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Materials, Volume 17, Issue 23 (December-1 2024) – 347 articles

Cover Story (view full-size image): In this paper, a planar defect in visible-light-activated CoOx-TiO2 inverse opals is implemented through the fabrication of trilayer films incorporating a thin mesoporous interlayer. The formation of “donor”-like states was realized within the photonic band gap that moderated Bragg reflection and doubled the slow photon regions, resulting in markedly improved photocatalytic performance, organics degradation and photocurrent generation. Optical defect engineering in photonic photocatalysts can provide a versatile structural approach to enhance slow photon amplification effects that can be further combined with judicious compositional modifications for visible light photocatalysis. View this paper
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20 pages, 6033 KiB  
Article
Preparation and Mechanical Properties of (TiCrZrNb)C4-SiC Multiphase High-Entropy Ceramics
by Chunmei Wen, Shuai Xu, Bingsheng Li, Shuyun Gan, Li Wang, Keyuan Chen, Yuwen Xue, Zhongqiang Fang and Fan Zhao
Materials 2024, 17(23), 6024; https://doi.org/10.3390/ma17236024 - 9 Dec 2024
Viewed by 526
Abstract
Five carbide powders, TiC, Cr3C2, ZrC, NbC and SiC, were selected as raw materials and mixed by dry or wet milling. Then (TiCrZrNb)C4-SiC multiphase ceramics were successfully prepared by spark plasma sintering (SPS) at 1900 °C, using [...] Read more.
Five carbide powders, TiC, Cr3C2, ZrC, NbC and SiC, were selected as raw materials and mixed by dry or wet milling. Then (TiCrZrNb)C4-SiC multiphase ceramics were successfully prepared by spark plasma sintering (SPS) at 1900 °C, using D-HECs-1900 (dry milling method) and W-HECs-1900 (wet milling method), respectively. In this study, the effects of the ball milling method on the microstructure and mechanical properties of the multiphase high-entropy ceramics were systematically investigated. Compared to D-HECs-1900, W-HECs-1900 has a more uniform elemental distribution and smaller grain size, with an average grain size of 1.8 μm, a higher Vickers hardness HV0.1 = 2178.41 kg/mm2 and a higher fracture toughness of KIC = 4.42 MPa·m1/2. W-HECs-1900 also shows better wear resistance with a wear rate 1.01 × 10−8 mm3·N−1·m−1. The oxide friction layer formed during friction is beneficial for reducing frictional wear, making W-HECs-1900 a potential wear-resistant material. Full article
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Figure 1
<p>Characteristic lengths of the Vickers indentations.</p> Full article ">Figure 2
<p>SEM images of NbC (<b>a</b>); ZrC (<b>b</b>); TiC (<b>c</b>); Cr<sub>3</sub>C<sub>2</sub> (<b>d</b>); SiC (<b>e</b>).</p> Full article ">Figure 3
<p>XRD patterns of W-GCP, D-GCP and carbide powders.</p> Full article ">Figure 4
<p>SEM images of D-GCP (<b>a</b>,<b>b</b>) and W-GCP (<b>c</b>,<b>d</b>).</p> Full article ">Figure 5
<p>Particle size distribution histogram of D-GCP (<b>a</b>) and W-GCP (<b>b</b>).</p> Full article ">Figure 6
<p>SEM image of D-HECs-1900 (<b>a</b>,<b>b</b>) and W-HECs-1900 (<b>c</b>,<b>d</b>).</p> Full article ">Figure 7
<p>SEM images, point scans and element distribution mappings of D-HECs-1900 (<b>a</b>) and W-HECs-1900 (<b>b</b>).</p> Full article ">Figure 8
<p>The XRD patterns of powders and sintered ceramics.</p> Full article ">Figure 9
<p>EBSD image of D-HECs-1900 (<b>a</b>); the corresponding EBSD phase distribution map (<b>b</b>); grain size distribution of D-HECs-1900 based on EBSD results (<b>c</b>).</p> Full article ">Figure 10
<p>EBSD image of W-HECs-1900 (<b>a</b>); the corresponding EBSD phase distribution map (<b>b</b>); grain size distribution of W-HECs-1900 based on EBSD results (<b>c</b>).</p> Full article ">Figure 11
<p>Vickers indentation SEM images of D-HECs-1900 (<b>a</b>) and W-HECs-1900 (<b>b</b>); Crack propagation diagram (<b>c</b>); section diagram (<b>d</b>,<b>e</b>); Comparison of hardness and fracture toughness (<b>f</b>).</p> Full article ">Figure 12
<p>Friction coefficient comparison diagram (<b>a</b>); Wear trajectory profile (<b>b</b>); D-HECs-1900 wear surface and three-dimensional contour map (<b>c</b>); W-HECs-1900 wear surface and three-dimensional contour map (<b>d</b>).</p> Full article ">Figure 13
<p>SEM images and element distribution mappings after friction wear of D-HECs-1900 (<b>a</b>) and W-HECs-1900 (<b>b</b>).</p> Full article ">
14 pages, 4426 KiB  
Article
Preparation of Alumina Oxo-Cluster/Cellulose Polymers and Dye Adsorption Application
by Henglong Tang, Simeng Yao, Zhu Long, Xuefei Yang, Pengxiang Si, Chang Sun and Dan Zhang
Materials 2024, 17(23), 6023; https://doi.org/10.3390/ma17236023 - 9 Dec 2024
Viewed by 573
Abstract
Aluminum oxide clusters (AlOCs) possess high surface areas and customizable pore structures, making them applicable in the field of environmental remediation. However, their practical use is hindered by stability issues, aggregation tendencies, and recycling challenges. This study presents an in -situ synthesis of [...] Read more.
Aluminum oxide clusters (AlOCs) possess high surface areas and customizable pore structures, making them applicable in the field of environmental remediation. However, their practical use is hindered by stability issues, aggregation tendencies, and recycling challenges. This study presents an in -situ synthesis of AlOCs on cellulose using a solvent thermal method. The resulting adsorbent’s structural and property profiles were thoroughly characterized using multiple analytical techniques. Batch adsorption experiments were performed to assess the adsorbent’s capacity and kinetics in removing selected dyes from aqueous solutions. Additionally, both real-environment simulation and regeneration experiments have been conducted to thoroughly assess the adsorbent’s reliability, stability, and practical applicability. The aim was to engineer an effective and recyclable adsorbent specifically tailored for dye-contaminated wastewater treatment. Full article
(This article belongs to the Special Issue Construction and Applications in Functional Polymers)
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Figure 1
<p>SEM images of the longitudinal sections (<b>a</b>) and cross-sections (<b>b</b>) of AlOC-15/Cellulose, as well as its EDX image (<b>c</b>); SEM images of the longitudinal sections (<b>d</b>) and cross-sections (<b>e</b>) of AlOC-20/Cellulose, along with its EDX image (<b>f</b>); SEM images of the longitudinal sections (<b>g</b>) and cross-sections (<b>h</b>) of AlOC-22/Cellulose, and its EDX image (<b>i</b>); SEM images of the longitudinal sections (<b>j</b>) and cross-sections (<b>k</b>) of AlOC-26-NC/Cellulose, as well as its EDX image (<b>l</b>).</p> Full article ">Figure 2
<p>(<b>a</b>) BET analysis of the adsorbents, and (<b>b</b>) FT-IR spectra of natural balsa wood, TEMPO-oxidized wood, and the AlOCs/Cellulose.</p> Full article ">Figure 3
<p>TG curves of AlOCs/Cellulose.</p> Full article ">Figure 4
<p>The adsorption effects of (<b>a</b>) natural balsa wood and TEMPO-oxidized wood, and (<b>b</b>) AlOCs/Cellulose (pH 7, <span class="html-italic">m</span> = 10 mg, CV: 204.00 mg/L, MB: 159.93 mg/L, TB: 233.30 mg/L, RRB: 239.51 mg/L, CBK: 293.20 mg/L, MO: 163.67 mg/L, CR: 348.34 mg/L, and CLR: 191.22 mg/L, 298 K, 24 h).</p> Full article ">Figure 5
<p>(<b>a</b>) the influence of solution pH on adsorption capacity (<span class="html-italic">m</span> = 10 mg, <span class="html-italic">C</span><sub>0</sub> = 491.00 mg/L, 298 K, 24 h); (<b>b</b>) Zeta potential of adsorbent at different pH.</p> Full article ">Figure 6
<p>(<b>a</b>) Influence of contact time on the adsorption properties; (<b>b</b>) PFO and (<b>c</b>) PSO models for MO adsorption (pH 5, <span class="html-italic">m</span> = 10 mg, <span class="html-italic">C</span><sub>0</sub> = 3600.63 mg/L, 298 K, 24 h).</p> Full article ">Figure 7
<p>(<b>a</b>) Influences of concentration on the adsorption properties of MO; (<b>b</b>) Langmuir and (<b>c</b>) Freundlich adsorption isotherm models for MO adsorption (pH 5, <span class="html-italic">m</span> = 10 mg, 298 K, 1230 min).</p> Full article ">Figure 8
<p>(<b>a</b>) Effect of ionic strength on MO dye removal of AlOC-26-NC/Cellulose; (<b>b</b>) Effect of competing ions on MO dye removal and (<b>c</b>) Effect of humic acid on MO dye removal (pH 5, <span class="html-italic">m</span> = 10 mg, <span class="html-italic">C</span><sub>0</sub> = 163.67 mg/L, 298 K, 24 h).</p> Full article ">Figure 9
<p>Reusability study of AlOC-26-NC/Cellulose (pH 5, <span class="html-italic">m</span> = 10 mg, <span class="html-italic">C</span><sub>0</sub> = 491.00 mg/L, 298 K, 24 h).</p> Full article ">Scheme 1
<p>Preparation of AlOCs modified wood.</p> Full article ">
20 pages, 7690 KiB  
Article
Determination of Strength Parameters of Composite Reinforcement Consisting of Steel Member, Adhesive, and Carbon Fiber Textile
by Maciej Adam Dybizbański, Katarzyna Rzeszut, Saydiolimkhon Abdusattarkhuja and Zheng Li
Materials 2024, 17(23), 6022; https://doi.org/10.3390/ma17236022 - 9 Dec 2024
Viewed by 560
Abstract
The main aim of the study was the determination of the strength parameters of composite bonded joints consisting of galvanised steel elements, an adhesive layer, and Carbon-Fiber-Reinforced Plastic (CFRP) fabric. For this purpose, shear laboratory tests were carried out on 60 lapped specimens [...] Read more.
The main aim of the study was the determination of the strength parameters of composite bonded joints consisting of galvanised steel elements, an adhesive layer, and Carbon-Fiber-Reinforced Plastic (CFRP) fabric. For this purpose, shear laboratory tests were carried out on 60 lapped specimens composed of 2 mm thick hot-dip galvanised steel plates of S350 GD. The specimens were overlapped on one side with SikaWrap 230 C carbon fibre textile (CFT) using SikaDur 330 adhesive. The tests were carried out in three series that differed in overlap length (15 mm, 25 mm, and 35 mm). A discussion on the failure mechanism in the context of the bonding capacity of the composite joint was carried out. We observed three forms of joint damage, namely, at the steel-adhesive interface, fibre rupture, and mixed damage behaviour. Moreover, an advanced numerical model using the commercial finite element (FE) program ABAQUS/Standard and the coupled cohesive zone model was developed. The material behaviour of the textile was defined as elastic-lamina and the mixed-mode Hashin damage model was implemented with bi-linear behaviour. Special attention was focused on the formulation of reliable methodologies to determine the load-bearing capacity, failure mechanisms, stress distribution, and the strength characteristics of a composite adhesive joint. In order to develop a reliable model, validation and verification were carried out and self-correlation parameters, which brought the model closer to the laboratory test, were proposed by the authors. Based on the conducted analysis, the strength characteristics including the load-bearing capacity, failure mechanisms, and stress distribution were established. The three forms of joint damage were observed as steel-adhesive interface failure, fibre rupture, and mixed-damage behaviour. Complex interactions between the materials were observed. The most dangerous adhesive failure was detected at the steel and adhesive interface. It was also found that an increase in adhesive thickness caused a decrease in joint strength. In the numerical analysis, two mechanical models were employed, namely, a sophisticated model of adhesive and fabric components. It was found that the fabric model was very sensitive to the density of the finite element mesh. It was also noticed that the numerical model referring to the adhesive layer was nonsensitive to the mesh size; thus, it was regarded as appropriate. Nevertheless, in order to increase the reliability of the numerical model, the authors proposed their own correlation coefficients α and β, which allowed for the correct mapping of adhesive damage. Full article
(This article belongs to the Special Issue New Perspectives in Welding and Joining Processes of Metallic Materials)
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Figure 1
<p>Schematic illustration of the mechanisms of adhesion and the various forces that exist between two surfaces in nature. (1) Van der Waals force; (2) capillary force; (3) electrostatic or coulomb force; (4) friction or interlocking force; (5) suction or vacuum force; (6) chemical force; (7) diffusion force; (8) magnetic force [<a href="#B3-materials-17-06022" class="html-bibr">3</a>].</p> Full article ">Figure 2
<p>Schematic of the sample.</p> Full article ">Figure 3
<p>Specimen in the grips of a testing machine.</p> Full article ">Figure 4
<p>Force-displacement diagram for A series.</p> Full article ">Figure 5
<p>Force-displacement diagram for B series.</p> Full article ">Figure 6
<p>Force-displacement diagram for C series.</p> Full article ">Figure 7
<p>Maximum force-adhesive thickness diagram for all series.</p> Full article ">Figure 8
<p>Maximum force-overlap length diagram for all series.</p> Full article ">Figure 9
<p>Observed forms of damage: (<b>a</b>) adhesive failure at steel/adhesive interface, (<b>b</b>) fabric rupture, (<b>c</b>) mixed failure.</p> Full article ">Figure 10
<p>Average force-displacement diagrams for each series—lab.</p> Full article ">Figure 11
<p>Block diagram for numerical model of textile.</p> Full article ">Figure 12
<p>Block diagram for numerical model of adhesive.</p> Full article ">Figure 13
<p>The ABAQUS anisotropic damage model, which is based on research conducted by Matzenmiller et al. [<a href="#B24-materials-17-06022" class="html-bibr">24</a>], Hashin and Rotem [<a href="#B22-materials-17-06022" class="html-bibr">22</a>], Hashin [<a href="#B23-materials-17-06022" class="html-bibr">23</a>], and Camanho and Davila [<a href="#B25-materials-17-06022" class="html-bibr">25</a>].</p> Full article ">Figure 14
<p>Applied boundary conditions.</p> Full article ">Figure 15
<p>Verification and validation of the fabric rupture model.</p> Full article ">Figure 16
<p>Verification and validation of CZM.</p> Full article ">
10 pages, 7283 KiB  
Article
Effect of Vanadium Addition on the Wear Resistance of Al0.7CoCrFeNi High-Entropy Alloy
by Marzena Tokarewicz, Malgorzata Gradzka-Dahlke, Wojciech J. Nowak, Andrzej Gradzik, Miroslaw Szala and Mariusz Walczak
Materials 2024, 17(23), 6021; https://doi.org/10.3390/ma17236021 - 9 Dec 2024
Viewed by 519
Abstract
High-entropy alloys are of interest to many researchers due to the possibility of shaping their functional properties by, among other things, the use of alloying additives. One approach to improving the wear resistance of the AlCoCrFeNi alloy is modification through the addition of [...] Read more.
