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Materials, Volume 18, Issue 9 (May-1 2025) – 154 articles

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15 pages, 3804 KiB  
Article
Electroanalysis of Apocynin Part 2: Investigations on a Boron-Doped Diamond Electrode in Aqueous Buffered Solutions
by Agata Skorupa, Magdalena Jakubczyk and Slawomir Michalkiewicz
Materials 2025, 18(9), 2044; https://doi.org/10.3390/ma18092044 (registering DOI) - 29 Apr 2025
Abstract
In this study, the voltammetric behavior of apocynin on a boron-doped diamond electrode in a phosphate buffer (pH 7.3) has been reported for the first time. The oxidation process is quasi-reversible, diffusion-controlled, and involves one electron and one proton. The product of the [...] Read more.
In this study, the voltammetric behavior of apocynin on a boron-doped diamond electrode in a phosphate buffer (pH 7.3) has been reported for the first time. The oxidation process is quasi-reversible, diffusion-controlled, and involves one electron and one proton. The product of the electrode reaction is an unstable radical that undergoes successive chemical transformations near the working electrode. The proposed mechanism of this process can be described as EqCi and served as the basis for the development of a new voltammetric method for determining apocynin in natural samples. The analytical signal was the anodic peak on DPV curves at a potential of 0.605 V vs. Ag/AgCl. A linear response was observed in the concentration range of 0.213–27.08 mg L−1. The estimated LOD and LOQ values were 0.071 and 0.213 mg L−1, respectively. The effectiveness of the method was demonstrated both in control determinations and in the analysis of the dietary supplement. This procedure is simple, fast, sensitive, selective, and requires no complicated sample preparation, which is limited only to a simple extraction with ethanol. The low consumption of non-toxic reagents makes it environmentally friendly. To the best of our knowledge, this is the first presentation of a voltammetric procedure to determine this analyte studied in a phosphate buffer solution on a boron-doped diamond electrode. It can also be easily adapted to determine other phenolic compounds with antioxidant properties in various matrices. Full article
(This article belongs to the Special Issue Advanced Research of Organic Molecules and Materials for Modern Chemical and Biological Applications)
15 pages, 4604 KiB  
Article
Preparation, Thermal, and Optical Properties of D-A-Type Molecules Based on 1,3,5-Triazine for Violet-Blue Fluorescent Materials
by Lu Wang, Enwang Du, Zhi Liu and Zhiqiang Liu
Materials 2025, 18(9), 2043; https://doi.org/10.3390/ma18092043 (registering DOI) - 29 Apr 2025
Abstract
Organic violet-blue fluorescent materials have garnered significant interest for a broad spectrum of applications. A series of triazine-based molecules, that is, 2,4,6-tri(9H-carbazol-9-yl)-1,3,5-triazine (TCZT), 2,4,6-tri(1H-indol-1-yl)-1,3,5-triazine (TIDT), and 2,4,6-tris(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,3,5-triazine (TDBCZT), exhibiting violet-blue emission were synthesized via a catalyst-free aromatic nucleophilic substitution reaction. These compounds possess [...] Read more.
Organic violet-blue fluorescent materials have garnered significant interest for a broad spectrum of applications. A series of triazine-based molecules, that is, 2,4,6-tri(9H-carbazol-9-yl)-1,3,5-triazine (TCZT), 2,4,6-tri(1H-indol-1-yl)-1,3,5-triazine (TIDT), and 2,4,6-tris(3,6-di-tert-butyl-9H-carbazol-9-yl)-1,3,5-triazine (TDBCZT), exhibiting violet-blue emission were synthesized via a catalyst-free aromatic nucleophilic substitution reaction. These compounds possess a non-planar and twisted structure with favorable charge-transfer characteristics, demonstrating excellent thermal stability (decomposition temperatures of 370 °C, 384 °C, and 230 °C, respectively). Cyclic voltammetry analysis, combined with time-dependent density functional theory (TD-DFT) calculations at the B3LYP/6-31G(d) level, offered detailed insights into their electronic structures and electrochemical properties. Optical properties were systematically characterized using Ultraviolet–visible (UV–Vis) absorption and photoluminescence (PL) spectroscopy. The compounds exhibited violet-blue luminescence with emission peaks located at 397 nm, 383 nm, and 402 nm in toluene, respectively. In their respective films, the compounds exhibited varying degrees of spectral shifts, with emission peaks at 408 nm, 381 nm, and 369 nm. Moreover, the CIE (Commission Internationale de l’Éclairage) coordinates of TIDT in toluene were (0.155, 0.067), indicative of excellent violet purity. These compounds demonstrated significant two-photon absorption (TPA) properties, with cross-sections of 4.6 GM, 15.3 GM, and 7.4 GM, respectively. Notably, they exhibited large molar absorptivities and substantial photoluminescence quantum yields (PLQYs), suggesting their potential for practical applications as violet-blue fluorescent materials. Full article
(This article belongs to the Section Optical and Photonic Materials)
25 pages, 18977 KiB  
Article
Development of a Color-Changing Face Mask for Fever Detection Applications
by Nareerut Jariyapunya, Sunee Hathaiwaseewong, Nanjaporn Roungpaisan and Mohanapriya Venkataraman
Materials 2025, 18(9), 2042; https://doi.org/10.3390/ma18092042 (registering DOI) - 29 Apr 2025
Abstract
This study focused on developing a color-changing fabric face mask for fever detection. Reversible Thermochromic Leuco dye (RTL) was applied as an indicator to alert wearers of elevated body temperatures, with the color change occurring at 37.5 °C. Five fabric types Polyethylene (PE), [...] Read more.
This study focused on developing a color-changing fabric face mask for fever detection. Reversible Thermochromic Leuco dye (RTL) was applied as an indicator to alert wearers of elevated body temperatures, with the color change occurring at 37.5 °C. Five fabric types Polyethylene (PE), cotton (CO), a cotton–polyester blend (TC), polyester (PL), and Polyamide (PA) were coated with blue RTL to evaluate their color change responsiveness. The results showed that fabrics with higher thermal conductivity (λ), thermal absorptivity (b), and heat flow (q) exhibited faster color transitions. RTL-coated PE fabric demonstrated the best performance, with a thermal absorptivity of 312.8 Ws0.5m−2K−1 and a heat flow of 2.11 Wm−2, leading to a rapid color-change time of approximately 4.20 s. Although PE fabric had a lower thermal conductivity (57.6 × 10−3 Wm−1K−1) compared to PA fabric 84.56 (10−3 Wm−1K−1), the highest thickness 0.65 mm of PA fabric slowed its color-change reaction to 11.8 s. When selecting fabrics for optimal heat transfer, relying solely on fiber type or thermal conductivity (λ) is insufficient. The fabric’s structural properties, particularly thickness, significantly impact thermal resistance (γ). Experimental results suggest that thermal absorptivity and heat flow are more effective criteria for fabric selection, as they directly correlate with color-change performance. Full article
(This article belongs to the Special Issue Synthesis–Processing–Structure–Property Interrelationship of Multifunctional Polymeric Materials and Natural Polymers)
14 pages, 1596 KiB  
Article
Performance Evolution and Damage Evaluation of CRTS I Track Slab in Service Status
by Hongyao Lu, Wentao Wu and Yuelei He
Materials 2025, 18(9), 2041; https://doi.org/10.3390/ma18092041 (registering DOI) - 29 Apr 2025
Abstract
This study develops a quantitative framework to assess performance degradation and damage evolution in CRTS I ballastless track slabs. Based on the impact-echo method, the internal void distribution characteristics of the new and old track slabs were obtained. The track slabs were sampled [...] Read more.
