Next Issue
Volume 14, June
Previous Issue
Volume 14, April
 
 

Crystals, Volume 14, Issue 5 (May 2024) – 91 articles

Cover Story (view full-size image): This study explores the growth of high-quality Ge1-xSnx thin films, crucial for near-infrared and mid-infrared applications such as lasers, detectors, and waveguides. Overcoming lattice mismatch and Sn segregation challenges, we investigate a novel growth technique utilizing ultra-high vacuum molecular beam epitaxy on a sapphire/III-V semiconductor substrate. We achieved Ge1-xSnx films with over 10% Sn content by employing composition and temperature gradients. Characterization via reflection high-energy electron diffraction, high-resolution X-ray diffraction, Raman spectroscopy, and photoluminescence confirms high-quality growth. This advancement opens avenues for microwave photonics on a single sapphire chip, leveraging sapphire's advantages for efficient waveguides and microwave electronics. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
38 pages, 22809 KiB  
Review
Nanoscale Cu2ZnSnSxSe(4−x) (CZTS/Se) for Sustainable Solutions in Renewable Energy, Sensing, and Nanomedicine
by Sayedmahdi Mohammadi, Navdeep Kaur and Daniela R. Radu
Crystals 2024, 14(5), 479; https://doi.org/10.3390/cryst14050479 - 19 May 2024
Viewed by 358
Abstract
The importance and breadth of applications of the family of quaternary chalcogenides with the formula Cu2ZnSnSxSe(4−x) (CZTS/Se) where x = 0–4 are steadily expanding due to the tunable optoelectronic properties of these compounds and the Earth abundance of [...] Read more.
The importance and breadth of applications of the family of quaternary chalcogenides with the formula Cu2ZnSnSxSe(4−x) (CZTS/Se) where x = 0–4 are steadily expanding due to the tunable optoelectronic properties of these compounds and the Earth abundance of the elements in their composition. These p-type semiconductors are viewed as a viable alternative to Si, gallium arsenide, CdTe, and CIGS solar cells due to their cost effectiveness, Earth’s crust abundance, and non-toxic elements. Additionally, CZTS/Se compounds have demonstrated notable capabilities beyond solar cells, such as photoelectrochemical CO2 reduction, solar water splitting, solar seawater desalination, hydrogen production, and use as an antibacterial agent. Various routes have been explored for synthesizing pure CZTS/Se nanomaterials and significant efforts have been dedicated to reducing the occurrence of secondary phases. This review focuses on synthetic approaches for CZTS/Se nanomaterials, with emphasis on controlling the size and morphology of the nanoparticles and their recent application in solar energy harvesting and beyond, highlighting challenges in achieving the desired purity required in all these applications. Full article
(This article belongs to the Special Issue Semiconductor Nanocrystal Studies for Optoelectronic Applications)
Show Figures

Figure 1

10 pages, 2783 KiB  
Article
Steric Effects of Alcohols on the [Mn4O4] Cubane-Type Structures
by Yan He, Zheng Zhou and Haixiang Han
Crystals 2024, 14(5), 478; https://doi.org/10.3390/cryst14050478 - 19 May 2024
Viewed by 227
Abstract
[M4O4] (M = 3d transition metal) represents an interesting class of compounds featuring cubane-type molecular structures, and particularly, [Mn4O4] cubanes or their derivatives attract much attention by virtue of their potential applications as single-molecule [...] Read more.
[M4O4] (M = 3d transition metal) represents an interesting class of compounds featuring cubane-type molecular structures, and particularly, [Mn4O4] cubanes or their derivatives attract much attention by virtue of their potential applications as single-molecule magnets (SMMs) or catalysts. However, the rational design of desired cubane-related structures is still a challenging subject due to the lack of readily available methods to effectively tune the construction patterns of the molecule assembly. In this work, we report the employment of different alcohols to prepare three cubane-related molecules, Mn2(dhd)4(iPrOH)2 (1), Mn4(dhd)4(OEt)4(EtOH)4 (2) and Mn4(dhd)6(OMe)2(MeOH)2 (3) (dhd = 5,5-dimethyl-2,4-hexanedione). Interestingly, the bulkiest iPrOH leads to simple rhombic dimer molecule 1. It can be deemed a rudimentary structure oftetranuclear [Mn4O4] cubane 2, which can be realized by the use of less bulky EtOH. In addition, the least bulky MeOH promotes the assembly of the cubanes, eventually bringing about defective dicubane molecular cluster 3. The accurate crystal structures of 13 were modeled by single-crystal X-ray diffraction, and their electronic structures were investigated through absorption spectroscopy coupled with theoretical calculations. Overall, this work demonstrates a systematic study on controlling cubane-type structures of Mn-based compounds by applying different solvents, which provides a new means to design functional molecules for specific applications. Full article
(This article belongs to the Section Organic Crystalline Materials)
22 pages, 5712 KiB  
Article
Study of the Microstructure and Mechanical Property Relationships of Gas Metal Arc Welded Dissimilar Protection 600T, DP450 and S275JR Steel Joints
by Mustafa Elmas, Oğuz Koçar and Nergizhan Anaç
Crystals 2024, 14(5), 477; https://doi.org/10.3390/cryst14050477 - 19 May 2024
Viewed by 210
Abstract
The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion [...] Read more.
The need for combining dissimilar materials is steadily increasing in the manufacturing industry, and the resulting products are expected to always have high performance. While there are various methods available for joining such material pairs, one of the commonly preferred techniques is fusion welding. In this study, three different steel materials (Protection 600T, DP450, and S275JR) were joined using gas metal arc welding (GMAW) in different combinations (similar/dissimilar). The microstructure and mechanical properties of the joints were evaluated. Tensile test, Vickers microhardness (HV 0.1), bending, Charpy V-notch impact testing, and microstructure examinations were conducted to analyze the weld and heat-affected zone. The tensile strengths of the base metal materials Protection 600T, DP450, and S275JR were found to be 1524.73 ± 18.7, 500.8 ± 10.4, and 508.5 ± 9.5 MPa, respectively. In welded samples of similar materials, the highest efficiency was found to be 103.05% for DP450/DP450, while in dissimilar welded joints, it was 105.5% for the DP450/S275JR pair. Hardness values for the base materials Protection 600T, DP450, and S275JR were measured as 526.5 ± 10.5, 153.8 ± 1.8, and 162.5 ± 5.2, respectively. In all welded samples, there was an increase in hardness in the weld zone (due to the welding wire) and the heat-affected zone (due to grain size refinement). While the impact energy values of similar material pairs were close to the base material impact energy values, the impact energy values of dissimilar material pairs varied according to the base materials. In addition, in joints made with similar materials, the bending force was close to the base materials, while a decrease in bending force was observed in joints formed with dissimilar materials. As a result, the welding of DP450 and S275JR materials was carried out efficiently. Protection 600T was welded with other materials, but its welding strength was limited to the strength of the material with low mechanical properties. Full article
Show Figures

