Crystals

Article

16 pages, 4704 KiB

Open AccessEditor’s ChoiceArticle

Simulation of Amorphous Silicon Carbide Photonic Crystal Absorption Layer for Solar Cells

by Lin Zhou, Yuwei Xu, Shuyu Tan, Meijie Liu and Yong Wan

Crystals 2022, 12(5), 665; https://doi.org/10.3390/cryst12050665 - 5 May 2022

Cited by 7 | Viewed by 3614

In this work, the amorphous silicon carbide (a-SiC) with low cost and high extinction coefficient was used as the light absorption layer of solar cells, and the photonic crystal (PC) structure and defect structure were introduced. By optimizing the scatterer shape, structural parameters [...] Read more.

In this work, the amorphous silicon carbide (a-SiC) with low cost and high extinction coefficient was used as the light absorption layer of solar cells, and the photonic crystal (PC) structure and defect structure were introduced. By optimizing the scatterer shape, structural parameters and defect types of photonic crystal, the absorption efficiency of the light absorption layer was further improved. The results show that the photonic crystal absorption layer with vacancy line defect is better than the perfect photonic crystal absorption layer. Meanwhile, the absorption efficiency of the photonic crystal absorption layer significantly improves in the case that the scatterer is an elliptical cylindrical air hole scatterer. When the incident light is in the wavelength range of 0.30~0.80 μm and the absorption layer height is 0.60 μm, the absorption efficiency of the absorption layer can reach 95.60%. Compared with the absorption layer without photonic crystal structure, the absorption layer is increased by 43.24%. At the same time, the absorption layer has little dependence on the incidence angle of sunlight. When the incidence angle is 65°, the absorption efficiency is still higher than 80%. Full article

(This article belongs to the Special Issue Advances of Perovskite Solar Cells)

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13 pages, 10543 KiB

Open AccessEditor’s ChoiceArticle

Fingerprints of Topotactic Hydrogen in Nickelate Superconductors

by Liang Si, Paul Worm and Karsten Held

Crystals 2022, 12(5), 656; https://doi.org/10.3390/cryst12050656 - 4 May 2022

Cited by 14 | Viewed by 4647

Abstract

Superconductivity has entered the nickel age marked by enormous experimental and theoretical efforts. Notwithstanding, synthesizing nickelate superconductors remains extremely challenging, not least due to incomplete oxygen reduction and topotactic hydrogen. Here, we present density-functional theory calculations for nickelate superconductors with additional topotactic hydrogen [...] Read more.

Superconductivity has entered the nickel age marked by enormous experimental and theoretical efforts. Notwithstanding, synthesizing nickelate superconductors remains extremely challenging, not least due to incomplete oxygen reduction and topotactic hydrogen. Here, we present density-functional theory calculations for nickelate superconductors with additional topotactic hydrogen or oxygen, namely La

_{1 - x}

Sr

_{x}

NiO

_{2}

H

_{δ}

and LaNiO

_{2 + δ}

. We identify a phonon mode as a possible indication for topotactic hydrogen and discuss the charge redistribution patterns around oxygen and hydrogen impurities. Full article

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

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14 pages, 3905 KiB

Open AccessEditor’s ChoiceArticle

Deformation Mechanism and Structural Changes in the Globular Ti-6Al-4V Alloy under Quasi-Static and Dynamic Compression: To the Question of the Controlling Phase in the Deformation of α+β Titanium Alloys

by Pavlo E. Markovsky, Jacek Janiszewski, Olexander Dekhtyar, Matthew Mecklenburg and Sergey V. Prikhodko

Crystals 2022, 12(5), 645; https://doi.org/10.3390/cryst12050645 - 1 May 2022

Cited by 4 | Viewed by 2694

Abstract

The deformation mechanism of the Ti-6Al-4V (wt.%) alloy with globular structure was studied under conditions of quasi-static and high-strain compression with rates 10⁻³ s⁻¹ and 2.1–3.3 × 10³ s⁻¹, respectively. High-strain compression was conducted using a Split Hopkinson [...] Read more.

