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Volume 14
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Crystals, Volume 14, Issue 6 (June 2024) – 50 articles

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17 pages, 1345 KiB  
Article
Evaluating the Effect of Hydrogen on the Tensile Properties of Cold-Finished Mild Steel
by Emmanuel Sey and Zoheir N. Farhat
Crystals 2024, 14(6), 529; https://doi.org/10.3390/cryst14060529 - 31 May 2024
Abstract
One of the major sources of catastrophic failures and deterioration of the mechanical properties of metals, such as ductility, toughness, and strength, in various engineering components during application is hydrogen embrittlement (HE). It occurs as a result of the adsorption, diffusion, and interaction [...] Read more.
One of the major sources of catastrophic failures and deterioration of the mechanical properties of metals, such as ductility, toughness, and strength, in various engineering components during application is hydrogen embrittlement (HE). It occurs as a result of the adsorption, diffusion, and interaction of hydrogen with various metal defects like dislocations, voids, grain boundaries, and oxide/matrix interfaces due to its small atomic size. Over the years, extensive effort has been dedicated to understanding hydrogen embrittlement sources, effects, and mechanisms. This study aimed at assessing the tensile properties, toughness, ductility, and susceptibility to hydrogen embrittlement of cold-finished mild steel. Steel coupons were subjected to electrochemical hydrogen charging in a carefully chosen alkaline solution over a particular time and at various charging current densities. Tensile property tests were conducted immediately after the charging process, and the results were compared with those of uncharged steel. The findings revealed a clear drop in toughness and ductility with increasing hydrogen content. Fracture surfaces were examined to determine the failure mechanisms. This evaluation has enabled the prediction of steel’s ability to withstand environments with elevated hydrogen concentrations during practical applications. Full article
(This article belongs to the Special Issue Hydrogen Embrittlement of Metals)
13 pages, 1629 KiB  
Article
A Comparative Study of Microstructural Characteristics and Mechanical Properties of High-Strength Low-Alloy Steel Fabricated by Wire-Fed Laser Versus Wire Arc Additive Manufacturing
by Dayue Zhang, Qian Fang, Binzhou Li, Yijia Wang, Shanshan Si, Yuanbo Jiang and Zhiping Hu
Crystals 2024, 14(6), 528; https://doi.org/10.3390/cryst14060528 - 31 May 2024
Abstract
This study evaluates the feasibility of producing high-strength low-alloy (HSLA) steel using advanced wire-fed laser additive manufacturing (LAM-W) and wire arc additive manufacturing (WAAM) technologies. Optimized parameters were independently developed for each heat source, utilizing a self-designed HSLA steel wire as the feedstock. [...] Read more.
This study evaluates the feasibility of producing high-strength low-alloy (HSLA) steel using advanced wire-fed laser additive manufacturing (LAM-W) and wire arc additive manufacturing (WAAM) technologies. Optimized parameters were independently developed for each heat source, utilizing a self-designed HSLA steel wire as the feedstock. Microstructural features and mechanical properties of the fabricated steels were characterized and compared, taking into account differences in heat input and cooling rates. LAM-W samples exhibited a finer columnar grain microstructure, while both LAM-W- and WAAM-produced steels predominantly showed lower bainite and granular bainite microstructures. LAM-W demonstrated higher strength and hardness, lower ductility, and comparable low-temperature toughness compared to WAAM. Both processes demonstrated an excellent balance between strength and ductility, with absorbed energy exceeding 100 J at −40 °C. The study confirms the feasibility of producing high-strength and tough HSLA steel parts using LAM-W and WAAM technologies, and compares the advantages and disadvantages of each method. These findings assist in selecting the most suitable wire-fed AM process for HSLA steel fabrication at high deposition rates. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
3 pages, 206 KiB  
Editorial
Mineralogical Crystallography Volume III
by Vladislav V. Gurzhiy
Crystals 2024, 14(6), 527; https://doi.org/10.3390/cryst14060527 - 31 May 2024
Abstract
The United Nations and UNESCO designated 2014 as the International Year of Crystallography, in which the scientific community celebrated the centenary of the discovery of X-ray diffraction [...] Full article
(This article belongs to the Special Issue Mineralogical Crystallography (3rd Edition))
12 pages, 3468 KiB  
Article
Numerical Simulations of the Impact of CaO/Al2O3 on the Structure and Crystallization Behavior of Red Mud
by Lei Xing, Zhi-Hui Li, Pei-Pei Du and Yue Long
Crystals 2024, 14(6), 526; https://doi.org/10.3390/cryst14060526 - 31 May 2024
Abstract
The problem of large stockpiles of red mud needs to be solved, and the use of red mud to prepare inorganic fibers is a new way of applying red mud on a large scale. The role of CaO/Al2O3 in the [...] Read more.
The problem of large stockpiles of red mud needs to be solved, and the use of red mud to prepare inorganic fibers is a new way of applying red mud on a large scale. The role of CaO/Al2O3 in the melting point and melt structure of red mud was investigated by molecular dynamics simulations and thermodynamic calculations. Liquid phase line temperatures for different CaO/Al2O3 systems were calculated using the Factsage program. The radial distribution function and the type of oxygen bonding were used to characterize the effect of different CaO/Al2O3 on the structure of the red mud melt. The melting point of MgAl2O4 is lower than that of CaTiO3 due to the fact that the type of oxygen bonding in MgAl2O4 is predominantly bridging oxygen bonds. When the red mud system has a low SiO2 content and CaO/Al2O3 is between 0.3 and 3.9, the melting point temperature increases significantly, which is not conducive to the fibrillation of the red mud melt. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Second Edition)
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14 pages, 12846 KiB  
Article
Molecular Dynamics Study of the Deformation Behavior and Strengthening Mechanisms of Cu/Graphene Composites under Nanoindentation
by Guangan Ren, Cong Zhou, Yongle Hu, Li Wang, Jingzhong Fang, Yejun Li, Yi Wang, Jian Liu, Mingjun Zhang and Yonggang Tong
Crystals 2024, 14(6), 525; https://doi.org/10.3390/cryst14060525 - 31 May 2024
Abstract
The mechanical performance of pure copper can be significantly strengthened by adding graphene without greatly sacrificing its electrical and thermal conductivity. However, it is difficult to observe the deformation behavior of Cu/graphene composites efficiently and optically using experiments due to the extremely small [...] Read more.
The mechanical performance of pure copper can be significantly strengthened by adding graphene without greatly sacrificing its electrical and thermal conductivity. However, it is difficult to observe the deformation behavior of Cu/graphene composites efficiently and optically using experiments due to the extremely small graphene size. Herein, Cu/graphene composites with different graphene positions and layers were built to investigate the effect of these factors on the mechanical performance of the composites and the deformation mechanisms using molecular dynamics simulations. The results showed that the maximum indentation force and hardness of the composites decreased significantly with an increase in the distance from graphene to the indentation surface. Graphene strengthened the mechanical properties of Cu/graphene composites by hindering the slip of dislocations. As the graphene layers increased, the strengthening effect became more pronounced. With more graphene layers, dislocations within the Cu matrix were required to overcome higher stress to be released towards the surface; thus, they had to store enough energy to allow more crystalline surfaces to slip, resulting in more dislocations being generated. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
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16 pages, 3965 KiB  
Review
A Review of Cu3BiS3 Thin Films: A Sustainable and Cost-Effective Photovoltaic Material
by Maxwell Santana Libório, José César Augusto de Queiroz, Sivabalan Maniam Sivasankar, Thercio Henrique de Carvalho Costa, António Ferreira da Cunha and Carlos de Oliveira Amorim
Crystals 2024, 14(6), 524; https://doi.org/10.3390/cryst14060524 - 31 May 2024
Abstract
The demand for sustainable and cost-effective materials for photovoltaic technology has led to an increasing interest in Cu3BiS3 thin films as potential absorber layers. This review provides a comprehensive overview of the main physical properties, synthesis methods, and theoretical studies [...] Read more.
The demand for sustainable and cost-effective materials for photovoltaic technology has led to an increasing interest in Cu3BiS3 thin films as potential absorber layers. This review provides a comprehensive overview of the main physical properties, synthesis methods, and theoretical studies of Cu3BiS3 thin films for photovoltaic applications. The high optical absorption coefficient and band gap energy around the optimal 1.4 eV make Cu3BiS3 orthorhombic Wittichenite-phase a promising viable alternative to conventional thin film absorber materials such as CIGS, CZTS, and CdTe. Several synthesis techniques, including sputtering, thermal evaporation, spin coating, chemical bath deposition, and spray deposition, are discussed, highlighting their impact on film quality and photovoltaic performance. Density Functional Theory studies offer insights into the electronic structure and optical properties of Cu3BiS3, aiding in the understanding of its potential for photovoltaic applications. Additionally, theoretical modeling of Cu3BiS3-based photovoltaic cells suggests promising efficiencies, although experimental challenges remain to be addressed. Overall, this review underscores the potential of CBS thin films as sustainable and cost-effective materials for future PV technology while also outlining the ongoing research efforts and remaining challenges in this field. Full article
(This article belongs to the Special Issue Advanced Research of Electroceramics for Energy Conversion, Storage and Devices)
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48 pages, 977 KiB  
Article
Three-Dimensional Singular Stress Fields and Interfacial Crack Path Instability in Bicrystalline Superlattices of Orthorhombic/Tetragonal Symmetries
by Reaz A. Chaudhuri
Crystals 2024, 14(6), 523; https://doi.org/10.3390/cryst14060523 - 30 May 2024
Abstract
First, a recently developed eigenfunction expansion technique, based in part on the separation of the thickness variable and partly utilizing a modified Frobenius-type series expansion technique in conjunction with the Eshelby–Stroh formalism, is employed to derive three-dimensional singular stress fields in the vicinity [...] Read more.
First, a recently developed eigenfunction expansion technique, based in part on the separation of the thickness variable and partly utilizing a modified Frobenius-type series expansion technique in conjunction with the Eshelby–Stroh formalism, is employed to derive three-dimensional singular stress fields in the vicinity of the front of an interfacial crack weakening an infinite bicrystalline superlattice plate, made of orthorhombic (cubic, hexagonal, and tetragonal serving as special cases) phases of finite thickness and subjected to the far-field extension/bending, in-plane shear/twisting, and anti-plane shear loadings, distributed through the thickness. Crack-face boundary and interface contact conditions as well as those that are prescribed on the top and bottom surfaces of the bicrystalline superlattice plate are exactly satisfied. It also extends a recently developed concept of the lattice crack deflection (LCD) barrier to a superlattice, christened superlattice crack deflection (SCD) energy barrier for studying interfacial crack path instability, which can explain crack deflection from a difficult interface to an easier neighboring cleavage system. Additionally, the relationships of the nature (easy/easy, easy/difficult, or difficult/difficult) interfacial cleavage systems based on the present solutions with the structural chemistry aspects of the component phases (such as orthorhombic, tetragonal, hexagonal, as well as FCC (face-centered cubic) transition metals and perovskites) of the superlattice are also investigated. Finally, results pertaining to the through-thickness variations in mode I/II/III stress intensity factors and energy release rates for symmetric hyperbolic sine-distributed loads and their skew-symmetric counterparts that also satisfy the boundary conditions on the top and bottom surfaces of the bicrystalline superlattice plate under investigation also form an important part of the present investigation. Full article
(This article belongs to the Section Crystal Engineering)
18 pages, 2848 KiB  
Article
Molecular Dynamics Analysis of Collison Cascade in Graphite: Insights from Multiple Irradiation Scenarios at Low Temperature
by Marzoqa M. Alnairi and Mosab Jaser Banisalman
Crystals 2024, 14(6), 522; https://doi.org/10.3390/cryst14060522 - 30 May 2024
Abstract
In our study, we utilize molecular dynamics simulations, specifically through the Reactive Empirical Bond Order, to unravel atomic-scale dynamics in graphite, an essential component in many advanced technologies, under varying irradiation scenarios. We shed light on the behavior of graphite when exposed to [...] Read more.
In our study, we utilize molecular dynamics simulations, specifically through the Reactive Empirical Bond Order, to unravel atomic-scale dynamics in graphite, an essential component in many advanced technologies, under varying irradiation scenarios. We shed light on the behavior of graphite when exposed to Primary Knock-on Atom (PKA) energies of 10, 20, 40, and 80 keV. The findings highlight the radiation vulnerability of graphite, especially when influenced by hydride inclusion. Both pristine graphite and its hydride variant exhibited an increase in Frenkel pairs (FPs) with escalating PKA energies. Notably, carbon PKAs manifested significant FP effects, whereas hydrogen PKAs influenced defect formation through variable diffusivity. In tested radiation scenarios, particularly in Mode C and the R1 region, cascade patterns identified distinct defect forms of diamond-like and elongated-diamond-like shapes, distinct from the typical PKA collision clusters. Furthermore, our cascade findings emphasize the formation of three-coordinated graphite rings, particularly as PKA energies increase. The graphite population statistics reveal a decline in threefold-coordinated atoms and an increase in other types of defects, with 7-carbon atom rings being the most common. Our research highlights the significance of understanding three-coordinated graphite rings, especially as PKA energies rise. Graphite population statistics reveal a decline in threefold-coordinated atoms and a rise in other defects. Notably, 7-carbon atom rings are the most common. From a clustering perspective, self-interstitial atom (SIA) clusters predominated in pristine graphite, while this trend balanced in the hydride variant. Our research highlights the importance of understanding atomic behaviors in graphite under several radiation scenarios. This knowledge is needed for advancing reliable and efficient technological applications, particularly in the field of nuclear technology. Our research underscores the need to understand atomic behaviors in graphite under radiation, paving the way for detailed study on reliable efficient technological applications. Full article
(This article belongs to the Special Issue Advances in Processing, Simulation and Characterization of Alloys)
28 pages, 10351 KiB  
Review
Two-Dimensional Pentamode Metamaterials: Properties, Manufacturing, and Applications
by Chuang Zhou, Qi Li, Xiaomei Sun, Zifei Xiao and Haichao Yuan
Crystals 2024, 14(6), 521; https://doi.org/10.3390/cryst14060521 - 30 May 2024
Abstract
Metamaterials are artificial materials with properties depending mainly on their designed structures instead of their materials. Pentamode metamaterials are one type of metamaterial. They have solid structures with fluid-like properties, which can only withstand compressive stresses, not shear stresses. Two-dimensional pentamode metamaterials are [...] Read more.
