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Materials, Volume 16, Issue 21 (November-1 2023) – 235 articles

Cover Story (view full-size image): The acetalization of glycerol, the main residue of biodiesel production industry, to prepare fuel additives such as solketal is of remarkable interest, promoting zero net emissions and a circular economy. Porous metal–organic framework (MOF) materials of the MOF-808 family were applied as heterogeneous catalysts to the valorization of glycerol with acetone for the first time. In particular, the MOF-808(Hf) demonstrated to be an effective sustainable catalyst to produce solketal under moderate conditions, revealing the potential for a future scaled-up investigation of the reported process. View this paper
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13 pages, 18141 KiB  
Article
The Microstructures and Deformation Mechanism of Hetero-Structured Pure Ti under High Strain Rates
by Shuaizhuo Wang, Haotian Yan, Dongmei Zhang, Jiajun Hu and Yusheng Li
Materials 2023, 16(21), 7059; https://doi.org/10.3390/ma16217059 - 6 Nov 2023
Cited by 2 | Viewed by 1306
Abstract
This study investigates the microstructures and deformation mechanism of hetero-structured pure Ti under different high strain rates (500 s−1, 1000 s−1, 2000 s−1). It has been observed that, in samples subjected to deformation, the changes in texture [...] Read more.
This study investigates the microstructures and deformation mechanism of hetero-structured pure Ti under different high strain rates (500 s−1, 1000 s−1, 2000 s−1). It has been observed that, in samples subjected to deformation, the changes in texture are minimal and the rise in temperature is relatively low. Therefore, the influence of these two factors on the deformation mechanism can be disregarded. As the strain rate increases, the dominance of dislocation slip decreases while deformation twinning becomes more prominent. Notably, at a strain rate of 2000 s−1, nanoscale twin lamellae are activated within the grain with a size of 500 nm, which is a rarely observed phenomenon in pure Ti. Additionally, martensitic phase transformation has also been identified. In order to establish a correlation between the stress required for twinning and the grain size, a modified Hall–Petch model is proposed, with the obtained value of Ktwin serving as an effective metric for this relationship. These findings greatly enhance our understanding of the mechanical responses of Ti and broaden the potential applications of Ti in dynamic deformation scenarios. Full article
(This article belongs to the Special Issue Materials under High Pressure)
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Figure 1
<p>(<b>a-1</b>) The schematics of the split Hopkinson pressure bar system; (<b>a-2</b>) specimen; (<b>b-1</b>–<b>b-3</b>) EBSD characterization of the initial hetero-structured sample. (<b>b-1</b>) Inverse polar figure (IPF) map; (<b>b-2</b>) distribution of grain boundary orientation; (<b>b-3</b>) distributions of grain size.</p> Full article ">Figure 2
<p>Mechanical properties of hetero-structured samples under different strain rate: (<b>a</b>) compressive engineering stress-strain curves; (<b>b</b>) true stress-strain curves from compressive tests; (<b>c</b>) strain hardening rate curves; (<b>d</b>) corresponding yield strength (YS), ultimate compressive strength (UCS) and compression strain of the samples under different strain rate.</p> Full article ">Figure 3
<p>Adiabatic temperature rises values for overall hetero-structured samples under different strain rate.</p> Full article ">Figure 4
<p>EBSD observations of deformed hetero-structured sample under a strain rate of 500 s<sup>−1</sup>, 1000 s<sup>−1</sup>, 2000 s<sup>−1</sup>, respectively: (<b>a-1</b>–<b>c-1</b>) IPF map; (<b>a-2</b>–<b>c-2</b>) twin boundary map; (<b>a-3</b>–<b>c-3</b>) distribution of grain boundary orientation; (<b>a-4</b>–<b>c-4</b>) statistical distributions of Local Misorientation.</p> Full article ">Figure 5
<p>(0001), (11<math display="inline"><semantics> <mover accent="true"> <mn>2</mn> <mo>¯</mo> </mover> </semantics></math>0) and (10<math display="inline"><semantics> <mover accent="true"> <mn>1</mn> <mo>¯</mo> </mover> </semantics></math>0) pole figures of deformed hetero-structured samples under different strain rate: (<b>a</b>) 500 s<sup>−1</sup>, (<b>b</b>) 1000s<sup>−1</sup>, (<b>c</b>) 2000 s<sup>−1</sup>.</p> Full article ">Figure 6
<p>TEM images of deformed hetero-structured sample with different strain rates. (<b>a-1</b>,<b>a-2</b>) 500 s<sup>−1</sup>; (<b>b-1</b>,<b>b-2</b>) 1000 s<sup>−1</sup>, The white arrows indicate dislocations.</p> Full article ">Figure 7
<p>Microstructure of deformed hetero-structured sample with a strain rate of 2000 s<sup>−1</sup>: (<b>a</b>,<b>b</b>) bright field TEM images; (<b>c-1</b>) The TEM image of martensitic phases; (<b>c-2</b>) close-up view of the area marked by the white dash line box in (<b>c-1</b>), the white arrows indicate needle-like martensitic phases.</p> Full article ">Figure 8
<p>TEM images of ultra-fine grain of deformed hetero-structured sample under a strain rate of 2000 s<sup>−1</sup>: (<b>a</b>) bright field TEM image of ultra-fine grain; (<b>b</b>) close-up view of the area marked by the white dash line box in (<b>a</b>), and the corresponding selected area diffraction pattern.</p> Full article ">
19 pages, 4608 KiB  
Article
Synergistic Effects of SAP, Limestone Powder and White Cement on the Aesthetic and Mechanical Properties of Fair-Faced Concrete
by Jun Shi, Zhangbao Wu, Jinping Zhuang, Fan Zhang, Tongran Zhu and Huixia Li
Materials 2023, 16(21), 7058; https://doi.org/10.3390/ma16217058 - 6 Nov 2023
Cited by 3 | Viewed by 1466
Abstract
In this investigation, a comprehensive assessment was conducted on the cooperative effects of Super Absorbent Polymers (SAP), limestone powder, and white cement within the realm of fair-faced concrete. We discerned that while white cement augments the color vibrancy of the concrete, its accelerated [...] Read more.
In this investigation, a comprehensive assessment was conducted on the cooperative effects of Super Absorbent Polymers (SAP), limestone powder, and white cement within the realm of fair-faced concrete. We discerned that while white cement augments the color vibrancy of the concrete, its accelerated hydration rate potentially induced early-stage cracks and compromised performance. To mitigate these challenges, SAP was incorporated to regulate early hydration, and limestone powder was introduced as a fortifying agent to bolster the mechanical robustness of the concrete. Our findings highlighted not only the capability of SAP to enhance concrete workability and longevity but also the pivotal role of limestone powder in amplifying its mechanical attributes. Microscopic evaluations, undertaken via Scanning Electron Microscopy (SEM), unveiled the potential of both SAP and limestone powder in refining the microstructure of the concrete, thereby elevating its performance metrics. Synthesizing the research outcomes, we pinpointed an optimal amalgamation of SAP, limestone powder, and white cement in fair-faced concrete, offering a valuable reference for prospective architectural applications. Full article
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Figure 1
<p>Flowchart of experimental scheme and procedure.</p> Full article ">Figure 2
<p>Influence of Different Factors on Slump. (<b>a</b>) Slump variation with SAP content (<b>b</b>) Slump variation pre-absorbed water ratio. (<b>c</b>) Slump variation with content of limestone.</p> Full article ">Figure 3
<p>RCPT value of fair-faced concrete; (<b>a</b>) RCPT value with different white cement content; (<b>b</b>) RCPT value with different SAP content; (<b>c</b>) RCPT value with a different water absorption rate; (<b>d</b>) RCPT value with a different content of limestone.</p> Full article ">Figure 4
<p>Strength of white cement with fair-faced concrete: (<b>a</b>) Compressive strength of white cement with fair-faced concrete; (<b>b</b>) tensile strength of white cement with fair-faced concrete.</p> Full article ">Figure 5
<p>Influence of SAP content on the strength of fair-faced concrete: (<b>a</b>) Influence of SAP content on compressive strength; (<b>b</b>) influence of SAP content on tensile strength.</p> Full article ">Figure 6
<p>Influence of SAP pre-absorbed water ratio on the strength of fair-faced concrete: (<b>a</b>) compressive strength; (<b>b</b>) tensile strength.</p> Full article ">Figure 7
<p>Strength curves of different types of fair-faced concrete: (<b>a</b>) Compressive strengths; (<b>b</b>) tensile strengths.</p> Full article ">Figure 8
<p>Appearance of fair-faced concrete with different white cement contents. (<b>a</b>) W-0: 0% white cement, (<b>b</b>) W-25: 25% white cement, (<b>c</b>) W-50: 50% white cement, (<b>d</b>) W-75: 75% white cement, (<b>e</b>) W-100: 100% white cement.</p> Full article ">Figure 9
<p>Appearance of fair-faced concrete with different limestone powder contents. (<b>a</b>) W-0: 0% white cement, (<b>b</b>) SW: 50% white cement, 0.2% SAP, (<b>c</b>) LSW-10: 50% white cement, 0.2% SAP, 10% limestone, (<b>d</b>) LSW-20: 50% white cement, 0.2% SAP, 20% limestone, (<b>e</b>) LSW-30: 50% white cement, 0.2% SAP, 30% limestone.</p> Full article ">Figure 10
<p>(<b>a</b>) 16× SEM image of group W-0; (<b>b</b>) 16× SEM image of group SW; (<b>c</b>) 16× SEM image of group LSW; (<b>d</b>) 3000× SEM image of group W-0; (<b>e</b>) 3000× SEM image of group SW; (<b>f</b>) 3000× SEM image of group LSW.</p> Full article ">
12 pages, 5190 KiB  
Article
Enhanced Mechanical Properties of Cast Cu-10 wt%Fe Alloy via Single-Pass Friction Stir Processing
by Xiaobo Yuan, Hui Wang, Ruilin Lai and Yunping Li
Materials 2023, 16(21), 7057; https://doi.org/10.3390/ma16217057 - 6 Nov 2023
Cited by 4 | Viewed by 1297
Abstract
In this study, Cu-10 wt% Fe alloy in as-cast state was modified using friction stir processing (FSP). The microstructure evolution of Cu-10 wt% Fe alloys in different states was characterized in detail using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission [...] Read more.
In this study, Cu-10 wt% Fe alloy in as-cast state was modified using friction stir processing (FSP). The microstructure evolution of Cu-10 wt% Fe alloys in different states was characterized in detail using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that due to dynamic recrystallization, the FSPed Cu-10 wt% Fe alloy obtained a uniformly equiaxed ultrafine microstructure with low density of dislocation, high proportion of high-angle grain boundaries (HAGBs), and high degree of recrystallization. Fine equiaxed grains with an average size of 0.6 μm were produced after FSP. Many fine-precipitate Fe-phases with an average size of 20 nm were uniformly distributed in the Cu matrix. The FSPed samples possessed excellent mechanical properties, such as high Vickers hardness (163.5 HV), ultimate tensile strength (538.5 MPa), and good elongation (16%). This single-pass FSP method does not require subsequent aging treatment and provides a simple and efficient way to improve the properties of Cu-Fe alloys. Full article
(This article belongs to the Special Issue State-of-the-Art Functional Materials and Nanomaterials in Asia 2023–2024)
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<p>Illustration of the experimental flow.</p> Full article ">Figure 2
<p>Macrostructure evolutions of Cu-10Fe alloy in different conditions: (<b>a</b>,<b>d</b>) as-cast sample, (<b>b</b>,<b>e</b>) cold-rolled sample, and (<b>c</b>,<b>f</b>) FSPed sample.</p> Full article ">Figure 3
<p>Microstructure evolutions of Cu-10Fe alloy in different conditions: (<b>a</b>) as-cast sample, (<b>b</b>) cold-rolled sample, (<b>c</b>) TMAZ of FSPed sample, and (<b>d</b>,<b>e</b>) WNZ of FSPed sample.</p> Full article ">Figure 4
<p>Band-contrast (BC) maps and corresponding inverse-pole-figure (IPF) maps of Cu-10Fe alloy in different conditions: (<b>a</b>,<b>e</b>) as-cast sample, (<b>b</b>,<b>f</b>) cold-rolled sample, (<b>c</b>,<b>g</b>) weld nugget zone of FSPed sample, and (<b>d</b>,<b>h</b>) thermomechanical affected zone of FSPed sample.</p> Full article ">Figure 5
<p>EBSD images of grain size distribution (in blue) and grain boundary misorientation distributions (in yellow) of (<b>a</b>,<b>d</b>) as-cast sample, (<b>b</b>,<b>e</b>) cold-rolled sample, and (<b>c</b>,<b>f</b>) FSPed sample.</p> Full article ">Figure 6
<p>Distribution maps of recrystallized (in blue), substructured (in yellow), and deformed (in red) grains, (<b>a</b>) weld nugget zone and (<b>b</b>) thermomechanical affected zone.</p> Full article ">Figure 7
<p>(<b>a</b>–<b>c</b>) Bright-field TEM images and (<b>d</b>–<b>f</b>) corresponding SAED of (<b>a</b>,<b>b</b>,<b>d</b>,<b>e</b>) as-cast sample and (<b>c</b>,<b>f</b>) FSPed sample.</p> Full article ">Figure 8
<p>(<b>a</b>,<b>b</b>) The high-resolution TEM images and (<b>c</b>) the corresponding FFT pattern of FSPed Cu-10Fe alloy.</p> Full article ">Figure 9
<p>Tensile stress–strain curves of Cu-10Fe alloy of three specimens.</p> Full article ">Figure 10
<p>Fracture morphologies of Cu-10Fe alloy in different conditions: (<b>a</b>,<b>d</b>) as-cast sample, (<b>b</b>,<b>e</b>) cold-rolled sample, and (<b>c</b>,<b>f</b>) FSPed sample.</p> Full article ">
17 pages, 10743 KiB  
Article
Hot Deformation Behavior and Processing Maps of 26CrMo7S Steel Used in Oil Exploration
by Hemiao Jiang, Hongying Li, Dianyuan Huang, Yinghui Zhao, Jiwen Liu, Qing Gao, Hang He and Ximao Liu
Materials 2023, 16(21), 7056; https://doi.org/10.3390/ma16217056 - 6 Nov 2023
Viewed by 1328
Abstract
The hot deformation behavior and flow stress characteristics of experimental 26CrMo7S steel were analyzed using a thermal simulator under a range of conditions, including a strain rate range of 0.01~10 s−1, a temperature range of 850~1250 °C, and a maximum deformation [...] Read more.
The hot deformation behavior and flow stress characteristics of experimental 26CrMo7S steel were analyzed using a thermal simulator under a range of conditions, including a strain rate range of 0.01~10 s−1, a temperature range of 850~1250 °C, and a maximum deformation amount of 70%. The Arrhenius constitutive model was built for the corresponding conditions, and the model’s accuracy was verified through error analysis. Additionally, hot processing maps were constructed to analyze the processing zone of the steel under different hot deformation conditions. Finally, the microstructure of the processing zones was observed and verified using the electron backscattered diffraction (EBSD). The results indicate that the interaction of work hardening and dynamic softening influences the hot deformation behavior of 26CrMo7S steel. The Arrhenius constitutive equation with a value of the correlation coefficient (r = 0.99523) accurately predicts the flow behavior of 26CrMo7S steel under different strains. The optimal processing zone obtained with the hot processing maps is within a deformation range of 1010~1190 °C and a strain rate range of 0.01~10−1.5 s−1, and the obtained microstructure is in good agreement with the analysis results. Full article
(This article belongs to the Special Issue Advanced Metal Matrix Functional Composites and Applications)
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Figure 1

Figure 1
<p>The images of microstructure of experimental steel: (<b>a</b>) OM; (<b>b</b>) IPF map.</p> Full article ">Figure 2
<p>Hot deformation process of 26CrMo7S steel.</p> Full article ">Figure 3
<p>Stress–strain curves of 26CrMo7S steel at different strains with a strain rate of (<b>a</b>) 0.01 s<sup>−1</sup>; (<b>b</b>) 0.1 s<sup>−1</sup>; (<b>c</b>) 1 s<sup>−1</sup>; (<b>d</b>) 5 s<sup>−1</sup>; (<b>e</b>) 10 s<sup>−1</sup>.</p> Full article ">Figure 4
<p>Relationships of (<b>a</b>) <math display="inline"><semantics> <mrow> <mrow> <mrow> <mi mathvariant="normal">ln</mi> </mrow> <mo>⁡</mo> <mrow> <mi>ε</mi> <mo>̇</mo> </mrow> </mrow> <mo>-</mo> <mi mathvariant="normal">l</mi> <mi mathvariant="normal">n</mi> <mi>σ</mi> </mrow> </semantics></math>; (<b>b</b>) <math display="inline"><semantics> <mrow> <mrow> <mrow> <mi mathvariant="normal">ln</mi> </mrow> <mo>⁡</mo> <mrow> <mi>ε</mi> <mo>̇</mo> </mrow> </mrow> <mo>-</mo> <mi>σ</mi> </mrow> </semantics></math>; (<b>c</b>) <math display="inline"><semantics> <mrow> <mrow> <mrow> <mi mathvariant="normal">ln</mi> </mrow> <mo>⁡</mo> <mrow> <mi>ε</mi> <mo>̇</mo> </mrow> </mrow> <mo>-</mo> <mi mathvariant="normal">s</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> <mi mathvariant="normal">h</mi> <mo>⁡</mo> <mo>(</mo> <mi>α</mi> <mi>σ</mi> </mrow> </semantics></math>); (<b>d</b>) <math display="inline"><semantics> <mrow> <mi mathvariant="normal">l</mi> <mi mathvariant="normal">n</mi> <mfenced open="[" close="]" separators="|"> <mrow> <mrow> <mrow> <mi mathvariant="normal">sinh</mi> </mrow> <mo>⁡</mo> <mrow> <mfenced separators="|"> <mrow> <mi>α</mi> <mi>σ</mi> </mrow> </mfenced> </mrow> </mrow> </mrow> </mfenced> <mo>−</mo> <mfrac> <mrow> <mn>1</mn> </mrow> <mrow> <mi>T</mi> </mrow> </mfrac> </mrow> </semantics></math>.</p> Full article ">Figure 4 Cont.
