Crystals

17 pages, 11192 KiB

Open AccessArticle

Microstructure and Mechanical Properties of a Weld Seam from Magnetron High-Current CO₂ Welding

by Jun-Yan Miao, Yi-Wen Li, Bo-Wen Ren, Hong-Lei Zhao, Si-Yu Zhang, Yun-Long Chang and Qiang Wang

Crystals 2024, 14(10), 911; https://doi.org/10.3390/cryst14100911 - 21 Oct 2024

Viewed by 700

Abstract

External magnetic field (EMF)-assisted high-current CO₂ welding is beneficial for improving the large spatter and poor performance of the welding heat-affected zone for mild steels under high-current welding specifications. In this paper, the droplet transfer behaviors were determined using a high-speed camera [...] Read more.

External magnetic field (EMF)-assisted high-current CO₂ welding is beneficial for improving the large spatter and poor performance of the welding heat-affected zone for mild steels under high-current welding specifications. In this paper, the droplet transfer behaviors were determined using a high-speed camera on a self-developed magnetically controlled CO₂ welding system. Based on these welding specifications, a three-dimensional, transient, multi-energy field coupling welding system model to investigate the mechanism of the droplet and molten pool in EMF-assisted welding was developed. The microstructure and mechanical properties of the welded joint were systematically studied. The results show that the Lorentz force applied by the EMF to twist the droplet decreases the accumulated energy in the short-circuited liquid bridge and changes the liquid metal flow condition, both of which reduce the spatter by 7% but increase the welded joint hardness by 10% and tensile strength by 8%. Full article

(This article belongs to the Special Issue Surface Modification Treatments of Metallic Materials)

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10 pages, 2482 KiB

Open AccessArticle

Effect of Sulfurization Temperature on Properties of Cu2ZnSnS4 Thin Films and Diffusion of Ti Substrate Elements

by Meihong Huang, Junhui Lin, Zhiyong Liang, Shaowei Chen, Yuling Zhong, Feng Wang, Bixian Chen and Dongxia Zhang

Crystals 2024, 14(10), 910; https://doi.org/10.3390/cryst14100910 - 20 Oct 2024

Viewed by 802

Abstract

The addition of flexible Cu2ZnSnS4 (CZTS) thin film solar cells to titanium (Ti) substrates is an attractive way to achieve the low-cost manufacturing of photovoltaics. Prior research has indicated that the appropriate diffusion of Ti elements can enhance the crystalline growth of CZTS [...] Read more.

The addition of flexible Cu2ZnSnS4 (CZTS) thin film solar cells to titanium (Ti) substrates is an attractive way to achieve the low-cost manufacturing of photovoltaics. Prior research has indicated that the appropriate diffusion of Ti elements can enhance the crystalline growth of CZTS films. However, the excessive diffusion of Ti has been shown to adversely affect the photovoltaic performance of CZTS photovoltaic devices. Therefore, it is essential to regulate the diffusion of Ti elements within CZTS thin films to optimize their photovoltaic properties. The tendency for Ti substrate elements to diffuse into CZTS films is also influenced by the activation energy associated with these Ti elements. The sulfurization temperature is posited to be a critical factor in modulating the diffusion and activation energy of Ti elements within CZTS thin films. Consequently, this research investigates the alteration of the sulfurization temperature of CZTS thin films in order to enhance the properties of these thin films and to examine the diffusion behavior of titanium elements. The results reveal that as the sulfurization temperature increases, the diffusion of Ti elements within the CZTS thin films initially increases, then decreases, and subsequently increases again. This pattern suggests that the diffusion of Ti elements is affected not only by the activation energy of the Ti elements but also by the defect hopping distance within the CZTS thin films. Notably, at a sulfurization temperature of 550 °C, the grains at the base of the CZTS thin film demonstrate an increased density, which is associated with a reduced defect hopping distance, thereby hindering the diffusion of Ti elements within the CZTS thin films. Furthermore, at this specific sulfurization temperature, the slope of the current–voltage (I–V) curve for the CZTS/Ti structure reaches its maximum, indicating optimal ohmic contact characteristics. Full article

(This article belongs to the Section Crystal Engineering)