Figure 1

14 pages, 3473 KiB  
Communication
R-Phase Transformation Evolution in NiTi SMA Wires Studied via the Internal Friction Technique
by Yuhao Xu, Junlan Chen, Xinggang Wang, Meng Sun, Xianping Wang and Weibin Jiang
Crystals 2024, 14(5), 476; https://doi.org/10.3390/cryst14050476 - 18 May 2024
Viewed by 306
Abstract
The specific damping capacity variation of heat-treated NiTi was observed during a pseudoelasticity test. The detailed B2 → R-phase transformation process in cold-drawn NiTi wires undergoing middle-temperature aging was studied via X-ray diffraction, transmission electron microscope, and internal friction technique. Results show that, [...] Read more.
The specific damping capacity variation of heat-treated NiTi was observed during a pseudoelasticity test. The detailed B2 → R-phase transformation process in cold-drawn NiTi wires undergoing middle-temperature aging was studied via X-ray diffraction, transmission electron microscope, and internal friction technique. Results show that, as aging time increased at 450 °C, the dynamic phase transition splitting from B2 → R to B2 → R1 and B2 → R2 became evident. However, such a splitting process was not observed for the sample after aging at 400 °C. The reason for R-phase generation is attributed to non-uniformly distributed stress fields. The splitting of the internal friction peak, in conjunction with high-resolution transmission electron microscope and mechanic results, suggests a substantial occurrence of short-range segregation of Ni atoms in the B2-NiTi matrix. Furthermore, the specific damping capacity (SDC) exhibits a gradual increase with prolonged annealing time. Specifically, the sample with significant dynamic phase transition splitting reaches an SDC value of 0.60. Full article
(This article belongs to the Special Issue Advances of Shape Memory Alloys)
Show Figures

Figure 1

16 pages, 2876 KiB  
Article
Reactive Magnetron Sputtering for Y-Doped Barium Zirconate Electrolyte Deposition in a Complete Protonic Ceramic Fuel Cell
by Victoire Lescure, Mélanie François, Maëlys Charleux, Eric Aubry, Lionel Combemale, Pascal Briois and Gilles Caboche
Crystals 2024, 14(5), 475; https://doi.org/10.3390/cryst14050475 - 18 May 2024
Viewed by 197
Abstract
Yttrium-doped barium zirconate is a commonly used electrolyte material for Protonic Ceramic Fuel Cells (PCFC) due to its high protonic conductivity and high chemical stability. However, it is also known for its poor sinterability and poor grain boundary conductivity. In this work, in [...] Read more.
Yttrium-doped barium zirconate is a commonly used electrolyte material for Protonic Ceramic Fuel Cells (PCFC) due to its high protonic conductivity and high chemical stability. However, it is also known for its poor sinterability and poor grain boundary conductivity. In this work, in response to these issues, reactive magnetron sputtering was strategically chosen as the electrolyte deposition technique. This method allows the creation of a 4 µm tick electrolyte with a dense columnar microstructure. Notably, this technique is not widely utilized in PCFC fabrication. In this study, a complete cell is elaborated without exceeding a sintering temperature of 1350 °C. Tape casting is used for the anode, and spray coating is used for the cathode. The material of interest is yttrium-doped barium zirconate with the formula BaZr0.8Y0.2O3−δ (BZY). The anode consists of a NiO-BZY cermet, while the cathode is composed of BZY and Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSFC) in a 50:50 weight ratio. The electrochemical impedance spectroscopy analysis reveals a global polarization resistance of 0.3 Ω cm2, indicating highly efficient interfaces between electrolytes and electrodes. Full article
(This article belongs to the Section Materials for Energy Applications)
25 pages, 11877 KiB  
Review
Chiral 4f and 3d-4f Complexes from Enantiopure Salen-Type Schiff Base Ligands
by Catherine P. Raptopoulou
Crystals 2024, 14(5), 474; https://doi.org/10.3390/cryst14050474 - 18 May 2024
Viewed by 304
Abstract
This review summarizes the structural characteristics and physicochemical properties of chiral 4f and 3d-4f complexes based on enantiopure salen-type Schiff base ligands. The chirality originates from the enantiopure diamines and is imparted to the Schiff base ligands and complexes and finally to the [...] Read more.
This review summarizes the structural characteristics and physicochemical properties of chiral 4f and 3d-4f complexes based on enantiopure salen-type Schiff base ligands. The chirality originates from the enantiopure diamines and is imparted to the Schiff base ligands and complexes and finally to the crystal structures. The reported enantiopure Schiff base ligands derive from the condensation of aromatic aldehydes, such as salicylaldehyde and its various derivatives, and the enantiopure diamines, (1R,2R) or (1S,2S)-1,2-diamino-cyclohexane, (1R,2R) or (1S,2S)-1,2-diamino-1,2-diphenylethane, (R) or (S)-2,2′-diamino-1,1′-binaphthalene, and 1,2-diaminopropane. Full article
(This article belongs to the Section Crystal Engineering)
Show Figures

Figure 1

11 pages, 2462 KiB  
Article
Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method
by Lin Li, Peixiong Zhang, Zhen Li and Zhenqiang Chen
Crystals 2024, 14(5), 473; https://doi.org/10.3390/cryst14050473 - 17 May 2024
Viewed by 219
Abstract
PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF [...] Read more.
PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method. Full article
(This article belongs to the Special Issue Photoelectric Functional Crystals)
Show Figures

Figure 1

21 pages, 12476 KiB  
Article
Al-Rich Titanites from Mont Blanc Alpine Fissures: Evidence of Ti-Nb-Y-REE Mobility during Water–Rock Interactions
by Michel Cathelineau and Chantal Peiffert
Crystals 2024, 14(5), 472; https://doi.org/10.3390/cryst14050472 - 17 May 2024
Viewed by 256
Abstract
Titanites can be excellent markers of element transfer in medium-temperature retrograde metamorphism. Euhedral titanites from several alpine fissures from Mont Blanc, particularly those of Périades and Courtes, crystallised at the end of the main quartz stage and are synchronous with the formation of [...] Read more.
Titanites can be excellent markers of element transfer in medium-temperature retrograde metamorphism. Euhedral titanites from several alpine fissures from Mont Blanc, particularly those of Périades and Courtes, crystallised at the end of the main quartz stage and are synchronous with the formation of green biotites and albite before chlorite formation. Micro-XRF, SEM, electron probe, and LA-ICP-MS analyses show that these titanites have a wide range of Al2O3 content from 1 to 8%, are dominated by -OH versus F, and have a wide range of Nb (up to 4500 ppm), Y (up to 3000 ppm), Zr (up to 1800 ppm), and Sn (up to 1400 ppm) concentrations. The allanite from the granite, partly destabilised into epidote, is the most likely source of Nb, Y, Zr, Sn, and REE. Titanites are enriched in HREE and show variations in LREE depending on the studied sites. Like quartz, they formed at around 400 ± 20 °C, which is compatible with the formation of green biotites after the destabilisation of granite Fe-Mg silicates. This early stage of fluid circulation, synchronous with the Mont Blanc massif uplift, is therefore marked by the titanite formation at the transition between the biotite and chlorite stability fields. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
Show Figures

