Materials

19 pages, 2995 KB

Open AccessReview

Review of the Relationship Between the Composition, Strength, and Ultimate Tensile Strain of Engineering Geopolymer Composites

by Xiaomei Wan, Weili Guo, Jiahao Cong, Chen Wang and Mingjin Han

Materials 2025, 18(24), 5603; https://doi.org/10.3390/ma18245603 (registering DOI) - 13 Dec 2025

Abstract

Engineered Geopolymer Composites (EGC) combine the high ductility and multi-crack characteristics of traditional Engineered Cementitious Composites (ECC) with the sound low-carbon advantages of geopolymers, making them a research hotspot in the green high-performance materials. This study focuses on the influence of EGC composition [...] Read more.

Engineered Geopolymer Composites (EGC) combine the high ductility and multi-crack characteristics of traditional Engineered Cementitious Composites (ECC) with the sound low-carbon advantages of geopolymers, making them a research hotspot in the green high-performance materials. This study focuses on the influence of EGC composition (precursor, activator, fiber and fine aggregate) on its tensile properties and the curing regime for different precursor compositions. The reported results data (with ultimate tensile strain exceeding 2%) from recent EGC studies are collected and reviewed. It concludes the systems and mix proportion ranges that are beneficial to tensile properties in current EGC research: blended system of fly ash and slag as the precursor; blended system of sodium hydroxide and water glass (with a modulus ranging from 1.2 to 1.4 and an alkali equivalent from 4% to 8%) as the activator; PE fiber (with a content of 2.0% and an aspect ratio of 500–750) or PVA fiber (with a content of 1.8–2.0% and an aspect ratio of approximately 300) as the reinforced fiber; silica sand (with a particle size of 100–300 μm) as the fine aggregate. Different curing regimes are selected according to different precursor types, and segmented curing and normal-temperature curing are widely adopted currently. This study reveals the relationship between compressive strength and tensile strain. When the EGC matrix strength is in the range of 25–45 MPa, it is easier to achieve excellent ductility. This study provides a theoretical basis and design reference for the material optimization and engineering application of EGC. Full article

(This article belongs to the Section Construction and Building Materials)

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14 pages, 3366 KB

Open AccessArticle

Engineering WO₃ Nanostructures via Carboxylic Acid Anodization for Advanced Lithium-Ion Battery Anodes

by Elianny Da Silva, Javier Estarelles Nácher, Rut Sanchis, Vicenta González, Gemma Roselló-Márquez, Ramon Manuel Fernández-Domene, Rita Sánchez-Tovar and Benjamin Solsona

Materials 2025, 18(24), 5602; https://doi.org/10.3390/ma18245602 (registering DOI) - 13 Dec 2025

Abstract

WO₃ nanorods were fabricated following electrochemical anodization of tungsten, under controlled hydrodynamic conditions, in electrolytes containing three distinct carboxylic acids: citric, tartaric and L-aspartic acids, to study the influence of these complexing agents on the morphology and arrangement of the oxide layers. [...] Read more.

WO₃ nanorods were fabricated following electrochemical anodization of tungsten, under controlled hydrodynamic conditions, in electrolytes containing three distinct carboxylic acids: citric, tartaric and L-aspartic acids, to study the influence of these complexing agents on the morphology and arrangement of the oxide layers. The samples were characterized by FESEM, TEM and XRD, and electrochemical analyses (EIS and ECSA) to assess their potential as anode materials for lithium-ion batteries. This characterization showed the nanostructures anodized in the presence of tartaric acid exhibit uniform morphology and lower total charge transfer resistance associated with the nanostructured layer of WO₃ and cycling stability, resulting in more efficient electrochemical processes, better conductivity and stability, making these nanostructures promising for anodes in lithium-ion batteries. The cycling of the batteries was also conducted to understand the behavior of the nanostructures as anodes against metallic lithium. The results showed that the nanostructures analyzed in the presence of tartaric acid exhibited the best initial specific capacity, improving the capacity provided by the graphite ones. These samples also showed a good recovery after faster cycling. These findings demonstrate the effectiveness of complexing-agent-assisted anodization as a strategy for tailoring WO₃ nanostructures with enhanced electrochemical performance. Full article

(This article belongs to the Section Energy Materials)

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15 pages, 5221 KB

Open AccessArticle

Concertation of Anti-Reflective, Superhydrophobic Surface Based on Rational Assembly of Dual-Size Silica

by Lu Xu, Lei Niu, Shuqun Chen, Ting He, Junshu Wu, Jianbo Ai and Yongli Li

Materials 2025, 18(24), 5601; https://doi.org/10.3390/ma18245601 - 12 Dec 2025

Abstract

Silica-based multifunctional coatings hold great promise for applications in optical devices, lenses, and solar panels. Herein, we report a facile, low-temperature route to integrate super-hydrophobicity with high transparency and low haze. By precisely controlling particle gradation and applying fluorine passivation, a multi-scale structure [...] Read more.