The deformation mechanism of the Ti-6Al-4V (wt.%) alloy with globular structure was studied under conditions of quasi-static and high-strain compression with rates 10⁻³ s⁻¹ and 2.1–3.3 × 10³ s⁻¹, respectively. High-strain compression was conducted using a Split Hopkinson Pressure Bar (SHPB). The details of the deformation mechanism were evaluated based on the analysis of the deformation hardening curves using the strain hardening exponent concept developed for titanium alloys in tension conditions. The used approach allowed us to identify the stages of plastic deformation observed and the controlling phase in deformation of two-phase alloy through the assessment of the strengthening index, n. It has been found that three deformation stages can be identified in quasi-static conditions. However, when the alloy is compressed at a high strain rate, the third deformation stage does not develop due to the high process rate. Further analysis of deformation curves reveals the leading role of the β-phase under the quasi-static conditions and the essential contribution of the second, α-phase, at a high compression rate. The findings on the deformation mechanism based on the analysis of hardening curves were supported by a detailed structural study. Full article

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

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9 pages, 2502 KiB

Open AccessEditor’s ChoiceArticle

The Growth of High-Quality Hexagonal GaTe Nanosheets Induced by ZnO Nanocrystals

by Quan Chen, Yu Chen, Jun Wang, Meizhuang Liu and Zuxin Chen

Crystals 2022, 12(5), 627; https://doi.org/10.3390/cryst12050627 - 27 Apr 2022

Cited by 1 | Viewed by 2392

Abstract

The monoclinic and hexagonal gallium tellurides (m-GaTe and h-GaTe) show different applications in optoelectronic devices. Compared to the m-GaTe, the h-GaTe is a metastable phase, which generally exists in ultrathin samples and is difficult to obtain by direct [...] Read more.

The monoclinic and hexagonal gallium tellurides (m-GaTe and h-GaTe) show different applications in optoelectronic devices. Compared to the m-GaTe, the h-GaTe is a metastable phase, which generally exists in ultrathin samples and is difficult to obtain by direct chemical reaction. Herein, a hexagonal ZnO-induced crystal growth strategy was used for the design and fabrication of h-GaTe. The high-quality h-GaTe nanosheets were successfully grown on the (001) surface of hexagonal ZnO by the chemical vapor deposition method under ambient pressure. The SEM, XPS, XRD, and HRTEM characterizations uncovered a flower-like nanosheet morphology and a hexagonal crystal structure for the obtained GaTe samples. Meanwhile, the conductive atomic force microscope measurement indicates that the obtained h-GaTe nanosheet is a p-type semiconductor. Based on the electron localization function simulation, the lattice-induced crystal growth of h-GaTe was demonstrated. The results give an insight into the synthesis of metastable phase crystal and open an avenue for fabricating new two-dimensional devices by p-type h-GaTe. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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13 pages, 433 KiB

Open AccessEditor’s ChoiceArticle

Homogenization of Complex Lattices for Metamaterials: Open Problems and Conjectures

by Paolo Maria Mariano

Crystals 2022, 12(5), 612; https://doi.org/10.3390/cryst12050612 - 26 Apr 2022

Viewed by 1982

Abstract

Based on concrete examples dealing with one-level periodic and quasi-periodic, and two-level periodic lattices, we show that the homogenization of complex lattices generically requires a multi-field continuum approach. We do not present results for specific cases, rather we discuss some related open problems [...] Read more.

Based on concrete examples dealing with one-level periodic and quasi-periodic, and two-level periodic lattices, we show that the homogenization of complex lattices generically requires a multi-field continuum approach. We do not present results for specific cases, rather we discuss some related open problems and formulate pertinent conjectures. In this way, we suggest in essence a possible research program addressed towards the design of metamaterials. Full article

(This article belongs to the Special Issue Advances in Metamaterials)

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13 pages, 4397 KiB

Open AccessEditor’s ChoiceArticle

Radiation Modification of Optical Characteristics of LiNbO₃:Zn and LiNbO₃:Mg Crystals

by Mikhail Palatnikov, Nikolay Sidorov, Sergey Panasjuk, Natalya Teplyakova and Olga Makarova

Crystals 2022, 12(5), 600; https://doi.org/10.3390/cryst12050600 - 25 Apr 2022

Cited by 2 | Viewed by 2181

Abstract

The modification of the optical characteristics of LiNbO₃:Zn and LiNbO₃:Mg crystals grown by the Czochralski method was investigated using β and γ radiation. The photorefractive effect was found to be inhibited by ionizing radiation in the LiNbO₃:Zn [...] Read more.

The modification of the optical characteristics of LiNbO₃:Zn and LiNbO₃:Mg crystals grown by the Czochralski method was investigated using β and γ radiation. The photorefractive effect was found to be inhibited by ionizing radiation in the LiNbO₃:Zn ([ZnO] ≈ 2.1 mol%) crystal, which belonged to a below-threshold concentration range. The inhibition was attributed to a stepwise radiation annealing of charged defects. Ionizing radiation increased the general optical uniformity of above-threshold crystals LiNbO₃:Zn ([ZnO] ≈ 5.9 mol%) and LiNbO₃:Mg([MgO] ≈ 5.6 mol%). In addition, we determined that radiation annealing substantially influenced photorefraction dynamics in lightly doped LiNbO₃:Zn ([ZnO] ≈ 0.1 mol%) crystals, which widens their application areas. Full article