Figure 1

8 pages, 7054 KiB  
Communication
Role of Longitudinal Temperature Gradients in Eliminating Interleaving Inclusions in Casting of Monocrystalline Silicon Ingots
by Lindong Li and Changbo Fu
Crystals 2024, 14(5), 471; https://doi.org/10.3390/cryst14050471 - 17 May 2024
Viewed by 178
Abstract
Infrared analysis reveals the presence of interwoven inclusions, primarily comprised of silicon nitride and silicon carbide, in the casting process of monocrystalline silicon ingots. This study investigates how the longitudinal temperature gradient affects the removal of inclusions during the casting of monocrystalline silicon [...] Read more.
Infrared analysis reveals the presence of interwoven inclusions, primarily comprised of silicon nitride and silicon carbide, in the casting process of monocrystalline silicon ingots. This study investigates how the longitudinal temperature gradient affects the removal of inclusions during the casting of monocrystalline silicon ingots through simulations and comparative experiments. Two monocrystalline silicon ingots were cast, each using different longitudinal temperature gradients: one employing smaller gradients and the other conventional gradients. CGSim (Version Basic CGSim 23.1) simulation software was utilized to analyze the melt flow and temperature distribution during the growth process of quasi–monocrystalline silicon ingots. The findings indicate that smaller longitudinal temperature gradients lead to a more robust upward flow of molten silicon at the solid–liquid interface, effectively carrying impurities away from this interface and preventing their inclusion formation. Analysis of experimental photoluminescence and IR results reveals that although inclusions may not be observed, impurities persist but are gradually displaced to the top of the silicon melt through a stable growth process. Full article
(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Second Edition)
Show Figures

Figure 1

14 pages, 8409 KiB  
Article
Surface Enhancement of Titanium-Based Coatings on Commercial Hard Steel Cutting Tools
by Minh Nhat Dang, Surinder Singh, Hannah J. King, John H. Navarro-Devia, Hoang Le, Thomas G. Pattison, Rosalie K. Hocking, Scott A. Wade, Guy Stephens, Angelo Papageorgiou, Armando Manzano and James Wang
Crystals 2024, 14(5), 470; https://doi.org/10.3390/cryst14050470 - 17 May 2024
Viewed by 266
Abstract
This study investigates the mechanical properties, surface integrity, and chemical configuration of PVD-coated high-speed steel (HSS) cutting tools, with a particular focus on titanium nitride (TiN) and titanium aluminium nitride (TiAlN) coatings. A range of characterisation methodologies were employed to examine the impact [...] Read more.
This study investigates the mechanical properties, surface integrity, and chemical configuration of PVD-coated high-speed steel (HSS) cutting tools, with a particular focus on titanium nitride (TiN) and titanium aluminium nitride (TiAlN) coatings. A range of characterisation methodologies were employed to examine the impact of pre-coating surface conditions on the resulting coatings. This impact includes the effects of gas bubble production and unequal distribution of elements, which are two unwanted occurrences. Notwithstanding these difficulties, coatings applied on surfaces that were highly polished exhibited more consistency in their mechanical and elemental characteristics, with a thickness ranging from 2 to 4 µm. The study of mechanical characteristics confirms a significant increase in hardness, from an initial value of roughly 1000 HV0.5 for untreated tools to 1300 HV0.5 for tools with physical vapour deposition (PVD) coatings. Although PVD coatings produced on an industrial scale might not exceed the quality of coatings manufactured in a laboratory, they do offer substantial enhancements in terms of hardness. This study highlights the significant importance of thorough surface preparation in achieving enhanced coating performance, hence contributing to the efforts to prolong the lifespan of tools and enhance their performance even under demanding operational circumstances. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
Show Figures

Figure 1

14 pages, 7900 KiB  
Article
Cobalt and Iron Cyano Benzene Bis(Dithiolene) Complexes
by António G. Costa, Gonçalo Lopes, João F. G. Rodrigues, Isabel C. Santos, Dulce Simão, Elsa B. Lopes, Laura C. J. Pereira, Nolwenn Le Breton, Sylvie Choua, Stéphane A. Baudron, Manuel Almeida and Sandra Rabaça
Crystals 2024, 14(5), 469; https://doi.org/10.3390/cryst14050469 - 17 May 2024
Viewed by 349
Abstract
New iron and cobalt bis(dithiolene) complexes [M(3cbdt)2] (3cbdt = 3-cyanobenzene-1,2-dithiolate) were prepared as tetraphenylphosphonium (Ph4P+) salts for Fe in the monoanionic state and for Co in both the dianionic and monoanionic states: (Ph4P)2[Fe(III)(3cbdt) [...] Read more.
New iron and cobalt bis(dithiolene) complexes [M(3cbdt)2] (3cbdt = 3-cyanobenzene-1,2-dithiolate) were prepared as tetraphenylphosphonium (Ph4P+) salts for Fe in the monoanionic state and for Co in both the dianionic and monoanionic states: (Ph4P)2[Fe(III)(3cbdt)2]2 (1); (Ph4P)2[Co(III)(3cbdt)2]2 (2); (Ph4P)2[Co(II)(3cbdt)2] (3). These compounds were characterized by single-crystal X-ray diffraction, cyclic voltammetry, EPR, and static magnetic susceptibility. Their properties are discussed in comparison with the corresponding complexes based on the isomer ligand 4-cyanobenzene-1,2-dithiolate (4cbdt) and 4,5-cyanobenzene-1,2-dithiolate (dcbdt), previously described by us. The Fe(III) and the Co(III) compounds (1 and 2) are isostructural, crystallizing in the triclinic P1¯ space group, with cis [M(III)(3cbdt)2] complexes dimerized in a trans fashion, and the transition metal (M = Fe, Co) has a distorted 4+1 square pyramidal coordination geometry. The Co(II) compound (3) crystallizes in the triclinic P1¯ space group, with the unit cell containing one cis and three trans inequivalent [Co(II)(3cbdt)2] complexes with the transition metal (Co) and having a square planar coordination geometry. The Fe(III) complex (1) is EPR-silent, and the static magnetic susceptibility shows a temperature dependence typical of dimers of antiferromagnetically coupled S = 3/2 spins with −J/kB = 233.6 K and g = 1.8. Static magnetic susceptibility measurements of compound (3) show that this Co(II) complex is paramagnetic, corresponding to an S = ½ state with g = 2, in agreement with EPR spectra showing in solid state a hyperfine structure typical of the I(59Co) = 7/2. Static susceptibility measurements of Co(III) complex (2) showed an increase in the paramagnetic susceptibility upon warming above 100 K, which is consistent with strong AFM coupling between dimerized S = 1 units with a constant −J/kB ~1286 K. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
Show Figures

