Crystals

10 pages, 2661 KiB

Open AccessEditor’s ChoiceArticle

Scintillation Properties of Pr-Doped Lanthanum Pyrosilicate Single Crystals

by Prom Kantuptim, Takumi Kato, Daisuke Nakauchi, Noriaki Kawaguchi and Takayuki Yanagida

Crystals 2022, 12(4), 459; https://doi.org/10.3390/cryst12040459 - 25 Mar 2022

Cited by 9 | Viewed by 4314

Five samples of lanthanum pyrosilicate (La₂Si₂O₇) single crystals with 0.5–10.0% Praseodymium (Pr)-doping concentrations were synthesized by the floating-zone method. Photoluminescence and scintillation properties of these crystals were investigated in this study for the first time. The multiple [...] Read more.

Five samples of lanthanum pyrosilicate (La₂Si₂O₇) single crystals with 0.5–10.0% Praseodymium (Pr)-doping concentrations were synthesized by the floating-zone method. Photoluminescence and scintillation properties of these crystals were investigated in this study for the first time. The multiple emissions from electron transitions of Pr³⁺ were observed on both a photoluminescence emission map and scintillation spectra, including the desired emission band of Pr³⁺ 5d–4f transition at 250–310 nm. The major photoluminescence and scintillation decay times were approximately 19 and 26 ns, respectively. When compared with commercial scintillators such as Tl-doped cesium iodide (CsI), the Pr-doped La₂Si₂O₇ samples presented a respectively low afterglow level of 32 ppm after 20 ms of X-ray irradiation. Under 662 keV γ-ray irradiation from ¹³⁷Cs, the 3.0% Pr-doped La₂Si₂O₇ sample presented a scintillation light yield of 3200 ph/MeV, which was the best value among the tested samples. Full article

(This article belongs to the Special Issue Optoelectronics and Photonics in Crystals)

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10 pages, 19907 KiB

Open AccessEditor’s ChoiceArticle

Second-Order Raman Scattering in Ferroelectric Ceramic Solid Solutions LiNb_xTa_1−xO₃

by Nikolay Sidorov, Mikhail Palatnikov, Alexander Pyatyshev and Pavel Sverbil

Crystals 2022, 12(4), 456; https://doi.org/10.3390/cryst12040456 - 24 Mar 2022

Cited by 4 | Viewed by 2191

Abstract

In the second-order Raman spectra of ceramic solid solutions, LiNb_xTa_1−xO₃ weak overtone bands of fully symmetric fundamental polar excitations were observed for the first time. The frequencies of the two bands exceeded the value of the overtone frequency [...] Read more.

In the second-order Raman spectra of ceramic solid solutions, LiNb_xTa_1−xO₃ weak overtone bands of fully symmetric fundamental polar excitations were observed for the first time. The frequencies of the two bands exceeded the value of the overtone frequency corresponding to the fully symmetrical vibration 4A₁(z). The possibility of the existence of phonon bound states of the antipolar type in the vibrational spectrum of LiNb_xTa_1−xO₃ ceramics is predicted. Full article

(This article belongs to the Special Issue Multiferroic Ceramics and Thin Film Nanostructures for Logic and Memory Applications)

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12 pages, 1319 KiB

Open AccessEditor’s ChoiceArticle

Phase Diagram of a Strained Ferroelectric Nanowire

by Maksim A. Pavlenko, Franco Di Rino, Leo Boron, Svitlana Kondovych, Anaïs Sené, Yuri A. Tikhonov, Anna G. Razumnaya, Valerii M. Vinokur, Marcelo Sepliarsky and Igor A. Lukyanchuk

Crystals 2022, 12(4), 453; https://doi.org/10.3390/cryst12040453 - 24 Mar 2022

Cited by 6 | Viewed by 4709

Abstract

Ferroelectric materials manifest unique dielectric, ferroelastic, and piezoelectric properties. A targeted design of ferroelectrics at the nanoscale is not only of fundamental appeal but holds the highest potential for applications. Compared to two-dimensional nanostructures such as thin films and superlattices, one-dimensional ferroelectric nanowires [...] Read more.

Ferroelectric materials manifest unique dielectric, ferroelastic, and piezoelectric properties. A targeted design of ferroelectrics at the nanoscale is not only of fundamental appeal but holds the highest potential for applications. Compared to two-dimensional nanostructures such as thin films and superlattices, one-dimensional ferroelectric nanowires are investigated to a much lesser extent. Here, we reveal a variety of the topological polarization states, particularly the vortex and helical chiral phases, in loaded ferroelectric nanowires, which enable us to complete the strain–temperature phase diagram of the one-dimensional ferroelectrics. These phases are of prime importance for optoelectronics and quantum communication technologies. Full article

(This article belongs to the Special Issue Research and Development of Ferroelectric Material)

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10 pages, 4411 KiB

Open AccessEditor’s ChoiceArticle

Molecular Self-Assembly of an Unusual Dinuclear Ruthenium(III) Complex Based on the Nucleobase Guanine

by Marta Orts-Arroyo, Adriana Silvestre-Llora, Isabel Castro and José Martínez-Lillo

Crystals 2022, 12(4), 448; https://doi.org/10.3390/cryst12040448 - 23 Mar 2022

Cited by 4 | Viewed by 2314

Abstract

The study of crystal structures based on complexes containing purine nucleobases is a significant research subject, mainly regarding the diagnosis and treatment of some diseases and the investigation of genetic mutations and biochemical structures in life sciences. We have obtained and characterized a [...] Read more.

The study of crystal structures based on complexes containing purine nucleobases is a significant research subject, mainly regarding the diagnosis and treatment of some diseases and the investigation of genetic mutations and biochemical structures in life sciences. We have obtained and characterized a new dinuclear ruthenium(III) complex based on guanine with the formula [{Ru(µ-Cl)(µ-gua)}₂Cl₄]·2H₂O (1) (gua = guanine). 1 was characterized by means of Fourier transform infrared spectroscopy (FT–IR), scanning electron microscopy and energy dispersive X-ray analysis (SEM–EDX), single-crystal X-ray diffraction (XRD), Hirshfeld surface analysis and cyclic voltammetry (CV). The study of its electrochemical properties allowed us to investigate the presence of guanine molecules when linked to the ruthenium(III) ion in 1. The well-resolved voltammetric response together with the reliability and stability achieved through 1 could provide a step forward to developing new ruthenium-based platforms, devices and modified electrodes adequate to study this purine nucleobase. Full article

(This article belongs to the Special Issue Self-Assembled Complexes: “Love at First Sight”)

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12 pages, 5222 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Structural Characterization of a New 1,2,3-Triazole Derivative of Pentacyclic Triterpene

by Ewa Bębenek, Monika Kadela-Tomanek, Elwira Chrobak, Maria Jastrzębska and Maria Książek

Crystals 2022, 12(3), 422; https://doi.org/10.3390/cryst12030422 - 18 Mar 2022

Cited by 3 | Viewed by 2283

Abstract

The new 30-substituted triazole derivative of 3,28-O,O′-diacetylbetulin was obtained in the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC). The title compound was characterized by NMR, IR, HR-MS, and X-ray diffraction techniques. The X-ray diffraction study showed that the 1,2,3-triazole derivative crystallizes [...] Read more.

The new 30-substituted triazole derivative of 3,28-O,O′-diacetylbetulin was obtained in the copper(I) catalyzed azide-alkyne cycloaddition (CuAAC). The title compound was characterized by NMR, IR, HR-MS, and X-ray diffraction techniques. The X-ray diffraction study showed that the 1,2,3-triazole derivative crystallizes in the orthorhombic space group P2₁2₁2₁, Z = 4, and unit cell parameters are as follows a = 9.4860(10) Å, b = 13.9440(2) Å, and c = 30.2347(4) Å. The molecular packing is stabilized by intermolecular hydrogen interactions C-H…O. The Hirshfeld surface analysis showed the presence of the O…H interactions with a percentage of the 16.5% in the total Hirshfeld area. The MEP analysis showed that the nucleophilic regions are located near the oxygen atoms of the acyl and carbonyl groups of betulin moiety and the sulfur atom in the triazole linker. The HOMO and LUMO orbitals are located near the triazole moiety. The obtained results indicated that this new betulin derivative is more reactive with electrophilic than nucleophilic molecules. Full article

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13 pages, 4335 KiB

Open AccessEditor’s ChoiceArticle

Scalable and Blue Photoluminescence Emissions of (C₄H₉NH₃)₂PbBr₄ 2D Perovskite Fabricated by the Dip-Coating Method Using a Co-Solvent System

by Chia-Man Chou, Yuan-Tung Liu, Pei-Ching Wei, Yi-Jhen Li, Yu-Han Kung, Vincent K. S. Hsiao and Chih-Chien Chu

Crystals 2022, 12(3), 418; https://doi.org/10.3390/cryst12030418 - 18 Mar 2022

Viewed by 2629

Abstract

The improved efficiency of perovskite-related photovoltaic devices, such as light-emitting diodes (LEDs), is related to film uniformity, the compactness of each layer, and thickness. Herein, we improved the traditional single-solvent, solution-processed method and developed a co-solvent method to prepare a two-dimensional (2D) (C [...] Read more.

The improved efficiency of perovskite-related photovoltaic devices, such as light-emitting diodes (LEDs), is related to film uniformity, the compactness of each layer, and thickness. Herein, we improved the traditional single-solvent, solution-processed method and developed a co-solvent method to prepare a two-dimensional (2D) (C₄H₉NH₃)₂PbBr₄ perovskite film for blue photoluminescence (PL) emissions. A poor film-forming uniformity was observed for the use of the single-solvent, dimethylformamide (DMF) method. In adding 1,2-dichlorobenzene (ODCB) of a smaller polarity to DMF, the co-solvent engineering dramatically changed the film-forming properties. Optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffractometer (XRD), and time-resolved PL (TR-PL) spectroscopy analyses confirmed that the perovskite film prepared by the co-solvent system had a good crystallinity, fewer defects, and a longer carrier lifetime. These experimental results show a simple, scalable (1.23 × 1.23 cm²), and stable reproducibility method for preparing 2D perovskite of 415 nm wavelength PL emissions that might be beneficial for the development of ultraviolet (UV) photodetectors, blue LEDs, and high-resolution displays. Full article

(This article belongs to the Special Issue Advance in Application of Perovskite Materials in Optoelectronic Devices)

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11 pages, 2975 KiB

Open AccessEditor’s ChoiceArticle

Compressive Mechanics and Hyperelasticity of Ni-Ti Lattice Structures Fabricated by Selective Laser Melting

by Cong Zhang, Jiulu Jin, Meng He and Lei Yang

Crystals 2022, 12(3), 408; https://doi.org/10.3390/cryst12030408 - 17 Mar 2022

Cited by 10 | Viewed by 3085

Abstract

Additively manufactured Ni-Ti lattice structures have controllable bio/mechanical properties, as well as excellent large deformation and damping properties similar to those of natural bone. They have broad application prospects in the field of bone implantation. Triply Periodic Minimal Surface (TPMS) structures are believed [...] Read more.