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

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8 pages, 2057 KiB

Open AccessEditor’s ChoiceArticle

Effect of Hydrogen Migration in SiO₂/Al₂O₃ Stacked Gate Insulator of InGaZnO Thin-Film Transistors

by Shinyoung Park, Sangwook Youn, Jun Tae Jang, Hyungjin Kim and Dae Hwan Kim

Crystals 2022, 12(5), 594; https://doi.org/10.3390/cryst12050594 - 23 Apr 2022

Cited by 5 | Viewed by 3207

Abstract

In this work, the correlation between SiO₂ deposition thickness and hydrogen content is discussed and the effect of the SiO₂ layer on the properties of synaptic InGaZnO (IGZO) TFTs is analyzed. Three types of IGZO synaptic thin-film transistors (TFTs) were fabricated [...] Read more.

In this work, the correlation between SiO₂ deposition thickness and hydrogen content is discussed and the effect of the SiO₂ layer on the properties of synaptic InGaZnO (IGZO) TFTs is analyzed. Three types of IGZO synaptic thin-film transistors (TFTs) were fabricated with different gate insulators, and the effect of SiO₂ as a gate insulator was investigated. XPS analysis confirmed that the hydrogen content in the Al₂O₃ and SiO₂ layers increased during SiO₂ deposition step for all depth regions. Hydrogen injected by the SiO₂ layer deposition step was confirmed to improve the memory window through more threshold voltage shift under positive bias stress (PBS) and negative bias stress (NBS) conditions. In addition, the retention characteristics were improved due to the low hydrogen movement velocity in the SiO₂ layer. These results contribute to the optimization of the amount of hydrogen, and the proposed device has potential as a synaptic device capable of neuromorphic computing. Full article

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17 pages, 38131 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, X-ray, Hirshfeld, and AIM Studies on Zn(II) and Cd(II) Complexes with Pyridine Ligands

by Mezna Saleh Altowyan, Eman M. Fathalla, Dalia Hawas, Jörg H. Albering, Assem Barakat, Morsy A. M. Abu-Youssef, Saied M. Soliman, Taher S. Kassem and Ahmed M. A. Badr

Crystals 2022, 12(5), 590; https://doi.org/10.3390/cryst12050590 - 22 Apr 2022

Cited by 2 | Viewed by 2373

Abstract

The synthesis and crystal structures of three heteroleptic complexes of Zn(II) and Cd(II) with pyridine ligands (ethyl nicotinate (EtNic), N,N-diethylnicotinamide (DiEtNA), and 2-amino-5-picoline (2Ampic) are presented. The complex [Zn(EtNic)₂Cl₂] (1) showed [...] Read more.

The synthesis and crystal structures of three heteroleptic complexes of Zn(II) and Cd(II) with pyridine ligands (ethyl nicotinate (EtNic), N,N-diethylnicotinamide (DiEtNA), and 2-amino-5-picoline (2Ampic) are presented. The complex [Zn(EtNic)₂Cl₂] (1) showed a distorted tetrahedral coordination geometry with two EtNic ligand units and two chloride ions as monodentate ligands. Complexes [Zn(DiEtNA)(H₂O)₄(SO₄)]·H₂O (2) and [Cd(OAc)₂(2Ampic)₂] (3) had hexa-coordinated Zn(II) and Cd(II) centers. In the former, the Zn(II) was coordinated with three different monodentate ligands, which were DiEtNA, H₂O, and SO₄²⁻. In 3, the Cd(II) ion was coordinated with two bidentate acetate ions and two monodentate 2Ampic ligand units. The supramolecular structures of the three complexes were elucidated using Hirshfeld analysis. In 1, the most important interactions that governed the molecular packing were O···H (15.5–15.6%), Cl···H (13.6–13.8%), Cl···C (6.3%), and C···H (10.3–10.6%) contacts. For complexes 2 and 3, the H···H, O···H, and C···H contacts dominated. Their percentages were 50.2%, 41.2%, and 7.1%, respectively, for 2 and 57.1%, 19.6%, and 15.2%, respectively, for 3. Only in complex 3, weak π-π stacking interactions between the stacked pyridines were found. The Zn(II) natural charges were calculated using the DFT method to be 0.8775, 1.0559, and 1.2193 for complexes 1–3, respectively. A predominant closed-shell character for the Zn–Cl, Zn–N, Zn–O, Cd–O, and Cd–N bonds was also concluded from an atoms in molecules (AIM) study. Full article

