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Materials, Volume 15, Issue 21 (November-1 2022) – 462 articles

Cover Story (view full-size image): Information coding via magnetic state is an idea dating back to the 1970s, when bubble domains in micrometric ferrite films were investigated. Half a century later, this idea has been revisited, backed by a breakthrough in ultra-thin film technologies, as well as progress in the solid-state physics of ferromagnetic chiral nanostructures such as skyrmions. Theoretically predicted in 2006 as topologically protected local whirls of the spin configuration, the skyrmions hosted in ultra-thin FM films (1–5 nm) in contact with a heavy metal are regarded as promising candidates for the role of information carriers in next-generation magnetic computing. View this paper
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15 pages, 4798 KiB  
Article
Study on Low-Temperature Index and Improvement Measures of Emulsified Asphalt Cold Recycled Mixture
by Xiaoqing Yu, Zhanchuang Han, Yu Cai, Liping Liu and Lijun Sun
Materials 2022, 15(21), 7867; https://doi.org/10.3390/ma15217867 - 7 Nov 2022
Cited by 4 | Viewed by 1736
Abstract
With the promotion of cold recycled mixture (CRM) in cold areas and the improvement of its application layer, the enhancement of the low-temperature performance of mixtures is particularly important. The applicability of the current low-temperature bending test method to CRM is controversial. Firstly, [...] Read more.
With the promotion of cold recycled mixture (CRM) in cold areas and the improvement of its application layer, the enhancement of the low-temperature performance of mixtures is particularly important. The applicability of the current low-temperature bending test method to CRM is controversial. Firstly, the low-temperature crack resistance of CRM with different gradations and emulsified asphalt contents was studied by the indirect tensile (IDT) test and the semi-circular bending (SCB) test. Thereafter, the low-temperature performance evaluation index suitable for CRM was put forward. Then, the low-temperature performance of CRM with different gradations, fiber types, and contents was evaluated by using the above low-temperature evaluation index. The results show that the low-temperature performance of CRM with different gradations and emulsified asphalt contents can be distinguished by fracture work (W) and fracture energy (Gf). Not only do the test results have little variability (about 12% and 15%, respectively), but also the correlation coefficient with the new asphalt film thickness is the highest (0.8595 and 0.8939, respectively). Compared with coarse gradation (AC-25) and fine gradation (AC-13), medium-gradation (AC-20) CRM has higher low-temperature performance, and polyester fiber can significantly improve the low-temperature performance of CRM. Compared with non-fiber, the W and Gf of CRM of polyester fiber (0.3% content) can be increased by at least 42% and 30%, respectively. Full article
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<p>Different gradation types of CRM.</p>
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<p>Three gradation types of CRM.</p>
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<p>Low-temperature performance test results of CRM under different grades and emulsified asphalt dosage (SCB test). (<b>a</b>) Gf; (<b>b</b>) S; (<b>c</b>) KIC; (<b>d</b>) JC.</p>
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<p>Low-temperature performance test results of CRM with different gradations and emulsified asphalt contents (IDT test). (<b>a</b>) Ls; (<b>b</b>) |m<sub>75</sub>|; (<b>c</b>) W; (<b>d</b>) <span class="html-italic">I</span><sub>CT</sub>.</p>
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<p>Correlation analysis between new asphalt film thickness and low-temperature crack resistance index.</p>
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<p>Performance and voids test results of CRM under different gradation. (<b>a</b>) Voids and R<sub>T</sub>; (<b>b</b>) W and G<sub>f</sub>; (<b>c</b>) DWR and TSR; (<b>d</b>) UCS and DS.</p>
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<p>Low-temperature performance of CRM under different fiber types. (<b>a</b>) Voids; (<b>b</b>) R<sub>T</sub>; (<b>c</b>) W; (<b>d</b>) G<sub>f</sub>.</p>
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<p>Low-temperature performance of CRM under different fiber contents. (<b>a</b>) TSR; (<b>b</b>) R<sub>T</sub>; (<b>c</b>) W; (<b>d</b>) G<sub>f</sub>.</p>
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9 pages, 5552 KiB  
Article
Enhanced Mechanical Properties of Yellow ZrN Ceramic with Addition of Solid Solution of TiN
by Zongpeng Wu, Zhen Gao, Jun Zhao, Saisai Li, Qi Hao and Songlin Ran
Materials 2022, 15(21), 7866; https://doi.org/10.3390/ma15217866 - 7 Nov 2022
Cited by 2 | Viewed by 1623
Abstract
As a superhard ceramic with a yellow color and excellent electrical conductivity, ZrN has potential applications in the field of decoration, but it is limited by its poor mechanical properties. In this work, the mechanical properties of ZrN ceramic were improved by forming [...] Read more.
As a superhard ceramic with a yellow color and excellent electrical conductivity, ZrN has potential applications in the field of decoration, but it is limited by its poor mechanical properties. In this work, the mechanical properties of ZrN ceramic were improved by forming a (Zr, Ti)N solid solution via spark plasma sintering of a ZrN and TiN powder mixture. The influences of the amount of TiN additive on the sinterability, microstructure, color, and mechanical properties of ZrN ceramic were investigated. X-ray diffraction analysis, energy-dispersive spectroscopy, and microstructural images indicated that Ti atoms dissolved into a ZrN lattice, and a (Zr, Ti)N solid solution was formed during the sintering process. When the content of TiN was 10 vol%, the obtained (Zr, Ti)N composite exhibited the best comprehensive mechanical properties; the Vickers hardness, flexural strength, and fracture toughness were 15.17 GPa, 520 MPa, and 6.03 MPa·m1/2, respectively. The color coordinates and color temperature diagram revealed the addition of TiN hardly impacted the color performance of the ZrN ceramic. Full article
(This article belongs to the Special Issue Recent Studies in Advanced Structural Ceramics)
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<p>XRD patterns of raw ZrN powders and TiN powders.</p>
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<p>(<b>a</b>) XRD patterns of the sintered samples: (<b>b</b>) high-angle area expanded pattern; (<b>c</b>) lattice parameter <span class="html-italic">a</span>; (<b>d</b>) FWHM of (111) and (200) planes.</p>
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<p>Backscattered electron (BSE) images from the polished surface of the sintered samples. (<b>a</b>) ZN, (<b>b</b>) ZT10, (<b>c</b>) ZT20, (<b>d</b>) ZT30.</p>
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<p>(<b>a</b>) BSE image of sample ZT10, (<b>b</b>)–(<b>d</b>) EDS mapping of N, Ti, and Zr, (<b>e</b>) and (<b>f</b>) EDS spectra of spots 1 and 2, respectively.</p>
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<p>Scanning electron microscopy (SEM) images of the fractured surface of the sintered samples. (<b>a</b>) ZN, (<b>b</b>) ZT10, (<b>c</b>) ZT20, (<b>d</b>) ZT30.</p>
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<p>Pictures of the as-prepared ceramics: (<b>a</b>) ZN, (<b>b</b>) ZT10, (<b>c</b>) ZT20, (<b>d</b>) ZT30; (<b>e</b>) the corresponding color coordinates and color temperature diagram.</p>
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<p>The relative density and apparent porosity of the sintered samples.</p>
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<p>The mechanical properties of the sintered samples.</p>
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<p>The crack propagation of sample ZT10.</p>
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15 pages, 4125 KiB  
Article
Synthesis of Superhydrophobic Barium Hexaferrite Coatings with Low Magnetic Hardness
by Arsen E. Muslimov, Makhach Kh Gadzhiev and Vladimir M. Kanevsky
Materials 2022, 15(21), 7865; https://doi.org/10.3390/ma15217865 - 7 Nov 2022
Cited by 3 | Viewed by 1874
Abstract
Using the multifunctional material barium hexaferrite as an example, the prospects for treatment at a quasi-equilibrium low temperature in an open atmosphere to form superhydrophobic magnetic coatings with pronounced crystalline and magnetic anisotropy have been demonstrated for the first time. The relationship between [...] Read more.
Using the multifunctional material barium hexaferrite as an example, the prospects for treatment at a quasi-equilibrium low temperature in an open atmosphere to form superhydrophobic magnetic coatings with pronounced crystalline and magnetic anisotropy have been demonstrated for the first time. The relationship between plasma treatment conditions, structural-phase composition, morphology, and superhydrophobic properties of (0001) films of barium hexaferrite BaFe12O19 on C-sapphire is studied. X-ray photoelectron spectroscopy (XPS), X-ray diffractometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), as well as magnetometry and moisture resistance analysis, were used as research methods. During plasma treatment with a mass-average temperature of 8–10 kK, intense evaporation and surface melting were observed, and texturing of the deposit along (0001) is found. When the treatment temperature was reduced to 4–5 kK, the evaporation of the material was minimized and magnetic and crystal anisotropy increased. However, the increase in the size of crystallites was accompanied by the transition of oxygen atoms from lattice nodes to interstitial positions. All samples exhibited low coercive fields below 500 Oe, associated with the frustration of the magnetic subsystem. Features of growth of materials with a wurtzite structure were used to form a superhydrophobic coating of barium hexaferrite. Plasma treatment regimes for obtaining self-cleaning coatings are proposed. The use of magnetically hard barium hexaferrite to radically change the properties of a coating is demonstrated herein as an example. Full article
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<p>Microscopic images of BaM samples: type (I) (<b>a</b>), type M (<b>b</b>), type M, enlarged image of the regions indicated by dark and white arrows (<b>c</b>), type A (<b>d</b>).</p>
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<p>X-ray diffraction pattern of the corresponding BaM samples normalized to maximum. Insets: cross section images. Designations: *, reflection of the sapphire substrate. S—standart, I—initial, М—treatment at 4 ÷ 5 kK, A—treatment at 8 ÷ 10 kK.</p>
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<p>AFM images of 2D, 3D, and topographic cross-sections of the surface of type M (<b>a</b>,<b>c</b>,<b>e</b>) and type A (<b>b</b>,<b>d</b>,<b>f</b>) films, respectively.</p>
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<p>Panoramic XPS spectra of type M and A samples.</p>
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<p>XPS spectra of Ba3d (<b>a</b>), Fe2p (<b>b</b>), N1s (<b>c</b>), and O1s (<b>d</b>).</p>
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<p>XPS spectra of Ba3d (<b>a</b>), Fe2p (<b>b</b>), N1s (<b>c</b>), and O1s (<b>d</b>).</p>
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<p>XPS spectra of Ba3d (<b>a</b>), Fe2p (<b>b</b>), N1s (<b>c</b>), and O1s (<b>d</b>).</p>
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<p>Curves of the magnetic hysteresis of BaM films processed in the M (<b>a</b>) and A (<b>b</b>) modes. Designations: 1—out-of-plane; 2—in-plane.</p>
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<p>Optical images of the shape of a water drop on the surface of the samples: type I (<b>a</b>), M (<b>b</b>), A (<b>c</b>).</p>
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31 pages, 13008 KiB  
Article
The Influence of Graded Amount of Potassium Permanganate on Corrosion of Hot-Dip Galvanized Steel in Simulated Concrete Pore Solutions
by Petr Pokorný, Vítězslav Vacek, Nikola Prodanovic, Adam Zabloudil, Jaroslav Fojt and Viktor Johánek
Materials 2022, 15(21), 7864; https://doi.org/10.3390/ma15217864 - 7 Nov 2022
Cited by 6 | Viewed by 2444
Abstract
This paper evaluates the amount of KMnO4 in simulated concrete pore solution (pH 12.8) on the corrosion behaviour of hot-dip galvanized steel (HDG). In the range of used MnO4 (10−4, 10−3, 10−2 mol·L−1), [...] Read more.
This paper evaluates the amount of KMnO4 in simulated concrete pore solution (pH 12.8) on the corrosion behaviour of hot-dip galvanized steel (HDG). In the range of used MnO4 (10−4, 10−3, 10−2 mol·L−1), corrosion behaviour is examined with regard to hydrogen evolution and composition (protective barrier properties) of forming corrosion products. The corrosion behaviour of HDG samples is evaluated using Rp/Ecorr and EIS. The composition of corrosion products is evaluated using SEM, XRD, XPS and AAS. The effective MnO4 ion concentration to prevent the corrosion of coating with hydrogen evolution is 10−3 mol·L−1; lower concentrations only prolong the time to passivation (corrosion with hydrogen evolution). The highest used MnO4 concentration ensures corrosion behaviour without hydrogen evolution but also leads to the formation of less-protective amorphous corrosion products rich in MnII/MnIII phases. Full article
(This article belongs to the Special Issue Advanced Processing Methods for Metals and Their Alloys)
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<p>Flow chart of experimental program of this study.</p>
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<p>Cross cut of HDG zinc coating on flat steel sheets—overview.</p>
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<p>Cross cut of HDG zinc coating on flat steel sheets—detail view of the outer layer.</p>
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<p>Time dependency of E<sub>corr</sub> for 4 parallel samples in simulated concrete pore solutions.</p>
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<p>Time dependency of R<sub>P</sub> for 4 parallel samples in simulated concrete pore solutions.</p>
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<p>E-pH (equilibrium) diagram of manganese, marked areas signify stability ranges for individual phases E<sub>corr</sub> of HDG in simulated concrete pore solutions with KMnO<sub>4</sub> [<a href="#B88-materials-15-07864" class="html-bibr">88</a>].</p>
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<p>Equivalent circuit used to evaluate EIS spectra.</p>
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<p>Time-dependent impedance spectra for reference solution (Bode plot: log Z<sub>mod</sub> vs. log frequency and phase angle vs. log frequency).</p>
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<p>Time-dependent impedance spectra for Mn<sup>(1)</sup> solution (Bode plot: log Z<sub>mod</sub> vs. log frequency and phase angle vs. log frequency).</p>
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<p>Time-dependent impedance spectra for Mn<sup>(2)</sup> solution (Bode plot: log Z<sub>mod</sub> vs. log frequency and phase angle vs. log frequency).</p>
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<p>Time-dependent impedance spectra for Mn<sup>(3)</sup> solution (Bode plot: log Zmod vs. log frequency and phase angle vs. log frequency).</p>
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<p>Point evaluation of CPE (t) EIS spectra for simulated concrete pore solution with graded amount of MnO<sub>4</sub><sup>−</sup>.</p>
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<p>Point evaluation of R (t) EIS spectra for simulated concrete pore solution with graded amount of MnO<sub>4</sub><sup>−</sup>.</p>
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<p>Morphology of precipitated corrosion products on HDG after 3 months’ exposure in simulated concrete pore solution of pH 12.8 without KMnO<sub>4</sub>.</p>
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<p>Detail view of corrosion products shown in <a href="#materials-15-07864-f014" class="html-fig">Figure 14</a>.</p>
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<p>SEM—distribution of Zn/Ca/Mn/O on cross section in precipitate of corrosion products (exposure in simulated concrete pore solution of pH 12.8 without MnO<sub>4</sub><sup>−</sup> addition).</p>
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<p>Morphology of precipitated corrosion products on the surface of HDG sample after exposure (3 months) in model concrete pore solution of pH 12.8 with addition of KMnO<sub>4</sub><sup>−</sup> (solution Mn<sup>(1)</sup>).</p>
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<p>Detail view of precipitated corrosion products shown in <a href="#materials-15-07864-f017" class="html-fig">Figure 17</a>.</p>
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<p>SEM—distribution of Zn/Ca/Mn/O on cross section in precipitate of corrosion products (exposure in simulated concrete pore solution of pH 12.8 with addition of KMnO<sub>4</sub> (Mn<sup>(1)</sup>)).</p>
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<p>Morphology of precipitated corrosion products on the surface of HDG sample after exposure (3 months) in simulated concrete pore solution of pH 12.8 with addition of KMnO<sub>4</sub><sup>−</sup> (solution Mn<sup>(2)</sup>).</p>
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<p>Detail view of precipitated corrosion products shown in <a href="#materials-15-07864-f020" class="html-fig">Figure 20</a>.</p>
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<p>SEM—distribution of Zn/Ca/Mn/O on cross section in precipitate of corrosion products (exposure in simulated concrete pore solution with KMnO<sub>4</sub> (Mn<sup>(2)</sup>)).</p>
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<p>Morphology of precipitated corrosion products on the surface of HDG sample after exposure (3 months) in model concrete pore solution with addition of KMnO<sub>4</sub><sup>−</sup> (solution Mn<sup>(3)</sup>).</p>
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<p>Detail view of precipitated corrosion products shown in <a href="#materials-15-07864-f023" class="html-fig">Figure 23</a>.</p>
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<p>SEM—distribution of Zn/Ca/Mn/O on cross section in precipitate of corrosion products (exposure in simulated concrete pore solution with KMnO<sub>4</sub> (Mn<sup>(3)</sup>)).</p>
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<p>XRD analysis of HDG sample exposed for the duration of 3 months in simulated concrete pore solution of pH 12.8 without addition of MnO<sub>4</sub><sup>−</sup>.</p>
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<p>XRD analysis of HDG sample exposed for the duration of 3 months in simulated concrete pore solution of pH 12.8 with addition of MnO<sub>4</sub><sup>−</sup> (Mn(<sup>1</sup>)).</p>
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<p>XRD analysis of HDG sample exposed for the duration of 3 months in simulated concrete pore solution of pH 12.8 with addition of MnO<sub>4</sub><sup>−</sup> (Mn(<sup>2</sup>)).</p>
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<p>XRD analysis of HDG sample exposed for the duration of 3 months in simulated concrete pore solution of pH 12.8 with addition of MnO<sub>4</sub><sup>−</sup> (Mn(3)).</p>
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<p>XPS spectrum of spectral region Mn 2p from all exposure—background subtracted from all spectra.</p>
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<p>XPS spectrum of spectral region O 1s from all exposure—background subtracted from all spectra.</p>
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<p>Resulst of AAS analysis comparing the content of Ca/Mn in corrosion products after pickling in HCl.</p>
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14 pages, 1934 KiB  
Article
Kinetics of Catalyst-Free and Position-Controlled Low-Pressure Chemical Vapor Deposition Growth of VO2 Nanowire Arrays on Nanoimprinted Si Substrates
by Sergey V. Mutilin, Lyubov V. Yakovkina, Vladimir A. Seleznev and Victor Ya. Prinz
Materials 2022, 15(21), 7863; https://doi.org/10.3390/ma15217863 - 7 Nov 2022
Cited by 4 | Viewed by 1809
Abstract
In the present article, the position-controlled and catalytic-free synthesis of vanadium dioxide (VO2) nanowires (NWs) grown by the chemical vapor deposition (CVD) on nanoimprinted silicon substrates in the form of nanopillar arrays was analyzed. The NW growth on silicon nanopillars with [...] Read more.
In the present article, the position-controlled and catalytic-free synthesis of vanadium dioxide (VO2) nanowires (NWs) grown by the chemical vapor deposition (CVD) on nanoimprinted silicon substrates in the form of nanopillar arrays was analyzed. The NW growth on silicon nanopillars with different cross-sectional areas was studied, and it has been shown that the NWs’ height decreases with an increase in their cross-sectional area. The X-ray diffraction technique, scanning electron microscopy, and X-ray photoelectron spectroscopy showed the high quality of the grown VO2 NWs. A qualitative description of the growth rate of vertical NWs based on the material balance equation is given. The dependence of the growth rate of vertical and horizontal NWs on the precursor concentration in the gas phase and on the growth time was investigated. It was found that the height of vertical VO2 NWs along the [100] direction exhibited a linear dependence on time and increased with an increase in the precursor concentration. For horizontal VO2 NWs, the height along the direction [011] varied little with the growth time and precursor concentration. These results suggest that the high-aspect ratio vertical VO2 NWs formed due to different growth modes of their crystal faces forming the top of the growing VO2 crystals and their lateral crystal faces related to the difference between the free energies of these crystal faces and implemented experimental conditions. The results obtained permit a better insight into the growth of high-aspect ratio VO2 NWs and into the formation of large VO2 NW arrays with a controlled composition and properties. Full article
(This article belongs to the Section Advanced Nanomaterials and Nanotechnology)
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<p>(<b>a</b>,<b>b</b>) Typical SEM images of the ordered array of free-standing vertical VO<sub>2</sub> NWs grown on a Si substrate in the form of a square nanopillar array. The lateral dimensions of each NW were 80 × 80 nm<sup>2</sup>; they coincided with the lateral dimensions of the silicon nanopillars, their length being about 400 nm. (<b>c</b>) Typical SEM image of the ordered array of horizontal VO<sub>2</sub> NWs grown on a Si substrate in the form of an array of 80 nm width nanostrips with a 180-nm pitch. The approximate lengths of horizontal NWs are indicated with arrows. The height of these NWs was almost independent of their contact area with the substrate. (<b>d</b>) Schematic representation of an array of vertical VO<sub>2</sub> NWs. The purple arrows in (<b>d</b>) illustrate the mechanism of VO<sub>2</sub> NW growth, which includes the direct precursor deposition onto the NW apex (A), diffusion of precursor species to the NW apex from the lateral crystal faces of VO<sub>2</sub> NWs (B) and from the substrate surface through the lateral crystal faces (C).</p>
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<p>The X-ray diffraction spectrum of the horizontally and vertically oriented VO<sub>2</sub> NWs synthesized on the nanoimprinted Si substrate.</p>
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<p>The XPS fine spectrum (O1s and V2p levels) of the VO<sub>2</sub> NWs. Two peaks at 515.8 and 523.5 eV corresponded to V2p<sub>3/2</sub> and V2p<sub>1/2</sub> and showed the V<sup>+4</sup> oxidation state. The presence of the V<sup>+5</sup> component in the VO<sub>2</sub> NWs denotes an over-oxidation, due to the existence of V<sub>2</sub>O<sub>5</sub> at the surface of the VO<sub>2</sub> NWs from air exposure.</p>
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<p>SEM images (side view) of the free-standing vertical VO<sub>2</sub> NWs (upper part of the figure) grown on silicon nanopillars with different cross-sectional areas; the diagrams are shown in the lower part of the figure. SEM image and cross-sectional area of single Si nanopillar with: (<b>a</b>,<b>f</b>) square section of 80 × 80 nm<sup>2</sup>; (<b>b</b>,<b>g</b>) rectangular section of 80 × 180 nm<sup>2</sup>; (<b>c</b>,<b>h</b>) rectangular section of 80 × 440 nm<sup>2</sup>; (<b>d</b>,<b>i</b>) square section of 260 × 260 nm<sup>2</sup>, and (<b>e</b>,<b>j</b>) rectangular section of 260 × 440 nm<sup>2</sup>. In the schematic image, the gray area shows the surface of the silicon nanopillars on which the NWs grow; the light area around is the part of the substrate that was subject to etching during the formation of the periodic nanostructures and on which no crystal nucleation occurred.</p>
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<p>The height of vertical VO<sub>2</sub> NWs as a function of their cross-sectional area. Black squares are the experimental points, straight line <b>A</b> (green dash dot) is the NW height dependence on the NW base area calculated on the assumption of the direct deposition of VO<sub>2</sub> species from the gas phase, and curves <b>B</b> (blue short dot) and <b>C</b> (red short dash) are the dependences calculated by taking into account the diffusion of VO<sub>2</sub> particles to the NW apices from the lateral surface of NWs and from the region of the substrate around the NWs, where there is no VO<sub>2</sub> crystal growth.</p>
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<p>The growth rate of the VO<sub>2</sub> NWs and a polycrystalline VO<sub>2</sub> film as obtained by dividing the NW height by the synthesis time versus the location of NWs relative to the substrate holder edge. The gas flow is directed from left to right.</p>
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<p>Dependence of the height of the VO<sub>2</sub> NWs and a polycrystalline VO<sub>2</sub> film on the synthesis time.</p>
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22 pages, 11885 KiB  
Article
Effect of Air Storage on Stress Corrosion Cracking of ZK60 Alloy Induced by Preliminary Immersion in NaCl-Based Corrosion Solution
by Evgeniy Merson, Vitaliy Poluyanov, Pavel Myagkikh, Dmitri Merson and Alexei Vinogradov
Materials 2022, 15(21), 7862; https://doi.org/10.3390/ma15217862 - 7 Nov 2022
Cited by 6 | Viewed by 1842
Abstract
The preliminary exposure of Mg alloys to corrosion solutions can cause their embrittlement. The phenomenon is referred to as pre-exposure stress corrosion cracking (PESCC). It has been reported that relatively long storage in air after pre-exposure to the corrosion solution is capable of [...] Read more.
The preliminary exposure of Mg alloys to corrosion solutions can cause their embrittlement. The phenomenon is referred to as pre-exposure stress corrosion cracking (PESCC). It has been reported that relatively long storage in air after pre-exposure to the corrosion solution is capable of eliminating PESCC. This effect was attributed to the egress of diffusible hydrogen that accumulated in the metal during pre-exposure. However, recent findings challenged this viewpoint and suggested that the corrosion solution retained within the side surface layer of corrosion products could be responsible for PESCC. The present study is aimed at the clarification of the role of hydrogen and the corrosion solution sealed within the corrosion products in the “healing” effect caused by post-exposure storage in air. Using the slow strain rate tensile (SSRT) testing in air and detailed fractographic analysis of the ZK60 specimens subjected to the liquid corrosion followed by storage in air, we found that PESCC was gradually reduced and finally suppressed with the increasing time and temperature of air storage. The complete elimination of PESCC accompanied by recovery of elongation to failure from 20% to 38% was achieved after 24 h of air storage at 150–200 °C. It is established that the characteristic PESCC zone on the fracture surface is composed of two regions, of which the first is always covered by the crust of corrosion products, whereas the second one is free of corrosion products and is characterised by quasi-brittle morphology. It is argued that the corrosion solution and hydrogen stored within the corrosion product layer are responsible for the formation of these two zones, respectively. Full article
(This article belongs to the Special Issue Corrosion and Mechanical Behavior of Metal Materials)
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<p>Stress–strain diagrams corresponding to the specimens of the ZK60 alloy which were SSRT tested in the reference and CP-free state as well as after pre-exposure to the corrosion solution followed by storage in air. Temperatures of air storage (in °C) are provided at the arrows. The duration of storage in air was 24 h, if not marked otherwise.</p>
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<p>The effect of temperature of air storage on elongation to failure (<b>a</b>) and ultimate tensile strength (<b>b</b>) of the reference, CP-free, and pre-exposed specimens of the ZK60 alloy. The open and filled symbols indicate the pre-exposed specimens after air storage for 2 min and 24 h, respectively.</p>
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<p>Whole views of the fracture surfaces of the specimens SSRT tested after pre-exposure followed by storage in air at 24 °C for 2 min (<b>a</b>) and by 24 h, at 24 °C (<b>b</b>), 50 °C (<b>c</b>), 80 °C (<b>d</b>), 100 °C (<b>e</b>), 120 °C (<b>f</b>), 150 °C (<b>g</b>), and 200 °C (<b>h</b>).</p>
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<p>The effect of temperature of post-exposure storage on the areal fractographic characteristics of the ZK60 specimens tested after pre-exposure followed by air storage (<b>a</b>) and the correlation between these characteristics and the elongation to failure of the specimens (<b>b</b>). The open and filled symbols correspond to the pre-exposed samples subjected to air storage for 2 min and 24 h, respectively.</p>
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<p>SEM images of side surfaces of the specimens SSRT tested after pre-exposure followed by air storage at 24 °C for 2 min (<b>a</b>), and by 24 h at 24 °C (<b>b</b>), 50 °C (<b>c</b>), 80 °C (<b>d</b>), 100 °C (<b>e</b>), 120 °C (<b>f</b>), 150 °C (<b>g</b>), and 200 °C (<b>h</b>).</p>
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<p>The appearance of the side surface cracks in the specimens SSRT tested after pre-exposure followed by 24 h of air storage at: 24 °C (<b>a</b>,<b>d</b>), 80 °C (<b>b</b>,<b>e</b>), and 100 °C (<b>c</b>,<b>f</b>). The magnified SEM images of the regions outlined by the frames A–C in (<b>a</b>–<b>c</b>) are represented in (<b>d</b>–<b>f</b>) to show the microscopic characteristics of side surface cracks.</p>
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<p>The fractographic features of the specimen SSRT tested after pre-exposure followed by 24 h of air storage at 24 °C: (<b>a</b>) the peripheral region of the fracture surface with PESCC zone delimited from the ductile region by the dotted curve. The vertical white and inclined red arrows indicate the nucleation points of the multiple cracks and the shearing ligaments between them, respectively; (<b>b</b>) the magnified SEM image with elemental EDS maps of the region outlined by the frame A in (<b>a</b>) showing the boundaries of the specific regions; (<b>c</b>) the magnified SEM image of the region outlined by the frame B in (<b>b</b>) showing the crack’s nucleation part of the corrosion product region (CPR) characterised by cleavage and intergranular facets and corrosion products; (<b>d</b>) the magnified SEM image of the region outlined by the frame C in (<b>b</b>) showing the transition region between CPR and the quasi-brittle region (QBR); (<b>e</b>) the magnified SEM image of the region outlined by the frame D in (<b>b</b>) showing the transition region between QBR and the ductile region; (<b>f</b>–<b>k</b>) the magnified SEM images of the regions outlined by the frames E–J in (<b>c</b>–<b>e</b>) showing the characteristic morphologies of the specific regions.</p>
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<p>The fractographic features of the specimen SSRT tested after pre-exposure followed by 24 h of air storage at 80 °C: (<b>a</b>) the peripheral region of the fracture surface with isolated islands of PESCC zone delimited from the ductile region by the dotted curve. The vertical white arrows indicate the nucleation points of the multiple cracks; (<b>b</b>) the magnified SEM image with elemental EDX maps of the region outlined by the frame A in (<b>a</b>) showing the boundaries of the specific regions; (<b>c</b>) the magnified SEM image of the region outlined by the frame B in (<b>b</b>) showing the crack’s nucleation part of CPR; (<b>d</b>) the magnified SEM image of the region outlined by the frame C in (<b>b</b>) showing the transition region between CPR and QBR; (<b>e</b>) the magnified SEM image of the region outlined by the frame D in (<b>b</b>) showing the transition region between QBR and ductile region; (<b>f</b>–<b>j</b>) the magnified SEM images of the regions outlined by the frames E–I in (<b>c</b>–<b>e</b>) showing the morphologies characteristic of the specific regions.</p>
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<p>The effect of temperature of post-exposure storage on the linear fractographic characteristics of the ZK60 specimens tested after pre-exposure followed by air storage (<b>a</b>) and the correlation between these characteristics and the elongation to failure of the specimens (<b>b</b>). The open and filled symbols correspond to the pre-exposed samples subjected to air storage for 2 min and 24 h, respectively. CPR—the region covered by the crust of corrosion products, QBR—the quasi-brittle region free of corrosion products.</p>
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<p>The distribution of oxygen on the peripheral part of the fracture surface for the specimens SSRT tested after pre-exposure followed by storage in air at different temperatures and durations. The red solid horizontal lines show the boundary between the CPR and QBR. The dashed line indicates the boundary between the side and fracture surfaces.</p>
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<p>The SEM images and elemental maps obtained by EDX from the side surface of the specimen SSRT tested after pre-exposure in the 4% NaCl + 4% K<sub>2</sub>Cr<sub>2</sub>O<sub>7</sub> corrosion solution (<b>a</b>) and from the fracture surface of the specimen SSRT tested in the same corrosion solution (<b>b</b>).</p>
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<p>The effect of temperature and time of air storage on the concentration of hydrogen extracted in different temperature intervals (<b>a</b>) and on the thermal desorption spectra of hydrogen (<b>b</b>) for ZK60 subjected to pre-exposure followed by air storage at different temperatures. The open and filled symbols in (<b>a</b>) correspond to the pre-exposed samples subjected to air storage for 2 min and 24 h, respectively.</p>
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<p>The correlation between the concentration of hydrogen extracted in different temperature intervals and the elongation to failure (<b>a</b>) and the lengths of specific zones on the fracture surface (<b>b</b>) of the specimens SSRT tested after pre-exposure followed by air storage at different temperatures and durations.</p>
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12 pages, 4228 KiB  
Article
Basic Characteristics of Dose Distributions of Photons Beam for Radiotherapeutic Applications Using YAG:Ce Crystal Detectors
by Janusz Winiecki, Sandra Witkiewicz-Lukaszek, Paulina Michalska, Seweryn Jakubowski, Sergiy Nizhankovskiy and Yuriy Zorenko
Materials 2022, 15(21), 7861; https://doi.org/10.3390/ma15217861 - 7 Nov 2022
Cited by 4 | Viewed by 2285
Abstract
Thermostimulated luminescence (TSL) dosimetry is a versatile tool for the assessment of dose from ionizing radiation. In this work, the Ce3+ doped Y3Al5O12 garnet (YAG:Ce) with a density ρ = 4.56 g/cm3 and effective atomic number [...] Read more.
Thermostimulated luminescence (TSL) dosimetry is a versatile tool for the assessment of dose from ionizing radiation. In this work, the Ce3+ doped Y3Al5O12 garnet (YAG:Ce) with a density ρ = 4.56 g/cm3 and effective atomic number Zeff = 35 emerged as a prospective TSL material in radiotherapy applications due to its excellent radiation stability, uniformity of structural and optical properties, high yield of TSL, and good position of main glow peak around 290–300 °C. Namely, the set of TSL detectors produced from the YAG:Ce single crystal is used for identification of the uniformity of dose and energy spectra of X-ray radiation generated by the clinical accelerator with 6 MV and 15 MV beams located in Radiotherapy Department at the Oncology Center in Bydgoszcz, Poland. We have found that the YAG:Ce crystal detects shows very promising results for registration of X-ray radiation generated by the accelerator with 6 MV beam. The next step in the research is connected with application of TSL detectors based on the crystals of much heavier garnets than YAG. It is estimated that the LuAG:Ce garnet crystals with high density ρ = 6.0 g/cm3 and Zeff = 62 can be used to evaluate the X-rays produced by the accelerator with the 15 MV beam. Full article
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<p>The position of the samples on the table of Clinac 2300CD Silhouette (Varian Medical Systems, Palo Alto, CA, USA) accelerator relative to the center of target (<b>left side</b>) and the position of the YAG:Ce detectors on the experimental x-y plane (<b>right side</b>). The positions of the detectors are also identified by numbers in the x-y plane of the right figure.</p>
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<p>TSL reader at Chair for Optoelectronic Materials of the Institute of Physics Kazimierz Wielki University in Bydgoszcz.</p>
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<p>Different types of radiation used in this work (<b>top</b>); the schematic dependence of wavelength λ of X-rays on the type of radiation (<b>bottom</b>).</p>
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<p>Typical beam profile for radiotherapeutic applications.</p>
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<p>Diagram of the beam collimation system in a standard medical accelerator—Linac head.</p>
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<p>High energy X-ray (6 MV and 15 MV) intensity (I) and radiation quality (QI) off-axis characteristics at selected stages of therapeutic beam generation in a classic medical accelerator—simplification.</p>
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<p>Influence of wedge filter on beam intensity distribution: (<b>a</b>) open field (no wedge), (<b>b</b>) left side wedge orientation, (<b>c</b>) right side wedge orientation.</p>
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<p>Effect of simultaneous work of flattening filter and hard wedge for both wedge orientations.</p>
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<p>(<b>a</b>) Dependence of TSL peak intensity and peak position for YAG:Ce crystal sample on irradiation dose by continuous X-ray photons working with NAP in the 40–140 KV range and current in the 200–400 mA range; (<b>b</b>) TSL intensity as a function of the dose of irradiation for the YAG:Ce crystal detector.</p>
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<p>(<b>a</b>) TSL glow curves for YAG:Ce crystal samples irradiated by 6 MV X-ray photons from a Clinac 2300 accelerator in open field mode; (<b>b</b>) dependence of intensity of TSL peaks on the distance x between sample and centers of target (see <a href="#materials-15-07861-f001" class="html-fig">Figure 1</a>).</p>
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<p>(<b>a</b>) TSL glow curves for YAG:Ce crystal samples irradiated by 6 MV X-ray photons from Clinac 2300 accelerator in the case of using additional 60°_Left (<b>a</b>) and 60°_Right (<b>b</b>) wedges (see <a href="#materials-15-07861-f008" class="html-fig">Figure 8</a>).</p>
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<p>(<b>a</b>) Dependence of intensity of TSL glow curves for YAG:Ce crystal detector on the dose of irradiation by <sup>60</sup>Co source; (<b>b</b>) intensity of TSL glow peaks of YAG:Ce crystal at 220 °C (1) and 285 °C (2) source and I<sub>285</sub>/I<sub>220</sub> ratio of intensity of these peaks (3) on dose of γ rays irradiation by <sup>60</sup>Co.</p>
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<p>(<b>a</b>) TSL glow curves for YAG:Ce crystal detector irradiated by 15 MV X-ray photons from a Clinac 2300 accelerator in open field mode; (<b>b</b>) dependence of the intensity of two TSL peaks of YAG:Ce crystal at 220 °C (1) and 285 °C (2) on the distance x between sample and centers of target.</p>
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<p>(<b>a</b>,<b>b</b>) TSL glow curves for YAG:Ce crystal detectors irradiated by 15 MV X-ray photons from a Clinac 2300 accelerator in the case of using additional wedges 60o_Left (<b>a</b>) and 60o_R-right (<b>b</b>); (<b>c</b>) dependence of the intensity of TSL peaks on distance x between sample and center of target (see <a href="#materials-15-07861-f001" class="html-fig">Figure 1</a> and <a href="#materials-15-07861-f009" class="html-fig">Figure 9</a>).</p>
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<p>(<b>a</b>) Position of LuAG:Ce crystal samples on the experimental x-y plane. (<b>b</b>) TSL glow curves for set of LuAG:Ce crystal detectors irradiated by 15 MV X-ray photons from a Clinac 2300 accelerator in the open field mode.</p>
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10 pages, 5023 KiB  
Article
Quasi-One-Dimensional Linarite-Type PbCu(SeO4)(OH)2 with Competing Nearest-Neighbor and Next-Nearest-Neighbor Intrachain Exchange Interactions
by Maria Markina, Konstantin Zakharov, Yevgeniy Ovchenkov, Grigoriy Pashkov, Konstantin Lyssenko, Petr Berdonosov, Zlata Pchelkina and Alexander Vasiliev
Materials 2022, 15(21), 7860; https://doi.org/10.3390/ma15217860 - 7 Nov 2022
Viewed by 1774
Abstract
PbCu(SeO4)(OH)2, the selenate sibling of the mineral linarite, was synthesized hydrothermally, investigated in measurements of magnetization M, specific heat Cp and dielectric permittivity ε, and analyzed within density functional theory formalism. This quasi-one-dimensional compound evidences formation [...] Read more.
PbCu(SeO4)(OH)2, the selenate sibling of the mineral linarite, was synthesized hydrothermally, investigated in measurements of magnetization M, specific heat Cp and dielectric permittivity ε, and analyzed within density functional theory formalism. This quasi-one-dimensional compound evidences formation of a short-range correlation regime at T* ~ 8 K and experiences a long-range magnetic order at TN = 4.3 K. A magnetization saturation of approximately 1 µB is reached at µ0Hflip ~ 16 T preceded by a jump at µ0Hflop = 2.4 T. Additionally, there are multiple indicators of the formation of an additional electrically active phase above the Neel temperature, which suggests that PbCu(SeO4)(OH)2 is a multiferroic system. Full article
(This article belongs to the Section Materials Physics)
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<p>The crystal structure of PbCu(SeO<sub>4</sub>)(OH)<sub>2</sub>. CuO<sub>4</sub> squares and SeO<sub>4</sub> groups are shown. The chain of CuO<sub>4</sub> squares is shown at the low part of the figure.</p>
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<p>Temperature dependences of magnetic susceptibility <span class="html-italic">χ</span> in PbCu(SeO<sub>4</sub>)(OH)<sub>2</sub> taken at <span class="html-italic">µ<sub>0</sub>H</span> = 0.1 T in both FC and ZFC regimes. Inset: <span class="html-italic">dχ</span>/<span class="html-italic">dT</span> curves taken at various magnetic fields.</p>
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<p>Field dependence of magnetization <span class="html-italic">M</span> in PbCu(SeO<sub>4</sub>)(OH)<sub>2</sub> in a pulsed magnetic field at <span class="html-italic">T</span> = 2.4 K normalized by measurements in the static magnetic field. Inset: <span class="html-italic">dM</span>/<span class="html-italic">dH</span> curve.</p>
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<p>Temperature dependence of specific heat <span class="html-italic">C<sub>p</sub></span> in PbCu(SeO<sub>4</sub>)(OH)<sub>2</sub>. Inset: <span class="html-italic">C<sub>p</sub></span>(<span class="html-italic">T</span>) curves taken at various magnetic fields.</p>
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<p>Temperature dependences of dielectric permittivity <span class="html-italic">ε/ε<sub>0</sub></span> in PbCu(SeO<sub>4</sub>)(OH)<sub>2</sub> taken at <span class="html-italic">f</span> = 5 kHz in various magnetic fields. Inset: temperature dependences of dielectric permittivity taken at <span class="html-italic">µ<sub>0</sub>H</span> = 7 T for various frequencies.</p>
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<p>Magnetic phase diagram in PbCu(SeO<sub>4</sub>)(OH)<sub>2</sub> as derived from measurements of magnetization <span class="html-italic">M</span>, specific heat <span class="html-italic">C<sub>p</sub></span> and dielectric permittivity <span class="html-italic">ε</span>.</p>
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14 pages, 3858 KiB  
Article
Computational Probing of Tin-Based Lead-Free Perovskite Solar Cells: Effects of Absorber Parameters and Various Electron Transport Layer Materials on Device Performance
by Arunkumar Prabhakaran Shyma and Raja Sellappan
Materials 2022, 15(21), 7859; https://doi.org/10.3390/ma15217859 - 7 Nov 2022
Cited by 18 | Viewed by 2867
Abstract
Tin-based perovskite solar cells have gained global research attention due to the lead toxicity and health risk associated with its lead-based analog. The promising opto-electrical properties of the Tin-based perovskite have attracted researchers to work on developing Tin-based perovskite solar cells with higher [...] Read more.
Tin-based perovskite solar cells have gained global research attention due to the lead toxicity and health risk associated with its lead-based analog. The promising opto-electrical properties of the Tin-based perovskite have attracted researchers to work on developing Tin-based perovskite solar cells with higher efficiencies comparable to lead-based analogs. Tin-based perovskites outperform lead-based ones in areas such as optimal band gap and carrier mobility. A detailed understanding of the effects of each parameter and working conditions on Tin-based perovskite is crucial in order to improve efficiency. In the present work, we have carried out a numerical simulation of a planar heterojunction Tin-based (CH3NH3SnI3) perovskite solar cell employing a SCAPS 1D simulator. Device parameters, namely, the thickness of the absorber layer, the defect density of the absorber layer, working temperature, series resistance, and metalwork function, were exclusively investigated. ZnO was employed as the ETL (electron transport layer) material in the initial simulation to obtain optimized parameters and attained a maximum efficiency of 19.62% with 1.1089 V open circuit potential (Voc) at 700 nm thickness (absorber layer). Further, different ETL materials were introduced into the optimized device architecture, and the Zn2SnO4-based device delivered an efficiency of 24.3% with a Voc of 1.1857 V. The obtained results indicate a strong possibility to model and construct better-performing perovskite solar cells based on Tin (Sn) with Zn2SnO4 as the ETL layer. Full article
(This article belongs to the Topic Perovskites for Energy Applications)
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<p>(<b>a</b>) Device architecture of the Sn based perovskite solar cell and (<b>b</b>) Energy band alignment for the proposed devices.</p>
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<p>Equivalent electrical circuit diagram for a solar cell under illumination.</p>
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<p>Effect of absorber layer thickness on (<b>a</b>) efficiency and (<b>b</b>) V<sub>oc</sub>.</p>
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<p>(<b>a</b>) Efficiency as a function of metal work function with varying back contacts and metal built in potential according to the metal contact (Inset). (<b>b</b>) Band diagram of constructed perovskite solar cell with different back contacts.</p>
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<p>Effect of density of States on (<b>a</b>) efficiency and (<b>b</b>) V<sub>oc</sub> of the device.</p>
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<p>Effect of device temperature on (<b>a</b>) efficiency, (<b>b</b>) V<sub>oc</sub> (<b>c</b>) J<sub>sc</sub> and (<b>d</b>) Fill factor.</p>
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<p>Effect of absorber layer defect density on (<b>a</b>) efficiency, (<b>b</b>) V<sub>oc</sub>, (<b>c</b>) fill factor and (<b>d</b>) J<sub>sc</sub> (<b>e</b>) recombination rate inside perovskite.</p>
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<p>Effect of series resistance on (<b>a</b>) efficiency and (<b>b</b>) fill factor.</p>
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<p>(<b>a</b>) J-V curves and (<b>b</b>) external quantum efficiency of initial and final device based on ZnO ETL.</p>
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<p>J-V curves for different ETL materials.</p>
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11 pages, 978 KiB  
Article
Comparative Evaluation of Two Different Fiber-Reinforced Composite Materials in Class 1 Post-Endodontic Restorations in Molars—A Randomized Clinical Study
by Suwidhi Ranka, Ajay Singh Rao, Unnati Shah, Dikshit Solanki, Ajinkya M. Pawar, Rodolfo Reda, Alessio Zanza and Luca Testarelli
Materials 2022, 15(21), 7858; https://doi.org/10.3390/ma15217858 - 7 Nov 2022
Cited by 8 | Viewed by 3258
Abstract
This study aimed to evaluate and compare two different fiber-reinforced composite materials in class I post-endodontic restoration in molars. A total of 50 patients were randomly assigned into two groups (n = 25 for each group); group A: everX Posterior (packable composite) [...] Read more.
This study aimed to evaluate and compare two different fiber-reinforced composite materials in class I post-endodontic restoration in molars. A total of 50 patients were randomly assigned into two groups (n = 25 for each group); group A: everX Posterior (packable composite) with a top layer of solareX (nano-hybrid composite) and group B: everX Flow (flowable composite) with a top layer of G-aenial universal injectable (flowable composite). Patients were evaluated immediately after the procedure (baseline), at 6 months, and at 1 year time intervals based on the modified USPHS criteria. The statistical analysis using a chi-square test showed no statistically significant difference in the clinical performance of group A and group B. Clinical performance of the combination of everX Flow with overlying G-aenial universal injectable composite proved to be comparable with everX Posterior with overlying solareX composite as post-endodontic restorations in class I lesions in permanent molars. Full article
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<p>(<b>a</b>) Endodontically treated tooth; (<b>b</b>) application of universal bonding agent; (<b>c</b>) placement of everX posterior composite; (<b>d</b>) everX posterior composite material; (<b>e</b>) placement of solareX composite; (<b>f</b>) at baseline; (<b>g</b>) 6 months follow-up; (<b>h</b>) 1 year follow-up.</p>
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<p>(<b>a</b>) Endodontically treated tooth; (<b>b</b>) application of universal bonding agent; (<b>c</b>) application of everX flow composite; (<b>d</b>) application of <span class="html-italic">g-aenial</span> universal injectable composite; (<b>e</b>) everX flow composite; (<b>f</b>) g-aenial universal injectable composite; (<b>g</b>) at baseline; (<b>h</b>) 6 months follow-up; (<b>i</b>) 1 year follow-up.</p>
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15 pages, 3395 KiB  
Article
Experimental Study on the Mechanical Properties of Diatomite-Modified Coastal Cement Soil
by Jiyuan Fang, Yunfeng Wang, Kefa Wang, Wenhao Dai, Yanfei Yu and Cuihong Li
Materials 2022, 15(21), 7857; https://doi.org/10.3390/ma15217857 - 7 Nov 2022
Cited by 6 | Viewed by 1968
Abstract
Diatomite is a non-metallic mineral resource rich in SiO2, which can be used to modify coastal cement soil. In order to explore the mechanical modification effect of diatomite on coastal cement soil at the age of 7 days, based on coastal [...] Read more.