This study develops a quantitative framework to assess performance degradation and damage evolution in CRTS I ballastless track slabs. Based on the impact-echo method, the internal void distribution characteristics of the new and old track slabs were obtained. The track slabs were sampled separately by drilling cores to verify the distribution of voids, and uniaxial compression tests were conducted simultaneously to quantify the attenuation of bearing capacity. The on-site wheel–rail force and temperature field data were monitored, based on the established three-dimensional finite element model of CRTS I ballastless track, and the damage distribution characteristics of the track slab under different load combinations after performance degradation were studied. The results show the following: (1) As the performance of the track slabs gradually deteriorated, it was reflected in the increasing internal void distribution area from 0.5% to 3.6%, corresponding to a 22.4% decrease in core strength. (2) The on-site monitoring results showed that the average wheel–rail force was 84.5 kN. The temperature gradient range varied from -50.4 °C/m to 100.0 °C/m, exceeding the allowable value of the design specifications. (3) The actual damage distribution of the track slab after performance degradation under different load combinations significantly increased at key stress locations such as near fasteners, convex abutments, and anchor holes of prestressed steel bars, which required special attention in actual maintenance and repair. Full article
(This article belongs to the Section Construction and Building Materials)
15 pages, 2487 KiB  
Article
Selenium-Containing Multi-Resonance Thermally Activated Delayed Fluorescence Host Material for Green and Red Phosphorescent OLEDs
by Hyukmin Kwon, Seokwoo Kang, Sangwook Park, Saeyoung Oh, Sang-Tae Kim, Kiho Lee, Hayoon Lee and Jongwook Park
Materials 2025, 18(9), 2040; https://doi.org/10.3390/ma18092040 (registering DOI) - 29 Apr 2025
Abstract
We report the molecular design and synthesis of a novel selenium-containing multi-resonance thermally activated delayed fluorescence (MR-TADF) host material, 3,6-di-tert-butyl-9,16-dioxa-15-selena-4b-boraindeno[2,1-a]naphtho[3,2,1-de]anthracene (TDBA-SePh), for green and red phosphorescent organic light-emitting diodes (PhOLEDs). By incorporating selenium into the DOBNA-based MR-TADF backbone, the reverse intersystem crossing (RISC) [...] Read more.
We report the molecular design and synthesis of a novel selenium-containing multi-resonance thermally activated delayed fluorescence (MR-TADF) host material, 3,6-di-tert-butyl-9,16-dioxa-15-selena-4b-boraindeno[2,1-a]naphtho[3,2,1-de]anthracene (TDBA-SePh), for green and red phosphorescent organic light-emitting diodes (PhOLEDs). By incorporating selenium into the DOBNA-based MR-TADF backbone, the reverse intersystem crossing (RISC) process was effectively activated, leading to enhanced utilization of triplet excitons. The corresponding RISC rate was determined to be 3.91 × 104 s−1. When applied to PhOLED devices, TDBA-SePh-based green and red OLEDs exhibited higher external quantum efficiency (EQE) and reduced efficiency roll-off compared to conventional mCP-based host materials. At a luminance of 1000 cd m−2, the green and red devices exhibited roll-off values of 2.5% and 4.3%, respectively. This improvement is attributed to the incorporation of selenium as a heteroatom, which accelerates the RISC process, thereby suppressing triplet-triplet annihilation (TTA). These results suggest that adopting a similar molecular design strategy can not only reduce efficiency roll-off but also enhance device efficiency and operational stability, offering significant potential for future OLED applications. Full article
(This article belongs to the Special Issue Enhancement Strategies for High External Quantum Efficiency of Organic Light Emitting Diodes (OLEDs) and the Analyses)
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24 pages, 16143 KiB  
Article
Influence of UV Radiation on the Appearance Quality of Fair-Faced Concrete and Mitigation Approaches
by Ao Wu, Jia Ke, Zhijie Liu and Zhonghe Shui
Materials 2025, 18(9), 2039; https://doi.org/10.3390/ma18092039 (registering DOI) - 29 Apr 2025
Abstract
Fair-faced concrete has garnered substantial attention in recent years owing to its aesthetic appeal and eco-friendly attributes. However, as a construction material, its long-term performance is highly dependent on its service environment, particularly ultraviolet (UV) radiation. This research focuses on examining the influence [...] Read more.
Fair-faced concrete has garnered substantial attention in recent years owing to its aesthetic appeal and eco-friendly attributes. However, as a construction material, its long-term performance is highly dependent on its service environment, particularly ultraviolet (UV) radiation. This research focuses on examining the influence of UV exposure and managing the admixtures employed in concrete and investigating the effects of UV radiation on the appearance quality, pore distribution, and micro-composition of fair-faced concrete. Results indicate that UV radiation enhances moisture evaporation, increases surface and bulk porosity, and accelerates carbonation and early hydration reactions, forming more calcite on the surface. These factors degrade the appearance quality of fair-faced concrete. To mitigate UV-aging damage, two common anti-UV admixtures, nano-silica (NS) and water-based fluorocarbon paint (FC), were evaluated. Results show that both admixtures effectively improve the UV-resistance of fair-faced concrete, particularly when combined. The FC+NS group reduced the surface glossiness loss rate from 28.63% to 12.95% after 28 days of UV exposure, with surface porosity and maximum pore diameter recorded at 0.157% and 3.66 mm, respectively, indicating excellent appearance quality. These findings underscore the potential of these admixtures, both individually and in combination, to enhance the UV resistance of fair-faced concrete, sustaining its durability under prolonged UV exposure. Full article
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17 pages, 6625 KiB  
Article
Mechanical Properties of Aluminum Alloy Tubes Fabricated Through Surface Mechanical Grinding Treatment and Graphene Lubrication Under Biaxial Stress States
by Yang Cai, Xiao-Lei Cui, Chunhuan Guo, Fengchun Jiang and Piaoping Yang
Materials 2025, 18(9), 2038; https://doi.org/10.3390/ma18092038 (registering DOI) - 29 Apr 2025
Abstract
To enhance the mechanical properties of 6063-T4 aluminum alloy tubes, surface mechanical grinding treatment was conducted under graphene-assisted lubrication. The effects of rotational speed and cooling conditions on the mechanical properties of aluminum alloy tubes under biaxial stress were systematically explored. It was [...] Read more.
To enhance the mechanical properties of 6063-T4 aluminum alloy tubes, surface mechanical grinding treatment was conducted under graphene-assisted lubrication. The effects of rotational speed and cooling conditions on the mechanical properties of aluminum alloy tubes under biaxial stress were systematically explored. It was found that increasing the rotational speed and cooling rate facilitates the formation of finer lamellar grains, higher-density nano-precipitates, and a reduced dislocation density on the tube surface. These microstructural characteristics significantly contribute to an increased yield strength and sustained strain hardening capacity during bulging deformation. This study proposes an innovative approach for improving the strength and toughness of light alloy components during integral forming, providing meaningful insights for future engineering applications. Full article
(This article belongs to the Special Issue Mechanical Performance and Microstructural Characterization of Light Alloys (2nd Edition))
3 pages, 149 KiB  
Editorial
Metallurgical Process Simulation and Optimization—2nd Volume
by Jiangshan Zhang, Jiali Tang and Qing Liu
Materials 2025, 18(9), 2037; https://doi.org/10.3390/ma18092037 (registering DOI) - 29 Apr 2025
Abstract
As the cornerstone of industrial civilization, metallurgical engineering has consistently driven materials innovation and advanced manufacturing technologies [...] Full article
(This article belongs to the Special Issue Metallurgical Process Simulation and Optimization—2nd Volume)
35 pages, 5269 KiB  
Article
The Quantum Transport of Dirac Fermions in Selected Graphene Nanosystems Away from the Charge Neutrality Point
by Adam Rycerz
Materials 2025, 18(9), 2036; https://doi.org/10.3390/ma18092036 - 29 Apr 2025
Abstract
The peculiar electronic properties of graphene, including the universal dc conductivity and the pseudodiffusive shot noise, are usually found in a small vicinity close to the charge neutrality point, away from which the electron’s effective mass raises, and nanostructures in graphene start to [...] Read more.
The peculiar electronic properties of graphene, including the universal dc conductivity and the pseudodiffusive shot noise, are usually found in a small vicinity close to the charge neutrality point, away from which the electron’s effective mass raises, and nanostructures in graphene start to behave similarly to familiar Sharvin contacts in semiconducting heterostructures. Recently, it was pointed out that as long as abrupt potential steps separate the sample area from the leads, some graphene-specific features can be identified relatively far from the charge neutrality point. These features include greater conductance reduction and shot noise enhancement compared to the standard Sharvin values. The purpose of this paper is twofold: First, we extend the previous analysis based on the effective Dirac equation, and derive the formulas that allow the calculation of the arbitrary charge transfer cumulant for doped graphene. Second, the results of the analytic considerations are compared with numerical simulations of quantum transport on the honeycomb lattice for selected nanosystems for which considerations starting from the Dirac equation cannot be directly adapted. For a wedge-shaped constriction with zigzag edges, the transport characteristics can be tuned from graphene-specific (sub-Sharvin) values to standard Sharvin values by varying the electrostatic potential profile in the narrowest section. A similar scenario is followed by the half-Corbino disk. In contrast, a circular quantum dot with two narrow openings showing a mixed behavior appears: the conductance is close to the Sharvin value, while the Fano factor approaches the value characterizing the symmetric chaotic cavity. Carving a hole in the quantum dot to eliminate direct trajectories between the openings reduces the conductance to sub-Sharvin value, but the Fano factor is unaffected. Our results suggest that experimental attempts to verify the predictions for the sub-Sharvin transport regime should focus on systems with relatively wide openings, where the scattering at the sample edges is insignificant next to the scattering at the sample–lead interfaces. Full article
(This article belongs to the Special Issue Quantum Transport in Novel 2D Materials and Structures)
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16 pages, 3051 KiB  
Article
Recycling End-of-Life Bituminous Membranes in Asphalt Mixtures: A Laboratory Study
by Marco Pasetto, Safeer Haider, Andrea Baliello and Emiliano Pasquini
Materials 2025, 18(9), 2035; https://doi.org/10.3390/ma18092035 - 29 Apr 2025
Abstract
The circular economy (i.e., reuse and recycling of waste materials) is gaining attention for the goal of achieving net-zero waste. In this regard, the use of waterproofing membrane waste in bituminous materials can be a valid option, as every year, a lot of [...] Read more.
The circular economy (i.e., reuse and recycling of waste materials) is gaining attention for the goal of achieving net-zero waste. In this regard, the use of waterproofing membrane waste in bituminous materials can be a valid option, as every year, a lot of bituminous membrane wastes are generated both as production scraps or end-of-life wastes. Given this background, the recycling feasibility of end-of-life bituminous membrane waste (MW) in asphalt mixtures was assessed in this research study. To this aim, MW shreds (≤20 mm) were added to dense-graded bituminous mixtures using the dry-mixing method. The shreds were dosed at 0.5% by the mix weight (mix coded as SH−) or at 2% by mix weight (mix coded as SH+). A corresponding reference mix without MW was also tested for comparison purposes. The mixtures’ workability, strength and stiffness as well as permanent deformation, moisture and fatigue resistance were evaluated. Overall, the laboratory experimental findings showed that MW-modified bituminous mixtures with a higher dosage of membrane waste (SH+) have relatively higher moisture resistance, fatigue resistance, stiffness and high-temperature performance with respect to the corresponding reference mix. Moreover, both the reference and MW-modified mixtures showed similar workability regardless of the MW content. Full article
(This article belongs to the Special Issue Innovative Materials and Technologies for Road Pavements)
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16 pages, 7782 KiB  
Article
Microstructural Evolution and Internal Hydrogen Content of Ultra-High-Strength Automotive Steels During Two Typical Industrial Production Flows
by Zhiyuan Chang, Jingjing Yin, Long Li, Xingzhao Chen, Xinyi Ruan and Liangyun Lan
Materials 2025, 18(9), 2034; https://doi.org/10.3390/ma18092034 - 29 Apr 2025
Abstract
Hot stamping is a promising method to manufacture ultra-high-strength automotive steel components with high dimension accuracy. In this work, two actual industrial production flows (with and without Al-Si hot dipping) were investigated to reveal their microstructural evolution and hydrogen content at different production [...] Read more.
Hot stamping is a promising method to manufacture ultra-high-strength automotive steel components with high dimension accuracy. In this work, two actual industrial production flows (with and without Al-Si hot dipping) were investigated to reveal their microstructural evolution and hydrogen content at different production steps. Meanwhile, the variations in composition and phase structures of the Al-Si coating layer were studied in terms of energy-dispersive spectrometry and electron backscattering diffraction techniques. The results showed that the microstructure at the steel substrate changed from the pancake-shaped pearlite and ferrite, degenerated pearlite and annealed ferrite, lath martensite, and then tempered martensite with the progress of the production steps, which was not affected by the Al-Si hot dipping. The final coating layer exhibited a multi-sublayer structure with the alternative distribution of FeAl and Fe2Al5, which contained many microcracks on the brittle phase Fe2Al5. The Al-Si-coated specimens always had higher hydrogen content than the bare steel specimens because of the hydrogen generation at the hot stamping stage and hydrogen absorption during the hot-dip aluminizing stage. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
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17 pages, 5128 KiB  
Article
Effect of Temperature on Material Removal Rate During Shear-Thickening Polishing
by Zhong Yu, Jiahuan Wang, Jiahui Du, Lanying Shao and Binghai Lyu
Materials 2025, 18(9), 2033; https://doi.org/10.3390/ma18092033 - 29 Apr 2025
Abstract
Shear-thickening polishing (STP) technology achieves efficient processing by modulating the non-Newtonian properties of the slurry, while temperature has an important effect on its rheological behavior. To reveal the effect of temperature on material removal rate (MRR) during the shear-thickening polishing process, this study [...] Read more.
