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Crystals
Volume 13
Issue 5
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Crystals, Volume 13, Issue 5 (May 2023) – 143 articles

Cover Story (view full-size image): The Fe alkoxide was initially fabricated by a facile solvothermal method. It was then converted into γ-Fe2O3, α-Fe2O3, and mixed-phase α/γ-Fe2O3 with a nanosheet-assembled flower-like structure at different annealing temperatures. The α/γ-Fe2O3, which annealed at 400 °C, included 18% α-Fe2O3, demonstrating excellent sensing performance towards acetone compared to that of γ-Fe2O3 and α-Fe2O3. It showed a response of 353 to 200 ppm acetone, a low limit of detection of 0.5 ppm at 160 °C, good reproducibility as well as selectivity, and a fast response time (22 s) as well as recovery time (14 s). The potential sensing mechanism is mainly ascribed to the unique microstructure and mixed phases of α/γ-Fe2O3. View this paper
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19 pages, 4055 KiB  
Article
Phase Field Modeling of Crack Growth with Viscoplasticity
by Qianyu Shi, Hongjun Yu, Xiangyuhan Wang, Kai Huang and Jian Han
Crystals 2023, 13(5), 854; https://doi.org/10.3390/cryst13050854 - 22 May 2023
Viewed by 1480
Abstract
The fracture of viscoplastic materials is a complex process due to its time-dependent and plastic responses. Numerical simulation for fractures plays a significant role in crack prediction and failure analysis. In recent years, the phase field model has become a competitive approach to [...] Read more.
The fracture of viscoplastic materials is a complex process due to its time-dependent and plastic responses. Numerical simulation for fractures plays a significant role in crack prediction and failure analysis. In recent years, the phase field model has become a competitive approach to predict crack growth and has been extended to inelastic materials, such as elasto-plastic, viscoelastic and viscoplastic materials, etc. However, the contribution of inelastic energy to crack growth is seldom studied. For this reason, we implement the fracture phase field model coupled with a viscoplastic constitutive in a finite element framework, in which the elastic energy and inelastic energy are used as crack driving forces. The implicit algorithm for a viscoplastic constitutive is presented; this procedure is suitable for other viscoplastic constitutive relations. The strain rate effect, creep effect, stress relaxation effect and cyclic loading responses are tested using a single-element model with different inelastic energy contributions. A titanium alloy plate specimen and a stainless-steel plate specimen under tension are studied and compared with the experimental observations in the existing literature. The results show that the above typical damage phenomenon and fracture process can be well reproduced. The inelastic energy significantly accelerates the evolution of the phase field of viscoplastic materials. For cyclic loadings, the acceleration effect for low frequency is more significant than for high frequency. The influence of the weight factor of inelastic energy β on the force-displacement curve mainly occurs after reaching the maximum force point. With the increase of β, the force drops faster in the force-displacement curve. The inelastic energy has a slight effect on the crack growth paths. Full article
(This article belongs to the Special Issue Crack Propagation and Fracture of Composites)
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22 pages, 37232 KiB  
Article
Crystal Structure, Thermal Expansion and Luminescence of Ca10.5−xNix(VO4)7
by Houri S. Rahimi Mosafer, Wojciech Paszkowicz, Roman Minikayev, Christine Martin, Mirosław Kozłowski, Oksana Chukova, Yaroslav Zhydachevskyy and Serhii Nedilko
Crystals 2023, 13(5), 853; https://doi.org/10.3390/cryst13050853 - 22 May 2023
Cited by 1 | Viewed by 1218
Abstract
The structural and luminescence properties of a new material, Ca10.5−xNix(VO4)7, formed by substitution of a fraction of calcium by nickel, are studied as a function of the Ni content (x). The powder [...] Read more.
The structural and luminescence properties of a new material, Ca10.5−xNix(VO4)7, formed by substitution of a fraction of calcium by nickel, are studied as a function of the Ni content (x). The powder X-ray diffraction results for the polycrystals, synthesized using a solid-state reaction method, show that in the studied temperature range (300–1150 K), the structure of the unsubstituted material (space group R3c, whitlockite-β-Ca3(PO4)2 structure type) is conserved up to the solubility limit, x = 0.72(2), determined on the basis of variation of unit cell size with x. The samples of nominal composition exceeding this limit contain a significant amount of the impurity phase.The structural refinements demonstrate that Ni atoms preferentially occupy the M5 site (one of the five independent Ca sites, M1–M5). The unit cell size was equally studied in the range of 300–1150 K, leading to the determination of the thermal expansion coefficients. It was found that with rising Ni content, the room temperature volumetric thermal expansion decreases from 41.80 MK−1 (x = 0.16) to 39.24 MK−1 (x = 0.66) and to 38.92 MK−1 at the solubility limit, this reduction being in line with earlier reported data for x=0. In the unit cell variation, around 800–900 K, a weak anomaly is observed, detectable most clearly for the axial ratio; it is also visible at thermal expansion coefficient temperature dependence. Substitution of Ca by Ni ions reduces the optical band gap of Ca10.5−xNix(VO4)7 from 3.56 (x = 0) to 3.29 and 3.16 eV observed for Ni-containing samples (x = 0.33 and 0.66, respectively). Observed bands in the absorption and photoluminescence spectra are assigned to electronic transitions in both VO43− groups and Ni2+ ions, confirming that Ni mainly occupies the M5 site. The band gap narrowing and decrease in photoluminescence intensity when the Ni concentration increases makes Ni-substituted compounds attractive for application, e.g., as photocatalysts. Full article
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12 pages, 6304 KiB  
Article
Shape Memory Properties and Microstructure of FeNiCoAlTaB Shape Memory Alloys
by Li-Wei Tseng, Po-Yu Lee, Nian-Hu Lu, Yi-Ting Hsu and Chih-Hsuan Chen
Crystals 2023, 13(5), 852; https://doi.org/10.3390/cryst13050852 - 22 May 2023
Viewed by 1009
Abstract
The three-point-bending shape memory properties, microstructure, and magnetic properties of Fe40.95Ni28Co17Al11.5Ta2.5B0.05 (at.%) alloys were investigated. The magnetic results showed a martensitic transformation in the samples that were aged at 700 °C for [...] Read more.