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

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9 pages, 1515 KiB

Open AccessEditor’s ChoiceArticle

Pressure Induced Superconductivity and Multiple Structural Transitions in CsCl-Type Cubic CeZn Single Crystal

by Xiaoling Shen, Hanming Ma, Dilip Bhoi, Jun Gouchi, Yoshiya Uwatoko, Alisha Dalan, Yukihiro Kawamura, Hiroyasu Sato, Izuru Umehara and Masatomo Uehara

Crystals 2022, 12(5), 571; https://doi.org/10.3390/cryst12050571 - 20 Apr 2022

Cited by 3 | Viewed by 2273

Abstract

CsCl-type cubic compound CeZn exhibits a paramagnetic (PM) to antiferromagnetic (AFM) first-order transition at T_N ~ 30 K accompanied by a simultaneous structural transition from cubic to tetragonal structure as temperature decreases. Applying the pressure, the coupled magnetic and crystal structural transition [...] Read more.

CsCl-type cubic compound CeZn exhibits a paramagnetic (PM) to antiferromagnetic (AFM) first-order transition at T_N ~ 30 K accompanied by a simultaneous structural transition from cubic to tetragonal structure as temperature decreases. Applying the pressure, the coupled magnetic and crystal structural transition becomes separated above 1.0 GPa and then the AFM order changes to ferromagnetic (FM). The FM ordering temperature decreases with further applying pressure and changes to a nonmagnetic state above ~3.0 GPa. In the nonmagnetic state, we discovered superconductivity below T_sc ~ 1.3 K over 5.5 GPa, which survives even up to 9.5 GPa. Investigation of single crystal X-ray diffraction at room temperature reveals that CeZn undergoes a sequential crystal structural change with increasing pressure from cubic at ambient pressure to the monoclinic structure at 8.2 GPa via tetragonal and orthorhombic structure. The detailed analysis of crystal structure in CeZn single crystal evidenced that the emergence of superconductivity is related to the orthorhombic-to-monoclinic transition implying a nonmagnetic origin of the Cooper pair formation. Full article

(This article belongs to the Special Issue Superconductors: Materials, Microstructures and Applications)

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11 pages, 3163 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Structural Deviation of Cu/Cu₂O Nanocomposite Using the X-ray Diffraction Analysis Methods

by Nguyen Hoang Lam, Ryan P. Smith, Nam Le, Chau Thi Thanh Thuy, Mohaseen S. Tamboli, Asiya M. Tamboli, Sultan Alshehri, Mohammed M. Ghoneim, Nguyen Tam Nguyen Truong and Jae Hak Jung

Crystals 2022, 12(4), 566; https://doi.org/10.3390/cryst12040566 - 18 Apr 2022

Cited by 18 | Viewed by 6949

Abstract

We successfully synthesized Cu/Cu₂O nanocomposites using the wet chemical synthesis method. All X-ray diffraction (XRD), Reference Intensity Ratio (RIR), and Rietveld refinement methods confirmed that the compounds Cu and Cu₂O are free of impurities. Scanning Electron Microscope (SEM) and [...] Read more.

We successfully synthesized Cu/Cu₂O nanocomposites using the wet chemical synthesis method. All X-ray diffraction (XRD), Reference Intensity Ratio (RIR), and Rietveld refinement methods confirmed that the compounds Cu and Cu₂O are free of impurities. Scanning Electron Microscope (SEM) and Transmission electron microscopy (TEM) images show the morphology and interactions of Cu and Cu₂O in the structure. The formation mechanism is also explained by five stages: precursor, nucleation, growth, aging, and reduction. The changes in crystallization parameters under variations in reaction temperature (T_v) and stirring speed (S_v) were confirmed by agreement with the XRD database. The lattice constant in the crystal of nanocomposite increases with rising temperature in the reaction, leading to unit cell expansion, while increasing the stirring—rate leads to a random size distribution of the lattice parameter. Due to the imperfect growth of the crystal, the induced crystallite size was calculated using the Williamson-Hall model, and the precise lattice parameter values were calculated using the Nelson-Riley function. Full article

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7 pages, 2519 KiB

Open AccessEditor’s ChoiceArticle

Growth and Passive Q-Switching Application of Cr:TiTe₃O₈ Crystal

by Chengcheng Li, Zeliang Gao, Zhongjun Zhai, Shuai Ye and Youxuan Sun

Crystals 2022, 12(4), 558; https://doi.org/10.3390/cryst12040558 - 15 Apr 2022

Cited by 1 | Viewed by 2094

Abstract

A Cr⁴⁺-doped TiTe₃O₈ crystal with dimensions up to 21 mm × 21 mm × 11 mm was grown successfully by the top-seeded solution growth method. A high-resolution X-ray diffraction experiment showed that the full width at half-maximum of [...] Read more.

