Crystals

9 pages, 1121 KiB

Open AccessArticle

Double-Layer Superhydrophobic Anti-Icing Coating Based on Carbon Nanoparticles

by Sergey Kapustin, Sergey Zabolotny, Marat Eseev and Yuliana Tsykareva

Crystals 2022, 12(10), 1501; https://doi.org/10.3390/cryst12101501 - 21 Oct 2022

Cited by 3 | Viewed by 1307

The previous article introduced the idea of a superhydrophobic coating from carbon nanoparticles that can combine the lotus effect, the slip effect and electric current heating. A further development of this idea was suggested. The article demonstrated the possibility of a practical implementation [...] Read more.

The previous article introduced the idea of a superhydrophobic coating from carbon nanoparticles that can combine the lotus effect, the slip effect and electric current heating. A further development of this idea was suggested. The article demonstrated the possibility of a practical implementation of the suggested approach using two coating layers—the electro-thermal layer from carbon nanotubes and the water-repellent layer from onion-like carbons. This coating allows to conserve energy during periods of slight cooling simply due to the use of the lotus effect. The heating is used to prevent icing at lower temperatures. The best contact angle achieved equals 155.9 ± 0.5 degrees at a slip start angle of 1.2 ± 0.5 degrees. Full article

► Show Figures

Figure 1

18 pages, 16120 KiB

Open AccessArticle

Research on Microstructure and Cracking Behavior of Al-6.2Zn-2Mg-xSc-xZr Alloy Fabricated by Selective Laser Melting

by Wei Pan, Ziyu Zhai, Yantao Liu, Bo Liang, Zhuoheng Liang and Yongzhong Zhang

Crystals 2022, 12(10), 1500; https://doi.org/10.3390/cryst12101500 - 21 Oct 2022

Cited by 4 | Viewed by 1362

Abstract

Selective laser melting (SLM) offers obvious advantages in the production of complex parts. However, the traditional 7xxx series aluminum alloy has a serious cracking tendency in the SLM process. Therefore, in order to analyze the microstructure and cracking mechanism, and obtain crack-free aluminum [...] Read more.

Selective laser melting (SLM) offers obvious advantages in the production of complex parts. However, the traditional 7xxx series aluminum alloy has a serious cracking tendency in the SLM process. Therefore, in order to analyze the microstructure and cracking mechanism, and obtain crack-free aluminum alloy fabricated by SLM, this paper studied the microstructure characteristics of as-deposited Al-6.2Zn-2Mg-xSc-xZr alloy with different Sc, Zr content, as well as the influence mechanism of Sc, Zr on cracking. The results show that with the increase of Sc and Zr content, the crack tendency and grain size decrease. When Sc and Zr content reach 0.6% and 0.36% respectively, cracks can no longer be observed in the as deposited alloy. The microstructure of the as deposited Al-6.2Zn-2Mg-0.6Sc-0.36Zr alloy consists of fine equiaxed and columnar crystals, in which Sc and Zr mainly exist in the aluminum matrix as solid solutions, and some exist in the form of Al₃(Sc, Zr). The immediate reason for the absence of cracks is that the microstructure changes from coarse columnar grains to fine equiaxed-columnar grains when the content of Sc and Zr increases. The refined grain size may have the following beneficial effects: It helps with reducing the thickness of the liquid films. This will increase the tear sensitivity of the liquid film and the cracking tendency and therefore lowers the hot cracking tendency; And a refined grain size improves fracture roughness, leading to an enhanced cracking resistance. At the same time, the refinement of the grains will make the feeding channel of the grain boundary shorter and easy to feed, and the fine equiaxed grains can coordinate stress-strain during solidification more effectively than coarse columnar grains, which will decrease the cracking tendency. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

► Show Figures

Figure 1

13 pages, 3485 KiB

Open AccessArticle

Structure and Properties of Cubic PuH₂ and PuH₃: A Density Functional Theory Study

by Thomas Smith, Samuel Moxon, David J. Cooke, Lisa J. Gillie, Robert M. Harker, Mark T. Storr, Estelina Lora da Silva and Marco Molinari

Crystals 2022, 12(10), 1499; https://doi.org/10.3390/cryst12101499 - 21 Oct 2022

Cited by 2 | Viewed by 1847

Abstract

The presence of cubic PuH₂ and PuH₃, the products of hydrogen corrosion of Pu, during long-term storage is of concern because of the materials’ pyrophoricity and ability to catalyse the oxidation reaction of Pu to form PuO₂. Here, [...] Read more.

The presence of cubic PuH₂ and PuH₃, the products of hydrogen corrosion of Pu, during long-term storage is of concern because of the materials’ pyrophoricity and ability to catalyse the oxidation reaction of Pu to form PuO₂. Here, we modelled cubic PuH₂ and PuH₃ using Density Functional Theory (DFT) and assessed the performance of the PBEsol+U+SOC (0 ≤ U ≤ 7 eV) including van der Waals dispersion using the Grimme D3 method and the hybrid HSE06sol+SOC. We investigated the structural, magnetic and electronic properties of the cubic hydride phases. We considered spin–orbit coupling (SOC) and non-collinear magnetism to study ferromagnetic (FM), longitudinal and transverse antiferromagnetic (AFM) orders aligned in the <100>, <110> and <111> directions. The hybrid DFT confirmed that FM orders in the <110> and <111> directions were the most stable for cubic PuH₂ and PuH₃, respectively. For the standard DFT, the most stable magnetic order is dependent on the value of U used, with transitions in the magnetic order at higher U values (U > 5 eV) seen for both PuH₂ and PuH₃. Full article

(This article belongs to the Special Issue Radioactive Isotopes Based Materials Characterization)

► Show Figures

Figure 1

16 pages, 6693 KiB

Open AccessArticle

A Study on the Brittle-to-Ductile Transition Temperature of Forged β-Solidifying TiAlMn and TNM Alloys

by Xiang Su, Pei Li, Hongjie Qu, Chenming Feng, Rui Hou, Weidong Song, Bo Tian and Hao Xu

Crystals 2022, 12(10), 1498; https://doi.org/10.3390/cryst12101498 - 21 Oct 2022

Cited by 2 | Viewed by 1670

Abstract

To further determine the brittle-to-ductile transition temperature, the microstructures and mechanical properties of typical forged β-solidifying Ti-42Al-5Mn (TiAlMn) and Ti-43Al-4Nb-1Mo-0.5B (TNM) alloys were studied. The results show that the microstructures of both heat-treated alloys consist of γ/α₂ lamellar colony, equiaxed γ phase, [...] Read more.

To further determine the brittle-to-ductile transition temperature, the microstructures and mechanical properties of typical forged β-solidifying Ti-42Al-5Mn (TiAlMn) and Ti-43Al-4Nb-1Mo-0.5B (TNM) alloys were studied. The results show that the microstructures of both heat-treated alloys consist of γ/α₂ lamellar colony, equiaxed γ phase, and β₀ phase. In addition, the globular α₂ phase appears in the TNM alloy. The yield strength of TiAlMn alloy increases gradually with the testing temperature, whereas a significant drop from 605 MPa to 469 MPa occurs between 650 °C and 700 °C. In contrast, the TNM alloy exhibits a declining trend with the increasing testing temperature, and a remarkable reduction is observed in the temperature range of 700 °C–750 °C. Moreover, the fracture mode transition from transcrystalline cleavage to intercrystalline with increasing testing temperature was applied to the auxiliary judgment of brittle-to-ductile transition. As a result, the brittle-to-ductile transition temperatures of TiAlMn alloy and TNM alloy are about 650 °C–700 °C and 700 °C–750 °C, which may provide a reference for service temperature range of both alloys. Full article

(This article belongs to the Section Biomolecular Crystals)

► Show Figures

Figure 1

6 pages, 2680 KiB

Open AccessEditor’s ChoiceArticle

Nickel-Assisted Transfer-Free Technology of Graphene Chemical Vapor Deposition on GaN for Improving the Electrical Performance of Light-Emitting Diodes

by Penghao Tang, Fangzhu Xiong, Zaifa Du, Kai Li, Yu Mei, Weiling Guo and Jie Sun

Crystals 2022, 12(10), 1497; https://doi.org/10.3390/cryst12101497 - 21 Oct 2022

Cited by 2 | Viewed by 1547

Abstract

With the rapid development of graphene technology, today graphene performs well in the application of light-emitting diode (LED) transparent electrodes. Naturally, high-quality contact between the graphene and the GaN underneath is very important. This paper reports a process for nickel-assisted transfer-free technology of [...] Read more.

With the rapid development of graphene technology, today graphene performs well in the application of light-emitting diode (LED) transparent electrodes. Naturally, high-quality contact between the graphene and the GaN underneath is very important. This paper reports a process for nickel-assisted transfer-free technology of graphene chemical vapor deposition on GaN. The nickel film plays the dual role of etching mask and growth catalyst, and is removed by the subsequent “penetration etching” process, achieving good direct contact between the graphene and GaN. The results show that the graphene effectively improves the current spreading of GaN-based LEDs and enhances their electrical performance. This scheme avoids the wrinkles and cracks of graphene from the transfer process, and is not only suitable for the combination of graphene and GaN-based LEDs, but also provides a solution for the integration of graphene and other materials. Full article

(This article belongs to the Special Issue Recent Advances in III-Nitride Semiconductors)

► Show Figures

Figure 1

19 pages, 2593 KiB

Open AccessArticle

Frictionless Motion of Diffuse Interfaces by Sharp Phase-Field Modeling

by Michael Fleck, Felix Schleifer and Patrick Zimbrod

Crystals 2022, 12(10), 1496; https://doi.org/10.3390/cryst12101496 - 21 Oct 2022

Cited by 2 | Viewed by 1421

Abstract

Diffuse interface descriptions offer many advantages for the modeling of microstructure evolution. However, the numerical representation of moving diffuse interfaces on discrete numerical grids involves spurious grid friction, which limits the overall performance of the model in many respects. Interestingly, this intricate and [...] Read more.

Diffuse interface descriptions offer many advantages for the modeling of microstructure evolution. However, the numerical representation of moving diffuse interfaces on discrete numerical grids involves spurious grid friction, which limits the overall performance of the model in many respects. Interestingly, this intricate and detrimental effect can be overcome in finite difference (FD) and fast Fourier transformation (FFT)-based implementations by employing the so-called sharp phase-field method (SPFM). The key idea is to restore the discretization-induced broken translational invariance (TI) in the discrete phase-field equation by using analytic properties of the equilibrium interface profile. We prove that this method can indeed eliminate spurious grid friction in the three-dimensional space. Focusing on homogeneous driving forces, we quantitatively evaluate the impact of spurious grid friction on the overall operational performance of different phase-field models. We show that the SPFM provides superior degrees of interface isotropy with respect to energy and kinetics. The latter property enables the frictionless motion of arbitrarily oriented diffuse interfaces on a fixed 3D grid. Full article

(This article belongs to the Special Issue Nanocrystalline Bulk Materials at Multiple Scales)

► Show Figures

Figure 1

12 pages, 575 KiB

Open AccessArticle

Mathematical Modeling of Nucleation and Growth Processes of Ellipsoidal Crystals in Binary Melts

by Margarita A. Nikishina and Dmitri V. Alexandrov

Crystals 2022, 12(10), 1495; https://doi.org/10.3390/cryst12101495 - 21 Oct 2022

Viewed by 1222

Abstract

The transient behavior of an ensemble of ellipsoidal particles in a supercooled binary melt is considered. The model laws, based on the Fokker-Planck type kinetic equation for the particle-volume distribution function, the thermal and mass integral balances for the binary melt temperature and [...] Read more.

The transient behavior of an ensemble of ellipsoidal particles in a supercooled binary melt is considered. The model laws, based on the Fokker-Planck type kinetic equation for the particle-volume distribution function, the thermal and mass integral balances for the binary melt temperature and solute concentration, as well as the corresponding boundary and initial conditions, are formulated and solved analytically. We show that the temperature and concentration increase with time due to the effects of impurity displacement and latent heat emission by the growing ellipsoidal particles. These effects are also responsible for metastability reduction. As this takes place, increasing the initial solute concentration in a metastable binary melt increases the intensity of its desupercooling. The theory is developed for arbitrary nucleation frequency with special consideration of two important nucleation kinetics according to the Meirs and Weber-Volmer-Frenkel Zel’dovich mechanisms. An analytical solution to the integrodifferential model equations is found in a parametric form. The theory contains all limiting transitions to previously developed analytical approaches. Namely, it contains the growth of spherical crystals in binary melts and ellipsoidal crystals in single-component melts. Full article

(This article belongs to the Special Issue Phase Transition in External Fields)

► Show Figures

Figure 1

11 pages, 1806 KiB

Open AccessArticle

The Influence of Internal Stress on the Nanocrystal Formation of Amorphous Fe_73.8Si₁₃B_9.1Cu₁Nb_3.1 Microwires and Ribbons

by Artem Fuks, Galina Abrosimova, Oleg Aksenov, Margarita Churyukanova and Alexandr Aronin

Crystals 2022, 12(10), 1494; https://doi.org/10.3390/cryst12101494 - 21 Oct 2022

Cited by 3 | Viewed by 1042

Abstract

The early stages of nanocrystallization in amorphous Fe_73.8Si₁₃B_9.1Cu₁Nb_3.1 ribbons and microwires were compared in terms of their internal stress effects. The microstructure was investigated by the X-ray diffraction method. Classical expressions of crystal nucleation [...] Read more.

The early stages of nanocrystallization in amorphous Fe_73.8Si₁₃B_9.1Cu₁Nb_3.1 ribbons and microwires were compared in terms of their internal stress effects. The microstructure was investigated by the X-ray diffraction method. Classical expressions of crystal nucleation and growth were modified for microwires while accounting for the internal stress distribution, in order to justify the XRD data. It was assumed that, due to the strong compressive stresses on the surface part and tensile stresses on the central part, crystallization on the surface part of the microwire proceeded faster than in the central part. The results revealed more rapid nanocrystallization in microwires compared to that in ribbons. During the initial period of annealing, the compressive surface stress of a microwire caused the formation of a predominantly crystallized surface layer. The results obtained open up new possibilities for varying the high-frequency properties of microwires and their application in modern sensorics. Full article

(This article belongs to the Special Issue Emerging Topics on High Performance Alloys)

► Show Figures

Figure 1

18 pages, 24231 KiB

Open AccessArticle

Microstructure and Properties of Microwave-Sintered Nd₂Fe₁₄B_p/2024 Aluminum-Alloy–Co Composites

by Tao Qin, Guirong Li, Hongming Wang, Wenxue Su, Chao Dong and Jincheng Yu

Crystals 2022, 12(10), 1493; https://doi.org/10.3390/cryst12101493 - 20 Oct 2022

Cited by 1 | Viewed by 1014

Abstract

This study aimed at the preparation of a 2024 aluminum alloy (2024Al) matrix composite with high strength, high toughness and high magnetic properties that can be used in practical applications. Therefore, Nd₂Fe₁₄B_p/2024Al–Co composites with different Co contents [...] Read more.

This study aimed at the preparation of a 2024 aluminum alloy (2024Al) matrix composite with high strength, high toughness and high magnetic properties that can be used in practical applications. Therefore, Nd₂Fe₁₄B_p/2024Al–Co composites with different Co contents (wt.%) were prepared by ball milling, cold isostatic pressing and microwave sintering. The effects of the Co content on the microstructure, mechanical properties and magnetic properties of the prepared composites were studied. Under the conditions of the sintering temperature of 490 °C, heating rate of 20 min/°C and soaking time of 30 min, it was found that with the increase in Co content (0→2.5%→5%→7.5%→10%), the grain size first decreased and then increased, and reached the optimal value of about 3–5 μm when the Co content was 7.5%, with the microstructure being relatively uniform. At the same time, the compactness of the composite arrived at a maximum of 95.4%. The main particle phases in the composite were Nd₂Fe₁₄B, Nd₂ (Fe, Co)₁₄B and Co particles. In the nanoindentation test, the interface strength of the 7.5% Co sample was significantly higher than that of the Co-free sample. In addition, the microhardness, yield strength and compressive strength of the 7.5% Co sample were 152 HV, 210 MPa and 269 MPa, respectively, which increased by 67%, 78% and 75%, respectively, compared with the Co-free sample. With the increase in Co content, the remanence (Br), coercivity (H_cj) and maximum magnetic energy product ((BH) max) of the composites first increased and then decreased. When the Co content was 7.5%, the three performance indicators reached their optimum values, which were Br: 0.20 (T), H_cj: 4.6 (kOe) and (BH)_max: 28.36 (kJ/m³). The expected goal of the lightweight magnetic materials was achieved, and the action mechanism of Co addition in the composites was also analyzed in detail. Full article

(This article belongs to the Special Issue Progress in Light Alloys)

► Show Figures

Figure 1

9 pages, 2318 KiB

Open AccessArticle

Band Alignments of GeS and GeSe Materials

by Miłosz Grodzicki, Agata K. Tołłoczko, Dominika Majchrzak, Detlef Hommel and Robert Kudrawiec

Crystals 2022, 12(10), 1492; https://doi.org/10.3390/cryst12101492 - 20 Oct 2022

Cited by 2 | Viewed by 1886

Abstract

Here we present new findings of a comprehensive study of the fundamental physicochemical properties for GeS and GeSe in bulk form. UV and X-ray photoelectron spectroscopies (UPS/XPS) were employed for the experiments, which were carried out on in situ cleaned (100) surfaces free [...] Read more.

Here we present new findings of a comprehensive study of the fundamental physicochemical properties for GeS and GeSe in bulk form. UV and X-ray photoelectron spectroscopies (UPS/XPS) were employed for the experiments, which were carried out on in situ cleaned (100) surfaces free from contamination. This allowed to obtain reliable results, also unchanged by effects related to charging of the samples. The work functions, electron affinities and ionization energies as well as core level lines were found. The band gaps of the investigated materials were determined by photoreflectance and optical absorption methods. As a result, band energy diagrams relative to the vacuum level for GeS and GeSe were constructed. The diagrams provide information about the valence and conduction band offsets, crucial for the design of various electronic devices and semiconducting heterostructures. Full article

(This article belongs to the Special Issue Thermoelectric Semiconductor Materials and Devices)

► Show Figures

Figure 1

20 pages, 3479 KiB

Open AccessArticle

Anomalous In Vitro Corrosion Behaviour of Rolled Mg-1 wt. % Zn Alloy Due to Buffer-Microstructure Interactions

by Ryan N. Wilkes, George Dias and Mark P. Staiger

Crystals 2022, 12(10), 1491; https://doi.org/10.3390/cryst12101491 - 20 Oct 2022

Cited by 1 | Viewed by 1461

Abstract

In this study, the influence of microstructure and buffer system on the corrosion behaviour of Mg-1 wt. % Zn is examined. The grain size of the alloy was refined from 700 µm to under 15 µm by rolling with varying reduction percentages per [...] Read more.

In this study, the influence of microstructure and buffer system on the corrosion behaviour of Mg-1 wt. % Zn is examined. The grain size of the alloy was refined from 700 µm to under 15 µm by rolling with varying reduction percentages per pass. The effects of the rolling procedure on the resulting corrosion profile were analysed with immersion and electrochemical methods. Though the rolling procedure resulted in significant grain refinement, the as-cast samples had the lowest corrosion rate of 2.8 mm/yr, while those of the rolled samples were as high as 15.8 mm/yr. The HEPES buffer system did not control the pH or support the formation of insoluble precipitates as well as the NaHCO3/CO2 buffer system, leading to more severe localised pitting corrosion in samples immersed in HEPES buffered media. While reducing grain size generally corresponds to a lower corrosion rate in Mg alloys, this study provides evidence that other factors such as texture and buffer system must also be considered to accurately test candidate alloys for biodegradable orthopaedic applications. Full article

(This article belongs to the Special Issue Relationships between Processing and Properties of Magnesium-Based Alloys)

► Show Figures

Figure 1

2 pages, 153 KiB

Open AccessEditorial

Editorial for Special Issue Cement and Construction Materials

by Payam Hosseini and Baoguo Han

Crystals 2022, 12(10), 1490; https://doi.org/10.3390/cryst12101490 - 20 Oct 2022

Viewed by 822

Abstract

Cement-based materials have always been the main choice for the construction of civil engineering infrastructures [...] Full article

(This article belongs to the Special Issue Advances in Cement-Based and Construction Materials)

14 pages, 14452 KiB

Open AccessArticle

Quasi-In Situ EBSD Study of Anisotropic Mechanical Behavior and Associated Microstructure Evolution in Zircaloy-4

by Huanzheng Sun, Yan Zhang, Chao Sun, Bingcheng Li, Xiaoyong Zhu, Yihong Sun and Baifeng Luan

Crystals 2022, 12(10), 1489; https://doi.org/10.3390/cryst12101489 - 20 Oct 2022

Cited by 1 | Viewed by 1544

Abstract

The anisotropic mechanical behavior and associated microstructure evolution in annealed Zircaloy-4 were investigated at room temperature, using quasi-in situ tensile tests along the typical direction, rolling direction (RD), and transverse direction (TD). Herein, the in-grain misorientation axes (IGMA) and the nominal Schmid factors [...] Read more.

The anisotropic mechanical behavior and associated microstructure evolution in annealed Zircaloy-4 were investigated at room temperature, using quasi-in situ tensile tests along the typical direction, rolling direction (RD), and transverse direction (TD). Herein, the in-grain misorientation axes (IGMA) and the nominal Schmid factors were evaluated to analyze the slip mode based on the electron backscatter diffraction. The IGMA result shows that there were anisotropic slip modes within grains, whose basal poles were parallel with the TD (TB) and placed within 40 to 50 degrees from the normal direction (ND) to the transverse direction (N (40°–50°) TB)), under different loading directions. When loading along the RD, the basal <a> slips were activated in the N (40°–50°) TB and TB orientation grains, while the second-order pyramidal slips were activated in the grains when loading along the TD. The relatively higher ultimate tensile strength and elongation in Zircaloy-4 when tensile along RD occurs due to its much higher frequency of soft grains (88.54%) than the TD sample (64.29%), and the synergy deformation among local grains. The present study demonstrated that the anisotropic mechanical behavior of Zircaloy-4 was attributed to the combined effects that exist between the anisotropic slip behavior and the different compatible deformation capabilities. Many shallow dimples and cleavage regions were observed on the fracture surface in the TD sample. Such fracture features are consistent with the lower ultimate tensile strength ~470 MPa and elongation ~14.5% in the deformed tensile Zircaloy-4 along the TD. Full article

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

► Show Figures

Figure 1

16 pages, 10964 KiB

Open AccessArticle

Tribological Characteristics of High-Chromium Based Multi-Component White Cast Irons

by Riki Hendra Purba, Kazumichi Shimizu, Kenta Kusumoto, Yila Gaqi and Mohammad Jobayer Huq

Crystals 2022, 12(10), 1488; https://doi.org/10.3390/cryst12101488 - 20 Oct 2022

Cited by 4 | Viewed by 1563

Abstract

It has been evaluated the relationship between the microstructure and three-body abrasive wear behavior of high-chromium (18 and 27 mass % Cr) based (3 mass % each of V, Mo, W, and Co) multicomponent white cast iron materials (high-Cr MWCIs). It was also [...] Read more.

It has been evaluated the relationship between the microstructure and three-body abrasive wear behavior of high-chromium (18 and 27 mass % Cr) based (3 mass % each of V, Mo, W, and Co) multicomponent white cast iron materials (high-Cr MWCIs). It was also compared to MWCI to determine the service life of the materials. The results indicate that the microstructure of the material is composed of mainly martensite matrix and different types of precipitated carbides. The wear resistances of both the high-Cr MWCIs are higher than MWCI owing to the higher hardness (4–18% increment in hardness), although they contain fewer carbide types. The carbide volume fraction of high-Cr MWCI increases with increase in the Cr content, but the hardness decreases, leading to a reduction in wear resistance. This is because the transition metal significantly consumes C atoms to form more eutectic carbides during solidification, which is exacerbated by the depletion of C in the matrix during heat treatment to form coarser secondary carbides. This means that increasing the addition of Cr does not always lead to an increase in the hardness or wear resistance of the material. In addition, the wear resistance of 27Cr MWCI after tempering (wear rate: 8.80 × 10⁻⁵ g/m) is higher than that after quenching (wear rate: 9.25 × 10⁻⁵ g/m) owing to the increase in the fracture toughness of M₇C₃ carbide. This is contrary to the case of 18Cr-MWCI; the wear resistance after tempering (wear rate: 5.29 × 10⁻⁵ g/m) is worse than that after quenching (wear rate: 5.11 × 10⁻⁵ g/m) owing to the reduction in hardness as a stress-relieving effect. Full article

(This article belongs to the Special Issue Recent Advances in Low-Density Steels)

► Show Figures

Figure 1

8 pages, 2785 KiB

Open AccessArticle

Improved Growth Techniques for Nonlinear Optical Crystal CsB₃O₅ Based on the Investigation of Defects

by Jingcheng Feng, Yuwei Chen, Feidi Fan, Heng Tu, Guochun Zhang and Yicheng Wu

Crystals 2022, 12(10), 1487; https://doi.org/10.3390/cryst12101487 - 19 Oct 2022

Viewed by 1182

Abstract

Growth defects in CsB₃O₅ (CBO) crystals grown using the seed-submerged growth technique (SSGT), which includes parallel grouping, growth step, and inclusion, were observed and analyzed. Dislocation was investigated using the chemical etching method for the first time. Relationships between defects [...] Read more.

Growth defects in CsB₃O₅ (CBO) crystals grown using the seed-submerged growth technique (SSGT), which includes parallel grouping, growth step, and inclusion, were observed and analyzed. Dislocation was investigated using the chemical etching method for the first time. Relationships between defects and growth conditions are discussed, and ways to overcome growth defects are suggested. Using the cool-end compensation of thermocouples, a CBO crystal measuring 63 × 40 × 30 mm³ (weighing 190 g) was successfully grown using the SSGT. Adopting the top seeded solution growth (TSSG) method, a scattering centers-free CBO crystal measuring 75 × 52 × 46 mm³ (weighing 480 g) was obtained from the improved Cs₂O–B₂O₃–MoO₃ system with a molar ratio of (1–3):(1.5–3.5):(1–4), which is the largest CBO single crystal to date. Full article

(This article belongs to the Special Issue Recent Advances in Nonlinear Optical Crystals)

► Show Figures

Figure 1

13 pages, 3946 KiB

Open AccessArticle

Determination of Cooling Rate and Temperature Gradient during Formation of Cathode Spot Craters in a Vacuum Arc

by Johann Peter Mogeritsch, Robert Franz, Mehran Golizadeh, Christian Mitterer and Abdellah Kharicha

Crystals 2022, 12(10), 1486; https://doi.org/10.3390/cryst12101486 - 19 Oct 2022

Cited by 2 | Viewed by 1157

Abstract

Due to the extreme thermal conditions and short lifetimes, experimental exploration of cathode spots in vacuum arcs is very difficult. The intensive heat in the cathode spot is believed to be generated by ion bombardment and by Joule heating. However, thermal conditions occurring [...] Read more.

Due to the extreme thermal conditions and short lifetimes, experimental exploration of cathode spots in vacuum arcs is very difficult. The intensive heat in the cathode spot is believed to be generated by ion bombardment and by Joule heating. However, thermal conditions occurring inside the re-melted material in craters created by cathode spots are not accurately known. During the exposure to cathodic arc plasmas, an Al-Cr cathode’s surface was locally melted by successive ignition and extinction of cathode spots. The melted layer, that quickly solidified, was characterized by the formation of several thin layers with a thickness of a few micrometers that were stacked on top of each other. The corresponding solidification patterns displayed cellular and dendritic microstructures. A phase field-based model was used to simulate and determine the thermal process conditions that led to the dendritic structures observed within the re-melted layer. Different combinations of cooling rates and temperature gradients were numerical explored to determine the most probable thermal conditions under which the cathode material re-solidifies. The results showed that the material in the vicinity of the cathode spot crater re-solidified under the condition of a cooling rate of about 3 × 10⁵ K/s and a temperature gradient of about 6 × 10⁷ K/m. These results constitute valuable data for the validation of numerical models dedicated to cathode spot formation. Full article

► Show Figures

Figure 1

15 pages, 10501 KiB

Open AccessArticle

The Effect of Ne⁺ Ion Implantation on the Crystal, Magnetic, and Domain Structures of Yttrium Iron Garnet Films

by Igor Fodchuk, Andrij Kotsyubynsky, Andrii Velychkovych, Ivan Hutsuliak, Volodymyra Boychuk, Volodymyr Kotsyubynsky and Liubomyr Ropyak

Crystals 2022, 12(10), 1485; https://doi.org/10.3390/cryst12101485 - 19 Oct 2022

Cited by 1 | Viewed by 1501

Abstract

The mechanism of the influence of crystal inhomogeneities on the magnetic and domain microstructures of functional materials based on yttrium iron garnet heterostructures is an important subject of investigation due to the aim to predict parameters for manufacturingpurposes. A study of the structural [...] Read more.

The mechanism of the influence of crystal inhomogeneities on the magnetic and domain microstructures of functional materials based on yttrium iron garnet heterostructures is an important subject of investigation due to the aim to predict parameters for manufacturingpurposes. A study of the structural and magnetic characteristics of a set of yttrium iron garnet films grown on gadolinium–gallium garnet substrate is presented. High-resolution X-ray diffractometry, Mössbauer spectroscopy, MFM, as well as ion implantation simulation and X-ray diffraction simulation were used together to determine the features of the effect of Ne⁺ ion implantation with different dose rates on the samples. The simulation of ion implantation with E = 82 keV showed energy loss profiles of Ne ions with subsequent defect formation up to amorphization of near-surface layers at high doses. Implantation creates two magnetically non-equivalent types of tetrahedrally located Fe³⁺ ions, which leads to a rotation of the total magnetic moment relative to the film surface and a change in the width of the magnetic domain stripes. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (Volume II))

► Show Figures

Figure 1

19 pages, 7652 KiB

Open AccessArticle

Hyaluronic Acid-Protein Conjugate Modified Iron-Based MOFs (MIL-101 (Fe)) for Efficient Therapy of Neuroblastoma: Molecular Simulation, Stability and Toxicity Studies

by Ajinkya N. Nikam, Abhijeet Pandey, Shivanand H. Nannuri, Gasper Fernandes, Sanjay Kulkarni, Bharath Singh Padya, Sumit Birangal, Gautham G. Shenoy, Sajan D. George and Srinivas Mutalik

Crystals 2022, 12(10), 1484; https://doi.org/10.3390/cryst12101484 - 19 Oct 2022

Cited by 5 | Viewed by 2526

Abstract

Iron-based metal-organic frameworks (MIL (101)) have recently gained attention in materials science for biomedical applications. In the present work, Iron-based MOF (MIL-101(Fe)) were coated with lactoferrin (Lf) conjugated with hyaluronic acid (HA) and investigated its potential for delivering 5-fluorouracil (5-FU), along with assessing [...] Read more.

Iron-based metal-organic frameworks (MIL (101)) have recently gained attention in materials science for biomedical applications. In the present work, Iron-based MOF (MIL-101(Fe)) were coated with lactoferrin (Lf) conjugated with hyaluronic acid (HA) and investigated its potential for delivering 5-fluorouracil (5-FU), along with assessing the toxicity profile. The synthesised nanoparticles were extensively characterised using spectroscopic, X-Ray, thermal and electron microscopic techniques. 5-FU was loaded into MOFs, and the drug-loading efficiency and drug release pattern were studied, along with stability testing in pH and serum protein. The toxicity of MIL-101(Fe) was assessed using both in vitro and in vivo techniques such as the haemolysis assay, cell viability assay and acute and subacute toxicity studies in animals. In silico molecular simulation was done to assess the Lf and Tf interaction. The molecular interaction of Lf with Transferrin (Tf) showed strong molecular interaction and negligible fluctuation in the RMSD (root mean square deviation) values. The MOFs were stable and demonstrated sustained drug release patterns. The in vitro cell studies demonstrated biocompatibility and enhanced cellular internalisation of MOFs. The in vivo toxicity studies supported the in vitro results. The synthesised MOFs demonstrated potential as a targeted delivery platform for cancer targeting. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

► Show Figures

Figure 1

10 pages, 4263 KiB

Open AccessArticle

Effect of Al Content on the Microstructure and Tensile Properties of Zr-Co-Al Alloy Prepared by Rapid Solidification

by Zixiang Wu, Wenfei Lu, Caiju Li, Peng Gao, Xin You and Jun Tan

Crystals 2022, 12(10), 1483; https://doi.org/10.3390/cryst12101483 - 19 Oct 2022

Cited by 2 | Viewed by 1058

Abstract

The Zr_50−x/2Co_50−x/2Al_x (x = 0, 4, 5, 6, 7, 8) alloy sheets were prepared by copper mold suction casting, and the effect of Al content on the mechanical properties and the strengthening mechanism was thoroughly investigated. With Al [...] Read more.

The Zr_50−x/2Co_50−x/2Al_x (x = 0, 4, 5, 6, 7, 8) alloy sheets were prepared by copper mold suction casting, and the effect of Al content on the mechanical properties and the strengthening mechanism was thoroughly investigated. With Al addition, a Zr₅Co₇Al₃ intermetallic compound formed and precipitated at the grain boundaries or inside the grains, which produced strong synergistic effects of secondary phase strengthening, fine grain strengthening and solid solution strengthening. However, the precipitation of intermetallic compounds can lead to the formation of shrinkage cavities at grain boundaries, and the negative effect of adding too much Al is greater than the strengthening effect, resulting in a gradual decrease in strength. Therefore, the best synergistic strengthening effect is achieved when the Al content is 5 at.%, the grain size of the alloy is reduced from 60 μm to 4 μm, and the room temperature tensile strength is increased from 240 MPa to 464 MPa. Full article

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

► Show Figures

Figure 1

8 pages, 1315 KiB

Open AccessArticle

The Effect of Chemically Modified Multi-Walled Carbon Nanotubes on the Electro-Optical Properties of a Twisted Nematic Liquid Crystal Display Mode

by Zheng Ma, Yanzi Gao and Hui Cao

Crystals 2022, 12(10), 1482; https://doi.org/10.3390/cryst12101482 - 19 Oct 2022

Cited by 3 | Viewed by 1328

Abstract

In this study, we have chemically modified multi-walled carbon nanotubes (MWNTs) with different side chains for better dispersion in liquid crystal solutions, and fabricated twisted nematic liquid crystal cells doped with such MWNT derivatives. The introduction of MWNT derivatives affects the alignment of [...] Read more.

In this study, we have chemically modified multi-walled carbon nanotubes (MWNTs) with different side chains for better dispersion in liquid crystal solutions, and fabricated twisted nematic liquid crystal cells doped with such MWNT derivatives. The introduction of MWNT derivatives affects the alignment of LC molecules with or without external electric fields. Electro-optical property tests showed that the contrast ratio changed slightly with the sharp decrease in drive voltage, improving the drive ability of the twisted nematic liquid crystal display (TN-LCD) mode. Full article

(This article belongs to the Section Liquid Crystals)

► Show Figures

Figure 1

8 pages, 2753 KiB

Open AccessArticle

Effect of Load and Fiber Orientation on Wear Properties of Additively Manufactured Continuous CFRP Composites under Dry Sliding Conditions

by Mahesh Naik, Dineshsingh G. Thakur, Sunil Chandel, Sachin Salunkhe and Hussein Mohamed Abdelmoneam Hussein

Crystals 2022, 12(10), 1481; https://doi.org/10.3390/cryst12101481 - 19 Oct 2022

Cited by 1 | Viewed by 1019

Abstract

The present research investigates the wear properties of a continuous carbon fiber-reinforced additively manufactured polymer composite under dry sliding conditions. The effect of load and fiber orientation is examined on polymer composite specimens. The wear test of the additively manufactured polymer composite specimens [...] Read more.

The present research investigates the wear properties of a continuous carbon fiber-reinforced additively manufactured polymer composite under dry sliding conditions. The effect of load and fiber orientation is examined on polymer composite specimens. The wear test of the additively manufactured polymer composite specimens is conducted on pin-on-disk test equipment. The result shows that the applied load and fiber orientation significantly affect the composite specimen’s wear properties. The wear and coefficient of friction (COF) increase with load. The minimum effect on wear and COF is observed for 0° fiber orientation, and the maximum effect is observed for 90° fiber orientation. Finally, morphological analysis is conducted using an optical micrograph of the worn-out surfaces to understand the failure type for different fiber orientations. Full article

► Show Figures

Figure 1

18 pages, 8185 KiB

Open AccessReview

A Review on Ultrafast-Laser Power Bed Fusion Technology

by Yuxiang Wu, Yongxiong Chen, Lingchao Kong, Zhiyuan Jing and Xiubing Liang

Crystals 2022, 12(10), 1480; https://doi.org/10.3390/cryst12101480 - 18 Oct 2022

Cited by 7 | Viewed by 2202

Abstract

Additive manufacturing of metals by employing continuous wave and short pulse lasers completely changes the way of modern industrial production. But the ultrafast laser has the superiority to short pulse laser and continuous wave laser in additive manufacturing. It has higher peak power, [...] Read more.

Additive manufacturing of metals by employing continuous wave and short pulse lasers completely changes the way of modern industrial production. But the ultrafast laser has the superiority to short pulse laser and continuous wave laser in additive manufacturing. It has higher peak power, small thermal effect, high machining accuracy and low damage threshold. It can effectively perform additive manufacturing for special materials and improve the mechanical properties of parts. This article reviews the mechanism of the interaction between ultrafast laser and metal materials to rule the manufacturing processes. The current application of ultrafast laser on forming and manufacturing special materials, including refractory metals, transparent materials, composite materials and high thermal conductivity materials are also discussed. Among the review, the shortcomings and challenges of the current experimental methods are discussed as well. Finally, suggestions are provided for the industrial application of ultrashort pulse laser in the field of additive manufacturing in the future. Full article

(This article belongs to the Special Issue Additive Manufacturing (AM) for Advanced Materials and Structures: Green and Intelligent Development Trend)

► Show Figures

Figure 1

24 pages, 10152 KiB

Open AccessArticle

Intermolecular Hydrogen Bonding in Alpha-Hydroxy Carboxylic Acids Crystals: Connectivity, Synthons, Supramolecular Motifs

by Alexander A. Bredikhin, Robert R. Fayzullin, Aidar T. Gubaidullin and Zemfira A. Bredikhina

Crystals 2022, 12(10), 1479; https://doi.org/10.3390/cryst12101479 - 18 Oct 2022

Cited by 4 | Viewed by 1521

Abstract

Synthon theory underlies the analysis and empirical prediction of the crystal structure. Supramolecular synthons (SMSs) formed by intermolecular hydrogen bonds, such as carboxylic

R_{2}^{2}

(8) and

C_{1}^{1}

(4) and alcoholic

C_{1}^{1}

(2) ones, are among the most [...] Read more.

Synthon theory underlies the analysis and empirical prediction of the crystal structure. Supramolecular synthons (SMSs) formed by intermolecular hydrogen bonds, such as carboxylic

R_{2}^{2}

(8) and

C_{1}^{1}

(4) and alcoholic

C_{1}^{1}

(2) ones, are among the most popular. The subject of this publication is the identification of specific synthons in alpha-hydroxycarboxylic acids (AHAs) crystals, in which carboxyl and alcohol fragments are present simultaneously. A series of 11 single-enantiomeric and racemic crystals of substituted lactic acids, the simplest chiral AHA family, were prepared and studied by the single-crystal X-ray diffraction (SC-XRD) method. Advanced analysis of our own and published (Cambridge Structural Database) data on the 33 crystal structures of lactic and achiral AHAs of diverse structures revealed that their supramolecular organization differs significantly from that of simple carboxylic acids. We found that in AHA crystals, hydrogen bonds RC(O)O−H···O(H)−C(R′R′′)C(O)OH (in our notation HB 12) and O=C(OH)C(R′R′′)−O−H···O=C(OH)R′ (HB 23) predominate. The frequency of intermolecular hydrogen bonds is interconnected with the frequency of SMSs. Thus, the synthons mentioned above occur but do not dominate in AHA crystals. Linear synthons

C_{2}^{2}

(6):12/23 and cyclic synthons

R_{2}^{2}

(10):23/23 and

R_{3}^{3}

(11):12/23/23 are most often implemented. An essential role in the choice of cyclic synthons is played by the chiral characteristics of the sample. Full article

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

► Show Figures

Figure 1

15 pages, 5396 KiB

Open AccessArticle

Coincident Nodal Line and Nodal Surface Phonon States in Ternary Phosphide Compound BaLiP

by Hong Cui, Yunjian Chen, Qin Kang, Pengyue Shan, Tie Yang and Peng Wang

Crystals 2022, 12(10), 1478; https://doi.org/10.3390/cryst12101478 - 18 Oct 2022

Viewed by 1440

Abstract

With the continuous development of topological properties in condensed matter systems, the current research focus has been expanded into phononic bosonic states. Compared with the conventional electronic fermions, topological phonons exhibit very distinct features. In this study, based on density functional calculations, we [...] Read more.

With the continuous development of topological properties in condensed matter systems, the current research focus has been expanded into phononic bosonic states. Compared with the conventional electronic fermions, topological phonons exhibit very distinct features. In this study, based on density functional calculations, we have systematically investigated the topological phonons in the ternary phosphide compound BaLiP. Coincident nodal line and nodal surface states are revealed in the middle part of the phononic spectrum and they are formed by the same two phonon bands. Detailed band structure mechanism and symmetry operation formalism are provided. More importantly, evident surface states are observed from the entire nodal line and they are all well separated from the bulk state projection, very beneficial and preferable for future experimental investigation. Lastly, the mechanical properties are also examined and several important parameters are provided, which can be very useful for the practical application. Considering the multiple advantages of the topological nodal states in this material, the corresponding experimental study can be immediately inspired. Full article

► Show Figures

Figure 1

9 pages, 3016 KiB

Open AccessArticle

Wafer-Scale Fabrication of Silicon Film on Lithium Niobate on Insulator (LNOI)

by Yang Chen, Xiaomeng Zhao, Zhongxu Li, Xinjian Ke, Chengli Wang, Min Zhou, Wenqin Li, Kai Huang and Xin Ou

Crystals 2022, 12(10), 1477; https://doi.org/10.3390/cryst12101477 - 18 Oct 2022

Cited by 2 | Viewed by 2321

Abstract

Hybrid integration of silicon photonics with lithium niobate (LN) devices provides a promising route to enable an excellent modulation performance in silicon photonic integrated circuits. To realize this purpose, a substrate containing a Si film on an LNOI substrate, called Si on the [...] Read more.

Hybrid integration of silicon photonics with lithium niobate (LN) devices provides a promising route to enable an excellent modulation performance in silicon photonic integrated circuits. To realize this purpose, a substrate containing a Si film on an LNOI substrate, called Si on the LNOI structure, was analyzed and fabricated. The mode propagation properties in the Si-on-LNOI structure were simulated in detail and a vertical adiabatic coupler (VAC) between the Si waveguide and LN waveguide was simulated to help in the determination of the dimension of this structure. A 4-inch wafer-scale Si on an LNOI hybrid structure was fabricated through the ion-cut process. This structure has a single-crystalline quality, high thickness uniformity, smooth surface, and sharp bonding interface, which are practical for realizing low loss and high coupling efficiency. Full article

(This article belongs to the Topic Optoelectronic Materials)

► Show Figures

Figure 1

11 pages, 3876 KiB

Open AccessArticle

Understanding the Semiconducting-to-Metallic Transition in the CF₂Si Monolayer under Shear Tensile Strain

by Tarik Ouahrani and Reda M. Boufatah

Crystals 2022, 12(10), 1476; https://doi.org/10.3390/cryst12101476 - 18 Oct 2022

Cited by 1 | Viewed by 1081

Abstract

With the ever-increasing interest in low-dimensional materials, it is urgent to understand the effect of strain on these kinds of structures. In this study, taking the CF

_{2}

Si monolayer as an example, a computational study was carried out to investigate the effect [...] Read more.

With the ever-increasing interest in low-dimensional materials, it is urgent to understand the effect of strain on these kinds of structures. In this study, taking the CF

_{2}

Si monolayer as an example, a computational study was carried out to investigate the effect of tensile shear strain on this compound. The structure was dynamically and thermodynamically stable under ambient conditions. By applying tensile shear, the structure showed a strain-driven transition from a semiconducting to a metallic behavior. This electronic transition’s nature was studied by means of the electron localization function index and an analysis of the noncovalent interactions. The result showed that the elongation of covalent bonds was not responsible for this metallization but rather noncovalent interactions governing the nonbonded bonds of the structure. This strain-tuned behavior might be capable of developing new devices with multiple properties involving the change in the nature of chemical bonding in low-dimensional structures. Full article

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

► Show Figures

Figure 1

12 pages, 4237 KiB

Open AccessArticle

Long-Distance High-Power Wireless Optical Energy Transmission Based on VECSELs

by Zhuo Zhang, Jianwei Zhang, Yuxiang Gong, Yinli Zhou, Xing Zhang, Chao Chen, Hao Wu, Yongyi Chen, Li Qin, Yongqiang Ning and Lijun Wang

Crystals 2022, 12(10), 1475; https://doi.org/10.3390/cryst12101475 - 18 Oct 2022

Cited by 2 | Viewed by 1490

Abstract

Wireless charging systems are critical for safely and efficiently recharging mobile electronic devices. Current wireless charging technologies involving inductive coupling, magnetic resonance coupling, and microwave transmission are bulky, require complicated systems, expose users to harmful radiation, and have very short energy transmission distances. [...] Read more.

Wireless charging systems are critical for safely and efficiently recharging mobile electronic devices. Current wireless charging technologies involving inductive coupling, magnetic resonance coupling, and microwave transmission are bulky, require complicated systems, expose users to harmful radiation, and have very short energy transmission distances. Herein, we report on a long-distance optical power transmission system by optimizing the external cavity structure of semiconductor lasers for laser charging applications. An ultra-long stable oscillating laser cavity with a transmission distance of 10 m is designed. The optimal laser cavity design is determined by simulating the structural parameters for stable operation, and an improved laser cavity that produces an output of 2.589 W at a transmission distance of 150 cm is fabricated. The peak power attenuation when the transmission distance increases from 50 to 150 cm is only approximately 6.4%, which proves that this wireless power transfer scheme based on a vertical external cavity surface-emitting laser can be used to realize ultra-long-distance power transmission. The proposed wireless energy transmission scheme based on a VECSEL laser is the first of its kind to report a 1.5 m transmission distance output power that exceeds 2.5 W. Compared with other wireless energy transmission technologies, this simple, compact, and safe long-distance wireless laser energy transmission system is more suitable for indoor charging applications. Full article

(This article belongs to the Special Issue Frontiers of Semiconductor Lasers)

► Show Figures

Figure 1

14 pages, 2315 KiB

Open AccessArticle

New Voltammetric Sensor Based on LDH and H₂O₂ for L-Proline Determination in Red and White Wines

by Mauro Tomassetti, Claudio Leonardi, Riccardo Pezzilli, Giuseppe Prestopino, Corrado Di Natale and Pier Gianni Medaglia

Crystals 2022, 12(10), 1474; https://doi.org/10.3390/cryst12101474 - 18 Oct 2022

Cited by 3 | Viewed by 1298

Abstract

Taking inspiration from our recent work in which a new sensor for hydrogen peroxide was proposed, our research group has now developed a simple, fast, and inexpensive voltametric system for determining proline concentration both in standard solutions and in real samples (red and [...] Read more.

Taking inspiration from our recent work in which a new sensor for hydrogen peroxide was proposed, our research group has now developed a simple, fast, and inexpensive voltametric system for determining proline concentration both in standard solutions and in real samples (red and white wines). This system uses a non-enzymatic sensor based on a working electrode of glassy carbon (GC) modified with a layered double hydroxide (LDH) compound, of the type GC-Ag_(paste)-LDH-H₂O₂, with hydrogen peroxide in solution at fixed concentration, in a three electrode cyclic voltammetry setup. Using an increasing concentration of standard solutions of L-proline, the method shows a linearity range, in semilogarithmic coordinates, between 125 μmol L⁻¹ and 3200 μmol L⁻¹ of proline, with a limit of detection (LOD) value of 85.0 μmol L⁻¹ and a limit of quantitation (LOQ) value of 95.0 μmol L⁻¹. The developed method is applied to the determination of proline in several samples of commercial Italian wines. The results are compared with those obtained by applying the classic spectrophotometric method of ninhydrin, obtaining a good correlation of the results. Full article

► Show Figures

Figure 1

12 pages, 3484 KiB

Open AccessArticle

New As-Rich Arsenato-Polyoxovanadate Clusters: Solvothermal Synthesis and Selected Properties of [V₆^IVAs₈^IIIO₂₆]⁴⁻ Cluster-Containing Compounds

by Maren Rasmussen, Christian Näther and Wolfgang Bensch

Crystals 2022, 12(10), 1473; https://doi.org/10.3390/cryst12101473 - 18 Oct 2022

Cited by 1 | Viewed by 1101

Abstract

Three new arsenato-polyoxovanadates with the composition [M(en)₃]₂[V₆As₈O₂₆] (M = Co²⁺ (I), Zn²⁺ (II), and Cd²⁺ (III)) were synthesized under solvothermal conditions in high yields, thus significantly enhancing the knowledge of [...] Read more.

Three new arsenato-polyoxovanadates with the composition [M(en)₃]₂[V₆As₈O₂₆] (M = Co²⁺ (I), Zn²⁺ (II), and Cd²⁺ (III)) were synthesized under solvothermal conditions in high yields, thus significantly enhancing the knowledge of As-rich polyoxovanadate cluster chemistry. The compounds are isostructural and feature the very rare [V₆^IVAs₈^IIIO₂₆]⁴⁻ cluster anion. The cluster shell is constructed by interconnection of two trimeric {V₃O₁₁} groups consisting of three edge-sharing VO₅ polyhedra and four As₂O₅ units, which are formed by two corner-sharing AsO₃ pyramids. While the As₂O₅ group is a common structural feature in arsenato-polyoxovanadates, the {V₃O₁₁} unit is only observed in V-rich high-nuclear heteroatom-containing polyoxovanadates {V₁₄E₈} (E = As, Sb, Ge). The complexes adopt the Λ (δδδ) conformation, which is the most stable arrangement. Interestingly, the unit cell parameters do not scale with the volume of the [M(en)₃]²⁺ complexes, assuming a constant volume of the anion. Only a very detailed Hirshfeld surface analysis revealed that the van der Waals volume of the {V₆As₈O₂₆} moiety is the smallest for the Cd-containing compound, while the volumes of the anions in the other two compounds are very similar. Therefore, the observed trends of the lattice parameters can be explained on the basis of these findings. Furthermore, intermolecular interactions include As⋯H contacts in addition to O⋯H and H⋯H interactions. The electronic spectrum of I contains d–d transitions of the vanadyl group and of the Co²⁺ cation. As expected only the d–d transitions of the VO²⁺ unit occur for II and III. Full article

(This article belongs to the Special Issue Mixed-Metal Coordination Polymers)

► Show Figures

Figure 1

15 pages, 5450 KiB

Open AccessArticle

First-Principles Investigation of Structural, Thermoelectric, and Optical Properties of Half-Heusler Compound ScRhTe under Varied Pressure

by Junhong Wei, Yongliang Guo and Guangtao Wang

Crystals 2022, 12(10), 1472; https://doi.org/10.3390/cryst12101472 - 17 Oct 2022

Cited by 3 | Viewed by 1251

Abstract

We thoroughly investigated the electronic structure and various properties of the half-Heusler compound ScRhTe using density functional theory calculations. The electronic structure shows that ScRhTe is a narrow-band-gap semiconductor. Owing to its characteristic conduction-band structure, ScRhTe has a higher Seebeck coefficient and a [...] Read more.

We thoroughly investigated the electronic structure and various properties of the half-Heusler compound ScRhTe using density functional theory calculations. The electronic structure shows that ScRhTe is a narrow-band-gap semiconductor. Owing to its characteristic conduction-band structure, ScRhTe has a higher Seebeck coefficient and a higher power factor for n-type doping than for p-type doping, with the maximum value of −493 µV K⁻¹ appearing at 900 K. The optimal carrier concentration is approximately 5 × 10¹⁹ cm⁻³–1 × 10²⁰ cm⁻³. In addition, ZT_e is estimated as 0.95 at a doping level of approximately 10¹⁹ cm⁻³. Under pressure, the band structure changes from a direct to an indirect band gap, and the band gap increases as the pressure changes from tensile to compressive. The thermoelectric properties of ScRhTe improve under compressive pressure, whereas the optical properties improve greatly under tensile pressure. By varying the pressure, the electronic structure and various properties of ScRhTe can be effectively adjusted, which signifies that ScRhTe has the potential to become an important optoelectronic or thermoelectric material. Full article

(This article belongs to the Special Issue Advanced Materials and Composites for Thermoelectric Applications)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Crystals, Volume 12, Issue 10 (October 2022) – 177 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI