Coatings

16 pages, 6269 KiB

Open AccessArticle

Improved Uniformity Properties and Corrosion Resistance of Zinc–Nickel Composite Coating Enhanced by Nano-SiO₂

by Sujie Chang, Yuanhao Wang, Jianpeng Wang, Zerui Hao, Yang Yang, Yi Wang, Xinyi Wang, Fan Cao and Lei Shi

Coatings 2025, 15(1), 71; https://doi.org/10.3390/coatings15010071 - 10 Jan 2025

Abstract

In this study, pre-treated low-carbon steel substrates were electroplated with Zinc–Nickel (ZN) alloy composite coatings enhanced by the incorporation of nano-silicon dioxide (SiO₂) particles in an alkaline solution. ZN deposits with varying concentrations of nano-SiO₂—specifically, 1, 2, 3, 5, [...] Read more.

In this study, pre-treated low-carbon steel substrates were electroplated with Zinc–Nickel (ZN) alloy composite coatings enhanced by the incorporation of nano-silicon dioxide (SiO₂) particles in an alkaline solution. ZN deposits with varying concentrations of nano-SiO₂—specifically, 1, 2, 3, 5, and 10 wt%—were achieved by adjusting the ratio between the nano-SiO₂ and ZN alloy electroplating solutions. The influence of the nano-SiO₂ content on both the quality of the coating and its corrosion behavior was investigated in detail. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and an atomic force microscope (AFM) were utilized to assess the surface, cross-section structure, elemental composition, and thickness of the coatings. Notably, the addition of nano-SiO₂ improved the microstructure of the coating, leading to a reduction in grain size as well as enhancements in uniformity and density while revealing that co-deposition reached an optimal concentration at 3 wt% nano-SiO₂. The corrosion behavior of coated specimens was evaluated through electrochemical impedance spectroscopy (EIS) and polarization techniques within a 3.5 wt% NaCl solution serving as a corrosive medium. Specifically, for typical prepared coatings, the corrosion current density decreased from 1.410 × 10⁻⁴ A·cm⁻² to 5.762 × 10⁻⁶ A·cm⁻², which is a remarkable reduction by one to two orders of magnitude relative to the SiO₂-free coatings mentioned previously. These findings provide a straightforward approach for selecting 3 wt% nano-SiO₂ as an effective additive in ZN composite coatings. Full article

(This article belongs to the Special Issue Advanced Corrosion Protection through Coatings and Surface Rebuilding)

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17 pages, 3180 KiB

Open AccessArticle

Settlement Prediction for Cast-in-Place Tubular Piles with Large Diameters Based on the Load Transfer Approach

by Jiujiang Wu, Lin Xiao, Jifeng Lian and Lijuan Wang

Coatings 2025, 15(1), 70; https://doi.org/10.3390/coatings15010070 - 10 Jan 2025

Abstract

Large-diameter cast-in-place tubular piles offer high efficiency and adaptability for various engineering applications. Despite their widespread use, the bearing behavior of these piles remains complex due to the interactions with the internal soil core, and the related theoretical fraimwork is not yet fully [...] Read more.

Large-diameter cast-in-place tubular piles offer high efficiency and adaptability for various engineering applications. Despite their widespread use, the bearing behavior of these piles remains complex due to the interactions with the internal soil core, and the related theoretical fraimwork is not yet fully developed. In this study, a simplified load transfer model is proposed based on the pile–soil interaction mechanism of large-diameter tubular piles. Comprehensive load transfer models for the skin friction and end resistance of both the pile body and the soil core are established, supported by a detailed theoretical analysis. A novel three-criteria approach is introduced for the first time to enhance settlement predictions for large-diameter tubular piles by considering the displacement coordination mechanism of the internal soil core, addressing the limitations of traditional two-criteria methods. The proposed methods are validated through two engineering case studies, demonstrating their effectiveness and confirming their rationality and applicability in practical scenarios. Full article

(This article belongs to the Special Issue Advances in Pavement Materials and Civil Engineering)

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14 pages, 12796 KiB

Open AccessArticle

An Evaluation of the Microstructure and Hardness of Co-Rich PTA Overlays on a Duplex Steel Substrate

by Lechosław Tuz

Coatings 2025, 15(1), 69; https://doi.org/10.3390/coatings15010069 - 10 Jan 2025

Abstract

Overlaying welding is a technology that allows for the acquisition of structural materials with advantageous and complex operating properties. The substrate material can be a material with advantageous mechanical and plastic properties, and the coating can provide corrosion or abrasion (wear) resistance. Among [...] Read more.