Metamaterials are artificial materials with properties depending mainly on their designed structures instead of their materials. Pentamode metamaterials are one type of metamaterial. They have solid structures with fluid-like properties, which can only withstand compressive stresses, not shear stresses. Two-dimensional pentamode metamaterials are easier to manufacture than three-dimensional models, so they have received wide attention. In this review, the properties, manufacturing, and applications of two-dimensional pentamode metamaterials will be discussed. Their water-like properties are their most important properties, and their velocities and anisotropy can be designed. They can be processed by wire-cut electrical discharge machining, waterjet cutting, and additive manufacturing techniques. They have a broad application prospect in acoustic fields such as acoustic stealth cloaks, acoustic waveguides, flat acoustic focusing lenses, pentamode acoustic meta-surfaces, etc. Full article
(This article belongs to the Special Issue Two-Dimensional Materials: Synthesis, Characterization and Device Applications)
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14 pages, 3111 KiB  
Article
Combustion-Induced Endothermic Process in Carbon Dots Synthesized on Magnetite Nanoparticle Substrate
by Khalid Zouhri, Luke J. Snyder, Michael McFarland, Parker O. Laubie, K. A. Shiral Fernando and Christopher E. Bunker
Crystals 2024, 14(6), 520; https://doi.org/10.3390/cryst14060520 - 30 May 2024
Viewed by 82
Abstract
Carbon dots are synthesized alone and in the presence of commercial magnetite nanoparticles using a simple hydrothermal reaction. The spectroscopic and structural characteristics of CDot and CDot–magnetite materials are presented and their behaviors under combustion conditions are studied. A careful examination of their [...] Read more.
Carbon dots are synthesized alone and in the presence of commercial magnetite nanoparticles using a simple hydrothermal reaction. The spectroscopic and structural characteristics of CDot and CDot–magnetite materials are presented and their behaviors under combustion conditions are studied. A careful examination of their combustion behaviors reveals interesting results for the CDot–magnetite material: it undergoes early catalytic combustion at ~200 °C and a strong endothermic process that quenches combustion. By investigating the physical mixtures of pre-formed CDots and magnetite and the starting material ascorbic acid and magnetite, it is determined that the strong endothermic behavior requires intimate interactions between the carbon source and the magnetite, highlighting the importance of the nano-interface of the CDots being synthesized onto the magnetite substrate. The results are discussed in the context of the fuels used for low-temper combustion, materials with stored endothermic potential, and the use of combustion-quenching materials for fire control. Full article
(This article belongs to the Special Issue Synthesis and Application of Nanocomposite Materials)
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11 pages, 5467 KiB  
Article
Tailoring the Magnetic and Hyperthermic Properties of Biphase Iron Oxide Nanocubes through Post-Annealing
by Supun B. Attanayake, Amit Chanda, Raja Das, Manh-Huong Phan and Hariharan Srikanth
Crystals 2024, 14(6), 519; https://doi.org/10.3390/cryst14060519 - 30 May 2024
Viewed by 133
Abstract
Tailoring the magnetic properties of iron oxide nanosystems is essential to expanding their biomedical applications. In this study, 34 nm iron oxide nanocubes with two phases consisting of Fe3O4 and α-Fe2O3 were annealed for 2 h in [...] Read more.
Tailoring the magnetic properties of iron oxide nanosystems is essential to expanding their biomedical applications. In this study, 34 nm iron oxide nanocubes with two phases consisting of Fe3O4 and α-Fe2O3 were annealed for 2 h in the presence of O2, N2, He, and Ar to tune the respective phase volume fractions and control their magnetic properties. X-ray diffraction and magnetic measurements were carried out post-treatment to evaluate changes in the treated samples compared to the as-prepared samples, showing an enhancement of the α-Fe2O3 phase in the samples annealed with O2 while the others indicated a Fe3O4 enhancement. Furthermore, the latter samples indicated enhancements in crystallinity and saturation magnetization, while coercivity enhancements were the most significant in samples annealed with O2, resulting in the highest specific absorption rates (of up to 1000 W/g) in all the applied fields of 800, 600, and 400 Oe in agar during magnetic hyperthermia measurements. The general enhancement of the specific absorption rate post-annealing underscores the importance of the annealing atmosphere in the enhancement of the magnetic and structural properties of nanostructures. Full article
(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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11 pages, 5283 KiB  
Article
Highly Efficient Terahertz Waveguide Using Two-Dimensional Tellurium Photonic Crystals with Complete Photonic Bandgaps
by Yong Wang, Luyao Feng, Hongwei Huang, Zhifeng Zeng, Yuhan Liu, Xiaotong Liu, Xingquan Li, Kaiming Yang, Zhijian Zheng, Biaogang Xu, Wenlong He, Shaobin Zhan and Wenli Wang
Crystals 2024, 14(6), 518; https://doi.org/10.3390/cryst14060518 - 29 May 2024
Viewed by 177
Abstract
A novel, highly efficient terahertz fully polarized transmission line is designed by two-dimensional tellurium photonic crystals consisting of square lattice rod arrays with a complete photonic bandgap. The TE and TM photonic bandgaps of the tellurium photonic crystals, which are computed by plane [...] Read more.
