Materials

19 pages, 6994 KB

Open AccessArticle

Corrosion Behavior of Bubble Tubes in Glass Curing Furnaces Under the Heat–Flow Coupling Effect

by Heyi Guo, Ce Zheng, Yingjv Li, Qiuyan Huang, Qingbin Zhao, Minhang Sun and Yuansheng Yang

Materials 2026, 19(11), 2429; https://doi.org/10.3390/ma19112429 - 5 Jun 2026

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Abstract

The bubble tube of a glass curing furnace was subjected to extreme heat–flow coupling conditions for a long time due to the scouring of melt flow caused by the gas flow bubbling in a high-temperature molten glass environment at 1150 °C, resulting in [...] Read more.

The bubble tube of a glass curing furnace was subjected to extreme heat–flow coupling conditions for a long time due to the scouring of melt flow caused by the gas flow bubbling in a high-temperature molten glass environment at 1150 °C, resulting in severe corrosion and structural failure. This paper conducts post-service sampling analysis of an Inconel 690 bubble tube, and systematically studies its corrosion morphologies, product distribution and corrosion mechanisms. The results show that the outer wall of the bubble tube undergoes an oxidation reaction in the high-temperature molten glass to form a Cr-rich oxide layer. However, local spalling occurs under the scouring of the molten glass flow, resulting in continuous corrosion. The corrosion behavior shows obvious asymmetry. The average corrosion rate near the bubble flow side (the inner curve side, 0.118 mm/day) is significantly higher than that on the outer side (0.051 mm/day) due to the higher partial pressure of oxygen and greater flow rate of molten glass. It reveals the synergistic mechanism by which fluid scouring continuously removes the protective Cr-rich oxide scale, thereby accelerating the oxidation–erosion cycle under the heat-flow coupling effect. The results provided experimental evidence and theoretical reference for the material optimization and life prediction of bubble tubes. Full article

(This article belongs to the Section Corrosion)

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18 pages, 3322 KB

Open AccessArticle

Acoustic-Emission-Based Multiscale Tensile Constitutive Model for Ultra-High-Performance Concrete Considering Steel-Fiber Parameters and Beam-Scale Validation

by Zhenyu Bao, Qing Wang, Jinlan Deng and Meng Zhang

Materials 2026, 19(11), 2428; https://doi.org/10.3390/ma19112428 - 5 Jun 2026

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Abstract

Ultra-high-performance concrete (UHPC) has attracted extensive attention because of its superior mechanical performance and durability. However, many existing tensile constitutive models are still obtained mainly by fitting macroscopic stress–strain curves, and the coupling among tensile damage development, steel-fiber parameters, and structural-scale response has [...] Read more.

Ultra-high-performance concrete (UHPC) has attracted extensive attention because of its superior mechanical performance and durability. However, many existing tensile constitutive models are still obtained mainly by fitting macroscopic stress–strain curves, and the coupling among tensile damage development, steel-fiber parameters, and structural-scale response has not been sufficiently clarified. In this work, an acoustic-emission-informed tensile damage model was established for UHPC. Direct tensile tests were carried out on UHPC specimens containing steel fibers with aspect ratios of 43, 65, and 100 and volume fractions ranging from 0.5% to 3.0%, while acoustic emission signals were collected during loading. The normalized cumulative AE count was adopted as a damage indicator, and its evolution with tensile strain was described using a Weibull-type function. A fiber factor combining fiber volume fraction and aspect ratio was further incorporated into the damage constitutive equation. The proposed relationship was checked against 14 independent tensile datasets reported in the literature. After correction, the mean relative error of the predicted model parameter was reduced to 2.6%, with a standard deviation of 4.1%, and the fitted stress–strain curves all achieved R² values above 0.85. The constitutive model was then implemented in ABAQUS for the simulation of reinforced UHPC beams. By introducing a member-level reduction coefficient of μ = 0.84, the numerical load–deflection curve showed improved agreement with the experimental beam response. The coefficient is empirical and is applicable only to the beam configuration investigated here unless further validation is performed. Overall, the proposed model provides a damage-based link among AE monitoring, steel-fiber reinforcement parameters, and member-scale numerical analysis. Full article

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

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20 pages, 69209 KB

Open AccessArticle

A Study on the Orientation Relationship and Interface Structure of the α₂ (Ti₃Al) and B2 Phases in the TiAl-Nb Sheets After Heat Treatment

by Jiyao Liu, Laiqi Zhang, Muyu Li, Dan Yao, Yixu Niu, Bin Li and Yahu Song

Materials 2026, 19(11), 2427; https://doi.org/10.3390/ma19112427 - 5 Jun 2026

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Abstract

In this paper, TiAl-Nb sheets were fabricated via elemental foil metallurgy using Ti, Al, and Nb foils. The microstructure of the TiAl-Nb sheet was regulated by a two-step heat treatment process, which involved short-time holding at 1410 °C, 1430 °C and 1450 °C, [...] Read more.

In this paper, TiAl-Nb sheets were fabricated via elemental foil metallurgy using Ti, Al, and Nb foils. The microstructure of the TiAl-Nb sheet was regulated by a two-step heat treatment process, which involved short-time holding at 1410 °C, 1430 °C and 1450 °C, followed by long-time holding at 1150 °C. Subsequently, the microstructure of the sheet was analyzed, emphasizing the orientation relationship and interface structure between the B2/β phase, Ti₃Al phase, and the TiAl matrix. The results indicated that, subsequent to diverse heat treatment processes, the TiAl-Nb sheet comprised α₂(Ti₃Al) and B2/β phases at the grain boundaries and within the grains, whereas the matrix structure was γ(TiAl). After TiAl-Nb sheets were heat-treated at 1410 °C for 3 min and then at 1150 °C for 2 h, the microstructure of the sheets was observed to be composed of relatively fine lamellar structures. The TiAl phase, Ti₃Al phase and B2/β phase existed in the form of coherent interfaces with extremely small misfit degrees. The interfacial energy between phases was small, making it easier to obtain an alloy microstructure with a higher content of the γ(TiAl) phase. To further provide a basis for the selection of heat treatment processes, the matrix method analysis indicated that, after holding at 1410 °C for 3 min and subsequently at 1150 °C for 2 h, the TiAl phase and Ti₃Al phase in the sheet structure exhibited obvious preferred orientations. A short β-phase holding (3 min) followed by a long α + γ two-phase holding was an effective process route for obtaining a fine lamellar structure. Full article

(This article belongs to the Section Metals and Alloys)

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23 pages, 23283 KB

Open AccessArticle

Multi-Scale Investigation of Carbonation Evolution and Microstructural Changes in Concrete Containing Fly Ash and Silica Fume

by Jianghuai Zhan, Lepeng Huang, Tiansheng Shang, Xuanyi Xue, Jing Li, Shuai Li, Jianmin Hua and Jilin Song

Materials 2026, 19(11), 2426; https://doi.org/10.3390/ma19112426 - 5 Jun 2026

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Abstract

This study systematically investigated the durability of low-carbon concrete under severe service conditions using industrial solid wastes. The mechanical properties and carbonation resistance (including carbonation depth, compressive strength after carbonation, and splitting tensile strength after carbonation) were tested. Multi-scale characterization techniques, including XRD, [...] Read more.