Figure 1

11 pages, 3675 KiB  
Article
Low Temperature Raman Spectroscopy of Tetrahydrofuran: Phonon Spectra Compared to Matrix Isolation Spectra in Air
by Vlasta Mohaček-Grošev
Crystals 2024, 14(5), 468; https://doi.org/10.3390/cryst14050468 - 16 May 2024
Viewed by 228
Abstract
The conformation of tetrahydrofuran (THF) molecules in vapor has been the subject of considerable computational and experimental studies, the most recent by Park and Kwon stated that the difference between the most stable, twisted C2 conformer and the bent Cs conformer [...] Read more.
The conformation of tetrahydrofuran (THF) molecules in vapor has been the subject of considerable computational and experimental studies, the most recent by Park and Kwon stated that the difference between the most stable, twisted C2 conformer and the bent Cs conformer is 17 ± 15 cm−1. Because of low symmetry, all modes from both conformers are allowed in the Raman and infrared spectra. In 1982, Aleksanyan and Antipov observed the emergence of two Raman bands at 249 and 303 cm−1 at 20 K, while only one band at 293 cm−1 was present in solid THF at 142. They assigned the 249 cm−1 band to the restricted pseudorotational motion of THF in the solid state, because on heating, the band diminishes and is too weak to be observed near melting point (at 142 K). Cadioli et al. reported a study of the vibrational spectrum of tetrahydrofuran, giving a complete assignment of all bands including those present in the low-temperature Raman spectrum at 85 K and infrared bands observed at 90 K. They assigned the band at 242 cm−1 in the Raman spectrum at 85 K as an overtone of the lowest normal mode (pseudorotational mode), while the 299 cm−1 band in the same spectrum was assigned as a radial mode. In the following, low-temperature Raman spectra of solid THF together with the Raman matrix isolated spectrum of THF in air will be presented and compared to published data. Our results indicate that the band observed at 245 cm−1 at 10 K is too strong to be assigned as an overtone, since its intensity is of the same magnitude as the 299 cm−1 band. Full article
(This article belongs to the Section Organic Crystalline Materials)
Show Figures

Figure 1

14 pages, 5726 KiB  
Article
First-Principles Calculations of P-B Co-Doped Cluster N-Type Diamond
by Huaqing Lan, Sheng Yang, Wen Yang, Maoyun Di, Hongxing Wang, Yuming Tian and Kaiyue Wang
Crystals 2024, 14(5), 467; https://doi.org/10.3390/cryst14050467 - 16 May 2024
Viewed by 177
Abstract
To achieve n-type doping in diamond, extensive investigations employing first principles have been conducted on various models of phosphorus doping and boron–phosphorus co-doping. The primary focus of this study is to comprehensively analyze the formation energy, band structure, density of states, and ionization [...] Read more.
To achieve n-type doping in diamond, extensive investigations employing first principles have been conducted on various models of phosphorus doping and boron–phosphorus co-doping. The primary focus of this study is to comprehensively analyze the formation energy, band structure, density of states, and ionization energy of these structures. It is observed that within a diamond structure solely composed of phosphorus atoms, the formation energy of an individual carbon atom is excessively high. However, the P-V complex substitutes 2 of the 216 carbon atoms, leading to the transformation of diamond from an insulator to a p-type semiconductor. Upon examining the P-B co-doped structure, it is revealed that the doped impurities exhibit a tendency to form more stable cluster configurations. As the separation between the individually doped atoms and the cluster impurity structure increases, the overall stability of the structure diminishes, consequently resulting in an elevation of the ionization energy. Examination of the electronic density of states indicates that the contribution of B atoms to the impurity level is negligible in the case of P-B doping. Full article
(This article belongs to the Section Crystal Engineering)
Show Figures

Figure 1

14 pages, 4769 KiB  
Review
Reversible Crosslinking of LC-Materials by Gel-Formation
by Rudolf Zentel
Crystals 2024, 14(5), 466; https://doi.org/10.3390/cryst14050466 - 16 May 2024
Viewed by 223
Abstract
The topic of this review is the physical gelling of liquid crystalline (LC) phases. It allows the combination of order and mobility of the LC-phase with macroscopic stability, which makes it a soft material. Thus, the gelled LCs acquire properties of LC-elastomers without [...] Read more.
The topic of this review is the physical gelling of liquid crystalline (LC) phases. It allows the combination of order and mobility of the LC-phase with macroscopic stability, which makes it a soft material. Thus, the gelled LCs acquire properties of LC-elastomers without the need for complicated chemistry to allow polymerization and crosslinking. But, instead, an LC-material (either a pure compound or a mixture) can be mixed with a few percent of a gel-forming agent, which self-assembles into long fibers that span the volume of the gel and make it a soft-solid. The use of azo-containing gel-forming agents thereby allows us to make gelation not only thermo-responsive, but also photo-responsive (trans-cis isomerization). This review discusses the micro-morphology of the gelled LCs and their influence on the mechanical properties and the switching in external electric fields. In addition, the potential of reversibility is discussed, which is not only interesting for recycling purposes, but also offers a route to inscribe a complex director pattern into the gelled liquid crystal. Full article
(This article belongs to the Special Issue Liquid Crystal Materials and Devices)
Show Figures

Figure 1

10 pages, 3851 KiB  
Article
Microstructural Optimization of Sn-58Bi Low-Temperature Solder Fabricated by Intense Pulsed Light (IPL) Irradiation
by Hyeri Go, Taejoon Noh, Seung-Boo Jung and Yoonchul Sohn
Crystals 2024, 14(5), 465; https://doi.org/10.3390/cryst14050465 - 16 May 2024
Viewed by 209
Abstract
In this study, intense pulsed light (IPL) soldering was employed on Sn-58Bi solder pastes with two distinct particle sizes (T3: 25–45 μm and T9: 1–8 μm) to investigate the correlation between the solder microstructure and mechanical properties as a function of IPL irradiation [...] Read more.
In this study, intense pulsed light (IPL) soldering was employed on Sn-58Bi solder pastes with two distinct particle sizes (T3: 25–45 μm and T9: 1–8 μm) to investigate the correlation between the solder microstructure and mechanical properties as a function of IPL irradiation times. During IPL soldering, a gradual transition from an immature to a refined to a coarsened microstructure was observed in the solder, impacting its mechanical strength (hardness), which initially exhibited a slight increase followed by a subsequent decrease. It is noted that hardness measurements taken during the immature stage may exhibit slight deviations from the Hall–Petch relationship. Experimental findings revealed that as the number of IPL irradiation sessions increased, solder particles progressively coalesced, forming a unified mass after 30 sessions. Subsequently, after 30–40 IPL sessions, notable voids were observed within the T3 solder, while fewer voids were detected at the T9-ENIG interface. Following IPL soldering, a thin layered structure of Ni3Sn4 intermetallic compound (IMC) was observed at the Sn-58Bi/ENIG interface. In contrast, reflow soldering resulted in the abundant formation of rod-shaped Ni3Sn4 IMCs not only at the reaction interface but also within the solder bulk, accompanied by the notable presence of a P-rich layer beneath the IMC. Full article
Show Figures

