Coatings

15 pages, 4332 KB

Open AccessArticle

Effect of Dimensional Compatibility Between rGO Sheets and B₄C Particles on the Microstructure and Mechanical Properties of rGO–B₄C Composites

by Lanxin Hu, Qianglong He, Aiyang Wang, Yating Zheng and Weimin Wang

Coatings 2026, 16(9), 1108; https://doi.org/10.3390/coatings16091108 - 17 Sep 2026

Abstract

The effect of dimensional compatibility between rGO sheets and B₄C particles plays a critical role in governing the microstructure evolution and mechanical performance of rGO–B₄C composites. In this work, rGO–B₄C composites (5 wt.% GO addition) with varied [...] Read more.

The effect of dimensional compatibility between rGO sheets and B₄C particles plays a critical role in governing the microstructure evolution and mechanical performance of rGO–B₄C composites. In this work, rGO–B₄C composites (5 wt.% GO addition) with varied initial B₄C particle sizes were fabricated via self-assembly polymerization combined with spark plasma sintering. The influence of B₄C powder particle size on the microstructure and mechanical properties of rGO–B₄C composite ceramics was investigated, and the dimensional compatibility of B₄C powder particle size to rGO sheet size was analyzed, further verifying the toughening mechanism of rGO–B₄C composite ceramics. The study showed that the dimensional compatibility of rGO sheet size to W3.5 B₄C raw material powder particle size is the best. Through self-assembly polymerization combined with spark plasma sintering, a uniformly dispersed and interconnected network structure of rGO in W3.5 rGO–B₄C composite ceramics can be obtained. This dense microstructure with an interconnected rGO network helps rGO–B₄C composite ceramics achieve optimal mechanical properties, with the highest relative density, hardness, bending strength, and fracture toughness, which are 99.67%, 31.07 GPa, 496 MPa, and 5.45 MPa·m^1/2, respectively. Full article

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

► Show Figures

Figure 1

21 pages, 24253 KB

Open AccessArticle

Interfacial Effects and Wetting–Drying Cycle Damage Inhibition of Coastal Saline Soil Modified by Xanthan Gum Biopolymer Coating

by Shuwei Dong, Xinxin Cao, Yongjie Ding, Yangfei Chen and Chien-Ta Chen

Coatings 2026, 16(9), 1107; https://doi.org/10.3390/coatings16091107 - 17 Sep 2026

Abstract

Coastal saline soils are vulnerable to degradation under repeated wetting–drying (W–D) exposure, while conventional inorganic stabilizers are associated with high energy consumption and environmental burdens. To address this issue, an environmentally friendly ternary stabilization system consisting of local sandy silt, low-dose cement, and [...] Read more.

Coastal saline soils are vulnerable to degradation under repeated wetting–drying (W–D) exposure, while conventional inorganic stabilizers are associated with high energy consumption and environmental burdens. To address this issue, an environmentally friendly ternary stabilization system consisting of local sandy silt, low-dose cement, and xanthan gum (XG) at different dosages was developed, with emphasis on the particle-scale coating effect of hydrated XG. Accelerated laboratory W–D cycling (0–20 cycles), direct shear tests, unconfined compressive strength (UCS) tests, binary-image crack analysis, and field-emission scanning electron microscopy (FE-SEM) were used to evaluate the effects of W–D cycling and XG dosage (0%–2.0%) on mechanical properties, interfacial bonding, surface deterioration, and microstructural evolution. An optimum XG dosage of 1.5% was identified. Before W–D cycling, the UCS of the 1.5% XG group reached 1005.4 kPa, 94.9% higher than that of the 0% XG control. After 20 W–D cycles, the 1.5% XG group exhibited a mass loss rate of 3.7%, a crack ratio below 4.3%, and a compressive strength retention of 83.8%, whereas the 0% XG control showed more pronounced mass loss and strength degradation. The XG coating limited water and salt migration and provided flexible interparticle bridging that mitigated shrinkage-induced stress concentration. FE-SEM observations further indicated that XG and cement hydration products formed a relatively continuous organic–inorganic interfacial network, which helped preserve particle contacts and restrain microcrack propagation during cyclic exposure. These results demonstrate the potential of particle-scale XG coating for improving the W–D durability of modified saline soil. Full article

(This article belongs to the Special Issue Polymer-Based Thin Films and Coatings: Analysis, Preparation and Applications)

► Show Figures

Figure 1

19 pages, 6717 KB

Open AccessArticle

Carbon and Oxygen Addition Influence on NiCr Coatings Obtained by TVA Technology

by Cornel Staicu, Bianca-Georgiana Solomonea, Alexandru Anghel, Cristian P. Lungu, Bogdan Butoi, Corneliu Porosnicu, Paul Dinca, Oana Pompilian, Arcadie Sobetkii, Valentina Capatina, Emilia Visan, Anca Constantina Parau, Mihaela Dinu, Iulian Pana, Alina Vladescu (Dragomir) and Catalin Vitelaru

Coatings 2026, 16(9), 1106; https://doi.org/10.3390/coatings16091106 - 17 Sep 2026

Abstract

NiCr composite coatings on stainless steel were obtained by the simultaneous deposition of Cr and Ni, using thermionic vacuum arc (TVA) technology. The main aim of this paper is to study the influence of graphite and oxygen incorporation on the structural, mechanical, and [...] Read more.

NiCr composite coatings on stainless steel were obtained by the simultaneous deposition of Cr and Ni, using thermionic vacuum arc (TVA) technology. The main aim of this paper is to study the influence of graphite and oxygen incorporation on the structural, mechanical, and tribological properties of the resulting coatings. The deposition geometry was designed to maintain a relative constant Cr/Ni ratio while inducing a controlled compositional gradient in carbon content. An additional batch of samples was synthesized under reactive conditions by introducing a controlled O₂ flow while maintaining the same plasma parameters during deposition. The coatings were deposited on both Si wafers and AISI 304 stainless steel substrates. The elemental composition and phase structure were analyzed by scanning electron microscopy- energy dispersive spectroscopy (SEM-EDS) and grazing-incidence X-ray diffraction (GIXRD), revealing the formation of mixed CrNi intermetallic phases, nickel carbide (Ni₃C), and, under reactive conditions, chromium and nickel oxides. Increasing the oxygen content led to a progressive structural transition from metallic–carbide mixtures to predominantly crystalline oxide phases. Tribological performance was evaluated using a ball-on-disk tribometer, and the results demonstrated a significant reduction and stabilization of the friction coefficient for oxygen-containing coatings, together with enhanced wear resistance. SEM and EDS analyses of the wear tracks confirmed the formation of protective oxide layers that effectively reduced coating removal during sliding. Nanoindentation measurements revealed a substantial increase in hardness from ~4 GPa for binary Cr–Ni coatings to ~9 GPa for ternary Cr–Ni–C films, with the highest hardness values obtained for oxygen-enriched coatings. The results highlight the synergistic role of carbon and oxygen in tailoring the microstructure and enhancing the mechanical and tribological performance of Cr–Ni-based composite coatings deposited by TVA, demonstrating their potential for protective applications under demanding operating conditions. This work demonstrates that controlled oxygen incorporation during TVA deposition can be used as an effective tool to tailor simultaneously the phase composition, surface chemistry, mechanical response, and tribological behavior of Cr–Ni–C coatings without compromising coating integrity. Full article

(This article belongs to the Special Issue Advances in Metal Composite Coatings and Films: Microstructure, Physicochemical and Mechanical Properties)

► Show Figures

Figure 1

19 pages, 4300 KB

Open AccessArticle

Effect of Mineral Pigment Processing on the Colorimetric Response and Weathering Deterioration of Coatings for Heritage Architecture

by Carlos Guillermo Vargas Febres

Coatings 2026, 16(9), 1105; https://doi.org/10.3390/coatings16091105 - 17 Sep 2026

Abstract

The effect of mineral pigment processing by sedimentation (MS) and ball milling (MG) on the colorimetric response and surface deterioration under weathering of coatings formulated with polyvinyl acetate (PVAc) at 20%, 40% and 60% was comparatively evaluated; 78 coating formulations with valid records [...] Read more.

The effect of mineral pigment processing by sedimentation (MS) and ball milling (MG) on the colorimetric response and surface deterioration under weathering of coatings formulated with polyvinyl acetate (PVAc) at 20%, 40% and 60% was comparatively evaluated; 78 coating formulations with valid records were evaluated, with five replicate specimens prepared for each formulation, resulting in 39 paired MS-MG comparisons for colorimetric analysis. The pigments were characterized by particle-size analysis, scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS), while the coatings were evaluated using the NCS system and natural weathering exposure. The colorimetric comparison showed predominant stability between MS and MG, with 23 comparisons retaining blackness, 23 chromaticness and 22 hue. The differences depended on the pigment and PVAc concentration. During exposure, MG presented lower maximum levels of cracking, detachment and blistering than MS; however, discoloration showed a differentiated response, with higher values in MG-20% and MG-40%. The results indicate that pigment processing influences coating performance, but its effect is not uniform across all evaluated properties. MG showed a more favorable surface response under the experimental conditions studied, without demonstrating overall superiority in chromatic stability. Full article

(This article belongs to the Special Issue New Insights into Everyday Heritage: Surface Analysis and Conservation)

► Show Figures

Figure 1

26 pages, 3070 KB

Open AccessArticle

Engineering Low-Friction Carbonitrided Steel Surfaces: A Joint RSM–ANN Study of Multi-Pass Scratch Behavior in AISI 4130

by Siwar Toumi, Abdel Karim Ghanem, Borhen Louhichi and Mohamed Ali Terres

Coatings 2026, 16(9), 1104; https://doi.org/10.3390/coatings16091104 - 16 Sep 2026

Abstract

This paper concerns the optimization of the tribological properties of carbonitrided steel, a matter of particular significance in the design of highly stressed, hardened mechanical components. The study aims to explore the simultaneous treatment of microhardness, normal load and number of passes as [...] Read more.