The three-point-bending shape memory properties, microstructure, and magnetic properties of Fe40.95Ni28Co17Al11.5Ta2.5B0.05 (at.%) alloys were investigated. The magnetic results showed a martensitic transformation in the samples that were aged at 700 °C for 6 and 12 h under the applied magnetic fields of 0.05 and 7 Tesla. The martensitic start temperature increased from −113 °C to −97 °C as aging times increased from 6 to 12 h. Increasing the magnetic fields from 0.05 to 7 Tesla, the transformation temperatures increased to a higher temperature. Both samples reach saturation magnetization (140 emu/g) under 7 Tesla. The 98.5% cold-rolled alloys that were annealed at 1250 °C for 0.5 h presented a strong <100> texture in the rolling direction with an average grain size of 360 μm. Increasing the annealing time to 1 h, the intensity of texture reduced from 31.61 to 23.19. The fraction of low angle grain boundaries (LABs) for the 98.5% CR samples after annealing at 1250 °C for 0.5 h and 1 h was about 24.6% and 16.1%, respectively. Three-point-bending results show that the sample aged at 700 °C for 6 h displayed 0.2% recoverable strain at a stress level of 800 MPa. Failure occurred before the 900 MPa cycle could be completed. The sample aged at 700 °C for 12 h shows no transformation before the applied stress level of 300 MPa. As the stress levels increase to 400 MPa, the sample shows the shape memory effect and displayed 0.8% recoverable strain at a stress level of 400 MPa. The samples are failures during the 500 MPa cycle. The observed recoverable strain values were lower than those that were theoretically predicted, which was possibly due to the larger volume fraction of high-angle grain boundary and the slightly lower than expected average grain size. Full article
(This article belongs to the Special Issue Crystal Plasticity (Volume III))
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11 pages, 664 KiB  
Article
Optical Gain of a Spherical InAs Quantum Dot under the Effects of the Intense Laser and Magnetic Fields
by Noreddine Aghoutane, Laura M. Pérez, David Laroze, Pablo Díaz, Miguel Rivas, Mohamed El-Yadri and El Mustapha Feddi
Crystals 2023, 13(5), 851; https://doi.org/10.3390/cryst13050851 - 21 May 2023
Cited by 1 | Viewed by 1262
Abstract
In quantum dots, where confinement is strong, interactions between charge carriers play an essential role in the performance of semiconductor materials for optical gain. Therefore, understanding this phenomenon is critical for achieving new devices with enhanced features. In this context, the current study [...] Read more.
In quantum dots, where confinement is strong, interactions between charge carriers play an essential role in the performance of semiconductor materials for optical gain. Therefore, understanding this phenomenon is critical for achieving new devices with enhanced features. In this context, the current study examines the optical properties of an exciton confined in a spherical InAs quantum dot under the influence of magnetic and intense laser fields. We investigate the oscillator strength, exciton lifetime, and optical gain, considering the effects of both external fields. We also pay particular attention to the influence of quantum dot size on the results. Our calculations show that the two external fields have opposite effects on our findings. Specifically, the applied magnetic field increases the oscillator strength while the intense laser reduces it. In addition, the optical gain peaks are redshifted under the application of the intense laser, whereas the magnetic field causes a blueshift of the peak threshold. We also find that both external perturbations significantly influence the exciton lifetime. Our study considers the outcomes of both the exciton’s ground (1s) and first excited (1p) states. The theoretical results obtained in this study have promising implications for optoelectronic devices in the ∼3–4 μm wavelength range only through the control of quantum dot sizes and external perturbations. Full article
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0 pages, 3158 KiB  
Article
Investigation of Structural and Electrical Properties of Al2O3/Al Composites Prepared by Aerosol Co-Deposition
by Victor Regis, Matej Šadl, Geoff Brennecka, Andraž Bradeško, Urban Tomc and Hana Uršič
Crystals 2023, 13(5), 850; https://doi.org/10.3390/cryst13050850 - 21 May 2023
Cited by 2 | Viewed by 1364
Abstract
As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. Al2O3 is widely present in electronic applications as a protective coating or as an electrical and [...] Read more.
As the microelectronic industry develops, components that can perform several different tasks receive increasingly more attention, resulting in multifunctional materials being highly sought after. Al2O3 is widely present in electronic applications as a protective coating or as an electrical and thermal insulator due to its mechanical and thermal stabilities and chemical inertness. Al2O3 is also an important dielectric material, with high resistivity and stable permittivity over a wide range of temperatures and electric fields, but its modest permittivity necessitates large effective areas or extremely thin layers when a large capacitance is desired. Composites consisting of discrete conducting phases within an insulating matrix can produce large capacitance via Maxwell–Wagner polarization. In this work, Al2O3/Al composite thick films with different volume ratios of Al were prepared using the aerosol deposition method. A relative dielectric permittivity (εr′) of 800 at 1 MHz was achieved at 27 vol% of Al, a sixty-sevenfold enhancement compared to Al2O3. On the other hand, dielectric losses, tan(δ), at 1 MHz increased from 0.01 for Al2O3 up to 0.58 for the composite with 27 vol% of Al. A finite-element model of the composites was implemented, supporting the nonlinear electrical behavior of the composites as function of vol% of Al. Our results show novel possibilities for the applications of Al2O3-based materials in the microelectronic industry, especially for temperature-sensitive applications, for which the integration strengths of aerosol deposition are valuable. Full article
(This article belongs to the Special Issue Advanced Electronic Ceramics)
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7 pages, 2616 KiB  
Communication
Improving Texture Prediction by Increasing Mesh Resolution in Submodel: A Crystal Plasticity FE Study and Experiment Verification
by Yu Liu, Qi Zhang, Qinqin Ge, Xingxing Wang and Yifu Shen
Crystals 2023, 13(5), 849; https://doi.org/10.3390/cryst13050849 - 20 May 2023
Viewed by 1001
Abstract
Crystal plasticity finite element simulations require tremendous computation time and, accordingly, coarse mesh is generally used. To improve the texture prediction, Submodelling was applied to feature grains in this study. A simulation of the Wholemodel (whole sample) was firstly carried out to obtain [...] Read more.
Crystal plasticity finite element simulations require tremendous computation time and, accordingly, coarse mesh is generally used. To improve the texture prediction, Submodelling was applied to feature grains in this study. A simulation of the Wholemodel (whole sample) was firstly carried out to obtain the global texture, and then a smaller region from the Wholemodel was selected, reconstructed and finely meshed in the Submodel. The movement on the selected region boundary, obtained from the Wholemodel, was used to deform the Submodel. The Submodel reproduced the predictions in the Wholemodel, and the texture prediction, especially at micro-scale, was greatly enhanced in the Submodel due to the fine mesh. This significant drop in the Submodel computation time marks an ~85% decrease compared to the Wholemodel. Full article
(This article belongs to the Special Issue Characterization and Modelling of the Deformation and Failure of Engineering Metallic Materials)
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15 pages, 3772 KiB  
Article
Effect of Cu2Te Back Surface Interfacial Layer on Cadmium Telluride Thin Film Solar Cell Performance from Numerical Analysis
by Muhammad Najib Harif, Camellia Doroody, Allina Nadzri, Hasrul Nisham Rosly, Nur Irwany Ahmad, Mustapha Isah and Nowshad Amin
Crystals 2023, 13(5), 848; https://doi.org/10.3390/cryst13050848 - 20 May 2023
Cited by 1 | Viewed by 1493
Abstract
Even though substantial advances made in the device configuration of the frontal layers of the superstrate cadmium telluride (CdTe) solar cell device have contributed to conversion efficiency, unresolved challenges remain in regard to controlling the self-compensation and minority carrier recombination at the back [...] Read more.