High-entropy alloys are of interest to many researchers due to the possibility of shaping their functional properties by, among other things, the use of alloying additives. One approach to improving the wear resistance of the AlCoCrFeNi alloy is modification through the addition of titanium. However, in this study, an alternative solution was explored by adding vanadium, which has a completely different effect on the material’s structure compared to titanium. The effect of vanadium additives on changes in the microstructure, hardness, and wear resistance of the Al0.7CoCrFeNi alloy. The base alloys Al0.7CoCrFeNi and Al0.7CoCrFeNiV0.5 were obtained by induction melting. The results showed that the presence of vanadium changes the microstructure of the material. In the case of the base alloy, the structure is biphasic with a visible segregation of alloying elements between phases. In contrast, the Al0.7CoCrFeNiV0.5 alloy has a homogeneous solid solution bcc structure. The presence of vanadium increased hardness by 33%, while it significantly reduced friction wear by 73%. Microscopic observations of friction marks indicate differences in the wear mechanisms of the two materials. Full article
(This article belongs to the Special Issue Advances in Multicomponent Alloy Design, Simulation and Properties)
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Figure 1

Figure 1
<p>SEM image of the Al<sub>0.7</sub>CoCrFeNi alloy microstructure.</p> Full article ">Figure 2
<p>EDS maps of the Al<sub>0.7</sub>CoCrFeNi alloy.</p> Full article ">Figure 3
<p>SEM image of the Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub> alloy microstructure.</p> Full article ">Figure 4
<p>XRD patterns of analyzed HEAs: (<b>a</b>) Al<sub>0.7</sub>CoCrFeNi, (<b>b</b>) Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub>.</p> Full article ">Figure 4 Cont.
<p>XRD patterns of analyzed HEAs: (<b>a</b>) Al<sub>0.7</sub>CoCrFeNi, (<b>b</b>) Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub>.</p> Full article ">Figure 5
<p>Measurement scheme of the linear wear of the Al<sub>0.7</sub>CoCrFeNi alloy in a friction path.</p> Full article ">Figure 6
<p>Measurement scheme of the linear wear of the Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub> alloy in a friction path.</p> Full article ">Figure 7
<p>Comparison of hardness and depth of friction paths measurement of tested alloys.</p> Full article ">Figure 8
<p>Wear tracks after friction on the surface of the following: (<b>a</b>) Al<sub>0.7</sub>CoCrFeNi, (<b>b</b>) Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub> alloy.</p> Full article ">Figure 9
<p>SEM micrographs of the worn surface of the Al<sub>0.7</sub>CoCrFeNi alloy: (<b>a</b>) magn. 100×, (<b>b</b>) magn. 500×.</p> Full article ">Figure 10
<p>Cross section of the wear track of the Al<sub>0.7</sub>CoCrFeNi alloy: (<b>a</b>) Position of the cross-section on the friction track, magn. 3500×, (<b>b</b>) sectional view, magn. 10,000×.</p> Full article ">Figure 11
<p>SEM micrographs of the worn surface of the Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub> alloy: (<b>a</b>) magn. 150×, (<b>b</b>) magn. 650×.</p> Full article ">Figure 12
<p>Cross section of the wear track of the Al<sub>0.7</sub>CoCrFeNiV<sub>0.5</sub> alloy.</p> Full article ">
15 pages, 4240 KiB  
Article
Improved Method for the Calculation of the Air Film Thickness of an Air Cushion Belt Conveyor
by Bo Song, Hongliang Chen, Long Sun, Kunpeng Xu and Xiaoyong Ren
Materials 2024, 17(23), 6020; https://doi.org/10.3390/ma17236020 - 9 Dec 2024
Viewed by 452
Abstract
The air film thickness is an important parameter of an air cushion belt conveyor, which directly affects the compressed air supply power and operating resistance of the system. Therefore, it is important to calculate the bottom thickness of the gas film accurately in [...] Read more.
The air film thickness is an important parameter of an air cushion belt conveyor, which directly affects the compressed air supply power and operating resistance of the system. Therefore, it is important to calculate the bottom thickness of the gas film accurately in the design stage. A calculation method for the thickness of a conveyor air cushion was derived based on the mathematical model of the air cushion flow field for a multi row uniformly distributed air cushion structure. Meanwhile, the algorithm was validated based on a Fluent 3D flow field numerical simulation and experiments. Through verification, it was found that due to the algorithm’s assumption that the increase in the gas flow rate only existed at the axis of the gas hole, there was a sudden change in the calculation results of the gas flow rate at the axis of the gas hole. The sudden change in the gas flow rate had caused the calculation results of the air cushion thickness to experience abrupt and discontinuous changes. Furthermore, the calculation method for air cushion thickness was revised based on the verification results. Compared with the experimental test results, the average error of the calculation results of the algorithm proposed in this paper was 14.27%. Full article
(This article belongs to the Special Issue Theoretical and Computational Modeling of Material Surfaces and Interfaces)
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<p>Schematic cross-sectional view of air cushion belt conveyor. 1—material. 2—conveyor belt. 3—air cushion. 4—tray slot. 5—air chamber.</p> Full article ">Figure 2
<p>Schematic diagram of air cushion flow field zoning.</p> Full article ">Figure 3
<p>Schematic diagram of the structure of the test tray slot.</p> Full article ">Figure 4
<p>Three-dimensional model of air cushion flow field. (<b>a</b>) Geometric model; (<b>b</b>) Mesh model.</p> Full article ">Figure 5
<p>Schematic diagram of test site. 1—centrifugal high pressure fan. 2—control and data comprehensive display system. 3—digital pressure gauge. 4—central control electrical cabinet. 5—conveyor belt. 6—material. 7—tray slot. 8—digital tension meter. 9—air chamber. (<b>a</b>) Control and testing equipment; (<b>b</b>) Air cushion conveyor.</p> Full article ">Figure 6
<p>Theoretical distribution of air cushion pressure.</p> Full article ">Figure 7
<p>Air cushion thickness distribution curve. (<b>a</b>) Substitute Experiment 1 data; (<b>b</b>) substitution of Experiment 2 data; (<b>c</b>) substitution of Experiment 3 data.</p> Full article ">Figure 7 Cont.
<p>Air cushion thickness distribution curve. (<b>a</b>) Substitute Experiment 1 data; (<b>b</b>) substitution of Experiment 2 data; (<b>c</b>) substitution of Experiment 3 data.</p> Full article ">Figure 8
<p>Comparison of simulation and theoretical pressure distribution. (<b>a</b>) Pressure Comparison 1; (<b>b</b>) Pressure Comparison 2; (<b>c</b>) Pressure Comparison 3.</p> Full article ">Figure 8 Cont.
<p>Comparison of simulation and theoretical pressure distribution. (<b>a</b>) Pressure Comparison 1; (<b>b</b>) Pressure Comparison 2; (<b>c</b>) Pressure Comparison 3.</p> Full article ">Figure 9
<p>Gas flow at a certain location and its corresponding pore area.</p> Full article ">Figure 10
<p>Comparison of results before and after improvement of air cushion thickness calculation method. (<b>a</b>) Global distribution; (<b>b</b>) local enlargement schematic.</p> Full article ">Figure 10 Cont.
<p>Comparison of results before and after improvement of air cushion thickness calculation method. (<b>a</b>) Global distribution; (<b>b</b>) local enlargement schematic.</p> Full article ">
30 pages, 7774 KiB  
Review
Perovskite in Triboelectric Nanogenerator and the Hybrid Energy Collection System
by Tong Wu, Zequan Zhao, Yin Lu, Hanzhang Yang, Xiaoning Liu, Xia Cao and Ning Wang
Materials 2024, 17(23), 6019; https://doi.org/10.3390/ma17236019 - 9 Dec 2024
Viewed by 564
Abstract
In the context of escalating energy demands and environmental sustainability, the paradigm of global energy systems is undergoing a transformative shift to innovative and reliable energy-harvesting techniques ranging from solar cells to triboelectric nanogenerators (TENGs) to hybrid energy systems, where a fever in [...] Read more.
In the context of escalating energy demands and environmental sustainability, the paradigm of global energy systems is undergoing a transformative shift to innovative and reliable energy-harvesting techniques ranging from solar cells to triboelectric nanogenerators (TENGs) to hybrid energy systems, where a fever in the study of perovskite materials has been set off due to the excellent optoelectronic properties and defect tolerance features. This review begins with the basic properties of perovskite materials and the fundamentals of TENGs, including their working principles and general developing strategy, then delves into the key role of perovskite materials in promoting TENG-based hybrid technologies in terms of energy conversion. While spotlighting the coupling of triboelectric–optoelectronic effects in harnessing energy from a variety of sources, thereby transcending the limitations inherent to single-source energy systems, this review pays special attention to the strategic incorporation of perovskite materials into TENGs and TENG-based energy converting systems, which heralds a new frontier in enhancing efficiency, stability, and adaptability. At the end, this review highlights the remaining challenges such as stability, efficiency, and functionality for applications in TENG-based energy-harvesting systems, aiming to provide a comprehensive overview of the current landscape and the prospective trajectory of the role of perovskite materials in TENG-based energy-harvesting technologies within the renewable energy sector. Full article
(This article belongs to the Special Issue Featured Papers and Reviews of Advanced Materials for Sensing, Energy Conversion and Storage)
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<p>TENG-based hybrid energy-harvesting system.</p> Full article ">Figure 2
<p>Photovoltaic and triboelectric effects: (<b>a</b>) Working principle. (<b>b</b>) I-V curve. (<b>c</b>) Different types of solar cells: (<b>d</b>) working principle, (<b>e</b>) I-t curve, and (<b>f</b>) working modes of TENGs [<a href="#B65-materials-17-06019" class="html-bibr">65</a>]. Wu et al. (Elsevier, 2021).</p> Full article ">Figure 3
<p>(<b>a</b>) The working mechanism of a perovskite TENG. (Royal Society of Chemistry, 2020). (<b>b</b>) Illustration of the perovskite TENG device and the crystal structure of inorganic perovskite materials. (Elsevier, 2020). (<b>c</b>) Vertical contact-separation mode TENGs with the structure of FTO/perovskite-PVDF/Ag and working mechanism. Electrical output performance. (ACS, 2021). (<b>d</b>) Schematic diagram of a perovskite TENG device. (Elsevier, 2020). (<b>e</b>) Illustration of the Au/perovskite TENG structure. (Elsevier, 2020). (<b>f</b>) Schematic diagram of electron migration in the PVDF-HFP + 5% AgNWs nanofiber tribonegative layer and in the PVDF-HFP + 5% Mn-BNT-BT + 5% AgNWs nanofiber tribonegative layer. (Elsevier, 2022).</p> Full article ">Figure 4
<p>(<b>a</b>) Design of a single–structured multifunctional device and characterization of a MAPbI<sub>3</sub>-PVDF composite film: Schematic of multifunctional device. (ACS, 2020). (<b>b</b>) Principle of MAPbI<sub>3</sub> perovskite photodetectors. (Royal Society of Chemistry, 2020). (<b>c</b>) Schematic structure and an optical image of the PT–/PA–PVK TENG. (Wiley-VCH, 2020). (<b>d</b>) Device structure of PEDOT:PSS–CsFAMA–based DC–TENG and atomic structures of ChCl and CsFAMA. (Elsevier, 2023).</p> Full article ">Figure 5
<p>(<b>a</b>) Schematic diagram of the hybrid TENG device and energy level alignment diagrams of the hybrid TENGs with pristine PDMS and (<b>b</b>) PC composite film under friction-illumination working condition. (Wiley-VCH, 2021). (<b>c</b>) Schematic structure of a rolling–mode DCTENG based on metal/perovskite Schottky junction and crystal structure. (Wiley-VCH, 2022). (<b>d</b>) The structure and characterization of a TENG: the schematic structure of the CBI/PDMS TENG. (Elsevier, 2023). (<b>e</b>) Schematic image of a solar cell structure fabricated with the composite thin films. (Elsevier, 2023). (<b>f</b>) Schematic diagram of the vertical contact–separation CsPb<sub>1−x</sub>M<sub>x</sub>Br<sub>3</sub> perovskite TENG and the working mechanism of a full “press–release” cycle. (Elsevier, 2020).</p> Full article ">Figure 6
<p>(<b>a</b>) Demonstration of the materials, device structures, experimental setup, and preparation process of a (DF-CBA)<sub>2</sub>CuCl<sub>4</sub>-based TVNG device, including side and top views of the crystal structures and eight polarization directions. (Wiley-VCH, 2021). (<b>b</b>) The crystal structure of an inorganic halide perovskite unit and an illustration of charge generation, distribution, and transfer in a press–release cycle. (Royal Society of Chemistry, 2020). (<b>c</b>) Schematic illustration of a fabricated DAPPbI<sub>4</sub>–PVDF TENG and a photograph of the device. (Elsevier, 2022). (<b>d</b>) Schematic diagram of the “dielectric-on-perovskite” TENG with vertical contact-separation mode. (Elsevier, 2020).</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic diagram and photographs of a self-powered optical communication system (SOCS). (Elsevier, 2019). (<b>b</b>) Structure and working principle of the hybridized electromagnetic-TENG. (Springer, 2022). (<b>c</b>) Schematic diagram of the PA–TENG fabrication process. (Elsevier, 2022). (<b>d</b>) Schematic illustration of photopolymerization of PEGDMA with bond breaking and forming details. (Wiley-VCH, 2023). (<b>e</b>) Schematic illustrations of the synthesis of BKBFT via the molten salt method and the preparation and fabrication of the composite film and HNG devices. (ACS, 2023).</p> Full article ">Figure 8
<p>(<b>a</b>) Schematic diagram of the sunlight response to the pristine Si solar cell and the down–conversion mechanism of the PQDP–based solar cell. (Elsevier, 2023). (<b>b</b>) Physical structure and electrical outputs of I–TENG, including the structural diagram, the equivalent working circuit diagram, the electric–double–layer model, and a photograph of the I–TENG lighting up LEDs. (Wiley-VCH). (<b>c</b>) Schematic diagram of the hybridized nanogenerator and optical image of the device. (Elsevier, 2023). (<b>d</b>) Basic principle to design the R–TENG array, including the schematic diagram, the structure diagram of a single unit, an SEM image, and a contact angle photograph of the FEP film. (Wiley-VCH). (<b>e</b>) Schematic diagram for a TENG/Si tandem hybrid solar cell and top–view SEM images. (Elsevier, 2021).</p> Full article ">Figure 9
<p>(<b>a</b>) Characterization of the multilayered disk TENG performance and material composition. (Elsevier, 2020). (<b>b</b>) Concept, structure, and working principle of the hybrid all-in-one power source (AoPS) for harvesting environmental energy. (Wiley-VCH). (<b>c</b>) Schematic diagram of the hybrid energy system with the SH-TENG and solar cell, mechanism of self-healing SH-PDMS, chemical structures, SEM image, and contact angle image. (Elsevier, 2021).</p> Full article ">Figure 10
<p>(<b>a</b>) Architecture of the HEHD and schematic illustration of the local view, consisting of TENGs, EMGs, and commercial SCs. (Elsevier, 2022). (<b>b</b>) Structural design of the WH-EH for wireless natural disaster monitoring, including functional components, detailed structure of the TENG unit, and an optical image of the device. (Elsevier, 2018). (<b>c</b>) The arch-shaped TENG integrated with HNMA-PDMS and ZnO NWs and the hybrid energy cell consisting of a TENG and a DSSC. (ACS, 2016). (<b>d</b>) Schematic diagram and photograph of the fabricated hybridized nanogenerator. (ACS, 2016).</p> Full article ">
15 pages, 12983 KiB  
Article
Study on the Macro-/Micrometric Characteristics and Mechanical Properties of Clayey Sandy Dredged Fill in the Guangdong Area
by Qiunan Chen, Xiaodi Xu, Ao Zeng, Yunyang Yan, Yan Feng, Kun Long and Chenna Qi
Materials 2024, 17(23), 6018; https://doi.org/10.3390/ma17236018 - 9 Dec 2024
Viewed by 401
Abstract
The study of dredged fill in Guangdong (GD), China, is of great significance for reclamation projects. Currently, there are relatively few studies on dredged fill in Guangdong, and there are many differences in the engineering characteristics of dredged fill foundations formed through land [...] Read more.
