Crystals

20 pages, 6430 KiB

Open AccessEditor’s ChoiceArticle

Multi-Scale Numerical Simulation of Short Tungsten Fiber Reinforced Tungsten–Copper Composites: Influence Mechanisms of Fiber Parameters

by Longchao Zhuo, Yixing Xie, Hang Xu, Bin Luo, Nan Liu, Bingqing Chen and Hao Wang

Crystals 2025, 15(3), 209; https://doi.org/10.3390/cryst15030209 - 22 Feb 2025

Viewed by 411

Abstract

Tungsten fiber reinforced tungsten–copper (W_f/W-Cu) composites have broad application prospects in fields such as electronic packaging due to their excellent comprehensive properties. However, the correlation between fiber parameters (content, aspect ratio, orientation) and the mechanical behavior of the materials is not [...] Read more.

Tungsten fiber reinforced tungsten–copper (W_f/W-Cu) composites have broad application prospects in fields such as electronic packaging due to their excellent comprehensive properties. However, the correlation between fiber parameters (content, aspect ratio, orientation) and the mechanical behavior of the materials is not yet clear. In this study, a combination of numerical simulation and experimental research was employed to construct a three-dimensional microstructural mechanic model and systematically investigate the influence of fiber parameters on the tensile properties and mechanisms of W_f/W-Cu composites. The results show that: (1) The critical fiber aspect ratio is 7.6. When below this value, fiber pullout dominates, and when above this value, fiber tensile fracture is the main mechanism. (2) As the fiber content increases from 1% to 6%, the tensile strength of the composite increases by 9.6%, the yield strength increases by 10.2%, while the elongation after fracture decreases by 18.6%. (3) As the fiber orientation angle increases from 0° to 90°, the material strength first increases and then decreases, while the toughness first decreases and then increases. (4) Short fibers achieve interface toughening through fiber pullout, crack deflection, and fiber bridging, while long fibers improve the strength and toughness of the composite through load transfer and fiber bridging effects. (5) The damage evolution mechanism reveals the regulation effect of fiber parameters on the multi-scale mechanical behavior of the material. The research results can guide the composition and structure optimization design of W_f/W-Cu composites, provide new ideas for the research of high-performance fiber composites, and have important significance for their engineering applications in extreme environments. Full article

(This article belongs to the Special Issue Advances in Metal Matrix Composites: Structure, Properties and Applications)

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29 pages, 8842 KiB

Open AccessEditor’s ChoiceReview

Development and Research Status of Wear-Resistant Coatings on Copper and Its Alloys: Review

by Fei Meng, Yifan Zhou, Hongliang Zhang, Zhilan Wang, Dehao Liu, Shuhe Cao, Xue Cui, Zhisheng Nong, Tiannan Man and Teng Liu

Crystals 2025, 15(3), 204; https://doi.org/10.3390/cryst15030204 - 20 Feb 2025

Viewed by 752

Abstract

Wear-resistant coatings applied to the surface of copper and copper alloys through diverse advanced technologies can substantially enhance their wear resistance and broaden their application spectrum. This paper provides a comprehensive review of the development and current research status of wear-resistant coatings fabricated [...] Read more.

Wear-resistant coatings applied to the surface of copper and copper alloys through diverse advanced technologies can substantially enhance their wear resistance and broaden their application spectrum. This paper provides a comprehensive review of the development and current research status of wear-resistant coatings fabricated on copper and its alloys. It presents the research findings on the preparation of wear-resistant coatings using both one-step methods (such as laser cladding, electroplating, thermal spraying, cold spraying, electro-spark deposition, etc.) and two-step methods (chemical plating and heat treatment, electrodeposition and laser cladding, laser cladding and in situ synthesis, etc.). This paper provides an in-depth examination of the characteristics, operating principles, and effects of various coating techniques on enhancing the wear resistance of copper and copper alloys. The advantages and disadvantages of different coating preparation methods are compared and analyzed; meanwhile, a prospective outlook on the future development trends is also offered. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials: 2nd Edition)

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10 pages, 2660 KiB

Open AccessEditor’s ChoiceArticle

Crystal Growth and Energy Transfer Study in Ce³⁺ and Pr³⁺ Co-Doped Lu₂Si₂O₇

by Yuka Abe, Takahiko Horiai, Yuui Yokota, Masao Yoshino, Rikito Murakami, Takashi Hanada, Akihiro Yamaji, Hiroki Sato, Yuji Ohashi, Shunsuke Kurosawa, Kei Kamada and Akira Yoshikawa

Crystals 2025, 15(3), 202; https://doi.org/10.3390/cryst15030202 - 20 Feb 2025

Viewed by 353

Abstract

Ce-doped Lu₂Si₂O₇ has a high density, high luminescence efficiency even at high temperatures, and a high effective atomic number, making it a promising candidate for use as a radiation detector in medical devices and resource exploration equipment. In [...] Read more.

Ce-doped Lu₂Si₂O₇ has a high density, high luminescence efficiency even at high temperatures, and a high effective atomic number, making it a promising candidate for use as a radiation detector in medical devices and resource exploration equipment. In this study, we grow and characterize Pr³⁺ and Ce³⁺-doped Lu₂Si₂O₇ single crystals by systematically varying the Ce³⁺ to Pr³⁺ ratio to further improve scintillation properties. The optical characterization results show a bidirectional energy transfer: from the Pr³⁺ 5d levels to the Ce³⁺ 5d levels and from the Ce³⁺ 5d levels to the Pr³⁺ 4f levels. Consistently with this result, the PL decay time of emission from the Pr³⁺ 5d–4f transition tends to become faster as the Ce³⁺/Pr³⁺ ratio increases, due to the energy transfer from the Pr³⁺ 5d levels to the Ce³⁺ 5d levels. Additionally, (Ce_0.0022 Pr_0.0016 Lu_0.9962)₂Si₂O₇ exhibits a high light yield comparable to Ce-doped Lu₂Si₂O₇ and a slightly faster decay time than Ce-doped Lu₂Si₂O₇. Full article

(This article belongs to the Special Issue Growth and Properties of Novel Scintillator Crystals)

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57 pages, 13524 KiB

Open AccessEditor’s ChoiceReview

Recent Developments in Transmission Electron Microscopy for Crystallographic Characterization of Strained Semiconductor Heterostructures

by Tao Gong, Longqing Chen, Xiaoyi Wang, Yang Qiu, Huiyun Liu, Zixing Yang and Thomas Walther

Crystals 2025, 15(2), 192; https://doi.org/10.3390/cryst15020192 - 17 Feb 2025

Viewed by 1012

Abstract

With recent electronic devices relying on sub-nanometer features, the understanding of device performance requires a direct probe of the atomic arrangement. As an ideal tool for crystallographic analysis at the nanoscale, aberration-corrected transmission electron microscopy (ACTEM) has the ability to provide atomically resolved [...] Read more.

With recent electronic devices relying on sub-nanometer features, the understanding of device performance requires a direct probe of the atomic arrangement. As an ideal tool for crystallographic analysis at the nanoscale, aberration-corrected transmission electron microscopy (ACTEM) has the ability to provide atomically resolved images and core-loss spectra. Herein, the techniques for crystallographic structure analysis based on ACTEM are reviewed and discussed, particularly ACTEM techniques for measuring strain, dislocations, phase transition, and lattice in-plane misorientation. In situ observations of crystal evolution during the application of external forces or electrical fields are also introduced, so a correlation between crystal quality and device performance can be obtained. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 4387 KiB

Open AccessEditor’s ChoiceArticle

Polymorphism of the Transition Metal Oxidotellurates NiTeO₄ and CuTe₂O₅

by Matthias Weil and Enrique J. Baran

Crystals 2025, 15(2), 183; https://doi.org/10.3390/cryst15020183 - 14 Feb 2025

Viewed by 485

Abstract

As part of crystal growth experiments on transition metal oxidotellurates using chemical vapor transport reactions or hydrothermal conditions, single crystals of Ni^IITe^VIO₄ and Cu^IITe^IV₂O₅ were obtained for the first time in the [...] Read more.

As part of crystal growth experiments on transition metal oxidotellurates using chemical vapor transport reactions or hydrothermal conditions, single crystals of Ni^IITe^VIO₄ and Cu^IITe^IV₂O₅ were obtained for the first time in the form of new modifications, as revealed by crystal structure determinations from X-ray data. In the course of these investigations, the crystal structure model of the only phase of Ni^IITe^VIO₄ reported so far (from now on named α-) was corrected. Both α-(space group P2₁/c, Z = 2) and the new β-polymorph of Ni^IITe^VIO₄ (space group I4₁/a, Z = 8) can be considered derivatives (hettotypes) of the rutile structure (aristotype), as shown by detailed symmetry relationships. For CuTe₂O₅ also, only one crystalline phase has been described so far (from now on named α-) that corresponds to the mineral rajite (space group P2₁/c, Z = 2). Its anion comprises two different trigonal-pyramidal TeO₃ groups linked through corner-sharing into a ditellurite unit. The anion part of the new β-CuTe₂O₅ modification (space group P2₁/c, Z = 2), likewise, comprises two Te^IV atoms but is more complex. Here, one Te^IV atom exhibits a coordination number of 4 and is part of a

{}_{\propto}^{1}[

TeO_2/2O_2/1] chain, and the other has a coordination number of 5 and is part of a

{}_{\propto}^{1}[

TeO_2/2O_3/1]₂ dimer. The two types of anions are linked into a tri-periodic framework where both Te^IV atoms are stereochemically active. The α- and β-CuTe₂O₅ modifications show no closer structural relationship, which is also reflected in their clearly different Raman spectra. Data mining for knowledge discovery in a structure database reveals that polymorphism is a rather common phenomenon for the family of inorganic oxidotellurates. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

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21 pages, 17365 KiB

Open AccessEditor’s ChoiceArticle

Regulating the Mechanical and Corrosion Properties of Mg-2Zn-0.1Y Alloy by Trace SiC with Different Morphologies

by Furong Guo, Kaibo Nie, Kunkun Deng and Yanan Li

Crystals 2025, 15(2), 166; https://doi.org/10.3390/cryst15020166 - 8 Feb 2025

Viewed by 407

Abstract

Traditional magnesium structural materials are used widely due to their light weight; however, their corrosion resistance is poor. In order to address this problem and improve the strength simultaneously, SiCp-, SiCnp-, and SiCnw-reinforced Mg-2Zn-0.1Y (wt. %, MZY alloy) matrix composites (SiC/MZY composites) with [...] Read more.

Traditional magnesium structural materials are used widely due to their light weight; however, their corrosion resistance is poor. In order to address this problem and improve the strength simultaneously, SiCp-, SiCnp-, and SiCnw-reinforced Mg-2Zn-0.1Y (wt. %, MZY alloy) matrix composites (SiC/MZY composites) with the same contents (0.3 wt. %) were prepared and extruded at low temperature in this paper. The effects of SiC morphology on the microstructure, mechanical properties and corrosion resistance of MZY alloy were studied. The results show that the grain size can be refined by adding SiC reinforcement. Compared with the unreinforced MZY alloy, the strengths of the SiC/MZY composites were all improved, with a yield strength of more than 440 MPa and an ultimate tensile strength of more than 450 MPa. However, only the corrosion rate of the composites reinforced by submicron SiCp was improved significantly. The hydrogen evolution corrosion rate (P_H) was reduced by 81% relative to the MZY alloy. This can be attributed to the decreased galvanic corrosion pairs, as well as the decreased potential difference between the second phase and the matrix in the SiCp/MZY composite. Additionally, a compact product film on the surface of the SiCp/MZY composite can also protect the matrix. The materials prepared in this study showed excellent strength and high corrosion resistance at relatively low cost, providing valuable insights and design ideas for the development and application of those materials in marine and offshore engineering applications. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Composites)

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15 pages, 3338 KiB

Open AccessEditor’s ChoiceArticle

One-Pot Strategies for Lithium Recovery from Beta-Spodumene and LTA-Type Zeolite Synthesis

by Leonardo Leandro dos Santos, Rubens Maribondo do Nascimento and Sibele Berenice Castellã Pergher

Crystals 2025, 15(2), 161; https://doi.org/10.3390/cryst15020161 - 8 Feb 2025

Viewed by 571

Abstract

This study presents a groundbreaking method for extracting lithium from beta-spodumene while simultaneously achieving the sustainable synthesis of LTA-type zeolite, designated as LPM-15, without relying on organic solvents or calcination. Lithium extraction was efficiently performed using sodium salts, accompanied by the recycling of [...] Read more.

