - 15 Dec 2023
Viewed by 714
Abstract
Gypsum, from either nature or industrial by-products, can be a lower-cost and cleaner alternative binder to Portland cement used in construction projects, such as affordable housing in developing countries. Although various building products have successfully used gypsum as the binder, some drawbacks of [...] Read more.
Gypsum, from either nature or industrial by-products, can be a lower-cost and cleaner alternative binder to Portland cement used in construction projects, such as affordable housing in developing countries. Although various building products have successfully used gypsum as the binder, some drawbacks of this material have still been claimed, for example, in the aspects of mechanical strength and some other physical properties. Using mineral additions to gypsum seems to be a possible solution to create composite gypsum with improved properties. This work has investigated the possibility of two common minerals (silica flour and talc powder) in modifying composite gypsum’s physical and mechanical performance at elevated temperatures (100–1100 °C), including hydration, strength, thermal conduction and stability, and microstructure. The results suggest that 10% gypsum replacement by silica flour or talc powder modifies gypsum’s physical and mechanical properties, with silica flour performing better than talc powder. The performance of composite gypsum at elevated temperatures depends on the treatment temperature and reflects the combined effects of gypsum phase change and the filler effects of silica flour or talc powder. Thermal treatment at ≤200 °C increased the thermal resistance of all gypsum boards but decreased their compressive strength. Thermal treatment at ≥300 °C significantly increased the compressive strength of gypsum with silica flour and talc powder but induced intensive microcracks and thus failed the thermal insulation. This investigation indicates that silica flour can potentially raise the mechanical performance of gypsum. At the same time, talc powder can hold water and lubricate, which may help with the continuous hydration of gypsum phases and the rheology of its mixtures. Full article
(This article belongs to the Special Issue Effective Coating Barriers for Protection of Reinforced Concrete)
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16 pages, 20813 KiB  
Article
Tribological and Corrosion Performance of CrAlN/CrN Coatings in Artificial Seawater under Varied Nitrogen Pressures
Coatings 2023, 13(12), 2090; https://doi.org/10.3390/coatings13122090 - 15 Dec 2023
Viewed by 606
Abstract
This study employed arc ion plating technology to deposit CrAlN/CrN coatings on stainless steel substrates, adjusting deposition pressures ranging from 1.0 Pa to 4.0 Pa. A detailed analysis of the coatings’ microstructure, wear, and corrosion features was performed using X-ray diffraction, scanning electron [...] Read more.
This study employed arc ion plating technology to deposit CrAlN/CrN coatings on stainless steel substrates, adjusting deposition pressures ranging from 1.0 Pa to 4.0 Pa. A detailed analysis of the coatings’ microstructure, wear, and corrosion features was performed using X-ray diffraction, scanning electron microscopy, nanoindentation, tribometers, profilometers, and electrochemical workstations. The study revealed that the crystalline structure of the CrAlN/CrN coatings primarily consists of cubic crystals of AlN, (Cr, Al)N, and CrN. Diffraction peak intensity analysis revealed preferential orientation in the CrAlN coatings along the (111) and (200) crystal planes. As the pressure increased to 3.0 Pa, the content of Al elements peaked, and the columnar structure became denser; at this point, the H/E* ratio reached a maximum of 0.079, indicating excellent delamination and fracture resistance of the CrAlN/CrN coating at this pressure. Tests in artificial seawater environments showed that with the increase in nitrogen pressure, the friction coefficient gradually decreased, reaching its lowest at 3 Pa, approximately 0.19. The wear rate trend aligned with the friction coefficient, recorded at a mere 2.20 × 10−7 mm3/Nm. Electrochemical polarization curve tests revealed that at 3 Pa pressure, the CrAlN/CrN coating had a corrosion potential of −0.04 V, a polarization resistance of 9.28 × 105 Ω·cm2, and a very low corrosion current of 4.81 × 10−8 A/cm2, demonstrating excellent corrosion resistance. Full article
(This article belongs to the Special Issue Mechanical Properties and Tribological Behavior of Alloy/Coatings)
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14 pages, 10522 KiB  
Article
Effect of Minor Mo Addition on Microstructure and Corrosion Resistance of High-Velocity Air Fuel-Sprayed Fe-Based Amorphous Coatings
Coatings 2023, 13(12), 2089; https://doi.org/10.3390/coatings13122089 - 15 Dec 2023
Viewed by 676
Abstract
In this work, Fe64Nb3B17Si6Cr6Ni4 and Fe60Nb3B17Si6Cr6Ni4Mo4 (at. %) coatings were prepared with a high-velocity air fuel spraying method, and [...] Read more.
