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Crystals
Volume 14
Issue 8
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Crystals, Volume 14, Issue 8 (August 2024) – 76 articles

Cover Story (view full-size image): Metallic layers that are deposited on hot semiconductor surfaces can turn into nanometer-sized droplets. These droplets drill tiny holes in the semiconductor by etching. When these holes are filled, quantum dots are created, which are excellent quantum light emitters. In the study, the authors investigate the threshold of droplet formation and its dependencies. Critically, the density and shape of the holes change drastically around this threshold. This has a decisive influence on the optical properties of the quantum light emitters. View this paper
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10 pages, 3191 KiB  
Article
Magnetic Flux Concentration Technology Based on Soft Magnets and Superconductors
by Yue Wu, Liye Xiao, Siyuan Han and Jiamin Chen
Crystals 2024, 14(8), 747; https://doi.org/10.3390/cryst14080747 - 22 Aug 2024
Viewed by 599
Abstract
High-sensitivity magnetic sensors are fundamental components in fields such as biomedicine and non-destructive testing. Flux concentration technology enhances the sensitivity of magnetic sensors by amplifying the magnetic field to be measured, making it the most effective method to improve the magnetic field resolution [...] Read more.
High-sensitivity magnetic sensors are fundamental components in fields such as biomedicine and non-destructive testing. Flux concentration technology enhances the sensitivity of magnetic sensors by amplifying the magnetic field to be measured, making it the most effective method to improve the magnetic field resolution of magnetic sensors. Superconductors and high-permeability soft magnetic materials exhibit completely different magnetic effects. The former possesses complete diamagnetism, while the latter has extremely high magnetic permeability. Both types of materials can be used to fabricate flux concentrators. This paper compares superconducting and soft magnetic flux concentration technologies through theoretical simulations and experiments, investigating the impact of different structural parameters on the magnetic field amplification performance of superconducting and soft magnetic concentrators. This research is significant for the development of magnetic focusing technology and its applications in weak magnetic detection and other fields. Full article
(This article belongs to the Special Issue Superconductors and Magnetic Materials)
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10 pages, 2372 KiB  
Article
Influence of Ni Doping on Oxygen Vacancy-Induced Changes in Structural and Chemical Properties of CeO2 Nanorods
by Yuanzheng Zhu, Weixia Wang, Gejunxiang Chen, Huyi Li, Yuedie Zhang, Chang Liu, Hao Wang, Ping Cheng, Chunguang Chen and Gimyeong Seong
Crystals 2024, 14(8), 746; https://doi.org/10.3390/cryst14080746 - 22 Aug 2024
Viewed by 3659
Abstract
In recent years, cerium dioxide (CeO2) has attracted considerable attention owing to its remarkable performance in various applications, including photocatalysis, fuel cells, and catalysis. This study explores the effect of nickel (Ni) doping on the structural, thermal, and chemical properties of [...] Read more.
In recent years, cerium dioxide (CeO2) has attracted considerable attention owing to its remarkable performance in various applications, including photocatalysis, fuel cells, and catalysis. This study explores the effect of nickel (Ni) doping on the structural, thermal, and chemical properties of CeO2 nanorods, particularly focusing on oxygen vacancy-related phenomena. Utilizing X-ray powder diffraction (XRD), alterations in crystal structure and peak shifts were observed, indicating successful Ni doping and the formation of Ni2O3 at higher doping levels, likely due to non-equilibrium reactions. Thermal gravimetric analysis (TGA) revealed changes in oxygen release mechanisms, with increasing Ni doping resulting in the release of lattice oxygen at lower temperatures. Raman spectroscopy corroborated these findings by identifying characteristic peaks associated with oxygen vacancies, facilitating the assessment of Ni doping levels. Ni-doped CeO2 can catalyze the ultrasonic degradation of methylene blue, which has good application prospects for catalytic ultrasonic degradation of organic pollutants. Overall, this study underscores the substantial impact of Ni doping on CeO2 nanorods, shedding light on tailored catalytic applications through the modulation of oxygen vacancies while preserving the nanorod morphology. Full article
(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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12 pages, 3922 KiB  
Article
A New Type of Acidic OH-Groups in the LTL Zeolite
by Alessandro Contini, Martin Jendrlin and Vladimir Zholobenko
Crystals 2024, 14(8), 745; https://doi.org/10.3390/cryst14080745 - 21 Aug 2024
Viewed by 782
Abstract
Acidic properties of ion-exchanged LTL zeolites have been studied using FTIR spectroscopy, complemented by X-ray powder diffraction, SEM-EDX, XRF and N2 physisorption. Infrared spectra of the ion-exchanged zeolites show the presence of two intense bands of the bridging OH-groups: a narrow band [...] Read more.
Acidic properties of ion-exchanged LTL zeolites have been studied using FTIR spectroscopy, complemented by X-ray powder diffraction, SEM-EDX, XRF and N2 physisorption. Infrared spectra of the ion-exchanged zeolites show the presence of two intense bands of the bridging OH-groups: a narrow band at ~3640 cm−1 that is attributed to Si(OH)Al groups freely vibrating in 12 MR and a broad, intense band at ~3250 cm−1 that is assigned to bridging OH groups forming hydrogen bond with neighbouring oxygen atoms, e.g., in six-membered rings. The former can be selectively removed by caesium or rubidium cations with up to 3 Cs+ or Rb+ per unit cell readily ion-exchanged into the LTL zeolite, replacing an equivalent number of acidic OH-groups or K+ cations within the structure. The cation migration of the larger cation, evaluated by the Rietveld refinement method, occurs mostly via the main 12 MR channels. By contrast, less than 1 Li+ or Na+ cation per unit cell can be introduced under similar conditions. Accordingly, the concentration of Si(OH)Al groups in back-exchanged NH4-K-LTL with smaller cations (Li+, Na+) does not differ considerably from the concentration of Brønsted acid sites in the original NH4-K-LTL. Lower concentrations of acid sites have been detected in the samples back-exchanged with Cs+, Rb+ and K+. In addition, the acidic properties of NH4-LTL samples have been compared with a structurally related NH4-MAZ zeolite. Full article
(This article belongs to the Special Issue Feature Papers on "Hybrid and Composite Crystalline Materials" 2023–2024)
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17 pages, 4885 KiB  
Article
Effect of Phase Composition Variation of Oxy–Nitride Composite Ceramics on Heat Resistance and Preservation of Strength Parameters
by Daryn B. Borgekov, Serik B. Azambayev, Artem L. Kozlovskiy and Dmitriy I. Shlimas
Crystals 2024, 14(8), 744; https://doi.org/10.3390/cryst14080744 - 21 Aug 2024
Viewed by 464
Abstract
The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of [...] Read more.