Silica-based multifunctional coatings hold great promise for applications in optical devices, lenses, and solar panels. Herein, we report a facile, low-temperature route to integrate super-hydrophobicity with high transparency and low haze. By precisely controlling particle gradation and applying fluorine passivation, a multi-scale structure with micro-scale uniformity and nano-scale asperity was constructed. This unique architecture, combined with low surface energy, effectively reduces light scattering and enhances air trapping. Consequently, the coated glass achieves a high optical transmittance of 95.24% with a low haze of 0.97%, alongside a water contact angle of 153° and a sliding angle of 3°. The coating also exhibits distinct anti-reflection (an improvement of ~5.0% relative to the bare substrate) and self-cleaning properties. Furthermore, it demonstrates impressive robustness and durability, withstanding extreme conditions including cryogenic temperatures (−50 °C), hygrothermal environments, and long-term outdoor exposure. This work demonstrates the versatile potential of our strategy for fabricating highly transparent and superhydrophobic surfaces. Full article

(This article belongs to the Section Thin Films and Interfaces)

28 pages, 22964 KB

Open AccessArticle

The Influence of Model Orientation on the Surface Roughness of Polymeric Models Produced by FFF, mSLA, PJ, and SLS Methods

by Anna Bazan, Paweł Turek, Grzegorz Budzik, Piotr Niesłony, Roman Grygoruk and Przemysław Siemiński

Materials 2025, 18(24), 5600; https://doi.org/10.3390/ma18245600 - 12 Dec 2025

Abstract

The research methodology involved creating a 3D sample model that featured both flat and cylindrical surfaces inclined at angles ranging from 0° to 90° relative to the XY plane. The study investigated the surface topography of additively manufactured samples produced using various technologies, [...] Read more.

The research methodology involved creating a 3D sample model that featured both flat and cylindrical surfaces inclined at angles ranging from 0° to 90° relative to the XY plane. The study investigated the surface topography of additively manufactured samples produced using various technologies, including Fused Filament Fabrication (FFF), masked Stereolithography (mSLA), PolyJet (PJ), and Selective Laser Sintering (SLS). The focus was on how material type, print angle, and measurement location influenced the results. The materials used in the study included PLA, PETG, acrylic resins, PA2200, and VeroClear. Due to the optical properties of the materials used, measurements were carried out on replicas that were prepared using a RepliSet F5 silicone compound from Struers. Consequently, a methodology was developed for measuring surface roughness using the Alicona microscope based on these replicas. A 10× objective lens was used during the measurements, and the pixel size was 0.88 µm × 0.88 µm. Each time, an area of approximately 1 mm × 4 mm was measured. The lowest roughness values were observed for mSLA samples (Sa = 6.72–8.54 µm, Spk + Sk + Svk = 33.36–42.16 µm), whereas SLS exhibited the highest roughness (Sa = 27.86 µm, Spk + Sk + Svk = 183.79 µm). PJ samples exhibited intermediate roughness with significant anisotropy (Sa = 11.65 µm, Spk + Sk + Svk = 72.1 µm), which was strongly influenced by the print angle. FFF surfaces showed directional patterns and layer-dependent roughness, with the Sa parameter being the same (12.44 µm) for both PETG and PLA materials. The steepest slopes were observed for SLS surfaces (Sdq = 7.67), while mSLA exhibited the flattest microstructure (Sdq = 0.48–0.89). Statistical analysis confirmed that material type significantly influenced topography in mSLA, while print angle strongly affected PJ and FFF (although for FFF, further studies would be beneficial). The results of the research conducted can be used to develop a methodology for optimizing the printing process to achieve the required geometric surface structure. Full article

(This article belongs to the Special Issue 3D & 4D Printing—Metrological Problems)

17 pages, 7695 KB

Open AccessArticle

Composite Structure as a Stress Wave Barrier Zone Under Impulse Loading: Microscale Numerical Analysis of Attenuation

by Zuzana Murčinková, Dominik Sabol and Petr Baron

Materials 2025, 18(24), 5599; https://doi.org/10.3390/ma18245599 - 12 Dec 2025

Abstract

This study investigates the design factors of stress wave barrier zones intended for manufacturing machines under impulse loading, using polymer discontinuously reinforced composites with specified internal microstructures, which effectively suppress stress at the wave front, promote uniform stress distribution, improve impact resistance, and [...] Read more.