Even though substantial advances made in the device configuration of the frontal layers of the superstrate cadmium telluride (CdTe) solar cell device have contributed to conversion efficiency, unresolved challenges remain in regard to controlling the self-compensation and minority carrier recombination at the back contact that limits the efficiency. In this study, a SCAPS-1D simulator was used to analyze the loss mechanism and performance limitations due to the band-bending effect upon copper chloride treatment and subsequent Cu2Te layer formation as the back contact buffer layer. The optimal energy bandgap range for the proposed back surface layer of Cu2Te is derived to be in the range of 1.1 eV to 1.3 eV for the maximum conversion efficiency, i.e., around 21.3%. Moreover, the impacts of absorber layer’s carrier concentration with respect to CdTe film thickness, bandgap, and operational temperature are analyzed. The optimized design reveals that the acceptor concentration contributes significantly to the performance of the CdTe devices, including spectral response. Consequently, the optimized thickness of the CdTe absorber layer with a Cu-based back contact is found to be 2.5 µm. Moreover, the effect of temperature ranging from 30 °C to 100 °C as the operating condition of the CdTe thin-film solar cells is addressed, which demonstrates an increasing recombination tread once the device temperature exceeds 60 °C, thus affecting the stability of the solar cells. Full article
(This article belongs to the Special Issue Advances in Thin Structures and Materials Modelling)
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9 pages, 25476 KiB  
Article
Analogous Black Holes in Type-III Dirac Semimetal Ni3In2X2 (X = S, Se)
by Christopher Sims
Crystals 2023, 13(5), 847; https://doi.org/10.3390/cryst13050847 - 20 May 2023
Cited by 1 | Viewed by 1217
Abstract
Black holes are objects that have a large mass and curve space time, characterized by their event horizon and singularity. Recently, an interesting concept of analogous black holes has emerged in the field of condensed matter physics. In this work, the possibility of [...] Read more.
Black holes are objects that have a large mass and curve space time, characterized by their event horizon and singularity. Recently, an interesting concept of analogous black holes has emerged in the field of condensed matter physics. In this work, the possibility of realizing analogous black holes in topological material is Ni3In2X2 (X = S, Se) discussed. This work shows that the type-III Dirac cones of the material can lead to the emergence of an event horizon and the formation of a black hole-like region near the Dirac point. In addition, the possible experimental signatures of such a system are discussed and the potential implications of an analogous black hole for the study of black hole physics in condensed matter systems. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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19 pages, 9053 KiB  
Article
Reflections of High-Frequency Pulsed Ultrasound by Underwater Acoustic Metasurfaces Composed of Subwavelength Phase-Gradient Slits
by Jin-Chen Hsu, Herwandi Alwi, Chun-Hao Wei, Kai-Li Liao and Che-Ting Huang
Crystals 2023, 13(5), 846; https://doi.org/10.3390/cryst13050846 - 20 May 2023
Cited by 3 | Viewed by 1235
Abstract
We numerically and experimentally investigated the behavior of high-frequency underwater ultrasounds reflected by gradient acoustic metasurfaces. Metasurfaces were fabricated with a periodic array of gradient slits along the surface of a steel specimen. The finite element method was adopted for the acoustics–structure interaction [...] Read more.
We numerically and experimentally investigated the behavior of high-frequency underwater ultrasounds reflected by gradient acoustic metasurfaces. Metasurfaces were fabricated with a periodic array of gradient slits along the surface of a steel specimen. The finite element method was adopted for the acoustics–structure interaction problem to design the metasurfaces and simulate the reflected fields of the incident ultrasound. Our metasurfaces yielded anomalous reflection, specular reflection, apparent negative reflection, and radiation of surface-bounded modes for ultrasonic waves impinging on the metasurfaces at different incident angles. The occurrence of these reflection behaviors could be explained by the generalized Snell’s law for a gradient metasurface with periodic supercells. We showed that at some incident angles, strong anomalous reflection could be generated, which could lead to strong retroreflection at specific incident angles. Furthermore, we characterized the time evolution of the reflections using pulsed ultrasound. The simulated transient process revealed the formation of propagating reflected ultrasound fields. The experimentally measured reflected ultrasound signals verified the distinct reflection behaviors of the metasurfaces; strong anomalous reflection steering the ultrasound pulse and causing retroreflection was observed. This study paves the way for designing underwater acoustic metasurfaces for ultrasound imaging and caustic engineering applications using pulsed ultrasound in the high-frequency regime. Full article
(This article belongs to the Special Issue Recent Advances in Phononic Crystals and Acoustic Metamaterials (Volume II))
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16 pages, 5370 KiB  
Article
Ternary Hybrid Materials for Highly Sensitive Acetone Sensing at Room Temperature
by Nurul Athirah Abu Hussein, Yew Hoong Wong, Zainal Arif Burhanudin and Huzein Fahmi Hawari
Crystals 2023, 13(5), 845; https://doi.org/10.3390/cryst13050845 - 20 May 2023
Cited by 2 | Viewed by 994
Abstract
The performance of a conventional metal oxide sensor (MOX) is highly dependent on its high operating temperature. Many researchers have tried to solve the problem by exploring hybrid materials. On the other hand, ternary hybrid materials have emerged as a promising class of [...] Read more.
The performance of a conventional metal oxide sensor (MOX) is highly dependent on its high operating temperature. Many researchers have tried to solve the problem by exploring hybrid materials. On the other hand, ternary hybrid materials have emerged as a promising class of materials with unique properties and potential applications in various fields, be it environmental or medical, such as in breath analyzers for prediabetes analysis. This article focuses on the synthesis method, characterization, and application of ternary hybrid materials for room-temperature sensors, as well as recent advances and future developments in the field. The materials consist of three different components, metal oxide (Fe3O4), polymer (polyaniline) and carbon-based materials (reduced graphene oxide), which were synthesized using in-situ methods. Five samples were prepared in different ratios. The properties of these materials were characterized using techniques such as X-ray diffraction (XRD), Raman, scanning electron microscope (SEM) and transmission electron microscopy (TEM). The XRD and Raman analyses showed the existence of all the individual constituents in the hybrid sample. SEM and TEM also showed a strong interaction between the constituent materials as a hybrid nanocomposite. The response and recovery time were studied against 1, 10 and 100 ppm acetone. The results show that the sample with 10 wt%Fe3O4-PANI-RGO (S2_10) has a reaction and recovery time < 32 s against the above ppm and has the highest sensing response at room temperature. Full article
(This article belongs to the Special Issue Hybrid Organic–Inorganic Materials Used to Improve the Environment and Human Health (2nd Edition))
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12 pages, 2317 KiB  
Article
Hetero-Deformation Induced Hardening in a CoCrFeNiMn High-Entropy Alloy
by Hamed Shahmir, Parham Saeedpour, Mohammad Sajad Mehranpour, Seyed Amir Arsalan Shams and Chong Soo Lee
Crystals 2023, 13(5), 844; https://doi.org/10.3390/cryst13050844 - 19 May 2023
Cited by 4 | Viewed by 1514
Abstract
One of the most important issues in materials science is to overcome the strength–ductility trade-off in engineering alloys. The formation of heterogeneous and complex microstructures is a useful approach to achieving this purpose. In this investigation, a CoCrFeNiMn high-entropy alloy was processed via [...] Read more.