A Cr⁴⁺-doped TiTe₃O₈ crystal with dimensions up to 21 mm × 21 mm × 11 mm was grown successfully by the top-seeded solution growth method. A high-resolution X-ray diffraction experiment showed that the full width at half-maximum of the rocking curve was 41.90″. Energy-dispersive spectrometry (EDS) and X-ray fluorescence spectroscopy (XRF) proved that Cr⁴⁺ ions have been doped into the TiTe₃O₈ crystal with molar percentage of 4.9%. The Cr:TiTe₃O₈ crystal exhibited an absorption range from 995 to 1565 nm, which is suitable for passive Q switch at 1064 nm. Then, a passive Q-switching solid-state laser operating at 1064 nm was realized using a Cr:TiTe₃O₈ crystal as the saturable absorber. The maximum laser pulse energy is calculated to be 0.7 μJ, and the maximum peak power reaches 0.7 W. Full article

(This article belongs to the Special Issue Feature Papers in Crystal Engineering in 2022)

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10 pages, 6130 KiB

Open AccessEditor’s ChoiceArticle

On Stress-Induced Polarization Effect in Ammonothermally Grown GaN Crystals

by Karolina Grabianska, Robert Kucharski, Tomasz Sochacki, Jan L. Weyher, Malgorzata Iwinska, Izabella Grzegory and Michal Bockowski

Crystals 2022, 12(4), 554; https://doi.org/10.3390/cryst12040554 - 15 Apr 2022

Cited by 6 | Viewed by 2042

Abstract

The results of basic ammonothermal crystallization of gallium nitride are described. The material is mainly analyzed in terms of the formation of stress (called stress-induced polarization effect) and defects (threading dislocations) appearing due to a stress relaxation process. Gallium nitride grown in different [...] Read more.

The results of basic ammonothermal crystallization of gallium nitride are described. The material is mainly analyzed in terms of the formation of stress (called stress-induced polarization effect) and defects (threading dislocations) appearing due to a stress relaxation process. Gallium nitride grown in different positions of the crystallization zone is examined in cross-polarized light. Interfaces between native ammonothermal seeds and new-grown gallium nitride layers are investigated in ultraviolet light. The etch pit densities in the seeds and the layers is determined and compared. Based on the obtained results a model of stress and defect formation is presented. New solutions for improving the structural quality of basic ammonothermal gallium nitride crystals are proposed. Full article

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15 pages, 2040 KiB

Open AccessEditor’s ChoiceArticle

Resonance Analysis of Piezoelectric Bulk Acoustic Wave Devices Based on YCOB Crystals with Monoclinic Symmetry Excited by Lateral Electric Fields

by Dudu Chen, Peng Zhao, Fei Sun, Tingfeng Ma, Lili Yuan, Rongxing Wu, Peng Li and Zhenghua Qian

Crystals 2022, 12(4), 542; https://doi.org/10.3390/cryst12040542 - 12 Apr 2022

Cited by 2 | Viewed by 2021

Abstract

The monoclinic YCOB crystal still maintains good piezoelectric properties at 800 °C; thus, it has a good application prospect in high-temperature piezoelectric acoustic wave sensors. However, due to the lower symmetry compared crystals in trigonal and tetragonal systems, the exciting characteristics of piezoelectric [...] Read more.

The monoclinic YCOB crystal still maintains good piezoelectric properties at 800 °C; thus, it has a good application prospect in high-temperature piezoelectric acoustic wave sensors. However, due to the lower symmetry compared crystals in trigonal and tetragonal systems, the exciting characteristics of piezoelectric plates based on monoclinic YCOB crystals are more complicated. The vibration analysis model of lateral-field-excitation (LFE) devices based on monoclinic crystals is scarce; thus, the coupling relationships between different vibration modes and energy-trapping characteristics of the devices are unclear, which hinders the optimal design of devices. In this paper, by using Mindlin plate theory, the high-frequency vibrations of piezoelectric resonators based on monoclinic YCOB crystal plates excited by a lateral electric field are modeled and analyzed. The coupling relationships between the vibration modes of the device are clarified. The influences of the electrode width, electrode/plate mass ratio and electrode gap value on resonances and energy-trapping characteristics of the device are achieved. In addition, the effects of the structure parameters on the mass sensitivity of the monoclinic YCOB LFE devices are investigated, which are further verified by FEM simulations. The results are crucial to obtaining good resonance and sensing characteristics for LFE high-temperature piezoelectric sensors based on crystals with monoclinic symmetry. Full article

(This article belongs to the Special Issue Ferroelectrics)

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12 pages, 3020 KiB

Open AccessEditor’s ChoiceArticle

Periodicity of Superatomic Hybrid Orbitals in Substituted Superatoms and Superatomic-like X@Ga₁₂ (X = Li~Kr) Clusters

by Takaki Nishimura, Teruyuki Toba, Genta Sakane and Tomohiko Ishii

Crystals 2022, 12(4), 543; https://doi.org/10.3390/cryst12040543 - 12 Apr 2022

Cited by 1 | Viewed by 2179

Abstract

A superatom is a cluster composed of a specific number of atoms. We recently found that the superatom-like X@Ga₁₂ (X = Li~Kr) clusters has the periodic energy levels of the specific orbitals 2S and 2P by means of the DV-Xα molecular orbital [...] Read more.

A superatom is a cluster composed of a specific number of atoms. We recently found that the superatom-like X@Ga₁₂ (X = Li~Kr) clusters has the periodic energy levels of the specific orbitals 2S and 2P by means of the DV-Xα molecular orbital calculation method. This periodicity in energy levels has not been seen in 1D or 1F orbitals. We supposed that the periodicity of the energy levels of the 2S and 2P superatomic-like orbitals come from the same symmetry between atomic orbitals as the central atom X and the surrounding specific orbitals, according to the Jellium model. Both the s and p atomic orbitals of the central atom X in the superatom-like X@Ga₁₂ have a large shielding effect, suggesting that the s and p atomic orbitals interact strongly with both 2S and 2P superatomic-like orbitals. The energy level periodicity has the potential to periodically change the number of electrons located in the 1D and 1F orbitals, which is related to magnetic properties and is expected to be useful for novel magnetic devices by periodically controlling the magnetism of superatoms. Full article

(This article belongs to the Topic First-Principles Simulation—Nano-Theory)

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8 pages, 2876 KiB

Open AccessEditor’s ChoiceArticle

Envelope Function Analysis of Quasicrystals

by Radosław Strzałka, Łukasz Chuchra and Janusz Wolny

Crystals 2022, 12(4), 536; https://doi.org/10.3390/cryst12040536 - 11 Apr 2022

Viewed by 1760

Abstract

Quasicrystals have attracted a growing interest in material science because of their unique properties and applications. Proper determination of the atomic structure is important in designing a useful application of these materials, for which a difficult phase problem of the structure factor must [...] Read more.

Quasicrystals have attracted a growing interest in material science because of their unique properties and applications. Proper determination of the atomic structure is important in designing a useful application of these materials, for which a difficult phase problem of the structure factor must be solved. Diffraction patterns of quasicrystals consist of a periodic series of peaks, which can be reduced to a single envelope. Knowing the distribution of the diffraction image into series, it is possible to recover information about the phase of the structure factor without using time-consuming iterative methods. By the inverse Fourier transform, the structure factor can be obtained (enclosed in the shape of the average unit cell, or atomic surface) directly from the diffraction patterns. The method based on envelope function analysis was discussed in detail for a model 1D (Fibonacci chain) and 2D (Penrose tiling) quasicrystal. First attempts to apply this technique to a real Al-Cu-Rh decagonal quasicrystal were also made. Full article

(This article belongs to the Special Issue Frontiers of Intermetallic Compounds)

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11 pages, 2691 KiB

Open AccessEditor’s ChoiceArticle

Zeolitic Imidazolate Framework 67-Derived Ce-Doped CoP@N-Doped Carbon Hollow Polyhedron as High-Performance Anodes for Lithium-Ion Batteries

by Yanjun Zhai, Shuli Zhou, Linlin Guo, Xiaole Xin, Suyuan Zeng, Konggang Qu, Nana Wang and Xianxi Zhang

Crystals 2022, 12(4), 533; https://doi.org/10.3390/cryst12040533 - 11 Apr 2022

Cited by 11 | Viewed by 3972

Abstract

Zeolitic Imidazolate Framework 67 (ZIF-67) and its derivates have attracted extensive interest for lithium-ion batteries (LIBs). Here, Cerium-doped cobalt phosphide@nitrogen-doped carbon (Ce-doped CoP@NC) with hollow polyhedron structure materials were successfully synthesized via ionic-exchange with Co and Ce ions using the ZIF-67 as a [...] Read more.