Additively manufactured Ni-Ti lattice structures have controllable bio/mechanical properties, as well as excellent large deformation and damping properties similar to those of natural bone. They have broad application prospects in the field of bone implantation. Triply Periodic Minimal Surface (TPMS) structures are believed to be the most potential and ideal bionic bone structures. In this work, Ni-Ti Gyroid-type TPMS lattice structures were fabricated by selective laser melting (SLM) and their manufacturing fidelity and compression properties were evaluated. By changing the maximum strain value, the hyperelastic recovery performance under cyclic stress was investigated. The results showed that the Ni-Ti Gyroid lattice structures fabricated by SLM had excellent manufacturability (relative density can reach 98.93%) and mechanical properties (elastic modulus is about 130.8 MPa, ultimate strength is about 2.7 MPa). The hyperelastic cycle testing showed that the elastic modulus, yield strength and ultimate strength of the lattice structures tended to stablilize gradually with increasing numbers of cycles. The residual strain increased with the number of cycles, and as the maximum strain increased from 4% to 8%, the residual strain also increased from 1% to 4%. Full article

(This article belongs to the Special Issue Powder Bed Fusion Additive Manufacturing: Materials, Processes, and Structures)

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18 pages, 6051 KiB

Open AccessEditor’s ChoiceArticle

Influence of Solidification Parameters on the Amount of Eutectic and Secondary Arm Spacing of Al–7wt% Si Alloy Solidified under Microgravity

by András Roósz, Arnold Rónaföldi, Yuze Li, Nathalie Mangelinck-Noël, Gerhard Zimmermann, Henri Nguyen-Thi, Mária Svéda and Zsolt Veres

Crystals 2022, 12(3), 414; https://doi.org/10.3390/cryst12030414 - 17 Mar 2022

Cited by 5 | Viewed by 2223

Abstract

During the solidification of hypoeutectic Al–7% Si alloy, density differences develop in the melt due to variations in concentration and temperature. On Earth, melt flow can occur due to gravity, which then affects the solidification process. The microgravity environment strongly eliminates convection in [...] Read more.

During the solidification of hypoeutectic Al–7% Si alloy, density differences develop in the melt due to variations in concentration and temperature. On Earth, melt flow can occur due to gravity, which then affects the solidification process. The microgravity environment strongly eliminates convection in the melt and allows investigation of the solidification process in purely diffusive circumstances. In this study, four solidification experiments were performed on grain-refined and non-grain-refined Al–7 wt% Si alloy on-board the International Space Station (ISS) in the Materials Science Lab (MSL) to study the effect of solidification parameters (solid/liquid front velocity (v) and temperature gradient (G)) on the grain structure and dendritic microstructure. The grain structure has been analyzed in detail in some earlier studies. The aim of this work was to carry out detailed analysis of the macrosegregation caused by the diffusion of Si from the initial mushy zone during the homogenization step and the subsequent solidification phase of the experiments as well as the correlated distribution of eutectic along the solidification direction. The secondary dendrite arm spacing (SDAS) for different process conditions was also studied. For these two issues, microgravity experimental results were compared to simulation results. The macrosegregation was calculated by the finite difference method. Because the steady-state solidification conditions were never reached, the solidification process was characterized by the average front velocity and temperature gradient. Considering the actual liquidus temperature (T_L) caused by macrosegregation, the SDAS was calculated as a function of the average processing parameters and the actual liquidus temperature with the classical Kirkwood’s equation. As a result, good agreement was obtained between the calculated and measured SDAS. Full article

(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)

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9 pages, 1675 KiB

Open AccessEditor’s ChoiceArticle

Influence of Surface Relief on Orientation of Nematic Liquid Crystals: Polyimide Doped with WS₂ Nanotubes

by Natalia Kamanina, Andrey Toikka, Yaroslav Barnash, Alla Zak and Reshef Tenne

Crystals 2022, 12(3), 391; https://doi.org/10.3390/cryst12030391 - 14 Mar 2022

Cited by 8 | Viewed by 2586

Abstract

Among the different methods for orienting liquid crystal (LC) molecules, adding nanoparticles into the matrix of the substrate material towards modifying its surface, is actively pursued. In this context, the influence of the nanoparticle content on the texture of the surface of polymer [...] Read more.

Among the different methods for orienting liquid crystal (LC) molecules, adding nanoparticles into the matrix of the substrate material towards modifying its surface, is actively pursued. In this context, the influence of the nanoparticle content on the texture of the surface of polymer film used as the substrate for the LC orientation is of particular interest. Thus, in the current paper, WS₂ nanotubes were used to dope the polyimide (PI) substrate-film in order to modify and control its surface morphology/roughness and properties. The modified organic surface structure is applied in order to achieve a new means for controlling the orientation of the LC molecules. This tool adds to the classical methods for controlling the orientation of the LC molecules, such as the display technique. Full article

(This article belongs to the Special Issue Feature Articles in Liquid Crystals from Our Editorial Board Members and Their Colleagues, 2022/2023)

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12 pages, 3554 KiB

Open AccessEditor’s ChoiceArticle

An Investigation of the Pressure-Induced Structural Phase Transition of Nanocrystalline α-CuMoO₄

by Vinod Panchal, Catalin Popescu and Daniel Errandonea

Crystals 2022, 12(3), 365; https://doi.org/10.3390/cryst12030365 - 9 Mar 2022

Cited by 2 | Viewed by 2794

Abstract

The structural behavior of nanocrystalline α-CuMoO₄ was studied at ambient temperature up to 2 GPa using in situ synchrotron X-ray powder diffraction. We found that nanocrystalline α-CuMoO₄ undergoes a structural phase transition into γ-CuMoO₄ at 0.5 GPa. The structural sequence [...] Read more.

The structural behavior of nanocrystalline α-CuMoO₄ was studied at ambient temperature up to 2 GPa using in situ synchrotron X-ray powder diffraction. We found that nanocrystalline α-CuMoO₄ undergoes a structural phase transition into γ-CuMoO₄ at 0.5 GPa. The structural sequence is analogous to the behavior of its bulk counterpart, but the transition pressure is doubled. A coexistence of both phases was observed till 1.2 GPa. The phase transition gives rise to a change in the copper coordination from square-pyramidal to octahedral coordination. The transition involves a volume reduction of 13% indicating a first-order nature of the phase transition. This transformation was observed to be irreversible in nature. The pressure dependence of the unit-cell parameters was obtained and is discussed, and the compressibility analyzed. Full article

(This article belongs to the Special Issue Pressure-Induced Phase Transformations (Volume II))

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8 pages, 2494 KiB

Open AccessEditor’s ChoiceArticle

The Growth of Hexagonal Boron Nitride Quantum Dots on Polycrystalline Nickel Films by Plasma-Assisted Molecular Beam Epitaxy

by Nurzal Nurzal, Wei-Cyuan Huang, Cheng-Yu Liu, Su-Hua Chen and Ing-Song Yu

Crystals 2022, 12(3), 347; https://doi.org/10.3390/cryst12030347 - 3 Mar 2022

Cited by 3 | Viewed by 2476

Abstract

In this report, quantum dots of hexagonal boron nitride (h-BN) were fabricated on the surface of polycrystalline Ni film at low growth temperatures (700, 750, and 800 °C) by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction could trace the surface condition during [...] Read more.

In this report, quantum dots of hexagonal boron nitride (h-BN) were fabricated on the surface of polycrystalline Ni film at low growth temperatures (700, 750, and 800 °C) by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction could trace the surface condition during the growth and perform the formation of BN. The observation of surface morphology by scanning electron microscopy and atomic force microscopy showed the nanodots of BN on Ni films. The existence of crystal h-BN quantum dots was determined by the analysis of Raman spectra and Kevin probe force microscopy. The cathodoluminescence of h-BN quantum dots performed at the wavelength of 546 and 610 nm, attributed to the trapping centers involving impurities and vacancies. Moreover, the influence of temperatures for the substrate and boron source cell was also investigated in the report. When the k-cell temperature of boron and growth temperature of substrate increased, the emission intensity of cathodoluminescence spectra increased, indicating the better growth parameters for h-BN quantum dots. Full article

(This article belongs to the Special Issue Confined Crystals, Quantum Dots, and Nano Crystals)

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14 pages, 7150 KiB

Open AccessEditor’s ChoiceArticle

Unusual Lattice Parameters Behavior for La_1.9Ca_0.1NiO_4+δ at the Temperatures below Oxygen Loss

by Denis Mishchenko, Zakhar Vinokurov, Evgeny Gerasimov, Elena Filonova, Alexander Shmakov and Elena Pikalova

Crystals 2022, 12(3), 344; https://doi.org/10.3390/cryst12030344 - 2 Mar 2022

Cited by 5 | Viewed by 2853

Abstract

In this work, we studied the structural features of La_1.9Ca_0.1NiO_4.11, which is considered a promising cathode material for intermediate temperature solid-oxide fuel cells (IT-SOFC). The effect of different pretreatments on the structural characteristics of the sample was [...] Read more.

In this work, we studied the structural features of La_1.9Ca_0.1NiO_4.11, which is considered a promising cathode material for intermediate temperature solid-oxide fuel cells (IT-SOFC). The effect of different pretreatments on the structural characteristics of the sample was studied using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) in order to elucidate the origin of a peculiar change of lattice parameters observed earlier during in situ XRD studies. The XRD studies have shown that anisotropic broadening for reflections with a high Miller index l appears after tempering of a quenched (from 1100 °C) sample at 250 °C. This temperature is too low for the release/incorporation of oxygen into the structure but is sufficient for oxygen migration inside the structure. The HRTEM assisted us in revealing differences in the defect structure after different pretreatments. Based on obtained results, the following possible explanation was proposed. Observed additional microstrains and non-oriented planar defects as well as a decrease in the coherent scattering region size in the [00l] direction are caused by the non-homogeneous redistribution of interstitial oxygen in the structure during tempering. Full article

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14 pages, 3664 KiB

Open AccessEditor’s ChoiceArticle

Theoretical Model for a Novel Electronic State in a Dirac Electron System Close to Merging: An Imaginary Element between Sulphur and Selenium

by Toshio Naito and Yoshikazu Suzumura

Crystals 2022, 12(3), 346; https://doi.org/10.3390/cryst12030346 - 2 Mar 2022

Cited by 7 | Viewed by 10351

Abstract

Topological materials with Dirac electron systems have been extensively studied. Organic crystalline materials form a unique group of such compounds with well-defined crystal structures. While most organic compounds require high pressures to exhibit Dirac-cone-type band structures, the title compound, α-STF₂I₃ [...] Read more.