The study of dredged fill in Guangdong (GD), China, is of great significance for reclamation projects. Currently, there are relatively few studies on dredged fill in Guangdong, and there are many differences in the engineering characteristics of dredged fill foundations formed through land reclamation and natural foundations. In order to have a more comprehensive understanding of the physico-mechanical properties of blowing fill in the coastal area of GD and to understand the effect of its long-term creep row on the long-term settlement and deformation of buildings, the material properties, microstructure, elemental composition, triaxial shear properties, and triaxial creep properties of dredged fill in Guangdong were studied and analyzed through indoor geotechnical tests, scanning electron microscopy (SEM), X-ray diffraction (XRD), and conventional triaxial shear tests and triaxial creep tests. The test results showed that the Guangdong dredged fill is characterized by a high water content, high pore ratio, and high-liquid-limit clayey sand, and the mineral composition is dominated by quartz and whitmoreite. The scanning electron microscopy results showed that the particles of the dredged fill showed an agglomerated morphology, and the surface of the test soil samples had scaly fine flakes and a fragmented structure. In the triaxial shear test, the GD dredged fill showed strain hardening characteristics, and the effective stress path showed continuous loading characteristics; the consolidated undrained shear test showed that the GD dredged fill had shear expansion characteristics under low-perimeter-pressure conditions. It was found that, with an increase in bias stress, the axial strain in the consolidated undrained triaxial creep test under the same perimeter pressure conditions gradually exceeded the axial strain in the consolidated drained triaxial creep test. The results of this study are of theoretical and practical significance for further understanding the mechanical properties of silty soils in the region and for the rational selection of soil strength parameters in practical engineering design. Full article
(This article belongs to the Special Issue Rock-Like Material Characterization and Engineering Properties)
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<p>Soil extraction site.</p> Full article ">Figure 2
<p>Dredged fill.</p> Full article ">Figure 3
<p>XRD pattern.</p> Full article ">Figure 4
<p>Elemental analysis of soil samples.</p> Full article ">Figure 5
<p>Soil samples magnified 4000 times.</p> Full article ">Figure 6
<p>Soil samples magnified 10,000 times.</p> Full article ">Figure 7
<p>GDS triaxial stress path test.</p> Full article ">Figure 8
<p>Triaxial creep test instrument and a tested soil sample.</p> Full article ">Figure 9
<p>CU shear test results.</p> Full article ">Figure 9 Cont.
<p>CU shear test results.</p> Full article ">Figure 10
<p>CD shear test results.</p> Full article ">Figure 11
<p>Shear end CU test specimens.</p> Full article ">Figure 12
<p>Shear end CD test specimens.</p> Full article ">Figure 13
<p>Full CU and CD triaxial creep results.</p> Full article ">Figure 14
<p>CU triaxial graded-loading creep curve.</p> Full article ">Figure 14 Cont.
<p>CU triaxial graded-loading creep curve.</p> Full article ">Figure 15
<p>CD triaxial graded-loading creep curve.</p> Full article ">
18 pages, 9431 KiB  
Article
Enhanced Wear Resistance and Thermal Dissipation of Copper–Graphene Composite Coatings via Pulsed Electrodeposition for Circuit Breaker Applications
by Daniele Almonti, Daniel Salvi, Nadia Ucciardello and Silvia Vesco
Materials 2024, 17(23), 6017; https://doi.org/10.3390/ma17236017 - 9 Dec 2024
Viewed by 582
Abstract
Copper, though highly conductive, requires improved wear resistance and thermal dissipation in applications that involve continuous movement and current-induced vibrations, such as power breakers. Conventional solutions, such as copper–tungsten alloys or lubricant use, face limitations in durability, friction, or environmental impact. This study [...] Read more.
Copper, though highly conductive, requires improved wear resistance and thermal dissipation in applications that involve continuous movement and current-induced vibrations, such as power breakers. Conventional solutions, such as copper–tungsten alloys or lubricant use, face limitations in durability, friction, or environmental impact. This study explores the development of copper–graphene (Cu-GNPs) composite coatings using pulsed electrodeposition to enhance the tribological, thermal, and mechanical properties of circuit breaker components by adopting an industrially scalable technique. The influence of deposition bath temperature, duty cycle, and frequency on coating morphology, hardness, wear resistance, and heat dissipation was systematically evaluated using a 23 full factorial design and an Analysis of Variance (ANOVA). The results revealed that optimized pulsed electrodeposition significantly improved coating performance: hardness increased by 76%, wear volume decreased by more than 99%, and friction coefficient stabilized at 0.2, reflecting effective graphene integration. The addition of graphene further improved thermal diffusivity by 19.5%, supporting superior heat dissipation. These findings suggest that pulsed copper–graphene composite coatings offer a promising alternative to traditional copper alloys, enhancing the lifespan and reliability of electronic components through improved wear resistance, lower friction, and superior heat transfer. Full article
(This article belongs to the Special Issue Advanced Coating Research for Metal Surface Protection)
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<p>(<b>a</b>) Experimental set-up for the electrodeposition; (<b>b</b>) pulsed wave function.</p> Full article ">Figure 2
<p>Three-dimensional maps of the coated surfaces.</p> Full article ">Figure 3
<p>(<b>a</b>) R<sub>a</sub> values; (<b>b</b>) R<sub>z</sub> values; (<b>c</b>) Main Effect Plot for R<sub>a</sub>.</p> Full article ">Figure 4
<p>Low-magnification (150×) SEM images of the coatings’ morphology.</p> Full article ">Figure 5
<p>High-magnification (3000×) SEM images of the coatings’ morphology.</p> Full article ">Figure 6
<p>Main Effect Plot for microhardness.</p> Full article ">Figure 7
<p>(<b>a</b>) Friction curves of 25 °C coated samples; (<b>b</b>) friction curves of 50 °C coated samples.</p> Full article ">Figure 8
<p>SEM images of the wear tracks.</p> Full article ">Figure 9
<p>(<b>a</b>) Wear volumes of the different scenarios; (<b>b</b>) Main Effect Plot of the wear volumes.</p> Full article ">Figure 10
<p>Optical images of the scratch grooves.</p> Full article ">Figure 11
<p>SEM images of the scratch grooves.</p> Full article ">Figure 12
<p>(<b>a</b>) NBL of the different coating scenarios; (<b>b</b>) Main Effect Plot of NBL.</p> Full article ">Figure 13
<p>(<b>a</b>) Thermal diffusivity values of the samples; (<b>b</b>) Main Effect Plot of thermal diffusivity.</p> Full article ">
14 pages, 3806 KiB  
Article
Experimental Evaluation of Concrete Blended with Eco-Friendly Bio-Sulfur as a Cement Replacement Material
by Wonchang Kim, Taehyung Kim and Taegyu Lee
Materials 2024, 17(23), 6016; https://doi.org/10.3390/ma17236016 - 9 Dec 2024
Viewed by 747
Abstract
Bio-sulfur (BS), extracted from landfill bio-gas via microbial methods, was examined herein as a potential cement replacement material. The study developed five modified BS variants through limestone incorporation processes (sulfur-to-limestone ratios of 1:0.5, 1:1, 1:1.5, 1:3, and 1:5). The study revealed that modified [...] Read more.
Bio-sulfur (BS), extracted from landfill bio-gas via microbial methods, was examined herein as a potential cement replacement material. The study developed five modified BS variants through limestone incorporation processes (sulfur-to-limestone ratios of 1:0.5, 1:1, 1:1.5, 1:3, and 1:5). The study revealed that modified BS with higher limestone ratios demonstrates significant workability and strength reductions of over 50% with increased content, leading to the adoption of a sulfur-to-limestone ratio of 1:1. The concrete specimens exhibited compressive strength improvements of up to 12% with increased BS content, while the UPV showed proportional increases with increased BS content that remained independent of the water/binder (W/B) ratio. Statistical analysis confirmed significance with p-values below 0.05. XRD analysis identified initial cement hydrate peaks at 3 d that evolved into distinct Mg-S hydrate and Ca-Al-S hydrate formations in the BS-containing specimens by 28 d. Full article
(This article belongs to the Section Construction and Building Materials)
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<p>Process for the production of BS.</p> Full article ">Figure 2
<p>BS production process using a bio-reactor.</p> Full article ">Figure 3
<p>Bio-sulfur.</p> Full article ">Figure 4
<p>Slump of fresh mortar.</p> Full article ">Figure 5
<p>Compressive strength of mortar.</p> Full article ">Figure 6
<p>Compressive strength of mortar.</p> Full article ">Figure 7
<p>Slump and flow of fresh concrete.</p> Full article ">Figure 8
<p>28 d unit weight of concrete.</p> Full article ">Figure 9
<p>Compressive strength of concrete according to BS admixture rate.</p> Full article ">Figure 10
<p>UPV of concrete according to BS admixture rate.</p> Full article ">Figure 11
<p>XRD analysis of concrete.</p> Full article ">Figure 12
<p>Regression analysis between compressive strength and UPV on concrete.</p> Full article ">
17 pages, 26738 KiB  
Article
Fatigue Crack Growth Performance of Q370qENH Weathering Bridge Steel and Butt Welds
by Yujie Yu, Xiang Zhang, Chunjian Hu, Liangkun Liu and Haibo Wang
Materials 2024, 17(23), 6015; https://doi.org/10.3390/ma17236015 - 9 Dec 2024
Viewed by 497
Abstract
Weathering steel possesses good atmospheric corrosion resistance and is increasingly applied in highway and railway bridges. The fatigue performance of the weld joint is an important issue in bridge engineering. This study experimentally investigates the microstructural properties and fracture crack growth behaviors of [...] Read more.
Weathering steel possesses good atmospheric corrosion resistance and is increasingly applied in highway and railway bridges. The fatigue performance of the weld joint is an important issue in bridge engineering. This study experimentally investigates the microstructural properties and fracture crack growth behaviors of a Q370qENH bridge weathering steel weld joint. The FCG parameters of the base steel, butt weld, and HAZs, considering the effect of different plate thicknesses and stress ratios, are analyzed. Microstructural features, microhardness, and fatigue fracture surfaces are carefully inspected. The FCG rates of different weld regions in the stable crack growth stage are obtained using integral formulas based on the Paris and Walker law. The test results indicate that the heating and cooling process during the welding of Q370qENH steel creates improved microstructures with refined grain sizes and fewer impurities, thus leading to improved FCG performances in the HAZ and weld regions. The crack growth rate of Q370qENH weld regions increases with the stress ratio, and the influencing extent increasingly ranks as the base steel, HAZ, and the weld. The thick plate has a slightly slower fatigue crack growth rate for the Q370qENH weld joints. The Q370qENH base steel presents the highest fatigue crack growth rate, followed by the heat-treated and HAZ cases, while the weld area exhibits the lowest FCG rate. The Paris law coefficients of different regions of Q370qENH welds are presented. The collected data serve as a valuable reference for future analyses of fatigue crack propagation problems of Q370qENH steel bridge joints. Full article
(This article belongs to the Special Issue Engineering Materials and Structural Integrity)
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<p>Design geometry and the practical product of butt welds.</p> Full article ">Figure 2
<p>The optical microscope scan specimen and the construction.</p> Full article ">Figure 3
<p>Metallographic structure: (<b>a</b>) weld joint region × 50 (Red spots indicate hardness measuring locations); (<b>b</b>) weld × 500; (<b>c</b>) CGHAZ × 500; (<b>d</b>) FGHAZ × 500; (<b>e</b>) base metal × 500.</p> Full article ">Figure 4
<p>Metallographic structure: (<b>a</b>) HV-1000Z Vickers indenter; (<b>b</b>) microhardness results; (<b>c</b>) Vickers indenter imprint.</p> Full article ">Figure 5
<p>CT specimen design: (<b>a</b>) specimen dimensions; (<b>b</b>) specimen figure; (<b>c</b>) specimen locations.</p> Full article ">Figure 6
<p>Fatigue crack growth test setup: (<b>a</b>) test setup; (<b>b</b>) specimen setup; (<b>c</b>) DIC measurement.</p> Full article ">Figure 7
<p>Fatigue crack growth curves: (<b>a</b>) crack propagation trajectory; (<b>b</b>) crack lengths of base metal; (<b>c</b>) crack lengths of HAZ; (<b>d</b>) crack lengths of weld.</p> Full article ">Figure 8
<p>Comparison of FCG rates under different stress ratios: (<b>a</b>) base metal—8 mm thick; (<b>b</b>) base metal—10 mm thick; (<b>c</b>) weld—8 mm thick; (<b>d</b>) HAZ—8 mm thick.</p> Full article ">Figure 9
<p>Comparison of FCG rates under different plate thicknesses: (<b>a</b>) base steel cases; (<b>b</b>) HAZ cases; (<b>c</b>) weld cases.</p> Full article ">Figure 10
<p>Comparison of FCG rates under different stress ratios: (<b>a</b>) 0.1 stress ratio; (<b>b</b>) 0.2 stress ratio; (<b>c</b>) 0.5 stress ratio.</p> Full article ">Figure 11
<p>Comparison of FCG rates between different CT groups: (<b>a</b>) CT specimens from weld joint; (<b>b</b>) CT specimens from heated plates.</p> Full article ">Figure 12
<p>FCG performance comparisons between Q370qENH, 14MNNbq, and Q500D.</p> Full article ">Figure 13
<p>Fracture morphology of 8H0.2-2.</p> Full article ">Figure 14
<p>Fracture surface and microscope morphology of critical regions: (<b>a</b>) weld—8W0.1; (<b>b</b>) HAZ—8H0.1; (<b>c</b>) base steel—8B0.1.</p> Full article ">Figure 14 Cont.