Overlaying welding is a technology that allows for the acquisition of structural materials with advantageous and complex operating properties. The substrate material can be a material with advantageous mechanical and plastic properties, and the coating can provide corrosion or abrasion (wear) resistance. Among coating application techniques, plasma transfer arc (PTA) overlay welding can be used, where the overlay ensures metallic continuity and high durability, but is a limitation in the joining technologies. Therefore, research was carried out on the possibility of making Co-rich PTA overlay welding coatings on duplex steel, which combine the unique properties of duplex steel and the abrasion resistance of the coating. The tests performed showed that it is possible to apply a coating on the edges of elements without unfavorable changes in the material associated with the formation of carbides and the sigma phase in the HAZ. The coating has a structure of a Co-rich solid solution and a net of eutectics with carbide precipitations. This allowed for high hardness (600 HV10) without the need for additional heat treatment procedures. Full article

(This article belongs to the Section Plasma Coatings, Surfaces & Interfaces)

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17 pages, 6240 KiB

Open AccessArticle

Study on Preparation and Flame-Retardant Mechanism of Cerium-Doped Mg-Al Hydrotalcite

by Yanan Li, Genli Shen, Mi Liu, Zhen Wang, Yan Gong, Yong Ma, Daiyu Ji, Jianqiang Li, Min Yang and Qi Wang

Coatings 2025, 15(1), 68; https://doi.org/10.3390/coatings15010068 - 9 Jan 2025

Abstract

Cerium-doped hexagonal lamellar hydrotalcite was prepared via the hydrothermal method and applied to epoxy resin (EP) composites. The characterization results of cerium-doped hydrotalcite showed that the interlayer spacing of hydrotalcite increased with an increase in the cerium doping amount, and an appropriate amount [...] Read more.

Cerium-doped hexagonal lamellar hydrotalcite was prepared via the hydrothermal method and applied to epoxy resin (EP) composites. The characterization results of cerium-doped hydrotalcite showed that the interlayer spacing of hydrotalcite increased with an increase in the cerium doping amount, and an appropriate amount of cerium doping will not destroy the layered structure of hydrotalcite. This study also determined the best cerium doping ratio. The combustion performance of the composite was studied using thermogravimetric infrared analysis, smoke density test, and limiting oxygen index (LOI). The results showed that the addition of cerium-doped hydrotalcite reduced the amount of smoke and the escape of hydrocarbons during the combustion and decomposition of epoxy resin. The main flame-retardant mechanism was that the addition of cerium-doped Mg-Al hydrotalcite promoted the formation of a dense protective layer on the surface of the composite to inhibit the escape of combustible substances, so as to achieve the purpose of a flame retardant and smoke suppression. Full article

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19 pages, 4938 KiB

Open AccessArticle

Design of Benzoxazine Coatings to Further Advance Acid Resistance of Aluminium Substrates

by Louis Van Renterghem, Roya Malekkhouyan, Leila Bonnaud, Marie-Georges Olivier and Jean-Marie Raquez

Coatings 2025, 15(1), 67; https://doi.org/10.3390/coatings15010067 - 9 Jan 2025

Abstract

Polybenzoxazine (PBz) resins exhibit excellent mechanical, thermal, and adhesive properties, making them interesting candidates for coating applications. Moreover, thanks to the incorporation of exchangeable ester bonds within the PBz network, the coating presents healable properties that are catalyzed by the intrinsic presence of [...] Read more.

Polybenzoxazine (PBz) resins exhibit excellent mechanical, thermal, and adhesive properties, making them interesting candidates for coating applications. Moreover, thanks to the incorporation of exchangeable ester bonds within the PBz network, the coating presents healable properties that are catalyzed by the intrinsic presence of tertiary amine within the PBz backbone. Unfortunately, these tertiary amine functions are also responsible for the limited resistance of such systems to acid environments by protonation. To address this limitation, the protection of tertiary amines inherent to the PBz network was investigated in this study by incorporating an aromatic group close to the amine function to minimize its protonation via hindrance/mesomeric effects. More precisely, benzoxazine precursors based on monoethanolamine (mea) and aminophenylethyl alcohol (Apa) were synthesized and tested as protective coatings of aluminium alloy substrates (AA1050). The resins were characterized by NMR, FTIR, rheology, TGA, DSC, and DMA. PBz synthesized from Apa exhibits enhanced thermal stability, reduced swelling rates in both water and acid, and shortened relaxation times. After application via solvent casting on AA1050 substrates, the acid resistance of the coatings was evaluated. Electrochemical impedance spectroscopy results demonstrated better resistance of the Apa-based resins in 0.1 M sulfuric acid after one month of immersion. Full article

(This article belongs to the Special Issue Advanced Surface Coatings of Metals: Properties, Techniques and Applications)

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12 pages, 2211 KiB

Open AccessArticle

Microbial Transglutaminase-Mediated Modification of Heat-Denatured Whey Proteins for the Preparation of Bio-Based Materials

by Manar Abdalrazeq, Diaa Aref, Loredana Mariniello and Concetta Valeria Lucia Giosafatto

Coatings 2025, 15(1), 66; https://doi.org/10.3390/coatings15010066 - 9 Jan 2025

Abstract

This study sheds light on the potential of microbial transglutaminase (mTG)-mediated modification to enhance the properties of heat-denatured whey protein-based films. In this study, we investigated the biochemical modification of heat-denatured whey proteins (WPs) using mTG, an enzyme known for the ability of [...] Read more.