This study presents a groundbreaking method for extracting lithium from beta-spodumene while simultaneously achieving the sustainable synthesis of LTA-type zeolite, designated as LPM-15, without relying on organic solvents or calcination. Lithium extraction was efficiently performed using sodium salts, accompanied by the recycling of the mother liquor, with lithium content in the supernatant precisely quantified via atomic absorption spectroscopy (AAS). The optimized synthesis route enables the concurrent production of Li₂CO₃ and LPM-15, distinguished by a powdered appearance without a well-defined geometric framework and a unique cubic morphology with spherical facets, respectively. To gain deeper insights into the process, density functional theory (DFT) simulations were conducted to analyze how different cation exchanges (Na⁺ replacing Al³⁺, NH₄⁺ replacing Al³⁺, and Ca²⁺ replacing Al³⁺) influence the structural stability and diffusion dynamics within the zeolitic pores of LPM-15. Additionally, cation-exchange capacity (CEC) measurements further assessed ion mobility within the LPM-15 framework. This integrative approach not only sheds light on the fundamental mechanisms underpinning LTA-type zeolite synthesis but also demonstrates their versatile applications, with particular emphasis on water purification technologies. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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15 pages, 4738 KiB

Open AccessEditor’s ChoiceArticle

Estimation of Hardness of Single-Phase Metallic Alloys

by Ottó K. Temesi, Nguyen Q. Chinh, Levente Vitos and Lajos K. Varga

Crystals 2025, 15(2), 156; https://doi.org/10.3390/cryst15020156 - 2 Feb 2025

Viewed by 660

Abstract

First, we discuss a common feature of single-phase pure metals and amorphous and high-entropy alloys: the maximum value of hardness corresponding to a valence electron count (VEC) value of around 6.5–7. This correlation is explained by the coincidence that by subtracting the number [...] Read more.

First, we discuss a common feature of single-phase pure metals and amorphous and high-entropy alloys: the maximum value of hardness corresponding to a valence electron count (VEC) value of around 6.5–7. This correlation is explained by the coincidence that by subtracting the number of sp valence electrons (Nsp = 2) from the VEC we obtain the maximal number of unpaired d electrons, N_d = 4.5–5 in the 3d, 4d, and 5d rows of transition elements. These unpaired d electrons form orbital overlap bonding, which is stronger than the isotropic metallic bonds of a delocalized electron cloud. The more unpaired d electrons there are, the higher the bonding strength. Second, we will discuss the hardness formulas derived from cohesion energy and shear modulus. We will demonstrate that both types of formulas originate in the electrostatic energy density of metallic bonds, expressing a 1/R⁴ dependence. Finally, we show that only two parameters are sufficient to estimate hardness: the atomic radius and the cohesion-based valence. In the case of alloys, our formula gives a lower bound on the hardness only. It is not suitable for calculation of the hardness increase caused by solid solution, grain size, precipitation, and phase mixture. Full article

(This article belongs to the Special Issue Microstructure and Deformation of Advanced Alloys)

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17 pages, 8260 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Selected Crystal Structures of Rod-like Molecules with Acid and Ester Terminal Groups

by Peter Zugenmaier

Crystals 2025, 15(2), 102; https://doi.org/10.3390/cryst15020102 - 21 Jan 2025

Viewed by 452

Abstract

The crystal structures of rod-like molecules with nitro-biphenyl or nitro-phenyl end groups and attached n-alkyl units with terminal acid or ester groups are determined by single crystal analysis and their arrangements are compared. The molecules are linked by head-to-tail arrangements and form strings. [...] Read more.

The crystal structures of rod-like molecules with nitro-biphenyl or nitro-phenyl end groups and attached n-alkyl units with terminal acid or ester groups are determined by single crystal analysis and their arrangements are compared. The molecules are linked by head-to-tail arrangements and form strings. They point in a single or two different directions and are placed side by side to create the crystal structure. Some of the space groups of the structures can only be determined by a statistical routine because strongly disordered structures prevent the use of extinction methods, since many extinction violations occur for monoclinic and orthorhombic unit cells. An agreement between experimental and calculated X-ray reflection intensities serves as proof of the correctness of the method as well as a test of the existence of an inversion center. The single crystals are grown in solution with ethanol, isopropanol, DMAc, and toluene as solvents. Cocrystals are formed in DMAc solutions by the dissolved acid compounds. The two-molecule asymmetric unit of the acid compound is reduced to a one-molecule asymmetric unit with one DMAc included which forms a hydrogen bond with the acid group of the biphenyl molecule. These changes alter the hydrogen bonding scheme along a string. Some structural similarities as the head-to-tail arrangement in the strings are maintained between the terminal acid and ester compounds despite disordered ester groups in the compounds and the ester molecules themselves at ambient temperature. Full article

(This article belongs to the Section Crystal Engineering)

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16 pages, 16085 KiB

Open AccessEditor’s ChoiceArticle

Impact of Diffraction Data Volume on Data Quality in Serial Crystallography

by Ki Hyun Nam

Crystals 2025, 15(2), 104; https://doi.org/10.3390/cryst15020104 - 21 Jan 2025

Cited by 1 | Viewed by 843

Abstract

Serial crystallography (SX) enables macromolecular structure determination at biologically relevant temperatures while minimizing radiation damage. This technique relies on processing numerous diffraction images from multiple crystals to construct a complete dataset for three-dimensional structure determination. Although increasing the volume of SX diffraction data [...] Read more.

Serial crystallography (SX) enables macromolecular structure determination at biologically relevant temperatures while minimizing radiation damage. This technique relies on processing numerous diffraction images from multiple crystals to construct a complete dataset for three-dimensional structure determination. Although increasing the volume of SX diffraction data improves data quality, excessive data collection reduces beamtime efficiency. Therefore, understanding the relationship between data volume and data quality is crucial for the efficient use of SX beamtime. In this study, serial synchrotron crystallography datasets from lysozyme and glucose isomerase were analyzed to assess the impact of varying diffraction data volumes on processing statistics and structural determination outcomes. Data processing statistics and structure refinement metrics improved as the volume of integrated diffraction data increased; however, the rate of improvement in data quality was not proportional to the number of integrated diffraction patterns. Furthermore, the rate of improvement in data processing statistics decreased beyond a certain threshold volume. These findings expand our understanding of SX data processing and provide insights into optimizing the efficiency of data processing. Full article

(This article belongs to the Section Biomolecular Crystals)

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12 pages, 2358 KiB

Open AccessEditor’s ChoiceArticle

Exploring Brannerite-Type Mg_1−xM_xV₂O₆ (M = Mn, Cu, Co, or Ni) Oxides: Crystal Structure and Optical Properties

by Hua-Chien Hsu, Narayanan Lakshminarasimhan, Jun Li, Arthur P. Ramirez and Mas A. Subramanian

Crystals 2025, 15(1), 86; https://doi.org/10.3390/cryst15010086 - 16 Jan 2025

Viewed by 1335

Abstract

Environmentally benign, highly stable oxides exhibiting desirable optical properties and high near-IR reflectance are being researched for their potential application as pigments. Mg_1−xM_xV₂O₆ (M = Mn, Cu, Co, or Ni) oxides with brannerite-type structures [...] Read more.

Environmentally benign, highly stable oxides exhibiting desirable optical properties and high near-IR reflectance are being researched for their potential application as pigments. Mg_1−xM_xV₂O₆ (M = Mn, Cu, Co, or Ni) oxides with brannerite-type structures were synthesized by the conventional solid-state reaction method to study their optical properties. These series exhibit structural transitions from brannerite (C2/m) to distorted brannerite (P

\bar{1}

) and NiV₂O₆-type (P

\bar{1}

) structures. The average color of Mg_1−xM_xV₂O₆ compounds varies from reddish-yellow to brown to dark brown. The L*a*b* color coordinates reveal that Mg_1−xCu_xV₂O₆ and Mg_1−xNi_xV₂O₆ show more red hues in color with x = 0.4 and x = 0.5, respectively. The UV–Vis diffuse reflectance spectra indicate a possible origin for these results include the ligand-to-metal charge transfer (O²⁻ 2p-V⁵⁺ 3d), metal-to-metal charge transfer (from Mn²⁺ 3d/Cu²⁺ 3d/Co²⁺ 3d/Ni²⁺ 3d to V⁵⁺ 3d), band gap transitions, and d–d transitions. Magnetic property measurements revealed antiferromagnetic behavior for the compounds Mg_1−xM_xV₂O₆ (M = Mn, Cu, Co, and Ni), and an oxidation state of +2 for the M ions was deduced from their Curie–Weiss behavior. The system Mg_1−xMn_xV₂O₆ has a NIR reflectance in the range between 40% and 70%, indicating its potential to be utilized in the pigment industry. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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13 pages, 1857 KiB

Open AccessEditor’s ChoiceArticle

The Effect of Gradient Cooling Behavior on the Microstructure and Mechanical Properties of Al-2at.% Nd Alloy in a Vacuum Environment

by Xiangjie Wang, Xinyu Zhang, Wenjie Wu and Shuchen Sun

Crystals 2025, 15(1), 81; https://doi.org/10.3390/cryst15010081 - 15 Jan 2025

Cited by 1 | Viewed by 611

Abstract

Al-2at.% Nd alloy with a gradient cooling rate was prepared using a wedge-shaped mold in a vacuum environment. The relationship between gradient cooling behavior and the microstructure and properties of the Al-2at.% Nd alloy was investigated. The stability of the Al₁₁Nd [...] Read more.

Al-2at.% Nd alloy with a gradient cooling rate was prepared using a wedge-shaped mold in a vacuum environment. The relationship between gradient cooling behavior and the microstructure and properties of the Al-2at.% Nd alloy was investigated. The stability of the Al₁₁Nd₃ phase and the mechanical properties were confirmed through first-principles calculations. The results indicated that as the cooling rate decreased, the transformation of grain morphology in Al-2at.% Nd occurred as follows: a mixture of columnar grains and equiaxed grains→equiaxed grains. The grain size of the alloy increased. Discontinuous skeletal eutectic phases, α-Al and Al₁₁Nd₃, formed within the alloy, resulting in a reduction in the number of phase boundaries and grain boundaries. The hardness of the alloy decreased by 25.53%, and this pattern of change closely aligned with the calculated results. Full article

(This article belongs to the Special Issue Development of Light Alloys and Their Applications)

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22 pages, 11041 KiB

Open AccessEditor’s ChoiceArticle

Effect of Dynamic Corrosion and Degradation on Fatigue Life of an AA2024-T3 Aircraft Profile: Experimental, Statistical, and Numerical Analyses

by Gilberto Daniel Conejo Magaña, Víctor García García, Daniel Cahue Díaz, Nicolás Herrera-Sandoval and Orlando Hernández Cristóbal

Crystals 2025, 15(1), 66; https://doi.org/10.3390/cryst15010066 - 11 Jan 2025

Viewed by 701

Abstract

The effect of parameters such as angle of attack, flow velocity, and electrolyte concentration (saline solution) on the extent of material degradation, as well as the morphology and depth of corrosion pits in an airfoil made of 2024-T3 aluminum alloy, was studied in [...] Read more.

