Coatings

9 pages, 704 KB

Open AccessArticle

Effect of Mid-Frequency and Inductively Coupled Plasma on the Properties of Molybdenum Nitride Thin Films

by Sung-Yong Chun

Coatings 2025, 15(10), 1155; https://doi.org/10.3390/coatings15101155 - 3 Oct 2025

This study focuses on the characterization of MoN thin films deposited by the direct current magnetron sputtering (dcMS), mid-frequency magnetron sputtering (mfMS), and inductively coupled plasma magnetron sputtering (ICPMS) methods. Two mixed metallic phases, namely, α-Mo and γ-Mo₂N, were detected from [...] Read more.

This study focuses on the characterization of MoN thin films deposited by the direct current magnetron sputtering (dcMS), mid-frequency magnetron sputtering (mfMS), and inductively coupled plasma magnetron sputtering (ICPMS) methods. Two mixed metallic phases, namely, α-Mo and γ-Mo₂N, were detected from the film obtained using the dcMS, whereas only single γ-Mo₂N phase was detected from the films obtained using the mfMS and ICPMS. Furthermore, the residual stress of the deposited thin films was strongly dependent on the sputtering process. As the mfMS and ICPMS deposition process were introduced, the film morphology changed from a porous columnar to a dense structure with finer grains than film deposited using dcMS. The surface roughness and crystal grain size of coated films were investigated by atomic force microscopy and X-ray diffraction analysis methods. Furthermore, the variation in hardness and electrical resistivity of the MoN thin films deposited by three plasma-enhanced magnetron sputtering was explained on the basis of microstructure and residual stress of the thin films. Full article

(This article belongs to the Section Thin Films)

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16 pages, 2994 KB

Open AccessArticle

Stiffness Degradation of Expansive Soil Stabilized with Construction and Demolition Waste Under Wetting–Drying Cycles

by Haodong Xu and Chao Huang

Coatings 2025, 15(10), 1154; https://doi.org/10.3390/coatings15101154 - 3 Oct 2025

Abstract

To address the challenge of long-term stiffness retention of subgrades in humid–hot climates, this study evaluates expansive soil stabilized with construction and demolition waste (CDW), focusing on the resilient modulus (M_r) under coupled stress states and wetting–drying histories. Basic physical [...] Read more.

To address the challenge of long-term stiffness retention of subgrades in humid–hot climates, this study evaluates expansive soil stabilized with construction and demolition waste (CDW), focusing on the resilient modulus (M_r) under coupled stress states and wetting–drying histories. Basic physical and swelling tests identified an optimal CDW incorporation of about 40%, which was then used to prepare specimens subjected to controlled. Wetting–drying cycles (0, 1, 3, 6, 10) and multistage cyclic triaxial loading across confining and deviatoric stress combinations. M_r increased monotonically with both stresses, with stronger confinement hardening at higher deviatoric levels; with cycling, M_r exhibited a rapid then gradual degradation, and for most stress combinations, the ten-cycle loss was 20%–30%, slightly mitigated by higher confinement. Grey relational analysis ranked influence as follows: the number of wetting–drying cycles > deviatoric stress > confining pressure. A Lytton model, based on a modified prediction method, accurately predicted M_r across conditions (R² ≈ 0.95–0.98). These results integrate stress dependence with environmental degradation, offering guidance on material selection (approximately 40% incorporation), construction (adequate compaction), and maintenance (priority control of early moisture fluctuations), and provide theoretical support for durable expansive soil subgrades in humid–hot regions. Full article

(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)

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24 pages, 2743 KB

Open AccessArticle

Pavement Performance and Mechanism of Asphalt Mixtures Reinforced with Different Diameters of Basalt Fibers for the Surface Layer

by Changjiang Kou, Shuxiang Xu, Jiyang Sun, Di Wang, Zikai Chen and Aihong Kang

Coatings 2025, 15(10), 1153; https://doi.org/10.3390/coatings15101153 - 3 Oct 2025

Abstract

The diameter of basalt fiber influences the reinforcement of basalt fiber asphalt mixtures. However, the performance evaluation and mechanistic analysis of asphalt mixtures reinforced with varying fiber diameters have been insufficiently studied. AC-13 asphalt mixtures were designed and prepared with four different fiber [...] Read more.