Shear-thickening polishing (STP) technology achieves efficient processing by modulating the non-Newtonian properties of the slurry, while temperature has an important effect on its rheological behavior. To reveal the effect of temperature on material removal rate (MRR) during the shear-thickening polishing process, this study measured the rheological profiles of the shear-thickening polishing slurry (STPS) at different temperatures and observed the rheological behavior using a high-speed video camera, as well as monitored the changes in the polishing force exerted on the workpieces, MRR, and the surface roughness. Experimental data show that the peak viscosity of the slurry in the shear-thickening state decreases from 0.81 Pa·s to 0.49 Pa·s as the temperature increases from 30 °C to 50 °C. High-speed video observations show that the wavy solid layer in the thickening area diminishes with increasing temperature, the distribution area shrinking, and nearly vanishing at 50 °C. When the temperature rises from 30 °C to 40 °C, the average polishing force at 30 min decreases from 25.3 N to 22.6 N by 10.6%. MRR decreases from 33.5 nm/min to 7.9 nm/min by 75.5%. The decrease in MRR is much greater than the polishing force. This study provides an experimental basis for the effect of temperature on STP. Full article
(This article belongs to the Section Manufacturing Processes and Systems)
18 pages, 5896 KiB  
Article
Efficiency of Alternative Reinforcement Methods for Wooden Ceilings and Their Ecological Aspects
by Karl Deix, Christian Huber and Josip Gogic
Materials 2025, 18(9), 2032; https://doi.org/10.3390/ma18092032 - 29 Apr 2025
Abstract
In the case of load increases and the refurbishment of existing buildings, it is often necessary to carry out strengthening measures on existing timber beams. When timber concrete composite (TCC) ceilings cannot be used, it is possible to reinforce the undersides of the [...] Read more.
In the case of load increases and the refurbishment of existing buildings, it is often necessary to carry out strengthening measures on existing timber beams. When timber concrete composite (TCC) ceilings cannot be used, it is possible to reinforce the undersides of the beams with structural steel or fiber composites (aramid or carbon-fiber-reinforced polymer). This work investigates how significant effects on the load-bearing and deformation behavior can be achieved with these materials in terms of construction practice. The article is intended to show structural engineers which reinforcement measures lead to which forces, deformations, etc., and how these are utilized. This should form the basis for the planning of reinforcement measures, as it is not clear from the beginning whether AFRP, CFRP, or steel is the most suitable material. For this purpose, a comparative parameter study was carried out under practical conditions and with a variable degree of reinforcement using the corresponding formulas. The internal forces in the timber and reinforcement cross-sections, the deflection behavior, and the failure loads at the strength and design levels were calculated. It was demonstrated that, particularly for steel and carbon-fiber-reinforced polymer (CFRP) reinforcements, significant increases in the ultimate load can be achieved and the often-important deformation behavior can be significantly improved. Especially the steel variant leads to high improvements in deflection and breaking load behavior, with the base material (wood) also being utilized more economically as a result. A comparative ecological study in the form of the global warming potential showed that reinforcement methods are also advantageous from the point of view of sustainability compared to renovations with timber concrete composite slabs or new concrete slabs. Full article
(This article belongs to the Section Advanced Composites)
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18 pages, 8668 KiB  
Article
The Preparation and Properties of Ultra-High-Performance Concrete with Aeolian Sand: A Lab Study on the Effect of the Curing Method
by Yang Lv, Boyu Zhao, Jie Zhu, Chenhao He, Yunlu Ge, Yuanshuai Wu, Yanchao Zhu, Jianming Dan, Yang Zhou and Xiangguo Li
Materials 2025, 18(9), 2031; https://doi.org/10.3390/ma18092031 - 29 Apr 2025
Abstract
The utilization of aeolian sand (AS) as a substitute for river sand (RS) in ultra-high-performance concrete (UHPC) offers a sustainable solution to address natural sand resource shortages while enhancing AS utilization. This study systematically evaluates the influence of AS content (0–100% RS replacement [...] Read more.
The utilization of aeolian sand (AS) as a substitute for river sand (RS) in ultra-high-performance concrete (UHPC) offers a sustainable solution to address natural sand resource shortages while enhancing AS utilization. This study systematically evaluates the influence of AS content (0–100% RS replacement by mass) on the workability, mechanical properties, and microstructure of UHPC under different curing regimes. All mixtures incorporate 0.65% by volume of straight steel fibers to ensure adequate fiber reinforcement. The results reveal that the spherical morphology, smooth surface nature, and fine particle size of AS enhance the matrix fluidity and reduce the early autogenous shrinkage of UHPC. By employing steam curing at 90 °C for 2 d followed by standard curing for 7 d (M3), UHPC samples with a 60% and 80% AS substitution achieve a compressive strength of 132.4 MPa and 130.8 MPa, respectively; a flexural strength exceeding 18 MPa; a porosity below 10%; and a gel pore content exceeding 60%. The steel fiber reinforcement contributes significantly to the flexural performance, with the fiber–matrix interface quality maintained even at high AS replacement levels. These findings highlight the feasibility of AS as an alternative fine aggregate in UHPC. Full article
(This article belongs to the Special Issue Sustainability in Asphalt, Concrete and Pavement Materials: Design, Performance, and Characterization)
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11 pages, 3775 KiB  
Article
Deformation Behavior of S32750 Duplex Stainless Steel Based on In Situ EBSD Technology
by Shun Bao, Han Feng, Zhigang Song, Jianguo He, Xiaohan Wu and Yang Gu
Materials 2025, 18(9), 2030; https://doi.org/10.3390/ma18092030 - 29 Apr 2025
Abstract
In this study, we investigated the two-phase hardening behavior and microstructural evolution of S32750 duplex stainless steel during the tensile deformation process. The analysis was conducted using in situ electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and microhardness testing. It was observed [...] Read more.
In this study, we investigated the two-phase hardening behavior and microstructural evolution of S32750 duplex stainless steel during the tensile deformation process. The analysis was conducted using in situ electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and microhardness testing. It was observed that strain transfer occurred between the two phases in the position away from the fracture. The ferrite phase exhibited softening, while the austenite phase underwent hardening. In the region less than 1 mm from the fracture site, both phases experienced a rapid hardening, with the maximum hardness difference between the two phases near the fracture reaching approximately 45 HV. In situ EBSD results indicate that the kernel average misorientation (KAM) value for the ferrite phase consistently exceeds that of the austenite phase during the initial stages of deformation. Conversely, in the final stages of deformation, the KAM value for austenite surpasses that of ferrite. In the initial stage of deformation, the type of grain boundaries in both phases remains largely unaltered. However, in the later stages of deformation, there is a marked increase in the number of small-angle grain boundaries within ferrite, which become approximately three times that of the large-angle grain boundaries. As deformation progresses, the maximum orientation distribution density of the ferrite phase is reduced by approximately 50%, with the preferred orientation shifting from the {100} plane to the {111} plane. In contrast, the orientation distribution of the austenite remains relatively uniform, with no significant change in the maximum orientation distribution density observed. This indicates that after substantial deformation, the rotation of ferrite grains significantly increases the deformation resistance, whereas the austenite phase continues to harden. This differential behavior leads to the continuous accumulation of strain at the phase boundaries, ultimately causing cracks to form at these boundaries and resulting in the sample’s fracture. Full article
(This article belongs to the Special Issue From Materials to Applications: High-Performance Steel Structures)
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13 pages, 5193 KiB  
Article
Deep-Subwavelength Composite Metamaterial Unit for Concurrent Ventilation and Broadband Acoustic Insulation
by Xiaodong Zhang, Jinhong He, Jing Nie, Yang Liu, Huiyong Yu, Qi Chen and Jianxing Yang
Materials 2025, 18(9), 2029; https://doi.org/10.3390/ma18092029 - 29 Apr 2025
Abstract
Balancing ventilation and broadband sound insulation remains a significant challenge in noise control engineering, particularly when simultaneous airflow and broadband noise reduction are required. Conventional porous absorbers and membrane-type metamaterials remain fundamentally constrained by ventilation-blocking configurations or narrow operational bandwidths. This study presents [...] Read more.
