Crystals

12 pages, 7029 KiB

Open AccessArticle

Cast Microstructure and Crystallographic Features of Al₃Sc Dendrites in High Sc-Contained Al-Sc Alloys

by Jinjiang He, Qian Jia, Zhaochong Ding, Xingquan Wang, Xiaomeng Cao, Ziqi Cao and Xinfu Gu

Crystals 2024, 14(2), 200; https://doi.org/10.3390/cryst14020200 - 19 Feb 2024

Viewed by 1330

Abstract

Al-Sc alloys containing high Sc content are employed as sputtering targets for the fabrication of high-performance piezoelectric films during magnetic sputtering. Due to the high proportion of the Al₃Sc phase, their workability is quite limited, and they are often used in [...] Read more.

Al-Sc alloys containing high Sc content are employed as sputtering targets for the fabrication of high-performance piezoelectric films during magnetic sputtering. Due to the high proportion of the Al₃Sc phase, their workability is quite limited, and they are often used in the as-cast state. In this study, the crystallography of Al₃Sc dendrites in as-casted Al-10at.%Sc and Al-20at.%Sc samples is examined using electron backscatter diffraction (EBSD). With increasing Sc content, the fraction of Al₃Sc also increases. The Al₃Sc dendrites exhibit a cubic relationship with the Al matrix in both alloys. However, in Al-10%Sc alloys, the facets of the Al₃Sc dendrites are parallel to {001} planes, while twinning is observed in Al-20at.%. The twinning plane is parallel to the {111} plane, and the dendrite growth direction aligns with the <110> directions. The different morphologies of the dendrite structures in these two alloys are discussed in relation to thermodynamic and kinetic considerations based on the phase diagram and nucleation rate. Full article

(This article belongs to the Special Issue Advanced Crystalline Materials, Mechanical Properties and Innovative Production Systems (2nd Edition))

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12 pages, 2347 KiB

Open AccessArticle

Crystallographic Data Collection Using a Multilayer Monochromator on an Undulator Beamline at the Shanghai Synchrotron Radiation Facility

by Chenyu Zhang, Qin Xu, Weiwei Wang, Miao Liang, Li Yu, Minjun Li, Zhimin Zhu, Liqing Huang, Qianhui Li, Feng Yu, Yuzhu Wang, Huan Zhou and Qisheng Wang

Crystals 2024, 14(2), 199; https://doi.org/10.3390/cryst14020199 - 19 Feb 2024

Viewed by 1473

Abstract

To resolve photons hungry for weak diffraction samples by the crystallographic method, a double-multilayer monochromator (DMM) was employed on an undulator beamline (BL17UM) at the Shanghai Synchrotron Radiation Facility (SSRF) to provide a focused sub-micron beam with high brightness for macromolecular crystallography experiments. [...] Read more.

To resolve photons hungry for weak diffraction samples by the crystallographic method, a double-multilayer monochromator (DMM) was employed on an undulator beamline (BL17UM) at the Shanghai Synchrotron Radiation Facility (SSRF) to provide a focused sub-micron beam with high brightness for macromolecular crystallography experiments. High-quality crystallographic datasets from model protein crystal samples were collected and processed by an existing crystallographic program for structure solution and refinement. The data quality was compared with datasets from a normal silicon crystal monochromator to evaluate the bandwidth of the DMM effect on these crystallographic data. This experiment demonstrates that multilayer optics on an undulator beamline may play a valuable role in satisfying the demands of structure-related research, which requires novel methods. Full article

(This article belongs to the Special Issue X-ray Protein Crystallography)

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20 pages, 9838 KiB

Open AccessArticle

Failure Mechanism and Residual Stress Analysis of Crystal Materials for the Thermal Battery

by Wei Su, Ming Chen, Zhizhe Wang, Butian Zhong and Zhenhua Nie

Crystals 2024, 14(2), 198; https://doi.org/10.3390/cryst14020198 - 19 Feb 2024

Viewed by 1227

Abstract

This paper investigates the thermal battery as a research topic. We conducted an in-depth analysis of various thermal battery aspects, such as the cathode material CoS₂ and electrolyte material morphology, crystal type, and interface state changes before and after service. The aim [...] Read more.

This paper investigates the thermal battery as a research topic. We conducted an in-depth analysis of various thermal battery aspects, such as the cathode material CoS₂ and electrolyte material morphology, crystal type, and interface state changes before and after service. The aim was to explore the core reaction and main failure mechanisms of the thermal battery. Prior to the reaction, the thermal battery cathode and electrolyte material consisted of pure-phase CoS₂ and a composition of MgO-LiF/LiBr/LiCl. After service, the cathode and electrolyte of the single thermal battery exhibited significant morphological alterations caused by the presence of a molten state. The cathode transformed from CoS₂ to Co₃S₄ and Co₉S₈ together with the presence of a marginal quantity of Co monomers visible throughout the discharge process, which was confirmed by means of XRD and XPS analyses. After the reaction, the electrolyte material was primarily made up of LiF, LiBr, and LiCl while the crystal components remained largely unaltered, albeit with apparent morphological variations. As was deduced from the thermodynamic analysis, the cathode material’s decomposition temperature stood at 655 °C, exceeding the working temperature of the thermal battery (500 °C) by a considerable margin, which is indicative of outstanding thermal durability within the thermal battery’s operational temperature range. Furthermore, the discharge reaction of the positive electrode was incomplete, resulting in reduced CoS₂ residue in the thermal battery monomer after service. The reaction yielded a combination of Co₃S₄, Co₉S₈, and small amounts of Co monomers, indicating possible inconsistencies in the phase composition of the pole piece during the reaction process. In this study, we examine the distribution of residual stress in the thermal battery under various operating conditions. The simulation results indicate that exposure to a 70 °C environment for 2 h causes the maximum residual stress of the battery, which had an initial temperature of 25 °C, to reach 0.26 GPa. The thermal battery subjected to an initial temperature of 25 °C exhibited a maximum residual stress of 0.42 GPa subsequent to a 2-hour exposure to a temperature of −50 °C. Full article

(This article belongs to the Special Issue Residual Stress Effects in Advanced Manufacturing and Electronics Packaging)

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14 pages, 4397 KiB

Open AccessArticle

Polymorphisms in M²⁺AlF₅(H₂O)₇ (M²⁺ = Fe²⁺, Co²⁺, or Ni²⁺): Syntheses, Crystal Structures, and Characterization of New Mixed Metal Fluoride Hydrates

by Jun Min Seo, Hongil Jo, Myung Ho Choi, Kang Min Ok, Hong Young Chang and Sun Woo Kim

Crystals 2024, 14(2), 197; https://doi.org/10.3390/cryst14020197 - 17 Feb 2024

Viewed by 1521

Abstract

Three new mixed metal fluoride hydrates, M²⁺AlF₅(H₂O)₇ (M²⁺ = Fe²⁺, Co²⁺, or Ni²⁺), were synthesized and characterized. The crystals of M²⁺AlF₅(H₂O)₇ [...] Read more.