Diatomite is a non-metallic mineral resource rich in SiO2, which can be used to modify coastal cement soil. In order to explore the mechanical modification effect of diatomite on coastal cement soil at the age of 7 days, based on coastal cement soil with cement content of 5% (mass fraction), diatomite of 0%, 5%, 10%, 15% and 20% (mass fraction) was mixed for modification. Through the unconfined compressive strength test, the triaxial unconsolidated undrained test, backscattered electron imaging (BSE), and energy-dispersive spectroscopy (EDS) technology, the influence of diatomite content and confining pressure on the peak strength of modified coastal cement soil was explored. The empirical formula between the peak strength of the DE specimen and the content of diatomite and confining pressure was established by curve fitting, and the fitting effect was ideal. When diatomite was mixed with coastal cement soil, the optimal dosage of diatomite was 5% from the perspective of mechanical properties and economic benefits of the maximum growth rate of compression and shear. The unconfined compressive strength test showed that the peak strength and elastic modulus of the modified coastal cement soil with 5% diatomite content were 37% and 57% higher than those of cement soil, respectively. The triaxial unconsolidated undrained test showed that the internal friction angle of the modified coastal cement soil was stable at about 30°, and cohesion of DE-5, DE-10, DE-15, and DE-20 increased by 28%, 48%, 78%, and 97%, respectively, compared to cement soil. The microscopic test found that the pore distribution of modified coastal cement soil is closely related to the strength change. The results show that the addition of diatomite can effectively improve the mechanical properties of soil-cement. Full article
(This article belongs to the Special Issue Mechanical Performance of Composite Geomaterials)
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<p>Grain-grading diagram of coastal soft soil with particle size below 2 mm.</p>
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<p>Schematic diagram of adding diatomite to cement soil.</p>
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<p>Standard specimen preparation diagram. (<b>a</b>–<b>g</b>). (<b>a</b>) is the drying soil in the process of sample preparation. (<b>b</b>) is the soil broken by the pulverizer during sample preparation. (<b>c</b>) is a mixture prepared during sample preparation. (<b>d</b>) shows the process of adding the mixture to the mold during sample preparation. (<b>e</b>) is a hydrostatic die during sample preparation to shape the soil sample. (<b>f</b>) shows the sample being pushed out of the die using jack pressure during the sample preparation process. (<b>g</b>) shows that the sample is prepared and put into the curing box for curing.</p>
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<p>Stress–strain curves of coastal cement soil modified with different amounts of diatomite. (<b>a</b>) and (<b>b</b>) are the initial and failure images of specimens, respectively.</p>
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<p>The elastic modulus of coastal cement soil specimens modified with different amounts of diatomite.</p>
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<p>Deviatoric stress–strain relationship curves of specimens with different diatomite contents. (1) and (2) are the initial and failure images of specimens, respectively.</p>
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<p>Deviatoric stress–strain relationship curves of specimens with different diatomite contents. (1) and (2) are the initial and failure images of specimens, respectively.</p>
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<p>Mohr envelope of specimens with different diatomite contents.</p>
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<p>Peak intensity of specimens with different diatomite contents under different confining pressures.</p>
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<p>Comparison of the measured and predicted peak intensities with 20% diatomite content.</p>
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<p>BSE photos and EDS images of coastal marine soil specimens modified with different amounts of diatomite. (<b>a</b>) BSE image of DE-0,500 times, (<b>b</b>) BSE image of DE-10,500 times, (<b>c</b>) BSE image of DE-15,500 times, (<b>d</b>) BSE image of DE-20,500 times, (<b>e</b>) BSE image of DE-0,500 times, and (<b>f</b>) EDS image of DE-5.</p>
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<p>Relationship between the porosity and strength of diatomite-modified coastal cement soil; the intensity or porosity of diatomite varied from one dosage to the next.</p>
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17 pages, 3855 KiB  
Article
Supercapacitor Properties of rGO-TiO2 Nanocomposite in Two-component Acidic Electrolyte
by Yury M. Volfkovich, Alexey Y. Rychagov, Valentin E. Sosenkin, Sergey A. Baskakov, Eugene N. Kabachkov and Yury M. Shulga
Materials 2022, 15(21), 7856; https://doi.org/10.3390/ma15217856 - 7 Nov 2022
Cited by 9 | Viewed by 2732
Abstract
The electrochemical properties of the highly porous reduced graphene oxide/titanium dioxide (rGO/TiO2) nanocomposite were studied to estimate the possibility of using it as a supercapacitor electrode. Granular aerogel rGO/TiO2 was used as an initial material for the first time of [...] Read more.
The electrochemical properties of the highly porous reduced graphene oxide/titanium dioxide (rGO/TiO2) nanocomposite were studied to estimate the possibility of using it as a supercapacitor electrode. Granular aerogel rGO/TiO2 was used as an initial material for the first time of manufacturing the electrode. For the aerogel synthesis, industrial TiO2 Hombikat UV100 with a high specific surface area and anatase structure was used, and the aerogel was carried out with hydrazine vapor. Porous structure and hydrophilic–hydrophobic properties of the nanocomposite were studied with a method of standard contact porosimetry. This is important for a supercapacitor containing an aqueous electrolyte. It was found that the hydrophilic specific surface area of the nanocomposite was approximately half of the total surface area. As a result of electrochemical hydrogenation in the region of zero potential according to the scale of a standard hydrogen electrode, a reversible Faraday reaction with high recharge rate (exchange currents) was observed. The characteristic charging time of the indicated Faraday reaction does not exceed several tens of seconds, which makes it possible to consider the use of this pseudocapacitance in the systems of fast energy storage such as hybrid supercapacitors. Sufficiently high limiting pseudo-capacitance (about 1200 C/g TiO2) of the reaction was obtained. Full article
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<p>Photographs of composite aerogel after reduction (<b>A</b>) and before reduction (<b>B</b>).</p>
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<p>Survey XPS spectrum of the nanocomposites containing 15 mass % TiO<sub>2</sub>. Insertion: elemental composition of the sample surface.</p>
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<p>High-resolution XPS spectra of C1s and N1s of the nanocomposites containing 15 mass % TiO<sub>2</sub>.</p>
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<p>SEM micrographs of composite (<b>A</b>) and pure (<b>B</b>) aerogels.</p>
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<p>Results of porosimetric investigation for the rGO/TiO<sub>2</sub> nanocomposite containing 30% TiO<sub>2</sub>: (<b>a</b>) integral pore volume distribution; (<b>b</b>) differential pore volume distribution; (<b>c</b>) differential pore surface distribution; (<b>d</b>) wetting angle as a function of pore radius. Data obtained using octane (1) and water (2) as working fluids.</p>
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<p>Cyclic cathodic polarization of the composite with 15 wt. % and 30 wt. % TiO<sub>2</sub>; 8 successive cycles are shown, they lead to an increase in the reversible hydrogen pseudocapacity.</p>
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<p>CVF curves: 1—rGO/TiO<sub>2</sub> 15% (EDL region before cathodic polarization), 2—rGO/TiO<sub>2</sub> 30% (EDL region before cathodic polarization), 3—rGO/TiO<sub>2</sub> 15% (after deep cathodic polarization), 4—rGO/TiO<sub>2</sub> 30% (after deep cathodic polarization).</p>
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<p>CVA curves (at 1 mV/s) in the field of reversible hydrogen pseudocapacitance after deep cathodic polarization: 1—rGO/TiO<sub>2</sub> 15%; 2—rGO/TiO<sub>2</sub> 30%.</p>
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<p>Galvanostatic charging curves of rGO/TiO<sub>2</sub> 15% (<b>a</b>), rGO/TiO<sub>2</sub> 30% (<b>b</b>) and composites, which were obtained at discharging current of 240 mA/g for different time of potentiostatic charging at −1.2 V: 1—5 s; 2—10 s; 3—20 s; 4—50 s; 5—100 s; 6—200 s; 7—500 s.</p>
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<p>Dependence of pseudocapacitance, which was obtained from the data of galvanostatic discharging (see <a href="#materials-15-07856-f008" class="html-fig">Figure 8</a>) and recalculated per mass unit of TiO<sub>2</sub>, on the square root of charging time. 1—rGO/TiO<sub>2</sub> 15%; 2—rGO/TiO<sub>2</sub> 30%.</p>
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<p>(<b>a</b>) Nyquist diagram for the rGO/TiO<sub>2</sub> 15% composite for different states of the electrode: 1—EDL region (−150 mV); 2—region of charged pseudocapacitance of TiO<sub>2</sub> (−880 mV). The insertion illustrates the region of mid frequencies in large scale. The frequency diapason was 100 kHz to 10 MHz. (<b>b</b>) Nyquist diagram for the rGO/TiO<sub>2</sub> 30% composite for different states of the electrode: 1—EDL region (−200 mV); 2—region of charged pseudocapacitance of TiO<sub>2</sub> (−900 mV). The insertion illustrates the region of mid frequencies in large scale. The frequency diapason was 100 kHz to 10 MHz.</p>
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<p>(<b>a</b>) Region of Bode diagram (from 100 Hz to 0.1 Hz) for the rGO/TiO<sub>2</sub> 15% composite: 1—(Re) for the EDL region (−150 mV); 2—(Re) for the region of charged pseudocapacitance of TiO<sub>2</sub> (−880 mV); 3—(−Im) for the region of charged pseudocapacitance of TiO<sub>2</sub> (−880 mV); 4—(−Im) for the EDL region (−150 mV). (<b>b</b>) Region of Bode diagram (from 100 Hz to 0.1 Hz) for the composites of rGO/TiO<sub>2</sub> 30%: 1—(Re) for the EDL region (−200 mV); 2—(Re) for the region of charged pseudocapacitance of TiO<sub>2</sub> (−900 mV); 3—(−Im) for the region of charged pseudocapacitance of (−900 mV); 4—(−Im) for he EDL region (−200 mV).</p>
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<p>Equivalent electrical circuit and Nyquist diagram for experimental spectra (red circles) and for spectra obtained by fitting an equivalent electrical circuit (black lines). 1, 3—for rGO/TiO<sub>2</sub> 15% composite; 2, 4—for rGO/TiO<sub>2</sub> 30% composite.</p>
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18 pages, 9126 KiB  
Article
Tensile Behaviour of Double- and Triple-Adhesive Single Lap Joints Made with Spot Epoxy and Double-Sided Adhesive Tape
by Przemysław Golewski
Materials 2022, 15(21), 7855; https://doi.org/10.3390/ma15217855 - 7 Nov 2022
Cited by 5 | Viewed by 2162
Abstract
Dual adhesives are mainly used to increase the strength of single lap joints (SLJs) by reducing the stress concentration at its ends. However, they can also be used to design the characteristics of the joint so that its operation and failure occur in [...] Read more.
Dual adhesives are mainly used to increase the strength of single lap joints (SLJs) by reducing the stress concentration at its ends. However, they can also be used to design the characteristics of the joint so that its operation and failure occur in several stages. This paper presents the results of uniaxial tensile tests for dual-adhesive and triple-adhesive SLJs. The adherends were made of aluminum and glass fiber-reinforced polymer (GFRP) composite. For dual-adhesive SLJs, 10 epoxies and 1.6 mm thick double-sided adhesive tape were used. The stiffest (Epidian 53 (100 g) + “PAC” hardener (80 g)) and most elastic (Scotch-Weld 2216 B/A Translucent) joints were determined, which were then used in a triple-adhesive joint with the same double-sided adhesive tape. Circular holes of different diameters from 8 mm to 20 mm were made in the double-sided adhesive tape, which were filled with liquid epoxy adhesive by injection after the adherends were joined. By using the double-sided adhesive tape, the geometry of the epoxy joints was perfect, free of spews, and had a constant thickness. The effect of the spot epoxy joint diameters and the arrangement of stiff and elastic joints in the SLJs were analyzed using digital image correlation (DIC). Full article
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<p>Structure of the dual-adhesive sample for the first stage of the study.</p>
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<p>Structure of the triple-adhesive sample in the second stage of study.</p>
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<p>Schemes of lap construction in triple-adhesive samples.</p>
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<p>Triple-adhesive samples: (<b>a</b>) stages of fabrication; (<b>b</b>) completed samples.</p>
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<p>Static tensile test for dual-adhesive type specimens: (<b>a</b>) specimen during testing, (<b>b</b>) force–displacement diagram (specimen 1_2).</p>
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<p>Summary of results of the first stage of joint operation: (<b>a</b>) summary of maximum forces, (<b>b</b>) comparison of stiffness for epoxy joints.</p>
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<p>Triple-adhesive samples, batch 1.</p>
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<p>Triple-adhesive samples, batch 2.</p>
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<p>Triple-adhesive samples, batch 3.</p>
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<p>Triple-adhesive samples, batch 4.</p>
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<p>Triple-adhesive samples, batch 5.</p>
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<p>Triple-adhesive group “S” samples after damage.</p>
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<p>Triple-adhesive group “E” samples after damage.</p>
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<p>Determination of maximum forces and energies for triple-adhesive specimens.</p>
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<p>Summary of maximum forces for samples of group: (<b>a</b>) “S” and (<b>b</b>) “E”.</p>
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<p>Summary of damage energy for samples of group: (<b>a</b>) “S” and (<b>b</b>) “E”.</p>
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<p>Comparison of principal strain maps for “S” and “E” batch 1 specimens for maximum force in the second stage of operation.</p>
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<p>Comparison of principal strain maps for “S” and “E” batch 2 specimens for maximum force in the second stage of operation.</p>
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<p>Comparison of principal strain maps for “S” and “E” batch 3 specimens for maximum force in the second stage of operation.</p>
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<p>Comparison of principal strain maps for “S” and “E” batch 4 specimens for maximum force in the second stage of operation.</p>
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<p>Comparison of principal strain maps for “S” and “E” batch 5 specimens for maximum force in the second stage of operation.</p>
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15 pages, 2270 KiB  
Article
Effect of Super-Absorbent Polymer (SAP) Incorporation Method on Mechanical and Shrinkage Properties of Internally Cured Concrete
by Xingliang Huang, Xiaoyu Liu, Hongliu Rong, Xiaolong Yang, Yunsheng Duan and Tingting Ren
Materials 2022, 15(21), 7854; https://doi.org/10.3390/ma15217854 - 7 Nov 2022
Cited by 13 | Viewed by 2870
Abstract
To study the effect of SAP incorporation on the early shrinkage of SAP internally cured concrete with the aim to solve the problems of early shrinkage and cracking of bridge leveling-layer concrete, using the SAP incorporation method as a parameter, the mechanical properties [...] Read more.
To study the effect of SAP incorporation on the early shrinkage of SAP internally cured concrete with the aim to solve the problems of early shrinkage and cracking of bridge leveling-layer concrete, using the SAP incorporation method as a parameter, the mechanical properties test of internally cured concrete, the shrinkage performance test of ring restraint and the scanning electron microscope observation test were carried out. The effects of the SAP content and incorporation method on the flowability, mechanical properties, shrinkage performance and microstructure of internally cured concrete were analyzed. The experimental results show that when the content of the SAP in concrete is 0.2% of the mass of cementitious materials, it has the least influence on the compressive strength of concrete. The addition of preabsorbed water to the SAP can delay early cement hydration, increase the later cement hydration rate and final hydration degree, and improve the concrete strength. Preabsorbed water mixed with an SAP can effectively improve the shrinkage of concrete, and the shrinkage reduction effect is more obvious than that from the dry addition of the SAP; the early cracking risk of concrete without an SAP is high, and it will crack before day 28. The addition of an SAP can strengthen the microstructure of concrete and improve its density and crack resistance, effectively avoiding concrete cracking. It is recommended that the water-absorbent resin be incorporated in a preabsorbent manner, and the SAP preabsorbent ratio is equal to the maximum water storage rate of the SAP. Full article
(This article belongs to the Collection Concrete and Building Materials)
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<p>Concrete slump with different SAP contents.</p>
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<p>The 28 d compressive strength of concrete.</p>
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<p>Development of concrete strength under different SAP incorporation methods.</p>
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<p>The strain value of the steel ring.</p>
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<p>Cracks in concrete rings (the left is J0, and the right is G0). (<b>a</b>) Two cracks appeared in the concrete ring; (<b>b</b>) A crack appeared in the concrete ring.</p>
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<p>SEM image of concrete sample. (<b>a</b>) J0 (×500); (<b>b</b>) J0 (×2000); (<b>c</b>) G0 (×500); (<b>d</b>) G0 (×2000); (<b>e</b>) Y1 (×500); (<b>f</b>) Y1 (×2000).</p>
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<p>Hydration mechanism of SAP internally cured concrete.</p>
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10 pages, 985 KiB  
Article
Possible Utilization of Distillery Waste in the Carbonization Process
by Jacek Kluska
Materials 2022, 15(21), 7853; https://doi.org/10.3390/ma15217853 - 7 Nov 2022
Cited by 1 | Viewed by 1657
Abstract
This paper characterizes the carbonization process in terms of the utilization of distillery waste in a laboratory-scale reactor. Due to the increase in market prices of wood and environmental protection laws, biomass waste, including distillery waste, is a potential source for biochar production. [...] Read more.
This paper characterizes the carbonization process in terms of the utilization of distillery waste in a laboratory-scale reactor. Due to the increase in market prices of wood and environmental protection laws, biomass waste, including distillery waste, is a potential source for biochar production. An experimental investigation of the carbonization process was carried out for different mixtures of distillery waste and oak sawdust. The obtained results showed that due to the European Standard, biochar from distillery waste could be used for the production of charcoal briquettes for barbecue applications. In addition, biochar from carbonization samples with 66, 50, and 33% distillery waste meet the standards defined by the International Biochar Initiative for HMs content. The analysis of the dynamics of the heating rate showed that adding wood to distillery waste significantly shortens the carbonization process, but this reduces the number of bio-oils produced and its calorific value. Full article
(This article belongs to the Special Issue Recent Progress of Biochar and Biomass Pyrolysis)
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<p>Sample pellets.</p>
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<p>The experimental setup.</p>
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<p>Characteristics of the heating rate of the fixed bed in the reactor for different proportions of distillery waste in the pellets.</p>
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<p>Characteristics of bulk density and heating rate for different proportions of distillery waste in the pellets.</p>
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<p>DTG curves of char from carbonization different pellets composition.</p>
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35 pages, 496 KiB  
Review
Biomechanical Modelling for Tooth Survival Studies: Mechanical Properties, Loads and Boundary Conditions—A Narrative Review
by Saúl Dorado, Ana Arias and Jesus R. Jimenez-Octavio
Materials 2022, 15(21), 7852; https://doi.org/10.3390/ma15217852 - 7 Nov 2022
Cited by 13 | Viewed by 4738
Abstract
Recent biomechanical studies have focused on studying the response of teeth before and after different treatments under functional and parafunctional loads. These studies often involve experimental and/or finite element analysis (FEA). Current loading and boundary conditions may not entirely represent the real condition [...] Read more.