Balancing ventilation and broadband sound insulation remains a significant challenge in noise control engineering, particularly when simultaneous airflow and broadband noise reduction are required. Conventional porous absorbers and membrane-type metamaterials remain fundamentally constrained by ventilation-blocking configurations or narrow operational bandwidths. This study presents a ventilated composite metamaterial unit (VCMU) co-integrating optimized labyrinth channels and the Helmholtz resonators within a single-plane architecture. This design achieves exceptional ventilation efficiency through a central flow channel while maintaining sub-λ/30 thickness (λ/31 at 860 Hz). Coupled transfer matrix modeling and finite-element simulations reveal that Fano–Helmholtz resonance mechanisms synergistically generate broadband transmission loss (STL) spanning 860–1634 Hz, with six STL peaks in the 860 and 1634 Hz bands (mean 18.4 dB). Experimental validation via impedance tube testing confirmed excellent agreement with theoretical and simulation results. The geometric scalability allows customizable acoustic bandgaps through parametric control. This work provides a promising solution for integrated ventilation and noise reduction, with potential applications in building ventilation systems, industrial pipelines, and other noise-sensitive environments. Full article
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14 pages, 9327 KiB  
Article
Evaluation of Crack Formation in Heat Pipe-Welded Joints
by Min Ji Song, Keun Hyung Lee, Jun-Seob Lee, Heesan Kim, Woo Cheol Kim and Soo Yeol Lee
Materials 2025, 18(9), 2028; https://doi.org/10.3390/ma18092028 - 29 Apr 2025
Abstract
This study investigates the failure of a 750A dual-insulated pipeline, where cracks developed along the weld joints during heat supply resumption at the district heating facility. A comprehensive analysis was conducted through visual inspection, mechanical testing, microstructural characterization, finite element analysis (FEA), and [...] Read more.
This study investigates the failure of a 750A dual-insulated pipeline, where cracks developed along the weld joints during heat supply resumption at the district heating facility. A comprehensive analysis was conducted through visual inspection, mechanical testing, microstructural characterization, finite element analysis (FEA), and electrochemical corrosion testing. The results indicate that cracks were generated in the heat-affected zone (HAZ), primarily caused by galvanic corrosion and thermal expansion-induced stress accumulation. Open circuit potential (OCP) measurements in a 3 M NaCl solution confirmed that the HAZ was anodic, leading to the most vulnerable position to corrosion. Furthermore, localized electrochemical tests were conducted for respective microstructural regions within the HAZ. The results reveal that coarse-grained HAZ exhibited the lowest corrosion potential, giving rise to preferential corrosion, promoting pit formation, and serving as initiation sites for stress concentration and crack propagation. FEA simulations demonstrate that pre-existing microvoids in the HAZ act as stress concentration sites, undergoing a localized stress exceeding 475 MPa. These findings emphasize the importance of controlling microstructural stability and mechanical integrity in welded pipelines, particularly in corrosive environments subjected to thermal stresses. Full article
(This article belongs to the Special Issue Corrosion Behavior and Mechanical Properties of Metallic Materials (Second Edition))
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20 pages, 8770 KiB  
Article
Failure and Energy Evolution Characteristics of Saturated Natural Defective Material Under Different Confining Pressures
by Zhihao Gao, Shihao Guo, Xiaoyong Yang, Shanchao Hu, Junhong Huang, Yafei Cheng, Dawang Yin and Jinhao Dou
Materials 2025, 18(9), 2027; https://doi.org/10.3390/ma18092027 - 29 Apr 2025
Abstract
In nature, many brittle materials contain natural defects such as microcracks or joints, for example, rocks. Under water-saturated conditions, the strength of defective materials undergoes varying degrees of attenuation, leading to material failure and even structural instability in engineering contexts. Moreover, the deformation [...] Read more.
In nature, many brittle materials contain natural defects such as microcracks or joints, for example, rocks. Under water-saturated conditions, the strength of defective materials undergoes varying degrees of attenuation, leading to material failure and even structural instability in engineering contexts. Moreover, the deformation and failure of defective brittle materials are essentially the result of the accumulation and dissipation of energy. Studying the energy evolution of defective brittle materials under load is more conducive to reflecting the intrinsic characteristics of strength changes and overall failure of brittle materials under external loading. Natural defective brittle rock materials were firstly water saturated and triaxial compression tests were performed to determine the mechanical properties of water-saturated materials. The energy evolution patterns of water-saturated materials under varying confining pressures were also obtained. Using the discrete element method, the macro- and micro-failure characteristics of water-saturated materials were investigated, revealing the mesoscopic mechanisms of deformation and failure evolution in these materials. The results indicate that confining pressure significantly enhances the peak compressive strength and elastic modulus of water-saturated defective materials. When the confining pressure increased from 0 MPa to 20 MPa, the peak strength and elastic modulus of the water-saturated materials increased by 126.8% and 91.9%, respectively. Confining pressure restricts the radial deformation of water-saturated materials and dominates the failure mode. As confining pressure increases, the failure mode transitions from tensile splitting (at 0 MPa confining pressure) to shear failure (at confining pressures ≥ 10 MPa), with the failure plane angle gradually decreasing as confining pressure rises. Confining pressure significantly alters the energy storage–release mechanism of water-saturated defective brittle materials. At peak load, the total energy, elastic energy, and dissipated energy increased by 347%, 321%, and 1028%, respectively. The ratio of elastic energy storage to peak strain ratio shows a positive correlation, and the elastic storage ratio of water-saturated defective brittle materials under confining pressure is always higher than that without confining pressure. When the strain ratio exceeds 0.94, a negative correlation between confining pressure and the rate of elastic storage ratio is observed. From the perspective of mesoscopic fracture evolution in water-saturated defective brittle materials, the crack propagation path shifts from the periphery to the center of the material, and the fracture angle decreases linearly from 89° to 58° as confining pressure increases. The dominant direction of crack development is concentrated within the 45–135° range. The findings elucidate the mechanisms by which water saturation and confining pressure influence the strength degradation of natural defective brittle materials from both mesoscopic and energy perspectives, providing theoretical support for the stability control of related engineering structures. Full article
(This article belongs to the Special Issue Advances in Material Structural Analysis: Finite Element Analysis and Numerical Modelling)
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14 pages, 9589 KiB  
Article
Evolutions in Microstructure and Mechanical Properties of Ultra-Thin Oligocrystalline Invar Alloy Strip During Cold Rolling
by Jianguo Yang, Yajin Xia, Qingke Zhang, Genbao Chen, Cheng Xu, Zhenlun Song and Jiqiang Chen
Materials 2025, 18(9), 2026; https://doi.org/10.3390/ma18092026 - 29 Apr 2025
Abstract
The ultra-thin Invar alloy strips are widely used in the manufacture of the fine masks; cold rolling of such thin strips (<100 μm) poses significant difficulties, primarily due to the limited number of grains within the thickness range. Consequently, it is important to [...] Read more.
