Coatings

26 pages, 8951 KiB

Open AccessArticle

Optimization of Welding Sequence and Improvement of Welding Process for Large-Diameter Curved Penetrations of Thick Plates

by Haipeng Miao, Yi Shen, Wenbo Xue, Sheng Zhang and Mingxin Yuan

Coatings 2025, 15(8), 923; https://doi.org/10.3390/coatings15080923 - 7 Aug 2025

Abstract

To reduce welding deformation during the automated welding of intersection seams on thick plate curved penetrations and thereby improve welding quality and efficiency, an optimized method for segmented and multi-layer multi-pass welding sequences, along with welding process improvement strategies, is proposed. First, based [...] Read more.

To reduce welding deformation during the automated welding of intersection seams on thick plate curved penetrations and thereby improve welding quality and efficiency, an optimized method for segmented and multi-layer multi-pass welding sequences, along with welding process improvement strategies, is proposed. First, based on the welding model of the curved penetrations, a multi-layer multi-pass welding trajectory equation is designed. Next, a Gaussian heat source model is selected, and numerical simulation theories for welding temperature and stress fields are established using finite-element theory. Then, for the intersection seams of curved components with three different thicknesses, four numerical tests of segmented welding sequence optimization are carried out using welding finite-element simulation theory. Finally, the optimal welding process for the welding sequence is improved using orthogonal experimental methods, and the optimal welding process parameters for curved components with different thicknesses are determined. The optimization of welding sequences for intersection seams on three types of thick plates shows that the optimal sequence for segmented welding is first to perform upper–lower diagonal symmetry, followed by left–right symmetry. Compared to other welding sequences, the proposed method reduces welding deformation by an average of 9.24% and welding stress by an average of 7.40%, which verifies the effectiveness of the welding sequence optimization presented in the paper. Full article

(This article belongs to the Special Issue Advances in Metal Additive Manufacturing Technique: Processes and Novel Materials)

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29 pages, 980 KiB

Open AccessReview

Recent Advances in Magnetron Sputtering: From Fundamentals to Industrial Applications

by Przemyslaw Borowski and Jaroslaw Myśliwiec

Coatings 2025, 15(8), 922; https://doi.org/10.3390/coatings15080922 - 7 Aug 2025

Abstract

Magnetron Sputter Vacuum Deposition (MSVD) has undergone significant advancements since its inception. This review explores the evolution of MSVD, encompassing its fundamental principles, various techniques (including reactive sputtering, pulsed magnetron sputtering, and high-power impulse magnetron sputtering), and its wide-ranging industrial applications. While detailing [...] Read more.

Magnetron Sputter Vacuum Deposition (MSVD) has undergone significant advancements since its inception. This review explores the evolution of MSVD, encompassing its fundamental principles, various techniques (including reactive sputtering, pulsed magnetron sputtering, and high-power impulse magnetron sputtering), and its wide-ranging industrial applications. While detailing the advantages of high deposition rates, versatility in material selection, and precise control over film properties, the review also addresses inherent challenges such as low target utilization and plasma instability. A significant portion focuses on the crucial role of MSVD in the automotive industry, highlighting its use in creating durable, high-quality coatings for both aesthetic and functional purposes. The transition from traditional electroplating methods to more environmentally friendly MSVD techniques is also discussed, emphasizing the growing demand for sustainable manufacturing processes. This review concludes by summarizing the key advancements, remaining challenges, and potential future trends in magnetron sputtering technologies. Full article

(This article belongs to the Special Issue Magnetron Sputtering Coatings: From Materials to Applications)

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10 pages, 1801 KiB

Open AccessArticle

Strong Radiative Cooling Coating Containing In Situ Grown TiO₂/CNT Hybrids and Polyacrylic Acid Matrix

by Jiaziyi Wang, Yong Liu, Dapeng Liu, Yong Mu and Xilai Jia

Coatings 2025, 15(8), 921; https://doi.org/10.3390/coatings15080921 - 7 Aug 2025

Abstract

Traditional forced-air cooling systems suffer from excessive energy consumption and noise pollution. This study proposes an innovative passive cooling strategy through developing aqueous radiative cooling coatings made from a combination of TiO₂-decorated carbon nanotube (TiO₂-CNT) hybrids and polyacrylic acid [...] Read more.