The aim of this study is to determine the effect of changes in the phase composition of Al2O3–Si3N4 ceramics that were obtained using the method of mechanochemical solid-phase grinding on their resistance to the process of long-term thermal exposure, accompanied by the processes of oxidation and softening. The relevance of this research consists of determining the influence of the phase composition of ceramics on the change in their strength and thermophysical parameters, on the basis of which, we can draw a conclusion about the optimal composition of composite ceramics that have great prospects in the field of fire-resistant, heat-resistant, or radiation-resistant structural materials. During this study, the dynamics of the changes in the phase transformations of the xAl2O3–(1−x)Si3N4 ceramics, with variations in the ratio of the components, initiated by the thermal annealing of the samples, was established. According to the assessment of the phase transformations with variations in the ratio of the components, it was found that thermal annealing in an air environment at an Al2O3 concentration in the order of 0.3–0.5 M leads to the formation of an orthorhombic Al2(SiO4)O phase and an elevation in its contribution at concentrations above 0.5 M, which causes a rise in the thermophysical parameters and resistance to high-temperature degradation. During the heat resistance tests, it was found that the formation of the composite ceramics with the Si3N4(SiO2)/Al2(SiO4)O/Al2O3 phase composition results in an increase in the stability of their strength properties when exposed to thermally induced oxidation, which has a negative impact on their resistance to softening and a decrease in hardness. Moreover, the presence of the Al2(SiO4)O phase in the composition of the ceramics causes a slowdown in the processes of thermal oxidation of the Si3N4 phase under prolonged temperature exposure, alongside an increase in the degradation resistance of strength properties by more than 4–7 times, in comparison with the softening data established for single-component ceramics. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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22 pages, 4598 KiB  
Review
The Unusual Functional Role of Protein Flexibility in Photosynthetic Light Harvesting: Protein Dynamics Studied Using Neutron Scattering
by Maksym Golub and Jörg Pieper
Crystals 2024, 14(8), 743; https://doi.org/10.3390/cryst14080743 - 21 Aug 2024
Viewed by 808
Abstract
In addition to investigations of the three-dimensional protein structure, information on the dynamical properties of proteins is indispensable for an understanding of protein function in general. Correlations between protein dynamics and function are typically anticipated when both molecular mobility and function are concurrently [...] Read more.
In addition to investigations of the three-dimensional protein structure, information on the dynamical properties of proteins is indispensable for an understanding of protein function in general. Correlations between protein dynamics and function are typically anticipated when both molecular mobility and function are concurrently affected under specific temperatures or hydration conditions. In contrast, excitation energy transfer within the major photosynthetic light-harvesting complex II (LHC II) presents an atypical case, as it remains fully operational even at cryogenic temperatures, primarily depending on the interactions between electronic states and involving harmonic protein vibrations only. This review summarizes recent work on vibrational and conformational protein dynamics of LHC II and directly relates these findings to its light-harvesting function. In addition, we give a comprehensive introduction into the use of neutron spectroscopy and molecular dynamics simulations to investigate the protein dynamics of photosynthetic protein complexes in solution, which is information complementary to that obtained by protein crystallography. Full article
(This article belongs to the Section Biomolecular Crystals)
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28 pages, 2846 KiB  
Review
Investigating the Effect of Pore Size Distribution on the Sorption Types and the Adsorption-Deformation Characteristics of Porous Continua: The Case of Adsorption on Carbonaceous Materials
by Grigorios L. Kyriakopoulos, Konstantinos Tsimnadis, Ioannis Sebos and Yassine Charabi
Crystals 2024, 14(8), 742; https://doi.org/10.3390/cryst14080742 - 20 Aug 2024
Viewed by 876
Abstract
In the chemical industry and in the manufacturing sector, the adsorption properties of porous materials have been proven to be of great interest for the removal of impurities from liquid and gas media. While it is acknowledged that significant progress and literature production [...] Read more.
In the chemical industry and in the manufacturing sector, the adsorption properties of porous materials have been proven to be of great interest for the removal of impurities from liquid and gas media. While it is acknowledged that significant progress and literature production have been developed in this field, there have been adsorption studies that failed to further advance our knowledge in generating a better understanding of the prevailing sorption types and dominant adsorption processes. Therefore, this review study has focused on porous materials, their sorption types and their adsorption properties, further investigating the adsorption properties of porous materials at either solid–gas and solid–liquid interfaces, underscoring both the properties of the materials, the characterization and the correlation between the porosity and the adsorption capacity, as well as the emergent interactions between the adsorbent and adsorbate molecules, including the adsorption mechanisms, the types of sorption and the kinetic and thermodynamic information conveyed. Full article
(This article belongs to the Special Issue Porous Materials and Their Adsorption Properties)
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15 pages, 3327 KiB  
Article
A High–Throughput Molecular Dynamics Study for the Modeling of Cryogenic Solid Formation
by Simone Giusepponi, Francesco Buonocore, Massimo Celino, Andrea Iaboni, Antonio Frattolillo and Silvio Migliori
Crystals 2024, 14(8), 741; https://doi.org/10.3390/cryst14080741 - 20 Aug 2024
Viewed by 576
Abstract
To predict the favorable thermodynamical conditions and characterize cryogenic pellet formations for applications in nuclear fusion reactors, a high–throughput molecular dynamics study based on a unified framework to simulate the growth process of cryogenic solids (molecular deuterium, neon, argon) under gas pressure have [...] Read more.
To predict the favorable thermodynamical conditions and characterize cryogenic pellet formations for applications in nuclear fusion reactors, a high–throughput molecular dynamics study based on a unified framework to simulate the growth process of cryogenic solids (molecular deuterium, neon, argon) under gas pressure have been designed. These elements are used in fusion nuclear plants as fuel materials and to reduce the damage risks for the plasma-facing components in case of a plasma disruption. The unified framework is based on the use of workflows that permit management in HPC facilities, the submission of a massive number of molecular dynamics simulations, and handle huge amounts of data. This simplifies a variety of operations for the user, allowing for significant time savings and efficient organization of the generated data. This approach permits the use of large-scale parallel simulations on supercomputers to reproduce the solid–gas equilibrium curves of cryogenic solids like molecular deuterium, neon, and argon, and to analyze and characterize the reconstructed solid phase in terms of the separation between initial and reconstructed solid slabs, the smoothness of the free surfaces and type of the crystal structure. These properties represent good indicators for the quality of the final materials and provide effective indications regarding the optimal thermodynamical conditions of the growing process. Full article
(This article belongs to the Section Materials for Energy Applications)
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14 pages, 6611 KiB  
Article
A Relationship between Fracture Toughness Kc and Energy Release Rate Gc According to Fracture Morphology Analysis
by Haohao Liu, Jinlun Yan, Aofei Li, Zhenyu He, Yuchen Xie, Han Yan and Dawei Huang
Crystals 2024, 14(8), 740; https://doi.org/10.3390/cryst14080740 - 20 Aug 2024
Viewed by 737
Abstract
This study investigated the relationship between fracture toughness (Kc) and energy release rate (Gc) through fracture morphology analysis, emphasizing the critical role of fractal dimensions in accurately characterizing fracture surfaces. Traditional linear elastic fracture mechanics (LEFM) models relate Gc [...] Read more.