This study investigates the design factors of stress wave barrier zones intended for manufacturing machines under impulse loading, using polymer discontinuously reinforced composites with specified internal microstructures, which effectively suppress stress at the wave front, promote uniform stress distribution, improve impact resistance, and reduce vibrations and noise. Two-dimensional representative unit cells and explicit finite element simulations were used to analyze stress wave propagation under impulse loading. The effects of inclusion shape, orientation, distribution, interlayer, and size of the interface on stress wave scattering and attenuation were examined. In our models, hollow inclusions demonstrated 20.6% higher attenuation compared to solid inclusions, with the hollow fiber inclusion showing the most significant improvement. Inclusion orientation relative to the stress wave direction affected attenuation by 18.5%, while redistribution of inclusions and addition of a compliant interlayer contributed additional increments of 3–11%. These results highlight the critical role of microscale topology in stress barrier zone designing, such that the combined adjustment of inclusion shape, orientation, interlayer presence, and spatial distribution provides an effective strategy to maximize stress wave attenuation. Full article

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18 pages, 6809 KB

Open AccessArticle

Laser Directed Energy Deposition of Inconel625 to Ti6Al4V Heterostructure via Nonlinear Gradient Transition Interlayers

by Wenbo Wang, Guojian Xu, Yaqing Hou, Chenyi Zhang, Guohao Cui, Pengyu Qin, Juncheng Shang and Xiuru Fan

Materials 2025, 18(24), 5598; https://doi.org/10.3390/ma18245598 - 12 Dec 2025

Abstract

Heterostructure (HS) refers to a class of structural materials composed of two or more different chemical components or crystal structures. Integration of Inconel 625 (IN625) nickel-based superalloy and Ti6Al4V (TC4) titanium alloy to a HS material offers a promising strategy to achieve graded [...] Read more.

Heterostructure (HS) refers to a class of structural materials composed of two or more different chemical components or crystal structures. Integration of Inconel 625 (IN625) nickel-based superalloy and Ti6Al4V (TC4) titanium alloy to a HS material offers a promising strategy to achieve graded thermo-mechanical properties, extended service temperature ranges, and significant weight reduction, which are highly desirable in aerospace applications. However, obtaining a better metallurgical bonding between the two alloys remains a critical challenge. In this study, laser directed energy deposition (L-DED) technology was employed to fabricate IN625/TC4 HS materials with a nonlinear gradient transition, following systematic investigations into the phase composition and crack sensitivity of IN625/TC4 gradient layers prepared from mixed powders of varying compositions. In addition, microstructure, phase distribution, and mechanical properties of HS materials at room temperature were characterized. The metallurgical defect-free IN625/TC4 HS material was successfully prepared, featuring a smooth transition of microstructure, reduced cracking sensitivity, and reliable metallurgical bonding. Furthermore, a novel design concept and illustrative reference for the L-DED fabrication of N625/TC4 HS material with excellent comprehensive performance was presented, while providing a theoretical metallurgical basis and data support for the potential applications of IN625/TC4 HS materials in the field of aerospace. Full article

(This article belongs to the Special Issue Development of Advanced Aluminum and Magnesium Alloys: Microstructure, Mechanical Properties and Processing—2nd Edition)

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18 pages, 2806 KB

Open AccessArticle

Flexural Performance of CLT Plates Under Coupling Effect of Load and Moisture Content

by Jinpeng Xu, Tianyi Zhang, Huanyu Wang, Aiguo Zhao and Peng Wu

Materials 2025, 18(24), 5597; https://doi.org/10.3390/ma18245597 - 12 Dec 2025

Abstract

As a green-material structure, cross-laminated timber (CLT) has attracted increasing attention and applications in construction. This study presents an analytical model for a CLT plate under the coupling effect of load and moisture content, where the moisture-induced deformation and moisture-dependent properties are both [...] Read more.

As a green-material structure, cross-laminated timber (CLT) has attracted increasing attention and applications in construction. This study presents an analytical model for a CLT plate under the coupling effect of load and moisture content, where the moisture-induced deformation and moisture-dependent properties are both considered. In the analytical model, state-space equations for moisture variables and for stresses and displacements in the CLT plate are established based on moisture diffusion theory and three-dimensional elasticity theory, respectively. Using the transfer matrix method, the relationships of moisture variables, stresses, and displacements between any two layers of the CLT plates are formulated. The analytical solutions are then determined by the load and moisture conditions applied to the top and bottom surfaces. Comparative analysis indicates that the proposed solution surpasses finite element methods in both computational accuracy and efficiency. In addition, the stress and displacement patterns of CLT plates under pure load and pure moisture conditions, as well as their interrelations, are investigated through a decoupled analysis. An applicable modified superposition principle is then proposed. Finally, a detailed parametric study is conducted to examine the effects of moisture distribution and wood species. Full article

(This article belongs to the Special Issue Modeling and Mechanical Analysis of Materials and Structures in Civil Engineering)

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19 pages, 4089 KB

Open AccessArticle

Improving the Strength of Eucalyptus Wood Joints Through Optimized Rotary Welding Conditions

by Jiankun Liang, Xiao Zhong, Yuqi Yang, Guifen Yang, Shuang Yin, Feiyan Gong, Chuchu Chen, Huali Li, Tong Meng, Yulan Jian, De Li, Caihong Long, Zhixian Song and Zhigang Wu

Materials 2025, 18(24), 5596; https://doi.org/10.3390/ma18245596 - 12 Dec 2025

Abstract

Conventional wood connections rely on adhesives and metal fasteners, causing environmental concerns. Wood rotary welding offers an adhesive-free alternative. This study systematically investigated rotary welding of eucalyptus wood, evaluating process parameters’ effects on joint performance. Chemical and microstructural transformations at the welding interface [...] Read more.