Traditional forced-air cooling systems suffer from excessive energy consumption and noise pollution. This study proposes an innovative passive cooling strategy through developing aqueous radiative cooling coatings made from a combination of TiO₂-decorated carbon nanotube (TiO₂-CNT) hybrids and polyacrylic acid (PAA), designed to simultaneously enhance the heat dissipation and improve the mechanical strength of the coating films. Based on CNTs’ exceptional thermal conductivity and record-high infrared emissivity, bead-like TiO₂-CNT architectures have been prepared as the filler in PAA. The TiO₂ nanoparticles were in situ grown on CNTs, forming a rough surface that can produce asperity contacts and enhance the strength of the TiO₂-CNT/PAA composite. Moreover, this composite enhanced heat dissipation and achieved remarkable cooling efficiency at a small fraction of the filler (0.1 wt%). The optimized coating demonstrated a temperature reduction of 23.8 °C at an operation temperature of 180.7 °C, coupled with obvious mechanical reinforcement (tensile strength from 13.7 MPa of pure PAA to 17.1 MPa). This work achieves the combination of CNT and TiO₂ nanoparticles for strong radiative cooling coating, important for energy-efficient thermal management. Full article

(This article belongs to the Special Issue Advanced Functional Nanostructured Films and Coatings for Energy Applications, 2nd Edition)

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22 pages, 5152 KiB

Open AccessArticle

Grain Boundary Regulation in Aggregated States of MnO_x Nanofibres and the Photoelectric Properties of Their Nanocomposites Across a Broadband Light Spectrum

by Xingfa Ma, Xintao Zhang, Mingjun Gao, Ruifen Hu, You Wang and Guang Li

Coatings 2025, 15(8), 920; https://doi.org/10.3390/coatings15080920 - 6 Aug 2025

Abstract

Improving charge transport in the aggregated state of nanocomposites is challenging due to the large number of defects present at grain boundaries. To enhance the charge transfer and photogenerated carrier extraction of MnO_x nanofibers, a MnO_x/GO (graphene oxide) nanocomposite was [...] Read more.

Improving charge transport in the aggregated state of nanocomposites is challenging due to the large number of defects present at grain boundaries. To enhance the charge transfer and photogenerated carrier extraction of MnO_x nanofibers, a MnO_x/GO (graphene oxide) nanocomposite was prepared. The effects of GO content and bias on the optoelectronic properties were studied. Representative light sources at 405, 650, 780, 808, 980, and 1064 nm were used to examine the photoelectric signals. The results indicate that the MnO_x/GO nanocomposites have photocurrent switching behaviours from the visible region to the NIR (near-infrared) when the amount of GO added is optimised. It was also found that even with zero bias and storage of the nanocomposite sample at room temperature for over 8 years, a good photoelectric signal could still be extracted. This demonstrates that the MnO_x/GO nanocomposites present a strong built-in electric field that drives the directional motion of photogenerated carriers, avoids the photogenerated carrier recombination, and reflect a good photophysical stability. The strength of the built-in electric field is strongly affected by the component ratios of the resulting nanocomposite. The formation of the built-in electric field results from interfacial charge transfer in the nanocomposite. Modulating the charge behaviour of nanocomposites can significantly improve the physicochemical properties of materials when excited by light with different wavelengths and can be used in multidisciplinary applications. Since the recombination of photogenerated electron–hole pairs is the key bottleneck in multidisciplinary fields, this study provides a simple, low-cost method of tailoring defects at grain boundaries in the aggregated state of nanocomposites. These results can be used as a reference for multidisciplinary fields with low energy consumption. Full article

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

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14 pages, 4458 KiB

Open AccessArticle

The Effect of Crevice Structure on Corrosion Behavior of P110 Carbon Steel in a Carbonated Simulated Concrete Environment

by Fanghai Ling, Chen Li, Hailin Guo and Yong Xiang

Coatings 2025, 15(8), 919; https://doi.org/10.3390/coatings15080919 - 6 Aug 2025

Abstract

This study systematically investigated the corrosion behavior of P110 pipeline steel in simulated carbonated concrete environments through a combination of electrochemical testing and multiphysics simulation, with particular focus on revealing the evolution mechanisms of corrosion product deposition and ion concentration distribution under half [...] Read more.

This study systematically investigated the corrosion behavior of P110 pipeline steel in simulated carbonated concrete environments through a combination of electrochemical testing and multiphysics simulation, with particular focus on revealing the evolution mechanisms of corrosion product deposition and ion concentration distribution under half crevice structures, providing new insights into localized corrosion in concealed areas. Experimental results showed that no significant corrosion occurred on the P110 steel surface in uncarbonated simulated pore solution. Conversely, the half crevice structure significantly promoted the development of localized corrosion in carbonated simulated pore solution, with the most severe corrosion and substantial accumulation of corrosion products observed at the crevice mouth region. COMSOL Multiphysics simulations demonstrated that this phenomenon was primarily attributed to local enrichment of Cl⁻ and H⁺ ions, leading to peak corrosion current density, and directional migration of Fe²⁺ ions toward the crevice mouth, causing preferential deposition of corrosion products at this location. This “electrochemical acceleration-corrosion product deposition” multiphysics coupling analysis of corrosion product deposition patterns within crevices represents a new perspective not captured by traditional crevice corrosion models. The established ion migration-corrosion product deposition model provides new theoretical foundations for understanding crevice corrosion mechanisms and predicting the service life of buried concrete pipelines. Full article

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

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17 pages, 2801 KiB

Open AccessArticle

The Influence of Substrate Preparation on the Performance of Two Alkyd Coatings After 7 Years of Exposure in Outdoor Conditions

by Emanuela Carmen Beldean, Maria Cristina Timar and Emilia-Adela Salca Manea

Coatings 2025, 15(8), 918; https://doi.org/10.3390/coatings15080918 - 6 Aug 2025

Abstract

Alkyd resins are among the most common coatings used for exterior wood joinery. In Romania, solvent-borne alkyd coatings are widely used to finish wood. The study aims to compare the performance after 7 years of outdoor exposure of two types of alkyd coatings, [...] Read more.

Alkyd resins are among the most common coatings used for exterior wood joinery. In Romania, solvent-borne alkyd coatings are widely used to finish wood. The study aims to compare the performance after 7 years of outdoor exposure of two types of alkyd coatings, a semi-transparent brown stain with micronized pigments (Alk1) and an opaque white enamel (Alk2), applied directly on wood or wood pre-treated with three types of resins: acryl-polyurethane (R1), epoxy (R2), and alkyd-polyurethane (R3). Fir (Abies alba) wood served as the substrate. Cracking, coating adhesion, and biological degradation were periodically assessed through visual inspection and microscopy. Additionally, a cross-cut test was performed, and the loss of coating on the directly exposed upper faces was measured using ImageJ. The results indicated that resin pretreatments somewhat reduced cracking but negatively affected coating adhesion after long-term exposure. All samples pretreated with resins and coated with Alk1 lost more than 50% (up to 78%) of the original finishing film by the end of the test. In comparison, coated control samples lost less than 50%. The Alk2 coating exhibited a film loss between 2% and 12%, compared to an average loss of 9% for the coated control. Overall, samples pretreated with alkyd-polyurethane resin (R3) and coated with alkyd enamel (Alk2) demonstrated the best performance in terms of cracking, adhesion, and discoloration. Full article

(This article belongs to the Collection Wood: Modifications, Coatings, Surfaces, and Interfaces)

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21 pages, 4264 KiB

Open AccessArticle

Study on the Performance Restoration of Aged Asphalt Binder with Vegetable Oil Rejuvenators: Colloidal Stability, Rheological Properties, and Solubility Parameter Analysis

by Heng Yan, Xinxin Cao, Wei Wei, Yongjie Ding and Jukun Guo

Coatings 2025, 15(8), 917; https://doi.org/10.3390/coatings15080917 - 6 Aug 2025

Abstract

This study evaluates the effectiveness of various rejuvenating oils, including soybean oil (N-oil), waste frying oil (F-oil), byproduct oil (W-oil), and aromatic hydrocarbon oil (A-oil), in restoring aged asphalt coatings by reducing asphaltene flocculation and improving colloidal stability. The rejuvenators were incorporated into [...] Read more.

This study evaluates the effectiveness of various rejuvenating oils, including soybean oil (N-oil), waste frying oil (F-oil), byproduct oil (W-oil), and aromatic hydrocarbon oil (A-oil), in restoring aged asphalt coatings by reducing asphaltene flocculation and improving colloidal stability. The rejuvenators were incorporated into aged asphalt binder via direct mixing at controlled dosages. Their effects were assessed using microscopy, droplet diffusion analysis, rheological testing (DSR and BBR), and molecular dynamics simulations. The aim is to compare the compatibility, solubility behavior, and rejuvenation potential of plant-based and mineral-based oils. The results indicate that N-oil and F-oil promote asphaltene aggregation, which supports structural rebuilding. In contrast, A-oil and W-oil act as solvents that disperse asphaltenes. Among the tested oils, N-oil exhibited the best overall performance in enhancing flowability, low-temperature flexibility, and chemical compatibility. This study presents a novel method to evaluate rejuvenator effectiveness by quantifying colloidal stability through grayscale analysis of droplet diffusion patterns. This integrated approach offers both mechanistic insights and practical guidance for selecting bio-based rejuvenators in asphalt recycling. Full article

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

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14 pages, 5840 KiB

Open AccessArticle

Paint Removal Performance and Sub-Surface Microstructural Evolution of Ti6Al4V Alloy Using Different Process Parameters of Continuous Laser Cleaning

by Haoye Zeng, Biwen Li, Liangbin Hu, Yun Zhang, Ruiqing Li, Chaochao Zhou and Pinghu Chen

Coatings 2025, 15(8), 916; https://doi.org/10.3390/coatings15080916 - 6 Aug 2025

Abstract

Laser cleaning technology has been increasingly applied in the removal of damaged protective coatings from aircraft components due to its environmental friendliness and high efficiency. Appropriate laser cleaning process parameters improve cleaning efficiency while preventing substrate damage. In this study, a Gaussian continuous-wave [...] Read more.

Laser cleaning technology has been increasingly applied in the removal of damaged protective coatings from aircraft components due to its environmental friendliness and high efficiency. Appropriate laser cleaning process parameters improve cleaning efficiency while preventing substrate damage. In this study, a Gaussian continuous-wave laser was used to remove the 120 μm coating on the surface of Ti6Al4V alloy. The influence of laser power (100 W to 200 W) and scanning speed (520 mm/min to 610 mm/min) on the paint removal effect was explored based on paint removal rate, surface roughness, microstructural evolution, and the hardness’ change in the direction of heat transfer. The results reveal that optimal paint removal parameters are achieved at a laser power of 100 W with a scanning speed of 550 mm/min. The surface roughness of the sample after paint removal (55 nm) is similar to that of the original substrate (56 nm). Through EBSD analysis, the influence of laser thermal accumulation on the microstructure of the substrate is relatively small. The average hardness of the cross-section after cleaning was 347 HV, which was only 3.41% higher than that of the original substrate. This confirms that parameter-controlled laser cleaning can effectively remove ~120 μm thick paint layers without inflicting damage on the substrate. Full article

(This article belongs to the Special Issue Multi-Principal Element Alloy Design and Surface Modification Technology)

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17 pages, 3870 KiB

Open AccessReview

Eco-Friendly, Biomass-Derived Materials for Electrochemical Energy Storage Devices

by Yeong-Seok Oh, Seung Woo Seo, Jeong-jin Yang, Moongook Jeong and Seongki Ahn

Coatings 2025, 15(8), 915; https://doi.org/10.3390/coatings15080915 - 5 Aug 2025

Abstract

This mini-review emphasizes the potential of biomass-derived materials as sustainable components for next-generation electrochemical energy storage systems. Biomass obtained from abundant and renewable natural resources can be transformed into carbonaceous materials. These materials typically possess hierarchical porosities, adjustable surface functionalities, and inherent heteroatom [...] Read more.

This mini-review emphasizes the potential of biomass-derived materials as sustainable components for next-generation electrochemical energy storage systems. Biomass obtained from abundant and renewable natural resources can be transformed into carbonaceous materials. These materials typically possess hierarchical porosities, adjustable surface functionalities, and inherent heteroatom doping. These physical and chemical characteristics provide the structural and chemical flexibility needed for various electrochemical applications. Additionally, biomass-derived materials offer a cost-effective and eco-friendly alternative to traditional components, promoting green chemistry and circular resource utilization. This review provides a systematic overview of synthesis methods, structural design strategies, and material engineering approaches for their use in lithium-ion batteries (LIBs), lithium–sulfur batteries (LSBs), and supercapacitors (SCs). It also highlights key challenges in these systems, such as the severe volume expansion of anode materials in LIBs and the shuttle effect in LSBs and discusses how biomass-derived carbon can help address these issues. Full article

(This article belongs to the Special Issue Surface Engineering for Advanced Applications in Electronics and Energy)

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14 pages, 2180 KiB

Open AccessArticle

Study on Preparation of Nano-CeO₂ Modified Aluminized Coating by Low Temperature Pack Aluminizing on γ-TiAl Intermetallic Compound

by Jiahui Song, Yunmei Long, Yifan He, Yichen Li, Dianqi Huang, Yan Gu, Xingyao Wang, Jinlong Wang and Minghui Chen

Coatings 2025, 15(8), 914; https://doi.org/10.3390/coatings15080914 - 5 Aug 2025

Abstract

TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it [...] Read more.

TiAl alloy offers advantages including low density, high specific strength and stiffness, and excellent high-temperature creep resistance. It is widely used in the aerospace, automotive, and chemical sectors, as well as in other fields. However, at temperatures of 800 °C and above, it forms a porous oxide film predominantly composed of TiO₂, which fails to provide adequate protection. Applying high-temperature protective coatings is therefore essential. Oxides demonstrating protective efficacy at elevated temperatures include Al₂O₃, Cr₂O₃, and SiO₂. The Pilling–Bedworth Ratio (PBR)—defined as the ratio of the volume of the oxide formed to the volume of the metal consumed—serves as a critical criterion for assessing oxide film integrity. A PBR value greater than 1 but less than 2 indicates superior film integrity and enhanced oxidation resistance. Among common oxides, Al₂O₃ exhibits a PBR value within this optimal range (1−2), rendering aluminum-based compound coatings the most extensively utilized. Aluminum coatings can be applied via methods such as pack cementation, thermal spraying, and hot-dip aluminizing. Pack cementation, being the simplest to operate, is widely employed. In this study, a powder mixture with the composition Al:Al₂O₃:NH₄Cl:CeO₂ = 30:66:3:1 was used to aluminize γ-TiAl intermetallic compound specimens via pack cementation at 600 °C for 5 h. Subsequent isothermal oxidation at 900 °C for 20 h yielded an oxidation kinetic curve adhering to the parabolic rate law. This treatment significantly enhanced the high-temperature oxidation resistance of the γ-TiAl intermetallic compound, thereby broadening its potential application scenarios. Full article