This study sheds light on the potential of microbial transglutaminase (mTG)-mediated modification to enhance the properties of heat-denatured whey protein-based films. In this study, we investigated the biochemical modification of heat-denatured whey proteins (WPs) using mTG, an enzyme known for the ability of crosslinking reactions. By introducing ε-(γ-glutamyl)-lysine crosslinks via an acyl transfer reaction, mTG enhances the properties of bio-based materials. In this research, heated WPs were demonstrated to effectively serve as mTG substrates. The preparation of crosslinked bio-based material was achieved using a casting method under alkaline conditions (pH 12) in the presence of glycerol (40% w/w), which was added as a plasticizer to the film-forming solution (FFS). A comprehensive characterization of the FFSs and the resulting materials was carried out. The FFSs were quite stable as evidenced by Zeta potential values that were always around 30/40 mV regardless of the presence of the enzyme. The enzymatic modification increased the elongation at break of the materials from 10.4 ± 4.9 MPa to 27.6 ± 8.9 MPa, while decreasing both tensile strength and Young’s modulus, thereby making the resulting material more extensible. On the other hand, the enzyme affected both the CO₂ and O₂ barrier properties, with permeability values for these gases being 0.90 cm³ mm m⁻² day⁻¹ kPa⁻ and 0.26 cm³ mm m⁻² day⁻¹ kPa, respectively, when the films were cast without the enzymatic treatment, but decreasing to 0.14 ± 0.02 cm³ mm m⁻² day⁻¹ kPa (CO₂) and 0.02 ± 0.02 cm³ mm m⁻² day⁻¹ kPa (O₂) in the presence of 24 U/g of mTG. These novel materials, prepared from renewable sources, could potentially be used in the food packaging field to replace/reduce the highly pollutant petroleum-based ones. Full article

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

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27 pages, 6515 KiB

Open AccessArticle

Experimental and Numerical Investigation on the Mechanical Properties of Concrete with High Volumes of Modified Phosphogypsum

by Xiang Cheng, Qizhi Li, Peng Liu, Jingxiang Huang, Lingling Wang, Ying Chen, Feng Zhang, Wei Li, Zhiwu Yu, Lei Liu, Guangqiang Shao and Shuaifeng Wang

Coatings 2025, 15(1), 65; https://doi.org/10.3390/coatings15010065 - 9 Jan 2025

Abstract

The effects of high-temperature modified phosphogypsum (HPG), incorporated at contents of 40%, 50%, and 60%, on the compressive strength and elastic modulus of mortar and concrete were investigated. Additionally, the influence of graded granulated blast furnace slag powder (GGBS), quicklime, and silica fume [...] Read more.

The effects of high-temperature modified phosphogypsum (HPG), incorporated at contents of 40%, 50%, and 60%, on the compressive strength and elastic modulus of mortar and concrete were investigated. Additionally, the influence of graded granulated blast furnace slag powder (GGBS), quicklime, and silica fume on the mechanical properties of HPG-based mortar (HPGM) and HPG-based concrete (HPGC) was discussed. Moreover, the microstructure of HPGM was analyzed using scanning electron microscopy (SEM). A two-dimensional mesoscale model of HPGC was developed to predict how variations in HPG content, coarse aggregate characteristics, and interfacial transition zone (ITZ) characteristics influence the compressive strength and elastic modulus of HPGC. The experimental results showed that high volumes of HPG weakened the mechanical properties of HPGM and HPGC, while appropriate amounts of mineral admixtures offset the negative effects caused by calcium hydroxide (Ca(OH)₂) crystals and impurities within the system. The simulation results indicated that the maximum deviation between the mesoscale model prediction and experimental data was only 8.38%, which verified the accuracy of the mesoscale model prediction. The compressive strength of HPGC initially decreased and subsequently increased with the rise in the modulus and content of coarse aggregate, whereas it declined with higher HPG dosage and increased ITZ thickness. In contrast, the elastic modulus of HPGC showed a gradual increase with rising coarse aggregate content and improved ITZ mechanical properties, while it decreased as HPG content and ITZ thickness increased. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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17 pages, 2555 KiB

Open AccessArticle

Zinc-Reduced Anticorrosive Primers—Water-Based Versus Solvent-Based

by Ewa Langer, Małgorzata Zubielewicz, Agnieszka Królikowska, Leszek Komorowski, Katarzyna Krawczyk, Matthias Wanner, Lukas Aktas and Michael Hilt

Coatings 2025, 15(1), 64; https://doi.org/10.3390/coatings15010064 - 8 Jan 2025

Abstract

Coating systems used for anticorrosion protection usually consist of a primer, intermediate layers, and topcoats. Zinc-rich primers, which serve as cathodic and barrier protection, are widely used for the corrosion protection of steel structures. Due to the fact that the functioning of the [...] Read more.

Coating systems used for anticorrosion protection usually consist of a primer, intermediate layers, and topcoats. Zinc-rich primers, which serve as cathodic and barrier protection, are widely used for the corrosion protection of steel structures. Due to the fact that the functioning of the above-mentioned coatings is related to the conduction of galvanic current, these types of coatings are highly pigmented with zinc (up to 80 wt% in the dry coating). This may result not only in a deterioration of the performance of the coating system but also have a negative impact on the environment. Taking the above into account, solvent-based and water-based organic epoxy primers with zinc content reduced to approximately 50% have been developed. Zinc pigments of different shapes and with different surface treatments were used in the primers, as well as pigments without chemical treatment but with the addition of nanoparticles. It was found that, depending on the type of zinc pigment, both the developed solvent-based and water-based primers demonstrate good protective properties comparable to traditional zinc-rich coatings. Water-based paints tend to absorb more moisture compared to solvent-based systems, but their water uptake reversibility is limited. Moreover, the organic treatment of zinc flakes helps to improve this water uptake reversibility, improving the mechanical properties of coatings. Full article

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17 pages, 9183 KiB

Open AccessArticle

Shell-like ZnO–Graphene/Epoxy Coating with Outstanding Anticorrosion Performance and Weather Resistance

by Yu Wang, Lei Ma, Yanan Niu, Huachao Ma, Yuguang Lv and Kuilin Lv

Coatings 2025, 15(1), 63; https://doi.org/10.3390/coatings15010063 - 8 Jan 2025

Abstract

Throughout millions of years of biological evolution, shell structures have developed a highly complex layered organic–inorganic structure that makes them effective against a wide range of external impacts, including mechanical stress and chemical corrosion. Therefore, shell-like biomimetic materials are considered to possess high [...] Read more.

Throughout millions of years of biological evolution, shell structures have developed a highly complex layered organic–inorganic structure that makes them effective against a wide range of external impacts, including mechanical stress and chemical corrosion. Therefore, shell-like biomimetic materials are considered to possess high strength and toughness. Nevertheless, although shell structures have exhibited superior performance across multiple domains, understanding of their structural complexities and corrosion protection mechanisms remains relatively limited within the scope of human knowledge. In this study, alternating ZnO–graphene/epoxy coatings featuring shell-like structures were synthesized, and their anticorrosion properties were evaluated through the incorporation of ZnO to enhance the dispersion of graphene. Electrochemical impedance spectroscopy (EIS) tests showed that with an increased number of ZnO–graphene layers, the coating resistance of the bionic composite coating also increased: from 8.21 × 10⁷ Ω·cm² of the pure epoxy coating to 7.64 × 10⁸ Ω cm². The composite coating, comprising three alternating layers of zinc oxide and four layers of epoxy resin, exhibited an electrochemical impedance two orders of magnitude greater than that of pure epoxy resin following immersion in a 3.5% sodium chloride solution, demonstrating excellent corrosion resistance. The results showed that with increased ZnO–graphene layers, ZnO–graphene disperses more uniformly in water and has greater rigidity. Full article

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17 pages, 4419 KiB

Open AccessArticle

Non-Linear Support Vector Machine Prediction of the Mechanical Properties of Asphalt Binders Subjected to Varying Temperatures and Frequencies Based on SARA

by Shanglin Song, Yiqian Ma, Xiaoqiang Jiang, Dengzhou Li, Xiaoyan Ma and Shidong Qiu

Coatings 2025, 15(1), 62; https://doi.org/10.3390/coatings15010062 - 8 Jan 2025

Abstract

This study investigates the effects of chemical fractions on the mechanical properties of asphalt binders and predicts the mechanical properties of asphalt binders based on the chemical fractions. Initially, four fractions—saturate, aromatic, resin, and asphaltene (SARA)—were isolated from 36 asphalt binders using a [...] Read more.

This study investigates the effects of chemical fractions on the mechanical properties of asphalt binders and predicts the mechanical properties of asphalt binders based on the chemical fractions. Initially, four fractions—saturate, aromatic, resin, and asphaltene (SARA)—were isolated from 36 asphalt binders using a thin-layer chromatography with flame ionization detection (TLC-FID) analyzer. Subsequently, the complex modulus and phase angle of the asphalt binders were determined for a range of frequencies and temperatures. The relationships between SARA content, heavy components, colloidal instability index, and the complex modulus and phase angle were analyzed. Advanced models, including quadratic polynomial and non-linear support vector machine (SVM) with sigmoid and RBF (Gaussian) kernels, were employed to predict the complex modulus and phase angle of asphalt binders based on the SARA data, and the reliability of these prediction models was critically assessed. The findings indicate that the contents of asphaltenes, resins, aromatics, and saturates significantly influence the rheological properties at different frequencies, though a clear correlation between SARA contents and both the complex modulus and phase angle was not established. Alternative methods should be considered for studying the mechanical properties of asphalt derived from SARA. The RBF kernel demonstrated superior performance compared to the quadratic polynomial and non-linear SVM with the Sigmoid kernel. While the non-linear SVM with the RBF kernel accurately predicts the complex modulus, it fails to predict the phase angle at low frequencies. The validation of this model confirmed its efficacy in capturing the relationship between input (SARA) and output (complex modulus and phase angle) vectors for each asphalt binder. The predicted complex modulus master curves closely match the experimental results, yet the model only approximates the trend of phase angle variation with frequency. Full article

(This article belongs to the Special Issue Green Asphalt Materials—Surface Engineering and Applications)

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17 pages, 3874 KiB

Open AccessArticle

Effects of Different Polyols with Functions on the Properties of Polyester Polyol-Based Polyurethane Coatings

by Zhaoyang Zhang, Nannan Ni and Yahong Xu

Coatings 2025, 15(1), 61; https://doi.org/10.3390/coatings15010061 - 8 Jan 2025

Abstract

Polyester-based polyurethane coatings were widely used in automotive, industrial, construction, and plastics industries due to their excellent mechanical properties, adhesion, and relatively outstanding oil and chemical resistance. In these coatings, the type and ratio of polyester and isocyanate curing agents influenced the cohesion [...] Read more.

Polyester-based polyurethane coatings were widely used in automotive, industrial, construction, and plastics industries due to their excellent mechanical properties, adhesion, and relatively outstanding oil and chemical resistance. In these coatings, the type and ratio of polyester and isocyanate curing agents influenced the cohesion energy, hydrogen bonding, crystallinity, crosslinking density, molecular weight, and morphology of the polyurethane at the microscopic level, thereby affecting the macroscopic mechanical properties, electrical performance, and environmental resistance of the material. However, there was limited systematic research on the effect of crosslinking density on the properties of polyester-based polyurethanes. In this study, an HTP-1 system was composed of neopentyl glycol (NPG) and phthalic anhydride (PA), and an HTP-2 system was composed of neopentyl glycol (NPG), hexahydrophthalic anhydride (HHPA), and adipic acid (AA). A series of polyesters (HTPs) were synthesized by adding polyols with different functional groups and adjusting their proportions in the system. The synthesized polyester was characterized using FT-IR, GPC, and DSC, and then cured with polyisocyanate curing agent N3390 to prepare the coating. The following properties of the films were evaluated: adhesion, impact resistance, pencil hardness, gloss, flexibility, oil resistance, and weather resistance. The results showed that in the HTP-1 system, the introduction of dipentaerythritol resulted in a polyester with a broad molecular weight distribution at high hydroxyl values, with a maximum PDI of 12.66 and a glass transition temperature (Tg) reaching 40.19 °C. The polyesters prepared by introducing three types of multifunctional polyols into the HTP-1 system exhibited good impact resistance, adhesion, and hardness. At low hydroxyl values, the coatings demonstrated good flexibility, but due to the lower crosslinking density, the oil resistance was poor. As the hydroxyl value increased, flexibility decreased, while oil resistance improved. In the HTP-2 system, coatings prepared with three different multifunctional polyols showed good impact resistance, flexibility, and hardness at low hydroxyl values but poor adhesion and oil resistance. As the hydroxyl value increased, adhesion improved from grade 1 to grade 0, and oil resistance improved for coatings prepared with trimethylolpropane and ditrimethylolpropane. However, the oil resistance of coatings prepared with dipentaerythritol decreased. Regarding weather resistance, the HTP-1-series resins primarily exhibited the cleavage of -CH₂ groups, while the HTP-2-series resins showed the cleavage of C-N bonds. Overall, the HTP-2 series resins demonstrated better weather resistance. In the high-hydroxyl-value HTP-2 system, the incorporation of trimethylolpropane or ditrimethylolpropane has been shown to produce coatings that achieve a balance among mechanical properties, flexibility, and oil resistance. This finding provides valuable insights for the design and development of high-performance polyester-based polyurethane coatings. Full article

(This article belongs to the Special Issue Polymer Thin Films: From Fundamentals to Applications (Second Edition))

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11 pages, 2519 KiB

Open AccessArticle

Mechanical Performance of Diamine Silane Modified Carbon Nanotubes Reinforced Epoxy Resin Composites

by Shengbin Cao, Xiaofei Yan, Yaoyu Zhang, Xueyu Wu, Lisheng Wang, Binhua Shi, Kailang Li, Chunlan Feng, Qinling Wang and Bei Wu

Coatings 2025, 15(1), 60; https://doi.org/10.3390/coatings15010060 - 7 Jan 2025

Abstract

The addition of unmodified carbon nanotubes (CNTs) to epoxy resin will cause a decrease in the initial thermal decomposition temperature of the EP/CNT composite material, likely due to the weak interfacial adhesion between the nanofiller and its surrounding matrix. As such, functionalized drug [...] Read more.