Topological materials with Dirac electron systems have been extensively studied. Organic crystalline materials form a unique group of such compounds with well-defined crystal structures. While most organic compounds require high pressures to exhibit Dirac-cone-type band structures, the title compound, α-STF₂I₃, has garnered increasing interest due to its Dirac-cone-type band structure under ambient pressure. Various experiments have been conducted under ambient pressure; their results can be compared with those of theoretical calculations to obtain insights into Dirac electron systems. However, structural disorder peculiar to the STF molecules in the solid-state has prevented any type of theoretical calculation of the states. In this study, we report a new method for calculating intermolecular interactions in disordered systems based on the extended Hückel approximation. This method enables band calculations, suggesting that this material is a rare example of a system close to merging. The obtained band structure indicates that the characteristic disorder in the STF solids distributed electrons equally on the sulphur and selenium atoms as if they belong to an imaginary element between sulphur and selenium and are arranged without disorder. Full article

(This article belongs to the Special Issue Organic Conductors)

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10 pages, 3422 KiB

Open AccessEditor’s ChoiceCommunication

Investigation of Lattice Plasmon Modes in 2D Arrays of Au Nanoantennas

by Antonio Ferraro, Joseph Marae Djouda, Giuseppe Emanuele Lio, Gaëtan Lévêque, Pierre-Michel Adam, Cesare Paolo Umeton, Thomas Maurer and Roberto Caputo

Crystals 2022, 12(3), 336; https://doi.org/10.3390/cryst12030336 - 28 Feb 2022

Cited by 3 | Viewed by 3027

Abstract

The coupling of gold nanoantennas (AuNAs) in the arrangement of monomers in bidimensional gratings is investigated both experimentally and numerically. The influence of edge diffraction, corresponding to the grazing propagation of specific diffracted orders, and the dependence of grating parameters on lattice plasmon [...] Read more.

The coupling of gold nanoantennas (AuNAs) in the arrangement of monomers in bidimensional gratings is investigated both experimentally and numerically. The influence of edge diffraction, corresponding to the grazing propagation of specific diffracted orders, and the dependence of grating parameters on lattice plasmon modes are studied. It is shown that the grating pitch influences the spectral position of the Rayleigh wavelength related to the grazing diffraction in air and/or in glass. In order to investigate the effect of diffraction and its interplay with the Rayleigh wavelength, extinction measurements with different incidence angles are carried out. For incidence angles above

θ = 20^{\circ}

, along with the excitation of quadrupolar and vertical modes, very narrow dips or sharp excitations are observed in the spectra. These ones strongly depend on the respective spectral position of Rayleigh anomaly and specific dipolar mode, on the propagation direction of the grazing diffraction, and on the considered plasmon mode. These features are explained in the light of numerical calculations obtained with Green’s tensor method. All the above different characteristics and couplings are of great practical interest, especially for a possible implementation in biosensor devices and for other technological applications spanning from precision medicine and life science to telecommunications and energy systems. Full article

(This article belongs to the Special Issue Active Hybrid Soft Metamaterials)

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11 pages, 12780 KiB

Open AccessEditor’s ChoiceArticle

Ice Dendrite Growth Atop a Frozen Drop under Natural Convection Conditions

by Chengzhi Huang, Yugang Zhao and Tian Gu

Crystals 2022, 12(3), 323; https://doi.org/10.3390/cryst12030323 - 25 Feb 2022

Cited by 4 | Viewed by 2984

Abstract

Condensation frosting is a type of icing encountered ubiquitously in our daily lives. Understanding the dynamics of condensation frosting is essential in developing effective technologies to suppress frost accretions that compromise heat transfer and system integrity. Here, we present an experimental study on [...] Read more.

Condensation frosting is a type of icing encountered ubiquitously in our daily lives. Understanding the dynamics of condensation frosting is essential in developing effective technologies to suppress frost accretions that compromise heat transfer and system integrity. Here, we present an experimental study on ice dendrite growth atop a single frozen drop, an important step affecting the subsequent frosting process, and the properties of fully-developed frost layers. We evaluate the effect of natural convection by comparing the growth dynamics of ice dendrites on the surface of a frozen drop with three different orientations with respect to gravity. The results show that both the average deposition rate and its spatial variations are profoundly altered by surface orientations. Such behavior is confirmed by a numerical simulation, showing how gravity-assisted (hindered) vapor diffusion yields the deposition outcomes. These findings benefit the optimization of anti-/de- frosting technologies and the rational design of heat exchangers. Full article

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8 pages, 12246 KiB

Open AccessEditor’s ChoiceCommunication

Spinel LiMn₂O₄ Cathode Materials in Wide Voltage Window: Single-Crystalline versus Polycrystalline

by Feng Yu, Yi Wang, Cong Guo, He Liu, Weizhai Bao, Jingfa Li, Panpan Zhang and Faxing Wang

Crystals 2022, 12(3), 317; https://doi.org/10.3390/cryst12030317 - 24 Feb 2022

Cited by 12 | Viewed by 4701

Abstract

Single-crystal (SC) layered oxides as cathodes for Li-ion batteries have demonstrated better cycle stability than their polycrystalline (PC) counterparts due to the restrained intergranular cracking formation. However, there are rare reports on comparisons between single-crystal LiMn₂O₄ (SC-LMO) and polycrystalline LiMn [...] Read more.

Single-crystal (SC) layered oxides as cathodes for Li-ion batteries have demonstrated better cycle stability than their polycrystalline (PC) counterparts due to the restrained intergranular cracking formation. However, there are rare reports on comparisons between single-crystal LiMn₂O₄ (SC-LMO) and polycrystalline LiMn₂O₄ (PC-LMO) spinel cathodes for Li-ion storage. In this work, the Li-ion storage properties of spinel LiMn₂O₄ single-crystalline and polycrystalline with similar particle sizes were investigated in a wide voltage window of 2–4.8 V vs. Li/Li⁺. The SC-LMO cathode exhibited a specific discharge capacity of 178 mA·h·g⁻¹, which was a bit larger than that of the PC-LMO cathode. This is mainly because the SC-LMO cathode showed much higher specific capacity in the 3 V region (Li-ion storage at octahedral sites with cubic to tetragonal phase transition) than the PC-LMO cathode. However, unlike layered-oxide cathodes, the PC-LMO cathode displayed better cycle stability than the SC-LMO cathode. Our studies for the first time demonstrate that the phase transition-induced Mn(II) ion dissolution in the 3 V region rather than cracking formation is the limiting factor for the cycle performance of spinel LiMn₂O₄ in the wide voltage window. Full article

(This article belongs to the Special Issue Supercapacitors with High Energy Density)

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11 pages, 3076 KiB

Open AccessEditor’s ChoiceArticle

Compositions of Gamma and Gamma Prime Phases in an As-Cast Nickel-Based Single Crystal Superalloy Turbine Blade

by KeeHyun Park and Paul Withey

Crystals 2022, 12(2), 299; https://doi.org/10.3390/cryst12020299 - 20 Feb 2022

Cited by 6 | Viewed by 4735

Abstract

The core and the interdendritic regions of an as-cast nickel based single crystal turbine blade were observed by electron microscopy to understand the microstructural development during an investment casting process. The dendrite core region shows an irregular morphology of gamma prime in gamma [...] Read more.

The core and the interdendritic regions of an as-cast nickel based single crystal turbine blade were observed by electron microscopy to understand the microstructural development during an investment casting process. The dendrite core region shows an irregular morphology of gamma prime in gamma due to a relatively short casting time, which prevented the development of gamma prime expected in a solution heat-treated microstructure. By comparison, the interdendritic region comprises three different regions composed of: several elongated gamma prime particles, relatively tiny and irregular gamma prime, and gamma prime with relatively regular morphology. The chemical analysis of these phases showed that, regardless of the analysis point in the core or the interdendritic region, almost the same compositions were acquired in the regular type of gamma and gamma prime phases. This result suggests that if the gamma prime forms in the gamma matrix, the composition of gamma prime is almost uniform regardless of the region and prevailing general chemical composition. In contrast, the composition of the elongated gamma prime in the interdendritic region was slightly different depending on the analysis point even within the same elongated particle. Full article

(This article belongs to the Topic Single-Crystal Ni-Based Alloys)

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26 pages, 2207 KiB

Open AccessEditor’s ChoiceReview

Current Methods for Synthesis and Potential Applications of Cobalt Nanoparticles: A Review

by Andrey A. Vodyashkin, Parfait Kezimana, Fedor Y. Prokonov, Ivan A. Vasilenko and Yaroslav M. Stanishevskiy

Crystals 2022, 12(2), 272; https://doi.org/10.3390/cryst12020272 - 17 Feb 2022

Cited by 23 | Viewed by 12331

Abstract

Cobalt nanoparticles (CoNPs) are promising nanomaterials with exceptional catalytic magnetic, electronic, and chemical properties. The nano size and developed surface open a wide range of applications of cobalt nanoparticles in biomedicine along with those properties. The present review assessed the current environmentally friendly [...] Read more.

Cobalt nanoparticles (CoNPs) are promising nanomaterials with exceptional catalytic magnetic, electronic, and chemical properties. The nano size and developed surface open a wide range of applications of cobalt nanoparticles in biomedicine along with those properties. The present review assessed the current environmentally friendly synthesis methods used to synthesize CoNPs with various properties, such as size, zeta potential, surface area, and magnetic properties. We systematized several methods and provided some examples to illustrate the synthetic process of CoNPs, along with the properties, the chemical formula of obtained CoNPs, and their method of analysis. In addition, we also looked at the potential application of CoNPs from water purification cytostatic agents against cancer to theranostic and diagnostic agents. Moreover, CoNPs also can be used as contrast agents in magnetic resonance imaging and photoacoustic methods. This review features a comprehensive understanding of the synthesis methods and applications of CoNPs, which will help guide future studies on CoNPs. Full article

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12 pages, 9070 KiB

Open AccessEditor’s ChoiceCommunication

Intermolecular Interactions Drive the Unusual Co-Crystallization of Different Calix[4]arene Conformations

by Dominic Taylor, Irene Ling, Filipe Vilela and Scott J. Dalgarno

Crystals 2022, 12(2), 250; https://doi.org/10.3390/cryst12020250 - 12 Feb 2022

Cited by 2 | Viewed by 2219

Abstract

Crystallization of 5,17-dibromo-11,27,23,25-tetraone-26,28-dipropoxycalix[4]arene results in the rare observation of two different calix[4]arene conformations (partial cone and 1,3-alternate) co-crystallized within the same single crystal X-ray structure. Analysis using ¹H and ¹³C NMR spectroscopy revealed that only a single conformation (the cone) was [...] Read more.

Crystallization of 5,17-dibromo-11,27,23,25-tetraone-26,28-dipropoxycalix[4]arene results in the rare observation of two different calix[4]arene conformations (partial cone and 1,3-alternate) co-crystallized within the same single crystal X-ray structure. Analysis using ¹H and ¹³C NMR spectroscopy revealed that only a single conformation (the cone) was present in solution, and in contrast to the structures of other reported calix[4]arenes and calix[4]quinones, both conformations of the compound present in this crystal structure have a “pinched” shape, drastically reducing Br-Br separation and associated cavity sizes. Full article

(This article belongs to the Special Issue Advances in Functional Cocrystals)

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17 pages, 1302 KiB

Open AccessEditor’s ChoiceArticle

Effects of Electron Correlation inside Disordered Crystals

by Sergei P. Kruchinin, Roberts I. Eglitis, Vitaliy P. Babak, Iryna G. Vyshyvana and Stanislav P. Repetsky

Crystals 2022, 12(2), 237; https://doi.org/10.3390/cryst12020237 - 9 Feb 2022

Cited by 3 | Viewed by 2698

Abstract

We propose a novel approach for characterising the electron spectrum of disordered crystals constructed from a Hamiltonian of electrons as well as phonons and a diagram approach for Green’s function. The system’s electronic states were modelled by means of the multi-band, tight-binding approach. [...] Read more.