Conventional wood connections rely on adhesives and metal fasteners, causing environmental concerns. Wood rotary welding offers an adhesive-free alternative. This study systematically investigated rotary welding of eucalyptus wood, evaluating process parameters’ effects on joint performance. Chemical and microstructural transformations at the welding interface were characterized using FT-IR, XPS, XRD, SEM, and TGA. Optimal parameters significantly enhanced connection strength compared to unwelded specimens. The welding process induced partial degradation of hemicellulose and cellulose, forming new chemical bonds and increasing carbonyl compounds. XRD revealed increased wood crystallinity, while SEM showed tighter interfaces with enhanced mechanical interlocking. TGA confirmed improved thermal stability at the welded interface. The findings demonstrate that rotary welding improves eucalyptus wood joint strength through combined chemical, thermal, and structural modifications, providing guidance for optimizing welding protocols in sustainable wood manufacturing. Full article

(This article belongs to the Special Issue Synthesis–Processing–Structure–Property Interrelationship of Multifunctional Polymeric Materials and Natural Polymers)

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18 pages, 9997 KB

Open AccessArticle

Directional Coupling of Surface Plasmon Polaritons at Exceptional Points in the Visible Spectrum

by Amer Abdulghani, Salah Abdo, Khalil As’ham, Ambali Alade Odebowale, Andrey E. Miroshnichenko and Haroldo T. Hattori

Materials 2025, 18(24), 5595; https://doi.org/10.3390/ma18245595 - 12 Dec 2025

Abstract

Robust control over the coupling and propagation of surface plasmon polaritons (SPPs) is essential for advancing various plasmonic applications. Traditional planar structures, commonly used to design SPP directional couplers, face limitations such as low extinction ratios and design complexities. These issues frequently hinder [...] Read more.

Robust control over the coupling and propagation of surface plasmon polaritons (SPPs) is essential for advancing various plasmonic applications. Traditional planar structures, commonly used to design SPP directional couplers, face limitations such as low extinction ratios and design complexities. These issues frequently hinder the dense integration and miniaturisation of photonic systems. Recently, exceptional points (EPs)—unique degeneracies within the parameter space of non-Hermitian systems—have garnered significant attention for enabling a range of counterintuitive phenomena in non-conservative photonic systems, including the non-trivial control of light propagation. In this work, we develop a rigorous temporal coupled-mode theory (TCMT) description of a non-Hermitian metagrating composed of alternating silicon–germanium nanostrips and use it to explore the unidirectional excitation of SPPs at EPs in the visible spectrum. Within this framework, EPs, typically associated with the coalescence of eigenvalues and eigenstates, are leveraged to manipulate light propagation in nonconservative photonic systems, facilitating the refined control of SPPs. By spatially modulating the permittivity profile at a dielectric–metal interface, we induce a passive parity–time (

PT

)-symmetry, which allows for refined tuning of the SPPs’ directional propagation by optimising the structure to operate at EPs. At these EPs, a unidirectional excitation of SPPs with a directional intensity extinction ratio as high as 40 dB between the left and right excited SPP modes can be reached, with potential applications in integrated optical circuits, visible communication technologies, and optical routing, where robust and flexible control of light at the nanoscale is crucial. Full article

(This article belongs to the Section Optical and Photonic Materials)

28 pages, 2901 KB

Open AccessArticle

The Effect of Continuous Carbon Fiber Reinforcement on 3D-Printed Honeycomb and Re-Entrant Sandwich Panels Subjected to In-Plane Compression

by Andrei Nenciu, Dragoş Alexandru Apostol and Dan Mihai Constantinescu

Materials 2025, 18(24), 5594; https://doi.org/10.3390/ma18245594 - 12 Dec 2025

Abstract

This study examines the in-plane compression behavior of sandwich panels produced with additive manufacturing. This study focuses on two types of honeycomb unit cell topologies with larger dimensions: a hexagonal one and a re-entrant one. For each panel geometry, two material configurations were [...] Read more.