In this work, Fe64Nb3B17Si6Cr6Ni4 and Fe60Nb3B17Si6Cr6Ni4Mo4 (at. %) coatings were prepared with a high-velocity air fuel spraying method, and the effects of minor Mo addition on the microstructure, glass formation, and corrosion resistance of the coating were studied. It was found that the Mo addition improves the glass-forming ability of the alloy and a fully amorphous structure with a higher compactness was obtained in the Mo-containing coating. The thermal stability of the coating is enhanced by Mo addition and the onset crystallization temperature was increased by 20 K. In addition, the Mo-containing amorphous coating exhibited higher corrosion resistance than the Mo-free coating. The superior corrosion resistance can be attributed to the increased proportion of protective, stable Cr, Nb, and Mo oxides in the passive film and fewer defects of the Mo-containing coating. Full article
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26 pages, 10667 KiB  
Review
Nanostructure Engineering of Alloy-Based Anode Materials with Different Dimensions for Sodium/Potassium Storage
Coatings 2023, 13(12), 2088; https://doi.org/10.3390/coatings13122088 - 15 Dec 2023
Viewed by 698
Abstract
Sodium/potassium-ion batteries have drawn intensive investigation interest from researchers owing to their abundant element resources and significant cost advantages. Anode materials based on alloy reaction mechanisms have the prominent merits of a suitable reaction potential and high theoretical specific capacity and energy density. [...] Read more.
Sodium/potassium-ion batteries have drawn intensive investigation interest from researchers owing to their abundant element resources and significant cost advantages. Anode materials based on alloy reaction mechanisms have the prominent merits of a suitable reaction potential and high theoretical specific capacity and energy density. However, very large volumetric stresses and volume changes during the charge/discharge process and the resulting electrode structural cracking, deactivation and capacity fading seriously hinder their development. To date, a series of modification strategies have been proposed to tackle these challenges and achieve good electrochemical performance. Herein, we review the recent advances in the structural engineering of alloy-type anodes for sodium/potassium storage, mainly including phosphorus, tin, antimony, bismuth and related alloy materials, from the perspective of dimensional structure. Furthermore, some future research directions and unresolved issues are presented for the investigation of alloy-based anode materials. It is hoped that this review can serve as a guide for the future development and practical application of sodium/potassium-ion batteries. Full article
(This article belongs to the Special Issue Research on Novel Energy Storage Materials and Devices)
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13 pages, 3042 KiB  
Article
The Effect of Precipitates on the Stress Rupture Properties of Laser Powder Bed Fusion Inconel 718 Alloy
Coatings 2023, 13(12), 2087; https://doi.org/10.3390/coatings13122087 - 14 Dec 2023
Viewed by 650
Abstract
Improving the high-temperature stress rupture properties of Inconel 718 (IN718) alloys is crucial for enhancing aircraft engine performance. By using the laser powder bed fusion (LPBF) technique, IN718 alloys were crafted at varying volumetric energy densities (VED) in this study. The dendrite growth [...] Read more.
Improving the high-temperature stress rupture properties of Inconel 718 (IN718) alloys is crucial for enhancing aircraft engine performance. By using the laser powder bed fusion (LPBF) technique, IN718 alloys were crafted at varying volumetric energy densities (VED) in this study. The dendrite growth mode, reinforcing phase distribution and high temperature stress rupture properties of various VED samples were investigated. The results showed that the stress rupture life and the uniform elongation of the samples both first increased and then decreased with the increase in VED. When the VED was 60 J/mm3, the maximum rupture life and elongation of the sample were 43 h and 3.8%, respectively. As the VED increased, the angle of dislocation in the dendrite decreased while the spacing between primary dendrite arms increased, resulting in an increase in the size and volume fraction of the Laves phase. Following a heat treatment, the δ phase would nucleate preferentially around the dissolved Laves phase causing an increase in the volume fraction of the δ phase with the increase in VED. The creep voids readily formed around the δ phase are distributed along the grain boundaries, while the inhomogeneous δ phase and fine grains facilitated crack initiation and propagation. Furthermore, a significant quantity of the δ phase consumed the Nb element, thereby hindering adequate precipitation in the γ″ phase and causing cracks. Full article
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20 pages, 8089 KiB  
Article
Analysis of Surface Roughness during Surface Polishing of ITO Thin Film Using Acoustic Emission Sensor Monitoring
Coatings 2023, 13(12), 2086; https://doi.org/10.3390/coatings13122086 - 14 Dec 2023
Cited by 1 | Viewed by 615
Abstract
This study investigates the intricate process of surface polishing for ITO-coated Pyrex glass utilizing magnetic abrasive polishing (MAP) while employing acoustic emission (AE) sensors for real-time defect monitoring. MAP, known for its versatility in achieving nanoscale thickness processing and uniform surfaces, has been [...] Read more.
