Coatings

19 pages, 7060 KB

Open AccessArticle

Non-Invasive Multi-Analytical Insights into Renaissance Wall Paintings by Bernardino Luini

by Eleonora Verni, Michela Albano, Curzio Merlo, Francesca Volpi, Chaehoon Lee, Chiara Andrea Lombardi, Valeria Comite, Paola Fermo, Andrea Bergomi, Vittoria Guglielmi, Mattia Borelli, Carlo Mariani, Sabrina Samela, Lorenzo Vinco, Marta Ghirardello, Tommaso Rovetta, Giacomo Fiocco and Marco Malagodi

Coatings 2025, 15(9), 1113; https://doi.org/10.3390/coatings15091113 - 22 Sep 2025

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Abstract

The findings of non-invasive, multi-analytical research on two wall paintings located in the Santuario della Beata Vergine dei Miracoli in Saronno (Varese, Italy)—The Marriage of the Virgin and The Adoration of the Christ Child—are presented in this paper. The authorship of [...] Read more.

The findings of non-invasive, multi-analytical research on two wall paintings located in the Santuario della Beata Vergine dei Miracoli in Saronno (Varese, Italy)—The Marriage of the Virgin and The Adoration of the Christ Child—are presented in this paper. The authorship of the latter is up for controversy, while the former is unquestionably attributed to Bernardino Luini. The objective was to assess the compatibility of their color palettes through material comparison. A complementary suite of non-invasive techniques, including X-ray fluorescence (XRF), external reflection FTIR, Raman, visible reflectance spectroscopy and hyperspectral imaging, were employed to characterize pigments and surface materials without sampling. Results confirm the use of historically consistent pigments such as calcium carbonate, ochres, Naples yellow, smalt, azurite and lapis lazuli. Differences in the application of blue pigments—lapis lazuli in The Marriage of the Virgin and azurite in The Adoration of the Christ Child—may reflect workshop variation rather than separate authorship. Spectral imaging revealed pigment mixing and layering strategies, especially in skin tones and shadow modeling. This study underscores the significance of diagnostics as an interpretive instrument, capable of contextualizing Luini’s paintings within the context of Renaissance creative practice, providing a framework relevant to analogous inquiries. Full article

(This article belongs to the Special Issue Surface and Interface Analysis of Cultural Heritage, 2nd Edition)

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29 pages, 5066 KB

Open AccessArticle

Preparation of Urea-Formaldehyde-Coated Cationic Red-Ternary System Microcapsules and Properties Optimization

by Jingyi Hang, Yuming Zou, Xiaoxing Yan and Jun Li

Coatings 2025, 15(9), 1112; https://doi.org/10.3390/coatings15091112 - 22 Sep 2025

Viewed by 207

Abstract

Thermochromic microcapsules were synthesized and optimized using crystal violet lactone, bisphenol A, and decanol as the core materials, a dispersible cationic red dye as the color-modifying additive, and urea-formaldehyde resin as the wall material, based on orthogonal and single-factor experiments. The effects of [...] Read more.

Thermochromic microcapsules were synthesized and optimized using crystal violet lactone, bisphenol A, and decanol as the core materials, a dispersible cationic red dye as the color-modifying additive, and urea-formaldehyde resin as the wall material, based on orthogonal and single-factor experiments. The effects of the proportion of cationic red dye in the core material, the mass ratio of formaldehyde to urea, the emulsifier HLB value, and the core–wall mass ratio on yield, encapsulation rate, thermochromic ΔE, and formaldehyde release of microcapsules were systematically investigated. The results showed that the core–wall ratio was the key factor affecting the comprehensive performance of the microcapsules. Through the comparison of orthogonal and single-factor tests, 11# microcapsule was identified as having the best overall performance in terms of ΔE, and encapsulation rate. The ΔE value was increased by about 165% compared with the lowest-performing sample, significantly enhancing the thermochromic response. The encapsulation rate was improved by nearly 40%, effectively enhancing the encapsulation quality and core stability, with overall performance standing out. The best preparation process was to add 0.5% of the core material mass of dispersible cationic red dye, the mass ratio of formaldehyde and urea was 1.2:1, the HLB value of emulsifier was 10, and the core–wall ratio was 1:1.1. The yield of 11# microcapsules prepared under this condition was 31.95%, the encapsulation rate was 68%, the thermochromic ΔE was 9.292, and the formaldehyde release concentration was 1.381 mg/m³. Furthermore, 11# microcapsules with different addition levels were introduced into the UV primer to evaluate their effects on the mechanical and optical properties of the coating. The results showed that the addition of microcapsules weakened the gloss and light transmittance of the coating, increased the surface roughness, and decreased the elongation at break. When the addition amount was 5%, the coating exhibited the best overall performance: UV-visible light transmittance reached 91.92%, 60° gloss was 42.2 GU, elongation at break was 9.3%, and surface roughness was 0.308 μm. This study developed a purple thermochromic microcapsule system by regulating the dispersible dye content and interfacial conditions. In coating applications, the system exhibited a strong ΔE response and excellent overall performance, offering great advantages over existing similar systems in terms of color-change efficiency, ΔE enhancement, and coating adaptability. Full article

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

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17 pages, 4884 KB

Open AccessArticle

Enhancing Mechanical, Impact, and Corrosion Resistance of Self-Healable Polyaspartic Ester Polyurea via Surface Modified Graphene Nanoplatelets

by Mingyao Xu, Jisheng Zhang, Yuhui Li, Ziyu Qi, Jiahua Liu, Zhanjun Liu and Sensen Han

Coatings 2025, 15(9), 1111; https://doi.org/10.3390/coatings15091111 - 21 Sep 2025

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Abstract

Polyaspartic ester polyurea (PEP) elastomers are highly promising for self-healable protective coatings in industrial applications, yet their broader adoption is limited by insufficient mechanical and corrosion resistance. Herein, we develop a multifunctional PEP nanocomposite by incorporating Jeffamine D2000-functionalized graphene nanoplatelets (F-GNPs), prepared through [...] Read more.

Polyaspartic ester polyurea (PEP) elastomers are highly promising for self-healable protective coatings in industrial applications, yet their broader adoption is limited by insufficient mechanical and corrosion resistance. Herein, we develop a multifunctional PEP nanocomposite by incorporating Jeffamine D2000-functionalized graphene nanoplatelets (F-GNPs), prepared through a one-step mechanochemical process. This strategy promotes strong interfacial bonding and uniform dispersion, yielding synergistic property enhancements. At an optimal loading of 0.3 wt%, the PEP/F-GNP nanocomposite exhibited a substantial performance enhancement, with its tensile and tear strengths augmented by 263.0% and 64.2%, respectively. Moreover, the resulting coating delivered an 84.0% boost in impact resistance on aluminum alloy, along with enhanced substrate adhesion. Electrochemical and salt spray tests further confirmed its exceptional anti-corrosion performance. While the reinforcement strategy presented a classic trade-off with self-healing, it is critical to note that the nanocomposite preserved a high healing efficiency of 83.3% after impact damage. Overall, this scalable interfacial engineering strategy simultaneously enhances the material’s mechanical robustness and protective performance, while striking a favorable balance with its intrinsic self-healing capability, paving the way for next-generation coatings. Full article

(This article belongs to the Special Issue Advanced Polymer Coatings: Materials, Methods, and Applications)

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36 pages, 1775 KB

Open AccessReview

Recent Trends in Gelatin Electrospun Nanofibers: Advances in Fabrication, Functionalization, and Applications

by Bruna Silva de Farias, Anelise Christ Ribeiro, Débora Pez Jaeschke, Eduardo Silveira Ribeiro, Janaína Oliveira Gonçalves, Ricardo Freitas Vergara, Sibele Santos Fernandes, Daiane Dias, Tito Roberto Sant’Anna Cadaval Jr. and Luiz Antonio de Almeida Pinto

Coatings 2025, 15(9), 1110; https://doi.org/10.3390/coatings15091110 - 21 Sep 2025

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Abstract

Bio-based nanofibers are gaining increasing attention in nanotechnology owing to their high surface area, interconnected porosity, and capacity to incorporate bioactive compounds. Among natural polymers, gelatin is particularly attractive because of its abundance, low cost, biodegradability, and versatile physicochemical properties. When processed by [...] Read more.