This study examines the in-plane compression behavior of sandwich panels produced with additive manufacturing. This study focuses on two types of honeycomb unit cell topologies with larger dimensions: a hexagonal one and a re-entrant one. For each panel geometry, two material configurations were examined: Onyx (a nylon-based composite) and Onyx reinforced with 10% continuous carbon fibers (CCFs) by mass. The objective was to assess the influence of fiber reinforcement on the mechanical performance and deformation response of the panel structures. In-plane compression tests were conducted to determine the stiffness, strength, and failure modes of the specimens. Additionally, the digital image correlation (DIC) technique was used to capture full-field strain distributions and analyze local deformation mechanisms during loading. The results revealed distinct mechanical responses between the two geometries: the re-entrant structure exhibited auxetic behavior and enhanced energy absorption characteristics. Although reinforced honeycomb panels have an average load capacity that is 35% higher, they fail at a displacement that is approximately 55% smaller compared to unreinforced panels. Despite accounting for only 25% of the total number of layers and 10% of the panel’s mass, the reinforcement achieved superior strength. Re-entrant panel testing showed a 25% force increase in favor of the reinforced variant. They fail at a displacement that is 36.5% greater than that of reinforced honeycombs. This demonstrates a more compliant response while also maintaining 4.9% greater strength, indicating the superior behavior of auxetic reinforced sandwich panels. Introducing CCF reinforcement increased the load-bearing capacity and reduced localized strain concentrations without altering the overall deformation pattern. These findings suggest that enhancing materials can increase the strength and flexibility of 3D-printed re-entrant structures, providing valuable insights for lightweight design and optimized material use in structural applications. Full article

(This article belongs to the Special Issue Novel Materials for Additive Manufacturing)

17 pages, 16918 KB

Open AccessArticle

Key Factors Influencing the Mechanical Properties of Binodal Decomposed Metallic Glass Composites

by Yongwei Wang, Guangping Zheng and Mo Li

Materials 2025, 18(24), 5593; https://doi.org/10.3390/ma18245593 - 12 Dec 2025

Abstract

Structural heterogeneity plays a crucial role in enhancing the mechanical properties of metallic glasses (MGs) by impeding the propagation of shear bands (SBs). Metallic glass matrix composites (MGCs) consisting of reinforcements are of great interest as they enhance the mechanical performance of brittle [...] Read more.

Structural heterogeneity plays a crucial role in enhancing the mechanical properties of metallic glasses (MGs) by impeding the propagation of shear bands (SBs). Metallic glass matrix composites (MGCs) consisting of reinforcements are of great interest as they enhance the mechanical performance of brittle MGs. However, managing the dispersity of hetero-phases within the glassy matrix presents technical challenges due to surface tension and thermal property incompatibility. Binodal phase separation is an effective approach for fabricating MGCs with uniformly dispersed glassy droplets or particles. The species of matrix and characteristics of particle reinforcements significantly influence mechanical properties. This study theoretically examines how the fraction, size, and variety of particle reinforcements influence performance using finite element models based on free volume theory. The synergistic mechanisms for performance tuning involve stress fields generated by particle reinforcements that modify the nucleation and propagation of SBs in the matrix. Additionally, the size effect of particles depends on their interaction with SBs. This comprehensive understanding could substantially enhance the design and optimization for MGCs. Full article

(This article belongs to the Special Issue Next-Generation Alloys: Nanostructured Metals, Complex Steels, and Multi-Component Systems)

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18 pages, 1784 KB

Open AccessArticle

Numerical Investigation on Tensile and Compressive Properties of 3D Four-Directional Braided Composites

by Longcan Chen, Feilong Dou, Jun Wang, Guangxi Li, Binchao Li, Jin Zhou, Yong Xue, Shenghao Zhang and Di Zhang

Materials 2025, 18(24), 5592; https://doi.org/10.3390/ma18245592 - 12 Dec 2025

Abstract

This study investigates the influence of braiding angles on the mechanical behavior and damage mechanisms of three-dimensional (3D) braided composites under uniaxial compressive and tensile loading. By integrating uniaxial compression and tension tests with finite element (FE) analysis, the relationships between mesoscale damage [...] Read more.

This study investigates the influence of braiding angles on the mechanical behavior and damage mechanisms of three-dimensional (3D) braided composites under uniaxial compressive and tensile loading. By integrating uniaxial compression and tension tests with finite element (FE) analysis, the relationships between mesoscale damage initiation, propagation, and the macroscopic mechanical properties were revealed. Results demonstrate that the 3D4d-20° model exhibits higher stiffness and compressive strength but lower compressive failure strain compared to the 3D4d-40° model, attributed to differences in fiber spatial arrangement and matrix cracking propagation. Conversely, the 3D4d-40° model shows enhanced tensile performance but greater matrix-dominated damage under tension. Moreover, as the braiding angle increases, the ratio of tensile strength to compressive strength in 3D braided composites decreases accordingly. Comparative analysis of damage evolution pathways reveals that smaller braiding angles (20°) initiate damage earlier under compression, while larger angles (40°) promote transverse fiber bundle failure and matrix degradation. This research not only elucidates the underlying microscale damage mechanisms of 3D braided composites under compression loading but also highlights the differences in damage patterns between compressive and tensile loading, providing theoretical foundations for structural design and performance optimization of such composite materials. Future work will focus on incorporating interfacial effects and manufacturing-induced defects to refine the model further. Full article

(This article belongs to the Section Advanced Composites)

39 pages, 17922 KB

Open AccessArticle

Efficient Tetracycline Adsorption by KOH-Activated Yak-Dung Biochar: Mechanistic Insights

by Wei Li, Yi Wu, Zengrui Gu, Chen Yang, Jiacheng Song, Jiaxuan Li, Yahao Zhang, Xuebin Lu and Jian Xiong

Materials 2025, 18(24), 5591; https://doi.org/10.3390/ma18245591 - 12 Dec 2025

Abstract

In this study, yak dung was used as a precursor to prepare biochar (KYBC600) via high-temperature pyrolysis and KOH modification for the adsorption of tetracycline hydrochloride (TCH) from aqueous solution. Compared with commonly used biomass feedstocks such as straw and fruit shells, the [...] Read more.