Zeolitic Imidazolate Framework 67 (ZIF-67) and its derivates have attracted extensive interest for lithium-ion batteries (LIBs). Here, Cerium-doped cobalt phosphide@nitrogen-doped carbon (Ce-doped CoP@NC) with hollow polyhedron structure materials were successfully synthesized via ionic-exchange with Co and Ce ions using the ZIF-67 as a template followed with a facile low-temperature phosphorization treatment. Benefitting from the well-designed hollow polyhedron, steady carbon network, and Ce-doping structural merits, the as-synthesized Ce-doped CoP@NC electrode demonstrated superior performance as the anode in LIBs: a superior cyclability (400 mA h g⁻¹ after 500 cycles) and outstanding rate-capability (590 mA h g⁻¹, reverted to 100 mA g⁻¹). These features not only produced more lithium-active sites for LIBs anode and a shorter Li-ion diffusion pathway to expedite the charge transfer, but also the better tolerance against volume variation of CoP during the repeated lithiation/delithiation process and greater electronic conductivity properties. These results provide a methodology for the design of well-organized ZIFs and rare earth element-doped transition metal phosphate with a hollow polyhedron structure. Full article

(This article belongs to the Special Issue Emerging Low-Dimensional Materials)

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10 pages, 11449 KiB

Open AccessEditor’s ChoiceArticle

Fullerene in a Magnetic Field

by Alexandr Lun-Fu, Vladislav Borodin, Mikhail Bubenchikov, Alexey Bubenchikov and Dmitriy Mamontov

Crystals 2022, 12(4), 521; https://doi.org/10.3390/cryst12040521 - 8 Apr 2022

Cited by 4 | Viewed by 1742

Abstract

The manuscript presents a trajectory method for describing the rotations of surface crystals such as fullerenes, nanotubes, and nanotori. This method does not require the implementation of successive rotations of the considered molecular structures around the axes of the selected basis. Therefore, it [...] Read more.

The manuscript presents a trajectory method for describing the rotations of surface crystals such as fullerenes, nanotubes, and nanotori. This method does not require the implementation of successive rotations of the considered molecular structures around the axes of the selected basis. Therefore, it is free from the shortcomings of the approaches of Euler and Hamilton. On its basis, an efficient algorithm for calculating the motions of a magneto-susceptible fullerene in an alternating magnetic field has been developed. The nature of rotation of fullerenes in fields of various configurations has been studied. Full article

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

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7 pages, 2597 KiB

Open AccessEditor’s ChoiceArticle

Properties of Sm-Doped SrCl₂ Crystalline Scintillators

by Daisuke Nakauchi, Yutaka Fujimoto, Takumi Kato, Noriaki Kawaguchi and Takayuki Yanagida

Crystals 2022, 12(4), 517; https://doi.org/10.3390/cryst12040517 - 8 Apr 2022

Cited by 13 | Viewed by 3002

Abstract

Sm-doped SrCl₂ crystals were prepared, and the scintillation properties such as emission spectra, decay profiles, and pulse height were investigated. Under X-ray irradiation, a broad band can be observed at 680 nm, which indicates that the major origin is due to 5d-4f [...] Read more.

Sm-doped SrCl₂ crystals were prepared, and the scintillation properties such as emission spectra, decay profiles, and pulse height were investigated. Under X-ray irradiation, a broad band can be observed at 680 nm, which indicates that the major origin is due to 5d-4f transitions of Sm²⁺. The decay curve is approximated by one exponential function with a decay time of 10 μs, and the decay time constant is typical for Sm²⁺. From the pulse height of ¹³⁷Cs γ-rays, 0.1% Sm:SrCl₂ shows a light yield of 33,000 photons/MeV. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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13 pages, 3553 KiB

Open AccessEditor’s ChoiceArticle

Effect of Non-Covalent Interactions on the 2,4- and 3,5-Dinitrobenzoate Eu-Cd Complex Structures

by Maxim A. Shmelev, Aleksandr S. Chistyakov, Galina A. Razgonyaeva, Vladimir V. Kovalev, Julia K. Voronina, Fedor M. Dolgushin, Natalia V. Gogoleva, Mikhail A. Kiskin, Alexey A. Sidorov and Igor L. Eremenko

Crystals 2022, 12(4), 508; https://doi.org/10.3390/cryst12040508 - 6 Apr 2022

Cited by 11 | Viewed by 2607

Abstract

Heterometallic {Eu₂Cd₂} complexes [Eu₂(NO₃)₂Cd₂(Phen)₂(2,4-Nbz)₈]_n·2nMeCN (I) and [Eu₂(MeCN)₂Cd₂(Phen)₂(3,5-Nbz)₁₀] (II) with the 2,4-dinitrobenzoate (2,4-Nbz) and [...] Read more.