Recent biomechanical studies have focused on studying the response of teeth before and after different treatments under functional and parafunctional loads. These studies often involve experimental and/or finite element analysis (FEA). Current loading and boundary conditions may not entirely represent the real condition of the tooth in clinical situations. The importance of homogenizing both sample characterization and boundary conditions definition for future dental biomechanical studies is highlighted. The mechanical properties of dental structural tissues are presented, along with the effect of functional and parafunctional loads and other environmental and biological parameters that may influence tooth survival. A range of values for Young’s modulus, Poisson ratio, compressive strength, threshold stress intensity factor and fracture toughness are provided for enamel and dentin; as well as Young’s modulus and Poisson ratio for the PDL, trabecular and cortical bone. Angles, loading magnitude and frequency are provided for functional and parafunctional loads. The environmental and physiological conditions (age, gender, tooth, humidity, etc.), that may influence tooth survival are also discussed. Oversimplifications of biomechanical models could end up in results that divert from the natural behavior of teeth. Experimental validation models with close-to-reality boundary conditions should be developed to compare the validity of simplified models. Full article
(This article belongs to the Special Issue Advances in Dental Composite Materials and Biomaterials)
28 pages, 4335 KiB  
Review
A Review of Radio Frequency Identification Sensing Systems for Structural Health Monitoring
by Muchao Zhang, Zhaoting Liu, Chuan Shen, Jianbo Wu and Aobo Zhao
Materials 2022, 15(21), 7851; https://doi.org/10.3390/ma15217851 - 7 Nov 2022
Cited by 12 | Viewed by 3976
Abstract
Structural health monitoring (SHM) plays a critical role in ensuring the safety of large-scale structures during their operational lifespan, such as pipelines, railways and buildings. In the last few years, radio frequency identification (RFID) combined with sensors has attracted increasing interest in SHM [...] Read more.
Structural health monitoring (SHM) plays a critical role in ensuring the safety of large-scale structures during their operational lifespan, such as pipelines, railways and buildings. In the last few years, radio frequency identification (RFID) combined with sensors has attracted increasing interest in SHM for the advantages of being low cost, passive and maintenance-free. Numerous scientific papers have demonstrated the great potential of RFID sensing technology in SHM, e.g., RFID vibration and crack sensing systems. Although considerable progress has been made in RFID-based SHM, there are still numerous scientific challenges to be addressed, for example, multi-parameters detection and the low sampling rate of RFID sensing systems. This paper aims to promote the application of SHM based on RFID from laboratory testing or modelling to large-scale realistic structures. First, based on the analysis of the fundamentals of the RFID sensing system, various topologies that transform RFID into passive wireless sensors are analyzed with their working mechanism and novel applications in SHM. Then, the technical challenges and solutions are summarized based on the in-depth analysis. Lastly, future directions about printable flexible sensor tags and structural health prognostics are suggested. The detailed discussion will be instructive to promote the application of RFID in SHM. Full article
(This article belongs to the Special Issue Electromagnetic Nondestructive Testing)
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<p>RFID sensor tags for SHM systems.</p>
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<p>Basic RFID sensing system.</p>
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<p>Equivalent circuit of LF/HF RFID tag.</p>
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<p>The equivalent circuit of UHF RFID tag.</p>
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<p>Diagram of RFID crack and corrosion sensor using backscattering: (<b>a</b>) COTS RFID tag as a crack sensor; (<b>b</b>) antenna-based RFID tag as a corrosion sensor.</p>
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<p>Multipath effect in RFID.</p>
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<p>Schematic diagrams of RFID sensing system: (<b>a</b>) deformation model, (<b>b</b>) vibration model.</p>
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<p>Schematic diagram of a vibration sensor tag with vibration-sensitive switches.</p>
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<p>Effects of cracks on current paths. (<b>a</b>) a crack parallel to the width of the rectangular patch leads to an increase in current path along the length of the rectangular path. (<b>b</b>) a crack parallel to the length of the rectangular patch leads to an increase in current path along the width of the rectangular path.</p>
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<p>Two-port sensor tag.</p>
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<p>Schematic of digital integrated RFID sensor tag.</p>
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<p>Block diagram of chipless RFID based sensor system.</p>
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<p>Sensing procedures of chipless RFID sensor tags.</p>
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<p>Effect of metallic surface on RFID tag antenna (image theory).</p>
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21 pages, 7819 KiB  
Article
An Investigation of the Contact Fatigue Characteristics of an RV Reducer Crankshaft, Considering the Hardness Gradients and Initial Residual Stress
by Xin Li, Wen Shao, Jinyuan Tang, Han Ding and Weihua Zhou
Materials 2022, 15(21), 7850; https://doi.org/10.3390/ma15217850 - 7 Nov 2022
Cited by 8 | Viewed by 3138
Abstract
The crankshaft is one of the core components of a Rotate Vector (RV) reducer. The fatigue life of the RV reducer is severely hindered by fatigue failure on the eccentric cylindrical surface of the crankshaft. The hardness gradients and residual stress in the [...] Read more.
The crankshaft is one of the core components of a Rotate Vector (RV) reducer. The fatigue life of the RV reducer is severely hindered by fatigue failure on the eccentric cylindrical surface of the crankshaft. The hardness gradients and residual stress in the crankshaft, associated with machining operations, exert an enormous impact on the rolling contact fatigue (RCF). In this work, a finite element method (FEM)-based three-dimensional elasto-plastic contact model is established to calculate the stress–strain field by taking hardness gradients and initial residual stress into account. The RCF characteristics of an RV reducer crankshaft is investigated by applying modified Fatemi–Socie (FS) multiaxial fatigue criterion. The results indicate that initial residual stress plays an influential role in the fatigue damage by altering the distribution of the maximum normal stress near the contact surface. The modified FS fatigue criterion could better consider the effect of initial residual stress and the shear stress, which significantly improves the prediction accuracy of the contact fatigue life model. The contact fatigue performance could be considerably improved by designing appropriate shot peening parameters to obtain optimized residual stress distribution. Therefore, the technique presented may serve as an important guideline for the anti-fatigue design of an RV reducer crankshaft. Full article
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<p>Fatigue life test system of RV Reducer.</p>
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<p>Macroscopic morphology of crankshaft: (<b>a</b>) the new part; (<b>b</b>) the failed part.</p>
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<p>The SEM micrographs of the eccentric cylindrical surface of the crankshaft: (<b>a</b>) surface of new parts; (<b>b</b>,<b>c</b>) surface after failure.</p>
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<p>Transmission schematic diagram of RV Reducer.</p>
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<p>The curve of the thermal treatment process.</p>
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<p>Schematic diagram: (<b>a</b>) force on cycloid gear; (<b>b</b>) force on cylindrical roller bearing.</p>
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<p>The variation of forces acting on the cylindrical roller bearings.</p>
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<p>The measured hardness data and the empirical hardness curve.</p>
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<p>Residual stress measurement: (<b>a</b>) X-ray diffractometer; (<b>b</b>) Electrolytic polisher.</p>
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<p>The measured residual stress data and the empirical stress curve.</p>
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<p>The residual stress distributions induced by shot peening.</p>
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<p>The contact model of the crankshaft and the cylindrical roller bearing.</p>
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<p>The numerical elasto-plastic contact model.</p>
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<p>The true stress-plastic strain curve.</p>
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<p>The actual residual stress after equilibrium (without external load).</p>
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<p>Definition of the Euler transformations and critical plane search method.</p>
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<p>Computational methodology of predicting fatigue life.</p>
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<p>Variation of <span class="html-italic">γ</span><sub>a</sub> and <span class="html-italic">FD</span><sub>mod</sub> under different lubrication conditions (<span class="html-italic">T<sub>out</sub></span> = 800 N·m, <span class="html-italic">P<sub>h</sub></span> = 1.56 GPa).</p>
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<p>Effect of initial residual stress on <span class="html-italic">σ<sub>n</sub></span><sub>,max</sub> and the fatigue damage (<span class="html-italic">T<sub>out</sub></span> = 800 N·m).</p>
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<p>Effect of output torque on the maximum equivalent plastic strain (Max PEEQ).</p>
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<p>The effect of initial residual stresses on the maximum equivalent plastic strain (Max PEEQ) in RCF cycle (<span class="html-italic">T<sub>out</sub></span> = 1800 N·m, <span class="html-italic">P<sub>h</sub></span> = 2.34 GPa).</p>
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<p>The effect of residual stress on the plastic region scope (<span class="html-italic">T<sub>out</sub></span> = 2000 N·m, <span class="html-italic">P<sub>h</sub></span> = 2.47 GPa).</p>
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<p>The effect of initial residual stress on the von Mises stress field (<span class="html-italic">P<sub>h</sub></span> = 1.56 GPa).</p>
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<p>Variation of contact fatigue life with different initial residual stress states (<span class="html-italic">P<sub>h</sub></span> = 1.56 GPa).</p>
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19 pages, 6527 KiB  
Article
Effect of Substrate Temperature on the Structural, Optical and Electrical Properties of DC Magnetron Sputtered VO2 Thin Films
by Chunzi Zhang, Ozan Gunes, Shi-Jie Wen, Qiaoqin Yang and Safa Kasap
Materials 2022, 15(21), 7849; https://doi.org/10.3390/ma15217849 - 7 Nov 2022
Cited by 5 | Viewed by 2461
Abstract
This study focuses on the effect of the substrate temperature (TS) on the quality of VO2 thin films prepared by DC magnetron sputtering. TS was varied from 350 to 600 °C and the effects on the surface morphology, [...] Read more.
This study focuses on the effect of the substrate temperature (TS) on the quality of VO2 thin films prepared by DC magnetron sputtering. TS was varied from 350 to 600 °C and the effects on the surface morphology, microstructure, optical and electrical properties of the films were investigated. The results show that TS below 500 °C favors the growth of V2O5 phase, whereas higher TS (≥500 °C) facilitates the formation of the VO2 phase. Optical characterization of the as-prepared VO2 films displayed a reduced optical transmittance (T˜) across the near-infrared region (NIR), reduced phase transition temperature (Tt), and broadened hysteresis width (ΔH) through the phase transition region. In addition, a decline of the luminous modulation (ΔT˜lum) and solar modulation (ΔT˜sol) efficiencies of the as-prepared films have been determined. Furthermore, compared with the high-quality films reported previously, the electrical conductivity (σ) as a function of temperature (T) reveals reduced conductivity contrast (Δσ) between the insulating and metallic phases of the VO2 films, which was of the order of 2. These outcomes indicated the presence of defects and unrelaxed lattice strain in the films. Further, the comparison of present results with those in the literature from similar works show that the preparation of high-quality films at TS lower than 650 °C presents significant challenges. Full article
(This article belongs to the Section Thin Films and Interfaces)
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<p>Raman spectra of VO<sub>2</sub> and V<sub>2</sub>O<sub>5</sub> thin films prepared at various substrate temperatures (<span class="html-italic">T<sub>S</sub></span>) on (<b>a</b>) Si and (<b>b</b>) sapphire substrates. Note that the vertical axes are in arbitrary units (a.u.), so the relative magnitudes of the spectra cannot be compared.</p>
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<p>XRD spectra of VO<sub>2</sub> and V<sub>2</sub>O<sub>5</sub> thin films prepared at various substrate temperatures (<span class="html-italic">T<sub>S</sub></span>) on (<b>a</b>) Si and (<b>b</b>) sapphire substrates. Note that the vertical axes are in arbitrary units (a.u.).</p>
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<p>Surface images of VO<sub>2</sub> and V<sub>2</sub>O<sub>5</sub> thin films prepared at various substrate temperatures (<span class="html-italic">T<sub>S</sub></span>) (<b>a</b>) 350 °C, (<b>b</b>) 400 °C, (<b>c</b>) 450 °C, (<b>d</b>) 500 °C, (<b>e</b>) 550 °C, and (<b>f</b>) 600 °C obtained by SEM.</p>
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<p>Surface profile images of VO<sub>2</sub> thin films deposited on Si and sapphire substrates at (<b>a</b>) 500 °C, (<b>b</b>) 550 °C, (<b>c</b>) 600 °C and (<b>d</b>) 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>]. The roughness of the surface is indicated by color mapping, where the maximum (peak), median and minimum (depth) points on the surface are indicated in red, green and blue, respectively. The scale bars are used as a measure of the peaks and depths on the surface of the films.</p>
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<p>Average grain size (GS<sub>avg</sub>) of VO<sub>2</sub> thin films prepared on (<b>a</b>) Si and (<b>b</b>) sapphire substrates. In (<b>b</b>) the dashed vertical line is an asymptote that indicates the near-epitaxial almost flat surface of the film prepared at 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>]. (<b>c</b>,<b>d</b>) present the average (<span class="html-italic">R<sub>a</sub></span>) and root-mean-square (<span class="html-italic">R<sub>q</sub></span>) roughness of films prepared on Si and sapphire substrates, respectively. The dashed lines between the data points are guides to the eye. The data points shown in hollow symbols belong to the films prepared at 650 °C (prepared as described in Ref. [<a href="#B17-materials-15-07849" class="html-bibr">17</a>] but not reported therein).</p>
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<p>Optical transmittance (<math display="inline"><semantics> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> </semantics></math>) spectra of VO<sub>2</sub> thin films deposited at (<b>a</b>) 500 °C, (<b>b</b>) 550 °C, and (<b>c</b>) 600 °C and (<b>d</b>) 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>] on Si and sapphire substrates at 300 K (insulating phase) and 368 K (metallic phase).</p>
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<p>(<b>a</b>) Temperature dependence of optical transmittance (<math display="inline"><semantics> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> </semantics></math>) obtained at a light wavelength of <span class="html-italic">λ</span> = 2500 nm for VO<sub>2</sub> thin films deposited at 500, 550, 600 and 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>]. The phase transition characteristics for heating and cooling cycles for films prepared at (<b>b</b>) 500 °C, (<b>c</b>) 550 °C, (<b>d</b>) 600 °C, and (<b>e</b>) 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>] on Si and sapphire substrates at 300 K (insulating phase) and 368 K (metallic phase).</p>
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<p>(<b>a</b>) Critical temperatures (<span class="html-italic">T</span><sub>IMT</sub>, <span class="html-italic">T</span><sub>MIT</sub> and <span class="html-italic">T<sub>t</sub></span>) of the VO<sub>2</sub> films on Si and sapphire prepared at various substrate temperatures (<span class="html-italic">T<sub>S</sub></span>) obtained at a light wavelength of <span class="html-italic">λ</span> = 2500 nm. (<b>b</b>) Hysteresis (Δ<span class="html-italic">H</span>) and sharpness (FWHM) of the Gaussian curves obtained from <math display="inline"><semantics> <mrow> <mi mathvariant="normal">d</mi> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mo>/</mo> <mi mathvariant="normal">d</mi> <mi>T</mi> </mrow> </semantics></math> vs. <span class="html-italic">T</span> plots in <a href="#materials-15-07849-f007" class="html-fig">Figure 7</a>. In (<b>a</b>) and (<b>b</b>) the data points for films prepared at 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>] are shown in hollow symbols. (<b>c</b>) Comparison of optical transmittance contrast, <math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mo>=</mo> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mo stretchy="false">(</mo> <mn>300</mn> <mrow> <mo> </mo> <mi mathvariant="normal">K</mi> <mo>)</mo> </mrow> <mo>−</mo> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mrow> <mo>(</mo> <mn>368</mn> <mo> </mo> <mi mathvariant="normal">K</mi> <mo>)</mo> </mrow> </mrow> </semantics></math>, obtained at NIR wavelengths <span class="html-italic">λ</span> = 1500 nm, 2000 nm and 2500 nm for films prepared at <span class="html-italic">T<sub>S</sub></span> = 500 (olive), 550 (orange), 600 (navy) and 650 [<a href="#B17-materials-15-07849" class="html-bibr">17</a>] (magenta) °C.</p>
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<p>(<b>a</b>) Luminous transmittance (<math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mrow> <mi>lum</mi> </mrow> </msub> </mrow> </semantics></math>) at 300 K and 368 K and luminous modulation efficiency (<math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <msub> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mrow> <mi>lum</mi> </mrow> </msub> </mrow> </semantics></math> ) obtained for films deposited at various substrates temperatures (<span class="html-italic">T<sub>S</sub></span>). (<b>b</b>) Solar transmittance (<math display="inline"><semantics> <mrow> <msub> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mrow> <mi>sol</mi> </mrow> </msub> </mrow> </semantics></math> ) at 300 K and 368 K and solar modulation efficiency (<math display="inline"><semantics> <mrow> <mi mathvariant="sans-serif">Δ</mi> <msub> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> <mrow> <mi>sol</mi> </mrow> </msub> </mrow> </semantics></math> ) obtained for films deposited at various substrates temperatures (<span class="html-italic">T<sub>S</sub></span>). Data for the substrate temperature (<span class="html-italic">T<sub>S</sub></span>) of 650 °C [<a href="#B17-materials-15-07849" class="html-bibr">17</a>] are presented in hollow symbols.</p>