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9 pages, 3629 KiB

Open AccessArticle

Threshold Switching and Resistive Switching in SnO₂-HfO₂ Laminated Ultrathin Films

by Kristjan Kalam, Mark-Erik Aan, Joonas Merisalu, Markus Otsus, Peeter Ritslaid and Kaupo Kukli

Crystals 2024, 14(10), 909; https://doi.org/10.3390/cryst14100909 - 19 Oct 2024

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Abstract

Polycrystalline SnO₂-HfO₂ nanolaminated thin films were grown by atomic layer deposition (ALD) on SiO₂/Si(100) and TiN substrates at 300 °C. The samples, when evaluated electrically, exhibited bipolar resistive switching. The sample object with a stacked oxide layer structure [...] Read more.

Polycrystalline SnO₂-HfO₂ nanolaminated thin films were grown by atomic layer deposition (ALD) on SiO₂/Si(100) and TiN substrates at 300 °C. The samples, when evaluated electrically, exhibited bipolar resistive switching. The sample object with a stacked oxide layer structure of SnO₂ | HfO₂ | SnO₂ | HfO₂ additionally exhibited bidirectional threshold resistive switching properties. The sample with an oxide layer structure of HfO₂ | SnO₂ | HfO₂ displayed bipolar resistive switching with a ratio of high and low resistance states of three orders of magnitude. Endurance tests revealed distinguishable differences between low and high resistance states after 2500 switching cycles. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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17 pages, 15714 KiB

Open AccessArticle

Effect of Loading Direction on Tensile-Compressive Mechanical Behaviors of Mg-5Zn-2Gd-0.2Zr Alloy with Heterogeneous Grains

by Jieming Chen, Lei Xiao, Xuefang Wang, Zhuo Li, Chen Wang, Bingshu Wang, Junfeng Chen, Pan Liu and Xinyao Zhang

Crystals 2024, 14(10), 908; https://doi.org/10.3390/cryst14100908 - 19 Oct 2024

Viewed by 670

Abstract

The tension-compression yield asymmetry caused by the strengthening of Mg-Zn-Gd-Zr alloy due to extrusion deformation is an important issue that must be addressed in its application. In this study, the effects of loading direction on the tensile and compressive mechanical behaviors of Mg-5Zn-2Gd-0.2Zr [...] Read more.

The tension-compression yield asymmetry caused by the strengthening of Mg-Zn-Gd-Zr alloy due to extrusion deformation is an important issue that must be addressed in its application. In this study, the effects of loading direction on the tensile and compressive mechanical behaviors of Mg-5Zn-2Gd-0.2Zr alloy were systematically investigated. As the loading angle (the angle between the loading direction and the extrusion direction) increases from 0° to 30°, 45°, 60° and 90°, the tensile yield strength decreases more significantly than the compressive yield strength. Consequently, the tension-compression yield asymmetry is gradually improved. Additionally, the ultimate compressive strength decreases more markedly than the ultimate tensile strength with the increment of the loading angle. In tensile tests conducted at 0°, 30° and 45°, two distinct stages of decreasing strain hardening rates are typically observed. For the 60° and 90° tensile tests, one unusual ascending stage of strain hardening rate is observed. For all compressive tests, three stages of strain hardening are consistently noted; however, the increment in strain hardening rate caused by {10–12} extension twinning decreases with the increasing loading angle. A model combining loading angle and Schmid factor distribution was established. The calculated results indicate that the dominant deformation modes during the yielding process also vary significantly with the loading conditions. This clarification highlights the differences in yield strength variations between tension and compression. Finally, an analysis of the plane trace and crack propagation direction near the fracture surface reveals the fracture mechanisms associated with tensile and compressive tests at different loading directions. This study promotes understanding of the mechanical behaviors of Mg-5Zn-2Gd-0.2Zr alloy under different loading directions, and helps to thoroughly elucidate the anisotropic effects of texture on the mechanical properties of magnesium alloys. Full article

(This article belongs to the Special Issue Structural and Mechanical Properties of Novel Mg Alloys)