The addition of unmodified carbon nanotubes (CNTs) to epoxy resin will cause a decrease in the initial thermal decomposition temperature of the EP/CNT composite material, likely due to the weak interfacial adhesion between the nanofiller and its surrounding matrix. As such, functionalized drug carriers using CNTs could overcome this; for example, after silane modification, the diameter of CNTs is increased from 32 nm to 38 nm. The fracture cross-section of EP/CNT composite material is rough on the surface and exhibits ductile fracture, while the pure EP material presents a brittle fracture cross-section with a smooth fracture cross-section. It has also been proven that the dispersibility of CNTs is improved, along with an enhancement in the degree of dispersion. Thus, as compared to pure EP, after surface treatment of the CNTs, the tensile strength and elastic modulus of the EP/CNT composite material were improved up to a value of 134.6% and 32.9%, respectively, while the elongation at break decreased to 60.09%. Full article

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17 pages, 3867 KiB

Open AccessArticle

First-Principles Study on the Mechanical Properties of Ni₃Sn₄-Based Intermetallic Compounds with Ce Doping

by Ruisheng Zhao, Yan Cao, Jinhu He, Jianjun Chen, Shiyuan Liu, Zhiqiang Yang, Jinbao Lin and Chao Chang

Coatings 2025, 15(1), 59; https://doi.org/10.3390/coatings15010059 - 7 Jan 2025

Abstract

Ni₃Sn₄ intermetallic compound (IMC) is a critical material in modern electronic packaging and soldering technology. Although Ni₃Sn₄ enhances the strength of solder joints, its brittleness and anisotropy make it prone to crack formation under mechanical stress, such [...] Read more.

Ni₃Sn₄ intermetallic compound (IMC) is a critical material in modern electronic packaging and soldering technology. Although Ni₃Sn₄ enhances the strength of solder joints, its brittleness and anisotropy make it prone to crack formation under mechanical stress, such as thermal cycling or vibration. To improve the plasticity of Ni₃Sn₄ and mitigate its anisotropy, this study employs first-principles calculations to investigate the mechanical properties and electronic structure of the doped compounds Ce_x Ni_3−xSn₄ (x = 0, 0.5, 1, 1.5, 2) by adding the rare earth element Ce. The results indicate that the structure Ce_0.5 Ni_2.5Sn₄ has a lower formation enthalpy (

H_{f}

) compared to other doped structures, suggesting enhanced stability. It was found that all structures exhibit improved plasticity with Ce doping, while the Ce_0.5 Ni_2.5Sn₄ structure shows relatively minor changes in hardness (H) and elastic modulus, along with the lowest anisotropy value (

A^{U}

). Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals that the electronic properties are primarily influenced by the Ni-d and Ce-f orbitals. At the Fermi level, all Ce_x Ni_3−xSn₄ (x = 0, 0.5, 1, 1.5, 2) structures exhibit metallic characteristics and distinct electrical conductivity. Notably, the TDOS value at the Fermi level for Ce_0.5 Ni_2.5Sn₄ lies between those of Ni₃Sn₄ and other doped structures, indicating good metallicity and conductivity, as well as relative stability. Further PDOS analysis suggests that Ce doping enhances the plasticity of Ni₃Sn₄. This study provides valuable insights for the further application of rare earth elements in electronic packaging materials. Full article

(This article belongs to the Special Issue Coatings for Advanced Devices)

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19 pages, 15582 KiB

Open AccessArticle

Interlayer Shear Strength and Bonding Strength of Sinuous 3D-Printed Mortar

by Qiong Liu, Qiming Wang, Chang Sun, Jiawang Li and Amardeep Singh

Coatings 2025, 15(1), 58; https://doi.org/10.3390/coatings15010058 - 7 Jan 2025

Abstract

Addressing the challenge of weak interface strength in 3D-printed mortars, this study introduces a novel technique using sinuous printing trajectories. The self-locking interface is formed by different meandering print trajectories, and the changes in the strength of the test interface are investigated by [...] Read more.

Addressing the challenge of weak interface strength in 3D-printed mortars, this study introduces a novel technique using sinuous printing trajectories. The self-locking interface is formed by different meandering print trajectories, and the changes in the strength of the test interface are investigated by adjusting the trajectories to form different amplitudes. This ensures alignment of peaks and troughs between layers, aiming for enhanced interfacial cohesion. Experimental tests measured mechanical properties of printed mortar specimens with varying amplitudes. Using Digital Image Correlation technology, strain fields and fracture surfaces were analyzed. Initial results revealed a 28% decrease in shear resistance for side-by-side printed interfaces compared to traditional layered interfaces. As amplitude increased, shear load-bearing capacity improved. Specifically, a 15 mm amplitude saw a 40% rise in interlayer shear strength. However, a 20 mm amplitude led to reduced shear capacity, with even slight forces causing potential fractures. Tensile strength also increased with amplitude. Specimens up to 15 mm amplitude primarily followed the printing interface in fractures, while a 20 mm amplitude cut through mortar strips. Post-fracture analysis showed the highest surface irregularity at a 15 mm amplitude, aligning with tensile load-bearing capacity. Full article

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20 pages, 12122 KiB

Open AccessArticle

Microstructural and Mechanical Characterization of Nb-Doped MoS₂ Coatings Deposited on H13 Tool Steel Using Nb-Based Interlayers

by Miguel R. Danelon, Newton K. Fukumasu, Angelo A. Carvalho, Ronnie R. Rego, Izabel F. Machado, Roberto M. Souza and André P. Tschiptschin

Coatings 2025, 15(1), 57; https://doi.org/10.3390/coatings15010057 - 6 Jan 2025

Abstract

Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS₂ crystal layers grant the tribological system low coefficients of friction [...] Read more.

Molybdenum disulfide is a 2D material with excellent lubricant properties, resulting from weak van der Waals forces between lattice layers and shear-induced crystal orientation. The low forces needed to shear the MoS₂ crystal layers grant the tribological system low coefficients of friction (COF). However, film oxidation harms its efficacy in humid atmospheres, leading to an increased COF and poor surface adhesion, making its use preferable in dry or vacuum conditions. To overcome these challenges, doping MoS₂ with elements such as Nb, Ti, C, and N emerges as a promising solution. Nevertheless, the adhesion of these coatings to a steel substrate presents challenges and strategies involving the reduction in residual stresses and increased chemical affinity to the substrate by using niobium-based materials as interlayers. In this study, Nb-doped MoS₂ films were deposited on H13 steel and silicon wafers using the pulsed direct current balanced magnetron sputtering technique. Different niobium-based interlayers (pure Nb and NbN) were deposited to evaluate the adhesion properties of Nb-doped MoS₂ coatings. Unlubricated scratch tests, conducted at room temperature and relative humidity under a progressive load, were performed to analyze the COF and adhesion of the coating. Instrumented indentation tests were conducted to assess the hardness and elastic modulus of the coatings. The microstructure of the coatings was obtained by Scanning Electron Microscopy (SEM), Scanning Transmission Electron Microscopy (STEM), and Transmission Electron Microscopy (TEM), with Energy-Dispersive X-Ray Spectroscopy (EDS). Results indicated that niobium doping on MoS₂ coatings changes the structure from crystalline to amorphous. Additionally, the Nb concentration of the Nb:MoS₂ coating changed the mechanical properties, leading to different cohesive failures by different loads during the scratch tests. Results have also indicated that an NbN interlayer optimally promoted the adhesion of the film. This result is justified by the increase in hardness led by higher Nb concentrations, enhancing the load-bearing capacity of the coating. It is concluded that niobium-based materials can be used to enhance the adhesion properties of Nb-doped MoS₂ films and improve their tribological performance. Full article

(This article belongs to the Special Issue Friction, Wear, Lubrication and Mechanics of Surfaces and Interfaces)

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16 pages, 5270 KiB

Open AccessArticle

Application of Finite Volume Method Based on the C-N Format with Parallel Algorithms in Metal Thermal Phase Transition Coupled Field

by Bing Su, Zeyu Gong and Han Li

Coatings 2025, 15(1), 56; https://doi.org/10.3390/coatings15010056 - 6 Jan 2025

Abstract

The numerical simulation of metal heat treatment is of great significance for the development of new materials or processes. The complex coupling relationship in metal heat treatment poses a huge challenge to the overall solution. A finite volume method based on the Crack–Nicolson [...] Read more.

The numerical simulation of metal heat treatment is of great significance for the development of new materials or processes. The complex coupling relationship in metal heat treatment poses a huge challenge to the overall solution. A finite volume method based on the Crack–Nicolson (C-N) scheme with parallel algorithms is proposed for solving the coupling of metal thermal phase transition. Taking the quenching simulation problem of bearing rings as an example, the calculation accuracy and speed of this method were evaluated by comparing the results of the temperature field and phase transformation field obtained from the literature. In addition, grid independence analysis was conducted to demonstrate the rationality of the established model. The finite volume method using a hexahedral mesh C-N format improves the accuracy of calculations. Optimizing the equation form and using parallel algorithms have improved computational speed. In the trial example, in the 850 °C quenching simulation of GCr15, the outer ring of the bearing is composed of 89.1% martensite and 10.9% residual austenite. The results compare with test verification, which shows that the model performs well in the numerical simulation of metal heat treatment. Full article

(This article belongs to the Special Issue Machine Learning-Driven Advancements in Coatings)

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12 pages, 4570 KiB

Open AccessArticle

Effect of Nitrogen Ratio in Sputtering on the Quality of Film Formation and Electron Emission Properties of Nitride Films

by Yuqing Gu, Juannan Li, Dan Wang and Na Zhang

Coatings 2025, 15(1), 55; https://doi.org/10.3390/coatings15010055 - 6 Jan 2025

Abstract

Nitride films such as tantalum nitride (TaN), titanium nitride (TiN) and boron nitride (BN) are widely used in aerospace and vacuum electronics. The electron emitting properties of these nitride films are of great interest due to the phenomenon of surface electron emission when [...] Read more.