Figure 1

18 pages, 4877 KiB  
Article
Removal of Organic Materials from Mytilus Shells and Their Morphological and Chemical-Physical Characterisation
by Alberto Ubaldini, Flavio Cicconi, Sara Calistri, Stefano Salvi, Chiara Telloli, Giuseppe Marghella, Alessandro Gessi, Stefania Bruni, Naomi Falsini and Antonietta Rizzo
Crystals 2024, 14(5), 464; https://doi.org/10.3390/cryst14050464 - 16 May 2024
Viewed by 307
Abstract
A simple and effective method to eliminate the organic component from mussel shells is presented. It is based on the use of hot hydrogen peroxide. Mollusc shells are composite materials made of a calcium carbonate matrix with different polymorphs and numerous biomacromolecules. The [...] Read more.
A simple and effective method to eliminate the organic component from mussel shells is presented. It is based on the use of hot hydrogen peroxide. Mollusc shells are composite materials made of a calcium carbonate matrix with different polymorphs and numerous biomacromolecules. The described method was used on mussel shells, but it is generalisable and allows the complete removal of these organic components, without altering the inorganic part. Specimens were kept in a H2O2 40% bath for few hours at 70 °C. The organic layers found on the faces of the shells were peeled away in this way, and biomacromolecules were degraded and removed. Their fragments are soluble in aqueous solution. This easily permits the chemical-physical characterisation and the study of the microstructure. The quality of calcite and aragonite microcrystals of biogenic origin is very high, superior to that of materials of geological or synthetic origin. This may suggest various industrial applications for them. Calcium carbonate is a useful precursor for cements and other building materials, and the one obtained in this way is of excellent quality and high purity. Full article
Show Figures

Figure 1

8 pages, 2251 KiB  
Article
Mineralization of Octacalcium Phosphate under Magnetic Field
by Wenhao He, Bingyu Xue, Qi Qian, Shenye Chen, Zhengyi Fu and Kun Wang
Crystals 2024, 14(5), 463; https://doi.org/10.3390/cryst14050463 - 16 May 2024
Viewed by 344
Abstract
The mineralization of octacalcium phosphate (OCP) crystals in gel media was studied in the presence of a magnetic field. OCP crystal growth was found to be dependent on mineralization temperature, mineralization time, and the magnetic field. Higher temperatures significantly reduced the mineralization time, [...] Read more.
The mineralization of octacalcium phosphate (OCP) crystals in gel media was studied in the presence of a magnetic field. OCP crystal growth was found to be dependent on mineralization temperature, mineralization time, and the magnetic field. Higher temperatures significantly reduced the mineralization time, which is crucial for directional growth of OCP crystals. The growth of OCP crystals was accelerated by the applied magnetic field, while OCP crystals generated in the presence of a magnetic field exhibited increased length and width of oriented growth. This study provides valuable insights into the influence of mineralization factors in bioprocessing-inspired manufacturing processes. Full article
(This article belongs to the Section Mineralogical Crystallography and Biomineralization)
Show Figures

Figure 1

21 pages, 10528 KiB  
Article
Ozone-Assisted Hydrothermal Synthesis Method of Sb-Doped SnO2 Conductive Nanoparticles for Carbon-Free Oxygen-Reduction-Reaction Catalysts of Proton-Exchange-Membrane Hydrogen Fuel Cells
by Takeshi Fukuda, Kenji Iimura, Takanori Yamamoto, Ryuki Tsuji, Maito Tanabe, Seiji Nakashima, Naoki Fukumuro and Seigo Ito
Crystals 2024, 14(5), 462; https://doi.org/10.3390/cryst14050462 - 15 May 2024
Viewed by 313
Abstract
Proton-exchange-membrane hydrogen fuel cells (PEMFCs) are an important energy device for achieving a sustainable hydrogen society. Carbon-based catalysts used in PEMFCs’ cathode can degrade significantly during operation-voltage shifts due to the carbon deterioration. The longer lifetime of the system is necessary for the [...] Read more.
Proton-exchange-membrane hydrogen fuel cells (PEMFCs) are an important energy device for achieving a sustainable hydrogen society. Carbon-based catalysts used in PEMFCs’ cathode can degrade significantly during operation-voltage shifts due to the carbon deterioration. The longer lifetime of the system is necessary for the further wide commercialization of PEMFCs. Therefore, carbon-free catalysts are required for PEMFCs. In this study, highly crystallized conducting Sb-doped SnO2 (Sb-SnO2) nanoparticles (smaller than 7 nm in size) were synthesized using an ozone-assisted hydrothermal synthesis. Pt nanoparticles were loaded on Sb-SnO2 supporting particles by polyol method to be “Pt/Sb-SnO2 catalyst”. The Pt/Sb-SnO2 catalyst showed a high oxygen reduction reaction (ORR) mass activity (178.3 A g−1-Pt @ 0.9 V), compared to Pt/C (149.3 A g−1-Pt @ 0.9 V). In addition, the retention ratio from the initial value of electrochemical surface area (ECSA) during 100,000-voltage cycles tests between 1.0 V and 1.5 V, Pt/SnO2 and Pt/Sb-SnO2 catalyst exhibited higher stability (90% and 80%), respectively, than that of Pt/C catalyst (47%). Therefore, the SnO2 and Sb-SnO2 nanoparticles synthesized using this new ozone-assisted hydrothermal method are promising as carbon-free catalyst supports for PEMFCs. Full article
Show Figures

Figure 1

17 pages, 4547 KiB  
Article
Influence of Austenite Grain Size on the Variant Configurations of Martensite in a Fe-30.5Ni-0.155C Alloy
by Loïc Malet and Stéphane Godet
Crystals 2024, 14(5), 461; https://doi.org/10.3390/cryst14050461 - 14 May 2024
Viewed by 303
Abstract
A Fe-30.5wt%Ni-0.155wt%C alloy was annealed at two different temperatures to produce two different austenite grain sizes. In the coarse-grained specimen, hierarchical configurations of variants are formed and carefully analyzed using EBSD. These typical patterns result from the alternate formation of two perpendicular plate [...] Read more.
A Fe-30.5wt%Ni-0.155wt%C alloy was annealed at two different temperatures to produce two different austenite grain sizes. In the coarse-grained specimen, hierarchical configurations of variants are formed and carefully analyzed using EBSD. These typical patterns result from the alternate formation of two perpendicular plate groups of variants over several length scales, and two distinct types of mechanical couplings are shown to occur sequentially in the process of the transformation of an austenitic grain. In the fine-grained specimen, the martensite start temperature is depressed below liquid nitrogen temperature, and the martensitic transformation can only occur under stress assistance. Grain size reduction brings about a dramatic change in the morphology of martensite and its configurations. Martensite is fully twinned, and martensite variants arrange themselves into self-accommodating configurations involving all four variants of the same plate group. Those specific configurations share striking similarities with those usually encountered in conventional shape memory alloys. The reversion of such microstructures upon heating is believed to be at the origin of the observed shape memory effect. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
Show Figures