One of the most important issues in materials science is to overcome the strength–ductility trade-off in engineering alloys. The formation of heterogeneous and complex microstructures is a useful approach to achieving this purpose. In this investigation, a CoCrFeNiMn high-entropy alloy was processed via cold rolling followed by post-deformation annealing over a temperature range of 650–750 °C, which led to a wide range of grain sizes. Annealing at 650 °C led to the formation of a heterogeneous structure containing recrystallized areas with ultrafine and fine grains and non-recrystallized areas with an average size of ~75 μm. The processed material showed strength–ductility synergy with very high strengths of over ~1 GPa and uniform elongations of over 12%. Different deformation mechanisms such as dislocation slip, deformation twinning and hetero-deformation-induced hardening were responsible for achieving this mechanical property. Increasing the annealing temperature up to 700 °C facilitated the acquisition of bimodal grain size distributions of ~1.5 and ~6 μm, and the heterogeneous structure was eliminated via annealing at higher temperatures, which led to a significant decrease in strength. Full article
(This article belongs to the Special Issue Crystal Plasticity (Volume III))
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13 pages, 8480 KiB  
Article
Role of Hydroxy Group in the Electro-Optical Properties of Polymer-Dispersed Liquid Crystals
by Meina Yu, Jianjun Xu, Lingpeng Luo, Luoning Zhang, Yanzi Gao, Cheng Zou, Qian Wang, Huiyun Wei, Xiao Wang and Huai Yang
Crystals 2023, 13(5), 843; https://doi.org/10.3390/cryst13050843 - 19 May 2023
Cited by 3 | Viewed by 1251
Abstract
In this work, hydroxylated compounds are applied to prepare polymer-dispersed liquid crystal (PDLC) films and the role of the hydroxy group is studied in detail by comparing the effects of the hydroxylated acrylate monomer, the hydroxylated mesogenic component and their corresponding non-hydroxylated components. [...] Read more.
In this work, hydroxylated compounds are applied to prepare polymer-dispersed liquid crystal (PDLC) films and the role of the hydroxy group is studied in detail by comparing the effects of the hydroxylated acrylate monomer, the hydroxylated mesogenic component and their corresponding non-hydroxylated components. It is revealed that the hydroxylated acrylate monomer plays a more important role in modifying the morphology of the polymer matrix and thereby the electro-optical performance of the PDLC films. Parameters of the polymer matrix, such as size and density of voids, can be affected by various components, but only the hydroxylated acrylate monomer can alter its type from the typical Swiss-cheese type to the polymer-microsphere type. Essentially, the hydroxylated mesogenic component takes effect through changing the ratio of the liquid crystal phase, while the hydroxylated acrylate monomer can participate in the polymerization and impact the development of the polymer matrix. It is anticipated that this research can help in understanding the role of the hydroxy group in PDLC films. Full article
(This article belongs to the Section Liquid Crystals)
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18 pages, 4291 KiB  
Article
Modeling Microsegregation during Metal Additive Manufacturing: Impact of Dendrite Tip Kinetics and Finite Solute Diffusion
by V. S. Hariharan, Baler Nithin, L. Ruban Raj, Surendra Kumar Makineni, B. S. Murty and Gandham Phanikumar
Crystals 2023, 13(5), 842; https://doi.org/10.3390/cryst13050842 - 19 May 2023
Cited by 1 | Viewed by 1595
Abstract
Rapid solidification during metal additive manufacturing (AM) leads to non-equilibrium microsegregation, which can result in the formation of detrimental phases and cracking. Most of the microsegregation models assume a Scheil-type solidification, where the solidification interface is planar and there exists a local equilibrium [...] Read more.
Rapid solidification during metal additive manufacturing (AM) leads to non-equilibrium microsegregation, which can result in the formation of detrimental phases and cracking. Most of the microsegregation models assume a Scheil-type solidification, where the solidification interface is planar and there exists a local equilibrium at the interface along with either zero or infinite solute diffusion in the respective participating phases—solid and liquid. This assumption leads to errors in prediction. One has to account for finite solute diffusion and the curvature at the dendritic tip for more accurate predictions. In this work, we compare different microsegregation models, that do and do not consider finite diffusion and dendrite tip kinetics, against experiments. We also propose a method to couple dendrite tip kinetics with the diffusion module (DICTRA®) implemented in Thermo-Calc®. The models which accounted for both finite diffusion and dendrite tip kinetics matched well with the experimental data. Full article
(This article belongs to the Special Issue Additive Manufacturing: Alloy Design, Process Optimization and Microstructure Engineering)
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13 pages, 14905 KiB  
Article
Experimental Evaluation on the Microstructural and Mechanical Response of Ce Microalloying AZ31 Fabricated by Multi-Pass Unidirectional and Cross Rolling after TRC
by Fangkun Ning, Shuping Kong, Weitao Jia and Xingrui Chen
Crystals 2023, 13(5), 841; https://doi.org/10.3390/cryst13050841 - 19 May 2023
Viewed by 900
Abstract
Conventional billet rolling is being widely used in magnesium (Mg) alloys products, but this method gives rise to biological and environmental problems. The advantages of the short process on sheet fabrication have been widely proved in Mg alloy twin-roll casting (TRC). In this [...] Read more.
Conventional billet rolling is being widely used in magnesium (Mg) alloys products, but this method gives rise to biological and environmental problems. The advantages of the short process on sheet fabrication have been widely proved in Mg alloy twin-roll casting (TRC). In this study, an attempt is made to create high-performance Mg alloy sheets via multi-pass unidirectional and cross hot rolling (UR, CR) after TRC for purposes of lowering edge defects and energy consumption. Then, the microstructural and mechanical response of Ce when microalloying AZ31 was observed using UR and CR, respectively. The mechanism of the performance improvement after the AZ31 microalloying is disclosed. In addition, the effect of the rolling parameters on the microstructural and mechanical properties are discussed. Experimental results revealed that the homogenization effect of the AZ31-0.2Ce alloy was the best after being kept at 440 °C for 24 h. The CR-rolled sheet had a more uniform and finer microstructure in the horizontal and center, while for the UR-rolled sheet, it was the opposing edge microstructure. This research is expected to prepare and optimize the microstructural and mechanical properties of microalloying AZ31 in a sheet-rolling process, a material that has important theoretical significance and engineering application value. Full article
(This article belongs to the Special Issue State-of-the-Art Magnesium Alloys)
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11 pages, 5033 KiB  
Article
Laser Textured Superhydrophobic SiC Ceramic Surface and the Performance of Condensation Heat Transfer
by Deyuan Lou, Gengxin Lu, Heng Li, Pengjian Chen, Qing Tao, Qibiao Yang and Dun Liu
Crystals 2023, 13(5), 840; https://doi.org/10.3390/cryst13050840 - 19 May 2023
Viewed by 1247
Abstract
Chemical modification is usually utilized for preparing superhydrophobic SiC surfaces, which has the problems of long processing time, high environmental contamination risk, and high cost. To enhance the condensation heat transfer efficiency of SiC, the superhydrophobic SiC surface was fabricated through laser texturing [...] Read more.
