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Crystals
Volume 14
Issue 12
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Crystals, Volume 14, Issue 12 (December 2024) – 100 articles

Cover Story (view full-size image): This study explores in situ microscopy with machine learning-based image analysis for real-time monitoring of protein crystallization in a 1 L stirred crystallizer. Batch crystallization experiments with a Lactobacillus brevis alcohol dehydrogenase (LbADH) and its mutants demonstrate precise correlations between crystal volumes and protein concentrations. The method provides comprehensive insights into crystallization dynamics, such as crystal growth rates, yields, and crystal size distribution. This scalable approach reduces the limitations of traditional analytical techniques and enables new insights into protein crystallization process dynamics. View this paper
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21 pages, 3925 KiB  
Article
Synthesis, Crystallographic Structure, Stability, and HSA-Binding Affinity of a Novel Copper(II) Complex with Pyridoxal-Semicarbazone Ligand
by Violeta Jevtovic, Aleksandra Rakić, Jelena M. Živković, Aljazi Abdullah Alrashidi, Maha Awjan Alreshidi, Elham A. Alzahrani, Odeh A. O. Alshammari, Sahar Y. Rajeh, Mostafa A. Hussien and Dušan Dimić
Crystals 2024, 14(12), 1106; https://doi.org/10.3390/cryst14121106 - 23 Dec 2024
Viewed by 696
Abstract
Copper–semicarbazone ligands have been extensively investigated for several medicinal applications. In this contribution, a novel copper(II) complex with a pyridoxal–semicarbazone ligand, [Cu(PLSC)Cl(H2O)](NO3)(H2O), was synthesized and characterized by X-ray crystallography, elemental analysis, UV-VIS, and FTIR spectroscopies. The stabilization [...] Read more.
Copper–semicarbazone ligands have been extensively investigated for several medicinal applications. In this contribution, a novel copper(II) complex with a pyridoxal–semicarbazone ligand, [Cu(PLSC)Cl(H2O)](NO3)(H2O), was synthesized and characterized by X-ray crystallography, elemental analysis, UV-VIS, and FTIR spectroscopies. The stabilization interactions within the structure were assessed using the Hirshfeld surface analysis. The crystallographic structure was optimized at the B3LYP/6-311++G(d,p)(H,C,N,O)/LanL2DZ(Cu) level of theory. A comparison between the experimental and theoretical bond lengths and angles was undertaken to verify the applicability of the selected level of theory. The obtained high correlation coefficients and low mean absolute errors confirmed that the optimized structure is suitable for further investigating the interactions between donor atoms and copper, along with the interactions between species in a neutral complex, using the Quantum Theory of Atoms in Molecules approach. The electrostatic potential surface map was used to reveal distinct charge distributions. The experimental and calculated FTIR spectra were compared, and the most prominent bands were assigned. The interactions with human serum albumin (HSA) were assessed by spectrofluorometric titration. The spontaneity of the process was proven, and the thermodynamic parameters of binding were calculated. Molecular docking analysis identified the most probable binding site, providing additional insight into the nature of the interactions. Full article
(This article belongs to the Special Issue Synthesis, Crystal Structures, and Biological Activities of Transition Metal Complexes)
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Figure 1
<p>Different binding modes of PLSC ligand.</p> Full article ">Figure 2
<p>(<b>a</b>) Molecular diagram of [Cu(PLSC)Cl(H<sub>2</sub>O)][NO<sub>3</sub>]∙H<sub>2</sub>O with non-hydrogen atoms represented by 50% displacement ellipsoids and hydrogen atoms as spheres of arbitrary size. (<b>b</b>) The overall structure is a 3-D hydrogen bonded network, comprised of parallel stacked 2-D sheets, supported by the Cu–OH<sub>2</sub> bond. (<b>c</b>) The structure is composed of infinite linear chains of [Cu(L)Cl(H<sub>2</sub>O)]<sup>+</sup> cations with N–H⋯O and O–H⋯O hydrogen bonds to the [NO<sub>3</sub>]<sup>−</sup> anions and water molecules. Further hydrogen bonding through the [NO<sub>3</sub>]<sup>−</sup> anion and the water molecules connects the chains into a 2-D sheet.</p> Full article ">Figure 3
<p>(<b>a</b>) Hirschfeld surface (normalized distances between −0.7021 (<b>red</b>) and 1.0586 (<b>blue</b>)) and (<b>b</b>) optimized structure (at B3LYP/6-311++G(d,p)(H,C,N,O)/LanL2DZ(Cu) level of theory) of [Cu(PLSC)Cl(H<sub>2</sub>O)](NO<sub>3</sub>)(H<sub>2</sub>O).</p> Full article ">Figure 4
<p>(<b>a</b>) BCPs (black circles) connecting atoms within the structure of [Cu(PLSC)Cl(H<sub>2</sub>O)](NO<sub>3</sub>)(H<sub>2</sub>O) and (<b>b</b>) electrostatic potential surfaces of the metal complex, nitrate ion, and free water molecule (<b>a</b>) and crystal structure (<b>b</b>). The potentials were calculated at the M06L-GD3/def2-TZVPP level and mapped at the surfaces defined by an electron density of 0.001 a.u. The atoms in the crystal structure are denoted with the following colors: hydrogen, white; carbon, gray; nitrogen, blue; oxygen, red; chlorine, green; and copper, orange.</p> Full article ">Figure 5
<p>Experimental (black line) and theoretical (at B3LYP/6-311++G(d,p)(H,C,N,O)/LanL2DZ(Cu), blue line) FTIR spectra of [Cu(PLSC)Cl(H<sub>2</sub>O)](NO<sub>3</sub>)(H<sub>2</sub>O).</p> Full article ">Figure 6
<p>Fluorescence emission spectra of HSA for the titration with various concentrations of [Cu(PLSC)Cl(H<sub>2</sub>O)](NO<sub>3</sub>) at (<b>a</b>) 27°, (<b>b</b>) 32°, and (<b>c</b>) 37 °C and (<b>d</b>) the Van ’t Hoff plot for the binding process.</p> Full article ">Figure 7
<p>(<b>a</b>) The pale gray structure represents HSA, with green ball-and-stick models indicating myristic acid molecules. In the FA8 binding site, dark gray spheres depict Trp214, while orange spheres represent the [Cu(PLSC)Cl(H<sub>2</sub>O)]<sup>+</sup> complex. The calculated (ΔG<sub>cal</sub>) and experimentally determined (ΔG<sub>exp</sub>) binding energies are provided. (<b>b</b>) Interactions of the Cu complex within the FA8 binding site of the HSA structure (PDB ID: 2BXN) in 3D representation and the calculated change in Gibbs free energy (ΔG<sub>cal</sub>).</p> Full article ">
14 pages, 4392 KiB  
Article
Syntheses and Crystal Structures of Two Metal–Organic Frameworks Formed from Cd2+ Ions Bridged by Long, Flexible 1,7-bis(4-Pyridyl)heptane Ligands with Different Counter-Ions
by M. John Plater, Ben M. De Silva, Mark R. St J. Foreman and William T. A. Harrison
Crystals 2024, 14(12), 1105; https://doi.org/10.3390/cryst14121105 - 23 Dec 2024
Viewed by 686
Abstract
The ethanol–water layered syntheses and crystal structures of the coordination polymers [Cd(C17H22N2)2(H2O)2]·2(ClO4)·C17H22N2·C2H5OH 2 and [Cd(C17H22N [...] Read more.
The ethanol–water layered syntheses and crystal structures of the coordination polymers [Cd(C17H22N2)2(H2O)2]·2(ClO4)·C17H22N2·C2H5OH 2 and [Cd(C17H22N2)2(NO3)2] 3 are reported, where C17H22N2 is a flexible spacer, 1,7-bis(4-pyridyl)heptane. In compound 2, trans-CdO2N4 octahedral nodes are linked by pairs of bridging ligands to result in [001] looped polymeric chains. The chains stack in the [100] direction to form (010) pseudo layers. Sandwiched between them are secondary sheets of free ligands, perchlorate ions and ethanol solvent molecules. Hydrogen bonds between these species help to consolidate the structure. Compound 3 contains trans-CdO2N4 octahedral nodes as parts of regular 44 nets, which propagate in the (103) plane. Three independent nets are interpenetrated. Full article
(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)
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<p>Structure of 1,7-<span class="html-italic">bis</span>(4-pyridyl)heptane.</p> Full article ">Figure 2
<p>The asymmetric unit of <b>2,</b> showing 50% displacement ellipsoids. The C-bound H atoms are omitted for clarity. Red is oxygen, green is chlorine and cadmium is orange.</p> Full article ">Figure 3
<p>Part of a looped [001] chain in the structure of <b>2</b>. In this and subsequent packing figures, the red, green and blue lines indicate the [100] (<span class="html-italic">a</span>-axis), [010] (<span class="html-italic">b</span>-axis) and [001] (<span class="html-italic">c</span>-axis) directions, respectively, with respect to the unit-cell origin, where the coloured lines intersect. The coordinated water is red.</p> Full article ">Figure 4
<p>The unit-cell packing for <b>2</b> viewed down [100], showing the (010) alternating sheets of [Cd(C<sub>17</sub>H<sub>22</sub>N<sub>2</sub>)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub><sup>2+</sup>]<span class="html-italic"><sub>n</sub></span> looped chains (at <span class="html-italic">y</span> ≈ 0, ½ and 1) and perchlorate ions, free ligands and ethanol solvent molecules (at <span class="html-italic">y</span> ≈ ¼ and ¾). Hydrogen bonds are indicated by black dashed lines. Oxygen is red and and chlorine is green.</p> Full article ">Figure 5
<p>The asymmetric unit of <b>3,</b> showing 50% displacement ellipsoids. The H atoms are omitted for clarity. Oxygen is red, nitrogen is blue and cadmium is orange.</p> Full article ">Figure 6
<p>Part of a 4<sup>4</sup> grid in the extended structure of <b>3</b>. Oxygen is red, nitrogen is blue and cadmium is yellow.</p> Full article ">Figure 7
<p>Interpenetrated (103) sheets of 4<sup>4</sup> grids coloured red, purple and blue in the structure of <b>3</b>. The three grids alternate in the [010] direction.</p> Full article ">Figure 8
<p>The unit-cell packing in <b>3</b> viewed down [010], showing the (103) sheets, which are alternately coloured green and orange for clarity.</p> Full article ">
12 pages, 3164 KiB  
Article
Simultaneous Improvement in Dissolution Behavior and Oral Bioavailability of Naproxen via Salt Formation
by Xian-Rui Zhang, Bao-Lin Wu, Jing-Jing Han and Jin-Qing Li
Crystals 2024, 14(12), 1104; https://doi.org/10.3390/cryst14121104 - 23 Dec 2024
Viewed by 842
Abstract
Naproxen (NAP) is a non-steroidal anti-inflammatory drug (NSAID) that belongs to the arylpropionic acid class. Classified as a Biopharmaceutical Classification System (BCS) class II drug, NAP exhibits low water solubility, thus resulting in restricted oral bioavailability. This study aimed to evaluate the effectiveness [...] Read more.
Naproxen (NAP) is a non-steroidal anti-inflammatory drug (NSAID) that belongs to the arylpropionic acid class. Classified as a Biopharmaceutical Classification System (BCS) class II drug, NAP exhibits low water solubility, thus resulting in restricted oral bioavailability. This study aimed to evaluate the effectiveness of pharmaceutical salts in enhancing the solubility and oral bioavailability of NAP. Two novel NAP salts, specifically naproxen-ethylenediamine (NAP-EDA) and naproxen-trometamol (NAP-TRIS), were synthesized using a 2:1 and 1:1 stoichiometric ratio, respectively. The NAP-EDA and NAP-TRIS powders were thoroughly characterized using single-crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC), providing a comprehensive understanding of their structural and thermal properties. Additionally, the solubilities and dissolution rates of NAP-EDA and NAP-TRIS salts were assessed in water and a pH 6.86 phosphate buffer. Notably, the solubility of NAP-TRIS salt increased markedly, by 397.5-fold in water and 6.2-fold at pH 6.86. Furthermore, in vivo pharmacokinetic studies in rats revealed that NAP-TRIS salt displayed faster absorption and higher peak blood concentrations compared to NAP. These results indicate that the NAP-TRIS salt effectively enhanced the solubility and oral bioavailability of naproxen. In conclusion, this study underscores the potential of pharmaceutical salts, particularly NAP-TRIS, in improving the solubility and oral bioavailability of drugs with low aqueous solubility, presenting a promising avenue for advancing drug delivery and therapeutic outcomes. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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Figure 1
<p>Molecule structures of NAP, EDA, and TRIS.</p> Full article ">Figure 2
<p>The 3D sandwich-like structure of NAP-EDA salts.</p> Full article ">Figure 3
<p>(<b>a</b>) The 2D laminar structure produced by the TRIS cations; (<b>b</b>) the 3D sandwich-type arrangement of NAP-TRIS salts, viewing from the <span class="html-italic">b</span> axis.</p> Full article ">Figure 4
<p>The carboxyl portion of NAP was trapped under hydrophobic group.</p> Full article ">Figure 5
<p>PXRD patterns of NAP, NAP-EDA and NAP-TRIS salts.</p> Full article ">Figure 6
<p>DSC curves of NAP, NAP-EDA and NAP-TRIS salts.</p> Full article ">Figure 7
<p>Dissolution profiles for NAP, NAP-EDA and NAP-TRIS salts in water and pH 6.86 solutions.</p> Full article ">Figure 8
<p>Pharmacokinetic profiles of NAP (black square) and NAP-TRIS (red circle) in male Sprague-Dawley rats. There were n = 6 rats in each group.</p> Full article ">
12 pages, 805 KiB  
Article
Axisymmetric Free Vibration of Functionally Graded Piezoelectric Circular Plates
by Yang Li and Yang Gao
Crystals 2024, 14(12), 1103; https://doi.org/10.3390/cryst14121103 - 22 Dec 2024
Viewed by 550
Abstract
An analytical solution is presented for axisymmetric free vibration analysis of a functionally graded piezoelectric circular plate on the basis of the three-dimensional elastic theory of piezoelectric materials. The material properties are assumed to follow an exponential law distribution through the thickness of [...] Read more.
An analytical solution is presented for axisymmetric free vibration analysis of a functionally graded piezoelectric circular plate on the basis of the three-dimensional elastic theory of piezoelectric materials. The material properties are assumed to follow an exponential law distribution through the thickness of the circular plate. The state space equations for the free vibration behavior of the functionally graded piezoelectric circular plate are developed based on the state space method. The finite Hankel transform is utilized to obtain an ordinary differential equation with variable coefficients. By virtue of the proposed exponential law model, we have ordinary differential equations with constant coefficients. Then, the free vibration behaviors of the functionally graded piezoelectric circular plate with two kinds of boundary conditions are investigated. Some numerical examples are given to validate the accuracy and stability of the present model. The influences of the exponential factor and thickness-to-span ratio on the natural frequency of the functionally graded piezoelectric circular plate, constrained by different boundary conditions, are discussed in detail. Full article
(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)
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Figure 1
<p>Configuration of an FGPM circular plate: (<b>a</b>) top view; (<b>b</b>) main view.</p> Full article ">Figure 2
<p>Variation in the first non-dimensional natural frequencies with respect to the exponential factor of the FGPM circular plate for different boundary conditions: (<b>a</b>) elastic simply support; (<b>b</b>) rigid slipping support.</p> Full article ">
12 pages, 5990 KiB  
Article
Mechanism of Aluminium Electrochemical Oxidation and Alumina Deposition Using a Carbon Sphere Electrode
by Shumin Yang, Ao Wang, Xuemei Lin, Yunkai Qi, Guochao Shi, Wei Han and Jianjun Gu
Crystals 2024, 14(12), 1102; https://doi.org/10.3390/cryst14121102 - 21 Dec 2024
Viewed by 735
Abstract
Using electromagnetic and electrochemical theories as a framework, this study examines the influence of carbon sphere electrodes on the distribution patterns of anodic oxidation and deposition current densities in metallic aluminium and porous anodic alumina. Theoretical calculations show that the current density symmetrically [...] Read more.