This study systematically investigated the durability of low-carbon concrete under severe service conditions using industrial solid wastes. The mechanical properties and carbonation resistance (including carbonation depth, compressive strength after carbonation, and splitting tensile strength after carbonation) were tested. Multi-scale characterization techniques, including XRD, SEM-EDS, and nanoindentation, were employed to investigate the microstructure. This approach revealed a synergistic mechanism linking microstructural evolution to the concrete’s macroscopic mechanical and durability performance. Results showed that incorporating 25% fly ash (FA) reduced compressive strength by 11.30% and 11.39% in CF-25 and BF-25 mixes, respectively, and increased carbonation depth by 58.46% in CF-25. In contrast, the addition of 5% silica fume (SF) produced different effects. It significantly enhanced the compressive strength of the CS-5 and BS-5 mixes by 18.92% and 9.94%, respectively. Furthermore, it improved the micromechanical properties of the interfacial transition zone (ITZ) and reduced its thickness. Micro-mechanistic analysis revealed that the low pozzolanic activity of FA at early ages led to insufficient hydration products, higher porosity, and a weaker ITZ. Conversely, SF, through its high pozzolanic reactivity and nano-filling effect, promoted a dense, highly polymerized gel structure and optimized pore size distribution. The distinct chemical characteristics of high-calcium and low-calcium cementitious systems further amplified the differential effects of these supplementary materials. Full article

(This article belongs to the Special Issue Advances in Sustainable Construction and Building Materials (4th Edition))

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26 pages, 7382 KB

Open AccessArticle

Multi-Field Coupling Analysis of Resistance Spot Welding of SUS301L/Q235B Dissimilar Steel Based on Nickel Intermediate Layer

by Xiaoqi Zhang, Jinhao Li, Chengxian Yuan, Long Wang and Zhongliang Gao

Materials 2026, 19(11), 2425; https://doi.org/10.3390/ma19112425 - 5 Jun 2026

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Abstract

With the widespread application of stainless steel rail vehicles, the resistance spot-welding process between stainless steel and low-carbon steel has become one of the key connection processes in vehicle body manufacturing. However, due to the differences in the material physical properties of these [...] Read more.

With the widespread application of stainless steel rail vehicles, the resistance spot-welding process between stainless steel and low-carbon steel has become one of the key connection processes in vehicle body manufacturing. However, due to the differences in the material physical properties of these two types of steel, problems such as center offset often occur during the welding process. This study adopts the finite element analysis method to systematically analyze the changes in the force field and the temperature field during the welding process after adding a nickel intermediate layer between the two materials, as well as its impact on the physical properties of the joint. The results of the finite element analysis and the physical experiments show that adding a nickel intermediate layer can effectively suppress the center deviation of the weld nugget, optimize the microstructure of the nugget, improve the continuity of the microhardness distribution, and thereby enhance the joint strength of the spot welding. Full article

(This article belongs to the Section Metals and Alloys)

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24 pages, 5744 KB

Open AccessArticle

Study of Localized Corrosion Susceptibility of Ni-Based Superalloys Employing Electrochemical Noise Technique

by Facundo Almeraya-Calderon, Miguel Sergio Huerta-Zavala, Erick Maldonado-Bandala, Demetrio Nieves-Mendoza, Jesus Manuel Jaquez-Muñoz, Miguel Angel Baltazar-Zamora, Laura Landa-Ruiz, Francisco Estupinan-Lopez, Javier Olguin-Coca, Juan Pablo Flores-De los Rios and Citlalli Gaona-Tiburcio

Materials 2026, 19(11), 2424; https://doi.org/10.3390/ma19112424 - 5 Jun 2026

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Abstract

Inconel superalloys are employed in demanding components of different equipment. However, they can be exposed to atmospheric corrosion systems, such as marine and industrial environments. This research is focused on studying the localized corrosion susceptibility of Inconel 600, 690 and 718 exposed to [...] Read more.

Inconel superalloys are employed in demanding components of different equipment. However, they can be exposed to atmospheric corrosion systems, such as marine and industrial environments. This research is focused on studying the localized corrosion susceptibility of Inconel 600, 690 and 718 exposed to H₂SO₄, 1 wt.% and 3.5 wt. % NaCl solutions, simulating marine and industrial atmospheres at 25 ± 0.5 °C. Localized corrosion behavior was characterized by electrochemical noise (EN) and cyclic potentiodynamic polarization (CPP) curves according to ASTM 6-199 ASTM G61 standards. The EN technique was analyzed through time series and analysis for chaotic systems, such as Hurst, Lyapunov and Husdorff coefficients, to determine the corrosion type of each system to reduce the uncertainty in common statistical analysis. The EN results show how Inconel superalloys tend to present localized attacks, being more notorious in NaCl. The application of specialized methods such as Hurst and Lyapunov helped to determine the corrosion system when alloys were characterized by EN. The results indicated that all superalloys exhibit positive hysteresis under CPP, indicating susceptibility to localized pitting corrosion. Full article

(This article belongs to the Special Issue Corrosion Behavior and Mechanical Properties of Metallic Materials (3rd Edition))

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18 pages, 7141 KB

Open AccessArticle

Process Optimization and Microstructure-Property Regulation of P20 Plastic Mold Steels

by Luliang Zhao, Zhenguo Hou, Chunqiao Xing, Min Yang, Jie Yan, Ziwen Li and Zan Yao

Materials 2026, 19(11), 2423; https://doi.org/10.3390/ma19112423 - 5 Jun 2026

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Abstract

This study systematically investigated the effects of air-cooled pre-hardening and oil-quenched quenching-and-tempering processes on the microstructure, mechanical properties, and polishing performance of P20 plastic mold steel. Increasing the austenitizing temperature from 820 °C to 940 °C resulted in a more uniform carbide distribution, [...] Read more.

This study systematically investigated the effects of air-cooled pre-hardening and oil-quenched quenching-and-tempering processes on the microstructure, mechanical properties, and polishing performance of P20 plastic mold steel. Increasing the austenitizing temperature from 820 °C to 940 °C resulted in a more uniform carbide distribution, a slight improvement in hardness, and enhanced polishing performance for both processes. However, grain coarsening at 940 °C reduced the impact toughness from 157.6 J to 111.7 J. After tempering at 650 °C, both processes yielded a tempered sorbite microstructure. However, in the air-cooled samples, the carbides were aligned along the bainite lath direction, whereas in the oil-quenched samples, they exhibited an equiaxed, non-directional distribution owing to the complete recovery of the matrix. Austenitizing at 940 °C followed by air cooling and tempering at 550 °C provides the optimal balance of hardness, toughness, and polishing performance. Mitigating elemental segregation and narrowing the segregation bands represent key strategies for further enhancing polishing performance. Full article

(This article belongs to the Section Metals and Alloys)

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20 pages, 2978 KB

Open AccessArticle

Comparative Study on the Engineering Performance of Lime- and Cement-Improved Argillaceous Siltstone

by Yi Chen, Fangcheng Huang, Rongcheng Zhan, Mengqi Zhou, Hui Weng and Hao Yang

Materials 2026, 19(11), 2422; https://doi.org/10.3390/ma19112422 - 5 Jun 2026

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Abstract

Argillaceous siltstone is widely distributed along expressways in southern China; however, its strong water sensitivity and slaking properties severely restrict its utilization as subgrade fill, particularly under wet–dry cyclic conditions where bearing capacity deteriorates sharply. Existing studies have predominantly focused on mechanical performance [...] Read more.

Argillaceous siltstone is widely distributed along expressways in southern China; however, its strong water sensitivity and slaking properties severely restrict its utilization as subgrade fill, particularly under wet–dry cyclic conditions where bearing capacity deteriorates sharply. Existing studies have predominantly focused on mechanical performance evaluation of stabilizers, while systematic comparisons of lime and cement improvement effects and durability evolution under wet–dry cycles remain insufficiently understood. Drawing on the Yongjin Expressway reconstruction and expansion project, this study systematically investigates the durability of lime- and cement-improved argillaceous siltstone fill. Through unconfined compressive strength (UCS) tests, California bearing ratio (CBR) tests, and five wetting–drying cycles, the evolution differences in strength development, water stability, and durability between the two improvement schemes are revealed. Results indicate that, under identical stabilizer contents (3–7%) and curing conditions, the UCS and CBR of cement-improved soil are significantly higher than those of lime-improved soil. At the same dosage, the strength of cement-improved soil is approximately 1.5–1.7 times that of lime-improved soil, and the absolute strength gap further widens with increasing dosage. Both stabilizers effectively inhibit water immersion swelling, but the swelling rate of lime-improved soil is about 1.3–1.5 times that of cement-improved soil at the same dosage. At 7% dosage, the swelling rates of cement- and lime-improved soils decrease to 0.40% and 0.60%, respectively, both meeting subgrade fill swelling control requirements. After five wet–dry cycles, the UCS retention rate of 7% cement-improved soil is 78.3%, while that of lime-improved soil is 69.0%; the residual strengths are 507.0 kPa and 303.6 kPa, respectively, both satisfying general subgrade engineering strength requirements. However, the 3% lime-improved soil declines to 47.5 kPa after cycling, falling below the engineering threshold. Integrating strength, deformation, and durability indices, high-grade highway roadbeds and other high-load-bearing sections should prioritize 7% cement improvement, whereas general subgrade sections and locations emphasizing crack resistance may adopt 7% lime improvement as an alternative. Low-dosage (<5%) lime improvement is not recommended for argillaceous siltstone subgrade engineering. The findings provide a scientific basis for the engineering application of argillaceous siltstone as subgrade fill and for optimization of improvement schemes. Full article

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

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19 pages, 3544 KB

Open AccessArticle

Study of Asymmetric Test Configurations by Means of Standard and Revised Virtual Crack-Closure Techniques

by Jorge Bonhomme and Victoria Mollón

Materials 2026, 19(11), 2421; https://doi.org/10.3390/ma19112421 - 5 Jun 2026

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Abstract

The objective of this article is to compare the standard two-step virtual crack-closure technique (VCCT) and the revised I–II and II–I VCCT developed by Valvo by studying two asymmetric test configurations commonly used to produce mixed-mode delamination in composite laminates—the asymmetric double cantilever [...] Read more.

The objective of this article is to compare the standard two-step virtual crack-closure technique (VCCT) and the revised I–II and II–I VCCT developed by Valvo by studying two asymmetric test configurations commonly used to produce mixed-mode delamination in composite laminates—the asymmetric double cantilever beam (ADCB) and asymmetric end-notched flexure (AENF) configurations—via finite element modelling (FEM). Scientific literature has revealed that highly asymmetric specimens may exhibit negative components of the energy release rate (ERR) under certain specific loading conditions when using the standard VCCT. The revised VCCTs establish an alternative ERR partition with energetically orthogonal components to solve this inconsistency. This study aims to better understand the mechanisms involved in the revised VCCTs. This study demonstrates that, when using the revised methods, there is a transfer of energy between modes I and II, unlike when using the standard VCCT. The values of the mode I and mode II components of the ERR produced by the standard VCCT fall between the values produced by the revised I–II and II–I VCCTs for the test configurations. Nevertheless, as expected, the total ERR calculated using the three procedures is the same. Finally, some considerations are drawn for the scenario when contact occurs between the specimen arms in the AENF configuration, as it can also lead to unrealistic negative mode I ERR values in the FEM analysis. Full article

(This article belongs to the Special Issue Advanced Fibrous Materials)

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18 pages, 960 KB

Open AccessArticle

Impact of Decorative Ceramic Screen Printing on the Optical and Photovoltaic Performance of Glass Covers for BIPV Applications

by Paweł Kwaśnicki, Anna Gronba-Chyła, Dariusz Augustowski, Ludmiła Marszałek, Agnieszka Generowicz, Anna Kochanek, Iga Pietrucha and Krzysztof Barbusiński

Materials 2026, 19(11), 2420; https://doi.org/10.3390/ma19112420 - 5 Jun 2026

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Abstract

This study evaluates the effect of decorative ceramic screen printing on the optical and photovoltaic performance of glass covers intended for building-integrated photovoltaics (BIPV). Nine ceramic-printed glass samples with different colors and optical densities were compared with a 4 mm Optiwhite reference glass [...] Read more.

This study evaluates the effect of decorative ceramic screen printing on the optical and photovoltaic performance of glass covers intended for building-integrated photovoltaics (BIPV). Nine ceramic-printed glass samples with different colors and optical densities were compared with a 4 mm Optiwhite reference glass and a bare silicon solar cell. The samples were characterized by UV-VIS-NIR spectrophotometry, energy-dispersive X-ray spectroscopy (EDS), and electrical measurements under simulated AM 1.5G irradiation at 1000 W/m². The optical results showed that the Optiwhite reference provided the highest transmittance, whereas the printed samples exhibited lower transmission, typically in the range of 60–80% in the visible region, depending on the coating type. Among the decorative variants, sample 1 showed the highest transparency, while sample 6 exhibited the lowest transmittance. The spectral behavior of the coated glasses indicates that the ceramic layers modify the photon flux reaching the solar cell through wavelength-dependent absorption and scattering effects. The photovoltaic measurements confirmed a clear relationship between decorative coating and electrical performance. Relative to the Optiwhite-covered reference cell, the printed samples showed power losses ranging from approximately 17% to 32%, with sample 1 achieving the highest maximum power among the decorative variants at 1.41 W, and sample 4 the lowest at 1.16 W. The main electrical effect of the ceramic coatings was a reduction in short-circuit current, whereas the open-circuit voltage remained nearly constant across the tested samples. EDS analysis identified the presence of ceramic-layer constituents associated with silica-, zinc-, titanium-, iron-, cobalt-, aluminum-, and fluorine-containing compounds, supporting the interpretation of vitrified decorative coatings formed during high-temperature processing. Overall, the results demonstrate that decorative ceramic printing can provide a practical compromise between architectural appearance and photovoltaic output when the optical density of the coating is appropriately controlled. Full article

(This article belongs to the Special Issue Solar Energy Harvesting Materials: Synthesis and Applications)

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20 pages, 6730 KB

Open AccessArticle

Design of MEMS Gas Sensors and Integration for Multiple Gas Classification for Lithium-Ion Battery Thermal Runaway Warning

by Haiping Liu, Sen Zhang, Shan Xue, Delong Liu, Zeyu Sun, Lianshi Li, Qi Zhang and Mingzhi Jiao

Materials 2026, 19(11), 2419; https://doi.org/10.3390/ma19112419 - 5 Jun 2026

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Abstract

Characteristic gas-based detection technology can facilitate the warning of lithium-ion battery thermal runaway with a high accuracy at an early stage. Microelectromechanical system (MEMS) metal–oxide–semiconductor (MOS) gas sensors have advantages of a low cost, a high accuracy, and low power consumption; therefore, they [...] Read more.

Characteristic gas-based detection technology can facilitate the warning of lithium-ion battery thermal runaway with a high accuracy at an early stage. Microelectromechanical system (MEMS) metal–oxide–semiconductor (MOS) gas sensors have advantages of a low cost, a high accuracy, and low power consumption; therefore, they are ideal candidates for the lithium-ion battery thermal-runaway warning. MEMS MOS gas sensors are composed of a micro-hotplate and gas-sensitive materials. The micro-hotplate component strongly influences the device’s mechanical and thermal properties. Initially, we used COMSOL to optimize the micro-hotplate component. Then, we fabricated the device based on the optimal micro-hotplate. Next, gas-sensitive materials made of ZnO and ZnO-Au were deposited on the micro-hotplate by radio-frequency magnetic sputtering. The self-made and commercial MEMS MOS sensors were integrated to form an electronic nose. The as-made electronic nose can classify hydrogen, ethylene, acetylene, methane, carbon monoxide, and ethanol with a maximum accuracy of 99.4% using gas response data acquired over only 20 s. The reported work can provide a solution for an early and accurate lithium-ion battery thermal runaway warning. Full article

(This article belongs to the Special Issue Advanced Thin-Film Technologies for Semiconductor Applications)

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16 pages, 3630 KB

Open AccessArticle

Utilization of Robust Zr-Based Metal–Organic Framework for Efficient N₂/H₂ Separation

by Jieru Zhang, Xia Chen, Zhilu Wang, Tianhao Wang, Wenxin Ma, Qiang Fu and Bao-Ju Wang

Materials 2026, 19(11), 2418; https://doi.org/10.3390/ma19112418 - 5 Jun 2026

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Abstract

The development of energy-efficient separation technologies for nitrogen (N₂)–hydrogen (H₂) mixtures under conventional industrial conditions remains a critical challenge. Adsorptive separation emerges as a promising strategy, contingent upon the design of high-performance adsorbents with tailored physicochemical properties. In this [...] Read more.

The development of energy-efficient separation technologies for nitrogen (N₂)–hydrogen (H₂) mixtures under conventional industrial conditions remains a critical challenge. Adsorptive separation emerges as a promising strategy, contingent upon the design of high-performance adsorbents with tailored physicochemical properties. In this study, three isoreticular zirconium-based metal–organic frameworks (UiO-66, UiO-66-CH=CH₂, and UiO-66-F₄) are systematically evaluated for the purification of industrial N₂-H₂ mixed gases. By integrating static adsorption isotherms, dynamic breakthrough experiments, and molecular dynamics (MD) simulations, we comprehensively characterize the adsorption mechanisms and diffusion kinetics. The results demonstrate that UiO-66-F₄ exhibits optimal performance in capturing N₂ from N₂-H₂ mixtures under simulated industrial conditions, owing to its balanced binding affinity, high nitrogen uptake, and favorable micro-/mesoporous diffusion dynamics. This work offers a promising alternative for N₂-H₂ separation in industrial applications. Full article

(This article belongs to the Special Issue Synthesis and Applications of Metal–Organic Frameworks)

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15 pages, 1921 KB

Open AccessArticle

Study of Single Crystal and X-Ray Detector Performance of Ti³⁺: β-Ga₂O₃

by Boyang Chen, Xinyu Liu, Yiyuan Liu, Zeliang Gao, Zhitai Jia and Wenxiang Mu

Materials 2026, 19(11), 2417; https://doi.org/10.3390/ma19112417 - 5 Jun 2026

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Abstract

Gallium oxide (Ga₂O₃) is emerging as a promising material for X-ray detectors due to its high sensitivity, high melting point, and stable physicochemical properties. However, intrinsic background shallow donors in raw materials hinder the preparation of high-resistance intrinsic crystals, [...] Read more.

Gallium oxide (Ga₂O₃) is emerging as a promising material for X-ray detectors due to its high sensitivity, high melting point, and stable physicochemical properties. However, intrinsic background shallow donors in raw materials hinder the preparation of high-resistance intrinsic crystals, making doping essential to tailor electrical properties. This study grew Ti³⁺-doped β-Ga₂O₃ single crystals via the Edge-defined Film-fed Growth (EFG) method using Ti₂O₃ as a dopant, achieving high resistivity and a moderate reduction in bandgap. High-resolution X-ray diffraction (HRXRD) showed a rocking curve full width at half maximum (FWHM) of 96.50 arcsec. Compared with the unintentionally doped (UID) crystal, the bandgap exhibited a slight reduction, decreasing from 4.76 eV to 4.59 eV. In the infrared transmission spectra, the onset wavelength of the decrease in transmittance for the Ti³⁺: β-Ga₂O₃ crystal showed a distinct redshift relative to that of the UID crystal, indicating effective suppression of free electrons within the crystal. X-ray photoelectron spectroscopy (XPS) revealed that Ti³⁺ incorporation minimally affected the valence states of Ga and O or the Ga/O ratio, with no significant shift in valence band maximum (EVBM). A metal–semiconductor–metal (MSM) structured X-ray detector fabricated on polished Ti³⁺: β-Ga₂O₃ (100) substrate with Ti/Au electrodes exhibited a peak sensitivity of 943.16 μC/(Gy·cm²) at 40 V bias and 2.944 μGy/s dose rate, surpassing the upper sensitivity limit reported for semi-insulating doping bulk β-Ga₂O₃ detectors. The rise and fall times were 0.23 s and 0.30 s, respectively, with a minimum detectable limit (MDL) of 164.26 nGy/s, demonstrating its potential for high-performance X-ray detection applications. Full article

(This article belongs to the Special Issue Functional Laser Materials)

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18 pages, 5059 KB

Open AccessArticle

Manganese-Functionalized Bentonite for Efficient Cadmium Ion Removal from Aqueous Systems

by Silvia Dolinská, Ingrid Znamenáčková, Věra Valovičová, Lenka Vaculíková, Slavomír Hredzák, Miroslava Václavíková and Lucia Ivaničová

Materials 2026, 19(11), 2416; https://doi.org/10.3390/ma19112416 - 5 Jun 2026

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Abstract

Bentonite is widely used as a sorbent due to its high specific surface area and ion-exchange capacity; however, its properties can be significantly influenced by the presence of additional mineral phases and chemical modification. In this study, the influence of manganese oxides and [...] Read more.

Bentonite is widely used as a sorbent due to its high specific surface area and ion-exchange capacity; however, its properties can be significantly influenced by the presence of additional mineral phases and chemical modification. In this study, the influence of manganese oxides and quartz sand on the sorption properties of bentonite from the Stará Kremnička was systematically investigated, with particular attention to surface characterization by X-ray photoelectron spectroscopy (XPS). The materials were also characterized by X-ray diffraction, FTIR spectroscopy, and zeta potential measurements. XPS analysis revealed that manganese in all modified samples was predominantly present in the Mn(IV) oxidation state, with Mn 2p₃/₂ binding energies of 642.5–642.7 eV, corresponding to MnO₂-type phases. Deconvolution of the O 1s spectra confirmed the presence of lattice oxygen, silicate oxygen, and surface hydroxyl groups. The reason for the modification of mainly natural materials with manganese oxides is their higher affinity for the adsorption of heavy metal cations. The maximum adsorption capacity of natural bentonite was 63.29 mg/g. In bentonite samples modified with manganese oxides, the value increased to 103.09 mg/g for BMn, and to 116.28 mg/g for the MMn mixture. The results demonstrate that sorption behavior is governed by a combination of ion exchange on bentonite and interactions with Mn oxide surface phases, providing new insight into the role of Mn(IV) species in surface-controlled metal binding processes. These findings highlight the importance of surface chemical states in designing efficient bentonite-based sorbents. Full article

(This article belongs to the Section Advanced Composites)

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30 pages, 7975 KB

Open AccessReview

Recent Development of Back-Contacted Single-Crystal Perovskite Solar Cells

by Xiao Cheng

Materials 2026, 19(11), 2415; https://doi.org/10.3390/ma19112415 - 5 Jun 2026

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Abstract

The efficiency of perovskite solar cells has increased to a certified value of 27% over the past decade, benefiting from the superior properties of metal halide perovskite materials. However, their long-term operational stability is still far inferior to that of commercial crystalline silicon [...] Read more.