The diameter of basalt fiber influences the reinforcement of basalt fiber asphalt mixtures. However, the performance evaluation and mechanistic analysis of asphalt mixtures reinforced with varying fiber diameters have been insufficiently studied. AC-13 asphalt mixtures were designed and prepared with four different fiber diameters 7 μm, 16 μm, 25 μm, and an equal-mass mixture of these. The reinforcement mechanisms were analyzed using the equal cross-section theory. Results indicate that the incorporation of 7 μm and mixed-diameter basalt fibers significantly enhances the pavement performance of the asphalt mixtures compared to the control group without fibers. Additionally, it is shown by triaxial shear tests that the cohesion of the asphalt mixtures with the aforementioned two diameters of basalt fibers is strengthened by 61.5% and 55.5%, respectively. The dynamic modulus values in the high-frequency range are found to be positively correlated with fiber diameters. Since the fiber mass content and modulus were held constant, a decrease in diameter was observed to lead to an increase in fiber quantity. This is manifested by a multiple-fold increase in the total transformed cross-section (TTC_R) index for 7 μm fiber asphalt mixtures, as described by the equal cross-section theory. It is concluded that the performance improvement of the asphalt mixtures can be further enhanced under the same fiber content and cost conditions by optimizing diameter parameters. Full article

(This article belongs to the Special Issue Mechanical Properties and Surface Engineering for Pavement Materials and Asphalt Mixtures)

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17 pages, 5383 KB

Open AccessArticle

High-Temperature Sulfate Corrosion Resistance and Wear Performance of NiCr-Cr₃C₂ Coatings for the Water Wall of Power Plant Boilers

by Hang Zhang, Zhao Zhang, Cheng Zhou, Fangzhou Jin, Yongfeng Cai, Yifan Ni, Xinmin Ma, Chenghao Fan, Shulin Xiang and Dan Song

Coatings 2025, 15(10), 1152; https://doi.org/10.3390/coatings15101152 - 3 Oct 2025

Abstract

Water walls in power plant boilers are prone to failure under extreme conditions involving high temperature, corrosion, and wear, which severely threaten unit reliability and operational economy. In this work, a NiCr-Cr₃C₂ protective coating was deposited on SA213-T12 steel substrates [...] Read more.

Water walls in power plant boilers are prone to failure under extreme conditions involving high temperature, corrosion, and wear, which severely threaten unit reliability and operational economy. In this work, a NiCr-Cr₃C₂ protective coating was deposited on SA213-T12 steel substrates using high-velocity oxy-fuel (HVOF) spraying, with arc-sprayed PS45 coating as a reference. The NiCr-Cr₃C₂ coating exhibited a dense, low-porosity structure with homogeneous dispersion of Cr₃C₂ hard phases in the NiCr matrix, forming a typical cauliflower-like composite morphology. During high-temperature sulfate corrosion tests at 750 °C, the NiCr-Cr₃C₂ coating demonstrated superior corrosion resistance, with a weight gain of only 2.7 mg/cm², significantly lower than that of the PS45 coating and the SA213-T12 substrate. The higher microhardness and lower friction coefficient also indicate excellent high-temperature wear resistance. The enhanced performance of the NiCr-Cr₃C₂ coating is attributed to the high Cr content, which promotes the formation of a continuous and protective scale composed of Cr₂O₃ and NiCr₂O₄, effectively inhibiting corrosive diffusion and penetration. This work demonstrates the application prospects of NiCr-Cr₃C₂ coatings on water walls of power plant boilers and guides the development of advanced HVOF coatings. Full article

(This article belongs to the Special Issue Anti-Corrosion Coatings: New Ideas to Make Them More Effective)

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30 pages, 9143 KB

Open AccessArticle

Numerical Simulation of Ultrasonic Field During Five-Source Ultrasound-Assisted Casting of 2219 Al Alloy

by Chengqun Zhou, Weimin Zhang, Ruiqing Li, Ripeng Jiang and Renjun Hu

Coatings 2025, 15(10), 1151; https://doi.org/10.3390/coatings15101151 - 3 Oct 2025

Abstract

In this study, the distribution of the acoustic pressure field and cavitation threshold region in Al alloy casting under two five-source ultrasound arrangements (A and B) is investigated, aiming to optimize the five-source ultrasound configuration to improve casting quality. Numerical simulations were conducted [...] Read more.

In this study, the distribution of the acoustic pressure field and cavitation threshold region in Al alloy casting under two five-source ultrasound arrangements (A and B) is investigated, aiming to optimize the five-source ultrasound configuration to improve casting quality. Numerical simulations were conducted using COMSOL software (COMSOL Multiphysics 6.0) to analyze the propagation characteristics of ultrasound in the Al melt and its influence on the cavitation effect under the two arrangements. The simulation results indicate that the cavitation threshold region for arrangement A is slightly larger than that for arrangement B. Furthermore, arrangement A demonstrates superior performance in terms of the uniformity of sound pressure distribution and the reduction in the cavitation threshold. Based on the simulation results, arrangement A was selected for experimental validation. The experimental results reveal that arrangement A, with a radial rod distance (L) of 200 mm from the center point and an insertion depth (H) of 270 mm, significantly refines the grains and improves the distribution of the second phase, thereby confirming the reliability of the simulation results. This study provides a theoretical foundation and practical guidance for the application of five-source ultrasound in Al alloy casting. Full article

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

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13 pages, 7148 KB

Open AccessArticle

Cutting Performance of TiN/DLC-Coated Cemented Carbide Tool in Dry Cutting of Laser-Clad Cr-Ni-Based Steel

by Zixiang Xia, Wenlong Song, Hongjin Yu, Xing Li, Yijia Yin and Weidong Xie

Coatings 2025, 15(10), 1150; https://doi.org/10.3390/coatings15101150 - 3 Oct 2025

Abstract

To improve the dry-machining performance of a traditional-coated cemented carbide tool when cutting the laser-clad Cr-Ni-based steel, TiN/DLC multilayer coatings were fabricated using physical vapor deposition (PVD). The coated tools were tested for their surface and cross-sectional morphology, roughness, and microhardness. Dry-cutting experiments [...] Read more.

To improve the dry-machining performance of a traditional-coated cemented carbide tool when cutting the laser-clad Cr-Ni-based steel, TiN/DLC multilayer coatings were fabricated using physical vapor deposition (PVD). The coated tools were tested for their surface and cross-sectional morphology, roughness, and microhardness. Dry-cutting experiments were conducted to compare the performance of a TiN monolayer-coated tool and a TiN/DLC multilayer-coated tool. The results indicated that the TiN/DLC multilayer coatings significantly improved the machining performance, lowered the cutting force and cutting temperature, decreased the average friction coefficient at the rake face, and reduced surface roughness compared to the TiN-coated tool. This improvement is mainly attributed to the low shear strength of the DLC layer, which effectively reduces surface friction and wear of the tool. The main failure modes were abrasive wear and adhesive wear. The results suggest that the composite coating offers a promising approach to improving traditional-coated tool life and enhancing machining efficiency in the dry cutting of laser-clad alloy components. Full article

(This article belongs to the Collection Hard Protective Coatings on Tools and Machine Elements)

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16 pages, 1400 KB

Open AccessArticle

Research on the SOH of Lithium Batteries Based on the TCN–Transformer–BiLSTM Hybrid Model

by Shaojian Han, Zhenyang Su, Xingyuan Peng, Liyong Wang and Xiaojie Li

Coatings 2025, 15(10), 1149; https://doi.org/10.3390/coatings15101149 - 2 Oct 2025

Abstract

Lithium-ion batteries are widely used in energy storage and power systems due to their high energy density, long cycle life, and stability. Accurate prediction of the state of health (SOH) of batteries is critical to ensuring their safe and reliable operation. However, the [...] Read more.

Lithium-ion batteries are widely used in energy storage and power systems due to their high energy density, long cycle life, and stability. Accurate prediction of the state of health (SOH) of batteries is critical to ensuring their safe and reliable operation. However, the prediction task remains challenging due to various complex factors. This paper proposes a hybrid TCN–Transformer–BiLSTM prediction model for battery SOH estimation. The model is first validated using the NASA public dataset, followed by further verification with dynamic operating condition simulation experimental data. Health features correlated with SOH are identified through Pearson analysis, and comparisons are conducted with existing LSTM, GRU, and BiLSTM methods. Experimental results demonstrate that the proposed model achieves outstanding performance across multiple datasets, with root mean square error (RMSE) values consistently below 2% and even below 1% in specific cases. Furthermore, the model maintains high prediction accuracy even when trained with only 50% of the data. Full article

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

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10 pages, 771 KB

Open AccessArticle

Multi-Factor Analysis of Cutting Parameters for Bamboo Milling

by Mengqi Hong, Dietrich Buck, Ziyi Yuan, Changshun Xu and Zhaolong Zhu

Coatings 2025, 15(10), 1148; https://doi.org/10.3390/coatings15101148 - 2 Oct 2025

Abstract

In industrial bamboo machining, the suboptimal selection of cutting parameters leads to elevated cutting power and increased surface roughness. To enhance the machinability of bamboo, a multi-objective optimization of cutting parameters was conducted using orthogonal experimental methods, with special focus on the influences [...] Read more.