The effect of parameters such as angle of attack, flow velocity, and electrolyte concentration (saline solution) on the extent of material degradation, as well as the morphology and depth of corrosion pits in an airfoil made of 2024-T3 aluminum alloy, was studied in detail. An orthogonal L9 design of experiments (Taguchi method) was applied to promote high pitting corrosion through the quality characteristic “the higher the better”. Potentiodynamic curves of the three experiments with low, medium, and high saline concentration were obtained through the CorrTest CS350 equipment. The above allowed the determination of the electrochemical corrosion parameters under static test conditions. The corroded airfoils were analyzed using light optical microscopy (LOM). In addition, the roughness measurements correlated with the extent of the degraded surface. A complete pit shape and depth characterization was obtained by applying mechanical ground, surface wear level monitoring (every 0.01 mm), and LOM observations. Pitting defects (depth and morphology) and mechanical strength reduction were considered by a finite element (FE) model to simulate the airfoil fatigue behavior. Numerical results helped to determine the contribution of pitting and the extent of degradation on sudden airfoil failure. Full article

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

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14 pages, 9251 KiB

Open AccessEditor’s ChoiceArticle

Synergistic Integration of Mesocarbon Microbeads, Graphitic Nanofibers, and Mesoporous Carbon for Advanced Supercapacitor Electrodes

by Palanisamy Rajkumar, Vediyappan Thirumal, Kisoo Yoo and Jinho Kim

Crystals 2025, 15(1), 64; https://doi.org/10.3390/cryst15010064 - 10 Jan 2025

Viewed by 548

Abstract

In this study, a novel multiscale carbon architecture was developed by integrating mesocarbon microbeads (MCMBs), graphitic nanofibers (GNFs), and mesoporous carbon, aimed at enhancing the performance of symmetric supercapacitors. The unique combination of spherical MCMB particles, conductive GNF nanofibers, and mesoporous carbon sheets [...] Read more.

In this study, a novel multiscale carbon architecture was developed by integrating mesocarbon microbeads (MCMBs), graphitic nanofibers (GNFs), and mesoporous carbon, aimed at enhancing the performance of symmetric supercapacitors. The unique combination of spherical MCMB particles, conductive GNF nanofibers, and mesoporous carbon sheets resulted in a highly effective electrode material, offering improved conductivity, increased active sites for charge storage, and enhanced structural stability. The fabricated MCMB/GNF/MC architecture demonstrated a remarkable specific capacitance of 393 F g⁻¹ at 1 A g⁻¹ in a three-electrode system, significantly surpassing the performance of individual MCMBs and MCMB/GNF electrodes. Furthermore, the architecture was incorporated into a symmetric supercapacitor (SSC) device, where it achieved a capacitance of 86 F g⁻¹ at 1 A g⁻¹. The device exhibited excellent cycling stability, retaining 92% of its initial capacitance after 10,000 charge–discharge cycles, with an outstanding coulombic efficiency of 99%. At optimal operating conditions, the SSC device delivered an energy density of 11 Wh kg⁻¹ at a power density of 500 W kg⁻¹, making it a promising candidate for high-performance energy-storage applications. This multiscale carbon architecture represents a significant advancement in the design of electrode materials for symmetric supercapacitors, offering a balance of high energy and power density, long-term stability, and excellent scalability for practical applications. This work not only contributes to the development of high-performance electrode materials but also paves the way for scalable, long-lasting supercapacitors for future energy-storage technologies. Full article

(This article belongs to the Special Issue Feature Papers on "Hybrid and Composite Crystalline Materials" 2023–2024)

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38 pages, 23114 KiB

Open AccessEditor’s ChoiceReview

Mathematical Modeling of Properties and Structures of Crystals: From Quantum Approach to Machine Learning

by Grzegorz Matyszczak, Christopher Jasiak, Gabriela Rusinkiewicz, Kinga Domian, Michał Brzozowski and Krzysztof Krawczyk

Crystals 2025, 15(1), 61; https://doi.org/10.3390/cryst15010061 - 9 Jan 2025

Viewed by 1704

Abstract

The crystalline state of matter serves as a reference point in the context of studies of properties of a variety of chemical compounds. This is due to the fact that prepared crystalline solids of practically useful materials (inorganic or organic) may be utilized [...] Read more.

The crystalline state of matter serves as a reference point in the context of studies of properties of a variety of chemical compounds. This is due to the fact that prepared crystalline solids of practically useful materials (inorganic or organic) may be utilized for the thorough characterization of important properties such as (among others) energy bandgap, light absorption, thermal and electric conductivity, and magnetic properties. For that reason it is important to develop mathematical descriptions (models) of properties and structures of crystals. They may be used for the interpretation of experimental data and, as well, for predictions of properties of novel, unknown compounds (i.e., the design of novel compounds for practical applications such as photovoltaics, catalysis, electronic devices, etc.). The aim of this article is to review the most important mathematical models of crystal structures and properties that vary, among others, from quantum models (e.g., density functional theory, DFT), through models of discrete mathematics (e.g., cellular automata, CA), to machine learning (e.g., artificial neural networks, ANNs). Full article

(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)

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21 pages, 8328 KiB

Open AccessEditor’s ChoiceArticle

Impact of Buffer Layer on Electrical Properties of Bow-Tie Microwave Diodes on the Base of MBE-Grown Modulation-Doped Semiconductor Structure

by Algirdas Sužiedėlis, Steponas Ašmontas, Jonas Gradauskas, Aurimas Čerškus, Aldis Šilėnas and Andžej Lučun

Crystals 2025, 15(1), 50; https://doi.org/10.3390/cryst15010050 - 3 Jan 2025

Cited by 2 | Viewed by 616

Abstract

Bow-tie diodes on the base of modulation-doped semiconductor structures are often used to detect radiation in GHz to THz frequency range. The operation of the bow-tie microwave diodes is based on carrier heating phenomena in an epitaxial semiconductor structure with broken geometrical symmetry. [...] Read more.

Bow-tie diodes on the base of modulation-doped semiconductor structures are often used to detect radiation in GHz to THz frequency range. The operation of the bow-tie microwave diodes is based on carrier heating phenomena in an epitaxial semiconductor structure with broken geometrical symmetry. However, the electrical properties of bow-tie diodes are highly dependent on the purity of the grown epitaxial layer—specifically, the minimal number of defects—and the quality of the ohmic contacts. The quality of MBE-grown semiconductor structure depends on the presence of a buffer layer between a semiconductor substrate and an epitaxial layer. In this paper, we present an investigation of the electrical and optical properties of planar bow-tie microwave diodes fabricated using modulation-doped semiconductor structures grown via the MBE technique, incorporating either a GaAs buffer layer or a GaAs–AlGaAs super-lattice buffer between the semi-insulating substrate and the active epitaxial layer. These properties include voltage sensitivity, electrical resistance, I–V characteristic asymmetry, nonlinearity coefficient, and photoluminescence. The investigation revealed that the buffer layer, as well as the illumination with visible light, strongly influences the properties of the bow-tie diodes. Full article

(This article belongs to the Special Issue Growth, Structural Identification, and Characterization of Semiconductor Alloys and Low-Dimensional Heterostructures)

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12 pages, 7472 KiB

Open AccessEditor’s ChoiceArticle

The Effect of the Film Thickness, Cooling Rate, and Solvent Evaporation on the Formation of L-Menthol Ring-Banded Spherulites

by Tamás Kovács, Tamás Kovács, Jr., Márton Detrich, Ferenc Gazdag, Masaki Itatani and István Lagzi

Crystals 2025, 15(1), 17; https://doi.org/10.3390/cryst15010017 - 27 Dec 2024

Viewed by 872

Abstract

Periodic pattern formation is a prominent phenomenon in chemical, physical, and geochemical systems. This phenomenon can arise from various processes, such as the reaction and mass transport of chemical species, solidification, or solvent evaporation. We investigated the formation of ring-banded spherulites of l [...] Read more.

Periodic pattern formation is a prominent phenomenon in chemical, physical, and geochemical systems. This phenomenon can arise from various processes, such as the reaction and mass transport of chemical species, solidification, or solvent evaporation. We investigated the formation of ring-banded spherulites of l-menthol using a thin liquid film in a Petri dish. We found that the film thickness and cooling rate strongly influence the generation of crystallization patterns. We performed two-dimensional numerical simulations using the Cahn–Hilliard model to support the experimentally observed trend on the dependence of the layer thickness on the periodicity of the generated macroscopic patterns. In a specific scenario, we observed the formation of rings consisting of needle-like crystals on the cover of the Petri dish. This phenomenon was due to the evaporation of the menthol and its subsequent crystallization. In addition to these findings, we created crystallization patterns by solvent evaporation (using tert-butyl alcohol, methyl alcohol, and acetone). Full article

(This article belongs to the Special Issue Crystallisation Advances)

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21 pages, 31902 KiB

Open AccessEditor’s ChoiceArticle

Analysis of Human Kidney Stones Using Advanced Characterization Techniques

by Jelena Brdarić Kosanović, Kristijan Živković, Vatroslav Šerić, Berislav Marković, Imre Szenti, Ákos Kukovecz, Nives Matijaković Mlinarić and Anamarija Stanković

Crystals 2025, 15(1), 6; https://doi.org/10.3390/cryst15010006 - 25 Dec 2024

Viewed by 864

Abstract

A comprehensive analysis of kidney stones is essential for the future treatment of patients. Almost all of the methods available for kidney stone analysis were used in this study. The chemical analysis included powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and [...] Read more.

A comprehensive analysis of kidney stones is essential for the future treatment of patients. Almost all of the methods available for kidney stone analysis were used in this study. The chemical analysis included powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA-DSC). Following the chemical analysis, a detailed morphological analysis was carried out using stereoscopic microscopy, scanning electron microscopy (SEM-EDX), and micro-computed tomography (micro-CT). These investigations showed that the sixteen kidney stones analyzed in detail had a heterogeneous mineralogical structure, consisting of at least two different minerals. Kidney stones consist mainly of calcium oxalate (whewellite or weddellite) but also contain significant amounts of phosphate (mainly apatite and struvite). A thorough analysis of kidney stones can determine the cause of their formation and investigate possible treatments. Full article

(This article belongs to the Section Biomolecular Crystals)

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30 pages, 11520 KiB

Open AccessEditor’s ChoiceReview

Progress in Tungsten Trioxide-Based Materials for Energy Storage and Smart Window Applications

by Khursheed Ahmad and Tae Hwan Oh

Crystals 2025, 15(1), 10; https://doi.org/10.3390/cryst15010010 - 25 Dec 2024

Viewed by 761

Abstract

Previous years have witnessed a rapid surge in WO₃-based experimental reports for the construction of energy storage devices (ESDs) and electrochromic devices (ECDs). WO₃ is a highly electrochromic (EC) material with a wide band gap that has been extensively used [...] Read more.

Previous years have witnessed a rapid surge in WO₃-based experimental reports for the construction of energy storage devices (ESDs) and electrochromic devices (ECDs). WO₃ is a highly electrochromic (EC) material with a wide band gap that has been extensively used for the construction of working electrodes for supercapacitor (SC) and ECD applications. Previously, WO₃-based hybrid composites were explored for SC and ECD applications. In this review report, we have compiled the WO₃-based hybrid electrode materials for SC and ECD applications. It is believed that the present review would benefit the researchers working on the fabrication of electrode materials for SC and ECD applications. In this review article, challenges and future perspectives have been discussed for the development of WO₃-based SCs and ECDs. Full article

(This article belongs to the Special Issue Metal Oxides: Crystal Structure, Synthesis and Characterization (2nd Edition))

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17 pages, 3033 KiB

Open AccessEditor’s ChoiceArticle

Advanced Copper Oxide Chemical and Green Synthesis: Characterization and Antibacterial Evaluation

by Ecaterina Magdalena Modan, Adriana-Gabriela Schiopu, Sorin Georgian Moga, Denis Aurelian Negrea, Daniela Istrate, Ion Ciuca and Mihai Oproescu

Crystals 2025, 15(1), 7; https://doi.org/10.3390/cryst15010007 - 25 Dec 2024

Viewed by 961

Abstract

Recent advancements in nanotechnology have improved the application of copper oxide (CuO) nanostructures, known for their diverse antibacterial, electrical, catalytic, optical, and pharmacological properties, which depend on nanoparticle morphology. This study investigated two synthesis methods for structured CuO: microwave-assisted hydrolysis and ultrasound using [...] Read more.

Recent advancements in nanotechnology have improved the application of copper oxide (CuO) nanostructures, known for their diverse antibacterial, electrical, catalytic, optical, and pharmacological properties, which depend on nanoparticle morphology. This study investigated two synthesis methods for structured CuO: microwave-assisted hydrolysis and ultrasound using copper acetate and KOH, and an eco-friendly method involving cholesterol-free egg white albumin and Solanum lycopersicum extract. Characterization techniques, including XRD, FTIR, and SEM-EDS, were utilized to analyze the produced CuO. XRD confirmed high-purity monoclinic CuO structures in the sample obtained via the chemical method, while characteristic peaks of tenorite and dolerophanite were observed in the albumin-synthesized sample. ATR-FTIR analysis revealed O-H stretching bands around 3400 cm⁻¹, indicating adsorbed H-OH or -OH and strong Cu-O bond peaks at 434 cm⁻¹. The CuO synthesized via microwave and ultrasound methods displayed superior crystallinity compared to commercial CuO. SEM illustrated various morphologies, such as flakes, microspheres, and irregular polyhedra, influenced by the presence of proteins and organic acids. Antibacterial tests demonstrated the effective inhibition of Escherichia coli and Enterococcus faecalis, confirming the potential of CuO as a promising antibacterial agent. Overall, the findings highlight the effectiveness of green chemistry in developing crystalline CuO for various applications. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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12 pages, 3272 KiB

Open AccessEditor’s ChoiceArticle

Microstructural Evolution and Thermal Stability of Long Period Stacking Ordered Phases in Mg₉₇Er₂Ni₁ and Mg₉₇Er₂Zn₁ Alloys

by Jian Yin, Yushun Liu and Guo-Zhen Zhu

Crystals 2024, 14(12), 1092; https://doi.org/10.3390/cryst14121092 - 19 Dec 2024

Viewed by 794

Abstract

The influence of transition metals (Ni and Zn) on the formation, morphology, and thermal stability of long-period stacking ordered (LPSO) phases in Mg₉₇Er₂N_i1 and Mg₉₇Er₂Zn₁ alloys was investigated. In the as-cast state, both [...] Read more.

The influence of transition metals (Ni and Zn) on the formation, morphology, and thermal stability of long-period stacking ordered (LPSO) phases in Mg₉₇Er₂N_i1 and Mg₉₇Er₂Zn₁ alloys was investigated. In the as-cast state, both alloys consist of α-Mg and LPSO phases. Heat treatment at 540 °C for 20 h dissolves block-like and lamellar LPSO phases into the α-Mg matrix in the Mg₉₇Er₂Zn₁ alloy, with lamellar LPSO phases reprecipitating during subsequent cooling from 540 °C to 400 °C. Comparative analysis shows that Ni significantly enhances the thermal stability of the LPSO phase compared to Zn. Ni favors the formation of block-shaped LPSO phases, while Zn facilitates lamellar LPSO precipitation within the α-Mg matrix. The LPSO phase in the Mg₉₇Er₂Ni₁ alloy exhibits an exceptionally high melting temperature of 605 °C, the highest reported for an LPSO phase. Additionally, heat treatment at 500 °C for 100 h preserves the area fraction of the LPSO phase in the Mg₉₇Er₂Ni₁ alloy, and at 540 °C for 100 h, the LPSO grains grow without phase dissolution or structural transformation of their 18R-type configuration. These findings provide valuable insights into the role of alloying transition metal elements in controlling the stability and morphology of LPSO phases, offering pathways for tailoring the morphology of the LPSO phase in the Mg-based alloys. Full article

(This article belongs to the Special Issue Advances in Metal Matrix Composites: Structure, Properties and Applications)

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16 pages, 8895 KiB

Open AccessEditor’s ChoiceArticle

Study on the Alleviation of Performance Degradation and Voltage Stability of PEMFC by Adding Silica Under Low-Temperature and Low-Humidity Conditions

by Qiang Bai, Chuangyu Hsieh, Zhenghong Liu, Qipeng Chen and Fangbor Weng

Crystals 2024, 14(12), 1089; https://doi.org/10.3390/cryst14121089 - 18 Dec 2024

Cited by 1 | Viewed by 636

Abstract

This study enhances PEMFC performance at low temperature and low humidity by incorporating hydrophilic inorganic silica materials inside the PEMFC. Firstly, the polarization performance of the cell under varying humidity levels was investigated using a controlled variable method. Secondly, the power stability of [...] Read more.

This study enhances PEMFC performance at low temperature and low humidity by incorporating hydrophilic inorganic silica materials inside the PEMFC. Firstly, the polarization performance of the cell under varying humidity levels was investigated using a controlled variable method. Secondly, the power stability of the PEMFC was examined by observing voltage stability under constant current. Finally, the cell’s transient response at startup was studied. Experimental results indicate that the addition of silica partially mitigates the significant performance decline of the cell under a high humidity range (100% RH–50% RH). However, the effect is relatively average in a low humidity range (50% RH–20% RH). Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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31 pages, 15017 KiB

Open AccessEditor’s ChoiceArticle

Green Synthesized Composite AB-Polybenzimidazole/TiO₂ Membranes with Photocatalytic and Antibacterial Activity

by Hristo Penchev, Katerina Zaharieva, Silvia Dimova, Ivelina Tsacheva, Rumyana Eneva, Stephan Engibarov, Irina Lazarkevich, Tsvetelina Paunova-Krasteva, Maria Shipochka, Ralitsa Mladenova, Ognian Dimitrov, Daniela Stoyanova and Irina Stambolova

Crystals 2024, 14(12), 1081; https://doi.org/10.3390/cryst14121081 - 16 Dec 2024

Viewed by 1125

Abstract

Novel AB-Polybenzimidazole (AB-PBI)/TiO₂ nanocomposite membranes have been prepared using a synthetic green chemistry approach. Modified Eaton’s reagent (methansulfonic acid/P₂O₅) was used as both reaction media for microwave-assisted synthesis of AB-PBI and as an efficient dispersant of partially agglomerated [...] Read more.

Novel AB-Polybenzimidazole (AB-PBI)/TiO₂ nanocomposite membranes have been prepared using a synthetic green chemistry approach. Modified Eaton’s reagent (methansulfonic acid/P₂O₅) was used as both reaction media for microwave-assisted synthesis of AB-PBI and as an efficient dispersant of partially agglomerated titanium dioxide powders. Composite membranes of 80 µm thickness have been prepared by a film casting approach involving subsequent anti-solvent inversion in order to obtain porous composite membranes possessing high sorption capacity. The maximal TiO₂ filler content achieved was 20 wt.% TiO₂ nanoparticles (NPs). Titania particles were green synthesized (using a different content of Mentha Spicata (MS) aqueous extract) by hydrothermal activation (150 °C), followed by thermal treatment at 400 °C. The various methods such as powder X-ray diffraction and Thermogravimetric analyses, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and Energy-dispersive X-ray spectroscopy, Electronic paramagnetic resonance, Scanning Electron Microscopy and Transmission Electron Microscopy have been used to study the phase and surface composition, structure, morphology, and thermal behavior of the synthesized nanocomposite membranes. The photocatalytic ability of the so-prepared AB-Polybenzimidazole/bio-TiO₂ membranes was studied for decolorization of Reactive Black 5 (RB5) as a model azo dye pollutant under UV light illumination. The polymer membrane in basic form, containing TiO₂ particles, was obtained with a 40 mL quantity of the MS extract, exhibiting the highest decolorization rate (96%) after 180 min of UV irradiation. The so-prepared AB-Polybenzimidazole/TiO₂ samples have a powerful antibacterial effect on E. coli when irradiated by UV light. Full article

(This article belongs to the Special Issue Photocatalysis and Targeted Sorbent Activity of Advanced Polymer-Based Composites)

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12 pages, 4142 KiB

Open AccessEditor’s ChoiceArticle

Batch Cooling Crystallization of a Model System Using Direct Nucleation Control and High-Performance In Situ Microscopy

by Josip Budimir Sacher, Nenad Bolf and Marko Sejdić

Crystals 2024, 14(12), 1079; https://doi.org/10.3390/cryst14121079 - 13 Dec 2024

Viewed by 1090

Abstract

The aim of this study was to investigate the use of automated high performance in situ microscopy (HPM) for monitoring and direct nucleation control (DNC) during cooling crystallization. Compared to other techniques, HPM enables the detection of small crystals in the range of [...] Read more.

The aim of this study was to investigate the use of automated high performance in situ microscopy (HPM) for monitoring and direct nucleation control (DNC) during cooling crystallization. Compared to other techniques, HPM enables the detection of small crystals in the range of 1 to 10 μm. Therefore, a novel DNC-controlled variable was investigated to determine the potential improvement of the method. The laboratory system and process control software were developed in-house. A well-studied crystallization model system, the seeded batch cooling crystallization of α-glycine from water, was investigated under normal conditions and temperatures below 60 °C. It was postulated that length-weighted edge-to-edge counts in the range of 1 to 10 μm would be most sensitive to the onset of secondary nucleation and are therefore, used as a control variable. Linear cooling experiments were conducted to determine the initial setpoint for the DNC experiments. Three DNC experiments were then performed with different setpoints and an upper and lower counts limit. It was found that the DNC method can be destabilized with a low setpoint and narrow counts limits. In addition, the new controlled variable is highly sensitive to the formation of bubbles at the microscope window and requires careful evaluation. To address the advantages of the DNC method, an additional linear cooling experiment of the same duration was performed, and it was found that the DNC method resulted in a larger average crystal size. Overall, it can be concluded that the HPM method is suitable for DNC control and could be improved by modifying the image processing algorithm. Full article

(This article belongs to the Special Issue Crystallization Process and Simulation Calculation, Third Edition)

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17 pages, 11260 KiB

Open AccessEditor’s ChoiceArticle

Surface Cladding of Mild Steel Coated with Ni Containing TiO₂ Nanoparticles Using a High-Temperature Arc from TIG Welding

by Kavian O. Cooke, Ayesha Mirza, Junlin Chen and Alaa Al Hausone

Crystals 2024, 14(12), 1048; https://doi.org/10.3390/cryst14121048 - 30 Nov 2024

Viewed by 871

Abstract

This study explores the use of a high-temperature arc generated during tungsten inert gas (TIG) welding to enhance the mechanical properties of the surface of AISI 1020 steel. An innovative two-step process involves using the high-temperature arc as an energy source to fuse [...] Read more.