This paper concerns the optimization of the tribological properties of carbonitrided steel, a matter of particular significance in the design of highly stressed, hardened mechanical components. The study aims to explore the simultaneous treatment of microhardness, normal load and number of passes as jointly optimized design variables for the multi-pass scratch friction response of carbonitrided AISI 4130 steel. It employs a full-factorial response-surface (RSM) approach, in conjunction with a desirability-function optimization and an artificial neural network (ANN) model, with the objective of both explaining and predicting this response. The microstructural and mechanical properties of carbonitrided AISI 4130 steel were first examined by looking at how the steel wears in tribological applications. The microstructure of the carbonitrided steel was analyzed using optical microscopy and X-ray diffraction (XRD), with varying carbon-potential and tempering parameters. As the tempering temperature increased, the carbonitrided steel demonstrated a decrease in microhardness, consistent with progressive relief of quenching-induced stresses and decomposition of retained austenite. The surface microhardness ranged from 630 HV0.1 (C12, tempered at 550 °C) to 980 HV0.1 (C2), against 270 HV0.1 for untreated steel. To investigate the friction coefficient, a multi-pass scratching approach was employed, utilizing a full-factorial design of experiments (4 × 4 × 4 combinations of hardness, normal load and number of passes). The experimental data were analyzed by response surface methodology (RSM) with a desirability-function approach, and by an artificial neural network (ANN) trained with the standard back-propagation algorithm. The correlation coefficient (R²) of 0.993 demonstrates a strong agreement between the model predictions and the experimental results. The findings establish a validated, transferable quantitative relationship between carbonitriding-induced hardness gradients and adhesive-wear friction behavior, providing a predictive framework that can be extended to other case-hardened low-alloy steels subjected to multi-pass sliding degradation. Full article

(This article belongs to the Section Metal Surface Process)

► Show Figures

Figure 1

16 pages, 2279 KB

Open AccessArticle

Five-Parameter Identification Method for Multi-Type Photovoltaic Modules Based on Genetic Algorithm

by Jicheng Zhou, Xingrong Zhu, Jianyong Zhan, Linzhao Hao and Linfei Feng

Coatings 2026, 16(9), 1103; https://doi.org/10.3390/coatings16091103 - 16 Sep 2026

Abstract

Existing parameter extraction methods for photovoltaic modules are mostly developed for specific module types or structural configurations, making it difficult to achieve unified modeling across different materials, structures, and operating conditions. To address this issue, this study proposes a unified five-parameter identification method [...] Read more.

Existing parameter extraction methods for photovoltaic modules are mostly developed for specific module types or structural configurations, making it difficult to achieve unified modeling across different materials, structures, and operating conditions. To address this issue, this study proposes a unified five-parameter identification method based on the single-diode model of photovoltaic cells and combines it with a genetic algorithm. The photocurrent, reverse saturation current, series resistance, shunt resistance, and diode ideality factor are selected as the identification parameters, and the parameter extraction problem is formulated as a global optimization problem. On this basis, a cell-unit-based parameter correction model considering the effects of irradiance and temperature is established, and unified modeling of photovoltaic modules with different architectures is achieved according to their internal electrical connections, enabling the prediction of their electrical characteristics. The proposed method is validated using experimental data from a half-cell mono-crystalline silicon module under different shading conditions, as well as mono-crystalline silicon, multi-crystalline silicon, and thin-film modules under varying irradiance and temperature conditions. In addition, the RTC France solar cell and Photowatt-PWP201 module benchmark datasets are employed to further assess the reliability of the parameter identification procedure. The results demonstrate that the proposed method can effectively reproduce the electrical characteristics of the investigated photovoltaic modules, with maximum relative errors of 2.48%, 2.17%, and 4.32% for open-circuit voltage, short-circuit current, and maximum power, respectively. The benchmark validation further demonstrates that the proposed method achieves fitting accuracy comparable to that of other representative optimization algorithms while exhibiting good repeatability and convergence performance. These results collectively demonstrate the feasibility of the proposed cell-unit-based five-parameter modeling framework for photovoltaic modules with different materials and structures under the investigated operating conditions, providing a simple and feasible approach for unified parameter identification, performance characterization, and engineering modeling. Full article

► Show Figures

Figure 1

16 pages, 3185 KB

Open AccessArticle

Diode Laser Processing of 3D-Printed Polymers for Microchannel Fabrication and Surface Modification

by Elizabeta Forjan, Marijan-Pere Marković, Lara Štorga and Domagoj Vrsaljko

Coatings 2026, 16(9), 1102; https://doi.org/10.3390/coatings16091102 - 16 Sep 2026

Abstract

Additive manufacturing enables rapid fabrication of polymer components, but the direct production of well-defined microchannels remains challenging. Laser processing offers an attractive approach for introducing microscale features and modifying polymer surface properties. This study investigates visible diode laser processing of four additively manufactured [...] Read more.

Additive manufacturing enables rapid fabrication of polymer components, but the direct production of well-defined microchannels remains challenging. Laser processing offers an attractive approach for introducing microscale features and modifying polymer surface properties. This study investigates visible diode laser processing of four additively manufactured polymers: acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol (PETG), Anycubic Standard resin, and Industrial Rigid resin. Laser-processing conditions were screened and selected for each material, and surface modifications were evaluated using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, contact angle measurements, and surface free energy calculations. ABS and PETG enabled successful microchannel formation, whereas continuous microchannels could not be obtained in the photopolymer resins under the investigated conditions. ATR-FTIR analysis revealed material-dependent surface modifications while largely preserving the characteristic polymer fingerprints. Laser treatment increased the water contact angle of ABS from 88.9° to 122.3° and PETG from 73.5° to 92.2°. In contrast, it decreased from 85.4° to 59.0° for Anycubic Standard resin and from 103.7° to 81.6° for Industrial Rigid resin. These contrasting responses demonstrate that diode laser processing can induce microstructuring, surface modification, or both, depending on the polymer substrate. Full article

(This article belongs to the Special Issue Recent Developments in Additive Manufacturing of Functional Coatings)

► Show Figures

Graphical abstract

19 pages, 29240 KB

Open AccessArticle

Unraveling Microstructural Evolution and Mechanical Enhancements in LPBFed 316L Stainless Steel Under Ultrasonic Impact Treatment

by Quan Bai, Panlong Hu, Jianmin Zhang, Mingming Tang and Xiankai Meng

Coatings 2026, 16(9), 1101; https://doi.org/10.3390/coatings16091101 - 16 Sep 2026

Abstract

Laser powder bed fusion (LPBF) has emerged as a pivotal method for manufacturing intricate metal components using 316L stainless steel. Despite its effectiveness, LPBFed parts often suffer from coarse columnar grains, suboptimal surface finish, and mechanical properties. This study explores the transformative impact [...] Read more.

Laser powder bed fusion (LPBF) has emerged as a pivotal method for manufacturing intricate metal components using 316L stainless steel. Despite its effectiveness, LPBFed parts often suffer from coarse columnar grains, suboptimal surface finish, and mechanical properties. This study explores the transformative impact of ultrasonic impact treatment (UIT) on LPBFed 316L stainless steel, meticulously examining its effects on surface morphology, residual stress distribution, microstructure, and mechanical characteristics. The findings reveal a significant reduction in surface roughness due to UIT, accompanied by a remarkable conversion of residual tensile stress into compressive stress within the surface layer. Notably, the coarse columnar grains prevalent in the specimens undergo a substantial transformation, evolving into irregularly shaped equiaxed grains, characterized by reduced average grain size, elevated low-angle grain boundaries, and increased dislocation density. The ensuing microstructural evolution results in a substantial enhancement, with the maximum surface hardness reaching 303.4 HV, signifying a noteworthy 17.64% improvement compared to the original specimens. Additionally, significant improvements in both tensile strength and ductility are observed. These enhancements are primarily attributed to UIT-induced severe plastic deformation and dislocation strengthening, together with localized grain refinement and the conversion of tensile residual stress into compressive residual stress. This study not only unveils the underlying mechanisms of UIT but also underscores its pivotal role in augmenting the structural and mechanical integrity of LPBFed 316L stainless steel, offering valuable insights for advancing materials science and engineering applications. Full article

(This article belongs to the Special Issue Effects of Laser Treatment on Surface Characterization and Mechanical Properties of Alloys, 2nd Edition)

► Show Figures

Figure 1

10 pages, 2671 KB

Open AccessArticle

Eco-Friendly Synthesis of Ag NPs Using Polygoni ciliinerve Extract for Multifunctional Silk Finishing

by Xiaocui Huang, Chen Liu, Jingyi Huang, Xiangyin You and Guangyu Zhang

Coatings 2026, 16(9), 1100; https://doi.org/10.3390/coatings16091100 - 16 Sep 2026

Abstract

This study developed a simple method for the environmentally friendly preparation of silver nanoparticles (Ag NPs) using Polygonum ciliinerve extract, which was then applied to the functional finishing of silk fabrics. This extract functioned as an efficient bio-reducing agent, reducing silver ions into [...] Read more.

This study developed a simple method for the environmentally friendly preparation of silver nanoparticles (Ag NPs) using Polygonum ciliinerve extract, which was then applied to the functional finishing of silk fabrics. This extract functioned as an efficient bio-reducing agent, reducing silver ions into spherical Ag NPs with uniform size (approximately 50 nm). Following treatment with the prepared Ag NPs solution, silk fabrics demonstrated antibacterial inhibition rates that exceeded 99% against both Escherichia coli and Staphylococcus aureus. This finding indicates that the fabricated solution exhibited excellent antimicrobial efficacy, a property that was maintained even after 20 standard washes. The ultraviolet protection factor (UPF) demonstrated a substantial enhancement, with UVA and UVB transmittance both reduced to below 5%. This study proposes a novel strategy for the development of highly effective, eco-friendly, multifunctional textiles. Full article

(This article belongs to the Special Issue Recent Progress on Functional Films and Surface Science)

► Show Figures

Figure 1

75 pages, 22341 KB

Open AccessReview

Carbon Nano-Onion-Based Sensors for Relative Humidity, Gas, and Temperature Monitoring: A Review

by Bogdan-Catalin Serban, Octavian Buiu, Marius Bumbac, Mihai Brezeanu, Roxana Marinescu, Niculae Dumbrăvescu, Maria Ruxandra Sălăgean, Caterina-Maria Zetu, Matei Ursachescu and Vlad Diaconescu

Coatings 2026, 16(9), 1099; https://doi.org/10.3390/coatings16091099 - 16 Sep 2026

Abstract

In recent years, carbon nano-onions (CNOs), together with their functionalized derivatives, nanocomposites, and nanohybrids, have attracted increasing attention as sensing materials for monitoring relative humidity (RH), gases, and temperature. Their concentric graphitic structure provides good electrical conductivity, chemical and thermal stability, accessible surface [...] Read more.

In recent years, carbon nano-onions (CNOs), together with their functionalized derivatives, nanocomposites, and nanohybrids, have attracted increasing attention as sensing materials for monitoring relative humidity (RH), gases, and temperature. Their concentric graphitic structure provides good electrical conductivity, chemical and thermal stability, accessible surface sites, tunable surface chemistry, and compatibility with polymer matrices and flexible substrates. This review highlights recent advances in the synthesis and functionalization of CNOs and examines their integration into chemiresistive, surface acoustic wave, flexible, and printed sensing platforms. Particular attention is devoted to pristine and oxidized CNOs, heteroatom-doped materials, and composites incorporating hydrophilic or conducting polymers, metal oxides, and other functional fillers. CNO-based sensing layers demonstrate room-temperature (RT) detection of RH, hydrogen, ammonia, acetone, ethanol, isopropanol, carbon dioxide, hydrogen sulfide, and other volatile organic compounds. In addition, CNOs and CNO–polymer films exhibit significant temperature-dependent resistance variations, supporting their potential use in flexible and wearable temperature sensors. Although several CNO-based devices show superior performance in sensitivity, response, recovery characteristics, mechanical flexibility, and low-power operation, the studies on CNOs available in the literature remain limited compared with those on carbon nanotubes, graphene derivatives, and other carbonaceous materials. Further progress on CNO-based structures requires reproducible, large-scale synthesis; improved film uniformity and selectivity; standardized testing; compensation for temperature–humidity cross-sensitivity; and long-term stability studies. This review concludes by highlighting research directions to bridge the gap between laboratory prototypes and commercially viable CNO-based sensing devices. Full article

(This article belongs to the Special Issue Advanced Thin Films Technologies for Optics, Electronics, and Sensing, 2nd Edition)

► Show Figures

Figure 1

23 pages, 16484 KB

Open AccessArticle

Surface Properties of Mg–3.5Y Alloy Treated by Micro-Arc Oxidation Using Eggshells and Ammonium Hydrogen Phosphate-Added Electrolyte

by Song-Jeng Huang, Chuan Li, Cheng Kai Lai and Sathiyalingam Kannaiyan

Coatings 2026, 16(9), 1098; https://doi.org/10.3390/coatings16091098 - 15 Sep 2026

Abstract

Magnesium–yttrium (Mg–Y) alloys are promising biodegradable orthopedic implant materials because of their mechanical compatibility with bone tissue; however, their degradation rate in physiological environments requires further control. In this study, the surfaces of gravity-cast Mg–3.5Y alloy were treated with micro-arc oxidation (MAO) in [...] Read more.

Magnesium–yttrium (Mg–Y) alloys are promising biodegradable orthopedic implant materials because of their mechanical compatibility with bone tissue; however, their degradation rate in physiological environments requires further control. In this study, the surfaces of gravity-cast Mg–3.5Y alloy were treated with micro-arc oxidation (MAO) in Na₂SiO₃-based electrolytes supplemented with diammonium hydrogen phosphate ((NH₄)₂HPO₄), eggshell powder, or a mixture of both, to form corrosion-resistant ceramic coatings containing calcium and phosphates. The MAO process utilized a bipolar pulsed DC power supply for 8 min, and the resulting coating characteristics were analyzed via FESEM, EDS, XRD, Vickers microhardness, electrochemical test (potentiodynamic polarization), and simulated body fluid immersion tests. Cross-sectional SEM and EDS revealed that all MAO-treated samples contain Mg, Na, O, Si, and elements derived from the electrolyte additives. Electrolytes containing diammonium hydrogen phosphate not only produced thicker films but also facilitated the deposition of calcium-related species derived from eggshells; in contrast, the deposition of calcium is limited when only eggshell powder is added to the electrolyte. X-ray diffraction analysis confirms the formation of MgO, Mg₂SiO₄, and calcium-containing compounds within the coating. Energy-dispersive X-ray spectroscopy spectrum further verified the presence of these compounds in the deposited films. Electrochemical tests in simulated body fluid revealed that the electrolyte containing only diammonium hydrogen phosphate yields the highest open-circuit potential and corrosion current; further immersion tests demonstrate better corrosion resistance. Overall, the results show that combining diammonium hydrogen phosphate with eggshell-derived calcium compounds can be an effective method for producing multifunctional MAO coatings on Mg–Y alloys. For microhardness, adding diammonium hydrogen phosphate and eggshell to Na₂SiO₃-based MAO electrolytes yields a harder coating, whereas Na₂SiO₃-based electrolytes with only diammonium hydrogen phosphate would lead to a better corrosion-resistant coating. These differences are caused by differences in composition and microstructure in the deposited films. This study offers a viable production method for application in biodegradable materials. Full article

(This article belongs to the Section Metal Surface Process)

► Show Figures

Graphical abstract

15 pages, 24807 KB

Open AccessArticle

The Effect of Ultrasonic Surface Modification of Nanocrystals on the Surface, Microstructure, and Mechanical Properties of a WC-12Co Coating Deposited by Detonation Spraying

by Nurtoleu Magazov, Bauyrzhan Rakhadilov, Auezhan Amanov, Arystanbek Kussainov, Dauir Kakimzhanov and Yermakhan Molbossynov

Coatings 2026, 16(9), 1097; https://doi.org/10.3390/coatings16091097 - 15 Sep 2026

Abstract

This study investigates the effect of a static contact load applied during ultrasonic nanocrystal surface modification (UNSM) on WC-12Co coatings deposited by detonation spraying. Surface roughness, surface and cross-sectional microstructure, mechanical properties, and adhesion–cohesion strength were evaluated using contact profilometry, scanning electron microscopy [...] Read more.

This study investigates the effect of a static contact load applied during ultrasonic nanocrystal surface modification (UNSM) on WC-12Co coatings deposited by detonation spraying. Surface roughness, surface and cross-sectional microstructure, mechanical properties, and adhesion–cohesion strength were evaluated using contact profilometry, scanning electron microscopy (SEM), instrumental indentation (ISO 14577-1), and progressive-load scratch testing (ASTM C1624) under static contact loads of P = 10, 20, 30, and 40 N at fixed amplitude, frequency, and travel speed. Among the treated samples, the arithmetic mean roughness decreased monotonically with increasing load—from Ra = 1.468 ± 0.098 μm at 10 N to 1.158 ± 0.244 μm at 40 N (−21%); pairwise differences fell within the margin of error (p ≥ 0.26), but the linear trend with load was significant (p = 0.039). Maximum profile height (Rz) did not depend on load. The asymmetry Rsk remained negative at all loads, reaching its most negative value at 30 N. Quantitative analysis of the cross-sections yielded coating thicknesses of 230 ± 12, 246 ± 9, 40 ± 6, and 82 ± 7 μm for samples processed at 10, 20, 30, and 40 N, respectively; this variation in thickness is taken into account when interpreting the scratch tests. The average Vickers hardness and indentation modulus exceeded the values for the sprayed material at any load; the EIT peaked at 20 N; and the coefficient of friction in the range Fn = 0–30 N decreased by 17% between 10 and 40 N. We determined P = 30 N as the optimal static contact load: it provides the smallest residual scratch depth (5.5 ± 1.8 μm) and the highest cohesive critical load (Lc1 = 50.2 N), whereas 40 N further reduces roughness but decreases Lc1 to 38.3 N. This conclusion is preliminary because coating thickness varies across the series, and at the final scratching load the indenter extends beyond the coating boundaries on the thinnest samples. The results identify a provisional useful load range for this specimen series. Establishing whether the deposition route changes the UNSM processing window requires a controlled comparison with coatings deposited by other methods, together with measurements of residual stress and near-surface microstructure. Full article

(This article belongs to the Section High-Energy Beam Surface Engineering and Coatings)

► Show Figures

Figure 1

18 pages, 27516 KB

Open AccessArticle

Trace Y₂O₃-Mediated Interface Engineering Breaks the Conductivity–Wear Trade-Off in Spark-Plasma-Sintered Cu-Ni-Mn-Si Alloy

by Wei Lisi, Bo Zhang, Sarula Xi, Wei Lesi, Dihao Wang and Xinba Yaer

Coatings 2026, 16(9), 1096; https://doi.org/10.3390/coatings16091096 - 15 Sep 2026

Abstract

Achieving simultaneous enhancement of electrical conductivity and wear resistance in copper alloys remains challenging because conventional strengthening strategies often introduce additional electron-scattering sources and degrade electrical transport. In this work, a trace Y₂O₃-assisted interface-engineering strategy was developed to regulate [...] Read more.

Achieving simultaneous enhancement of electrical conductivity and wear resistance in copper alloys remains challenging because conventional strengthening strategies often introduce additional electron-scattering sources and degrade electrical transport. In this work, a trace Y₂O₃-assisted interface-engineering strategy was developed to regulate the microstructural evolution of spark-plasma-sintered Cu-Ni-Mn-Si alloys. The effects of Y₂O₃ addition on phase constitution, grain-boundary evolution, electrical transport, and tribological behavior were systematically investigated. The results demonstrate that Y₂O₃ does not significantly alter the Cu matrix phase constitution but effectively modifies interfacial evolution during SPS consolidation. Moderate Y₂O₃ addition (0.08 wt.%) produces the most homogeneous grain structure with the smallest average grain size of 4.83 μm through grain-boundary stabilization and particle-pinning effects. However, the optimum functional performance is achieved at a higher Y₂O₃ content of 0.15 wt.%, exhibiting the highest electrical conductivity of 55.37%IACS, the lowest wear loss of 1.24 mg, and the narrowest wear scar width and depth of 861 μm and 23 μm, respectively. The superior conductivity–wear synergy of the 0.15 wt.% Y₂O₃ alloy is associated with the combined effects of microstructural and interfacial regulation, which may influence electron transport and resistance to material removal during sliding. This work reveals that trace additions of rare-earth oxides provide an effective interface-engineering approach to overcoming the conventional conductivity–wear trade-off in powder-metallurgy copper alloys and offer new insights into the design of multifunctional electrical contact materials. Full article

(This article belongs to the Section Metal Surface Process)

► Show Figures

Figure 1

24 pages, 4176 KB

Open AccessArticle

Mechanical and Electrical Responses of Magnetron-Sputtered AgNi Coatings Under Radial Fretting: A Contact Model Incorporating Residual Stress

by Xue Zhou, Mingxu Zhang, Donghui Li and Guofu Zhai

Coatings 2026, 16(9), 1095; https://doi.org/10.3390/coatings16091095 - 15 Sep 2026

Abstract

Stable electrical contacts must maintain mechanical integrity and low electrical resistance under fretting conditions, but the influence of deposition-induced residual stress on coated rough interfaces remains unclear. In this paper, 2.8 μm AgNi coatings containing 1–8 at.% Ni were deposited by magnetron sputtering. [...] Read more.

Stable electrical contacts must maintain mechanical integrity and low electrical resistance under fretting conditions, but the influence of deposition-induced residual stress on coated rough interfaces remains unclear. In this paper, 2.8 μm AgNi coatings containing 1–8 at.% Ni were deposited by magnetron sputtering. Their microstructure, mechanical properties, residual stress, resistivity, and coupled force–resistance responses were examined over 20 displacement-controlled radial-fretting cycles to resolve the early-cycle evolution from initial asperity accommodation to electromechanical stabilization. A residual-stress-aware multiasperity model was developed to interpret the stabilized high- and low-load electrical responses by coupling elastic–plastic asperity contact with finite-thickness constriction resistance and conducting-spot interactions. Increasing Ni content increased the magnitude of the compressive residual stress from 35.3 to 312.3 MPa. The stabilized R_min increased from 0.464 ± 0.028 to 0.575 ± 0.029 mΩ, whereas R_max decreased from 3.064 ± 0.151 to 1.797 ± 0.083 mΩ across the composition series. The cycle-resolved histories showed that R_min was weakly cycle-dependent, whereas R_max increased markedly in the low-Ni coatings as the return-point preload progressively relaxed. At the stabilized cycle, the multiasperity model reproduced the contrasting composition-dependent resistance trends at the high- and low-load endpoints. A paired sensitivity analysis showed that residual stress had a minor influence on R_min but reduced R_max by up to 20.3% by suppressing accumulated plastic settlement and preserving the return-point conducting network. These results reveal a mechanical–electrical design trade-off in which Ni enrichment increases high-load resistance but is associated with improved preload retention and early cycle-to-cycle electrical stability. Full article

(This article belongs to the Special Issue Tribology of Advanced Films and Coatings: Mechanisms, Properties, and Applications)

► Show Figures

Figure 1

20 pages, 16359 KB

Open AccessFeature PaperArticle

Multi-Ligand-Modified Sodium Lignosulfonate-Doped Phenolic Foam as a Flame-Retardant Thermal Insulation Coating

by Wenqian Qu, Wenqi Song, Min Wang, Daoyu Chen and Yujun Song

Coatings 2026, 16(9), 1094; https://doi.org/10.3390/coatings16091094 - 15 Sep 2026

Abstract

Sodium lignosulfonate (SLS) is an abundant and low-cost by-product generated during the sulfite pulping process, which is typically conducted at 120–180 °C depending on the pulping pH and base cation. Due to its richness in phenylpropane structural units, it holds significant potential as [...] Read more.

Sodium lignosulfonate (SLS) is an abundant and low-cost by-product generated during the sulfite pulping process, which is typically conducted at 120–180 °C depending on the pulping pH and base cation. Due to its richness in phenylpropane structural units, it holds significant potential as a bio-based resource for the synthesis of phenolic resins. However, its broad molar-mass distribution, limited flame retardance and low reactivity (particularly for SLS obtained from acidic solution process) limit how much of it can be built into phenolic resins. Here, SLS was activated through catalytic oxidation with air over a mixed manganese/cerium/cobalt acetate catalyst under alkaline conditions at 90 °C, then functionalized through an aqueous treatment-blending sequence with sodium hypophosphite, sodium pyroantimonate and triethylenetetramine and recovered as its aluminum salt, referred to as lignosulfonate–aluminum–amine (LAA) salt, to enhance its flame retardance. Gel permeation chromatography showed that scission and coupling run in parallel: the population at Mn = 745 g/mol fell from 98.46% to 95.67% of the peak area, while the high-molar-mass population rose from 1.54% to 4.33% and its Mn from 20,168 to 38,338 g/mol. For SLS oxidized with 0.5 wt% catalyst for 4 h, the onset of the first DSC endotherm shifted from 92.9 to 139.7 °C and the decomposition endotherm from about 230 to about 247 °C. Replacing 30 wt% of the phenol charge with LAA gave a foamed insulation layer of apparent density 43 kg/m³ and thermal conductivity 0.044 W/(m·K). In comparative handling observations, the modified foam appeared tougher than the unmodified foam; in a non-standardized open-flame screening test, it carbonized at the surface and self-extinguished within 10 s after flame removal. These foam coatings are much more suitable for a thick insulation layer foamed and cured in place rather than a thin film. The catalytic process performed at 90 °C using air as the O₂ provider avoids the hydrothermal activation normally conducted at 170–260 °C and provides a lower-temperature route to a multi-ligand-modified bio-based resource for phenolic insulation coatings with high bio-based content. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

► Show Figures

Figure 1

23 pages, 33042 KB

Open AccessArticle

Defect Characterization and Segmentation in APS Thermal Barrier Coatings SEM Images Using BES-YOLO11

by Dan Shan, Zongyang Li, Xiangdong Meng, Tianmeng Huang, Min Zhang, Xiao Shan and Xiaofeng Zhao

Coatings 2026, 16(9), 1093; https://doi.org/10.3390/coatings16091093 - 14 Sep 2026

Abstract

Automatic defect segmentation of atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) from scanning electron microscopy (SEM) images is essential for quantitative microstructural assessment; however, existing instance segmentation models often exhibit insufficient multi-scale representation and excessive computational cost. To address these limitations, we [...] Read more.