We propose a novel approach for characterising the electron spectrum of disordered crystals constructed from a Hamiltonian of electrons as well as phonons and a diagram approach for Green’s function. The system’s electronic states were modelled by means of the multi-band, tight-binding approach. The system’s Hamiltonian is described based on the electron wave functions at the field of the atom nucleus. Our novel approach incorporates the long-range Coulomb interplay of electrons located in different lattice positions. Explicit interpretations of Green’s functions are derived using a diagram method. Equations are obtained for the vertex components for the mass operators of the electron–electron as well aselectron–phonon interplays. A system of equations for the spectrum of elementary excitations in the crystal is obtained, in which the vertex components for the mass operators of electron–electron as well as electron–phonon interplays are renormalised. Thismakes it possible to perform numerical computationsfor the system’s energy spectrum with a predetermined accuracy. In contrast to other approaches in which electron correlations are only taken into account in the limiting cases of an infinitely large and infinitesimal electron density, in this method, electron correlations are described in the general case of an arbitrary density. We obtained the cluster expansion of the density of states (DOS) of the disordered systems. We demonstrate that the addition of the electron-scattering mechanismsto the clusters is decreasing. This happens due to a growing number of positions in the cluster, which hang ontothe small parameter. The computing exactness is fixed by a small parameter for cluster expansion of Green’s functions of electrons as well as phonons. Full article

(This article belongs to the Special Issue Diffusion and Degradation Phenomena in Solid Oxide Materials)

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12 pages, 1309 KiB

Open AccessEditor’s ChoiceArticle

CO₂ and CH₂ Adsorption on Copper-Decorated Graphene: Predictions from First Principle Calculations

by Oleg Lisovski, Sergei Piskunov, Dmitry Bocharov, Yuri F. Zhukovskii, Janis Kleperis, Ainars Knoks and Peteris Lesnicenoks

Crystals 2022, 12(2), 194; https://doi.org/10.3390/cryst12020194 - 28 Jan 2022

Cited by 9 | Viewed by 4901

Abstract

Single-layer graphene decorated with monodisperse copper nanoparticles can support the size and mass-dependent catalysis of the selective electrochemical reduction of CO

_{2}

to ethylene (C

_{2}

H

_{4}

). In this study, various active adsorption sites of nanostructured Cu-decorated graphene have been calculated [...] Read more.

Single-layer graphene decorated with monodisperse copper nanoparticles can support the size and mass-dependent catalysis of the selective electrochemical reduction of CO

_{2}

to ethylene (C

_{2}

H

_{4}

). In this study, various active adsorption sites of nanostructured Cu-decorated graphene have been calculated by using density functional theory to provide insight into its catalytic activity toward carbon dioxide electroreduction. Based on the results of our calculations, an enhanced adsorption of the CO

_{2}

molecule and CH

_{2}

counterpart placed atop of Cu-decorated graphene compared to adsorption at pristine Cu metal surfaces was predicted. This approach explains experimental observations for carbon-based catalysts that were found to be promising for the two-electron reduction reaction of CO

_{2}

to CO and, further, to ethylene. Active adsorption sites that lead to a better catalytic activity of Cu-decorated graphene, with respect to general copper catalysts, were identified. The atomic configuration of the most selective CO

_{2}

toward the reduction reaction nanostructured catalyst is suggested. Full article

(This article belongs to the Special Issue Fabrication of Carbon and Related Materials/Metal Hybrids and Composites)

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9 pages, 4661 KiB

Open AccessEditor’s ChoiceArticle

Microstructure Evolution of Mg-Sn-Y Alloy Solidified under High Pressure and Temperature Gradient

by Chunming Zou, Rong Zhang, Zunjie Wei and Hongwei Wang

Crystals 2022, 12(2), 149; https://doi.org/10.3390/cryst12020149 - 21 Jan 2022

Cited by 1 | Viewed by 2367

Abstract

The microstructures of Mg-1Sn-2.5Y (wt%) alloys solidified under high pressures were investigated. In addition, a mathematical model was established to analyze the effects of solidification pressure and cooling rate on the average grain size. The results show that the alloy was solidified under [...] Read more.

The microstructures of Mg-1Sn-2.5Y (wt%) alloys solidified under high pressures were investigated. In addition, a mathematical model was established to analyze the effects of solidification pressure and cooling rate on the average grain size. The results show that the alloy was solidified under high pressure and temperature gradient using the cooling rate difference in the high pressure chamber, resulting in the formation of the outer equiaxed zone, the columnar zone, and the equiaxed zone in the sample. With an increase in the solidification pressure, the columnar-to-equiaxed transition was inhibited in Mg-1Sn-2.5Y alloy. In the outer fine equiaxed zone and the columnar zone, the solubility of Sn in the Mg matrix increased with an increase in solidification pressure. The average secondary dendrite arm spacing decreased from 14–17 μm under 1 GPa to 9–11 μm under 1.5 GPa. Increases in pressure and cooling rate resulted in a reduction in average grain size. Full article

(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)

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8 pages, 3278 KiB

Open AccessEditor’s ChoiceCommunication

Microstructure Characterization and Battery Performance Comparison of MOF-235 and TiO₂-P25 Materials

by Zilong Zhao, Xiaowei Jiang, Sirui Li, Liang Li, Zhiyuan Feng and Huansheng Lai

Crystals 2022, 12(2), 152; https://doi.org/10.3390/cryst12020152 - 21 Jan 2022

Cited by 7 | Viewed by 3292

Abstract

The growing interest in energy storage has led to the urgent need for the development of high-performance cathode electrodes. The commercialized materials MOF-235 and TiO₂-P25 exhibit characteristics that may be suitable as electrodes but there are inherent challenges that have yet [...] Read more.

The growing interest in energy storage has led to the urgent need for the development of high-performance cathode electrodes. The commercialized materials MOF-235 and TiO₂-P25 exhibit characteristics that may be suitable as electrodes but there are inherent challenges that have yet to be addressed in the literature. In this study, a high-pressure hydrothermal synthesized MOF-235 and sol-gel-made TiO₂-P25 were tested for battery performance. The results indicate that MOF-235 does not possess the desired performance due to uncontrollable agglomeration. On the other hand, TiO₂-P25 showed good cycling life, and the performance can be further optimized by doping and minimizing the particle size. Additionally, SEM and TEM were applied for surface characterization, providing evidence that mesoporous TiO₂-25 inhibits photo-generated carrier recombination. The mesoporous energy storage mechanism of those two materials is also discussed. This research will provide technical support for the industrialization of those two mesoporous materials. Full article

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11 pages, 9356 KiB

Open AccessEditor’s ChoiceArticle

Variation of Surface Nanostructures on (100) PbS Single Crystals during Argon Plasma Treatment

by Sergey P. Zimin, Nikolai N. Kolesnikov, Ildar I. Amirov, Viktor V. Naumov, Egor S. Gorlachev, Sara Kim and Nam-Hoon Kim

Crystals 2022, 12(1), 111; https://doi.org/10.3390/cryst12010111 - 15 Jan 2022

Cited by 2 | Viewed by 2153

Abstract

The nanostructuring of the (100) PbS single crystal surface was studied under varying argon plasma treatment conditions. The initial PbS single crystals were grown by high-pressure vertical zone melting, cut into wafer samples, and polished. Subsequently, the PbS single crystals were treated with [...] Read more.

The nanostructuring of the (100) PbS single crystal surface was studied under varying argon plasma treatment conditions. The initial PbS single crystals were grown by high-pressure vertical zone melting, cut into wafer samples, and polished. Subsequently, the PbS single crystals were treated with inductively coupled argon plasma under varying treatment parameters such as ion energy and sputtering time. Plasma treatment with ions at a minimum energy of 25 eV resulted in the formation of nanotips with heights of 30–50 nm. When the ion energy was increased to 75–200 eV, two types of structures formed on the surface: high submicron cones and arrays of nanostructures with various shapes. In particular, the 120 s plasma treatment formed specific cruciform nanostructures with lateral orthogonal elements oriented in four <100> directions. In contrast, plasma treatment with an ion energy of 75 eV for 180 s led to the formation of submicron quasi-spherical lead structures with diameters of 250–600 nm. The nanostructuring mechanisms included a surface micromasking mechanism with lead formation and the vapor–liquid–solid mechanism, with liquid lead droplets acting as self-forming micromasks and growth catalysts depending on the plasma treatment conditions (sputtering time and rate). Full article

(This article belongs to the Special Issue Multiscale Interactions between Surface Topographies, Their Functions and Formation Technologies for Crystalline Materials)

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6 pages, 4411 KiB

Open AccessEditor’s ChoiceCommunication

Crystallographic Orientation Relationship between α and β Phases during Non-Equilibrium Heat Treatment of Cu-37 wt. % Zn Alloy

by Akbar Heidarzadeh, Mousa Javidani and Lyne St-Georges

Crystals 2022, 12(1), 97; https://doi.org/10.3390/cryst12010097 - 13 Jan 2022

Viewed by 2175

Abstract

The crystallographic orientation relationship between α and β phases during the non-equilibrium heat treatment of a Cu-37 wt. % Zn alloy was investigated. With this aim, Cu-37 wt. % Zn alloy plates with a thickness of 2 mm were heated at 810 °C [...] Read more.

The crystallographic orientation relationship between α and β phases during the non-equilibrium heat treatment of a Cu-37 wt. % Zn alloy was investigated. With this aim, Cu-37 wt. % Zn alloy plates with a thickness of 2 mm were heated at 810 °C for 1 h and then were quenched in water. The microstructure and texture of heat-treated samples were analyzed using optical microscopy and electron backscattered diffraction. By this non-equilibrium heat treatment, β phase was formed on both the grain boundaries and grain interiors. In addition, the Σ3 twin boundaries acted as preferred areas for α→β transformation. The orientation imaging microscopy results revealed a Kurdjumov–Sachs (K–S) orientation relationship between α and β phases. Furthermore, the details of microstructural evolution and texture analysis were discussed. Full article

(This article belongs to the Special Issue Microstructure Characterization and Design of Alloys)

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12 pages, 2316 KiB

Open AccessEditor’s ChoiceArticle

Processing of Multicrystal Diffraction Patterns in Macromolecular Crystallography Using Serial Crystallography Programs

by Ki Hyun Nam

Crystals 2022, 12(1), 103; https://doi.org/10.3390/cryst12010103 - 13 Jan 2022

Cited by 7 | Viewed by 2995

Abstract

Cryocrystallography is a widely used method for determining the crystal structure of macromolecules. This technique uses a cryoenvironment, which significantly reduces the radiation damage to the crystals and has the advantage of requiring only one crystal for structural determination. In standard cryocrystallography, a [...] Read more.

Cryocrystallography is a widely used method for determining the crystal structure of macromolecules. This technique uses a cryoenvironment, which significantly reduces the radiation damage to the crystals and has the advantage of requiring only one crystal for structural determination. In standard cryocrystallography, a single crystal is used for collecting diffraction data, which include single-crystal diffraction patterns. However, the X-ray data recorded often may contain diffraction patterns from several crystals. The indexing of multicrystal diffraction patterns in cryocrystallography requires more precise data processing techniques and is therefore time consuming. Here, an approach for processing multicrystal diffraction data using a serial crystallography program is introduced that allows for the integration of multicrystal diffraction patterns from a single image. Multicrystal diffraction data were collected from lysozyme crystals and processed using the serial crystallography program CrystFEL. From 360 images containing multicrystal diffraction patterns, 1138 and 691 crystal lattices could be obtained using the XGANDALF and MOSFLM indexing algorithms, respectively. Using this indexed multi-lattice information, the crystal structure of the lysozyme could be determined successfully at a resolution of 1.9 Å. Therefore, the proposed approach, which is based on serial crystallography, is suitable for processing multicrystal diffraction data in cryocrystallography. Full article

(This article belongs to the Special Issue Serial X-ray Crystallography)

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14 pages, 6346 KiB

Open AccessEditor’s ChoiceArticle

Numerical Investigation into the Influence of Grain Orientation Distribution on the Local and Global Elastic-Plastic Behaviour of Polycrystalline Nickel-Based Superalloy INC-738 LC

by Benedikt Engel, Mark Huth and Christopher Hyde

Crystals 2022, 12(1), 100; https://doi.org/10.3390/cryst12010100 - 13 Jan 2022

Cited by 6 | Viewed by 2635

Abstract

Polycrystalline nickel-based superalloys tend to have large grains within component areas where high loads are dominant during operation. Due to these large grains, caused by the manufacturing and cooling process, the orientation of each grain becomes highly important, since it influences the elastic [...] Read more.

Polycrystalline nickel-based superalloys tend to have large grains within component areas where high loads are dominant during operation. Due to these large grains, caused by the manufacturing and cooling process, the orientation of each grain becomes highly important, since it influences the elastic and plastic behaviour of the material. With the usage of the open source codes NEPER and FEPX, polycrystalline models of Inconel 738 LC were generated and their elastic and crystal plasticity behaviour simulated in dependence of different orientation distributions under uniaxial loading. Orientation distributions close to the [100] direction showed the lowest Young’s moduli as well as the highest elastic strains before yielding, as expected. Orientations close to the [

\bar{5}

89] direction, showed the lowest elastic strains and therefore first plastic deformation under strain loading due to the highest shear stress in the slip systems caused by the interaction of Young’s modulus and the Schmid factor. Full article

(This article belongs to the Special Issue Crystal Plasticity (Volume II))

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12 pages, 4397 KiB

Open AccessEditor’s ChoiceArticle

Synthesis of Spinel-Hydroxyapatite Composite Utilizing Bovine Bone and Beverage Can

by Agus Pramono, Gerald Ensang Timuda, Ganang Pramudya Ahmad Rifai and Deni Shidqi Khaerudini

Crystals 2022, 12(1), 96; https://doi.org/10.3390/cryst12010096 - 13 Jan 2022

Cited by 4 | Viewed by 2607

Abstract

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage [...] Read more.

Spinel-based hydroxyapatite composite (SHC) has been synthesized utilizing bovine bones as the source of the hydroxyapatite (HAp) and beverage cans as the aluminum (Al) source. The bovine bones were defatted and calcined in the air atmosphere to transform them into hydroxyapatite. The beverage cans were cut and milled to obtain fine Al powder and then sieved to obtain three different particle mesh size fractions: +100#, −140# + 170#, and −170#, or Al particle size of >150, 90–150, and <90 µm, respectively. The SHC was synthesized using the self-propagating intermediate-temperature synthesis (SIS) method at 900 °C for 2 h with (HAp:Al:Mg) ratio of (87:10:3 wt.%) and various compaction pressure of 100, 171, and 200 MPa. It was found that the mechanical properties of the SHC are influenced by the Al particle size and the compaction pressure. Smaller particle size produces the tendency of increasing the hardness and reducing the porosity of the composite. Meanwhile, increasing compaction pressure produces a reduction of the SHC porosity. The increase in the hardness is also observed by increasing the compaction pressure except for the smallest Al particle size (<90 µm), where the hardness instead becomes smaller. Full article

(This article belongs to the Special Issue Mineralogical Crystallography (2nd Edition))

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17 pages, 4993 KiB

Open AccessEditor’s ChoiceReview

Recent Progresses on Experimental Investigations of Topological and Dissipative Solitons in Liquid Crystals

by Yuan Shen and Ingo Dierking

Crystals 2022, 12(1), 94; https://doi.org/10.3390/cryst12010094 - 11 Jan 2022

Cited by 14 | Viewed by 3228

Abstract

Solitons in liquid crystals have received increasing attention due to their importance in fundamental physical science and potential applications in various fields. The study of solitons in liquid crystals has been carried out for over five decades with various kinds of solitons being [...] Read more.

Solitons in liquid crystals have received increasing attention due to their importance in fundamental physical science and potential applications in various fields. The study of solitons in liquid crystals has been carried out for over five decades with various kinds of solitons being reported. Recently, a number of new types of solitons have been observed, among which, many of them exhibit intriguing dynamic behaviors. In this paper, we briefly review the recent progresses on experimental investigations of solitons in liquid crystals. Full article

(This article belongs to the Special Issue State-of-the-Art Liquid Crystals Research in UK)

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15 pages, 30288 KiB

Open AccessEditor’s ChoiceArticle

Influence of Cooling Scenarios on the Evolution of Microstructures in Nickel-Based Single Crystal Superalloys

by Zhengxing Feng, Zhixun Wen, Guangxian Lu and Yanchao Zhao

Crystals 2022, 12(1), 74; https://doi.org/10.3390/cryst12010074 - 6 Jan 2022

Cited by 5 | Viewed by 1949

Abstract

The reprecipitation and evolution of γ’ precipitates during various cooling approaches from supersolvus temperature are studied experimentally and via phase field simulation in nickel-based single crystal superalloys. The focus of this paper is to explore the influence of cooling methods on the evolution [...] Read more.

The reprecipitation and evolution of γ’ precipitates during various cooling approaches from supersolvus temperature are studied experimentally and via phase field simulation in nickel-based single crystal superalloys. The focus of this paper is to explore the influence of cooling methods on the evolution of the morphology and the distribution of γ’ precipitates. It is demonstrated that small and uniform spherical shape γ’ particles formed with air cooling method. When the average cooling rate decreases, the particle number decreases while the average matrix and precipitate channel widths increase. The shape of γ’ precipitates which changed from spherical to cubic and irregular characteristics due to the elastic interaction and elements diffusion are observed with the decrease of the average cooling rate. The phase field simulation results are in good agreement with the experimental results in this paper. The research is a benefit for the study of the rejuvenation heat treatment in re-service nickel-based superalloys. Full article

(This article belongs to the Topic Single-Crystal Ni-Based Alloys)

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12 pages, 2592 KiB

Open AccessEditor’s ChoiceArticle

Effects of Grain Boundary Angles on Initial Deformation of 304 Austenitic Stainless Steel under Nanoindentation: A Molecular Dynamics Simulation

by Longlong Yang, Kun Sun, Weixiang Peng, Xuejie Li and Liang Zhang

Crystals 2022, 12(1), 58; https://doi.org/10.3390/cryst12010058 - 1 Jan 2022

Cited by 4 | Viewed by 2055

Abstract

Nitrogen-containing 0Cr19Ni10 (304 NG) austenitic stainless steel plays a significant role in Generation IV reactor pressure vessels. The structure and properties of 304 NG are heavily influenced by the grain boundaries (GBs), especially the initial mechanical response and dislocation evolutions. Hence, in this [...] Read more.

Nitrogen-containing 0Cr19Ni10 (304 NG) austenitic stainless steel plays a significant role in Generation IV reactor pressure vessels. The structure and properties of 304 NG are heavily influenced by the grain boundaries (GBs), especially the initial mechanical response and dislocation evolutions. Hence, in this paper, we carried out molecular dynamics (MD) simulations to investigate the effects of the GB angles on the initial deformation of 304 models under nanoindentation. It is found that the GB angle has great effects on the mechanical properties of 304 NG. With the GB angles changing from 90° to 150°, the values of Young’s modulus and maximum shear stress first decrease and then increase due to decreasing of the interaction among the GBs and the grain interiors (GIs) and the smoother shape of GBs. The hardening region slope decreases rapidly result from the GB angles changing the grain size on the both sides, which fully fits the Hall–Petch relationship. After the dislocations reaching the GBs along the slip system, the dislocation piles-up on the GBs at first, and then GBs serve as a source of dislocation and emit dislocation to free surface with the depth of nanoindentation increasing. This work provides a better understanding on the angle effects of GBs in materials. Full article

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13 pages, 304 KiB

Open AccessEditor’s ChoiceArticle

Semi-Experimental Determination of the Linear Clamped Electro-Optical Coefficients of Polar Crystals from Vibrational Spectroscopic Data

by Eric Bouhari, Ballo Mohamadou and Patrice Bourson

Crystals 2022, 12(1), 52; https://doi.org/10.3390/cryst12010052 - 31 Dec 2021

Viewed by 1409

Abstract

The present work highlights a new general method devoted to computations of the clamped linear electro-optical coefficients from the measured fundamental vibrational frequencies and the nonlinear dielectric susceptibility constants. The calculations are based on the formula analog to that of the Lyddane–Sachs–Teller relation, [...] Read more.

The present work highlights a new general method devoted to computations of the clamped linear electro-optical coefficients from the measured fundamental vibrational frequencies and the nonlinear dielectric susceptibility constants. The calculations are based on the formula analog to that of the Lyddane–Sachs–Teller relation, which is systematically used for the calculations of the clamped linear electro-optical coefficient of oxide ferroelectric crystals such as LiNbO₃, LiTaO₃, BaTiO₃, PbTiO₃, and KNbO₃. The computed electro-optical coefficients are in good agreement with those obtained from direct measurements and the first-principles calculations or other semi-empirical models. In addition, the famous

r 51

or

r 42

coefficients of the tetragonal BaTiO₃, PbTiO₃, and KNbO₃ crystals are finally calculated with high accuracy and discussed in connection with the soft mode behavior. Full article

27 pages, 3121 KiB

Open AccessEditor’s ChoiceReview

Recent Developments on Relaxor-PbTiO₃ Ferroelectric Crystals

by Lkhagvasuren Baasandorj and Zibin Chen

Crystals 2022, 12(1), 56; https://doi.org/10.3390/cryst12010056 - 31 Dec 2021

Cited by 16 | Viewed by 3251

Abstract

Numerous investigations on the development of the relaxor-PbTiO₃ ferroelectric crystals have been carried out since their extraordinary properties were revealed. Recent developments on these crystals have offered further advances in electromechanical applications. In this review, recent developments on relaxor-PbTiO₃ crystals and [...] Read more.

Numerous investigations on the development of the relaxor-PbTiO₃ ferroelectric crystals have been carried out since their extraordinary properties were revealed. Recent developments on these crystals have offered further advances in electromechanical applications. In this review, recent developments on relaxor-PbTiO₃ crystals and their practical applications are reviewed. The single crystal growth methods are first discussed. Two different strategies, poling and doping, for piezoelectric improvement are surveyed in the following section. After this, the anisotropic features of the single crystals are discussed. Application perspectives arising from the property improvements for electromechanical devices are finally reviewed. Full article

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21 pages, 31906 KiB

Open AccessEditor’s ChoiceArticle

Stabilizing DNA–Protein Co-Crystals via Intra-Crystal Chemical Ligation of the DNA

by Abigail R. Orun, Sara Dmytriw, Ananya Vajapayajula and Christopher D. Snow

Crystals 2022, 12(1), 49; https://doi.org/10.3390/cryst12010049 - 30 Dec 2021

Cited by 8 | Viewed by 3242

Abstract

Protein and DNA co-crystals are most commonly prepared to reveal structural and functional details of DNA-binding proteins when subjected to X-ray diffraction. However, biomolecular crystals are notoriously unstable in solution conditions other than their native growth solution. To achieve greater application utility beyond [...] Read more.

Protein and DNA co-crystals are most commonly prepared to reveal structural and functional details of DNA-binding proteins when subjected to X-ray diffraction. However, biomolecular crystals are notoriously unstable in solution conditions other than their native growth solution. To achieve greater application utility beyond structural biology, biomolecular crystals should be made robust against harsh conditions. To overcome this challenge, we optimized chemical DNA ligation within a co-crystal. Co-crystals from two distinct DNA-binding proteins underwent DNA ligation with the carbodiimide crosslinking agent 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) under various optimization conditions: 5′ vs. 3′ terminal phosphate, EDC concentration, EDC incubation time, and repeated EDC dose. This crosslinking and DNA ligation route did not destroy crystal diffraction. In fact, the ligation of DNA across the DNA–DNA junctions was clearly revealed via X-ray diffraction structure determination. Furthermore, crystal macrostructure was fortified. Neither the loss of counterions in pure water, nor incubation in blood serum, nor incubation at low pH (2.0 or 4.5) led to apparent crystal degradation. These findings motivate the use of crosslinked biomolecular co-crystals for purposes beyond structural biology, including biomedical applications. Full article

(This article belongs to the Special Issue State-of-the-Art Research in Biomolecular Crystals)

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12 pages, 5699 KiB

Open AccessEditor’s ChoiceArticle

The Influence of Grain Boundaries on Crystal Structure and Tensile Mechanical Properties of Al_0.1CoCrFeNi High-Entropy Alloys Studied by Molecular Dynamics Method

by Cuixia Liu, Rui Wang and Zengyun Jian

Crystals 2022, 12(1), 48; https://doi.org/10.3390/cryst12010048 - 30 Dec 2021

Cited by 6 | Viewed by 2611

Abstract

The mechanical properties of high-entropy alloys are superior to those of traditional alloys. However, the key problem of finding a strengthening mechanism is still challenging. In this work, the molecular dynamics method is used to calculate the tensile properties of face-centered cubic Al [...] Read more.

The mechanical properties of high-entropy alloys are superior to those of traditional alloys. However, the key problem of finding a strengthening mechanism is still challenging. In this work, the molecular dynamics method is used to calculate the tensile properties of face-centered cubic Al_0.1CoCrFeNi high-entropy alloys containing Σ3 grain boundaries and without grain boundary. The atomic model was established by the melting rapid cooling method, then stretched by the static drawing method. The common neighbor analysis and dislocation extraction algorithm are used to analyze the crystal evolution mechanism of Σ3 grain boundaries to improve the material properties of high-entropy alloys during the tensile test. The results show that compared with the mechanical properties Al_0.1CoCrFeNi high-entropy alloys without grain boundary, the yield strength and Young’s modulus of a high-entropy alloy containing Σ3 grain boundary are obviously larger than that of high-entropy alloys without grain boundary. Dislocation type includes mainly 1/6<112> Shockley partial dislocations, a small account of 1/6<110> Stair-rod, 1/2<110>perfect dislocation, and 1/3<111> Hirth dislocations. The mechanical properties of high-entropy alloys are improved by dislocation entanglement and accumulation near the grain boundary. Full article

(This article belongs to the Special Issue Photovoltaic Functional Crystals and Ceramics)

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8 pages, 1346 KiB

Open AccessEditor’s ChoiceCommunication

Sequence Analysis and Preliminary X-ray Crystallographic Analysis of an Acetylesterase (LgEstI) from Lactococcus garvieae

by Hackwon Do, Ying Wang, Chang Woo Lee, Wanki Yoo, Sangeun Jeon, Jisub Hwang, Min Ju Lee, Kyeong Kyu Kim, Han-Woo Kim, Jun Hyuck Lee and T. Doohun Kim

Crystals 2022, 12(1), 46; https://doi.org/10.3390/cryst12010046 - 29 Dec 2021

Cited by 3 | Viewed by 1957

Abstract

A gene encoding LgEstI was cloned from a bacterial fish pathogen, Lactococcus garvieae. Sequence and bioinformatic analysis revealed that LgEstI is close to the acetyl esterase family and had maximum similarity to a hydrolase (UniProt: Q5UQ83) from Acanthamoeba polyphaga mimivirus [...] Read more.

A gene encoding LgEstI was cloned from a bacterial fish pathogen, Lactococcus garvieae. Sequence and bioinformatic analysis revealed that LgEstI is close to the acetyl esterase family and had maximum similarity to a hydrolase (UniProt: Q5UQ83) from Acanthamoeba polyphaga mimivirus (APMV). Here, we present the results of LgEstI overexpression and purification, and its preliminary X-ray crystallographic analysis. The wild-type LgEstI protein was overexpressed in Escherichia coli, and its enzymatic activity was tested using p-nitrophenyl of varying lengths. LgEstI protein exhibited higher esterase activity toward p-nitrophenyl acetate. To better understand the mechanism underlying LgEstI activity and subject it to protein engineering, we determined the high-resolution crystal structure of LgEstI. First, the wild-type LgEstI protein was crystallized in 0.1 M Tris-HCl buffer (pH 7.1), 0.2 M calcium acetate hydrate, and 19% (w/v) PEG 3000, and the native X-ray diffraction dataset was collected up to 2.0 Å resolution. The crystal structure was successfully determined using a molecular replacement method, and structure refinement and model building are underway. The upcoming complete structural information of LgEstI may elucidate the substrate-binding mechanism and provide novel strategies for subjecting LgEstI to protein engineering. Full article

(This article belongs to the Special Issue Crystallographic Studies of Enzymes (Volume II))

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15 pages, 5569 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Simultaneous Control of Bandfilling and Bandwidth in Electric Double-Layer Transistor Based on Organic Mott Insulator κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl

by Yoshitaka Kawasugi and Hiroshi M. Yamamoto

Crystals 2022, 12(1), 42; https://doi.org/10.3390/cryst12010042 - 28 Dec 2021

Cited by 6 | Viewed by 2652

Abstract

The physics of quantum many-body systems have been studied using bulk correlated materials, and recently, moiré superlattices formed by atomic bilayers have appeared as a novel platform in which the carrier concentration and the band structures are highly tunable. In this brief review, [...] Read more.

The physics of quantum many-body systems have been studied using bulk correlated materials, and recently, moiré superlattices formed by atomic bilayers have appeared as a novel platform in which the carrier concentration and the band structures are highly tunable. In this brief review, we introduce an intermediate platform between those systems, namely, a band-filling- and bandwidth-tunable electric double-layer transistor based on a real organic Mott insulator κ-(BEDT-TTF)₂Cu[N(CN)₂]Cl. In the proximity of the bandwidth-control Mott transition at half filling, both electron and hole doping induced superconductivity (with almost identical transition temperatures) in the same sample. The normal state under electric double-layer doping exhibited non-Fermi liquid behaviors as in many correlated materials. The doping levels for the superconductivity and the non-Fermi liquid behaviors were highly doping-asymmetric. Model calculations based on the anisotropic triangular lattice explained many phenomena and the doping asymmetry, implying the importance of the noninteracting band structure (particularly the flat part of the band). Full article

(This article belongs to the Special Issue New Spin on Metal-Insulator Transitions)

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9 pages, 3415 KiB

Open AccessEditor’s ChoiceArticle

Flux Growth and Properties of Volatile Bromine-Containing UV Nonlinear Optical Crystal K₃B₆O₁₀Br

by Huaiyu Hu, Chen Zhou, Jiahao Jiao, Siru Guo, Yanna Chen and Min Zhang

Crystals 2022, 12(1), 33; https://doi.org/10.3390/cryst12010033 - 26 Dec 2021

Cited by 2 | Viewed by 2485

Abstract

A UV Nonlinear optical (NLO) crystal is one of the key devices in all-solid-state laser technology, and borate halides show outstanding potential due to their abundant structural diversity and short UV cut-off edges. In this article, the sizable UV NLO crystal of K [...] Read more.

A UV Nonlinear optical (NLO) crystal is one of the key devices in all-solid-state laser technology, and borate halides show outstanding potential due to their abundant structural diversity and short UV cut-off edges. In this article, the sizable UV NLO crystal of K₃B₆O₁₀Br (KBOB) has been grown with lead-containing and lead-free fluxes systems using the high-temperature top-seeded solution growth (TSSG) method. Energy Dispersive X-ray Spectroscopy (EDS) and transmittance spectra illustrate the influence of Pb²⁺ ions on the transmittance properties and laser-induced damage threshold (LDT). The thermal property, namely, thermal expansion, thermal conductivity, and thermal diffusivity curves, were characterized. Moreover, a small variation of thermal refractive indexes was analyzed to illustrate the advantage of KBOB in the application for temperature-fluctuated specific regions. Full article

(This article belongs to the Special Issue Advances in High-Temperature Top-seeded Solution Growth)

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8 pages, 3185 KiB

Open AccessEditor’s ChoiceArticle

Metallic Conduction and Carrier Localization in Two-Dimensional BEDO-TTF Charge-Transfer Solid Crystals

by Hiroshi Ito, Motoki Matsuno, Seiu Katagiri, Shinji K. Yoshina, Taishi Takenobu, Manabu Ishikawa, Akihiro Otsuka, Hideki Yamochi, Yukihiro Yoshida, Gunzi Saito, Yongbing Shen and Masahiro Yamashita

Crystals 2022, 12(1), 23; https://doi.org/10.3390/cryst12010023 - 24 Dec 2021

Cited by 2 | Viewed by 3175

Abstract

Charge-transfer salts based on bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF or BO for short) provide a stable two-dimensional (2D) metallic state, while the electrical resistance often shows an upturn at low temperatures below ~10 K. Such 2D weak carrier localization was first recognized for BO salts in [...] Read more.

Charge-transfer salts based on bis(ethylenedioxy)tetrathiafulvalene (BEDO-TTF or BO for short) provide a stable two-dimensional (2D) metallic state, while the electrical resistance often shows an upturn at low temperatures below ~10 K. Such 2D weak carrier localization was first recognized for BO salts in the Langmuir–Blodgett films fabricated with fatty acids; however, it has not been characterized in charge-transfer solid crystals. In this paper, we discuss the carrier localization of two crystalline BO charge-transfer salts with or without magnetic ions at low temperatures through the analysis of the weak negative magnetoresistance. The phase coherence lengths deduced with temperature dependence are largely dominated by the electron–electron scattering mechanism. These results indicate that the resistivity upturn at low temperatures is caused by the 2D weak localization. Disorders causing elastic scattering within the metallic domains, such as those of terminal ethylene groups, should be suppressed to prevent the localization. Full article

(This article belongs to the Special Issue New Spin on Metal-Insulator Transitions)

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9 pages, 4468 KiB

Open AccessEditor’s ChoiceArticle

Self-Localized Liquid Crystal Micro-Droplet Arrays on Chemically Patterned Surfaces

by Jakub Kołacz and Qi-Huo Wei

Crystals 2022, 12(1), 13; https://doi.org/10.3390/cryst12010013 - 22 Dec 2021

Cited by 5 | Viewed by 3587

Abstract

Liquid crystal (LC) micro-droplet arrays are elegant systems that have a range of applications, such as chemical and biological sensing, due to a sensitivity to changes in surface properties and strong optical activity. In this work, we utilize self-assembled monolayers (SAMs) to chemically [...] Read more.

Liquid crystal (LC) micro-droplet arrays are elegant systems that have a range of applications, such as chemical and biological sensing, due to a sensitivity to changes in surface properties and strong optical activity. In this work, we utilize self-assembled monolayers (SAMs) to chemically micro-pattern surfaces with preferred regions for LC occupation. Exploiting discontinuous dewetting, dragging a drop of fluid over the patterned surfaces demonstrates a novel, high-yield method of confining LC in chemically defined regions. The broad applicability of this method is demonstrated by varying the size and LC phase of the droplets. Although the optical textures of the droplets are dictated by topological constraints, the additional SAM interface is shown to lock in inhomogeneous alignment. The surface effects are highly dependent on size, where larger droplets exhibit asymmetric director configurations in nematic droplets and highly knotted structures in cholesteric droplets. Full article

(This article belongs to the Special Issue Self-Assembly in Liquid Crystalline Materials)

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13 pages, 11787 KiB

Open AccessEditor’s ChoiceArticle

[3+2] Cycloaddition Reaction for the Stereoselective Synthesis of a New Spirooxindole Compound Grafted Imidazo[2,1-b]thiazole Scaffold: Crystal Structure and Computational Study

by Mezna Saleh Altowyan, Saied M. Soliman, Matti Haukka, Nora Hamad Al-Shaalan, Aminah A. Alkharboush and Assem Barakat

Crystals 2022, 12(1), 5; https://doi.org/10.3390/cryst12010005 - 21 Dec 2021

Cited by 4 | Viewed by 3581

Abstract

A new spirooxindole hybrid engrafted imidazo[2,1-b]thiazole core structure was designed and achieved via [3+2] cycloaddition reaction approach. One multi-component reaction between the ethylene derivative based imidazo[2,1-b]thiazole scaffold with 6-Cl-isatin and the secondary amine under heat conditions afforded the desired [...] Read more.

A new spirooxindole hybrid engrafted imidazo[2,1-b]thiazole core structure was designed and achieved via [3+2] cycloaddition reaction approach. One multi-component reaction between the ethylene derivative based imidazo[2,1-b]thiazole scaffold with 6-Cl-isatin and the secondary amine under heat conditions afforded the desired compound in a stereoselective manner. The relative absolute configuration was assigned based on single-crystal X-ray diffraction analysis. Hirshfeld calculations for 4 revealed the importance of the H…H (36.8%), H…C (22.9%), Cl…H (10.4%) and S…H (6.6%), as well as the O…H (4.7%), N…H (5.3%), Cl…C (1.6%), Cl…O (1.0%) and N…O (0.5%) contacts in the crystal stability. DFT calculations showed excellent straight-line correlations (R² = 0.9776–0.9962) between the calculated and experimental geometric parameters. The compound has polar nature (3.1664 Debye). TD-DFT and GIAO calculations were used to assign and correlate the experimental UV-Vis and NMR spectra, respectively. Full article

(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)

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15 pages, 2018 KiB

Open AccessEditor’s ChoiceArticle

Director Fluctuations in Two-Dimensional Liquid Crystal Disclinations

by Olaf Stenull and Tom C. Lubensky

Crystals 2022, 12(1), 1; https://doi.org/10.3390/cryst12010001 - 21 Dec 2021

Cited by 4 | Viewed by 2658

Abstract

We present analytical calculations of the energies and eigenfunctions of all normal modes of excitation of charge

+ 1

two-dimensional splay (bend) disclinations confined to an annular region with inner radius

R_{1}

and outer radius

R_{2}

and with perpendicular (tangential) boundary [...] Read more.

We present analytical calculations of the energies and eigenfunctions of all normal modes of excitation of charge

+ 1

two-dimensional splay (bend) disclinations confined to an annular region with inner radius

R_{1}

and outer radius

R_{2}

and with perpendicular (tangential) boundary conditions on the region’s inner and outer perimeters. Defects such as these appear in islands in smectic-C films and can in principle be created in bolaamphiphilic nematic films. Under perpendicular boundary conditions on the two surfaces and when the ratio

β = K_{s} / K_{b}

of the splay to bend 2D Frank constants is less than one, the splay configuration is stable for all values

μ = R_{2} / R_{1}

. When

β > 1

, the splay configuration is stable only for

μ

less than a critical value

μ_{c} (β)

, becoming unstable to a “spiral” mixed splay-bend configuration for

μ > μ_{c}

. The same behavior occurs in trapped bend defects with tangential boundary conditions but with

K_{s}

and

K_{b}

interchanged. By calculating free energies, we verify that the transition from a splay or bend configuration to a mixed one is continuous. We discuss the differences between our calculations that yield expressions for experimentally observable excitation energies and other calculations that produce the same critical points and spiral configurations as ours but not the same excitation energies. We also calculate measurable correlation functions and associated decay times of angular fluctuations. Full article

(This article belongs to the Special Issue In Celebration of Noel A. Clark’s 80th Birthday)

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13 pages, 3550 KiB

Open AccessEditor’s ChoiceArticle

Partially Yttria-Stabilized Zirconia Crystals Co-Doped with Neodymium, Cerium, Terbium, Erbium or Ytterbium Oxides

by Mikhail A. Borik, Alexey V. Kulebyakin, Elena E. Lomonova, Filipp O. Milovich, Valentina A. Myzina, Polina A. Ryabochkina, Natalia Y. Tabachkova, Natalia V. Sidorova and Artem S. Chislov

Crystals 2021, 11(12), 1587; https://doi.org/10.3390/cryst11121587 - 20 Dec 2021

Cited by 3 | Viewed by 3025

Abstract

In this work, we studied the phase composition, local structure and mechanical characteristics of ZrO₂ crystals partially stabilized with Y₂O₃ and co-doped with Nd₂O₃, CeO₂, Er₂O₃, Tb₂O [...] Read more.

In this work, we studied the phase composition, local structure and mechanical characteristics of ZrO₂ crystals partially stabilized with Y₂O₃ and co-doped with Nd₂O₃, CeO₂, Er₂O₃, Tb₂O₃ and Yb₂O₃. Crystals were grown by directional melt crystallization in a cold container. The phase composition and structure of crystals were studied by X-ray diffractometry and transmission electron microscopy. The study of the features of the incorporation of rare-earth cations with different ionic radii into the transformable (t) and nontransformable (t’) tetragonal phases was carried out by the method of selective laser spectroscopy and time-resolved spectroscopy. Mechanical characteristics such as microhardness and fracture toughness were studied by the indentation method. It is shown that the phase composition and structure of crystals at the same total concentration of doping oxides depends on the degree of substitution of Y³⁺ cations by rare-earth cations. Rare earth ions of the beginning of the lanthanide series predominantly occupy positions in the nontransformable tetragonal phase of crystals based on zirconium dioxide. Ions of the end of a series of lanthanides do not show selectivity when entering the transformable (t) phase and nontransformable (t’) phase. The study of the mechanical characteristics of the crystals showed that the values of fracture toughness increase with an increase in the ionic radius of the rare earth element of the co-doped oxide, while the values of the microhardness of the crystals slightly decrease. Full article

(This article belongs to the Special Issue Advances in Zr-Based Alloys)

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12 pages, 2897 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Crystal Structures, and Molecular Properties of Three Nitro-Substituted Chalcones

by Alam Yair Hidalgo, Manuel Velasco, Eduardo Sánchez-Lara, Abraham Gómez-Rivera, Miguel A. Vilchis-Reyes, Cuauhtémoc Alvarado, Maribel Herrera-Ruiz, Ricardo López-Rodríguez, Nancy Romero-Ceronio and Carlos E. Lobato-García

Crystals 2021, 11(12), 1589; https://doi.org/10.3390/cryst11121589 - 20 Dec 2021

Cited by 5 | Viewed by 4317

Abstract

Three functionalized chalcones containing combinations of nitro functional groups have been synthesized via Claisen-Schmidt condensation between 2-nitroacetophenone and nitrobenzaldehyde, and the crystal structures obtained ((E)-1,3-bis(2-nitrophenyl)prop-2-en-1-one, 1a, (E)-1-(2-nitrophenyl)-3-(3-nitrophenyl)prop-2-en-1-one, 1b and (E)-1-(2-nitrophenyl)-3-(4-nitrophenyl)prop-2-en-1-one, 1c), C₁₅H₁₀ [...] Read more.

Three functionalized chalcones containing combinations of nitro functional groups have been synthesized via Claisen-Schmidt condensation between 2-nitroacetophenone and nitrobenzaldehyde, and the crystal structures obtained ((E)-1,3-bis(2-nitrophenyl)prop-2-en-1-one, 1a, (E)-1-(2-nitrophenyl)-3-(3-nitrophenyl)prop-2-en-1-one, 1b and (E)-1-(2-nitrophenyl)-3-(4-nitrophenyl)prop-2-en-1-one, 1c), C₁₅H₁₀N₂O_5, are reported. Compounds 1a and 1c crystallized in the triclinic centrosymmetric space group P

\bar{1}

, whereas compound 1b crystallized in the orthorhombic space group Pbca. The X-ray analysis reveals that structures 1a and 1b exhibits s-trans conformation, whereas structure 1c exists in s-cis conformation, concerning the olefinic double bonds. In addition, the results show that the position of the nitro substituent attached to the aromatic B-ring has a direct effect on the molecular coplanarity of these compounds. The Hirshfeld surface analysis suggests that the non-covalent π-π stacking interactions are the most important contributors for the crystal packing of 1a and 1b. In 1c, the crystal packing is mainly stabilized by weak intermolecular C―H···O interactions due to the planar nature of the molecule. Full article

(This article belongs to the Section Organic Crystalline Materials)

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10 pages, 3022 KiB

Open AccessEditor’s ChoiceArticle

Optically Tunable and Thermally Erasable Terahertz Intensity Modulators Using Dye-Doped Liquid Crystal Cells with Metasurfaces

by Yi-Hong Shih, Harry Miyosi Silalahi, Ting-I Tsai, Yi-Chen Chen, Jou-Yu Su, Chia-Rong Lee and Chia-Yi Huang

Crystals 2021, 11(12), 1580; https://doi.org/10.3390/cryst11121580 - 18 Dec 2021

Cited by 7 | Viewed by 2570

Abstract

A terahertz metasurface that is imbedded into a dye-doped liquid crystal (DDLC) cell is fabricated in this work. After the metasurface-imbedded DDLC cell is irradiated with a linearly polarized pump beam, the irradiated cell is measured with a terahertz spectrometer. The irradiation of [...] Read more.