<p>Fracture surface and microscope morphology of critical regions: (<b>a</b>) weld—8W0.1; (<b>b</b>) HAZ—8H0.1; (<b>c</b>) base steel—8B0.1.</p> Full article ">Figure 15
<p>Fracture surface and microscope morphology of critical regions.</p> Full article ">Figure 16
<p>Fracture surface of 6 mm and 8 mm thick 0.1 stress ratio cases.</p> Full article ">
16 pages, 5877 KiB  
Article
Modification of Uniaxial Stress–Strain Model of Concrete Confined by Pitting Corroded Stirrups
by Zhiwei Miao, Yifan Liu, Kangnuo Chen and Xinping Niu
Materials 2024, 17(23), 6014; https://doi.org/10.3390/ma17236014 - 9 Dec 2024
Viewed by 526
Abstract
To investigate the impact of stirrup pitting corrosion on the stress–strain model of core concrete under compression, this study, based on existing corroded steel specimens, establishes a probabilistic model of the residual cross-sectional area distribution of steel bars to reasonably evaluate the effect [...] Read more.
To investigate the impact of stirrup pitting corrosion on the stress–strain model of core concrete under compression, this study, based on existing corroded steel specimens, establishes a probabilistic model of the residual cross-sectional area distribution of steel bars to reasonably evaluate the effect of pitting on the mechanical performance of stirrups. Considering the tension stiffening effect in reinforced concrete, a time-dependent damage model of corroded steel bars in concrete was determined, and the existing stress–strain model of concrete confined by stirrups was ultimately modified, establishing a time-dependent constitutive model that incorporates the effects of stirrup pitting corrosion. A comparison with previous experimental results indicates that the revised model presented in this paper can appropriately reflect the changes in the mechanical performance of concrete confined by corroded stirrups. The results of this study can provide theoretical support for the refined numerical analysis of reinforced concrete structures under the erosion of chloride ions. Full article
(This article belongs to the Section Construction and Building Materials)
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<p>Flowchart of research methodology.</p> Full article ">Figure 2
<p>Spatial distribution of remaining cross-sectional areas of 8 mm corroded rebars along the longitudinal direction [<a href="#B9-materials-17-06014" class="html-bibr">9</a>].</p> Full article ">Figure 3
<p>Fitting analysis: (<b>a</b>) the corrosion distribution along the rebar axis and (<b>b</b>) the histogram representing the residual cross-sectional area of the steel bars along with their corresponding fitted probability density curves [<a href="#B9-materials-17-06014" class="html-bibr">9</a>].</p> Full article ">Figure 4
<p>The regression analysis results of the dual-cluster GMM parameters [<a href="#B9-materials-17-06014" class="html-bibr">9</a>].</p> Full article ">Figure 5
<p>The computational procedure for the micro-segment deformation accumulation method.</p> Full article ">Figure 6
<p>Section dimensions and reinforcement retails (mm) [<a href="#B40-materials-17-06014" class="html-bibr">40</a>].</p> Full article ">Figure 7
<p>Comparison between test results [<a href="#B40-materials-17-06014" class="html-bibr">40</a>] and calculation results for rectangular section specimens.</p> Full article ">Figure 8
<p>Comparison between test results [<a href="#B40-materials-17-06014" class="html-bibr">40</a>] and calculation results for circular section specimens.</p> Full article ">Figure 9
<p>Flowchart of lifetime mechanical properties for concrete confined by pitted stirrups.</p> Full article ">Figure 10
<p>Time-variant probabilistic density curves of GMM.</p> Full article ">Figure 11
<p>Time-variant stress–strain curves of corroded rebars.</p> Full article ">Figure 12
<p>Time-dependent damage curves for concrete confined by pitting corroded stirrups.</p> Full article ">
1 pages, 139 KiB  
Retraction
RETRACTED: Xu et al. Cr–Diamond/Cu Composites with High Thermal Conductivity Fabricated by Vacuum Hot Pressing. Materials 2024, 17, 3711
by Qiang Xu, Xiaodie Cao, Yibo Liu, Yanjun Xu and Jiajun Wu
Materials 2024, 17(23), 6013; https://doi.org/10.3390/ma17236013 - 9 Dec 2024
Viewed by 511
Abstract
The journal retracts the article titled “Cr–Diamond/Cu Composites with High Thermal Conductivity Fabricated by Vacuum Hot Pressing” [...] Full article
24 pages, 3475 KiB  
Article
Investigation of the Method for Measuring the Surface Property Parameters of Variable Charge Minerals Using Ion Selection Electrode
by Jiaqi Sun, Xinmin Liu, Hang Li and Deyuan Ma
Materials 2024, 17(23), 6012; https://doi.org/10.3390/ma17236012 - 9 Dec 2024
Viewed by 401
Abstract
In this study, the surface property parameters of non-swelling variable charge minerals, kaolinite and goethite, were determined using the ion-selective electrode method. The effects of experimental conditions, such as pH, ion concentration ratio, and liquid addition method, on the measurement results were clarified [...] Read more.
In this study, the surface property parameters of non-swelling variable charge minerals, kaolinite and goethite, were determined using the ion-selective electrode method. The effects of experimental conditions, such as pH, ion concentration ratio, and liquid addition method, on the measurement results were clarified to provide a reference for accurately assessing the surface properties of variable charge materials. The research employed ion adsorption equilibrium experiments under varying pH levels, ion concentration ratios, and liquid addition methods. A combined surface property analysis was conducted using K+ and Ca2+ as indicator ions to characterize surface parameters. The results were compared with the specific surface area obtained via the BET method to verify accuracy, thereby identifying optimal measurement conditions. The study led to the following five conclusions. (1) pH significantly affected the adsorption amount and ratio of indicator cations, thereby influencing the accuracy of surface property parameters. (2) The addition method and concentration ratio of electrolytes influenced the measurement accuracy by affecting the adsorption state and equilibrium time of the two indicator cations. (3) For kaolinite, the optimal initial pH ranged from 7.5 to 8.5 in the KOH + Ca(OH)2 system and from 8.0 to 8.5 in the KOH + CaCl2 system, while the equilibrium pH was 7.5 to 8.0 in both systems. The optimal ion concentration ratios were cK:cCa = 2:1 and 9:1, respectively. (4) For goethite, the optimal initial and equilibrium pH values were 8.5 to 9.0 and 7.5 to 8.0, respectively, in both KOH + Ca(OH)2 and KOH + CaCl2 systems. The optimal ion concentration ratios were 4:1 and 20:1, respectively. (5) Through comparison, the optimal initial pH for measuring the two variable charge minerals was determined to be 8.5 ± 0.1, with the optimal equilibrium pH at 7.5 ± 0.1. However, the concentration ratios varied significantly, suggesting the need for systematic research by adjusting a series of ion concentration ratios based on the initial pH. Full article
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<p>The relationship between the measured specific surface area and the initial pH conditions of kaolinite.</p> Full article ">Figure 2
<p>The relationship between the specific surface area and the ion concentration ratio of kaolinite.</p> Full article ">Figure 3
<p>The relationship between the specific surface area and the ion concentration ratio of kaolinite.</p> Full article ">Figure A1
<p>The specific surface area of the saturated sample of H<sup>+</sup>-kaolinite measured by the BET method.</p> Full article ">Figure A2
<p>Specific surface area of H<sup>+</sup>-goethite saturated sample measured by BET method.</p> Full article ">
17 pages, 1513 KiB  
Article
Performance and Emission Characteristics of a Small Gas Turbine Engine Using Hexanol as a Biomass-Derived Fuel
by Tomasz Suchocki
Materials 2024, 17(23), 6011; https://doi.org/10.3390/ma17236011 - 9 Dec 2024
Viewed by 480
Abstract
The global transition to renewable energy has amplified the need for sustainable aviation fuels. This study investigates hexanol, a biomass-derived alcohol, as an alternative fuel for small-scale gas turbines. Experimental trials were conducted on a JETPOL GTM-160 turbine, assessing blends of 25% (He25) [...] Read more.
The global transition to renewable energy has amplified the need for sustainable aviation fuels. This study investigates hexanol, a biomass-derived alcohol, as an alternative fuel for small-scale gas turbines. Experimental trials were conducted on a JETPOL GTM-160 turbine, assessing blends of 25% (He25) and 50% (He50) hexanol with kerosene (JET A) under rotational velocities ranging from 40,000 to 110,000 RPM. The parameters measured included thrust-specific fuel consumption (TSFC), turbine inlet and outlet velocities, and the emission indices of NOx and CO. The results demonstrated that the He25 and He50 blends achieved comparable thermal efficiency to pure JET A at high rotational velocities, despite requiring higher fuel flows due to hexanol’s lower heating value. CO emissions decreased significantly at higher velocities, reflecting improved combustion efficiency with hexanol blends, while NOx emissions exhibited a slight increase, attributed to the oxygen content of the fuel. This study contributes a novel analysis of hexanol-kerosene blends in gas turbines, offering insights into their operational and emission characteristics. These findings underscore hexanol’s potential as an environmentally friendly alternative fuel, aligning with global efforts to reduce fossil fuel dependency and carbon emissions. Full article
(This article belongs to the Special Issue Advances in Biomass-Based Materials and Their Applications)
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<p>Schematic diagram of a miniature gas turbine engine experimental facility and measurements [<a href="#B3-materials-17-06011" class="html-bibr">3</a>].</p> Full article ">Figure 2
<p>TSFC as a function of RPM for three fuel types: JET A, He25, and He50.</p> Full article ">Figure 3
<p>TSFC as a function of RPM for three fuel types: JET A, He25, and He50.</p> Full article ">Figure 4
<p>Turbine inlet temperature as a function of RPM for three fuel types: JET A, He25, and He50.</p> Full article ">Figure 5
<p>Emission Index of NO (g/kN·s) as a function of RPM for three fuel types: JET A, He25, and He50.</p> Full article ">Figure 6
<p>Emission index of CO (g/kN·s) as a function of RPM for three fuel types: JET A, He25, and He50.</p> Full article ">
13 pages, 2680 KiB  
Article
Study on the Preparation and Test Method of Transformer Oil Used in Laboratory
by Zeming Sun and Minxia Shi
Materials 2024, 17(23), 6010; https://doi.org/10.3390/ma17236010 - 9 Dec 2024
Viewed by 507
Abstract
The power transformer is one of the most important parts of a power system. The transformer oil in a transformer not only increases its insulation strength, but also helps its cooling. Cellulose particles are one of the main factors affecting the breakdown characteristics [...] Read more.
The power transformer is one of the most important parts of a power system. The transformer oil in a transformer not only increases its insulation strength, but also helps its cooling. Cellulose particles are one of the main factors affecting the breakdown characteristics of transformer oil, and the withstand voltage test can effectively detect the quality of transformer oil. Therefore, the withstand voltage test on transformer oil with different cellulose particle content levels in the laboratory can determine the breakdown characteristics of transformer oil and the method of improving the insulation strength of power transformers. However, there is lack of a set of effective preparation and test methods of transformer oil for laboratory use in the industry. Based on national standards and engineering practice, this paper puts forward a method of preparing transformer oil with different cellulose particle content levels in the laboratory and a method of the withstand voltage test on transformer oil in the laboratory, which can improve the efficiency and the scientificity of such experiments. Full article
(This article belongs to the Section Electronic Materials)
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<p>Microscopic photograph of impurity particles in transformer oil after pretreatment. (<b>a</b>) Impurity particle morphology 1. (<b>b</b>) Impurity particle morphology 2.</p> Full article ">Figure 2
<p>Microscopic photograph of microcrystalline cellulose.</p> Full article ">Figure 3
<p>Distribution of particle numbers in transformer oil samples.</p> Full article ">Figure 4
<p>Distribution of impurity particles in the “High-pollution transformer oil sample”. (<b>a</b>) Standing for 8 min. (<b>b</b>) Standing for 8 min. (<b>c</b>) Standing for 15 min. (<b>d</b>) Standing for 15 min.</p> Full article ">Figure 5
<p>Circuit diagram of the laboratory impulse voltage test platform.</p> Full article ">Figure 6
<p>Measured waveform of the laboratory impulse voltage test platform. (<b>a</b>) Measured waveform of standard lightning impulse voltage. (<b>b</b>) Measured waveform of oscillation lightning impulse voltage.</p> Full article ">Figure 7
<p>Uniform electric field test container. (<b>a</b>) Structure of the uniform electric field test container. (<b>b</b>) Electric field distribution between the plate-plate electrodes. (<b>c</b>) Photograph of the test container.</p> Full article ">Figure 8
<p>Uneven electric field test container. (<b>a</b>) Structure of the uneven electric field test container. (<b>b</b>) Electric field distribution between the needle-ball electrodes. (<b>c</b>) Photograph of the test container.</p> Full article ">Figure 9
<p>Power frequency voltage test procedure.</p> Full article ">Figure 10
<p>Lightning impulse voltage test procedure.</p> Full article ">
14 pages, 5535 KiB  
Article
Optimization of Turning of Inconel 625 to Improve Surface Quality After Finishing Process
by Magdalena Machno, Wojciech Zębala and Emilia Franczyk
Materials 2024, 17(23), 6009; https://doi.org/10.3390/ma17236009 - 8 Dec 2024
Viewed by 661
Abstract
The process of machining the modern engineering materials, such as nickel-based superalloys, still requires improvement. This paper focuses on comparing the turning process of Inconel 625 superalloy using three types of cutting inserts to obtain the finishing process. The influence of cutting data, [...] Read more.