This study investigated the relationship between fracture toughness (Kc) and energy release rate (Gc) through fracture morphology analysis, emphasizing the critical role of fractal dimensions in accurately characterizing fracture surfaces. Traditional linear elastic fracture mechanics (LEFM) models relate Gc to Kc by combining energy principles with the nominal area of the fracture surface. However, real materials often exhibit plasticity, and their fracture surfaces are not regular planes. To address these issues, this research applied fractal theory and introduced the concept of ubiquitiform surface area to refine the calculation of fracture surfaces, leading to more accurate estimates of Gc and Kc. The method was validated through standard compact tensile specimen tests on a nickel-based superalloy at 550 °C. Additionally, the analysis of fractal dimension differences and dispersion in various fracture regions provides a novel perspective for evaluating the fracture toughness of materials. Full article
(This article belongs to the Special Issue Fatigue and Fracture of Anisotropic Materials)
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14 pages, 2477 KiB  
Article
Technology and Dielectric Properties of BLT4 Ceramics Modified with Special Glass
by Beata Wodecka-Dus, Jolanta Makowska, Tomasz Pikula, Rafał Panek, Małgorzata Adamczyk-Habrajska and Katarzyna Osińska
Crystals 2024, 14(8), 739; https://doi.org/10.3390/cryst14080739 - 20 Aug 2024
Viewed by 531
Abstract
Lead-boron special glass was doped into Ba0.996La0.004Ti0.999O3 (BLT4) ceramics in order to control the sintering process and grain growth, consequently obtaining materials with a well-developed microstructure. Changes in the microstructure resulted in a significant decrease in [...] Read more.
Lead-boron special glass was doped into Ba0.996La0.004Ti0.999O3 (BLT4) ceramics in order to control the sintering process and grain growth, consequently obtaining materials with a well-developed microstructure. Changes in the microstructure resulted in a significant decrease in electrical permittivity along with a substantial increase in its frequency dispersion. Glass-doped ceramics, similar to pure BLT4, are characterized by a first-order phase transition from the ferroelectric phase to the paraelectric phase. The temperature of this transition shifts slightly towards higher values with the increase in glass dopant concentration. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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3 pages, 171 KiB  
Editorial
Advances in Geopolymer Composites: From Synthesis to Sustainable Applications
by Shima Pilehvar and Luís G. Baltazar
Crystals 2024, 14(8), 738; https://doi.org/10.3390/cryst14080738 - 19 Aug 2024
Viewed by 1118
Abstract
The increasing demand for sustainable construction materials has brought significant attention to geopolymers as a viable alternative to traditional Portland cement [...] Full article
(This article belongs to the Special Issue Geopolymer Composites)
15 pages, 4885 KiB  
Article
Exploring the Premelting Transition through Molecular Simulations Powered by Neural Network Potentials
by Limin Zeng and Ang Gao
Crystals 2024, 14(8), 737; https://doi.org/10.3390/cryst14080737 - 19 Aug 2024
Viewed by 550
Abstract
The premelting layer on crystal surfaces significantly affects the stability, surface reactivity, and phase transition behaviors of crystals. Traditional methods for studying this layer—experimental techniques, classical simulations, and even first-principle simulations—have significant limitations in accuracy and scalability. To overcome these challenges, we employ [...] Read more.
The premelting layer on crystal surfaces significantly affects the stability, surface reactivity, and phase transition behaviors of crystals. Traditional methods for studying this layer—experimental techniques, classical simulations, and even first-principle simulations—have significant limitations in accuracy and scalability. To overcome these challenges, we employ molecular dynamic simulations based on neural network potentials to investigate the structural and dynamic behavior of the premelting layer on ice. This approach matches the accuracy of first-principle calculations while greatly improving computational efficiency, allowing us to simulate the ice–vapor interface on a much larger scale. In this study, we conducted a one-nanosecond simulation of the ice–vapor interface involving 1024 water molecules. This significantly exceeds the time and size scales of previous first-principle studies. Our simulation results indicate complete surface melting. Furthermore, our simulation results reveal dynamic heterogeneity within the premelting layer, with molecules segregated into clusters of low and high mobility. Full article
(This article belongs to the Section Crystal Engineering)
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12 pages, 3344 KiB  
Article
Effect of Ceria Doping on the Mechanical Properties and Phase Stability of Partially Samaria-Stabilized Zirconia Crystals
by Mikhail Borik, Artem Chislov, Alexej Kulebyakin, Elena Lomonova, Filipp Milovich, Valentina Myzina, Vladimir Pankratov, Alexandr Poselennov, Polina Ryabochkina, Natalia Sidorova, Nataliya Tabachkova, Denis Zakharov and Dmitry Kiselev
Crystals 2024, 14(8), 736; https://doi.org/10.3390/cryst14080736 - 19 Aug 2024
Viewed by 572
Abstract
The effect of ceria doping of (ZrO2)1−x(Sm2O3)x crystals on their phase composition, microhardness and fracture toughness was studied. The (ZrO2)0.995−x(Sm2O3)x(CeO2) [...] Read more.
The effect of ceria doping of (ZrO2)1−x(Sm2O3)x crystals on their phase composition, microhardness and fracture toughness was studied. The (ZrO2)0.995−x(Sm2O3)x(CeO2)0.005 crystals (where x = 0.032, 0.037 and 0.04) were grown using directional melt crystallization in a cold crucible. The mechanical properties, such as microhardness and fracture toughness, were explored using Vickers indentation. It was shown that the (ZrO2)0.995−x(Sm2O3)x(CeO2)0.005 solid-solution crystals contained both Ce4+ and Ce3+ ions. Phase analysis data suggested that CeO2 doping increased the tetragonality degree of the transformable t phase and reduced the tetragonality degree of the non-transformable t’ phase as compared to the (ZrO2)1−x(Sm2O3)x crystals. As a result, the t→m phase transition triggered by the indentation-induced stress in the CeO2-doped crystals was more intense and covered greater regions. CeO2 doping of the solid solutions increased the fracture toughness of all the crystals studied, whereas the microhardness of the crystals changed only slightly. CeO2 doping of the (ZrO2)1−x(Sm2O3)x solid solutions in the experimental concentration range did not improve the high-temperature phase stability of the crystals and did not prevent high-temperature degradation of their fracture toughness. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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14 pages, 72398 KiB  
Article
Development of Reconfigurable High-Frequency Devices Using Liquid Crystal in Substrate-Integrated Gap Waveguide Technology
by Aleksandr Andreyevich Voronov, Carmen Bachiller, Belén Villacampa and Vicente E. Boria
Crystals 2024, 14(8), 735; https://doi.org/10.3390/cryst14080735 - 19 Aug 2024
Viewed by 3551
Abstract
This article presents the theoretical study, numerical simulation and fabrication of a phase shifter and a stub resonator for use in microstrip ridge gap waveguide (MRGW) technology, using a liquid crystal (LC) in the substrate as a reconfigurable material. The phase shifter and [...] Read more.
This article presents the theoretical study, numerical simulation and fabrication of a phase shifter and a stub resonator for use in microstrip ridge gap waveguide (MRGW) technology, using a liquid crystal (LC) in the substrate as a reconfigurable material. The phase shifter and the stub resonator are filled with LC, and thanks to the LC’s dielectric anisotropy properties, the phase shift and the resonance response can be easily controlled using an external electric or magnetic bias field. The phase shifter was designed to operate in the range of 10 to 20 GHz, and the resonator was designed to operate in the range of 7.8 to 8.8 GHz. The phase shifter’s responses (including both phase shift and insertion losses), associated with both the parallel and perpendicular permittivity values of the LC, were computed and measured, and then the corresponding figure of merit (FoM) was extracted. The resonator’s frequency responses, associated with both the LC’s parallel and perpendicular permittivity, were computed. The resonator’s frequency responses, which provided different polarization voltages, were measured and compared to the simulation results. All technological issues related to both prototypes are also discussed here. The good agreement between the simulation and measurement results confirm this technology as a viable approach to the practical implementation of these microwave reconfigurable devices. Full article
(This article belongs to the Special Issue Synthesis of Liquid Crystals and Cellulose Derivatives Liquid Crystalline Phases: Recent Advances)
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14 pages, 4227 KiB  
Article
Boosted Electrochemical Activity with SnO2 Nanostructures Anchored on α-Fe2O3 for Improved Charge Transfer and Current Density
by Itheereddi Neelakanta Reddy, Bhargav Akkinepally, Jaesool Shim and Cheolho Bai
Crystals 2024, 14(8), 734; https://doi.org/10.3390/cryst14080734 - 18 Aug 2024
Viewed by 693
Abstract
This study presents a straightforward and cost-effective method to enhance the photoelectrochemical (PEC) water-splitting performance of α-Fe2O3 (F), SnO2 (S), and α-Fe2O3 decorated with SnO2 quantum dots (FS) photoanodes in a NaOH electrolyte. The FS [...] Read more.
This study presents a straightforward and cost-effective method to enhance the photoelectrochemical (PEC) water-splitting performance of α-Fe2O3 (F), SnO2 (S), and α-Fe2O3 decorated with SnO2 quantum dots (FS) photoanodes in a NaOH electrolyte. The FS electrode demonstrated a notable improvement in PEC efficiency within the electrolyte. In particular, the generated charges of the FS anode in the NaOH electrolyte reached approximately 12.01 mA cm−2 under illumination, indicating that the developed heterostructures effectively enhanced kinetics, leading to improved separation of induced carrier pairs. This active carrier-pair separation mechanism contributed considerably to the increased PEC activity in the 0.1 M NaOH electrolyte. The reduction in the bandgap of FS increased its absorption capability in visible light, which further enhanced the current density. Furthermore, the reduction in electrolyte resistance (9.71 Ω), internal resistance (20.19 Ω), charge transfer resistance (3.21 kΩ), Tafel slope (45.5 mV dec-1), limiting current density (−2.09 mA cm−2), and exchange current density (−3.68 mA cm−2) under illumination at the interface enhanced the charge density of FS. Further, a strong interaction among photoanode nanostructures significantly enhances PEC activity by improving efficient charge separation and transport, reducing recombination rates, and enabling quicker movement of charge carriers to the electrode/electrolyte interface. Thus, this study provides an effective approach to increasing the PEC activity of heterostructures. Full article
(This article belongs to the Special Issue Hybrid Materials for Energy Storage and Conversion)
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20 pages, 7589 KiB  
Article
Recurrent Supramolecular Patterns in a Series of Salts of Heterocyclic Polyamines and Heterocyclic Dicarboxylic Acids: Synthesis, Single-Crystal X-ray Structure, Hirshfeld Surface Analysis, Energy Framework, and Quantum Chemical Calculations
by Joanna Bojarska, Krzysztof Łyczko, Martin Breza and Adam Mieczkowski
Crystals 2024, 14(8), 733; https://doi.org/10.3390/cryst14080733 - 17 Aug 2024
Cited by 1 | Viewed by 810
Abstract
A series of novel salts based on aromatic polyamines and 2,3-pyrazinedicarboxylic acid, such as C10H12N6O5 (1), C10H9ClN6O4 (2), C11H10N8O [...] Read more.
A series of novel salts based on aromatic polyamines and 2,3-pyrazinedicarboxylic acid, such as C10H12N6O5 (1), C10H9ClN6O4 (2), C11H10N8O4 (3), and C14H17N16O5.5 (4) or 3,4-thiophenedicarboxylic acid, such as C10H10N4O4S (5), C10H9ClN4O4S (6), and C10H10N4O4S2 (7), were synthesized and characterized by single-crystal X-ray diffraction. All compounds crystallize in a monoclinic space group. The structure was subjected to complex Hirshfeld surface analysis, molecular electrostatic potential, enrichment ratio, and energy framework calculations. The influence of different cations on the packing of 3-carboxypyrazine-2-carboxylate and 4-carboxythiophene-3-carboxylate anions in the crystal lattice was studied. O…H/H…O interactions are the main contributor in all crystals. In addition, in a series of pyrazine-containing structures, N(C)…H/H…N(C) interactions have relevance, while in a series of thiophene-based compounds, C…H/H…C and S…H(O)/H(O)…S. In addition, Cl-based interactions are observed in compound 2. According to the enrichment ratio calculations, O…H/H…O and C…C are the most preferable interactions in all structures. The energy frameworks are dominated by the dispersive contribution, only in compound 3 is the electrostatic term dominant. The analyzed structures reveal intra- and intermolecular recurrent supramolecular synthons. In both series of crystals, the robust H-bonded centrosymmetric dimer R22(8) as homo- or as heterosynthon (in compounds 2, 3, 6, and 7) and the intramolecular synthon S(7) generated by O-H…O interactions (in compounds 2, 6, and 7) are present. The supramolecular patterns formed by π…π (C…C) and C-O(Cl,S)…C are also noticeable. Notably, a dual synthon linking the supramolecular chain via π…π interactions and the homosynthon R22(8) via N-H…N interactions is visible in both series of new salts. A library of H-bonding motifs at diverse levels of supramolecular architecture is provided. We extended the analysis of intramolecular H-bonding motifs to similar structures deposited in the Cambridge Structural Database. Another important feature is the existence of an intramolecular O…H…O bridge between two neighboring carboxylic groups as substituents in anions in compounds 3 and 5. In this context, we performed quantum theory of atoms-in-molecule calculations to reveal more details. Full article
(This article belongs to the Special Issue Heterocyclic Organic Compounds: Crystal Structure and Their Properties)
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10 pages, 2705 KiB  
Article
High Energy Storage Performance in Pb1−xLax(Hf0.45Sn0.55)0.995O3 Antiferroelectric Ceramics
by Erping Wang, Liqin Yue, Yuanhong Chu, Caixia Sun, Jinyu Zhao, Siyu Zhang, Jiale Liu, Yangyang Zhang and Ling Zhang
Crystals 2024, 14(8), 732; https://doi.org/10.3390/cryst14080732 - 17 Aug 2024
Viewed by 492
Abstract
Energy storage efficiency (η) and large recoverable energy density (Wre) are necessary for antiferroelectric materials in order to develop antiferroelectric-based dielectric capacitors with exceptional energy storage capacity. In the present paper, the effect of doping La3+ on [...] Read more.
Energy storage efficiency (η) and large recoverable energy density (Wre) are necessary for antiferroelectric materials in order to develop antiferroelectric-based dielectric capacitors with exceptional energy storage capacity. In the present paper, the effect of doping La3+ on the energy storage capacity of Pb1−xLax(Hf0.45Sn0.55)0.995O3 antiferroelectric ceramics was studied. Adjusting the content of La and changing the phase structure of PLHS from antiferroelectric to relaxor ferroelectric gradually, which narrowed its hysteresis loop, yielded a high energy storage efficiency of 81.9% and the maximum breakdown field strength of 200 kV/cm when x = 2 mol%. In addition, the recoverable energy density and energy storage efficiency both showed excellent temperature stability and frequency stability in the temperature range of 10–110 °C and the frequency range of 10–100 Hz, suggesting that Pb0.98La0.02(Hf0.45Sn0.55)0.995O3 are favorable materials candidates for the preparation of pulsed-power capacitors that can be used in a wide range of conditions. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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11 pages, 3392 KiB  
Article
First Examples of Metal-Organic Frameworks with Pore-Encapsulated [Co(CO)4]− Anions: Facile Synthesis, Crystal Structures and Stability Studies
by Caihong Xiao and Shaowu Du
Crystals 2024, 14(8), 731; https://doi.org/10.3390/cryst14080731 - 17 Aug 2024
Viewed by 706
Abstract
Three ionic metal-organic frameworks (MOFs) with pore-capsulated Co(CO)4− anions, formulated as [Co(bix)3][Co(CO)4]2 (1), [Co(bibp)3][Co(CO)4]2 (2), and [Co(bmibp)2][Co(CO)4]2 (3); (bix = [...] Read more.
Three ionic metal-organic frameworks (MOFs) with pore-capsulated Co(CO)4− anions, formulated as [Co(bix)3][Co(CO)4]2 (1), [Co(bibp)3][Co(CO)4]2 (2), and [Co(bmibp)2][Co(CO)4]2 (3); (bix = 1,4-bis(imidazol-1-yl-methyl)-benzene); bibp = 4,4′-bis(imidazolyl)biphenyl); bmibp = 4,4′-bis(2-methyl-imidazolyl)biphenyl), have been facilely synthesized for the first time through direct reactions of Co2(CO)8 with the respective bis(imidazole) ligands under mild hydro(solvo)thermal conditions. Single-crystal X-ray diffraction analysis reveals distinct structural motifs among the frameworks: MOF 1 exhibits a single pcu net, MOF 2 features a 3-fold interpenetrating pcu net, both based on 6-connected Co2+ centers and ditopic bix or bibp ligands, while MOF 3 forms a 2-fold interpenetrating sql layer constructed by 4-connected Co2+ ions and bmibp linkers. The [Co(CO)4]− anions reside within the channels of the cationic frameworks. Moreover, these MOFs, characterized by periodically ordered tetracarbonylcobaltate arrays, demonstrate notable thermal stability and maintain structural integrity in air, water, and alkaline solutions for several days. Full article
(This article belongs to the Section Organic Crystalline Materials)
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13 pages, 3503 KiB  
Article
The Thermal Stability and Photoluminescence of ZnSeO3 Nanocrystals Chemically Synthesized into SiO2/Si Track Templates
by Gulnara Aralbayeva, Gulnaz Sarsekhan, Aiman Akylbekova, Liudmila A. Vlasukova, Zein Baimukhanov, Vera Yuvchenko, Assyl-Dastan Bazarbek, Alma Dauletbekova, Gaukhar Kabdrakhimova and Abdirash T. Akilbekov
Crystals 2024, 14(8), 730; https://doi.org/10.3390/cryst14080730 - 17 Aug 2024
Viewed by 620
Abstract
We report the effect of high-temperature treatment on the structure and photoluminescence of zinc selenite nanocrystals (ZnSeO3) deposited into SiO2/Si track templates. The templates were formed via irradiation with Xe ions (200 MeV, 108 ions/cm2) followed [...] Read more.
We report the effect of high-temperature treatment on the structure and photoluminescence of zinc selenite nanocrystals (ZnSeO3) deposited into SiO2/Si track templates. The templates were formed via irradiation with Xe ions (200 MeV, 108 ions/cm2) followed by etching in HF solution. ZnSeO3 nanocrystals were obtained via chemical deposition from the aqueous solution of ZnCl2 and SeO2 as Zn-, Se- and O-precursors. To estimate the thermal stability of the deposited precipitates, heat treatment was carried out at 800 and 1000 °C for 60 min in a vacuum environment. Scanning electron microscopy (SEM), X-ray diffractometry (XRD), photoluminescence (PL) spectroscopy, and electrical measurements were used for the characterization of ZnSeO3/SiO2nanoporous/Si nanocomposites. Thermal treatment of the synthesized nanocomposites resulted in structural transformations with the formation of ZnSe and ZnO phases while the content of the ZnSeO3 phase decreased. For the as-deposited and annealed precipitates, an emission in the range of (400 to 600) nm was observed. PL spectra were approximated by four Gaussian curves with maxima at ~550 nm (2.2 eV), 488 nm (2.54 eV), ~440 nm (2.82 eV), and 410 nm (3.03 eV). Annealing resulted in a decrease in PL intensity that was possibly due to the weight loss of the deposited substance during high-temperature treatment. The redistribution of maxima intensities after annealing was also observed with an increase in blue and violet emissions. The origin of the observed PL is discussed. The I–V curve analysis revealed an electronic type of conductivity for the ZnSeO3(NCs)/SiO2nanoporous/Si structure. The values of the specific conductivity were calculated within the percolation model. The sample annealed at 800 °C showed the highest specific conductivity of 8.5 × 10−6 Ohm−1·cm−1. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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11 pages, 5426 KiB  
Article
Simulation Analysis of Three-Point Bending Fracture Process of Yellow River Ice
by Yu Deng, Juan Wang, Yuhan Meng and Yong Zhu
Crystals 2024, 14(8), 729; https://doi.org/10.3390/cryst14080729 - 17 Aug 2024
Viewed by 545
Abstract
During the ice flood period of the Yellow River, the fracture and destruction of river ice can easily lead to the formation of ice jams and ice dams in the curved and narrow reaches. However, the occurrence and development mechanism of river ice [...] Read more.
During the ice flood period of the Yellow River, the fracture and destruction of river ice can easily lead to the formation of ice jams and ice dams in the curved and narrow reaches. However, the occurrence and development mechanism of river ice fracture remain incompletely understood in the Yellow River. Therefore, based on the three-point bending physical test of the Yellow River ice, a three-point bending fracture numerical model of the Yellow River ice was constructed. The fracture failure process of the Yellow River ice under three-point bending was simulated, and the effects of the crack-to-height ratio and ice grain size on the fracture properties of the river ice were analyzed. By comparing the results with those of physical tests on river ice, it is evident that the fracture model can effectively simulate the cracking process of river ice. Within the confines of the simulated sample size spectrum, as the crack-to-height ratio varies from 0.2 to 0.8, the fracture toughness value of the Yellow River ice spans a range from 115.01 to 143.37 KPa·m1/2. Correspondingly, within the simulated calculation values ranging from 5.38 mm to 24.07 mm for ice crystal size, the fracture toughness value of the Yellow River ice exhibits a range from 116.89 to 143.37 KPa·m1/2. The findings reveal that an increase in the crack-to-depth ratio leads to a decrement in the fracture toughness of river ice. Within the scale range encompassed by the model calculations, as the average size of the ice crystal grains augments, the fracture toughness of the river ice exhibits a gradual ascending trend. The research results provide a parameter basis for studying the fracture performance of the Yellow River ice using a numerical simulation method and lays a foundation for investigating the cracking process of river ice from macro and micro multi-scales. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials)
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9 pages, 2526 KiB  
Article
Enhanced Thermoelectric Transport Properties of Electronegative-Element-Filled and (Ni, Te) Co-Doped Skutterudites through S Filling
by Boyu Wang and Zhiyuan Jiang
Crystals 2024, 14(8), 728; https://doi.org/10.3390/cryst14080728 - 16 Aug 2024
Viewed by 440
Abstract
Recently, there has been a growing interest in skutterudite (SKD) compounds containing electronegative elements such as Br, Cl, S, Se, and Te, owing to their increased diversity and the versatility of filler atoms. This study focused on the thermoelectric performance of a series [...] Read more.
Recently, there has been a growing interest in skutterudite (SKD) compounds containing electronegative elements such as Br, Cl, S, Se, and Te, owing to their increased diversity and the versatility of filler atoms. This study focused on the thermoelectric performance of a series of (Ni, Te) co-doped SKDs filled with the electronegative element S, denoted as SxNi0.4Co3.6Sb11.2Te0.8 (x = 0, 0.1, 0.2, and 0.3). These compounds were prepared using a combination of a solid-state reaction and spark plasma sintering techniques. The results showed that (Ni, Te) co-doping introduced excess electrons in the SKD lattice, while the incorporation of the element S into the SKD voids optimized carrier concentration. This led to a considerable increase in the absolute Seebeck coefficient to 110.6 μV K−1 at ambient temperatures. The presence of S fillers induced phonon resonance scattering and point scattering, which reduced lattice thermal conductivity and ultimately improved the thermoelectric figure of merit zT, which reached 0.93 for S0.3Ni0.4Co3.6Sb11.2Te0.8 at 823 K. Full article
(This article belongs to the Section Polycrystalline Ceramics)
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37 pages, 14896 KiB  
Review
Microstructural and Textural Evolution in Hexagonal Close-Packed Metals: The Case of Zirconium, Magnesium, and Titanium
by Khushahal Thool, K. U. Yazar, V. Kavimani, Aman Gupta and Shi-Hoon Choi
Crystals 2024, 14(8), 727; https://doi.org/10.3390/cryst14080727 - 16 Aug 2024
Viewed by 1242
Abstract
Hexagonal close-packed (HCP) metals, particularly Zirconium (Zr), Titanium (Ti), and Magnesium (Mg) alloys, have attracted significant attention due to their unique properties and wide-ranging applications in the aerospace, biomedical, and energy industries. This review paper provides a comprehensive analysis of the microstructural and [...] Read more.
Hexagonal close-packed (HCP) metals, particularly Zirconium (Zr), Titanium (Ti), and Magnesium (Mg) alloys, have attracted significant attention due to their unique properties and wide-ranging applications in the aerospace, biomedical, and energy industries. This review paper provides a comprehensive analysis of the microstructural and textural evolution in these HCP materials under various conditions, including rolling, extrusion, drawing, and annealing. The focus of the present work lies on the deformed microstructure and texture development in HCP metals, thus elucidating the fundamental mechanisms that govern their response to mechanical stress. The interaction between dislocation movements, twinning, and slip systems is discussed in detail, illustrating how these factors contribute to the anisotropic behavior characteristic of low-symmetry HCP structures. Unlike high-symmetry metals, deformation in Zr alloys depends on the activation of various slips and twin deformation modes, which are sensitive to crystallographic orientation and strain. Like Zr, Ti alloys present a more complex deformation behavior, heavily influenced by their crystallographic orientation. The most common deformation textures in Ti alloys include split-transverse direction (split-TD), split-rolling direction (split-RD), and normal direction (ND) symmetric basal fiber textures. These textures emerge due to the activation of multiple slip systems and twinning, which are dependent on external factors such as temperature, strain rate, and alloy composition. For Mg alloys, the poor formability and brittleness associated with the dominance of the basal slip system under ambient conditions is a critical material development challenge. The activation of non-basal slip systems introduces complexities in controlling texture and microstructure. However, their activation is crucial for optimizing mechanical properties such as strength and fatigue resistance. The tendency for twinning in Mg alloys further complicates their deformation behavior, leading to challenges in ensuring uniform mechanical performance. Modifying the alloy composition, grain size, and texture can additionally influence the activation of these deformation mechanisms. This review further explores the roles of dynamic recrystallization and grain growth in tailoring mechanical properties, with a particular focus on microstructure and texture evolution during annealing. Through this detailed review, we aim to present a thorough understanding of the microstructural and textural evolution in HCP materials, thereby guiding future research and industrial applications. Full article
(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials)
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35 pages, 1599 KiB  
Review
Recent Advances in Laser Surface Hardening: Techniques, Modeling Approaches, and Industrial Applications
by Łukasz Łach
Crystals 2024, 14(8), 726; https://doi.org/10.3390/cryst14080726 - 15 Aug 2024
Cited by 2 | Viewed by 2259
Abstract
The article provides a comprehensive review of the latest developments in the field of laser surface hardening (LSH) and its modeling techniques. LSH is a crucial process for enhancing the surface properties of metals, particularly their hardness and wear resistance, without compromising their [...] Read more.
The article provides a comprehensive review of the latest developments in the field of laser surface hardening (LSH) and its modeling techniques. LSH is a crucial process for enhancing the surface properties of metals, particularly their hardness and wear resistance, without compromising their bulk properties. This review highlights the fundamental principles of LSH, the types of lasers used, and the key parameters influencing the hardening process. It delves into various modeling approaches, including finite element method (FEM) simulations, analytical models, and empirical models (using statistical methods), emphasizing the integration of advanced computational techniques such as machine learning and artificial intelligence to improve the accuracy and efficiency of LSH simulations. The review also explores practical applications across different industries, showcasing how LSH models have been used to solve real-world challenges in the automotive, aerospace, and tool manufacturing sectors. Finally, it addresses current limitations and outlines future research directions, suggesting potential areas for further advancements in the modeling and application of LSH processes. Full article
(This article belongs to the Special Issue Laser Surface Modification of Materials)
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16 pages, 4292 KiB  
Article
Recovery of Zinc and Rhenium for the Production of Zinc Perrhenates
by Katarzyna Leszczyńska-Sejda, Joanna Malarz, Dorota Kopyto, Karolina Goc, Alicja Grzybek, Mateusz Ciszewski, Arkadiusz Palmowski, Grzegorz Benke and Karolina Pianowska
Crystals 2024, 14(8), 725; https://doi.org/10.3390/cryst14080725 - 14 Aug 2024
Viewed by 644
Abstract
This study outlines findings from an investigation into the development of a hydrometallurgical process for manufacturing various forms of zinc perrhenate, entirely from waste from recycling and from the Zn–Pb industry. Scraps of Re-bearing Ni-based superalloys and acidic waste, circulating zinc solutions generated [...] Read more.
This study outlines findings from an investigation into the development of a hydrometallurgical process for manufacturing various forms of zinc perrhenate, entirely from waste from recycling and from the Zn–Pb industry. Scraps of Re-bearing Ni-based superalloys and acidic waste, circulating zinc solutions generated during the production of Zn by the electrolytic method and which contain >45 g/dm3 of Zn, Na, Mn, and Mg, were used in the research. In the publication, the conditions for the production of three types of zinc perrhenate, i.e., Zn(ReO4)2·4H2O, Zn(ReO4)2, and Zn(ReO4)2·2H2O, are presented. As a result of the analysis of the obtained results, it was concluded that to obtain the above-mentioned forms of zinc perrhenate, zinc carbonate can be used, precipitated from acidic, waste, and multi-component solutions after their prior neutralization to pH 4.0 and partial purification from Mn, Mg, and Na using metallurgical zinc oxide. Zinc carbonate should be precipitated using Na2CO3 at pH 6.3 and subsequently purified from other impurities, i.e., Mg, Na, and Mn, using aqueous ammonia solutions. As a result, zinc carbonate was obtained, which was used in a reaction with an aqueous solution of HReO4 to produce zinc perrhenate. The precipitated forms of Zn(ReO4)2 were obtained by appropriately drying the crude and hydrated Zn(ReO4)2 to obtain its tetrahydrate, dihydrate, and anhydrous forms, respectively, using drying temperatures of 55, 135, and 185 °C. The developed technology has been submitted for a patent and is an example of a technology founded on the principles of sustainable development, with a particular emphasis on the minimalization of loss of rhenium and zinc at all stages of its realization. Full article
(This article belongs to the Topic Advances in Inorganic Synthesis)
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12 pages, 5019 KiB  
Article
High-Quality Single-Step Growth of GaAs on C-Plane Sapphire by Molecular Beam
by Emmanuel Wangila, Calbi Gunder, Mohammad Zamani-Alavijeh, Fernando Maia de Oliveira, Serhii Kryvyi, Aida Sheibani, Yuriy I. Mazur, Shui-Qing Yu and Gregory J. Salamo
Crystals 2024, 14(8), 724; https://doi.org/10.3390/cryst14080724 - 14 Aug 2024
Viewed by 823
Abstract
We report on the growth of high-quality GaAs semiconductor materials on an AlAs/sapphire substrate by molecular beam epitaxy. The growth of GaAs on sapphire centers on a new single-step growth technique that produces higher-quality material than a previously reported multi-step growth method. Omega-2theta [...] Read more.
We report on the growth of high-quality GaAs semiconductor materials on an AlAs/sapphire substrate by molecular beam epitaxy. The growth of GaAs on sapphire centers on a new single-step growth technique that produces higher-quality material than a previously reported multi-step growth method. Omega-2theta scans confirmed the GaAs (111) orientation. Samples grown at 700 °C displayed the highest crystal quality with minimal defects and strain, evidenced by narrow FWHM values of the rocking curve. By varying the As/Ga flux ratio and the growth temperature, we significantly improved the quality of the GaAs layer on sapphire, as compared to that obtained in multi-step studies. Photoluminescence measurements at room temperature and 77 K further support these findings. This study underscores the critical role of the As/Ga flux ratio and growth temperature in optimizing GaAs epitaxial growth on sapphire. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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17 pages, 4121 KiB  
Article
Plasma-Enhanced Atomic Layer Deposition of Hematite for Photoelectrochemical Water Splitting Applications
by Thom R. Harris-Lee, Andrew Brookes, Jie Zhang, Cameron L. Bentley, Frank Marken and Andrew L. Johnson
Crystals 2024, 14(8), 723; https://doi.org/10.3390/cryst14080723 - 13 Aug 2024
Viewed by 985
Abstract
Hematite (α-Fe2O3) is one of the most promising and widely used semiconductors for application in photoelectrochemical (PEC) water splitting, owing to its moderate bandgap in the visible spectrum and earth abundance. However, α-Fe2O3 is limited by [...] Read more.
Hematite (α-Fe2O3) is one of the most promising and widely used semiconductors for application in photoelectrochemical (PEC) water splitting, owing to its moderate bandgap in the visible spectrum and earth abundance. However, α-Fe2O3 is limited by short hole-diffusion lengths. Ultrathin α-Fe2O3 films are often used to limit the distance required for hole transport, therefore mitigating the impact of this property. The development of highly controllable and scalable ultrathin film deposition techniques is therefore crucial to the application of α-Fe2O3. Here, a plasma-enhanced atomic layer deposition (PEALD) process for the deposition of homogenous, conformal, and thickness-controlled α-Fe2O3 thin films (<100 nm) is developed. A readily available iron precursor, dimethyl(aminomethyl)ferrocene, was used in tandem with an O2 plasma co-reactant at relatively low reactor temperatures, ranging from 200 to 300 °C. Optimisation of deposition protocols was performed using the thin film growth per cycle and the duration of each cycle as optimisation metrics. Linear growth rates (constant growth per cycle) were measured for the optimised protocol, even at high cycle counts (up to 1200), confirming that all deposition is ‘true’ atomic layer deposition (ALD). Photoelectrochemical water splitting performance was measured under solar simulated irradiation for pristine α-Fe2O3 deposited onto FTO, and with a α-Fe2O3-coated TiO2 nanorod photoanode. Full article
(This article belongs to the Special Issue Advances in Synthesis, Characterization, and Application of Thin Films)
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10 pages, 2005 KiB  
Article
A Novel Insensitive Cocrystal Explosive Composed of BTF and the Non-Energetic 2-Nitroaniline
by Sijia Du, Yunshu Zhao, Yapeng Ou, Zijie Bi, Shanhu Sun and Tao Yan
Crystals 2024, 14(8), 722; https://doi.org/10.3390/cryst14080722 - 13 Aug 2024
Viewed by 645
Abstract
Benzotrifuroxan (BTF) is a powerful energetic material (EM) with high density that can be used both as a primary and a secondary explosive. However, high mechanical sensitivity limits its application prospects. To actualize its potential, cocrystallization was introduced into BTF-based EMs for insensitivity [...] Read more.
Benzotrifuroxan (BTF) is a powerful energetic material (EM) with high density that can be used both as a primary and a secondary explosive. However, high mechanical sensitivity limits its application prospects. To actualize its potential, cocrystallization was introduced into BTF-based EMs for insensitivity improvement in the current work. A novel cocrystal explosive composed of BTF and a non-energetic molecule (2-Nitroaniline (ONA)) was prepared with a molar ratio of 1:1. The possible mechanism of cocrystal formation was studied by the analysis and characterization of its crystal structure, and the crystal structure, thermal decomposition, and energetic properties were investigated. The results indicate that the formation of the BTF/ONA cocrystal is mainly attributed to the strong interactions of the hydrogen bonds formed between the hydrogen on the amino group in the ONA molecule and the oxygen and nitrogen atoms in BTF. The impact sensitivity of BTF/ONA is obviously reduced, with the drop height of 50% explosion probability (H50) increasing from 56.0 to 90.0 cm. The calculated detonation velocity and detonation pressure of the BTF/ONA cocrystal are 7115.26 m/s and 20.51 GPa, respectively. The decomposition peak temperature of the BTF/ONA cocrystal (191.1 °C) decreases by about 90.9 °C compared to BTF (282.0 °C). This suggests that cocrystallization could effectively reduce its impact sensitivity and produce an explosive with excellent comprehensive properties. Full article
(This article belongs to the Special Issue Co-Crystals and Polymorphic Transition in Energetic Materials)
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11 pages, 3160 KiB  
Article
Ferroelectric and Structural Properties of Cobalt-Doped Lead Ferrite Thin Films Formed by Reactive Magnetron Sputtering
by Benas Beklešovas, Vytautas Stankus, Aleksandras Iljinas and Liutauras Marcinauskas
Crystals 2024, 14(8), 721; https://doi.org/10.3390/cryst14080721 - 12 Aug 2024
Viewed by 556
Abstract
Cobalt-doped lead ferrite (Pb2Fe2O5) thin films were deposited by reactive magnetron sputtering. The influence of the cobalt concentration and synthesis temperature on the structure, phase composition and ferroelectric properties of Pb2Fe2O5 thin [...] Read more.
Cobalt-doped lead ferrite (Pb2Fe2O5) thin films were deposited by reactive magnetron sputtering. The influence of the cobalt concentration and synthesis temperature on the structure, phase composition and ferroelectric properties of Pb2Fe2O5 thin films was investigated. It was determined that the increase in deposition temperature increased the grain size and density of the Co-doped PFO thin films. The XRD data demonstrated that the Co-doped Pb2Fe2O5 thin films consisted of Pb2Fe2O5 and PbO phases with a low amount of CoO and Co3O4 phases. The increase in the cobalt concentration in the Pb2Fe2O5 films slightly enhanced the cobalt oxide phase content. Polarization dependence on electric field measurement demonstrated that the highest ferroelectric properties of the Co-doped Pb2Fe2O5 films were obtained when the synthesis was performed at 550 °C temperatures. The increase in the cobalt concentration in the films enhanced the remnant polarization and coercive field values. It was found that the Co-doped Pb2Fe2O5 film deposited at 550 °C temperature and containing 10% cobalt had the highest remnant polarization (72 µC/cm2) and coercive electric field (105 kV/cm). Full article
(This article belongs to the Special Issue Magnetoelectric Materials and Their Application)
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22 pages, 14183 KiB  
Article
Microwave Bow-Tie Diodes on Bases of 2D Semiconductor Structures
by Steponas Ašmontas, Maksimas Anbinderis, Aurimas Čerškus, Jonas Gradauskas, Andžej Lučun and Algirdas Sužiedėlis
Crystals 2024, 14(8), 720; https://doi.org/10.3390/cryst14080720 - 11 Aug 2024
Viewed by 517
Abstract
Planar microwave bow-tie diodes on bases of selectively doped semiconductor structures are successfully used in the detection and imaging of electromagnetic radiation in millimeter and submillimeter wavelength ranges. Although the signal formation mechanism in these high-frequency diodes is said to be based on [...] Read more.
Planar microwave bow-tie diodes on bases of selectively doped semiconductor structures are successfully used in the detection and imaging of electromagnetic radiation in millimeter and submillimeter wavelength ranges. Although the signal formation mechanism in these high-frequency diodes is said to be based on charge-carrier heating in a semiconductor in a strong electric field, the nature of the electrical signal across the bow-tie diodes is not yet properly identified. In this research paper, we present a comprehensive study of a series of various planar bow-tie diodes, starting with a simple asymmetrically shaped submicrometer-thick n-GaAs layer and finishing with bow-tie diodes based on selectively doped GaAs/AlGaAs structures of different electrical conductivity. The planar bow-tie diodes were fabricated on two different types of high-resistivity substrates: bulky semi-insulating GaAs substrate and elastic dielectric polyimide film of micrometer thickness. The microwave diodes were investigated using DC and high-frequency probe stations, which allowed us to examine a sufficient number of diodes and collect a large amount of data to perform a statistical analysis of the electrical parameters of these diodes. The use of probe stations made it possible to analyze the properties of the bow-tie diodes and clarify the nature of the detected voltage in the dark and under white-light illumination. The investigation revealed that the properties of various bow-tie diodes are largely determined by the energy states residing in semiconductor bulk, surface, and interfaces. It is most likely that these energy states are responsible for the slow relaxation processes observed in the studied bow-tie diodes. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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15 pages, 3529 KiB  
Article
Early Stages of Crack Nucleation Mechanism in Fe39Mn20Co20Cr15Si5Al1 High-Entropy Alloy during Stress Corrosion Cracking Phenomenon: Pit Initiation and Growth
by Pranshul Varshney and Nilesh Kumar
Crystals 2024, 14(8), 719; https://doi.org/10.3390/cryst14080719 - 11 Aug 2024
Viewed by 657
Abstract
This study investigated the susceptible sites for pit nucleation in a transformation-induced plasticity (TRIP) Fe39Mn20Co20Cr15Si5Al1 (at.%) high-entropy alloy (HEA) in 3.5 wt.% NaCl solution. The investigation involved a constant-load stress corrosion cracking [...] Read more.
This study investigated the susceptible sites for pit nucleation in a transformation-induced plasticity (TRIP) Fe39Mn20Co20Cr15Si5Al1 (at.%) high-entropy alloy (HEA) in 3.5 wt.% NaCl solution. The investigation involved a constant-load stress corrosion cracking (SCC) experiment. The SCC testing was interrupted at different pre-determined time intervals to characterize the specimen surface using a scanning electron microscope (SEM), electron backscattered diffraction (EBSD), and a three-dimensional optical stereomicroscope. The EBSD results revealed pit nucleation at the susceptible γ–ε interphase and ε–ε interlath/plate boundaries. The three-dimensional profile and SEM results indicated an increase in pit depth with no change in pit diameter on the surface of the specimen as the experiment progressed over time. This study highlights the importance of microstructural features and mechanical loading in the corrosion behavior of TRIP HEAs, providing insights into the mechanisms of pit nucleation and growth under aggressive environmental conditions. Full article
(This article belongs to the Special Issue Preparation and Applications of High-Entropy Materials)
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12 pages, 4922 KiB  
Article
Atomistic Simulation Studies of Na4SiO4
by Mallikage Shalani Shanika, Poobalasingam Abiman, Poobalasuntharam Iyngaran and Navaratnarajah Kuganathan
Crystals 2024, 14(8), 718; https://doi.org/10.3390/cryst14080718 - 10 Aug 2024
Viewed by 701
Abstract
Tetrasodium silicate (Na4SiO4) has emerged as a promising candidate for battery applications due to its favorable ionic transport properties. Atomic-scale simulations employing classical pair potentials have elucidated the defect mechanisms and ion migration dynamics in Na4SiO4 [...] Read more.
Tetrasodium silicate (Na4SiO4) has emerged as a promising candidate for battery applications due to its favorable ionic transport properties. Atomic-scale simulations employing classical pair potentials have elucidated the defect mechanisms and ion migration dynamics in Na4SiO4. The Na Frenkel defect, characterized by the creation of a Na vacancy and an interstitial Na⁺ ion, is identified as the most energetically favorable defect process, facilitating efficient vacancy-assisted Na⁺ ion migration. This process results in three-dimensional ion diffusion with a low activation energy of 0.55 eV, indicating rapid ion movement within the material. Among monovalent dopants (Li⁺, K⁺, and Rb⁺), K⁺ was found to be the most advantageous for substitution on the Na site. For trivalent doping, Al is the most favorable on the Si site, generating additional Na⁺ ions and potentially enhancing ionic conductivity. Ge was identified as a promising isovalent dopant for the Si site. These theoretical findings suggest that Na4SiO4 could offer high ionic conductivity and stability when optimized through appropriate doping. Experimental validation of these predictions could lead to the development of advanced battery materials with improved performance and durability. Full article
(This article belongs to the Section Materials for Energy Applications)
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