The efficiency of perovskite solar cells has increased to a certified value of 27% over the past decade, benefiting from the superior properties of metal halide perovskite materials. However, their long-term operational stability is still far inferior to that of commercial crystalline silicon solar cells. A key source of this instability is field-driven ion migration in vertical architectures, along with the consequent degradation at the absorber–electrode interfaces. Compared with the widely investigated vertical structures, back-contacted (BC) perovskite solar cells—wherein both electrodes are positioned on the same side of the absorber—offer a unique route to suppress interfacial ion migration and thereby enhance long-term device stability. These advantages are especially pronounced when combined with single-crystal perovskites, which possess low charge trap densities, long carrier diffusion lengths, and high bulk ion migration barriers. Unfortunately, only a handful of research groups have participated in the development of single-crystal BC perovskite solar cells; thus, the advancement of this area lags far behind that of its vertical counterpart. Therefore, a review that discusses the recent developments and challenges of single-crystal BC perovskite solar cells is urgently required to provide guidelines for this emerging field. In this progress report, we first introduce the main growth methods of single-crystal wafers compatible with BC architectures, followed by an outline of the developmental history of BC perovskite solar cells. Finally, the core bottlenecks facing single-crystal BC devices and corresponding optimization strategies are discussed in detail. Full article

(This article belongs to the Special Issue Halide Perovskite Crystal Materials and Optoelectronic Devices)

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20 pages, 8477 KB

Open AccessArticle

Systematic Evaluation of Strain Rate and Environmental Conditions Effects on Stress Corrosion Cracking of an Al-Cu Alloy

by Sergio Lorenzi, Lorenzo Nani, Samuel Ferrari, Mattia Locatelli, Luca Gritti, Sara Bocchi and Marina Cabrini

Materials 2026, 19(11), 2414; https://doi.org/10.3390/ma19112414 - 5 Jun 2026

Viewed by 328

Abstract

The aim of this study is to comprehensively investigate and quantify the effect of strain rate (SR) and environmental parameters on the stress corrosion cracking (SCC) behavior of a high-strength, aluminum–copper alloy. Slow strain rate (SSR) tests were carried out in air at [...] Read more.

The aim of this study is to comprehensively investigate and quantify the effect of strain rate (SR) and environmental parameters on the stress corrosion cracking (SCC) behavior of a high-strength, aluminum–copper alloy. Slow strain rate (SSR) tests were carried out in air at 25 °C, over a SR range from 10⁻⁴ to 10⁻⁷ s⁻¹ and controlled relative humidity (RH) between 40% and 80%. The influence of the pre-soaking period in 3.5 wt.% NaCl solution was also assessed. A major effect of pre-soaking was identified, as it was necessary for the onset of SCC. Increasing RH over 40% and decreasing SR below 10⁻⁵ s⁻¹ significantly intensified SCC susceptibility, leading to ductility loss up to 84%. SSR test results were supported by microstructural investigations, with particular emphasis on the role of second phases. Their electrochemical activity was examined by scanning Kelvin probe force microscopy (SKPFM), while intergranular corrosion (IGC) susceptibility was evaluated according to the ISO 11846 standard. The pronounced IGC susceptibility of the alloy led to predominantly intergranular fracture morphologies in cross-section peripheral areas after SSR testing. The results confirmed the synergistic effect among microstructure, IGC susceptibility and SCC behavior, identifying a critical window of mechanical and environmental parameters governing SCC. Full article

(This article belongs to the Special Issue Corrosion Behavior and Mechanical Properties of Metallic Materials (3rd Edition))

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33 pages, 8120 KB

Open AccessReview

A Review on the Evolution of Thermal and Environmental Barrier Coating Systems and Their High-Temperature Degradation Mechanisms in Advanced Aero-Engines

by Saijun Ren, Yukang Sun, Han Yan, Xuyang Zhang, Yiwang Bao and Kuilin Lv

Materials 2026, 19(11), 2413; https://doi.org/10.3390/ma19112413 - 5 Jun 2026

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Abstract

With the continuous advancement of thrust-to-weight ratios in modern aero-engines, turbine inlet temperatures have reached levels that far exceed the thermal endurance limits of conventional superalloys and emerging ceramic matrix composites (CMCs). Consequently, thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) have [...] Read more.

With the continuous advancement of thrust-to-weight ratios in modern aero-engines, turbine inlet temperatures have reached levels that far exceed the thermal endurance limits of conventional superalloys and emerging ceramic matrix composites (CMCs). Consequently, thermal barrier coatings (TBCs) and environmental barrier coatings (EBCs) have become indispensable multifunctional systems for hot-section component protection. This review systematically delineates the evolutionary trajectory of TBC/EBC systems, transitioning from traditional yttria-stabilized zirconia (YSZ) and simple silicates to advanced multi-rare-earth-doped oxides, A₂B₂O₇ pyrochlore structures, and high-entropy ceramic systems. A critical comparative assessment is provided regarding their phase stability, thermal-physical properties, and durability challenges above 1200 °C. Furthermore, this paper provides an in-depth analysis of high-temperature degradation mechanisms, focusing on the thermochemical and thermomechanical interactions under calcium-magnesium-alumino-silicate (CMAS) attack, water-oxygen corrosion, and molten salt infiltration. By synthesizing current research gaps, we highlight the trade-offs between low thermal conductivity, high toughness, and environmental resistance. Finally, a strategic roadmap for next-generation coatings is proposed, emphasizing the integration of high-entropy material design, multi-scale structural optimization, and AI-driven life prediction models to meet the stringent reliability requirements of future propulsion systems. Full article

(This article belongs to the Special Issue Advances in High-Temperature Ceramic Matrix Composites and Coatings)

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14 pages, 39920 KB

Open AccessArticle

Martensitic Transformation and Strengthening Mechanism in a 304 Stainless Steel Subjected to Wire Drawing

by Yongjie Yu, Wujing Fu, Feng Dai, Rengeng Li and Qingquan Lai

Materials 2026, 19(11), 2412; https://doi.org/10.3390/ma19112412 - 5 Jun 2026

Viewed by 336

Abstract

Wire drawing is a key processing method for producing ultrahigh-strength stainless steel wires. In metastable austenitic steels, the strain-induced martensitic transformation is known to govern strain hardening. However, the transformation mechanism and kinetics behavior under wire drawing remain unclear due to the distinct [...] Read more.

Wire drawing is a key processing method for producing ultrahigh-strength stainless steel wires. In metastable austenitic steels, the strain-induced martensitic transformation is known to govern strain hardening. However, the transformation mechanism and kinetics behavior under wire drawing remain unclear due to the distinct deformation conditions compared to those of conventional loading modes. In this work, the microstructural evolution, transformation kinetics and strengthening behavior of the 304 stainless steel during cold wire drawing are systematically analyzed. The results show that the transformation is dominated by the austenite → twin→ α′-martensite pathway, with the ε-martensite effectively suppressed. The martensite fraction follows a sigmoidal evolution with the equivalent drawing strain and could be well described by the Olson–Cohen model. The yield strength is increased from 320 MPa to 2 GPa and exhibits a linear relationship with the martensite fraction, indicating a dominant composite strengthening mechanism. These findings clarify the deformation-mode-dependent transformation mechanism and its role in governing mechanical properties during wire drawing. Full article

(This article belongs to the Section Metals and Alloys)

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20 pages, 10223 KB

Open AccessArticle

Predictions of Crack Growth Rates, R-Ratio and Overload Effects Based on Smooth Specimen LCF Data and the Moving Plastic Stress Field Ahead of the Crack Tip

by Steve Williams, Mark Whittaker and Mark Hardy

Materials 2026, 19(11), 2411; https://doi.org/10.3390/ma19112411 - 5 Jun 2026

Viewed by 289

Abstract

The use of the stress intensity factor K to characterize the severity of crack tip stress fields is widespread throughout engineering. The relationship between K and the crack growth rate is then usually represented empirically by a straight line Paris law relationship on [...] Read more.

The use of the stress intensity factor K to characterize the severity of crack tip stress fields is widespread throughout engineering. The relationship between K and the crack growth rate is then usually represented empirically by a straight line Paris law relationship on logarithmic axes. This study develops an analytical relationship between the two by linking crack growth to the accumulation of fatigue damage ahead of the moving crack tip. A stress-based fatigue model was used, with inputs from plastic 2D plane stress FE analyses representing an edge crack by a sharp semi-circular notch. Stress–distance profiles ahead of the crack tip were extracted at the maximum and minimum points of a range of fatigue loading cycles. These were then used with data from smooth specimen LCF tests to predict the build-up of fatigue damage at regularly spaced locations ahead of the crack tip and hence crack growth rates. Full da/dN–ΔK curves were generated for the nickel-based superalloy RR1000 at 20 °C with loading R-ratios of 0, −1 and 0.5. The R = 0 and R = −1 crack growth rate predictions agreed well with experimental data, as did the steeper growth rate slope calculated at R = 0.5. The method was then extended to predict overload behaviour. Full article

(This article belongs to the Special Issue Fatigue Crack Growth in Metallic Materials (3rd Edition))

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16 pages, 13866 KB

Open AccessCommunication

Rheology and Shape Stability Control of 3D-Printed White Calcium Sulfoaluminate Cement Composites Containing Oyster Shell and Cuttlebone Powder

by Xingyu Qu, Qinyuan Wang, Jiafeng Kong, Junyu Wang, Jie Wang, Xingang Xu, Yan Zheng, Heyang Wu and Mingxu Chen

Materials 2026, 19(11), 2410; https://doi.org/10.3390/ma19112410 - 5 Jun 2026

Viewed by 296

Abstract

To optimize the shape stability of 3D-printed white calcium sulfoaluminate (WCSA) cement composites, oyster shell powder (OSP) and cuttlebone powder (CBP) were introduced as white admixtures to regulate rheological properties and printability. The setting behavior, rheological properties, and shape stability of the WCSA [...] Read more.

To optimize the shape stability of 3D-printed white calcium sulfoaluminate (WCSA) cement composites, oyster shell powder (OSP) and cuttlebone powder (CBP) were introduced as white admixtures to regulate rheological properties and printability. The setting behavior, rheological properties, and shape stability of the WCSA cement composites were evaluated by Vicat setting-time tests, rotational rheological measurements, three-stage thixotropic recovery tests, and structural deformation measurements, together with mechanical strength tests, XRD, and SEM analyses. The results showed that the incorporation of OSP and CBP shortened the setting time of WCSA cement composites. The initial and final setting times decreased from 41 min and 67 min to 17 min and 30 min in the WCSA cement composites with OSP, and from 42 min and 66 min to 20 min and 33 min in the WCSA cement composites with CBP, which improved printing operability. As the OSP and CBP content increases from 0% to 24%, the dynamic yield stress of WCSA cement composites increased from 48.83 Pa to 530.59 Pa and 60.30 Pa to 1085.80 Pa, respectively. The thixotropic recovery degree of WCSA cement composites increased from 57.89% to 86.46%, and 56.60% to 92.14%, respectively. As the OSP and CBP contents increase from 0% to 24%, the structural deformation decreased from 12.39% to 6.91% and 13.29% to 5.12% respectively, which improved buildability of the printed structures. In addition, although OSP and CBP reduced the mechanical strength of WCSA cement composites compared with the control group, the flexural and compressive strengths gradually recovered as the contents increased from 6% to 24% due to the enhanced filling effect and improved particle packing. This study provides a reference for the application of marine calcareous solid wastes in sustainable 3D-printed cementitious materials. Full article

(This article belongs to the Special Issue Advanced Experimental Technology, Theory and Numerical Methods in Concrete Materials)

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15 pages, 6923 KB

Open AccessArticle

Effects of Nanosecond Pulsed Laser Cleaning Parameters on the Removal of Thick Paint Coatings from Shipbuilding Steel

by Thongchuea Nutchanat, Satsuki Hiura, Keita Marumoto, Toshitaka Uchida, Takuya Matsuzaki and Motomichi Yamamoto

Materials 2026, 19(11), 2409; https://doi.org/10.3390/ma19112409 - 5 Jun 2026

Viewed by 257

Abstract

Thick paint coatings on ship hulls must be periodically removed before repainting; however, conventional abrasive blasting generates secondary waste and poses environmental and occupational health concerns. This study investigates nanosecond pulsed laser cleaning as a non-contact alternative for removing thick marine paint coatings [...] Read more.

Thick paint coatings on ship hulls must be periodically removed before repainting; however, conventional abrasive blasting generates secondary waste and poses environmental and occupational health concerns. This study investigates nanosecond pulsed laser cleaning as a non-contact alternative for removing thick marine paint coatings from KE36 shipbuilding steel. A two-layer coating system consisting of anti-fouling and anti-corrosive layers with a total thickness of approximately 1000 μm was examined. The effects of pulse energy, pulse overlap number, and scanning pitch on removal depth, cleaning efficiency, and surface morphology were systematically evaluated. Increasing the pulse energy enhanced coating ablation and enabled complete removal when sufficient heat input density was supplied. A higher pulse overlap number promoted cumulative energy deposition and improved removal depth. Smaller scanning pitches improved spatial overlap between adjacent scan paths and produced more uniform cleaning, whereas excessive pitches caused incomplete removal and periodic surface undulations. The cleaning efficiency approached 100% at a heat input density of approximately 4–5 J/mm². These results indicate that heat input density is a useful process indicator for determining the minimum energy conditions required for full removal of thick coating layers while minimizing thermal effects on the substrate. Full article

(This article belongs to the Special Issue Laser-Based Surface Processing: Techniques, Mechanisms, and Advanced Applications)

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19 pages, 4209 KB

Open AccessArticle

Optimization and Performance of Sustainable Mortar Incorporating High-Volume Alkali Bypass Dust: A Synergistic Approach Using Silica Fume and Water Reducer

by Riyadh Alturki and Muhammad Imran Khan

Materials 2026, 19(11), 2408; https://doi.org/10.3390/ma19112408 - 5 Jun 2026

Viewed by 271

Abstract

This study investigates the use of Alkali Bypass Dust (ABD), a cement kiln waste, as a supplementary cementitious material in mortar. Direct ABD incorporation reduced workability and strength. A dual-modification strategy employing a water reducer (WR) and silica fume (SF) was implemented. Mortars [...] Read more.

This study investigates the use of Alkali Bypass Dust (ABD), a cement kiln waste, as a supplementary cementitious material in mortar. Direct ABD incorporation reduced workability and strength. A dual-modification strategy employing a water reducer (WR) and silica fume (SF) was implemented. Mortars with 0–50% cement replaced by ABD were tested, with and without modifiers. Results showed that WR effectively restored workability and improved early strength, while SF enhanced long-term performance through pozzolanic reactions. A synergistic effect in ternary blends (ABD + WR + SF) yielded 28-day compressive strength at 50% ABD replacement comparable to the control (49.9 MPa). Statistical analysis via Response Surface Methodology confirmed that material interactions, not individual amounts, primarily govern strength development. All models are significant where R² value is higher than 0.80. The statistically validated models can be used to optimize the mix proportions for desired compressive and flexural performance. The study concludes that optimized blends with 30–50% ABD are viable for non-structural applications, offering a sustainable pathway for waste valorization and reduced cement consumption. Full article

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

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17 pages, 3876 KB

Open AccessArticle

Molecular Design of Underwater Adhesive Copolymers: Synergy Between Long-Chain Alkyl Crystallization–Melting Switching and Carboxyl Group Interfacial Interactions

by Han Liu and Lei Hou

Materials 2026, 19(11), 2407; https://doi.org/10.3390/ma19112407 - 5 Jun 2026

Viewed by 326

Abstract

Achieving strong adhesion in underwater or humid environments remains challenging because the interfacial hydration layer prevents direct contact between the adhesive and the substrate. Conventional adhesives typically fail under these conditions, so new strategies are needed to actively displace the water layer and [...] Read more.

Achieving strong adhesion in underwater or humid environments remains challenging because the interfacial hydration layer prevents direct contact between the adhesive and the substrate. Conventional adhesives typically fail under these conditions, so new strategies are needed to actively displace the water layer and create stable interfacial interactions. In this study, we prepared a series of copolymers with different monomer ratios via photocuring, using methacrylic acid (MAA) and stearyl methacrylate (SMA) as monomers. We focused on their thermal transition behavior and adhesion performance under both dry and underwater conditions. The results show that at an SMA molar fraction of 85%, the copolymer exhibits crystalline melting between 30 and 40 °C, where the storage modulus drops from approximately 10⁷ Pa to 10⁴ Pa, indicating a stiff-to-soft transition. Under dry conditions, this composition shows an adhesion strength of 1.67 MPa to glass, which remains 1.2 MPa underwater, and it can support a hanging load of 5 kg. The copolymer adheres well to glass and aluminum but shows weak adhesion to PTFE. After surface abrasion, the adhesion strength to glass increases to 1.6–1.8 MPa. In summary, the copolymer achieves effective underwater adhesion through the synergy of hydrophobic water displacement, thermally induced stiff-to-soft switching, and hydrogen bonding. Full article

(This article belongs to the Section Polymeric Materials)

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16 pages, 970 KB

Open AccessArticle

Repair Performance of Additively and Subtractively Manufactured Permanent Crown Materials: A Combined Mechanical and Optical Evaluation

by İrem Karagözoğlu, Özge Parlar Öz, Nermin Demirkol, Tan Fırat Eyüboğlu and Mutlu Özcan

Materials 2026, 19(11), 2406; https://doi.org/10.3390/ma19112406 - 5 Jun 2026

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Abstract

This study aimed to investigate the repair performance of these materials subjected to different surface treatment protocols using combined mechanical and optical evaluations. Four resin-matrix materials were evaluated: two CAD/CAM materials (HIPC Plus and GC Cerasmart) and two additively manufactured resins (VarseoSmile TriniQ [...] Read more.

This study aimed to investigate the repair performance of these materials subjected to different surface treatment protocols using combined mechanical and optical evaluations. Four resin-matrix materials were evaluated: two CAD/CAM materials (HIPC Plus and GC Cerasmart) and two additively manufactured resins (VarseoSmile TriniQ and CrownTec). Standardized disc specimens were fabricated and thermocycled prior to repair. Three surface treatments were applied: airborne particle abrasion (APA), tribochemical silica coating (TSC) with silane, and laser treatment (LT). Micro-shear bond strength (µSBS) was measured using composite cylinders bonded to treated surfaces. For optical evaluation, standardized cavities were restored with composite resin, and color measurements were obtained at baseline (T0) and after aging (T1) using a spectrophotometer. Color mismatch and color stability were calculated. Data were analyzed using two-way ANOVA and Tukey tests (α = 0.05). Material type and surface treatment significantly affected µSBS (p < 0.001). CAD/CAM materials had higher bond strength than additively manufactured ones. The TSC group showed the highest µSBS. Aging increased color mismatch, with post-aging ΔE00 values surpassing clinical thresholds. Additively manufactured materials experienced greater color changes. Repair performance depends on manufacturing method and surface treatment. The higher bond strength in the TSC group likely results from silica coating and silanization. CAD/CAM materials showed better optical stability. Full article

(This article belongs to the Section Biomaterials)

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23 pages, 37779 KB

Open AccessArticle

Crashworthiness of a Modular Assembled Multi-Cell CFRP Structure: Experimental and Numerical Investigation

by Tianli Chen, Hehe Kang, Huile Zhang, Pengpeng Zhi, Wei Wang and Zhonglai Wang

Materials 2026, 19(11), 2405; https://doi.org/10.3390/ma19112405 - 5 Jun 2026

Viewed by 336

Abstract

Lightweight thin-walled energy-absorbing structures play a critical role in passive safety systems for automotive and aerospace engineering applications, yet simultaneously achieving high specific energy absorption and stable crushing behavior remains a persistent challenge. Inspired by the topology of natural honeycombs, this study proposes [...] Read more.

Lightweight thin-walled energy-absorbing structures play a critical role in passive safety systems for automotive and aerospace engineering applications, yet simultaneously achieving high specific energy absorption and stable crushing behavior remains a persistent challenge. Inspired by the topology of natural honeycombs, this study proposes a novel modular assembled multi-cell carbon fiber reinforced polymer (CFRP) structure (MAMCS), fabricated via a cost-effective modular assembly strategy based on a wrapping process. Quasi-static axial crushing experiments combined with validated finite element simulations were employed to systematically investigate the effects of inner layup configurations ([0°/90°], [30°/−60°], [45°/−45°]), cell number, and inner sub-cell size on crushing behavior. Among the investigated layup configurations, the [0°/90°] inner layup exhibited superior mean crushing force (MCF) and specific energy absorption (SEA). Multi-cell architectures significantly enhanced load-bearing capacity and crushing stability through mechanical interactions among internal sub-cells. Parametric analyses further revealed that enlarging the inner sub-cell size elevates both MCF and SEA, although at the expense of a higher peak crushing force (PCF). A TOPSIS-based multi-criteria decision-making framework was applied to identify a preferred configuration that achieves a favorable balance between peak load mitigation and energy absorption efficiency. The proposed MAMCS, characterized by its simple modular assembly, cost-effective fabrication, and superior crashworthiness performance, offers a promising bio-inspired design strategy for developing high-performance lightweight energy-absorbing structures in axial impact applications. Full article

(This article belongs to the Special Issue Mechanical Behavior and Functional Applications of Fiber-Reinforced Composite Materials and Structures)

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19 pages, 6341 KB

Open AccessArticle

Flexible Graphene-Based S-Band Metasurface Conformal Array Antenna for UAV Platforms

by Jinling Li, Peng Li, Meng Zeng, Yitong Xin, Haoran Zu and Rongguo Song

Materials 2026, 19(11), 2404; https://doi.org/10.3390/ma19112404 - 4 Jun 2026

Viewed by 283

Abstract

There is a substantial demand for lightweight, low-profile, and conformal antenna integration on the wing platforms of unmanned aerial vehicles (UAVs). This paper presents an S-band (2–4 GHz) flexible conformal metasurface array antenna based on a highly conductive graphene-assembled film (GAF). The main [...] Read more.

There is a substantial demand for lightweight, low-profile, and conformal antenna integration on the wing platforms of unmanned aerial vehicles (UAVs). This paper presents an S-band (2–4 GHz) flexible conformal metasurface array antenna based on a highly conductive graphene-assembled film (GAF). The main contributions of this work are twofold. First, flexible and highly conductive GAF is used as the conductor together with a flexible polyimide (PI) dielectric substrate to form a GAF-based wing-conformal antenna configuration with a low-profile, lightweight, and easily conformal performance. Second, a GAF conformal antenna element is developed by combining a dipole antenna with a directive and reflective frequency selective surface (FSS), achieving effective control of the beam and stable directional radiation at 2.4 GHz. Full-wave simulations using CST Studio Suite show that the directive FSS narrows the feed beam, whereas the reflective FSS redirects and narrows the H-plane radiation. The simulated results show that the integrated wing-conformal antenna operates over 2.19–2.65 GHz and achieves a gain of 4.65 dBi at 2.4 GHz. The measurement results indicate that the GAF conformal antenna and 1 × 4 GAF conformal array antenna shows measured reflection coefficients below

- 10

dB at 2.4 GHz and effective adjacent-element isolation. In addition, simulated results indicate that the GAF array antenna can perform beam scanning within the ±40° range, verifying the beam-control capability of this structure for UAV forward communication. Overall, this work highlights the feasibility of using GAF as a conductive material for both a high-efficiency radiator and an FSS beamforming structure, offering a practical material and design approach for lightweight, low-profile, and wing-conformal airborne array antennas. Full article

(This article belongs to the Special Issue Innovations in Metasurfaces and Metamaterials Design)

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32 pages, 2120 KB

Open AccessReview

Review of the Properties of Cement-Based Composites with Carbon-Based Nanomaterials for Potential Functional Applications

by Eryk Goldmann, Marcin Górski, Barbara Klemczak and Rafat Siddique

Materials 2026, 19(11), 2403; https://doi.org/10.3390/ma19112403 - 4 Jun 2026

Viewed by 455

Abstract

The inclusion of carbon nanomaterials in cement-based materials influences a variety of properties, ranging from basic properties to electrical conductivity, which allows for the creation of functional materials. These materials can be utilized as sensors of strain and cracks, as well as to [...] Read more.