Heterometallic {Eu₂Cd₂} complexes [Eu₂(NO₃)₂Cd₂(Phen)₂(2,4-Nbz)₈]_n·2nMeCN (I) and [Eu₂(MeCN)₂Cd₂(Phen)₂(3,5-Nbz)₁₀] (II) with the 2,4-dinitrobenzoate (2,4-Nbz) and 3,5-dinitrobenzoate (3,5-Nbz) anions and 1,10-phenanthroline were synthesized. The compounds obtained were characterized by X-ray single-crystal analysis, powder X-ray diffraction analysis, IR spectroscopy, and elemental analysis. Moreover, the thermal stability of the complexes was also studied. Analysis of the crystal packing showed that where 1,10-phenanthroline is combined with various isomers of dinitrobenzoate anions, different arrangements of non-covalent interactions are observed in the complex structures. In the case of the compound with the 2,4-dinitrobenzoate anion, these interactions lead to a significant distortion of the metal core geometry and formation of a polymeric structure, while the complex with the 3,5-dinitrobenzoate anion has a structure that is typical of similar systems. The absence of europium metal-centered luminescence at 270 nm wavelength was shown. For all the reported compounds, a thermal stability study was carried out that showed that the compounds decomposed with a significant thermal effect. Full article

(This article belongs to the Special Issue Feature Papers in Organic Crystalline Materials)

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13 pages, 2583 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Crystalline State Hydrogen Bonding of 2-(2-Hydroxybenzylidene)Thiazolo[3,2-a]Pyrimidines: A Way to Non-Centrosymmetric Crystals

by Artem S. Agarkov, Igor A. Litvinov, Elina R. Gabitova, Alexander S. Ovsyannikov, Pavel V. Dorovatovskii, Andrey K. Shiryaev, Svetlana E. Solovieva and Igor S. Antipin

Crystals 2022, 12(4), 494; https://doi.org/10.3390/cryst12040494 - 2 Apr 2022

Cited by 7 | Viewed by 3001

Abstract

Thiazolopyrimidines are attractive to medical chemists as new antitumor agents due to their high inhibiting activity towards the tumor cells replication process and easy modification of their structure by varying of the number and nature of substituents. The presence of asymmetric C5 carbon [...] Read more.

Thiazolopyrimidines are attractive to medical chemists as new antitumor agents due to their high inhibiting activity towards the tumor cells replication process and easy modification of their structure by varying of the number and nature of substituents. The presence of asymmetric C5 carbon atoms requires the development of racemic mixture separation procedures for these heterocycles. One of the more effective ways is the crystallization of a racemic compound as a conglomerate. A prerequisite for such separation is the formation of non-centrosymmetric crystals presenting Sohncke space groups. For the construction of chiral supramolecular ensembles in a crystalline state, hydrogen bonds were chosen as supramolecular synthons. In this context, salicylic derivatives at the C2 atom of thiazolopyrimidines were synthesized. The crystal structures of the obtained compounds were established by SCXRD. The regularities of the solvent’s influence on the crystal packaging were revealed. The conditions for the preparation of crystals with the chiral space group due to intermolecular hydrogen bonds were discovered. Full article

(This article belongs to the Special Issue Advances in Chiral Crystallization, Resolution and Deracemization)

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11 pages, 2792 KiB

Open AccessEditor’s ChoiceArticle

Phase Transitions and Amorphization of M₂AgF₄ (M = Na, K, Rb) Compounds at High Pressure

by Jakub Gawraczyński, Łukasz Wolański, Adam Grzelak, Zoran Mazej, Viktor Struzhkin and Wojciech Grochala

Crystals 2022, 12(4), 458; https://doi.org/10.3390/cryst12040458 - 25 Mar 2022

Cited by 2 | Viewed by 2214

Abstract

We report the results of high-pressure Raman spectroscopy studies of alkali metal fluoroargentates (M₂AgF₄, where M = Na, K, Rb) combined with theoretical and X-ray diffraction studies for the K member of the series. Theoretical density functional calculations predict [...] Read more.

We report the results of high-pressure Raman spectroscopy studies of alkali metal fluoroargentates (M₂AgF₄, where M = Na, K, Rb) combined with theoretical and X-ray diffraction studies for the K member of the series. Theoretical density functional calculations predict two structural phase transitions for K₂AgF₄: one from low-pressure monoclinic P2₁/c (beta) phase to intermediate-pressure tetragonal I42d structure at 6 GPa, and another to high-pressure triclinic P1 phase at 58 GPa. However, Raman spectroscopy and X-ray diffraction data indicate that both polymorphic forms of K₂AgF₄, as well as two other fluoroargentate phases studied here, undergo amorphization at pressures as low as several GPa. Full article

(This article belongs to the Special Issue Advances in Halide Perovskite Materials)

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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 4273

Abstract

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 2153

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 4635

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 2291

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 2236

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 2587

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 3014

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 2181

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 2555

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 2739

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 2433

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 2809

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 10309

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 2983

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 2921

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 4600

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 4639

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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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 2190

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 2664

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 4800

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 2335

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 3218

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 2099

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 2143

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 2938

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 2588

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 2565

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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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 1917

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 1999

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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