Using electromagnetic and electrochemical theories as a framework, this study examines the influence of carbon sphere electrodes on the distribution patterns of anodic oxidation and deposition current densities in metallic aluminium and porous anodic alumina. Theoretical calculations show that the current density symmetrically decreases from the centre outward under the effect of carbon sphere electrodes. Increasing the electrode distance improves the uniformity of the current distribution across the film, while decreasing the distance increases the rate of gradient change in current density. Simulation results reveal that at electrode spacings of 15 cm and 1 cm, the oxidation current density at the film centre is 1333 A/m2 and 2.9 × 105 A/m2, respectively. The current density gradually decreases outward along the radius, reaching 1330 A/m2 and 1.8 × 105 A/m2 at the edges, with observed current density gradient change rates of 500 A/m3 and 1.83 × 107 A/m3, respectively. Experimental results confirm that carbon sphere counter electrodes can create non-uniform oxidation and deposition electric fields. Microstructures with gradually varying symmetry can be generated by adjusting the electrode spacing, resulting in porous anodic alumina and composite films exhibiting iridescent, ring-like structural colours. The experimental findings align well with theoretical calculations and simulation results. Full article
(This article belongs to the Section Materials for Energy Applications)
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Figure 1
<p>Schematic diagram of electrochemical reaction electrolyser.</p> Full article ">Figure 2
<p>Schematic diagrams of the current lines for a carbon sphere electrode: (<b>a</b>) anodic oxidation; (<b>b</b>) electrodeposition.</p> Full article ">Figure 3
<p>Current density diagram of MATLAB simulation with different electrode spacing: (<b>a</b>) <span class="html-italic">h</span> = 15 cm; (<b>b</b>) <span class="html-italic">h</span> = 1 cm.</p> Full article ">Figure 4
<p>Digital photos of AAO thin films oxidised with a voltage of 30 V, electrode spacing of 15 cm for 7.5, 9, 10, 11, and 12 min. The regions labeled A and B correspond to the center and edge regions of the film, respectively.</p> Full article ">Figure 5
<p>SEM images of the surface and cross-section of the AAO thin film with an oxidation voltage of 30 V and an electrode distance of 15 cm for 11 min. (<b>a</b>) surface image of region A; (<b>b</b>) surface image of region B; (<b>c</b>) cross-section image of region A; (<b>d</b>) cross-section image of region B.</p> Full article ">Figure 6
<p>Digital photos of AAO thin films oxidised with a voltage of 30 V, electrode spacing of 1 cm for 1, 2, 3, and 4 min. The regions labeled A, B, C, and D correspond to distinct color zones extending outward from the film center.</p> Full article ">Figure 7
<p>SEM images of the surface of the AAO thin film. Parts (<b>a</b>–<b>d</b>) correspond to positions A to D in <a href="#crystals-14-01102-f006" class="html-fig">Figure 6</a> (3 min).</p> Full article ">Figure 8
<p>SEM images of the cross-section of the AAO thin film. Parts (<b>a</b>–<b>d</b>) correspond to positions A to D in <a href="#crystals-14-01102-f006" class="html-fig">Figure 6</a> (3 min).</p> Full article ">Figure 9
<p>Digital photos of AAO and Co@AAO composite films: (<b>a</b>) AAO thin films oxidised with a voltage of 30 V, electrode spacing of 15 cm for 12 min; (<b>b</b>–<b>e</b>) corresponding Co@AAO composite films were deposited with a voltage of 25 V for 20 s with electrode spacing of 5, 4, 3, and 2 cm, respectively.</p> Full article ">Figure 10
<p>SEM images of the cross-section of the Co@AAO composite film. Parts (<b>a</b>–<b>d</b>) correspond to positions A to D in <a href="#crystals-14-01102-f009" class="html-fig">Figure 9</a>e.</p> Full article ">Figure 11
<p>Hysteresis loops of the Co@AAO composite film at room temperature. Curves A and C correspond to positions A and C in <a href="#crystals-14-01102-f009" class="html-fig">Figure 9</a>e.</p> Full article ">
21 pages, 2882 KiB  
Article
Research on the Modulation Characteristics of LiNbO3 Crystals Based on the Three-Dimensional Ray Tracing Method
by Houpeng Sun, Yingchun Li, Laixian Zhang, Huichao Guo, Chenglong Luan, Haijing Zheng, Rong Li and Youchen Fan
Crystals 2024, 14(12), 1101; https://doi.org/10.3390/cryst14121101 - 20 Dec 2024
Viewed by 647
Abstract
To further study the electro-optical modulation characteristics of LiNbO3 crystals and analyze their modulation performance, a method for studying the modulation characteristics of LiNbO3 crystals, based on the three-dimensional ray tracing method, is introduced. With the help of the refractive index [...] Read more.
To further study the electro-optical modulation characteristics of LiNbO3 crystals and analyze their modulation performance, a method for studying the modulation characteristics of LiNbO3 crystals, based on the three-dimensional ray tracing method, is introduced. With the help of the refractive index ellipsoidal theory, the optical properties of LiNbO3 crystals under the influence of the Pockels effect are systematically investigated. The research results show that the optical properties of LiNbO3 crystals under the action of an external electric field can be divided into two cases: the crystal optical axis is parallel to the clear light direction, and the crystal optical axis is perpendicular to the clear light direction. Subsequently, starting from Maxwell’s equation and the matter equation, the analytical expressions of optical parameters such as refractive index, wave vector, light vector, optical path, and phase delay in electro-optical crystals are derived. Finally, the propagation law of LiNbO3 crystals when the light is incident in any direction, i.e., when the optical axis of the crystal is parallel to the clear direction and perpendicular to the clear direction, and the light intensity and field of view of the LiNbO3 crystal for electro-optical modulation are discussed. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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Figure 1
<p>The refractive index ellipsoid of a crystal.</p> Full article ">Figure 2
<p>Cartesian coordinate system of LiNbO<sub>3</sub> crystals when the optical axis of the crystal is parallel to the direction of clear light.</p> Full article ">Figure 3
<p>Cartesian coordinate system of LiNbO<sub>3</sub> crystals when the optical axis of the crystal is parallel to the direction of clear light.</p> Full article ">Figure 4
<p>Birefringence at the interface between an isotropic medium and a LiNbO<sub>3</sub> crystal.</p> Full article ">Figure 5
<p>Propagation of abnormal light in LiNiO<sub>3</sub> crystals.</p> Full article ">Figure 6
<p>Refractive index ellipsoid.</p> Full article ">Figure 7
<p>Crystal conoscopic interferogram when V = 0: (<b>a</b>) interference light intensity distribution; (<b>b</b>) influence of polarization direction on light intensity <math display="inline"><semantics> <mrow> <msup> <mrow> <mi>sin</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">[</mo> <mn>2</mn> <mi>ϕ</mi> <mo stretchy="false">(</mo> <mi>α</mi> <mo>,</mo> <mi>β</mi> <mo stretchy="false">)</mo> <mo stretchy="false">]</mo> </mrow> </semantics></math>; (<b>c</b>) influence of phase difference on light intensity <math display="inline"><semantics> <mrow> <msup> <mrow> <mi>sin</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">[</mo> <mstyle scriptlevel="0" displaystyle="true"> <mfrac> <mrow> <mi>θ</mi> <mo stretchy="false">(</mo> <mi>α</mi> <mo>,</mo> <mi>β</mi> <mo stretchy="false">)</mo> </mrow> <mn>2</mn> </mfrac> </mstyle> <mo stretchy="false">]</mo> </mrow> </semantics></math>; (<b>d</b>–<b>f</b>) is a magnification of the field of view at the center of (<b>a</b>–<b>c</b>) of the figure.</p> Full article ">Figure 8
<p>Crystal conoscopic interferogram when V = V<sub>π</sub>: (<b>a</b>) interference light intensity distribution; (<b>b</b>) influence of polarization direction on light intensity <math display="inline"><semantics> <mrow> <msup> <mrow> <mi>sin</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">[</mo> <mn>2</mn> <mi>ϕ</mi> <mo stretchy="false">(</mo> <mi>α</mi> <mo>,</mo> <mi>β</mi> <mo stretchy="false">)</mo> <mo stretchy="false">]</mo> </mrow> </semantics></math>; (<b>c</b>) influence of phase difference on light intensity <math display="inline"><semantics> <mrow> <msup> <mrow> <mi>sin</mi> </mrow> <mn>2</mn> </msup> <mo stretchy="false">[</mo> <mstyle scriptlevel="0" displaystyle="true"> <mfrac> <mrow> <mi>θ</mi> <mo stretchy="false">(</mo> <mi>α</mi> <mo>,</mo> <mi>β</mi> <mo stretchy="false">)</mo> </mrow> <mn>2</mn> </mfrac> </mstyle> <mo stretchy="false">]</mo> </mrow> </semantics></math>; (<b>d</b>–<b>f</b>) is a magnification of the field of view at the center of (<b>a</b>–<b>c</b>) of the figure.</p> Full article ">
8 pages, 2942 KiB  
Communication
Crystal Structure of the Biocide Methylisothiazolinone
by Richard Goddard, Rüdiger W. Seidel, Michael Patzer and Nils Nöthling
Crystals 2024, 14(12), 1100; https://doi.org/10.3390/cryst14121100 - 20 Dec 2024
Viewed by 575
Abstract
Methylisothiazolinone (MIT) is widely used as a biocide in numerous personal care products, glass-cleaning liquids, paints, and industrial applications. MIT and related isothiazolinones have attracted much attention for their allergenic properties such as contact dermatitis. Although the compound was first prepared in 1964 [...] Read more.
Methylisothiazolinone (MIT) is widely used as a biocide in numerous personal care products, glass-cleaning liquids, paints, and industrial applications. MIT and related isothiazolinones have attracted much attention for their allergenic properties such as contact dermatitis. Although the compound was first prepared in 1964 and has been widely used as a biocide since the 1970s, its crystal structure has so far not been reported. Here we report the solid state structure of MIT as determined by single crystal X-ray diffraction (SC-XRD) analysis of a crystal grown from the melt. MIT crystallizes as a layered structure with short C-H···O hydrogen bonding interactions within the sheets. The average distance between the sheets parallel to (1 0 2) is ca. 3.2 Å. The molecule exhibits a small C-S-N angle of 90.81(2)° and a methyl group that is slightly bent out of the plane of the planar five-membered ring. The sulfur atom does not undergo any significant intermolecular interactions. Full article
(This article belongs to the Section Crystal Engineering)
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Figure 1

Figure 1
<p>(<b>a</b>) Molecular structure of MIT in the crystal. Displacement ellipsoids are drawn at the 50% probability level. (<b>b</b>) Packing of the two molecules of MIT in the triclinic unit cell. Hydrogen atoms are omitted for clarity. o, a, b, and c, denote the origin and unit cell axes, respectively.</p> Full article ">Figure 2
<p>(<b>a</b>) Depiction of the layered arrangement of the molecules in the crystal of MIT. (<b>b</b>) View approximately perpendicular to the sheet highlighting the close packing of the molecules. Hydrogen atoms have been omitted for clarity. 0, a, b, and c, denote the origin and unit cell axes, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) Hirshfeld surface mapped with <span class="html-italic">d</span><sub>norm</sub> showing the major intermolecular interactions within the crystalline structure of MIT; (<b>b</b>) 2D fingerprint plot of the Hirshfeld surface providing an overview of the intermolecular interactions.</p> Full article ">Figure 4
<p>Superposition of the N-S-C units of the experimentally determined geometry of MIT (green) with those of the DFT optimized structure of the free molecule (pink) and MCI in the crystal structure (blue, CSD refcode: XIFRIO), illustrating the non-planarity of the nitrogen atom in the crystal structures of MIT and MCI and the different arrangements of the methyl hydrogen atoms.</p> Full article ">Scheme 1
<p>Structural formula of 2-methyl-2<span class="html-italic">H</span>-isothiazol-3-one (MIT).</p> Full article ">
13 pages, 3345 KiB  
Article
Rapid Assessment of Stable Crystal Structures in Single-Phase High-Entropy Alloys via Graph Neural Network-Based Surrogate Modelling
by Nicholas Beaver, Aniruddha Dive, Marina Wong, Keita Shimanuki, Ananya Patil, Anthony Ferrell and Mohsen B. Kivy
Crystals 2024, 14(12), 1099; https://doi.org/10.3390/cryst14121099 - 20 Dec 2024
Viewed by 729
Abstract
To develop a rapid, reliable, and cost-effective method for predicting the structure of single-phase high-entropy alloys, a Graph Neural Network (ALIGNN-FF)-based approach was introduced. This method was successfully tested on 132 different high-entropy alloys, and the results were analyzed and compared with density [...] Read more.
To develop a rapid, reliable, and cost-effective method for predicting the structure of single-phase high-entropy alloys, a Graph Neural Network (ALIGNN-FF)-based approach was introduced. This method was successfully tested on 132 different high-entropy alloys, and the results were analyzed and compared with density functional theory and valence electron concentration calculations. Additionally, the effects of various factors on prediction accuracy, including lattice parameters and the number of supercells with unique atomic configurations, were investigated. The ALIGNN-FF-based approach was subsequently used to predict the structure of a novel cobalt-free 3d high-entropy alloy, and the result was experimentally verified. Full article
(This article belongs to the Special Issue Preparation and Applications of High-Entropy Materials)
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<p>The flowchart summarizes our approach for rapidly predicting the stable crystal structure of HEAs. The first step involves generating a supercell with random atomic configuration for a selected composition of HEA. A Monte Carlo approach is used to sample 1000 configurations in the design space by randomly interchanging the positions of atoms in the supercell. Lastly, ALIGNN-FF was utilized to predict the lowest energy-stable crystal structure for any given composition of HEAs.</p> Full article ">Figure 2
<p>The representative starting configuration for Al<sub>2</sub>FeCuNiMn alloy, as generated by our approach in (<b>a</b>) BCC and (<b>b</b>) FCC supercell.</p> Full article ">Figure 3
<p>Calculated configurational energy for 792 distinct structures using DFT and ALIGNN-FF.</p> Full article ">Figure 4
<p>The comparison of stable crystal structures for 132 HEAs predicted by ALIGNN-FF (bottom two rows) and LSS1 (top three rows). Blue datapoints represent alloys wherein the predicted structures match experimental data. Red datapoints represent the alloys wherein the predicted structure did not match the experimentally reported structures.</p> Full article ">Figure 5
<p>Calculated mean energies (E<sub>m</sub>) for selected 132 HEAs. FCC and BCC supercells are represented as square and triangular datapoints, respectively. The dashed lines show the difference between the mean energies for FCC and BCC configurations that were sampled. Blue datapoints represent the alloys wherein the predicted structures matched experimental data. Red datapoints represent the alloys wherein the predicted structure did not match the experimentally reported structures.</p> Full article ">Figure 6
<p>Calculated average accuracy for predicting the structures of selected 132 HEAs as a function of sampling iterations. The error bars represent the accuracy for 9 iteration runs for each supercell.</p> Full article ">Figure 7
<p>The average accuracy of prediction of stable structures of selected 132 HEAs as a function of lattice parameters for FCC and BCC supercells.</p> Full article ">Figure 8
<p>Experimental characterizations of as-cast Al<sub>2</sub>FeCuNiMn HEA: (<b>top left</b>) SEM micrograph, (<b>top right</b>) XRF spectroscopy, and (<b>bottom</b>) XRD pattern.</p> Full article ">
18 pages, 16446 KiB  
Article
Effect of Zr, Zn, and Cu on Corrosion Resistance of As-Extruded Mg-3Sn-1Ca Alloy
by Zheng Jia, Sichao Du and Xiaowei Niu
Crystals 2024, 14(12), 1098; https://doi.org/10.3390/cryst14121098 - 20 Dec 2024
Viewed by 507
Abstract
TX31 (Mg-3Sn-1Ca) is an alloy with promising future applications. This study enhances the corrosion resistance of the TX31 alloy through the addition of Zr and Zn and compares the effects of individual Cu addition and Zn/Cu composite addition on the corrosion resistance of [...] Read more.