Chemical modification is usually utilized for preparing superhydrophobic SiC surfaces, which has the problems of long processing time, high environmental contamination risk, and high cost. To enhance the condensation heat transfer efficiency of SiC, the superhydrophobic SiC surface was fabricated through laser texturing and heat treatment. In this study, the SiC surface was processed by laser texturing with a nanosecond laser, followed by heat treatment. Surface microstructures and compositions were investigated with SEM and XPS, and the heat transfer coefficient of the superhydrophobic SiC surface was tested. The results indicated that the laser-textured SiC surface had a super hydrophilic contact angle of 0°; after heat treatment, SiC ceramic became superhydrophobic (surface contact angle reaches 164°) because organic contamination on the original SiC surface could be cleaned by using laser texturing, which caused a chemical reaction and the formation of SiO2 on the surface. Moreover, the distribution of relatively low-energy SiOX was formed after heat treatment; then, SiC ceramic became superhydrophobic. Due to the formation of nanoscale sheet-like protrusion structures by heat treatment, the SiC superhydrophobic surface exhibited typical dropwise condensation, and the condensation heat transfer coefficient reached 331.8 W/(m2·K), which was 2.3 times higher than that of the original surface. Full article
(This article belongs to the Special Issue Recent Developments of Inorganic Crystalline Materials)
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13 pages, 3195 KiB  
Article
The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide
by Elena S. Zhitova, Rezeda M. Sheveleva, Andrey A. Zolotarev and Sergey V. Krivovichev
Crystals 2023, 13(5), 839; https://doi.org/10.3390/cryst13050839 - 19 May 2023
Cited by 1 | Viewed by 1517
Abstract
The crystal structure of quintinite, Mg4Al2(OH)12(CO3)·3H2O, from the Jacupiranga alkaline complex (Cajati, São Paulo, Brazil), was refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the [...] Read more.
The crystal structure of quintinite, Mg4Al2(OH)12(CO3)·3H2O, from the Jacupiranga alkaline complex (Cajati, São Paulo, Brazil), was refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the P-3c1 space group, a = 5.246/5.298, c = 15.110/15.199 Å for samples 91002/C7029. The crystal structure consists of octahedral sheets with Mg and Al ordering according to a 3 × 3 superstructure. The Mg and Al atoms are coordinated by six hydroxylated oxygen atoms; the average <Mg–O> and <Al–O> bond distances are in the ranges 2.022–2.053 Å and 1.974–1.978 Å, respectively. The interlayer structures are identical (in contradiction to the previous assumptions), and consist of disordered (CO3)2− groups and (H2O)0 molecules. The samples from Jacupiranga can be identified as quintinite-2T, which is the second finding of this polytype after the Kovdor alkaline complex (Kola peninsula, Russia). The powder X-ray diffraction pattern of quintinite-2T contains weak superstructure reflection at 4.57 Å (010), indicative of Mg and Al ordering. An important crystal-chemical criterion of quintinite is the interlayer distance (d00n-value) of ~7.56 Å, which is steady among natural specimens from various findings worldwide. Full article
(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))
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14 pages, 12870 KiB  
Review
Magnetic Force Microscopy of Multiferroic Bulk Ceramic Oxides
by Hana Uršič, Matej Šadl, Uroš Prah and Val Fišinger
Crystals 2023, 13(5), 838; https://doi.org/10.3390/cryst13050838 - 19 May 2023
Cited by 1 | Viewed by 1356
Abstract
Bulk multiferroic ceramics have been extensively studied due to their great potential for magneto-electric coupling applications such as low-power and multifunctional nano-electronic devices. In most of these studies the macroscopic magnetic performance was investigated, while the magnetic response on the micro- and nano-scale [...] Read more.
Bulk multiferroic ceramics have been extensively studied due to their great potential for magneto-electric coupling applications such as low-power and multifunctional nano-electronic devices. In most of these studies the macroscopic magnetic performance was investigated, while the magnetic response on the micro- and nano-scale was not examined in detail. Local magnetic phenomena can be studied using magnetic force microscopy (MFM), a technique derived from atomic force microscopy. MFM measures the magnetic force between the magnetised tip and the magnetic sample. It is one of the most used methods to characterise the structure of ferromagnetic domains, because the sample preparation is simple, non-destructive and provides a relatively high-resolution image. In this review paper we focus on the MFM analyses of bulk multiferroic ceramics. The core of the article is divided into four sections: the introduction, the preparation of samples prior to MFM examination, the reviews of MFM analyses performed on bulk multiferroic ceramics with and without external magnetic fields, and finally the conclusions and an outlook for the future. Full article
(This article belongs to the Special Issue Advanced Electronic Ceramics)
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15 pages, 4059 KiB  
Article
Structure Guiding Supramolecular Assemblies in Metal-Organic Multi-Component Compounds of Mn(II): Experimental and Theoretical Studies
by Manjit K. Bhattacharyya, Kamal K. Dutta, Pranay Sharma, Rosa M. Gomila, Miquel Barceló-Oliver and Antonio Frontera
Crystals 2023, 13(5), 837; https://doi.org/10.3390/cryst13050837 - 18 May 2023
Cited by 2 | Viewed by 972
Abstract
Two multi-component coordination compounds of Mn(II), viz. [Mn(H2O)6](2-Mepy)2(4-NO2bz)2·2H2O (1) and [Mn(H2O)6][Mn(2,3-PDCH)3]2 (2) (where, 2-Mepy = 2-methylpyridine, 4-NO2bz = [...] Read more.
Two multi-component coordination compounds of Mn(II), viz. [Mn(H2O)6](2-Mepy)2(4-NO2bz)2·2H2O (1) and [Mn(H2O)6][Mn(2,3-PDCH)3]2 (2) (where, 2-Mepy = 2-methylpyridine, 4-NO2bz = 4-nitrobenzoate, 2,3-PDC = 2,3-pyridinedicarboxylate), have been synthesized and characterized using elemental, spectroscopic (FT-IR and electronic), TGA and single-crystal X-ray diffraction analyses. Complex 1 is a co-crystal hydrate of Mn(II) involving uncoordinated 2-Mepy, 4-NO2bz and water molecules; while compound 2 is a multi-component molecular complex salt of Mn(II) comprising cationic [Mn(H2O)6]2+ and anionic [Mn(2,3-PDCH)3]−complex moieties. The uncoordinated 2-Mepy and 4-NO2bz moieties of 1 are involved in lone-pair (l.p)-π and C–H⋯π interactions which stabilize the layered assembly of the compound. The crystal structure of compound 2 has been previously reported. However, we have explored the unusual enclathration of complex cationic moieties within the supramolecular host cavities formed by the molecular assembly of complex anionic moieties. The supramolecular assemblies obtained in the crystal structure have been further studied theoretically using DFT calculations, quantum theory of atoms-in-molecules (QTAIM) and non-covalent interaction plot (NCI plot) computational tools. Theoretical studies reveal that the combination of π-staking interactions (l.p-π, π-π and C–H···π) have more structure-guiding roles compared to the H-bonds. The large binding energy of π-stacking interactions in 2 is due to the antiparallel orientation of aromatic rings and their coordination to the metal centers, thereby increasing the contribution of the dipole–dipole interactions. Full article
(This article belongs to the Special Issue Mixed-Metal Coordination Polymers)
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15 pages, 4427 KiB  
Article
Febuxostat–p-Toluenesulfonic Acid Multi-Component Crystal: Characterization, Crystal Growth and Elucidation of the Salt/Co-Crystal Nature
by Doriana T. Ungur, Gustavo Santiso-Quinones, Mihaela M. Pop, Tudor L. Tamas, Carmen Guguta, Danny Stam, Alice Mija and Coca A. Iordache
Crystals 2023, 13(5), 836; https://doi.org/10.3390/cryst13050836 - 18 May 2023
Cited by 1 | Viewed by 1543
Abstract
The multi-component solid form of febuxostat (FEB) with p-toluenesulfonic acid was synthesized by solvent-drop grinding and cooling-evaporative crystallization and characterized by powder X-ray diffraction (XRPD), thermogravimetry (TGA), differential scanning calorimetry (DSC), and infrared spectroscopy (FT-IR). The multi-component form was stable after exposure [...] Read more.
The multi-component solid form of febuxostat (FEB) with p-toluenesulfonic acid was synthesized by solvent-drop grinding and cooling-evaporative crystallization and characterized by powder X-ray diffraction (XRPD), thermogravimetry (TGA), differential scanning calorimetry (DSC), and infrared spectroscopy (FT-IR). The multi-component form was stable after exposure at elevated temperature and relative humidity and powder dissolution measurements revealed five-fold aqueous solubility improvement relative to FEB. Additionally, the decrease in pH after dissolution suggests a potential for enhancing the drug absorption in the lower stomach. In the context of the regulatory requirements, the salt/co-crystal nature of the form was elucidated by a combination of crystallization process development and crystal growth, followed by SC-XRD and FT-IR. Despite the very weak basicity of the drug, crystal structure determination combined with spectroscopy analysis revealed salt formation by the transfer of the acidic proton from p-toluenesulfonic acid to FEB. Our study emphasizes the importance of the crystal structure knowledge in understanding the type of interactions present in multi-component crystals as well as complying with the specific regulatory requirements. Full article
(This article belongs to the Special Issue Multicomponent Pharmaceutical Solids (2nd Edition))
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14 pages, 2644 KiB  
Article
Preparation of Laterally Chloro-Substituted Schiff Base Ester Liquid Crystals: Mesomorphic and Optical Properties
by Violeta Jevtovic, Hoda A. Ahmed, Mohd Taukeer Khan, Salma A. Al-Zahrani, Najat Masood and Yassin Aweis Jeilani
Crystals 2023, 13(5), 835; https://doi.org/10.3390/cryst13050835 - 18 May 2023
Cited by 5 | Viewed by 1232
Abstract
A new class of Schiff base/ester compounds: ICln, 4-((2′-chlorophenylimino)methyl)phenyl-4″-alkoxy benzoates, were synthesized and their mesophase characteristics and thermal behavior were evaluated. Differential scanning calorimetry (DSC) was used to study mesophase transitions, and polarized optical microscopy was carried out to identify the phases (POM). [...] Read more.
A new class of Schiff base/ester compounds: ICln, 4-((2′-chlorophenylimino)methyl)phenyl-4″-alkoxy benzoates, were synthesized and their mesophase characteristics and thermal behavior were evaluated. Differential scanning calorimetry (DSC) was used to study mesophase transitions, and polarized optical microscopy was carried out to identify the phases (POM). The results show that all compounds are monomorphic, and enantiotropic nematic (N) phases were seen at all side chains. It was found that lateral Cl atoms in the terminal benzene ring influence both conformation and mesomorphic properties. Comparisons between the present investigated lateral Cl derivatives and their laterally neat, as well as their isomeric, compounds have been briefly discussed. Results revealed that the insertion of lateral Cl substituent in the molecular structure impacts the type and stability of the formed mesophases. The exchanges of the ester-connecting moiety improve their thermal nematic stability than their previously prepared structurally isomeric derivatives. These compounds exhibit a broad absorption in the UV-Visible region, including a peak in UV region and a tail around 550 nm, and there were observed to be absorption tail increases and energy band gap decreases with the increase of the alkoxy side chain length. The photoluminescence (PL) intensity was noted to be quenched for the bulky alkoxy group ascribed to non-radiative recombination through the defect states. Moreover, time resolved fluorescence decay spectra reveal that both the radiative and non-radiative recombination lifetime increases with the increase of alkoxy side chain length. Full article
(This article belongs to the Special Issue Optical and Molecular Aspects of Liquid Crystals)
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8 pages, 1188 KiB  
Article
Analysis of Photo-Generated Carrier Escape in Multiple Quantum Wells
by Jiaping Guo, Weiye Liu, Ding Ding, Xinhui Tan, Wei Zhang, Lili Han, Zhaowei Wang, Weihua Gong, Jiyun Li, Ruizhan Zhai, Zhongqing Jia, Ziguang Ma, Chunhua Du, Haiqiang Jia and Xiansheng Tang
Crystals 2023, 13(5), 834; https://doi.org/10.3390/cryst13050834 - 17 May 2023
Viewed by 1074
Abstract
Recent experiments have shown that more than 85% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (PIN). In this work, we quantitatively analyze the relationship between the energy of carriers and the height of potential [...] Read more.
Recent experiments have shown that more than 85% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (PIN). In this work, we quantitatively analyze the relationship between the energy of carriers and the height of potential barriers to be crossed, based on the GaAs/InGaAs quantum well structure system, combined with the Heisenberg uncertainty principle. It was found that that the energy obtained by electrons from photons is just enough for them to escape, and it was found that the energy obtained by the hole is just enough for it to escape due to the extra energy calculated, based on the uncertainty principle. This extra energy is considered to come from photo-generated thermal energy. The differential reflection spectrum of the structure is then measured by pump–probe technology to verify the assumption. The experiment shows that the photo-generated carrier has a longer lifetime in its short circuit (SC) state, and thus it possesses a lower structure temperature than that in open circuit (OC). This can only explain a thermal energy reduction caused by the continuous carrier escape in SC state, indicating an extra thermal energy transferred to the escaping carriers. This study is of great significance to the design of new optoelectronic devices and can improve the theory of photo-generated carrier transports. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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13 pages, 8460 KiB  
Article
Double-Layer Kagome Metals Pt3Tl2 and Pt3In2
by Michael A. McGuire, Eleanor M. Clements, Qiang Zhang and Satoshi Okamoto
Crystals 2023, 13(5), 833; https://doi.org/10.3390/cryst13050833 - 17 May 2023
Viewed by 1473
Abstract
The connectivity and inherent frustration of the kagome lattice can produce interesting electronic structures and behaviors in compounds containing this structural motif. Here we report the properties of Pt3X2 (X = In and Tl) that adopt a double-layer kagome [...] Read more.
The connectivity and inherent frustration of the kagome lattice can produce interesting electronic structures and behaviors in compounds containing this structural motif. Here we report the properties of Pt3X2 (X = In and Tl) that adopt a double-layer kagome net structure related to that of the topologically nontrivial high-temperature ferromagnet Fe3Sn2 and the density wave hosting compound V3Sb2. We examined the structural and physical properties of single crystal Pt3Tl2 and polycrystalline Pt3In2 using X-ray and neutron diffraction, magnetic susceptibility, heat capacity, and electrical transport measurements, along with density functional theory calculations of the electronic structure. Our calculations show that Fermi levels lie in pseudogaps in the densities of states with several bands contributing to transport, and this is consistent with our Hall effect, magnetic susceptibility, and heat capacity measurements. Although electronic dispersions, characteristic of simple kagome nets with nearest-neighbor hopping, are not clearly seen, likely due to the extended nature of the Pt 5d states, we do observe moderately large and non-saturating magnetoresistance values and quantum oscillations in the magnetoresistance and magnetization associated with the kagome nets of Pt. Full article
(This article belongs to the Special Issue Advances in Intermetallic and Metal-Like Compounds)
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12 pages, 3700 KiB  
Article
Ultrafast Mechanism of Material Removal in the Femtosecond Laser Ablation of WS2 and Its Diode Rectification Characteristics
by Kai Wang, Zhicheng Chen, Xu Wu, Changji Pan, Feifei Wang, Jiaxing Wang, Ke Zhang, Yang Yang and Jingya Sun
Crystals 2023, 13(5), 832; https://doi.org/10.3390/cryst13050832 - 17 May 2023
Viewed by 1263
Abstract
The study investigates the two different underlying ablation mechanisms of WS2 processed by femtosecond (fs) laser with different fluences. With increasing fluence, the saturable expansion of craters and the transformation of three distinct crater morphologies are found. The material response and the [...] Read more.
The study investigates the two different underlying ablation mechanisms of WS2 processed by femtosecond (fs) laser with different fluences. With increasing fluence, the saturable expansion of craters and the transformation of three distinct crater morphologies are found. The material response and the transfer and deposition of laser energy are tracked by using a plasma model based on the classical single rate equation model and the Drude model. The results of the numerical simulation and time-resolved transient reflectivity reveal the two different ablation mechanisms, which are coulomb explosion and phase explosion. The mechanism of material removal is distinguished by the critical threshold of 0.85 J/cm2. In addition, the internal ablation region exhibits a high concentration of defects and WO3 according to the results of Raman spectra, X-ray photoelectron spectra, and morphology-dependent photoluminescence mapping. Due to the high concentration with high fluence, the device of WS2/Si p-n junction exhibits a 2.6 times enhancement on the current under forward bias. The findings would be of value to engineer structures to tailor the optoelectronic response of WS2 and to develop potential future optoelectronic devices. Full article
(This article belongs to the Special Issue Recent Advances in Transition Metal Dichalcogenides (TMDCs) and Their Applications)
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10 pages, 5484 KiB  
Communication
Linear-to-Dual-Circular Polarization Decomposition Metasurface Based on Rotated Trimming-Stub-Loaded Circular Patch
by Tao Zhang, Haoran Wang, Chongmei Peng and Zhaohui Chen
Crystals 2023, 13(5), 831; https://doi.org/10.3390/cryst13050831 - 17 May 2023
Cited by 1 | Viewed by 1097
Abstract
This paper presents a linear-to-dual-circular polarization metasurface decomposer, which decomposes a linearly polarized (LP) planar incident wave into a pair of circular polarized (CP) waves, namely, a right-handed circular polarized (RHCP) wave and a left-handed circular polarized (LHCP) wave, and scatters them into [...] Read more.
This paper presents a linear-to-dual-circular polarization metasurface decomposer, which decomposes a linearly polarized (LP) planar incident wave into a pair of circular polarized (CP) waves, namely, a right-handed circular polarized (RHCP) wave and a left-handed circular polarized (LHCP) wave, and scatters them into different directions. The proposed metasurface polarization decomposer is composed of a series of rotated trimming stub loaded circular patches. The two CP components are excited due to the perturbation introduced by the trimming stubs, and the different phase gradients added to the RHCP and LHCP components are realized by rotating the circular patches with different angles. A 12×12 metasurface polarization decomposer is designed, fabricated, and measured, which scatters the RHCP and LHCP into −30∘ and 30∘, respectively. The simulated and measured results agree well with each other, which demonstrates the proposed design. Full article
(This article belongs to the Special Issue Metamaterials and Metasurfaces for Microwave and THz Applications)
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17 pages, 18386 KiB  
Article
Towards Closed-Loop Recycling of Ceramic Particle-Reinforced Aluminium Alloys: Comparative Study of Resistance-Heating Sintered Primary and Solid-State Recycled Secondary SiCp/AlSi7Mg Composites
by Sarah Johanna Hirsch, Thomas Grund and Thomas Lampke
Crystals 2023, 13(5), 830; https://doi.org/10.3390/cryst13050830 - 17 May 2023
Cited by 2 | Viewed by 1050
Abstract
Particle-reinforced aluminium matrix composites (AMC) with a high-volume fraction of ceramic reinforcement (>30 vol.%) combine high specific strength and stiffness with good wear resistance and thermal stability, resulting in their increasing popularity in high-load applications, such as brake discs and bearings. It is [...] Read more.
Particle-reinforced aluminium matrix composites (AMC) with a high-volume fraction of ceramic reinforcement (>30 vol.%) combine high specific strength and stiffness with good wear resistance and thermal stability, resulting in their increasing popularity in high-load applications, such as brake discs and bearings. It is hence assumed that AMC will accumulate as scrap in the near future. Appropriate recycling strategies must therefore be developed to maintain AMC’s inherent properties. Melt-metallurgical recycling routes bear the danger of dissolving the ceramic reinforcement in the liquid metallic matrix and contaminating primary melts or forming intermetallic phases in secondary melts. Here, a solid-state AMC recycling route with crushing and sintering is investigated, wherein all steps are carried out below the solidification temperature of the aluminium matrix. A sintered primary AMC is mechanically converted into a particulate/powdery secondary raw AMC in coarse, medium, and milled quality (i.e., with d ≈ 7–12 mm, d ≈ 3–7 mm, and d < 300 µm) and subsequently resistance heating sintered to a secondary AMC under a variation of the sintering pressure. The two AMC generations are analysed and discussed regarding their microstructure and mechanical properties. Since the secondary AMC show reduced the mechanical strength, the fracture surfaces are analysed, revealing iron contaminations from the mechanical processing. Full article
(This article belongs to the Special Issue Current Status and Recent Progress on Advanced Aluminum Alloys)
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14 pages, 4498 KiB  
Article
Theoretical Study on (n,n)-Nanotubes Rolled-up from B/N Substituted Me-Graphene
by Hong-Chao Luo, Feng-Yin Li, Ya-Nan Zhang, Hong-Xing Zhang, Roberts I. Eglitis and Ran Jia
Crystals 2023, 13(5), 829; https://doi.org/10.3390/cryst13050829 - 17 May 2023
Cited by 1 | Viewed by 1157
Abstract
In this work, the n,n-type nanotube systems rolled up from the B/N substituted Me-graphene (i.e., Me-CBNT and Me-CNN, respectively) were investigated with the aid of the density functional theory (DFT). Due to the lattice dynamic instabilities until n=10 [...] Read more.