<p>Relationships of (<b>a</b>) <math display="inline"><semantics> <mrow> <mrow> <mrow> <mi mathvariant="normal">ln</mi> </mrow> <mo>⁡</mo> <mrow> <mi>ε</mi> <mo>̇</mo> </mrow> </mrow> <mo>-</mo> <mi mathvariant="normal">l</mi> <mi mathvariant="normal">n</mi> <mi>σ</mi> </mrow> </semantics></math>; (<b>b</b>) <math display="inline"><semantics> <mrow> <mrow> <mrow> <mi mathvariant="normal">ln</mi> </mrow> <mo>⁡</mo> <mrow> <mi>ε</mi> <mo>̇</mo> </mrow> </mrow> <mo>-</mo> <mi>σ</mi> </mrow> </semantics></math>; (<b>c</b>) <math display="inline"><semantics> <mrow> <mrow> <mrow> <mi mathvariant="normal">ln</mi> </mrow> <mo>⁡</mo> <mrow> <mi>ε</mi> <mo>̇</mo> </mrow> </mrow> <mo>-</mo> <mi mathvariant="normal">s</mi> <mi mathvariant="normal">i</mi> <mi mathvariant="normal">n</mi> <mi mathvariant="normal">h</mi> <mo>⁡</mo> <mo>(</mo> <mi>α</mi> <mi>σ</mi> </mrow> </semantics></math>); (<b>d</b>) <math display="inline"><semantics> <mrow> <mi mathvariant="normal">l</mi> <mi mathvariant="normal">n</mi> <mfenced open="[" close="]" separators="|"> <mrow> <mrow> <mrow> <mi mathvariant="normal">sinh</mi> </mrow> <mo>⁡</mo> <mrow> <mfenced separators="|"> <mrow> <mi>α</mi> <mi>σ</mi> </mrow> </mfenced> </mrow> </mrow> </mrow> </mfenced> <mo>−</mo> <mfrac> <mrow> <mn>1</mn> </mrow> <mrow> <mi>T</mi> </mrow> </mfrac> </mrow> </semantics></math>.</p> Full article ">Figure 5
<p>Calculation of the error between the predicted value of the peak stress and the experimental value: (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>r</mi> </mrow> </semantics></math>; (<b>b</b>) <span class="html-italic">AE</span>.</p> Full article ">Figure 6
<p>The illustration of the energy dissipation mechanism.</p> Full article ">Figure 7
<p>Material system energy dissipation map. (<b>a</b>) Nonlinear dissipation (0 &lt; <span class="html-italic">m</span> &lt; 1); (<b>b</b>)linear dissipation (<span class="html-italic">m</span> = 1).</p> Full article ">Figure 8
<p>Energy dissipation maps with strain of (<b>a</b>) 0.1; (<b>b</b>) 0.4; (<b>c</b>) 0.7.</p> Full article ">Figure 9
<p>Hot processing maps of 26CrMo7S steel with strains of (<b>a</b>) 0.1; (<b>b</b>) 0.4; (<b>c</b>) 0.7.</p> Full article ">Figure 9 Cont.
<p>Hot processing maps of 26CrMo7S steel with strains of (<b>a</b>) 0.1; (<b>b</b>) 0.4; (<b>c</b>) 0.7.</p> Full article ">Figure 10
<p>The EBSD images of the specimens under different hot conditions: (<b>a</b>) 850 °C, 5 s<sup>−1</sup>; (<b>b</b>) 1050 °C, 5 s<sup>−1</sup>; (<b>c</b>) 1150 °C, 0.01 s<sup>−1</sup>; (1) IPF map; (2) grain boundary misorientation; (3) recrystallized distribution.</p> Full article ">Figure 11
<p>The EBSD results of the specimens: (<b>a</b>) statistics of grain boundaries; (<b>b</b>) grain boundary distribution; (<b>c</b>) recrystallized fraction.</p> Full article ">
16 pages, 10621 KiB  
Article
Experimental and Numerical Study on the Perforation Behavior of an Aluminum 6061-T6 Cylindrical Shell
by Seon-Woo Byun, Young-Jung Joo, Soo-Yong Lee and Sang-Woo Kim
Materials 2023, 16(21), 7055; https://doi.org/10.3390/ma16217055 - 6 Nov 2023
Viewed by 1314
Abstract
The modified Johnson–Cook (MJC) material model is widely used in simulation under high-velocity impact. There was a need to estimate a strain rate parameter for the application to the impact analysis, where the method typically used is the Split Hopkinson bar. However, this [...] Read more.
The modified Johnson–Cook (MJC) material model is widely used in simulation under high-velocity impact. There was a need to estimate a strain rate parameter for the application to the impact analysis, where the method typically used is the Split Hopkinson bar. However, this method had a limit to the experiment of strain rate. This study proposed to estimate the strain rate parameter of the MJC model based on the impact energy and obtained a parameter. The proposed method of strain rate parameter calculation uses strain parameters to estimate from the drop weight impact and high-velocity impact experiments. Then, the ballistic experiment and analysis were carried out with the target of the plate and cylindrical shape. These analysis results were then compared with those obtained from the experiment. The penetration velocities of plates could be predicted with an error of a maximum of approximately 3.7%. The penetration shape of the cylindrical target has a similar result shape according to impact velocity and had an error of approximately 6%. Full article
(This article belongs to the Special Issue Fracture Behaviour of Structural Materials)
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Figure 1

Figure 1
<p>Coefficient of Cockcroft–Lathan fracture model by quasi-static experiment.</p> Full article ">Figure 2
<p>Experimental results showing the strain hardening.</p> Full article ">Figure 3
<p>Schematic diagram of the ball impact process.</p> Full article ">Figure 4
<p>Drop weight impact equipment for low-velocity impact experiment.</p> Full article ">Figure 5
<p>High-velocity impact experimental equipment.</p> Full article ">Figure 6
<p>Experimental result based on the low-velocity impact (v = 4.2 m/s).</p> Full article ">Figure 7
<p>Experimental result based on the low-velocity impact (v = 71.4 m/s).</p> Full article ">Figure 8
<p>Damaged shapes of experiment and analysis results: (<b>a</b>) thickness: 3 × 10<sup>−3</sup> m; (<b>b</b>) thickness: 6 × 10<sup>−3</sup> m; (<b>c</b>) thickness: 8 × 10<sup>−3</sup> m.</p> Full article ">Figure 9
<p>Penetration velocity based on the thickness of the plate according to analysis models.</p> Full article ">Figure 10
<p>Penetration velocity based on the thickness of the plate according to method.</p> Full article ">Figure 11
<p>Ballistic experiment equipment.</p> Full article ">Figure 12
<p>Comparison of calculated velocity and experimental velocity.</p> Full article ">Figure 13
<p>Sabot with impactor blade.</p> Full article ">Figure 14
<p>Projectile impact angle schematic for ballistic impact experiments: (<b>a</b>) schematic of experiment; (<b>b</b>) target engine case assembly.</p> Full article ">Figure 15
<p>Blade containment case model for ballistic impact analysis: (<b>a</b>) aluminum 6061 for aircraft engine case; (<b>b</b>) analysis model of the aluminum 6061 for aircraft engine case.</p> Full article ">Figure 15 Cont.
<p>Blade containment case model for ballistic impact analysis: (<b>a</b>) aluminum 6061 for aircraft engine case; (<b>b</b>) analysis model of the aluminum 6061 for aircraft engine case.</p> Full article ">Figure 16
<p>Comparisons of the damage patterns for engine case: (<b>a</b>) ballistic impact velocity: 105.4 m/s; (<b>b</b>) ballistic impact velocity: 163.8 m/s; (<b>c</b>) ballistic impact velocity: 244.3 m/s.</p> Full article ">Figure 16 Cont.
<p>Comparisons of the damage patterns for engine case: (<b>a</b>) ballistic impact velocity: 105.4 m/s; (<b>b</b>) ballistic impact velocity: 163.8 m/s; (<b>c</b>) ballistic impact velocity: 244.3 m/s.</p> Full article ">
33 pages, 12872 KiB  
Review
Critical Review on Magnetically Impelled Arc Butt Welding: Challenges, Perspectives and Industrial Applications
by Mukti Chaturvedi, Arungalai Vendan Subbiah, George Simion, Carmen Catalina Rusu and Elena Scutelnicu
Materials 2023, 16(21), 7054; https://doi.org/10.3390/ma16217054 - 6 Nov 2023
Cited by 2 | Viewed by 2367
Abstract
Magnetically Impelled Arc Butt (MIAB) welding is a cutting-edge joining method that replaces the conventional welding procedures such as resistance, friction, flash and butt welding. It is a solid-state process that uses a rotating arc to heat up the butt ends of tubes, [...] Read more.
Magnetically Impelled Arc Butt (MIAB) welding is a cutting-edge joining method that replaces the conventional welding procedures such as resistance, friction, flash and butt welding. It is a solid-state process that uses a rotating arc to heat up the butt ends of tubes, being followed by a forging process that completes the joining of the workpieces The magnetic flux density and the current interact to develop the Lorentz force that impels the arc along the faying surfaces. This process is found to produce high tensile strength and defect-free welds in ferrous materials and for this reason, it is predominantly employed in automobile applications for joining metallic tubes. Also, this joining procedure can be applied in the fabrication of boilers, heat exchangers, furnace piping in petrochemical industry and other safety-critical high-pressure machinery parts. The MIAB method has several advantages such as a shorter welding cycle, lower input energy requirement and lower loss of material. Compared to other solid-state welding processes, the MIAB welding has an important advantage in terms of cost-efficient welds with better control and reliability. Moreover, there are researchers who have investigated the joining of non-ferrous dissimilar materials using this welding procedure. The studies have been focused on process parametric analysis that involves optimizing and forecasting the magnetic field and thermal profile distribution. This review article provides competitive insights into various design features, computational methods, tests and material characterization, technical issues and workarounds, as well as automation aspects related to the MIAB-welding process. This work will prove to be a quick reference for researchers, useful to identify the research gaps and conflicting ideas that can be further explored for advancements in joining the similar and dissimilar materials. Full article
(This article belongs to the Special Issue Recent Advances and Perspectives in Welding and Joining Process and Technology)
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<p>Schematic representation of the MIAB-welding process [<a href="#B9-materials-16-07054" class="html-bibr">9</a>].</p> Full article ">Figure 2
<p>Illustration of magnetic flux, current vectors, and Lorentz force.</p> Full article ">Figure 3
<p>Magnetic flux density versus distance from the tubes outer surface for different coil positions distances and constant current of 1.0 A [<a href="#B12-materials-16-07054" class="html-bibr">12</a>].</p> Full article ">Figure 4
<p>Magnetic flux density versus distance from the tubes outer surface for different current values. Reproduced from [<a href="#B13-materials-16-07054" class="html-bibr">13</a>], Multidiscipline Modeling in Materials and Structures, with permission from Emerald Group Publishing Limited, 2009.</p> Full article ">Figure 5
<p>Schematic diagram of MIAB-welding process [<a href="#B16-materials-16-07054" class="html-bibr">16</a>].</p> Full article ">Figure 6
<p>Profile of predicted (dashed line) and experimental (solid line) heat flow [<a href="#B26-materials-16-07054" class="html-bibr">26</a>].</p> Full article ">Figure 7
<p>Temperature distribution for high-speed arc or analogous multi-arc system. Reproduced from [<a href="#B14-materials-16-07054" class="html-bibr">14</a>], International Journal of Applied Electromagnetics and Mechanics, with permission from IOS Press, 2014.</p> Full article ">Figure 8
<p>MIAB device design: (<b>a</b>) parts of the device (<b>b</b>) longitudinal small coils. Reproduced from [<a href="#B29-materials-16-07054" class="html-bibr">29</a>], Annals of “Dunarea de Jos” University of Galati, Fascicle XII, Welding Equipment and Technology, with permission of “Dunarea de Jos” University of Galati, 2001.</p> Full article ">Figure 9
<p>Principle sketch of the transverse magnetizing system: (<b>a</b>) superior half-disk (<b>b</b>) parts of the device and radial arrangement of coils. Reproduced from [<a href="#B30-materials-16-07054" class="html-bibr">30</a>], Annals of “Dunarea de Jos” University of Galati, Fascicle XII, Welding Equipment and Technology, with permission of “Dunarea de Jos” University of Galati, 2000.</p> Full article ">Figure 10
<p>Preparation of materials’ edges [<a href="#B40-materials-16-07054" class="html-bibr">40</a>].</p> Full article ">Figure 11
<p>Original longitudinal magnetisation system with multiple solenoids. Reproduced from [<a href="#B10-materials-16-07054" class="html-bibr">10</a>], Journal of Materials Processing Technology, with permission from Elsevier, 2010.</p> Full article ">Figure 12
<p>Arc stability zones vs. different gap lengths and welding current. Reproduced from [<a href="#B10-materials-16-07054" class="html-bibr">10</a>], Journal of Materials Processing Technology, with permission from Elsevier, 2010.</p> Full article ">Figure 13
<p>Weld (right side). Reproduced from [<a href="#B10-materials-16-07054" class="html-bibr">10</a>], Journal of Materials Processing Technology, with permission from Elsevier, 2010.</p> Full article ">Figure 14
<p>Weld (left side). Reproduced from [<a href="#B10-materials-16-07054" class="html-bibr">10</a>], Journal of Materials Processing Technology, with permission from Elsevier, 2010.</p> Full article ">Figure 15
<p>HAZ with partially and completely recrystallised region. Reproduced from [<a href="#B11-materials-16-07054" class="html-bibr">11</a>], Welding in the World, with permission from Springer Nature, 2002.</p> Full article ">Figure 16
<p>SEM image of TMAZ1. Reproduced from [<a href="#B5-materials-16-07054" class="html-bibr">5</a>], Materials Today: Proceedings, with permission from Elsevier, 2020.</p> Full article ">Figure 17
<p>SEM image of WI. Reproduced from [<a href="#B5-materials-16-07054" class="html-bibr">5</a>], Materials Today: Proceedings, with permission from Elsevier, 2020.</p> Full article ">Figure 18
<p>SEM image of TMAZ3. Reproduced from [<a href="#B5-materials-16-07054" class="html-bibr">5</a>], Materials Today: Proceedings, with permission from Elsevier, 2020.</p> Full article ">Figure 19
<p>SEM Microstructure [<a href="#B45-materials-16-07054" class="html-bibr">45</a>].</p> Full article ">Figure 20
<p>W-H Plot of weld region [<a href="#B49-materials-16-07054" class="html-bibr">49</a>].</p> Full article ">Figure 21
<p>XRD Spectral analysis of weld region [<a href="#B49-materials-16-07054" class="html-bibr">49</a>].</p> Full article ">Figure 22
<p>Comparison of B-scan and CT results in the cross sections of the shaft A–A, C–C, D–D and detail B [<a href="#B55-materials-16-07054" class="html-bibr">55</a>].</p> Full article ">
13 pages, 9851 KiB  
Article
Microstructural Inhomogeneity in the Fusion Zone of Laser Welds
by Libo Wang, Xiuquan Ma, Gaoyang Mi, Lei Su and Zhengwu Zhu
Materials 2023, 16(21), 7053; https://doi.org/10.3390/ma16217053 - 6 Nov 2023
Cited by 2 | Viewed by 1230
Abstract
This paper investigated evolutions of α-Al sub-grains’ morphology and crystalline orientation in the fusion zone during laser welding of 2A12 aluminum alloys. Based on this, a new method for assessing the weldability of materials was proposed. In laser deep-penetration welding, in addition to [...] Read more.
This paper investigated evolutions of α-Al sub-grains’ morphology and crystalline orientation in the fusion zone during laser welding of 2A12 aluminum alloys. Based on this, a new method for assessing the weldability of materials was proposed. In laser deep-penetration welding, in addition to the conventional columnar and equiaxed dendrites, there also exhibited a corrugated structure with several ‘fine-coarse-fine’ transformations. In such regions, an abnormal α-Al coarsening phenomenon was encountered, with a more dispersed crystalline orientation arrangement and a decreased maximum pole density value. Particularly, structural alterations appeared more frequently in the weld bottom than the top. The above results indicated that the laser-induced keyhole presented a continually fluctuating state. Under such a condition, the solid–liquid transformation exhibited an unstable solidification front, a fluctuant undercooling, and a variational solidification rate. Meanwhile, the welding quality of this material is in a critical state to generate pores. Therefore, the appearance and relevant number of corrugated regions can be considered as a new way for judging the weldability, which will help to narrow the processing window with better welding stability. Full article
(This article belongs to the Special Issue Advanced Materials – Microstructure, Manufacturing and Analysis)
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<p>Cross-sectional morphology and major composition profiles of the 2A12 aluminum alloy. (<b>a</b>) Dispersed secondary phase particles in the BM; (<b>b</b>–<b>f</b>) mappings of the Al, Cu, Mg, Mn, and Fe elements.</p> Full article ">Figure 2
<p>Cross-sectional morphology features of the weld bead, precipitation-type pore (round frame), and process-type pore (square).</p> Full article ">Figure 3
<p>Microstructure and classification of the fusion zone. The squares show the columnar zone (<b>a</b>) near the fusion line; the central zone (<b>b</b>) in the center of the weld; and the fine zone (<b>c</b>) in the upper surface; (<b>d</b>) subregions: the BM (① and ⑤), columnar (② and ④), center (③), and fine grain (⑥); where the circles represent locally anisotropic equiaxial crystals.</p> Full article ">Figure 4
<p>IPF-ND crystalline orientation figures and statistical distributions of the upper FZ.</p> Full article ">Figure 5
<p>{1 0 0} pole figures and statistical distributions of each subregion in the FZ.</p> Full article ">Figure 6
<p>Microstructure evolution of α-Al sub-grains from the BM to the weld center. (<b>a</b>) Tip branching and coarsening near the FL; (<b>b</b>) cellular refinement; (<b>c</b>) fine-coarse-fine transformation in the cellular zone; (<b>d</b>) cellular coarsening refinement and changed to tiny equiaxed; (<b>e</b>) tiny equiaxed; and (<b>f</b>) fine-coarse-fine transformation in the equiaxed.</p> Full article ">Figure 7
<p>Evolutions of microstructure and crystalline orientation at the weld bottom. (<b>a</b>) Morphology of α-Al sub-grains; and (<b>b</b>) orientation map of IPF-ND.</p> Full article ">Figure 8
<p>{1 0 0} pole figures and pole point arrangement of α-Al sub-grains at the weld bottom.</p> Full article ">Figure 9
<p>Schematic diagram of the keyhole oscillation principle in the fusion zone. (<b>a</b>) The distribution of keyhole, molten pool and solidification region; (<b>b</b>) oscillating impact energy transfer, where d1, d2, d3 represent the distance between the back wall of the keyhole and the solidification boundary; (<b>c</b>,<b>d</b>) undercooling at the S/L.</p> Full article ">
15 pages, 15165 KiB  
Article
Grouting Mechanism of Polyurethane Composite Materials in Asphalt Pavement Subsidence
by Maoping Ran, Xinxing Zhou, Yuan Yan, Ruiqie Jiang and Xinglin Zhou
Materials 2023, 16(21), 7052; https://doi.org/10.3390/ma16217052 - 6 Nov 2023
Cited by 6 | Viewed by 1544
Abstract
The mechanical properties of polyurethane grouting materials were significantly improved when cement, sodium meta-silicate, red mud, slag, and fly ash were added. However, the grouting mechanisms of polyurethane composite materials are not clear. The grouting mechanisms of polyurethane composite materials in asphalt pavement [...] Read more.
The mechanical properties of polyurethane grouting materials were significantly improved when cement, sodium meta-silicate, red mud, slag, and fly ash were added. However, the grouting mechanisms of polyurethane composite materials are not clear. The grouting mechanisms of polyurethane composite materials in asphalt pavement subsidence were investigated. The results of computed tomography analysis show that polyurethane foam is filled with geopolymer hydration products. The results from ground penetrating radar after grouting show that mapping has no significant fluctuation or dislocation effect, which indicates that the grouting effect is strong. The high-density electrometer can also test the pavement subsidence place and distribution. The grouting mechanisms indicate that polyurethane foam acts as the consolidation structure, and the geopolymer filled with the foam pores of polyurethane and geopolymer forms a stable consolidated body. The seriflux includes under-layer seriflux (red mud, slag, water, and polyurethane composite materials) and upper-layer seriflux (polyurethane seriflux), and there exists a weak phase separation phenomenon, in which the separation phase is mainly polyurethane with little red mud-based geopolymer. Full article
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<p>The picture of ground penetrating radar before grouting.</p> Full article ">Figure 2
<p>The picture from the high-density electrometer before grouting.</p> Full article ">Figure 3
<p>The grouting design of polyurethane composite materials: (<b>a</b>) the grouting roadmap of polyurethane composite materials, (<b>b</b>) <b>design schematic diagram of stop valve for double liquid grouting method</b>.</p> Full article ">Figure 4
<p>Schematic diagram of grouting construction process: (<b>a</b>) trepanning, (<b>b</b>) installing the hole sealer, (<b>c</b>) grouting, (<b>d</b>) hole sealing.</p> Full article ">Figure 5
<p>The picture of ground penetrating radar after grouting: (<b>a</b>) 5#, (<b>b</b>) 4#, (<b>c</b>) 3#, (<b>d</b>) 2#, (<b>e</b>) 1#.</p> Full article ">Figure 5 Cont.
<p>The picture of ground penetrating radar after grouting: (<b>a</b>) 5#, (<b>b</b>) 4#, (<b>c</b>) 3#, (<b>d</b>) 2#, (<b>e</b>) 1#.</p> Full article ">Figure 6
<p>The picture from the high-density electrometer after grouting: (<b>a</b>) 5#, (<b>b</b>) 4#, (<b>c</b>) 3#, (<b>d</b>) 2#, (<b>e</b>) 1#.</p> Full article ">Figure 6 Cont.
<p>The picture from the high-density electrometer after grouting: (<b>a</b>) 5#, (<b>b</b>) 4#, (<b>c</b>) 3#, (<b>d</b>) 2#, (<b>e</b>) 1#.</p> Full article ">Figure 7
<p>CT of polyurethane composite material (sample 5#) consolidated core samples: (<b>a</b>) cross section, (<b>b</b>) three dimensional top view, (<b>c</b>) three dimensional color view, (<b>d</b>) the inner view of core sample.</p> Full article ">Figure 8
<p>The vertical section CT of polyurethane composite materials’ (sample 5#) core sample: (<b>a</b>) surface 0 cm, (<b>b</b>) 1 cm depth, (<b>c</b>) 2 cm depth, (<b>d</b>) 3 cm depth, (<b>e</b>) 4 cm depth, (<b>f</b>) 5 cm depth.</p> Full article ">Figure 9
<p>The polyurethane composite materials’ (sample 5#) consolidated core samples: (<b>a</b>) core samples, (<b>b</b>) drilling the core.</p> Full article ">Figure 10
<p>The CT of polyurethane composite materials’ (sample 5#) consolidated core samples: (<b>a</b>) upper layer, (<b>b</b>) lower layer.</p> Full article ">Figure 11
<p>SEM image of polyurethane composite materials’ consolidated core samples: (<b>a</b>) 1#, (<b>b</b>) 2#, (<b>c</b>) 3#, (<b>d</b>) 4#, (<b>e</b>) 5#.</p> Full article ">Figure 12
<p>Energy spectrum of polyurethane composite materials’ (sample 5#) consolidated core samples: (<b>a</b>) point 1, (<b>b</b>) point 2.</p> Full article ">Figure 13
<p>The grouting model of polyurethane composite materials.</p> Full article ">
17 pages, 6839 KiB  
Article
AC Electromagnetic Field Controls the Biofilms on the Glass Surface by Escherichia coli & Staphylococcus epidermidis Inhibition Effect
by Natsu Aoyama, Hideyuki Kanematsu, Dana M. Barry, Hidekazu Miura, Akiko Ogawa, Takeshi Kogo, Risa Kawai, Takeshi Hagio, Nobumitsu Hirai, Takehito Kato, Michiko Yoshitake and Ryoichi Ichino
Materials 2023, 16(21), 7051; https://doi.org/10.3390/ma16217051 - 6 Nov 2023
Cited by 2 | Viewed by 1838
Abstract
Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials [...] Read more.
Biofilms, mainly comprised of bacteria, form on materials’ surfaces due to bacterial activity. They are generally composed of water, extracellular polymeric substances (polysaccharides, proteins, nucleic acids, and lipids), and bacteria. Some bacteria that form biofilms cause periodontal disease, corrosion of the metal materials that make up drains, and slippage. Inside of a biofilm is an environment conducive to the growth and propagation of bacteria. Problems with biofilms include the inability of disinfectants and antibiotics to act on them. Therefore, we have investigated the potential application of alternating electromagnetic fields for biofilm control. We obtained exciting results using various materials’ specimens and frequency conditions. Through these studies, we gradually understood that the combination of the type of bacteria, the kind of material, and the application of an electromagnetic field with various low frequencies (4 kHz–12 kHz) changes the circumstances of the onset of the biofilm suppression effect. In this study, relatively high frequencies (20 and 30 kHz) were applied to biofilms caused by Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis), and quantitative evaluation was performed using staining methods. The sample surfaces were analyzed by Raman spectroscopy using a Laser Raman spectrometer to confirm the presence of biofilms on the surface. Full article
(This article belongs to the Special Issue Science and Technology of Advanced Materials Applied to Society: Including Collections from the Latest Papers of KRIS 2023)
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<p>An electromagnetic coil box and a well.</p> Full article ">Figure 2
<p>The control system of experimental apparatus.</p> Full article ">Figure 3
<p>The process of biofilm quantification using staining by crystal violet solution.</p> Full article ">Figure 4
<p>Surface image and Raman spectrum of the sample before the experiment.</p> Full article ">Figure 5
<p>Surface image and Raman spectrum of biofilm caused by <span class="html-italic">Escherichia coli</span> (<b>a</b>) 20 kHz nEM, (<b>b</b>) 20 kHz EM, (<b>c</b>) 30 kHz nEM, (<b>d</b>) 30 kHz EM.</p> Full article ">Figure 5 Cont.
<p>Surface image and Raman spectrum of biofilm caused by <span class="html-italic">Escherichia coli</span> (<b>a</b>) 20 kHz nEM, (<b>b</b>) 20 kHz EM, (<b>c</b>) 30 kHz nEM, (<b>d</b>) 30 kHz EM.</p> Full article ">Figure 6
<p>Biofilm surface image and Raman spectrum of <span class="html-italic">Staphylococcus epidermidis</span> (<b>a</b>) 20 kHz nEM, (<b>b</b>) 20 kHz EMm, (<b>c</b>) 30 kHz nEM, (<b>d</b>) 30 kHz EM.</p> Full article ">Figure 6 Cont.
<p>Biofilm surface image and Raman spectrum of <span class="html-italic">Staphylococcus epidermidis</span> (<b>a</b>) 20 kHz nEM, (<b>b</b>) 20 kHz EMm, (<b>c</b>) 30 kHz nEM, (<b>d</b>) 30 kHz EM.</p> Full article ">Figure 7
<p>Absorbance measurement results during biofilm staining with <span class="html-italic">E. coli</span>; (<b>a</b>) All data when 20 kHz AC electromagnetic field was applied. (<b>b</b>) Median data when 20 kHz AC electromagnetic field was applied. (<b>c</b>) All data when 30 kHz AC electromagnetic field was applied. (<b>d</b>) Median data when 30 kHz AC electromagnetic field was applied.</p> Full article ">Figure 8
<p>Absorbance measurements during biofilm staining by <span class="html-italic">Staphylococcus epidermidis</span>. (<b>a</b>) All data when 20 kHz AC electromagnetic field is applied. (<b>b</b>) Median data when 20 kHz AC electromagnetic field is applied. (<b>c</b>) All data when 30 kHz AC electromagnetic field is applied. (<b>d</b>) Median data when 30 kHz AC electromagnetic field is applied.</p> Full article ">Figure 9
<p>The laboratory biofilm reactor to investigate the effect of alternating electromagnetic fields on biofilm formation by environmental biota.</p> Full article ">
16 pages, 2863 KiB  
Article
The Influence of Acid Casein on the Selected Properties of Lime–Metakaolin Mortars
by Przemysław Brzyski and Renata Boris
Materials 2023, 16(21), 7050; https://doi.org/10.3390/ma16217050 - 6 Nov 2023
Viewed by 1387
Abstract
One of the ways to modify selected parameters of lime mortars is the use of biopolymers of animal origin, such as bone glue, skin glue, bovine blood, eggs, and casein. These are protein-based biopolymers. Casein is an example of an organic polymer produced [...] Read more.
One of the ways to modify selected parameters of lime mortars is the use of biopolymers of animal origin, such as bone glue, skin glue, bovine blood, eggs, and casein. These are protein-based biopolymers. Casein is an example of an organic polymer produced from cow’s milk. The aim of the work was to investigate the possibilities of improving selected properties of mortars based on hydrated lime and metakaolin. The mixture was modified with powdered technical casein in amounts of 0.5%, 1.5%, 1%, 1.5%, and 2% as a partial mass replacement for the binding mixture. Additionally, the influence of increasing the amount of water on the properties of the mortar with a casein admixture of 2% was checked. This study examined consistency, shrinkage, water absorption, capillary action, porosity, flexural, compressive strength, and Young’s modulus. The admixture of casein influenced the properties of the mortar, but not in all cases, and it was possible to determine a clear trend related to the variable amount of casein. Strength properties deteriorated as the amount of casein increased. When air bubbles were introduced into the mortar after the casein was dissolved, the porosity increased as the amount of admixture increased. The moisture properties improved; namely, casein led to a reduction in water absorption and water absorption caused by capillary action. No relationship was observed between the amount of casein and the drying shrinkage. Increasing the amount of water in the mixture led to the expected effects, i.e., an increase in porosity, shrinkage, and water absorption, and a decrease in mechanical strength. Full article
(This article belongs to the Special Issue Advances in Natural Building and Construction Materials)
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<p>Consistency results tested using the flow table method (<b>left</b>) and the plunger penetration method (<b>right</b>).</p> Full article ">Figure 2
<p>The average decrease in the length of the sample as a result of shrinkage.</p> Full article ">Figure 3
<p>Average values of mass absorptivity of the mortars tested.</p> Full article ">Figure 4
<p>Average values of the capillary absorption coefficient of the mortars tested.</p> Full article ">Figure 5
<p>The dependence of the bending force on the displacement of the press head. Each graph shows the results of 3 samples from a given recipe.</p> Full article ">Figure 6
<p>Stress–strain relationship as a result of the compressive strength test. Each graph shows the results of 6 samples from a given recipe.</p> Full article ">Figure 7
<p>Average values of flexural strength (on the <b>left</b>) and compressive strength (on the <b>right</b>) of the tested samples (error bars mean standard deviation).</p> Full article ">Figure 8
<p>Young’s modulus of the tested mortars.</p> Full article ">Figure 9
<p>Relationship between mass absorptivity and total porosity of the tested mortars.</p> Full article ">Figure 10
<p>Relationship between casein content, displacement (deflection), and maximum force (on the <b>left</b>) and between the water/binder ratio, displacement (deflection), and maximum force (on the <b>right</b>).</p> Full article ">Figure 11
<p>Relationship between casein content, strain, and maximum stress (on the <b>left</b>) and between the water/binder ratio, strain, and maximum stress (on the <b>right</b>).</p> Full article ">Figure 12
<p>Young’s modulus and compressive strength relationship.</p> Full article ">
14 pages, 3250 KiB  
Article
Optical Properties of Amorphous Carbon Thin Films Fabricated Using a High-Energy-Impulse Magnetron-Sputtering Technique
by Lukasz Skowronski, Rafal Chodun, Marek Trzcinski and Krzysztof Zdunek
Materials 2023, 16(21), 7049; https://doi.org/10.3390/ma16217049 - 6 Nov 2023
Cited by 5 | Viewed by 1493
Abstract
This paper reports the results of amorphous carbon thin films fabricated by using the gas-impulse-injection magnetron-sputtering method and differing the accelerating voltage (1.0–1.4 kV). The obtained layers were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XRD), and spectroscopic ellipsometry (SE). The analysis of [...] Read more.
This paper reports the results of amorphous carbon thin films fabricated by using the gas-impulse-injection magnetron-sputtering method and differing the accelerating voltage (1.0–1.4 kV). The obtained layers were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XRD), and spectroscopic ellipsometry (SE). The analysis of the Raman and XPS spectra point to the significant content of sp3 hybridization in the synthesized materials (above 54–73%). The refractive index of the films is very high—above 2.45 in the infrared spectral range. The band-gap energy (determined using the inversed-logarithmic-derivative method) depends on the discharging voltage and is in the range from 1.58 eV (785 nm) to 2.45 eV (506 nm). Based on the obtained results, we have elaborated a model explaining the a-C layers’ formation process. Full article
(This article belongs to the Section Carbon Materials)
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<p>Diagram of the apparatus used in the experiment.</p> Full article ">Figure 2
<p>The Raman spectra registered for the a-C thin films irradiated by 266 nm (<b>left</b>) and 532 nm (<b>right</b>) lasers and fitted with D and G elementary spectra.</p> Full article ">Figure 3
<p>C1s and O1s XPS spectra of the fabricated a-C films.</p> Full article ">Figure 4
<p>Measured and calculated Ψ and Δ ellipsometric azimuths for the aC1.0 sample (for the experimental data, every fifth data point has been plotted). The MSE value of the fit was 1.39.</p> Full article ">Figure 5
<p>(<b>a</b>) Real part of the complex refractive index and (<b>b</b>) extinction coefficient of the carbon films.</p> Full article ">Figure 6
<p>Absorption coefficient of the deposited a-C thin layers.</p> Full article ">Figure 7
<p>Density of electronic states for C-based materials.</p> Full article ">Figure 8
<p>The ILD plot of the carbon films.</p> Full article ">
7 pages, 1007 KiB  
Communication
Ferromagnetic Fluctuations in the Heavily Overdoped Regime of Single-Layer High-Tc Cuprate Superconductors
by Tadashi Adachi, Koshi Kurashima, Takayuki Kawamata, Takashi Noji, Satoru Nakajima and Yoji Koike
Materials 2023, 16(21), 7048; https://doi.org/10.3390/ma16217048 - 6 Nov 2023
Viewed by 1323
Abstract
To investigate proposed ferromagnetic fluctuations in the so-called single-layer Bi-2201 and La-214 high-Tc cuprates, we performed magnetization and electrical resistivity measurements using single-layer Tl-2201 cuprates Tl2Ba2CuO6+δ and La-214 La2−xSrxCuO4 in [...] Read more.
To investigate proposed ferromagnetic fluctuations in the so-called single-layer Bi-2201 and La-214 high-Tc cuprates, we performed magnetization and electrical resistivity measurements using single-layer Tl-2201 cuprates Tl2Ba2CuO6+δ and La-214 La2−xSrxCuO4 in the heavily overdoped regime. Magnetization of Tl2Ba2CuO6+δ and La2−xSrxCuO4 exhibited the tendency to be saturated in high magnetic fields at low temperatures, suggesting the precursor behavior toward the formation of a ferromagnetic order. It was found that the power of temperature n obtained from the temperature dependence of the electrical resistivity is ~4/3 and ~5/3 for Bi-2201 and La2−xSrxCuO4, respectively, and is ~4/3 at high temperatures and ~5/3 at low temperatures in Tl2Ba2CuO6+δ. These results suggest that two- and three-dimensional ferromagnetic fluctuations exist in Bi-2201 and La2−xSrxCuO4, respectively. In Tl2Ba2CuO6+δ, it is suggested that the dimension of ferromagnetic fluctuations is two at high temperatures and three at low temperatures, respectively. The dimensionality of ferromagnetic fluctuations is understood in terms of the dimensionality of the crystal structure and the bonding of atoms in the blocking layer. Full article
(This article belongs to the Special Issue Structure and Electronic Properties of Emerging Superconductor and Related Materials)
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<p>Magnetization curves of heavily overdoped (<b>a</b>) Tl<sub>2</sub>Ba<sub>2</sub>CuO<sub>6+δ</sub> (<span class="html-italic">p</span> = 0.265) and (<b>b</b>) La<sub>2−</sub><span class="html-italic"><sub>x</sub></span>Sr<span class="html-italic"><sub>x</sub></span>CuO<sub>4</sub> (<span class="html-italic">x</span> = 0.29).</p> Full article ">Figure 2
<p>Temperature dependence of the electrical resistivity plotted against (<b>a</b>) <span class="html-italic">T</span>, (<b>b</b>) <span class="html-italic">T</span><sup>4/3</sup>, and (<b>c</b>) <span class="html-italic">T</span><sup>5/3</sup> in heavily overdoped Tl<sub>2</sub>Ba<sub>2</sub>CuO<sub>6+δ</sub> (<span class="html-italic">p</span> = 0.265), La<sub>2−</sub><span class="html-italic"><sub>x</sub></span>Sr<span class="html-italic"><sub>x</sub></span>CuO<sub>4</sub> (<span class="html-italic">x</span> = 0.29), and Bi<sub>1.77</sub>Pb<sub>0.33</sub>Sr<sub>1.90</sub>CuO<sub>6+δ</sub> (<span class="html-italic">p</span> = 0.281) [<a href="#B14-materials-16-07048" class="html-bibr">14</a>]. Orange arrows in (<b>b</b>,<b>c</b>) indicate the temperature where the resistivity deviates from the linear relation between the resistivity and <span class="html-italic">T</span><sup>4/3</sup> (<span class="html-italic">T</span><sup>5/3</sup>). Note that the resistivity of La<sub>2−</sub><span class="html-italic"><sub>x</sub></span>Sr<span class="html-italic"><sub>x</sub></span>CuO<sub>4</sub> and Bi<sub>1.77</sub>Pb<sub>0.33</sub>Sr<sub>1.90</sub>CuO<sub>6+δ</sub> is the ab-plane resistivity <span class="html-italic">ρ</span><sub>ab</sub>.</p> Full article ">Figure 3
<p>Hole-concentration <span class="html-italic">p</span> dependence of (<b>a</b>) the power of temperature <span class="html-italic">n</span> of <span class="html-italic">ρ</span> = A + B<span class="html-italic">T<sup>n</sup></span> and (<b>b</b>) <span class="html-italic">T</span><sub>c</sub> in Tl<sub>2</sub>Ba<sub>2</sub>CuO<sub>6+δ</sub> and La<sub>2−</sub><span class="html-italic"><sub>x</sub></span>Sr<span class="html-italic"><sub>x</sub></span>CuO<sub>4</sub>. Solid lines are to guide the reader’s eye. Open symbols are preceding results of Tl<sub>2</sub>Ba<sub>2</sub>CuO<sub>6+δ</sub> [<a href="#B25-materials-16-07048" class="html-bibr">25</a>], La<sub>2−</sub><span class="html-italic"><sub>x</sub></span>Sr<span class="html-italic"><sub>x</sub></span>CuO<sub>4</sub> [<a href="#B13-materials-16-07048" class="html-bibr">13</a>], and (Bi,Pb)<sub>2</sub>Sr<sub>2</sub>CuO<sub>6+δ</sub> [<a href="#B14-materials-16-07048" class="html-bibr">14</a>]. In (<b>a</b>), circles indicate <span class="html-italic">n</span> obtained by fitting in a wide temperature range, while diamonds and squares indicate <span class="html-italic">n</span> obtained by fitting at low and high temperatures, respectively.</p> Full article ">
19 pages, 19869 KiB  
Article
Tensile and Tearing Properties of a Geocomposite Mechanically Damaged by Repeated Loading and Abrasion
by José Ricardo Carneiro, Filipe Almeida, Filipa Carvalho and Maria de Lurdes Lopes
Materials 2023, 16(21), 7047; https://doi.org/10.3390/ma16217047 - 5 Nov 2023
Cited by 2 | Viewed by 1468
Abstract
The behaviour of geosynthetics can be affected by many agents, both in the short and long term. Mechanical damage caused by repeated loading or abrasion are examples of agents that may induce undesirable changes in the properties of geosynthetics. The research conducted in [...] Read more.
The behaviour of geosynthetics can be affected by many agents, both in the short and long term. Mechanical damage caused by repeated loading or abrasion are examples of agents that may induce undesirable changes in the properties of geosynthetics. The research conducted in this work complemented previous studies and consisted of submitting a geocomposite, isolated and successively, to two degradation tests: mechanical damage under repeated loading and abrasion. The geocomposite (a nonwoven geotextile reinforced with polyethylene terephthalate filaments) was tested on both sides (with or without filaments) and directions (machine and cross-machine). The impact of the degradation tests on the geocomposite was quantified by monitoring changes in its tensile and tearing behaviour. The results showed that, in most cases, the degradation tests caused the deterioration of the tensile and tearing behaviour of the geocomposite, affecting its reinforcement function. The decline in tensile strength correlated reasonably well with the decline in tearing strength. Changing the side and direction tested influenced, in some cases (those involving abrasion), the degradation experienced by the geocomposite. The reduction factors (referring to tensile and tearing strength) for the combined effect of the degradation agents tended to be lower when determined by using the common method (compared to those resulting directly from the successive exposure to both agents). Full article
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<p>Geocomposite (intact sample): side with filaments and side without filaments. 1—MD filament; 2—CMD filament; 3—geotextile; 4—seam.</p> Full article ">Figure 2
<p>Damaged geocomposite samples (tests in the CMD): (<b>a</b>) sample RL: sF; (<b>b</b>) sample RL: sWF; (<b>c</b>) sample A: sF; (<b>d</b>) sample A: sWF; (<b>e</b>) sample RL-A: sF; (<b>f</b>) sample RL-A: sWF. Note: the arrow indicates the CMD.</p> Full article ">Figure 3
<p>Tensile force–elongation curves of the geocomposite (examples in the CMD).</p> Full article ">Figure 4
<p>Tensile strength of the geocomposite (PET filaments) vs. maximum tensile force of the PP geotextile (percentage residual values). Note: results obtained in the CMD.</p> Full article ">Figure 5
<p>Residual tensile strength of the geocomposite: MD vs. CMD.</p> Full article ">Figure 6
<p>Residual tearing strength of the geocomposite.</p> Full article ">Figure 7
<p>Relationship between the residual tensile and tearing strength of the geocomposite.</p> Full article ">Figure 8
<p>Reduction factors obtained for the combined effect of the RL and abrasion tests: common method vs. double testing condition.</p> Full article ">
23 pages, 15845 KiB  
Review
A Review: Design from Beta Titanium Alloys to Medium-Entropy Alloys for Biomedical Applications
by Ka-Kin Wong, Hsueh-Chuan Hsu, Shih-Ching Wu and Wen-Fu Ho
Materials 2023, 16(21), 7046; https://doi.org/10.3390/ma16217046 - 5 Nov 2023
Cited by 11 | Viewed by 5016
Abstract
β-Ti alloys have long been investigated and applied in the biomedical field due to their exceptional mechanical properties, ductility, and corrosion resistance. Metastable β-Ti alloys have garnered interest in the realm of biomaterials owing to their notably low elastic modulus. Nevertheless, the inherent [...] Read more.
β-Ti alloys have long been investigated and applied in the biomedical field due to their exceptional mechanical properties, ductility, and corrosion resistance. Metastable β-Ti alloys have garnered interest in the realm of biomaterials owing to their notably low elastic modulus. Nevertheless, the inherent correlation between a low elastic modulus and relatively reduced strength persists, even in the case of metastable β-Ti alloys. Enhancing the strength of alloys contributes to improving their fatigue resistance, thereby preventing an implant material from failure in clinical usage. Recently, a series of biomedical high-entropy and medium-entropy alloys, composed of biocompatible elements such as Ti, Zr, Nb, Ta, and Mo, have been developed. Leveraging the contributions of the four core effects of high-entropy alloys, both biomedical high-entropy and medium-entropy alloys exhibit excellent mechanical strength, corrosion resistance, and biocompatibility, albeit accompanied by an elevated elastic modulus. To satisfy the demands of biomedical implants, researchers have sought to synthesize the strengths of high-entropy alloys and metastable β-Ti alloys, culminating in the development of metastable high-entropy/medium-entropy alloys that manifest both high strength and a low elastic modulus. Consequently, the design principles for new-generation biomedical medium-entropy alloys and conventional metastable β-Ti alloys can be converged. This review focuses on the design from β-Ti alloys to the novel metastable medium-entropy alloys for biomedical applications. Full article
(This article belongs to the Special Issue Advanced Biomaterials for Dental Implants: Design and Mechanical Properties)
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<p>Comparison of the modulus among published biomedical metastable Ti alloys, conventional biomedical alloys, and cortical bone [<a href="#B17-materials-16-07046" class="html-bibr">17</a>,<a href="#B18-materials-16-07046" class="html-bibr">18</a>,<a href="#B19-materials-16-07046" class="html-bibr">19</a>,<a href="#B20-materials-16-07046" class="html-bibr">20</a>,<a href="#B21-materials-16-07046" class="html-bibr">21</a>,<a href="#B22-materials-16-07046" class="html-bibr">22</a>,<a href="#B23-materials-16-07046" class="html-bibr">23</a>,<a href="#B24-materials-16-07046" class="html-bibr">24</a>,<a href="#B25-materials-16-07046" class="html-bibr">25</a>,<a href="#B26-materials-16-07046" class="html-bibr">26</a>,<a href="#B27-materials-16-07046" class="html-bibr">27</a>].</p> Full article ">Figure 2
<p>Number of international journal publications on (<b>a</b>) high-entropy alloys and medium-entropy alloys from 2004 to 2022 and (<b>b</b>) biomedical high-entropy alloys/medium-entropy alloys from 2017 to 2022 (Source: <a href="http://www.webofscience.com" target="_blank">www.webofscience.com</a>).</p> Full article ">Figure 3
<p>The four core effects of high-entropy alloys.</p> Full article ">Figure 4
<p>Biocompatibility of SUS–316L, CP-Ti, equiatomic Ti–Nb–Ta–Zr–Mo, and non-equiatomic Ti<sub>(2−x)</sub>–Zr<sub>(2−x)</sub>–Nb<sub>x</sub>–Ta<sub>x</sub>–Mo<sub>x</sub> (x = 0.6, 1.4) (x = 0.6, 1.4) Bio-HEAs. (<b>a</b>) Giemsa staining images of osteoblasts, (<b>b</b>) fluorescent images of osteoblast adhesion, and (<b>c</b>) quantitative analysis of fibrillar adhesion size regulation [<a href="#B32-materials-16-07046" class="html-bibr">32</a>]. (Reprinted with permission under the terms of the Creative Commons CC-BY license from Elsevier: Scr. Mater.)</p> Full article ">Figure 5
<p>Types and proportions of elements used in biomedical high-entropy alloys/medium-entropy alloys (Bio-HEAs/MEAs) in international journals from 2017 to 2022 (Source: <a href="http://www.webofscience.com" target="_blank">www.webofscience.com</a>).</p> Full article ">Figure 6
<p>Microstructures of as-cast Ti-rich MEAs: Ti<sub>50</sub>–Zr<sub>25</sub>–Nb<sub>15</sub>–Mo<sub>10</sub> (Ti50), Ti<sub>58</sub>–Zr<sub>23</sub>–Nb<sub>12</sub>–Mo<sub>7</sub> (Ti58), and Ti<sub>65</sub>–Zr<sub>20</sub>–Nb<sub>10</sub>–Mo<sub>5</sub> (Ti65). (<b>a</b>) Optical micrographs, (<b>b</b>) backscattering electron images (BEI), and (<b>c</b>) element mapping images obtained through electron microprobe analysis using wavelength dispersive spectrometers [<a href="#B73-materials-16-07046" class="html-bibr">73</a>]. (Reprinted with permission from Elsevier: J. Alloys Compd. Copyright 2023, License: 5655690226569).</p> Full article ">Figure 7
<p>TEM images and SAED patterns of metastable Ti-rich MEA (Ti<sub>65</sub>–Zr<sub>18</sub>–Nb<sub>16</sub>–Mo<sub>1</sub>). (<b>a</b>) SAED of the [011] zone axes, (<b>b</b>) HR-TEM image in [011] direction (additional streaking is marked by blue arrows), and (<b>c</b>) SAED of the [111] zone axes, and (<b>d</b>) HR-TEM image in [111] direction (additional streaking is marked by blue arrows) [<a href="#B78-materials-16-07046" class="html-bibr">78</a>]. (Reprinted with permission from Springer Nature: Met. Mater. Int. Copyright 2023, License: 501856029).</p> Full article ">Figure 8
<p>Microstructures and elemental analyses of as-cast Ti<sub>65</sub>–Zr<sub>20</sub>–Nb<sub>14</sub>–Mo<sub>1</sub> and Ti<sub>65</sub>–Zr<sub>18</sub>–Nb<sub>16</sub>–Mo<sub>1</sub>. (<b>a</b>,<b>d</b>) backscattering electron images, (<b>b</b>,<b>e</b>) element mapping images obtained through electron microprobe analysis using wavelength dispersive spectrometers, and (<b>c</b>,<b>f</b>) line scan curves obtained through an electron microprobe analysis using wavelength dispersive spectrometers [<a href="#B78-materials-16-07046" class="html-bibr">78</a>]. (Reprinted with permission from Springer Nature: Met. Mater. Int. Copyright 2023, License: 501856029).</p> Full article ">Figure 9
<p>Relationships between the moduli and thermodynamic parameters, as well as between the moduli and phase stability parameters, of biomedical high-entropy alloys/medium-entropy alloys [<a href="#B51-materials-16-07046" class="html-bibr">51</a>,<a href="#B70-materials-16-07046" class="html-bibr">70</a>,<a href="#B72-materials-16-07046" class="html-bibr">72</a>,<a href="#B73-materials-16-07046" class="html-bibr">73</a>,<a href="#B75-materials-16-07046" class="html-bibr">75</a>,<a href="#B76-materials-16-07046" class="html-bibr">76</a>,<a href="#B78-materials-16-07046" class="html-bibr">78</a>,<a href="#B79-materials-16-07046" class="html-bibr">79</a>,<a href="#B80-materials-16-07046" class="html-bibr">80</a>,<a href="#B81-materials-16-07046" class="html-bibr">81</a>,<a href="#B82-materials-16-07046" class="html-bibr">82</a>,<a href="#B83-materials-16-07046" class="html-bibr">83</a>,<a href="#B84-materials-16-07046" class="html-bibr">84</a>,<a href="#B85-materials-16-07046" class="html-bibr">85</a>,<a href="#B86-materials-16-07046" class="html-bibr">86</a>,<a href="#B87-materials-16-07046" class="html-bibr">87</a>]. The red line indicates data trend. (<b>a</b>) modulus vs. ΔS<sub>mix</sub>/R, (<b>b</b>) modulus vs. ΔH<sub>mix</sub>, (<b>c</b>) modulus vs. δ, (<b>d</b>) modulus vs. [Mo]<sub>eq</sub>, (<b>e</b>) modulus vs. VEC, and (<b>f</b>) modulus vs. M<sub>s</sub>.</p> Full article ">Figure 10
<p>Bo-Md diagram of biomedical high-entropy alloys/medium-entropy alloys (Bio-HEAs/MEAs) with a low elastic modulus (&lt;80 GPa) [<a href="#B75-materials-16-07046" class="html-bibr">75</a>,<a href="#B76-materials-16-07046" class="html-bibr">76</a>,<a href="#B78-materials-16-07046" class="html-bibr">78</a>,<a href="#B80-materials-16-07046" class="html-bibr">80</a>,<a href="#B81-materials-16-07046" class="html-bibr">81</a>,<a href="#B82-materials-16-07046" class="html-bibr">82</a>,<a href="#B83-materials-16-07046" class="html-bibr">83</a>,<a href="#B84-materials-16-07046" class="html-bibr">84</a>,<a href="#B85-materials-16-07046" class="html-bibr">85</a>,<a href="#B86-materials-16-07046" class="html-bibr">86</a>,<a href="#B87-materials-16-07046" class="html-bibr">87</a>].</p> Full article ">
18 pages, 1894 KiB  
Review
Controlled-Release Materials for Remediation of Trichloroethylene Contamination in Groundwater
by Shan Zhao, Jianhua Wang and Wenjin Zhu
Materials 2023, 16(21), 7045; https://doi.org/10.3390/ma16217045 - 5 Nov 2023
Cited by 3 | Viewed by 2374
Abstract
Groundwater contamination by trichloroethylene (TCE) presents a pressing environmental challenge with far-reaching consequences. Traditional remediation methods have shown limitations in effectively addressing TCE contamination. This study reviews the limitations of conventional remediation techniques and investigates the application of oxidant-based controlled-release materials, including encapsulated, [...] Read more.
Groundwater contamination by trichloroethylene (TCE) presents a pressing environmental challenge with far-reaching consequences. Traditional remediation methods have shown limitations in effectively addressing TCE contamination. This study reviews the limitations of conventional remediation techniques and investigates the application of oxidant-based controlled-release materials, including encapsulated, loaded, and gel-based potassium permanganate since the year 2000. Additionally, it examines reductant controlled-release materials and electron donor-release materials such as tetrabutyl orthosilicate (TBOS) and polyhydroxybutyrate (PHB). The findings suggest that controlled-release materials offer a promising avenue for enhancing TCE degradation and promoting groundwater restoration. This study concludes by highlighting the future research directions and the potential of controlled-release materials in addressing TCE contamination challenges. Full article
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<p>Release mechanism of controlled-release materials.</p> Full article ">Figure 2
<p>Observed TCE concentrations during batch degradation tests with microcapsules with t<sub>0.5</sub> 5.26 and 3.29 (the time required to release half of C<sub>r,max</sub>), and during a control test with no microcapsules (revised from [<a href="#B42-materials-16-07045" class="html-bibr">42</a>]).</p> Full article ">Figure 3
<p>ESEM images of the oxidant-releasing material surface for the original material (before experimentation) ((<b>a</b>), 20,000×) and residual material (after experimentation) ((<b>b</b>), 10,000×) (revised from [<a href="#B43-materials-16-07045" class="html-bibr">43</a>]).</p> Full article ">Figure 4
<p>PHB facilitating bioelectrochemical dechlorination of TCE and recovery of valuable ethylene (revised from [<a href="#B62-materials-16-07045" class="html-bibr">62</a>]).</p> Full article ">Figure 5
<p>Challenges and opportunities for controlled-release materials.</p> Full article ">
20 pages, 8002 KiB  
Review
Recent Progress in Resonant Acoustic Metasurfaces
by Dongan Liu, Limei Hao, Weiren Zhu, Xiao Yang, Xiaole Yan, Chen Guan, You Xie, Shaofang Pang and Zhi Chen
Materials 2023, 16(21), 7044; https://doi.org/10.3390/ma16217044 - 5 Nov 2023
Cited by 5 | Viewed by 2991
Abstract
Acoustic metasurfaces, as two-dimensional acoustic metamaterials, are a current research topic for their sub-wavelength thickness and excellent acoustic wave manipulation. They hold significant promise in noise reduction and isolation, cloaking, camouflage, acoustic imaging, and focusing. Resonant structural units are utilized to construct acoustic [...] Read more.
Acoustic metasurfaces, as two-dimensional acoustic metamaterials, are a current research topic for their sub-wavelength thickness and excellent acoustic wave manipulation. They hold significant promise in noise reduction and isolation, cloaking, camouflage, acoustic imaging, and focusing. Resonant structural units are utilized to construct acoustic metasurfaces with the unique advantage of controlling large wavelengths within a small size. In this paper, the recent research progresses of the resonant metasurfaces are reviewed, covering the design mechanisms and advances of structural units, the classification and application of the resonant metasurfaces, and the tunable metasurfaces. Finally, research interest in this field is predicted in future. Full article
(This article belongs to the Special Issue Metamaterials and Metasurfaces: Fundamentals and Applications)
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<p>The HR structures used for acoustic wave manipulation. (<b>a</b>) schematic cross-sectional view of a Helmholtz resonator, reproduced from [<a href="#B12-materials-16-07044" class="html-bibr">12</a>]; (<b>b</b>) a model of double ‘c’ resonator (DCR), reproduced from [<a href="#B21-materials-16-07044" class="html-bibr">21</a>]; (<b>c</b>) cross-sectional diagram of one double-split hollow sphere (DSHS), reproduced from [<a href="#B19-materials-16-07044" class="html-bibr">19</a>]; (<b>d</b>) three-dimensional (3D) view and cross-section of the system of the asymmetric acoustic wave guide with shunted HRs, reproduced from [<a href="#B22-materials-16-07044" class="html-bibr">22</a>]; (<b>e</b>) 3D views of the absorber, reproduced from [<a href="#B23-materials-16-07044" class="html-bibr">23</a>].</p> Full article ">Figure 2
<p>The membrane resonant structures used for acoustic wave manipulation. (<b>a</b>) Schematic drawing of subunit for the proposed reflection metasurface, reproduced from [<a href="#B40-materials-16-07044" class="html-bibr">40</a>]; (<b>b</b>) schematic drawing of transmission metasurface consisting of a series of structurally simple microunits, reproduced from [<a href="#B49-materials-16-07044" class="html-bibr">49</a>]; (<b>c</b>) schematic drawing of the double-negative metamaterial, reproduced from [<a href="#B29-materials-16-07044" class="html-bibr">29</a>]; (<b>d</b>) schematic of the sandwich structure of double-membrane-type acoustic metamaterials combined with a Helmholtz resonator, reproduced from [<a href="#B30-materials-16-07044" class="html-bibr">30</a>]; (<b>e</b>) metasurface unit cell constructed by steel, reproduced from [<a href="#B31-materials-16-07044" class="html-bibr">31</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) The proposed metasurface-based Schroeder diffuser (MSD); (<b>b</b>) a two-dimensional Schroeder diffuser (2D SD); (<b>c</b>) the analytical and simulated relationship between the phase shift and the geometrical parameter w of the MSD. The triangles represent the discrete points for generating the phase of 0–2π × 6/7 with a step of 2π × 1/7; and (<b>d</b>) the measured (<b>upper</b>) and simulated (<b>lower</b>) scattered acoustic field distributions of the MSD, SD and flat plate in the <span class="html-italic">x</span>-<span class="html-italic">z</span> plane. Reproduced from [<a href="#B58-materials-16-07044" class="html-bibr">58</a>].</p> Full article ">Figure 4
<p>(<b>a</b>) (<b>Left</b>) 2D schematic diagram of the supercell of a multifunctional acoustic metasurface. A supercell consists of three cavities with different depths. (<b>Right</b>) the effective circuit model of the proposed supercell of the metasurface. (<b>b</b>) The simulated results for achromatic −45° extraordinary reflection at the three frequencies. (<b>c</b>) The corresponding results for achromatic acoustic focusing at (0 m, 0.6 m). (<b>d</b>) The simulated and experimental acoustic pressure distributions of the extraordinary reflection and acoustic focusing at the three frequencies. Reproduced from [<a href="#B59-materials-16-07044" class="html-bibr">59</a>].</p> Full article ">Figure 5
<p>(<b>a</b>) Schematic of a square lattice of circular holes with gradient annular bumps; reproduced from [<a href="#B62-materials-16-07044" class="html-bibr">62</a>]; (<b>b</b>) Metasurface unit cell constructed by aluminum; (<b>c</b>) phase shift as a function of ratio <span class="html-italic">r</span> for ali unit; (<b>d</b>) phase shift as a function of ratio <span class="html-italic">r</span> for steel unit; (<b>e</b>) phase shift as a function of thickness <span class="html-italic">t</span> for aluminum; (<b>f</b>) phase shift as a function of thickness <span class="html-italic">t</span> for steel; reproduced from [<a href="#B31-materials-16-07044" class="html-bibr">31</a>,<a href="#B72-materials-16-07044" class="html-bibr">72</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Schematic of the proposed anisotropic resonant unit; reproduced from [<a href="#B73-materials-16-07044" class="html-bibr">73</a>]. (<b>b</b>) The calculation region and a magnified view of the geometry of the inclusion; reproduced from [<a href="#B74-materials-16-07044" class="html-bibr">74</a>]. (<b>c</b>) Schematic of the experimental setup. The sample with positive index and negative index (PI-NI) interface is composed of an array of the designed different HRs from an aluminum plate. Unit cells of each half part and the corresponding inductor–capacitor circuit analogy are shown in the insets; the normalized pressure field distribution at 60.5 kHz, (<b>d</b>) measured, and (<b>e</b>) simulated pressure field map of the acoustic NI metamaterial and (<b>f</b>) line plot of pressure field crosses the focal plane parallel to interface. Reproduced from [<a href="#B78-materials-16-07044" class="html-bibr">78</a>].</p> Full article ">Figure 7
<p>(<b>a</b>) An array of passive elements, (<b>b</b>) phase shift (red, solid) and transmission rate (blue, solid) of the hybrid structure as a function of height ratio h<sub>1</sub> = h (or, correspondingly, h<sub>3</sub> = h), and a comparison with that of HRs (red and blue dashed), reproduced from [<a href="#B34-materials-16-07044" class="html-bibr">34</a>]; (<b>c</b>) anomalous refractions of theoretical (<b>up</b>) and simulated (<b>down</b>) pressure fields, reproduced from [<a href="#B80-materials-16-07044" class="html-bibr">80</a>]; and (<b>d</b>) acoustic metasurface for the non-diffracting Bessel beam, reproduced from [<a href="#B79-materials-16-07044" class="html-bibr">79</a>]. Study of a bianisotropic acoustic cell. (<b>e</b>) Geometry of a cell with four side-loaded resonators. The height of the HRs is varied to create different bianisotropic responses. Definition of the forward (+) and backward (−) illuminations; (<b>f</b>) amplitude and phase of the transmission and reflection coefficients of an arbitrary cell. Reproduced from [<a href="#B83-materials-16-07044" class="html-bibr">83</a>].</p> Full article ">Figure 8
<p>(<b>a</b>) Illustration of a resonant planar layer (blue) converting an in-coming axisymmetric wave without orbital angular momentum (OAM) to an outgoing beam with a helical wave front-carrying OAM (wave fronts are shown in gray), (<b>b</b>) schematic of the assembled layer consisting of eight fanlike sections of resonators, (<b>c</b>) an individual section consisting of three rows of resonators in the radial r direction, (<b>d</b>) the effective wave number <span class="html-italic">k<sup>eff</sup></span> (red; normalized by <span class="html-italic">k</span> = 2π/<span class="html-italic">λ</span>) and transmission coefficient [T] (blue), (<b>e</b>) airborne sound pressure field on the outgoing surface of the planar layer, (<b>f</b>) phase (<b>top</b>) and amplitude (<b>bottom</b>) of the field at four cross-sections, illustrating the transition from the near to the far field, where the geometric centers of the cross-sections are denoted by the white dots. Reproduced from [<a href="#B85-materials-16-07044" class="html-bibr">85</a>].</p> Full article ">Figure 9
<p>(<b>a</b>) Schematic of the symmetric unit, reproduced from [<a href="#B86-materials-16-07044" class="html-bibr">86</a>]; (<b>b</b>) the top view of the first subunit. In order to conveniently calibrate the parameters of the structure, the figure is not the actual scale (<b>left</b>) schematic demonstration of the designed sample consisting of six subunits (<b>right</b>), reproduced from [<a href="#B87-materials-16-07044" class="html-bibr">87</a>]; (<b>c</b>) HR unit with rectangular ridges inside, reproduced from [<a href="#B89-materials-16-07044" class="html-bibr">89</a>]; (<b>d</b>) schematic illustration of an individual element of the metasurface made of four decorated membrane resonators and a straight pipe. Red solid lines refer to membranes, reproduced from [<a href="#B91-materials-16-07044" class="html-bibr">91</a>]; (<b>e</b>) schematic illustration of the unit cell’s components and geometry. Here, a is the radius of the membrane, s is the depth of the sealed gas cell and k denotes the incident wavevector, reproduced from [<a href="#B92-materials-16-07044" class="html-bibr">92</a>]; and (<b>f</b>) schematic cutoff view of the flat panel composite absorber. Reproduced from [<a href="#B93-materials-16-07044" class="html-bibr">93</a>].</p> Full article ">Figure 10
<p>(<b>a</b>) Conceptual view of the thin panel placed on a rigid wall with N = 4 layers of square cross-section HRs, reproduced from [<a href="#B95-materials-16-07044" class="html-bibr">95</a>]; (<b>b</b>) illustration of a resonator with a spiral extended neck and a coiled backing cavity, reproduced from [<a href="#B97-materials-16-07044" class="html-bibr">97</a>]; (<b>c</b>) cross-sectional schematic of the absorber composed of two ellipse-shaped split tubes denoted by 1 and 2, reproduced from [<a href="#B98-materials-16-07044" class="html-bibr">98</a>]; (<b>d</b>) the single HR with olive neck, reproduced from [<a href="#B102-materials-16-07044" class="html-bibr">102</a>]; (<b>e</b>) the sketch of sound absorptive panel with arrays of embedded coplanar spiral tubes, reproduced from [<a href="#B104-materials-16-07044" class="html-bibr">104</a>].</p> Full article ">Figure 11
<p>(<b>a</b>) Photographs of a realistic unit cell fabricated with polylacticacid (PLA) by means of (<b>left</b>) 3D printing and (<b>right</b>) its inner structure, reproduced from [<a href="#B107-materials-16-07044" class="html-bibr">107</a>]; (<b>b</b>) bending quarter wavelength resonators, reproduced from [<a href="#B108-materials-16-07044" class="html-bibr">108</a>]; (<b>c</b>) a schematic representation of a tunable subwavelength unit cell, which is composed of a straight channel and five shunted HRs. The cavity sizes are controlled by pumping fluid into/out of the unit cell, (<b>d</b>) numerical characterization of unit cell. By changing the cavity height of <span class="html-italic">h</span><sub>1</sub>, the acoustic phase can be tuned in the full range of [−π, π] while maintaining high transmission amplitude. When the cavity height is over 18 mm, the transmission coefficient drops to zero, (<b>e</b>) analytical (<b>up</b>) and experimental (<b>down</b>) results for acoustic beam engineering. Analytical energy fields of five different acoustic beams, which demonstrate beamforming, tuning the focal distance, steering the beam direction, generating a tweezer-like beam and guiding energy along a parabolic trajectory, respectively, (<b>f</b>) experimental results for on/off switching of acoustic energy flow. Acoustic energy fields at (<b>left</b>) on and (<b>middle</b>) off states. (<b>Right</b>) comparison of pressure amplitudes along a line at <span class="html-italic">y</span> = 25 mm between on and off states. Reproduced from [<a href="#B82-materials-16-07044" class="html-bibr">82</a>].</p> Full article ">Figure 12
<p>(<b>a</b>) The cylindrical unit of the tunable metasurface, reproduced from [<a href="#B110-materials-16-07044" class="html-bibr">110</a>,<a href="#B111-materials-16-07044" class="html-bibr">111</a>]; (<b>b</b>) schematic of helix, reproduced from [<a href="#B112-materials-16-07044" class="html-bibr">112</a>]; (<b>c</b>) (<b>left</b>) schematic sketch and (<b>middle</b>) equivalent circuit of the coupled structure by split hollow sphere (SHS) and hollow tube (HT). (<b>Right</b>) schematic sketch of the optimized model based on (<b>left</b>); the inner ring can be spun freely to arbitrary angle θ around its center axis, reproduced from [<a href="#B118-materials-16-07044" class="html-bibr">118</a>]; (<b>d</b>) the unit cell design. The membrane can be electrically switched between two states; one (denoted OFF state) has one fixed boundary at its edge and the other (denoted ON state) has two fixed boundaries, reproduced from [<a href="#B122-materials-16-07044" class="html-bibr">122</a>]; (<b>e</b>) schematic diagram of the proposed magnetic-controlled metasurface, reproduced from [<a href="#B41-materials-16-07044" class="html-bibr">41</a>]; (<b>f</b>) (<b>up</b>) unit cell consisting of a piezoelectric membrane. The cell acoustic response is controlled by a digital electronic circuit that can be reconfigured in real-time, (<b>down</b>) photograph of the fabricated unit cell. Reproduced from [<a href="#B124-materials-16-07044" class="html-bibr">124</a>].</p> Full article ">
21 pages, 2168 KiB  
Review
Corrosion by Polythionic Acid in the Oil and Gas Sector: A Brief Overview
by Mohammadtaghi Vakili, Petr Koutník and Jan Kohout
Materials 2023, 16(21), 7043; https://doi.org/10.3390/ma16217043 - 5 Nov 2023
Cited by 2 | Viewed by 2936
Abstract
Polythionic acid (PTA) corrosion is a significant challenge in the refinery industry, leading to equipment degradation, safety risks, and costly maintenance. This paper comprehensively investigates the origin, progression, mechanism, and impact of PTA corrosion on various components within refinery operations. Special attention is [...] Read more.
Polythionic acid (PTA) corrosion is a significant challenge in the refinery industry, leading to equipment degradation, safety risks, and costly maintenance. This paper comprehensively investigates the origin, progression, mechanism, and impact of PTA corrosion on various components within refinery operations. Special attention is afforded to the susceptibility of austenitic stainless steels and nickel-based alloys to PTA corrosion and the key factors influencing its occurrence. Practical strategies and methods for mitigating and preventing PTA corrosion are also explored. This paper underscores the importance of understanding PTA corrosion and implementing proactive measures to safeguard the integrity and efficiency of refinery infrastructure. Full article
(This article belongs to the Topic Materials for Corrosion Protection)
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<p>Energy cycle in metal corrosion.</p> Full article ">Figure 2
<p>Structure of polythionic acid.</p> Full article ">Figure 3
<p>Structure of micelles in hydrophilic micellar colloids.</p> Full article ">Figure 4
<p>PTA preparation factors.</p> Full article ">Figure 5
<p>The key factors that contribute to stress corrosion cracking (SCC).</p> Full article ">Figure 6
<p>Intergranular fracture along (<b>a</b>) and transgranular fracture through (<b>b</b>) grain boundaries.</p> Full article ">Figure 7
<p>Intergranular cracking caused by PTASCC at grain boundaries.</p> Full article ">
11 pages, 6026 KiB  
Article
Size Effect of Graphene Oxide on Graphene-Aerogel-Supported Au Catalysts for Electrochemical CO2 Reduction
by Shuling Shen, Xuecong Pan, Jin Wang, Tongyu Bao, Xinjuan Liu, Zhihong Tang, Huixin Xiu and Jing Li
Materials 2023, 16(21), 7042; https://doi.org/10.3390/ma16217042 - 5 Nov 2023
Cited by 9 | Viewed by 1450
Abstract
The lateral size of graphene nanosheets plays a critical role in the properties and microstructure of 3D graphene as well as their application as supports of electrocatalysts for CO2 reduction reactions (CRRs). Here, graphene oxide (GO) nanosheets with different lateral sizes (1.5, [...] Read more.
The lateral size of graphene nanosheets plays a critical role in the properties and microstructure of 3D graphene as well as their application as supports of electrocatalysts for CO2 reduction reactions (CRRs). Here, graphene oxide (GO) nanosheets with different lateral sizes (1.5, 5, and 14 µm) were utilized as building blocks for 3D graphene aerogel (GA) to research the size effects of GO on the CRR performances of 3D Au/GA catalysts. It was found that GO-L (14 µm) led to the formation of GA with large pores and a low surface area and that GO-S (1.5 µm) induced the formation of GA with a thicker wall and isolated pores, which were not conducive to the mass transfer of CO2 or its interaction with catalysts. Au/GA constructed with a suitable-sized GO (5 µm) exhibited a hierarchical porous network and the highest surface area and conductivity. As a result, Au/GA-M exhibited the highest Faradaic efficiency (FE) of CO (FECO = 81%) and CO/H2 ratio at −0.82 V (vs. a Reversible Hydrogen Electrode (RHE)). This study indicates that for 3D GA-supported catalysts, there is a balance between the improvement of conductivity, the adsorption capacity of CO2, and the inhibition of the hydrogen evolution reaction (HER) during the CRR, which is related to the lateral size of GO. Full article
(This article belongs to the Special Issue Preparation and Application of High-Performance Multifunctional Graphene Macroscopic Assemblies and Composites)
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<p>AFM images and sizes of (<b>a</b>) GO-L, (<b>b</b>) GO-M, and (<b>c</b>) GO-S. (<b>d</b>) XRD patterns and (<b>e</b>) FTIR and (<b>f</b>) Raman spectra of GO-L, GO-M, and GO-S.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>,<b>b</b>) Au/GA-L, (<b>c</b>,<b>d</b>) Au/GA-M, and (<b>e</b>,<b>f</b>) Au/GA-S.</p> Full article ">Figure 3
<p>(<b>a</b>) XRD patterns, (<b>b</b>) Raman spectra, and (<b>c</b>) Nyquist plots of Au/GA-L, Au/GA-M, and Au/GA-S.</p> Full article ">Figure 4
<p>LSV curves of (<b>a</b>) Au/GA-L, (<b>b</b>) Au/GA-M, and (<b>c</b>) Au/GA-S and (<b>d</b>) current densities of three samples in 0.1 mol/L KHCO<sub>3</sub> electrolytes.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>c</b>) FEs and (<b>d</b>) CO/H<sub>2</sub> ratios of Au/GA-L, Au/GA-M, and Au/GA-S at different potentials.</p> Full article ">Figure 6
<p>Stability analysis of Au/GA-M over 7 h at -8.2 V.</p> Full article ">Figure 7
<p>(<b>a</b>) CO<sub>2</sub>-TPD analysis and (<b>b</b>) pore size distribution of Au/GA-L, Au/GA-M, and Au/GA-S.</p> Full article ">
19 pages, 24581 KiB  
Article
Study on the Mechanical Properties and Mechanism of a Nickel-Iron Slag Cement-Based Composite under the Action of Sodium Sulfate
by Jingyu Zhang, Yuwan Zhou, Sili Chen, Jinzhu Meng and Junxiang Wang
Materials 2023, 16(21), 7041; https://doi.org/10.3390/ma16217041 - 4 Nov 2023
Viewed by 1293
Abstract
The accumulated amount of nickel–iron slag has increased with the rapid development of the nickel-iron industry. To determine a method for comprehensively utilizing nickel–iron slag, triaxial compression tests of nickel–iron slag cement-based composite materials under the action of sodium sulfate were conducted, and [...] Read more.
The accumulated amount of nickel–iron slag has increased with the rapid development of the nickel-iron industry. To determine a method for comprehensively utilizing nickel–iron slag, triaxial compression tests of nickel–iron slag cement-based composite materials under the action of sodium sulfate were conducted, and the effects of the sodium sulfate concentration on the stress-strain relation, shear strength, cohesion, and internal friction angle of the composite materials were analyzed. In addition, the influence mechanism of the nickel–iron slag content and sodium sulfate concentration on the composite was examined. The results revealed that the stress–strain curve of the nickel–iron slag cement-based composites reflected softening. With the increase in the sodium sulfate concentration, the brittleness increased, while the shear strength, cohesion, and internal friction angle decreased; the addition of nickel–iron slag slowed down the rate at which these parameters decrease. Scanning electron microscopy images revealed that nickel–iron slag can improve the internal structure of the cement composite soil, enhance its compactness, and improve its corrosion resistance. The optimum nickel–iron slag content of 14% can improve the cementitious composites’ resistance to sodium sulfate erosion in terms of solid waste utilization and cementitious soil performance. The results obtained can provide technical parameters for preparing and designing cement-based composite materials as well as certain theoretical significance and engineering reference value. Full article
(This article belongs to the Section Advanced Composites)
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<p>Mechanism of sulfate erosion.</p> Full article ">Figure 2
<p>Nickel–iron slag powder.</p> Full article ">Figure 3
<p>X-ray diffraction (XRD) pattern of the nickel–iron slag.</p> Full article ">Figure 4
<p>Schematic of the specimen preparation process.</p> Full article ">Figure 5
<p>Failure characteristics and crack angles (red lines) of the cement-based composites at a confining pressure of 0.8 MPa. (<b>a</b>) Sodium sulfate 0 g/L; (<b>b</b>) Sodium sulfate 2.5 g/L; (<b>c</b>) Sodium sulfate 6 g/L; (<b>d</b>) Sodium sulfate 12 g/L.</p> Full article ">Figure 6
<p>Fracture characteristics and crack angles (red lines) of the nickel–iron slag cement-based composites at a confining pressure of 0.8 MPa. (<b>a</b>) Sodium sulfate 0 g/L; (<b>b</b>) Sodium sulfate 2.5 g/L; (<b>c</b>) Sodium sulfate 6 g/L; (<b>d</b>) Sodium sulfate 12 g/L.</p> Full article ">Figure 7
<p>Failure characteristics and crack angles (red lines) of cement-based composite materials with a nickel–iron slag content of 14%.</p> Full article ">Figure 8
<p>Stress–strain curve of the composites at a confining pressure of 0.2 MPa.</p> Full article ">Figure 9
<p>Stress–strain curve of the composites at a confining pressure of 0.5 MPa.</p> Full article ">Figure 10
<p>Stress–strain curve at a confining pressure of 0.8 MPa.</p> Full article ">Figure 11
<p>Strain values corresponding to the peak stresses at different confining pressures.</p> Full article ">Figure 12
<p>Effect of sodium sulfate concentration on shear strength.</p> Full article ">Figure 13
<p>Shear strength envelope line at a sodium sulfate concentration of 0 g/L.</p> Full article ">Figure 14
<p>Shear strength envelope line at a sodium sulfate concentration of 2.5 g/L.</p> Full article ">Figure 15
<p>Shear strength envelope line at a sodium sulfate concentration of 6 g/L.</p> Full article ">Figure 16
<p>Shear strength envelope line at a sodium sulfate concentration of 12 g/L.</p> Full article ">Figure 17
<p>Effect of sodium sulfate concentration on cohesion.</p> Full article ">Figure 18
<p>Effect of sodium sulfate concentration on the internal friction angle.</p> Full article ">Figure 19
<p>Scanning electron microscopy (SEM) image of the composite at a sodium sulfate concentration of 0 g/L at 20,000× magnification.</p> Full article ">Figure 20
<p>SEM image of the composite at a sodium sulfate concentration of 2.5 g/L at 20,000× magnification.</p> Full article ">Figure 21
<p>SEM image of the composite at a sodium sulfate concentration of 6 g/L at 20,000× magnification.</p> Full article ">Figure 22
<p>SEM image of the composite at a sodium sulfate concentration of 12 g/L at 20,000× magnification.</p> Full article ">
15 pages, 5592 KiB  
Article
Innovative Post-Processing for Complex Geometries and Inner Parts of 3D-Printed AlSi10Mg Devices
by Martí Calvet, Anna Domènech, Sergi Vilaró, Toni Meseguer and Lorenzo Bautista
Materials 2023, 16(21), 7040; https://doi.org/10.3390/ma16217040 - 4 Nov 2023
Viewed by 1797
Abstract
A new technology consisting of new and sustainable chemical polishing treatment for aluminum components with complex shapes, such as heat exchangers, manifolds, busbars, aerospace devices, etc., manufactured by Additive Manufacturing (AM) technologies is described in this paper. This technology will contribute to the [...] Read more.
A new technology consisting of new and sustainable chemical polishing treatment for aluminum components with complex shapes, such as heat exchangers, manifolds, busbars, aerospace devices, etc., manufactured by Additive Manufacturing (AM) technologies is described in this paper. This technology will contribute to the development of a more efficient manufacturing process driven by AM, reinforcing the main idea of AM, which is based on reducing the amount of material and achieving cost savings through smart and improved designs. The present study shows a significant reduction in the surface roughness of consolidated AlSi10Mg metal parts manufactured by the SLM technique after carrying out the new chemical polishing post-process investigated in this work. Roughness values have been measured by mechanical and optical profilometry. The results obtained demonstrate the effectiveness of the chemical polishing, decreasing the roughness by up to 40%, being a reproducible and repeatable post-process. The presence of smut as solid residues on such types of chemical treatments has been also analyzed with XRF and ICP-MS techniques. The results obtained show that Si and Mg precipitates are removed from the metal surface at the last step of the investigated post-process. The percentages of the elements decrease from 25.0% to 8.09% Si and from 0.86% to 0.42% Mg, achieving the alloy smut-free composition on the metal surface. Tensile strength measurements have shown that the post-process described not only maintains the mechanical properties of the bulk material but, in comparison with non-post-processed parts, a slight improvement is observed with respect to the initial values, Young modulus (61.1 GPa to final 62.2 GPa), yield strength (from 236.8 to 246.7 MPa), and tensile strength (from 371.9 to 382.5 MPa) is observed, suggesting that the post-process has positive impact on the printed metal part. Full article
(This article belongs to the Topic Advanced Manufacturing and Surface Technology)
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<p>AlSi10Mg metal parts design for post-processing tests; on the left is a schematic design, on the right is a picture of the consolidated metal part.</p> Full article ">Figure 2
<p>Schematic representation of steps followed on polishing AlSi10Mg using patent WO 2021/094641 [<a href="#B19-materials-16-07040" class="html-bibr">19</a>].</p> Full article ">Figure 3
<p>Specimen measurements. A—5.08 mm; B—10.00 mm; C—12.25 mm; D—51.47 mm; D<sub>2</sub>—36.04 mm; E—76.02 mm.</p> Full article ">Figure 4
<p>(<b>a</b>) AlSi10Mg tensile strength specimen consolidated by SLM technique, (<b>b</b>) sections measured by JENOPTIK Waveline W10 optic profilometer.</p> Full article ">Figure 5
<p>From left to right, a consolidated aluminum metal part as-printed, smut-treated, and a desmutted sample.</p> Full article ">Figure A1
<p>Elongation curves from the stress–strain tests corresponding to the treated aluminum samples (<b>a</b>) compared with the nontreated ones (<b>b</b>).</p> Full article ">Figure A1 Cont.
<p>Elongation curves from the stress–strain tests corresponding to the treated aluminum samples (<b>a</b>) compared with the nontreated ones (<b>b</b>).</p> Full article ">
20 pages, 5934 KiB  
Review
Research and Application Progress of Vegetation Porous Concrete
by Chang Liu, Yangyang Xia, Jianguo Chen, Kai Huang, Jing Wang, Chaojie Wang, Zhuojie Huang, Xunhuai Wang, Cong Rao and Mingsheng Shi
Materials 2023, 16(21), 7039; https://doi.org/10.3390/ma16217039 - 4 Nov 2023
Cited by 7 | Viewed by 2958
Abstract
Vegetation porous concrete is a novel material that integrates concrete technology with plant growth, offering excellent engineering applicability and environmental friendliness. This material is mainly utilized in eco-engineering projects such as riverbank protection, architectural greening, and slope protection along roads. This paper systematically [...] Read more.
Vegetation porous concrete is a novel material that integrates concrete technology with plant growth, offering excellent engineering applicability and environmental friendliness. This material is mainly utilized in eco-engineering projects such as riverbank protection, architectural greening, and slope protection along roads. This paper systematically reviews the current research progress of vegetation porous concrete by collecting and analyzing the relevant literature from both domestic and international sources. It covers several aspects including the material components of vegetation porous concrete, such as aggregates, cementitious materials, chemical admixtures, and plant species, as well as aspects like mix design, workability, porosity, pH value, mechanical strength, and vegetative performance. Furthermore, the application of vegetation porous concrete in riverbank protection, slope protection along highways, and urban architecture is discussed, along with a prospective outlook on future research directions for vegetation porous concrete. Full article
(This article belongs to the Section Construction and Building Materials)
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<p>Schematic diagram and physical diagram [<a href="#B10-materials-16-07039" class="html-bibr">10</a>] of vegetation porous concrete.</p> Full article ">Figure 2
<p>Different types of aggregates: (<b>a</b>) coral aggregates [<a href="#B18-materials-16-07039" class="html-bibr">18</a>]; (<b>b</b>) zeolite; (<b>c</b>) blast furnace slag [<a href="#B7-materials-16-07039" class="html-bibr">7</a>]; (<b>d</b>) recycled aggregates [<a href="#B33-materials-16-07039" class="html-bibr">33</a>].</p> Full article ">Figure 3
<p>Different types of mineral admixtures: (<b>a</b>) fly ash; (<b>b</b>) mineral powder; (<b>c</b>) silica fume.</p> Full article ">Figure 4
<p>Different plant varieties: (<b>a</b>) tall fescue; (<b>b</b>) Bermuda grass [<a href="#B59-materials-16-07039" class="html-bibr">59</a>]; (<b>c</b>) alfalfa; (<b>d</b>) <span class="html-italic">Paspalum wettsteinii</span>.</p> Full article ">Figure 5
<p>(<b>a</b>) Image processing of vegetation porous concrete section [<a href="#B32-materials-16-07039" class="html-bibr">32</a>]; (<b>b</b>) connected pores and ineffective pores [<a href="#B75-materials-16-07039" class="html-bibr">75</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) A two-dimensional model of vegetation porous concrete; (<b>b</b>) three-dimensional numerical model of vegetation porous concrete [<a href="#B11-materials-16-07039" class="html-bibr">11</a>].</p> Full article ">Figure 7
<p>X-ray tomography images [<a href="#B82-materials-16-07039" class="html-bibr">82</a>]: (<b>a</b>) corn biological substrate; (<b>b</b>) sunflower metakaolin (voxel size 4 mm).</p> Full article ">Figure 8
<p>Changes in vegetation porous concrete after planting plants: (<b>a</b>) compressive strength [<a href="#B43-materials-16-07039" class="html-bibr">43</a>]; (<b>b</b>) permeability coefficient [<a href="#B43-materials-16-07039" class="html-bibr">43</a>]; (<b>c</b>) frost thawing resistance [<a href="#B43-materials-16-07039" class="html-bibr">43</a>].</p> Full article ">Figure 9
<p>Slope application of vegetation porous concrete: (<b>a</b>) repair process [<a href="#B83-materials-16-07039" class="html-bibr">83</a>]; (<b>b</b>) construction application effect [<a href="#B83-materials-16-07039" class="html-bibr">83</a>].</p> Full article ">Figure 10
<p>(<b>a</b>) The moss wall of the Reykjavik City Hall [<a href="#B9-materials-16-07039" class="html-bibr">9</a>]; (<b>b</b>) concept of vegetation porous concrete office building construction [<a href="#B9-materials-16-07039" class="html-bibr">9</a>].</p> Full article ">
14 pages, 9389 KiB  
Article
Microstructural Characterization of Al0.5CrFeNiTi High Entropy Alloy Produced by Powder Metallurgy Route
by Laura Elena Geambazu, Dorinel Tălpeanu, Robert Viorel Bololoi, Ciprian Alexandru Manea, Alina Elena Bololoi, Florin Miculescu, Delia Pătroi and Vasile Dănuţ Cojocaru
Materials 2023, 16(21), 7038; https://doi.org/10.3390/ma16217038 - 4 Nov 2023
Cited by 3 | Viewed by 1247
Abstract
Alloys with superior properties represent the main topic of recent studies due to their effectiveness in reducing the cost of equipment maintenance and enhancing usage time, in addition to other benefits in domains such as geothermal, marine, and airspace. Al0.5CrFeNiTi was [...] Read more.
Alloys with superior properties represent the main topic of recent studies due to their effectiveness in reducing the cost of equipment maintenance and enhancing usage time, in addition to other benefits in domains such as geothermal, marine, and airspace. Al0.5CrFeNiTi was produced by solid state processing in a planetary ball mill, with the objective of obtaining a high alloying degree and a homogenous composition that could be further processed by pressing and sintering. The metallic powder was technologically characterized, indicating a particle size reduction following mechanical alloying processing when compared to the elemental raw powder materials. The microstructural analysis presented the evolution of the alloying degree during milling but also a compact structure with no major defects in the pressed and sintered bulk samples. The X-ray diffraction results confirmed the presence of face-centered cubic (FCC) and body-centered cubic (BCC) phases, predicted by the theoretical calculations, along with a hexagonal close-packed (HCP) phase, where the Al, Cr, Fe, Ni, and Ti phase was identified in both the alloyed powder material and sintered sample. Full article
(This article belongs to the Special Issue State-of-the-Art Materials Science and Engineering in Romania 2023)
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<p>Schematic representation of slope angle and flow rate measurement setup.</p> Full article ">Figure 2
<p>Sintering curve for Al<sub>0.5</sub>CrFeNiTi high entropy alloy.</p> Full article ">Figure 3
<p>SEM analyses results for the raw elemental powders before mixing; (<b>a</b>) Al, (<b>b</b>) Cr, (<b>c</b>) Fe, (<b>d</b>) Ni, and (<b>e</b>) Ti.</p> Full article ">Figure 4
<p>Al<sub>0.5</sub>CrFeNiTi high entropy alloy SEM and EDS analysis results (inset): mixed powders sample (<b>a</b>) and mixture alloyed for 5 h (<b>b</b>), 10 h (<b>c</b>), 20 h (<b>d</b>).</p> Full article ">Figure 4 Cont.
<p>Al<sub>0.5</sub>CrFeNiTi high entropy alloy SEM and EDS analysis results (inset): mixed powders sample (<b>a</b>) and mixture alloyed for 5 h (<b>b</b>), 10 h (<b>c</b>), 20 h (<b>d</b>).</p> Full article ">Figure 5
<p>Particle size distribution for the Al<sub>0.5</sub>CrFeNiTi HEA obtained by mechanical alloying.</p> Full article ">Figure 6
<p>X-ray diffraction results for the Al<sub>0.5</sub>CrFeNiTi HEA mechanically milled sample for 5 h, 10 h, and 20 h.</p> Full article ">Figure 7
<p>Microstructural analyses results for the sintered samples at (<b>a</b>) 750 °C cooled in air, (<b>b</b>) 875 °C cooled in air, (<b>c</b>) 1000 °C cooled in air, and (<b>d</b>) 1000 °C cooled with the furnace.</p> Full article ">Figure 8
<p>X-ray diffraction results for the Al<sub>0.5</sub>CrFeNiTi high entropy alloy sintered sample.</p> Full article ">Figure 9
<p>EDS analyses results at different points of the selected surface area.</p> Full article ">
16 pages, 5090 KiB  
Article
Annual Transmittance Behavior of Light-Transmitting Concrete with Optical Fiber Bundles
by Adithya Shenoy, Gopinatha Nayak, Adithya Tantri, Kiran Kumar Shetty and Mangeshkumar R. Shendkar
Materials 2023, 16(21), 7037; https://doi.org/10.3390/ma16217037 - 4 Nov 2023
Cited by 4 | Viewed by 1484
Abstract
This study characterizes the transmittance behavior of structural light-transmitting concrete under natural sunlight. The experimentation involves the use of a novel test setup and a detailed analysis considering the variation and dependence on time of day, month of the year and seasonal variations. [...] Read more.
This study characterizes the transmittance behavior of structural light-transmitting concrete under natural sunlight. The experimentation involves the use of a novel test setup and a detailed analysis considering the variation and dependence on time of day, month of the year and seasonal variations. The test set consisted of 28 variations of fiber configurations, with two different diameters, spacing and bundling techniques used to increase the area of fibers while maintaining spacing to aid the placing of concrete without compromising on transmittance. The study provides a real-time observational understanding of the behavior of light-transmitting concrete, a result usually obtained by modelling and simulation. The statistical analysis helps in understanding the impact of various variables as well as their interrelationships, which can help in design optimization. Based on the behavior as well as the stipulations of standards, the applicability of the material to various structural applications has been identified. Full article
(This article belongs to the Special Issue Concrete in Structural Engineering: Fabrication and Mechanical Behavior ‖)
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<p>SEM results of optical fibers: (<b>a</b>) cut surface, (<b>b</b>) longitudinal surface.</p> Full article ">Figure 2
<p>Special molds and light-transmitting concrete with different fiber bundle sizes.</p> Full article ">Figure 3
<p>Vertical lightbox to measure the transmittance of natural light.</p> Full article ">Figure 4
<p>Variation of luminance based on the time of the day, for different samples from M11 to M74.</p> Full article ">Figure 5
<p>Residual plots for average annual illumination.</p> Full article ">Figure 6
<p>Variation of average monthly luminance vs. time of day for M11 and M73 mixes.</p> Full article ">Figure 7
<p>Annual variation of luminance based on the season for M11 and M73 mixes.</p> Full article ">Figure 8
<p>Seasonal illumination concerning the seasonal solar inclination.</p> Full article ">Figure 9
<p>Plot of mix vs. annual average luminance and area of fibers with regression analysis.</p> Full article ">Figure 10
<p>Comparison of the irradiance characteristics and transmittance behavior of mixes.</p> Full article ">Figure 11
<p>Residual plots of annual illumination compared with irradiance.</p> Full article ">
13 pages, 3240 KiB  
Article
Effect of the Solid Solution and Aging Treatment on the Mechanical Properties and Microstructure of a Novel Al-Mg-Si Alloy
by Yan Chen, Wu Wei, Yu Zhao, Wei Shi, Xiaorong Zhou, Li Rong, Shengping Wen, Xiaolan Wu, Kunyuan Gao, Hui Huang and Zuoren Nie
Materials 2023, 16(21), 7036; https://doi.org/10.3390/ma16217036 - 4 Nov 2023
Cited by 6 | Viewed by 2224
Abstract
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and [...] Read more.
A novel Al-Mg-Si aluminum alloy with the addition of the micro-alloying element Er and Zr that was promptly quenched after extrusion has been studied. The solid solution and aging treatment of the novel alloy are studied by observing the microstructure, mechanical properties, and strengthening mechanism. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques are employed to examine the changes in the microstructure resulting from various solid solution treatments and aging treatments. The best strengthening effect can be achieved when the solubility of the MgSi phase and precipitate β″ (Mg2Si phase) is at their maximum. The addition of Er and Zr elements promotes the precipitation of the β″ phase and makes the b″ phase more finely dispersed. The aging strengthening of alloys is a comprehensive effect of the dislocation cutting mechanism and bypass mechanism, the joint effect of diffusion strengthening of Al3(Er,Zr) particles and the addition of Er and Zr elements promoting the precipitation strengthening of β″ phases. In this paper, by adding Er and Zr elements and exploring the optimal heat treatment system, the yield strength of the alloy reaches 437 MPa and the tensile strength reaches 453 MPa after solid solution treatment at 565 °C/30 min and aging at 175 °C/10 h. Full article
(This article belongs to the Special Issue Metallic Materials: Structure Transition, Processing, Characterization and Applications)
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<p>Schematic diagram of room temperature tensile specimen (unit: mm).</p> Full article ">Figure 2
<p>DSC curve of sample.</p> Full article ">Figure 3
<p>BSE images and residual phases area fraction statistics at different solid solution temperatures: (<b>a</b>) T4 extruded state; (<b>b</b>) 555 °C; (<b>c</b>) 565 °C; (<b>d</b>) 575 °C; (<b>e</b>) 585 °C; (<b>f</b>) Residual phase area fraction statistics.</p> Full article ">Figure 4
<p>EBSD maps of grain orientation distribution of Al-Mg-Si alloy under (<b>a</b>) the extruded state; (<b>b</b>) solid solution for 565 °C/30 min.</p> Full article ">Figure 5
<p>Microhardness curves of the Al-Mg-Si alloy at various solid solution temperatures and aging at 175 °C for 8 h.</p> Full article ">Figure 6
<p>Al-Mg-Si alloy microhardness curves at various aging temperatures.</p> Full article ">Figure 7
<p>SEM images of the fracture surface morphology of Al-Mg-Si alloy under different aging treatments: (<b>a</b>) 175 °C/8 h, (<b>b</b>) 175 °C/10 h, (<b>c</b>) 175 °C/12 h.</p> Full article ">Figure 8
<p>TEM images of T6 alloy: (<b>a</b>) β″ precipitate morphology, (<b>b</b>) Al<sub>3</sub>(Er,Zr) precipitate morphology, (<b>c</b>) bright field; (<b>d</b>) grain-boundary precipitates; (<b>e</b>) EDS spectra of encircled region in (<b>d</b>); (<b>f</b>) β″ histogram of phase-length size distribution.</p> Full article ">
15 pages, 12763 KiB  
Article
Possibilities of Using Geopolymers in Welding Processes and Protection against High Temperatures
by Sławomir Parzych, Maja Paszkowska, Dawid Stanisz, Agnieszka Bąk and Michał Łach
Materials 2023, 16(21), 7035; https://doi.org/10.3390/ma16217035 - 3 Nov 2023
Cited by 1 | Viewed by 1073
Abstract
Geopolymer materials have long been known for their competitive properties against traditional construction materials. Their special features include high resistance to elevated temperatures and good fire resistance. They are typically used as insulating materials at temperatures not exceeding 100 °C (because they can [...] Read more.
Geopolymer materials have long been known for their competitive properties against traditional construction materials. Their special features include high resistance to elevated temperatures and good fire resistance. They are typically used as insulating materials at temperatures not exceeding 100 °C (because they can achieve a thermal conductivity coefficient of 0.060 W/m × K or less under these conditions). Still, they can also be used as thermal insulation at temperatures exceeding 1000 °C. One technology that uses very high temperatures is metal welding technology, where temperatures often exceed as many as 3000 °C. Geopolymers, due to their properties, can also be an interesting new alternative in various welding applications. This paper presents the preliminary results of pot-proofing the resistance of geopolymers to temperatures exceeding 3000 °C. Test results of a foamed geopolymer insulating a steel substrate are presented, and a geopolymer mold for thermite rail welding was made and realistically tested. The results confirmed the feasibility of using cast geopolymer molds for thermite welding of railroad rails. The geopolymer material performed well during the test and no cracks or other damage occurred. The following article presents the potential of using geopolymer materials for welding applications. Full article
(This article belongs to the Special Issue Geopolymers and Fiber-Reinforced Concrete Composites)
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<p>Number of publications on fire resistance of geopolymers according to SCOPUS database.</p> Full article ">Figure 2
<p>Countries where scientists most often undertake research on geopolymers as fireproofing.</p> Full article ">Figure 3
<p>Prepared models for making a thermite welding mold from geopolymers.</p> Full article ">Figure 4
<p>Models (pattern) of the mold flooded with silicone and the finished mold.</p> Full article ">Figure 5
<p>Thermite welding molds made of geopolymers by casting and bonding.</p> Full article ">Figure 6
<p>Oxy-acetylene torch testing of a coating (sample fragment—preliminary tests) of foamed geopolymer applied to a steel sheet (<b>left</b>) and the microstructure of foamed geopolymer (<b>right</b>).</p> Full article ">Figure 7
<p>A foamed geopolymer panel attached to a steel sheet (<b>left</b>) and the appearance of the surface after an acetylene-oxygen torch test (<b>right</b>).</p> Full article ">Figure 8
<p>Structure (SEM) of foamed geopolymer containing microspheres.</p> Full article ">Figure 9
<p>Fire resistance test results for a 160 mm thick board (beige color—temperature measured on the outside of the board; brown color—temperature on the side of the burner operation).</p> Full article ">Figure 10
<p>Geopolymer plate before thermal treatment at 800 °C (<b>left</b>); geopolymer plate after thermal treatment at 800 °C—surface with no signs of mesh cracks after high-temperature treatment (<b>right</b>). (Samples measuring 25 × 25 × 2 cm.)</p> Full article ">Figure 11
<p>Stand prepared for thermite welding using specially prepared geopolymer molds.</p> Full article ">Figure 12
<p>Visualization of the conducted test of thermite welding of railroad rails using geopolymer molds.</p> Full article ">Figure 13
<p>Images from a thermal imaging camera showing the temperature distribution during a rail thermite welding test using geopolymer molds.</p> Full article ">Figure 14
<p>Photos after the test using geopolymer molds.</p> Full article ">
29 pages, 13467 KiB  
Review
Mechanical Properties of Bulk Metallic Glasses Additively Manufactured by Laser Powder Bed Fusion: A Review
by Haojie Luo and Yulei Du
Materials 2023, 16(21), 7034; https://doi.org/10.3390/ma16217034 - 3 Nov 2023
Cited by 8 | Viewed by 2113
Abstract
Bulk metallic glasses (BMGs) display excellent strength, high hardness, exceptional wear resistance and corrosion resistance owing to its amorphous structure. However, the manufacturing of large-sized and complex shaped BMG parts faces significant difficulties, which seriously hinders their applications. Laser powder bed fusion (LPBF) [...] Read more.
Bulk metallic glasses (BMGs) display excellent strength, high hardness, exceptional wear resistance and corrosion resistance owing to its amorphous structure. However, the manufacturing of large-sized and complex shaped BMG parts faces significant difficulties, which seriously hinders their applications. Laser powder bed fusion (LPBF) is a typical additive manufacturing (AM) technique with a cooling rate of up to 108 K/s, which not only allows for the formation of amorphous structures but also solves the forming problem of complex-shaped BMG parts. In recent years, a large amount of work has been carried out on the LPBF processing of BMGs. This review mainly summarizes the latest progress in the field of LPBF additively manufactured BMGs focusing on their mechanical properties. We first briefly review the BMG alloy systems that have been additively manufactured using LPBF, then the mechanical properties of LPBF-fabricated BMGs including the micro- and nano-hardness, micropillar compressive performance, and macro-compressive and tensile performance are clarified. Next, the relationship between the mechanical properties and microstructure of BMGs produced via LPBF are analyzed. Finally, the measures for improving the mechanical properties of LPBF-fabricated BMGs are discussed. This review can provide readers with an essential comprehension of the structural and mechanical properties of LPBF-manufactured BMGs. Full article
(This article belongs to the Special Issue Additive Manufacturing of Metals and Alloys: Recent Advances and Challenges)
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<p>Schematic of the LPBF process [<a href="#B35-materials-16-07034" class="html-bibr">35</a>].</p> Full article ">Figure 2
<p>Amorphous Zr<sub>52.5</sub>Cu<sub>17.9</sub>Ni<sub>14.6</sub>Al<sub>10</sub>Ti<sub>5</sub> BMG parts manufactured using LPBF: (<b>a</b>) gear sample; (<b>b</b>) TOS structure and two gyroid structures [<a href="#B39-materials-16-07034" class="html-bibr">39</a>]. Amorphous Zr<sub>60.14</sub>Cu<sub>22.31</sub>Fe<sub>4.85</sub>Al<sub>9.7</sub>Ag<sub>3</sub> BMG components produced using LPBF for biomaterial applications: (<b>c</b>) acetabular cup; (<b>d</b>) femoral prosthesis [<a href="#B46-materials-16-07034" class="html-bibr">46</a>]. (<b>e</b>) Amorphous Zr<sub>60</sub>Fe<sub>10</sub>Cu<sub>20</sub>Al<sub>10</sub> BMG gear sample (diameter 35 mm and height 5 mm) [<a href="#B48-materials-16-07034" class="html-bibr">48</a>]. (<b>f</b>) Amorphous Zr<sub>52.5</sub>Ti<sub>5</sub>Al<sub>10</sub>Ni<sub>14.6</sub>Cu<sub>17.9</sub> BMG scaffolds produced using LPBF [<a href="#B40-materials-16-07034" class="html-bibr">40</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) The 3D scaffold structure of partially crystallized Fe<sub>74</sub>Mo<sub>4</sub>P<sub>10</sub>C<sub>7.5</sub>B<sub>2.5</sub>Si<sub>2</sub>, where the arrows indicate the position of the X-ray diffraction measures of the samples; (<b>b</b>) XRD patterns of a corner of the scaffold and the cylinder, showing obvious crystal phases [<a href="#B38-materials-16-07034" class="html-bibr">38</a>]. (<b>c</b>) An FeCrMoCB BMG cylinder with a size of Ø 45 × 30 mm, (<b>d</b>) XRD of FeCrMoCB cylinders (bottom, middle, and top) [<a href="#B49-materials-16-07034" class="html-bibr">49</a>].</p> Full article ">Figure 4
<p>(<b>a</b>) Fully crystallized Al<sub>85</sub>Ni<sub>5</sub>Y<sub>6</sub>Co<sub>2</sub>Fe<sub>2</sub> gear prepared using LPBF, with CAD model of the gear in the upper left corner; (<b>b</b>) corresponding XRD pattern showing obvious crystallization peaks [<a href="#B58-materials-16-07034" class="html-bibr">58</a>].</p> Full article ">Figure 5
<p>(<b>a</b>–<b>d</b>) Some amorphous Cu<sub>50</sub>Zr<sub>43</sub>Al<sub>7</sub> parts with large sizes and complex shapes, which were produced with the optimal LPBF process parameters (E = 25 J/mm<sup>3</sup>); (<b>e</b>) XRD plots of different energy densities, where the samples with E = 25 J/mm<sup>3</sup> are almost completely amorphous; (<b>f</b>) DSC plots of the optimized sample and the original powder, which shows the typical features of amorphous phase, where the arrows point to the glass transition temperature (T<sub>g</sub>) and the crystallization onset temperature (T<sub>x</sub>) [<a href="#B61-materials-16-07034" class="html-bibr">61</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Amorphous and complex structural Ti<sub>47</sub>Cu<sub>38</sub>Zr<sub>7.5</sub>Fe<sub>2.5</sub>Sn<sub>2</sub>Si<sub>1</sub>Ag<sub>2</sub> components made using LPBF. (<b>b</b>) The corresponding XRD patterns of cylindrical LPBF-fabricated samples and cast rods. Crystal peaks only occur in gas-atomized powders [<a href="#B56-materials-16-07034" class="html-bibr">56</a>].</p> Full article ">Figure 7
<p>(<b>a</b>) The μ-CT image of Pd-based BMG prepared using optimized LPBF parameters (P = 60 W), exhibiting no cracks and high densities, with a porosity of only 0.4%; (<b>b</b>) XRD patterns from two cross-sections of printed samples, X-Y and X-Z; (<b>c</b>) Fracture morphology of the optimized cylinder; (<b>d</b>) compression stress–strain curve, showing excellent compressive strength [<a href="#B64-materials-16-07034" class="html-bibr">64</a>].</p> Full article ">Figure 8
<p>(<b>a</b>) Microhardness results (HV0.1). (<b>b</b>) Hardness map obtained from 165 indentations [<a href="#B64-materials-16-07034" class="html-bibr">64</a>].</p> Full article ">Figure 9
<p>(<b>a</b>) Schematic of the nanoindentation test locations of LPBF-fabricated AMZ4 BMG samples. (<b>b</b>) SEM of 1600 indentations performed. (<b>c</b>) The 10 × 10 μm<sup>2</sup> nanohardness testing area. (<b>d</b>) A histogram displaying the Gaussian distribution of hardness [<a href="#B36-materials-16-07034" class="html-bibr">36</a>].</p> Full article ">Figure 10
<p>(<b>a</b>,<b>b</b>) SEM images of LPBF-fabricated Fe<sub>55</sub>Cr<sub>25</sub>Mo<sub>16</sub>B<sub>2</sub>C<sub>2</sub> BMG micropillars in compression tests; (<b>c</b>) stress–strain curves; (<b>d</b>) cross-sectional microscope images of BMGs [<a href="#B52-materials-16-07034" class="html-bibr">52</a>].</p> Full article ">Figure 11
<p>(<b>a</b>) Compressive stress–strain curves of as-cast and LPBF-fabricated samples, where the E = 14.3 J/mm<sup>3</sup> sample has the highest fracture strength of 1560 MPa, but is still lower than the corresponding cast sample; (<b>b</b>) fracture surface of LPBF-fabricated samples with E = 14.3 J/mm<sup>3</sup>, where a clear crack is observed; (<b>c</b>) higher magnification image of region in (<b>b</b>), which shows the presence of unmelted powder [<a href="#B62-materials-16-07034" class="html-bibr">62</a>].</p> Full article ">Figure 12
<p>(<b>a</b>) Tensile test results of AMZ4 BMG fabricated using LPBF with a maximum strength of 1080 MPa; (<b>b</b>,<b>c</b>) SEM images of the fracture surface, where (<b>b</b>) shows lack of fusion defects and unmelted powder particles, and (<b>c</b>) shows a dimple pattern [<a href="#B101-materials-16-07034" class="html-bibr">101</a>].</p> Full article ">Figure 13
<p>(<b>a</b>) 3D spatial distribution and morphology of porosity defects inside the cylinder revealed by μ-CT images; (<b>b</b>) the size distribution of the porosity defects; snapshots of the X-Y (<b>c</b>) and X-Z (<b>d</b>) cross-sections, with the porosity flaws displayed in black [<a href="#B36-materials-16-07034" class="html-bibr">36</a>].</p> Full article ">Figure 14
<p>(<b>a</b>) The μ-CT of the LPBF-fabricated Zr-based BMG compression sample. (<b>b</b>,<b>c</b>) Fracture surfaces of the LPBF-fabricated BMG sample. Two intersecting fracture surfaces can be seen in (<b>b</b>), and unmelted powder particles were found in some larger LoFs in (<b>c</b>) [<a href="#B40-materials-16-07034" class="html-bibr">40</a>].</p> Full article ">Figure 15
<p>SEM-BSE images of X-Y sections of single-track molten pools fabricated using LPBF: (<b>a</b>) 200 W; (<b>b</b>) 160 W; (<b>c</b>) 120 W; and (<b>d</b>) 80 W. White arrows point to cracks and red arrows point to pores [<a href="#B57-materials-16-07034" class="html-bibr">57</a>].</p> Full article ">Figure 16
<p>(<b>a</b>) Side view of 3D-printed Zr-based BMG revealing the distribution of the MP and HAZ; (<b>b</b>) TEM bright-field picture displaying the MP and HAZ borders; (<b>c</b>) diffraction pattern of selected locations in the HAZ [<a href="#B41-materials-16-07034" class="html-bibr">41</a>].</p> Full article ">Figure 17
<p>(<b>a</b>) Relative density plots of LPBF-fabricated Fe<sub>68.3</sub>C<sub>6.9</sub>Si<sub>2.5</sub>B<sub>6.7</sub>P<sub>8.7</sub>Cr<sub>2.3</sub>Mo<sub>2.5</sub>Al<sub>2.1</sub> BMG samples versus process parameters, where the darker the color, the higher the densities. (<b>b</b>–<b>d</b>) OM images of LPBF-fabricated samples, where white arrows correspond to different densities [<a href="#B51-materials-16-07034" class="html-bibr">51</a>].</p> Full article ">Figure 18
<p>(<b>a</b>) LPBF processing maps displaying different feature regions. Different colors and markings are used to highlight areas processed by different laser powers and scanning speeds; (<b>b</b>) printed samples of the corresponding LPBF process parameters [<a href="#B52-materials-16-07034" class="html-bibr">52</a>].</p> Full article ">Figure 19
<p>(<b>a</b>) P-R scanning strategy: using a chessboard strategy to melt powder for the first time, followed by melting again using random pulses [<a href="#B53-materials-16-07034" class="html-bibr">53</a>]. (<b>b</b>) Nanoindentation spectra of Zr<sub>52.5</sub>Ti<sub>5</sub>Cu<sub>17.9</sub>Ni<sub>14.6</sub>Al<sub>10</sub> BMG under different scanning speeds and strategies [<a href="#B39-materials-16-07034" class="html-bibr">39</a>]. (<b>c</b>–<b>h</b>) The μ- CT plots and porosity distribution of Zr<sub>52.5</sub>Cu<sub>17.9</sub>Ni<sub>14.6</sub>Al<sub>10</sub>Ti<sub>5</sub> samples under different scanning strategies. Sample 1: (<b>c</b>,<b>d</b>), a filling line scan with 200 μm distance (E = 13 J/mm<sup>3</sup>, ρ<sub>Relative</sub> = 97.7%). Sample 2: (<b>e</b>,<b>f</b>), a chessboard strategy (E = 12 J/mm<sup>3</sup> ρ<sub>Relative</sub> = 97.2%). Sample 3: (<b>g</b>,<b>h</b>), a unidirectional scanning vector rotated 90 ° in adjacent layers (E = 13 J/mm<sup>3</sup>, ρ<sub>Relative</sub> = 98.5%) [<a href="#B40-materials-16-07034" class="html-bibr">40</a>].</p> Full article ">
14 pages, 2457 KiB  
Article
Influence Analysis of Polyvinyl Alcohol on the Degradation of Artificial Leather with Cellulose Nitrate Coating Originating from a Suitcase Stored in the Collection of the Auschwitz-Birkenau State Museum in Oświęcim, Poland
by Nel Jastrzębiowska, Anna Wawrzyk and Natalia Uroda
Materials 2023, 16(21), 7033; https://doi.org/10.3390/ma16217033 - 3 Nov 2023
Cited by 2 | Viewed by 1387
Abstract
The aim of this study was to assess the influence of a protective layer of polyvinyl alcohol on the degradation process of artificial leather based on cellulose nitrate. Samples of the artificial leather were obtained from a suitcase dating back to the first [...] Read more.
The aim of this study was to assess the influence of a protective layer of polyvinyl alcohol on the degradation process of artificial leather based on cellulose nitrate. Samples of the artificial leather were obtained from a suitcase dating back to the first half of the 20th century, not considered a historical artifact. The analysis involved Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR-ATR) and X-ray photoelectron spectroscopy (XPS). Artificial aging was employed for the study. The artificial leather sample with a protective coating of polyvinyl alcohol on a cellulose nitrate base exhibited the lowest degree of degradation due to minimal chemical changes in cellulose esters. The obtained FTIR-ATR spectrum indicated significantly higher nitration of cellulose and, consequently, a lower degree of polymer degradation. The sample without the protective polyvinyl alcohol coating and the sample with the coating removed before artificial aging showed similar reactions. Full article
(This article belongs to the Special Issue Advanced Materials & Methods for Heritage & Archaeology)
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<p>Suitcases covered with artificial leather, stored in the A-BSM Collections: (<b>a</b>) A suitcase covered with artificial leather based on cellulose nitrate, in black color, with the addition of dibutyl phthalate as a plasticizer, on a cotton substrate; (<b>b</b>) A suitcase covered with artificial leather based on cellulose nitrate, in brown color, with the addition of dibutyl phthalate, on a cotton substrate; (<b>c</b>) A suitcase covered with artificial leather based on cellulose nitrate, in black color, with the addition of dibutyl phthalate and rosin, on a paper substrate with a predominance of wood pulp; (<b>d</b>) A suitcase covered with artificial leather based on cellulose nitrate, in brown color, with the addition of dibutyl phthalate, on a cotton substrate. Photos by S. Mrozek.</p> Full article ">Figure 2
<p>FTIR spectrum for a sample with confirmed presence of cellulose nitrate.</p> Full article ">Figure 3
<p>Samples of artificial leather with cellulose nitrate coating: (<b>a</b>) CN sample; (<b>b</b>) CN + PVA sample; (<b>c</b>) CN − PVA sample. Photo by M. Maciaszczyk.</p> Full article ">Figure 4
<p>Experimental diagram.</p> Full article ">Figure 5
<p>FTIR-ATR spectra for three samples subjected to artificial aging processes: (<b>a</b>) CN, (<b>b</b>) CN + PVA, and (<b>c</b>) CN − PVA.</p> Full article ">Figure 6
<p>XPS spectra of samples: (<b>a</b>) an artificial leather sample without protective coating (CN), (<b>b</b>) an artificial leather sample with protective coating (CN + PVA), and (<b>c</b>) an artificial leather sample with the protective coating removed (CN − PVA).</p> Full article ">Figure 6 Cont.
<p>XPS spectra of samples: (<b>a</b>) an artificial leather sample without protective coating (CN), (<b>b</b>) an artificial leather sample with protective coating (CN + PVA), and (<b>c</b>) an artificial leather sample with the protective coating removed (CN − PVA).</p> Full article ">Figure 7
<p>Percentage distribution of individual elements constituting the outer layer of the investigated cellulose-nitrate-based artificial leather samples.</p> Full article ">
21 pages, 9027 KiB  
Article
Interaction Mechanism between Slags and Alkali Silicate Activators: An Approach Based on the Al Phases
by Yu Jin, Weipeng Feng, Dapeng Zheng and Zhijun Dong
Materials 2023, 16(21), 7032; https://doi.org/10.3390/ma16217032 - 3 Nov 2023
Viewed by 1030
Abstract
In this study, we examined the early-stage interaction of three types of slag and six activators with different chemical compositions. To determine the degree of hydration (DOH) and hydrate assemblage in alkali-activated slag (AAS), we employed EDX, XRD, and NMR analyses. We found [...] Read more.
In this study, we examined the early-stage interaction of three types of slag and six activators with different chemical compositions. To determine the degree of hydration (DOH) and hydrate assemblage in alkali-activated slag (AAS), we employed EDX, XRD, and NMR analyses. We found that with increasing silicate concentration in the activator, the DOH in the AAS varied, whereas the proportion of C-(N)-A-S-H increased and the other Al-containing phase decreased. When examining the impact of the activator on glass dissolution, it is apparent that an index based on the degree of depolymerization of the glass structure correlates with the DOH and the proportion of hydrotalcite in the AAS. Coupled with the activator’s modulus, this index can be utilised to elucidate the dissolution–reprecipitation mechanism that governs the interaction between the activator and slag. Full article
(This article belongs to the Collection Alkali‐Activated Materials for Sustainable Construction)
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<p>Image processing steps via ImageJ (the texts are the menu commands in the software).</p> Full article ">Figure 2
<p>(<b>a</b>) The EDX mapping image of the Si-rich particles (in orange) in S2-A50 (false colours coded to the different elements: blue—Al; purple—Na; light green—Mg; green—Ca, and Orange—Si); (<b>b</b>) the SEM image of the Si-rich particles in sample S2-A50.</p> Full article ">Figure 2 Cont.
<p>(<b>a</b>) The EDX mapping image of the Si-rich particles (in orange) in S2-A50 (false colours coded to the different elements: blue—Al; purple—Na; light green—Mg; green—Ca, and Orange—Si); (<b>b</b>) the SEM image of the Si-rich particles in sample S2-A50.</p> Full article ">Figure 3
<p>Mg/Si versus Al/Si in the alkali-activated slag pastes with various slag–activator combinations: (<b>a</b>) S1/S2/S3-A30; (<b>b</b>) S1/S2/S3-A50; (<b>c</b>) S1/S2/S3-A31; (<b>d</b>) S1/S2/S3-A51; (<b>e</b>) S1/S2/S3-A32; (<b>f</b>) S1/S2/S3-A52 (blue solid and open circles refer to the samples associated with S1; green solid and open triangles refer to the samples associated with S2; deep red solid and open squares refer to the samples associated with S3).</p> Full article ">Figure 4
<p>XRD spectra of the alkali-activated slag pastes with various slag–activator combinations: (<b>a</b>) S1/S2/S3-A30/A50; (<b>b</b>) S1/S2/S3-A31/A51; (<b>c</b>) S1/S2/S3-A32/A52 (Ht-s: Mg-Al LDH with polysulfide anions in the interlayer; Ht-c: Mg-Al LDH with carbonate anions in the interlayer; Cc: calcite; A: åkermanite).</p> Full article ">Figure 5
<p>The <sup>29</sup>Si MAS-NMR spectra of alkali-activated slag pastes with different alkali–activator combinations: (<b>a</b>) A30; (<b>b</b>) A50; (<b>c</b>) A31; (<b>d</b>) A51; (<b>e</b>) A32; (<b>f</b>) A52 (blue solid line: paste associated with S1; green dotted line: paste associated with S2; deep red dashed line: paste associated with S3; blue, green, and deep red shadows represent the spectra of the anhydrous slag S1, S2, and S3 scaled by the corresponding DOH listed in <a href="#materials-16-07032-t004" class="html-table">Table 4</a>, respectively). Note: the intensity of the spectra is normalized.</p> Full article ">Figure 5 Cont.
<p>The <sup>29</sup>Si MAS-NMR spectra of alkali-activated slag pastes with different alkali–activator combinations: (<b>a</b>) A30; (<b>b</b>) A50; (<b>c</b>) A31; (<b>d</b>) A51; (<b>e</b>) A32; (<b>f</b>) A52 (blue solid line: paste associated with S1; green dotted line: paste associated with S2; deep red dashed line: paste associated with S3; blue, green, and deep red shadows represent the spectra of the anhydrous slag S1, S2, and S3 scaled by the corresponding DOH listed in <a href="#materials-16-07032-t004" class="html-table">Table 4</a>, respectively). Note: the intensity of the spectra is normalized.</p> Full article ">Figure 6
<p>The <sup>27</sup>Al MAS-NMR spectra of alkali-activated slag pastes with different alkali–activator combinations: (<b>a</b>) A30; (<b>b</b>) A50; (<b>c</b>) A31; (<b>d</b>) A51; (<b>e</b>) A32; (<b>f</b>) A52 (blue solid line: paste associated with S1; green dotted line: paste associated with S2; deep red dashed line: paste associated with S3; blue, green, and deep red shadows are the spectra of the anhydrous slag S1, S2, and S3 scaled by the corresponding DOH listed in <a href="#materials-16-07032-t004" class="html-table">Table 4</a>, respectively). Note: the intensity of the spectra is normalized.</p> Full article ">Figure 7
<p>Pastes S1-A32 and S1-A52 after 3 days of hydration.</p> Full article ">Figure 8
<p>Deconvolution of Al(VI) peak in the <sup>27</sup>Al MAS-NMR spectra of S2-A50 (red dotted line is the cumulative spectrum, which is composed of the sub-peaks as shown in pink, purple, and olive shadows).</p> Full article ">Figure 9
<p>The DOH plotted against the NBO/T* ratio (black open circle refers to the samples associated with A30 and A50; yellow triangle refers to the samples associated with A31 and A51; violet open square refers to the samples associated with A32 and A52).</p> Full article ">Figure 10
<p>(<b>a</b>) the ratio of Al(VI) from LDH (designated as non-Al-O-Si) and (<b>b</b>) the relationship between the ratio of non-Al-O-Si and DOH, plotted against the NBO/T<sup>*</sup> ratio and grouped by the modulus of the activators (open circle refers to the samples associated with A30 and A50; solid triangle refers to the samples associated with A31 and A51; open square refers to the samples associated with A32 and A52).</p> Full article ">Figure 11
<p>Schematic illustration of interaction between slag and alkali silicate activator.</p> Full article ">
11 pages, 1448 KiB  
Article
Study of Elastic and Structural Properties of BaFe2As2 Ultrathin Film Using Picosecond Ultrasonics
by Di Cheng, Boqun Song, Jong-Hoon Kang, Chris Sundahl, Anthony L. Edgeton, Liang Luo, Joong-Mok Park, Yesusa G. Collantes, Eric E. Hellstrom, Martin Mootz, Ilias E. Perakis, Chang-Beom Eom and Jigang Wang
Materials 2023, 16(21), 7031; https://doi.org/10.3390/ma16217031 - 3 Nov 2023
Viewed by 1321
Abstract
We obtain the through-thickness elastic stiffness coefficient (C33) in nominal 9 nm and 60 nm BaFe2As2 (Ba-122) thin films by using picosecond ultrasonics. Particularly, we reveal the increase in elastic stiffness as film thickness decreases from bulk [...] Read more.
We obtain the through-thickness elastic stiffness coefficient (C33) in nominal 9 nm and 60 nm BaFe2As2 (Ba-122) thin films by using picosecond ultrasonics. Particularly, we reveal the increase in elastic stiffness as film thickness decreases from bulk value down to 9 nm, which we attribute to the increase in intrinsic strain near the film-substrate interface. Our density functional theory (DFT) calculations reproduce the observed acoustic oscillation frequencies well. In addition, temperature dependence of longitudinal acoustic (LA) phonon mode frequency for 9 nm Ba-122 thin film is reported. The frequency change is attributed to the change in Ba-122 orthorhombicity (a−b)/(a+b). This conclusion can be corroborated by our previous ultrafast ellipticity measurements in 9 nm Ba-122 thin film, which exhibit strong temperature dependence and indicate the structural phase transition temperature Ts. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Materials Physics)
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<p>Scheme of ultrafast pump-probe measurement and information of sample: (<b>a</b>) Crystal structures of Ba-122 and LiF at room temperature [<a href="#B40-materials-16-07031" class="html-bibr">40</a>]. (<b>b</b>) Generation and detection of coherent acoustic phonons in Ba-122 thin films. The coherent phonons generated by the 800 nm pump pulse can be detected by the time-delayed 400 nm probe pulse through the photoelastic effect. (<b>c</b>) Schematics of <span class="html-italic">a</span>–<span class="html-italic">c</span> over layers for Ba-122 thin film. Note the <math display="inline"><semantics> <msup> <mi>a</mi> <mo>′</mo> </msup> </semantics></math> and <math display="inline"><semantics> <msup> <mi>c</mi> <mo>′</mo> </msup> </semantics></math> denote the lattice parameters near the LiF substrate.</p> Full article ">Figure 2
<p>Transient reflectivity change <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <mi>R</mi> <mo>/</mo> <mi>R</mi> </mrow> </semantics></math> with corresponding biexponential fitting and residuals of (<b>a</b>) 9 nm and (<b>b</b>) 60 nm Ba-122 thin film at 160 K. Data are offset for clarity. Fourier spectra for the residuals of (<b>c</b>) 9 nm and (<b>d</b>) 60 nm Ba-122 thin film transient reflectivity, insets show the zoom-in data with frequency ranges from 170 to 195 GHz. Clearly, the peak at 182.6 GHz in (<b>c</b>) is absent in (<b>d</b>). (<b>e</b>) 9 nm Ba-122 thin film temperature-dependent transient reflectivity <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <mi>R</mi> <mo>/</mo> <mi>R</mi> </mrow> </semantics></math> change (with offset) and acoustic phonon frequency change for the (<b>f</b>) first dominant peak and (<b>g</b>) second peak (blue triangles) plotted together with temperature-dependent photoinduced ellipticity amplitude (red squares) [<a href="#B11-materials-16-07031" class="html-bibr">11</a>]. The transition temperature has a range of ∼110–160 K.</p> Full article ">Figure 3
<p>Calculated DFT results with different parameters: (<b>a</b>) Lattice parameter <span class="html-italic">c</span> as a function of lattice parameter <span class="html-italic">a</span>. (<b>b</b>) Cell volumes as a function of lattice parameter <span class="html-italic">a</span>. (<b>c</b>) <span class="html-italic">C</span><sub>33</sub> dependence of <span class="html-italic">a</span>. (<b>d</b>) Sound speeds as a function of lattice parameter <span class="html-italic">a</span>. (<b>e</b>) Strain energy function <span class="html-italic">E</span> for 9 nm thin film (red dots, solid blue line is fitting) and bulk (red dots, solid red line is fitting). (<b>f</b>) Energy as a function of strain <math display="inline"><semantics> <mi>ϵ</mi> </semantics></math> when <span class="html-italic">a</span> = 0.399 nm (red dots, solid black line is fitting).</p> Full article ">
11 pages, 2234 KiB  
Communication
The Role of Carbon in Metal–Organic Chemical Vapor Deposition-Grown MoS2 Films
by Tianyu Hou, Di Li, Yan Qu, Yufeng Hao and Yun Lai
Materials 2023, 16(21), 7030; https://doi.org/10.3390/ma16217030 - 3 Nov 2023
Viewed by 1598
Abstract
Acquiring homogeneous and reproducible wafer-scale transition metal dichalcogenide (TMDC) films is crucial for modern electronics. Metal–organic chemical vapor deposition (MOCVD) offers a promising approach for scalable production and large-area integration. However, during MOCVD synthesis, extraneous carbon incorporation due to organosulfur precursor pyrolysis is [...] Read more.
Acquiring homogeneous and reproducible wafer-scale transition metal dichalcogenide (TMDC) films is crucial for modern electronics. Metal–organic chemical vapor deposition (MOCVD) offers a promising approach for scalable production and large-area integration. However, during MOCVD synthesis, extraneous carbon incorporation due to organosulfur precursor pyrolysis is a persistent concern, and the role of unintentional carbon incorporation remains elusive. Here, we report the large-scale synthesis of molybdenum disulfide (MoS2) thin films, accompanied by the formation of amorphous carbon layers. Using Raman, photoluminescence (PL) spectroscopy, and transmission electron microscopy (TEM), we confirm how polycrystalline MoS2 combines with extraneous amorphous carbon layers. Furthermore, by fabricating field-effect transistors (FETs) using the carbon-incorporated MoS2 films, we find that traditional n-type MoS2 can transform into p-type semiconductors owing to the incorporation of carbon, a rare occurrence among TMDC materials. This unexpected behavior expands our understanding of TMDC properties and opens up new avenues for exploring novel device applications. Full article
(This article belongs to the Special Issue Advances of Photoelectric Functional Materials and Devices)
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<p>Optical characterizations of wafer-scale MOCVD-grown MoS<sub>2</sub> films. (<b>a</b>) The photograph of MoS<sub>2</sub> film grown on a sapphire substrate. (<b>b</b>) White-light microscope image of the as-grown large-area MoS<sub>2</sub> film transferred onto the SiO<sub>2</sub>/Si substrate. (<b>c</b>) Raman spectra of transferred MOCVD-grown MoS<sub>2</sub> films, exfoliated MoS<sub>2</sub>, and CVD-grown MoS<sub>2</sub>. (<b>d</b>) Photoluminescence spectra of the transferred MOCVD-grown MoS<sub>2</sub> films, exfoliated MoS<sub>2</sub>, and CVD-grown MoS<sub>2</sub>.</p> Full article ">Figure 2
<p>Structure characterizations of the transferred MoS<sub>2</sub>/carbon composite film. (<b>a</b>) The high-resolution bright-field TEM image of a freely suspended MoS<sub>2</sub>/carbon composite film on a TEM grid. The inset shows the FFT pattern of the TEM image and the intensity profile of the corresponding white dashed box. (<b>b</b>) The grain boundary is highlighted by the white dashed box with a rotation angle of ~21°, as confirmed by the FFT pattern shown in the inset. (<b>c</b>) The false color-coded HAADF-TEM image. Corresponding EDS elemental maps display the composition and distribution of each chemical element.</p> Full article ">Figure 3
<p>(<b>a</b>) The cross-sectional TEM of the MoS<sub>2/</sub>amorphous carbon composite film grown on sapphire. The EDS elemental maps are on the right panel. (<b>b</b>) The AFM image of the MoS<sub>2</sub>/amorphous carbon composite film edge transferred onto the SiO<sub>2</sub>/Si substrate.</p> Full article ">Figure 4
<p>XPS spectra of the MOCVD-grown MoS<sub>2</sub>/carbon film on the sapphire substrate. The XPS spectrum of (<b>a</b>) the C 1s orbit, (<b>b</b>) the Mo 3d orbit, and (<b>c</b>) the S 2p orbit of MOCVD-grown MoS<sub>2</sub>/carbon films. (<b>d</b>) The XPS spectrum of the sapphire substrate.</p> Full article ">Figure 5
<p>Electrical characterization of MoS<sub>2</sub>/carbon FETs. (<b>a</b>) The optical micrograph of the MoS<sub>2</sub>/carbon film transferred onto the patterned SiO<sub>2</sub>/Si substrate. (<b>b</b>) Typical transfer characteristics (I<sub>d</sub>-V<sub>g</sub>) of as-fabricated MoS<sub>2</sub>/carbon FETs. Schematics of the valence band position (E<sub>VB</sub>) near the source for pristine (<b>c</b>) and carbon-incorporated (<b>d</b>) FET devices. For the pristine devices, the hole conduction is prevented by a wide Φ<sub>SB-P,</sub> so the device shows n-type behavior. However, after carbon incorporation, the Au Fermi level pins closer to the VB of MoS<sub>2</sub>, leading to a smaller Φ<sub>SB-P</sub> for the hole injection.</p> Full article ">
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