A terahertz metasurface that is imbedded into a dye-doped liquid crystal (DDLC) cell is fabricated in this work. After the metasurface-imbedded DDLC cell is irradiated with a linearly polarized pump beam, the irradiated cell is measured with a terahertz spectrometer. The irradiation of the pump beam causes the adsorption of the dye on one of the substrates of the cell, scattering incident terahertz waves and decreasing the transmittances of the terahertz metasurface at all the frequencies of its resonance spectrum. In addition, these transmittances decrease with an increase in the irradiation times of the pump beam. The adsorbed dye molecules are erased from the substrate after the cell is heated by a hot plate. The cell has similar spectra before the irradiation of the pump beam and after the heating of the hot plate. The aforementioned results reveal that the metasurface-imbedded DDLC cell is an optically tunable and thermally erasable terahertz intensity modulator. Therefore, this cell has the potential in developing intensity attenuators for terahertz imaging, frequency isolators for terahertz telecommunication, and spatial light modulators for terahertz information encryption and decryption. Full article

(This article belongs to the Special Issue Liquid Crystals-Based Metamaterials)

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10 pages, 3528 KiB

Open AccessEditor’s ChoiceArticle

Acoustic Tunneling Study for Hexachiral Phononic Crystals Based on Dirac-Cone Dispersion Properties

by Luyun Chen, Yong Liu and Hui Kong

Crystals 2021, 11(12), 1577; https://doi.org/10.3390/cryst11121577 - 17 Dec 2021

Cited by 2 | Viewed by 2587

Abstract

Acoustic tunneling is an essential property for phononic crystals in a Dirac-cone state. By analyzing the linear dispersion relations for the accidental degeneracy of Bloch eigenstates, the influence of geometric parameters on opening the Dirac-cone state and the directional band gaps’ widths are [...] Read more.

Acoustic tunneling is an essential property for phononic crystals in a Dirac-cone state. By analyzing the linear dispersion relations for the accidental degeneracy of Bloch eigenstates, the influence of geometric parameters on opening the Dirac-cone state and the directional band gaps’ widths are investigated. For two-dimensional hexachiral phononic crystals, for example, the four-fold accidental degenerate Dirac point emerges at the center of the irreducible Brillouin zone (IBZ). The Dirac cone properties and the band structure inversion problem are discussed. Finally, to verify acoustic transmission properties near the double-Dirac-cone frequency region, the numerical calculation of the finite-width phononic crystal structure is carried out, and the acoustic transmission tunneling effect is proved. The results enrich and expand the manipulating method in the topological insulator problem for hexachiral phononic crystals. Full article

(This article belongs to the Section Liquid Crystals)

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14 pages, 3325 KiB

Open AccessEditor’s ChoiceArticle

Negative Thermal Quenching of Photoluminescence from Liquid-Crystalline Molecules in Condensed Phases

by Hussain Sami, Osama Younis, Yui Maruoka, Kenta Yamaguchi, Kumar Siddhant, Kyohei Hisano and Osamu Tsutsumi

Crystals 2021, 11(12), 1555; https://doi.org/10.3390/cryst11121555 - 13 Dec 2021

Cited by 7 | Viewed by 3521

Abstract

The luminescence of materials in condensed phases is affected by not only their molecular structures but also their aggregated structures. In this study, we designed new liquid-crystalline luminescent materials based on biphenylacetylene with a bulky trimethylsilyl terminal group and a flexible alkoxy chain. [...] Read more.

The luminescence of materials in condensed phases is affected by not only their molecular structures but also their aggregated structures. In this study, we designed new liquid-crystalline luminescent materials based on biphenylacetylene with a bulky trimethylsilyl terminal group and a flexible alkoxy chain. The luminescence properties of the prepared materials were evaluated, with a particular focus on the effects of phase transitions, which cause changes in the aggregated structures. The length of the flexible chain had no effect on the luminescence in solution. However, in crystals, the luminescence spectral shape depended on the chain length because varying the chain length altered the crystal structure. Interestingly, negative thermal quenching of the luminescence from these materials was observed in condensed phases, with the isotropic phase obtained at high temperatures exhibiting a considerable increase in luminescence intensity. This thermal enhancement of the luminescence suggests that the less- or nonemissive aggregates formed in crystals are dissociated in the isotropic phase. These findings can contribute toward the development of new material design concepts for useful luminescent materials at high temperatures. Full article

(This article belongs to the Special Issue Synthesis and Properties of Light-Emitting Liquid Crystals (Volume II))

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19 pages, 5047 KiB

Open AccessEditor’s ChoiceArticle

Effects of Cr Doping and Water Content on the Crystal Structure Transitions of Ba₂In₂O₅

by Raphael Finger, Marc Widenmeyer, Thomas C. Hansen, Dirk Wallacher, Stanislav Savvin, Marko Bertmer, Anke Weidenkaff and Holger Kohlmann

Crystals 2021, 11(12), 1548; https://doi.org/10.3390/cryst11121548 - 10 Dec 2021

Cited by 1 | Viewed by 2550

Abstract

Temperature-dependent crystal structure alterations in the brownmillerite-type material Ba₂In₂O₅ play a fundamental role in its applications: (i) photocatalytic CO₂ conversion; (ii) oxygen transport membranes; and (iii) proton conduction. This is connected to a reversible uptake of up [...] Read more.

Temperature-dependent crystal structure alterations in the brownmillerite-type material Ba₂In₂O₅ play a fundamental role in its applications: (i) photocatalytic CO₂ conversion; (ii) oxygen transport membranes; and (iii) proton conduction. This is connected to a reversible uptake of up an equimolar amount of water. In this study, in situ X-ray and neutron diffraction were combined with Raman spectroscopy and solid-state nuclear magnetic resonance experiments to unravel the effects of Cr doping and water content on the crystal structure transitions of Ba₂In₂O₅(H₂O)_x over a wide temperature range (10 K ≤ T ≤ 1573 K, x < 1). A mixture of isolated and correlated protons was identified, leading to a highly dynamic situation for the protons. Hence, localisation of the protons by diffraction techniques was not possible. Cr doping led to an overall higher degree of disorder and stabilisation of the tetragonal polymorph, even at 10 K. In contrast, a further disordering at high temperatures, leading to a cubic polymorph, was found at 1123 K. Cr doping in Ba₂In₂O₅ resulted in severe structural changes and provides a powerful way to adjust its physical properties to the respective application. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 4034 KiB

Open AccessEditor’s ChoiceArticle

Crystal Structure, Microstructure and Electronic Properties of a Newly Discovered Ternary Phase in the Al-Cr-Sc System

by Monika Kušter, Anton Meden, Boštjan Markoli, Zoran Samardžija, Maja Vončina, Pascal Boulet, Émilie Gaudry, Jean-Marie Dubois and Sašo Šturm

Crystals 2021, 11(12), 1535; https://doi.org/10.3390/cryst11121535 - 9 Dec 2021

Cited by 2 | Viewed by 2929

Abstract

This study focused on the crystal and electronic structures of a newly discovered phase in the Al-Cr-Sc system. The latter two species do not mix in a binary alloy, but can be alloyed with aluminium in the vicinity of the Al_2−xCr [...] Read more.

This study focused on the crystal and electronic structures of a newly discovered phase in the Al-Cr-Sc system. The latter two species do not mix in a binary alloy, but can be alloyed with aluminium in the vicinity of the Al_2−xCr_xSc composition, where 0.3 < x < 0.5. After preparation of the pure constituents via arc melting, high-temperature annealing at 990 °C for 240 h was required to achieve full mixing of the elements. A detailed characterisation of the crystal structure, alloy microstructure and stability was obtained using single-crystal X-ray diffraction (SCXRD) and powder X-ray diffraction (PXRD), in addition to transmission electron microscopy (TEM), especially in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) mode, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDXS) and differential scanning calorimetry (DSC) measurements. The crystal structure was refined to a hexagonal unit cell of the MgZn₂ type, space group no. 194, P6₃/mmc, which belongs to the Laves phases family. Special attention was paid to the occupancy of the crystallographic sites that were filled by both Cr and Al atoms. First-principles calculations based on the density functional theory (DFT) were performed to investigate the electronic structure of this ternary phase. The total density of states (DOS) exhibited a pronounced sp character, where a shallow pseudo-gap was visible 0.5 eV below the Fermi energy that brought a small but definite contribution to the thermodynamic stability of the compound. Full article

(This article belongs to the Special Issue Crystallography of Structural Phase Transformations (Volume II))

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15 pages, 5526 KiB

Open AccessEditor’s ChoiceArticle

Simultaneous Dirac-like Cones at Two Energy States in Tunable Phononic Crystals: An Analytical and Numerical Study

by Mustahseen M. Indaleeb and Sourav Banerjee

Crystals 2021, 11(12), 1528; https://doi.org/10.3390/cryst11121528 - 7 Dec 2021

Cited by 4 | Viewed by 3059

Abstract

Simultaneous occurrence of Dirac-like cones at the center of the Brillouin zone (Γ) at two different energy states is termed Dual-Dirac-like cones (DDC) in this article. The occurrence of DDC is a rare phenomenon. Thus, the generation of multiple Dirac-like cones at the [...] Read more.

Simultaneous occurrence of Dirac-like cones at the center of the Brillouin zone (Γ) at two different energy states is termed Dual-Dirac-like cones (DDC) in this article. The occurrence of DDC is a rare phenomenon. Thus, the generation of multiple Dirac-like cones at the center of the Brillouin zone is usually non-manipulative and poses a challenge to achieve through traditional accidental degeneracy. However, if predictively created, DDC will have multiple engineering applications with acoustics and vibration. Thus, the possibilities of creating DDC have been identified herein using a simple square periodic array of tunable square phononic crystals (PnCs) in air media. It was found that antisymmetric deaf bands may play critical roles in tracking the DDC. Hence, pivoting on the deaf bands at two different energy states, an optimized tuning parameter was found to achieve Dirac-like cones at two distinct frequency states, simultaneously. Orthogonal wave transport identified as key Dirac phenomena was achieved at two frequencies, herein. It was identified that beyond the Dirac-like cone, the Dirac phenomena remain dominant when a doubly degenerated state created by a top band with positive curvature and a near-flat deaf band are lifted from a bottom band with negative curvature. Utilizing a mechanism of rotating the PnCs near a fixed deaf band, frequencies are tracked to form the DDC, and orthogonal wave transport is demonstrated. Exploiting the dispersion behavior, unique acoustic phenomena, such as ballistic wave transmission, pseudo diffusion and acoustic cloaking are also demonstrated at the Dirac frequencies using numerical simulation. The proposed tunable acoustic PnCs will have important applications in acoustic and ultrasonic imaging, waveguiding and even acoustic computing. Full article

(This article belongs to the Special Issue Recent Advances in Phononic Crystals and Acoustic Metamaterials)

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