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Keywords = durability

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12 pages, 3596 KiB  
Article
Development of Superhydrophobic Reduced Graphene Oxide (rGO) for Potential Applications in Advanced Materials
by Enoch Adotey, Aliya Kurbanova, Aigerim Ospanova, Aida Ardakkyzy, Zhexenbek Toktarbay, Nazerke Kydyrbay, Mergen Zhazitov, Nurxat Nuraje and Olzat Toktarbaiuly
Nanomaterials 2025, 15(5), 363; https://doi.org/10.3390/nano15050363 (registering DOI) - 27 Feb 2025
Abstract
Reduced graphene oxide (rGO) was synthesized by chemically reducing graphene oxide (GO) using a reducing agent. The product, rGO, showed excellent hydrophobicity, as indicated by its high-water contact angle, which was greater than 150°. Characterizations using Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and [...] Read more.
Reduced graphene oxide (rGO) was synthesized by chemically reducing graphene oxide (GO) using a reducing agent. The product, rGO, showed excellent hydrophobicity, as indicated by its high-water contact angle, which was greater than 150°. Characterizations using Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) were used to analyze the composition and structural differences between GO and the superhydrophobic rGO material. Scanning electron microscopy (SEM) showed that GO particles exhibited a plate-like morphology with layers of stacked plates, while rGO displayed fewer stacks that show a more separated structure of layers. The increasing demand for superhydrophobic materials in advanced materials industries, due to their potential to enhance performance, durability, and safety, makes rGO a promising candidate for use in composite materials. Full article
(This article belongs to the Section 2D and Carbon Nanomaterials)
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28 pages, 26021 KiB  
Article
Multi-temporal Relative Sea Level Rise Scenarios up to 2150 for the Venice Lagoon (Italy)
by Marco Anzidei, Cristiano Tolomei, Daniele Trippanera, Tommaso Alberti, Alessandro Bosman, Carlo Alberto Brunori, Enrico Serpelloni, Antonio Vecchio, Antonio Falciano and Giuliana Deli
Remote Sens. 2025, 17(5), 820; https://doi.org/10.3390/rs17050820 (registering DOI) - 26 Feb 2025
Viewed by 1
Abstract
The historical City of Venice, with its lagoon, has been severely exposed to repeated marine flooding since historical times due to the combined effects of sea level rise (SLR) and land subsidence (LS) by natural and anthropogenic causes. Although the sea level change [...] Read more.
The historical City of Venice, with its lagoon, has been severely exposed to repeated marine flooding since historical times due to the combined effects of sea level rise (SLR) and land subsidence (LS) by natural and anthropogenic causes. Although the sea level change in this area has been studied for several years, no detailed flooding scenarios have yet been realized to predict the effects of the expected SLR in the coming decades on the coasts and islands of the lagoon due to global warming. From the analysis of geodetic data and climatic projections for the Shared Socioeconomic Pathways (SSP1-2.6; SSP3-7.0 and SSP5-8.5) released in the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC), we estimated the rates of LS, the projected local relative sea level rise (RSLR), and the expected extent of flooded surfaces for 11 selected areas of the Venice Lagoon for the years 2050, 2100, and 2150 AD. Vertical Land Movements (VLM) were obtained from the integrated analysis of Global Navigation Satellite System (GNSS) and Interferometry Synthetic Aperture Radar (InSAR) data in the time spans of 1996–2023 and 2017–2023, respectively. The spatial distribution of VLM at 1–3 mm/yr, with maximum values up to 7 mm/yr, is driving the observed variable trend in the RSLR across the lagoon, as also shown by the analysis of the tide gauge data. This is leading to different expected flooding scenarios in the emerging sectors of the investigated area. Scenarios were projected on accurate high-resolution Digital Surface Models (DSMs) derived from LiDAR data. By 2150, over 112 km2 is at risk of flooding for the SSP1-2.6 low-emission scenario, with critical values of 139 km2 for the SSP5-8.5 high-emission scenario. In the case of extreme events of high water levels caused by the joint effects of astronomical tides, seiches, and atmospheric forcing, the RSLR in 2150 may temporarily increase up to 3.47 m above the reference level of the Punta della Salute tide gauge station. This results in up to 65% of land flooding. This extreme scenario poses the question of the future durability and effectiveness of the MoSE (Modulo Sperimentale Elettromeccanico), an artificial barrier that protects the lagoon from high tides, SLR, flooding, and storm surges up to 3 m, which could be submerged by the sea around 2100 AD as a consequence of global warming. Finally, the expected scenarios highlight the need for the local communities to improve the flood resiliency plans to mitigate the consequences of the expected RSLR by 2150 in the UNESCO site of Venice and the unique environmental area of its lagoon. Full article
(This article belongs to the Section Environmental Remote Sensing)
16 pages, 1913 KiB  
Article
Optimizing Strength Prediction for Cemented Paste Backfills with Various Fly Ash Substitution: Computational Approach with Machine Learning Algorithms
by Ayse Nur Adiguzel Tuylu, Serkan Tuylu, Deniz Adiguzel, Ersin Namli, Can Gungoren and Ismail Demir
Minerals 2025, 15(3), 234; https://doi.org/10.3390/min15030234 - 26 Feb 2025
Viewed by 1
Abstract
In cemented paste backfill (CPB), fly ash (FA) can reduce cement costs. However, the chemical compositions of FA and tailings used in the CPB can vary significantly, affecting the strength values of CPBs, which can be determined through laboratory tests and play a [...] Read more.
In cemented paste backfill (CPB), fly ash (FA) can reduce cement costs. However, the chemical compositions of FA and tailings used in the CPB can vary significantly, affecting the strength values of CPBs, which can be determined through laboratory tests and play a crucial role in design operations. Therefore, developing a predictive model would be advantageous in terms of time and cost. The most critical aspect of this study is that machine learning (ML) models demonstrate high accuracy in the performance of strength prediction in experimental studies, especially in nonlinear and complex data structures, and even in the presence of uncertainty in geochemical and geophysical parameters. Among the ML algorithms, random forest (RF), artificial neural network (ANN), linear regression (LR), voting, and extreme gradient boosting (XGBoost) algorithms were used in this study. According to the results obtained, the XGBoost model exhibited the most robust predictive performance, evidenced by the highest correlation coefficient (R) (0.922) and the lowest mean absolute error (0.666). XGBoost also demonstrated its durability and stability by achieving the lowest relative absolute error (18.81%) and root mean square error (41.10%). Therefore, it has been understood that significant time and resource savings can be achieved in important projects by eliminating the need for experimental tests. Full article
(This article belongs to the Special Issue Cemented Mine Waste Backfill: Experiment and Modelling: 2nd Edition)
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16 pages, 1317 KiB  
Article
Influence of Pavement Material and Structure on Low-Temperature Crack Resistance for Double-Layer Asphalt Surface One-Time Paving
by Bingyang Wu, Zhanchuang Han, Yunbo Mao, Shuai Wang, Hui Zhao, Shuo Zhang and Mingchen Li
Materials 2025, 18(5), 1037; https://doi.org/10.3390/ma18051037 - 26 Feb 2025
Viewed by 79
Abstract
The double-layer one-time-paving technology for asphalt mixtures enhances the interlayer adhesion and stability of pavement by simultaneously laying and compacting two layers of asphalt mixture, demonstrating improvements over traditional layer-by-layer paving and compaction methods. Based on this technology, the effects of paving techniques, [...] Read more.
The double-layer one-time-paving technology for asphalt mixtures enhances the interlayer adhesion and stability of pavement by simultaneously laying and compacting two layers of asphalt mixture, demonstrating improvements over traditional layer-by-layer paving and compaction methods. Based on this technology, the effects of paving techniques, mixture types, and structural layer thickness on the low-temperature crack resistance of pavement at −10 °C were investigated. Results indicated that, compared to traditional paving methods, the maximum tensile strain and bending strain energy density of pavement using the double-layer one-time-paving technique increased by at least 14% and 20%, respectively, under a 95% confidence level. Compared to the AC-13 + AC-25 mixture combination, the AC-16 + AC-20, AC-16 + AC-25, and AC-13 + AC-20 combinations showed increases in maximum tensile strain by at least 25%, 15%, and 15%, and in bending strain energy density by at least 57%, 38%, and 31%, respectively. Compared to the 5 cm + 5 cm thickness combination, the 4 cm + 6 cm and 3 cm + 7 cm combinations exhibited increases in maximum tensile strain by at least 14% and 22%, and in bending strain energy density by at least 16% and 29%, respectively. To effectively improve the low-temperature crack resistance of asphalt pavement at −10 °C, it is recommended to adopt a double-layer one-time-paving structure with a 3 cm AC-16 upper layer and a 7 cm AC-20 lower layer, providing insights for more durable asphalt pavements in cold climates. Full article
(This article belongs to the Special Issue Advances in Material Characterization and Pavement Modeling)
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23 pages, 3256 KiB  
Article
Leveraging Delayed Strength Gains in Supplementary Cementitious Material Concretes: Rethinking Mix Design for Enhanced Cost Efficiency and Sustainability
by Wanderson Santos de Jesus, Thalles Murilo Santos de Almeida, Suânia Fabiele Moitinho da Silva, Marcelo Tramontin Souza, Eduarda Silva Leal, Ramon Santos Souza, Laio Andrade Sacramento, Ivan Bezerra Allaman and José Renato de Castro Pessôa
J. Compos. Sci. 2025, 9(3), 110; https://doi.org/10.3390/jcs9030110 - 26 Feb 2025
Viewed by 95
Abstract
Engineers commonly use the 28-day characteristic strength of concrete for project calculations, but this may not reflect the full-strength potential, especially in concretes with supplementary cementitious materials (SCMs). SCMs, known for their slow reactivity, often delay optimal strength beyond 28 days, requiring higher [...] Read more.
Engineers commonly use the 28-day characteristic strength of concrete for project calculations, but this may not reflect the full-strength potential, especially in concretes with supplementary cementitious materials (SCMs). SCMs, known for their slow reactivity, often delay optimal strength beyond 28 days, requiring higher cement content to speed up early strength development, thus increasing production costs. This study examined the relationship between concrete age and mechanical strength across eight cement types, including tests for axial compression, water absorption, void index, and specific mass. The findings showed that pozzolan and slag cements gained significant long-term strength due to slow pozzolanic reactions. Conversely, limestone filler mixes had lower initial strength and slower progress, likely due to increased porosity from fine fillers. A correlation was found between higher pozzolan content and improved durability, including reduced water absorption and void index. Cost analysis indicated that optimizing cement mix designs for targeted strength levels could reduce production costs, especially for concretes with high SCM content. Using long-term characteristic strength rather than the traditional 28-day strength resulted in approximately 14% savings, particularly for slag- and pozzolan-based cements. The savings were less significant for other cement types, emphasizing the importance of adjusting mix designs based on both performance and financial considerations. Full article
18 pages, 11860 KiB  
Article
Composite Treatment of Mortar Through Nano-Ion-Based Capillary Crystalline and Silane Hydrophobic Processing to Enhance Its Corrosion Resistance in the Cl-Contained Environment
by Quan Hua, Changyun Wu, Yangshun Zhu, Haoyu Wang, Guowei Wang, Shuguang Zhang and Dan Song
Coatings 2025, 15(3), 278; https://doi.org/10.3390/coatings15030278 - 26 Feb 2025
Viewed by 114
Abstract
The inherent porous structure of concrete enables the penetration of water and Cl ions through its pores, which eventually leads to rebar corrosion within the concrete. Consequently, the densification and impermeability of concrete protective layers play a critical role in the durability [...] Read more.
The inherent porous structure of concrete enables the penetration of water and Cl ions through its pores, which eventually leads to rebar corrosion within the concrete. Consequently, the densification and impermeability of concrete protective layers play a critical role in the durability of reinforced concrete structures. This study proposes a composite anti-corrosion treatment for mortar protective layers by integrating nano-ion capillary crystalline with silane hydrophobic processing. Targeting existing mortar samples, a series of experiments were conducted, utilizing scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray computed tomography (X-CT), contact angle measurements, permeability tests, and electrochemical tests. These experiments systematically evaluated the effects of composite anti-corrosion treatment on the microstructure of hydration products, pore characteristics, surface hydrophobicity, impermeability, and the overall corrosion resistance of mortar-rebar samples in a Cl-contained environment. The results reveal that nano-ion capillary crystalline materials react with free calcium ions in the mortar to produce secondary hydration products, effectively filling micro-pores, densifying the pore structure and inhibiting the invasion of Cl ions. The combination of capillary crystalline and silane hydrophobic processing synergistically enhances surface hydrophobicity and impermeability, preventing the ingress of corrosive agents, such as Cl ions, and significantly improving the anti-corrosion performance of mortar in a Cl-contained environment. Full article
(This article belongs to the Special Issue Superhydrophobic Coatings, 2nd Edition)
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31 pages, 27163 KiB  
Article
Synergistic Use of Nanosilica and Basalt Fibers on Mechanical Properties of Internally Cured Concrete with SAP: An Experimental Analysis and Optimization via Response Surface Methodology
by Said Mirgan Borito, Han Zhu, Yasser E. Ibrahim, Sadi Ibrahim Haruna and Zhao Bo
Fibers 2025, 13(3), 25; https://doi.org/10.3390/fib13030025 - 26 Feb 2025
Viewed by 116
Abstract
This study explores the combined effects of nanosilica (NS) and basalt fibers (BF) on the mechanical and microstructural properties of superabsorbent polymer (SAP)-modified concrete. NS (0–1.5% replaced by cement weight) and BF (0–1.2% by volume fraction) were incorporated to optimize compressive, flexural, and [...] Read more.
This study explores the combined effects of nanosilica (NS) and basalt fibers (BF) on the mechanical and microstructural properties of superabsorbent polymer (SAP)-modified concrete. NS (0–1.5% replaced by cement weight) and BF (0–1.2% by volume fraction) were incorporated to optimize compressive, flexural, and split-tensile strengths using response surface methodology. Digital Image Correlation (DIC) was employed to analyze failure mechanisms. Results show that while SAP alone reduced strength, the addition of NS and BF mitigated this loss through synergistic microstructure enhancement and crack-bridging reinforcement. The optimal mix (0.9% NS and 1.2% BF) increased compressive, flexural, and split-tensile strengths by 15.3%, 10.0%, and 14.0%, respectively. SEM analysis revealed that NS filled SAP-induced pores, while BF limited crack propagation, contributing to improved mechanical strength of SAP-modified concrete. This hybrid approach offers a promising solution for durable and sustainable concrete pavements. Full article
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16 pages, 1923 KiB  
Article
Multi-Objective Optimization of Low-Velocity Impact and Compression Behavior of 3D-Printed PLA Cubic Samples
by Oguz Dogan, Muhammed S. Kamer and Mehmet F. Sahan
Polymers 2025, 17(5), 627; https://doi.org/10.3390/polym17050627 - 26 Feb 2025
Viewed by 40
Abstract
This study investigates how various 3D printing parameters influence mechanical properties, specifically strength in compression and low-velocity impact (LVI) tests, and identifies the best printing parameters (layer thickness, nozzle diameter, and infill density) that lead to durable samples. Utilizing a Taguchi L9 [...] Read more.
This study investigates how various 3D printing parameters influence mechanical properties, specifically strength in compression and low-velocity impact (LVI) tests, and identifies the best printing parameters (layer thickness, nozzle diameter, and infill density) that lead to durable samples. Utilizing a Taguchi L9 orthogonal array, the study systematically examined the effects of three critical 3D printing parameters on the mechanical strength of cubic test samples. Nine experimental configurations were tested, each subjected to compression and LVI tests according to ASTM standards. Statistical analyses, including analysis of variance (ANOVA) and grey relational analysis (GRA), were employed to evaluate parameter significance and optimize results. Infill density significantly influenced the compression tests, while nozzle diameter was the most impactful parameter in LVI tests. Layer thickness had a minimal influence on both outcomes. Additionally, applying GRA revealed that optimal 3D printing parameters differ when considering the two mechanical properties simultaneously, highlighting the complexity of achieving balanced performance in 3D-printed structures. The application of the Taguchi method to optimize 3D printing parameters improved the mechanical properties of printed materials while significantly reducing the number of required experiments. By employing an efficient experimental design, this research demonstrates how to achieve high-quality results in compression and LVI tests with minimal resource use and time investment. Additionally, integrating GRA for the simultaneous optimization of multiple performance characteristics further enhances the practical applicability of the findings in additive manufacturing. Full article
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18 pages, 6983 KiB  
Article
Toughening of Composite Interfaces for Damage Resistance with Nanoparticle Interleaves
by Nithya Subramanian and Chiara Bisagni
J. Compos. Sci. 2025, 9(3), 109; https://doi.org/10.3390/jcs9030109 - 26 Feb 2025
Viewed by 32
Abstract
Composite interfaces, particularly in joints, play a critical role in the damage resistance and durability of structures for aeronautics applications. This study investigates the use of carbon nanotube (CNT) interleaves for the co-cured joining of composite parts and its effects on fracture toughness [...] Read more.
Composite interfaces, particularly in joints, play a critical role in the damage resistance and durability of structures for aeronautics applications. This study investigates the use of carbon nanotube (CNT) interleaves for the co-cured joining of composite parts and its effects on fracture toughness and damage progression at the co-cured interface. CNT dispersed in a thermoset resin and partially cured into thin film interleaves at three weight concentrations (0.5% wt., 1% wt., and 2% wt.) of two discrete thicknesses (200 µ and 500 µ) were investigated. The fracture toughness of the co-cured interface with CNT interleaves in mode I and mode II loading conditions was determined through double cantilever beam and end-notched flexure tests, respectively. The results reveal that despite the occurrence of a stick–slip damage progression in mode I, the crack arrest mechanisms and forces are surprisingly predictable based on interleaf thickness. At CNT concentrations above 1% wt., there was no significant enhancement of toughening, and interleaf thickness controlled the crack arrest loads. Damage delay also occurred at the interface due to the activation of multiscale toughening mechanisms. Toughening in mode II was dominated by CNT pullout resistance and, therefore, yielded up to six-fold improvement in critical fracture toughness. These insights offer significant potential for designing joints with nanocomposites for aerospace applications, incorporating inherent toughening and damage delay mechanisms. Full article
(This article belongs to the Special Issue Feature Papers in Journal of Composites Science in 2024)
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22 pages, 8509 KiB  
Article
Design and Preparation of a Novel Double-Modified Cement-Based Protective Coating Material and Its Improved Protection Performance Against Chloride Corrosion
by Quan Hua, Changyun Wu, Yangshun Zhu, Juhang Wang, Zhou Zhou, Xing Wang, Guowei Wang, Shuguang Zhang and Dan Song
Coatings 2025, 15(3), 277; https://doi.org/10.3390/coatings15030277 - 26 Feb 2025
Viewed by 61
Abstract
The service of reinforced concrete structures (RCSs) in harsh coastal environments is often threatened by chloride corrosion. The penetration of chloride ions through concrete pores into the steel/concrete interface will cause the depassivation and corrosion of steel rebars, which will lead to the [...] Read more.
The service of reinforced concrete structures (RCSs) in harsh coastal environments is often threatened by chloride corrosion. The penetration of chloride ions through concrete pores into the steel/concrete interface will cause the depassivation and corrosion of steel rebars, which will lead to the deterioration and failure of RCSs durability. It is important to repair and protect the corrosion damage of existing concrete structures and ensure their high durability, and the high performance of repairing and protecting materials is crucial. In this paper, a novel cement-based protective coating material with low porosity, high impermeability and chloride-corrosion resistance was designed and prepared by introducing polypropylene fiber and high-performance cement into commercial cement-based protective materials through the double modification strategy of fiber-toughening and substrate-enhancing, in order to provide a reliable corrosion protection solution for the high durability and long life of RCSs under chloride erosion environment. Based on this, the microstructure and pore structure of the double-modified coating material was systematically analyzed by SEM, XRD, X-CT and other characterization methods. The impermeability and chloride corrosion resistance of this material were scientifically evaluated, and the protection mechanism was systematically discussed. The results show that the impermeability of the double-modified coating material is about 2.8 times higher than that of the untreated mortar. At the same time, the corrosion current density was significantly reduced to 8.60 × 10−7 A·cm−2, which was about 86% lower than that of the untreated sample (6.11 × 10−6 A·cm−2). The new cement-based coating material optimized by double-modification effectively inhibits the formation and propagation of microcracks in the protective coating through the bridging effect of fibers. At the same time, the regulation of cement hydration products and the densification of pore structure are realized by adjusting the composition of cement matrix. Based on the above two aspects of microstructure improvement, the chloride-corrosion protection performance of the novel cement-based protective coating material has been greatly improved. Full article
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13 pages, 2425 KiB  
Article
An Acid–Base Proton Transfer Approach to Robust Superhydrophobic Self-Cleaning Surfaces for the Corrosion Protection of Magnesium
by Junjie Chen, Baoshan Xu, Yunhao Zhao, Ke Zhou, Ruijuan Shao, Xiaowei Xun, Fan Zhang and Dongmian Zang
Materials 2025, 18(5), 1028; https://doi.org/10.3390/ma18051028 - 26 Feb 2025
Viewed by 84
Abstract
In this study, an acid–base proton transfer method was used to fabricate functional coatings on Mg surfaces with the cooperative effect of durable superhydrophobic and exceptional self-cleaning properties, providing high-efficiency corrosion protection. In this context, aluminum chloride served as a precursor for the [...] Read more.
In this study, an acid–base proton transfer method was used to fabricate functional coatings on Mg surfaces with the cooperative effect of durable superhydrophobic and exceptional self-cleaning properties, providing high-efficiency corrosion protection. In this context, aluminum chloride served as a precursor for the direct growth of aluminum hydroxide on the Mg surface. Without the addition of any solvent, the densely arranged absolute palmitic acid was strongly bonded to the grown aluminum hydroxide on the Mg substrate, which acted as an effective anti-water barrier that can impede the penetration of water, as well as the oxygen and chloridion involved. Full article
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25 pages, 4688 KiB  
Article
Enhancing Mechanical and Thermal Performance of Recycled PA6/PP Blends: Chain Extension and Carbon Fiber Reinforcement Synergy
by Neslihan Ergun, Mustafa Oksuz and Aysun Ekinci
Materials 2025, 18(5), 1027; https://doi.org/10.3390/ma18051027 - 26 Feb 2025
Viewed by 77
Abstract
To develop novel materials through the recycling of waste polymers and to enhance their mechanical and thermal properties, composites were synthesized using chain extenders (CEs), compatibilizers (PP-g-MA), and short carbon fiber (CF) reinforcements within recycled polyamide 6 (rPA6) and polypropylene (rPP) blends. The [...] Read more.
To develop novel materials through the recycling of waste polymers and to enhance their mechanical and thermal properties, composites were synthesized using chain extenders (CEs), compatibilizers (PP-g-MA), and short carbon fiber (CF) reinforcements within recycled polyamide 6 (rPA6) and polypropylene (rPP) blends. The recycling of waste polymers holds paramount importance in the context of environmental sustainability. This study investigates the role of additives in effectively improving the properties of recycled polymers. The composites were fabricated using the twin-screw extrusion method and subjected to a comprehensive range of characterizations, including Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC), molecular weight analysis, melt flow index (MFI), heat deflection temperature (HDT), tensile testing, impact testing, and Scanning Electron Microscopy (SEM). Additionally, ANOVA statistical methods were applied to analyze HDT, tensile, and impact test results. The findings of this research demonstrate that chain extenders and compatibilizers significantly enhance the mechanical properties of rPA6/rPP blends, while carbon fiber reinforcements markedly improve both tensile strength and impact resistance. Furthermore, the incorporation of rPP led to an approximately 4% reduction in hardness values; however, this loss was effectively compensated by the addition of chain extenders and CF reinforcements, resulting in an overall increase in hardness. It was observed that chain extenders enhanced the elastic modulus and tensile strength by reinforcing interphase bonding, whereas CF reinforcements strengthened the polymer matrix, leading to improved impact resistance. These findings emphasize the synergistic role of chain extenders, compatibilizers, and CF reinforcements in enhancing the mechanical properties of rPA6/rPP blends. The study underscores recycling as both an environmentally beneficial and effective strategy for developing durable, high-performance composites for industrial use. Consequently, the utilization of recycled polymers contributes substantially to the circular and sustainable materials economy, demonstrating the potential for the widespread industrial adoption of such composites. Full article
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17 pages, 4398 KiB  
Article
Construction of PdCu Alloy Decorated on the N-Doped Carbon Aerogel as a Highly Active Electrocatalyst for Enhanced Oxygen Reduction Reaction
by Yangxin Bai, Wenke Hao, Aleeza Altaf, Jiaxin Lu, Liu Liu, Chuanyong Zhu, Xindi Gu, Xiaodong Wu, Xiaodong Shen, Sheng Cui and Xiangbao Chen
Gels 2025, 11(3), 166; https://doi.org/10.3390/gels11030166 - 26 Feb 2025
Viewed by 150
Abstract
Fuel cells/zinc–air cells represent a transformative technology for clean energy conversion, offering substantial environmental benefits and exceptional theoretical efficiency. However, the high cost and limited durability of platinum-based catalysts for the sluggish oxygen reduction reaction (ORR) at the cathode severely restrict their scalability [...] Read more.
Fuel cells/zinc–air cells represent a transformative technology for clean energy conversion, offering substantial environmental benefits and exceptional theoretical efficiency. However, the high cost and limited durability of platinum-based catalysts for the sluggish oxygen reduction reaction (ORR) at the cathode severely restrict their scalability and practical application. To address these critical challenges, this study explores a groundbreaking approach to developing ORR catalysts with enhanced performance and reduced costs. We present a novel Pd3Cu alloy, innovatively modified with N-doped carbon aerogels, synthesized via a simple self-assembly and freeze-drying method. The three-dimensional carbon aerogel-based porous structures provide diffusion channels for oxygen molecules, excellent electrical conductivity, and abundant ORR reaction sites. The Pd3Cu@2NC-20% aerogel exhibits a remarkable enhancement in ORR activity, achieving a half-wave potential of 0.925 V, a limiting current density of 6.12 mA/cm2, and excellent long-term stability. Density functional theory (DFT) calculations reveal that electrons tend to transfer from the Pd atoms to the neighboring *O, leading to an increase in the negative charge around the *O. This, in turn, weakens the interaction between the catalyst surface and the *O and optimizes the elementary steps of the ORR process. Full article
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11 pages, 900 KiB  
Article
Aortic Valve Replacement with Rapid-Deployment Bioprostheses: Long-Term Single-Center Results After 1000 Consecutive Implantations
by Iuliana Coti, Paul Werner, Alexandra Kaider, Jasmine El-Nashar, Alfred Kocher, Guenther Laufer, Daniel Zimpfer and Martin Andreas
J. Clin. Med. 2025, 14(5), 1552; https://doi.org/10.3390/jcm14051552 - 26 Feb 2025
Viewed by 34
Abstract
Introduction: This study aimed to analyze long-term survival and valve-related adverse events after 1000 consecutive rapid-deployment surgical aortic valve replacements (RD-SAVRs) in a single center. Methods: A total of 1000 patients following RD-SAVR at our institution were included in a prospective database. Median [...] Read more.
Introduction: This study aimed to analyze long-term survival and valve-related adverse events after 1000 consecutive rapid-deployment surgical aortic valve replacements (RD-SAVRs) in a single center. Methods: A total of 1000 patients following RD-SAVR at our institution were included in a prospective database. Median follow-up was 68 months (IQR: 37–91). Preoperative and operative parameters, survival and valve-related adverse events were assessed. Results: Mean age was 73 ± 7 years (45% female). Median EuroSCORE II was 2.7% (IQR: 1.4–5.5). Concomitant procedures were performed in 50% of patients. In the case of isolated SAVR, minimally invasive access was conducted in 415 patients (83%). New early pacemaker implantation was required in 9.1%. Perioperative stroke was observed in 1.6%, and the cumulative incidence of thromboembolic and major bleeding events at 10 years was 8.1% (95% CI: 6.2–10.4%). The 5- and 10-year incidences of severe structural valve degeneration were 0.8% (95% CI: 0.3–2.1%) and 9.2% (95% CI: 4.5–15.9%). Overall re-intervention or re-operation with valve explantation occurred in 38 cases, with a 10-year incidence of 7.7% (95% CI: 5.0–11.2%). Overall 30-day mortality was 0.3% (n = 3) and survival at 1, 5 and 10 years FU was 95% (95% CI: 93–96%), 81% (95% CI: 78–84%) and 58% (95% CI: 51–64%). Age, diabetes, COPD and creatinine, concomitant procedures and acute indication were independent predictive factors of mortality. Conclusions: Rapid-deployment valves appear to support minimally invasive access and can be potentially used with low operative mortality in a real-world collective. Favorable durability with acceptable valve-related event rates and mortality were observed at long-term follow-up. Full article
(This article belongs to the Special Issue Current Concepts in Diagnosis and Therapy of Aortic Valve Disease)
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17 pages, 6251 KiB  
Article
High-Performance Oil Well Cement with Modified Calcium Carbonate Whiskers: Enhancing Durability Under HTHP Conditions
by Xingguo Liu, Jiankun Qin, Rongdong Dai, Hanguo Zhou, Xueyu Pang and Xuhui Chen
Materials 2025, 18(5), 1021; https://doi.org/10.3390/ma18051021 - 26 Feb 2025
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Abstract
This study investigates the effect of incorporating modified calcium carbonate whiskers, treated with tetraethyl orthosilicate (TEOS), to enhance the mechanical properties and sealing integrity of oil well cement under high-temperature and high-pressure (HTHP) conditions. Traditional cement systems are prone to brittleness and cracking [...] Read more.
This study investigates the effect of incorporating modified calcium carbonate whiskers, treated with tetraethyl orthosilicate (TEOS), to enhance the mechanical properties and sealing integrity of oil well cement under high-temperature and high-pressure (HTHP) conditions. Traditional cement systems are prone to brittleness and cracking under dynamic loads, leading to compromised wellbore sealing performance. Our findings demonstrate that fiber-toughened cement slurry improves the toughness and sealing performance of the cement annulus, maintaining gas tightness and mechanical integrity under cyclic alternating pressures at 150 °C. Specifically, the inclusion of 5% modified whisker fibers improves compressive strength by 24.5% and flexural strength by 43.3% while maintaining stable rheological and thickening properties. These results support the hypothesis that modified whisker fibers enhance the durability and sealing integrity of cement wellbores under extreme conditions, providing a practical solution for challenging cementing applications. Full article
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