Bio-based nanofibers are gaining increasing attention in nanotechnology owing to their high surface area, interconnected porosity, and capacity to incorporate bioactive compounds. Among natural polymers, gelatin is particularly attractive because of its abundance, low cost, biodegradability, and versatile physicochemical properties. When processed by electrospinning, gelatin combines its amphiphilic nature with the structural advantages of nanofibers, enabling efficient interactions with a wide range of molecules. Nevertheless, pure gelatin nanofibers have drawbacks, such as poor mechanical strength and high-water solubility. To address these limitations, strategies including polymer blending, chemical and physical crosslinking, and multilayer biomaterials have been developed, resulting in improved stability, functionality, and application-specific performance. Therefore, this review summarizes recent advances in the fabrication and functionalization of gelatin nanofibers, highlighting how processing parameters and gelatin source influence electrospinning outcomes and fiber properties. Key applications are also discussed, with emphasis on biomedical, food, environmental, and biosensing. Therefore, gelatin nanofibers represent a sustainable and versatile biomaterial with high potential for advanced technological applications. Full article

(This article belongs to the Special Issue Advances and Trends in Bio-Based Electrospun Nanofibers)

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19 pages, 2333 KB

Open AccessArticle

Quantifying Moisture Susceptibility in Asphalt Mixtures Using Dynamic Mechanical Analysis

by Yanzhu Wang, Wanguo Zhang, Jincheng Wei, Yuanshun Xiong, Yuanhui Qiao and Xudong Wang

Coatings 2025, 15(9), 1109; https://doi.org/10.3390/coatings15091109 - 21 Sep 2025

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Abstract

Moisture damage remains a primary distress mechanism in asphalt pavements, leading to reduced service life and viscoelastic property loss due to weakened asphalt–aggregate adhesion. This study evaluated moisture susceptibility in eight asphalt mixtures combining two aggregates (limestone/granite) and four binders (two neat, two [...] Read more.

Moisture damage remains a primary distress mechanism in asphalt pavements, leading to reduced service life and viscoelastic property loss due to weakened asphalt–aggregate adhesion. This study evaluated moisture susceptibility in eight asphalt mixtures combining two aggregates (limestone/granite) and four binders (two neat, two SBS-modified) using dynamic mechanical analysis (DMA). Thin-section specimens underwent DMA temperature sweeps under dry and water-immersed conditions to characterize shifts in viscoelastic properties. Results demonstrated that moisture exposure significantly reduced complex modulus values and shifted characteristic temperatures (T₀, T₁, T₂, T_g) toward lower ranges, indicating compromised performance. Specifically, granite mixtures showed average reductions in T₀, T₁, and T_g of 2.9 °C, 1.8 °C, and 3.7 °C, respectively, compared to 2.1 °C, 1.5 °C, and 1.7 °C for limestone mixtures. The magnitude of these changes—quantified by residual modulus (RM) ratios and characteristic temperature differentials—effectively ranked mixture susceptibility, with granite mixtures and specific binders (A1, B1) showing higher sensitivity. Notably, minimum residual modulus (RM_min) values ranged from 28.2% to 65.8%, and its critical temperature (T_RM) identified the most severe moisture damage conditions (approximately 40 °C for neat asphalt; 60 °C for modified asphalt). The DMA-derived indices correlated with surface free energy-based adhesion work, confirming the method’s reliability for rapid moisture sensitivity assessment. This approach provides an efficient basis for selecting moisture-resistant materials tailored to operational temperature environments. Full article

(This article belongs to the Special Issue Surface and Interface Characteristics of Pavements: New Perspectives and Applications)

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12 pages, 1526 KB

Open AccessArticle

A Comprehensive Study of Oxide Skin Formation on the Surface of Dichalcogenides and Its Effect on Sensing Properties

by Aigul Shongalova, Danil W. Boukhvalov, Abay S. Serikkanov and Nikolay A. Chuchvaga

Coatings 2025, 15(9), 1108; https://doi.org/10.3390/coatings15091108 - 20 Sep 2025

Viewed by 175

Abstract

This study systematically investigates the structural stability and surface chemical behavior of selected transition metal dichalcogenides (AX₂, where A = V, Mo, Pt; X = S, Se, Te) in both 1T and 2H phases. We evaluate surface chemical stability by computing [...] Read more.

This study systematically investigates the structural stability and surface chemical behavior of selected transition metal dichalcogenides (AX₂, where A = V, Mo, Pt; X = S, Se, Te) in both 1T and 2H phases. We evaluate surface chemical stability by computing the energetics of oxygen molecule adsorption and subsequent decomposition, simulating the formation of an AO₂ surface dioxide monolayer across all compounds. Additionally, the impact of surface oxidation on NO₂ sensing performance under varying temperatures and analyte concentrations is examined. Our findings emphasize the critical role of surface oxidation and oxygen competition in accurately predicting and understanding the chemical properties of these materials. Full article

(This article belongs to the Special Issue Electrochemical Properties and Applications of Thin Films)

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15 pages, 6731 KB

Open AccessArticle

Research on the Effect of Argon–Nitrogen Ratio on the Mechanical Properties and Corrosion Behavior of CrN-Ag Self-Lubricating Coatings

by Yanbing Zhang, Huayong Hu, Xiangdong Ma, Liqing Chao, Zhiping Fu, Zhong Zeng and Bing Yang

Coatings 2025, 15(9), 1107; https://doi.org/10.3390/coatings15091107 - 20 Sep 2025

Viewed by 233

Abstract

Self-lubricating coatings are an effective solution for achieving stable and reliable lubrication in mechanical equipment; however, most self-lubricating coatings currently available still have certain shortcomings in terms of lubricity. In this paper, by regulating the argon and nitrogen flow ratio, a CrN-Ag composite [...] Read more.

Self-lubricating coatings are an effective solution for achieving stable and reliable lubrication in mechanical equipment; however, most self-lubricating coatings currently available still have certain shortcomings in terms of lubricity. In this paper, by regulating the argon and nitrogen flow ratio, a CrN-Ag composite self-lubricating coating with excellent lubrication performance was prepared, with a minimum wear rate and friction coefficient of only 2.3 mm³·10⁻⁵/N·m and 0.15, respectively, and a stable performance during long-term service. Furthermore, through systematic characterization of the coating composition, structure, and performance, the laws of the coating’s evolution were revealed based on the argon–nitrogen ratio. The results confirmed that the argon-to-nitrogen ratio had no significant effect on the coating composition and structure, while the addition of Ag dominated the high-temperature oxidation process of the coating and improved its tribological properties. In addition, while increasing the nitrogen flow ratio to a certain extent is beneficial for preparing coatings with high bonding strength and low wear rates and friction coefficients, at the same time, an excessively high nitrogen flow ratio can reduce the density of the coating, increase its hydrophilicity, and deteriorate its corrosion resistance. Full article

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

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23 pages, 10643 KB

Open AccessArticle

Microstructure Development of a Functionalized Multilayer Coating System of 316L Austenitic Steel on Grey Cast Iron Under Braking Force in a Corrosive Environment

by Mohammad Masafi, Achim Conzelmann, Heinz Palkowski and Hadi Mozaffari-Jovein

Coatings 2025, 15(9), 1106; https://doi.org/10.3390/coatings15091106 - 20 Sep 2025

Viewed by 228

Abstract

Grey cast iron brake discs with lamellar graphite (GJL) offer excellent strength and thermal conductivity but are prone to wear and dust emissions. To mitigate these issues, a multilayer coating was applied via Laser Metal Deposition (LMD), comprising a 316L stainless steel base [...] Read more.

Grey cast iron brake discs with lamellar graphite (GJL) offer excellent strength and thermal conductivity but are prone to wear and dust emissions. To mitigate these issues, a multilayer coating was applied via Laser Metal Deposition (LMD), comprising a 316L stainless steel base layer and a WC-reinforced top layer. This study examines the microstructural evolution of the coatings under simulated thermomechanical and corrosive conditions using a brake shock corrosion test. Microstructural characterization was performed via Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), focusing on grain size, orientation, and texture before and after testing. EBSD analysis revealed significant grain coarsening, with sizes increasing from below 20 µm to 30–60 µm, and a shift toward <101> texture. Hardness measurements showed a reduction in the WC-reinforced layer from 478 HV to 432 HV and in the 316L base layer from 232 HV to 223 HV, confirming the influence of thermomechanical stress. SEM analysis revealed a transition from horizontal cracks—caused by residual stress during LMD—to vertical microcracks propagating from the substrate, activated by braking-induced loads. These findings provide insights into the microstructural response of LMD coatings under realistic service conditions and underscore the importance of grain boundary control in designing durable brake disc systems. Full article

(This article belongs to the Special Issue Novel Protective Coatings on Anti-Oxidation, Anti-Wear, and Corrosion Resistance Properties)

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28 pages, 8495 KB

Open AccessArticle

Preparation of Tea Tree Essential Oil@Chitosan-Arabic Gum Microcapsules and Its Effect on the Properties of Waterborne Coatings

by Nana Zhang, Ye Zhu, Xiaoxing Yan and Jun Li

Coatings 2025, 15(9), 1105; https://doi.org/10.3390/coatings15091105 - 20 Sep 2025

Viewed by 258

Abstract

Furniture surfaces are prone to the accumulation of bacteria, fungi and other micro-organisms, especially in humid environments such as kitchens and bathrooms. The antimicrobial treatment of coatings has been demonstrated to enhance the performance of wood, prolong its service life, and improve hygiene [...] Read more.

Furniture surfaces are prone to the accumulation of bacteria, fungi and other micro-organisms, especially in humid environments such as kitchens and bathrooms. The antimicrobial treatment of coatings has been demonstrated to enhance the performance of wood, prolong its service life, and improve hygiene and safety. Consequently, by investigating the most effective preparation process for antimicrobial microcapsules and incorporating them into the coating, the coating can be endowed with antimicrobial properties, thereby expanding its application range. Microcapsules were prepared using a composite wall material consisting of chitosan (CS) and Arabic gum (AG), with tea tree essential oil (TTO) serving as the core material. The best CS-AG coated TTO microcapsules were prepared when the core–wall ratio was 1.2:1, the emulsifier concentration was 2%, the pH was 3, and the mass ratio of AG to CS (m_AG:m_CS) was 3:1. The m_AG:m_CS was identified as the most significant factor affecting the microcapsule yield and encapsulation rate. With the increase in m_AG:m_CS, the antimicrobial rate of the coating against Escherichia coli (E. coli) exhibited a trend of first rising and then falling, while the antimicrobial rate against Staphylococcus aureus (S. aureus) demonstrated a trend of first rising, then falling, and then rising again. The colour difference (ΔE) and gloss exhibited an overall downward trend, the light loss rate demonstrated a fluctuating upward trend, and the roughness exhibited a trend of first falling and then rising. The visible light band transmittance exhibited minimal variation, ranging from 86.43% to 92.76%. Microcapsule 14# (m_AG:m_CS = 3:1) demonstrated remarkable antimicrobial properties (E. coli 65.55%, S. aureus 73.29%), exceptional optical characteristics (light transmittance 92.12%, 60° gloss 24.0 GU), and notable flexibility (elongation at break 18.10%, modulus 0.10 GPa). The waterborne coating was modified by microcapsule technology, thus endowing the coating with antimicrobial properties and concomitantly broadening the scope of application of antimicrobial microcapsules. Full article

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

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21 pages, 6297 KB

Open AccessReview

Research Progress on the Preparation and Tribological Properties of Self-Lubricating Coatings Fabricated on Light Alloys

by Ruimeng Zhang, Rui Li, Zhen Yang, Jiayi Cheng, Hongliang Zhang, Xue Cui and Zhisheng Nong

Coatings 2025, 15(9), 1104; https://doi.org/10.3390/coatings15091104 - 20 Sep 2025

Viewed by 285

Abstract

Lightweight alloys, such as aluminum, magnesium, and titanium alloys, are extensively utilized in the aerospace, transportation, and military domains owing to their low density, high specific strength, and outstanding fatigue resistance. Nevertheless, their inherently low hardness and inferior wear resistance give rise to [...] Read more.

Lightweight alloys, such as aluminum, magnesium, and titanium alloys, are extensively utilized in the aerospace, transportation, and military domains owing to their low density, high specific strength, and outstanding fatigue resistance. Nevertheless, their inherently low hardness and inferior wear resistance give rise to substantial friction and wear issues, thereby restricting their operational reliability and service lifespan. To address this concern, surface treatments employed in the preparation of self-lubricating coatings have assumed a pivotal role. This study conducts a comprehensive review of the research advancements regarding typical self-lubricating coatings, with a particular emphasis on their preparation methodologies and performance characteristics. Ultimately, the principal challenges within this field are systematically summarized, and prospects for future development are put forward. Full article

(This article belongs to the Special Issue Tribological and Mechanical Properties of Coatings)

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14 pages, 2938 KB

Open AccessArticle

Influence of Beryllium Addition on the Microstructure, Corrosion, and Wear Properties of Cu-Al-Ni Shape Memory Alloys

by Luis Olmos, Omar Jimenez, Ivon Alanis, Francisco Alvarado-Hernández, Jorge Chavez, Bertha Alejandra Olmos, Max Flores-Jiménez, David Israel Bravo-Bárcenas and Martín Flores

Coatings 2025, 15(9), 1103; https://doi.org/10.3390/coatings15091103 - 20 Sep 2025

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Abstract

Cu–Al–Ni shape memory alloys (SMAs) are attractive for structural and functional applications due to their cost-effectiveness and shape memory behavior. This study systematically investigated the effect of beryllium (Be) addition on the phase stability, microstructure, transformation temperatures, mechanical hardness, corrosion resistance, and wear [...] Read more.

Cu–Al–Ni shape memory alloys (SMAs) are attractive for structural and functional applications due to their cost-effectiveness and shape memory behavior. This study systematically investigated the effect of beryllium (Be) addition on the phase stability, microstructure, transformation temperatures, mechanical hardness, corrosion resistance, and wear behavior of Cu–Al–Ni alloys. Alloys with Be contents ranging from 0 to 1.5 wt.% were fabricated via arc melting and subjected to thermal treatment. Characterization techniques included dilatometry, X-ray diffraction (XRD), microhardness testing, potentiodynamic polarization, and pin-on-flat wear testing. The results showed that Be additions ≤ 0.4 wt.% stabilized the martensitic β′ phase, while higher concentrations favored the formation of austenitic β phase with a BCC structure. Hardness increased with Be content, especially in austenitic samples. Corrosion tests revealed that while the 0.2 wt.% Be alloy exhibited the most positive corrosion potential (Ecorr), it also had a higher corrosion rate. Overall, corrosion resistance declined with Be concentrations ≥ 0.6 wt.%. Wear tests demonstrated improved resistance in martensitic alloys, attributed to pseudoplastic deformation. These findings highlight the dual role of Be in modifying phase stability and functional properties, offering useful guidance for designing Cu-based SMAs with tailored performance. Full article

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12 pages, 2206 KB

Open AccessArticle

The Influence of Wire Type on the Properties and Characteristics of Coatings Obtained by the Arc Metallization Method

by Akbota Apsezhanova, Bauyrzhan Rakhadilov, Dastan Buitkenov, Nurtoleu Magazov and Dauir Kakimzhanov

Coatings 2025, 15(9), 1102; https://doi.org/10.3390/coatings15091102 - 19 Sep 2025

Viewed by 222

Abstract

Electric arc spraying is a promising technique for enhancing the wear resistance of components operating under abrasive and mechanical loads, particularly in agricultural soil-processing machinery. This study aims to comparatively analyze the properties of coatings formed using electric arc metallization with cored and [...] Read more.

Electric arc spraying is a promising technique for enhancing the wear resistance of components operating under abrasive and mechanical loads, particularly in agricultural soil-processing machinery. This study aims to comparatively analyze the properties of coatings formed using electric arc metallization with cored and solid wires of 30KhGSA and 51KhFA steel grades. Experimental investigations were carried out to evaluate the influence of wire type on the microstructure, microhardness, adhesion strength, and wear resistance of the sprayed coatings. Metallographic analysis and microhardness measurements revealed that coatings produced with cored wire exhibited a finer lamellar structure and higher hardness values compared to those formed with solid wire. Wear tests demonstrated improved resistance under abrasive conditions for cored wire coatings, indicating better performance under operational loads. The optimized spraying parameters were determined to ensure uniform and adherent coatings. The results suggest that using cored wire in electric arc spraying offers significant advantages in forming high-quality protective layers. These findings support the potential application of the developed coatings in extending the service life of soil-engaging machine parts under intensive field conditions. Full article

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

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20 pages, 9930 KB

Open AccessArticle

Effect of Microbial Activity on the Rheological Behavior of Asphalt Under Thin-Film Inoculation

by Tao Shen, Shaopeng Zheng, Xiang Liu, Xiaolong Li, Jingpeng Jia and Zhibo Wang

Coatings 2025, 15(9), 1101; https://doi.org/10.3390/coatings15091101 - 19 Sep 2025

Viewed by 260

Abstract

Microorganisms present in asphalt pavement service environments can alter the composition of asphalt through metabolic activities, thereby affecting its rheological properties. To investigate this influence and compare performance variations across asphalt types, two asphalt-degrading bacterial strains were isolated from in-service pavements. Following 16S [...] Read more.

Microorganisms present in asphalt pavement service environments can alter the composition of asphalt through metabolic activities, thereby affecting its rheological properties. To investigate this influence and compare performance variations across asphalt types, two asphalt-degrading bacterial strains were isolated from in-service pavements. Following 16S rRNA gene sequencing and phylogenetic analysis, the strains were identified as Pseudomonas putida and a putative novel species within the Citrobacter genus. Using a custom-designed thin-film inoculation system, the performance evolution of base asphalt and styrene-butadiene-styrene (SBS) modified asphalt was systematically evaluated after microbial activity periods of 5, 10, and 15 days. Conventional property tests and multi-temperature rheological analyses (temperature sweep, multiple stress creep recovery test, linear amplitude sweep, 4 mm DSR) were conducted. Results demonstrated that microbial action reduced penetration, elevated softening point, and decreased ductility in both asphalt types, with more pronounced changes observed in base asphalt. High-temperature rheological parameters (G*/sinδ), recovery rate, and non-recoverable creep compliance indicated compromised resistance to permanent deformation. SBS-modified asphalt substantially mitigated these detrimental effects. Fatigue life of base asphalt decreased overall with periodic fluctuations, whereas SBS-modified asphalt exhibited superior fatigue stability: after an initial decline at 5 days, performance recovered and stabilized between 10 and 15 days. Low-temperature performance showed slight improvement in base asphalt, while SBS-modified asphalt demonstrated significant enhancement during later activity stages. Full article

(This article belongs to the Special Issue Synthesis and Application of Functional Polymer Coatings)

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23 pages, 6000 KB

Open AccessArticle

Performance Analysis of Stainless Steel Fiber Recycled Aggregate Concrete Under Dry and Wet Cycles Based on Response Surface Methodology

by Chuheng Zhong, Changlong Chen, Shuai Wang, Jianan Shi, Weiqi Mao, Sijia Xing, Jinhui Chen, Yuan Xiao and Jinzhi Zhou

Coatings 2025, 15(9), 1100; https://doi.org/10.3390/coatings15091100 - 19 Sep 2025

Viewed by 240

Abstract

Recycled aggregate concrete refers to concrete made by using recycled aggregates produced from construction waste to replace natural aggregates. The performance of recycled aggregate concrete is extremely unstable. Internal factors such as water–cement ratio, porosity, and the properties of recycled aggregates, as well [...] Read more.

Recycled aggregate concrete refers to concrete made by using recycled aggregates produced from construction waste to replace natural aggregates. The performance of recycled aggregate concrete is extremely unstable. Internal factors such as water–cement ratio, porosity, and the properties of recycled aggregates, as well as external factors like temperature, humidity, environmental erosion, and the addition of improvement materials, may all have an impact on its mechanical properties. The response surface analysis method was employed to investigate the impact of three key factors—the number of dry–wet cycles, the content of stainless steel fibers, and the concentration of Na₂SO₄—on the mechanical properties of stainless steel fiber recycled aggregate concrete (SSFRAC) under dry–wet cycling conditions in the study. By incorporating stainless steel fibers into the cementitious gel network, SSFRAC is conceptualized as a composite material where the metal fibers are integrated into the gel matrix, forming a hybrid system akin to metallogels. The response models for compressive strength durability coefficient S_c and flexural strength durability coefficient S_f are established using Design-Expert software to evaluate the significance of these factors and their interactions. The version of Design-Expert used in this study is Design Expert 13.0. The results demonstrated that both S_c and S_f models exhibit high fitting accuracy, effectively capturing the relationships among the factors. The number of dry–wet cycles exhibit the highest significance, followed by Na₂SO₄ concentration and stainless steel fiber content. The interaction between dry–wet cycle number and Na₂SO₄ concentration has a particularly significant impact on S_c. For S_f, stainless steel fiber content is the most significant factor, followed by dry–wet cycle number and Na₂SO₄ concentration, with the interaction between fiber content and Na₂SO₄ concentration exerting a notably strong influence. This study highlights the potential of cement-based gels as raw materials for synthesizing functional composite materials, where the incorporation of metal fibers enhances mechanical performance and durability under aggressive environmental conditions. The findings provide insights into the design and optimization of hybrid gel–metal systems for advanced construction applications. Full article

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

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15 pages, 3711 KB

Open AccessArticle

Unveiling the Microstructure Evolution Mechanism of A356 Aluminum Alloy During Squeeze Casting Torsional Formation

by Zhenhu Wang, Biwu Zhu, Heng Li, Xiao Liu, Guoqiang Chen, Shengkai Xiong, Wenhui Liu, Ganlin Qin, Congchang Xu and Luoxing Li

Coatings 2025, 15(9), 1099; https://doi.org/10.3390/coatings15091099 - 19 Sep 2025

Viewed by 233

Abstract

In this study, a novel casting–forging hybrid forming technique, introducing torsional shear during squeeze casting, was investigated. This approach enhances the forming efficiency and refines the grain size. Using a finite element method coupled with a viscoplastic self-consistent model, a macro-microscopic simulation model [...] Read more.

In this study, a novel casting–forging hybrid forming technique, introducing torsional shear during squeeze casting, was investigated. This approach enhances the forming efficiency and refines the grain size. Using a finite element method coupled with a viscoplastic self-consistent model, a macro-microscopic simulation model of the squeeze casting torsional forming process was established. The introduction of torsional shear in SQ results in a more uniform distribution and lower equivalent stress, thereby improving the forming efficiency. Additionally, the shear force is increased during the forming process, the shear force is greater with the distance from the torsional axis increasing, and the great shear force could be maintained for a long time. Ultimately, this leads to a thinner wall thickness, finer secondary dendrites, and eutectic Si in the workpiece. During the SQT process, for introducing

(1 \bar{1} 1) [10 \bar{1}]

slip during the late stage of deformation, a significant shift in grain rotation directions happens and the grain rotation angles increase, finally attributed to the development of the

(1 \bar{1} \bar{1}) [0 \bar{1} 1]

texture. Full article

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

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11 pages, 2575 KB

Open AccessArticle

The Tribological Properties of the CoCrFeNiMn High-Entropy Alloy Matrix Composites with Solid Lubrication

by Zhiming Guo, Xiaoyan Ren, Jingdan Li and Guowei Zhang

Coatings 2025, 15(9), 1098; https://doi.org/10.3390/coatings15091098 - 19 Sep 2025

Viewed by 224

Abstract

CoCrFeNiMn HEA-based composites with Cr₃C₂, 15% Ag, and different mass fractions of CaF₂/BaF₂ eutectic fluoride were fabricated by spark plasma sintering. The tribological properties and wear mechanism of the composites were investigated from RT to 800 [...] Read more.

CoCrFeNiMn HEA-based composites with Cr₃C₂, 15% Ag, and different mass fractions of CaF₂/BaF₂ eutectic fluoride were fabricated by spark plasma sintering. The tribological properties and wear mechanism of the composites were investigated from RT to 800 °C. The friction coefficients of CoCrFeNiMn-Cr₃C₂-Ag-CaF₂/BaF₂ composites decrease from RT to 800 °C except for 400 °C. At 800 °C, with the increasing mass fraction of the eutectic fluoride, the friction coefficient of the composite decreases from 0.53 to 0.25. The wear rates of the composite with 15% CaF₂/BaF₂ eutectic fluoride decrease significantly at high temperatures. The CoCrFeNiMn-Cr₃C₂-Ag-15%CaF₂/BaF₂ composite exhibits the lowest wear rates at 400 °C, 600 °C, and 800 °C, which are 4.47 × 10⁻⁶ mm³/N·m, 5.15 × 10⁻⁶ mm³/N·m, and 2.42 × 10⁻⁶ mm³/N·m, respectively. At low temperatures, the tribological mechanisms of the composites are micro-plowing and micro-cutting, and Ag is formed as a lubricating film to reduce the friction coefficient. At high temperature, fluorides form a transfer film on the wear scar surface, providing a lubricating effect. Also, the oxide layers and chromate are formed on the worn surfaces of the composites, which are beneficial for improving the wear resistance. Based on the mechanical properties and tribological behavior, the CoCrFeNiMn-Cr₃C₂-Ag-15%CaF₂/BaF₂ composite demonstrates the best comprehensive properties. Full article

(This article belongs to the Special Issue Microstructure and Corrosion Behavior of High-Entropy Coatings)

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26 pages, 8999 KB

Open AccessArticle

Experimental Study on Overlay Tester of Asphalt Mixture Based on Discrete Element Method

by Jianhui Wei, Xiangyang Fan and Tao Fu

Coatings 2025, 15(9), 1097; https://doi.org/10.3390/coatings15091097 - 19 Sep 2025

Viewed by 255

Abstract

To evaluate the feasibility of a virtual overlay tester (OT), a modeling approach was proposed based on the discrete element method (DEM). Simulations were conducted on three types of asphalt mixtures across three different thickness conditions. Through the analysis of the load/displacement curves, [...] Read more.

To evaluate the feasibility of a virtual overlay tester (OT), a modeling approach was proposed based on the discrete element method (DEM). Simulations were conducted on three types of asphalt mixtures across three different thickness conditions. Through the analysis of the load/displacement curves, crack propagation paths, force chains, and contact force characteristics, it was observed that the peak loads decrease with increasing thicknesses, indicating a notable size effect. The complexity of the crack path was positively correlated with the particle size along the path and the fractal dimension. Coarse aggregates can inhibit crack propagation to some extent. Prior to reaching the peak load, compressive force chains in asphalt concrete-13 (AC13) and large stone porous asphalt mixture-30 (LSPM30) exhibited a symmetrical and divergent distribution along the crack, while tensile force chains formed an arch-like pattern. After the peak load, compressive force chains were symmetrically distributed in an arch shape along the crack. In stone mastic asphalt-13 (SMA13), compressive forces were transmitted along coarse aggregates, forming several continuous vertical paths. The proportion of strong compressive force chains to total compressive force chains across the three gradations ranged from 0.74 to 0.83, while the corresponding proportion for tensile force chains ranged from 0.72 to 0.78. Full article

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

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16 pages, 1880 KB

Open AccessArticle

Theoretical Insight into the Cooperative Strengthening of Interstitial Atoms(C/N/O) and Cr in Dilute Fe-Cr System

by Fang Wang, Tengge Mi, Pinghu Chen, Hongmei Zhu, Yong Chen, Pengbo Zhang, Ruiqing Li and Changjun Qiu

Coatings 2025, 15(9), 1096; https://doi.org/10.3390/coatings15091096 - 18 Sep 2025

Viewed by 262

Abstract

Solution strengthening is an effective strategy to improve the properties of martensitic steels (MSs). However, the microscopic mechanism of solution strengthening between Cr and interstitial atoms (IAs; C/N/O) remains elusive in dilute Fe-Cr system. Herein, this research aimed to ascertain the stability of [...] Read more.

Solution strengthening is an effective strategy to improve the properties of martensitic steels (MSs). However, the microscopic mechanism of solution strengthening between Cr and interstitial atoms (IAs; C/N/O) remains elusive in dilute Fe-Cr system. Herein, this research aimed to ascertain the stability of Cr and IAs, and the interaction mechanisms between Cr and IAs by energy analysis and four-level electronic structure analysis (projected density of states, Electron Localization Function, crystal orbital Hamiltonian population, and charge density difference) in Fe-Cr alloys based on the first-principles calculations. First, studies on the thermostability of Cr and IAs show that Cr tends to occupy a central substitution site, IAs prefer to occupy octahedral interstitial sites (O-sites), whereas Fe₅₃Cr₁N/O is the most stable structure in the Cr-rich region. Therefore, the Fe₅₃Cr₁X (X=C/N/O) is selected to investigate the interaction between Cr and IAs. Moreover, the formation energy of IAs in the Fe-Cr system is significantly lower than the solid solution of IAs in the pure Fe system, indicating that there is a cooperative effect between Cr and IAs. Then, the four-level electronic structure analyses of Fe₅₃Cr₁X reveal the strong bonding between IAs and Cr, implying that the system has high stability. Furthermore, compared to the pure iron system, the increase in the dissociation temperature of IAs in the Fe-Cr system again verifies the enhancement of stability by cooperative strengthening. The results provide a theoretical basis for understanding the solid solution strengthening of IAs and Cr in martensitic steels. Full article

(This article belongs to the Special Issue Microstructure, Fatigue and Wear Properties of Steels, 2nd Edition)

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18 pages, 5263 KB

Open AccessArticle

Novel Poly(butylene succinate-dilinoleic succinate) Films in Packaging Systems for Fresh Cut Chicory

by Szymon Macieja, Małgorzata Mizielińska, Mirosława El Fray and Artur Bartkowiak

Coatings 2025, 15(9), 1095; https://doi.org/10.3390/coatings15091095 - 18 Sep 2025

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Abstract

Ready-to-eat products, such as mixed-cut leafy vegetables, require packaging that provides adequate mechanical protection, a barrier against UV radiation, gases, and water vapor, as well as microbiological safety. In this study, thin films made of polybutylene succinate (PBS) and poly (butylene succinate-dilinoleic succinate) [...] Read more.

Ready-to-eat products, such as mixed-cut leafy vegetables, require packaging that provides adequate mechanical protection, a barrier against UV radiation, gases, and water vapor, as well as microbiological safety. In this study, thin films made of polybutylene succinate (PBS) and poly (butylene succinate-dilinoleic succinate) (PBS-DLS) copolyester were prepared by casting a film-forming solution onto a glass plate and spreading it with a roller. These films were compared to commercial thin films made of oriented polypropylene (OPP). OPP films exhibited ten times higher tensile strength than PBS films (104.36 ± 10.03 MPa for OPP, 10.96 ± 0.68 MPa for PBS, and 6.36 ± 0.62 MPa for PBS-DLS). Incorporation of co-monomeric units of dilinoleic succinate (DLS) into PBS structure significantly improved elongation at break, increasing from 38.16% ± 12.36% for PBS to 132.30% ± 25.08% for PBS-DLS. However, commercial OPP had the highest elongation at break, reaching 231.84% ± 20.30%. OPP films exhibited the highest transparency in the visible light range but also in the UV range. In contrast, PBS and PBS-DLS films provided better UV radiation blocking. The films were used to create sachets by heat sealing, into which freshly cut chicory leaves were placed. The packaged product was stored under refrigerated conditions for 48 h and 120 h. While OPP and PBS-DLS films provided good protection against moisture loss in chicory, leaves packed in PBS sachets lost significant weight during storage. The packaged product contained considerable microbial contamination, but the type of packaging did not influence its reduction or increase. Ultimately, the PBS-DLS copolymer exhibited higher elongation at break and greater water vapor barrier properties than PBS. Protection against moisture loss in packaged chicory for PBS-DLS packaging was similar to that for commercial OPP. Despite their weaker mechanical properties, PBS-DLS films appear to be a promising alternative to OPP films for packaging fresh food products. Full article

(This article belongs to the Special Issue Preparation and Applications of Bio-Based Polymer Coatings)

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16 pages, 3378 KB

Open AccessArticle

Influence of Wood Fiber on Mechanical and Thermal Insulation Properties of Lightweight Mortar

by Mo Zhou, Guimeng Ban, Yuanming Luo, Qin Hu, Jintuan Zhang, Ke Yu, Xue Hong and Huixin Zhong

Coatings 2025, 15(9), 1094; https://doi.org/10.3390/coatings15091094 - 18 Sep 2025

Viewed by 244

Abstract

To advance the development of green building materials and achieve high-value utilization of waste resources, this study investigates the mechanistic influence of incorporating waste wood fibers on the mechanical and thermal insulation properties of lightweight mortar. Five fiber contents were designed—0%, 0.4%, 0.8%, [...] Read more.

To advance the development of green building materials and achieve high-value utilization of waste resources, this study investigates the mechanistic influence of incorporating waste wood fibers on the mechanical and thermal insulation properties of lightweight mortar. Five fiber contents were designed—0%, 0.4%, 0.8%, 1.2%, and 1.6%—to systematically evaluate their effects on compressive strength, flexural strength, and tensile bond strength, as well as thermal conductivity, pore structure, and microstructural interfaces. The results demonstrate that at low fiber dosages (particularly 0.4% and 0.8%), wood fibers can significantly enhance both the mechanical strength and thermal insulation performance of mortar. Specifically, at a fiber content of 0.8%, the 28-day compressive strength increased by 10.62%, and the flexural strength by 23.8%; the tensile bond strength reached its peak at 0.4%, with a 14.8% improvement. The lowest thermal conductivity recorded was 0.16 W/(m·K), accompanied by a remarkable 61.9% reduction in porosity compared to the control group. Low-field nuclear magnetic resonance (LF-NMR) analysis revealed that wood fiber incorporation markedly increased the proportion of capillary pores, reduced total porosity, and enhanced mortar compactness; scanning electron microscopy (SEM) observations further indicated that the honeycomb-like morphology and surface roughness of wood fibers substantially improved interfacial bonding performance and microcrack-bridging capacity. The findings suggest that an optimal fiber content—recommended to not exceed 0.8%—can synergistically improve the mechanical and thermal insulation properties of lightweight mortar, providing both theoretical support and practical guidance for its application in green building wall materials. Full article

(This article belongs to the Special Issue Development of Low-Carbon Coatings/Materials and Intelligent Construction Protection Technology)

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16 pages, 8471 KB

Open AccessArticle

The Effect of LaPO₄ Crystal Morphology on Gas-Phase Catalytic Synthesis of Anisole

by Wei Wang, Qiwen Zhang, Fan Zhang, Hongyue Li, Ying Liu, Kemeng Wei, Yan Zhao, Songlin Yu, Yajun Li, Feng Zhang, Meili Yang, Qing-Qing Hao and Xiaolin Luo

Coatings 2025, 15(9), 1093; https://doi.org/10.3390/coatings15091093 - 18 Sep 2025

Viewed by 246

Abstract

The gas-phase synthesis of anisole from methanol and phenol is currently recognized as the process with the most theoretical research value and industrial application prospect. LaPO₄ has attracted widespread attention due to its excellent catalytic activity, robust water resistance, and high-temperature performance. [...] Read more.

The gas-phase synthesis of anisole from methanol and phenol is currently recognized as the process with the most theoretical research value and industrial application prospect. LaPO₄ has attracted widespread attention due to its excellent catalytic activity, robust water resistance, and high-temperature performance. In this work, rod-like monoclinic, mixed phase, and hexagonal LaPO₄ were synthesized using the hydrothermal method, and their catalytic activity was evaluated. The results showed that the catalytic activity of the hexagonal phase is higher than that of the monoclinic phase. By combining relevant characterization methods and DFT theoretical calculations, it is clarified that the higher acidity and stronger alkalinity of the exposed surface of hexagonal LaPO₄ are the main reasons for its higher activity. Further research has revealed that the main cause of LaPO₄ deactivation is carbon deposition on the catalyst surface. Full article

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

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18 pages, 2876 KB

Open AccessArticle

Theoretical Approach of Stability and Mechanical Properties in (TiZrHf)_1−x(AB)_x (AB = NbTa, NbMo, MoTa) Refractory High-Entropy Alloys

by Heng Luo, Yuanyuan Zhang, Zixiong Ruan, Touwen Fan, Te Hu and Hongge Yan

Coatings 2025, 15(9), 1092; https://doi.org/10.3390/coatings15091092 - 17 Sep 2025

Viewed by 274

Abstract

The stability and mechanical properties of (TiZrHf)_1−x(AB)_x (AB = NbTa, NbMo, MoTa) refractory high-entropy alloys have been investigated by combining the first-principles with special quasi-random structure (SQS) method. It is found that with the increase in solute concentration x, [...] Read more.

The stability and mechanical properties of (TiZrHf)_1−x(AB)_x (AB = NbTa, NbMo, MoTa) refractory high-entropy alloys have been investigated by combining the first-principles with special quasi-random structure (SQS) method. It is found that with the increase in solute concentration x, the ΔH_mix of (TiZrHf)_1−x(AB)_x (AB = NbMo, MoTa) linearly decreases, whereas both ΔH_mix and ΔS_mix of (TiZrHf)_1−x(NbTa)_x increase initially and subsequently decrease, with the crossover occurring at x = 0.56. The ΔH_mix of (TiZrHf)_1−x(NbTa)_x and (TiZrHf)_1−x(AB)_x (AB = NbMo, MoTa) alloys are larger and lower than that of TiZrHf, respectively, while the ΔS_mix of all (TiZrHf)_1−x(AB)_x is larger than that of TiZrHf. The formation possibility parameter Ω of all (TiZrHf)_1−x(AB)_x (AB = NbMo, MoTa) first decreases sharply, followed by a gradual decrease. And the local lattice distortion (LLD) parameter δ remains relatively stable around x = 0.56 for all cases, after which it decreases sharply until x = 0.89. The δ value of (TiZrHf)_1−x(AB)_x is higher than that of TiZrHf for x < 0.56 but becomes lower beyond this composition. The valence electron concentration (VEC), a possible indicator for a single-phase solution, of (TiZrHf)_1−x(AB)_x increases nearly linearly, while the formation energy ΔH_f of (TiZrHf)_1−x(AB)_x shows the opposite tendency, except for (TiZrHf)_0.67(NbTa)_0.33. Furthermore, the VEC of all (TiZrHf)_1−x(AB)_x alloys increases, whereas their ΔH_f decreases compared to that of TiZrHf. The ideal strength σ_p of (TiZrHf)_1−x(AB)_x increases linearly, reaching approximately 2.12 GPa. The bulk modulus (B), elastic modulus (E), and shear modulus (G) also exhibit linear increases, and their values in all (TiZrHf)_1−x(AB)_x alloys are higher than those of TiZrHf, with some exceptions. The Cauchy pressure (C₁₂–C₄₄) and Pugh’s ratio G/B of all (TiZrHf)_1−x(AB)_x alloys increase, whereas the Poisson’s ratio ν exhibits the opposite trend. Moreover, the C₁₂–C₄₄ and G/B ratio of TiZrHf are lower and higher, respectively, than those of (TiZrHf)_1−x(AB)_x, and the ν of TiZrHf is lower than that of (TiZrHf)_1−x(AB)_x. This study provides valuable insights for the design of high-performance TiZrHf-based refractory high-entropy alloys. Full article

(This article belongs to the Special Issue Innovations, Applications and Advances of High-Entropy Alloy Coatings)

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14 pages, 4508 KB

Open AccessArticle

Remineralizing Effect of Three Fluorinated Varnishes on Dental Enamel Analyzed by Raman Spectroscopy, Roughness, and Hardness Surface

by Karla Itzel Pineda-Domínguez, Samuel Eloy Morales-Gonzalez, Sandra E. Rodil, Isela Lizbeth Arredondo-Velazquez, Nelly Rivera-Yañez, Cesar Adolfo Callejas-Gomez, Oscar Nieto-Yañez and Cecilia Carlota Barera-Ortega

Coatings 2025, 15(9), 1091; https://doi.org/10.3390/coatings15091091 - 17 Sep 2025

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Abstract

Dental caries is a prevalent health condition affecting 87% of the population. The application of fluorinated varnishes to incipient lesions promotes remineralization. To evaluate the remineralizing effect of three fluorinated varnishes through chemical and physical characterization of incipient enamel lesions in vitro, a [...] Read more.

Dental caries is a prevalent health condition affecting 87% of the population. The application of fluorinated varnishes to incipient lesions promotes remineralization. To evaluate the remineralizing effect of three fluorinated varnishes through chemical and physical characterization of incipient enamel lesions in vitro, a total of 150 enamel surfaces were randomly divided into five groups (n = 30): healthy enamel, initial lesion, Fluor-Protector, β-Clinpro-White-Varnish, and Duraphat. All groups, except for the healthy enamel, were immersed in a demineralizing solution (pH 4.4) for 96 h. Remineralization was assessed using a pH cycling model over 5, 10, and 15 days. Fluoride release was measured via ISE-F, and enamel was analyzed by Raman spectroscopy (PO₄³⁻), roughness, and Vickers hardness. Data were analyzed using ANOVA and a post hoc test (Tukey). Ion Selective Electron-Fluor showed a residual F concentration of 0.40 ppm for the Fluor-Protector remineralizing solution: 40.00 ppm for Clinpro-White-Varnish, and 50.0 ppm for Duraphat. Raman analysis confirmed PO₄³⁻ at 956 cm⁻¹ mainly in CDu group. Roughness decreased with varnish application: Fluor-Protector (0.36 µm), β-Clinpro-White-Varnish (0.73 µm), and Duraphat (0.65 µm). Hardness increased with Fluor-Protector. Statistically significant differences were found between FP and other types of varnish. Fluorinated varnishes enhance remineralization and reduce enamel roughness and demineralization. Fluor Protector and β-Clinpro-White-Varnish showed the most favorable results, suggesting their recommendation for high-risk pediatric patients. Full article

(This article belongs to the Special Issue Surface Properties of Dental Materials and Instruments, 3rd Edition)

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21 pages, 12217 KB

Open AccessArticle

Low-Energy Nanoporous Silicon Processing Technology for Next-Generation Optoelectronic Devices

by Chao-Ching Chiang and Philip Nathaniel Immanuel

Coatings 2025, 15(9), 1090; https://doi.org/10.3390/coatings15091090 - 17 Sep 2025

Viewed by 337

Abstract

This study develops a low-energy, high-precision nanoporous silicon process technology combining electrochemical etching with multi-wavelength laser irradiation and ultrasonic vibration to precisely control the size, porosity, and distribution of the nanoporous silicon structure and examines its potential applications in next-generation optoelectronic devices. This [...] Read more.

This study develops a low-energy, high-precision nanoporous silicon process technology combining electrochemical etching with multi-wavelength laser irradiation and ultrasonic vibration to precisely control the size, porosity, and distribution of the nanoporous silicon structure and examines its potential applications in next-generation optoelectronic devices. This approach overcomes the challenges of poor pore uniformity and structural stability in conventional processes. The effects of different laser parameters, electrochemical conditions, and plasma bonding on the morphology are systematically analyzed. Additionally, the luminescence of the nanoporous silicon layer and its effectiveness in porous silicon diode devices were evaluated. Under 633 nm laser irradiation at 20 mW, the porosity reached 31.24%, exceeding that obtained with longer-wavelength lasers. The PS diode devices exhibited stable electroluminescence with a clear negative differential resistance (NDR) effect at 0~5.6 V. This technique is expected to significantly reduce energy consumption and simplify the manufacturing of silicon-based light-emitting devices. It also offers a scalable solution for next-generation silicon-based optoelectronic devices and advances the development of solid-state lighting and optoelectronics research. Full article

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

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14 pages, 2423 KB

Open AccessArticle

Precision-Tuned Magnetron Sputtering for High-Performance Metallized Copper Films

by Ying Yang, Xiaoyu Hao, Liuyan Zhang, Jicheng Ding, Lanfang Geng and Jun Zheng

Coatings 2025, 15(9), 1089; https://doi.org/10.3390/coatings15091089 - 17 Sep 2025

Viewed by 258

Abstract

In the present study, copper (Cu) films were deposited on polyethylene terephthalate (PET) substrates using direct-current (DC) magnetron sputtering technology. A systematic investigation was conducted on the effects of process parameters, such as target power, gas flow rate, and substrate temperature, on the [...] Read more.

In the present study, copper (Cu) films were deposited on polyethylene terephthalate (PET) substrates using direct-current (DC) magnetron sputtering technology. A systematic investigation was conducted on the effects of process parameters, such as target power, gas flow rate, and substrate temperature, on the microstructure and properties of copper films. The results showed that an increase in the target power resulted in enhanced film grain size, accompanied by a reduction in resistivity and an improvement in adhesion strength. Furthermore, resistivity increased monotonically with elevated gas flow rates, whereas the adhesion strength was found to achieve its maximum at a flow rate of 350 mL/min. In addition, substrate temperature variations had negligible influence on the film grain size and resistivity; nevertheless, the adhesion progressively decreased with increasing substrate temperature. A set of optimal parameters (3 kW, 350 mL/min, −15 °C) was determined based on the comprehensive evaluation of deposition efficiency, conductivity and adhesion performance. The Cu film prepared under these conditions exhibited low resistivity (8.37 × 10⁻⁸ Ω·m) and improved adhesion strength (166 gf/mm). Therefore, it is concluded that high performance of metallized Cu films could be achieved by fine-tuning deposition parameters. Full article

(This article belongs to the Special Issue Recent Progress in Thin Films and Surfaces: Deposition, Characterization and Various Applications)

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14 pages, 4714 KB

Open AccessArticle

Study of Surface Wear of Punches and Molds for Optimization of Nuclear Fuel Production

by Bauyrzhan Rakhadilov, Nurtoleu Magazov, Aidar Kengesbekov, Manarbek Kylyshkanov and Arystanbek Kussainov

Coatings 2025, 15(9), 1088; https://doi.org/10.3390/coatings15091088 - 16 Sep 2025

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Abstract

This paper presents the results of a comprehensive study of the wear processes of press tools used in the molding of uranium dioxide (UO₂) nuclear fuel pellets. Particular attention is paid to the analysis of the influence of operating conditions on [...] Read more.

This paper presents the results of a comprehensive study of the wear processes of press tools used in the molding of uranium dioxide (UO₂) nuclear fuel pellets. Particular attention is paid to the analysis of the influence of operating conditions on changes in microstructure, geometry and physical and mechanical properties of working surfaces of molds and punches. The studies using scanning electron microscopy (SEM), X-ray fluorescence (XRF) and X-ray phase analysis (XRD) methods, as well as evaluation of microhardness and roughness, allowed to identify the dominant failure mechanisms—abrasive and adhesive wear, microcrack formation and local degradation of coatings. The results of the experiments confirmed the presence of progressive changes on the working surfaces of the tool, affecting the formation of defects of fuel pellets and reducing the service life of the press equipment. This work allows us to not only better understand the wear patterns in the batch production of nuclear fuel, but also to formulate practical recommendations to increase tool life by optimizing pressing modes and using wear-resistant coatings. Full article

(This article belongs to the Special Issue Surface Engineering Processes for Reducing Friction and Wear)

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15 pages, 3517 KB

Open AccessArticle

Evaluation of Oxinium (Oxidized Zr2.5Nb) Femoral Heads in Hip Endoprostheses—Case Report

by Boštjan Kocjančič, Ema Kocjančič, Špela Tadel Kocjančič, Janez Kovač, Monika Jenko and Mojca Debeljak

Coatings 2025, 15(9), 1087; https://doi.org/10.3390/coatings15091087 - 16 Sep 2025

Viewed by 358

Abstract

Total hip arthroplasty (THA) is a widely performed and successful surgical treatment for degenerative joint disease. With increasing use in younger and more active patients, the demand for durable, biocompatible, and low-wear implant materials has grown. Oxidized zirconium (Oxinium, Zr2.5Nb) was introduced as [...] Read more.

Total hip arthroplasty (THA) is a widely performed and successful surgical treatment for degenerative joint disease. With increasing use in younger and more active patients, the demand for durable, biocompatible, and low-wear implant materials has grown. Oxidized zirconium (Oxinium, Zr2.5Nb) was introduced as a promising femoral head material, combining the strength of metal with the low-friction properties of ceramic. Despite encouraging early results, clinical reports have documented complications including head wear, especially after dislocation, and metallosis. We present the case of a 64-year-old male who underwent primary THA in 2009 and required revision in 2021 due to severe metallosis. Notably, no dislocation was observed that could explain the damage to the Oxinium head. Surface and subsurface analyses using X-ray photoelectron spectroscopy (XPS) and micro-indentation hardness testing revealed wear and deformation inconsistent with Oxinium’s anticipated durability. These findings highlight the importance of the femoral head–polyethylene liner interface in implant longevity. Although Oxinium–XLPE articulations remain promising, risks such as damage to the femoral head, liner dislocation, impingement, and metallosis must be carefully considered. Surgical technique, liner placement, and locking mechanisms play critical roles in preventing failure. Further biomechanical and clinical studies are needed to optimize implant design and improve long-term outcomes. Full article

(This article belongs to the Section Bioactive Coatings and Biointerfaces)

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15 pages, 4443 KB

Open AccessArticle

Effects of Ti6Al4V Substrate Roughness on the Surface Morphology, Mechanical Properties, and Cell Proliferation of Diamond-like Carbon Films

by Chehung Wei, Bo-Cheng Wu and Min-Sheng Hung

Coatings 2025, 15(9), 1086; https://doi.org/10.3390/coatings15091086 - 16 Sep 2025

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Abstract

This study investigated how Ti6Al4V substrate topography affects the performance of diamond-like carbon (DLC) coatings. Substrates with four finishes (unpolished, #100, #400, #800 grit) were coated, and their morphology, wettability, bonding structure, mechanical properties, and biological response were examined. Characterization was performed using [...] Read more.

This study investigated how Ti6Al4V substrate topography affects the performance of diamond-like carbon (DLC) coatings. Substrates with four finishes (unpolished, #100, #400, #800 grit) were coated, and their morphology, wettability, bonding structure, mechanical properties, and biological response were examined. Characterization was performed using AFM, SEM, contact angle tests, Raman spectroscopy, and nanoindentation. Biocompatibility was evaluated with A549 epithelial cells. DLC deposition reduced roughness while partly preserving surface features. Increasing Ra was associated with lower surface free energy and ID/IG ratios. It also correlated with higher hardness and modulus, reflecting greater sp³ bonding. Biological results, however, indicated that surface organization was more decisive than Ra magnitude. The #100-grit surface, with aligned anisotropic grooves, supported uniform wetting, protein adsorption, and sustained proliferation. In contrast, the unpolished and smoother surfaces did not maintain long-term growth. These findings suggest that anisotropy, rather than Ra alone, plays a key role in optimizing DLC-coated Ti6Al4V implants. Full article

(This article belongs to the Special Issue Advanced Biomaterials, Coatings and Techniques: Applications in Medicine and Dentistry, 2nd Edition)

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21 pages, 1945 KB

Open AccessArticle

Sustainable Edible Coatings Enriched with Bioactive Extracts from Exhausted Olive Pomace, Fucus Spiralis, and Limnospira sp. for the Postharvest Preservation of Strawberries

by Valter F. R. Martins, Manuela Pintado, Rui M. S. C. Morais and Alcina M. M. B. Morais

Coatings 2025, 15(9), 1085; https://doi.org/10.3390/coatings15091085 - 16 Sep 2025

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Abstract

Exhausted olive oil pomace (EOP), Fucus spiralis, and Limnospira sp. extracts—rich in bioactives, polysaccharides, or proteins—were incorporated into alginate-based edible coatings and applied to strawberries to evaluate their effects on postharvest quality parameters, including decay, weight loss, color, antioxidant activity, and microbial [...] Read more.

Exhausted olive oil pomace (EOP), Fucus spiralis, and Limnospira sp. extracts—rich in bioactives, polysaccharides, or proteins—were incorporated into alginate-based edible coatings and applied to strawberries to evaluate their effects on postharvest quality parameters, including decay, weight loss, color, antioxidant activity, and microbial growth. Among the tested formulations, the EOP-based coating (0.25% bioactive rich-extract) was the most effective, reducing weight loss to approximately 18% after 10 days at 10 °C, compared with higher losses in the control and other coatings, while also better preserving color through higher hue and chroma retention. Antioxidant activity, measured by ABTS and DPPH assays, was consistently higher in EOP-coated strawberries, despite a general decline in total phenolic content across treatments. Specifically, ABTS values decreased from 21.43 ± 0.90 (day 0) to 12.88 ± 0.39 (day 10) mmol TE/100 mg DW, while DPPH values declined from 10.23 ± 1.39 (day 0) to 5.96 ± 1.03 (day 10) mmol TE/100 mg DW. Microbial analyses further showed that the EOP coating strongly inhibited spoilage fungi, yeasts, and bacteria, whereas coatings containing Fucus spiralis or Limnospira sp. extracts (0.25% bioactive rich-extract plus 0.5% polysaccharide- or protein-rich extract) offered only moderate protection and, in some cases, promoted microbial growth. Overall, the EOP coating demonstrated superior performance in maintaining freshness, delaying microbial spoilage, and extending the shelf life of strawberries, highlighting its potential as a sustainable and functional strategy for fruit preservation. Full article

(This article belongs to the Section Coatings for Food Technology and System)

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20 pages, 3079 KB

Open AccessArticle

Taguchi Optimization of Corrosion Resistance and Wettability of a-C Films on SS316L Deposited via Magnetron Sputtering Technique

by Xiaoxing Yang, Cunlong Zhou, Zhengyi Jiang, Jingwei Zhao, Tianxiang Wang and Haojie Duan

Coatings 2025, 15(9), 1084; https://doi.org/10.3390/coatings15091084 - 16 Sep 2025

Viewed by 381

Abstract

Due to the exceptional corrosion resistance, chemical stability, and dense microstructure, carbon-based thin films are extensively employed in hydrogen energy systems. This study employed magnetron sputtering to fabricate amorphous carbon (a-C) films on SS316L substrates, aiming to improve the corrosion resistance of bipolar [...] Read more.

Due to the exceptional corrosion resistance, chemical stability, and dense microstructure, carbon-based thin films are extensively employed in hydrogen energy systems. This study employed magnetron sputtering to fabricate amorphous carbon (a-C) films on SS316L substrates, aiming to improve the corrosion resistance of bipolar plates (BPs) in proton exchange membrane fuel cells (PEMFCs). Using a Taguchi design, the effects of working pressure, sputtering power, substrate bias, and deposition time on film properties were systematically examined and optimized. Films were examined via field emission scanning electron microscopy (FE-SEM), contact angle measurements, and electrochemical tests. Comprehensive evaluation by the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method identified optimal conditions of 1.5 Pa pressure, 150 W radio frequency (RF) power, −250 V bias voltage, and 60 min deposition, yielding dense, uniform films with a corrosion current density of 1.61 × 10⁻⁶ A·cm⁻² and a contact angle of 106.36°, indicative of lotus leaf-like hydrophobicity. This work enriches the theoretical understanding of a-C film process optimization, offering a practical approach for modifying fuel cell bipolar plates to support hydrogen energy applications. Full article

(This article belongs to the Section Thin Films)

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Coatings, Volume 15, Issue 9 (September 2025) – 134 articles

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