The process of machining the modern engineering materials, such as nickel-based superalloys, still requires improvement. This paper focuses on comparing the turning process of Inconel 625 superalloy using three types of cutting inserts to obtain the finishing process. The influence of cutting data, such as cutting speed, feed rate, and cutting depth, on the machined surface quality, surface quality were selected. The novelty of the research, described in the article, is the optimization of the machining of Inconel 625 by using the stepwise selection of parameters. The most important issue is that the stepwise method can be used in industry, where increasingly new nickel-chromium materials with more specific strength properties are used for parts. Full article
(This article belongs to the Special Issue Precision and Ultra-Precision Subtractive and Additive Manufacturing Processes of Alloys and Steels, 2nd Edition)
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<p>(<b>a</b>) Cutting inserts used in experimental test; (<b>b</b>) cutting insert of geometry.</p> Full article ">Figure 2
<p>Experimental test stand and marked directions the components of the total cutting force.</p> Full article ">Figure 3
<p>The scheme of the experimental test.</p> Full article ">Figure 4
<p>Results of surface roughness vs. feed rate (<span class="html-italic">f</span>), cutting speed (<span class="html-italic">v<sub>c</sub></span>), and used tool No. 1, No. 2, and No. 3: (<b>a</b>) Ra and (<b>b</b>) Rz—for depth of cut <span class="html-italic">a<sub>p</sub></span> = 0.1 mm; (<b>c</b>) Ra and (<b>d</b>) Rz—for depth of cut <span class="html-italic">a<sub>p</sub></span> = 0.5 mm.</p> Full article ">Figure 5
<p>Chips after turning with the parameters: (<b>a</b>) <span class="html-italic">v<sub>c</sub></span> = 130 m/min, <span class="html-italic">f</span> = 0.115 mm/rev, <span class="html-italic">a<sub>p</sub></span> = 0.1 mm; (<b>b</b>) <span class="html-italic">v<sub>c</sub></span> = 100 m/min, <span class="html-italic">f</span> = 0.077 mm/rev, <span class="html-italic">a<sub>p</sub></span> = 0.1 mm.</p> Full article ">Figure 6
<p>Results of surface roughness vs. feed rate (<span class="html-italic">f</span>), cutting speed (<span class="html-italic">v<sub>c</sub></span>), and used tools No. 2 and No. 3: (<b>a</b>) Ra and (<b>b</b>) Rz—for depth of cut <span class="html-italic">a<sub>p</sub></span> = 0.1 mm; (<b>c</b>) Ra and (<b>d</b>) Rz—for depth of cut <span class="html-italic">a<sub>p</sub></span> = 0.5 mm.</p> Full article ">Figure 6 Cont.
<p>Results of surface roughness vs. feed rate (<span class="html-italic">f</span>), cutting speed (<span class="html-italic">v<sub>c</sub></span>), and used tools No. 2 and No. 3: (<b>a</b>) Ra and (<b>b</b>) Rz—for depth of cut <span class="html-italic">a<sub>p</sub></span> = 0.1 mm; (<b>c</b>) Ra and (<b>d</b>) Rz—for depth of cut <span class="html-italic">a<sub>p</sub></span> = 0.5 mm.</p> Full article ">Figure 7
<p>Cutting forces measurements: (<b>a</b>) <span class="html-italic">F<sub>c</sub></span>; (<b>b</b>) <span class="html-italic">F<sub>f</sub></span>; (<b>c</b>) <span class="html-italic">F<sub>p</sub></span>, for vs. feed rate, cutting speed and depth of cut 0.1 mm, with three tools used.</p> Full article ">Figure 8
<p>The surface roughness and interval plot for: Ra (<b>a</b>); Rz (<b>b</b>).</p> Full article ">Figure 9
<p>The applied algorithm for stepwise selection of parameters.</p> Full article ">
14 pages, 7359 KiB  
Article
An Efficient Strength Evaluation Method Based on Shell-Fastener Model for Large Hybrid Joint Structures of C/SiC Composites
by Maoqing Fu, Jiapeng Chen, Ben Wang and Biao Wang
Materials 2024, 17(23), 6008; https://doi.org/10.3390/ma17236008 - 8 Dec 2024
Viewed by 675
Abstract
C/SiC composites are widely used in aerospace thermal structures. Due to the high manufacturing complexity and cost of C/SiC composites, numerous hybrid joints are required to replace large and complex components. The intricate contact behavior within these hybrid joints reduces the computational efficiency [...] Read more.
C/SiC composites are widely used in aerospace thermal structures. Due to the high manufacturing complexity and cost of C/SiC composites, numerous hybrid joints are required to replace large and complex components. The intricate contact behavior within these hybrid joints reduces the computational efficiency of damage analysis methods based on solid models, limiting their effectiveness in large-scale structural design. According to the structure characteristic, a fractal contact stiffness model considering bonded behaviors is established in this paper. By introducing this model, it is proved that the bonded layer can affect the interface strength between plates but not the bearing strength of the specimen for the bolt/bonded hybrid joint structure. Furthermore, by introducing the strength envelope method, this paper overcomes the problem wherein the shell-fastener model cannot accurately describe the complex stress field. Validation through experimental comparison confirms that this approach can accurately predict both the failure mode and strength of multi-row hybrid joint structures in C/SiC composites at a detailed level with an error of 5.4%, including the shear failure of bolts. This method offers a robust foundation for the design of large-scale C/SiC composite structures. Full article
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<p>The “pyramid” of tests in the “building-block” approach [<a href="#B13-materials-17-06008" class="html-bibr">13</a>].</p> Full article ">Figure 2
<p>Tensile test of C/SiC composite multi-row hybrid joint structures: (<b>a</b>) anti-deflection fixture; (<b>b</b>) specimen assembled anti-deflection fixture; (<b>c</b>) specimen of C/SiC composite three-row, single-lap, three-bolt joint; (<b>d</b>) clamping method.</p> Full article ">Figure 3
<p>Numbering rule of bolts.</p> Full article ">Figure 4
<p>Results of tensile tests: (<b>a</b>) tensile failure mode of specimen No. 1; (<b>b</b>) tensile failure mode of specimen No. 2; (<b>c</b>) surface morphology of lap joint area; (<b>d</b>) load–displacement curves.</p> Full article ">Figure 5
<p>Equivalent contact stiffness: (<b>a</b>) interface of bolted hybrid joints; (<b>b</b>) parallel stiffness model of clamping area.</p> Full article ">Figure 6
<p>C/SiC bolted-bonded hybrid single-lap joint structure: (<b>a</b>) size of C/SiC composite joint plate; (<b>b</b>) finite element model.</p> Full article ">Figure 7
<p>Simulation results: (<b>a</b>) bearing damage distribution; (<b>b</b>) damage expansion of bonded layer between nut and plate; (<b>c</b>) damage expansion of bonded layer between plate and plate.</p> Full article ">Figure 8
<p>Tensile load–displacement curves of specimens with different porosity bonded layers.</p> Full article ">Figure 9
<p>Finite element model of C/SiC composite three-row, three-pin single-lap bolted joint specimen: (<b>a</b>) solid model; (<b>b</b>) shell-fastener model.</p> Full article ">Figure 10
<p>Strength envelope of typical mechanical joint structures.</p> Full article ">Figure 11
<p>The various strengths required to draw the strength envelope: (<b>a</b>) the size of C/SiC composite plate; (<b>b</b>) tensile strength of C/SiC composite plate; (<b>c</b>) the size of plate with opening hole; (<b>d</b>) tensile failure process simulation of plate with opening hole; (<b>e</b>) tensile load–displacement curve of plate with opening hole; (<b>f</b>) bearing strength of specimen (red star which represents the intersection of the 2% bearing deformation and the curve).</p> Full article ">Figure 12
<p>Tensile strength envelope of C/SiC composite three-row, three-pin single-lap bolted joint specimen.</p> Full article ">Figure 13
<p>Simulation results of shell-fastener model: (<b>a</b>) comparing the tensile load–displacement curves obtained by tests and shell-fastener model of specimen No. 2; (<b>b</b>) bolt load history curve of specimen No. 2.</p> Full article ">
10 pages, 4348 KiB  
Communication
Enhanced Barrier and Optical Properties of Inorganic Nano-Multilayers on PEN Substrate Through Hybrid Deposition
by Xiaojie Sun, Lanlan Chen and Wei Feng
Materials 2024, 17(23), 6007; https://doi.org/10.3390/ma17236007 - 8 Dec 2024
Viewed by 579
Abstract
In this study, an inorganic multilayer barrier film was fabricated on the polyethylene naphthalate (PEN) substrate, which was composed of a SiO2 layer prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and a Al2O3/ZnO nanolaminate produced by [...] Read more.
In this study, an inorganic multilayer barrier film was fabricated on the polyethylene naphthalate (PEN) substrate, which was composed of a SiO2 layer prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and a Al2O3/ZnO nanolaminate produced by plasma-enhanced atomic layer deposition (PEALD). The multilayer composite film with a structure of 50 nm SiO2 + (4.5 nm Al2O3/6 nm ZnO) × 4 has excellent optical transmittance (88.1%) and extremely low water vapor permeability (3.3 × 10−5 g/m2/day, 38 °C, 90% RH), indicating the cooperation of the two advanced film growth methods. The results suggest that the defects of the SiO2 layer prepared by ICP-CVD were effectively repaired by the PEALD layer, which has excellent defect coverage. And Al2O3/ZnO nanolaminates have advantages over single-layer Al2O3 due to their complex diffusion pathways. The multilayer barrier film offers potential for encapsulating organic electronic devices that require a longer lifespan. Full article
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<p>Schematic of the preparation of the multilayer barrier film.</p> Full article ">Figure 2
<p>Schematic of the structure of multilayer barrier films and defect coverage in the SiO<sub>2</sub> film.</p> Full article ">Figure 3
<p>Surface and cross-sectional SEM images of SiO<sub>2</sub> (<b>A</b>,<b>a</b>), Al<sub>2</sub>O<sub>3</sub> (<b>B</b>,<b>b</b>), SiO<sub>2</sub> + Al<sub>2</sub>O<sub>3</sub> (<b>C</b>,<b>c</b>), SiO<sub>2</sub> + (6 nm Al<sub>2</sub>O<sub>3</sub>/4.5 nm ZnO) × 4 (<b>D</b>,<b>d</b>), SiO<sub>2</sub> + (4.5 nm Al<sub>2</sub>O<sub>3</sub>/6 nm ZnO) × 4 (<b>E</b>,<b>e</b>), and SiO<sub>2</sub> + (3 nm Al<sub>2</sub>O<sub>3</sub>/7.5 nm ZnO) × 4 (<b>F</b>,<b>f</b>).</p> Full article ">Figure 4
<p>Low-resolution (<b>a</b>–<b>c</b>) and high-resolution (<b>d</b>) HRTEM cross-sectional images and FFT (<b>e</b>,<b>f</b>) of the SiO<sub>2</sub> + Al<sub>2</sub>O<sub>3</sub>/ZnO multilayer films.</p> Full article ">Figure 5
<p>Images and surface roughness measurements via AFM. (<b>a</b>) SiO<sub>2</sub>, (<b>b</b>) Al<sub>2</sub>O<sub>3</sub>, (<b>c</b>) SiO<sub>2</sub> + Al<sub>2</sub>O<sub>3</sub>, SiO<sub>2</sub> + (6 nm Al<sub>2</sub>O<sub>3</sub>/4.5 nm ZnO) × 4 (<b>d</b>), SiO<sub>2</sub> + (4.5 nm Al<sub>2</sub>O<sub>3</sub>/6 nm ZnO) × 4 (<b>e</b>), and SiO<sub>2</sub> + (3 nm Al<sub>2</sub>O<sub>3</sub>/7.5 nm ZnO) × 4 (<b>f</b>).</p> Full article ">Figure 6
<p>(<b>a</b>) Test curves of water vapor permeability for different films measured by a MOCON Aquatran 3; (<b>b</b>) WVTR values of (A) SiO<sub>2</sub>, (B) Al<sub>2</sub>O<sub>3</sub>, (C) SiO<sub>2</sub> + Al<sub>2</sub>O<sub>3</sub>, and (D) SiO<sub>2</sub> + Al<sub>2</sub>O<sub>3</sub>/ZnO multilayer films.</p> Full article ">Figure 7
<p>XPS analysis of Al<sub>2</sub>O<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub>/ZnO nanolaminate (<b>a</b>), ZnO and Al<sub>2</sub>O<sub>3</sub>/ZnO nanolaminate (<b>b</b>).</p> Full article ">Figure 8
<p>Optical transmittance of the films by UV-vis measurements.</p> Full article ">
11 pages, 1555 KiB  
Article
A Comparative Analysis of the Electrical Properties of Silicone Rubber Composites with Graphene and Unwashed Magnetite
by Iosif Malaescu, Paula Sfirloaga, Octavian M. Bunoiu and Catalin N. Marin
Materials 2024, 17(23), 6006; https://doi.org/10.3390/ma17236006 - 8 Dec 2024
Viewed by 494
Abstract
Three elastomer samples were prepared using GS530SP01K1 silicone rubber (ProChima). The samples included pure silicone rubber (SR), a silicone rubber-graphene composite (SR-GR), and a silicone rubber-magnetite composite (SR-Fe3O4). The magnetite was synthesized via chemical precipitation but was not washed [...] Read more.
Three elastomer samples were prepared using GS530SP01K1 silicone rubber (ProChima). The samples included pure silicone rubber (SR), a silicone rubber-graphene composite (SR-GR), and a silicone rubber-magnetite composite (SR-Fe3O4). The magnetite was synthesized via chemical precipitation but was not washed to remove residual ions. The dielectric response and electrical conductivity of these samples were analyzed across a frequency range of 500 Hz to 2 MHz. The analysis of the complex dielectric permittivity and Cole–Cole plots indicated a mixed dielectric response, combining dipolar behavior and charge carrier hopping. Despite this mixed response, electrical conductivity followed Jonscher’s power law, with the exponent values (0.5 < n < 0.9) confirming the dominance of electron hopping over dipolar behavior in SR-GR and SR-Fe3O4 samples. The SR-Fe3O4 sample demonstrated higher dielectric permittivity and electrical conductivity than SR-GR, even though graphene is inherently more conductive than magnetite. This discrepancy is likely due to the presence of residual ions on the magnetite surface from the chemical precipitation process as the magnetite was only decanted and dried without washing. These findings suggest that the ionic residue significantly influences the dielectric and conductive properties of the composite. Full article
(This article belongs to the Special Issue Flexible Electronic Materials and Devices: Preparation and Application)
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<p>SEM images and elemental analysis of the samples: (<b>a</b>) SR sample; (<b>b</b>) SR-GR sample; and (<b>c</b>) SR-Fe<sub>3</sub>O<sub>4</sub> sample.</p> Full article ">Figure 2
<p>Frequency dependence of the complex dielectric permittivity of samples: (<b>a</b>) the real component, ε′(f), and (<b>b</b>) the imaginary component, ε″(f).</p> Full article ">Figure 3
<p>Cole–Cole plots of the samples: silicon rubber (SR)—(<b>a</b>), silicon rubber-graphene (SR-GR)—(<b>b</b>), and silicon rubber-magnetite (SR-Fe<sub>3</sub>O<sub>4</sub>)—(<b>c</b>).</p> Full article ">Figure 4
<p>Plots of the electrical conductivity of samples versus ω = 2πf in logarithmic scales and the best fit of Equation (9) to experimental data.</p> Full article ">
16 pages, 11395 KiB  
Article
Hydrated Calcium Silicate Erosion in Sulfate Environments a Molecular Dynamics Simulation Study
by Mengjie You, Xiaosan Yin, Yuzhou Sun, Hairong Wu, Jimin Li and Xiangming Zhou
Materials 2024, 17(23), 6005; https://doi.org/10.3390/ma17236005 - 7 Dec 2024
Viewed by 710
Abstract
To investigate the micro-mechanism of the erosion of hydrated calcium silicate (C-S-H gel) in a sulfate environment, a solid–liquid molecular dynamics model of C-S-H gel/sodium sulfate was developed. This model employs molecular dynamics methods to simulate the transport processes between C-S-H gel and [...] Read more.