A novel, highly efficient terahertz fully polarized transmission line is designed by two-dimensional tellurium photonic crystals consisting of square lattice rod arrays with a complete photonic bandgap. The TE and TM photonic bandgaps of the tellurium photonic crystals, which are computed by plane wave expansion, happen to coincide, and the complete photonic bandgap covers from 2.894 to 3.025 THz. The function of the designed waveguide is simulated by the finite element method, and the transmission characteristics are optimized by accurately adjusting its structural parameters. The transmission efficiency of the waveguide for TE mode achieves a peak value of −0.34 dB at a central frequency of 2.950 THz and keeps above −3 dB from 2.82 THz to 3.02 THz, obtaining a broad relative bandwidth of about 6.84 percent. The operating bandwidth of the tellurium photonic crystals’ waveguide for TM mode is narrower than that of TE mode, whose relative bandwidth is about 4.39 percent or around 2.936 THz above −5 dB. The designed terahertz photonic crystals’ waveguide can transmit both TE and TM waves, and not only can it be used as a high-efficiency transmission line, but it also provides a promising approach for implementing fully polarized THz devices for future 6G communication systems. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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11 pages, 6906 KiB  
Article
Effect of Nonmagnetic Hf Addition on Magnetic Properties of Melt-Spun Misch Metal-Fe-B Ribbons
by Mihaela Lostun, Marian Grigoraș, Luiza C. Budeanu, Tiberiu Roman, Gabriela Buema, Gabriel Ababei, George Stoian and Nicoleta Lupu
Crystals 2024, 14(6), 517; https://doi.org/10.3390/cryst14060517 - 29 May 2024
Viewed by 158
Abstract
Misch Metal (MM)-Fe-B magnets are proposed to develop permanent magnets with a high performance/cost ratio and to balance the disproportionate use of rare earth (RE) resources. To improve the magnetic performance of (MM)-Fe-B ribbons precursors of magnets, the addition of non-magnetic hafnium (Hf) [...] Read more.
Misch Metal (MM)-Fe-B magnets are proposed to develop permanent magnets with a high performance/cost ratio and to balance the disproportionate use of rare earth (RE) resources. To improve the magnetic performance of (MM)-Fe-B ribbons precursors of magnets, the addition of non-magnetic hafnium (Hf) was used. MM14Fe80−xHfxB6 (x = 0–3 at. %) ribbons were fabricated by melt-spinning technique at a wheel velocity of 35 m/s and were then annealed to obtain a nanocrystalline structure. The ribbons’ magnetic properties, morphology, and structure were investigated methodically. It was found that the coercivity, Hc, of the MM14Fe80−xHfxB6 (x = 0–3 at. %) as-spun ribbons increased significantly from 5.85 kOe to 9.25 kOe with an increase in the Hf content from 0 to 2 at. %, while the remanence decreased slightly for the whole 0–3 range at. % Hf. The grain size of the RE2Fe14B phase gradually decreased as the Hf addition content increased from 0 to 3 at. %. As a result, the best combination of magnetic properties, such as Hc = 9.25 kOe, Mr = 87 emu/g, and maximum energy product (BH)max = 9.75 MGOe, was obtained in the ribbons with 2 at. % Hf addition was annealed at an optimal temperature of 650 degrees Celsius for 20 min. This work can serve as a useful reference for the further development of a new permanent magnet based on MM and Hf elements and can provide a feasible way for the efficient use of rare earth resources. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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16 pages, 5860 KiB  
Article
Grain Refinement and Mechanical Enhancement of Titanium Matrix Composites with Nickel-Coated Graphene Nanoflakes: Influence of Particle-Size Mismatch
by Jie Zhang, Byung-Won Min, Hai Gu, Guo-Qing Wu, Guo-Qing Dai and Zhong-Gang Sun
Crystals 2024, 14(6), 516; https://doi.org/10.3390/cryst14060516 - 29 May 2024
Viewed by 137
Abstract
A novel type of titanium matrix composite (TMC) with a uniform network microstructure has been successfully fabricated by adjusting particle-size mismatch (Φ). This study can also improve the understanding of the effects of particle size on microstructure and mechanical properties, particularly in titanium [...] Read more.
A novel type of titanium matrix composite (TMC) with a uniform network microstructure has been successfully fabricated by adjusting particle-size mismatch (Φ). This study can also improve the understanding of the effects of particle size on microstructure and mechanical properties, particularly in titanium matrix composites reinforced with graphite flakes (GNFs). Microstructural analysis reveals the absence of noticeable defects, and significant grain refinements have been realized. The experimental results indicate that the yield strength of the mismatched composite is improved by 24.75% compared to that of normal composites. The micro-hardness also exhibits a 10.3% increase. These enhancements can be attributed to the introduction of particle-size mismatch, the refinement of the microstructure, and the deflection of interface cracks. The presence of distorted GNF lattices in the interface micro-region of the composites primarily results from the appropriate sizing of different particles. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
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15 pages, 4345 KiB  
Article
New fac-[Re(CO)3(OO)(L)] and [Re(CO)2(OO)(L)2] Complexes Bearing Two Natural Food Additives, Maltol and Kojic Acid, as OO Ligands
by Angeliki Panagiotopoulou, Patricia Kyprianidou, Charalampos Tsoukalas, Vassilis Psycharis, Catherine P. Raptopoulou, Ioannis Pirmettis, Minas S. Papadopoulos and Maria Pelecanou
Crystals 2024, 14(6), 515; https://doi.org/10.3390/cryst14060515 - 29 May 2024
Viewed by 155
Abstract
The synthesis and structural characterization of new “2+1” mixed ligand fac-[Re(CO)3(OO)(L)] and Re(CO)2(OO)(L)2 complexes are reported herein. Maltol and kojic acid were chosen as bidentate OO ligands, while imidazole, isocyanocyclohexane or triphenylphosphine were selected as the monodentate [...] Read more.
The synthesis and structural characterization of new “2+1” mixed ligand fac-[Re(CO)3(OO)(L)] and Re(CO)2(OO)(L)2 complexes are reported herein. Maltol and kojic acid were chosen as bidentate OO ligands, while imidazole, isocyanocyclohexane or triphenylphosphine were selected as the monodentate ligands. The synthesis of the rhenium complexes was based on the reaction of [NEt4]2[Re(CO)3Br3] with maltol and kojic acid to generate the intermediate aqua complex fac-[Re(CO)3(OO)(H2O)], followed by the replacement of the labile aqua ligand by the monodentate ligand. Structural characterization of all Re complexes was established by NMR and IR spectroscopies, as well as two of them by single-crystal X-ray crystallography, revealing distorted octahedral geometry around the Re center. In the crystal lattice, the complexes form supramolecular networks due to the development of intermolecular interactions of the N-H⋯O, C-H⋯O and C-H⋯π type. Full article
(This article belongs to the Special Issue Coordination Complexes: Synthesis, Characterization and Application)
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9 pages, 3463 KiB  
Article
High-Temperature (Cu,C)Ba2Ca3Cu4Oy Superconducting Films with Large Irreversible Fields Grown on SrLaAlO4 Substrates by Pulsed Laser Deposition
by Yugang Li, Zhiyong Liu, Ping Zhu, Jinyu He and Chuanbing Cai
Crystals 2024, 14(6), 514; https://doi.org/10.3390/cryst14060514 - 28 May 2024
Viewed by 191
Abstract
(Cu,C)Ba2Ca3Cu4Oy is a nontoxic cuprate superconducting material with a superconducting transition temperature of about 116 K. Recently, it was found that bulk samples of this material synthesized under high pressure hold the highest irreversibility line among [...] Read more.
(Cu,C)Ba2Ca3Cu4Oy is a nontoxic cuprate superconducting material with a superconducting transition temperature of about 116 K. Recently, it was found that bulk samples of this material synthesized under high pressure hold the highest irreversibility line among all the superconductors, which is very promising for its application in the liquid nitrogen temperature field. In this work, high-temperature (Cu,C)Ba2Ca3Cu4Oy superconducting films with large irreversible fields were prepared on SrLaAlO4(00l) substrates by pulsed laser deposition. The substrate temperature during deposition proved to be the most important parameter determining the morphology and critical temperature of the superconductors, with 680 °C considered to be the optimum temperature. X-ray diffraction (XRD) results showed that the (Cu,C)Ba2Ca3Cu4Oy films prepared under optimal conditions exhibited epitaxial growth with the a-axis perpendicular to the film surface and the b- and c-axes parallel to the substrate, with no evidence of any other orientation. In addition, resistivity measurements showed that the onset transition temperature (Tconset) was approximately 116 K, the zero-resistance critical temperature (Tc0) was around 53 K, and the irreversible field (Hirr) was about 9 T at 37 K for (Cu,C)Ba2Ca3Cu4Oy films under optimal temperature. This is the first example of the successful growth of superconducting (Cu,C)Ba2Ca3Cu4Oy films on SrLaAlO4(00l) substrates. This will facilitate high-performance applications of (Cu,C)Ba2Ca3Cu4Oy superconducting materials in the liquid nitrogen temperature field. Full article
(This article belongs to the Special Issue Advances in Synthesis, Characterization, and Application of Thin Films)
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13 pages, 4496 KiB  
Article
Effect of Cubic Crystal Morphology on Thermal Characteristics and Mechanical Sensitivity of PYX
by Xi Luo, Qiong Wang, Hongni Liu, Wenjie Li, Ruixue Zheng and Weiqiang Pang
Crystals 2024, 14(6), 513; https://doi.org/10.3390/cryst14060513 - 28 May 2024
Viewed by 167
Abstract
To investigate the influence of the cubic crystal morphology on the thermal properties and sensitivity of 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), cubic PYX (CPYX) crystals were prepared using the antisolvent method. Scanning electron microscopy (SEM), laser particle size analysis, X-ray diffraction (XRD) and Fourier transform infrared [...] Read more.
To investigate the influence of the cubic crystal morphology on the thermal properties and sensitivity of 2,6-bis(picrylamino)-3,5-dinitropyridine (PYX), cubic PYX (CPYX) crystals were prepared using the antisolvent method. Scanning electron microscopy (SEM), laser particle size analysis, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to characterize the morphology, particle size and structure of the prepared products. The thermal behavior, thermal decomposition kinetics, thermal safety parameters and thermal decomposition mechanism of CPYX were investigated by differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectrometry (DSC-TG-MS-FT-IR) and in situ FT-IR experiments. Meanwhile, the mechanical sensitivity of CPYX was determined by means of the explosion probability method. The results showed that the product had a smooth cubic morphology and small crystal aspect ratio with an average particle size (d50) of 10.65 μm, but it had no distinct differences from the crystal structure of raw PYX (RPYX). The thermal decomposition peak temperature, the self-accelerating decomposition temperature and the critical temperature of the thermal explosion of CPYX increased by 7.2 °C, 6.1 °C and 10.4 °C, respectively, compared to RPYX. Similarly, the apparent activation energy increased by 15%. Besides these, the impact sensitivity and friction sensitivity of CPYX decreased by 36% and 20%, respectively, compared to RPYX. The decomposition process of CPYX contains two stages. The first stage involves the breakage of N-H bonds and -NO2 groups with the release of CO2, N2O, NO, HCN and H2O, followed by the thermal decomposition of the resulting intermediate and the release of CO2, N2O and HCN in the second stage. Full article
(This article belongs to the Section Materials for Energy Applications)
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14 pages, 592 KiB  
Review
Photonic Devices with Multi-Domain Liquid Crystal Structures
by Aleksey Kudreyko, Vladimir Chigrinov, Kristiaan Neyts, Denis Chausov and Arina Perestoronina
Crystals 2024, 14(6), 512; https://doi.org/10.3390/cryst14060512 - 28 May 2024
Viewed by 159
Abstract
Photoalignment by azo dye nanolayers can provide high alignment quality for large-area liquid crystal devices. Application of this technology to active optical elements for signal processing and communications is a hot topic of photonics research. In this article, we review recent demonstrations and [...] Read more.
Photoalignment by azo dye nanolayers can provide high alignment quality for large-area liquid crystal devices. Application of this technology to active optical elements for signal processing and communications is a hot topic of photonics research. In this article, we review recent demonstrations and performance of liquid crystal photonic devices, discuss the advantages of the proposed technology, and identify challenges and future prospects in the research field of photoaligned multi-domain liquid crystal structures. We believe that the developments discussed here can provide directions for future research and potential opportunities for applications of liquid crystal devices based on multi-domain photoalignment. Full article
(This article belongs to the Special Issue Optical Crystals and Their Applications in Optical Devices)
9 pages, 1931 KiB  
Article
Influence of Stress on the Chiral Polarization and Elastrocaloric Effect in BaTiO3 with 180° Domain Structure
by Yuanyuan Shi and Bo Li
Crystals 2024, 14(6), 511; https://doi.org/10.3390/cryst14060511 - 28 May 2024
Viewed by 163
Abstract
The polarization and elastrocaloric effect of chiral barium titanate (BaTiO3) with an Ising–Bloch-type domain wall under stress was investigated using the Landau–Ginzburg–Devonshire (LGD) theory. It has been shown that tensile stresses increase the magnitude of the Ising polarization component in barium [...] Read more.
The polarization and elastrocaloric effect of chiral barium titanate (BaTiO3) with an Ising–Bloch-type domain wall under stress was investigated using the Landau–Ginzburg–Devonshire (LGD) theory. It has been shown that tensile stresses increase the magnitude of the Ising polarization component in barium titanate, together with a decrease in the domain wall width. Compressive stresses cause a reduction in the Ising polarization component and an increase in the domain width. Under compressive stress, barium titanate exhibits a negative elastrocaloric effect and temperature changes with increasing stress, while BaTiO3 exhibits a positive elastrocaloric effect under tensile stress. Bloch polarization shows angle-dependent polarization under external force, but the temperature change from the elastrocaloric effect is smaller than that of Ising polarization under stress. This work contributes to the understanding of polarization evolution under tension in ferroelectrics with chiral structure. Full article
(This article belongs to the Special Issue Emerging Applications of Ferroelectrics in Nanoelectronics and Renewable Energy)
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17 pages, 4683 KiB  
Article
Syzygium aromaticum Bud Extracted Core–Shell Ag–Fe Bimetallic Nanoparticles: Phytotoxic, Antioxidant, Insecticidal, and Antibacterial Properties
by Farah Murtaza, Naseem Akhter, Muhammad Azam Qamar, Asma Yaqoob, Anis Ahmad Chaudhary, Bhagyashree R. Patil, Salah Ud-Din Khan, Nasir Adam Ibrahim, Nosiba S. Basher, Mohammed Saad Aleissa, Iqra Kanwal and Mohd Imran
Crystals 2024, 14(6), 510; https://doi.org/10.3390/cryst14060510 - 27 May 2024
Viewed by 312
Abstract
Today, there is the roar of sustainable material development around the globe. Green nanotechnology is one of the extensions of sustainability. Due to its sustainable approach, the green fabrication of nanoparticles has recently surpassed their classical synthesis in popularity. Among metal nanoparticles, contemporary [...] Read more.
Today, there is the roar of sustainable material development around the globe. Green nanotechnology is one of the extensions of sustainability. Due to its sustainable approach, the green fabrication of nanoparticles has recently surpassed their classical synthesis in popularity. Among metal nanoparticles, contemporary findings have demonstrated that bimetallic nanoparticles possess more potential for different applications than monometallic nanoparticles due to the synergistic effects of the two metals. So, we are presenting facile, one-vessel, and one-step phyto-fabrication of Ag–Fe BMNPs using the bud extract of Syzygiumaromaticum. The synthesized nanoparticles were characterized by UV-VIS, XRD, EDX, FTIR, and SEM. The synthesized NPs and the extract underwent biological studies. The radical scavenging potential of the NPs and the extract was found to be 64% and 73%, and the insecticidal potential was found to be 80% and 100%, respectively. Similarly, the NPs and the extract both exhibited good antibacterial activity. The zone of inhibition using 100 mg/mL of extract and NPs was found to be 1 cm against all bacterial species, i.e., K. pneumonia, E. coli, and S. aureus. It was 1.5 cm, 1.3 cm, and 1 cm against K. pneumonia, E. coli, and S. aureus, respectively, showing that the antibacterial activity of the extract is higher than that of the NPs. So, this study unlocks the synthesis of Ag–Fe bimetallic nanoparticles using eco-safe, cost-effective, facile, and least-harmful green methodology with potential applications of both NPs and SA extract in medical and agricultural fields, a step towards sustainability. Full article
(This article belongs to the Special Issue Metal Oxide Thin Films, Nanomaterials and Nanostructures)
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15 pages, 41098 KiB  
Article
Preparation, Characterization, and High-Temperature Anti-Seizing Application of CrAlN-Based Gradient Multilayer Coatings
by Chunmei Tang, Dingjun Li, Xiaohu Yuan, Wei Wang, Xianping Guo, Yu Fang, Xiufang Gong and Quande Li
Crystals 2024, 14(6), 509; https://doi.org/10.3390/cryst14060509 - 27 May 2024
Viewed by 232
Abstract
High-temperature fasteners are metal parts of gas turbines and steam turbines, which work at high temperatures and under stress for a long time. However, the frequent seizures of fasteners bring great trouble to the normal maintenance of power plants. In this paper, three [...] Read more.
High-temperature fasteners are metal parts of gas turbines and steam turbines, which work at high temperatures and under stress for a long time. However, the frequent seizures of fasteners bring great trouble to the normal maintenance of power plants. In this paper, three kinds of dense and controllable CrAlN-based gradient multilayer coatings were prepared on the samples and screws by arc ion plating (AIP) technology. The morphology, composition, structure, nano hardness, adhesion, residual stress, and room temperature tribological performance of the coating were investigated. To evaluate the high-temperature, anti-seizing performance, coated screws were heated to 700 °C for 140 h with a torque of 20 N·m. The results indicate that the CrN/CrAlN multilayer coating shows better comprehensive properties. The characterization of coated screws proved that the coating structures obtained on the screws were similar to the flat samples. However, the as-prepared coating on the screws showed different thickness variation rules, which was related to the clamping method, deposition distance, and screw shape. After a simulation service, the thread of the screw remained intact with similar structure and thinner thickness. The above results indicate that the high-temperature seize prevention of fasteners can be successfully achieved by preparing a CrAlN-based multilayer coating, which is suitable for fasteners with service temperatures below 700 °C. Full article
(This article belongs to the Special Issue Advanced Surface Modifications on Materials)
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13 pages, 4211 KiB  
Article
Efficient Adsorption Removal of Tetrabromobisphenol A from Water by Using a Magnetic Composite Fe3O4/GO/ZIF-67
by Sumei Li, Jian Ji, Saisai Shan, Sha Chen, Hanbing Li, Qian Xu and Yixuan Liang
Crystals 2024, 14(6), 508; https://doi.org/10.3390/cryst14060508 - 27 May 2024
Viewed by 178
Abstract
Tetrabromobisphenol A (TBBPA) is a kind of widely used brominated flame retardant (BFR), which is proven to be harmful to ecological systems and public health. It is very important to remove TBBPA from the environment. In our study, a magnetic composite named Fe [...] Read more.
Tetrabromobisphenol A (TBBPA) is a kind of widely used brominated flame retardant (BFR), which is proven to be harmful to ecological systems and public health. It is very important to remove TBBPA from the environment. In our study, a magnetic composite named Fe3O4/GO/ZIF-67 was synthesized by a coprecipitation method and applied in the highly efficient adsorption of TBBPA from water. Static adsorption experiments demonstrated that the adsorption capacity could reach 232 mg·g−1 within 120 min, which is much higher than those reported in the other literature. The experimental results show that the adsorption of TBBPA on Fe3O4/GO/ZIF-67 followed Langmuir and pseudo-second-order kinetic adsorption models. The main mechanisms for these adsorptions were identified as hydrogen bonds between OH groups in TBBPA and COOHs of Fe3O4/GO/ZIF-67, and π-π stacking between Fe3O4/GO/ZIF-67 and TBBPA. This study provides a method with great promise for the design and synthesis of better adsorbents for the removal of TBBPA from the water environment. Full article
(This article belongs to the Special Issue Recent Advances in Metal-Organic Frameworks: Synthesis, Characterization and Application)
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11 pages, 2872 KiB  
Article
First-Principles Study of Ti-Doping Effects on Hard Magnetic Properties of RFe11Ti Magnets
by Chengyuan Xu, Lin Wen, Anjian Pan, Lizhong Zhao, Yuansen Liu, Xuefeng Liao, Yu Pan and Xuefeng Zhang
Crystals 2024, 14(6), 507; https://doi.org/10.3390/cryst14060507 - 27 May 2024
Viewed by 259
Abstract
Due to the rare earth supply shortage, ThMn12-type RFe12-based (R is the rare earth element) magnets with lean rare earth content are gaining more concern. Most ThMn12-type RFe12 structures are thermodynamically metastable and require doping of [...] Read more.