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<p>Temperature (<span class="html-italic">T</span>) dependence of electrical conductivity (<span class="html-italic">σ</span>) of VO<sub>2</sub> films prepared at various substrate temperatures (<span class="html-italic">T<sub>S</sub></span>). (<b>a</b>) Comparison of <span class="html-italic">T</span> dependence of <span class="html-italic">σ</span> of films prepared at <span class="html-italic">T<sub>S</sub></span> = 500 °C, 550 °C, 600 °C, and 650 °C [<a href="#B32-materials-15-07849" class="html-bibr">32</a>]. The phase transition characteristics for heating and cooling cycles for films prepared at <span class="html-italic">T<sub>S</sub></span> = (<b>b</b>) 500 °C, (<b>c</b>) 550 °C, (<b>d</b>) 600 °C and (<b>e</b>) 650 °C [<a href="#B32-materials-15-07849" class="html-bibr">32</a>].</p>
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<p>Electrical conductivity phase transition properties of VO<sub>2</sub> films prepared on sapphire substrates at various substrate temperatures (<span class="html-italic">T<sub>S</sub></span>). (<b>a</b>) Critical temperatures of the phase transition (<span class="html-italic">T</span><sub>IMT</sub>, <span class="html-italic">T</span><sub>MIT</sub> and <span class="html-italic">T<sub>t</sub></span>). (<b>b</b>) Phase transition parameters (Δ<span class="html-italic">H</span>, FWHM (IMT), and FWHM (MIT)) and the contrast of conductivity, Δ<span class="html-italic">σ</span> = <span class="html-italic">σ</span>(368 K)/<span class="html-italic">σ</span>(300 K). The data points for the substrate temperature 650 °C are from Ref. [<a href="#B32-materials-15-07849" class="html-bibr">32</a>] and displayed in hollow symbols.</p>
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<p>Arrhenius plot of conductivity (<span class="html-italic">σ</span>) data obtained from VO<sub>2</sub> films in their insulating phases. Data set for VO<sub>2</sub> film prepared at 650 °C is extracted from the <span class="html-italic">σ</span> vs. <span class="html-italic">T</span> plot in Ref. [<a href="#B32-materials-15-07849" class="html-bibr">32</a>].</p>
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<p>X-ray diffraction of (011) planes of VO<sub>2</sub> thin films deposited at <span class="html-italic">T<sub>S</sub></span> = 500, 550, and 600 °C on (<b>a</b>) Si and (<b>b</b>) sapphire substrates.</p>
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<p>Comparison of VO<sub>2</sub> thin films deposited at various temperatures studied in different works. (<b>a</b>) Comparison of <span class="html-italic">T<sub>t</sub></span> obtained from optical (O-) switching measurements. (<b>b</b>) Hysteresis width (Δ<span class="html-italic">H</span>) of the films that are obtained from the temperature (<span class="html-italic">T</span>) dependence of optical transmittance (<math display="inline"><semantics> <mover accent="true"> <mi>T</mi> <mo>˜</mo> </mover> </semantics></math>). (<b>c</b>) Comparison of phase transition temperature (<span class="html-italic">T<sub>t</sub></span>) obtained from electrical (E-) switching. (<b>d</b>) Hysteresis width (Δ<span class="html-italic">H</span>) of the films that are obtained from the <span class="html-italic">T</span>-dependence of electrical conductivity or resistance. Note that Kana et al. (2010) is [<a href="#B30-materials-15-07849" class="html-bibr">30</a>]; Kang et al. (2019) is [<a href="#B57-materials-15-07849" class="html-bibr">57</a>]; Koughia et al. (2020) is [<a href="#B32-materials-15-07849" class="html-bibr">32</a>]; Lee et al. (2020) is [<a href="#B28-materials-15-07849" class="html-bibr">28</a>]; Melnik et al. (2012) is [<a href="#B26-materials-15-07849" class="html-bibr">26</a>]; Sato et al. (2012) is [<a href="#B21-materials-15-07849" class="html-bibr">21</a>]; Zhang et al. (2015) is [<a href="#B36-materials-15-07849" class="html-bibr">36</a>]; Zhang et al. (2020) is [<a href="#B17-materials-15-07849" class="html-bibr">17</a>].</p>
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21 pages, 6576 KiB  
Article
Formation of Shaped Charge Projectile in Air and Water
by Zhifan Zhang, Hailong Li, Longkan Wang, Guiyong Zhang and Zhi Zong
Materials 2022, 15(21), 7848; https://doi.org/10.3390/ma15217848 - 7 Nov 2022
Cited by 4 | Viewed by 2644
Abstract
With the improvement of the antiknock performance of warships, shaped charge warheads have been focused on and widely used to design underwater weapons. In order to cause efficient damage to warships, it is of great significance to study the formation of shaped charge [...] Read more.
With the improvement of the antiknock performance of warships, shaped charge warheads have been focused on and widely used to design underwater weapons. In order to cause efficient damage to warships, it is of great significance to study the formation of shaped charge projectiles in air and water. This paper uses Euler governing equations to establish numerical models of shaped charges subjected to air and underwater explosions. The formation and the movement of Explosively Formed Projectiles (EFPs) in different media for three cases: air explosion and underwater explosions with and without air cavities are discussed. First, the velocity distributions of EFPs in the formation process are discussed. Then, the empirical coefficient of the maximum head velocity of EFPs in air is obtained by simulations of air explosions of shaped charges with different types of explosives. The obtained results agree well with the practical solution, which validates the numerical model. Further, this empirical coefficient in water is deduced. After that, the evolutions of the head velocity of EFPs in different media for the above three cases are further compared and analyzed. The fitting formulas of velocity attenuation of EFPs, which form and move in different media, are gained. The obtained results can provide a theoretical basis and numerical support for the design of underwater weapons. Full article
(This article belongs to the Special Issue Materials under High Pressure)
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<p>Materials transported in Euler.</p>
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<p>Numerical model of the air explosion of the shaped charge.</p>
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<p>Numerical model of the underwater explosion of a shaped charge without an air cavity.</p>
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<p>Numerical model of the underwater explosion of a shaped charge with air cavity.</p>
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<p>Comparison of experimental results [<a href="#B39-materials-15-07848" class="html-bibr">39</a>] and numerical simulation.</p>
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<p>Head X-velocity of a projectile with different grid numbers.</p>
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<p>Velocity distribution of EFPs in a formation process in air.</p>
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<p>Velocity distribution of the EFP in a formation process in water.</p>
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<p>Velocity distribution of the EFP for Case 3.</p>
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<p>Velocity distribution of the EFP for Case 4.</p>
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<p>Velocity distribution of the EFP for Case 5.</p>
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<p>Evolutions of the maximum head velocity of projectiles with different types of charges in air.</p>
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<p>Evolution of the velocity of EFPs with different types of charge.</p>
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<p>Evolution of velocity of projectile in water without air cavity.</p>
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<p>The fitting curve of underwater velocity attenuation of the EFP at the third stage.</p>
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<p>Evolution of mass of the shaped charge projectile in water.</p>
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<p>Evolution of the projectile entering water from air.</p>
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<p>Shock wave propagation in the pit stage.</p>
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<p>Comparison analysis diagram of the pitting stage and maximum velocity.</p>
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<p>Attenuation curve of the shaped charge projectile entering water.</p>
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18 pages, 4106 KiB  
Article
Strength and Permeability Properties of Pervious Concrete Containing Coal Bottom Ash Aggregates
by Ji-Hun Park, Seung-Tae Jeong, Quang-The Bui and In-Hwan Yang
Materials 2022, 15(21), 7847; https://doi.org/10.3390/ma15217847 - 7 Nov 2022
Cited by 11 | Viewed by 1802
Abstract
This study investigates the strength and permeability properties of pervious concrete-containing coal bottom ash (CBA) aggregates. Two pervious concrete mixtures were fabricated with different aggregate size distributions. One mixture contained CBA aggregates with a single-type distribution and the other mixture contained CBA aggregates [...] Read more.
This study investigates the strength and permeability properties of pervious concrete-containing coal bottom ash (CBA) aggregates. Two pervious concrete mixtures were fabricated with different aggregate size distributions. One mixture contained CBA aggregates with a single-type distribution and the other mixture contained CBA aggregates with a hybrid-type distribution. The test parameters of the CBA pervious concrete included the water/cement (W/C) ratio and compaction level to investigate their effects on the properties. W/C ratios of 0.25, 0.30, and 0.35 were considered for the mixture, and compaction levels of 0.5, 1.5, and 3.0 MPa were applied to fabricate the pervious specimen. The increase in the W/C ratio reduced the strength by approximately 20% to 30% of the CBA pervious concrete. The increase in the compaction level reduced the permeability by approximately four to five times but significantly increased the strength of the CBA pervious concrete. The test results indicate that the use of single-type CBA or hybrid CBA aggregates with different size distributions affected the properties of the pervious concrete. The strength of specimens, including hybrid CBA aggregates, was 30% to 45% greater than that of the specimens containing single-type CBA aggregates. Meanwhile, the use of hybrid CBA aggregates reduced the permeability of the CBA pervious concrete by approximately 20% to 35%. Finally, relationships between the strength properties, permeability characteristics and total void ratios of the CBA pervious concrete specimens are suggested based on the test results. Full article
(This article belongs to the Special Issue Convergence & Sustainable Technology in Building Materials)
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<p>CBA used: (<b>a</b>) 1.2~2.5 mm; (<b>b</b>) 2.5~5.0 mm.</p>
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<p>Relationship between absorption and density of CBA types.</p>
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<p>Schematic compacting method. (<b>a</b>) Compaction on a cylindrical specimen; (<b>b</b>) compaction on a prismatic specimen.</p>
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<p>Compacted CBA pervious concrete specimens. (<b>a</b>) Cylindrical specimen; (<b>b</b>) prismatic specimen.</p>
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<p>Permeability test setup. (<b>a</b>) Schematic of the permeability test; (<b>b</b>) performance of the permeability test.</p>
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<p>Total void ratio results.</p>
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<p>Extraction method. (<b>a</b>) Illustration of the extraction method; (<b>b</b>) extraction positions in two series.</p>
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<p>SEM results.</p>
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<p>Permeability coefficient results.</p>
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<p>Compressive strength results.</p>
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<p>Splitting tensile strength results.</p>
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<p>Flexural tensile strength results.</p>
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<p>Relationship between compressive strength and total void ratio.</p>
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<p>Relationship between the spitting tensile strength and total void ratio.</p>
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<p>Relationship between the permeability and total void ratio.</p>
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14 pages, 3172 KiB  
Article
Optimization of Wire Electric Discharge Machining (WEDM) Process Parameters for AISI 1045 Medium Carbon Steel Using Taguchi Design of Experiments
by Uzair Khaleeq uz Zaman, Usman Ahmed Khan, Shahid Aziz, Aamer Ahmed Baqai, Sajid Ullah Butt, Danish Hussain, Ali Siadat and Dong Won Jung
Materials 2022, 15(21), 7846; https://doi.org/10.3390/ma15217846 - 7 Nov 2022
Cited by 13 | Viewed by 3483
Abstract
With the growth of the manufacturing industry, the demand for alloy materials with high hardness, toughness, and impact strength has increased. Since products from such alloy materials are extremely difficult to manufacture with high accuracy and reduced surface roughness using traditional machining techniques, [...] Read more.
With the growth of the manufacturing industry, the demand for alloy materials with high hardness, toughness, and impact strength has increased. Since products from such alloy materials are extremely difficult to manufacture with high accuracy and reduced surface roughness using traditional machining techniques, wire electric discharge machining can be used to machine such complex parts with more precision. In this case-study-based research, machining factors such as current, pulse-on time, and voltage are studied to determine their effects on the material removal rate for AISI 1045 medium carbon steel. The Taguchi L9 orthogonal array is used in the design of experiments for optimization. Statistical techniques such as analysis of variance and signal-to-noise ratio are used to identify the control parameters that matter most in bringing about optimal results. Based on the results, the current is the most crucial control variable in this investigation. Moreover, the maximum material removal rate obtained was 0.7112 mm3/min with the obtained optimized values of current (I) = 16 A, voltage (V) = 50 V, and pulse-on time (Ton) = 100 µs. Full article
(This article belongs to the Special Issue Recent Advances in Metal Forming Technology (Second Volume))
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<p>Proposed Methodology for selection of optimal process parameter settings (modified from Zaman et al. [<a href="#B43-materials-15-07846" class="html-bibr">43</a>]).</p>
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<p>Wire cut electric discharge digital control machine—DK7725.</p>
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<p>Molybdenum wire.</p>
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<p>Wire cut electric discharge digital control machining showing (<b>a</b>) profile of timing chain sprocket gear teeth (all measurements in mm) and (<b>b</b>) the system working on a gear profile.</p>
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<p>Base of desired part.</p>
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<p>Final part design of timing chain sprocket.</p>
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<p>Main effects plot for means (pulse-on time is in µs, current in amperes, and voltage in volts).</p>
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<p>Main effects plot for S/N ratios (pulse-on time is in µs, current in amperes, and voltage in volts).</p>
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12 pages, 1900 KiB  
Article
Tooth Bleaching of Discolorations Caused by Hydraulic Cements in Regenerative Endodontic Treatment: A 3-Year In Vitro Study
by Carmen Llena, Manuel Iglesias-Diaz, Paula Ciscar-Muñoz, Ana Belén Bataller-Martínez, María Melo and José Luis Sanz
Materials 2022, 15(21), 7845; https://doi.org/10.3390/ma15217845 - 7 Nov 2022
Viewed by 1394
Abstract
This study aimed to evaluate the color change caused by hydraulic cements after 3 years in vitro by simulating their use in regenerative endodontic treatment (RET) and to quantify the color change after external bleaching with 40% hydrogen peroxide at 1, 6, and [...] Read more.
This study aimed to evaluate the color change caused by hydraulic cements after 3 years in vitro by simulating their use in regenerative endodontic treatment (RET) and to quantify the color change after external bleaching with 40% hydrogen peroxide at 1, 6, and 12 months of follow-up. Fifty teeth were treated simulating RET. Samples were distributed according to the hydraulic cement to be used (n = 10 per group): negative control (no cement), ProRoot-MTA, MM-MTA, TotalFill BC-RRM, or Biodentine. Three years after RET, two sessions of external bleaching with Opalescence Boost were performed. The color was measured in the cervical and incisal halves of the teeth at different time points: baseline, 3 years after performing RET, and after 1, 6, and 12 months after bleaching. The ΔL, Δa, and Δb were determined. A generalized linear model was used to compare color considering group and time. The ΔEab and the ΔE00 were calculated and the acceptability in color change was determined. Three years after RET, a reduction in lightness (negative ΔL values) was found in all groups. These values significantly increased 1 month after bleaching in all groups (p < 0.05) and reversed at 6 months. One month after bleaching, ΔE00 values (color difference tolerance (CIEDE2000)) ranged from very good (>3.6 ≤ 5.4) to excellent (>5.4). One year after bleaching, the color reverted to values similar to those found 3 years after RET. All groups became darker after RET. The color recovered and even improved compared with the baseline measurement after one month of bleaching but did not remain stable over time. Full article
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<p>Study protocol flowchart.</p>
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<p>(<b>A</b>) Variations in ΔL (lightness) in the incisal halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>B</b>) Variations in Δa (red–green distance) in the incisal halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>C</b>) Variations in Δb (yellow–blue distance) in the incisal halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05.</p>
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<p>(<b>A</b>) Variations in ΔL (lightness) in the incisal halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>B</b>) Variations in Δa (red–green distance) in the incisal halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>C</b>) Variations in Δb (yellow–blue distance) in the incisal halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05.</p>
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<p>(<b>A</b>) Variations in ΔL (lightness) in the cervical halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>B</b>) Variations in Δa (red–green distance) in the cervical halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>C</b>) Variations in Δb (yellow–blue distance) in the cervical halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05.</p>
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<p>(<b>A</b>) Variations in ΔL (lightness) in the cervical halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>B</b>) Variations in Δa (red–green distance) in the cervical halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05. (<b>C</b>) Variations in Δb (yellow–blue distance) in the cervical halves. Boxplots showing the median values and IQR of the baseline and subsequent color measurements. * <span class="html-italic">p</span> &lt; 0.05.</p>
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23 pages, 8265 KiB  
Article
New Platforms Based on Frontal Cellular Automata and Lattice Boltzmann Method for Modeling the Forming and Additive Manufacturing
by Łukasz Łach and Dmytro Svyetlichnyy
Materials 2022, 15(21), 7844; https://doi.org/10.3390/ma15217844 - 7 Nov 2022
Cited by 2 | Viewed by 1958
Abstract
Materials science gives theoretical and practical tools, while new modeling methods and platforms provide rapid and efficient development, improvement, and optimization of old and new technologies. Recently, impressive progress has been made in the development of computer software and systems. The frontal cellular [...] Read more.
Materials science gives theoretical and practical tools, while new modeling methods and platforms provide rapid and efficient development, improvement, and optimization of old and new technologies. Recently, impressive progress has been made in the development of computer software and systems. The frontal cellular automata (FCA), lattice Boltzmann method (LBM), and modeling platforms based on them are considered in the paper. The paper presents basic information on these methods and their application for modeling phenomena and processes in materials science. Recrystallization, crystallization, phase transformation, processes such as flat and shape rolling, additive manufacturing technologies (Selective Laser Sintering (SLS)/ Selective Laser Melting (SLM)), and others are examples of comprehensive and effective modeling by the developed systems. Selected modeling results are also presented. Full article
(This article belongs to the Special Issue Polish Achievements in Materials Science and Engineering)
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<p>FCA communication direction using the Moore (<b>a</b>) and von Neumann (<b>b</b>) neighborhoods.</p>
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<p>The front of the growing grain with cells in the state: 1, initial; 2,frontal (transitional); 3, final.</p>
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<p>Structure of the LBM calculation algorithm.</p>
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<p>Structure of the platform for modeling microstructure evolution in technological processes.</p>
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<p>Space reorganization methods.</p>
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<p>The modeling scheme of the initial microstructure.</p>
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<p>Initial microstructure under different boundary conditions: (<b>a</b>) open and (<b>b</b>) periodic.</p>
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<p>The algorithm for modeling the initial microstructure with a given grain size distribution.</p>
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<p>Initial microstructure with an average grain size <span class="html-italic">d<sub>av</sub></span> = 100 µm (<b>a</b>) and final microstructure <span class="html-italic">d<sub>av</sub></span> = 75 μm (<b>b</b>).</p>
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<p>Microstructure before deformation (<b>a</b>) and after deformation: without recrystallization (<b>b</b>), with dynamic recrystallization (<b>c</b>), and after metadynamic recrystallization (<b>d</b>).</p>
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<p>Microstructure before deformation (<b>a</b>) and after deformation: without recrystallization (<b>b</b>), with dynamic recrystallization (<b>c</b>), and after metadynamic recrystallization (<b>d</b>).</p>
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<p>Structure of the hybrid model for modeling diffusional phase transformations.</p>
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<p>Growth of the new phase in the selected plane: (<b>a</b>) CA states and (<b>b</b>) temperature distribution.</p>
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<p>Flat rolling scheme.</p>
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<p>The general scheme of shape rolling modeling.</p>
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<p>Schematic representation of interconnection between analyzed process physical phenomena and models [<a href="#B45-materials-15-07844" class="html-bibr">45</a>].</p>
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<p>Modeling results showing inflows and outflows in the removal equipment.</p>
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<p>Simulation results of the SLM process: (<b>a</b>) one material and (<b>b</b>) two different materials.</p>
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<p>3D perspective views of the modeled SLM process with three passes: (<b>a</b>) the first, (<b>b</b>) the second, and (<b>c</b>) the third.</p>
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15 pages, 6270 KiB  
Article
Numerical Analysis of Zirconium and Titanium Implants under the Effect of Critical Masticatory Load
by Miguel Martinez-Mondragon, Guillermo Urriolagoitia-Sosa, Beatriz Romero-Ángeles, Daniel Maya-Anaya, Jacobo Martínez-Reyes, Francisco Javier Gallegos-Funes and Guillermo Manuel Urriolagoitia-Calderón
Materials 2022, 15(21), 7843; https://doi.org/10.3390/ma15217843 - 7 Nov 2022
Cited by 8 | Viewed by 2205
Abstract
Dental implants have become an alternative to replace the teeth of people suffering from edentulous and meet the physiological and morphological characteristics (recovering 95% of the chewing function). The evolution and innovation of biomaterials for dental implants have had a trajectory that dates [...] Read more.
Dental implants have become an alternative to replace the teeth of people suffering from edentulous and meet the physiological and morphological characteristics (recovering 95% of the chewing function). The evolution and innovation of biomaterials for dental implants have had a trajectory that dates back to prehistory, where dental pieces were replaced by ivory or seashells, to the present day, where they are replaced by metallic materials such as titanium or ceramics such as zirconium or fiberglass. The numerical evaluation focuses on comparing the stress distribution and general displacement between different dental implants and a healthy tooth when applying a force of 850 N. For the analysis, a model of the anatomical structure was developed of a healthy tooth considering three essential parts of the tooth (enamel, dentin, and pulp). The tooth biomodel was established through computed tomography. Three dental implant models were considered by changing the geometry of the abutment. A structural simulation was carried out by applying the finite element method (FEM). In addition, the material considered for the analyses was zirconium oxide (ZrO2), which was compared against titanium alloy (Ti6Al4V). The analyses were considered with linear, isotropic, and homogeneous properties. The variables included in the biomodeling were the modulus of elasticity, Poisson’s ratio, density, and elastic limit. The results obtained from the study indicated a significant difference in the biomechanical behavior of the von Mises forces and the displacement between the healthy tooth and the titanium and zirconium implant models. However, the difference between the titanium implant and the zirconium implant is minimal because one is more rigid, and the other is more tenacious. Full article
(This article belongs to the Special Issue Dental Implants and Materials (Second Volume))
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<p>Dental implant with components.</p>
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<p>Development of biomodeling of anatomical structures.</p>
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<p>Modeling methodology.</p>
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<p>Biomodeling assembly.</p>
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<p>Biomodel of the lower right first molar.</p>
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<p>Boundary conditions and external loads on the molar.</p>
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<p>Implant models with different abutment geometry.</p>
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<p>Boundary conditions and external loads on the implant.</p>
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<p>Total general displacement of the molar.</p>
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<p>Von Mises stress for tooth.</p>
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<p>Total general displacement for Snappy type implant (Ti<math display="inline"><semantics> <msub> <mrow/> <mn>6</mn> </msub> </semantics></math>Al<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>V).</p>
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<p>Von Mises stress for Snappy-type implant (Ti<math display="inline"><semantics> <msub> <mrow/> <mn>6</mn> </msub> </semantics></math>Al<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>V).</p>
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<p>Total general displacement for Universal-type implant (Ti<math display="inline"><semantics> <msub> <mrow/> <mn>6</mn> </msub> </semantics></math>Al<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>V).</p>
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<p>Von Mises stress for Universal-type implant (Ti<math display="inline"><semantics> <msub> <mrow/> <mn>6</mn> </msub> </semantics></math>Al<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>V).</p>
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<p>Total general displacement for On1 Esthethic-type implant (Ti<math display="inline"><semantics> <msub> <mrow/> <mn>6</mn> </msub> </semantics></math>Al<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>V).</p>
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<p>Von Mises stress for On1 Esthethic-type implant (Ti<math display="inline"><semantics> <msub> <mrow/> <mn>6</mn> </msub> </semantics></math>Al<math display="inline"><semantics> <msub> <mrow/> <mn>4</mn> </msub> </semantics></math>V).</p>
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<p>Total general displacement for Snappy-type implant (ZrO<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>).</p>
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<p>Von Mises stress for Snappy-type implant (ZrO<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>).</p>
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<p>Total general displacement for Universal-type implant (ZrO<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>).</p>
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<p>Von Mises stress for Universal-type implant (ZrO<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>).</p>
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<p>Total general displacement for On1 Esthetic-type implant (ZrO<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>).</p>
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<p>Von Mises stress for On1 Esthetic-type implant (ZrO<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>).</p>
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22 pages, 8483 KiB  
Article
Effect of Pro-Ecological Cooling and Lubrication Methods on the Sharpening Process of Planar Blades Used in Food Processing
by Bartosz Zieliński, Krzysztof Nadolny, Wojciech Zawadka, Tomasz Chaciński, Wojciech Stachurski and Gilmar Ferreira Batalha
Materials 2022, 15(21), 7842; https://doi.org/10.3390/ma15217842 - 7 Nov 2022
Cited by 4 | Viewed by 1786
Abstract
This work presents the results of an experimental study of the sharpening of planar technical blades used in the fish processing industry. Sharpening was carried out in the grinding process using several environmentally friendly methods of cooling and lubricating the machining zone (MQL [...] Read more.
This work presents the results of an experimental study of the sharpening of planar technical blades used in the fish processing industry. Sharpening was carried out in the grinding process using several environmentally friendly methods of cooling and lubricating the machining zone (MQL method, CAG nozzle, hybrid method that is a combination of MQL and CAG methods, as well as WET flooding method as reference). The purpose of the research was to determine the possibility of reducing the negative environmental impact of the sharpening process of technical blades by minimizing the expenditure of coolant. The application of the MQL method and the hybrid MQL + CAG method provided a very good realization of the lubricating function so that the share of friction of dulled cutting vertices against the workpiece surface is reduced, which manifests itself in the reduction of the grinding force and the correlated grinding power. In the case of grinding under cooled compressed air delivery conditions, the average cutting force was as much as 91.6% higher (F = 22.63 N) compared to the result obtained for the most favorable flooding method, demonstrating the insufficient quality of the blade shaped under such conditions. A comprehensive comparison of test results on grinding power gain, cutting force and surface texture suggests that the most favorable sharpening results were obtained using the environmentally friendly MQL method of cooling and lubricating the grinding zone. Full article
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<p>Test and measurement stands used in the described research: (<b>a</b>) five-axis CNC special grinder for sharpening technical blades; (<b>b</b>) special device for removing rewind from the blade after grinding; (<b>c</b>) position for contact measurements of surface texture equipped with a stylus profilometer Hommel-Tester T8000 by Hommelwerke GmbH, Villingen-Schwenningen, Germany [<a href="#B38-materials-15-07842" class="html-bibr">38</a>]; (<b>d</b>) digital measuring microscope Dino-Lite Edge AM7515MT8A, AnMo Electronics Corporation, New Taipei City, Taiwan, China [<a href="#B39-materials-15-07842" class="html-bibr">39</a>,<a href="#B40-materials-15-07842" class="html-bibr">40</a>,<a href="#B41-materials-15-07842" class="html-bibr">41</a>]; (<b>e</b>) special test stand for cutting force measurement.</p>
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<p>View of the grinding zone in a configuration that allows the use of (<b>a</b>) flooding method (WET); (<b>b</b>) minimum quantity lubrication (MQL); (<b>c</b>) cooling with cooled compressed air (CAG); (<b>d</b>) hybrid method involving the simultaneous use of MQL and CAG nozzle (MQL + CAG).</p>
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<p>Diagram of the angular positioning of the grinding wheel in three planes with respect to the planar blade: (<b>a</b>) side view; (<b>b</b>) front view (angle values used in the described tests: <span class="html-italic">α<sub>s</sub></span> = 85°, <span class="html-italic">β<sub>s</sub></span> = 5°, <span class="html-italic">χ<sub>s</sub></span> = 20°).</p>
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<p>The average values of the grinding power gain <span class="html-italic">ΔP</span> determined during grinding tests carried out with 5 repetitions using four methods of delivering coolants to the machining zone (flooding method WET, MQL, cooling using cooled compressed air generated by CAG nozzle and the hybrid method MQL + CAG) (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Average values (from 5 repetitions) of cutting force <span class="html-italic">F</span> determined from measurements of blades shaped using four methods of supplying coolants to the grinding zone: flooding method WET, MQL, cooling using cooled compressed air generated by CAG nozzle and the hybrid method MQL + CAG (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>View of surface microtopography (1.0 × 1.0 mm) of planar knives measured on a test stand equipped with a Hommel-Tester T8000 stylus profilometer from Hommelwerke GmbH (Villingen-Schwenningen, Germany): (<b>a</b>–<b>c</b>) blades No. 1–3 ground under WET method conditions; (<b>d</b>–<b>f</b>) blades No. 4–6 ground under MQL method conditions; (<b>g</b>–<b>i</b>) blades No. 7–9 ground under CAG method conditions; (<b>j</b>–<b>l</b>) blades No. 10–12 ground under MQL + CAG method conditions.</p>
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<p>Chart of changes in the arithmetic mean deviation of the surface <span class="html-italic">Sa</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the total height of the surface <span class="html-italic">St</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the mean void volume ratio <span class="html-italic">Smvr</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the density of summits of the surface <span class="html-italic">Sds</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the texture aspect ratio of the surface <span class="html-italic">Str</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the root-mean-square slope of the surface <span class="html-italic">Sdq</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the developed interfacial area ratio <span class="html-italic">Sdr</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Chart of changes in the bearing index <span class="html-italic">Sbi</span>: (<b>a</b>) results for the twelve blades selected for the surface texture measurements; (<b>b</b>) mean values of the parameters divided by cooling and lubrication methods of the grinding zone used during the shaping of the blades (error bars represent the standard error equal to the standard deviation <span class="html-italic">σ</span> divided by the square root of the total number of samples).</p>
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<p>Microscopic views of the blade surfaces of five planar knives shaped using flooding (WET) cooling recorded with a Dino-Lite Edge AM7515MT8A digital measuring microscope from AnMo Electronics Corp. (New Taipei City, Taiwan, China) at a magnification of approximately 700×: (<b>a</b>) blade No. 1; (<b>b</b>) blade No. 2; (<b>c</b>) blade No. 3; (<b>d</b>) blade No. 4; (<b>e</b>) blade No. 5.</p>
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<p>Microscopic views of the blade surfaces of five planar knives shaped using the MQL method recorded with a Dino-Lite Edge AM7515MT8A digital measuring microscope from AnMo Electronics Corp. (New Taipei City, Taiwan, China) at a magnification of approximately 700×: (<b>a</b>) blade No. 1; (<b>b</b>) blade No. 2; (<b>c</b>) blade No. 3; (<b>d</b>) blade No. 4; (<b>e</b>) blade No. 5.</p>
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<p>Microscopic views of the blade surfaces of five planar knives shaped using cooled compressed air (CAG) recorded with a Dino-Lite Edge AM7515MT8A digital measuring microscope from AnMo Electronics Corp. (New Taipei City, Taiwan, China) at a magnification of approximately 700×: (<b>a</b>) blade No. 1; (<b>b</b>) blade No. 2; (<b>c</b>) blade No. 3; (<b>d</b>) blade No. 4; (<b>e</b>) blade No. 5.</p>
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<p>Microscopic views of the blade surfaces of five planar knives shaped using a hybrid method combining MQL and CAG nozzle at the same time (MQL + CAG) were recorded with a Dino-Lite Edge AM7515MT8A digital measuring microscope from AnMo Electronics Corp. (New Taipei City, Taiwan, China) at a magnification of approximately 700×: (<b>a</b>) blade No. 1; (<b>b</b>) blade No. 2; (<b>c</b>) blade No. 3; (<b>d</b>) blade No. 4; (<b>e</b>) blade No. 5.</p>
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16 pages, 8130 KiB  
Article
Welding Defect and Mechanical Properties of Nanosecond Laser Cleaning 6005A Aluminum Alloy
by Yuelai Zhang, Qi Yao, Weifeng Long, Chunming Wang, Ji Lin and Zehui Liu
Materials 2022, 15(21), 7841; https://doi.org/10.3390/ma15217841 - 7 Nov 2022
Cited by 4 | Viewed by 2184
Abstract
Nanosecond laser cleaning effectively removes oxide film and dirt from the surface of aluminum body parts for rail transit, as well as improving surface properties. The effect of laser cleaning on the quality of weld was studied in detail for different scanning frequencies [...] Read more.