Figure 1

14 pages, 10035 KiB  
Article
Effect of Polyoxyethylene-Based Nonionic Surfactants on Chemical–Mechanical Polishing Performance of Monocrystalline Silicon Wafers
by Bowen Jiang, Jie Guan, Peng Zhao, Yulin Chen and Zefang Zhang
Crystals 2024, 14(5), 460; https://doi.org/10.3390/cryst14050460 - 14 May 2024
Viewed by 322
Abstract
The use of surfactants is crucial in the chemical–mechanical polishing fluid system for silicon wafers. This paper examines the impact of the functional group structure of polyoxyethylene-based nonionic surfactants and the variation in the polyoxyethylene (EO) addition number on the polishing performance of [...] Read more.
The use of surfactants is crucial in the chemical–mechanical polishing fluid system for silicon wafers. This paper examines the impact of the functional group structure of polyoxyethylene-based nonionic surfactants and the variation in the polyoxyethylene (EO) addition number on the polishing performance of monocrystalline silicon wafers, to achieve the appropriate material removal rate and surface quality. The results demonstrated that the straight-chain structure of fatty alcohol polyoxyethylene ether (AEO-9) exhibited superior performance in wafer polishing compared to octylphenol polyoxyethylene ether (OP-9) and isoprenol polyoxyethylene ether (TPEG) and polyethylene glycol (PEG). By varying the number of EO additions of AEO-type surfactants, this study demonstrated that the polishing performance of monocrystalline silicon wafers was affected by the number of EO additions. The best polishing effect was achieved when the number of EO additions was nine. The mechanism of the role of polyoxyethylene-type nonionic surfactants in silicon wafer polishing was derived through polishing experiments, the contact angle, abrasive particle size analysis, zeta potential measurement, XPS, and other means of characterization. Full article
(This article belongs to the Special Issue Surface Modification Treatments of Metallic Materials)
Show Figures

Figure 1

12 pages, 4828 KiB  
Article
Structural and Optical Characterization of a New Tetra- and Hexa-Coordinated Cd-Based Hybrid Compound with White Light Emission
by Imen Sayer, Rawia Msalmi, Edoardo Mosconi, Ahlem Guesmi, Ammar Houas, Naoufel Ben Hamadi and Houcine Naïli
Crystals 2024, 14(5), 459; https://doi.org/10.3390/cryst14050459 - 12 May 2024
Viewed by 494
Abstract
The present paper deals with a new two-in-one zero-dimensional (0D) organic–inorganic hybrid compound namely (C6H10N2)4[CdBr6][CdBr4]2. This molecular crystal structure contains isolated CdBr4 tetrahedra and CdBr6 octahedra. The [...] Read more.
The present paper deals with a new two-in-one zero-dimensional (0D) organic–inorganic hybrid compound namely (C6H10N2)4[CdBr6][CdBr4]2. This molecular crystal structure contains isolated CdBr4 tetrahedra and CdBr6 octahedra. The optical characterization by UV–Vis–NIR spectroscopy shows that the (C6H10N2)4[CdBr6][CdBr4]2 exhibits a large gap energy of 4.97 eV. Under UV excitation, this hybrid material shows a bright cold white light emission (WLE) at room temperature. The photoluminescence (PL) analysis suggests that the WLE originates from the organic molecules. Density of states (DOS) analysis using the density functional theory (DFT) demonstrates that the calculated HOMO(Br)→LUMO(organic) absorption transition (4.1 eV) does not have significant intensity, while, the transition involving the valence band (VB) and the second and third conduction bands (CB) around 5 eV are allowed, which is in good agreement with the experimental gap value. The interesting theoretical result is that the LUMO(organic)→HOMO(Br) emission is allowed, which confirms the important role of the organic molecule in the emission mechanism, in good agreement with the experimental PL analysis. Full article
(This article belongs to the Special Issue Advances in Organic Semiconductors)
Show Figures

Figure 1

13 pages, 3322 KiB  
Article
Two Consecutive Negative Electrocaloric Peaks in <001>-Oriented PMN-30PT Single Crystals
by Yu Zhang, Weiping Gong, Zhen Li, Jianting Li, Changyu Li, Jun Chen, Yaodong Yang, Yang Bai and Wei-Feng Rao
Crystals 2024, 14(5), 458; https://doi.org/10.3390/cryst14050458 - 12 May 2024
Viewed by 370
Abstract
The versatile electrocaloric (EC) behaviors of the (1-x)Pb(Mg1/3Nb2/3)O3-xPT (PMN-100xPT) single crystal are closely related to the multiple phase transitions under the multiple fields of electric field and temperature. In this work, the EC effect of [...] Read more.
The versatile electrocaloric (EC) behaviors of the (1-x)Pb(Mg1/3Nb2/3)O3-xPT (PMN-100xPT) single crystal are closely related to the multiple phase transitions under the multiple fields of electric field and temperature. In this work, the EC effect of <001>-oriented PMN-30PT single crystals with chemical composition at morphotropic phase boundary has been studied during the phase transformation process from the ferroelectric rhombohedral (R) phase to the tetragonal (T) phase. Two consecutive negative EC peaks have been achieved for the first time. Based on the projection of the EC effect in the electric field-temperature phase diagram, the relationship between the EC behaviors and the phase transitions is further established. It was found that the monoclinic (M) phase actually existed during the transformation from the R phase to the T phase, and the related R-M phase transition and M-T phase transition could both induce negative EC peaks. Under the electric field of E = 10 kV/cm, the first negative EC peaks induced by the R-M phase transition is at 57 °C with ΔTmax = −0.11 K. And the M-T phase transition can produce a higher negative EC peak, and its value can reach −0.22 K at 68 °C. Based on thermodynamic calculations, the relationship between the entropy change in different phase transitions and the EC behaviors has been further elucidated. The negative EC effect originates from the structural entropy increase in the electric field-induced phase transition process. This work not only advances the research on the electrical properties of relaxor ferroelectric single crystals but also provides a new insight into high-performance ferroelectric materials design. Full article
(This article belongs to the Special Issue Advanced Ferroelectric, Piezoelectric and Dielectric Ceramics)
Show Figures

Figure 1

14 pages, 16132 KiB  
Article
Hierarchically Porous Carbon Cloth–Polyaniline (CC–PANI) Composite Supercapacitor Electrodes with Enhanced Stability
by Svetlana V. Stakhanova, Ilya S. Krechetov, Kristina E. Shafigullina, Tatiana L. Lepkova, Valentine V. Berestov, Eugene S. Statnik, Zlatotsveta E. Zyryanova, Elena A. Novikova and Alexander M. Korsunsky
Crystals 2024, 14(5), 457; https://doi.org/10.3390/cryst14050457 - 12 May 2024
Viewed by 355
Abstract
In this work, hierarchically porous composites were prepared in the form of activated carbon cloth (CC) Busofit T–1–055 filled with an electrically conductive polymer, polyaniline (PANI), for use as pseudocapacitive electrodes of electrochemical supercapacitors (SCs). CC fibers have high nanoporosity and specific surface [...] Read more.
In this work, hierarchically porous composites were prepared in the form of activated carbon cloth (CC) Busofit T–1–055 filled with an electrically conductive polymer, polyaniline (PANI), for use as pseudocapacitive electrodes of electrochemical supercapacitors (SCs). CC fibers have high nanoporosity and specific surface area, so it was possible to deposit (via the chemical oxidative polymerization of aniline) a significant amount of PANI on them in the form of a thin layer mainly located on the inner surface of the pores. Such morphology of the composite made allowed the combining of the high capacitive characteristics of PANI with the reversibility of electrochemical processes, high columbic efficiency and cyclic stability rather typical for carbon materials of double-layer SCs. The highest capacitance of composite electrodes of about 4.54 F/cm2 with high cyclic stability (no more than 8% of capacity loss after 2000 charge–discharge cycles with a current density of 10 A/cm2) and columbic efficiency (up to 98%) was achieved in 3 M H2SO4 electrolyte solution when PANI was synthesized from an aniline hydrochloride solution with a concentration of 0.25 M. Trasatti analysis revealed that 27% of specific capacitance corresponded to pseudocapacitance, and 73% to the double-layer capacitance. Full article
Show Figures