TX31 (Mg-3Sn-1Ca) is an alloy with promising future applications. This study enhances the corrosion resistance of the TX31 alloy through the addition of Zr and Zn and compares the effects of individual Cu addition and Zn/Cu composite addition on the corrosion resistance of the TX31 alloy. This study investigates the corrosion properties of TX31 alloys, focusing on the effects of the grain size, second phase, corrosion product film, and texture intensity. The addition of Zr and Zn changed the second-phase area fraction, while Cu introduced a new Mg2Cu phase. The TXZ311 alloy (Mg-3Sn-1Ca-1Zn) exhibited the best corrosion resistance, with a corrosion rate as low as 1.68 mm·year−1, a significant reduction compared to other alloys. This improvement is attributed to its higher fraction of high-angle grain boundaries (HAGBs) and the enhanced stability of the corrosion product film. The TXK311 alloy (Mg-3Sn-1Ca-1Zr) showed superior corrosion resistance, with a rate of 2.97 mm·year−1, due to its uniform and fine grain structure. In contrast, the TX31 alloy had the poorest corrosion resistance, with a corrosion rate of 3.66 mm·year−1, due to its bimodal microstructure. The addition of Cu in the TXC311 (Mg-3Sn-1Ca-1Cu) and TXCZ3111 (Mg-3Sn-1Ca-1Cu-1Zn) alloys resulted in micro-galvanic corrosion between α-Mg and Mg2Cu, which decreased the corrosion resistance. Full article
(This article belongs to the Special Issue Corrosion Phenomena in Metals)
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<p>Metallographic sampling location.</p> Full article ">Figure 2
<p>XRD patterns of six as-extruded alloys: (<b>a</b>) T3, (<b>b</b>) TX31, (<b>c</b>) TXK311, (<b>d</b>) TXZ311, (<b>e</b>) TXC311, and (<b>f</b>) TXCZ3111.</p> Full article ">Figure 3
<p>SEM images of six as-extruded alloys: (<b>a</b>) T3, (<b>b</b>) TX31, (<b>c</b>) TXK311, (<b>d</b>) TXZ311, (<b>e</b>) TXC311, and (<b>f</b>) TXCZ3111.</p> Full article ">Figure 4
<p>Inverse pole figure maps and pole figures: (<b>a</b>) T3, (<b>b</b>) TX31, (<b>c</b>) TXK311, (<b>d</b>) TXZ311, (<b>e</b>) TXC311, and (<b>f</b>) TXCZ3111.</p> Full article ">Figure 5
<p>Misorientation angle area fraction distribution: (<b>a</b>) T3, (<b>b</b>) TX31, (<b>c</b>) TXK311, (<b>d</b>) TXZ311, (<b>e</b>) TXC311, and (<b>f</b>) TXCZ3111.</p> Full article ">Figure 6
<p>The potentiodynamic polarization curves of six as-extruded alloys in 3.5 wt.% NaCl solution.</p> Full article ">Figure 7
<p>The EIS plots of six as-extruded alloys: (<b>a</b>) Bode diagram, (<b>b</b>) phase angle diagram, (<b>c</b>) Nyquist curves, and (<b>d</b>,<b>e</b>) equivalent circuit diagram.</p> Full article ">Figure 8
<p>(<b>a</b>) H<sub>2</sub> evolution volume; (<b>b</b>) corrosion rate.</p> Full article ">Figure 9
<p>Macroscopic and SEM images: (<b>a</b>,<b>d</b>) T3, (<b>b</b>,<b>e</b>) TX31, (<b>c</b>,<b>f</b>) TXK311, (<b>g</b>,<b>j</b>) TXZ311, (<b>h</b>,<b>k</b>) TXC311, and (<b>i</b>,<b>l</b>) TXCZ3111.</p> Full article ">Figure 10
<p>SEM/EDS plots of the corrosion product film: (<b>a</b>) T3, (<b>b</b>) TX31, (<b>c</b>) TXK311, (<b>d</b>) TXZ311, (<b>e</b>) TXC311, and (<b>f</b>) TXCZ3111.</p> Full article ">Figure 11
<p>XPS analysis of the TXZ311 alloy: (<b>a</b>) survey spectrum, (<b>b</b>–<b>f</b>) binding energy of Mg 1s, Sn 3d, Ca 2p, Zn2p, and O 1s in dry air, respectively, and (<b>g</b>–<b>k</b>) binding energy of Mg 1s, Sn 3d, Ca 2p, Zn2p, and O 1s in 3.5wt.%NaCl solution, respectively.</p> Full article ">Figure 12
<p>Longitudinal section corrosion morphology and local enlarged view of six as-extruded alloys: (<b>a</b>) T3, (<b>b</b>) TX31, (<b>c</b>) TXK311, (<b>d</b>) TXZ311, (<b>e</b>) TXC311, and (<b>f</b>) TXCZ3111.</p> Full article ">Figure 13
<p>Corrosion schematic model of the TX31 and TXZ311 alloys.</p> Full article ">Figure 14
<p>Corrosion rates of Mg-Sn-Ca alloys [<a href="#B7-crystals-14-01098" class="html-bibr">7</a>,<a href="#B48-crystals-14-01098" class="html-bibr">48</a>,<a href="#B49-crystals-14-01098" class="html-bibr">49</a>,<a href="#B50-crystals-14-01098" class="html-bibr">50</a>,<a href="#B51-crystals-14-01098" class="html-bibr">51</a>].</p> Full article ">
18 pages, 5161 KiB  
Article
Minimum and Stable Coefficient of Thermal Expansion by Three-Step Heat Treatment of Invar 36
by Mehmet Kul, Bekir Akgül, Yusuf Ziya Karabay, Leonhard Hitzler, Enes Sert and Markus Merkel
Crystals 2024, 14(12), 1097; https://doi.org/10.3390/cryst14121097 - 19 Dec 2024
Viewed by 885
Abstract
The low coefficient of thermal expansion of Invar 36 represents a significant consideration in light of its potential effects, particularly in industrial applications where thermal stability is of paramount importance. In light of this, a three-step heat treatment was employed, to reduce the [...] Read more.
The low coefficient of thermal expansion of Invar 36 represents a significant consideration in light of its potential effects, particularly in industrial applications where thermal stability is of paramount importance. In light of this, a three-step heat treatment was employed, to reduce the thermal expansion coefficient, and enhance the thermal dimensional stability. The ingots produced by vacuum induction melting were subjected to a warm-rolling process at 900 °C, followed by a three-step heat treatment consisting of water quenching at 850 °C, tempering at 350 °C with a holding time of 1 h, and aging at 100 °C for 24 h. This process enabled the coefficient of thermal expansion to remain almost unchanged, exhibiting values between 0.5 and 0.6 × 10−6/°C up to 150 °C. Following the heat treatment, the total elongation increased up to 40% as a natural consequence of the reduction of residual stresses, while a slight decrease in tensile strength was observed. The implementation of a three-step heat treatment process has facilitated an enhancement of the soft magnetic property, which has exhibited a decline in coercivity and an increase in saturation magnetization. As a consequence, three-step heat-treated Invar 36 alloys are emerging as a potential candidate for utilization in the aerospace and precision electronics industries, given their satisfactory physical and mechanical characteristics. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>The production processes of samples; (<b>a</b>) casting process by VIM, (<b>b</b>) warm–rolling adopted from [<a href="#B21-crystals-14-01097" class="html-bibr">21</a>] and (<b>c</b>) heat treatment diagram.</p> Full article ">Figure 2
<p>The normalized X-ray diffraction (XRD) patterns of the Invar samples in various states.</p> Full article ">Figure 3
<p>The optical microstructures images of the (<b>a</b>) as-cast (AC), (<b>b</b>) warm rolled at 900 °C (ACWT), (<b>c</b>) quenched from 850 °C and tempered at 350 °C for 1-h (ACQT) and (<b>d</b>) aged at 100 °C for 24 h (ACA).</p> Full article ">Figure 4
<p>The Fe-Ni phase diagram adopted from [<a href="#B49-crystals-14-01097" class="html-bibr">49</a>].</p> Full article ">Figure 5
<p>The SEM images of the (<b>a</b>) as-cast (AC), (<b>b</b>) warm rolled at 900 °C (ACWT), (<b>c</b>) quenched from 850 °C and tempered at 350 °C for 1 h (ACQT) and (<b>d</b>) aged at 100 °C for 24 h (ACA).</p> Full article ">Figure 6
<p>EDS (<b>a</b>) point and (<b>b</b>) mapping analysis.</p> Full article ">Figure 7
<p>CTE results of the as-cast (AC), warm rolled at 900 °C (ACWT), quenched from 850 °C and tempered at 350 °C for 1-h (ACQT) and aged at 100 °C for 24 h (ACA) samples.</p> Full article ">Figure 8
<p>(<b>a</b>) Stress–Strain curves of the samples and (<b>b</b>) the UTS, total elongation, micro-hardness (HV5) results of the different samples.</p> Full article ">Figure 9
<p>The magnetization versus magnetic-field hysteresis loop was measured at room temperature for the different-condition Invar 36 samples.</p> Full article ">
13 pages, 5166 KiB  
Article
A Design of Vanadium Dioxide for Dynamic Color Gamut Modulation Based on Fano Resonance
by Junyang Zhu, Ruimei Zeng, Yiwen Yang, Yiqun Zhou, Zhen Gao, Qi Wang, Ruijin Hong and Dawei Zhang
Crystals 2024, 14(12), 1096; https://doi.org/10.3390/cryst14121096 - 19 Dec 2024
Viewed by 559
Abstract
In this paper, a design of vanadium dioxide for dynamic color gamut modulation based on Fano resonance is proposed. This approach facilitates color modulation by manipulating the phase transition state of vanadium dioxide. The device integrates both broadband and narrowband filters, featuring a [...] Read more.
In this paper, a design of vanadium dioxide for dynamic color gamut modulation based on Fano resonance is proposed. This approach facilitates color modulation by manipulating the phase transition state of vanadium dioxide. The device integrates both broadband and narrowband filters, featuring a structure consisting of a top silver mesh, a layer of vanadium dioxide, and a Fabry–Pérot cavity, which allows for effective modulation of the reflectance spectrum. Simulation results demonstrate that when vanadium dioxide is in its insulating state, the maximum reflectivity observed in the device spectrum, reaching 43.1%, appears at 475 nm. Conversely, when vanadium dioxide transitions to its metallic state, the peak wavelength shifts to 688 nm, accompanied by an increased reflectance peak of 59.3%. Analysis of electric field distributions reveals that the intensity caused by surface plasmonic resonance dominates over the excited Fano resonance while vanadium dioxide is in its insulating state, which is the opposite of when vanadium dioxide transitions to its metallic state. This behavior exhibits an excellent dynamic color-tuning capability. Specifically, the phase transition of vanadium dioxide results in a color difference ∆E2000 of up to 36.7, while maintaining good color saturation. This technique holds significant potential for applications such as dynamic color display and anti-counterfeit labeling. Full article
(This article belongs to the Special Issue Preparation and Characterization of Optoelectronic Functional Films)
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<p>Refractive index of VO<sub>2</sub>, (<b>a</b>) in the insulating state, (<b>b</b>) in the metallic state.</p> Full article ">Figure 2
<p>Structure of the designed FROC; (<b>a</b>) top view, (<b>b</b>) front view. (<b>c</b>) Schematic of the FROC array.</p> Full article ">Figure 3
<p>Reflection spectrum of (<b>a</b>) broadband filter, (<b>b</b>) narrowband filter.</p> Full article ">Figure 4
<p>(<b>a</b>) Reflection spectrum when incident light vertically irradiates. (<b>b</b>) Chromaticity coordinates marked in the CIE1931 chromaticity diagram according to the spectrum shown in (<b>a</b>).</p> Full article ">Figure 5
<p>Reflection spectra (<b>a</b>) of the broadband filter (upper part of the FROC), (<b>b</b>) of the FROC, when <span class="html-italic">h</span><sub>2</sub> is varied from 20 nm to 60 nm at a step of 10 nm. (<b>c</b>) Chromaticity coordinates marked in the CIE1931 chromaticity diagram according to the spectrum shown in (<b>b</b>). The black solid lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its insulating state, and the white dashed lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its metallic state.</p> Full article ">Figure 6
<p>(<b>a</b>) Reflection spectrum of the FROC when <span class="html-italic">h</span><sub>3</sub> is varied from 10 nm to 40 nm at a step of 10 nm. (<b>b</b>) Chromaticity coordinates marked in the CIE1931 chromaticity diagram according to the spectrum shown in (<b>a</b>). The black solid lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its insulating state, and the white dashed lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its metallic state.</p> Full article ">Figure 7
<p>Reflection spectra (<b>a</b>) of the upper broadband filter, (<b>b</b>) of the FROC, when <span class="html-italic">L</span> is varied from 190 nm to 130 nm at a step of 10 nm. (<b>c</b>) Chromaticity coordinates marked in the CIE1931 chromaticity diagram according to the spectrum shown in (<b>b</b>). The black solid lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its insulating state, and the white dashed lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its metallic state.</p> Full article ">Figure 8
<p>Reflection spectra (<b>a</b>) of the upper broadband filter, (<b>b</b>) of the FROC, when <span class="html-italic">h</span><sub>4</sub> is varied from 30 nm to 70 nm at a step of 10 nm. (<b>c</b>) Chromaticity coordinates marked in the CIE1931 chromaticity diagram according to the spectrum shown in (<b>b</b>). The black solid lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its insulating state, and the white dashed lines show the movement trajectory of the chromaticity coordinates when VO<sub>2</sub> is in its metallic state.</p> Full article ">Figure 9
<p>Electric field distributions of the broadband filter in the x-z plane; (<b>a</b>) wavelength of 695 nm light normally illustrated on VO<sub>2</sub> (insulating state); (<b>b</b>) wavelength of 688 nm light vertically irradiates on VO<sub>2</sub> (metallic state). Electric field distributions of the FROC in the x-z plane; (<b>c</b>) wavelength of 695 nm light vertically irradiates on VO<sub>2</sub> (insulating state); (<b>d</b>) wavelength of 688 nm light vertically irradiates on VO<sub>2</sub> (metallic state). The structures of the broadband filter and FROC depicted by the solid black lines are shown in the figure.</p> Full article ">Figure 10
<p>(<b>a</b>) “USST” pattern arranged by the array of the designed FROCs, which can be reversibly switched between visible and invisible by changing the temperature. The yellowish area is reflected by the structures without the top square grids (<span class="html-italic">L</span> is set as 0). (<b>b</b>) Butterfly patterns when VO<sub>2</sub> is in the insulating or metallic state and the length <span class="html-italic">L</span> is set as 190 nm or 160 nm, respectively.</p> Full article ">
9 pages, 2206 KiB  
Article
Development of Model Representations of Materials with Ordered Distribution of Vacancies
by Ekaterina N. Muratova, Vyacheslav A. Moshnikov and Anton A. Zhilenkov
Crystals 2024, 14(12), 1095; https://doi.org/10.3390/cryst14121095 - 19 Dec 2024
Viewed by 496
Abstract
This paper presents an overview of research results on the physical and technological features of crystal formation with an ordered distribution of vacancies. It is noted that the composition and properties of complex chalcogenide phases are not always described by the traditional concepts [...] Read more.
This paper presents an overview of research results on the physical and technological features of crystal formation with an ordered distribution of vacancies. It is noted that the composition and properties of complex chalcogenide phases are not always described by the traditional concepts behind Kroeger’s theory. Model concepts are considered in which the carriers of properties in the crystalline state are not molecules, but an elementary crystalline element with a given arrangement of nodes with atoms and vacancies. It is established that the introduction of the term “quasi-element atom” of the zero group for a vacancy allows us to predict a number of compounds with an ordered distribution of vacancies. Examples of the analysis of peritectic multicomponent compounds and solid solutions based on them are given. Quasi-crystalline concepts are applicable to perovskite materials used in solar cells. It is shown that the photoluminescence of perovskite lead-cesium halides is determined by crystalline structural subunits i.e., the anionic octets. This is the reason for the improvement in the luminescent properties of colloidal quantum CsPbBr3 dots under radiation exposure conditions. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>Triangulation of the ternary system Ag-In-S, (In<sub>2</sub>S-Ag<sub>2</sub>S<sub>3</sub> is the “four” line, In<sub>2</sub>S<sub>3</sub>-Ag<sub>2</sub>S is the “eight” line).</p> Full article ">Figure 2
<p>Triangulation of the pseudo-triple system [V]-In-S, (In<sub>2</sub>S-[V]S<sub>2</sub> is the “four” line, In<sub>2</sub>S<sub>3</sub>-[V] is the “eight” line).</p> Full article ">Figure 3
<p>Tetrahedration of the pseudo-quaternary system [V]-Ag-In-S. The arrow points to a known chemical compound that we have marked in <a href="#crystals-14-01095-f001" class="html-fig">Figure 1</a>.</p> Full article ">Figure 4
<p>State diagram of the PbTe-Ga<sub>2</sub>Te<sub>3</sub> system.</p> Full article ">Figure 5
<p>The main compounds of three-component systems of lead-cesium halides on the Gibbs triangle (underlined binary compounds do not exist for all halogens X from the series Cl, Br, I) and partial triangulation of the system using the example of CsPbCl<sub>3</sub>) [<a href="#B17-crystals-14-01095" class="html-bibr">17</a>].</p> Full article ">Figure 6
<p>High-resolution transmission electron microscopy images of CsPbBr<sub>3</sub> nanocrystal [<a href="#B17-crystals-14-01095" class="html-bibr">17</a>]. (<b>a</b>) TEM images with 100 nm resolution; (<b>b</b>) TEM images with 5 nm resolution.</p> Full article ">Figure 7
<p>Dynamics of changes in photoluminescence spectra during the anionic substitution of Br–I: triangles represent the time dependence of the energy corresponding to the maximum PL intensity, and dots represent the time dependence of the half-width of the PL line [<a href="#B17-crystals-14-01095" class="html-bibr">17</a>].</p> Full article ">
17 pages, 4267 KiB  
Article
Crystallographic and NMR Study of Streptococcus pneumonia LCP Protein PsrSp Indicate the Importance of Dynamics in Four Long Loops for Ligand Specificity
by Tatyana Sandalova, Benedetta Maria Sala, Martin Moche, Hans-Gustaf Ljunggren, Evren Alici, Birgitta Henriques-Normark, Tatiana Agback, Dmitry Lesovoy, Peter Agback and Adnane Achour
Crystals 2024, 14(12), 1094; https://doi.org/10.3390/cryst14121094 - 19 Dec 2024
Viewed by 746
Abstract
The crystal structure of the extracellular region of the second pneumococcal LCP, a polyisoprenyl-teichoic acid-peptidoglycan teichoic acid transferase PsrSp, was determined and refined to 2.15 Å resolution. Despite the low sequence homology with other LCP proteins, the PsrSp maintains the [...] Read more.
The crystal structure of the extracellular region of the second pneumococcal LCP, a polyisoprenyl-teichoic acid-peptidoglycan teichoic acid transferase PsrSp, was determined and refined to 2.15 Å resolution. Despite the low sequence homology with other LCP proteins, the PsrSp maintains the fold of the LCP domain, and the positions of the residues suggested to participate in the transferase function are conserved. The tunnel found in the PsrSp between the central β-sheet and three α-helices is wide enough to accommodate polyisoprenyl-teichoic acid. Comparison of the crystallographic temperature factors of LCP from distinct bacteria demonstrated that the four long loops located close to the teichoic acid and peptidoglycan binding sites have different relative mobilities. To compare the dynamics of the PsrSp in crystalline state and in solution, NMR spectra were recorded, and 88% of the residues were assigned in the 1H-15N TROSY HSQC spectra. Perfect accordance in the secondary structure of the crystal structure of PsrSp with NMR data demonstrated correct assignment. Moreover, the relative mobility of the essential loops estimated from the crystallographic B-factor is in good agreement with order parameter S2, predicted from chemical shift. We hypothesize that the dynamics of these loops are important for the substrate promiscuity of LCP proteins. Full article
(This article belongs to the Special Issue Crystallography of Enzymes)
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<p><b>Crystal structure of the <span class="html-italic">S. pneumoniae</span>-associated Psr<sub>Sp</sub>.</b> (<b>a</b>). Superposition of the three Psr<sub>Sp</sub> molecules found in the asymmetric unit of the crystal structure indicates flexibility in three different regions annotated by the corresponding residues. The three Psr<sub>Sp</sub> molecules A, B and C found in the asymmetric unit are in red, blue, and green, respectively. (<b>b</b>). The crystal structure of Psr<sub>Sp</sub> reveals a typical overall LCP fold despite low sequence homology to other members of the LCP protein family. (<b>c</b>). Superposition of Psr<sub>Sp</sub> (in green) on the crystal structures of the three most similar LCP, LcpA<sub>Sa</sub> from <span class="html-italic">Staphylococcus aureus</span> (in blue, 6uex.pdb), TagT from <span class="html-italic">Bacillus subtilis</span> (in red, 6uf5.pdb) and Cps2A from <span class="html-italic">S. pneumoniae</span> (in orange, 4de8.pdb) demonstrates that the main difference between these LCP molecules resides in the length of the P1–P3 protrusions and in the conformations of four loops, that we named A, B, C, and D. (<b>d</b>). The A, B, C, and D regions of Psr<sub>Sp</sub>, suggested to be important for substrate binding, are displayed in red, blue, yellow and magenta, respectively. The localization of the substrate binding tunnel is indicated.</p> Full article ">Figure 2
<p><b>Superposition of LcpA<sub>Sa</sub>/C<sub>40</sub>-PP-GlcNAc onto ligand-free Psr<sub>Sp</sub> reveals that the ligand fits well to the substrate-binding site of Psr<sub>Sp</sub> and that all catalytic residues are located appropriately.</b> (<b>a</b>). The C<sub>40</sub>-PP-GlcNAc ligand found in the active site of LcpA<sub>Sa</sub>, is displayed as light blue spheres inside the tunnel within Psr<sub>Sp</sub>. The four regions A–D that are suggested to be important for substrate binding are colored in red, blue, orange and magenta, respectively. (<b>b</b>). LCP-conserved residues are located in Psr<sub>Sp</sub> close to the pyrophosphate moiety of the ligand. (<b>c</b>). The hydrophobic part of the ligand is surrounded either by conserved residues (pink) or non-conserved but still hydrophobic residues (gray) of Psr<sub>Sp</sub>.</p> Full article ">Figure 3
<p><b>Comparison of electrostatic surface potentials in different LCP indicates different substrate preferences.</b> The surfaces of LCP from different bacterial species, including Psr<sub>Sp</sub>, LcpA<sub>Sa</sub>, Cps2A, and TagT<sub>Bs</sub> are colored according to their electrostatic potential. Positively and negatively charged regions are in blue and red, respectively. The entry of the tunnel for the ligand is indicated by a yellow arrowed circle. This structural comparison indicates differences in sizes at the entry of the tunnel. It also reveals that the entry of the tunnel is surrounded mainly by positively charged residues. Differences in size and in residue charge distribution can be related to different substrate preferences.</p> Full article ">Figure 4
<p><b>Comparison of crystallographic temperature B-factors in LCP crystal structures from different bacteria demonstrates differences in the mobility of specific loops.</b> The rigid parts of each LCP protein are colored in blue, while the flexible parts are in red. This comparison allowed us to differentiate between the relative flexibility of the loops in the LCP proteins, allowing us to establish patterns. While loops A and B are significantly more flexible than C and D in Psr<sub>Sp</sub> (A = B &gt;&gt; C = D), loops B and C are more flexible than loop A, which in turn is much more flexible than loop D in Csp2A from <span class="html-italic">S. pneumoniae</span> (B = C &gt; A &gt;&gt; D). In contrast, the LCP protein LcpA from <span class="html-italic">S. aureus</span> has a pattern in which D = C &gt; B &gt;&gt; A».</p> Full article ">Figure 5
<p><b><sup>1</sup>H-<sup>15</sup>N TROSY HSQC spectra of Psr<sub>Sp</sub> at T = 308 K with backbone amide assignments.</b> (<b>a</b>). The amino acid sequence of the Psr<sub>Sp</sub> construct used in our NMR analyses is presented. Residues from the His-tag are indicated in italic blue. (<b>b</b>). <sup>1</sup>H-<sup>15</sup>N TROSY HSQC spectrum at T = 308 K with its extended crowded part (<b>c</b>). from the <sup>15</sup>N, <sup>13</sup>C, <sup>2</sup>H labeled Psr<sub>Sp</sub> at 0.7 mM concentration in a 25 mM sodium phosphate buffer (Na<sup>2</sup>HPO<sub>4</sub><sup>+</sup>NaH<sub>2</sub>PO<sub>4</sub>) PO<sub>4</sub><sup>3-</sup>, pH 6.8 containing 100 mM NaCl, 1 mM NaN<sub>3</sub>, 10 (<span class="html-italic">v</span>/<span class="html-italic">v</span>) % D<sub>2</sub>O and 0.1 mM DSS. The chemical shift assignment of NH backbone is shown by the number and amino acid symbols corresponding to the sequence. The assignment is presented only for residues which have cross-peaks observed at T = 308 K. (<b>d</b>). Residues of Psr<sub>Sp</sub> with fully assigned peaks in the NMR spectrum are displayed in yellow. Carbon-assigned residues are shown in green, and non-assigned residues in red. (<b>e</b>). The overall structure of Psr<sub>Sp</sub> colored in red–white–blue according to the predicted order parameter S<sup>2</sup> with flexible regions in red, and rigid regions in blue.</p> Full article ">
9 pages, 2897 KiB  
Article
Optical Parameters of Deuterated Triglycine Sulfate in Terahertz Range
by Kirill Brekhov, Anastasia Gorbatova, Ekaterina Lebedeva, Pavel Avdeev, Andrey Kudryavtsev, Oleg Chefonov, Sergey Zhukov and Elena Mishina
Crystals 2024, 14(12), 1093; https://doi.org/10.3390/cryst14121093 - 19 Dec 2024
Viewed by 535
Abstract
In this work, the optical parameters of a 550 μm thick deuterated triglycine sulfate (DTGS) crystal in the range of 0.3–1.5 THz were investigated in low and high fields by time-domain spectroscopy. The X and Z axes of the refractive index ellipsoid were [...] Read more.
In this work, the optical parameters of a 550 μm thick deuterated triglycine sulfate (DTGS) crystal in the range of 0.3–1.5 THz were investigated in low and high fields by time-domain spectroscopy. The X and Z axes of the refractive index ellipsoid were identified, and the refractive indices and extinction coefficients were determined. In addition, it was shown that, in strong THz fields, a phonon A-mode with a frequency of about 40 cm−1 can be excited in the DTGS crystal when the THz wave vector coincides with the polar axis of the crystal and the polarization of the THz radiation coincides with the X-axis of the crystal. The use of the observed effect and the determination of the mode excitation parameters can be twofold. First, they show the limits of the THz field for non-invasive action on the crystal. Second, they present the mode excitation conditions that can be used, for example, in controllable absorbers. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>XRD pattern of the DTGS crystal.</p> Full article ">Figure 2
<p>Schematic and photo of the experimental terahertz spectroscopy facilities used in this work: (<b>a</b>) Facility 1, (<b>b</b>) Facility 2–commercial THz spectrometer Tera K15 (Menlo System) [<a href="#B27-crystals-14-01093" class="html-bibr">27</a>], (<b>c</b>) Facility 3.</p> Full article ">Figure 3
<p>Azimuthal dependences of the (<b>a</b>) X-and (<b>b</b>) Y-components of the THz signal on DTGS crystal rotation angle (Facility 1). X- and Y-components of the THz field are directed along the X and Y axes of the laboratory frame (blue axes in the left panel). The gray area is the refractive indices ellipsoid. Red axes on the left panel denote its main axes.</p> Full article ">Figure 4
<p>Temporal (<b>left panels</b>) and spectral (<b>right panels</b>) forms of the THz signals for facilities 2 and 3.</p> Full article ">Figure 5
<p>Optical constants of DTGS crystal for different THz field strength and two sample orientations: (<b>a</b>) spectra of the refractive indices <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>n</mi> </mrow> <mrow> <mi>x</mi> </mrow> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>n</mi> </mrow> <mrow> <mi>z</mi> </mrow> </msub> </mrow> </semantics></math> (Facility 2); (<b>d</b>) spectra of the extinction coefficients <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>x</mi> </mrow> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>z</mi> </mrow> </msub> </mrow> </semantics></math> (Facility 2); (<b>b</b>,<b>c</b>,<b>e</b>,<b>f</b>) spectra of the optical constants for different values of the maximum field strength: <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>n</mi> </mrow> <mrow> <mi>x</mi> </mrow> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>n</mi> </mrow> <mrow> <mi>z</mi> </mrow> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>x</mi> </mrow> </msub> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <msub> <mrow> <mi>k</mi> </mrow> <mrow> <mi>z</mi> </mrow> </msub> </mrow> </semantics></math>, correspondingly (Facility 3).</p> Full article ">
12 pages, 3272 KiB  
Article
Microstructural Evolution and Thermal Stability of Long Period Stacking Ordered Phases in Mg97Er2Ni1 and Mg97Er2Zn1 Alloys
by Jian Yin, Yushun Liu and Guo-Zhen Zhu
Crystals 2024, 14(12), 1092; https://doi.org/10.3390/cryst14121092 - 19 Dec 2024
Viewed by 698
Abstract
The influence of transition metals (Ni and Zn) on the formation, morphology, and thermal stability of long-period stacking ordered (LPSO) phases in Mg97Er2Ni1 and Mg97Er2Zn1 alloys was investigated. In the as-cast state, both [...] Read more.
The influence of transition metals (Ni and Zn) on the formation, morphology, and thermal stability of long-period stacking ordered (LPSO) phases in Mg97Er2Ni1 and Mg97Er2Zn1 alloys was investigated. In the as-cast state, both alloys consist of α-Mg and LPSO phases. Heat treatment at 540 °C for 20 h dissolves block-like and lamellar LPSO phases into the α-Mg matrix in the Mg97Er2Zn1 alloy, with lamellar LPSO phases reprecipitating during subsequent cooling from 540 °C to 400 °C. Comparative analysis shows that Ni significantly enhances the thermal stability of the LPSO phase compared to Zn. Ni favors the formation of block-shaped LPSO phases, while Zn facilitates lamellar LPSO precipitation within the α-Mg matrix. The LPSO phase in the Mg97Er2Ni1 alloy exhibits an exceptionally high melting temperature of 605 °C, the highest reported for an LPSO phase. Additionally, heat treatment at 500 °C for 100 h preserves the area fraction of the LPSO phase in the Mg97Er2Ni1 alloy, and at 540 °C for 100 h, the LPSO grains grow without phase dissolution or structural transformation of their 18R-type configuration. These findings provide valuable insights into the role of alloying transition metal elements in controlling the stability and morphology of LPSO phases, offering pathways for tailoring the morphology of the LPSO phase in the Mg-based alloys. Full article
(This article belongs to the Special Issue Advances in Metal Matrix Composites: Structure, Properties and Applications)
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<p>XRD patterns of as-cast (<b>a</b>) Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> and (<b>b</b>) Mg<sub>97</sub>Er<sub>2</sub>Zn<sub>1</sub> alloys.</p> Full article ">Figure 2
<p>SEM images of the as-cast alloys: (<b>a</b>,<b>c</b>) Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> and (<b>b</b>,<b>d</b>) Mg<sub>97</sub>Er<sub>2</sub>Zn<sub>1</sub>, along with (<b>e</b>) the corresponding EDS results.</p> Full article ">Figure 3
<p>DTA curves of the as-cast Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> and Mg<sub>97</sub>Er<sub>2</sub>Zn<sub>1</sub> alloys.</p> Full article ">Figure 4
<p>SEM images of (<b>a</b>,<b>c</b>) Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> and (<b>b</b>,<b>d</b>) Mg<sub>97</sub>Er<sub>2</sub>Zn<sub>1</sub> alloys after heat treatment at 540 °C for 20 h, along with (<b>e</b>) the corresponding EDS results.</p> Full article ">Figure 5
<p>SEM images of (<b>a</b>,<b>c</b>) Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> and (<b>b</b>,<b>d</b>) Mg<sub>97</sub>Er<sub>2</sub>Zn<sub>1</sub> alloys after heat treatment at 540 °C for 20 h and subsequent furnace cooling to 400 °C followed by quenching in the water, along with (<b>e</b>) the corresponding EDS results.</p> Full article ">Figure 6
<p>SEM images of Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> alloys: (<b>a</b>,<b>b</b>) in the as-cast condition, (<b>c</b>,<b>d</b>) after heat treatment at 500 °C for 100 h, and (<b>e</b>,<b>f</b>) after heat treatment at 540 °C for 100 h. The corresponding EDS results for the heat-treated alloys are presented in (<b>g</b>).</p> Full article ">Figure 7
<p>High-resolution TEM image and corresponding SAED pattern of the LPSO phase in the Mg<sub>97</sub>Er<sub>2</sub>Ni<sub>1</sub> alloys: (<b>a</b>,<b>b</b>) as-cast; (<b>c</b>,<b>d</b>) heat-treated alloys at 540 °C for 100 h. The electron beam is parallel to [11<math display="inline"><semantics> <mover accent="true"> <mn>2</mn> <mo>¯</mo> </mover> </semantics></math>0] of the α-Mg.</p> Full article ">
11 pages, 2514 KiB  
Article
The Synthesis and Characterization of CdS Nanostructures Using a SiO2/Si Ion-Track Template
by Aiman Akylbekova, Kyzdarkhan Mantiyeva, Alma Dauletbekova, Abdirash Akilbekov, Zein Baimukhanov, Liudmila Vlasukova, Gulnara Aralbayeva, Ainash Abdrakhmetova, Assyl-Dastan Bazarbek and Fariza Abdihalikova
Crystals 2024, 14(12), 1091; https://doi.org/10.3390/cryst14121091 - 19 Dec 2024
Viewed by 832
Abstract
In the present work, we present the process of preparing CdS nanostructures based on templating synthesis using chemical deposition (CD) on a SiO2/Si substrate. A 0.7 μm thick silicon dioxide film was thermally prepared on the surface of an n-type conduction [...] Read more.
In the present work, we present the process of preparing CdS nanostructures based on templating synthesis using chemical deposition (CD) on a SiO2/Si substrate. A 0.7 μm thick silicon dioxide film was thermally prepared on the surface of an n-type conduction Si wafer, followed by the creation of latent ion tracks on the film by irradiating them with swift heavy Xe ions with an energy of 231 MeV and a fluence of 108 cm−2. As a result of etching in hydrofluoric acid solution (4%), pores in the form of truncated cones with different diameters were formed. The filling of the nanopores with cadmium sulfide was carried out via templated synthesis using CD methods on a SiO2 nanopores/Si substrate for 20–40 min. After CdS synthesis, the surfaces of nanoporous SiO2 nanopores/Si were examined using a scanning electron microscope to determine the pore sizes and the degree of pore filling. The crystal structure of the filled silica nanopores was investigated using X-ray diffraction, which showed CdS nanocrystals with an orthorhombic structure with symmetry group 59 Pmmn observed at 2θ angles of 61. 48° and 69.25°. Photoluminescence spectra were recorded at room temperature in the spectral range of 300–800 nm at an excitation wavelength of 240 nm, where emission bands centered around 2.53 eV, 2.45 eV, and 2.37 eV were detected. The study of the CVCs showed that, with increasing forward bias voltage, there was a significant increase in the forward current in the samples with a high degree of occupancy of CdS nanoparticles, which showed the one-way electronic conductivity of CdS/SiO2/Si nanostructures. For the first time, CdS nanostructures with orthorhombic crystal structure were obtained using track templating synthesis, and the density of electronic states was modeled using quantum–chemical calculations. Comparative analysis of experimental and calculated data of nanostructure parameters showed good agreement and are confirmed by the results of other authors. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>SEM images of nanopores: (<b>a</b>) before nanopore deposition, (<b>b</b>) after 30 min of CD at T = 75 °C, and (<b>c</b>) size of nanopores filled with CdS.</p> Full article ">Figure 2
<p>X-ray patterns of CdS nanostructures after CD deposition times of 20 min (1), 30 min (2), and 40 min (3).</p> Full article ">Figure 3
<p>Raman light scattering spectrum of CdS nanostructures after CD time 40 min.</p> Full article ">Figure 4
<p>(<b>a</b>)—Primitive unit cell of CdS; (<b>b</b>)—The density of states and the zone structure of orthorhombic CdS.</p> Full article ">Figure 5
<p>Decomposition of (PL) spectra of CdS/SiO<sub>2 nanopores</sub>/Si after 30 min of CD into independent Gaussians.</p> Full article ">Figure 6
<p>CVCs of CdS/SiO<sub>2 nanopores</sub>/Si nanostructures after different CD times: 1—initial template SiO<sub>2 nanopores</sub>/Si; 2—20 min; 3—30 min; 4—40 min.</p> Full article ">
15 pages, 3467 KiB  
Article
First Principle Analysis on Elastic and Mechanical Behavior of High-Pressure Hexagonal MgZn2 Phase
by Chuncai Xiao, Baiyuan Yang, Zhangli Lai, Xianshi Zeng, Zhiquan Chen, Yunzhi Zhou and Donglan Wu
Crystals 2024, 14(12), 1090; https://doi.org/10.3390/cryst14121090 - 18 Dec 2024
Viewed by 620
Abstract
There is a paucity of previous related studies exploring hexagonal MgZn2 in high-pressure environments. This study systematically analyzes the mechanical behavior of MgZn2 hexagonal alloys under high-pressure conditions using first principle calculations, bridging the gap in research in this area in [...] Read more.
There is a paucity of previous related studies exploring hexagonal MgZn2 in high-pressure environments. This study systematically analyzes the mechanical behavior of MgZn2 hexagonal alloys under high-pressure conditions using first principle calculations, bridging the gap in research in this area in the field. The results reveal that, with increasing pressure, the crystallite spacing (a/a0,c/c0) and ratio of volumes (V/V0) decrease significantly, indicating the structural condensation of the material under high pressure. Elastic constant analysis showed a notable enhancement in all constants, except for C13. Among them, C11 increased from 87.399 GPa to 311.45 GPa, and C33 increased from 135.279 GPa to 341.739 GPa, showing a faster growth rate, suggesting improved tensile strength in the material along the tensile direction. Mechanical stability assessments confirmed that the alloy remains stable over the 0 to 30 GPa pressure range. Further material characterization indicated that Poisson’s ratio remained above 0.26 at pressures from 0 to 30 GPa, suggesting excellent ductility and agreeing with the ratio of the shear modulus to the bulk modulus. As the pressure increases, both the hardness and sound velocity of MgZn2 increase, while the degree of anisotropy decreases. The present work gives important insights on the mechanical behavior of MgZn2 under high pressure, contributing to its application and property optimization. Full article
(This article belongs to the Special Issue Advances of High Entropy Alloys)
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<p>Hexagonal MgZn<sub>2</sub> unit cell structure.</p> Full article ">Figure 2
<p>The fluctuation curve of the predicted total energy as a function of the MgZn<sub>2</sub> conventional cell volume.</p> Full article ">Figure 3
<p>Variation in structural parameter ratios of <math display="inline"><semantics> <mrow> <mi>a</mi> <mo>/</mo> <msub> <mi>a</mi> <mn>0</mn> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mi>c</mi> <mo>/</mo> <msub> <mi>c</mi> <mn>0</mn> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>V</mi> <mo>/</mo> <msub> <mi>V</mi> <mn>0</mn> </msub> </mrow> </semantics></math> depending on pressure for MgZn<sub>2</sub>.</p> Full article ">Figure 4
<p>Bulk (<span class="html-italic">B</span>), shearing (<span class="html-italic">G</span>) and Young’s (<span class="html-italic">E</span>) modulus for different pressures of MgZn<sub>2</sub>.</p> Full article ">Figure 5
<p>Variation in Poisson’s ratio (<math display="inline"><semantics> <mi>ν</mi> </semantics></math>) and modulus ratio (<math display="inline"><semantics> <mrow> <mi>G</mi> <mo>/</mo> <mi>B</mi> </mrow> </semantics></math>) with pressure in MgZn, (<b>a</b>) is Poisson’s ratio, (<b>b</b>) is modulus ratio.</p> Full article ">Figure 6
<p>Cauchy pressure of MgZn<sub>2</sub> alloy under different pressures.</p> Full article ">Figure 7
<p>Hardness of MgZn<sub>2</sub> alloys under various pressures.</p> Full article ">Figure 8
<p>(<b>a</b>) <math display="inline"><semantics> <msub> <mi>A</mi> <mrow> <mo>{</mo> <mn>100</mn> <mo>}</mo> </mrow> </msub> </semantics></math>, <math display="inline"><semantics> <msub> <mi>A</mi> <mrow> <mo>{</mo> <mn>010</mn> <mo>}</mo> </mrow> </msub> </semantics></math> and <math display="inline"><semantics> <msub> <mi>A</mi> <mrow> <mo>{</mo> <mn>001</mn> <mo>}</mo> </mrow> </msub> </semantics></math> anisotropy factors; (<b>b</b>) broad spectrum index of anisotropy <math display="inline"><semantics> <msup> <mi>A</mi> <mi>U</mi> </msup> </semantics></math> and log Euclidean index of anisotropy <math display="inline"><semantics> <msup> <mi>A</mi> <mi>L</mi> </msup> </semantics></math>; and (<b>c</b>) percentage of compressive anisotropy <math display="inline"><semantics> <msup> <mi>A</mi> <mi>B</mi> </msup> </semantics></math> and percentage of shear anisotropy <math display="inline"><semantics> <msup> <mi>A</mi> <mi>G</mi> </msup> </semantics></math> for MgZn<sub>2</sub> at different pressures.</p> Full article ">Figure 9
<p>(<b>a</b>) Sound velocities in longitudinal (<math display="inline"><semantics> <msub> <mi>v</mi> <mi>l</mi> </msub> </semantics></math>) and transverse (<math display="inline"><semantics> <msub> <mi>v</mi> <mrow> <mi>t</mi> <mn>1</mn> </mrow> </msub> </semantics></math>,<math display="inline"><semantics> <msub> <mi>v</mi> <mrow> <mi>t</mi> <mn>2</mn> </mrow> </msub> </semantics></math>) directions in [100] direction of MgZn<sub>2</sub> under varying pressures; (<b>b</b>) velocities of sound in longitudinal (<math display="inline"><semantics> <msub> <mi>v</mi> <mi>l</mi> </msub> </semantics></math>) and transverse (<math display="inline"><semantics> <msub> <mi>v</mi> <mrow> <mi>t</mi> <mn>1</mn> </mrow> </msub> </semantics></math>, <math display="inline"><semantics> <msub> <mi>v</mi> <mrow> <mi>t</mi> <mn>2</mn> </mrow> </msub> </semantics></math>) directions in [001] direction of MgZn<sub>2</sub> for varying pressures; and (<b>c</b>) sound velocity in longitudinal direction (<math display="inline"><semantics> <msub> <mi>V</mi> <mi>L</mi> </msub> </semantics></math>), sound velocity in transverse direction (<math display="inline"><semantics> <msub> <mi>V</mi> <mi>T</mi> </msub> </semantics></math>) and average sound velocity (<math display="inline"><semantics> <msub> <mi>V</mi> <mi>M</mi> </msub> </semantics></math>) of MgZn<sub>2</sub> crystal at different pressures.</p> Full article ">
16 pages, 8895 KiB  
Article
Study on the Alleviation of Performance Degradation and Voltage Stability of PEMFC by Adding Silica Under Low-Temperature and Low-Humidity Conditions
by Qiang Bai, Chuangyu Hsieh, Zhenghong Liu, Qipeng Chen and Fangbor Weng
Crystals 2024, 14(12), 1089; https://doi.org/10.3390/cryst14121089 - 18 Dec 2024
Viewed by 502
Abstract
This study enhances PEMFC performance at low temperature and low humidity by incorporating hydrophilic inorganic silica materials inside the PEMFC. Firstly, the polarization performance of the cell under varying humidity levels was investigated using a controlled variable method. Secondly, the power stability of [...] Read more.
This study enhances PEMFC performance at low temperature and low humidity by incorporating hydrophilic inorganic silica materials inside the PEMFC. Firstly, the polarization performance of the cell under varying humidity levels was investigated using a controlled variable method. Secondly, the power stability of the PEMFC was examined by observing voltage stability under constant current. Finally, the cell’s transient response at startup was studied. Experimental results indicate that the addition of silica partially mitigates the significant performance decline of the cell under a high humidity range (100% RH–50% RH). However, the effect is relatively average in a low humidity range (50% RH–20% RH). Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>Performance curve with different proportions of silica added.</p> Full article ">Figure 2
<p>AC impedance curve under 100% humidification (65 °C).</p> Full article ">Figure 3
<p>AC impedance curve under 50% humidification (65 °C).</p> Full article ">Figure 4
<p>Polarization curves of PEMFC at 65 °C under various humidification levels.</p> Full article ">Figure 5
<p>Polarization curves of PEMFC at 80 °C under various humidification.</p> Full article ">Figure 6
<p>Polarization curves of PEMFC at 85 °C under various humidification.</p> Full article ">Figure 7
<p>Performance Curve of PEMFC under Constant Current in Low Humidity at 65 °C.</p> Full article ">Figure 8
<p>Performance Curve of PEMFC under Constant Current in Low Humidity at 80 °C.</p> Full article ">Figure 9
<p>Performance Curve of PEMFC under Constant Current in Low Humidity at 85 °C.</p> Full article ">Figure 10
<p>Transient Startup Curves under Constant Current (0 A–30 A) at 65 °C and Various Humidity.</p> Full article ">Figure 11
<p>Performance Curves of Transient Startup under Various Current at 65 °C with Full Humidification.</p> Full article ">Figure 12
<p>Transient Startup Curves under Constant Current (0 A–30 A) at 80 °C and Various Humidity.</p> Full article ">Figure 13
<p>Performance Curves of Transient Startup under Various Current at 80 °C with Full Humidification.</p> Full article ">Figure 14
<p>Transient Startup Curves under Constant Current (0 A–30 A) at 85 °C and Various Humidity.</p> Full article ">Figure 15
<p>Performance Curves of Transient Startup under Various Current at 85 °C with Full Humidification.</p> Full article ">
12 pages, 6992 KiB  
Article
High-Efficiency Long-Wave Infrared Quantum Well Photodetector Based on Cascaded Dielectric Metasurfaces with Almost 100% Absorption
by Zihui Ge, Bo Cheng, Kunpeng Zhai and Guofeng Song
Crystals 2024, 14(12), 1088; https://doi.org/10.3390/cryst14121088 - 18 Dec 2024
Viewed by 691
Abstract
Quantum well infrared photodetectors (QWIPs) are popular due to their following advantages: low cost, maturity of manufacturing, high uniformity, ease of wavelength adjustment, resistance to heat, and resistance to ionizing radiation. However, their low absorption efficiency due to their unique anisotropic absorption properties [...] Read more.
Quantum well infrared photodetectors (QWIPs) are popular due to their following advantages: low cost, maturity of manufacturing, high uniformity, ease of wavelength adjustment, resistance to heat, and resistance to ionizing radiation. However, their low absorption efficiency due to their unique anisotropic absorption properties and ohmic loss of the metal grating severely limit their further adoption. We cleverly used cascaded dielectric metasurfaces to replace the traditional single-layer metal grating, which increased the absorption efficiency to near the upper limit of 100%. By analyzing the near-field profile of the electric field of the miniaturized device, we found that the upper grating, QWIP, and lower grating formed a high-efficiency FP cavity with a strong photon localization capability, allowing the microdevice to effectively achieve 99.3% absorption. In addition, QWIPs with cascade gratings can be incorporated into a polarimeter, allowing for the comprehensive detection of linear polarization information at a wavelength of 14 μm through rational rotations. Our proposed double-layer grating coupling method can be considered a technology that can effectively address the low-absorption problem associated with QWIPs. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>(<b>a</b>) Three-dimensional structure diagram of the ultra-high-efficiency QWIP with integrated cascade metasurfaces. (<b>b</b>) Front view of QWIP with double grating; <span class="html-italic">p</span>1 = 12.4 μm, <span class="html-italic">h</span>1 = 1.1 μm, <span class="html-italic">h</span>2 = 3.5 μm, <span class="html-italic">p</span>1 = 12.4 μm, <span class="html-italic">a</span>1 = 5.7 μm, <span class="html-italic">a</span>2 = 4.96 μm, <span class="html-italic">p</span>1 = 12.4 μm, <span class="html-italic">hb</span> = 1 μm, <span class="html-italic">ha</span> = 3 μm, <span class="html-italic">ht</span> = 1 μm, <span class="html-italic">hs</span> = 3 μm. BCL and TCL are abbreviations for bottom contact layer and top contact layer, respectively. (<b>c</b>) Optical model for analysis of the optical properties of the QWIP.</p> Full article ">Figure 2
<p>(<b>a</b>) Standard 45° edge facet-coupled QWIP; (<b>b</b>) QWIP with bottom grating; (<b>c</b>) QWIP without grating; (<b>d</b>) absorption efficiency spectra for these devices; and (<b>e</b>) electric field distribution at different wavelengths. The electric field of IR is the in-plane vector.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>h</b>) The effects of parameters <span class="html-italic">p</span>1, <span class="html-italic">a</span>1, <span class="html-italic">a</span>2, <span class="html-italic">h</span>1, <span class="html-italic">h</span>2, <span class="html-italic">hb</span>, <span class="html-italic">ht,</span> and <span class="html-italic">hs</span> on the QWIP with cascaded metasurfaces; the (<b>i</b>) absorption spectra of the optimized devices.</p> Full article ">Figure 4
<p>(<b>a</b>) The effect of parameter <span class="html-italic">h</span>2 in the range of 0 to 7 μm on the QWIP with cascaded metasurfaces in the case of a wavelength of 14 μm; (<b>b</b>) electric field distribution at certain absorption peaks; (<b>c</b>) electric field local quantities associated with limiting factors; (<b>d</b>) effects of thickness of cascade metasurface cavity; and (<b>e</b>) effect of the direction of the electric field of incident light on the microdevice.</p> Full article ">Figure 5
<p>(<b>a</b>–<b>f</b>) Effects of the mesh size, etching deviation, number of polynomials, data on different materials [<a href="#B11-crystals-14-01088" class="html-bibr">11</a>,<a href="#B12-crystals-14-01088" class="html-bibr">12</a>], and etching depth (the black dotted line represents the theoretical grating boundary) (i.e., under-etching and over-etching) on the QWIP with cascaded metasurfaces in the case of a 14 μm wavelength incidence.</p> Full article ">Figure 6
<p>(<b>a</b>) The integrated linear polarimeter consisting of the 0-degree, 90-degree, 45-degree, and 135-degree linear polarization detectors (the incident light is a vertical beam from the top); (<b>b</b>) the absorption efficiency, LD and LPER of the 0-degree linear polarization detector; and (<b>c</b>) the Dolp of the microdevice.</p> Full article ">
17 pages, 6438 KiB  
Article
Synthesis and Study of Oxide Semiconductor Nanoheterostructures in SiO2/Si Track Template
by Alma Dauletbekova, Diana Junisbekova, Zein Baimukhanov, Aivaras Kareiva, Anatoli I. Popov, Alexander Platonenko, Abdirash Akilbekov, Ainash Abdrakhmetova, Gulnara Aralbayeva, Zhanymgul Koishybayeva and Jonibek Khamdamov
Crystals 2024, 14(12), 1087; https://doi.org/10.3390/cryst14121087 - 18 Dec 2024
Viewed by 950
Abstract
In this study, chemical deposition was used to synthesize structures of Ga2O3 -NW/SiO2/Si (NW—nanowire) at 348 K and SnO2-NW/SiO2/Si at 323 K in track templates SiO2/Si (either n- or p-type). The resulting [...] Read more.