Nanosecond laser cleaning effectively removes oxide film and dirt from the surface of aluminum body parts for rail transit, as well as improving surface properties. The effect of laser cleaning on the quality of weld was studied in detail for different scanning frequencies and cleaning speeds. The effect of post-weld laser cleaning on weld quality was investigated. After laser cleaning at different parameters, the surface oxygen content was decreased and the surface roughness and surface hardness were increased. Variation of surface oxygen content was related to energy density and spot density. The lowest oxygen content was obtained at 150 W, 100 Hz and 0.8 m/min. Laser-generated craters changed surface morphology and improved surface roughness. The mechanical properties of the welded joints were slightly improved, which relates to a decrease in porosity. The minimum porosity of the laser-cleaned weld was 0.021%. This work provides new ideas for the nanosecond laser cleaning of aluminum alloy and its welding properties. Full article
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<p>(<b>a</b>) Schematic of laser cleaning system and (<b>b</b>) the scanning path of the beam.</p>
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<p>The variation of the surface oxygen content with the process parameters: (<b>a</b>) laser power; (<b>b</b>) scanning frequency; (<b>c</b>) cleaning speed.</p>
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<p>The results of EDS on the surface of samples: (<b>a</b>) untreated; (<b>b</b>) laser-cleaned.</p>
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<p>The XPS spectrum of the surface of 6005A alloy with untreated and laser cleaned.</p>
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<p>The XPS spectrum of Al 2p: (<b>a</b>) untreated; (<b>b</b>) laser cleaning.</p>
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<p>The variation of the surface roughness with the process parameters: (<b>a</b>) laser power; (<b>b</b>) scanning frequency; (<b>c</b>) cleaning speed.</p>
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<p>The variation of the surface hardness with the process parameters: (<b>a</b>) laser power; (<b>b</b>) scanning frequency; (<b>c</b>) cleaning speed.</p>
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<p>The top view micrograph of laser-cleaned and untreated surfaces: (<b>a</b>) untreated; (<b>b</b>) laser-cleaned.</p>
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<p>(<b>a</b>) The weld structure; (<b>b</b>) the dimension of the shear specimen and the variation of the shear strength with the process parameters: (<b>c</b>) scanning frequency; (<b>d</b>) cleaning speed.</p>
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<p>The weld formation on sample with: (<b>a</b>) oil; (<b>b</b>) water; (<b>c</b>) laser cleaning.</p>
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<p>The result of the permeation testing and the porosity at sample with: (<b>a</b>) oil; (<b>b</b>) water; (<b>c</b>) laser cleaning.</p>
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<p>The result of the permeation testing and the porosity: (<b>a</b>) the lap surface was not cleaned; (<b>b</b>) the lap surface was cleaned.</p>
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<p>The result of the permeation testing and the porosity under different scanning frequencies: (<b>a</b>) 100 Hz; (<b>b</b>) 125 Hz.</p>
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<p>The result of the permeation testing and the porosity under different cleaning speeds: (<b>a</b>) 0.5 m/min; (<b>b</b>) 0.7 m/min.</p>
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<p>The weld formation before and after laser cleaning of black ash.</p>
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<p>The shear strength of the samples before and after black ash removal.</p>
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<p>The result of the permeation testing: (<b>a</b>) black ash without laser cleaning; (<b>b</b>) black ash with laser cleaning.</p>
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<p>The schematic of laser cleaning principle.</p>
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14 pages, 3565 KiB  
Article
Effect of Two-Step Sintering on Properties of Alumina Ceramics Containing Waste Alumina Powder
by Milan Vukšić, Irena Žmak, Lidija Ćurković and Andraž Kocjan
Materials 2022, 15(21), 7840; https://doi.org/10.3390/ma15217840 - 7 Nov 2022
Cited by 2 | Viewed by 2273
Abstract
This study aims to evaluate the recycling potential of solid waste alumina powder (WAP) by utilization of the two-step sintering (TSS) process. For the study, WAP was collected as an industrial scrap after the machining process for the formation of green alumina compacts. [...] Read more.
This study aims to evaluate the recycling potential of solid waste alumina powder (WAP) by utilization of the two-step sintering (TSS) process. For the study, WAP was collected as an industrial scrap after the machining process for the formation of green alumina compacts. The alumina samples were prepared according to the slip casting method by preparing suspensions containing commercial alumina with 0.8 μm average particle size and by adding up to 20 dwb. % (i.e., expressed on a dry weight basis) of WAP with 3.4 μm average particle size. The samples were sintered at optimized TSS conditions and compared with conventional one-step sintering (OSS) by conducting morphological analyses. The average grain size (AGS) was determined from the obtained field emission scanning electron microscopy (FESEM) images, while the sample porosity was calculated based on apparent densities. The obtained micrographs after TSS implementation revealed a partially textured microstructure. Furthermore, a comparison of the mechanical properties of alumina samples lacking or containing 20 dwb. % of WAP obtained after sintering is presented. The indentation fracture toughness (~3.2 MPa m1/2) and Vickers hardness data (~14.5 GPa) showed a positive effect of adding WAP to alumina samples. The slightly improved mechanical properties of ceramic samples containing waste alumina are a consequence of lower porosity, which is due to the remaining sintering additives in WAP. The collected results demonstrate the possibility of using TSS for sintering ceramic materials that contain WAP. Full article
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<p>DTA/TG curves of: (<b>a</b>) waste alumina powder and (<b>b</b>) pure alumina powder.</p>
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<p>Dilatometry analysis of alumina containing 20 dwb. % of WAP sintered at optimal TSS conditions.</p>
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<p>3D response surface and contour plots depicting influence of: (<b>a</b>) sintering temperature of second step (X<sub>1</sub>) and heating rate (X<sub>2</sub>) and (<b>b</b>) holding time (X<sub>3</sub>) and heating rate (X<sub>2</sub>) on apparent density.</p>
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<p>FESEM images of alumina surface microstructure. (<b>a</b>) OSS/0 dwb. % WAP; (<b>c</b>) OSS/20 dwb. % WAP; (<b>e</b>) TSS/0 dwb. % WAP; (<b>g</b>) TSS/20 dwb. % WAP and of respective sample fracture surface: (<b>b</b>) OSS/0 dwb. % WAP; (<b>d</b>) OSS/20 dwb. % WAP; (<b>f</b>) TSS/0 dwb. % WAP; (<b>h</b>) TSS/20 dwb. % WAP.</p>
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<p>FESEM images of alumina surface microstructure. (<b>a</b>) OSS/0 dwb. % WAP; (<b>c</b>) OSS/20 dwb. % WAP; (<b>e</b>) TSS/0 dwb. % WAP; (<b>g</b>) TSS/20 dwb. % WAP and of respective sample fracture surface: (<b>b</b>) OSS/0 dwb. % WAP; (<b>d</b>) OSS/20 dwb. % WAP; (<b>f</b>) TSS/0 dwb. % WAP; (<b>h</b>) TSS/20 dwb. % WAP.</p>
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<p>Cumulative volume grain size distribution versus Feret’s diameter of sintered samples with different waste alumina content.</p>
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<p>The calculated fracture toughness according to median crack models for: (a) OSS/0 dwb. % WAP; (b) OSS/20 dwb. % WAP; (c) TSS/0 dwb. % WAP; (d) TSS/20 dwb. % WAP.</p>
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11 pages, 3304 KiB  
Article
Enhanced Piezoelectric Properties in a Single-Phase Region of Sm-Modified Lead-Free (Ba,Ca)(Zr,Ti)O3 Ceramics
by Andong Xiao, Xuefan Xie, Liqiang He, Yang Yang and Yuanchao Ji
Materials 2022, 15(21), 7839; https://doi.org/10.3390/ma15217839 - 7 Nov 2022
Cited by 4 | Viewed by 1982
Abstract
In ferroelectric materials, phase boundaries such as the morphotropic phase boundary (MPB) and polymorphic phase boundary (PPB) have been widely utilized to enhance the piezoelectric properties. However, for a single-ferroelectric-phase system, there are few effective paradigms to achieve the enhancement of piezoelectric properties. [...] Read more.
In ferroelectric materials, phase boundaries such as the morphotropic phase boundary (MPB) and polymorphic phase boundary (PPB) have been widely utilized to enhance the piezoelectric properties. However, for a single-ferroelectric-phase system, there are few effective paradigms to achieve the enhancement of piezoelectric properties. Herein, we report an unexpected finding that largely enhanced piezoelectric properties occur in a single-tetragonal-ferroelectric-phase region in the Sm-modified (Ba0.85Ca0.15)(Zr0.1Ti0.9)O3 (BCZT-xSm) system. An electrostrain maximum (0.13%) appears in the single-phase region of the BZCT-0.5Sm composition with the maximum polarization (Pm = 18.37 µC/cm2) and piezoelectric coefficient (d33 = 396 pC/N) and the minimum coercive field (EC = 3.30 kV/cm) at room temperature. Such an enhanced piezoelectric effect is due to the synergistic effect of large lattice distortion and domain miniaturization on the basis of the transmission electron microscope (TEM) observation and X-ray diffraction (XRD) Rietveld refinement. Our work may provide new insights into the design of high-performance ferroelectrics in the single-phase region. Full article
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<p>(<b>a1</b>–<b>a6</b>) SEM images and (<b>b1</b>–<b>b6</b>) normal distribution diagrams of the grain size statistics of BCZT-<span class="html-italic">x</span>Sm (<span class="html-italic">x</span> = 0, 0.25, 0.5, 0.75, 1 and 1.5) ceramics; mean values and standard deviations are marked in the statistics diagram. XRD patterns and the Rietveld refinement of the XRD data for BCZT-<span class="html-italic">x</span>Sm with (<b>c1</b>) <span class="html-italic">x</span> = 0, (<b>c2</b>) <span class="html-italic">x</span> = 0.25, (<b>c3</b>) <span class="html-italic">x</span> = 0.5, (<b>c4</b>) <span class="html-italic">x</span> = 0.75, (<b>c5</b>) <span class="html-italic">x</span> = 1, and (<b>c6</b>) <span class="html-italic">x</span> = 1.5.</p>
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<p>(<b>a</b>–<b>f</b>) Temperature-dependent permittivity of the BCZT-<span class="html-italic">x</span>Sm ceramics at different frequencies (1 kHz, 10 kHz, and 100 kHz), where <span class="html-italic">x</span> = 0, 0.25, 0.5, 0.75, 1, and 1.5, respectively; (<b>g</b>) the dielectric loss at 100 kHz and (<b>h</b>) corresponding temperature composition phase diagram showing the Curie temperature (<span class="html-italic">T<sub>C</sub></span>) and the phase transition temperature (<span class="html-italic">T<sub>T-O</sub></span>) from the tetragonal phase to the orthorhombic phase.</p>
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<p>(<b>a</b>) Polarization-electric field loops and (<b>b</b>) electrostrain loops of the BCZT-<span class="html-italic">x</span>Sm (<span class="html-italic">x</span> = 0, 0.25, 0.5, 0.75, 1, and 1.5) ceramics; composition-dependent (<b>c</b>) maximum polarization (<span class="html-italic">P</span><sub>m</sub>), (<b>d</b>) coercive field (<span class="html-italic">E</span><sub>C</sub>), (<b>e</b>) strain, and (<b>f</b>) piezoelectric coefficient (<span class="html-italic">d</span><sub>33</sub>) curves measured in the tetragonal-phase region.</p>
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<p>(<b>a1</b>–<b>c2</b>) The temperature-dependent polarization (<span class="html-italic">P</span>)-electric field (<span class="html-italic">E</span>) loop and strain of the BCZT-<span class="html-italic">x</span>Sm (<span class="html-italic">x</span> = 0.25, 0.5, 0.75) ceramics; temperature-dependent (<b>d</b>) maximum polarization (<span class="html-italic">P</span><sub>m</sub>), (<b>e</b>) coercive field (<span class="html-italic">E</span><sub>C</sub>), (<b>f</b>) strain, and (<b>g</b>) piezoelectric coefficient (<span class="html-italic">d</span><sub>33</sub>) curves of the BCZT-<span class="html-italic">x</span>Sm (<span class="html-italic">x</span> = 0.25, 0.5, and 0.75) ceramics.</p>
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<p>(<b>a1</b>–<b>f1</b>) Transmission electron microscope (TEM) observation of the (100) zone axis and (<b>a2</b>–<b>f2</b>) the corresponding domain size distribution of the BCZT-<span class="html-italic">x</span>Sm ceramics with <span class="html-italic">x</span> = 0, 0.25, 0.5, 0.75, 1, and 1.5, where BCZT-0.5Sm displayed unexpected miniaturized domains.</p>
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<p>Schematic diagram of the enhanced piezoelectric effect in a single-tetragonal-phase region due to (<b>a</b>) the increased <span class="html-italic">c/a</span> ratio and miniaturized domain, compared with those of the adjacent compositions, showing (<b>b</b>) an increased <span class="html-italic">P</span><sub>m</sub>, strain, and <span class="html-italic">d</span><sub>33</sub> and a reduced <span class="html-italic">E</span><sub>C</sub>.</p>
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16 pages, 5756 KiB  
Article
Microextrusion Printing of Hierarchically Structured Thick V2O5 Film with Independent from Humidity Sensing Response to Benzene
by Philipp Yu. Gorobtsov, Artem S. Mokrushin, Tatiana L. Simonenko, Nikolay P. Simonenko, Elizaveta P. Simonenko and Nikolay T. Kuznetsov
Materials 2022, 15(21), 7837; https://doi.org/10.3390/ma15217837 - 7 Nov 2022
Cited by 10 | Viewed by 2227
Abstract
The process of V2O5 oxide by the combination of sol-gel technique and hydrothermal treatment using heteroligand [VO(C5H7O2)2–x(C4H9O)x] precursor was studied. Using thermal analysis, X-ray powder diffraction [...] Read more.
The process of V2O5 oxide by the combination of sol-gel technique and hydrothermal treatment using heteroligand [VO(C5H7O2)2–x(C4H9O)x] precursor was studied. Using thermal analysis, X-ray powder diffraction (XRD) and infra-red spectroscopy (IR), it was found that the resulting product was VO2(B), which after calcining at 300 °C (1 h), oxidized to orthorhombic V2O5. Scanning electron microscopy (SEM) results for V2O5 powder showed that it consisted of nanosheets (~50 nm long and ~10 nm thick) assembled in slightly spherical hierarchic structures (diameter ~200 nm). VO2 powder dispersion was used as functional ink for microextrusion printing of oxide film. After calcining the film at 300 °C (30 min), it was found that it oxidized to V2O5, with SEM and atomic force microscopy (AFM) results showing that the film structure retained the hierarchic structure of the powder. Using Kelvin probe force microscopy (KPFM), the work function value for V2O5 film in ambient conditions was calculated (4.81 eV), indicating a high amount of deficiencies in the sample. V2O5 film exhibited selective response upon sensing benzene, with response value invariable under changing humidity. Studies of the electrical conductivity of the film revealed increased resistance due to high film porosity, with conductivity activation energy being 0.26 eV. Full article
(This article belongs to the Section Materials Chemistry)
Show Figures

Figure 1

Figure 1
<p>Scheme of V<sub>2</sub>O<sub>5</sub> powder and film preparation.</p>
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<p>Results of simultaneous thermal analysis for oxide powder after drying: (<b>a</b>) IR-spectra for the powder after drying and after annealing at 300 °C; (<b>b</b>) Diffractograms for the powder after drying and after annealing at 300 °C (<b>c</b>).</p>
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<p>SEM results for oxide powder after annealing at 300 °C.</p>
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<p>Diffractogram for V<sub>2</sub>O<sub>5</sub> film on Pt/Al<sub>2</sub>O<sub>3</sub>/Pt chip.</p>
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<p>Microstructure for the printed V<sub>2</sub>O<sub>5</sub> film (according to SEM).</p>
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<p>AFM results for the printed V<sub>2</sub>O<sub>5</sub> film: Topography (<b>a</b>,<b>b</b>), maps of potential surface distribution (<b>c</b>), and gradient in capacity of “probe tip-sample surface” capacitor distribution (<b>d</b>).</p>
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<p>Experimental curves of changes in sensing response during detection of benzene in the concentration range of 4–100 ppm (<b>a</b>); Dependence of sensing response to benzene from its concentration (<b>b</b>).</p>
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<p>Experimental curves of resistance change upon sensing 20 ppm of benzene at varying relative humidity (<b>a</b>); Dependence of sensing response to 20 ppm of benzene from relative humidity (<b>b</b>); Selectivity diagram: sensing responses to various analyte gases at 300 °C (<b>c</b>).</p>
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<p>Frequency dependencies of the printed V<sub>2</sub>O<sub>5</sub> film conductivity at various temperatures (<b>a</b>); Temperature dependence of conductivity for the film (<b>b</b>).</p>
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