Three new mixed metal fluoride hydrates, M²⁺AlF₅(H₂O)₇ (M²⁺ = Fe²⁺, Co²⁺, or Ni²⁺), were synthesized and characterized. The crystals of M²⁺AlF₅(H₂O)₇ were obtained using a hydrothermal method with a CF₃COOH aqueous solution. The crystal structures displayed polymorphisms in C2/m (No. 12) or P-1 (No. 2) space groups, depending on temperature variations. The observed polymorphisms in M²⁺AlF₅(H₂O)₇ are associated with changes in the bonding environment of [M(H₂O)₆]²⁺ and [AlF₅(H₂O)]²⁻ octahedra, along with changes in hydrogen bonds and unit cell volumes. Infrared spectra and thermogravimetric analyses confirmed the presence of water molecules. The ultraviolet–visible spectra of M²⁺AlF₅(H₂O)₇ revealed distinctive absorption bands dependent on the [M(H₂O)₆]²⁺ complex. This work provides a detailed account of the synthetic procedure, crystal structures, and spectroscopic characterization of M²⁺AlF₅(H₂O)₇. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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13 pages, 3024 KiB

Open AccessArticle

Coumarin Derivatives: The Influence of Cycloalkyl Groups at the C-3 Position on Intermolecular Interactions—Synthesis, Structure and Spectroscopy

by Katarzyna Szwaczko, Daniel M. Kamiński and Anna E. Koziol

Crystals 2024, 14(2), 196; https://doi.org/10.3390/cryst14020196 - 17 Feb 2024

Viewed by 1428

Abstract

In this study, we explore the synthesis and solid-state characterization of four coumarin-3-carboxylic acid esters, each modified at the C-3 position with different cycloalkyl groups: cyclohexyl, menthyl, and iso-pulegyl. We conducted a detailed analysis of these compounds utilizing a variety of techniques such [...] Read more.

In this study, we explore the synthesis and solid-state characterization of four coumarin-3-carboxylic acid esters, each modified at the C-3 position with different cycloalkyl groups: cyclohexyl, menthyl, and iso-pulegyl. We conducted a detailed analysis of these compounds utilizing a variety of techniques such as a single-crystal X-ray diffraction, nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy. Additionally, we calculated the dipole moments for these molecules. Our findings include a thorough structural assessment, highlighting the role of noncovalent interactions through Full Interaction Maps and Hirshfeld surface analysis. This study reveals the critical influence of the weak C-H…O hydrogen bonds in determining the solid-state architecture of these esters, whereas π-π stacking interactions appear to be negligible among the studied derivatives. Full article

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14 pages, 3715 KiB

Open AccessArticle

Al₂O₃ Thin Layer Formed inside Porous Membrane Using Spray Synthesis Method and Its Application

by Masato Imai, Tadahiko Kubota, Atsushi Miyazawa, Masahiro Aoki, Haruna Mori, Yuta Komaki and Kenji Yoshino

Crystals 2024, 14(2), 195; https://doi.org/10.3390/cryst14020195 - 17 Feb 2024

Viewed by 1380

Abstract

Aluminum oxide (Al₂O₃) films have been investigated for use in various applications, and numerous deposition techniques have been reported. The spray synthesis method has the advantage of forming a thin layer of crystal at low temperatures using the appropriate [...] Read more.

Aluminum oxide (Al₂O₃) films have been investigated for use in various applications, and numerous deposition techniques have been reported. The spray synthesis method has the advantage of forming a thin layer of crystal at low temperatures using the appropriate precursors. A precursor prepared by diluting Methylaluminoxane with N-methyl pyrrolidone was sprayed onto a porous membrane while varying conditions such as the substrate temperature, feeding speed, and spray amount. The solution penetrated the film during spray application, and the ultra-thin layers deposited on the side wall of the internal pores were observed using a cross-sectional transmission electron microscope (XTEM). The lattice image obtained using the TEM and the composition analysis conducted using a scanning TEM and an energy-dispersive X-ray spectroscope suggest that this thin layer is a layer of Al₂O₃. The formation of Al₂O₃ occurred at lower temperatures than in previous reports. This is a major advantage for applications with low-melting-point materials. The most suitable spraying conditions were determined based on the state of deposition on the surface and inside the membrane. These conditions were applied to a three-layer separator for lithium-ion batteries and their effect on thermal stability was investigated. Through heating experiments and XRD analysis, it was confirmed that the shrinkage and melting of the separator are suppressed by spraying. This process can be expected to have wide applications in low-melting-point materials such as polyolefin. Full article

(This article belongs to the Special Issue Synthesis, Structure and Property Analysis of Crystalline Layers (Volume II))

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16 pages, 869 KiB

Open AccessArticle

From the Fibonacci Icosagrid to E₈ (Part II): The Composite Mapping of the Cores

by Richard Clawson, Fang Fang and Klee Irwin

Crystals 2024, 14(2), 194; https://doi.org/10.3390/cryst14020194 - 15 Feb 2024

Viewed by 1219

Abstract

This paper is part of a series that describes the Fibonacci icosagrid quasicrystal (FIG) and its relation to the

E_{8}

root lattice. The FIG was originally constructed to represent the intersection points of an icosahedrally symmetric collection of planar grids in three [...] Read more.

This paper is part of a series that describes the Fibonacci icosagrid quasicrystal (FIG) and its relation to the

E_{8}

root lattice. The FIG was originally constructed to represent the intersection points of an icosahedrally symmetric collection of planar grids in three dimensions, with the grid spacing of each following a Fibonacci chain. It was found to be closely related to a five-fold compound of 3D sections taken from the 4D Elser–Sloane quasicrystal (ESQC), which is derived via a cut-and-project process from

E_{8}

. More recently, a direct cut-and-project from

E_{8}

has been found which yields the FIG (presented in another paper of this series). The present paper focuses not on the full quasicrystal, but on the relationship between the root polytope of

E_{8}

(Gosset’s

4_{21}

polytope) and the core polyhedron generated in the FIG, a compound of 20 tetrahedra referred to simply as a 20-Group. In particular, the

H_{3}

symmetry of the FIG can be seen as a five-fold or “golden” composition of tetrahedral symmetry (referring to the characteristic appearance of the golden ratio). This is shown to mirror a connection between tetrahedral and five-fold symmetries present in the

4_{21}

. Indeed, the rotations that connect tetrahedra contained within the

4_{21}

are shown to induce, in a certain natural way, the tetrahedron orientations in the 20-Group. Full article

(This article belongs to the Special Issue Periodic and Quasi-periodic Structures)

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10 pages, 9191 KiB

Open AccessArticle

Scattering of Ultrashort X-ray Pulses from Oriented NV Centers in the Diamond Structure

by Dmitry Makarov, Marat Eseev, Eugeny Gusarevich, Viktor Matveev, Ksenia Makarova and Mark Borisov

Crystals 2024, 14(2), 193; https://doi.org/10.3390/cryst14020193 - 14 Feb 2024

Viewed by 1222

Abstract

It is well known that the basis of diffraction analysis of matter is scattering, including the scattering of ultrashort laser pulses. In the theory of scattering of ultrashort pulses, the pulse duration parameter is usually not taken into account, which leads to some [...] Read more.

It is well known that the basis of diffraction analysis of matter is scattering, including the scattering of ultrashort laser pulses. In the theory of scattering of ultrashort pulses, the pulse duration parameter is usually not taken into account, which leads to some error. This error may be more significant than the considered effects in the scattering of the pulse on the studied structure. In this paper, it is shown that the pulse duration parameter should be taken into account when scattering X-ray pulses on oriented diamonds with NV centers. It is shown that the scattering spectra can be used to judge the orientation of NV centers in the diamond structure. The obtained results may be very different from the widely used theory of diffraction analysis, which confirms the necessity of taking into account the pulse duration parameter in the diagnosis of complex structures. Full article

(This article belongs to the Special Issue Application of X-ray and Electron to Crystal Structure Characterization)

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19 pages, 3519 KiB

Open AccessArticle

Preparation and Investigation of Sol–Gel TiO₂-NiO Films: Structural, Optical and Electrochromic Properties

by Tatyana Ivanova, Antoaneta Harizanova, Tatyana Koutzarova and Benedicte Vertruyen

Crystals 2024, 14(2), 192; https://doi.org/10.3390/cryst14020192 - 14 Feb 2024

Cited by 3 | Viewed by 1668

Abstract

TiO₂ and TiO₂-NiO films were successfully derived by a sol–gel dip coating technology. The impact of the thermal treatments (300–600 °C) on the structural, optical and electrochromic properties was investigated. X-ray diffraction (XRD) analysis showed that TiO₂ films were [...] Read more.

TiO₂ and TiO₂-NiO films were successfully derived by a sol–gel dip coating technology. The impact of the thermal treatments (300–600 °C) on the structural, optical and electrochromic properties was investigated. X-ray diffraction (XRD) analysis showed that TiO₂ films were polycrystalline and evolved in the anatase phase. The composite TiO₂-NiO films, treated at annealing temperatures below 500 °C, contained anatase titania, a small inclusion of cubic NiO and an amorphous fraction. The formation of NiTiO₃ was exposed after the highest annealing at 600 °C. The presence of Ti-O-Ni bonds was determined in the composite films by Fourier-transform infrared (FTIR) spectroscopy. The optical properties and the optical band gap of TiO₂-NiO films were investigated and discussed. The transparency of the electrochromic TiO₂-NiO films was 76.8 and 78.3% in the 380–700 nm spectral range after film thermal treatments at 300 and 500 °C. NiO incorporation led to the narrowing of the optical band gap. The electrochromic (EC) properties of the composite films were improved compared to TiO₂ films. They had higher diffusion coefficients. Their color efficiencies are 37.6 (550 nm) and 52.2 cm²/C (600 nm). Full article

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14 pages, 2407 KiB

Open AccessArticle

Ba_0.9A_0.1MnO₃ (A = Ce, La, Mg) Perovskite-Type Mixed Oxides: Effect of Partial Substitution of Ba on the Catalytic Performance for the Oxidation of CO in Simulated Automobile Exhaust Conditions

by Nawel Ghezali, Álvaro Díaz Verde and María José Illán Gómez

Crystals 2024, 14(2), 191; https://doi.org/10.3390/cryst14020191 - 14 Feb 2024

Cited by 1 | Viewed by 1308

Abstract

BaMnO₃ (BM) and Ba_0.9A_0.1MnO₃ (BM-A) (A = Ce, La or Mg) perovskite-type mixed oxides were synthesized by the aqueous sol–gel method; thoroughly characterized by ICP-OES, XRD, H₂-TPR, BET, and O₂-TPD; and tested as [...] Read more.

BaMnO₃ (BM) and Ba_0.9A_0.1MnO₃ (BM-A) (A = Ce, La or Mg) perovskite-type mixed oxides were synthesized by the aqueous sol–gel method; thoroughly characterized by ICP-OES, XRD, H₂-TPR, BET, and O₂-TPD; and tested as catalysts for CO oxidation under simulated automobile exhaust conditions. The characterization results indicate that the main effects of the partial substitution of Ba with A-metal in BM perovskite are the maintenance of the hexagonal structure of the perovskite and the increase in reducibility and oxygen mobility. All samples catalyze the CO to CO₂ oxidation reaction in the different reactant mixtures employed, showing the best performance for the mixture with the lowest CO/O₂ ratio and in the presence of a dopant in the BM perovskite formulation. BM-La is the most active catalyst for improving CO oxidation, as it is the most reducible, and because is able to evolve oxygen at intermediate temperatures. Full article

(This article belongs to the Special Issue Perovskites – New and Old Materials)

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14 pages, 4901 KiB

Open AccessArticle

Ultrathin Encapsulation Strategies with Predefined Gate Dielectric Surface Area for Flexible Crystalline Silicon Nanomembrane-Based MOS Capacitors

by Zhuofan Wang, Hongliang Lu, Yuming Zhang and Chen Liu

Crystals 2024, 14(2), 190; https://doi.org/10.3390/cryst14020190 - 14 Feb 2024

Viewed by 1172

Abstract

Ultrathin encapsulation strategies show huge potential in wearable and implantable electronics. However, insightful efforts are still needed to improve the electrical and mechanical characteristics of encapsulated devices. This work introduces Al₂O₃/alucone nanolaminates using hybrid atomic/molecular layer deposition for ultrathin [...] Read more.

Ultrathin encapsulation strategies show huge potential in wearable and implantable electronics. However, insightful efforts are still needed to improve the electrical and mechanical characteristics of encapsulated devices. This work introduces Al₂O₃/alucone nanolaminates using hybrid atomic/molecular layer deposition for ultrathin encapsulation structures employed in crystalline silicon nanomembrane (Si NM)-based metal-oxide-semiconductor capacitors (MOSCAPs). The comprehensive electrical and mechanical analysis focused on the encapsulated and bare MOSCAPs with three gate dielectric diameters (Ø) under planar and bending conditions, including concave bending radii of 110.5 mm and 85 mm as well as convex bending radii of 77.5 mm and 38.5 mm. Combined with the Ø-related mechanical analysis of the maximum strain in the critical layers and the practical investigations of electrical parameters, the encapsulated MOSCAPs with Ø 160 μm showed the most stable electro-mechanical performance partly due to the optimized position of the neutral mechanical plane. Comparison of the electrical changes in Al₂O₃/alucone-encapsulated MOSCAPs with Ø 160 μm, Ø 240 μm, and Ø 320 μm showed that it is beneficial to define the gate dielectric surface area of 0.02 to 0.05 mm² for Si NM-based wearable electronics. These findings are significant for leveraging the practical applications in ultrathin encapsulation strategies for reliable operations of crystalline Si NM-based integrated circuits. Full article

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14 pages, 4544 KiB

Open AccessEditor’s ChoiceArticle

The Crystal Structure and Physicochemical Properties of New Complexes Containing a Cu^II-Ln^III-Cu^II Core

by Beata Cristóvão, Dariusz Osypiuk and Barbara Mirosław

Crystals 2024, 14(2), 189; https://doi.org/10.3390/cryst14020189 - 14 Feb 2024

Viewed by 1271

Abstract

Three new cationic complexes, [Cu₄Tb₂(H₂L)₄(NO₃)₄(H₂O)₃](NO₃)₂·5.5H₂O·2MeOH (1), [Cu₄Ho₂(H₂L)₄(NO₃)₄(H [...] Read more.