This study explores the use of a high-temperature arc generated during tungsten inert gas (TIG) welding to enhance the mechanical properties of the surface of AISI 1020 steel. An innovative two-step process involves using the high-temperature arc as an energy source to fuse a previously electrodeposited Ni/TiO₂ coating to the surface of the substrate. The cladded surface is characterised by a scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS), an optical microscope (O.M.) equipped with laser-induced breakdown spectroscopy (LIBS), Vicker’s microhardness testing, and pin-on-plate wear testing. The treated surface exhibits a unique amalgamation of hardening mechanisms, including nanoparticle dispersion strengthening, grain size reduction, and solid solution strengthening. The thickness of the electrodeposited layer appears to strongly influence the hardness variation across the width of the treated layer. The hardness of the treated layer when the Ni coating contains 30 nm TiO₂ particles was found to be 451 VHN, validating an impressive 2.7-fold increase in material hardness compared to the untreated substrate (165 VHN). Similarly, the treated surface exhibits a twofold improvement in wear resistance (9.0 × 10² µm³/s), making it substantially more durable in abrasive environments than the untreated surface. Microstructural and EDS analysis reveal a significant reduction in grain size and the presence of high concentrations of Ni and TiO₂ within the treated region, providing clear evidence for the activation of several strengthening mechanisms. Full article

(This article belongs to the Special Issue Advances in Surface Modifications of Metallic Materials)

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15 pages, 290 KiB

Open AccessEditor’s ChoiceReview

A Survey of Crystals for SPECT Imaging

by Shuyu Xu, Zijun Yan and Qingyang Wei

Crystals 2024, 14(12), 1039; https://doi.org/10.3390/cryst14121039 - 29 Nov 2024

Cited by 1 | Viewed by 1013

Abstract

Single-photon emission computed tomography (SPECT) is an important nuclear medicine imaging tool for diagnosis and drug research. The gamma-ray detector is the core component of the SPECT system and influences the overall system performance. The detector crystals, which can be divided into scintillation [...] Read more.

Single-photon emission computed tomography (SPECT) is an important nuclear medicine imaging tool for diagnosis and drug research. The gamma-ray detector is the core component of the SPECT system and influences the overall system performance. The detector crystals, which can be divided into scintillation crystals and semiconductor crystals, are among the main determinants of the detector’s performance. The development of these crystal materials plays an important role in improving SPECT imaging. This paper provides a survey of the technological development and applications of several crystals currently used in SPECT detectors. Furthermore, it explores future research directions for the development of detector crystals. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

17 pages, 2970 KiB

Open AccessEditor’s ChoiceArticle

Synthesis and Characterization of New Organoammonium, Thiazolium, and Pyridinium Triiodide Salts: Crystal Structures, Polymorphism, and Thermal Stability

by Madhushi Bandara, Khadijatul Kobra, Spencer R. Watts, Logan Grady, Connor Hudson, Claudina Veas, Timothy W. Hanks, Rakesh Sachdeva, Jorge Barroso, Colin D. McMillen and William T. Pennington

Crystals 2024, 14(12), 1020; https://doi.org/10.3390/cryst14121020 - 25 Nov 2024

Viewed by 954

Abstract

Triiodide salts are of interest for a variety of applications, including but not limited to electrochemical and photochemical devices, as antimicrobials and disinfectants, in supramolecular chemistry and crystal engineering, and in ionic liquids and deep eutectic solvents. Our work has focused on the [...] Read more.

Triiodide salts are of interest for a variety of applications, including but not limited to electrochemical and photochemical devices, as antimicrobials and disinfectants, in supramolecular chemistry and crystal engineering, and in ionic liquids and deep eutectic solvents. Our work has focused on the design of salt–solvate cocrystals and deep eutectic solvents in which the triiodide anion interacts as a halogen bond acceptor with organoiodine molecules. To understand structure–property relationships in these hybrid materials, it is essential to have benchmark structural and physical data for the parent triiodide salt component. Herein, we report the structure and thermal properties of eight new triiodide salts, three of which exhibit polymorphism: tetrapentylammonium triiodide (1a and 1b), tetrahexylammonium triiodide (2), trimethylphenylammonium triiodide (3), trimethylbenzylammonium triiodide (4), triethylbenzylammonium triiodide (5), tri-n-butylbenzylammonium triiodide (6), 3-methylbenzothizolium triiodide (7a and 7b), and 2-chloro-1-methylpyridinium triiodide (8a and 8b). The structural features of the triiodide anion, Raman spectroscopic analysis, and melting and thermal decomposition behavior of the salts, as well as a computational analysis of the polymorphs, are discussed. The polymorphic pairs here are distinguished by symmetric versus asymmetric triiodide anions, as well as different packing patterns. Computational analyses revealed more subtle differences in their isosurface plots. Importantly, this study provides reference data for these new triiodide salts for comparison to hybrid cocrystals and deep eutectic solvents formed from their combination with various organoiodines. Full article

(This article belongs to the Special Issue Crystalline Materials: Polymorphism)

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16 pages, 4032 KiB

Open AccessEditor’s ChoiceArticle

In Situ Microscopy with Real-Time Image Analysis Enables Online Monitoring of Technical Protein Crystallization Kinetics in Stirred Crystallizers

by Julian Mentges, Daniel Bischoff, Brigitte Walla and Dirk Weuster-Botz

Crystals 2024, 14(12), 1009; https://doi.org/10.3390/cryst14121009 - 21 Nov 2024

Viewed by 1294

Abstract

Controlling protein crystallization processes is essential for improving downstream processing in biotechnology. This study investigates the combination of machine learning-based image analysis and in situ microscopy for real-time monitoring of protein crystallization kinetics. The experimental research is focused on the batch crystallization of [...] Read more.

Controlling protein crystallization processes is essential for improving downstream processing in biotechnology. This study investigates the combination of machine learning-based image analysis and in situ microscopy for real-time monitoring of protein crystallization kinetics. The experimental research is focused on the batch crystallization of an alcohol dehydrogenase from Lactobacillus brevis (LbADH) and two selected rational crystal contact mutants. Technical protein crystallization experiments were performed in a 1 L stirred crystallizer by adding polyethyleneglycol 550 monomethyl ether (PEG 550 MME). The estimated crystal volumes from online microscopy correlated well with the offline measured protein concentrations in solution. In addition, in situ microscopy was superior to offline data if amorphous protein precipitation occurred. Real-time image analysis provides the data basis for online estimation of important batch crystallization performance indicators like yield, crystallization kinetics, crystal size distributions, and number of protein crystals. Surprisingly, one of the LbADH mutants, which should theoretically crystallize more slowly than the wild type based on molecular dynamics (MD) simulations, showed better crystallization performance except for the yield. Thus, online monitoring of scalable protein crystallization processes with in situ microscopy and real-time image analysis improves the precision of crystallization studies for industrial settings by providing comprehensive data, reducing the limitations of traditional analytical techniques, and enabling new insights into protein crystallization process dynamics. Full article

(This article belongs to the Section Biomolecular Crystals)

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14 pages, 4748 KiB

Open AccessEditor’s ChoiceArticle

Growth and Characterization of High-Quality YTiO₃ Single Crystals: Minimizing Ti⁴⁺ Containing Impurities and TiN Formation

by Yong Liu, David Wenhua Bi and Arnaud Magrez

Crystals 2024, 14(11), 989; https://doi.org/10.3390/cryst14110989 - 16 Nov 2024

Cited by 1 | Viewed by 736

Abstract

We report the growth of YTiO₃ single crystals using different starting materials with the nominal compositions, (1) stoichiometric YTiO₃; (2) oxygen deficient YTiO_2.925; (3) oxygen deficient YTiO_2.85, and different atmospheres, (1) 97%Ar/3%H₂; (2) Ar; [...] Read more.

We report the growth of YTiO₃ single crystals using different starting materials with the nominal compositions, (1) stoichiometric YTiO₃; (2) oxygen deficient YTiO_2.925; (3) oxygen deficient YTiO_2.85, and different atmospheres, (1) 97%Ar/3%H₂; (2) Ar; (3) forming gas 95%N₂/5%H₂, using the laser floating zone growth technique. The oxygen-deficient starting materials were prepared by mixing Y₂O₃, Ti₂O₃, and Ti powder according to the YTiO_3-δ stoichiometry. The addition of Ti powder to the starting materials effectively reacts with the oxygen in the floating zone furnace chamber, reducing Ti⁴⁺ ion-containing impurities. High-quality YTiO₃ single crystals with (2 0 0) facet were grown from the starting materials corresponding to the nominal composition YTiO_2.925. YTiO₃ single crystals grown from different starting materials are characteristic of oxygen content of 3 in both pure crystals and crystals containing impurities, revealed by the same oxygen occupancy in single crystal X-ray diffraction measurements. When forming gas was used, a golden TiN coating formed on the surface of rod. Full article

(This article belongs to the Special Issue Advances in Crystal Growth: Pioneering Materials for Tomorrow's Technologies)

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17 pages, 10195 KiB

Open AccessEditor’s ChoiceArticle

In Situ Synthesis of NPC-Cu₂O/CuO/rGO Composite via Dealloying and Microwave-Assisted Hydrothermal Technique

by Mircea Nicolaescu, Sebastian Ambrus, Petru Hididis, Mina Morariu (Popescu), Iosif Hulka, Corina Orha, Carmen Lazau, Cosmin Codrean and Cornelia Bandas

Crystals 2024, 14(11), 968; https://doi.org/10.3390/cryst14110968 - 8 Nov 2024

Cited by 1 | Viewed by 1180

Abstract

The nanoporous copper (NPC)-copper oxides (Cu₂O/CuO)/reduced graphene oxide (rGO) composite structure was synthesized by combining the dealloying process of Cu₄₈Zr₄₇Al₅ amorphous ribbons with a microwave-assisted hydrothermal technique at a temperature of 200 °C. The main advantage [...] Read more.

The nanoporous copper (NPC)-copper oxides (Cu₂O/CuO)/reduced graphene oxide (rGO) composite structure was synthesized by combining the dealloying process of Cu₄₈Zr₄₇Al₅ amorphous ribbons with a microwave-assisted hydrothermal technique at a temperature of 200 °C. The main advantage of the microwave-assisted hydrothermal process is the oxidation of nanoporous copper together with the in situ reduction of graphene oxide to form rGO. The integration of rGO with NPC improves electrical conductivity and streamlines the process of electron transfer. This composite exhibit considerable potential in electrochemical catalysis application, due to the combined catalytic activity of NPC and the chemical reactivity of rGO. Our study relates the transition to n-type rGO in microwave-assisted hydrothermal reactions, and also the development of an electrode material suitable for electrochemical applications based on the p-p-n junction NPC-Cu₂O/CuO/rGO heterostructure. To confirm the formation of the composite structure, structural, morphological, and optical techniques as XRD, SEM/EDX, UV-Vis and Raman spectroscopy were used. The composite’s electrochemical properties were measured by EIS and Mott-Schottky analyses, showing a charge transfer resistance (Rp) of 250 Ω and indicating the type of the semiconductor properties. The calculated carrier densities of 4.2 × 10¹⁸ cm⁻³ confirms n-type semiconductor characteristic for rGO, and 7.22 × 10¹⁸ cm⁻³ for Cu₂O/CuO indicating p-type characteristic. Full article

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

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14 pages, 3865 KiB

Open AccessEditor’s ChoiceArticle

Assessment of Classical Force-Fields for Graphene Mechanics

by Zhiwei Ma, Yongkang Tan, Xintian Cai, Xue Chen, Tan Shi, Jianfeng Jin, Yifang Ouyang and Qing Peng

Crystals 2024, 14(11), 960; https://doi.org/10.3390/cryst14110960 - 2 Nov 2024

Cited by 1 | Viewed by 1212

Abstract

The unique properties of graphene have attracted the interest of researchers from various fields, and the discovery of graphene has sparked a revolution in materials science, specifically in the field of two-dimensional materials. However, graphene synthesis’s costly and complex process significantly impairs researchers’ [...] Read more.

The unique properties of graphene have attracted the interest of researchers from various fields, and the discovery of graphene has sparked a revolution in materials science, specifically in the field of two-dimensional materials. However, graphene synthesis’s costly and complex process significantly impairs researchers’ endeavors to explore its properties and structure experimentally. Molecular dynamics simulation is a well-established and useful tool for investigating graphene’s atomic structure and dynamic behavior at the nanoscale without requiring expensive and complex experiments. The accuracy of the molecular dynamics simulation depends on the potential functions. This work assesses the performance of various potential functions available for graphene in mechanical properties prediction. The following two cases are considered: pristine graphene and pre-cracked graphene. The most popular fifteen potentials have been assessed. Our results suggest that diverse potentials are suitable for various applications. REBO and Tersoff potentials are the best for simulating monolayer pristine graphene, and the MEAM and the AIREBO-m potentials are recommended for those with crack defects because of their respective utilization of the electron density and inclusion of the long-range interaction. We recommend the AIREBO-m potential for a general case of classical molecular dynamics study. This work might help to guide the selection of potentials for graphene simulations and the development of further advanced interatomic potentials. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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17 pages, 9453 KiB

Open AccessEditor’s ChoiceReview

Progress and Prospect of Liquid Crystal Droplets

by Le Zhou, Tingjun Zhong, Huihui Wang, Ke Xu, Pouya Nosratkhah and Kristiaan Neyts

Crystals 2024, 14(11), 934; https://doi.org/10.3390/cryst14110934 - 29 Oct 2024

Cited by 1 | Viewed by 1705

Abstract

Liquid crystal (LC) droplets are highly attractive for applications in privacy windows, optical switches, optical vortices, optical microresonators, microlenses, and biosensors due to their ease of fabrication and easy alignment at surfaces. This review presents the latest advancements in LC droplets, which have [...] Read more.

Liquid crystal (LC) droplets are highly attractive for applications in privacy windows, optical switches, optical vortices, optical microresonators, microlenses, and biosensors due to their ease of fabrication and easy alignment at surfaces. This review presents the latest advancements in LC droplets, which have nematic, chiral nematic, and twist–bend nematic and ferroelectric nematic phases, or blue phases. Finally, it discusses the challenges and opportunities for applications based on LC droplets. The main challenges encompass the precise control of internal structures and defects to meet diverse application requirements, enhancing stability and durability across various environments, reducing large-scale production costs to improve commercial feasibility, increasing response speeds to external stimuli to adapt to rapidly changing scenarios, and developing tunable LC droplets to achieve broader functionalities. Full article

(This article belongs to the Special Issue Liquid Crystal Materials and Devices)

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9 pages, 2324 KiB

Open AccessEditor’s ChoiceArticle

Electrochemical Properties of Ultrathin LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) Slurry-Cast Li-Ion Battery

by Byoung-Nam Park

Crystals 2024, 14(10), 882; https://doi.org/10.3390/cryst14100882 - 10 Oct 2024

Cited by 2 | Viewed by 1256

Abstract

In thin LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) electrodes, pseudocapacitive behavior is notably enhanced due to their increased surface-to-volume ratio, which intensifies the role of the electrode–electrolyte interface. This behavior is driven by fast, reversible redox reactions and ion intercalation [...] Read more.

In thin LiNi_1/3Mn_1/3Co_1/3O₂ (NMC111) electrodes, pseudocapacitive behavior is notably enhanced due to their increased surface-to-volume ratio, which intensifies the role of the electrode–electrolyte interface. This behavior is driven by fast, reversible redox reactions and ion intercalation occurring near the surface, where the shorter diffusion path allows for more efficient ionic transport. The reduced thickness of the electrodes shortens the Li-ion diffusion distance, improving the diffusion coefficient by a factor of 40 compared to thicker electrodes, where ion transport is hindered by longer diffusion paths. The increased surface area and shorter diffusion paths promote faster electrochemical kinetics, allowing for quicker ion intercalation and deintercalation processes. The thin-film configuration enhances pseudocapacitive charge storage, which is essential for applications requiring rapid charge and discharge cycles. As a result, the combination of improved Li-ion diffusion and enhanced surface activity contributes to superior electrochemical performance, offering higher power densities, faster energy delivery, and better rate capability. This improvement in performance makes thin NMC111 electrodes particularly advantageous for applications such as high-power energy storage systems, where fast kinetics and high power densities are critical. These findings highlight the importance of interface engineering and material morphology in optimizing the performance of Li-ion batteries and similar electrochemical energy storage devices. Full article

(This article belongs to the Section Materials for Energy Applications)

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17 pages, 9494 KiB

Open AccessEditor’s ChoiceArticle

Influences of Zr and V Addition on the Crystal Chemistry of θ-Al₁₃Fe₄ and the Grain Refinement of α-Al in an Al-4Fe Alloy Based on Experiment and First-Principle Calculations

by Zhongping Que, Changming Fang, Junhai Xia and Zhongyun Fan

Crystals 2024, 14(10), 879; https://doi.org/10.3390/cryst14100879 - 9 Oct 2024

Viewed by 1070

Abstract

Fe-containing intermetallic compounds (IMCs) are among the most detrimental second phases in aluminum alloys. One particularly harmful type is θ-Al₁₃Fe₄, which exhibits a needle- or plate-like morphology, leading to greater degradation of mechanical properties compared to other Fe-IMCs with [...] Read more.

Fe-containing intermetallic compounds (IMCs) are among the most detrimental second phases in aluminum alloys. One particularly harmful type is θ-Al₁₃Fe₄, which exhibits a needle- or plate-like morphology, leading to greater degradation of mechanical properties compared to other Fe-IMCs with more compact structures, such as α-Al₁₅(Fe,Mn)₃Si₂. The addition of alloying elements is a crucial strategy for modifying the microstructure during the solidification process of aluminum alloys. This study investigates the effects of adding vanadium (V) and zirconium (Zr) on the morphology and crystal chemistry of θ-Al₁₃Fe₄ in an Al-4Fe alloy, employing a combination of experimental observations, first-principle calculations, and thermodynamic analysis. Our findings indicate that zirconium significantly refines both the primary θ-Al₁₃Fe₄ particles and the α-Al grains. Additionally, a small amount of vanadium can be incorporated into one of the Wyckoff 4i Al sites in θ-Al₁₃Fe₄, rather than occupying any Fe sites, under casting conditions, in addition to the formation of binary Al-V phases. Full article

(This article belongs to the Special Issue Microstructure and Properties of Intermetallic Compounds)

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15 pages, 11097 KiB

Open AccessEditor’s ChoiceArticle

Structural Analysis of Coordination Cage/Guest Complexes Prepared with the ‘Crystalline Sponge’ Methodology

by Christopher G. P. Taylor, James R. Williams, Stephen P. Argent and Michael D. Ward

Crystals 2024, 14(10), 873; https://doi.org/10.3390/cryst14100873 - 2 Oct 2024

Viewed by 1300

Abstract

The crystalline sponge method has proven invaluable in the preparation and analysis of supramolecular host/guest complexes if the host can be obtained in a suitable crystalline form, allowing the analysis of guest binding modes inside host cavities which can inform other studies into [...] Read more.

The crystalline sponge method has proven invaluable in the preparation and analysis of supramolecular host/guest complexes if the host can be obtained in a suitable crystalline form, allowing the analysis of guest binding modes inside host cavities which can inform other studies into processes such as catalysis. Here, we report the structures of a set of ten host/guest complexes using an octanuclear coordination cage host with a range of small-molecule neutral organic guests including four aromatic aldehydes and ketones, three cyclic lactams, and three epoxides. In all cases, the cavity-bound guests are anchored by a collection of CH•••O hydrogen-bonding interactions between an O atom on the guest and a convergent set of CH protons at a pocket on the cage interior surface. Depending on guest size and the presence of solvent molecules as additional guests, there may be one or two cavity-bound guests, with small aromatic guests forming π-stacked pairs. Some guests (the lactams) participate in additional NH•••F H-bonding interactions with surface-bound fluoroborate anions, which indicate the type of anion/guest interactions thought to be responsible for solution-phase catalytic reactions of bound guests. Full article

(This article belongs to the Section Macromolecular Crystals)

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24 pages, 31908 KiB

Open AccessEditor’s ChoiceArticle

Fabrication of Textured 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃ Electrostrictive Ceramics by Templated Grain Growth Using NaNbO₃ Templates and Characterization of Their Electrical Properties

by Kiran Andleeb, Doan Thanh Trung, John G. Fisher, Tran Thi Huyen Tran, Jong-Sook Lee, Woo-Jin Choi and Wook Jo

Crystals 2024, 14(10), 861; https://doi.org/10.3390/cryst14100861 - 30 Sep 2024

Viewed by 1344

Abstract

Electrostrictive materials based on (Na_0.5Bi_0.5)TiO₃ are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na_0.5Bi_0.5)TiO₃ [...] Read more.

Electrostrictive materials based on (Na_0.5Bi_0.5)TiO₃ are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO₃ templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, S_max/E_max (d₃₃*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q₃₃ increased from 0.017 m⁴C⁻² for untextured ceramics to 0.043 m⁴C⁻² for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na_0.5Bi_0.5)TiO₃-0.065BaTiO₃-0.25SrTiO₃ composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the “two” law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified. Full article

(This article belongs to the Special Issue Advanced Ferroelectric, Piezoelectric and Dielectric Ceramics)

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18 pages, 3414 KiB

Open AccessEditor’s ChoiceArticle

Crystallographic Studies on Non-Covalent Interactions in Aryl-Substituted Antimony Organometallics

by Ana Torvisco, Melanie Wolf, Roland C. Fischer and Frank Uhlig

Crystals 2024, 14(10), 860; https://doi.org/10.3390/cryst14100860 - 29 Sep 2024

Viewed by 1016

Abstract

A series of novel and previously published organoantimony compounds (R_nSbX_3−n, X = Cl, Br; R = o-tolyl, 2,6-xylyl, 1-naphthyl, and 9-anthracenyl), were synthesized and characterized. In addition, single-crystal X-ray diffraction was employed to elucidate the molecular structures of [...] Read more.

A series of novel and previously published organoantimony compounds (R_nSbX_3−n, X = Cl, Br; R = o-tolyl, 2,6-xylyl, 1-naphthyl, and 9-anthracenyl), were synthesized and characterized. In addition, single-crystal X-ray diffraction was employed to elucidate the molecular structures of all solid species. These compounds display non-covalent intermolecular interactions in the form of edge-to-face, π···π stacking, and CH₃···π interactions, and the effects of the substituent type and substituent bulk on the nature of these interactions present will be highlighted and discussed. Full article

(This article belongs to the Section Crystal Engineering)

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29 pages, 9007 KiB

Open AccessEditor’s ChoiceReview

The Role of Liquid Crystal Elastomers in Pioneering Biological Applications

by Faeze Shiralipour, Yeganeh Nik Akhtar, Ashley Gilmor, Gisele Pegorin, Abraham Valerio-Aguilar and Elda Hegmann

Crystals 2024, 14(10), 859; https://doi.org/10.3390/cryst14100859 - 29 Sep 2024

Cited by 2 | Viewed by 2869

Abstract

Liquid crystal elastomers have shown an attractive potential for various biological applications due to their unique combination of mechanical flexibility and responsiveness to external stimuli. In this review, we will focus on a few examples of LCEs used with specific applications for biological/biomedical/environmental [...] Read more.

Liquid crystal elastomers have shown an attractive potential for various biological applications due to their unique combination of mechanical flexibility and responsiveness to external stimuli. In this review, we will focus on a few examples of LCEs used with specific applications for biological/biomedical/environmental systems. So far, areas of innovation have been concentrating on the integration of LCEs to enhance stability under physiological conditions, ensure precise integration with biological systems, and address challenges related to optical properties and spatial control of deformation. However, several challenges and limitations must still be addressed to fully realize their potential in biomedical and environmental fields, and future research should focus on continuing to improve biocompatibility, response to the environment and chemical cues, mechanical properties, ensuring long-term stability, and establishing cost-effective production processes. So far, 3D/4D printing appears as a great promise to develop materials of high complexity, almost any shape, and high production output. However, researchers need to find ways to reduce synthesis costs to ensure that LCEs are developed using cost-effective production methods at a scale necessary for their specific applications’ needs. Full article

(This article belongs to the Special Issue Liquid Crystal Research and Novel Applications in the 21st Century)

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19 pages, 3747 KiB

Open AccessEditor’s ChoiceArticle

Ductility Index for Refractory High Entropy Alloys

by Ottó K. Temesi, Lajos K. Varga, Nguyen Quang Chinh and Levente Vitos

Crystals 2024, 14(10), 838; https://doi.org/10.3390/cryst14100838 - 27 Sep 2024

Cited by 1 | Viewed by 1200

Abstract

The big advantage of refractory high entropy alloys (RHEAs) is their strength at high temperatures, but their big disadvantage is their brittleness at room temperature, which prevents their machining. There is a great need to classify the alloys in terms of brittle-ductile (B-D) [...] Read more.

The big advantage of refractory high entropy alloys (RHEAs) is their strength at high temperatures, but their big disadvantage is their brittleness at room temperature, which prevents their machining. There is a great need to classify the alloys in terms of brittle-ductile (B-D) properties, with easily obtainable ductility indices (DIs) ready to help design these refractory alloys. Usually, the DIs are checked by representing them as a function of fraction strain, ε. The critical values of DI and ε divide the DI—ε area into four squares. In the case of a successful DI, the points representing the alloys are located in the two diagonal opposite squares, well separating the alloys with (B-D) properties. However, due to the scatter of the data, the B-D separation is not perfect, and it is difficult to establish the critical value of DI. In this paper, we solve this problem by replacing the fracture strain parameter with new DIs that scale with the old DIs. These new DIs are based on the force constant and amplitude of thermal vibration around the Debye temperature. All of them are easily available and can be calculated from tabulated data. Full article

(This article belongs to the Special Issue Advances in Processing, Simulation and Characterization of Alloys)

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16 pages, 323 KiB

Open AccessEditor’s ChoiceArticle

Three-Dimensional and Two-Dimensional Green Tensors of Piezoelectric Quasicrystals

by Markus Lazar and Eleni Agiasofitou

Crystals 2024, 14(10), 835; https://doi.org/10.3390/cryst14100835 - 26 Sep 2024

Cited by 2 | Viewed by 1306

Abstract

In this work, within the framework of the linear piezoelectricity theory of quasicrystals, the three-dimensional and two-dimensional Green tensors for arbitrary piezoelectric quasicrystals are derived. In the piezoelectricity of quasicrystals, where phonon, phason and electric fields exist, we introduce the corresponding multifields by [...] Read more.

In this work, within the framework of the linear piezoelectricity theory of quasicrystals, the three-dimensional and two-dimensional Green tensors for arbitrary piezoelectric quasicrystals are derived. In the piezoelectricity of quasicrystals, where phonon, phason and electric fields exist, we introduce the corresponding multifields by developing a hyperspace notation for piezoelectric quasicrystals. Using Fourier transform and the multifield formalism, the three-dimensional Green tensor for piezoelectric quasicrystals as well as its spatial gradient necessary for applications, are derived. The solutions for the “displacement”, “distortion” and “stress” multifields in the presence of a “force” multifield in a piezoelectric quasicrystal as well as the solution of the generalised Kelvin problem, are given. In addition, the two-dimensional Green tensors of piezoelectric quasicrystals as well as of quasicrystals, are determined. Full article

(This article belongs to the Special Issue Structures, Properties and Applications of Quasicrystals)

12 pages, 3037 KiB

Open AccessEditor’s ChoiceArticle

Density Functional Theory Study of Lanthanide Monoxides under High Pressure: Pressure-Induced B1–B2 Transition

by Sergio Ferrari and Daniel Errandonea

Crystals 2024, 14(10), 831; https://doi.org/10.3390/cryst14100831 - 25 Sep 2024

Cited by 2 | Viewed by 1207

Abstract

Using density functional theory, we study the influence of hydrostatic pressure on the crystal structure of lanthanide monoxides, focusing on the monoxides formed by the fifteen elements of the lanthanide series, from La to Lu. Calculations are performed using two methods for the [...] Read more.

Using density functional theory, we study the influence of hydrostatic pressure on the crystal structure of lanthanide monoxides, focusing on the monoxides formed by the fifteen elements of the lanthanide series, from La to Lu. Calculations are performed using two methods for the ambient pressure B1 (NaCl type) structure, the general gradient approximation (GGA) and the local density approximation (LDA). Through a systematic comparison with existent experimental data, we find that the first method agrees better with the experiments. In addition, considering other cubic structures previously reported for lanthanide monoxides, as B2 (CsCl type) and B3 (ZnS type), we explore the possibility of the occurrence of pressure-induced phase transitions. Based on the better accuracy of GGA to describe the B1 phase at ambient conditions, we exclusively use GGA for the high pressure study. We find, for the fifteen studied compounds, that, at ambient pressure, the B1 structure is the one with the lowest enthalpy, being therefore the most thermodynamically stable structure. We also determine that, at elevated pressures, all the studied compounds undergo a structural phase transition to the B2 phase. We finally establish the relationship between pressure and volume of the unit cell, along with the associated isothermal equation of state, determining the bulk modulus. Full article

(This article belongs to the Special Issue Pressure-Induced Phase Transformations (Third Edition))

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16 pages, 6665 KiB

Open AccessEditor’s ChoiceReview

Doped, Two-Dimensional, Semiconducting Transition Metal Dichalcogenides in Low-Concentration Regime

by Mallesh Baithi and Dinh Loc Duong

Crystals 2024, 14(10), 832; https://doi.org/10.3390/cryst14100832 - 25 Sep 2024

Cited by 2 | Viewed by 2512

Abstract

Doping semiconductors is crucial for controlling their carrier concentration and enabling their application in devices such as diodes and transistors. Furthermore, incorporating magnetic dopants can induce magnetic properties in semiconductors, paving the way for spintronic devices without an external magnetic field. This review [...] Read more.

Doping semiconductors is crucial for controlling their carrier concentration and enabling their application in devices such as diodes and transistors. Furthermore, incorporating magnetic dopants can induce magnetic properties in semiconductors, paving the way for spintronic devices without an external magnetic field. This review highlights recent advances in growing doped, two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductors through various methods, like chemical vapor deposition, molecular beam epitaxy, chemical vapor transport, and flux methods. It also discusses approaches for achieving n- and p-type doping in 2D TMDC semiconductors. Notably, recent progress in doping 2D TMDC semiconductors to induce ferromagnetism and the development of quantum emitters is covered. Experimental techniques for achieving uniform doping in chemical vapor deposition and chemical vapor transport methods are discussed, along with the challenges, opportunities, and potential solutions for growing uniformly doped 2D TMDC semiconductors. Full article

(This article belongs to the Section Crystal Engineering)

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27 pages, 6432 KiB

Open AccessEditor’s ChoiceReview

Supramolecular Arrangement and Conformational and Dynamic Properties of Chiral Smectic Liquid Crystals Obtained through Nuclear Magnetic Resonance: A Brief Review

by Valentina Domenici

Crystals 2024, 14(9), 823; https://doi.org/10.3390/cryst14090823 - 20 Sep 2024

Cited by 2 | Viewed by 1003

Abstract

Ferroelectric and antiferroelectric smectic liquid crystalline (LC) phases are still at the center of investigations and interests for both their fundamental properties and variety of technological applications. This review aims to report the main contributions based on different nuclear magnetic resonance (NMR) techniques [...] Read more.

Ferroelectric and antiferroelectric smectic liquid crystalline (LC) phases are still at the center of investigations and interests for both their fundamental properties and variety of technological applications. This review aims to report the main contributions based on different nuclear magnetic resonance (NMR) techniques to the study of chiral liquid crystalline calamitic mesogens forming smectic phases, such as the SmA, the SmC* (ferroelectric), and the SmC*_A (antiferroelectric) phases. ²H NMR and ¹³C NMR techniques and their combination were of help in clarifying the local orientational properties (i.e., the molecular and fragments’ main orientational order parameters) at the transition between the SmA and the SmC* phases, and in the particular case of de Vries liquid crystals, NMR studies gave important clues regarding the actual models describing the molecular arrangement in these two phases formed by de Vries LCs. Moreover, this review describes how the combination of ²H NMR relaxation times’ analysis, ¹H NMR relaxometry, and ¹H NMR diffusometry was successfully applied to the study of chiral smectogens forming the SmC* and SmC*_A phases, with the determination of relevant parameters describing both rotational molecular and internal motions, collective dynamics, and translational self-diffusion motions. Several cases will be reported concerning NMR investigations of chiral ferroelectric and antiferroelectric phases, underlining the great potential of combined NMR approaches to the study of supramolecular, conformational, and dynamic properties of liquid crystals. Full article

(This article belongs to the Section Liquid Crystals)

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9 pages, 4348 KiB

Open AccessEditor’s ChoiceArticle

Surface Electronic Structure of Cr Doped Bi₂Se₃ Single Crystals

by Turgut Yilmaz, Xiao Tong, Zhongwei Dai, Jerzy T. Sadowski, Genda Gu, Kenya Shimada, Sooyeon Hwang, Kim Kisslinger, Elio Vescovo and Boris Sinkovic

Crystals 2024, 14(9), 812; https://doi.org/10.3390/cryst14090812 - 14 Sep 2024

Viewed by 1241

Abstract

Here, by using angle-resolved photoemission spectroscopy, we showed that Bi_2−xCr_xSe₃ single crystals have a distinctly well-defined band structure with a large bulk band gap and undistorted topological surface states. These spectral features are unlike their thin film forms [...] Read more.

Here, by using angle-resolved photoemission spectroscopy, we showed that Bi_2−xCr_xSe₃ single crystals have a distinctly well-defined band structure with a large bulk band gap and undistorted topological surface states. These spectral features are unlike their thin film forms in which a large nonmagnetic gap with a distorted band structure was reported. We further provide laser-based high resolution photoemission data which reveal a Dirac point gap even in the pristine sample. The gap becomes more pronounced with Cr doping into the bulk of Bi₂Se₃. These observations show that the Dirac point can be modified by the magnetic impurities as well as the light source. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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48 pages, 7039 KiB

Open AccessEditor’s ChoiceReview

A Review of Nanocarbon-Based Anode Materials for Lithium-Ion Batteries

by Nagaraj Nandihalli

Crystals 2024, 14(9), 800; https://doi.org/10.3390/cryst14090800 - 10 Sep 2024

Cited by 6 | Viewed by 3936

Abstract

Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their [...] Read more.