(This article belongs to the Special Issue High-Temperature Protective Coatings)

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9 pages, 1868 KiB

Open AccessCommunication

Research on the Temperature Dependence of Deformation and Residual Stress via Image Relative Method

by Haiyan Li, Lei Zhang, Yudi Mao, Jinlun Zhang, Detian Wan and Yiwang Bao

Coatings 2025, 15(8), 913; https://doi.org/10.3390/coatings15080913 - 5 Aug 2025

Abstract

Temperature dependence of the deformation behavior and the residual stress in 304 stainless steel beams with single-sided Al₂O₃ coatings of varying thicknesses are analyzed using the image relative method. The results demonstrate that, due to the mismatch of thermal expansion [...] Read more.

Temperature dependence of the deformation behavior and the residual stress in 304 stainless steel beams with single-sided Al₂O₃ coatings of varying thicknesses are analyzed using the image relative method. The results demonstrate that, due to the mismatch of thermal expansion coefficient between the coating and substrate, residual stresses were produced, which caused the bending deformation of the single-side coated specimens. Moreover, coating thickness significantly influences the deformation behavior of specimens. Within the elastic deformation regime, the single-side coated specimens would exhibit alternating bending and flattening deformations in response to the fluctuations of temperature. The higher ratio of the coating thickness to the substrate thickness is, the smaller bending curvature of specimens becomes, and the lower residual compressive stresses in the coating are. For the specimens undergoing elastic deformation, residual stresses can be effectively calculated through the Stoney’s formula. However, as the thickness of coating is close to that of substrate (the corresponding specimens would be regarded as the laminated composites), plastic deformation occurs. And the residual stresses in those specimens vary along the direction of the thickness and the length. In addition, the residual stress decreased with increasing temperature because of the stress relaxation. Full article

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

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15 pages, 3705 KiB

Open AccessArticle

Mechanical Properties and Modification Mechanism of Thermosetting Polyurethane-Modified Asphalt

by Wei Zhuang, Tingting Ding, Chuanqin Pang, Xuwang Jiao, Litao Geng and Min Sun

Coatings 2025, 15(8), 912; https://doi.org/10.3390/coatings15080912 - 4 Aug 2025

Abstract

To study the mechanical properties and modification mechanism of thermosetting polyurethane (PU)-modified asphalt, the effects of polyurethane dosage on the workability of polyurethane-modified asphalt were analyzed by means of rotational viscosity tests. The mechanical properties of polyurethane-modified asphalt with different polyurethane dosages were [...] Read more.

To study the mechanical properties and modification mechanism of thermosetting polyurethane (PU)-modified asphalt, the effects of polyurethane dosage on the workability of polyurethane-modified asphalt were analyzed by means of rotational viscosity tests. The mechanical properties of polyurethane-modified asphalt with different polyurethane dosages were explored using tensile tests and dynamic mechanical analysis (DMA). In addition, the thermodynamic behavior and micromorphology of polyurethane-modified asphalt were also thoroughly investigated using the test results of differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results showed that PU obtained the optimum workability when the polyurethane dose was 50%: at 120 min, its rotational viscosity was 1005 cp, which was lower than 2800 cp (40% PU) and 760 cp (60% PU). Additionally, the results of fracture elongation and fracture strength indicated that the PU-modified asphalt had good flexibility and strength. Compared with base asphalt, the tensile strength of 50% PU-modified asphalt increased by 509%, which was significantly higher than 157% (40% PU) and more balanced than 897% (60% PU) in terms of strength and flexibility. Added PU can significantly improve the elasticity of asphalt at high temperatures, while increasing the proportion of asphalt adhesive components, enhancing the deformation ability and temperature stability of asphalt. As the dose of PU increases, the interface between asphalt and PU blended more fully, and the surface became smoother. When the dose of PU was 50% or more, the interface between asphalt and PU was well integrated with a smooth and flat surface, forming a more uniform and stable cross-linked network structure. Full article

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

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16 pages, 5703 KiB

Open AccessArticle

Optimization of Multi-Objective Process Parameters and Performance Analysis of High-Speed Laser Cladding of TC4/AISI431 Composite Coatings

by Fumin Hong and Tianlu Wei

Coatings 2025, 15(8), 911; https://doi.org/10.3390/coatings15080911 - 4 Aug 2025

Abstract

The authors of this paper investigated the process parameters of high-speed laser cladding of TC4/AISI431 composite coatings on the surface of C45 steel, choosing laser power, scanning speed, and TC4 addition as the experimental factors, and porosity, microhardness, and corrosion resistance as the [...] Read more.

The authors of this paper investigated the process parameters of high-speed laser cladding of TC4/AISI431 composite coatings on the surface of C45 steel, choosing laser power, scanning speed, and TC4 addition as the experimental factors, and porosity, microhardness, and corrosion resistance as the target indices. A regression model was established based on the response surface methodology BBD, and the reliability of the model was analyzed using an ANOVA. Then, the WOA was used for multi-objective optimization. The optimal parameter set was determined as follows: a laser power of 5315 W, a scanning speed of 378 mm/s, and a TC4 addition of 3.6%. The microstructure and surface elemental composition of the coating were analyzed. The results showed that the porosity reduced by 60% and that the corrosion resistance improved by 79.98%, while the microhardness remained essentially unchanged. Full article

(This article belongs to the Section Laser Coatings)

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10 pages, 1588 KiB

Open AccessArticle

385 nm AlGaN Near-Ultraviolet Micro Light-Emitting Diode Arrays with WPE 30.18% Realized Using an AlN-Inserted Hole Spreading Enhancement S Electron Blocking Layer

by Qi Nan, Shuhan Zhang, Jiahao Yao, Yun Zhang, Hui Ding, Qian Fan, Xianfeng Ni and Xing Gu

Coatings 2025, 15(8), 910; https://doi.org/10.3390/coatings15080910 - 3 Aug 2025

Abstract

In this work, we demonstrate high-efficiency 385 nm AlGaN-based near-ultraviolet micro light emitting diode (NUV-Micro LED) arrays. The epi structure is prepared using a novel AlN-inserted superlattice electrical blocking layer which enhances hole spreading in the p-type region significantly. The NUV-Micro LED arrays [...] Read more.

In this work, we demonstrate high-efficiency 385 nm AlGaN-based near-ultraviolet micro light emitting diode (NUV-Micro LED) arrays. The epi structure is prepared using a novel AlN-inserted superlattice electrical blocking layer which enhances hole spreading in the p-type region significantly. The NUV-Micro LED arrays in this work comprise 228 chips in parallel with wavelengths at 385 nm, and each single chip size is 15 × 30 μm². Compared with conventional bulk AlGaN-based EBL structures, the NUV-Micro LED arrays that implemented the new hole spreading enhanced superlattice electrical blocking layer (HSESL-EBL) structure proposed in this work had a remarkable increase in light output power (LOP) at current density, increasing the range down from 0.02 A/cm² to as high as 97 A/cm². The array’s light output power is increased up to 1540% at the lowest current density 0.02 A/cm², and up to 58% at the highest current density 97 A/cm², measured under room temperature (RT); consequently, the WPE is increased from 13.4% to a maximum of 30.18%. This AlN-inserted HESEL-EBL design significantly enhances both the lateral expansion efficiency and the hole injection efficiency into the multi quantum well (MQW) in the arrays, improving the concentration distribution of the holes in MQW while maintaining good suppression of electron leakage. The array’s efficiency droop has also been greatly reduced. Full article

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

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27 pages, 11202 KiB

Open AccessArticle

Durability Analysis of Brick-Faced Clay-Core Walls in Traditional Residential Architecture in Quanzhou, China

by Yuhong Ding, Ruiming Guan, Li Chen, Jinxuan Wang, Yangming Zhang, Yili Fu and Canjin Zhang

Coatings 2025, 15(8), 909; https://doi.org/10.3390/coatings15080909 - 3 Aug 2025

Abstract

This study analyzes the durability of brick-faced clay-core walls (BCWs) in the traditional residential architecture of Quanzhou—a UNESCO World Heritage City. Taking the northern gable of Ding Gongchen’s former residence as an example, the mechanical properties, microscopic structure, and changes in chemical symbol, [...] Read more.

This study analyzes the durability of brick-faced clay-core walls (BCWs) in the traditional residential architecture of Quanzhou—a UNESCO World Heritage City. Taking the northern gable of Ding Gongchen’s former residence as an example, the mechanical properties, microscopic structure, and changes in chemical symbol, oxides and minerals of the red bricks and clay-cores were analyzed using finite element mechanics analysis (FEM), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and X-ray diffraction (XRD). The results indicate a triple mechanism: (1) The collaborative protection and reinforcement mechanism of “brick-wrapped-clay”. (2) The infiltration and destruction mechanism of external pollutants. (3) The material stability mechanism of silicate minerals. Therefore, the key to maintaining the durability of BCWs lies in the synergistic effect of brick and clay materials and the stability of silicate mineral materials, providing theoretical and methodological support for sustainable research into brick and clay constructions. Full article

(This article belongs to the Special Issue New Insights into Earthen Site Conservation: Methods, Techniques, Management, and Key Case Studies)

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25 pages, 10097 KiB

Open AccessArticle

Biocrusts Alter the Pore Structure and Water Infiltration in the Top Layer of Rammed Soils at Weiyuan Section of the Great Wall in China

by Xiaoju Yang, Fasi Wu, Long Li, Ruihua Shang, Dandan Li, Lina Xu, Jing Cui and Xueyong Zhao

Coatings 2025, 15(8), 908; https://doi.org/10.3390/coatings15080908 - 3 Aug 2025

Abstract

The surface of the Great Wall harbors a large number of non-vascular plants dominated by cyanobacteria, lichens and mosses as well as microorganisms, and form biocrusts by cementing with the soils and greatly alters the pore structure of the soil and the ecohydrological [...] Read more.

The surface of the Great Wall harbors a large number of non-vascular plants dominated by cyanobacteria, lichens and mosses as well as microorganisms, and form biocrusts by cementing with the soils and greatly alters the pore structure of the soil and the ecohydrological processes associated with the soil pore space, and thus influences the soil resistance to erosion. However, the microscopic role of the biocrusts in influencing the pore structure of the surface of the Great Wall is not clear. This study chose the Warring States Qin Great Wall in Weiyuan, Gansu Province, China, as research site to quantify thepore structure characteristics of the three-dimensional of bare soil, cyanobacterial-lichen crusts, and moss crusts at the depth of 0–50 mm, by using optical microscopy, scanning electron microscopy, and X-ray computed tomography and image analysis, and the precipitation infiltration process. The results showed that the moss crust layer was dominated by large pores with long extension and good connectivity, which provided preferential seepage channels for precipitation infiltration, while the connectivity between the cyanobacterial-lichen crust voids was poor; The porosity of the cyanobacterial-lichen crust and the moss crust was 500% and 903.27% higher than that of the bare soil, respectively. The porosity of the subsurface layer of cyanobacterial-lichen crust and moss crust was significantly lower than that of the biocrusts layer by 92.54% and 97.96%, respectively, and the porosity of the moss crust was significantly higher than that of the cyanobacterial-lichen crust in the same layer; Cyanobacterial-lichen crusts increased the degree of anisotropy, mean tortuosity, moss crust reduced the degree of anisotropy, mean tortuosity. Biocrusts increased the fractal dimension and Euler number of pores. Compared with bare soil, moss crust and cyanobacterial-lichen crust increased the isolated porosity by 2555% and 4085%, respectively; Biocrusts increased the complexity of the pore network models; The initial infiltration rate, stable infiltration rate, average infiltration rate, and the total amount of infiltration of moss crusted soil was 2.26 and 3.12 times, 1.07 and 1.63 times, respectively, higher than that of the cyanobacterial-lichen crusts and the bare soil, by 1.53 and 2.33 times, and 1.13 and 2.08 times, respectively; CT porosity and clay content are significantly positively correlated with initial soil infiltration rate (|r| ≥ 0.85), while soil type and organic matter content are negatively correlated with initial soil infiltration rate. The soil type and bulk density are directly positively and negatively correlated with CT porosity, respectively (|r| ≥ 0.52). There is a significant negative correlation between soil clay content and porosity (|r| = 0.15, p < 0.001). Biocrusts alter the erosion resistance of rammed earth walls by affecting the soil microstructure of the earth’s great wall, altering precipitation infiltration, and promoting vascular plant colonisation, which in turn alters the erosion resistance of the wall. The research results have important reference for the development of disposal plans for biocrusts on the surface of archaeological sites. Full article

(This article belongs to the Special Issue New Insights into Earthen Site Conservation: Methods, Techniques, Management, and Key Case Studies)

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22 pages, 3994 KiB

Open AccessArticle

Analysis of Foaming Properties, Foam Stability, and Basic Physicochemical and Application Parameters of Bio-Based Car Shampoos

by Bartosz Woźniak, Agata Wawrzyńczak and Izabela Nowak

Coatings 2025, 15(8), 907; https://doi.org/10.3390/coatings15080907 - 2 Aug 2025

Abstract

Environmental protection has become one of the key challenges of our time. This has led to an increase in pro-environmental activities in the field of cosmetics and household chemicals, where manufacturers are increasingly trying to meet the expectations of consumers who are aware [...] Read more.

Environmental protection has become one of the key challenges of our time. This has led to an increase in pro-environmental activities in the field of cosmetics and household chemicals, where manufacturers are increasingly trying to meet the expectations of consumers who are aware of the potential risks associated with the production of cosmetics and household chemistry products. This is one of the most important challenges of today’s industry, given that some of the raw materials still commonly used, such as surfactants, may be toxic to aquatic organisms. Many companies are choosing to use natural raw materials that have satisfactory performance properties but are also environmentally friendly. In addition, modern products are also characterized by reduced consumption of water, resources, and energy in production processes. These measures reduce the carbon footprint and reduce the amount of plastic packaging required. In the present study, seven formulations of environmentally friendly car shampoo concentrates were developed, based entirely on mixtures of bio-based surfactants. The developed formulations were tested for application on the car body surface, allowing the selection of the two best products. For these selected formulations, an in-depth physicochemical analysis was carried out, including pH, density, and viscosity measurements. Comparison of the results with commercial products available on the market was also performed. Additionally, using the multiple light scattering method, the foamability and foam stability were determined for the car shampoos developed. The results obtained indicate the very high application potential of the products under study, which combine high performance and environmental concerns. Full article

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

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12 pages, 3794 KiB

Open AccessArticle

Enhanced Energy Storage Properties of Ba_0.96Ca_0.04TiO₃ Ceramics Through Doping Bi(Li_1/3Zr_2/3)O₃

by Zhiwei Li, Dandan Zhu, Xuqiang Ding, Lingling Cui and Junlong Wang

Coatings 2025, 15(8), 906; https://doi.org/10.3390/coatings15080906 - 2 Aug 2025

Abstract

The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ (x = 0.03–0.15) ceramics were fabricated via the traditional solid reaction method. Characterization results revealed that each component exhibited a pure perovskite structure, and the average grain size significantly diminishes [...] Read more.

The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ (x = 0.03–0.15) ceramics were fabricated via the traditional solid reaction method. Characterization results revealed that each component exhibited a pure perovskite structure, and the average grain size significantly diminishes with increasing x. The (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ ceramics exhibited prominent relaxor ferroelectric behavior, whose characteristic narrow hysteresis loops effectively enhanced the energy storage performance of the material. Most importantly, the composition with x = 0.10 demonstrated exceptional energy storage properties at 150 kV/cm, achieving a high recoverable energy storage density (W_rec = 1.91 J/cm³) and excellent energy efficiency (η = 90.87%). Under the equivalent electric field, this composition also displayed a superior pulsed discharge performance, including a high current density (871 A/cm²), a high power density (67.3 MW/cm³), an ultrafast discharge time (t_0.9 = 109 ns), and a discharged energy density of 1.47 J/cm³. These results demonstrate that the (1−x)Ba_0.96Ca_0.04TiO₃−xBi(Li_1/3Zr_2/3)O₃ ceramic system establishes a promising design paradigm for the creation and refinement of next-generation dielectrics for pulse power applications. Full article

(This article belongs to the Section Ceramic Coatings and Engineering Technology)

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26 pages, 7634 KiB

Open AccessArticle

Research on the Preparation and Performance of Wood with High Negative Oxygen Ion Release Induced by Moisture

by Min Yin, Yuqi Zhang, Yun Lu, Zongying Fu, Haina Mi, Jianfang Yu and Ximing Wang

Coatings 2025, 15(8), 905; https://doi.org/10.3390/coatings15080905 - 2 Aug 2025

Abstract

With the growing severity of environmental pollution, people are paying increasing attention to their health. However, naturally occurring wood with health benefits and applications in human healthcare is still scarce. Natural wood exhibits a limited negative oxygen ion release capacity, and this release [...] Read more.

With the growing severity of environmental pollution, people are paying increasing attention to their health. However, naturally occurring wood with health benefits and applications in human healthcare is still scarce. Natural wood exhibits a limited negative oxygen ion release capacity, and this release has a short duration, failing to meet practical application requirements. This study innovatively developed a humidity-responsive, healthy wood material with a high negative oxygen ion release capacity based on fast-growing poplar. Through vacuum cyclic impregnation technology, hexagonal stone powder was infused into the pores of poplar wood, endowing it with the ability to continuously release negative oxygen ions. The healthy wood demonstrated a static average negative oxygen ion release rate of 537 ions/cm³ (peaking at 617 ions/cm³) and a dynamic average release rate of 3,170 ions/cm³ (peaking at 10,590 ions/cm³). The results showed that the particle size of hexagonal stone powder in suspension was influenced by the dispersants and dispersion processes. The composite dispersion process demonstrated optimal performance when using 0.5 wt% silane coupling agent γ-(methacryloxy)propyltrimethoxysilane (KH570), achieving the smallest particle size of 8.93 μm. The healthy wood demonstrated excellent impregnation performance, with a weight gain exceeding 14.61% and a liquid absorption rate surpassing 165.18%. The optimal impregnation cycle for vacuum circulation technology was determined to be six cycles, regardless of the type of dispersant. Compared with poplar wood, the hygroscopic swelling rate of healthy wood was lower, especially in PEG-treated samples, where the tangential, radial, longitudinal, and volumetric swelling rates decreased by 70.93%, 71.67%, 69.41%, and 71.35%, respectively. Combining hexagonal stone powder with fast-growing poplar wood can effectively enhance the release of negative oxygen ions. The static average release of negative oxygen ions from healthy wood is 1.44 times that of untreated hexagonal stone powder, and the dynamic release reaches 2 to 3 times the concentration of negative oxygen ions specified by national fresh air standards. The water-responsive mechanism revealed that negative oxygen ion release surged when ambient humidity exceeded 70%. This work proposes a sustainable and effective method to prepare healthy wood with permanent negative oxygen ion release capability. It demonstrates great potential for improving indoor air quality and enhancing human health. Full article

(This article belongs to the Special Issue Recent Developments in the Surface Modification of Lignocellulosic Materials)

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