Three new cationic complexes, [Cu₄Tb₂(H₂L)₄(NO₃)₄(H₂O)₃](NO₃)₂·5.5H₂O·2MeOH (1), [Cu₄Ho₂(H₂L)₄(NO₃)₄(H₂O)₃](NO₃)₂·7.5H₂O (2), and [Cu₄Er₂(H₂ L)₄(NO₃)₄(H₂O)₃](NO₃)₂·7H₂O·3MeOH (3), were synthesized and studied using elemental and TG/DTG/DSC analyses, single-crystal X-ray diffraction, and magnetic measurements. The structure analysis showed that 1–3 crystallize as (NO₃)-bridged compounds and that the lanthanide(III) ion acts as a joint connecting two [CuH₂L] coordination units. In each heterotrinuclear unit, an asymmetry in the degree of planarity of the bridging CuO₂Ln fragments is observed. The Cu^II ions are five- and six-coordinate, with distorted square pyramidal and octahedral geometry, respectively, whereas the Ln^III ions are nine-coordinate. The solvates 1–3 are stable at room temperature, and their desolvation process is consistent with the loss of water and/or methanol molecules. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicate the weak ferromagnetic interaction between the paramagnetic centers Cu^II and Tb^III/Ho^III 1 and 2. Full article

(This article belongs to the Special Issue Feature Papers in Crystals 2023)

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15 pages, 2198 KiB

Open AccessArticle

Thermodynamics of Iron Ammonia Synthesis Catalyst Sintering

by Walerian Arabczyk, Rafał Pelka, Izabella Jasińska and Zofia Lendzion-Bieluń

Crystals 2024, 14(2), 188; https://doi.org/10.3390/cryst14020188 - 13 Feb 2024

Cited by 1 | Viewed by 1612

Abstract

The sintering of iron ammonia synthesis catalysts (nanocrystalline iron promoted with: Al₂O₃, CaO and K₂O) was studied under a hydrogen atmosphere, in a temperature range of 773 to 973 K to obtain stationary states. The catalysts were [...] Read more.

The sintering of iron ammonia synthesis catalysts (nanocrystalline iron promoted with: Al₂O₃, CaO and K₂O) was studied under a hydrogen atmosphere, in a temperature range of 773 to 973 K to obtain stationary states. The catalysts were characterized by measuring the nitriding reaction rate under an ammonia atmosphere at 748 K to obtain steady states and the measurement of specific surface area. Chemical processes were conducted in a tubular differential reactor enabling thermogravimetric measurements and the chemical composition analysis of a gas phase under conditions allowing experiments to be carried out in the kinetic region of chemical reactions. An extended model of the active surface of the iron ammonia synthesis catalyst was presented, taking into account the influence of the gas phase composition and process temperature. The surface of iron nanocrystallites was wetted using promoters in an exothermic process associated with the formation of the surface Fe^s-O- bond and the change in the surface energy of iron nanocrystallites. Promoters formed on the surface of iron nanocrystallites with different structures of chemisorbed dipoles, depending on the composition of the gas phase. The occupied sites stabilized the structure, and the free sites were active sites in the process of adsorption of chemical reagents and in sintering. Based on the bonding energy of the promoter oxides and the difference in surface energy between the covered and uncovered surfaces, the wetting abilities of promoters, which can be arranged according to the order K₂O > Fe₃O₄ > Al₂O₃ > CaO, were estimated. By increasing the temperature in the endothermic sintering process, the degree of surface coverage with dipoles of promoters decreased, and thus the catalyst underwent sintering. The size distribution of nanocrystallites did not change with decreasing temperature. Only the equilibrium between the glass phase and the surface of iron nanocrystallites was then established. Full article

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13 pages, 3012 KiB

Open AccessArticle

Anionic Dye Alizarin Red S Removal Using Heat-Treated Dolomite

by Zhaohui Li, Anna Bowman, Angie Rayniak and Shangping Xu

Crystals 2024, 14(2), 187; https://doi.org/10.3390/cryst14020187 - 13 Feb 2024

Cited by 3 | Viewed by 1490

Abstract

In modern society, frequent use of synthetic materials in the household and industry presents a great challenge to environmental and water quality. As such, numerous types of research have been conducted for potential removal of emerging contaminants from water using advanced materials. Earth [...] Read more.

In modern society, frequent use of synthetic materials in the household and industry presents a great challenge to environmental and water quality. As such, numerous types of research have been conducted for potential removal of emerging contaminants from water using advanced materials. Earth materials, due to their low costs and vast reserves, have also been evaluated in great details for contaminant removal. In this study, a naturally occurring carbonate mineral dolomite (Dol) was assessed for the removal of an anionic dye alizarin red S (ARS) from aqueous solution before and after heat treatment to increase its performance. The ARS-removal capacities increased from 80 to 130 mmol/kg after heat treatment based on the isotherm study. And the ARS-removal efficiency rose by a factor of four as the partitioning coefficient increased from 1.5 to 6 L/mmol after heat treatment. The X-ray diffraction (XRD) analyses showed minute conversion of dolomite into calcite after samples being heated at 800 °C for 3 h. However, there were no phase changes for ARS before and after its sorption. Fourie transform infra-red (FTIR) results also showed a minute appearance of calcite after heating. Thus, the increase in ARS sorption could be due to surface reactivation of Dol after heating or due to formation of a minute amount of amorphous MgO in the system as a result of the conversion of Dol to calcite. The results from this study will add new perspectives to the utilization of Earth materials for environmental application. Full article

(This article belongs to the Special Issue Advanced Surface Modifications on Materials)

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11 pages, 7619 KiB

Open AccessArticle

Lattice Rotation Dependence on Microstructural Characteristics in a Low Carbon Steel

by Satish K. Shekhawat, Rajesh K. Khatirkar and Murat Demiral

Crystals 2024, 14(2), 186; https://doi.org/10.3390/cryst14020186 - 13 Feb 2024

Viewed by 1227

Abstract

The lattice rotation behavior of low-carbon (LC) steel subjected to tensile deformation was studied by electron backscatter diffraction (EBSD). The EBSD scans of the same region were taken before and after tensile deformation. The rotation of the grains was found to depend on [...] Read more.

The lattice rotation behavior of low-carbon (LC) steel subjected to tensile deformation was studied by electron backscatter diffraction (EBSD). The EBSD scans of the same region were taken before and after tensile deformation. The rotation of the grains was found to depend on a number of factors like the initial orientation, the size of the grains, the number of neighboring grains and the region of the grain. The region near the grain boundaries was found to have significant deviation from that of the interior of the grain. The lattice rotations were also simulated using DAMASK software. The simulations gave information about the state of stress for each grain and the strain gradients developed during the deformation. The orientation dependence of misorientation and geometrically necessary dislocations (GNDs) was also studied. It was found that the misorientations changed more gradually in α-fiber grains than in γ-fiber grains. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials)

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17 pages, 16492 KiB

Open AccessArticle

Effects of Rare-Earth Elements Doping on Micro-Structure and Fluorescence Performances of Fluorapatite

by Shao-Rong Bie, Ding-Shun She and Wen Yue

Crystals 2024, 14(2), 185; https://doi.org/10.3390/cryst14020185 - 13 Feb 2024

Viewed by 1646

Abstract

For purposes of optimizing the microstructure and fluorescence properties of rare-earth elements (REEs)-doped fluorapatites (FAps), various kinds of REEs (La, Pr, Sm, Eu, Gd, Ho, Er, and Yb) with the concentration of 2~20 mol.% have been inserted into the FAps framework via hydrothermal [...] Read more.

For purposes of optimizing the microstructure and fluorescence properties of rare-earth elements (REEs)-doped fluorapatites (FAps), various kinds of REEs (La, Pr, Sm, Eu, Gd, Ho, Er, and Yb) with the concentration of 2~20 mol.% have been inserted into the FAps framework via hydrothermal method, in order to investigate the influential mechanism of the REEs on the crystal structure, morphology, and fluorescence under the excitation of the near-ultraviolet light of the FAps. Experimental results show that the wavelength of the emitted light of the REEs-doped FAps is decided by the type of REEs. Unlike the Pr/Yb- and Ho-doped FAps and with the fluorescence of red and green emitted light, respectively, the Er-doped FAps show a blue light emission with wavelengths of 296, 401, and 505 nm, which is, moreover, different with the Eu-doped Faps, showing an orange light emission with wavelengths of 490, 594, and 697 nm. The emission luminous color is related to the lattice defects of the FAps doped with the various types and the effective doping concentration of the REEs. The luminous intensity increases with the increase in the effective doping concentration of the REEs. Nevertheless, the formation of rare-earth fluoride results in the decrease in the effective doping concentration of the REEs and the luminous intensity. The FAps with an effective doping concentration of 7 mol.% Er and 3 mol.% Eu show relative excellent fluorescence properties. Full article

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17 pages, 12553 KiB

Open AccessArticle

Metatungstate Chemical Vapor Deposition of WSe₂: Substrate Effects, Shapes, and Morphologies

by Krastyo Buchkov, Peter Rafailov, Nikolay Minev, Vladimira Videva, Velichka Strijkova, Todor Lukanov, Dimitre Dimitrov and Vera Marinova

Crystals 2024, 14(2), 184; https://doi.org/10.3390/cryst14020184 - 13 Feb 2024

Cited by 2 | Viewed by 2618

Abstract

Owing to their exceptional properties, which are usually determined by the growth conditions, 2D transition metal dichalcogenides (TMDCs) offer numerous research directions for applications in the fields of spintronics, valleytronics, and optoelectronics. Here, we focus on the chemical vapor deposition (CVD) synthesis of [...] Read more.

Owing to their exceptional properties, which are usually determined by the growth conditions, 2D transition metal dichalcogenides (TMDCs) offer numerous research directions for applications in the fields of spintronics, valleytronics, and optoelectronics. Here, we focus on the chemical vapor deposition (CVD) synthesis of WSe₂ (tungsten diselenide) nanoclusters/nanoflakes by using a liquid precursor for tungsten (ammonium metatungstate) on Si/SiO₂, fused silica, and sapphire substrates. Various WSe₂ clusters with different sizes, thicknesses, and geometries were analyzed by means of optical and atomic force microscopy (AFM) and Raman spectroscopy. The observed structures were mostly WSe₂ multilayers; however, monolayer formations were also found. They showed significant morphological differences, as well as wide nucleation density and size variations, possibly related to precursor/substrate surface interactions under the same CVD synthesis conditions. The largest WSe₂ domains with a lateral size of up to hundreds of micrometers were observed on sapphire, probably caused by a higher growth rate of singular nucleation sites. WSe₂ domains with irregular and triangular shapes were simultaneously identified on fused silica, whereas multilayered pyramidal WSe₂ structures dominated in the case of Si/SiO₂ substrates. The application of polarized Raman spectroscopy to precisely determine and differentiate the characteristic vibrational modes (

A_{1 g}

,

E_{2 g}

, and

2 L A (M)

) enabled the unambiguous identification of 2D and/or multilayered WSe₂ formations with a high crystallinity level. The presented comparative analysis of samples prepared in relatively simple synthesis conditions (moderate working temperatures and ambient pressure) provides a base for further progress of the facile metatungstate CVD method and relevant opportunities for the exploration of 2D TMDC materials. Full article

(This article belongs to the Special Issue Two-Dimensional Materials: Synthesis, Characterization and Device Applications)

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13 pages, 3731 KiB

Open AccessArticle

Crystal Structure of New Zinc-Hydroxy-Sulfate-Hydrate Zn₄(OH)₆SO₄·2–2.25H₂O

by Tsveta Stanimirova, Rositsa Nikolova and Nadia Petrova

Crystals 2024, 14(2), 183; https://doi.org/10.3390/cryst14020183 - 12 Feb 2024

Viewed by 1793

Abstract

A theoretical model of the crystal structure of the newly obtained compound Zn₄(OH)₆SO₄·2–2.25H₂O based on the compilation of the crystal–chemical properties of two known zinc-hydroxy-sulfate phases—mineral namuwite and hemihydrate—is proposed. The single XRD data confirmed [...] Read more.

A theoretical model of the crystal structure of the newly obtained compound Zn₄(OH)₆SO₄·2–2.25H₂O based on the compilation of the crystal–chemical properties of two known zinc-hydroxy-sulfate phases—mineral namuwite and hemihydrate—is proposed. The single XRD data confirmed the model and determined the structure, with a trigonal symmetry SG of P-3, the unit cell with a = 8.3418(15) Å and c = 17.595(7) Å, and a cell volume of 1060.3(6) Å³, with Z = 2. The results show that the Zn₄(OH)₆SO₄·2–2.5H₂O crystal structure consists of an alternating paired octahedral–tetrahedral doubly decorated hydroxide layer with cationic vacancies and an aqueous interlayer. Full article

(This article belongs to the Special Issue Feature Papers in Crystals 2023)

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16 pages, 3479 KiB

Open AccessArticle

Crystal and Molecular Structures of Two Phthalocyanines, Chloro(phthalocyaninato)gallium(III) (ClGaPc) and µ-Oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc)

by Peter Zugenmaier

Crystals 2024, 14(2), 182; https://doi.org/10.3390/cryst14020182 - 12 Feb 2024

Viewed by 1143

Abstract

The structure of µ-oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc) and the structure of a second modification of chloro(phthalocyaninato)gallium(III) (ClGaPc) has been determined by single-crystal X-ray analysis. Sublimation of the respective compounds led to single crystals suitable for an X-ray study. Both compounds crystallize in the triclinic space [...] Read more.