Due to the rare earth supply shortage, ThMn12-type RFe12-based (R is the rare earth element) magnets with lean rare earth content are gaining more concern. Most ThMn12-type RFe12 structures are thermodynamically metastable and require doping of the stabilizing element Ti. However, the Ti-doping effects on the hard magnetic properties of RFe11Ti have not been thoroughly investigated. Herein, based on density functional theory calculations, we report the Ti-doping effects on the phase stability, intrinsic hard magnetic properties and electronic structures of RFe11Ti (R = La, Ce, Pr, Nd, Sm, Y, Zr). Our results indicate that Ti-doping not only increases their phase stability, but also enhances the magnetic hardness of ground-state RFe12 phases. Particularly, it leads to the transition of CeFe11Ti and PrFe11Ti from easy-plane to easy-axis anisotropy. Charge density distributions demonstrate that Ti-doping breaks the original symmetry of the R-site crystal field, which alters the magnetic anisotropy of RFe11Ti. Projected densities of states reveal that the addition of Ti results in the shift of occupied and unoccupied f-electron energy levels of rare earth elements, affecting their magnetic exchange. This study provides an insight into regulating the hard magnetic properties of RFe12-based magnets by Ti-doping. Full article
(This article belongs to the Special Issue The Synthesis and Prospects of Magnetic Materials)
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15 pages, 9639 KiB  
Article
Multicomponent Nanoparticles Decorating a Lignin-Derived Biochar Composite for 2-Nitrophenol Sensing
by Tianshuang Bao, Qi Wang, Yuhang Jiang, Xiangchuan Zhao, Yue Cao, Jun Cao, Qiaoling Li and Weimeng Si
Crystals 2024, 14(6), 506; https://doi.org/10.3390/cryst14060506 - 27 May 2024
Viewed by 208
Abstract
Lignin, which contains aromatic phenols, is the second most abundant renewable biomass material in the world. It is the main byproduct of the paper industry and is characterized by abundant sources, renewability, and low cost. The present study focused on the extraction of [...] Read more.
Lignin, which contains aromatic phenols, is the second most abundant renewable biomass material in the world. It is the main byproduct of the paper industry and is characterized by abundant sources, renewability, and low cost. The present study focused on the extraction of lignin from poplar wood through a straightforward papermaking approach, thereafter utilizing the resultant black liquor containing lignin for synthesizing lignin-based phenolic resins. During the polymerization process, cobalt (Co) and nickel (Ni) species were introduced and, subsequently, a CoNi/biochar catalyst was obtained through pyrolysis in a nitrogen atmosphere. The prepared catalyst possessed rough spherical structures. The incorporation of Co and Ni enhanced charge redistribution, thereby imparting the catalyst with strong electron acceptance capabilities. The prepared lignin-based phenolic-resin-derived carbon was used for the electrochemical sensing of 2-nitrophenol. The limit of detection (LOD) for 2-nitrophenol was calculated to be 0.0132 µM, with good repeatability, stability, and selectivity. Full article
(This article belongs to the Section Hybrid and Composite Crystalline Materials)
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8 pages, 9329 KiB  
Article
Oxidized Graphite Nanocrystals for White Light Emission
by Patrik Ščajev, Saulius Miasojedovas, Algirdas Mekys, Gediminas Kreiza, Justinas Čeponkus, Valdas Šablinskas, Tadas Malinauskas and Arturs Medvids
Crystals 2024, 14(6), 505; https://doi.org/10.3390/cryst14060505 - 25 May 2024
Viewed by 366
Abstract
We investigated the formation of graphite nanocrystals covered with graphite oxide for white light generation. The nanoparticles were formed using cost-efficient oxidation of a carbon-based dye pigment at different temperatures and verified using X-ray diffraction and Raman measurements. Formation of the graphite nanoparticles [...] Read more.
We investigated the formation of graphite nanocrystals covered with graphite oxide for white light generation. The nanoparticles were formed using cost-efficient oxidation of a carbon-based dye pigment at different temperatures and verified using X-ray diffraction and Raman measurements. Formation of the graphite nanoparticles via thermal annealing was observed, while their light emission increased at higher oxidation temperatures. This was associated with a higher amount of oxygen defect groups. The time-resolved photoluminescence measurements showed linearly faster decays at shorter wavelengths and similar decays at different annealing temperatures. Broadband and linear vs. excitation emission spectra of the particles were found to be suitable for white-light-emitting devices and phosphor markers. The fast photoluminescence decay opens the possibility for the application of nanoparticles in optical wireless communication technology. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystal Studies for Optoelectronic Applications)
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11 pages, 1793 KiB  
Article
Dissociative Adsorption of O2 on Ag3Au(111) Surface: A Density Functional Theory Study
by Yanlin Yu, Mingan Fu, Huaizhang Gu, Lei Wang, Wanxiu Liu, Qian Xie and Guojiang Wu
Crystals 2024, 14(6), 504; https://doi.org/10.3390/cryst14060504 - 25 May 2024
Viewed by 223
Abstract
The catalytic efficiency of oxygen reduction catalysts is notably influenced by the dissociative adsorption of O2. We conducted a systematic investigation into the dissociative adsorption of O2 on the Ag3Au(111) surface using ab initio density functional theory (DFT) [...] Read more.
The catalytic efficiency of oxygen reduction catalysts is notably influenced by the dissociative adsorption of O2. We conducted a systematic investigation into the dissociative adsorption of O2 on the Ag3Au(111) surface using ab initio density functional theory (DFT) calculations. Our computational findings indicate that adsorption the configuration designated t-b-t exhibits favorable energetics on the Ag3Au(111) surface. Regarding the dissociation of O2, we identified a reasonable dissociation pathway, which proceeds from the initial t-b-t state to the creation of two oxygen atoms that occupy a set of neighboring fcc sites. Furthermore, our analysis indicates that the adsorption of O2 on the Ag3Au(111) surface is less favored thermodynamically and more difficult to dissociate than that on the Ag(111) surface. This study furnishes a theoretical framework elucidating the prospective utilization of Ag-Au alloy in the capacity of oxygen reduction catalysts. Full article
(This article belongs to the Section Materials for Energy Applications)
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10 pages, 3413 KiB  
Article
High-Efficiency Vertical-Chip Micro-Light-Emitting Diodes via p-GaN Optimization and Surface Passivation
by Yizhou Qian, En-Lin Hsiang, Yu-Hsin Huang, Kuan-Heng Lin and Shin-Tson Wu
Crystals 2024, 14(6), 503; https://doi.org/10.3390/cryst14060503 - 25 May 2024
Viewed by 357
Abstract
Micro-LEDs have found widespread applications in modular large-screen TVs, automotive displays, and high-resolution-density augmented reality glasses. However, these micron-sized LEDs experience a significant efficiency reduction due to the defects originating from the dry etching process. By controlling the current distribution via engineering the [...] Read more.