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17 pages, 6486 KiB

Open AccessArticle

Effect of Zn on Microstructure and Wear Resistance of Sn-Based Babbitt Alloy

by Xiaoyan Ren, Huimin Chen, Yuan Chang, Ningning Chen, Zhenghua Shi, Yougui Zhang, Zhiming Guo and Jinzhi Hu

Crystals 2024, 14(10), 907; https://doi.org/10.3390/cryst14100907 - 19 Oct 2024

Viewed by 535

Abstract

Tin-based Babbitt alloys are a widely used bearing bushing material which have good comprehensive properties. However, problems such as high-temperature softening and insufficient bearing capacity occur during their use, so the optimization of tin-based Babbitt alloys has become a research hotspot. In this [...] Read more.

Tin-based Babbitt alloys are a widely used bearing bushing material which have good comprehensive properties. However, problems such as high-temperature softening and insufficient bearing capacity occur during their use, so the optimization of tin-based Babbitt alloys has become a research hotspot. In this paper, ZChSnSb11-6 alloy was mainly prepared by the gravity casting method, and different amounts of Zn were added to the alloy (the mass fraction values were 0 wt.%, 0.05 wt.%, 0.1 wt.%, 0.15 wt.%, and 0.2 wt.%, respectively). Through the hardness test, the tensile test, the friction and wear test, and the microstructure observation of the prepared alloy, the influence of Zn on the organization and properties of the ZChSnSb11-6 alloy was analyzed. The results show that the size of the SnSb hard phase changed with the increasing content of Zn. The size of the hard phase of the SnSb tended to increase first and then decrease, and the number of phase particles increased first and then decreased, resulting in changes in performance. Through comparison, it was learned that the addition of Zn can effectively improve the hardness, tensile strength, yield strength, and wear resistance of the alloy, but the elongation rate was reduced. When the Zn content was 0.1 wt.%, the hardness value of the alloy reached the maximum value, 25.82 HB, which increased by 7.3% when compared with the sample without Zn. The hardness of the Zn, 0.15 wt.%, is close to that of the Zn, 0.1 wt.%. Compared to the sample without Zn, the tensile strength and elongation of the alloy were maximized at a Zn content of 0.15 wt.%. Compared to the sample without the Zn, the tensile strength was increased by 21.29%, and the elongation rate was increased by 46%. An analysis showed that the alloy has good comprehensive mechanical properties when the Zn content is 0.15 wt.%. Full article

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

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16 pages, 8157 KiB

Open AccessArticle

Molybdenum-Modified Niobium Oxide: A Pathway to Superior Electrochromic Materials for Smart Windows and Displays

by Rutuja U. Amate, Pritam J. Morankar, Aviraj M. Teli, Sonali A. Beknalkar and Chan-Wook Jeon

Crystals 2024, 14(10), 906; https://doi.org/10.3390/cryst14100906 - 18 Oct 2024

Viewed by 706

Abstract

Electrochromic materials enable the precise control of their optical properties, making them essential for energy-saving applications such as smart windows. This study focuses on the synthesis of molybdenum-doped niobium oxide (Mo-Nb₂O₅) thin films using a one-step hydrothermal method to [...] Read more.

Electrochromic materials enable the precise control of their optical properties, making them essential for energy-saving applications such as smart windows. This study focuses on the synthesis of molybdenum-doped niobium oxide (Mo-Nb₂O₅) thin films using a one-step hydrothermal method to investigate the effect of Mo doping on the material’s electrochromic performance. Mo incorporation led to distinct morphological changes and a transition from a compact granular structure to an anisotropic rod-like feature. Notably, the MN-3 (0.3% Mo) sample displayed an optimal electrochromic performance, achieving 77% optical modulation at 600 nm, a near-perfect reversibility of 99%, and a high coloration efficiency of 89 cm²/C. Additionally, MN-3 exhibited excellent cycling stability, with only 0.8% degradation over 5000 s. The MN-3 device also displayed impressive control over color switching, underscoring its potential for practical applications. These results highlight the significant impact of Mo doping on improving the structural and electrochromic properties of Nb₂O₅ thin films, offering improved ion intercalation and charge transport. This study underscores the potential of Mo-Nb₂O₅ for practical applications in energy-efficient technologies. Full article

(This article belongs to the Special Issue Organic Photonics: Organic Optical Functional Materials and Devices)

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19 pages, 2336 KiB

Open AccessArticle

Crystallographic and Optical Spectroscopic Study of Metal–Organic 2D Polymeric Crystals of Silver(I)– and Zinc(II)–Squarates

by Bojidarka Ivanova

Crystals 2024, 14(10), 905; https://doi.org/10.3390/cryst14100905 - 18 Oct 2024

Viewed by 605

Abstract

Metal–organic framework materials, as innovative functional materials for nonlinear optical technologies, feature linear and nonlinear optical responses, such as a laser damage threshold, outstanding mechanical properties, thermal stability, and optical transparency. Their non-centrosymmetric crystal structure induces a higher-order nonlinear optical response, which guarantees [...] Read more.

Metal–organic framework materials, as innovative functional materials for nonlinear optical technologies, feature linear and nonlinear optical responses, such as a laser damage threshold, outstanding mechanical properties, thermal stability, and optical transparency. Their non-centrosymmetric crystal structure induces a higher-order nonlinear optical response, which guarantees technological applications. Zn^II– and Ag^I–squarate complexes are attractive templates for these purposes due to their good crystal growth, optical transparency, high thermal stability, etc. However, the space group type of the catena-((μ₂-squarato)-tetra-aqua-zinc(II)) complex ([Zn(C₄O₄)(H₂O)₄]) is debatable, (1) showing centro- and non-centrosymmetric monoclinic C2/c and Cc phases. The same is valid for the catena-((μ₃-squarato)-(μ₂-aqua)-silver(I)) complex (Ag₂C₄O₄), (2) exhibiting, so far, only a C2/c phase. This study is the first to report new crystallographic data on (1) and (2) re-determined at different temperatures (293(2) and 300(2)K) and the non-centrosymmetric Cc phase of (2), having different numbers of molecules per unit cell compared with the C2/c phase. There are high-resolution crystallographic measurements of single crystals, experimental electronic absorption, and vibrational spectroscopic data, together with ultra-high-resolution mass spectrometric ones. The experimental results are supported for theoretical optical and nonlinear optical properties obtained via high-accuracy static computational methods and molecular dynamics, using density functional theory as well as chemometrics. Full article

(This article belongs to the Special Issue Exploring the Frontier of MOFs through Crystallographic Studies)

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8 pages, 1311 KiB

Open AccessArticle

High-Temperature SHS Heat Insulators Based on Pre-Activated Mineral Raw Materials

by Bakhtiyar Sadykov, Ainur Khairullina, Aida Artykbayeva, Alua Maten, Anar Zhapekova, Timur Osserov and Ayagoz Bakkara

Crystals 2024, 14(10), 904; https://doi.org/10.3390/cryst14100904 - 18 Oct 2024

Viewed by 454

Abstract

In this paper, the results of the technological combustion of SHS heat insulators based on mineral origins are presented. It is shown that after mechanochemical treatment of minerals—diatomite—the kinetic characteristics of the combustion process change, providing targeted formation of the phase composition, structure, [...] Read more.

In this paper, the results of the technological combustion of SHS heat insulators based on mineral origins are presented. It is shown that after mechanochemical treatment of minerals—diatomite—the kinetic characteristics of the combustion process change, providing targeted formation of the phase composition, structure, and properties of the SHS composite. A positive effect of using various modifiers during the MCT of diatomite—the activation of the combustion process—was established. The selection of modifiers provides an increase in the strength of the synthesized SHS composites as a result of the formation of aluminate compounds in the synthesis products, and a decrease in thermal conductivity to 0.157 W/m*K due to the formation of the ultraporous structure of the samples. Full article

(This article belongs to the Special Issue Structural and Characterization of Composite Materials)

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15 pages, 4943 KiB

Open AccessArticle

In-Depth Characterization of Natural Clays from Southeast Albania

by Altin Mele, Viviana Scognamiglio, Valeria Nocerino, Luca De Stefano, Arben Memo, Roberta G. Toro, Manuela Rossi, Francesco Baldassarre and Francesco Capitelli

Crystals 2024, 14(10), 903; https://doi.org/10.3390/cryst14100903 - 18 Oct 2024

Viewed by 694

Abstract

Clays have been exploited in the manufacture of diverse products from ceramics to paints, pharmaceuticals, plastics, cosmetics, and more. Thus, they can be used in many industrial applications, showing good adsorbent ability thanks to their lamellar structure, high cation exchange capacity, pore size [...] Read more.