To investigate the micro-mechanism of the erosion of hydrated calcium silicate (C-S-H gel) in a sulfate environment, a solid–liquid molecular dynamics model of C-S-H gel/sodium sulfate was developed. This model employs molecular dynamics methods to simulate the transport processes between C-S-H gel and corrosive ions at concentrations of 5%, 8%, and 10% sodium sulfate (Na2SO4), aiming to elucidate the interaction mechanism between sulfate and C-S-H gel. The micro-morphology of the eroded samples was also investigated using scanning electron microscopy (SEM). The findings indicate that the adsorption capacity of C-S-H for ions significantly increases with higher concentrations of Na2SO4 solution. Notably, the presence of sulfate ions facilitates the decalcification reaction of C-S-H, leading to the formation of swollen gypsum and AFt (ettringite). This process results not only in the hydrolysis of the C-S-H gel but also in an increase in the diffusion coefficients of Na+ and Ca2+, thereby exacerbating the erosion. Additionally, the pore surfaces of the C-S-H structure exhibited strong adsorption of Na+, and as the concentration of Na2SO4 solution increased, Na+ was more stably adsorbed onto the C-S-H pore surfaces via Na-Os bonds. The root-mean-square displacement curves of water molecules were significantly higher than those of SO42−, Na+ and Ca2+, which indicated that SO42− could co-penetrate and migrate with water molecules faster compared with other ions in the solution containing SO42−, resulting in stronger corrosion and hydrolysis effects on the C-S-H structure. Full article
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Initial structure of Tobermorite and optimized crystal models.</p> Full article ">Figure 2
<p>Convergence curve of the C-S-H model.</p> Full article ">Figure 3
<p>Energy profile after dynamics optimization.</p> Full article ">Figure 4
<p>C-S-H/Na<sub>2</sub>SO<sub>4</sub> solid–liquid modeling process.</p> Full article ">Figure 5
<p>Solid–liquid ionic model.</p> Full article ">Figure 6
<p>SEM images of concrete before erosion at different magnifications.</p> Full article ">Figure 7
<p>Scanning electron microscope images of 5% sodium sulphate eroded concrete for 90 days at different magnifications.</p> Full article ">Figure 8
<p>Scanning electron microscope images of concrete after 90 days of 8% sodium sulphate erosion at different magnifications.</p> Full article ">Figure 9
<p>Calcium and Sulfate Ion Distribution at Initial (0 ps) and (50 ps) Time Points. (<b>a</b>) Concentration of 5%; (<b>b</b>) Concentration of 8%; (<b>c</b>) Concentration of 10%.</p> Full article ">Figure 10
<p>Relative concentrations at the C-S-H/sodium sulfate interface. (<b>a</b>) Concentration of 5%; (<b>b</b>) Concentration of 8%; (<b>c</b>) Concentration of 10%.</p> Full article ">Figure 11
<p>Distribution of sodium and silicon ions at initial (0 ps) and (50 ps) time points. (<b>a</b>) Concentration of 5%; (<b>b</b>) Concentration of 8%; (<b>c</b>) Concentration of 10%.</p> Full article ">Figure 12
<p>Radial distribution function and average coordination number at different concentrations. (<b>a</b>) Concentration of 5%; (<b>b</b>) Concentration of 8%; (<b>c</b>) Concentration of 10%.</p> Full article ">Figure 13
<p>Real-time screenshot at pore surface (green for Ca<sup>2+</sup>, yellow for sulphur atoms, red for O, purple for Na<sup>+</sup>). (<b>a</b>) Concentration of 5%; (<b>b</b>) Concentration of 8%; (<b>c</b>) Concentration of 10%.</p> Full article ">Figure 14
<p>MSD at different concentrations. (<b>a</b>) Concentration of 5%; (<b>b</b>) Concentration of 8%; (<b>c</b>) Concentration of 10%.</p> Full article ">
12 pages, 5804 KiB  
Article
VN Quantum Dots Anchored onto Carbon Nanofibers as a Superior Anode for Sodium Ion Storage
by Xiaoyu Wu, Haimin Zhang, Jiachen Yanghe and Sainan Liu
Materials 2024, 17(23), 6004; https://doi.org/10.3390/ma17236004 - 7 Dec 2024
Viewed by 504
Abstract
Vanadium-based compounds exhibit a high theoretical capacity to be used as anode materials in sodium-ion batteries, but the volume change in the active ions during the process of release leads to structural instability during the cycle. The structure of carbon nanofibers is stable, [...] Read more.
Vanadium-based compounds exhibit a high theoretical capacity to be used as anode materials in sodium-ion batteries, but the volume change in the active ions during the process of release leads to structural instability during the cycle. The structure of carbon nanofibers is stable, while it is difficult to deform. At the same time, the huge specific surface area energy of quantum dot materials can speed up the electrochemical reaction rate. Here, we coupled quantum-grade VN nanodots with carbon nanofibers. The strong coupling of VN quantum dots and carbon nanofibers makes the material have a network structure of interwoven nanofibers. Secondly, the carbon skeleton provides a three-dimensional channel for the rapid migration of sodium ions, and the material has low charge transfer resistance, which promotes the diffusion, intercalation and release of sodium ions, and significantly improves the electrochemical activity of sodium storage. When the material is used as the anode material in sodium ion batteries, the specific capacity is stable at 230.3 mAh g−1 after 500 cycles at 0.5 A g−1, and the specific capacity is still maintained at 154.7 mAh g−1 after 1000 cycles at 2 A g−1. Full article
(This article belongs to the Special Issue Advanced Energy Storage Materials: Preparation, Characterization and Applications (3rd Edition))
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<p>Schematic synthesis steps of VN/CNF.</p> Full article ">Figure 2
<p>XRD patterns of VN/CNF and VN.</p> Full article ">Figure 3
<p>(<b>a</b>) Raman spectra and (<b>b</b>) TG-DSC curves of VN/CNF.</p> Full article ">Figure 4
<p>(<b>a</b>) Survey and high-resolution (<b>b</b>) V 2p, (<b>c</b>) N 1s and (<b>d</b>) C 1s spectra recorded for the VN/CNF.</p> Full article ">Figure 5
<p>SEM image of (<b>a</b>,<b>b</b>) VN and (<b>c</b>,<b>d</b>) VN/CNF, (<b>e</b>) HAADF image, and corresponding elemental mapping distribution of VN/CNF.</p> Full article ">Figure 6
<p>(<b>a</b>,<b>b</b>) TEM and (<b>c</b>) HRTEM image of VN/CNF and (<b>d</b>) HAADF image of VN/CNF. (<b>e</b>) the corresponding elemental mapping of C, N, O and V elements and (<b>f</b>) SAED images of VN/CNF.</p> Full article ">Figure 7
<p>CV of (<b>a</b>) VN/CNF and (<b>b</b>) VN-containing anodes recorded at 0.1 mV s<sup>−1</sup> and 0.2 mV s<sup>−1</sup>, respectively.</p> Full article ">Figure 8
<p>Cycling performance of (<b>a</b>) VN/CNF and (<b>c</b>) VN-based SIB at 0.5 A g<sup>−1</sup>; GCD curves of (<b>b</b>) VN/CNF and (<b>d</b>) VN anodes at 0.5 A g<sup>−1</sup>.</p> Full article ">Figure 9
<p>(<b>a</b>) Long-term cycling performance of VN/CNF-based SIB at 2 A g<sup>−1</sup>. (<b>b</b>) Rate capability of VN/CNF and VN-based SIB.</p> Full article ">
17 pages, 3675 KiB  
Article
Modification of Light-Cured Composition for Permanent Dental Fillings; Mass Stability of New Composites Containing Quinoline and Quinoxaline Derivatives in Solutions Simulating the Oral Cavity Environment
by Ilona Pyszka and Beata Jędrzejewska
Materials 2024, 17(23), 6003; https://doi.org/10.3390/ma17236003 - 7 Dec 2024
Viewed by 444
Abstract
Billions of patients struggle with dental diseases every year. These mainly comprise caries and related diseases. This results in an extremely high demand for innovative, polymer composite filling materials that meet a number of dental requirements. The aim of the study was to [...] Read more.
Billions of patients struggle with dental diseases every year. These mainly comprise caries and related diseases. This results in an extremely high demand for innovative, polymer composite filling materials that meet a number of dental requirements. The aim of the study was to modify the light-cured composition of permanent dental fillings by changing the composition of the liquid organic matrix. New photoinitiators (DQ1-DQ5) based on a quinoline or quinoxaline skeleton and a co-initiator-(phenylthio)acetic acid (PhTAA) were used. In addition, monomers that have been traditionally used in dental materials were replaced by trimethylolpropane triacrylate (TMPTA). The neutral dental glass IDG functioned as an inorganic filler. The influence of the storage conditions of the developed composites in solutions simulating the natural oral environment during the consumption of different meals on sorption, solubility, and mass changes was assessed. For the tests, fifty-four cylindrical composite samples were prepared according to ISO 4049 guidelines and stored in different solutions. Distilled water, artificial saliva, heptane, 10% ethanol, and 3% acetic acid, as well as solutions containing pigments such as coffee, tea, red wine, and Coca-Cola, were used for the studies. The samples were stored in these solutions for 7, 14, 28, 35, 42, 49, 56, and 63 days at 37 °C. The sorption, solubility, and mass changes in the tested samples were determined, and the trend of these changes as a function of storage time was presented. The results were analyzed considering the nature of the solution used, i.e., aqueous, hydrophobic, and acidic. The properties evaluated changed in a different way, characteristic for each of the abovementioned solution groups. It was found that the type of solution simulating the natural environment of the oral cavity has the greatest influence on the sorption, solubility, and changes in the mass of the tested material. Full article
(This article belongs to the Special Issue From Conventional to Modern Biomaterials in Dentistry—2nd Edition)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Heat maps of polymerization rates (μmol s<sup>−1</sup>) obtained during photoinitiated polymerization using initiators: DQ1, DQ4 and CQ, co-initiators: PhTAA and EDMAB (0.1 M) and monomers: (<b>a</b>) TMPTA, (<b>b</b>) Bis-GMA. The light po of the dental lamp was 20 mW cm<sup>−2</sup>; the right panel of the graphs shows the initial polymerization rate gradient; the numbers inside the graph are the initial polymerization rate (in μmol s<sup>−1</sup>) for a specific photoinitiating system containing a photoinitiator and a co-initiator as indicated on the x and y axes.</p> Full article ">Figure 2
<p>Kinetic curves recorded during the polymerization of (1) TMPTA and (2) Bis-GMA photoinitiated by quinoline [2,3-b]-1<span class="html-italic">H</span>-imidazo [1,2-a]pyridinium bromide (DQ1), 6-methyl-6<span class="html-italic">H</span>-indolo [2,3-b]quinoxaline (DQ4) and camphorquinone (CQ) in the presence of co-initiators: (<b>a</b>) (phenylthio)acetic acid (PhTAA) and (<b>b</b>) ethyl 4-dimethylaminobenzoate (EDMAB). The co-initiator concentration was 0.1 M, and the dental lamp light intensity was 20 mW/cm<sup>2</sup>.</p> Full article ">Figure 3
<p>The course of the dependence of the average values of sorption changes in the tested materials on the conditioning time in a 3% acetic acid solution—S2, in artificial saliva—S3, in heptane—S5, in 10% ethanol solution—S4, and in Coca-Cola—S8.</p> Full article ">Figure 4
<p>The course of the dependence of the average solubility values of the tested materials on the conditioning time in 3% acetic acid solution—S2, in artificial saliva—S3, in 10% ethanol solution S4, in Coca-Cola—S8, in heptane—S5, in coffee—S6, in red wine—S9, and in tea—S7.</p> Full article ">Figure 5
<p>Correlation between the average values of the mass change in the tested materials and the conditioning time in the solutions simulating the oral cavity environment.</p> Full article ">Figure 5 Cont.
<p>Correlation between the average values of the mass change in the tested materials and the conditioning time in the solutions simulating the oral cavity environment.</p> Full article ">
15 pages, 2732 KiB  
Article
Synthetic Aggregates and Bituminous Materials Based on Industrial Waste
by Alexandrina Nan, Cristina Dima, Marinela Ghita, Iolanda-Veronica Ganea, Teodora Radu and Alexander Bunge
Materials 2024, 17(23), 6002; https://doi.org/10.3390/ma17236002 - 7 Dec 2024
Viewed by 603
Abstract
The transition to a circular economy requires new materials and products with new production designs, technologies, and processes. In order to create new materials with physico-chemical qualities suitable for application in the building materials engineering sector, stone dust and polymer waste—two environmentally hazardous [...] Read more.
The transition to a circular economy requires new materials and products with new production designs, technologies, and processes. In order to create new materials with physico-chemical qualities suitable for application in the building materials engineering sector, stone dust and polymer waste—two environmentally hazardous industrial wastes—were combined in this study. The materials obtained were evaluated based on an analysis performed using the Micro-Deval test. The results obtained showed a Micro-Deval coefficient value of 7.7%, indicating that these artificial aggregates can replace the natural aggregates used in road construction. Additionally, it was shown that the stone dust used could be applied as a sorbent for dyes without later leaching this dye from the final synthetic stones. Another category of materials that meets the principles of the circular economy and was developed in this study is bituminous mastic, which is currently used for the hot sealing of joints in road infrastructure. For this purpose, a composite material was developed using stone dust and cooking oil to replace the filler, a non-regenerable source used for obtaining bituminous mixtures. Specific standard methods were used to assess the degree to which the new materials approach the behavior of commercially available products. Full article
(This article belongs to the Special Issue Sustainability, Circular Economy and Waste Recycling: Advances in Materials Research (2nd Edition))
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<p>Schematic representation of the steps necessary to carry out the proposed study. In the first stage, the bituminous materials will be prepared. Characterization of the materials obtained will be performed, and based on the results achieved, the preparation method will be optimized. Evaluation of mechanical performance and durability by specific testing protocols will be performed. The arrows between stage blocks indicate the feedback loop for material preparation and testing. After their evaluations, the most promising materials for the targeted applications will be selected.</p> Full article ">Figure 2
<p>Stone dust (<b>a</b>), stone dust after CV adsorption (<b>b</b>), example of the S2 synthetic aggregates (<b>c</b>), example of synthetic aggregates with CV-embedded stone dust (<b>d</b>).</p> Full article ">Figure 3
<p>Direct comparison of dissipation module <span class="html-italic">G</span>″ and storage module <span class="html-italic">G</span>′ for M4 and M6 and commercial mastic (CM).</p> Full article ">Figure 4
<p>Exemplification for testing selected compositions in exposure conditions similar to real-life ones: variations in temperature, pressure, and mechanical vibrations.</p> Full article ">Figure 5
<p>Determination of the softening point using a ball (<b>a</b>) and ring (<b>b</b>), according to SR EN 1427:2002. The determined soaking point is the temperature at which the bituminous material with added waste under standard test conditions reaches the specified consistency.</p> Full article ">
16 pages, 4681 KiB  
Article
Preliminary Aspects Regarding the Anticorrosive Effect of Multi-Layered Silane–Hydroxyapatite Coatings Deposited on Titanium Grade 2 for Medical Applications
by Agata Dudek and Oliwia Kierat
Materials 2024, 17(23), 6001; https://doi.org/10.3390/ma17236001 - 7 Dec 2024
Viewed by 600
Abstract
This paper presents a method for producing VTMS/HAp/VTMS/VTMS multilayer coatings on a Grade 2 titanium substrate and characterizes their structure and functional properties. Two solutions were used to produce the coatings: one based on vinyltrimethoxysilane (VTMS) and the other on hydroxyapatite (HAp) powder. [...] Read more.