The inclusion of carbon nanomaterials in cement-based materials influences a variety of properties, ranging from basic properties to electrical conductivity, which allows for the creation of functional materials. These materials can be utilized as sensors of strain and cracks, as well as to generate heat and harvest electricity. Through the combination of standard applications of construction materials and added functionality, it is possible to create modern construction materials combining higher durability and strength with additional functionality. The enhanced durability of functional cementitious nanocomposites can reduce the need for retrofitting and decrease resource consumption. Together with the increased safety offered by their functional applications, these characteristics make them well aligned with the growing demand for environmentally sustainable construction materials. The presented paper describes the application of various carbon nanomaterials in cement-based composites. Current research directions concerning the influence of the carbon nanomaterial addition on the most important properties of cement pastes, mortars and concretes have been described, along with a critical analysis of the acquired results and further recommendations. Furthermore, recent progress in the development of functional cement-based nanocomposites has also been reviewed. Full article

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

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40 pages, 1546 KB

Open AccessReview

Nature-Inspired Trojan Materials as Invisible Enablers of Advanced Humidity Sensors

by Daniela S. Oliveira, Elizabeth S. Vieira, Gabriela V. Martins, Joana J. Costa, Rafaela M. Meira, Carlos A. Ramos, Daniela Campanhã, Gina Vilão, Joaquim Alves, P. Filipe Santos and Felismina T. C. Moreira

Materials 2026, 19(11), 2402; https://doi.org/10.3390/ma19112402 - 4 Jun 2026

Viewed by 510

Abstract

Nature offers a robust conceptual framework for designing next-generation adaptive, multifunctional sensing systems. Also, in sensing systems, Trojan materials add a functional dimension to the microstructure, enabling the development of high-performance humidity sensors without interfering with their macrostructure. Thus, based on a brief [...] Read more.

Nature offers a robust conceptual framework for designing next-generation adaptive, multifunctional sensing systems. Also, in sensing systems, Trojan materials add a functional dimension to the microstructure, enabling the development of high-performance humidity sensors without interfering with their macrostructure. Thus, based on a brief overview of how inspiration from plants, animals, and membranes can be used to engineer high-performance platforms for environmental humidity monitoring, combined with the functional dimension of Trojan materials, this review presents a critical framework detailing the key developments in the main categories of self-sensing materials within the scope of humidity sensors. The review addresses electronically and ionically conductive polymers, polymer composites with dispersed active fillers, and hydrogel-based or other water-compatible systems. Additionally, commercially available sensors are described, and the main challenges and future directions are identified. Full article

(This article belongs to the Special Issue Trojan Materials in Science, Technology and Biomedicine: Invisibility Leading to Success)

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24 pages, 4266 KB

Open AccessArticle

Preparation and Properties of Transparent, Thermally Insulating, and Flexible SiO₂ Aerogels

by Jian Li, Shuhang Shi, Haitao Shu, Qianyu Chen, Yun Zhou, Ying Yuan and Xiaotian Peng

Materials 2026, 19(11), 2401; https://doi.org/10.3390/ma19112401 - 4 Jun 2026

Viewed by 254

Abstract

SiO₂ aerogels are promising candidates for energy-efficient glazing because of their low thermal conductivity and optical transparency; however, conventional formulations often fail to reconcile optical, thermal, and mechanical performance. This work aimed to resolve this bottleneck via controllable sol–gel synthesis and ambient [...] Read more.

SiO₂ aerogels are promising candidates for energy-efficient glazing because of their low thermal conductivity and optical transparency; however, conventional formulations often fail to reconcile optical, thermal, and mechanical performance. This work aimed to resolve this bottleneck via controllable sol–gel synthesis and ambient pressure drying. Using methyltrimethoxysilane (MTMS) as the single silicon source, this study systematically explored the effects of alkaline catalyst type, water-to-MTMS ratio, and surfactant selection, and further developed an MTMS–dimethyl dimethoxy silicane (DMDMS) composite silicon source. Tetramethylammonium hydroxide (TMAOH) catalysis, a water-to-MTMS molar ratio of 7:1, and Pluronic F-127 (F127) surfactant yielded a uniform, hydrophobic aerogel with 93.50% porosity and 89.74% transmittance at 800 nm. The optimized composite system (MTMS:DMDMS = 9:1, 6 mL water, 2.0 g F127) enhanced compressive strength by 22.4% relative to pure MTMS aerogel, with 70.15% visible transmittance and thermal conductivity of 0.027 W/(m·K). These results demonstrate that multi-parameter formulation control can achieve a practical balance among mechanical robustness, optical transparency, and thermal insulation. This study provides a theoretical and process foundation for the engineering application of high-performance transparent thermal insulation materials. Full article

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

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20 pages, 2943 KB

Open AccessArticle

Theoretical and Experimental Study of the Effect of Functional Groups on the Thiazole-5H Proton Chemical Shift in ¹H NMR Spectroscopy

by Angelika Baranowska-Łączkowska and Krzysztof Z. Łączkowski

Materials 2026, 19(11), 2400; https://doi.org/10.3390/ma19112400 - 4 Jun 2026

Viewed by 227

Abstract

The relationship between the position of the thiazole-5H proton signal and the presence of various substituents in the molecule was investigated in detail from an experimental and theoretical point of view. For this purpose, twenty 2,4-disubstituted thiazole derivatives were carefully chosen and synthesized, [...] Read more.

The relationship between the position of the thiazole-5H proton signal and the presence of various substituents in the molecule was investigated in detail from an experimental and theoretical point of view. For this purpose, twenty 2,4-disubstituted thiazole derivatives were carefully chosen and synthesized, and their NMR spectra were recorded. Density functional theory calculations of ¹H NMR chemical shifts, frontier molecular orbitals, and molecular electrostatic potential surfaces were performed. The position of the thiazole-5H proton signal in the NMR spectrum is shown to strongly depend on the type and position of substituents in the molecule. Based on the obtained results, we can conclude that compounds with the smallest values of thiazole-5H proton shift are simultaneously those with small electron affinity, ionization potential and molecular electronegativity values, while compounds with the largest values of thiazole-5H proton shift have large electron affinity, ionization potential, and molecular electronegativity and a small HOMO-LUMO energy gap. These relationships become less clear in the case of compounds with intermediate values of the proton shift. Present research is a step towards an easy-to-use tool for predicting electronic effects in materials containing thiazole, based on the position of the thiazole-5H proton NMR signal. Full article

(This article belongs to the Special Issue Computational Simulation for Material Applications: From Density Functional Theory (DFT) to Molecular Dynamics (MD))

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Materials, Volume 19, Issue 11 (June-1 2026) – 252 articles

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