In this study, chemical deposition was used to synthesize structures of Ga2O3 -NW/SiO2/Si (NW—nanowire) at 348 K and SnO2-NW/SiO2/Si at 323 K in track templates SiO2/Si (either n- or p-type). The resulting crystalline nanowires were δ-Ga2O3 and orthorhombic SnO2. Computer modeling of the delta phase of gallium oxide yielded a lattice parameter of a = 9.287 Å, which closely matched the experimental range of 9.83–10.03 Å. The bandgap is indirect with an Eg = 5.5 eV. The photoluminescence spectra of both nanostructures exhibited a complex band when excited by light with λ = 5.16 eV, dominated by luminescence from vacancy-type defects. The current–voltage characteristics of δ-Ga2O3 NW/SiO2/Si-p showed one-way conductivity. This structure could be advantageous in devices where a reverse current is undesirable. The p-n junction with a complex structure was formed. This junction consists of a polycrystalline nanowire base exhibiting n-type conductivity and a monocrystalline Si substrate with p-type conductivity. The I–V characteristics of SnO2-NW/SiO2/Si suggested near-metallic conductivity due to the presence of metallic tin. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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<p>Electronic and nuclear energy losses for the 200 MeV Xe ion in the SiO<sub>2</sub>/Si structure calculated by the SRIM code.</p> Full article ">Figure 2
<p>SEM image of surface of track template a-SiO<sub>2</sub>/Si.</p> Full article ">Figure 3
<p>Current–voltage characteristic (CVC) measurement circuit.</p> Full article ">Figure 4
<p>SEM image of the surface of the p-type template after CD of Ga<sub>2</sub>O<sub>3</sub> (t = 15 min), at T = 348 K.</p> Full article ">Figure 5
<p>X-ray diffractograms of SiO<sub>2</sub>/Si-p templates after chemical deposition (CD) are as follows: (N1) with a deposition time of t = 15 min at T = 348 K (75 °C); (N2) with a deposition time of t = 30 min at T = 348 K.</p> Full article ">Figure 6
<p>X-ray diffractograms of SiO<sub>2</sub>/Si-n type templates after chemical deposition (CD) at T = 348 K (75 °C) were obtained for two different deposition durations: (N3) for a deposition time of 15 min; (N4) for a deposition time of 30 min.</p> Full article ">Figure 7
<p>Crystallographic cell of δ-Ga<sub>2</sub>O<sub>3</sub> consisting of 80 atoms. Gallium atoms are shown in brown, and oxygen is shown in red.</p> Full article ">Figure 8
<p>Band structure and density of states of δ-Ga<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 9
<p>The SEM image of the SiO<sub>2</sub>/Si-n template surface after SnO<sub>2</sub> CD for 20 min at a temperature of 323 K.</p> Full article ">Figure 10
<p>X-ray diffractogram of SnO<sub>2</sub> samples obtained by chemical deposition for 20 min at a temperature of 323 K.</p> Full article ">Figure 11
<p>The PL spectrum of δ-Ga<sub>2</sub>O<sub>3</sub>-NW/SiO<sub>2</sub>/Si obtained by (CD) at T = 348 K (75 °C) with a deposition time of 15 min. The excitation was carried out using light with a wavelength of λ = 5.16 eV. The hollow circle line represents the experimental curve, while the red line indicates the set of Gauss components.</p> Full article ">Figure 12
<p>The PL spectrum of SnO<sub>2</sub>-NW/SiO<sub>2</sub>/Si, excited at a wavelength of λ = 240 nm. The hollow circle line represents the experimental curve, while the blue line indicates the set of Gauss components.</p> Full article ">Figure 13
<p>Current–voltage (I–V) characteristics of δ-Ga<sub>2</sub>O<sub>3</sub>-NW/SiO<sub>2</sub>/Si-p. The dashed curve represents the original, untreated sample. The red curve corresponds to the sample with δ-Ga<sub>2</sub>O<sub>3</sub> deposited for 15 min, a p-type Si substrate. The blue curve corresponds to the sample with δ-Ga<sub>2</sub>O<sub>3</sub> deposited for 30 min, a p-type Si substrate.</p> Full article ">Figure 14
<p>Current–voltage (I–V) characteristics of SnO<sub>2</sub>-NW/SiO<sub>2</sub>/Si-n. The solid curve represents the original, untreated sample. The dashed curve represents the sample after CD with a deposition time of 20 min.</p> Full article ">
15 pages, 1691 KiB  
Article
Study on the Characteristics of Crystal Formation and Transformation of Alkali-Activated Slag Minerals Induced by Weak Alkali
by Guodong Huang, Yonghao Huang, Xiaojun Zheng, Fengan Zhang, Jiahao Xu, Jun Qi and Zijian Chen
Crystals 2024, 14(12), 1086; https://doi.org/10.3390/cryst14121086 - 17 Dec 2024
Viewed by 669
Abstract
Strong-alkali activation is a prerequisite needed to ensure the full polymerization activity of alkali slag binder and establish excellent mechanical properties; however, it substantially increases the preparation cost. In this study, the effects of both strong and weak alkaline activators on the activation [...] Read more.
Strong-alkali activation is a prerequisite needed to ensure the full polymerization activity of alkali slag binder and establish excellent mechanical properties; however, it substantially increases the preparation cost. In this study, the effects of both strong and weak alkaline activators on the activation performance of alkali slag were examined, using a combination of X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy analysis methods. The reaction mechanism was analyzed under different alkaline conditions, and the preparation cost could be significantly reduced without significantly degrading mechanical properties. The results indicate that Ca(OH)2 can stimulate the reactivity of slag, resulting in a 40% decrease in compressive strength (compared to NaOH) but a 25–50% reduction in preparation cost. With increasing Ca(OH)2 dosage, the compressive strength first increases and then decreases. The best excitation effect is achieved at a dosage of 40 g Ca(OH)2 per 450 g GBFS. The formation of aluminosilicate is the main driving force for the observed increase in compressive strength. Excessive dosage of Ca(OH)2 will lead to its deposition in the specimen, thus affecting the development of compressive strength. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
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<p>Analysis of NaOH-, Ca(OH)<sub>2</sub>-, and Na<sub>2</sub>CO<sub>3</sub>-induced compressive strength.</p> Full article ">Figure 2
<p>XRD analysis.</p> Full article ">Figure 3
<p>SEM analysis. (<b>a</b>) Specimen N0; (<b>b</b>) specimen N20; (<b>c</b>) specimen N40; (<b>d</b>) specimen C20; (<b>e</b>) specimen C40; (<b>f</b>) specimen C60.</p> Full article ">Figure 4
<p>FT-IR analysis. (<b>a</b>) NaOH excitation; (<b>b</b>) Ca(OH)<sub>2</sub> excitation.</p> Full article ">
14 pages, 34360 KiB  
Article
Understanding the Effect of Austempering Temperature on the Crystallographic Features and Mechanical Properties of Low-Carbon Bainitic Steel
by Hao Wu, Jieru Yu, Ziqi Wang, Guangjie Qi, Bai Xiao, Bin Hu, Shilong Liu and Yishuang Yu
Crystals 2024, 14(12), 1085; https://doi.org/10.3390/cryst14121085 - 17 Dec 2024
Viewed by 567
Abstract
The effect of austempering temperature on crystallographic features and mechanical properties is investigated in low-carbon bainitic steel, focusing on the relationship between microstructure and mechanical properties. After isothermal holding at, above, and below martensite start (MS) temperatures and tempering, a mixed [...] Read more.
The effect of austempering temperature on crystallographic features and mechanical properties is investigated in low-carbon bainitic steel, focusing on the relationship between microstructure and mechanical properties. After isothermal holding at, above, and below martensite start (MS) temperatures and tempering, a mixed microstructure of martensite/bainite and martensite/austenite (M/A) constituents is obtained. The fraction of M/A constituents increases as the austempering temperature increases, while the density of block boundaries decreases. The instantaneous work hardening rate exhibits continuous decay without a notable transition because of the retained austenite in the M/A constituents. The toughness decreases with increasing austempering temperature, which is related not only to the fraction of M/A constituents but also to the density of block boundaries. Isothermal treatment below the MS temperature enables the formation of structures with fewer M/A constituents and high-density block boundaries, through which excellent toughness can be achieved. Full article
(This article belongs to the Special Issue Advanced High-Strength Steel)
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<p>(<b>a</b>) calculated TTT curve of the steel, and (<b>b</b>) schematic diagram illustrating the heat treatment processes.</p> Full article ">Figure 2
<p>Mechanical properties of the steels: (<b>a</b>) engineering stress-strain curves and (<b>b</b>) Charpy impact energy plotted as a function of test temperature.</p> Full article ">Figure 3
<p>SEM micrographs of the steels: (<b>a</b>) A950T, (<b>b</b>) IT330T, (<b>c</b>) IT380T, and (<b>d</b>) IT430T. M: martensite, LB/GB: lath/granular bainite, M/A: martensite/austenite.</p> Full article ">Figure 4
<p>Band contrast (BC) maps overlapped with phase distribution depicting the microstructure morphology of the steels: (<b>a</b>) A950T, (<b>b</b>) IT330T, (<b>c</b>) IT380T, and (<b>d</b>) IT430T.</p> Full article ">Figure 5
<p>Inverse pole figures of the steels: (<b>a</b>) A950T, (<b>b</b>) IT330T, (<b>c</b>) IT380T, and (<b>d</b>) IT430T.</p> Full article ">Figure 6
<p>Band contrast maps with boundary distribution of the steels: (<b>a</b>) A950T, (<b>b</b>) IT330T, (<b>c</b>) IT380T, and (<b>d</b>) IT430T.</p> Full article ">Figure 7
<p>Kernel average misorientation maps of the steels: (<b>a</b>) A950T, (<b>b</b>) IT330T, (<b>c</b>) IT380T, and (<b>d</b>) IT430T.</p> Full article ">Figure 8
<p>Volume fraction of M/A constituents (<b>a</b>), grain size distribution (<b>b</b>), boundary density (<b>c</b>) and GND density (<b>d</b>) of the steels.</p> Full article ">Figure 9
<p>Density of intervariant boundaries of the steels: (<b>a</b>) A950T, (<b>b</b>) IT330T, (<b>c</b>) IT380T, and (<b>d</b>) IT430T.</p> Full article ">Figure 10
<p>Schematics illustrating the heat treatment processes (<b>a</b>) and crystallographic features (<b>b</b>) of the steels depending on continuous cooling and isothermal transformation. In the schematic grains, white and black lines stand for low and high angle boundaries, respectively. I, II, III and IV represent the processes of direct quenching and tempering, as well as isothermal holding below, at, and above M<sub>S</sub> temperatures and tempering, respectively, and corresponding types of crystallographic features.</p> Full article ">Figure 11
<p>Extended K-M curves of the studied steels. The transition marked by dots representing the yield strength.</p> Full article ">Figure 12
<p>Relationship between crystallographic features and toughness of the steels: (<b>a</b>) boundary density vs. toughness, (<b>b</b>) M/A fraction vs. toughness.</p> Full article ">
11 pages, 1197 KiB  
Article
Ab Initio Investigation of the Mechanics and Thermodynamics of the Cubic EuAlO3 and GdAlO3 Perovskites for Optoelectronic Applications
by Adel Bandar Alruqi and Nicholas O. Ongwen
Crystals 2024, 14(12), 1084; https://doi.org/10.3390/cryst14121084 - 16 Dec 2024
Viewed by 778
Abstract
Perovskites are currently becoming common in the field of optoelectronics, owing to their promising properties such as electrical, optical, thermoelectric, and electronic. Although mechanical and thermal properties also play a crucial part in the functioning of the optoelectronic devices, they have scarcely been [...] Read more.
Perovskites are currently becoming common in the field of optoelectronics, owing to their promising properties such as electrical, optical, thermoelectric, and electronic. Although mechanical and thermal properties also play a crucial part in the functioning of the optoelectronic devices, they have scarcely been explored. The present work performed an ab initio study of the mechanical and thermal properties of the cubic EuAlO3 and GdAlO3 perovskites for the first time using density functional theory. Quantum Espresso and Themo_pw codes were utilized by employing the generalized gradient approximation. Although the results showed that both materials have good mechanical and thermal properties that are ideal for the above–mentioned applications, EuAlO3 possessed better structural and thermal stability, bulk modulus, Poisson ratio, thermal expansion coefficient, and thermal stress; while GdAlO3 possessed better Young’s modulus and shear modulus. Moreover, the mechanical properties of the two materials turned out to be much better than those of the common materials for optoelectronic applications, while their thermal properties were comparable to that of sapphire glass. Since this study was computational, an experimental verification of the computed properties of the two materials needs to be carried out before they can be commercialized. Full article
(This article belongs to the Special Issue Crystal Structures and Applications of Perovskite Halides in Solar Cells)
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<p>The 3D structures of <b>(a)</b> EuAlO<sub>3</sub> and <b>(b)</b> GdAlO<sub>3</sub>.</p> Full article ">Figure 2
<p>Total energy per atom against unit cell volumes for both EuAlO<sub>3</sub> and GdAlO<sub>3</sub>.</p> Full article ">Figure 3
<p>Elastic constants of EuAlO<sub>3</sub> and GdAlO<sub>3</sub> as functions of temperature.</p> Full article ">Figure 4
<p>Thermal expansion coefficients of EuAlO<sub>3</sub> and GdAlO<sub>3</sub> as a function of temperature.</p> Full article ">Figure 5
<p>Thermal stress of EuAlO<sub>3</sub> and GdAlO<sub>3</sub> as a function of temperature.</p> Full article ">
14 pages, 9112 KiB  
Article
Efficient Dye Contaminant Elimination and Simultaneous Electricity Production via a Carbon Quantum Dots/TiO2 Photocatalytic Fuel Cell
by Zixuan Feng, Xuechen Li, Yueying Lv and Jie He
Crystals 2024, 14(12), 1083; https://doi.org/10.3390/cryst14121083 - 16 Dec 2024
Viewed by 617
Abstract
Conventional wastewater treatment methods do not fully utilize the energy in wastewater. This study uses a photocatalytic fuel cell (PFC) to remove dye impurities and generate electricity with that energy. Pt serves as the PFC’s cathode, while the carbon quantum dots (CQDs)/anatase TiO [...] Read more.
Conventional wastewater treatment methods do not fully utilize the energy in wastewater. This study uses a photocatalytic fuel cell (PFC) to remove dye impurities and generate electricity with that energy. Pt serves as the PFC’s cathode, while the carbon quantum dots (CQDs)/anatase TiO2 (A-TiO2) serve as its photoanode. The visible light absorption range of A-TiO2 can be increased by combining CQDs with A-TiO2. The composite of CQD and A-TiO2 broadens the absorption edge from 364 nm to 538 nm. TiO2’s different crystal structures and particle sizes impact the PFC’s power generation and dye contaminant removal. The 30 min photodegradation rate of methylene blue by the 20 nm A-TiO2 was 97.3%, higher than that of the 5 nm A-TiO2 (75%), 100 nm A-TiO2 (92.1%), and A-TiO2 (93%). The photocurrent density of the 20 nm A-TiO2 can reach 4.41 mA/cm2, exceeding that of R-TiO2 (0.64 mA/cm2), 5 nm A-TiO2 (1.97 mA/cm2), and 100 nm A-TiO2 (3.58 mA/cm2). The photodegradative and electrochemical test results show that the 20 nm A-TiO2 delivers a better degradation and electrochemical performance than other samples. When the 20 nm A-TiO2 was used in the PFC photoanode, the photocurrent density, open-circuit voltage, and maximum power density of the PFC were found to be 0.6 mA/cm2, 0.41 V, and 0.1 mW/cm2, respectively. The PFC prepared in this study shows a good level of performance compared to recent similar systems. Full article
(This article belongs to the Special Issue Synthesis and Properties of Photocatalysts)
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Graphical abstract
Full article ">Figure 1
<p>XRD of R-TiO<sub>2</sub>, A-TiO<sub>2</sub>, and 10% CQDs/A-TiO<sub>2</sub>.</p> Full article ">Figure 2
<p>SEM images of (<b>a</b>) A-TiO<sub>2</sub> and (<b>b</b>) 10% CQDs/A-TiO<sub>2</sub>; TEM images of (<b>c</b>) TiO<sub>2</sub> and (<b>d</b>) 10% CQDs/A-TiO<sub>2</sub>.</p> Full article ">Figure 3
<p>The A-TiO<sub>2</sub> and 10% CQDs/A-TiO<sub>2</sub> XPS spectra: (<b>a</b>) survey spectra, (<b>b</b>) O 1s, (<b>c</b>) C 1s, and (<b>d</b>) Ti 2p.</p> Full article ">Figure 4
<p>(<b>a</b>) Typical UV-VIS absorption spectra and (<b>b</b>) the Tauc plot of R-TiO<sub>2</sub>, A-TiO<sub>2</sub>, and 10% CQDs/A-TiO<sub>2</sub>.</p> Full article ">Figure 5
<p>FTIR spectra of 10% CQDs/A-TiO<sub>2</sub>.</p> Full article ">Figure 6
<p>Photodegradation curves (<b>a</b>) and pseudo-first-order rate kinetics curves of (<b>b</b>) R-TiO<sub>2</sub>, 5 nm A-TiO<sub>2</sub>, 20 nm A-TiO<sub>2</sub>, 100 nm A-TiO<sub>2</sub>, and 10% CQDs/A-TiO<sub>2</sub>.</p> Full article ">Figure 7
<p>Photocurrent density profiles of (<b>a</b>) A-TiO<sub>2</sub> with different particle sizes and R-TiO<sub>2</sub> and (<b>b</b>) different ratios of CQDs/A-TiO<sub>2</sub>.</p> Full article ">Figure 8
<p>PFC: (<b>a</b>) photocurrent density curve; (<b>b</b>) open-circuit voltage curve; (<b>c</b>) polarization curve; (<b>d</b>) power density curve.</p> Full article ">Figure 9
<p>Photodegradation curves of PFC at different voltages.</p> Full article ">
11 pages, 7797 KiB  
Article
Comparative Analysis of the Effects of Additives of Nanostructured Functional Ceramics on the Properties of Welding Electrodes
by Saidov Rustam Mannapovitch, Rakhimov Rustam Khalidov and Kamel Touileb
Crystals 2024, 14(12), 1082; https://doi.org/10.3390/cryst14121082 - 16 Dec 2024
Viewed by 701
Abstract
The synthesis of special photocatalysts of nanostructured functional ceramics (PNFC) under the ZKHM brand under the influence of concentrated solar radiation showed the effectiveness of these ceramic materials in multifunctional use, in particular as additives for coatings of welding electrodes. However, problems with [...] Read more.
The synthesis of special photocatalysts of nanostructured functional ceramics (PNFC) under the ZKHM brand under the influence of concentrated solar radiation showed the effectiveness of these ceramic materials in multifunctional use, in particular as additives for coatings of welding electrodes. However, problems with producing these materials in solar ovens on an industrial scale did not allow the widespread use of this method. This problem was solved using the technique of PNFC synthesis, followed by activation by pulsed radiation generated by functional ceramics. The ceramic material obtained by this method under the brand name ZB-1 also showed its effectiveness when used as an additive in welding electrode coatings. A comparative analysis of the effectiveness of the actions of additives from the ZKHM and ZB-1 brands on the welding and technological properties of welding electrodes from the MR-3 brand was carried out. Comparative results for the formation of weld beads showed that beads with high-quality formation without external defects were achieved when surfaced with electrodes with additives from both brands at concentrations up to 1%. Also, at concentrations up to 1%, these additives increased the breaking length of the arc and the stability of arc welding. The different effects of these additives were observed in a comparative analysis of their impacts on the size of the visor at the end of the electrode, the coefficients of melting and surfacing, and the loss factor for fumes and splashing of electrode metal. Full article
(This article belongs to the Special Issue Ceramics: Processes, Microstructures, and Properties)
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<p>Electrode preparation steps.</p> Full article ">Figure 2
<p>The installation for the determination of the breaking length of the arc (“Lbla”).</p> Full article ">Figure 3
<p>The visor at the end of the electrode (“hk”).</p> Full article ">Figure 4
<p>The dependence of the arc breaking length (“L<sub>bla</sub>”) on the contents of the ZKHM and ZB-1 additives in the MR-3 electrode coating.</p> Full article ">Figure 5
<p>The dependence of the “h<sub>k</sub>” indicator on the proportion of the ZKHM and ZB-1 additives in the MR-3 electrode coating.</p> Full article ">Figure 6
<p>The dependence of the melting coefficient (“α<sub>p</sub>”) on the proportions of the ZKHM and ZB-1 additives in the MR-3 electrode coating.</p> Full article ">Figure 7
<p>The dependence of the surfacing coefficient (“α<sub>H</sub>”) on the proportions of the ZKHM and ZB-1 additives in the MR-3 electrode coating.</p> Full article ">Figure 8
<p>The effect of the ZKHM and ZB-1 proportions in the MR-3 electrode coating on the “ψ” indicator.</p> Full article ">
31 pages, 15017 KiB  
Article
Green Synthesized Composite AB-Polybenzimidazole/TiO2 Membranes with Photocatalytic and Antibacterial Activity
by Hristo Penchev, Katerina Zaharieva, Silvia Dimova, Ivelina Tsacheva, Rumyana Eneva, Stephan Engibarov, Irina Lazarkevich, Tsvetelina Paunova-Krasteva, Maria Shipochka, Ralitsa Mladenova, Ognian Dimitrov, Daniela Stoyanova and Irina Stambolova
Crystals 2024, 14(12), 1081; https://doi.org/10.3390/cryst14121081 - 16 Dec 2024
Viewed by 995
Abstract
Novel AB-Polybenzimidazole (AB-PBI)/TiO2 nanocomposite membranes have been prepared using a synthetic green chemistry approach. Modified Eaton’s reagent (methansulfonic acid/P2O5) was used as both reaction media for microwave-assisted synthesis of AB-PBI and as an efficient dispersant of partially agglomerated [...] Read more.
Novel AB-Polybenzimidazole (AB-PBI)/TiO2 nanocomposite membranes have been prepared using a synthetic green chemistry approach. Modified Eaton’s reagent (methansulfonic acid/P2O5) was used as both reaction media for microwave-assisted synthesis of AB-PBI and as an efficient dispersant of partially agglomerated titanium dioxide powders. Composite membranes of 80 µm thickness have been prepared by a film casting approach involving subsequent anti-solvent inversion in order to obtain porous composite membranes possessing high sorption capacity. The maximal TiO2 filler content achieved was 20 wt.% TiO2 nanoparticles (NPs). Titania particles were green synthesized (using a different content of Mentha Spicata (MS) aqueous extract) by hydrothermal activation (150 °C), followed by thermal treatment at 400 °C. The various methods such as powder X-ray diffraction and Thermogravimetric analyses, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Energy-dispersive X-ray spectroscopy, Electronic paramagnetic resonance, Scanning Electron Microscopy and Transmission Electron Microscopy have been used to study the phase and surface composition, structure, morphology, and thermal behavior of the synthesized nanocomposite membranes. The photocatalytic ability of the so-prepared AB-Polybenzimidazole/bio-TiO2 membranes was studied for decolorization of Reactive Black 5 (RB5) as a model azo dye pollutant under UV light illumination. The polymer membrane in basic form, containing TiO2 particles, was obtained with a 40 mL quantity of the MS extract, exhibiting the highest decolorization rate (96%) after 180 min of UV irradiation. The so-prepared AB-Polybenzimidazole/TiO2 samples have a powerful antibacterial effect on E. coli when irradiated by UV light. Full article
(This article belongs to the Special Issue Photocatalysis and Targeted Sorbent Activity of Advanced Polymer-Based Composites)
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<p>TEM micrographs and particle size distribution of M0 (<b>a</b>), M1 (<b>b</b>), and M2 (<b>c</b>) particles.</p> Full article ">Figure 1 Cont.
<p>TEM micrographs and particle size distribution of M0 (<b>a</b>), M1 (<b>b</b>), and M2 (<b>c</b>) particles.</p> Full article ">Figure 2
<p>Diffuse-reflection spectra of green synthesized TiO<sub>2</sub> particles.</p> Full article ">Figure 3
<p>Absorption spectra of the green synthesized TiO<sub>2</sub> particles with Kubelka–Munk conversion.</p> Full article ">Figure 4
<p>Tauc’s plots of green synthesized TiO<sub>2</sub> particles.</p> Full article ">Figure 5
<p>EPR spectra (right) of green synthesized TiO<sub>2</sub> particles.</p> Full article ">Figure 6
<p>General preparation scheme for the synthesis of composite AB-PBI/TiO<sub>2</sub> membranes and reaction parameter comparison of the conventional (<b>left</b>) and microwave-assisted approaches (<b>right</b>).</p> Full article ">Figure 7
<p>PXRD patterns of (<b>a</b>) green synthesized TiO<sub>2</sub> and (<b>b</b>) AB-PBI/bio-TiO<sub>2</sub> membranes and (<b>c</b>) pristine AB-PBI.</p> Full article ">Figure 8
<p>Deconvolution of C1s, O1s, and N1s core level spectra of the AB-PBI-TiO<sub>2</sub>, M1 membranes (neutralized and acid-doped forms).</p> Full article ">Figure 9
<p>EPR spectra of 1—polybenzimidazole; 2—PBI/bio-TiO<sub>2</sub>, M1 before UV irradiation; 3—PBI/bio-TiO<sub>2</sub>, M1 after UV irradiation recorded at room temperature; 4—PBI/bio-TiO<sub>2</sub>, M1 after UV irradiation recorded at 123 K.</p> Full article ">Figure 10
<p>SEM images of (<b>A</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (basic form) and (<b>B</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (acid-doped form) membranes.</p> Full article ">Figure 11
<p>EDS mapping of (<b>A</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (neutralized form) and (<b>B</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (acid-doped form) membranes.</p> Full article ">Figure 11 Cont.
<p>EDS mapping of (<b>A</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (neutralized form) and (<b>B</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (acid-doped form) membranes.</p> Full article ">Figure 12
<p>FTIR spectra of green synthesized TiO<sub>2</sub> and AB-PBI/bio-TiO<sub>2</sub> membranes.</p> Full article ">Figure 13
<p>Thermogravimetric curves of AB-PBI/TiO<sub>2</sub> membranes.</p> Full article ">Figure 14
<p>Kinetic curves of UV decolorization of Reactive Black 5 dye using AB-PBI/bio-TiO<sub>2</sub> membranes as photocatalysts.</p> Full article ">Figure 15
<p>Degree of decolorization of RB 5 dye during UV irradiation time period using (<b>a</b>,<b>b</b>) AB-PBI/bio-TiO<sub>2</sub>, M0 (neutralized and acid-doped forms); (<b>c</b>,<b>d</b>) AB-PBI/bio-TiO<sub>2</sub>, M1 (neutralized and acid-doped forms); (<b>e</b>,<b>f</b>) AB-PBI/bio-TiO<sub>2</sub>, M2 (neutralized and acid-doped forms) membranes as photocatalysts.</p> Full article ">Figure 16
<p>UV–Vis absorption spectra of RB 5 dye during irradiation time period using AB-PBI/bio-TiO<sub>2</sub>, M1 (basic form) as the photocatalyst.</p> Full article ">Figure 17
<p>The adsorption capacities (Q) (mg/g) of (1) and (2) AB-PBI/bio-TiO<sub>2</sub>, M2 (acid-doped and neutralized forms); (3) and (4) AB-PBI/bio-TiO<sub>2</sub>, M1 (neutralized and acid-doped forms); (5) and (6) AB-PBI/bio-TiO<sub>2</sub>, M0 (acid-doped and neutralized forms) membranes after a 30 min dark period.</p> Full article ">Figure 18
<p>Degree of decolorization of RB 5 dye after 180 min under UV irradiation using basic form membranes in three photocatalytic runs. (<b>a</b>) AB-PBI/bio-TiO<sub>2</sub>, M0; (<b>b</b>) AB-PBI/bio-TiO<sub>2</sub>, M1; and (<b>c</b>) AB-PBI/bio-TiO<sub>2</sub>, M2.</p> Full article ">Figure 19
<p>(<b>A</b>) Antimicrobial effect of the UV-irradiated (violet columns) suspensions of M0, M1, and M2 (0.5 mg/mL) with <span class="html-italic">E. coli</span> compared with their equivalents kept in the dark (gray columns) expressed as CFU/mL. (<b>B</b>) The decrease of CFU under UV light is well visible in the petri dishes.</p> Full article ">Figure 20
<p>Antimicrobial effect of the composite membranes AB-PBI/bio-TiO<sub>2</sub>, M0, AB-PBI/bio-TiO<sub>2</sub>, M1, and AB-PBI/bio-TiO<sub>2</sub>, M2 on <span class="html-italic">E. coli</span> in the dark tested by the ASTM Standard Test Method E 2149–10. Control samples contain only bacterial suspension.</p> Full article ">Figure 21
<p>Effect of AB-PBI-TiO<sub>2</sub> composites on standard <span class="html-italic">E. coli</span> suspension under UV irradiation for 10 min. Control samples contain only bacterial suspension.</p> Full article ">Figure 22
<p>Representative SEM micrographs revealing the surface morphology and adhesion of <span class="html-italic">E. coli</span> 25922 during cultivation with composite membranes AB-PBI/bio-TiO<sub>2</sub>, M0 ((<b>a</b>)—treated with UV, 10 min. (<b>b</b>)—untreated), AB-PBI/bio-TiO<sub>2</sub>, M1 ((<b>c</b>)—treated with UV, 10 min. (<b>d</b>)—untreated) and AB-PBI/bio-TiO<sub>2</sub>, M2 ((<b>e</b>)—treated with UV, 10 min, (<b>f</b>)—untreated). Designations: White arrows—blebs or invaginations; white triangle—ruptured cells; white stars—amorphous substance. Zoom images highlight some of the damage in the bacterial cells. Bars = 5 μm.</p> Full article ">
8 pages, 2174 KiB  
Article
Effect of Pyrolysis Temperature on Microwave Heating Properties of Oxidation-Cured Polycarbosilane Powder
by Chang-Hun Hwang, Jong-Ha Beak, Sang-In Kim and Se-Yun Kim
Crystals 2024, 14(12), 1080; https://doi.org/10.3390/cryst14121080 - 14 Dec 2024
Viewed by 587
Abstract
Silicon carbide (SiC) has excellent mechanical and chemical properties and is used in a wide range of applications. It has the characteristic of rapidly heating up to several hundred degrees within one minute when irradiated with microwave radiation at 2.45 GHz. In this [...] Read more.
Silicon carbide (SiC) has excellent mechanical and chemical properties and is used in a wide range of applications. It has the characteristic of rapidly heating up to several hundred degrees within one minute when irradiated with microwave radiation at 2.45 GHz. In this study, we investigated the oxidation curing process and microwave heating properties of polycarbosilane (PCS). A PCS disk-shaped green body was fabricated via uniaxial pressure molding. Silicon carbide was prepared by varying the pyrolysis temperature, and the heating characteristics of the microwaves were evaluated. The results showed that the samples pyrolyzed at 1300 °C after oxidation curing for 2 h at 180 °C rapidly heated up to 802 °C within 1 min, and the temperature remained constant for 120 min. The maximum temperature of the samples pyrolyzed at 1500 °C was relatively low, but the rate of heating was the highest. The microstructures and crystal structures of the microwaves as a function of the pyrolysis temperature were investigated. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)
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<p>Sample shape after pyrolysis at 1300 °C under different oxidation curing conditions: (<b>a</b>) 180 °C and 30 min, (<b>b</b>) 180 °C and 60 min, (<b>c</b>) 180 °C and 120 min.</p> Full article ">Figure 2
<p>Microstructures according to the pyrolysis temperature: (<b>a</b>) 1200 °C, (<b>b</b>) 1300 °C, (<b>c</b>) 1400 °C, (<b>d</b>) 1500 °C (yellow points: pores size &gt; 0.5 µm).</p> Full article ">Figure 3
<p>Crystal structure analysis of the samples fabricated at various pyrolysis temperatures using XRD: (<b>a</b>) XRD pattern, (<b>b</b>) β-silicon carbide crystal size.</p> Full article ">Figure 4
<p>Microwave irradiation heating test of samples manufactured at different pyrolysis temperatures: (<b>a</b>) 60 s short time. Heating rate according to the thermal decomposition temperature conditions of PCS, (<b>b</b>) 60 min long time heating behavior of silicon carbide samples under microwave irradiation, (<b>c</b>) heating phenomenon according to microwave irradiation time for samples thermally decomposed at 1300 °C for 3 h.</p> Full article ">
12 pages, 4142 KiB  
Article
Batch Cooling Crystallization of a Model System Using Direct Nucleation Control and High-Performance In Situ Microscopy
by Josip Budimir Sacher, Nenad Bolf and Marko Sejdić
Crystals 2024, 14(12), 1079; https://doi.org/10.3390/cryst14121079 - 13 Dec 2024
Viewed by 896
Abstract
The aim of this study was to investigate the use of automated high performance in situ microscopy (HPM) for monitoring and direct nucleation control (DNC) during cooling crystallization. Compared to other techniques, HPM enables the detection of small crystals in the range of [...] Read more.
The aim of this study was to investigate the use of automated high performance in situ microscopy (HPM) for monitoring and direct nucleation control (DNC) during cooling crystallization. Compared to other techniques, HPM enables the detection of small crystals in the range of 1 to 10 μm. Therefore, a novel DNC-controlled variable was investigated to determine the potential improvement of the method. The laboratory system and process control software were developed in-house. A well-studied crystallization model system, the seeded batch cooling crystallization of α-glycine from water, was investigated under normal conditions and temperatures below 60 °C. It was postulated that length-weighted edge-to-edge counts in the range of 1 to 10 μm would be most sensitive to the onset of secondary nucleation and are therefore, used as a control variable. Linear cooling experiments were conducted to determine the initial setpoint for the DNC experiments. Three DNC experiments were then performed with different setpoints and an upper and lower counts limit. It was found that the DNC method can be destabilized with a low setpoint and narrow counts limits. In addition, the new controlled variable is highly sensitive to the formation of bubbles at the microscope window and requires careful evaluation. To address the advantages of the DNC method, an additional linear cooling experiment of the same duration was performed, and it was found that the DNC method resulted in a larger average crystal size. Overall, it can be concluded that the HPM method is suitable for DNC control and could be improved by modifying the image processing algorithm. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)
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<p>Experimental setup and communication protocol.</p> Full article ">Figure 2
<p>Laboratory system set-up.</p> Full article ">Figure 3
<p>DNC algorithm logic flow diagram.</p> Full article ">Figure 4
<p>Counts and temperature trends during linear cooling experiments.</p> Full article ">Figure 5
<p>Counts and temperature trends during DNC experiments.</p> Full article ">Figure 6
<p>Bubble formation on microscope window toward the end of the experiment D3.</p> Full article ">Figure 7
<p>Control variable comparison for experiment D3.</p> Full article ">Figure 8
<p>Sieving particle size distribution comparison between DNC and linear cooling.</p> Full article ">Figure 9
<p>Agglomerated crystals at the end of experiment D2.</p> Full article ">
12 pages, 3724 KiB  
Article
Corrosion and Cavitation Performance of Flame-Sprayed NiCrBSi Composite Coatings Reinforced with Hard Particles
by Doina Frunzaverde, Gabriela Marginean and Costel Relu Ciubotariu
Crystals 2024, 14(12), 1078; https://doi.org/10.3390/cryst14121078 - 13 Dec 2024
Viewed by 516
Abstract
To enhance the operational life of hydraulic machinery, protective coatings against wear, particularly cavitation erosion, and corrosion might be applied on the surfaces of components. The experiments conducted in this study aimed to assess the suitability of 80/20 NiCrBSi/WC-Co composite coatings for this [...] Read more.
To enhance the operational life of hydraulic machinery, protective coatings against wear, particularly cavitation erosion, and corrosion might be applied on the surfaces of components. The experiments conducted in this study aimed to assess the suitability of 80/20 NiCrBSi/WC-Co composite coatings for this purpose. A coating of NiCrBSi self-fluxing alloy, which served as the reference material, was deposited alongside a NiCrBSi coating reinforced with 20% WC-Co, both applied by flame spraying onto X3CrNiMo13-4 substrates, the martensitic stainless steel type frequently utilized in turbine blade manufacturing. The improved density of the coatings and adhesion to the substrate was achieved by remelting with an oxyacetylene flame. The cavitation and corrosion performance of both the reference and composite coating were evaluated through cavitation tests and electrochemical measurements conducted in the laboratory. The results demonstrate that the addition of 20% WC-Co significantly enhances the cavitation resistance of the composite material, as evidenced by the reduction to 3.76 times of the cumulative erosion (CE), while the stabilization rate remained at half the value observed for the reference self-fluxing alloy coating. Conversely, the addition of WC-Co into the NiCrBSi coating resulted in a slight decrease in the corrosion resistance of the self-fluxing alloy. Nevertheless, the corrosion rate of the composite coating (124.80 µm/year) did not significantly exceed the upper limit for excellent corrosion resistance (100 µm/year). Full article
(This article belongs to the Special Issue Modern Technologies in the Manufacturing of Metal Matrix Composites)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Cross-section SEM micrographs of the flame-sprayed and -remelted coating: SFA (<b>a</b>,<b>b</b>) and 80/20 (<b>c</b>,<b>d</b>).</p> Full article ">Figure 2
<p>EDX analysis of the microstructural constituents marked in <a href="#crystals-14-01078-f001" class="html-fig">Figure 1</a>b,d.</p> Full article ">Figure 3
<p>XRD pattern of the composite coating 80/20.</p> Full article ">Figure 4
<p>Current density vs. potential curves of the coatings (SFA compared to 80/20) evaluated in a 3.5% NaCl solution.</p> Full article ">Figure 5
<p>Cross-sectional SEM micrographs of the coatings following electrochemical corrosion testing, highlighting the penetration depth of the corrosion attack: (<b>a</b>) SFA and (<b>b</b>) 80/20.</p> Full article ">Figure 6
<p>Variation of eroded mass for the samples exposed to cavitation erosion up to 1800 min.</p> Full article ">
28 pages, 7320 KiB  
Review
Recent Advances in Lead-Free All-Inorganic Perovskite CsCdCl3 Crystals for Anti-Counterfeiting Applications
by Nankai Wang, Zhaojie Zhu, Jianfu Li, Chaoyang Tu, Weidong Chen and Yan Wang
Crystals 2024, 14(12), 1077; https://doi.org/10.3390/cryst14121077 - 13 Dec 2024
Viewed by 767
Abstract
This study reviews the advanced anti-counterfeiting applications of CsCdCl3, a lead-free all-inorganic perovskite crystal exhibiting dynamic luminescent properties responsive to temperature and UV light. Using synthesis methods such as Bridgman and hydrothermal techniques and incorporating dopants like bromine and tellurium, this [...] Read more.
This study reviews the advanced anti-counterfeiting applications of CsCdCl3, a lead-free all-inorganic perovskite crystal exhibiting dynamic luminescent properties responsive to temperature and UV light. Using synthesis methods such as Bridgman and hydrothermal techniques and incorporating dopants like bromine and tellurium, this research achieves improved luminescent stability, spectral diversity, and afterglow characteristics in CsCdCl3. The crystal demonstrates extended afterglow, photochromic shifts, and temperature-sensitive luminescence, enabling applications in 4D encoding for secure data encryption and in cold-chain temperature monitoring for pharmaceuticals. Despite these promising attributes, the challenges related to photostability, batch consistency, and environmental resilience persist, necessitating further exploration into the optimized synthesis and doping strategies to enhance material stability. These findings underscore the potential of CsCdCl3 for high-security information storage, pharmaceutical anti-counterfeiting, and real-time environmental sensing, positioning it as a valuable material for the next generation of secure, intelligent packaging solutions. Full article
(This article belongs to the Special Issue Recent Development and Research Trend of Laser Crystals)
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Figure 1

Figure 1
<p>(<b>a</b>) Crystal structure of CsCdCl<sub>3</sub> in the [001] direction. The blue unit is [Cd<sub>2</sub>Cl<sub>9</sub>]<sup>5−</sup> dimers and the yellow unit is [CdCl<sub>6</sub>]<sup>4−</sup> octahedron. (<b>b</b>) Bonding diagram of an octahedron to its surrounding units. (<b>c</b>) Bonding diagram of a dimer to its surrounding units [<a href="#B28-crystals-14-01077" class="html-bibr">28</a>].</p> Full article ">Figure 2
<p>Several crystals grown in our lab: (<b>a</b>) CsCdCl<sub>3</sub>: Tb crystal. (<b>b</b>) CsCdCl<sub>3</sub>: Cu crystal. (<b>c</b>) CsCdCl<sub>3</sub>: Eu crystal. (<b>d</b>) CsCdCl<sub>3</sub>: Pr crystal.</p> Full article ">Figure 3
<p>(<b>a</b>) Crystal structure of CsCdCl<sub>3</sub>. (<b>b</b>) XRD patterns showing CsCdCl<sub>3</sub> doped with various Br<sup>−</sup> concentrations. (<b>c</b>) Enlarged view of XRD patterns for CsCdCl<sub>3</sub> with different levels of Br<sup>−</sup> doping. (<b>d</b>) Fluorescence emission spectra for CsCdCl<sub>3</sub> crystals with increasing Br<sup>−</sup> doping concentrations. (<b>e</b>) Fluorescence decay curve at 480 nm under 254 nm UV excitation, analyzed for CsCdCl<sub>3</sub> with differing Br<sup>−</sup> amounts. (<b>f</b>) Fluorescence decay curve at 580 nm under 254 nm UV excitation for Br<sup>−</sup>-doped CsCdCl<sub>3</sub>. (<b>g</b>) In situ fluorescence spectra for CsCdCl<sub>3</sub>:12.5% Br recorded under 254 nm UV irradiation. (<b>h</b>) Time-resolved fluorescence intensity variations at 480 nm and 580 nm for CsCdCl<sub>3</sub>:12.5% Br, with images showing fluorescence changes over time [<a href="#B16-crystals-14-01077" class="html-bibr">16</a>].</p> Full article ">Figure 4
<p>Trap defect engineering and persistent luminescence in CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>/0.1% Sb<sup>3+</sup> crystals. (<b>a</b>) Depiction of the hexagonal CsCdCl<sub>3</sub> crystal structure and its modification via Mn<sup>2+</sup> and Sb<sup>3+</sup> doping. (<b>b</b>) XRD patterns for pure CsCdCl<sub>3</sub>, CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>, and CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>/0.1% Sb<sup>3+</sup>. (<b>c</b>) Trap distribution profiles of CsCdCl<sub>3</sub>, CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>, and CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>/0.1% Sb<sup>3+</sup>, shown through thermoluminescence glow curves measured at a heating rate of 60 K/min after X-ray irradiation. (<b>d</b>) Comparative radioluminescence afterglow decay curves for CsCdCl<sub>3</sub>, CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>, and CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>/0.1% Sb<sup>3+</sup> crystals at room temperature, following 3 min of X-ray excitation at 50 kV. (<b>e</b>) Sequential photographs of CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup> and CsCdCl<sub>3</sub>:5% Mn<sup>2+</sup>/0.1% Sb<sup>3+</sup> showing afterglow emission at various intervals after cessation of X-ray exposure at room temperature [<a href="#B17-crystals-14-01077" class="html-bibr">17</a>].</p> Full article ">Figure 5
<p>(<b>a</b>) PLE and PL spectra of CsCdCl<sub>3</sub> samples. (<b>b</b>) PL decay curves monitored at a wavelength of 580 nm for CsCdCl<sub>3</sub> (λex = 254 nm). (<b>c</b>) PL spectra of CsCdCl<sub>3</sub>:x Te<sup>4+</sup> (x = 0, 1, 5, 10, 15, and 20%) excited by 430 nm. The inset shows the PL intensity as a function of Te<sup>4+</sup> concentration. (<b>d</b>) PLE and PL spectra of CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> samples. (<b>e</b>) PL decay curves monitored at a wavelength of 580 nm for CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> (λex = 254 nm/λex = 430 nm) samples. (<b>f</b>) Luminescence mechanism of CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> [<a href="#B19-crystals-14-01077" class="html-bibr">19</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Photographs of CsCdCl<sub>3</sub> and CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> crystals under UV light at different temperatures. (<b>b</b>) Pseudocolor temperature-dependent PL maps for CsCdCl<sub>3</sub> under 254 nm excitation. (<b>c</b>) Pseudocolor temperature-dependent PL maps for CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> under 254 nm excitation. (<b>d</b>) Normalized PL spectra of CsCdCl<sub>3</sub> at three representative temperatures. (<b>e</b>) Normalized PL spectra of CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> at three selected temperatures. (<b>f</b>) PL intensity of CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> at different temperatures. (<b>g</b>) Fitted fwhm curve of CsCdCl<sub>3</sub>:10% Te<sup>4+</sup> as a function of temperature [<a href="#B19-crystals-14-01077" class="html-bibr">19</a>].</p> Full article ">Figure 7
<p>(<b>a</b>) Schematic of the custom-built optical setup. (<b>b</b>) CIE chromaticity coordinates and corresponding images of the CsCdCl<sub>3</sub>:0.5% Sb<sup>3+</sup> SC sample under 350 and 400 nm fs laser excitation. (<b>c</b>) PL spectra recorded with 350 and 400 nm fs laser excitation. (<b>d</b>) PL spectra obtained at various pump densities under 350 and 400 nm fs laser excitation. (<b>e</b>) Emission intensity as a function of pump density under 350 nm fs laser excitation. (<b>f</b>) Emission intensity as a function of pump density under 400 nm fs laser excitation. (<b>g</b>) PersL spectra recorded after pre-irradiation with 350 and 400 nm fs lasers for 1 s. (<b>h</b>) PersL decay curves with corresponding photographs recorded post-pre-irradiation with 350 and 400 nm fs laser excitation. (fs laser settings: 1 kHz, 150 fs; spot size: 200 µm) [<a href="#B15-crystals-14-01077" class="html-bibr">15</a>].</p> Full article ">Figure 8
<p>(<b>a</b>) Photographs of labels prepared byCsCdCl3:x%Br and CsCdCl3:x%Sn sample powders under 254 nm irradiation, along with corresponding afterglow emission after ceasing excitation at (<b>b</b>) 1 s, (<b>c</b>) 3 s and (<b>d</b>) 120 s. The symbol × in the figure represents an incorrect result, while the symbol √ represents the correct result after decryption [<a href="#B7-crystals-14-01077" class="html-bibr">7</a>].</p> Full article ">Figure 9
<p>(<b>a</b>) QR code anti-counterfeiting design with dynamic fluorescence. (<b>b</b>) Dynamic anti-counterfeiting pattern produced by CsCdCl<sub>2.92</sub>Br<sub>0.08</sub> encapsulated in PDMS. (<b>c</b>) Anti-counterfeiting pattern design based on the long afterglow properties of CsCdCl<sub>2.92</sub>Br<sub>0.08</sub>. (<b>d</b>) Design of dynamic 4D code [<a href="#B16-crystals-14-01077" class="html-bibr">16</a>].</p> Full article ">Figure 10
<p>Photographs of phosphors CsCdCl₃:0.6%Sb<sup>3+</sup>, 1%Mn<sup>2+</sup>, arranged in a “QR code” pattern, show cyan and orange colors under 254 nm and 365 nm UV irradiation, respectively [<a href="#B41-crystals-14-01077" class="html-bibr">41</a>].</p> Full article ">
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