In this study, yak dung was used as a precursor to prepare biochar (KYBC600) via high-temperature pyrolysis and KOH modification for the adsorption of tetracycline hydrochloride (TCH) from aqueous solution. Compared with commonly used biomass feedstocks such as straw and fruit shells, the resource-oriented utilization of yak dung holds dual significance: it contributes to regional environmental management and enables high-value conversion of waste, underscoring its distinct regional relevance and potential for synergistic environmental governance. The physicochemical properties of KYBC600 were characterized using BET surface area analysis, FTIR, XRD, and SEM. Adsorption behavior and mechanisms were systematically investigated through kinetic, isotherm, and thermodynamic studies, supplemented by response surface methodology (RSM). The results demonstrated that the adsorption of TCH onto KYBC600 followed pseudo-second-order kinetics and the Langmuir model, with a maximum adsorption capacity of 54.10 mg·g⁻¹. Multiple synergistic mechanisms governed the adsorption process, including pore filling, π–π stacking, electrostatic interactions, hydrogen bonding, and complexation with Ca²⁺, with chemical adsorption playing a dominant role. KYBC600 demonstrated excellent adsorption performance and regeneration capability across a wide pH range and in various real water matrices. This study provides novel perspectives on the resource utilization of livestock waste in plateau regions and provides a technical reference for treating low-concentration TCH-containing wastewater. Full article

(This article belongs to the Section Carbon Materials)

34 pages, 19352 KB

Open AccessReview

Gas Turbine Blade Failures Repaired Using Laser Metal Additive Remanufacturing

by Changjun Chen, Min Zhang, Haodong Liu and Qingfeng Yang

Materials 2025, 18(24), 5590; https://doi.org/10.3390/ma18245590 - 12 Dec 2025

Abstract

The production of reliable turbo machinery, particularly gas turbine blades, is a major global challenge. This capability serves as a key indicator of a nation’s industrial base, technological prowess, and comprehensive strength. Critical components in aircraft engines and gas turbines operate under extreme [...] Read more.

The production of reliable turbo machinery, particularly gas turbine blades, is a major global challenge. This capability serves as a key indicator of a nation’s industrial base, technological prowess, and comprehensive strength. Critical components in aircraft engines and gas turbines operate under extreme conditions, including high temperatures, high pressures, and substantial mechanical stresses. Consequently, there is a growing urgency to develop cost-effective and time-efficient repair strategies to enhance engine performance and efficiency. However, many mission-critical parts, especially high-pressure (HP) blades, are prone to severe damage. Moreover, taking equipment offline for blade maintenance and repair is a time-consuming process. It is also highly costly to restore these essential components to full functionality. Since 1996, researchers have focused on applying laser metal deposition (LMD) additive manufacturing technology for high-performance repair and remanufacturing of aerospace engines and industrial gas turbine (IGT) blades. Empirical studies have demonstrated that depositing a high-quality, erosion-resistant protective coating on the leading edge of HP blades effectively extends the service life of turbine blades in both aircraft engines and industrial gas turbines. This study systematically outlines the technical workflow of the proposed methodology and provides a concise perspective on emerging development trends. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

23 pages, 2418 KB

Open AccessArticle

Process Design of Vinyl-Coated Metal Sheet Stamping for Prevention of Delamination and Wrinkling by DNN-Based Multi-Objective Optimization

by Min-Gi Kim, Jae-Chang Ryu, Chan-Joo Lee, Jin-Seok Jang and Dae-Cheol Ko

Materials 2025, 18(24), 5589; https://doi.org/10.3390/ma18245589 - 12 Dec 2025

Abstract

The increasing use of vinyl-coated metal (VCM) sheets in home appliances requires robust forming processes to prevent defects such as delamination and wrinkling, especially under elevated temperatures and humidity. This study presents a deep neural network (DNN)-based multi-objective optimization framework to determine optimal [...] Read more.