This study investigates the intricate process of surface polishing for ITO-coated Pyrex glass utilizing magnetic abrasive polishing (MAP) while employing acoustic emission (AE) sensors for real-time defect monitoring. MAP, known for its versatility in achieving nanoscale thickness processing and uniform surfaces, has been widely used in various materials. However, the complexity of the process, influenced by multiple variables like cutting conditions, material properties, and environmental factors, poses challenges to maintaining high surface quality. To address this, a sensor monitoring system, specifically one that uses AE sensors, was integrated into the MAP process to detect and confirm defects, providing real-time insights into machining conditions and outcomes. AE sensors excel in identifying material deterioration, microcrack formation, and wear, even in cases of minor damage. Leveraging AE sensor data, this study aims to minimize surface defects in ITO thin films during MAP while optimizing surface roughness. The investigation involves theoretical validation, magnetic density simulations, and force sensor pressure measurements to identify factors influencing surface roughness. ANOVA analysis is employed to determine optimal processing conditions. Additionally, this study compares the identified optimal roughness conditions with those predicted by AE sensor parameters, aiming to establish a correlation between predicted and achieved surface quality. The integration of AE sensor monitoring within the MAP process offers a promising avenue for enhancing surface quality by effectively identifying and addressing defects in real time. This comprehensive analysis contributes to advancing the understanding of surface polishing methodologies for ITO-coated Pyrex glass, paving the way for improved precision and quality in thin-film surface processes. Full article
(This article belongs to the Special Issue Manufacturing and Surface Engineering IV)
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41 pages, 2562 KiB  
Review
Nanomaterials for Potential Detection and Remediation: A Review of Their Analytical and Environmental Applications
Coatings 2023, 13(12), 2085; https://doi.org/10.3390/coatings13122085 - 14 Dec 2023
Viewed by 764
Abstract
The rapid increase in industrialization and human population is leading to critical levels of environmental pollutants, such as agrochemicals or heavy metals, which affect the preservation and integrity of ecosystems, the accessibility to drinking water sources, and the quality of the air. As [...] Read more.
The rapid increase in industrialization and human population is leading to critical levels of environmental pollutants, such as agrochemicals or heavy metals, which affect the preservation and integrity of ecosystems, the accessibility to drinking water sources, and the quality of the air. As such, remediation of these issues demands strategies for implementing and designing novel technologies. In that regard, nanomaterials have unique physicochemical properties that make them desirable candidates for the detection and remediation of environmental pollutants. The scope of this review is to provide an analysis of the available nanomaterials that are being used as an approach to detect and remediate hazardous residues, comprising systems such as noble metals, biosensors, cyclodextrin-based polymers, and graphene oxide nanocomposites, to name a few. Furthermore, this work discusses said nanomaterials in terms of their effectiveness, sustainability, and selectivity as a guideline for researchers wishing to indulge in this relevant study area. Full article
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22 pages, 8021 KiB  
Article
Tailoring Mechanical Properties of a-C:H:Cr Coatings
Coatings 2023, 13(12), 2084; https://doi.org/10.3390/coatings13122084 - 14 Dec 2023
Viewed by 733
Abstract
The development of coatings with tunable performances is critical to meet a wide range of technological applications each one with different requirements. Using the plasma-enhanced chemical vapor deposition (PECVD) process, scientists can create hydrogenated amorphous carbon coatings doped with metal (a-C:H:Me) with a [...] Read more.
The development of coatings with tunable performances is critical to meet a wide range of technological applications each one with different requirements. Using the plasma-enhanced chemical vapor deposition (PECVD) process, scientists can create hydrogenated amorphous carbon coatings doped with metal (a-C:H:Me) with a broad range of mechanical properties, varying from those resembling polymers to ones resembling diamond. These diverse properties, without clear relations between the different families, make the material selection and optimization difficult but also very rich. An innovative approach is proposed here based on projected performance indices related to fracture energy, strength, and stiffness in order to classify and optimize a-C:H:Me coatings. Four different a-C:H:Cr coatings deposited by PECVD with Ar/C2H2 discharge under different bias voltage and pressures are investigated. A path is found to produce coatings with a selective critical energy release rate between 5–125 J/m2 without compromising yield strength (1.6–2.7 GPa) and elastic limit (≈0.05). Finally, fine-tuned coatings are categorized to meet desired applications under different testing conditions. Full article
(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)
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11 pages, 3113 KiB  
Article
ZnS:Cu/PDMS Composite Coating for Combating Marine Biofouling
Coatings 2023, 13(12), 2083; https://doi.org/10.3390/coatings13122083 - 14 Dec 2023
Viewed by 546
Abstract
Biofouling is a major concern in marine industries. The use of traditional toxic antifouling coatings is forbidden or severely restricted. This study aimed to provide a green and effective antifouling coating. The coating was prepared using a polydimethylsiloxane (PDMS) matrix and Cu-doped zinc [...] Read more.