The structure of µ-oxobis(phthalocyaninato)gallium(III) (PcGaOGaPc) and the structure of a second modification of chloro(phthalocyaninato)gallium(III) (ClGaPc) has been determined by single-crystal X-ray analysis. Sublimation of the respective compounds led to single crystals suitable for an X-ray study. Both compounds crystallize in the triclinic space group P

\bar{1}

, with a unit cell for ClGaPc a = 13.770 Å, b = 13.770 Å, c = 14.039 Å, α = 98.32°, β = 108.64°, γ = 90.01°, containing four disordered molecules (Z = 4). The unit cell of the dimeric PcGaOGaPc contains one molecule, with half a molecule as an asymmetric moiety (Z = 2) and a = 7.848 Å, b = 12.529 Å, c = 12.720 Å, α = 91.03°, β = 94.94°, γ = 89.98°. The Ga atoms for the two ClGaPc molecules are placed 0.44 Å above the plane formed by the respective isoindole nitrogen N1 to N4. The two rings of the asymmetric unit (molecule 1 and 2) are arranged in parallel, with ca. 3.4 Å distance within the unit cell. The Ga-Cl bond distances are ca. 2.20 Å for the two molecules. The gallium of PcGaOGaPc is placed 0.49 Å above the respective isoindole nitrogen plane and the Ga-O bond amounts to 1.734 Å. Full article

(This article belongs to the Special Issue Coordination Complexes: Synthesis, Characterization and Application)

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12 pages, 3721 KiB

Open AccessEditor’s ChoiceArticle

Combining a Drug and a Nutraceutical: A New Cocrystal of Praziquantel and Curcumin

by Camila Caro Garrido, Marie Vandooren, Koen Robeyns, Damien P. Debecker, Patricia Luis and Tom Leyssens

Crystals 2024, 14(2), 181; https://doi.org/10.3390/cryst14020181 - 11 Feb 2024

Cited by 2 | Viewed by 1806

Abstract

This study explores the co-crystallization between the drug praziquantel (PZQ) and the nutraceutical curcumin (CU). The investigation revealed two novel solid forms: a cocrystal solvate with ethyl acetate and a non-solvated cocrystal. This novel drug–nutraceutical cocrystal is a praziquantel–curcumin (2:1) cocrystal. The cocrystal [...] Read more.

This study explores the co-crystallization between the drug praziquantel (PZQ) and the nutraceutical curcumin (CU). The investigation revealed two novel solid forms: a cocrystal solvate with ethyl acetate and a non-solvated cocrystal. This novel drug–nutraceutical cocrystal is a praziquantel–curcumin (2:1) cocrystal. The cocrystal solvate has ethyl acetate molecules occupying the voids with minimal interactions within the crystal lattice. The application of heat treatment induces solvent removal and prompts the transition to the non-solvated cocrystal, as highlighted by variable-temperature X-ray powder diffraction (VT-XRPD). Thermal analyses demonstrate the stability of the cocrystal solvate up to approximately 100 °C, beyond which it transforms into the non-solvated phase, which eventually melts at 130 °C. Full article

(This article belongs to the Special Issue Feature Papers in Crystals 2023)

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15 pages, 3135 KiB

Open AccessArticle

Explaining Color Change in Gem-Quality Andradite Garnet

by Jia-Hong Xu, Xiao-Yan Yu, Mei Shen, Ying Yan and Guang-Ya Wang

Crystals 2024, 14(2), 180; https://doi.org/10.3390/cryst14020180 - 11 Feb 2024

Cited by 1 | Viewed by 2192

Abstract

The homomorphic substitution of the garnet group is common in nature. Two rare color-changing andradite garnets are studied in this paper. One color changes from yellowish-green in the presence of daylight to maroon under incandescent light; the other color changes from brownish yellow [...] Read more.

The homomorphic substitution of the garnet group is common in nature. Two rare color-changing andradite garnets are studied in this paper. One color changes from yellowish-green in the presence of daylight to maroon under incandescent light; the other color changes from brownish yellow to brownish red. In this study, conventional gemological instruments, infrared (IR) spectroscopy, ultraviolet–visible–near infrared (UV–Vis–NIR) spectroscopy, Raman spectroscopy, and electron probe microanalysis (EPMA) were used to explore the gemology and coloration mechanisms of color-changing garnets. Experiments revealed that the color-changing gemstones in the study are andradite garnets. There are two transmission windows in the UV–Vis spectrum: the red region (above 650 nm) and the green region (centered at 525 nm). The chemical compositional analysis indicates that the samples are very low in Cr (<1 ppm) and high in Fe²⁺ (from 2.31 wt.% to 4.66 wt.%). The combined spectra and chemical compositional analysis show that Fe²⁺ is the main cause of the color change. Based on the IR spectrum (complex water peaks), UV–Vis–NIR spectrum (similar to that of Namibian andradite garnet), and chemical compositional analysis (low Cr content), it is concluded that color-changing andradite may be related to skarn rock genesis. Full article

(This article belongs to the Section Mineralogical Crystallography and Biomineralization)

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12 pages, 2460 KiB

Open AccessArticle

Insights into the Electronic, Optical, and Anti-Corrosion Properties of Two-Dimensional ZnO: First-Principles Study

by Fatma Abd Elwahab, Nahed H. Teleb, Hazem Abdelsalam, Omar H. Abd-Elkader and Qinfang Zhang

Crystals 2024, 14(2), 179; https://doi.org/10.3390/cryst14020179 - 11 Feb 2024

Viewed by 1349

Abstract

The electronic, optical, and anticorrosion properties of planer ZnO crystal and quantum dots are explored using density functional theory calculations. The calculations for the finite ZnO quantum dots were performed in Gaussian 16 using the B3LYP/6-31g level of theory. The periodic calculations were [...] Read more.

The electronic, optical, and anticorrosion properties of planer ZnO crystal and quantum dots are explored using density functional theory calculations. The calculations for the finite ZnO quantum dots were performed in Gaussian 16 using the B3LYP/6-31g level of theory. The periodic calculations were carried out using VASP with the plane wave basis set and the PBE functional. The subsequent band structure calculations were performed using the hybrid B3LYP functional that shows accurate results and is also consistent with the finite calculations. The considered ZnO nanodots have planer hexagonal shapes with zigzag and armchair terminations. The binding energy calculations show that both structures are stable with negligible deformation at the edges. The ZnO nanodots are semiconductors with a moderate energy gap that decreases when increasing the size, making them potential materials for anticorrosion applications. The values of the electronic energy gaps of ZnO nanodots are confirmed by their UV-Vis spectra, with a wide optical energy gap for the small structures. Additionally, the calculated positive fraction of transferred electrons implies that electron transfer occurs from the inhibitor (ZnO) to the metal surface to passivate their vacant d-orbitals, and eventually prevent corrosion. The best anti-corrosion performance was observed in the periodic ZnO crystal with a suitable energy gap, electronegativity, and fraction of electron transfer. The effects of size and periodicity on the electronic and anticorrosion properties are also here investigated. The findings show that the anticorrosion properties were significantly enhanced by increasing the size of the quantum dot. Periodic ZnO crystals with an appropriate energy gap, electronegativity, and fraction of electron transfer exhibited the optimum anticorrosion performance. Thus, the preferable energy gap in addition to the most promising anticorrosion parameters imply that the monolayer ZnO is a potential candidate for coating and corrosion inhibitors. Full article

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12 pages, 6512 KiB

Open AccessArticle

Dynamic Compression and Constitutive Model in Fe-27Mn-10Al-1C Duplex Lightweight Steel

by Pengfei Cao, Dazhao Li, Shaobin Bai, Yongan Chen and Haitao Lu

Crystals 2024, 14(2), 178; https://doi.org/10.3390/cryst14020178 - 10 Feb 2024

Viewed by 1224

Abstract

Fe-Mn-Al-C lightweight steels have been of significant interest due to their excellent mechanical properties and unique microstructures. However, there has been limited focus on the dynamic deformation. Here, we systematically investigate the mechanical responses over various strain rates and corresponding microstructure evolution in [...] Read more.