This paper presents a method for producing VTMS/HAp/VTMS/VTMS multilayer coatings on a Grade 2 titanium substrate and characterizes their structure and functional properties. Two solutions were used to produce the coatings: one based on vinyltrimethoxysilane (VTMS) and the other on hydroxyapatite (HAp) powder. The coatings were applied using immersion using the sol-gel method. Microstructural tests of the multilayer coatings were performed, their chemical composition was determined, and the structure was characterized using Fourier Transform Infrared Spectroscopy (FTIR). A detailed analysis of the geometric structure of the coatings was carried out both before and after corrosion tests. The geometric structure of the multilayer coatings was analyzed using a light microscope and an atomic force microscope (AFM). The thickness of the coatings was determined using a Testan DT-10 AN 120 157 m, and the adhesion of the coatings to the substrate was analyzed using Scotch™ tape. The corrosion resistance of the coatings in simulated body fluid was tested to evaluate their suitability for implantology. As demonstrated by the research presented in this paper, the sol–gel process can successfully produce silane coatings by adding hydroxyapatite powder. The new materials proposed in this study can effectively protect metal materials used in medicine against corrosion. Full article
(This article belongs to the Special Issue Fabrication and Properties of Functional Coatings Under Extreme Conditions)
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<p>Methods of modifying the surface of titanium and its alloys—own study based on [<a href="#B15-materials-17-06001" class="html-bibr">15</a>,<a href="#B20-materials-17-06001" class="html-bibr">20</a>,<a href="#B21-materials-17-06001" class="html-bibr">21</a>,<a href="#B22-materials-17-06001" class="html-bibr">22</a>,<a href="#B23-materials-17-06001" class="html-bibr">23</a>,<a href="#B24-materials-17-06001" class="html-bibr">24</a>,<a href="#B25-materials-17-06001" class="html-bibr">25</a>,<a href="#B26-materials-17-06001" class="html-bibr">26</a>].</p> Full article ">Figure 2
<p>Microstructure of the hydroxyapatite powder used in the study, recorded with a KEYENCE VHX-7000 (Keyence, Mechelen, Belgium) digital microscope.</p> Full article ">Figure 3
<p>The microstructure of the VTMS/HAp/VTMS/VTMS coating deposited on Grade 2 titanium was imaged using a scanning electron microscope.</p> Full article ">Figure 4
<p>EDS spectrum recorded for the VTMS/HAp/VTMS/VTMS coating deposited on Grade 2 titanium, showing the distribution of individual elements.</p> Full article ">Figure 5
<p>FTIR spectra were recorded for hydroxyapatite powder (a) and the VTMS/HAp/VTMS/VTMS coating deposited on Grade 2 titanium (b).</p> Full article ">Figure 6
<p>Line roughness was measured using a KEYENCE VHX-7000 digital microscope for a Grade 2 titanium.</p> Full article ">Figure 7
<p>Line roughness was measured using a KEYENCE VHX-7000 digital microscope for a VTMS/HAp/VTMS/VTMS coating deposited on a Grade 2 titanium substrate.</p> Full article ">Figure 8
<p>Line roughness was measured using a KEYENCE VHX-7000 digital microscope for a VTMS/HAp/VTMS/VTMS coating deposited on a Grade 2 titanium substrate after corrosion testing in simulated body fluid.</p> Full article ">Figure 9
<p>Three-dimensional and two-dimensional topography and roughness profile of the VTMS/Hap/VTMS/VTMS coating deposited on Grade 2 titanium.</p> Full article ">Figure 10
<p>Potentiodynamic polarization curves (<b>A</b>) were analyzed in simulated body fluid for (a) Grade 2 titanium and (b) the coating deposited on Grade 2 titanium, along with the coating microstructure after corrosion tests in simulated body fluid (<b>B</b>).</p> Full article ">Figure 11
<p>Linear polarization resistance plots were recorded for (a) Grade 2 titanium and (b) the coating deposited on Grade 2 titanium in simulated body fluid.</p> Full article ">
17 pages, 2041 KiB  
Article
Styrene–Butadiene Rubber Latex Modified Mortars Prepared with High Early Strength Portland Cement
by Modestas Kligys and Giedrius Girskas
Materials 2024, 17(23), 6000; https://doi.org/10.3390/ma17236000 - 7 Dec 2024
Viewed by 611
Abstract
The increased early hydration rate of high early strength cement has economic advantages in many civil engineering fields (faster formwork removal or earlier demoulding of precast elements). Styrene–butadiene rubber (SBR) latex is the most common polymer in aqueous dispersions suitable for admixing in [...] Read more.
The increased early hydration rate of high early strength cement has economic advantages in many civil engineering fields (faster formwork removal or earlier demoulding of precast elements). Styrene–butadiene rubber (SBR) latex is the most common polymer in aqueous dispersions suitable for admixing in cement-based materials. It allows the designing of structures with specific properties for a variety of applications. The analysis of literature sources has shown that different properties of SBR latex-modified cement-based material samples reported were usually measured at 3, 7, 14, and 28 days of hardening. In this research, the authors decided to investigate a combined effect of high early strength Portland cement, characterized by an increased hydration rate, and SBR latex able to retard this process for a prolonged hardening period—up to 90 days in modified mortar samples. This study covers the results of the effect of different amounts of SBR latex (5%, 10%, 15%, and 20%) on the properties of modified mortar samples with a constant water-to-cement ratio prepared with high early strength Portland cement 42.5 R. The mortar samples were prepared from local raw materials produced by the Lithuanian companies. The properties, such as dry bulk density, ultrasonic pulse velocity, capillary water absorption, compressive and flexural strengths, and toughness, after three different hardening periods (7, 28, and 90 days) of the mortar samples were investigated. The applied mathematical–statistical methods allowed a detailed prognosis of the dependence between the dry bulk density and the strength properties of modified mortar samples. The combination of 42.5 R strength class Portland cement with the SBR latex in amounts ranging from 5% to 20% seems to be suitable for designing durable structures with specific properties. Full article
(This article belongs to the Special Issue The Development of Sustainable Concrete with Solid Waste and By-Products)
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<p>Testing of hardened mortar samples: (<b>a</b>)—flexural strength; (<b>b</b>)—compressive strength.</p> Full article ">Figure 2
<p>Relationship between the dry bulk density values and the amount of SBR latex.</p> Full article ">Figure 3
<p>Relationship between the ultrasonic pulse velocity values and the amount of SBR latex.</p> Full article ">Figure 4
<p>Relationship between the capillary water absorption values and the amount of SBR latex.</p> Full article ">Figure 5
<p>Relationship between the flexural strength values and the amount of SBR latex.</p> Full article ">Figure 6
<p>Relationship between the flexural strength and dry bulk density of the mortar samples: (<b>a</b>)—after 7 days; (<b>b</b>)—after 28 days; (<b>c</b>)—after 90 days.</p> Full article ">Figure 7
<p>Relationship between the compressive strength values and the amount of SBR latex.</p> Full article ">Figure 8
<p>Relationship between the compressive strength and the dry bulk density of mortar samples: (<b>a</b>)—after 7 days; (<b>b</b>)—after 28 days; (<b>c</b>)—after 90 days.</p> Full article ">Figure 9
<p>Relationship between the toughness values and the amount of SBR latex.</p> Full article ">
16 pages, 3137 KiB  
Article
Influence of Laser Micro-Texturing and Plasma Treatment on Adhesive Bonding Properties of WC-Co Carbides with Steel
by Tomasz Karol Wojdat and Tomasz Piwowarczyk
Materials 2024, 17(23), 5999; https://doi.org/10.3390/ma17235999 - 7 Dec 2024
Viewed by 555
Abstract
This article presents research on advanced surface preparation methods for sintered carbides (WC-Co, grade B2) commonly used in the tool industry, particularly in the context of bonding these materials with C45 steel using adhesives. Sintered carbides are widely used due to their high [...] Read more.
This article presents research on advanced surface preparation methods for sintered carbides (WC-Co, grade B2) commonly used in the tool industry, particularly in the context of bonding these materials with C45 steel using adhesives. Sintered carbides are widely used due to their high hardness, wear resistance, and good ductility, making them ideal for manufacturing tools operating in harsh conditions. Traditional bonding methods, such as brazing and welding, often result in stresses and cracks. Adhesive bonding has therefore emerged as an effective alternative to mitigate these challenges. The research focuses on comparing the results obtained through modern surface treatment techniques, such as laser micro-texturing and plasma treatment, with traditional methods like grinding, abrasive blasting, and electrolytic etching. The influence of these methods on adhesion properties and the strength of adhesive bonds was evaluated through mechanical tests, including static shear and pull-off tests. An approximately 50% increase in the mechanical strength of adhesive joints was observed for surfaces treated with low-temperature plasma (operating voltage: 18 kV, flow of gasses: 20 l/min., treatment time: 60 s) and laser micro-texturing (infrared fiber laser, wavelength: 1064 nm (±5 nm), power: 20 W), as compared to mechanical grinding. The shear strength of the adhesive joints was equal to 32 MPa and 30 MPa on average in the case of treatment with low-temperature plasma made of helium and argon, respectively. The highest strength of an adhesive joint was equal to 34.5 MPa on average in the case of laser micro-texturing. Full article
(This article belongs to the Special Issue Welding, Joining, and Additive Manufacturing of Metals and Alloys (Second Edition))
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<p>Shape and dimensions of WC-Co carbide grade B2 plates for static tests: shear (<b>a</b>) and pull-off (<b>b</b>).</p> Full article ">Figure 2
<p>Schema of a device for the low-temperature plasma treatment and types of plasma jets depending on plasma gas: He (<b>a</b>), Ar (<b>b</b>), and N<sub>2</sub> (<b>c</b>).</p> Full article ">Figure 3
<p>Model of WC-Co–C45 steel adhesive joints (<b>a</b>); instrumentation and method of fixing samples of adhesive joints for pull-off (<b>b</b>) and shear (<b>c</b>) tests.</p> Full article ">Figure 4
<p>Examples of wettability of WC-Co carbide surfaces with distilled water before and after low-temperature plasma treatment generated from various gasses.</p> Full article ">Figure 5
<p>The wettability angle average value of WC-Co carbides before and after low-temperature plasma treatment.</p> Full article ">Figure 6
<p>Surface profile of WC-Co carbide after laser and plasma treatments (<b>a</b>); example of measuring width (w) and depth (h) of grid texture (<b>b</b>).</p> Full article ">Figure 7
<p>The results of shear strength of WC-Co–C45 steel adhesive joints depending on the method of surface preparation.</p> Full article ">Figure 8
<p>Mixed adhesive–cohesive (AF+CF) fracture mechanism of WC-Co -C45 steel adhesive joints after shear test. Laser (<b>a</b>) and plasma (<b>b</b>) treated surfaces of WC-Co carbides.</p> Full article ">Figure 9
<p>SE (Secondary Electron) image of adhesive joint failure after shear test. WC-Co carbide after laser treatment (<b>a</b>,<b>b</b>) and WC-Co carbide after plasma treatment (<b>c</b>,<b>d</b>): 1—laser grooves, 2—adhesive particles, and 3—WC-Co carbide surface.</p> Full article ">Figure 10
<p>The pull-off strength of WC-Co–C45 steel adhesive joints depending on the method of surface preparation.</p> Full article ">
15 pages, 5821 KiB  
Article
On the Use of Cyclic Cryogenic Treatment to Improve the Properties of High-Speed Steel
by Paweł Pieśko, Jarosław Korpysa and Magdalena Zawada-Michałowska
Materials 2024, 17(23), 5998; https://doi.org/10.3390/ma17235998 - 7 Dec 2024
Viewed by 511
Abstract
Cryogenic treatment is a process of controlled gradual cooling of the workpiece to a temperature ranging from −60 °C to even below −190 °C, holding the workpiece at this temperature and then slowly reheating it to ambient temperature. According to the current state [...] Read more.
Cryogenic treatment is a process of controlled gradual cooling of the workpiece to a temperature ranging from −60 °C to even below −190 °C, holding the workpiece at this temperature and then slowly reheating it to ambient temperature. According to the current state of knowledge, the purpose of cryogenic treatment is to reduce the concentration of retained austenite by transforming it into hard martensite under low-temperature treatment. The retained austenite reduction in steels results in improved hardness, impact strength, and wear resistance. This study involved conducting comparative tests of the hardness, tensile strength, and impact strength of high-speed steel samples with and without cryogenic treatment, which made it possible to determine the effect of cyclic cryogenic treatment on the properties of this steel. In addition to that, machining tests were conducted to assess the life of a cutting tool edge made from both cryogenic-treated and non-cryogenic-treated high-speed steel. Also, the austenite concentration in the samples was measured by X-ray diffraction. Obtained results confirmed that the cyclic cryogenic treatment enhanced all tested properties of the high-speed steel. Full article
(This article belongs to the Special Issue Non-conventional Machining: Materials and Processes)
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<p>Cycle of temperature variations during cryogenic treatment.</p> Full article ">Figure 2
<p>Experimental setup.</p> Full article ">Figure 3
<p>Samples used for (<b>a</b>) hardness and impact strength tests; (<b>b</b>) retained austenite measurement and tensile strength tests.</p> Full article ">Figure 4
<p>Schematic design and basic geometric parameters of ISO 1 R tool that was used for cutting edge life tests.</p> Full article ">Figure 5
<p>Example of measurement of retained austenite.</p> Full article ">Figure 6
<p>Retained austenite volume fraction.</p> Full article ">Figure 7
<p>Results of hardness HRC.</p> Full article ">Figure 8
<p>Results of Charpy impact tests.</p> Full article ">Figure 9
<p>Tensile test results—tensile strength <span class="html-italic">R<sub>m</sub></span>.</p> Full article ">Figure 10
<p>Images of an ISO 1 R tool edge without cryogenic treatment: (<b>a</b>) before treatment; (<b>b</b>) after treatment.</p> Full article ">Figure 11
<p>Tool wear indicator <span class="html-italic">VB<sub>C</sub></span> versus machining time.</p> Full article ">Figure 12
<p>Tool wear indicator <span class="html-italic">KE</span> versus machining time.</p> Full article ">
27 pages, 6034 KiB  
Review
High-Performance Advanced Composites in Multifunctional Material Design: State of the Art, Challenges, and Future Directions
by Sónia Simões
Materials 2024, 17(23), 5997; https://doi.org/10.3390/ma17235997 - 7 Dec 2024
Viewed by 928
Abstract
This review examines high-performance advanced composites (HPACs) for lightweight, high-strength, and multi-functional applications. Fiber-reinforced composites, particularly those utilizing carbon, glass, aramid, and nanofibers, are highlighted for their exceptional mechanical, thermal, and environmental properties. These materials enable diverse applications, including in the aerospace, automotive, [...] Read more.