The ultra-thin Invar alloy strips are widely used in the manufacture of the fine masks; cold rolling of such thin strips (<100 μm) poses significant difficulties, primarily due to the limited number of grains within the thickness range. Consequently, it is important to understand the grain structure and property evolutions of the ultra-thin Invar alloy strips during cold rolling. In this study, an annealed Invar36 alloy strip, 100 µm thick, was cold rolled to different thicknesses, and the surface deformation morphologies, cross-sectional grain structure, intracrystalline microstructure and tensile properties of these thin strips were characterized and analyzed. The results show that plastic deformation of the initial annealed equiaxed grains is not uniform, depending on the grain orientation, resulting in different slip bands morphologies, unevenness and increase in roughness. Meanwhile, the grain rotation and rolling texture develop with increasing cold rolling reduction. The dislocation density in the 60% cold-rolled strip is about decuple that of the original annealed strip, and high-density tangled dislocations are formed, making the tensile strength increase from 430 MPa to 738 MPa. Grain refining and proper intermediate annealing are proposed to optimize the thickness uniformity, evenness and surface roughness. Full article
(This article belongs to the Special Issue Forming Technologies and Mechanical Properties of Advanced Materials - 2nd Volume)
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21 pages, 27535 KiB  
Article
A Comparative Study of A2SiF6 (A = Cs, K) Phosphor Host Matrices: Linear Combination of Atomic Orbital Hybrid Density Functional Theory Calculations
by Leonid L. Rusevich, Mikhail G. Brik, Denis Gryaznov, Alok M. Srivastava, Ilya D. Chervyakov, Guntars Zvejnieks, Dmitry Bocharov and Eugene A. Kotomin
Materials 2025, 18(9), 2025; https://doi.org/10.3390/ma18092025 - 29 Apr 2025
Abstract
Cesium hexafluorosilicate (Cs2SiF6, CSF) and potassium hexafluorosilicate (K2SiF6, KSF) compounds are suitable hosts for luminescent impurities. In this work, the results of first-principle calculations of the basic properties of both these compounds are discussed and [...] Read more.
Cesium hexafluorosilicate (Cs2SiF6, CSF) and potassium hexafluorosilicate (K2SiF6, KSF) compounds are suitable hosts for luminescent impurities. In this work, the results of first-principle calculations of the basic properties of both these compounds are discussed and compared with the available experimental and theoretical data. The simulations were performed using the CRYSTAL23 computer code within the linear combination of atomic orbitals (LCAO) method of the density functional theory (DFT) and the advanced hybrid DFT-HF exchange-correlation B1WC functional. A comparative study of the structural, electronic, and elastic properties of the two materials is presented, along with a study of the dependence of properties on external pressure in the range of 0–20 GPa. In particular, the electronic properties with an emphasis on the effective atomic charges (by means of Mulliken analysis) and the chemical bonding properties (by means of crystal orbital overlap population (COOP) analysis) were addressed, with regards to the pressure effects. The structure of the valence bands at 0 and 20 GPa was compared. The vibrational properties of CSF and KSF were calculated, including the simulation of the one-phonon IR and Raman spectra. The calculated Raman spectra exhibit excellent agreement with the experimental ones. The pressure dependences of sound speeds and the Debye temperature are evaluated. Full article
(This article belongs to the Section Materials Simulation and Design)
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15 pages, 6988 KiB  
Article
Discrete Element Method (DEM) Studies on Correcting the Particle Size Effect on the Shear Behaviors of Gravelly Soils
by Xiaolei Zhang, Zhenping Wu, Houyun Han, Yifeng Gao, Zhuofeng Li and Peng Xia
Materials 2025, 18(9), 2024; https://doi.org/10.3390/ma18092024 - 29 Apr 2025
Abstract
The presence of overlarge gravel particles poses significant challenges for laboratory testing on prototype gravelly soils due to sample size limitations. To address this issue, replacement techniques, such as substituting overlarge particles with finer materials, offer practical solutions. However, the impact of these [...] Read more.
The presence of overlarge gravel particles poses significant challenges for laboratory testing on prototype gravelly soils due to sample size limitations. To address this issue, replacement techniques, such as substituting overlarge particles with finer materials, offer practical solutions. However, the impact of these techniques on the mechanical behavior of gravelly soils, particularly shear strength and stiffness, remains poorly understood. This study aims to bridge this knowledge gap by investigating the particle size effect on the shear behaviors of binary mixtures using a series of Discrete Element Method (DEM) simulations. Updated scaling relations, based on Iai’s generalized scaling relations, were proposed to correct for particle size effects. DEM simulations, including drained triaxial tests and shear modulus measurements, were performed to validate the proposed law. The results indicate that the gravel replacement technique has a minor effect on peak shear strength but significantly reduces soil stiffness, especially at high gravel contents. The scaling relations effectively correct for the particle size effect, enabling the accurate prediction of shear behaviors of the prototype gravelly soils from those of the model gravelly soils. These validations demonstrate that for addressing the soil deformation problem instead of the stability problem in ultimate state, the developed scaling relations are highly effective for correcting the particle size effect. Based on the developed scaling relations, engineers can predict prototype-scale shear behaviors of gravelly soils with overlarge particles using scaled laboratory models, reducing reliance on costly large-scale equipment. Additionally, future studies, through both DEM simulations and laboratory experiments, are recommended to further validate and refine the proposed method across diverse soil conditions and loading scenarios, such as cyclic loadings. Full article
(This article belongs to the Special Issue Innovative Granular Materials in Civil Infrastructure: Characterization and Modeling)
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19 pages, 11572 KiB  
Article
Sustainable Material Selection for Interior Design Furniture: A Simple Procedure Based on Environmental Analysis and Structural Optimization
by Paolo Trucillo, Farah Chaouali and Francesco Paolo Antonio Portioli
Materials 2025, 18(9), 2023; https://doi.org/10.3390/ma18092023 - 29 Apr 2025
Abstract
A simple procedure is proposed for the sustainable selection of materials for interior design. The procedure is based on structural, environmental, and material cost analysis. For structural analysis, finite element models are used to analyze the behavior in terms of stress and strains [...] Read more.
A simple procedure is proposed for the sustainable selection of materials for interior design. The procedure is based on structural, environmental, and material cost analysis. For structural analysis, finite element models are used to analyze the behavior in terms of stress and strains and to optimize the product size. For environmental analysis, the assessment focuses on the carbon footprint of each material, considering CO2 emissions throughout its lifecycle. To show the potentialities of the proposed procedure, the Iso-Lounge chair by Jasper Morrison was selected as a case study. The research evaluates three materials (plywood, polypropylene, and polycarbonate), assessing their mechanical properties, cost implications, and CO2 emissions. Results indicate that plywood, with a reduced thickness in the redesigned model, maintains structural integrity while significantly lowering the amount of material used. Compared to polypropylene and polycarbonate, which required greater thickness, plywood demonstrated superior mechanical efficiency and cost-effectiveness. Additionally, CO2 emissions analysis revealed that plywood had a lower footprint than polycarbonate and was comparable to polypropylene. These findings highlight the advantages of engineered wood in sustainable furniture design, offering a balance between performance, affordability, and environmental responsibility. The redesign approach optimizes material use, demonstrating the potential for reducing waste and enhancing sustainability in structural applications. Full article
(This article belongs to the Special Issue Advances in Materials: Modelling Challenges and Technological Progress for Green Engineering and Sustainable Development)
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12 pages, 3049 KiB  
Article
Bandgap of Epitaxial Single-Crystal BiFe1−xMnxO3 Films Grown Directly on SrTiO3/Si(001)
by Samuel R. Cantrell, John T. Miracle, Ryan J. Cottier, Skyler Lindsey and Nikoleta Theodoropoulou
Materials 2025, 18(9), 2022; https://doi.org/10.3390/ma18092022 - 29 Apr 2025
Abstract
We report the growth and optical characterization of single-crystal BiFe1−xMnxO3 thin films directly on SrTiO3/Si(001) substrates using molecular beam epitaxy. X-ray diffraction confirmed epitaxial growth, film crystallinity, and sharp interface quality. Scanning electron microscopy and energy [...] Read more.
We report the growth and optical characterization of single-crystal BiFe1−xMnxO3 thin films directly on SrTiO3/Si(001) substrates using molecular beam epitaxy. X-ray diffraction confirmed epitaxial growth, film crystallinity, and sharp interface quality. Scanning electron microscopy and energy dispersive X-ray spectroscopy verified uniform film morphology and successful Mn incorporation. Spectroscopic ellipsometry revealed a systematic bandgap reduction with increasing Mn concentration, from 2.7 eV in BiFeO3 to 2.58 eV in BiFe0.74Mn0.26O3, consistent with previous reports on Mn-doped BiFeO3. These findings highlight the potential of BiFe1₋xMnxO3 films for bandgap engineering, advancing their integration into silicon-compatible multifunctional optoelectronic and photovoltaic applications. Full article
(This article belongs to the Section Electronic Materials)
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22 pages, 2398 KiB  
Review
Current State of Knowledge Regarding the Treatment of Cranial Bone Defects: An Overview
by Jagoda Kurowiak, Krystian Piesik and Tomasz Klekiel
Materials 2025, 18(9), 2021; https://doi.org/10.3390/ma18092021 - 29 Apr 2025
Abstract
In this article, an analysis of the problem of treating bone defects using cranial bone disorders as an example is presented. The study was performed in the context of the development of various implant biomaterials used to fill bone defects. An analysis of [...] Read more.
In this article, an analysis of the problem of treating bone defects using cranial bone disorders as an example is presented. The study was performed in the context of the development of various implant biomaterials used to fill bone defects. An analysis of the requirements for modern materials is undertaken, indicating the need for their further development. The article focuses particular attention on these biomaterial properties, which have an influence on bioresorbability and promote osteointegration and bone growth. The analysis showed the need for further development of biomaterials, the characteristics of which may be multifunctionality. Multifunctional scaffolds are those that simultaneously fill and stabilize the defect and contribute to the proper process of regeneration and reconstruction of cranial bones. Due to the complex structure of the skull and special protective functions, there is a need to develop innovative implants. Implants with complex geometries can be successfully manufactured using additive technologies. Full article
(This article belongs to the Special Issue Advances in Implant Materials and Biocompatibility)
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14 pages, 4115 KiB  
Article
Effect of Potential-Determining Ions on Rheological Properties of Calcite Paste
by Jizhi Huang, Ruyu Li, Jiacheng Cai, Yu Wang, Jiansheng Chen and Hengbin Zheng
Materials 2025, 18(9), 2020; https://doi.org/10.3390/ma18092020 - 29 Apr 2025
Abstract
The mechanical properties of calcite suspension are predominantly affected by different ions dissolved in solution. In this work, natural and synthetic calcites were employed to investigate the influence of potential-determining ions (PDIs) (Ca2+, Mg2+, OH−, CO3 [...] Read more.
The mechanical properties of calcite suspension are predominantly affected by different ions dissolved in solution. In this work, natural and synthetic calcites were employed to investigate the influence of potential-determining ions (PDIs) (Ca2+, Mg2+, OH−, CO32− and SO42−) on the zeta potential and rheological behavior of calcite paste. Electric double layer (EDL) models were proposed to further interpret the ionic adsorption mode and zeta potential evolution. Experimental results show that moderate addition of the positive PDIs Ca2+ and Mg2+ significantly increases the positive charge of calcite and enhances paste flow. Calcite exhibits higher zeta potential in Ca(NO3)2 but lower viscosity in Mg(NO3)2, which is attributed to the different affinity of Ca2+ and Mg2+ for the calcite surface. As for the negative PDIs OH−, CO32− and SO42−, they make the calcite negatively charged with the order of ξNa2CO3>ξNa2SO4>ξNaOH. The negatively charged calcite paste exhibits much higher viscosity, which is against the conventional DLVO (Derjaguin–Landau–Verwey–Overbeek) theory. Lattice site screening and specific attraction induced by negative PDIs may be the reason for the phenomenon. This work provides a comprehensive understanding on the correlation between ionic adsorption, surface charge and particle interactions. These theories are enlightening for calcite application in many areas such as paper manufacturing, wall coating and heritage conservation. Full article
(This article belongs to the Section Soft Matter)
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12 pages, 8197 KiB  
Article
Grain Growth Kinetics of a Nickel-Based Superalloy Under Electric Pulse Treatment
by Zhiyu Xiang, Hongwei Li, Xin Zhang, Pengfei Gao and Mei Zhan
Materials 2025, 18(9), 2019; https://doi.org/10.3390/ma18092019 - 29 Apr 2025
Abstract
Grain boundaries play a vital role in determining the mechanical and physical properties of metallic materials. Heat treatment (HT) is widely employed to modify the content and distribution of grain boundaries. However, achieving precise control by HT remains challenging due to the scale [...] Read more.
Grain boundaries play a vital role in determining the mechanical and physical properties of metallic materials. Heat treatment (HT) is widely employed to modify the content and distribution of grain boundaries. However, achieving precise control by HT remains challenging due to the scale mismatch between heat transfer and microstructure evolution. Electric pulse treatment (EPT) offers a breakthrough in microstructure control, by unifying the scales of microstructure and heat generation through a local Joule heating effect, with significant acceleration to microstructure evolution through athermal effects. Those two aspects establish EPT as an effective approach to grain boundary regulation. Despite its advantages, the mechanisms underlying the thermal and athermal effects of EPT remain unclear. To this end, a study of the grain growth kinetics of a nickel-based superalloy with an inhomogeneous microstructure under EPT was carried out through experimental and theoretical approaches. Grain boundary migration behaviors in both coarse- and fine-grained regions were investigated, corresponding grain growth kinetics were established, and effects were validated via annealing twin evolution. The results reveal that EPT accelerates grain boundary migration more than HT, exhibiting a “target effect” where growth rates correlate with grain boundary density. The efficacy of EPT depends on the balance between enhanced grain boundary migration and a reduced treatment time. Full article
(This article belongs to the Special Issue Energy Field-Assisted Metal Forming)
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15 pages, 6837 KiB  
Article
Research on the Influence of Recycled Fine Powder on Chloride Ion Erosion of Concrete in Different Chloride Salt Environments
by Lijun Chen, Gang Zhao and Ying Li
Materials 2025, 18(9), 2018; https://doi.org/10.3390/ma18092018 - 29 Apr 2025
Abstract
The Qinghai–Tibet Plateau features a high-altitude, cold, and arid climate, with harsh environmental conditions. It is also one of the regions in China where chloride-rich salt lakes are abundant. These circumstances pose significant challenges to the durability of concrete. This study explored the [...] Read more.