Figure 1

15 pages, 9317 KiB  
Article
Impact of Zinc Oxide on the Structure and Surface Properties of Magnesium–Potassium Glass–Crystalline Glazes
by Katarzyna Pasiut, Janusz Partyka, Dawid Kozień and Piotr Pańtak
Crystals 2024, 14(5), 456; https://doi.org/10.3390/cryst14050456 - 11 May 2024
Viewed by 453
Abstract
The present work describes test results for glass crystal materials based on the SiO2-Al2O3-MgO-K2O system after 5, 10, 15, and 20 wt.% zinc oxide was added. The glazing analysis involved determining the effect of the [...] Read more.
The present work describes test results for glass crystal materials based on the SiO2-Al2O3-MgO-K2O system after 5, 10, 15, and 20 wt.% zinc oxide was added. The glazing analysis involved determining the effect of the additive on the characteristic temperatures and properties of the surface obtained, such as color, gloss, and roughness, as expressed by a Ra parameter. The obtained glazes were also analyzed for changes in phase composition (quantitative and qualitative XRD tests), changes in microstructure (based on images obtained with a scanning electron microscope), and structure (based on analyses and decomposition of spectra obtained using mid-infrared spectroscopy). As a result, the maximum addition of zinc oxide provided the best results. Full article
(This article belongs to the Special Issue Porous Ceramics and Their Composite Materials)
Show Figures

Figure 1

13 pages, 9814 KiB  
Article
Aluminium-Silicon Lightweight Thermal Management Alloys with Controlled Thermal Expansion
by Peter Lewis, Andrew Tarrant, Andreas Frehn, Fritz Grensing, James Nicholson, Nick Farrah and Martyn Acreman
Crystals 2024, 14(5), 455; https://doi.org/10.3390/cryst14050455 - 11 May 2024
Viewed by 384
Abstract
With the ever-growing emphasis on global decarbonization and rapid increases in the power densities of electronics equipment in recent years, new methods and lightweight materials have been developed to manage heat load as well as interfacial stresses associated with coefficient of thermal expansion [...] Read more.
With the ever-growing emphasis on global decarbonization and rapid increases in the power densities of electronics equipment in recent years, new methods and lightweight materials have been developed to manage heat load as well as interfacial stresses associated with coefficient of thermal expansion (CTE) mismatches between components. The Al–Si system provides an attractive combination of CTE performance and high thermal conductivity whilst being a very lightweight option. Such materials are of interest to industries where thermal management is a key design criterion, such as the aerospace, automotive, consumer electronics, defense, EV, and space sectors. This paper will describe the development and manufacture of a family of high-performance hypereutectic Al–Si alloys (AyontEX™) by a powder metallurgy method. These alloys are of particular interest for structural heat sink applications that require high reliability under thermal cycling (CTE of 17 μm/(m·°C)), as well as reflective optics and instrument assemblies that require good thermal and mechanical stability (CTE of 13 μm/(m·°C)). Critical performance relationships are presented, coupled with the microstructural, physical, and mechanical properties of these Al–Si alloys. Full article
Show Figures

Figure 1

20 pages, 10466 KiB  
Article
Manufacturing of TiO2, Al2O3 and Y2O3 Ceramic Nanotubes for Application as Electrodes for Printable Electrochemical Sensors
by Alexandru Florentin Trandabat, Romeo Cristian Ciobanu, Oliver Daniel Schreiner, Mihaela Aradoaei and Sebastian Teodor Aradoaei
Crystals 2024, 14(5), 454; https://doi.org/10.3390/cryst14050454 - 11 May 2024
Viewed by 407
Abstract
This paper describes the process to obtain ceramic nanotubes from titanium dioxide, alumina and yttrium oxide by a feasible, replicable and reliable technology, including three stages, starting from an electrospinning process of poly(methyl methacrylate) solutions. A minimum diameter of 0.3 μm was considered [...] Read more.
This paper describes the process to obtain ceramic nanotubes from titanium dioxide, alumina and yttrium oxide by a feasible, replicable and reliable technology, including three stages, starting from an electrospinning process of poly(methyl methacrylate) solutions. A minimum diameter of 0.3 μm was considered optimal for PMMA nanofibers in order to maintain the structural stability of covered fibers, which, after ceramic film deposition, leads to a fiber diameter of 0.5–0.6 μm. After a chemical and physical analysis of the stages of obtaining ceramic nanotubes, in all cases, uniform deposition of a ceramic film on PMMA fibers and, finally, a uniform structure of ceramic nanotubes were noted. The technological purpose was to use such nanotubes as ingredients in screen-printing inks for electrochemical sensors, because no study directly targeted the subject of ceramic nanotube applications for printed electronics to date. The printing technology was analyzed in terms of the ink deposition process, printed electrode roughness vs. type of ceramic nanotubes, derived inks, thermal curing of the electrodes and the conductivity of electrodes on different support (rigid and flexible) at different curing temperatures. The experimental inks containing ceramic nanotubes can be considered feasible for printed electronics, because they offer fast curing at low temperatures, reasonable conductivity vs. electrode length, good printability on both ceramic or plastic (flexible) supports and good adhesion to surface after curing. Full article
(This article belongs to the Special Issue Metal Oxide Thin Films, Nanomaterials and Nanostructures)
Show Figures

Figure 1

27 pages, 16687 KiB  
Article
The Influence of Variations in Synthesis Conditions on the Phase Composition, Strength and Shielding Characteristics of CuBi2O4 Films
by Dauren B. Kadyrzhanov, Medet T. Idinov, Dmitriy I. Shlimas and Artem L. Kozlovskiy
Crystals 2024, 14(5), 453; https://doi.org/10.3390/cryst14050453 - 10 May 2024
Viewed by 438
Abstract
This paper presents the results of the influence of variation of the synthesis conditions of CuBi/CuBi2O4 films with a change in the applied potential difference, as well as a change in electrolyte solutions (in the case of adding cobalt or [...] Read more.
This paper presents the results of the influence of variation of the synthesis conditions of CuBi/CuBi2O4 films with a change in the applied potential difference, as well as a change in electrolyte solutions (in the case of adding cobalt or nickel sulfates to the electrolyte solution) on changes in the phase composition, structural parameters and strength characteristics of films obtained using the electrochemical deposition method. During the experiments, it was found that, in the case of the addition of cobalt or nickel to the electrolyte solutions, the formation of films with a spinel-type tetragonal CuBi2O4 phase is observed. In this case, a growth in the applied potential difference leads to the substitution of copper with cobalt (nickel), which in turn leads to an increase in the structural ordering degree. It should be noted that, during the formation of CuBi/CuBi2O4 films from solution–electrolyte №1, the formation of the CuBi2O4 phase is observed only with an applied potential difference of 4.0 V, while the addition of cobalt or nickel sulfates to the electrolyte solution results in the formation of the tetragonal CuBi2O4 phase over the entire range of the applied potential difference (from 2.0 to 4.0 V). Studies have been carried out on the strength and tribological characteristics of synthesized films depending on the conditions of their production. It has been established that the addition of cobalt or nickel sulfates to electrolyte solutions leads to an increase in the strength of the resulting films from 20 to 80%, depending on the production conditions (with variations in the applied potential difference). During the studies, it was established that substitution of copper with cobalt or nickel in the composition of CuBi2O4 films results in a rise in the shielding efficiency of low-energy gamma radiation by 3.0–4.0 times in comparison with copper films, and 1.5–2.0 times for high-energy gamma rays, in which case the decrease in efficiency is due to differences in the mechanisms of interaction of gamma quanta, as well as the occurrence of secondary radiation as a result of the formation of electron–positron pairs and the Compton effect. Full article
Show Figures

Figure 1

14 pages, 18688 KiB  
Article
Modification of LaB6 with ZrO2-Al2O3-TiO2 for Improvement of Density and Mechanical and Electrical Properties
by Sen Yang, Ruiqing Ba, Jingnan Hong, Jing Li, Jingdong Guo, Xinghui He, Hongwei Zhang, Naihe Yi and Weibing Ma
Crystals 2024, 14(5), 452; https://doi.org/10.3390/cryst14050452 - 9 May 2024
Viewed by 340
Abstract
Pure lanthanum hexaboride (LaB6) ceramics were prepared using powders of different grain sizes. The ceramics could reach a relative density of 98.2% at high temperatures and pressures, but had a low flexural strength (136.9 MPa). LaB6 ceramics were synthesized using [...] Read more.
Pure lanthanum hexaboride (LaB6) ceramics were prepared using powders of different grain sizes. The ceramics could reach a relative density of 98.2% at high temperatures and pressures, but had a low flexural strength (136.9 MPa). LaB6 ceramics were synthesized using ZrO2-Al2O3-TiO2 (ZAT) as sintering additives. The ceramics demonstrate high density and excellent mechanical properties. The hot pressure sintering (HPS) method was utilized in the synthesis of the ceramics. Investigations were conducted on the effects of ZAT content, as well as the effects of the sintering temperature and pressure on the sintering behavior, microstructure, and mechanical and electrical properties of LaB6 ceramics. LaB6 ceramics fabricated with a ZAT addition of 6 wt.%, at a sintering temperature of 1700 °C, and under a pressure of 50 MPa, exhibited superior sintering and electrical properties, including a relative density of 97%, a conductivity of 7.2 MS/m, a flexural strength of 281.5 MPa, and a Vickers hardness of 21.2 GPa. The LaB6 ceramics synthesized in this research exhibit promising potential as electron-emitting cathodes for field emission applications. Full article
(This article belongs to the Section Polycrystalline Ceramics)
Show Figures

Figure 1

19 pages, 21506 KiB  
Review
A Modern Approach to HEAs: From Structure to Properties and Potential Applications
by Radu Nartita, Daniela Ionita and Ioana Demetrescu
Crystals 2024, 14(5), 451; https://doi.org/10.3390/cryst14050451 - 9 May 2024
Viewed by 592
Abstract
High-entropy alloys (HEAs) are advanced materials characterized by their unique and complex compositions. Characterized by a mixture of five or more elements in roughly equal atomic ratios, these alloys diverge from traditional alloy formulations that typically focus on one or two principal elements. [...] Read more.
High-entropy alloys (HEAs) are advanced materials characterized by their unique and complex compositions. Characterized by a mixture of five or more elements in roughly equal atomic ratios, these alloys diverge from traditional alloy formulations that typically focus on one or two principal elements. This innovation has paved the way for subsequent studies that have expanded our understanding of HEAs, highlighting the role of high mixing entropy in stabilizing fewer phases than expected by traditional phase prediction methods like Gibbs’s rule. In this review article, we trace the evolution of HEAs, discussing their synthesis, stability, and the influence of crystallographic structures on their properties. Additionally, we highlight the strength–ductility trade-off in HEAs and explore strategies to overcome this challenge. Moreover, we examine the diverse applications of HEAs in extreme conditions and their promise for future advancements in materials science. Full article
(This article belongs to the Section Crystalline Metals and Alloys)
Show Figures

Figure 1

14 pages, 3689 KiB  
Article
Heat Treatment of Calcite to Enhance Its Removal of Color Dye Alizarin Red S
by Zhaohui Li, Anna Bowman, Angie Rayniak, Jadyn Strommen, Lori Allen and Shangping Xu
Crystals 2024, 14(5), 450; https://doi.org/10.3390/cryst14050450 - 8 May 2024
Viewed by 379
Abstract
The use of color dyes in modern society presents a great challenge to the environment. Thus, extensive studies have been conducted in the last 30 years on the removal of color dyes from aqueous solutions such industrial wastewater. In this study, the removal [...] Read more.
The use of color dyes in modern society presents a great challenge to the environment. Thus, extensive studies have been conducted in the last 30 years on the removal of color dyes from aqueous solutions such industrial wastewater. In this study, the removal of alizarin red S (ARS), an anionic dye, from solution by raw calcite (Cal) and heat-treated calcite (HCal) was conducted and compared under different physico-chemical conditions. Based on the isotherm study, the ARS removal capacities increased from 167 to 251 mmol/kg after the Cal was heated to 1000 °C for 3 h. The X-ray diffraction analyses showed no difference in the calcite phase between Cal and HCal after ARS sorption. Fourier-transform infrared results also showed no change in the calcite phase after ARS sorption, except a slightly increase in wavenumber from 713 to 727 cm−1 for the OCO bending of HCal at high ARS sorption levels. SEM observations showed about the same particle size and morphology before and after ARS sorption. The TGA data showed the formation of CaO after Cal was heated, and CaO converted back into calcite after being in contact with water or ARS solution for 24 h and then being air-dried. Thus, the high ARS removal could be due to CaO produced after Cal being heated. The findings from this research proved that there is great potential in the use of calcite, a low-cost and readily available Earth material, after heat treatment for the removal of contaminants from water. Full article
(This article belongs to the Special Issue Porous Materials and Their Adsorption Behaviors)
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop