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Volume 14
Issue 10
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Coatings, Volume 14, Issue 10 (October 2024) – 109 articles

Cover Story (view full-size image): In this work, we present a thermal model that predicts the temperature distribution at different substrate depths during the APS coating process, taking into account the effect caused by flame profiles. We define the heat flux contributed by the plasma plume to fit the simulation results with the experiments. The simple and low-cost experimental procedure measures the plasma plume temperature distribution of the APS coating arrangement, and results are then used to obtain the parameter values of each of the three proposed plasma temperature profiles. We demonstrate the approach on a thermal simulation model of a flat plate with three proposed flame plume profiles and compare the results with experimental data obtained using an in situ non-contact infrared pyrometry method. View this paper
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17 pages, 2026 KiB  
Article
High-Speed Removal Process for Organic Polymers by Non-Thermal Atmospheric-Pressure Spark Discharge at Room Temperature and Its Mechanism
by Yoshihiro Sakamoto, Takayoshi Tsutsumi, Hiromasa Tanaka, Kenji Ishikawa, Hiroshi Hashizume and Masaru Hori
Coatings 2024, 14(10), 1339; https://doi.org/10.3390/coatings14101339 (registering DOI) - 18 Oct 2024
Viewed by 161
Abstract
Heel marks (HMs) are a type of dirt stain consisting of polyester-based urethane rubber on polyvinyl chloride (PVC) floor surfaces. The rapid removal of HMs was achieved by using non-thermal atmospheric-pressure plasma technology. Mimetic HMs were prepared by coating PVC floor samples with [...] Read more.
Heel marks (HMs) are a type of dirt stain consisting of polyester-based urethane rubber on polyvinyl chloride (PVC) floor surfaces. The rapid removal of HMs was achieved by using non-thermal atmospheric-pressure plasma technology. Mimetic HMs were prepared by coating PVC floor samples with HMs to a thickness of 13.9 μm. The removal area, thickness, and volume were measured after applying spark discharges at high voltage and a repetition rate of 50 kHz. The treated surfaces were analyzed by using X-ray photoelectron spectroscopy (XPS) and pyrolysis–gas chromatography with time-of-flight mass spectrometry (Py-GC/TOFMS). Removal rates of 20 mm2/min in area, 52 mm3/min in volume, and 7 μm/min in depth were achieved with an inter-electrode distance of 10.0 mm and an air flow rate of 20 standard liters per minute. A removal depth of 10 μm/min was achieved without air supply. The mechanism of stain removal by spark discharge was modeled by decomposing the original high-molecular-weight molecules in polyester-based urethane rubber into low-molecular-weight molecules, such as methylene diisocyanate (MDI) components. The results of this study may facilitate the development of a novel electric vacuum cleaner capable of removing floor stains. Full article
27 pages, 1969 KiB  
Review
Research Progress on Polysaccharide Composite Films and Coatings with Antioxidant and Antibacterial Ingredients to Extend the Shelf Life of Animal-Derived Meat
by Ming Yuan, Jun Mei and Jing Xie
Coatings 2024, 14(10), 1338; https://doi.org/10.3390/coatings14101338 (registering DOI) - 18 Oct 2024
Viewed by 238
Abstract
Animal-derived meat is rich in proteins and other nutrients, but is prone to spoilage during storage, including microbial contamination and fat oxidation. Therefore, there is an urgent need to find effective solutions to extend the shelf life of animal-derived meat. Polysaccharides are natural [...] Read more.
Animal-derived meat is rich in proteins and other nutrients, but is prone to spoilage during storage, including microbial contamination and fat oxidation. Therefore, there is an urgent need to find effective solutions to extend the shelf life of animal-derived meat. Polysaccharides are natural macromolecules containing multi-hydroxyl structures and functional groups, which have good solubility, film-forming properties, etc., and can form edible films. Polysaccharide films can be combined with biopolymers, nanoparticles, and natural active agents to improve their properties and enhance the antioxidant and antimicrobial activities of the films. This review summarizes the various sources of polysaccharides, such as chitosan, hyaluronic acid, sodium alginate, carrageenan, starch, and pullulan polysaccharides and their combination with different substances to extend the shelf life of animal-derived meat. This review may serve as a reference for further development of polysaccharides in animal-derived meat preservation. Full article
(This article belongs to the Special Issue Advanced Coatings and Films for Food Packing and Storage, 2nd Edition)
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20 pages, 7384 KiB  
Article
Evolutionary Mechanism of Solidification Behavior in the Melt Pool during Disk Laser Cladding with 316L Alloy
by Chang Li, Jiabo Liu, Shuchao Li, Fanhong Kong, Xuan Wang, Han Sun and Yichang Sun
Coatings 2024, 14(10), 1337; https://doi.org/10.3390/coatings14101337 (registering DOI) - 18 Oct 2024
Viewed by 146
Abstract
Laser cladding is an emerging environmentally friendly surface-strengthening technology. During the cladding process, the changes in molten pool temperature and velocity directly affect the solidification process and element distribution. The quantitative revelation of the directional solidification mechanism in the molten pool during the [...] Read more.
Laser cladding is an emerging environmentally friendly surface-strengthening technology. During the cladding process, the changes in molten pool temperature and velocity directly affect the solidification process and element distribution. The quantitative revelation of the directional solidification mechanism in the molten pool during the cladding process is crucial for enhancing the quality of the cladding layer. In this study, a multi-field coupling numerical model was developed to simulate the coating process of 316L powder on 45 steel matrices using a disk laser. The instantaneous evolution law of the temperature and flow fields was derived, providing input conditions for simulating microstructure evolution in the molten pool’s paste zone. The behavior characteristics of the molten pool were predicted through numerical simulation, and the microstructure evolution was simulated using the phase field method. The phase field model reveals that dendrite formation in the molten pool follows a sequence of plane crystal growth, cell crystal growth, and columnar crystal growth. The dendrites can undergo splitting to form algal structures under conditions of higher cooling rates and lower temperature gradients. The scanning speed of laser cladding (6 mm/s) has minimal impact on dendrite growth; instead, convection within the molten pool primarily influences dendrite growth and tilt and solute distribution. Full article
(This article belongs to the Special Issue Effects of Laser Treatment on Surface Characterization and Mechanical Properties of Alloys)
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2 pages, 135 KiB  
Retraction
RETRACTED: Chupradit et al. Ultra-Sensitive Biosensor with Simultaneous Detection (of Cancer and Diabetes) and Analysis of Deformation Effects on Dielectric Rods in Optical Microstructure. Coatings 2021, 11, 1564
by Supat Chupradit, Shameen Ashfaq, Dmitry Bokov, Wanich Suksatan, Abduladheem Turki Jalil, Amer M. Alanazi and Mika Sillanpaa
Coatings 2024, 14(10), 1336; https://doi.org/10.3390/coatings14101336 - 18 Oct 2024
Viewed by 110
Abstract
The journal retracts the article, “Ultra-Sensitive Biosensor with Simultaneous Detection (of Cancer and Diabetes) and Analysis of Deformation Effects on Dielectric Rods in Optical Microstructure” [...] Full article
(This article belongs to the Special Issue Strengthening, Corrosion and Protection of High Temperature Structural Materials)
1 pages, 122 KiB  
Correction
Correction: Chen et al. Preparation of Pie-Shaped CoMoO4 with High Capacitive and Photocatalytic Properties by a Solvothermal Method. Coatings 2022, 12, 1771
by Shuoyan Chen, Juan Wu, Gang Wang, Jing Wang, Licai Fan, Jian Hao, Shen Wang, Yang Liu, Hongyu Wu, Yang Li, Jing Gao and Mingli Yang
Coatings 2024, 14(10), 1335; https://doi.org/10.3390/coatings14101335 - 18 Oct 2024
Viewed by 99
Abstract
Following publication, concerns were raised regarding the peer-review process related to the publication of this article [...] Full article
12 pages, 6333 KiB  
Article
Tribological and Corrosion Properties of Al2O3@Y2O3-Reinforced Ni60A Composite Coatings Deposited Using Laser Cladding
by Yu Yin, Xing-Hua Ma, Jingwei Li, Shuling Zhang, Zihao Yin, Minghao Ma and Feng Guo
Coatings 2024, 14(10), 1334; https://doi.org/10.3390/coatings14101334 - 18 Oct 2024
Viewed by 252
Abstract
Since rare earth oxides and hard ceramic particles improve coating quality, a novel Al2O3@Y2O3 core–shell structure was prepared. Then, Ni60A coatings with different amounts (2~6 wt.%) of Al2O3@Y2O3 core–shell [...] Read more.