Fe-Mn-Al-C lightweight steels have been of significant interest due to their excellent mechanical properties and unique microstructures. However, there has been limited focus on the dynamic deformation. Here, we systematically investigate the mechanical responses over various strain rates and corresponding microstructure evolution in quasi-static and dynamic compression to reveal the transition of deformation mechanisms. The present lightweight steel exhibits a significant strain rate effect, with the yield strength increasing from 735.8 to 1149.5 MPa when the strain rate increases from 10⁻³ to 3144 s⁻¹. The deformation in ferrite under high-strain-rate loading is dominated by wave slip, forming a cellular structure (cell block). Meanwhile, the deformation in austenite is dominated by planar slip, forming dislocation substructures such as high-density dislocation walls and microbands. In addition, the deformation twinning (including secondary twinning)- and microband-induced plasticity effects are responsible for the excellent dynamic compression properties. This alloy delays damage location while maintaining high strength, making it ideal for shock loading and high-strain-rate applications. The Johnson–Cook (J–C) constitutive model is used to predict the deformation behavior of lightweight steel under dynamic conditions, and the J–C model agrees well with the experimental results. Full article

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14 pages, 3787 KiB

Open AccessEditor’s ChoiceArticle

Investigating Influential Parameters for High-Purity Germanium Crystal Growth

by Sanjay Bhattarai, Dongming Mei, Narayan Budhathoki, Kunming Dong and Austin Warren

Crystals 2024, 14(2), 177; https://doi.org/10.3390/cryst14020177 - 10 Feb 2024

Viewed by 2025

Abstract

This paper focuses on the research and development of high-purity germanium (HPGe) crystals for detector fabrication, specifically targeting applications in rare-event physics searches. The primary objective was to produce large-scale germanium crystals weighing >1 kg with a controlled diameter of ∼10 cm and [...] Read more.

This paper focuses on the research and development of high-purity germanium (HPGe) crystals for detector fabrication, specifically targeting applications in rare-event physics searches. The primary objective was to produce large-scale germanium crystals weighing >1 kg with a controlled diameter of ∼10 cm and an impurity range of approximately

10^{10}

/cm

^{3}

. Ensuring structural integrity and excellent crystalline quality requires a thorough assessment of dislocation density, a critical aspect of the crystal development process. Dislocation density measurements play a crucial role in maximizing the sensitivity of HPGe detectors, and our findings confirmed that the dislocation density fell within acceptable ranges for detector fabrication. Additionally, this paper examines the segregation coefficient of various contaminants during the crystal development process. Comprehensive analysis of impurity segregation is essential for reducing contaminant quantities in the crystal lattice and customizing purification processes. This, in turn, minimizes undesired background noise, enhancing signal-to-noise ratios for rare-event physics searches and overall detector performance. The investigation included the segregation coefficients of three major acceptors and one donor in crystals grown at the University of South Dakota, providing valuable insights for optimizing crystal purity and detector efficiency. Full article

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31 pages, 1019 KiB

Open AccessArticle

Quantum Magnetism in Wannier-Obstructed Mott Insulators

by Xiaoyang Huang, Taige Wang, Shang Liu, Hong-Ye Hu and Yi-Zhuang You

Crystals 2024, 14(2), 176; https://doi.org/10.3390/cryst14020176 - 9 Feb 2024

Cited by 1 | Viewed by 1311

Abstract

We develop a strong coupling approach towards quantum magnetism in Mott insulators for Wannier-obstructed bands. Despite the lack of Wannier orbitals, electrons can still singly occupy a set of exponentially localized but nonorthogonal orbitals to minimize the repulsive interaction energy. We develop a [...] Read more.

We develop a strong coupling approach towards quantum magnetism in Mott insulators for Wannier-obstructed bands. Despite the lack of Wannier orbitals, electrons can still singly occupy a set of exponentially localized but nonorthogonal orbitals to minimize the repulsive interaction energy. We develop a systematic method to establish an effective spin model from the electron Hamiltonian using a diagrammatic approach. The nonorthogonality of the Mott basis gives rise to multiple new channels of spin-exchange (or permutation) interactions beyond Hartree–Fock and superexchange terms. We apply this approach to a Kagome lattice model of interacting electrons in Wannier-obstructed bands (including both Chern bands and fragile topological bands). Due to the orbital nonorthogonality, as parameterized by the nearest-neighbor orbital overlap g, this model exhibits stable ferromagnetism up to a finite bandwidth

W \sim U g

, where U is the interaction strength. This provides an explanation for the experimentally observed robust ferromagnetism in Wannier-obstructed bands. The effective spin model constructed through our approach also opens up the possibility for frustrated quantum magnetism around the ferromagnet-antiferromagnet crossover in Wannier-obstructed bands. Full article

(This article belongs to the Special Issue Two-Dimensional Materials: Synthesis, Property and Applications)

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18 pages, 23144 KiB

Open AccessArticle

The Effect of Sintering Temperature on Phase-Related Peculiarities of the Microstructure, Flexural Strength, and Fracture Toughness of Fine-Grained ZrO₂–Y₂O₃–Al₂O₃–CoO–CeO₂–Fe₂O₃ Ceramics

by Volodymyr Kulyk, Bogdan Vasyliv, Zoia Duriagina, Pavlo Lyutyy, Valentyna Vavrukh and Andrii Kostryzhev

Crystals 2024, 14(2), 175; https://doi.org/10.3390/cryst14020175 - 9 Feb 2024

Cited by 1 | Viewed by 1429

Abstract

The lifetime of products made of ceramic materials is related to their mechanical characteristics such as strength, hardness, wear resistance, and fracture toughness. The purpose of this work was to study the effect of sintering temperature on the phase-related peculiarities of the microstructures, [...] Read more.

The lifetime of products made of ceramic materials is related to their mechanical characteristics such as strength, hardness, wear resistance, and fracture toughness. The purpose of this work was to study the effect of sintering temperature on the phase-related peculiarities of the microstructures, causing changes in the flexural strength and fracture toughness of fine-grained ZrO₂–Y₂O₃–Al₂O₃–CoO–CeO₂–Fe₂O₃ ceramics. Flexural strength and fracture toughness tests were carried out using ceramics sintered in three modes (2 h at 1550 °C, 1580 °C, and 1620 °C in argon), and thorough phase, microstructure, and fractographic analyses were performed. For the ceramic sintered at 1550 °C, a mixed mechanism of intergranular fracture of the t-ZrO₂ phase particles and cleavage fracture of the Ce–Al–O phase particles was found, which is reflected in its comparatively low fracture toughness. For the ceramic sintered at 1580 °C, a fracture developed along the boundaries of the aggregates, made of completely recrystallized fine ZrO₂ grains with a high bond strength between adjacent t-ZrO₂ grains; this corresponds to the highest fracture toughness (5.61 ± 0.24 MPa·m^1/2) of this ceramic. For the ceramic sintered at 1620 °C, a transgranular fracture of the t-ZrO₂ phase and Ce–Al–O phase particles and crack propagation along the t-ZrO₂/Ce–Al–O interface were revealed; this caused a decrease in fracture toughness. Full article

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12 pages, 3200 KiB

Open AccessArticle

Growth, Structure, and Spectroscopic Properties of a Disordered Nd:SrLaGaO₄ Laser Crystal

by Shanshan Fang, Ling Liang, Wei Wang, Yiyang Lin, Yijian Sun, Guoliang Gong, Chaoyang Tu and Herui Wen

Crystals 2024, 14(2), 174; https://doi.org/10.3390/cryst14020174 - 9 Feb 2024

Viewed by 1237

Abstract

A disordered Nd:SrLaGaO₄ (Nd:SLG) laser crystal was successfully grown via the Czochralski (CZ) technique. The crystal structure, refractive index, polarized absorption spectra, and stimulated emission spectra were measured. The spectroscopic properties were studied intensively with the Judd–Ofelt (J-O) theory. The maximum absorption [...] Read more.

A disordered Nd:SrLaGaO₄ (Nd:SLG) laser crystal was successfully grown via the Czochralski (CZ) technique. The crystal structure, refractive index, polarized absorption spectra, and stimulated emission spectra were measured. The spectroscopic properties were studied intensively with the Judd–Ofelt (J-O) theory. The maximum absorption cross sections of π- and σ-polarization at 806 nm were calculated to be 3.73 × 10⁻²⁰ and 4.05 × 10⁻²⁰ cm², corresponding to FWHMs of 6.00 and 6.10 nm, respectively. The maximum emission cross sections of π- and σ-polarization at 1076 nm were 3.97 × 10⁻²⁰ and 4.12 × 10⁻²⁰ cm², with FWHMs of 30.21 and 19.44 nm, respectively. The decay life of the Nd³⁺:⁴F_3/2 energy level was fitted to be 0.152 ms, and the fluorescence quantum efficiency was 72.72%. The inhomogeneous broadening in spectra benefiting from the disordered structure indicates the Nd:SLG crystal is a promising gain medium for ultrafast laser and tunable laser generations in the near infrared region. Full article

(This article belongs to the Special Issue Photoelectric Functional Crystals)

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15 pages, 17818 KiB

Open AccessArticle

Particle Size Effect on Optical and Gas-Sensing Properties of La_0.67Ca_0.2Ba_0.13Fe_0.97M_0.03O₃ (M = Ti⁴⁺, Mn³⁺, and Cr³⁺) Compounds

by Ahmed Dhahri, H. Saoudi, S. R. Gavinho, A. Benali, N. Abdelmoula, R. Dhahri, Lin Peng, Jiangtao Wu, J. Pina and B. F. O. Costa

Crystals 2024, 14(2), 173; https://doi.org/10.3390/cryst14020173 - 8 Feb 2024

Viewed by 1235

Abstract

In the present work, the morphological, optical, and gas-sensing properties of La_0.67Ca_0.2Ba_0.13Fe_0.97M_0.03O₃ (M = Ti, Cr, and Mn) nano-powders prepared via the auto-combustion route, were investigated. TEM images prove the nanoscale particle [...] Read more.

In the present work, the morphological, optical, and gas-sensing properties of La_0.67Ca_0.2Ba_0.13Fe_0.97M_0.03O₃ (M = Ti, Cr, and Mn) nano-powders prepared via the auto-combustion route, were investigated. TEM images prove the nanoscale particle size of all the samples. Optical studies confirm the semiconductor behavior of the studied materials. The response of the prepared nano-powders towards the presence of two gas-reducing agents (ethanol and acetone) was investigated. From the resistance ratio under air and gas, it was possible to determine the response to different gases and deduce that La_0.67Ca_0.2Ba_0.13Fe_0.97Ti_0.03O₃ presents the highest responses to ethanol and acetone. Likewise, we deduced that the prepared materials were able to detect low concentrations of ethanol and acetone gases. Full article

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16 pages, 7808 KiB

Open AccessReview

Trends in Longer-Term Corrosion Loss of Magnesium Alloys

by Robert E. Melchers

Crystals 2024, 14(2), 172; https://doi.org/10.3390/cryst14020172 - 8 Feb 2024

Cited by 2 | Viewed by 1312

Abstract

The corrosion of magnesium alloys is often considered to differ in behaviour and development with time from most other metals and alloys because they show evolution of hydrogen right from first exposure. However, data extracted from the open literature indicate that magnesium alloys [...] Read more.

The corrosion of magnesium alloys is often considered to differ in behaviour and development with time from most other metals and alloys because they show evolution of hydrogen right from first exposure. However, data extracted from the open literature indicate that magnesium alloys develop corrosion mass-loss trends with time that are consistent with the so-called bimodal pattern, which is topologically similar to those of other alloys. Examples are given of such trending for magnesium alloys under immersion, half-tide and various atmospheric exposure conditions. The critical roles of corrosion pitting and its development into localised corrosion are discussed. For high-purity magnesium alloys, the transition to longer-term corrosion, which is rate-controlled by the hydrogen evolution cathodic reaction, occurs quickly, within days. Comments are made about the application of measurements of hydrogen evolution and of electrochemical methods to make rapid estimates of shorter-term corrosion rates. Full article

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15 pages, 5271 KiB

Open AccessArticle

Effect of Additive and Current Density on Microstructures and Corrosion Behavior of a Multi-Component NiFeCoCu Alloy Prepared by Electrodeposition

by Ying Wang, Bingyang Ma, Wei Li, Peter K. Liaw, Songpu Yang and Ning Zhong

Crystals 2024, 14(2), 171; https://doi.org/10.3390/cryst14020171 - 8 Feb 2024

Cited by 1 | Viewed by 1346

Abstract

High-entropy alloys (HEAs) have been attracting growing interest for decades due to their unique properties. Electrodeposition provides a low-cost and convenient route for producing classified types of HEAs, compared to other synthesis techniques, making it an attention-grabbing method. However, fabricating high-quality HEAs through [...] Read more.

High-entropy alloys (HEAs) have been attracting growing interest for decades due to their unique properties. Electrodeposition provides a low-cost and convenient route for producing classified types of HEAs, compared to other synthesis techniques, making it an attention-grabbing method. However, fabricating high-quality HEAs through electrodeposition in aqueous electrolytes remains a great challenge. In this study, the effects of additives and current densities on the compositions, surface morphologies, microstructures, and corrosion behavior of the electrodeposited NiFeCoCu alloy are studied. The results indicate that saccharin plays a key role in achieving a flat and bright surface for NiFeCoCu coatings, while also relieving the internal stress and improving anti-corrosion properties. Electrodeposition under a current density of 20–40 mA/cm² results in a uniform and dense deposit with favorable properties. The present work provides a low-cost and feasible industrial solution for the preparation of HEA coatings, which holds great potential for innovation in the field of HEA coatings through electrodeposition. Full article

(This article belongs to the Special Issue Corrosion Phenomena in Metals)

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