Biofouling is a major concern in marine industries. The use of traditional toxic antifouling coatings is forbidden or severely restricted. This study aimed to provide a green and effective antifouling coating. The coating was prepared using a polydimethylsiloxane (PDMS) matrix and Cu-doped zinc sulfide (ZnS:Cu). Four samples with different ZnS:Cu contents (1, 10, 20, and 50 wt%) were prepared. Pristine PDMS (0 wt%) was used as the control. The results showed that all coatings had hydrophobic surfaces conducive to combating biofouling. In tests against B. Subtilis, the 1, 10, 20, and 50 wt% samples showed enhanced antifouling capabilities compared to the 0 wt% sample. In static and dynamic tests against Chlorella, the antifouling capability increased with increasing ZnS:Cu content and the 50 wt% sample showed the best antifouling capability. The possible antifouling mechanisms of these coatings include the release of ions (Zn2+ and Cu+), induction of deformation, and fluorescence emission. This study provides a reference for the application of Zn2+/Cu+ combinations to combat marine biofouling. Full article
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16 pages, 3220 KiB  
Article
The Impact of Topological States on the Thermoelectric Performance of p- and n-Type Sb2Te3/Bi2Se3-Multiwalled Carbon Nanotubes Heterostructured Networks
Coatings 2023, 13(12), 2082; https://doi.org/10.3390/coatings13122082 - 14 Dec 2023
Viewed by 578
Abstract
The resistance and magnetoresistance of flexible thermoelectric p-type Sb2Te3-MWCNT, p-type Bi2Se3-MWCNT, and n-type Bi2Se3-MWCNT heterostructures were studied in the temperature range from 2 K to 300 K to reveal the conductance [...] Read more.
The resistance and magnetoresistance of flexible thermoelectric p-type Sb2Te3-MWCNT, p-type Bi2Se3-MWCNT, and n-type Bi2Se3-MWCNT heterostructures were studied in the temperature range from 2 K to 300 K to reveal the conductance mechanisms governing the thermoelectric properties of these heterostructured networks. It was found that the conductance in heterostructured networks at different temperatures is governed by different processes and components of the networks. This effect was found to be related to the growth mechanisms of the Sb2Te3 and Bi2Se3 nanostructures on the MWCNT networks. At near-room temperatures, the Sb2Te3 and Bi2Se3 nanostructures were found to have the dominant contribution to the total conductance of the p-type Sb2Te3-MWCNT and n-type Bi2Se3-MWCNT networks. In turn, the conduction of p-type Bi2Se3-MWCNT heterostructured networks in a full temperature range and p-type Sb2Te3-MWCNT and n-type Bi2Se3-MWCNT heterostructured networks at temperatures below 30 K was governed by the MWCNTs; however, with the contribution from 2D topological states of Sb2Te3 and Bi2Se3 nanostructures, these were manifested by the weak antilocalization effect (WAL) cusps observed at temperatures below 5–10 K for all heterostructured networks considered in this work. Full article
(This article belongs to the Topic Advances in Functional Thin Films)
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26 pages, 23060 KiB  
Review
Nanomaterials and Equipment for Chemical–Mechanical Polishing of Single-Crystal Sapphire Wafers
Coatings 2023, 13(12), 2081; https://doi.org/10.3390/coatings13122081 - 14 Dec 2023
Viewed by 929
Abstract
Single-crystal sapphire (α-Al2O3) has been widely used in semiconductor, optics, communication, national defense, and other fields. Before application, an ultra-smooth surface which is scratch free and subsurface damage free is essential. Furthermore, the sapphire has unique qualities such as [...] Read more.
Single-crystal sapphire (α-Al2O3) has been widely used in semiconductor, optics, communication, national defense, and other fields. Before application, an ultra-smooth surface which is scratch free and subsurface damage free is essential. Furthermore, the sapphire has unique qualities such as significant rigidity and chemical stability, which make it extremely arduous to process. Chemical mechanical polishing (CMP) is recognized as the final process to reduce the roughness and eliminate surface defects of a sapphire surface. In this review, the materials and equipment used for the chemical polishing of a sapphire wafer are summarized, and the surface nanoscale changes of sapphire wafer are reviewed from the angles of regulating polishing-process parameters, composition of polishing slurry including that which is nano-abrasive, a pH regulator, a complexing agent, and other additives, as well as hybrid CMP technologies. The outlook and future applications are also summarized. Full article
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23 pages, 3778 KiB  
Article
Modeling of Solid Particle Erosion for a Water–Sand Impingement System Using OpenFOAM
Coatings 2023, 13(12), 2080; https://doi.org/10.3390/coatings13122080 - 13 Dec 2023
Viewed by 781
Abstract
The development of accurate methodologies for a thorough comprehension of the erosion phenomenon is a challenging and necessary task. This study entailed an exhaustive analysis, incorporating empirical data obtained from an experiment involving the impingement of a sand and water jet on a [...] Read more.
The development of accurate methodologies for a thorough comprehension of the erosion phenomenon is a challenging and necessary task. This study entailed an exhaustive analysis, incorporating empirical data obtained from an experiment involving the impingement of a sand and water jet on a submerged stainless-steel plate and numerical simulations, employing the Oka Erosion model that was compilated in OpenFOAM. The primary focus of this study was to generate W-shaped profiles delineating the impingement zone, derived both from experimental observations and the developed numerical model. This comparative approach facilitated a robust evaluation of the model’s efficacy in replicating erosion patterns. The outcomes of this analysis revealed a concurrence between the experimental and simulated erosion contours, affirming the model’s proficiency in representing erosion phenomena. Nevertheless, a minor discrepancy was noted, characterized by a slight underestimation of erosion rate and thickness loss. Furthermore, the investigation unveiled a noteworthy time-dependent trend in mass loss from the experimental data denoting a pseudo stabilization of the erosion rate across the time. This research contributes to the refinement of erosion modeling parameters and underscores the nature of time-dependent erosion behavior, a pivotal consideration for optimizing material durability. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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19 pages, 11831 KiB  
Article
Fabrication of Vitrified Bond Diamond Grinding Wheel via LCD Photopolymerization
Coatings 2023, 13(12), 2079; https://doi.org/10.3390/coatings13122079 - 13 Dec 2023
Viewed by 595
Abstract
In this paper, a liquid crystal display (LCD) photopolymerization method is proposed, and a vitrified bond diamond grinding wheel is successfully prepared. A high-performance vitrified bond was obtained by melting SiO2-B2O3-Al2O3-Na2O [...] Read more.
In this paper, a liquid crystal display (LCD) photopolymerization method is proposed, and a vitrified bond diamond grinding wheel is successfully prepared. A high-performance vitrified bond was obtained by melting SiO2-B2O3-Al2O3-Na2O ceramic raw materials and used for grinding wheel preparation. LCD photopolymerization technology is characterized by high precision in shaping, fast processing speed, and superior quality, making it a promising technology for fabricating vitrified bond diamond grinding wheels. The preparation of vitrified bond slurry with high solid content and low viscosity was extensively investigated to meet the fabrication requirements. The effects of dispersant, the particle size of the vitrified bond, and solid content on the viscosity of the slurry were systematically analyzed. The vitrified bond slurry with solid content up to 65 wt.% (approximately 45.5 vol.%) was successfully prepared and met the requirements for printing. Furthermore, we explored the optimal formulation of the grinding wheel, debinding and sintering conditions, sintering temperature, grit-to-bond ratio, and the evaluation of the grinding performance of the wheel on hard and brittle materials, such as silicon carbide ceramic. Vitrified bond and abrasive slurry systems with a solid content of 65 wt.% (approximately 42.8 vol.%) were prepared. The results show that the vitrified bond diamond grinding wheel exhibits optimal comprehensive performance, with a sintering temperature of 680 °C and a grit-to-bond ratio of 4:6. The minimum surface roughness of the workpiece after grinding was 1.767 μm, the material removal rate was 5.08 mg/s, the grinding ratio was 9.78, and the friction coefficient was stabilized at about 0.5 during grinding. This paper guides the manufacturing of vitrified bond diamond grinding wheels via LCD photopolymerization. Full article
(This article belongs to the Special Issue Recent Advances in the Machining of Metals and Composites)
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12 pages, 2835 KiB  
Article
The Influence of Niobium and Zirconium Addition on the Structural and Mechanical Properties of Yttrium Nitride: A First-Principles Study
Coatings 2023, 13(12), 2078; https://doi.org/10.3390/coatings13122078 - 13 Dec 2023
Viewed by 548
Abstract
Yttrium nitride (YN) is a hard and refractory material with a high melting point. It is a semiconductor that has been investigated for its potential applications in the field of semiconductor technology, including as a material for electronic devices. It is also of [...] Read more.
Yttrium nitride (YN) is a hard and refractory material with a high melting point. It is a semiconductor that has been investigated for its potential applications in the field of semiconductor technology, including as a material for electronic devices. It is also of interest for its optical properties and its potential for use in optoelectronics. However, investigating its mechanical properties for a possible application in optical coatings has not been completed. This study involved the exploration of the mechanical properties of YN alloyed with niobium (Nb) and zirconium (Zr) for possible application in optical coatings using a first-principles approach. The result showed that the addition of Nb and Zr into the YN matrix had a profound effect on the mechanical properties of the modeled structures, with the Y-N-Nb (CYN_5) sample having the best mechanical properties. The bulk modulus was the most affected, with an increase of 26.48%, while the Vickers hardness had the smallest increase of 6.128% compared with those of pure YN. The modeled structures were thus found to be ideal alternative materials for optical coatings due to their improved mechanical properties. Full article
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22 pages, 10458 KiB  
Article
Cissus antractica-ZnO NPs Induce Apoptosis in A549 Cells through ROS-Generated p53/Bcl-2/Bax Signaling Pathways and Inhibition of Inflammatory Cytokines
Coatings 2023, 13(12), 2077; https://doi.org/10.3390/coatings13122077 - 13 Dec 2023
Viewed by 711
Abstract
Biogenic synthesis using medicinal plants has less harmful effects as compared to the chemical synthesis of nanoparticles. Here, for the first time, we successfully demonstrated the eco-friendly synthesis of zinc oxide nanoparticles (ZnO NPs) using an aqueous extract of Cissus antractica. The [...] Read more.
Biogenic synthesis using medicinal plants has less harmful effects as compared to the chemical synthesis of nanoparticles. Here, for the first time, we successfully demonstrated the eco-friendly synthesis of zinc oxide nanoparticles (ZnO NPs) using an aqueous extract of Cissus antractica. The green synthesis method offers great potential for developing new medications that enhance drug bioavailability. The current work highlighted the cytotoxicity, cell death, and routes of apoptosis in lung cancer cells (A549) and inflammatory effects through synthesizing zinc oxide nanoparticles (ZnO NPs) from the Cissus antractica plant using an eco-friendly methodology. UV–visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDS) were also used to characterize the synthesized ZnO nanoparticles. The average size of the NPs was 100 nm, and the NPs were crystalline in nature, as confirmed by FE-TEM and XRD analysis, respectively. In addition, the morphology of the nanoparticles analyzed by FE-TEM showed a spherical shape. The cell viability assay indicated that CA-ZnO NPs are non-toxic to normal cell lines at concentrations up to 20 µg/mL but showed significant toxicity in the A549 cell line. The nanoformulation also increased the ROS generation level in A549 lung cancer cells, and cellular apoptosis was confirmed via Hoechst and PI staining. The CA-ZnO NPs showed significant colony inhibition as well as cell migration ability that highlighted the CA-ZnO NPs as an anticancer agent. Additionally, this study demonstrated that NPs reduced the production of reactive oxygen species (ROS) and enhanced the expression of genes for BAX accumulation by releasing Cyto-c, but decreased Bcl-2 gene expression via the mitochondrial-mediated apoptosis pathway. In addition, the anti-inflammatory effect was also investigated; the CA-ZnO NPs showed significant NO inhibition ability with suppression of pro-inflammatory cytokines (TNF-α, iNOS, COX-2, IL-6, IL-8). In conclusion, Cissus antractica can be a source of significant Nano drugs with more advanced research in order to develop future anti-inflammatory and anticancer medications. Full article
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13 pages, 4375 KiB  
Article
Molecules from Sargassum algae as Green Inhibitor for C38 in HCl Medium: Extraction, Characterization and Electrochemical Study
Coatings 2023, 13(12), 2076; https://doi.org/10.3390/coatings13122076 - 13 Dec 2023
Viewed by 738
Abstract
The aim of this work is to develop new organic bio-sourced inhibitors that are ecofriendly and biodegradable. These natural inhibitors are organic, non-toxic molecules derived from plant extracts, containing numerous secondary metabolites, and are capable of being highly effective in protecting metals against [...] Read more.
The aim of this work is to develop new organic bio-sourced inhibitors that are ecofriendly and biodegradable. These natural inhibitors are organic, non-toxic molecules derived from plant extracts, containing numerous secondary metabolites, and are capable of being highly effective in protecting metals against corrosion. This study concerns the extraction, characterization and electrochemical study of natural organic compounds extracted from a species of Sargassum abundant on the coasts of Martinique, Sargassum fluitans III. The objective is to inhibit the corrosion of carbon steel. Electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques have led to new experimental results showing inhibitor efficacy. The results obtained show that this plant extract could serve as an effective inhibitor for the C38 steel in acidic media. Studies on the phytochemicals of the crude extract were also carried out. Electrochemical studies, on each chemical families present, were also established to find the main constituents responsible for corrosion inhibition properties of the algae extract. The adsorption of Sargassum fluitans III extract on the C38 steel surface, obeys the Langmuir adsorption isotherm. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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14 pages, 3552 KiB  
Article
Using Aquatic Plant-Derived Biochars as Carbon Materials for the Negative Electrodes of Li-Ion Batteries
Coatings 2023, 13(12), 2075; https://doi.org/10.3390/coatings13122075 - 13 Dec 2023
Viewed by 1005
Abstract
The current study focuses on the production of biochars derived from aquatic plants, specifically red seaweed Ahnfeltia and seagrass Zostera and Ruppia, found in brackish lagoons in the Sea of Okhotsk, Sakhalin Island. These biochars were obtained through a stepwise pyrolysis process [...] Read more.
The current study focuses on the production of biochars derived from aquatic plants, specifically red seaweed Ahnfeltia and seagrass Zostera and Ruppia, found in brackish lagoons in the Sea of Okhotsk, Sakhalin Island. These biochars were obtained through a stepwise pyrolysis process conducted at temperatures of 500 and 700 °C. The characteristics of the biochars, including their elemental composition, specific surface area, and particle size distribution, were found to be influenced by both the type of biomass used and the pyrolysis temperature. The primary objective of this research was to investigate the potential of these biochars to be used as negative electrodes for lithium ion batteries. Among the various samples we tested, the biochar derived from the macroalgae Ahnfeltia tobuchiensis, produced at 700 °C, exhibited the highest carbon content (70 at%) and nitrogen content (>5 at%). The reversible capacity of this particular biochar was measured to be 391 mAh g−1 during the initial cycles and remained relatively stable at around 300 mAh g−1 after 25 cycles. These findings suggest that biochars derived from aquatic plants have the potential to be utilized as effective electrode materials in lithium ion batteries. The specific properties of the biochar, such as its elemental composition and surface area, play a significant role in determining its electrochemical performance. Further research and optimization of the pyrolysis conditions may lead to the development of biochar-based electrodes with improved capacity and cycling stability, thereby contributing to the advancement of sustainable and environmentally friendly energy storage systems. Full article
(This article belongs to the Special Issue Advanced Materials for Electrocatalysis and Energy Storage)
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13 pages, 7102 KiB  
Article
Structure Optimization and Failure Mechanism of Metal Nitride Coatings for Enhancing the Sand Erosion Resistance of Aluminum Alloys
Coatings 2023, 13(12), 2074; https://doi.org/10.3390/coatings13122074 - 12 Dec 2023
Viewed by 568
Abstract
In this study, TiN/Ti coatings with various modulation ratios (TiN/Ti-4:1, TiN/Ti-1:1, and TiN/Ti-1:4) were deposited on 2A70 aluminum to improve its sand erosion performance. The structural design of ion implantation + high thickness Ti transition layer + TiN/Ti coatings was applied to alleviate [...] Read more.
In this study, TiN/Ti coatings with various modulation ratios (TiN/Ti-4:1, TiN/Ti-1:1, and TiN/Ti-1:4) were deposited on 2A70 aluminum to improve its sand erosion performance. The structural design of ion implantation + high thickness Ti transition layer + TiN/Ti coatings was applied to alleviate the differences in physical properties between hard nitride coatings and 2A70 aluminum. Surface roughness, XRD, elastic modulus, hardness, and the sand erosion failure mechanism of each coating were evaluated. The hardness of TiN/Ti-4:1, TiN/Ti-1:1, and TiN/Ti-1:4 on aluminum was 26.99 GPa, 21.70 GPa, and 10.99 GPa. Sand erosion test results showed that TiN/Ti-1:1 had the highest erosion rates due to its rougher surface. Under a 90° incident angle, TiN/Ti-4:1 and TiN/Ti-1:4 both exhibited vertical cracks parallel to the coating growth direction in the bottom TiN layer at the initial erosion stage. Also, a lateral crack caused by TiN layer crack deflection emerged due to a higher crack resistance in the thicker Ti layer of TiN/Ti-1:4. Furthermore, in comparison with the layer-by-layer spalling failure behavior of TiN/Ti-1:4, overall spallation induced by the crack coalescence of the TiN layer was exhibited in TiN/Ti-4:1. In addition, cracks formed and intersected in the inner TiN layer in TiN/Ti-1:1 and TiN/Ti-4:1, resulting in layer-by-layer spallation under a 45° incident angle. Full article
(This article belongs to the Special Issue Advanced Materials Processing Technology and Surface Engineering)
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17 pages, 5964 KiB  
Article
Hydration Heat and Hydration Kinetics of Cement Paste Compound with Molybdenum Tailings Powder: A Research Article
Coatings 2023, 13(12), 2073; https://doi.org/10.3390/coatings13122073 (registering DOI) - 12 Dec 2023
Viewed by 559
Abstract
Molybdenum tailings powder (MTs) has potential pozzolanic activity and can be used as a mineral admixture. In order to comprehend the influence of MTs powder on the cement hydration process, the hydration heat and kinetics of composite cementitious materials (CCMs) were investigated using [...] Read more.
Molybdenum tailings powder (MTs) has potential pozzolanic activity and can be used as a mineral admixture. In order to comprehend the influence of MTs powder on the cement hydration process, the hydration heat and kinetics of composite cementitious materials (CCMs) were investigated using an isothermal calorimeter and the Krstulovic–Dabic model. Furthermore, the influences of fly ash (FA), slag (SL), and MTs powder on hydration heat were compared and analyzed, considering the same content. The results show that the proper amount of MTs can promote the hydration of CCMs. When the content of MTs is 5% and 15%, the second exothermic peak of the CCMs appears 2.30% and 4.27% earlier, and the exothermic peak increases by 2.72% and 1.34%, respectively. The cumulative heat release of CCMs gradually decreases with an increasing content of MTs powder. When the replacement of MTs, FA, and SL is 15%, respectively, the second exothermic peak of CCMs increases by 1.34%, −16.13%, and −12.04% for MTs, FA, and SL, respectively. The final heat release of MTs is higher than that of FA, but lower than that of SL. The hydration process of CCMs undergoes three stages: nucleation and crystal growth (NG), interactions at phase boundaries (I), and diffusion (D). Full article
(This article belongs to the Special Issue Science and Technology of Pavement Coatings Materials)
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15 pages, 3576 KiB  
Article
Nickel Coatings on Ceramic Materials Using Different Diffusion Techniques
Coatings 2023, 13(12), 2072; https://doi.org/10.3390/coatings13122072 - 12 Dec 2023
Viewed by 613
Abstract
Diffusion bonding is a process that has proven effective for the joining of metal to ceramic, but the differences in coefficient of thermal expansion still pose challenges during and after the bonding process. This work details the exploration of traditional diffusion-bonding processes using [...] Read more.
Diffusion bonding is a process that has proven effective for the joining of metal to ceramic, but the differences in coefficient of thermal expansion still pose challenges during and after the bonding process. This work details the exploration of traditional diffusion-bonding processes using two traditional approaches, which include bonding of a 99.9+% pure Ni foil to SiC, Si3N4, and YSZ disks using (1) a hot isostatic press (HIP), with and without added weight to promote interfacial contact, and (2) field-assisted sintering (FAST). Samples were consolidated by heating to 1200 °C and held for 6 h under vacuum before cooling to room temperature during the HIP method. For the FAST technique, bonding experiments were performed at both 800 °C and 1200 °C in a vacuum environment under 10 MPa uniaxial pressure. After the Ni was bonded to the ceramics, diffusion heat treatments were carried out in the HIP. For electroless-plated samples, the heat-treatment temperature was chosen as 825 °C to avoid melting. For electroplated samples, heat treatment occurred at 925 °C or higher. Electroplated YSZ samples were heat-treated at 1150 °C as the Ni-Si eutectic is not a concern in this system. The time at temperature varied from 6 h to 48 h depending on the material combination tested. Post-heat-treatment diffusion characteristics were analyzed using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS). A main cause of poor bonding performance in the HIP samples was reduced interfacial contact, while cohesive failures in the FAST samples are likely due to the formation of brittle intermetallic Ni-Si phases. Preliminary results indicate success in bonding Ni to SiC, Si3N4, and YSZ using a diffusion-enhanced approach on electroplated specimens. Full article
(This article belongs to the Special Issue Nanostructured Materials Deposition Techniques and Characterization)
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