Since rare earth oxides and hard ceramic particles improve coating quality, a novel Al2O3@Y2O3 core–shell structure was prepared. Then, Ni60A coatings with different amounts (2~6 wt.%) of Al2O3@Y2O3 core–shell structures were prepared using laser cladding technology on an H13 steel surface. To demonstrate the unique effect of the core–shell structure on the performance of the coatings, a set of controlled experiments was also conducted with different proportions of Al2O3-Y2O3 mechanically mixed powders. The effect of Al2O3@Y2O3 addition on the phase composition, element distribution, microstructure, wear, and corrosion resistance of the coatings was characterized and tested thoroughly. By comparing the forming quality, hardness, wear, and corrosion resistance of the different coatings, 2 wt.% was confirmed as the optimal concentration of Al2O3@Y2O3, and its corresponding friction coefficient was about 0.44. The wear rate was approximately 4.15 × 10−3 mm3·(N·m)−1, the self-corrosion potential was around −0.3659 V, and the self-corrosion current density was about 1.248 × 10−6 A·cm−2. Full article
(This article belongs to the Section Laser Coatings)
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16 pages, 2719 KiB  
Article
Physical-Vapor-Deposition-Coated Natural Rocks as Sustainable Cutting Material: First Insights into the Effect of Substrate Integrity on Properties of TiN Thin Film
by Hilke Petersen, Dominic Graf, Nelson Filipe Lopes Dias, Wolfgang Tillmann, Philipp Dan Hendrik Wolters, Benjamin Bergmann and Bernd Breidenstein
Coatings 2024, 14(10), 1333; https://doi.org/10.3390/coatings14101333 - 17 Oct 2024
Viewed by 270
Abstract
The most important cutting materials for machining are carbides. Their production requires both tungsten and cobalt; however, these materials are becoming increasingly difficult to obtain and are sometimes mined under ethically questionable conditions. As a result, increasing efforts are being made to expand [...] Read more.
The most important cutting materials for machining are carbides. Their production requires both tungsten and cobalt; however, these materials are becoming increasingly difficult to obtain and are sometimes mined under ethically questionable conditions. As a result, increasing efforts are being made to expand the range of cutting materials. The basic suitability of natural rocks for cutting tools in less demanding processes has already been demonstrated. PVD coating of the natural rocks could improve their performance. The adhesion mechanisms in TiN-coated natural rock samples are discussed below. The TiN thin film is characterized in depth. Full article
(This article belongs to the Special Issue Modern Methods of Shaping the Structure and Properties of Coatings)
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21 pages, 10897 KiB  
Article
Enhancing Passivation Behaviors and Wear Resistance of Biomedical Ti-15Mo Alloy via {332} Twinning Pre-Tension and Aging
by Shanshan Zhang, Fazhan Yang, Wei Sun, Ning Cui and Tiewei Xu
Coatings 2024, 14(10), 1332; https://doi.org/10.3390/coatings14101332 - 17 Oct 2024
Viewed by 302
Abstract
The purpose of this investigation was to determine the extent to which a combination of pre-deformation and aging procedures could enhance the corrosion and wear resistance of the Ti-15Mo alloy for biomedical materials. The initial grains were refined with {332} twins and other [...] Read more.
The purpose of this investigation was to determine the extent to which a combination of pre-deformation and aging procedures could enhance the corrosion and wear resistance of the Ti-15Mo alloy for biomedical materials. The initial grains were refined with {332} twins and other defects after the pre-deformation, increasing the amount of precipitation nucleation and forming finer α phases during aging. The finer precipitates with numerous boundaries are beneficial in forming a thicker passivation film in phosphate-buffered saline (PBS) solution, and the corrosion resistance of the 20% pre-deform plus aged alloy is improved by 4.23 times. The result indicates that the corrosion passivation behavior and film structure of the biomedical Ti-15Mo alloy are significantly influenced by its microstructure. The worn track and debris of the alloy after pre-tension and aging gradually decreases with the increase in pre-deformation rates, caused by the increase in the hardness and wear resistance. The mechanism of corrosion and wear resistance in PBS solution were revealed, which showed the pre-tension and aging processes that were performed on the Ti-15Mo alloy. This study proposes that pre-tension with {332} twins contributed to precipitation refinement, which would enhance the passivation behaviors and wear resistance of the biomedical β titanium alloy. Full article
(This article belongs to the Special Issue Advances in Surface Engineering and Biocompatible Coatings for Biomedical Applications, 2nd Edition)
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15 pages, 3195 KiB  
Article
Sodium Alginate–Montmorillonite Composite Film Coatings for Strawberry Preservation
by Xiaoping Yan, Zuolong Yu, Yao Chen, Chao Han, Yunxiao Wei, Fan Yang, Yan Qian and Yong Wang
Coatings 2024, 14(10), 1331; https://doi.org/10.3390/coatings14101331 - 17 Oct 2024
Viewed by 395
Abstract
In this study, we prepared sodium alginate (SA) and montmorillonite (MMT) composite films for application in coatings for strawberry preservation. SA and MMT were used as the matrix and glycerol was used as a plasticizer. Six types of composite films with different MMT [...] Read more.
In this study, we prepared sodium alginate (SA) and montmorillonite (MMT) composite films for application in coatings for strawberry preservation. SA and MMT were used as the matrix and glycerol was used as a plasticizer. Six types of composite films with different MMT contents were compared by analyzing their mechanical properties, permeability, and preservation effects. The results show that the mechanical properties of the 10 and 20% MMT composite films were superior, with tensile strength and fracture elongation values reaching 63.09 and 48.06 MPa and 5.75 and 6.47%, respectively. Increased MMT content caused the water vapor permeability to decrease, while the effect on oil permeability was the opposite. A comparison of the preservation effect provided by the coatings showed that, on day 12, the weight loss, malondialdehyde content, and respiratory intensity of strawberries treated with the 20% MMT coating liquid decreased by 43.3, 25.8, and 57.1%, respectively, compared with the control. The contents of titratable acid, soluble sugar, total phenols, and soluble solids decreased by 25.8, 37.7, 25.9, and 14.5%, respectively. The results provide data support for the application of these new composite films as edible coatings for fruit preservation. Full article
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18 pages, 32353 KiB  
Article
Numerical Simulation and Experimental Study of Deposition Behavior for Cold Sprayed Dual Nano HA/30 wt.% Ti Composite Particle
by Miao Sun, Xiao Chen, Zecheng Wu, Chengdi Li and Xianfeng Deng
Coatings 2024, 14(10), 1330; https://doi.org/10.3390/coatings14101330 - 17 Oct 2024
Viewed by 220
Abstract
Hydroxyapatite (HA, Ca10(PO4)6(OH)2) composite coatings added in the second phase could improve the mechanical properties and bonding strength. The cold spraying technique, as a technology for the deposition of solid particles at low temperatures, is [...] Read more.
Hydroxyapatite (HA, Ca10(PO4)6(OH)2) composite coatings added in the second phase could improve the mechanical properties and bonding strength. The cold spraying technique, as a technology for the deposition of solid particles at low temperatures, is employed to deposit HA ceramic composite coatings. The nano HA material possesses characteristics that enhance properties and promote interface bonding. Due to the exceptional mechanical properties of Ti material, adding Ti particles could improve the mechanical properties of nano HA/Ti composite coatings. In order to explore the deposition deformation mechanism of composite particles under different cold spraying conditions, numerical simulation and experimental testing of deposition behaviors of dual nano HA/Ti composite particles were analyzed. As the particle velocity increased from 400 m/s to 800 m/s in the numerical simulation analysis, the more serious the deposition deformation. Meanwhile, more cracking and splashing phenomena occurred on the surface of the particle. By analyzing the stress value curve of Ti and HA units under different particle velocities, it was found that the adiabatic shear instability phenomenon occurred during the particle deposition on the substrate. In addition, the degree of particle deformation increased with the decrease in the particle size. The results of the experimental investigation were consistent with that of the numerical simulation. Full article
(This article belongs to the Special Issue Cold-Sprayed Coatings: Microstructure, Mechanical Properties, and Wear Behaviour)
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15 pages, 9405 KiB  
Article
Study on the Synergistic Effect of Several Sulfur Compounds to the Corrosion Attack of Copper in Liquefied Petroleum Gas
by Chaoben Wang, Yuan Lu, Jinghui Ma and Hu Wang
Coatings 2024, 14(10), 1329; https://doi.org/10.3390/coatings14101329 - 17 Oct 2024
Viewed by 226
Abstract
During the process of liquefied petroleum gas (LPG) exploitation, various sulfide-containing gases are produced, which significantly bring about corrosion attacks to copper equipment and facilities. Investigations on the effects of sulfides, hydrogen sulfide (H2S), carbonyl sulfide (COS), and ethanethiol (C2 [...] Read more.
During the process of liquefied petroleum gas (LPG) exploitation, various sulfide-containing gases are produced, which significantly bring about corrosion attacks to copper equipment and facilities. Investigations on the effects of sulfides, hydrogen sulfide (H2S), carbonyl sulfide (COS), and ethanethiol (C2H6S) on copper corrosion and synergistic mechanisms are of great significance for LPG production. This paper studied the synergistic corrosion effects of mixed sulfide-containing gases in LPG on copper plates, including the influence of H2S + COS, H2S + C2H6S, as well as H2S + COS + C2H6S. The results showed that there exists an apparent synergistic effect between different sulfide-containing gases, which decreased the critical point of corrosion and enhanced the severity of copper corrosion. SEM observation on corrosion products with the addition of different sulfide-containing gases demonstrated that the microstructures of corrosion products are significantly different, which reveals different corrosion mechanisms. By characterizing the corrosion products on copper surfaces, corresponding corrosion mechanisms were proposed. Individual H2S reacts with copper directly as chemical corrosion. The presence of water leads to the dissolution of H2S into water film at the copper surface and results in electrochemical corrosion in nature. COS tends to decompose into acidic gas H2S and CO2, which accelerates the electrochemical corrosion at the copper surface. C2H6S can react with copper directly as chemical corrosion. A mixture of different sulfur-containing gases enhanced the corrosion attack by synergistic effect. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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17 pages, 4305 KiB  
Article
Asymmetric Supercapacitor Performance Enhancement Through Fe-Doped MoS₂ Nanosheets Synthesized via Hydrothermal Method
by Pritam J. Morankar, Thupakula V. M. Sreekanth, Rutuja U. Amate, Manesh A. Yewale, Aviraj M. Teli, Sonali A. Beknalkar and Chan-Wook Jeon
Coatings 2024, 14(10), 1328; https://doi.org/10.3390/coatings14101328 - 17 Oct 2024
Viewed by 242
Abstract
As modern civilization’s energy demands continue to rise, the need for efficient renewable energy solutions becomes increasingly critical. In addressing this challenge, our research explores the potential of newly developed iron (Fe)-doped molybdenum disulfide (MoS2) thin-film electrodes, synthesized through a simple [...] Read more.
As modern civilization’s energy demands continue to rise, the need for efficient renewable energy solutions becomes increasingly critical. In addressing this challenge, our research explores the potential of newly developed iron (Fe)-doped molybdenum disulfide (MoS2) thin-film electrodes, synthesized through a simple hydrothermal method, as a promising energy storage device. By systematically varying the Fe doping levels, we aim to elucidate the relationship between Fe content and the structural, morphological, and electrochemical properties of the MoS2 electrodes. The optimized FM-3 electrode exhibited a remarkable areal capacitance of 8.25 F/cm2 at a current density of 10 mA/cm2 with an energy density of 0.22 mWh/cm2 and a power density of 2.2 mW/cm2. Furthermore, the FM-3 demonstrated impressive long-term cycling stability, retaining 85.58% of its initial capacitance after 10,000 charge–discharge cycles. To further explore practical applicability, an asymmetric pouch-type supercapacitor device was assembled using an FM-3 electrode and activated carbon. The device achieved an impressive areal capacitance of 0.43 F/cm2 at a current density of 20 mA/cm2, delivering an energy density of 0.133 mWh/cm2 and a power density of 7.5 mW/cm2. The exceptional performance of the FM-3 electrode can be attributed to the enhanced diffusion rate, charge transfer efficiency, and better carrier mobility induced by Fe doping. This work not only highlights the significant electrochemical performance improvements of Fe-doped MoS2 electrodes but also demonstrates their potential for scalable energy storage solutions, making a valuable contribution to the field of next-generation energy storage technologies. Full article
(This article belongs to the Special Issue Energy Storage and Conversion: From Materials, Devices to Applications)
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17 pages, 4527 KiB  
Article
Performance of Cobalt-Doped C3N5 Electrocatalysis Nitrate in Ammonia Production
by Boyu Liang, Yueqi Wu, Jing Han, Wenqiang Deng, Xinyao Zhang, Runrun Li, Yan Hong, Jie Du, Lichun Fu and Runhua Liao
Coatings 2024, 14(10), 1327; https://doi.org/10.3390/coatings14101327 - 16 Oct 2024
Viewed by 388
Abstract
In this experiment, C3N5 was synthesized by pyrolysis of 3-amino-1,2,4 triazole material, and then 1% Co-C3N5, 3% Co-C3N5, 5% Co-C3N5, 7% Co-C3N5, and 9% [...] Read more.
In this experiment, C3N5 was synthesized by pyrolysis of 3-amino-1,2,4 triazole material, and then 1% Co-C3N5, 3% Co-C3N5, 5% Co-C3N5, 7% Co-C3N5, and 9% Co-C3N5 were synthesized by varying the mass ratio of cobalt chloride to C3N5 by stirring and ultrasonic shaking. SEM, XPS, and XRD tests were performed on the synthesized materials. The experimental results showed that Co atoms were successfully doped into C3N5. The electrocatalytic reduction experiments were performed to evaluate their NH3 yields and electrochemical properties. The results showed that the ammonia yield obtained by the electrolysis of the 9% Co-C3N5 catalyst as the working electrode in a mixed electrolytic solution of 0.1 mol/L KNO3 and 0.1 mol/L KOH for 1 h at a potential of −1.0 V vs. RHE was 0.633 ± 0.02 mmol∙h−1∙mgcat−1, and the Faraday efficiency was 65.98 ± 2.14%; under the same experimental conditions, the ammonia production rate and Faraday efficiency of the C3N5 catalyst were 0.049 mmol∙h−1∙mgcat−1 and 16.41%, respectively, and the ammonia production rate of the C3N5 catalyst was nearly 13-fold worse than the 9% Co-C3N5, which suggests that Co can improve the Faraday efficiency and ammonia yield of the electrocatalytic reduction of NO3−. This is due to the strong synergistic effect between the cobalt and C3N5 components, with C3N5 providing abundant and homogeneous sites for nitrogen coordination and the Co-N species present in the material being highly efficient active sites. The slight change in current density after five trials of 9% Co-C3N5 and the decrease in ammonia yield by about 12% in five repetitions of the experiment indicate that 9% Co-C3N5 can be recycled and work stably in electrocatalytic reactions and has good application prospects. Full article
(This article belongs to the Special Issue Advanced Materials for Electrocatalysis and Energy Storage)
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16 pages, 10438 KiB  
Article
Assessing the Fire Properties of Various Surface Treatments on Timber Components in Ancient Chinese Buildings: A Case Study from the Xianqing Temple in Changzhi, Shanxi, China
by Yupeng Li, Sokyee Yeo, Weihan Zou and Shibing Dai
Coatings 2024, 14(10), 1326; https://doi.org/10.3390/coatings14101326 - 16 Oct 2024
Viewed by 322
Abstract
Traditional and modern coatings play a key role in enhancing the fire resistance of ancient Chinese buildings. However, further comparative analysis is needed on the fire properties of the two coatings and their effects on different timber structural components. This study focuses on [...] Read more.
Traditional and modern coatings play a key role in enhancing the fire resistance of ancient Chinese buildings. However, further comparative analysis is needed on the fire properties of the two coatings and their effects on different timber structural components. This study focuses on the main hall of the Shanxi Changzhi Xianqing Temple, a typical traditional column and beam construction built between the Song and Jin periods. Firstly, the combustion characteristics of various timber structural component samples with different surface treatments (traditional “Yi-ma-wu-hui” and modern flame retardants) were analyzed using cone calorimeter. Secondly, the fire development process of the Xianqing Temple building model was analyzed by a fire dynamics simulator (FDS), and the effect mechanism of different surface treatments on the burning process was further studied. The results show that the fire resistance of timber structural components is significantly improved after modern and traditional surface treatments. The traditional method is more effective in delaying the peak heat release rate and reducing the surface temperature during combustion, while the modern surface treatment significantly prolongs the ignition time of the timber structural components. The FDS results confirm that modern and traditional surface treatments significantly improve the fire resistance of the building, delaying the flashover time by about 300 s, with no collapse occurring within 800 s. In addition, the fire resistance of buildings after traditional surface treatment is better compared to traditional methods. The above research results can provide direct data support for the selection and optimization of fireproof coatings and treatment methods for ancient buildings. Full article
(This article belongs to the Special Issue Coatings for Cultural Heritage: Cleaning, Protection and Restoration)
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13 pages, 4630 KiB  
Article
Effect of Rare Earth Y on the Microstructure, Mechanical Properties and Friction of Sn-Babbitt Alloy
by Xiaoyan Ren, Yuan Chang, Shengsheng Chen, Ningning Chen, Zhenghua Shi, Yougui Zhang, Huimin Chen, Zhiming Guo, Jinzhi Hu, Guowei Zhang and Hong Xu
Coatings 2024, 14(10), 1325; https://doi.org/10.3390/coatings14101325 - 16 Oct 2024
Viewed by 392
Abstract
Babbitt alloy is a bearing material with excellent properties, including good anti-friction wear resistance, embeddedness, corrosion, and compliance, as well as sufficient bearing capacity. However, with the development of engines to have high speed and heavy load, the use of Babbitt alloy as [...] Read more.
Babbitt alloy is a bearing material with excellent properties, including good anti-friction wear resistance, embeddedness, corrosion, and compliance, as well as sufficient bearing capacity. However, with the development of engines to have high speed and heavy load, the use of Babbitt alloy as a bearing material exposes its weaknesses of low bearing capacity, insufficient fatigue strength and a sharp decline in mechanical properties with an increase in working temperature. Therefore, its application scope is gradually narrowed and subject to certain limitations. Improving the tensile strength and wear resistance of tin-based Babbitt alloy is of great significance to expanding its application. In this study, tin-based Babbitt alloy was taken as the main research object; the particle size, microstructure, mechanical properties, and friction were systematically studied after the single addition of Y-Cu composite in tin-based Babbitt alloy liquid. The wear performance and the strengthening, toughening and wear mechanisms of tin-based Babbitt alloy were investigated under the action of Y in order to prepare a high-performance tin-based Babbitt alloy for bimetallic bearing. It was found that when rare-earth Y was added to the Babbitt alloy body, the wear properties were greatly improved. Full article
(This article belongs to the Special Issue Advances in Wear-Resistant Coatings)
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12 pages, 6738 KiB  
Article
The Utilization of Central Composite Design for the Production of Hydrogel Blends for 3D Printing
by Thalita Fonseca Araujo and Luciano Paulino Silva
Coatings 2024, 14(10), 1324; https://doi.org/10.3390/coatings14101324 - 16 Oct 2024
Viewed by 403
Abstract
Central composite design (CCD) is a statistical experimental design technique that utilizes a combination of factorial and axial points to study the effects of multiple variables on a response. This study focused on optimizing hydrogel formulations for 3D printing using CCD. Three biopolymers [...] Read more.
Central composite design (CCD) is a statistical experimental design technique that utilizes a combination of factorial and axial points to study the effects of multiple variables on a response. This study focused on optimizing hydrogel formulations for 3D printing using CCD. Three biopolymers were selected: sodium alginate (SA), gelatin (GEL), and carboxymethyl cellulose (CMC). The maximum and minimum concentrations of each polymer were established using a Google Scholar search, and CCD was employed to generate various combinations for hydrogel preparation. The hydrogels were characterized in accordance with their swelling degree (SD) in phosphate-buffered saline (PBS) and Dulbecco’s Modified Eagle Medium (DMEM), as well as their printability in 2D and 3D assays. The formulation consisting of 7.5% SA, 7.5% GEL, and 2.5% CMC exhibited the best swelling properties and exceptional printability, surpassing all other tested formulations. This study highlights the effectiveness of design of experiment methodologies in accelerating the development of optimized hydrogel formulations for various applications in 3D printing and suggests avenues for future research to explore their performance in specific biological contexts. Full article
(This article belongs to the Special Issue Recent Advances in Multifunctional Hydrogel and Its Application)
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4 pages, 182 KiB  
Editorial
Trends in Coatings and Surface Technology
by Pooja Sharma and Fábio Ferreira
Coatings 2024, 14(10), 1323; https://doi.org/10.3390/coatings14101323 - 16 Oct 2024
Viewed by 404
Abstract
The advancement in material science, industrial evolution, and growing environmental concerns make it essential for continuous updates in coating and surface technology [...] Full article
(This article belongs to the Special Issue Trends in Coatings and Surface Technology)
18 pages, 4583 KiB  
Review
Ni Catalysts for Thermochemical CO2 Methanation: A Review
by Jungpil Kim
Coatings 2024, 14(10), 1322; https://doi.org/10.3390/coatings14101322 - 16 Oct 2024
Viewed by 334
Abstract
This review underscores the pivotal role that nickel-based catalysts play in advancing CO2 methanation technologies, which are integral to achieving carbon neutrality. This study meticulously examines various aspects of catalyst design, including the significance of support materials and co-catalysts in enhancing catalytic [...] Read more.
This review underscores the pivotal role that nickel-based catalysts play in advancing CO2 methanation technologies, which are integral to achieving carbon neutrality. This study meticulously examines various aspects of catalyst design, including the significance of support materials and co-catalysts in enhancing catalytic activity and selectivity. This discussion reveals that while nickel catalysts offer a cost-effective solution due to their availability and high performance, challenges such as sintering and carbon deposition at high temperatures remain. These issues necessitate the development of catalysts with superior thermal stability or those capable of maintaining high activity at lower temperatures. This review also highlights the innovative use of three-dimensional fiber deposition technology in fabricating catalysts, which has shown promising results in improving reaction efficiency and stability over prolonged operation. Moving forward, this research emphasizes the importance of optimizing catalyst structure and fabrication techniques to overcome existing limitations. The ongoing development in this field holds great promise for the industrial application of CO2 methanation, contributing significantly to global efforts in reducing greenhouse gas emissions and promoting sustainable energy use. Full article
(This article belongs to the Special Issue Advanced Research on Energy Storage Materials and Devices)
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17 pages, 20073 KiB  
Article
Effect of Zinc Powder Reduced Graphene Oxide on the Corrosion Resistance of Waterborne Inorganic Zinc-Rich Coatings
by Xuefei Fang, Yuchun Yuan, Qiuyue Wang, Chengwei Ji, Yuna Wu, Huan Liu, Jinghua Jiang and Aibin Ma
Coatings 2024, 14(10), 1321; https://doi.org/10.3390/coatings14101321 - 16 Oct 2024
Viewed by 374
Abstract
Graphene oxide (GO) is considered an ideal material for applications involving corrosion resistance due to its excellent properties. However, the structure, surface functional groups, and distribution of GO in zinc-rich coatings (ZRCs) have a remarkable influence on coating properties. GO was reduced in [...] Read more.
Graphene oxide (GO) is considered an ideal material for applications involving corrosion resistance due to its excellent properties. However, the structure, surface functional groups, and distribution of GO in zinc-rich coatings (ZRCs) have a remarkable influence on coating properties. GO was reduced in a hydrochloric acid environment using spherical zinc powder, and the resulting products were subsequently dried and incorporated into waterborne inorganic ZRCs. Results show that zinc powder effectively reduces oxygen-containing functional groups on the GO surface, and reduced GO (rGO) is deposited on the surface of zinc powder. This improves the electron migration efficiency of rGO and decreases its surface energy. The electrochemical impedance spectroscopy (EIS) and salt spray test results demonstrate that among the coatings, the ZRC containing 0.2 wt.% rGO (40Zn–0.2rGO) exhibits the highest impedance modulus at the low frequency end. Its impedance modulus reaches 1 × 104 Ω∙cm2 after 216 h immersion. Furthermore, 40Zn–0.2rGO exhibits no signs of corrosion at the marked areas even after 216 h of the salt spray test. The good dispersion effect of the added 0.2 wt.% rGO in the coating, coupled with its exceptional electrical conductivity, facilitates the enhanced contribution of zinc powder to cathodic protection, thereby mitigating the matrix erosion caused by corrosive media. Following zinc powder corrosion, the surface of the coating can still be adorned with insoluble corrosion products such as ZnO or Zn5(OH)8Cl2, thereby offering shielding protection to the substrate. Full article
(This article belongs to the Section Corrosion, Wear and Erosion)
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29 pages, 15808 KiB  
Article
Optimization of Pavement Structure Using High-Modulus Asphalt Coating Considering the Effects of Base-Course Combinations
by Hao Wang, Jincheng Wei, Jianmin Guo, Xizhong Xu, Chengji Sun and Jiabao Hu
Coatings 2024, 14(10), 1320; https://doi.org/10.3390/coatings14101320 - 16 Oct 2024
Viewed by 338
Abstract
High-modulus asphalt concrete (HMAC) has been widely used in the surface coating of high-grade pavement. Due to HMAC’s modulus being significantly higher than traditional asphalt concrete, the mechanical responses of a pavement structure using an HMAC coating must be notably different from those [...] Read more.
High-modulus asphalt concrete (HMAC) has been widely used in the surface coating of high-grade pavement. Due to HMAC’s modulus being significantly higher than traditional asphalt concrete, the mechanical responses of a pavement structure using an HMAC coating must be notably different from those of a traditional asphalt pavement structure. Moreover, when asphalt surface coating is fixed, the selection of base-course combinations will determine the mechanical response of the whole pavement structure. However, previous studies usually analyzed the mechanical response of pavement structures at limited combinations of base-courses, resulting in difficulties comprehensively understanding the laws of mechanics and effectively optimizing the HMAC pavement structure. Hence, in this study, a total of 108 groups of numerical experiments under six working conditions of base-course combinations are carried out using orthogonal experimental design to investigate the mechanical response of pavement structures using HMAC coatings using the PR MODULE high-modulus additive. The effects of pavement thickness, material modulus, and structural combination on mechanical responses are analyzed for the 108 groups to determine the optimal pavement combinations based on the balance of mechanical response and economic efficiency. The results show the following: The effect of the base layer type on mechanical response is more significant than that of the subbase layer type. Surface and undersurface layer thickness for the granular material base layer; surface and base layer thickness for the asphalt mixture base layer; and base layer thickness, subbase layer modulus, and base layer modulus for the inorganic binder mixture base layer are the key factors for mechanical response. Finally, six recommended HMAC pavement structure configurations for various base-courses are proposed. Full article
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19 pages, 10073 KiB  
Article
Predictive Modeling and Optimization of Layer-Cladded Ti-Al-Nb-Zr High-Entropy Alloys Using Machine Learning
by Ruirui Dai, Hua Guo, Jianying Liu, Marco Alfano, Junfeng Yuan and Zhiqiang Zhao
Coatings 2024, 14(10), 1319; https://doi.org/10.3390/coatings14101319 - 16 Oct 2024
Viewed by 326
Abstract
In this work, the influence of laser power (LP), scanning speed (SS), and powder feeding speed (PF) on the porosity, dilution, and microhardness of lightweight refractory high-entropy alloy (RHEA) coatings produced via laser cladding (LC) was investigated. Variance analysis (ANOVA) was deployed to [...] Read more.
In this work, the influence of laser power (LP), scanning speed (SS), and powder feeding speed (PF) on the porosity, dilution, and microhardness of lightweight refractory high-entropy alloy (RHEA) coatings produced via laser cladding (LC) was investigated. Variance analysis (ANOVA) was deployed to ascertain the effect of LP, SS, and PF on performance metrics such as porosity, dilution, and microhardness. The Non-dominated Sorting Genetic Algorithm II (NSGA-II) was then applied to optimize these processing parameters to minimize porosity, achieve suitable dilution, and maximize microhardness, enhancing the mechanical properties of RHEA coatings. Finally, machine learning models—Random Forest (RF), Gradient Boosting Decision Tree (GBDT), and Genetic Algorithm-enhanced GBDT (GA-GBDT)—were developed using orthogonal experimental data, with GA-GBDT demonstrating superior predictive accuracy. The proposed approach integrates statistical analysis and advanced ML techniques, providing a better understanding into optimizing LP, SS, and PF for improved RHEA coatings performance in industrial applications, thereby advancing laser cladding technology. Full article
(This article belongs to the Special Issue High-Temperature Protective Coatings)
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24 pages, 26404 KiB  
Article
Effects of Different Surface Treatment Methods on Laser Welding of Aluminum Alloy and Glass
by Changjun Chen, Lei Li, Min Zhang and Wei Zhang
Coatings 2024, 14(10), 1318; https://doi.org/10.3390/coatings14101318 - 15 Oct 2024
Viewed by 407
Abstract
Hermetic glass-to-metal sealing (GMTS) technology combines metal and glass and can be used to construct vacuum tubes; electric discharge tubes; semiconductor diodes; reed switches; and pressure-tight glass-to-metal windows, optical windows, and lenses in electronics or electronic systems. The hermetic and mechanically strong seals [...] Read more.
Hermetic glass-to-metal sealing (GMTS) technology combines metal and glass and can be used to construct vacuum tubes; electric discharge tubes; semiconductor diodes; reed switches; and pressure-tight glass-to-metal windows, optical windows, and lenses in electronics or electronic systems. The hermetic and mechanically strong seals engineered using GTMS are highly reliable, making them suitable for deployment in harsh environments and for applications requiring high performance. However, it has always been challenging to precisely and robustly join glass and metal due to the significant disparities in their properties. In this study, the laser transmission welding of borosilicate glass and aluminum alloy using a pulsed Nd:YAG laser to achieve hermetic glass–metal seals was experimentally investigated. This research focused on various processing parameters and the influence of surface conditions on bonding quality. Three different types of surfaces—a polished surface, a surface subjected to preoxidation, and a laser-modified surface—were compared. To evaluate the weld strength, shear-tensile separation forces were measured. The analysis of fracture and separation encompassed detailed examinations of the weld morphology, microstructure, and elemental composition. The results revealed that increasing the laser welding energy initially enhanced the weld strength until a saturation point was reached. Among the three different surface treatments tested, the laser surface modification of aluminum alloy yielded the highest weld strength. The maximum achieved bond force exceeded 35.38 N, demonstrating the feasibility of using cost-effective pulsed laser welding for glass-to-metal sealing. The results were significantly better than those from previous research in which aluminum alloy surfaces were pretreated using microarc oxidation. Full article
(This article belongs to the Special Issue Laser-Assisted Processes and Thermal Treatments of Materials)
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12 pages, 2861 KiB  
Article
Morphological and Corrosion Characterization of Electroless Ni-P Coatings Deposited on Ductile Iron
by Nicolás Ortiz, Jesús Rafael González-Parra, Jairo Olaya, Dayi Agredo, Raul Valdez, Helgi Waage, Ana María Bolarín, Félix Sánchez and Arturo Barba-Pingarrón
Coatings 2024, 14(10), 1317; https://doi.org/10.3390/coatings14101317 - 15 Oct 2024
Viewed by 343
Abstract
Ductile iron is distinguished by its balance of mechanical properties and other advantageous characteristics, including its capacity to absorb energy. This makes it suitable for applications requiring high strength. However, its performance is impaired by its low corrosion resistance. In this study, a [...] Read more.
Ductile iron is distinguished by its balance of mechanical properties and other advantageous characteristics, including its capacity to absorb energy. This makes it suitable for applications requiring high strength. However, its performance is impaired by its low corrosion resistance. In this study, a Ni-P coating was applied to the surface of ductile cast iron using electroless nickel plating to increase its corrosion resistance in 0.1 M NaCl. The characterization of the substrate and the coated materials was conducted using scanning electron microscopy, X-ray diffraction, electrochemical impedance spectroscopy, and electrochemical noise. The results show that the coating deposited on a ductile iron is amorphous, compact, homogeneous, and well-adhered. The surface hardness is increased by 53%. Also, a notable increase in corrosion resistance is evidenced by the blocking effect of the coating that delimits the access of the electrolyte to the ductile iron coating. The corrosion mechanism is related to the mixed and localized corrosion phenomena for the different evaluation times. Full article
(This article belongs to the Special Issue Corrosion Resistance of Innovative Composite Coatings Based on Nanoparticles)
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17 pages, 3688 KiB  
Article
Investigating the Inhibitory Effect of Sargassum natans and Sargassum fluitans Extracts on Iron Corrosion in 1.00 mol L−1 HCl Solution
by Stacy Melyon, Pau Reig Rodrigo, Manon Sénard, Laura Brelle, Muriel Sylvestre, Sarra Gaspard, Drochss Pettry Valencia and Gerardo Cebrian-Torrejon
Coatings 2024, 14(10), 1316; https://doi.org/10.3390/coatings14101316 - 15 Oct 2024
Viewed by 591
Abstract
This study deals with the efficacy of extracts of Sargassum natans and Sargassum fluitans, an invasive brown algae present in Guadeloupe, as novel and environmentally friendly corrosion inhibitors for iron in 1 mol L−1 hydrochloric acid solutions. Six different Sargassum extracts (SE) were [...] Read more.
This study deals with the efficacy of extracts of Sargassum natans and Sargassum fluitans, an invasive brown algae present in Guadeloupe, as novel and environmentally friendly corrosion inhibitors for iron in 1 mol L−1 hydrochloric acid solutions. Six different Sargassum extracts (SE) were obtained using Soxhlet extraction with ethyl acetate, acetone, and ethanol, respectively, as solvents; cold successive maceration with chloroform and methanol, respectively; and microwave-assisted extraction with water. Subsequent electrochemical analysis showed that extracts from ethanol and ethyl acetate exhibited remarkable inhibition efficiencies of, respectively, 72.6% and 70.2%, but the better one was the extract of the cold maceration from chloroform with an inhibition efficiency of 92.0%. These findings allow us to focus on the chloroform extract (SEd) in order to see the change happening during the corrosion process via SEM and EDX analyses. Also, NMR analysis was conducted to identify the main chemicals responsible for the anticorrosion effect. The successful demonstration of the corrosion inhibitor effectiveness of extracts of Sargassum natans and fluitans suggests a potentially valuable use for this invasive biomass. These encouraging results warrant further investigation to identify and elucidate the active inhibitors in these extracts to deepen our understanding of their mechanisms for corrosion prevention and potentially expand their utility as an environmentally conscious approach to corrosion control. Full article
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17 pages, 9928 KiB  
Article
Anti-Corrosion and Wave-Absorbing Properties of Epoxy-Based Coatings on Q235 Steel
by Rehan Zhang, Kai Yang, Bo Dang, Mengling Zhan, Pingze Zhang and Shuqin Li
Coatings 2024, 14(10), 1315; https://doi.org/10.3390/coatings14101315 - 15 Oct 2024
Viewed by 442
Abstract
Carbon nanotube/epoxy resin (CNE) coatings and carbon nanotube/carboxy iron powder/epoxy resin (CIE) coatings were applied on the surface of Q235 steel, and their corrosion, absorption properties and other characteristics were measured in this work. The results indicate that the average thickness of a [...] Read more.
Carbon nanotube/epoxy resin (CNE) coatings and carbon nanotube/carboxy iron powder/epoxy resin (CIE) coatings were applied on the surface of Q235 steel, and their corrosion, absorption properties and other characteristics were measured in this work. The results indicate that the average thickness of a single application was approximately 400 μm, and the surface of the CNE coating was still smooth and intact after a 3000 h copper ion accelerated salt spray test without bubbles, falling off or other corrosion phenomena. The same was true for 28 days of full immersion in solutions of 10% hydrochloric acid (HCl) and 10% sodium hydroxide (NaOH) of the coating. The electrochemical testing exhibited the corrosion current of the CNE coating as being markedly lower than that of Q235 steel, with a protection efficiency of 81.68% for the Q235 steel. The CNE-0.6 coating had the maximum corrosion voltage (−0.390 V), and the CNE-0.3 coating had the minimum corrosion current of 2.07 × 10−6 A·cm2. The adhesion between the coating and Q235 could reach level 0, and the tensile strength of the coating was up to 18.75 MPa. The coating was observed to remain intact and free from detachment upon undergoing a drop test from a height of 50 cm. In addition, the CIE-0.6 coating exhibited an effective absorption band of 9.1 GHz, covering the range from 8.2 to 13.7 GHz, and it achieved a maximum reflection loss of −15.1 dB at a frequency of 8.6 GHz. Full article
(This article belongs to the Special Issue Oxidation, Wear, Corrosion Behaviors and Activated Bonding Properties of Coatings Deposited on Metals)
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2 pages, 131 KiB  
Correction
Correction: Končan Volmajer et al. Electrochemical Impedance Spectroscopy Study of Waterborne Epoxy Coating Film Formation. Coatings 2019, 9, 254
by Natalija Končan Volmajer, Miha Steinbücher, Peter Berce, Peter Venturini and Miran Gaberšček
Coatings 2024, 14(10), 1314; https://doi.org/10.3390/coatings14101314 - 14 Oct 2024
Viewed by 220
Abstract
In the published version [...] Full article
16 pages, 4225 KiB  
Review
A Review on the Effect of Wood Surface Modification on Paint Film Adhesion Properties
by Jingyi Hang, Xiaoxing Yan and Jun Li
Coatings 2024, 14(10), 1313; https://doi.org/10.3390/coatings14101313 - 14 Oct 2024
Viewed by 606
Abstract
Wood surface treatment aims to improve or reduce the surface activity of wood by physical treatment, chemical treatment, biological activation treatment or other methods to achieve the purpose of surface modification. After wood surface modification, the paint film adhesion performance, gluing performance, surface [...] Read more.
Wood surface treatment aims to improve or reduce the surface activity of wood by physical treatment, chemical treatment, biological activation treatment or other methods to achieve the purpose of surface modification. After wood surface modification, the paint film adhesion performance, gluing performance, surface wettability, surface free energy and surface visual properties would be affected. This article aims to explore the effects of different modification methods on the adhesion of wood coating films. Modification of the wood surface significantly improves the adhesion properties of the paint film, thereby extending the service life of the coating. Research showed that physical external force modification improved the hydrophilicity and wettability of wood by changing its surface structure and texture, thus enhancing the adhesion of the coating. Additionally, high-temperature heat treatment modification reduced the risk of coating cracking and peeling by eliminating stress and moisture within the wood. Chemical impregnation modification utilized the different properties of organic and inorganic substances to improve the stability and durability of wood. Organic impregnation effectively filled the wood cell wall and increased its density, while inorganic impregnation enhanced the adhesion of the coating by forming stable chemical bonds. Composite modification methods combined the advantages of the above technologies and significantly improved the comprehensive properties of wood through multiple modification treatments, showing superior adhesion and durability. Comprehensive analysis indicated that selecting the appropriate modification method was key for different wood types and application environments. Full article
(This article belongs to the Special Issue Surface Properties and Surface Treatments of Wood and Wood-Based Composites)
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13 pages, 35411 KiB  
Article
The Effect of Shot Blasting Abrasive Particles on the Microstructure of Thermal Barrier Coatings Containing Ni-Based Superalloy
by Jianping Lai, Xin Shen, Xiaohu Yuan, Dingjun Li, Xiufang Gong, Fei Zhao, Xiaobo Liao and Jiaxin Yu
Coatings 2024, 14(10), 1312; https://doi.org/10.3390/coatings14101312 - 14 Oct 2024
Viewed by 371
Abstract
Grit particles remaining on the substrate surface after grit blasting are generally considered to impair the thermal performance of thermal barrier coatings (TBCs). However, the specific mechanisms by which these particles degrade the multilayer structure of TBCs during thermal cycling have not yet [...] Read more.
Grit particles remaining on the substrate surface after grit blasting are generally considered to impair the thermal performance of thermal barrier coatings (TBCs). However, the specific mechanisms by which these particles degrade the multilayer structure of TBCs during thermal cycling have not yet been fully elucidated. In this study, the superalloy substrate was grit-blasted using various processing parameters, followed by the deposition of thermal barrier coatings (TBCs) consisting of a metallic bond coat (BC) and a ceramic top coat (TC). After thermal shock tests, local thinning or discontinuities in the thermally grown oxide (TGO) layer were observed in TBCs where large grit particles were embedded at the BC/substrate interface. Moreover, cracks originated at the concave positions of the TGO layer and propagated vertically towards BC; these cracks may be associated with additional stress imposed by the foreign grit particles during thermal cycling. At the BC/substrate interface, crack origins were observed in the vicinity of large grit particles (~50 μm). Full article
(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings)
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15 pages, 2271 KiB  
Article
Preparation and Characterization of PLA-Based Films Fabricated with Different Citrus Species Peel Powder
by Antonios S. Koutoulis, Andreas E. Giannakas, Dimitrios G. Lazaridis, Apostolos-Panagiotis Kitsios, Vassilios K. Karabagias, Aris E. Giannakas, Athanasios Ladavos and Ioannis K. Karabagias
Coatings 2024, 14(10), 1311; https://doi.org/10.3390/coatings14101311 - 14 Oct 2024
Viewed by 484
Abstract
The present study aimed to investigate whether different citrus peel powders (orange, mandarin, and lemon) could be incorporated into polylactic acid (PLA), for the preparation and characterization of biodegradable films made of this fruit waste. In particular, films were prepared by the solvent [...] Read more.
The present study aimed to investigate whether different citrus peel powders (orange, mandarin, and lemon) could be incorporated into polylactic acid (PLA), for the preparation and characterization of biodegradable films made of this fruit waste. In particular, films were prepared by the solvent casting method and tested in terms of physicochemical and biochemical parameters, along with mechanical properties. Furthermore, the citrus peel powders were tested for their physicochemical and biochemical properties after ethanolic extraction. The results showed that the addition of citrus powders into PLA proved to be efficient compared to the control films (PLA). The citrus peel-based films showed high antioxidant capacity (38.37%–32.54%), a considerable total phenolic content (17.2–12.58 mg GAE/L), good lightness (L*: 42.83–41.93), elastic Young’s modulus (257.95–175.38 MPa), oxygen transmission rate (976.5 mL m−2 day−1–1218 mL m−2 day−1), elongation at break (183.06%–135.95%), and tensile strength (6.15–4.56 MPa), which were affected significantly (p < 0.05) by the botanical origin of citrus peel. Concerning the citrus peel extracts, the highest values in antioxidant capacity (52.56%), total phenolic content (724.8 mg GAE/L), and titratable acidity (714.67 mg of citric acid/L) were recorded in the extract of lemon peel powders. The corresponding values for orange peel powder extracts were 39.43%, 563.8 mg GAE/L, and 576 mg of citric acid/L, while those for mandarin were 33.01%, 558.46 mg GAE/L, and 54.67 mg of citric acid/L. The application of multivariate analysis of variance and linear discriminant analysis on the mechanical properties, physicochemical, and biochemical data resulted in the differentiation of pure PLA and PLA-based films fabricated with citrus peel powder. From the above findings, it is concluded that citrus peel powders are sources of phytochemicals and can be used for the preparation of PLA-based films for potential applications in food preservation. Full article
(This article belongs to the Special Issue Trends in Sustainable Food Packaging and Coatings)
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16 pages, 2447 KiB  
Article
Improving Hydrophobicity and Water Vapor Barrier Properties in Paper Using Cellulose Nanofiber-Stabilized Cocoa Butter and PLA Emulsions
by Shaydier Argel-Pérez, Jorge Velásquez-Cock, Robin Zuluaga and Catalina Gómez-Hoyos
Coatings 2024, 14(10), 1310; https://doi.org/10.3390/coatings14101310 - 13 Oct 2024
Viewed by 650
Abstract
This study explores the use of cellulose nanofiber (CNF)-stabilized Pickering emulsions for paper coatings, focusing on their rheological properties and effects on hydrophilicity and water vapor transmission rate (WVTR). Two types of Pickering emulsions, oil-in-water (O/W), were stabilized with 1 wt% CNF extracted [...] Read more.
This study explores the use of cellulose nanofiber (CNF)-stabilized Pickering emulsions for paper coatings, focusing on their rheological properties and effects on hydrophilicity and water vapor transmission rate (WVTR). Two types of Pickering emulsions, oil-in-water (O/W), were stabilized with 1 wt% CNF extracted from fique by-products. The oily phases of the emulsions were composed of poly(lactic acid) (PLA) and cocoa butter (CB). The physical stability, viscosity, and viscoelasticity of the emulsions were characterized. The emulsions were applied to the surfaces of Bond and Kraft papers using the rod-coating method. The coating process involved first applying a layer of the PLA emulsion followed by a layer of the CB emulsion. The coated papers were then evaluated by FE-SEM, contact angle, adhesion work, and water vapor transmission rate (WVTR). The results indicated that the coatings effectively produced a slightly hydrophobic surface on the papers, with contact angles approaching 90°. Initially, Kraft paper exhibited a WVTR value of 29.20 ± 1.13 g/m2·h, which significantly decreased to 7.06 ± 2.80 g/m2·h after coating, representing a reduction of 75.82%. Similarly, natural Bond paper showed a WVTR value of 30.56 ± 0.34 g/m2·h, which decreased to 14.37 ± 5.91 g/m2·h after coating, indicating a reduction of 47.02%. These findings demonstrate the potential of CNF-stabilized Pickering emulsions for enhancing the performance of paper coatings in terms of hydrophobicity and moisture barrier properties. The approach of this study aligns with global sustainability goals in packaging materials combining the use of PLA and CB to develop a waterborne coating to enhance the moisture barrier properties, demonstrated by a substantial reduction in water vapor transmission rates, and an improved hydrophobicity of coated papers. Full article
(This article belongs to the Special Issue Advanced Coatings and Films for Food Packing and Storage, 2nd Edition)
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