Renewable and non-renewable energy harvesting and its storage are important components of our everyday economic processes. Lithium-ion batteries (LIBs), with their rechargeable features, high open-circuit voltage, and potential large energy capacities, are one of the ideal alternatives for addressing that endeavor. Despite their widespread use, improving LIBs’ performance, such as increasing energy density demand, stability, and safety, remains a significant problem. The anode is an important component in LIBs and determines battery performance. To achieve high-performance batteries, anode subsystems must have a high capacity for ion intercalation/adsorption, high efficiency during charging and discharging operations, minimal reactivity to the electrolyte, excellent cyclability, and non-toxic operation. Group IV elements (Si, Ge, and Sn), transition-metal oxides, nitrides, sulfides, and transition-metal carbonates have all been tested as LIB anode materials. However, these materials have low rate capability due to weak conductivity, dismal cyclability, and fast capacity fading owing to large volume expansion and severe electrode collapse during the cycle operations. Contrarily, carbon nanostructures (1D, 2D, and 3D) have the potential to be employed as anode materials for LIBs due to their large buffer space and Li-ion conductivity. However, their capacity is limited. Blending these two material types to create a conductive and flexible carbon supporting nanocomposite framework as an anode material for LIBs is regarded as one of the most beneficial techniques for improving stability, conductivity, and capacity. This review begins with a quick overview of LIB operations and performance measurement indexes. It then examines the recently reported synthesis methods of carbon-based nanostructured materials and the effects of their properties on high-performance anode materials for LIBs. These include composites made of 1D, 2D, and 3D nanocarbon structures and much higher Li storage-capacity nanostructured compounds (metals, transitional metal oxides, transition-metal sulfides, and other inorganic materials). The strategies employed to improve anode performance by leveraging the intrinsic features of individual constituents and their structural designs are examined. The review concludes with a summary and an outlook for future advancements in this research field. Full article

(This article belongs to the Special Issue The Development of Advanced Materials for Electrochemical Energy Conversion and Storage)

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22 pages, 25791 KiB

Open AccessEditor’s ChoiceArticle

In Situ Synthesis and Characterization of Graphitic Carbon Nitride/Metakaolin Composite Photocatalysts Using a Commercial Kaolin

by Balázs Zsirka, Orsolya Fónagy, Veronika Vágvölgyi, Tatjána Juzsakova, Lajos Fodor and Csilla Őze

Crystals 2024, 14(9), 793; https://doi.org/10.3390/cryst14090793 - 7 Sep 2024

Viewed by 1158

Abstract

Kaolin-based graphitic carbon nitride (g-CNx) composite photocatalysts were synthesized from a urea precursor using a commercial kaolin. Structural characterization by X-ray diffraction and infrared spectroscopy (FTIR) verified the successful thermal polycondensation of g-CNx along the thermal dehydroxylation of kaolinite to metakaolin at 550 [...] Read more.

Kaolin-based graphitic carbon nitride (g-CNx) composite photocatalysts were synthesized from a urea precursor using a commercial kaolin. Structural characterization by X-ray diffraction and infrared spectroscopy (FTIR) verified the successful thermal polycondensation of g-CNx along the thermal dehydroxylation of kaolinite to metakaolin at 550 °C. The g-CNx content of the composites were estimated by thermogravimetry and CHN analysis, ranging from ca. 87 m/m% to ca. 2 m/m% of dry mass. The addition of kaolin during the composite synthesis was found to have a significant effect: the yield of in situ formed g-CNx drastically decreased (from ca. 4.9 m/m% to 3.8–0.1 m/m%) with increasing kaolin content. CHN and FTIR indicated the presence of nitrogen-rich g-CNx, having a specific surface area of 50 m²/g, which synergistically increased after composite synthesis to 67–82 m²/g. Estimated optical band gaps indicated the affinity to absorb in the visible light spectrum (λ < 413 nm). Photocatalytic activity upon both UV and artificial sunlight irradiation was observed by hydroxyl radical evolution, however, without the synergistic effect expected from the favorable porosity. Full article

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

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13 pages, 5828 KiB

Open AccessEditor’s ChoiceArticle

Influence of the Acetylene Flow Rate and Process Pressure on the Carbon Deposition Behavior by Thermal Chemical Vapor Deposition Process

by Gi-Hoon Kwon, Byoungho Choi, Young-Kook Lee and Kyoungil Moon

Crystals 2024, 14(9), 782; https://doi.org/10.3390/cryst14090782 - 31 Aug 2024

Cited by 1 | Viewed by 1534

Abstract

We used the chemical vapor deposition process to deposit carbon film at a high temperature (900 °C). The carbon films were deposited on AISI 1006 foils using an acetylene gas. We analyzed the carbon film deposited on the surface using Raman spectroscopy, scanning [...] Read more.

We used the chemical vapor deposition process to deposit carbon film at a high temperature (900 °C). The carbon films were deposited on AISI 1006 foils using an acetylene gas. We analyzed the carbon film deposited on the surface using Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy to define changes in the bonding structure of the carbon film. The results of Raman spectroscopy and high-resolution transmission electron microscopy revealed that as the acetylene flow rate increased, the shape of the deposited carbon film changed from graphene to graphite. In addition, in order to compare the quality of the carbon film in terms of mechanical and electrical properties, carbon films treated under various conditions were closely analyzed using nano-indenter and a sheet resistance meter. Therefore, the optimal condition (1 Torr-50 sccm) was selected in which graphene was uniformly deposited and had the lowest electrical resistance (500 Ω/sq) and highest hardness (12 GPa). Full article

(This article belongs to the Section Crystal Engineering)

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13 pages, 6423 KiB

Open AccessEditor’s ChoiceArticle

A Cost-Effective Strategy to Modify the Electrical Properties of PEDOT:PSS via Femtosecond Laser Irradiation

by Chi Zhang, Jiayue Zhou, Rui Han, Cheng Chen, Han Jiang, Xiaopeng Li, Yong Peng, Dasen Wang and Kehong Wang

Crystals 2024, 14(9), 775; https://doi.org/10.3390/cryst14090775 - 30 Aug 2024

Viewed by 1093

Abstract

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is a commonly used conductive polymer in organic optoelectronic devices. The conductivity and work function of the PEDOT:PSS are two important parameters that significantly determine the performance of the associated optoelectronic device. Traditionally, some solvents were doped in PEDOT:PSS solution or [...] Read more.

Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) is a commonly used conductive polymer in organic optoelectronic devices. The conductivity and work function of the PEDOT:PSS are two important parameters that significantly determine the performance of the associated optoelectronic device. Traditionally, some solvents were doped in PEDOT:PSS solution or soaked in PEDOT:PSS film to improve its electrical conductivity, but they damaged the integrity of PEDOT:PSS and reduce the film’s work function. Herein, for the first time, we use femtosecond laser irradiation to modify the electrical conductivity and work function of PEDOT:PSS film. We proposed that the femtosecond laser irradiation could selectively remove the superficial insulative PSS, thereby improving the electrical conductivity of the film. The femtosecond laser-irradiated PEDOT:PSS film was further employed as a hole injection layer within cutting-edge perovskite light-emitting diodes (PeLEDs). A maximum luminosity of 950 cd/m² was obtained in PeLEDs irradiated by femtosecond laser light in thin films, which is five times higher than that of the controlled device. Moreover, the external quantum efficiency of the devices was also increased from 4.6% to 6.3%. This work paved a cost-effective way to regulate the electrical properties of the PEDOT:PSS film. Full article

(This article belongs to the Section Organic Crystalline Materials)

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30 pages, 33889 KiB

Open AccessEditor’s ChoiceReview

A Review of Additively Manufactured Iron-Based Shape Memory Alloys

by Qian Sun, Xiaojun Tan, Mingjun Ding, Bo Cao and Takeshi Iwamoto

Crystals 2024, 14(9), 773; https://doi.org/10.3390/cryst14090773 - 29 Aug 2024

Cited by 2 | Viewed by 2597

Abstract

Iron-based shape memory alloys (Fe-SMAs), traditionally manufactured, are favored in engineering applications owing to their cost-effectiveness and ease of fabrication. However, the conventional manufacturing process of Fe-SMAs is time-consuming and raw-material-wasting. In contrast, additive manufacturing (AM) technology offers a streamlined approach to the [...] Read more.

Iron-based shape memory alloys (Fe-SMAs), traditionally manufactured, are favored in engineering applications owing to their cost-effectiveness and ease of fabrication. However, the conventional manufacturing process of Fe-SMAs is time-consuming and raw-material-wasting. In contrast, additive manufacturing (AM) technology offers a streamlined approach to the integral molding of materials, significantly reducing raw material usage and fabrication time. Despite its potential, research on AMed Fe-SMAs remains in its early stages. This review provides updated information on current AM technologies utilized for Fe-SMAs and their applications. It provides an in-depth discussion on how printing parameters, defects, and post-printing microstructure control affect the mechanical properties and shape memory effect (SME) of AMed Fe-SMAs. Furthermore, this review identifies existing challenges in the AMed Fe-SMA approach and proposes future research directions, highlighting potential areas for development. The insights presented aim to guide improvements in the material properties of AMed Fe-SMAs by optimizing printing parameters and enhancing the SME through microstructure adjustment. Full article

(This article belongs to the Special Issue Shape Memory Alloys: Recent Advances and Future Perspectives)

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15 pages, 9936 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effect of Methylxanthines on Urate Crystallization: In Vitro Models of Gout and Renal Calculi

by Jaume Dietrich, Felix Grases and Antonia Costa-Bauza

Crystals 2024, 14(9), 768; https://doi.org/10.3390/cryst14090768 - 29 Aug 2024

Cited by 1 | Viewed by 1219

Abstract

Background: Common forms of pathological crystals are uric acid or urates, which are responsible for gout, urolithiasis, and other conditions. Methods: We used a kinetic–turbidimetric crystallization assay to evaluate the effect of ten specific methylxanthines on the crystallization of monosodium urate, potassium urate, [...] Read more.

Background: Common forms of pathological crystals are uric acid or urates, which are responsible for gout, urolithiasis, and other conditions. Methods: We used a kinetic–turbidimetric crystallization assay to evaluate the effect of ten specific methylxanthines on the crystallization of monosodium urate, potassium urate, and ammonium urate in conditions that mimicked urine. We also studied the effect of different levels of 7-methylxanthine in the presence of other biological compounds (albumin and hyaluronic acid) on the solubility of monosodium urate in conditions that mimicked synovial fluid. Results: The results showed that 7-methylxanthine in the range of 16.61–49.84 mg/L inhibited the crystallization of each urate when the initial urate concentration was 3 × 10⁻³ M (500 mg/L) and the conditions mimicked urine, and that the greatest inhibitory effect was for monosodium urate. In addition, 7-methylxanthine at a concentration of 25 mg/L totally prevented the crystallization of monosodium urate at an initial urate concentration of 2.38 × 10⁻³ M (400 mg/L) in conditions that mimicked synovial fluid. Moreover, at a low concentration of 7-methylxanthine, albumin and hyaluronic acid increased this inhibitory effect. Conclusions: Our in vitro results demonstrate that 7-methylxanthine inhibits the crystallization of urates in conditions that mimic synovial fluid and urine. Full article

(This article belongs to the Special Issue Pathological Biomineralization: Recent Advances and Perspectives)

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