Automatic defect segmentation of atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) from scanning electron microscopy (SEM) images is essential for quantitative microstructural assessment; however, existing instance segmentation models often exhibit insufficient multi-scale representation and excessive computational cost. To address these limitations, we propose an improved YOLO11-seg–based framework that jointly optimizes accuracy and efficiency through two architectural enhancements: a Boundary-aware Recalibrated Bidirectional Pyramid Network (BRB-FPN) for strengthened cross-scale feature fusion and precise contour localization, and an Efficient Shared-Convolution Segmentation Head (ESCH) for reducing parameters and FLOPs while accelerating inference. Without introducing additional training strategies, the proposed method achieves consistent performance gains on a self-constructed APS–TBC SEM defect dataset, improving Mask mAP@50 by 6.9%, Mask mAP@50:95 by 4.4%, and recall by 5.5% over the baseline, while simultaneously lowering computational complexity and increasing FPS, and outperforming several mainstream segmentation approaches. These results demonstrate that the proposed framework provides an accurate and computationally efficient solution for industrial microscopic defect inspection. Full article

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

► Show Figures

Figure 1

1 pages, 123 KB

Open AccessRetraction

RETRACTED: Li et al. Research on the Properties of a New Type of Polyurethane Concrete for Steel Bridge Deck in Seasonally Frozen Areas. Coatings 2022, 12, 1732

by Li Li, Tianlai Yu, Yuxuan Wu, Yifan Wang, Chunming Guo and Jun Li

Coatings 2026, 16(9), 1092; https://doi.org/10.3390/coatings16091092 - 14 Sep 2026

Abstract

The Journal retracts the article “Research on the Properties of a New Type of Polyurethane Concrete for Steel Bridge Deck in Seasonally Frozen Areas” [...] Full article

19 pages, 19483 KB

Open AccessArticle

Strength Development and Stabilization Mechanism of Water-Based Drilling Cuttings Treated with a Multi-Source Solid-Waste Binder

by Qiqi Zhan, Bailin Shan, Xuejuan Cao, Yushan Wu, Cairui He and Zexun Liu

Coatings 2026, 16(9), 1091; https://doi.org/10.3390/coatings16091091 - 14 Sep 2026

Abstract

Water-based drilling cuttings (WBDCs) are a large-volume solid waste generated during oil and gas drilling. Their weak cementation and loose particle structure limit their direct engineering utilization. In this study, a multi-source solid-waste binder mainly composed of ground granulated blast furnace slag (GGBS) [...] Read more.

Water-based drilling cuttings (WBDCs) are a large-volume solid waste generated during oil and gas drilling. Their weak cementation and loose particle structure limit their direct engineering utilization. In this study, a multi-source solid-waste binder mainly composed of ground granulated blast furnace slag (GGBS) and fly ash (FA) was used to stabilize WBDCs. Portland cement was used as an auxiliary binder, and sodium silicate was used as the alkaline activator. The effects of sodium silicate modulus, sodium silicate dosage, cement dosage, and GGBS-to-FA mass ratio on strength development were investigated. XRD, FTIR, TG, MIP, and SEM-EDS were further employed to clarify the stabilization mechanism. The results showed that binder composition strongly affected the strength level and strength development rate of stabilized WBDCs. At a total binder dosage of 15%, the mixture with a sodium silicate modulus of 1.4, a sodium silicate dosage of 4%, a cement dosage of 10%, and a GGBS-to-FA mass ratio of 6:1 exhibited the best mechanical performance. Its unconfined compressive strengths reached 6.87, 9.74, and 10.17 MPa at 7, 14, and 28 d, respectively. Microstructural analyses indicated that the strength development of stabilized WBDCs was mainly associated with the formation and continued development of poorly crystalline C-S-H/C-(A)-S-H-type gels and a small amount of AFt. From 7 to 28 d, the porosity and total pore volume decreased by 9.5% and 11.0%, respectively, while the average pore diameter decreased by 31.2%. This study provides a basis for the resource utilization of WBDCs and the design of low-cement binders containing multiple industrial solid wastes. Full article

(This article belongs to the Special Issue Transportation Solid Waste in Pavement Maintenance: Materials Recycling, Surface Modification and Management)

► Show Figures

Figure 1

17 pages, 5368 KB

Open AccessArticle

An Experimental Study on Comparative Performance Analysis of Surface Milling of Ti-6Al-4V Titanium Alloy Using Coated Cutting Tools

by M. Hüsnü Dirikolu and Şakir Altınsoy

Coatings 2026, 16(9), 1090; https://doi.org/10.3390/coatings16091090 - 14 Sep 2026

Abstract

This study comparatively evaluates the performance of coated cutting tools in machining Ti6Al4V titanium alloy, which is widely used in the aerospace and defense industries as well as in biomedical applications. Surface milling operations were performed under both dry and wet conditions using [...] Read more.

This study comparatively evaluates the performance of coated cutting tools in machining Ti6Al4V titanium alloy, which is widely used in the aerospace and defense industries as well as in biomedical applications. Surface milling operations were performed under both dry and wet conditions using Al-Ti-N, Al-Ti-N/Ti-Si-N, Al-Cr-N, Al-Ti-Si-N, and uncoated tungsten carbide tools. The data obtained were analyzed based on tool wear, surface roughness, and chip formation. The results demonstrate that coating type and cutting parameters significantly affect tool life and surface quality. This study aims to contribute to tool selection processes for the above-mentioned industrial applications. Full article

(This article belongs to the Special Issue Advanced Functional Thin Films and Protective Coatings: Design, Processing, and Applications)

► Show Figures

Figure 1

Journal Description

Coatings

Latest Articles

Journal Menu

Journal Browser

Highly Accessed Articles

Latest Books

E-Mail Alert

News

Topics

Conferences

Special Issues

Topical Collections

Further Information

Guidelines

MDPI Initiatives

Follow MDPI