The Qinghai–Tibet Plateau features a high-altitude, cold, and arid climate, with harsh environmental conditions. It is also one of the regions in China where chloride-rich salt lakes are abundant. These circumstances pose significant challenges to the durability of concrete. This study explored the impact of recycled fine powders (RFP) on the resistance of concrete to chloride ion erosion. To evaluate this, a 3.5% sodium chloride solution and Qarhan Salt Lake brine were employed as erosion media. The depth and concentration of chloride ion penetration, the free chloride ion diffusion coefficient (Df), and the microstructure of the concrete were measured. The results demonstrated that when the replacement rate of RFP was 20%, the concrete displayed excellent resistance to chloride ion erosion in both the sodium chloride solution and the Salt Lake brine. XRD analysis and SEM images revealed that the addition of RFP enabled the concrete to bind more Cl− to form Friedel’s salt, which filled the pores of the concrete and reduced the diffusion of Cl− within the concrete. Moreover, as the soaking time extended continuously, the erosion and damage effects of the Salt Lake brine solution on the concrete were more severe than those of the sodium chloride solution. Full article
(This article belongs to the Section Construction and Building Materials)
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23 pages, 4082 KiB  
Article
Enhancing Electrochemical Properties of Vitreous Materials Based on CaO–Fe2O3–Fe–Pb and Recycled from Anodic Plate of a Spent Car Battery
by Delia Niculina Piscoiu, Simona Rada and Horatiu Vermesan
Materials 2025, 18(9), 2017; https://doi.org/10.3390/ma18092017 - 29 Apr 2025
Abstract
This paper presents a novel approach for the recycling of spent anodic plates from lead-acid batteries through the melt quenching method using iron and calcium oxides and iron powder. The resulting recycled samples, with a 3CaO·5Fe2O3·xFe·(92 − x)Pb composition, [...] Read more.
This paper presents a novel approach for the recycling of spent anodic plates from lead-acid batteries through the melt quenching method using iron and calcium oxides and iron powder. The resulting recycled samples, with a 3CaO·5Fe2O3·xFe·(92 − x)Pb composition, where x = 0, 1, 3, 5, 8, 10, 15, and 25% mol Fe, were characterized and analyzed in terms of their electrochemical performance. X-ray diffractograms show vitroceramic structures with varied crystalline phases. Analysis of the IR (infrared spectra) data shows a decrease of sulphate units due to doping with iron content. The ultraviolet–visible (UV-Vis) and electron spin resonance (ESR) data reveal the presence of Fe3+ ions with varied coordination geometries. Cyclic and linear sweep voltammograms demonstrate that the samples with 8 and 10% Fe exhibit superior electrochemical performance compared to other vitroceramics. The electrochemical impedance spectroscopy measurements indicate that the sample with 8% Fe had lower resistance compared to other analogues and had enhanced electrical conductivity. Full article
(This article belongs to the Section Electronic Materials)
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15 pages, 3156 KiB  
Article
Lithium Isotope Separation Using the 15-Crown-5 Ether System and Laboratory-Made Membranes
by Andreea Maria Iordache, Ana Maria Nasture, Ramona Zgavarogea, Radu Andrei, Roxana Mandoc, Erdin Feizula, Rui Santos and Constantin Nechita
Materials 2025, 18(9), 2016; https://doi.org/10.3390/ma18092016 - 29 Apr 2025
Abstract
The enrichment of 6Li isotopes from a natural stage of 7.6% to above 59% is required for the development of next-generation green technologies capable of sustaining climate change mitigation and energy-mix targets. In this study, we developed two categories of custom laboratory-made [...] Read more.
The enrichment of 6Li isotopes from a natural stage of 7.6% to above 59% is required for the development of next-generation green technologies capable of sustaining climate change mitigation and energy-mix targets. In this study, we developed two categories of custom laboratory-made organic membranes, membranes that were non-impregnated before electromigration (AI-1) and membranes impregnated with LiNTf2 (AI-2), to evaluate their performance in lithium isotope separation. Both types of membranes were exposed in synthesis to ionic liquid and crown ether. The objective of the study was to test the performance of membranes in separating lithium isotopes from a lithium-loaded organic phase in an aqueous solution with variable potentials and time intervals. The results show that the impregnated AI-2 membranes increased the enrichment of 6Li in the early stages, and the effect decreased after 25 h. The efficiency of lithium isotope enrichment was positively related to the potential profile applied, migration time, and concentration of organic solution in the anode chamber. The 0.5 mol/L Bis-(trifluoromethane) sulfonimide lithium salt (Li[NTf2]) with 0.1 M tetra butyl ammonium perchlorate (TBAP) in acetonitrile (CH3CN) ionic solution significantly improved Li isotope separation compared with an aqueous environment with higher salt concentrations. The maximum isotopic separation coefficient (α) for AI-1.2 (15-crown-5 ether and 1 mol/L LiNTf2 in TBAP solution after 48 h of electromigration) gradually increased to 1.0317. Our results demonstrated that in the laboratory-made setup described, the migration efficiency and Li isotope separation in the catholyte environment needed a minimum of 9 V and a migration time of 6 h, respectively; these values varied with the concentration of the organic solution in the anode chamber. The ability of laboratory-engineered membranes to impart isotope selectivity and enhance permselectivity or selectivity towards singly charged ions was demonstrated through the functionality of single-collector inductively coupled plasma mass spectrometry (ICP-MS). This technology is particularly valuable and commercially feasible for future lithium isotope research in nuclear technology. Full article
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19 pages, 3959 KiB  
Review
Soldering and Bonding in Contemporary Electronic Device Packaging
by Yuxuan Li, Bei Pan, Zhenting Ge, Pengpeng Chen, Bo Bi, Xin Yi, Chaochao Wu and Ce Wang
Materials 2025, 18(9), 2015; https://doi.org/10.3390/ma18092015 - 29 Apr 2025
Abstract
Electronic packaging can transform the chip to a device for assembly. Soldering and bonding are important procedures in the process of electronic packaging. The continuous development of packaging architecture has driven the emergence of improved soldering and bonding processes. At the same time, [...] Read more.
Electronic packaging can transform the chip to a device for assembly. Soldering and bonding are important procedures in the process of electronic packaging. The continuous development of packaging architecture has driven the emergence of improved soldering and bonding processes. At the same time, conventional soldering and bonding processes are still widely used in device packaging. This paper introduces two kinds of technologies in wafer bonding, direct and indirect, expounds on five kinds of die attachment processes, and also describes the process of ball bonding and wedge bonding in wire bonding in detail. Flip chip bonding and methods for making bumps are also described in depth. Bump bonding processes are vital for 3D-SiP packages, and the bonding technology of copper bumps is a research hotspot in the field of advanced packaging. The surface mount technology and sealing technology used in some electronic devices are also briefly introduced. This paper provides insights for researchers studying soldering and bonding in contemporary electronic device packaging. Full article
(This article belongs to the Special Issue Advanced Welding Technologies and Additive Manufacturing of Alloys and Metals (2nd Edition))
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