This review examines high-performance advanced composites (HPACs) for lightweight, high-strength, and multi-functional applications. Fiber-reinforced composites, particularly those utilizing carbon, glass, aramid, and nanofibers, are highlighted for their exceptional mechanical, thermal, and environmental properties. These materials enable diverse applications, including in the aerospace, automotive, energy, and defense sectors. In extreme conditions, matrix materials—polymers, metals, and ceramics—and advanced reinforcement materials must be carefully chosen to optimize performance and durability. Significant advancements in manufacturing techniques, such as automated and additive methods, have improved precision, reduced waste, and created highly customized and complex structures. Multifunctional composites integrating structural properties with energy storage and sensing capabilities are emerging as a breakthrough aligned with the trend toward smart material systems. Despite these advances, challenges such as recyclability, scalability, cost, and robust quality assurance remain. Addressing these issues will require the development of sustainable and bio-based composites, alongside efficient recycling solutions, to minimize their environmental impact and ensure long-term technological viability. The development of hybrid composites and nanocomposites to achieve multifunctionality while maintaining structural integrity will also be described. Full article
(This article belongs to the Special Issue Advanced High-Performance Metal Matrix Composites (MMCs))
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<p>Evolution of composites [<a href="#B15-materials-17-05997" class="html-bibr">15</a>].</p> Full article ">Figure 2
<p>Classification of composites.</p> Full article ">Figure 3
<p>Polymer matrix composite structure designs.</p> Full article ">Figure 4
<p>(<b>a</b>) Atomic force microscopy (AFM) image along with dimensional measurements (red line and green marked) showing the length (L) and thickness (t) of MoS₂ nanosheets; (<b>b</b>) scanning electron microscopy (SEM) image of exfoliated MoS<sub>2</sub> [<a href="#B34-materials-17-05997" class="html-bibr">34</a>].</p> Full article ">Figure 5
<p>Stress distribution of three-layer graphene/aluminum composite during tensile failure. (<b>a</b>–<b>f</b>) illustrates the sequence of events, from the initial formation of cracks in the matrix to the eventual failure of the material during stretching [<a href="#B42-materials-17-05997" class="html-bibr">42</a>].</p> Full article ">Figure 6
<p>SEM images and IQ maps with high- and low-angle boundaries (black and red, respectively) delimited and geometrically necessary dislocation (GND) density maps for (<b>a</b>,<b>b</b>) Ni green compact, (<b>c</b>,<b>d</b>) sintered Ni, (<b>e</b>,<b>f</b>) Ni-CNT green compact, and (<b>g</b>,<b>h</b>) Ni-CNT sintered samples [<a href="#B44-materials-17-05997" class="html-bibr">44</a>].</p> Full article ">Figure 7
<p>Microscopic morphology of the cross-section of 2.5D Cf/SiCs [<a href="#B51-materials-17-05997" class="html-bibr">51</a>].</p> Full article ">Figure 8
<p>GF/stainless-steel/PA6 hybrid composites: (<b>a</b>) tensile properties and (<b>b</b>) cross-sectional image of hybrid composite [<a href="#B84-materials-17-05997" class="html-bibr">84</a>].</p> Full article ">Figure 9
<p>Flowchart representing the materials selection and optimization for advanced high-performance composites.</p> Full article ">Figure 10
<p>Flowchart representing the materials selection and optimization for advanced high-performance composites.</p> Full article ">Figure 11
<p>The schematic draw of the interphase in the composite [<a href="#B107-materials-17-05997" class="html-bibr">107</a>].</p> Full article ">
13 pages, 4036 KiB  
Article
Improving Visible Light Photocatalysis Using Optical Defects in CoOx-TiO2 Photonic Crystals
by Alexia Toumazatou, Elias Sakellis and Vlassis Likodimos
Materials 2024, 17(23), 5996; https://doi.org/10.3390/ma17235996 - 7 Dec 2024
Viewed by 760
Abstract
The rational design of photonic crystal photocatalysts has attracted significant interest in order to improve their light harvesting and photocatalytic performances. In this work, an advanced approach to enhance slow light propagation and visible light photocatalysis is demonstrated for the first time by [...] Read more.
The rational design of photonic crystal photocatalysts has attracted significant interest in order to improve their light harvesting and photocatalytic performances. In this work, an advanced approach to enhance slow light propagation and visible light photocatalysis is demonstrated for the first time by integrating a planar defect into CoOx-TiO2 inverse opals. Trilayer photonic crystal films were fabricated through the successive deposition of an inverse opal TiO2 underlayer, a thin titania interlayer, and a photonic top layer, whose visible light activation was implemented through surface modification with CoOx nanoscale complexes. Optical measurements showed the formation of “donor”-like localized states within the photonic band gap, which reduced the Bragg reflection and expanded the slow photon spectral range. The optimization of CoOx loading and photonic band gap tuning resulted in a markedly improved photocatalytic performance for salicylic acid degradation and photocurrent generation compared to the additive effects of the constituent monolayers, indicative of light localization in the defect layer. The electrochemical impedance results showed reduced recombination kinetics, corroborating that the introduction of an optical defect into inverse opal photocatalysts provides a versatile and effective strategy for boosting the photonic amplification effects in visible light photocatalysis by evading the constraints imposed by narrow slow photon spectral regions. Full article
(This article belongs to the Special Issue Feature Papers in Materials Physics (2nd Edition))
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Graphical abstract
Full article ">Figure 1
<p>Schematic illustration of the PC/P25/PC trilayer deposition process.</p> Full article ">Figure 2
<p>SEM images of the (<b>a</b>) PC406 and (<b>b</b>,<b>c</b>) PC499 inverse opal substrates as well as (<b>d</b>–<b>f</b>) cross-sections of the PC406/P25/PC406 trilayer photonic films at different magnifications. Specular reflectance (R%) spectra for the (<b>g</b>) PC406/P25/PC406 και (<b>h</b>) PC499/P25/PC499 in comparison to the monolithic PC406 and PC499 inverse opals.</p> Full article ">Figure 3
<p>Raman spectra of the trilayer films CoO<sub>x</sub>-PC406/P25/PC406, PC406/CoO<sub>x</sub>-P25/PC406, and CoO<sub>x</sub>-PC406/CoO<sub>x</sub>-P25/PC406 in comparison to CoO<sub>x</sub>-P25/PC406, CoO<sub>x</sub>-PC406 and CoO<sub>x</sub>-P25 reference films at 785 nm and different intensity scales (<b>a</b>,<b>b</b>). Shaded bands indicate the Co<sub>3</sub>O<sub>4</sub> Raman modes.</p> Full article ">Figure 4
<p>Diffuse (DR%) reflectance spectra for the mono-, bi-, and tri-layer photonic films: (<b>a</b>) PC406, CoO<sub>x</sub>-P25/PC406, PC406/CoO<sub>x</sub>-P25/PC406 and (<b>b</b>) PC499, CoO<sub>x</sub>-P25/PC499, and PC499/CoO<sub>x</sub>-P25/PC499. (<b>c</b>) DR% and (<b>d</b>) the corresponding Kubelka–Munk F(DR) absorbance spectra of the PC406/CoO<sub>x</sub>-P25/PC406, CoO<sub>x</sub>-PC406/P25/PC406, and CoO<sub>x</sub>-PC406/CoOx-P25/PC406 trilayer films in comparison to the PC406 and PC406/P25/PC406 reference ones.</p> Full article ">Figure 5
<p>(<b>a</b>,<b>b</b>) SA photodegradation kinetics and (<b>c</b>) reaction rates for the CoO<sub>x</sub>-surface modified trilayer photonic films in comparison to the constituent monolithic CoO<sub>x</sub>-TiO<sub>2</sub> films under visible light (λ &gt; 400 nm) irradiation.</p> Full article ">Figure 6
<p>Transient photocurrent density and EIS Nyquist plots in 0.5 Μ NaOH electrolyte under visible light illumination for the mono-, bi-, and tri-layer films (<b>a</b>), (<b>b</b>) CoO<sub>x</sub>-PC406, CoO<sub>x</sub>-P25/PC406, PC406/CoO<sub>x</sub>-P25/PC406, and (<b>c</b>), (<b>d</b>) CoO<sub>x</sub>-PC499, CoO<sub>x</sub>-P25/PC499, PC499/CoO<sub>x</sub>-P25/PC499. (<b>e</b>) Mott–Schottky plots for the P25 και CoO<sub>x</sub>-P25 films at 1000 Hz.</p> Full article ">
11 pages, 2574 KiB  
Article
Photo-Excited Carrier Dynamics in Ammonothermal Mn-Compensated GaN Semiconductor
by Patrik Ščajev, Paweł Prystawko, Robert Kucharski and Irmantas Kašalynas
Materials 2024, 17(23), 5995; https://doi.org/10.3390/ma17235995 - 7 Dec 2024
Viewed by 589
Abstract
We investigated the carrier dynamics of ammonothermal Mn-compensated gallium nitride (GaN:Mn) semiconductors by using sub-bandgap and above-bandgap photo-excitation in a photoluminescence analysis and pump–probe measurements. The contactless probing methods elucidated their versatility for the complex analysis of defects in GaN:Mn crystals. The impurities [...] Read more.
We investigated the carrier dynamics of ammonothermal Mn-compensated gallium nitride (GaN:Mn) semiconductors by using sub-bandgap and above-bandgap photo-excitation in a photoluminescence analysis and pump–probe measurements. The contactless probing methods elucidated their versatility for the complex analysis of defects in GaN:Mn crystals. The impurities of Mn were found to show photoconductivity and absorption bands starting at the 700 nm wavelength threshold and a broad peak located at 800 nm. Here, we determined the impact of Mn-induced states and Mg acceptors on the relaxation rates of charge carriers in GaN:Mn based on a photoluminescence analysis and pump–probe measurements. The electrons in the conduction band tails were found to be responsible for both the photoconductivity and yellow luminescence decays. The slower red luminescence and pump–probe decays were dominated by Mg acceptors. After photo-excitation, the electrons and holes were quickly thermalized to the conduction band tails and Mg acceptors, respectively. The yellow photoluminescence decays exhibited a 1 ns decay time at low laser excitations, whereas, at the highest ones, it increased up to 7 ns due to the saturation of the nonradiative defects, resembling the photoconductivity lifetime dependence. The fast photo-carrier decay time observed in ammonothermal GaN:Mn is of critical importance in high-frequency and high-voltage device applications. Full article
(This article belongs to the Special Issue Optical Properties of Crystalline Semiconductors and Nanomaterials)
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Figure 1

Figure 1
<p>(<b>a</b>) The PL spectra of SI Am-GaN:Mn with conductive epitaxial GaN epilayer. For comparison purposes, the absorption and photoconductivity spectra adapted from Ref. [<a href="#B8-materials-17-05995" class="html-bibr">8</a>] are also shown. Near-band emission (NBE) PL was excited by 330 nm, while defect PL was excited by 400 nm wavelength at 300 K. Note: 1—fast band tail-to-hole transitions; 2—band tail-to-Mg<sup>0</sup> transitions; 3—internal Mn-IB-to-VB transitions; 4—Mn-IB-to-CB transition; 5—VB-to-free Mn-IB-state transition; 8—Mn-IB-to-band tail transition; 6—Urbach tail (95 meV); 7—high purity GaN band-edge absorption. (<b>b</b>) Tentative optical transitions via impurity states of Mn and Mg atoms. Note: Mg—acceptor; YL—yellow luminescence; RL—red luminescence. (<b>c</b>) Scheme of the electron transitions in the SI-n junction.</p> Full article ">Figure 2
<p>Fast BB (NBE1), e<sup>−</sup>Mg<sup>0</sup>(NBE2), YL, and RL TRPL decay at 300 K.</p> Full article ">Figure 3
<p>Slow YL (<b>a</b>) and RL (<b>b</b>) decays at 300 K. Straight lines show exponential fits. Excitation intensities are the same as in <a href="#materials-17-05995-f004" class="html-fig">Figure 4</a>.</p> Full article ">Figure 4
<p>YL excitation-dependent decay (<b>a</b>), and time-dependent PL spectra at 80 K (<b>b</b>), YL, and RL band intensity vs. excitation (<b>c</b>).</p> Full article ">Figure 5
<p>YL decays at high excitation at different temperatures (<b>a</b>). Initial YL lifetime vs. T at high and low excitations (<b>b</b>); Straight lines in (<b>a</b>) show exponential fits, while in (<b>b</b>) provides activation fit for BTs, function τ = 1/(a + b × exp(−E<sub>a</sub>/kT)) was applied for fitting; a = 3.6 × 10<sup>7</sup> s<sup>−1</sup>, b = 4 × 10<sup>9</sup> s<sup>−1</sup>.</p> Full article ">Figure 6
<p>PP decays vs. pump intensity at 527 nm and 1550 nm probes at 300 K (<b>a</b>); PP signal excitation dependence linearity (<b>b</b>).</p> Full article ">Figure 7
<p>Temperature-dependent PP decays (<b>a</b>) and their initial decay time thermal activation (<b>b</b>). Straight lines in (<b>a</b>) show exponential fits, while in (<b>b</b>) function τ = 1/(a + b × exp(–E<sub>a</sub>/kT)) was applied for fitting; a = 7.5 × 10<sup>6</sup> s<sup>−1</sup>, b = 7 × 10<sup>8</sup> s<sup>−1</sup>, with Ea = 69 meV and 77 meV for the fast and the slow parts, respectively. Initial (red points) and slow (green points) decay parts provide almost the same activation energy.</p> Full article ">Figure 8
<p>Photoconductive signal decays at different laser excitation pulse energies (corresponding to the carrier densities shown in <a href="#materials-17-05995-f009" class="html-fig">Figure 9</a>) at 16 V bias voltage at 300 K. The second decay peak at the 10 ns time mark corresponds to the decay excited by a parasitic (by a magnitude weaker) laser pulse arriving after the main pulse; solid lines are exponential fits providing PC lifetime in <a href="#materials-17-05995-f009" class="html-fig">Figure 9</a>.</p> Full article ">Figure 9
<p>Decay time vs. excited carrier density by time-resolved pump–probe (PP), photoluminescence (PL), and photoconductivity (PC) [<a href="#B8-materials-17-05995" class="html-bibr">8</a>]. For RL and YL, different time windows are indicated where lifetime was determined in <a href="#materials-17-05995-f003" class="html-fig">Figure 3</a>.</p> Full article ">
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