In this work, the n,n-type nanotube systems rolled up from the B/N substituted Me-graphene (i.e., Me-CBNT and Me-CNN, respectively) were investigated with the aid of the density functional theory (DFT). Due to the lattice dynamic instabilities until n=10, the n,0 and n,m nanotube systems were not involved in this study. According to our calculations at the Perdew-Burke-Ernzerhof (PBE) level, the n,n Me-CBNT and Me-CNNT systems possess excellent mechanical strengths. The Young’s moduli of Me-CBNTs can reach 60% of single-walled carbon nanotubes (SWCNTs), while their mass densities are only around 70% of SWCNTs. Based on the fully relaxed geometric configurations at the PBE level, the electronic configurations of the related nanotubes were evaluated by using the global hybrid functional B3LYP with 36% Fock exchanges. The n,n Me-CBNTs are metallic, while the n,n Me-CNNTs are semiconductors with the inherent band gaps in the range of 3.08 eV to 3.31 eV. The Bloch flat bands appear on both sides of their Fermi levels, indicating the localized charge carriers. Their band edge arrangements imply that these materials are promising candidates for the photocatalytic water splitting reactions at certain pH values. Full article
(This article belongs to the Special Issue Electronic Phenomena of Transition Metal Oxides Volume II)
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19 pages, 7937 KiB  
Article
Interface-Dominated Plasticity and Kink Bands in Metallic Nanolaminates
by Abhishek Arora, Rajat Arora and Amit Acharya
Crystals 2023, 13(5), 828; https://doi.org/10.3390/cryst13050828 - 17 May 2023
Cited by 2 | Viewed by 1871
Abstract
The theoretical and computational framework of finite deformation mesoscale field dislocation mechanics (MFDM) is used to understand the salient aspects of kink-band formation in Cu-Nb nano-metallic laminates (NMLs). A conceptually minimal, plane-strain idealization of the three-dimensional geometry, including crystalline orientation, of additively manufactured [...] Read more.
The theoretical and computational framework of finite deformation mesoscale field dislocation mechanics (MFDM) is used to understand the salient aspects of kink-band formation in Cu-Nb nano-metallic laminates (NMLs). A conceptually minimal, plane-strain idealization of the three-dimensional geometry, including crystalline orientation, of additively manufactured NML is used to model NMLs. Importantly, the natural jump/interface condition of MFDM imposing continuity of (certain components) of plastic strain rates across interfaces allows theory-driven ‘communication’ of plastic flow across the laminate boundaries in our finite element implementation. Kink bands under layer parallel compression of NMLs in accord with experimental observations arise in our numerical simulations. The possible mechanisms for the formation and orientation of kink bands are discussed, within the scope of our idealized framework. We also report results corresponding to various parametric studies that provide preliminary insights and clear questions for future work on understanding the intricate underlying mechanisms for the formation of kink bands. Full article
(This article belongs to the Special Issue Dislocation Mechanics of Crystal/Polycrystal Mechanical Strength Properties)
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12 pages, 2040 KiB  
Article
Impact of Input Signal Characteristics on Energy-Localization Performance of a Phononic Crystal with a Defect: A Comparative Study of Burst and Continuous Wave Excitation
by Soo-Ho Jo
Crystals 2023, 13(5), 827; https://doi.org/10.3390/cryst13050827 - 16 May 2023
Viewed by 876
Abstract
This study examines the energy-localization performance of a one-dimensional phononic crystal (PnC) with a defect when exposed to burst waves of different cycle numbers under longitudinal waves. Using the finite element method, band structures of the defect-introduced PnC were calculated, revealing a phononic [...] Read more.
This study examines the energy-localization performance of a one-dimensional phononic crystal (PnC) with a defect when exposed to burst waves of different cycle numbers under longitudinal waves. Using the finite element method, band structures of the defect-introduced PnC were calculated, revealing a phononic band-gap range, defect-band frequencies, and corresponding defect-mode shapes. The transient analysis examined the longitudinal displacement at the center of this defect in the time domain for various burst-wave scenarios. The results indicate that energy-localization performance inside the defect highly depended on the number of cycles. Energy-localization performance was better with larger cycles or continuous waves, although burst waves with a small number of cycles also showed some improvement, albeit limited. Moreover, burst waves with a small number of cycles did not clearly induce fixed-like boundary conditions (in other words, nodal points in standing waves) within the defect-introduced PnC, leading to obscure energy-localized behaviors. Key messages from this work can be summarized as follows. First, comparing the energy-localization performance under incident burst waves with different cycle numbers for different systems might not be appropriate. Second, the physically reasonable formation of defect-mode-enabled energy localization requires burst waves with a large (in the case study, over 500) number of cycles. Full article
(This article belongs to the Section Crystal Engineering)
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16 pages, 4448 KiB  
Article
A Locally Disordered Metamaterial for Directing and Trapping Water Waves
by Wei-Qi Sun, Yu-Han Wang, Zhu-Long Xu, Xiang Fang and Kuo-Chih Chuang
Crystals 2023, 13(5), 826; https://doi.org/10.3390/cryst13050826 - 16 May 2023
Cited by 1 | Viewed by 1123
Abstract
Manipulating the flow of water wave energy is crucial for ocean wave energy extraction or coastal protection, and the emergence of metamaterials paves a potential way for controlling water waves. In this work, by introducing a local disorder in a cavity-type metamaterial constructed [...] Read more.
Manipulating the flow of water wave energy is crucial for ocean wave energy extraction or coastal protection, and the emergence of metamaterials paves a potential way for controlling water waves. In this work, by introducing a local disorder in a cavity-type metamaterial constructed by split-tube resonators, we show that water waves can be guided in an open channel with multiple energy flow paths formed merely by surrounded disconnected concurrent resonators that can serve as invisible walls without the requirement of a whole array system such as general periodic structures or waveguides. Specifically, we numerically and experimentally validate that a T-shaped metamaterial can achieve free guiding of water waves in a narrow band and a band-edge state along a distinct path. This open-space water waveguiding is found to be dominated by Fano-type interference and Fabry–Pérot resonance. Two distinct propagating modes, a low-frequency “trapping mode” and a high-frequency “following mode”, are identified. By simply rotating two configuration-dependent unit cells at the intersection of the metamaterial, we achieve a variety of water waveguiding paths tuning along rectilinear or bending (splitting or turning) directions, which rely on the two different propagating modes. Full article
(This article belongs to the Special Issue Metamaterials and Their Devices)
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19 pages, 5283 KiB  
Article
Morphological Features of Polycrystalline CdS1−xSex Films Obtained by Screen-Printing Method
by Diana M. Strateichuk, Nikita V. Martyushev, Roman V. Klyuev, Vitaliy A. Gladkikh, Vladislav V. Kukartsev, Yadviga A. Tynchenko and Antonina I. Karlina
Crystals 2023, 13(5), 825; https://doi.org/10.3390/cryst13050825 - 16 May 2023
Cited by 32 | Viewed by 1355
Abstract
The results of studying the morphological peculiarities of polycrystalline CdS1−xSex films, obtained by screen printing, with well-formed grain boundaries of high structural quality are presented here. The developed method for screen printing provides the formation of polycrystalline films of a [...] Read more.
The results of studying the morphological peculiarities of polycrystalline CdS1−xSex films, obtained by screen printing, with well-formed grain boundaries of high structural quality are presented here. The developed method for screen printing provides the formation of polycrystalline films of a specified area per cycle, provided that there is a possibility for varying their thickness from tens of microns to units, which allows reducing the solar cell’s thickness and facilitating the process of its connection with the substrate. Therefore, the application of the films to a sitall substrate by screen printing contributes to reducing the product weight and facilitating the process of joining sheet materials intended for solar panels, namely attaching the lasing element to the substrate. The purpose of this work is to study the morphological peculiarities of polycrystalline CdS1−xSex films obtained by an optimized screen-printing method and to create a model of their formation process. The structural and morphological peculiarities of the samples were studied using electron microscopy, AFM, XPA, and XFS. As a result of the work, based on the obtained experimental data, a model of the film formation process was developed. The model validity is justified by the conformity of the data of the experiment performed on its basis. Full article
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