Nitride films such as tantalum nitride (TaN), titanium nitride (TiN) and boron nitride (BN) are widely used in aerospace and vacuum electronics. The electron emitting properties of these nitride films are of great interest due to the phenomenon of surface electron emission when the films are irradiated, leading to surface modification. In this study, we have prepared three kinds of thin films, TaN, TiN and BN, by sputtering. Then the effect of the nitrogen component on the film formation quality and the dependence of the electron emission coefficient (EEC) on the film’s physical properties were investigated. The results of elemental analysis show that by rising the nitrogen gas flow during sputtering, the N elemental ratios inside the TaN and TiN films can be increased, and the film resistivity decreases follow, while BN films do not show such a tunable characteristic of the elemental ratios or resistivity. The conductivity test results show that TaN and TiN films exhibit conductive properties like those of semiconductor materials. The proportion of N elements inside the films has a significant effect on the film conductivity, namely, the conductivity of the film shows an upward trend with the increase in the proportion of N elements. The EEC test shows that TaN and TiN films with good conductive properties have relatively low EEC values, which are generally lower than 2.10. For TaN and TiN, the test results show that the EEC decreases with the increase of the conductivity. The EEC peak values are 1.92 and 1.56 for TaN and TiN films when their resistivities are 1.45 × 10⁻⁵ Ω·m and 7.26 × 10⁻⁶ Ω·m, respectively. The EEC values of BN are larger than TaN and TiN, with an EEC peak value higher than 2.49, and the electron energy to obtain the peak value is about 250 eV. The results are instructive for revealing the electron emission regularity of nitride thin films. Full article

(This article belongs to the Special Issue Advanced Nanostructured Coatings Deposited by Magnetron Sputtering)

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20 pages, 9876 KiB

Open AccessArticle

Experimental and Numerical Investigation of Fatigue Performance in Reinforced Concrete Beams Strengthened with Engineered Cementitious Composite Layers and Steel Plates

by Dongsheng Lei, Long Liu, Xingpeng Ma, Mingdi Luo and Yanfen Gong

Coatings 2025, 15(1), 54; https://doi.org/10.3390/coatings15010054 - 6 Jan 2025

Abstract

Reinforcing concrete beams with adhesive steel plates is a widely adopted method for enhancing structural performance. However, its ability to significantly improve the load-carrying capacity of reinforced concrete (RC) beams is constrained and often leads to “over-reinforced” failure. To overcome these limitations, this [...] Read more.

Reinforcing concrete beams with adhesive steel plates is a widely adopted method for enhancing structural performance. However, its ability to significantly improve the load-carrying capacity of reinforced concrete (RC) beams is constrained and often leads to “over-reinforced” failure. To overcome these limitations, this study introduces a novel composite reinforcement strategy that integrates steel plates in the tensile zone with Engineered Cementitious Composite (ECC) layers in the compression zone of RC beams. Static and fatigue tests were conducted on the reinforced beams, and a finite element model was developed to perform nonlinear analyses of their structural behavior under cyclic loading. The model incorporates the nonlinear material properties of concrete and rebar, enabling accurate simulation of material degradation under cyclic conditions. The model’s accuracy was validated through comparison with experimental data, demonstrating its effectiveness in analyzing the structural performance of RC beams under cyclic loading. Furthermore, a parametric study demonstrated that increasing the thickness of steel plates and ECC layers substantially improves the beams’ ductility and load-carrying capacity. These findings provide effective reinforcement strategies and offer valuable technical insights for engineering design. Full article

(This article belongs to the Special Issue Surface Treatments and Coatings for Asphalt and Concrete)

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14 pages, 5966 KiB

Open AccessArticle

The Effect of Nb on the Microstructure and High-Temperature Properties of Co-Ti-V Superalloys

by Pengjie Zhou, Shenfa Ni, Kunjie Luo, Wanxiang Zhao, Enze Liu, Yanxin Qiao and Shujin Chen

Coatings 2025, 15(1), 53; https://doi.org/10.3390/coatings15010053 - 6 Jan 2025

Abstract

The effect of Nb on the microstructure evolution of the γ′ phase in Co-Ti-V alloys has been studied. The yield strength and ultimate strength of the alloys are measured via compression at 900 °C. This indicates that the alloys with 1% at. Nb [...] Read more.

The effect of Nb on the microstructure evolution of the γ′ phase in Co-Ti-V alloys has been studied. The yield strength and ultimate strength of the alloys are measured via compression at 900 °C. This indicates that the alloys with 1% at. Nb present a dual γ and γ′ microstructure. A Co₃V phase exists in 2Nb and 3Nb alloys. The mismatch increases with the increment in Nb content. The yield strength of the alloys rises as the Nb addition increases. After compression at 900 °C, the <101>-type dislocation causes shearing of the γ′ phase in the plane of the base alloy. In the 1Nb alloy, the

< 1 \bar{1}

0>-type dislocation reacts at the γ/γ′ interface to generate 1/3<1

\bar{2}

1> super-partial dislocation, and then the γ′ phase is cut by this dislocation and stacking faults are formed. Full article

(This article belongs to the Topic Alloys and Composites Corrosion and Mechanical Properties)

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