In industrial bamboo machining, the suboptimal selection of cutting parameters leads to elevated cutting power and increased surface roughness. To enhance the machinability of bamboo, a multi-objective optimization of cutting parameters was conducted using orthogonal experimental methods, with special focus on the influences of fiber direction, feed per tooth, and cutting speed on cutting power and surface roughness. The main findings of this study are summarized as follows: feed per tooth exhibited the greatest effect on cutting power, followed by cutting speed and fiber direction. In contrast, fiber direction exerted the most substantial influence on surface roughness, with feed per tooth and cutting speed ranking second and third, respectively. Furthermore, the optimal milling parameters for minimizing both cutting power and surface roughness were identified as a fiber direction of 0°, a feed per tooth of 0.2 mm/z, and a cutting speed of 400 m/min. Therefore, the obtained optimal parameters are recommended for industrial bamboo machining to achieve reduced cutting power and improved surface quality. Full article

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

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20 pages, 12909 KB

Open AccessArticle

Corrosion Behavior and Failure Mechanism of (Sm_0.2Gd_0.2Dy_0.2Er_0.2Yb_0.2)₂(Zr_0.7Hf_0.3)₂O₇ Double-Ceramic Thermal Barrier Coatings in Na₂SO₄ + V₂O₅ Environment

by Chunman Wang, Hao Mei, Yong Shang, Xunxun Hu, Huidong Wu, Haiyuan Yu, Keke Chang, Jian Sun, Guanghua Liu, Guijuan Zhou, Chunlei Wan and Shengkai Gong

Coatings 2025, 15(10), 1147; https://doi.org/10.3390/coatings15101147 - 2 Oct 2025

Abstract

To meet gas turbines’ growing demand for high-performance thermal barrier coatings (TBCs), this study addresses the limitations of traditional single-layer 8% Y₂O₃-stabilized ZrO₂ (YSZ) coatings in high-temperature corrosive environments. Atmospheric plasma spraying (APS) was used to fabricate the [...] Read more.

To meet gas turbines’ growing demand for high-performance thermal barrier coatings (TBCs), this study addresses the limitations of traditional single-layer 8% Y₂O₃-stabilized ZrO₂ (YSZ) coatings in high-temperature corrosive environments. Atmospheric plasma spraying (APS) was used to fabricate the double-ceramic TBCs with (Sm_0.2Gd_0.2Dy_0.2Er_0.2Yb_0.2)₂(Zr_0.7Hf_0.3)₂O₇ (RHZ) as the outer layer and YSZ as the inner layer; thermal cycling corrosion tests (1000 °C, Na₂SO₄ + V₂O₅ molten salt) were conducted to compare its performance with traditional single-layer YSZ. The results showed that the YSZ corrosion products were m-ZrO₂ and YVO₄, while RHZ/YSZ produced rare-earth vanadates, m-(Zr,Hf)O₂, and t′-(Zr,Hf)O₂, and corrosion degree was positively correlated with salt concentration (which was more impactful) and the number of cycles. Both coatings failed via molten salt penetration, thermochemical reaction, and crack-induced spallation. The corrosion mechanism between the RHZ/YSZ coating and the mixed salt can be explained based on the Lewis acid–base theory and the optical basicity. The RHZ layer on the surface of RHZ/YSZ coatings indeed hinders the penetration of corrosive molten salts into the underlying YSZ layer to some extent. Full article

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

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24 pages, 5930 KB

Open AccessArticle

Modulating Mechanisms of Surfactants on Fluid/Fluid/Rock Interfacial Properties for Enhanced Oil Recovery: A Multi-Scale Evaluation from SARA-Based Experiments to Atomistic Simulations

by Yiming Wang, Xinru Liang, Jinze Du, Yuxing Tan, Yu Sun, Gaobo Yu, Jinjian Hou, Zhenda Tan and Jiacheng Li

Coatings 2025, 15(10), 1146; https://doi.org/10.3390/coatings15101146 - 2 Oct 2025

Abstract

Low-Salinity Water Flooding (LSWF) has gained attention for its cost-effectiveness and environmental advantages, yet its underlying mechanisms remain not fully understood. Oil recovery in LSWF is primarily governed by interfacial dynamics and formation wettability. This research investigates the effects of seawater dilution in [...] Read more.

Low-Salinity Water Flooding (LSWF) has gained attention for its cost-effectiveness and environmental advantages, yet its underlying mechanisms remain not fully understood. Oil recovery in LSWF is primarily governed by interfacial dynamics and formation wettability. This research investigates the effects of seawater dilution in carbonate reservoirs through laboratory analyses and displacement experiments. Results show that oil recovery efficiency is largely driven by rock–fluid interactions rather than fluid–fluid interactions, with optimal brine concentrations enhancing wettability alteration, boundary flexibility, and mineral leaching. These findings highlight the importance of considering both fluid–rock interactions and mineral reactivity, rather than attributing recovery to a single mechanism. Molecular dynamics simulations further supported the experimental observations. Overall, the study emphasizes that early and well-designed low-salinity injection strategies can maximize LSWF performance. The results elucidate the key interaction mechanisms between surfactants and the various components of heavy oil through atomic-scale precision modeling and dynamic process tracking. These simulations clarify, at the microscopic level, the differences in displacement dynamics and efficiency of organic solvent systems toward different hydrocarbon components. Full article

(This article belongs to the Section Liquid–Fluid Coatings, Surfaces and Interfaces)

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11 pages, 3467 KB

Open AccessArticle

High-Temperature Effects on TGO Growth and Al Depletion in TBCs of Ni-Based Superalloy GTD111

by Nomin-Erdene Battulga, Yinsheng He, Youngdae Kim, Yeonkwan Kang, Jinesung Jung, Keesam Shin and Je-Hyun Lee

Coatings 2025, 15(10), 1145; https://doi.org/10.3390/coatings15101145 - 2 Oct 2025

Abstract

Thermal barrier coatings (TBCs) extend gas-turbine blade lifetime by improving high-temperature oxidation resistance and mechanical performance. We investigated the microstructural evolution, TGO growth, and Al depletion in air-plasma-sprayed (APS) single-layer YSZ top coat over a NiCrCoAlY bond coat on Ni-based superalloy circular plates, [...] Read more.

Thermal barrier coatings (TBCs) extend gas-turbine blade lifetime by improving high-temperature oxidation resistance and mechanical performance. We investigated the microstructural evolution, TGO growth, and Al depletion in air-plasma-sprayed (APS) single-layer YSZ top coat over a NiCrCoAlY bond coat on Ni-based superalloy circular plates, heat treated isothermally at 850 °C and 1000 °C for 50–5000 h. Cross-sectional SEM/EDS analysis showed TGO quadratic thickening kinetics at both temperatures, reaching ~10 µm at 1000 °C/5000 h, the growth rate of which was ~5.8 times higher than at 850 °C. On top of the single-layer TGO of Al₂O₃ observed from the onset, a NiCrCo oxide layer appeared and grew from ≥500 h at 850 °C, with increasing growth rate and cracking. The layer configuration of the YSZ top coat, the TGO of Al₂O₃, and the bond coat (comprising β-NiAl and γ-NiCr) on top of GTD111, showed an Al concentration gradient in the bond coat starting at 850 °C for 250 h, which intensified with increased duration and temperature. The decrease in Al concentration in the bond coat and the growth of TGO are due to the dissolution of β-NiAl and subsequent Al diffusion to the Al₂O₃ TGO. Full article

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

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13 pages, 10686 KB

Open AccessArticle

In Situ Observation of the Austenite Grains Growth Behavior in the Austenitizing Process of Nb–Ti Micro-Alloyed Medium Manganese Steel

by Guangpeng Yuan, Yu Du, Chao Sun, Xiuhua Gao, Hongyan Wu and Linxiu Du

Coatings 2025, 15(10), 1144; https://doi.org/10.3390/coatings15101144 - 2 Oct 2025

Abstract

In this paper, the austenite grains growth behavior in the austenitizing process of Nb–Ti micro-alloyed medium manganese steel was studied through in situ observation by high temperature laser confocal microscope. The results show that the average austenite grain sizes change from about 3 [...] Read more.

In this paper, the austenite grains growth behavior in the austenitizing process of Nb–Ti micro-alloyed medium manganese steel was studied through in situ observation by high temperature laser confocal microscope. The results show that the average austenite grain sizes change from about 3 μm at 1050 °C to over 50 μm at 1250 °C. When the grain boundary is a small-angle grain boundary, one grain boundary will split into several dislocations. With the extension of heating time, the lattice orientation difference further decreases, and the remaining dislocations may merge into new grain boundaries. The most suitable heating temperature for the medium manganese steel in this paper is from 1100 °C to 1150 °C, taking into account influences such as grain size, grain boundary damage, and deformation resistance. Full article

(This article belongs to the Special Issue Research in Laser Welding and Surface Treatment Technology)

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18 pages, 2429 KB

Open AccessArticle

Research on Fatigue Performance of Fast Melting Styrene-Butadiene-Styrene-Modified Asphalt with High Viscosity and Elasticity

by Hao Zhang, Fei Guo, Xiaoyu Li, Shige Wang and Jinchao Yue

Coatings 2025, 15(10), 1143; https://doi.org/10.3390/coatings15101143 - 2 Oct 2025

Abstract

To overcome the limitations of conventional high-viscosity high-elasticity modified asphalt, including high production costs, phase separation, and thermal degradation, this study introduces a novel fast melting Styrene-Butadiene-Styrene modifier (SBS-T) for asphalt modification. The primary novelty of SBS-T lies in its ability to mitigate [...] Read more.

To overcome the limitations of conventional high-viscosity high-elasticity modified asphalt, including high production costs, phase separation, and thermal degradation, this study introduces a novel fast melting Styrene-Butadiene-Styrene modifier (SBS-T) for asphalt modification. The primary novelty of SBS-T lies in its ability to mitigate phase separation and thermal degradation while simplifying the production process, thereby offering a more robust and cost-effective alternative. The viscoelastic properties of SBS-T-modified asphalt were characterized through frequency sweep tests under varying loading conditions, while its fatigue behavior was quantitatively assessed using the Simplified Viscoelastic Continuum Damage (S-VECD) model. The results indicate that the SBS-T-modified asphalt exhibits outstanding viscoelastic performance across a broad range of temperatures and loading frequencies, and can better adapt to the temperature and load changes in complex pavement environments. Among them, the influence of long-term aging on the linear viscoelastic characteristics of SBS-T-modified asphalt is greater than that of ultraviolet aging. The SBS-T-modified asphalt also shows better stiffness and resistance to shear deformation. The fatigue life of asphalt gradually decreases with the deepening of the aging degree, among which the impact of long-term aging on fatigue life is greater than that of ultraviolet aging. Under different aging conditions, SBS-T-modified asphalt has shown good fatigue performance and is suitable for practical engineering applications. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials)

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20 pages, 6891 KB

Open AccessArticle

Influence of TiO₂ Nanoparticle Concentration on Micro-Arc Oxidized Calcium–Phosphate Coatings: Corrosion Resistance and Biological Response

by Ainur Zhassulan, Bauyrzhan Rakhadilov, Daryn Baizhan, Aidar Kengesbekov, Dauir Kakimzhanov and Nazira Musataeva

Coatings 2025, 15(10), 1142; https://doi.org/10.3390/coatings15101142 - 2 Oct 2025

Abstract

Titanium and its alloys are widely used in biomedical implants due to their favorable mechanical properties and corrosion resistance; however, their natural surface lacks sufficient bioactivity and antibacterial performance. Micro-arc oxidation is a promising approach to producing bioactive coatings, and the incorporation of [...] Read more.

Titanium and its alloys are widely used in biomedical implants due to their favorable mechanical properties and corrosion resistance; however, their natural surface lacks sufficient bioactivity and antibacterial performance. Micro-arc oxidation is a promising approach to producing bioactive coatings, and the incorporation of nanoparticles such as TiO₂ may further improve their functionality. This study aimed to determine the optimal TiO₂ nanoparticle concentration in the micro-arc oxidation electrolyte that ensures coating stability and biological safety. Calcium–phosphate coatings were fabricated on commercially pure titanium using micro-arc oxidation with two TiO₂ concentrations: 0.5 wt.% (MAO 1) and 1 wt.% (MAO 2). Surface morphology, porosity, and phase composition were analyzed by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. Corrosion resistance was evaluated via potentiodynamic polarization in NaCl and Ringer’s solutions, while biocompatibility was assessed in vitro using HOS human osteosarcoma cells and MTT assays. Increasing the TiO₂ content to 1% decreased coating porosity (13.7% vs. 26.3% for MAO 1), enhanced corrosion protection, and reduced the friction coefficient compared to bare titanium. However, MAO 2 exhibited high cytotoxicity (81% cell death) and partial structural degradation in the biological medium. MAO 1 maintained integrity and showed no toxic effects (3% cell death). These results suggest that 0.5% TiO₂ is the optimal concentration, providing a balance between corrosion resistance, mechanical stability, and biocompatibility, supporting the development of safer implant coatings. Full article

(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications, 2nd Edition)

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19 pages, 19633 KB

Open AccessArticle

Effect of Top-Coat Structure on Thermal Stress in GdYb-YSZ/YSZ Double-Ceramic-Layer Thermal Barrier Coatings

by Haitao Yun, Yuhang Zhou, Tianjie Shi, Yuncheng Wang, Chunhua Cai, Xiaoxiao Pang, Peixuan Ouyang and Shuting Zhang

Coatings 2025, 15(10), 1141; https://doi.org/10.3390/coatings15101141 - 2 Oct 2025

Abstract

Investigating the relationship between coating structure and thermal stress is crucial for improving the service performance of double-ceramic-layer (DCL) thermal barrier coatings (TBCs). This study systematically examines a DCL TBC comprising a Gd₂O₃-Yb₂O₃-Y₂O [...] Read more.

Investigating the relationship between coating structure and thermal stress is crucial for improving the service performance of double-ceramic-layer (DCL) thermal barrier coatings (TBCs). This study systematically examines a DCL TBC comprising a Gd₂O₃-Yb₂O₃-Y₂O₃ co-doped ZrO₂ (GYYZ) top layer and Y₂O₃-stabilized ZrO₂ (YSZ) intermediate layer. Using combined finite element analysis and experimental validation, the influence of top-layer structural parameters (porosity, pore size, thickness) on thermal stress distribution under thermal shock conditions and resultant coating performance was investigated. Results indicate that coating interfaces, particularly GYYZ/YSZ and YSZ/bond coat (BC) interfaces, exhibit high sensitivity to top-layer structural parameters. Optimal GYYZ top-layer parameters were identified as: 10–15 vol.% porosity, 10–20 μm pore diameter, and ~0.15 mm thickness. Reducing the top-layer porosity from 20 vol.% to 15 vol.% increased microhardness by 12.8% and extended thermal cycling life by 87.5%. The coating failure mode shifted from the YSZ/BC interface to the GYYZ/YSZ interface, aligning with simulated thermal stress distributions. Full article

(This article belongs to the Special Issue Thermal Barrier Coatings: Materials, Processes, Properties and Applications)

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27 pages, 21927 KB

Open AccessArticle

Rapid Identification Method for Surface Damage of Red Brick Heritage in Traditional Villages in Putian, Fujian

by Linsheng Huang, Yian Xu, Yile Chen and Liang Zheng

Coatings 2025, 15(10), 1140; https://doi.org/10.3390/coatings15101140 - 2 Oct 2025

Abstract

Red bricks serve as an important material for load-bearing or enclosing structures in traditional architecture and are widely used in construction projects both domestically and internationally. Fujian red bricks, due to geographical, trade, and immigration-related factors, have spread to Taiwan and various regions [...] Read more.

Red bricks serve as an important material for load-bearing or enclosing structures in traditional architecture and are widely used in construction projects both domestically and internationally. Fujian red bricks, due to geographical, trade, and immigration-related factors, have spread to Taiwan and various regions in Southeast Asia, giving rise to distinctive red brick architectural complexes. To further investigate the types of damage, such as cracking and missing bricks, that occur in traditional red brick buildings due to multiple factors, including climate and human activities, this study takes Fujian red brick buildings as its research subject. It employs the YOLOv12 rapid detection method to conduct technical support research on structural assessment, type detection, and damage localization of surface damage in red brick building materials. The experimental model was conducted through the following procedures: on-site photo collection, slice marking, creation of an image training set, establishment of an iterative model training, accuracy analysis, and experimental result verification. Based on this, the causes of damage types and corresponding countermeasures were analyzed. The objective of this study is to attempt to utilize computer vision image recognition technology to provide practical, automated detection and efficient identification methods for damage types in red brick building brick structures, particularly those involving physical and mechanical structural damage that severely threaten the overall structural safety of the building. This research model will reduce the complex manual processes typically involved, thereby improving work efficiency. This enables the development of customized intervention strategies with minimal impact and enhanced timeliness for the maintenance, repair, and preservation of red brick buildings, further advancing the practical application of intelligent protection for architectural heritage. Full article

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

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13 pages, 7299 KB

Open AccessArticle

Effect of Solution and Aging Treatment on the Microstructural Evolution and Mechanical Properties of Cold-Rolled 2024 Aluminum Alloy Sheets

by Luxiang Zhang, Wei Liu, Erli Xia, Wanting Chen, Xuanxuan He and Dewen Tang

Coatings 2025, 15(10), 1139; https://doi.org/10.3390/coatings15101139 - 2 Oct 2025

Abstract

The cold-rolled 2024 aluminum alloy sheets were subjected to solution treatments at different temperatures followed by artificial aging. The microstructure and mechanical properties were investigated using Vickers microhardness testing, tensile testing, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). [...] Read more.

The cold-rolled 2024 aluminum alloy sheets were subjected to solution treatments at different temperatures followed by artificial aging. The microstructure and mechanical properties were investigated using Vickers microhardness testing, tensile testing, optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that as the solution temperature increases, the coarse particles gradually dissolved into the matrix. At a solution temperature of 500 °C, the grains become nearly equiaxed with an average size of ~16.47 μm, and no significant grain growth is observed compared to the as-rolled condition. The refined microstructure contributes to excellent mechanical properties. In contrast, when the solution temperature increases to 550 °C, the microstructure shows severe grain coarsening (up to ~61.39 μm), which indicates that overburning occurs, resulting in a drastic deterioration in mechanical performance. As the aging time increases, precipitates become more uniformly and densely distributed throughout the matrix, and the hardness initially increases and reaches a peak after approximately 6 h of aging at 180 °C. The optimal mechanical performance, characterized by a favorable combination of strength and ductility, is achieved at an aging time of 6 h. In summary, the optimal heat treatment condition for the cold-rolled 2024 aluminum alloy sheet is solution treatment at 500 °C for 1 h followed by aging at 180 °C for 6 h, resulting in a hardness of 154 HV, a tensile strength of 465 MPa and an elongation of 13%. Full article

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

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42 pages, 6991 KB

Open AccessReview

Phenomenological Analysis of Percolation Phenomena in Porous Low-k Dielectrics

by Mungunsuvd Gerelt-Od, Md Rasadujjaman, Valerii E. Arkhincheev, Konstantin A. Vorotilov and Mikhail R. Baklanov

Coatings 2025, 15(10), 1138; https://doi.org/10.3390/coatings15101138 - 1 Oct 2025

Abstract

This work reviews percolation-related phenomena in porous organosilica glass (OSG) low-k dielectrics and their critical impact on mass transport, electrical conductivity, mechanical integrity, and dielectric breakdown. We discuss how leakage current arises from the formation of minimal percolating conductive paths along pores [...] Read more.

This work reviews percolation-related phenomena in porous organosilica glass (OSG) low-k dielectrics and their critical impact on mass transport, electrical conductivity, mechanical integrity, and dielectric breakdown. We discuss how leakage current arises from the formation of minimal percolating conductive paths along pores and defect chains, while dielectric breakdown requires system-spanning pore connectivity, resulting in a higher effective percolation threshold. Mechanical properties similarly degrade when pores coalesce into a connected network, exhibiting multiple percolation thresholds due to both chemical network modifications and porosity. Experimental trends demonstrate that leakage current increases sharply at low porosity, whereas breakdown voltage and mechanical stiffness collapse at higher porosity levels (~20%–30%). We highlight that distinct percolation classes govern transport, mechanical, and nonlinear phenomena, with correlation length and diffusion timescales providing a unified framework for understanding these effects. The analysis underscores the fundamental role of network connectivity in determining the performance of organosilicate glass-based ultra-low-k dielectrics and offers guidance for material design strategies aimed at simultaneously improving electrical, mechanical, and chemical robustness. Full article

(This article belongs to the Special Issue Advanced Nanomaterials and Coating Technologies for High-Performance Electronic, Optoelectronic, Energy, and Sensing Devices)

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16 pages, 12504 KB

Open AccessArticle

Effect of Si Content on the Mechanical Behavior, Corrosion Resistance, and Passive Film Characteristics of Fe–Co–Ni–Cr–Si Medium-Entropy Alloys

by Sen Yang, Ran Wei, Xin Wei, Jiayi Cao and Jiepeng Ren

Coatings 2025, 15(10), 1137; https://doi.org/10.3390/coatings15101137 - 1 Oct 2025

Abstract

The nominal compositions of Fe₆₅Co_10−xNi_10−xCr₁₅Si_2x (x = 1, 2, and 3 at.%) medium-entropy alloys (MEAs) were designed and fabricated by vacuum arc melting. Their microstructure, hardness, and mechanical properties were [...] Read more.

The nominal compositions of Fe₆₅Co_10−xNi_10−xCr₁₅Si_2x (x = 1, 2, and 3 at.%) medium-entropy alloys (MEAs) were designed and fabricated by vacuum arc melting. Their microstructure, hardness, and mechanical properties were systematically characterized. Corrosion behavior was evaluated in 3.5 wt.% NaCl solution by potentiodynamic polarization and electrochemical impedance spectroscopy. The investigated MEAs exhibit a dual-phase microstructure composed of face-centered cubic (FCC) and body-centered-cubic (BCC) phases. With increasing Si content, yield strength and ultimate tensile strength increase, while uniform elongation decreases. Hardness also increases with increasing Si content. For the x = 3 MEA, the yield strength, ultimate tensile strength, and hardness of are ~518 MPa, ~1053 MPa, and 262 ± 4.8 HV, respectively. The observed strengthening can be primarily attributed to solid solution strengthening effect by Si. Polarization curves indicate that the x = 3 MEA exhibits the best corrosion resistance with the lowest corrosion current density ((0.401 ± 0.19) × 10⁻⁶ A × cm⁻²) and corrosion rate ((4.65 ± 0.19) × 10^–2 μm × year⁻¹)). Equivalent electric circuit analysis suggests the formation of a stable passive oxide film on the MEAs. This conclusion is supported by the capacitive behavior, high impedance values (> 10⁴ Ω cm²) at low frequencies, and phase angles within a narrow window of 80.05°~80.64° in the medium-frequency region. The passive-film thickness was calculated and the corrosion morphology was analyzed by SEM. These results provide a reference for developing high-strength, corrosion-resistant, medium-entropy alloys. Full article

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