Micro-LEDs have found widespread applications in modular large-screen TVs, automotive displays, and high-resolution-density augmented reality glasses. However, these micron-sized LEDs experience a significant efficiency reduction due to the defects originating from the dry etching process. By controlling the current distribution via engineering the electrode size, electrons will be less concentrated in the defect region. In this work, we propose a blue InGaN/GaN compound parabolic concentrator micro-LED with a metallic sidewall to boost efficiency by combining both an optical dipole cloud model and electrical TCAD (Technology Computer-Aided Design) model. By merely modifying the p-GaN contact size, the external quantum efficiency (EQE) can be improved by 15.6%. By further optimizing the passivation layer thickness, the EQE can be boosted by 52.1%, which helps enhance the display brightness or lower power consumption. Full article
(This article belongs to the Section Organic Crystalline Materials)
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11 pages, 1363 KiB  
Article
Thermal Characterization of [C2Im][NO3] and Multivalent Nitrate Salts Mixtures
by Pablo Vallet, Juan José Parajó, Antía Santiago-Alonso, María Villanueva, Luis Miguel Varela and Josefa Salgado
Crystals 2024, 14(6), 502; https://doi.org/10.3390/cryst14060502 - 25 May 2024
Viewed by 313
Abstract
Due to their intrinsic properties, the current applicability of ionic liquids is enormous. In particular, their use in electrochemistry is beyond question. Numerous studies on these compounds and their mixtures, especially with lithium salts, focus on their use as electrolytes for batteries and [...] Read more.
Due to their intrinsic properties, the current applicability of ionic liquids is enormous. In particular, their use in electrochemistry is beyond question. Numerous studies on these compounds and their mixtures, especially with lithium salts, focus on their use as electrolytes for batteries and other energy storage devices. This includes thermal energy storage devices, where 4th generation ionic liquids and their derivatives show a huge potential. Nevertheless, considering the uneven availability of the raw materials, such as lithium, research has extended to mixtures of these compounds with other salts of different metals that are more abundant and widely distributed, such as magnesium or aluminum. This work presents a comprehensive thermal characterization, using differential scanning calorimetry and thermogravimetry, of the protic ionic liquid ethylimidazolium nitrate and its mixture with magnesium and aluminum nitrate salts at different concentrations. Additionally, a comparison between these results and previous studies of mixtures of this ionic liquid with lithium nitrate, as well as mixtures of the protic ionic liquid EAN with the same metal salts, was also performed. The results indicated that the salt addition tends to broaden and reduce crystallization and melting peaks, while the glass transition becomes more visible and shifts to higher temperatures with increasing salt concentration. This is due to the disorder generated by the rearrangement of ions in the polar domains, which erodes the hydrogen bond network of the protic ionic liquid. Nevertheless, the thermal stability of the blended samples does not change significantly compared to the bulk ionic liquid. Full article
(This article belongs to the Section Materials for Energy Applications)
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13 pages, 752 KiB  
Review
Machine Learning Methods to Improve Crystallization through the Prediction of Solute–Solvent Interactions
by Aatish Kandaswamy and Sebastian P. Schwaminger
Crystals 2024, 14(6), 501; https://doi.org/10.3390/cryst14060501 - 24 May 2024
Viewed by 264
Abstract
Crystallization plays a crucial role in defining the quality and functionality of products across various industries, including pharmaceutical, food and beverage, and chemical manufacturing. The process’s efficiency and outcome are significantly influenced by solute–solvent interactions, which determine the crystalline product’s purity, size, and [...] Read more.
Crystallization plays a crucial role in defining the quality and functionality of products across various industries, including pharmaceutical, food and beverage, and chemical manufacturing. The process’s efficiency and outcome are significantly influenced by solute–solvent interactions, which determine the crystalline product’s purity, size, and morphology. These attributes, in turn, impact the product’s efficacy, safety, and consumer acceptance. Traditional methods of optimizing crystallization conditions are often empirical, time-consuming, and less adaptable to complex chemical systems. This research addresses these challenges by leveraging machine learning techniques to predict and optimize solute–solvent interactions, thereby enhancing crystallization outcomes. This review provides a novel approach to understanding and controlling crystallization processes by integrating supervised, unsupervised, and reinforcement learning models. Machine learning not only improves product the quality and manufacturing efficiency but also contributes to more sustainable industrial practices by minimizing waste and energy consumption. Full article
(This article belongs to the Section Biomolecular Crystals)
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13 pages, 2368 KiB  
Article
Crystal Growth and Spectroscopy of Yb2+-Doped CsI Single Crystal
by Dmitriy Sofich, Alexandra Myasnikova, Alexander Bogdanov, Viktorija Pankratova, Vladimir Pankratov, Ekaterina Kaneva and Roman Shendrik
Crystals 2024, 14(6), 500; https://doi.org/10.3390/cryst14060500 - 24 May 2024
Viewed by 342
Abstract
The single crystals of CsI-Yb2+ were grown, and their spectroscopic studies were conducted. The observed luminescence in CsI-Yb2+ is due to 5d–4f transitions in Yb2+ ions. Using time-resolved spectroscopy, spin-allowed and spin-forbidden radiative transitions of ytterbium ions at room temperature [...] Read more.
The single crystals of CsI-Yb2+ were grown, and their spectroscopic studies were conducted. The observed luminescence in CsI-Yb2+ is due to 5d–4f transitions in Yb2+ ions. Using time-resolved spectroscopy, spin-allowed and spin-forbidden radiative transitions of ytterbium ions at room temperature were found. The excitation spectra of Yb2+ luminescence bands were obtained in the range of 3–45 eV. The mechanism of charge compensation of Yb2+ ions in a CsI crystal was also studied, the spectrum of the thermally stimulated depolarization current was measured, and the activation energies of the two observed peaks were calculated. These peaks belong to impurity–vacancy complexes in two different positions. The charge compensation of Yb2+ occurs via cation vacancies in the nearest-neighbor and next-nearest-neighbor positions.The Yb2+ ions are promising dopants for CsI scintillators and X-ray phosphors in combination with SiPM photodetectors. Full article
(This article belongs to the Special Issue Crystals for Radiation Detectors, UV Filters and Lasers)
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