The increasing use of vinyl-coated metal (VCM) sheets in home appliances requires robust forming processes to prevent defects such as delamination and wrinkling, especially under elevated temperatures and humidity. This study presents a deep neural network (DNN)-based multi-objective optimization framework to determine optimal stamping parameters for VCM sheets. A delamination limit diagram (DLD) is experimentally established by combining limit dome height tests with immersion tests, defining the critical strain boundary under environmentally conditions. A finite element (FE) based dataset of four process variables was then used to train a DNN surrogate model with high predictive accuracy. Using the trained DNN model, Pareto-based optimization identifies nondominated solutions balancing delamination and wrinkling. The optimal condition was validated by FE simulation, confirming simultaneous suppression of both defects within the DLD. The proposed DNN–Pareto framework provides and efficient and reliable tool for defect prediction and optimization in VCM stamping, ensuring high surface quality and environmental durability. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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14 pages, 4122 KB

Open AccessArticle

Floatable Syntactic Magnesium Foam as a Marangoni-Induced Propulsion Microboat

by Gyorgy Thalmaier, Niculina Argentina Sechel and Ioan Vida-Simiti

Materials 2025, 18(24), 5588; https://doi.org/10.3390/ma18245588 - 12 Dec 2025

Abstract

This study reports the successful fabrication and application of floatable syntactic foams derived from fine magnesium powder (<45 µm) utilizing expanded perlite (0.25 g/cm³, 0.2–0.4 mm) as the pore former. Sample disks with densities as low as 0.9 g/cm³ were [...] Read more.

This study reports the successful fabrication and application of floatable syntactic foams derived from fine magnesium powder (<45 µm) utilizing expanded perlite (0.25 g/cm³, 0.2–0.4 mm) as the pore former. Sample disks with densities as low as 0.9 g/cm³ were produced via the classical press and sinter process. To ensure reasonable mechanical properties, the specimens were formed under a pressure of 200 MPa in a hardened steel die, followed by high-vacuum sintering (~3 × 10⁻⁶ torr) at 640 °C for 1 h. The resulting foams exhibited sufficient mechanical strength to allow for precision machining into a microboat. We demonstrated their potential use as a Marangoni-induced microswimmer. Spontaneous locomotion was observed when ethanol was used as a propellant, which generates a surface tension gradient between the upper and rear parts of the swimmer. The microboats achieved propulsion speeds of approximately 160 mm/s when propelled by a 95% ethanol + 5% ink mixture. Using a small volume (~4 µL) of the alcohol mixture, the swimmer could cover distances exceeding 350 mm. Full article

(This article belongs to the Special Issue Obtaining and Characterization of New Materials (5th Edition))

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15 pages, 1819 KB

Open AccessArticle

Development of a High-Sensitivity Humidity Sensor Using Fiber Bragg Grating Coated with LiCl@UIO-66-Doped Hydrogel

by Binxiaojun Liu, Zelin Gao, Runqi Yao, Liyun Ding and Xusheng Xia

Materials 2025, 18(24), 5587; https://doi.org/10.3390/ma18245587 - 12 Dec 2025

Abstract

Humidity monitoring is essential in industrial and scientific scenarios, yet remains challenging for compact EMI (electromagnetic interference)-immune sensors with high sensitivity and robust stability. A novel fiber Bragg grating (FBG) humidity sensor was developed, which incorporated LiCl@UIO-66 microfillers within a poly(N-isopropylacrylamide) (PNIPAM) hydrogel [...] Read more.

Humidity monitoring is essential in industrial and scientific scenarios, yet remains challenging for compact EMI (electromagnetic interference)-immune sensors with high sensitivity and robust stability. A novel fiber Bragg grating (FBG) humidity sensor was developed, which incorporated LiCl@UIO-66 microfillers within a poly(N-isopropylacrylamide) (PNIPAM) hydrogel matrix. Structural characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared (FTIR) spectroscopy confirms that LiCl is confined or nanodispersed within intact UIO-66, and that interfacial ion–dipole/hydrogen-bonding exists between the composite and water. Systematic variation in coating time (30–720 min) reveals monotonic growth of the total wavelength shift with diminishing returns. A coating time of 4 h was found to yield a wavelength shift of approximately 0.38–0.40 nm, representing about 82% of the maximum shift observed at 12 h, while maintaining good quasi-linearity and favorable kinetics. Calibration demonstrates sensitivities of 6.7 pm/%RH for LiCl@UIO-66_33 and 10.6 pm/%RH for LiCl@UIO-66_51 over ~0–95%RH. Stepwise tests show response times t90 of ≈14 min for both composites, versus ≈30 min for UIO-66 and ≈55 min for neat PNIPAM. Long-term measurements on the 51 wt.% device are stable over the first ~20 days, with only slow drift thereafter, and repeated humidity cycling is reversible. The wavelength decreases monotonically during drying while settling time increases toward low RH. The synergy of hydrogel–MOF–salt underpins high sensitivity, accelerated transport, and practical stability, offering a scalable route to high-performance optical humidity sensing. Full article

(This article belongs to the Special Issue Reinforced Polymer Composites with Natural and Nano Fillers)

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27 pages, 8431 KB

Open AccessArticle

A Comparison Between the Growth of Naturally Occurring Three-Dimensional Cracks in Scalmalloy^® and Pre-Corroded 7085-T7452 and Its Implications for Additively Manufactured Limited-Life Replacement Parts

by Daren Peng, Shareen S. L. Chan, Ben Main, Andrew S. M. Ang, Nam Phan, Michael R. Brindza and Rhys Jones

Materials 2025, 18(24), 5586; https://doi.org/10.3390/ma18245586 - 12 Dec 2025

Abstract

This paper is the first to reveal that the conventionally built aluminium alloy (AA) 7085-T7452 has mechanical properties, viz: a yield stress, ultimate strength, and an elongation to failure, that are similar to that of laser powder bed fusion (LPBF) built Scalmalloy^® [...] Read more.

This paper is the first to reveal that the conventionally built aluminium alloy (AA) 7085-T7452 has mechanical properties, viz: a yield stress, ultimate strength, and an elongation to failure, that are similar to that of laser powder bed fusion (LPBF) built Scalmalloy^®. Following this observation, the growth of cracks that nucleated from corrosion pits in AA7085-T7452 specimens that had been exposed to a 5 wt% NaCl salt fog environment at 35 °C according to ASTM B117-19 standard for fourteen days is then studied. The specimen geometries were chosen to be identical to those associated with a similar study on Boeing Space, Intelligence, and Weapon Systems (BSI&WS) LPBF built Scalmalloy^®. This level of prior exposure led to pits in AA7085-T7452 that were approximately 0.5 mm deep with a surface width/diameter of up to approximately 1.5 mm. These pit sizes are broadly consistent with those leading to fatigue crack growth (FCG) in AA 7050-T7451 structural parts on the RAAF F/A-18 Classic Hornet fleet operating in a highly corrosive environment. Fatigue tests on these AA7085-T7452 specimens, under the same spectrum as used in the BSI&WS LPBF Scalmalloy^® study, reveals that AA7085-T7452 and Scalmalloy^® have similar crack growth histories. This, in turn, leads to the discovery that the growth of naturally occurring three-dimensional (3D) cracks in AA 7085-T7452 could be predicted using the crack growth equation developed for BSI&WS LPBF Scalmalloy^®, albeit with allowance made for their different fracture toughness’s. These findings suggest that Scalmalloy^® may be suitable for printing parts for both current and future attritable aircraft. Full article

(This article belongs to the Section Manufacturing Processes and Systems)

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16 pages, 11074 KB

Open AccessArticle

Investigation of the Phosphorus Effect on Solidification Cracking in Cu–Steel Single-Mode Fiber-Laser Welds for Reliable Li-Ion Battery Busbar Assembly

by Ye-Ji Yoo, Jeong-Hoi Koo and Eun-Joon Chun

Materials 2025, 18(24), 5585; https://doi.org/10.3390/ma18245585 - 12 Dec 2025

Abstract

Solidification cracking is a critical defect in Cu–steel dissimilar laser welding for cylindrical lithium-ion battery busbar assembly, yet the metallurgical role of phosphorus (P) in crack formation has not been quantitatively established. In this study, the influence of phosphorus in the coating layer [...] Read more.

Solidification cracking is a critical defect in Cu–steel dissimilar laser welding for cylindrical lithium-ion battery busbar assembly, yet the metallurgical role of phosphorus (P) in crack formation has not been quantitatively established. In this study, the influence of phosphorus in the coating layer on weld solidification behavior was clarified by preparing Cu substrates with four different coating conditions—Ni–P-coated Cu (10 and 50 μm) and pure Ni-coated Cu (10 and 50 μm)—and performing high-speed single-mode fiber-laser welding under identical heat-input conditions. Shear-tensile testing, EPMA-based microstructural analysis, and Thermo-Calc solidification calculations were combined to correlate P segregation with solidification cracking susceptibility. The Ni–P 10 μm coating generated severe solidification cracking compared with the pure Ni 50 μm coating, which was attributed to excessive P enrichment in the terminal liquid phase (up to 8.8 mass%). This enrichment significantly expanded the mushy-zone width to approximately 869 K, yielding a highly solidification crack-susceptible fusion zone. In contrast, 50 μm pure Ni coatings produced narrow mushy-zone widths (200–400 K) and extremely low residual P levels (~0.1 mass%), resulting in fully crack-free microstructures. The 50 μm Ni coating exhibited the highest shear-tensile strength and largest rupture displacement among all conditions, confirming that suppression of P segregation directly improves both structural integrity and mechanical performance. Overall, this study demonstrates that phosphorus enrichment critically governs the solidification-cracking susceptibility of Cu–steel dissimilar welds by widening the solidification temperature range. Eliminating P from the coating layer and applying an adequately thick pure Ni coating constitute highly effective strategies for achieving crack-free, mechanically robust welds in lithium-ion battery busbar manufacturing. Full article

(This article belongs to the Special Issue Welding and Joining Technologies for Advanced Structural Alloys and Multifunctional Materials)

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