Clays have been exploited in the manufacture of diverse products from ceramics to paints, pharmaceuticals, plastics, cosmetics, and more. Thus, they can be used in many industrial applications, showing good adsorbent ability thanks to their lamellar structure, high cation exchange capacity, pore size distribution, and large surface area. For this reason, considerable attention has been paid to their in-depth characterization, for further integration in sectors such as biomedicine, construction, remediation, aerospace, and nanotechnology. For this aim, two samples of natural clays, ALO1 and PRE4, from the southeast part of Albania, were subject to a multi-methodological characterization, with the aim of addressing the use of such geomaterials in possible sensing applications. X-ray fluorescence analysis, morphological characterization of the samples, and energy-dispersive system spectroscopy pointed to an extreme mineralogical variety, with kaolinite in AL01 and montmorillonite in PRE4 as the most abundant phases. This fact was further confirmed by powder X-ray diffraction, showing a quartz content of 20%, a kaolinite content of 64%, and a muscovite content of 16% for ALO1; meanwhile, for PRE4, we found a content of quartz of 45%, a content of montmorillonite of 34.9%, and a content of clinochlore of 20%. Infrared spectroscopy and thermal analyses confirmed the presence of hydroxyl groups in both samples, suggesting a higher content in ALO1. Measurement of N₂ adsorption isotherms on the clay samples yields specific surface areas of 87 m²/g for PRE4 and 32 m²/g for ALO1, pore volumes of 0.721 cm³/g for PRE4 and 0.637 cm³/g for ALO1, and similar pore sizes in the range of 6–12 nm. Electrochemical analysis highlighted a good conductivity of ALO1 and PRE4 when used for the modification of commercial carbon-based screen-printed electrodes. In detail, higher currents were registered by differential pulse voltammetry for the electrodes modified with the clays with respect to bare electrodes, as well as good repeatability of the measurements. In addition, a comparative study with nanomaterials, known for their good conductivity, was achieved, using carbon black and gold nanoparticles as a reference, showing that the conductivity of the clays was lower than but not so different from those of the reference materials. Full article

(This article belongs to the Collection Topic Collection: Mineralogical Crystallography)

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15 pages, 5597 KiB

Open AccessArticle

Effects of Oxide Powders as Activating Flux on AMIG 304L Welds

by Kamel Touileb, Rachid Djoudjou, Abousoufiane Ouis, Abdeljlil Chihaoui Hedhibi, Hussein Alrobei, Ibrahim Abdullah Alnaser, Rizwan Ahmed Malik and Ubair Abdus Samad

Crystals 2024, 14(10), 902; https://doi.org/10.3390/cryst14100902 - 18 Oct 2024

Viewed by 475

Abstract

Activating metal inert gas (AMIG) welding was designed to address difficulties with MIG welding, such as the limitation on workpiece thickness that may be welded in a single pass. This investigation was carried out on 304L stainless steel using ER 308L as a [...] Read more.

Activating metal inert gas (AMIG) welding was designed to address difficulties with MIG welding, such as the limitation on workpiece thickness that may be welded in a single pass. This investigation was carried out on 304L stainless steel using ER 308L as a filler metal. Five oxides (SiO₂, TiO₂, Fe₂O₃, Mn₂O₃, and Cr₂O₃) have been investigated without edge preparation. The welded joints were evaluated for weld morphology, microstructure, mechanical properties, and corrosion, and the findings were compared. The depth of the AMIG weld was determined to be greater than that of the MIG weld. The microstructure is composed of austenitic and retained delta ferrite with 3.3% for MIG and up to 8% for AMIG weld carried out with Cr₂O₃ oxide flux, the tensile strength is up to 604 MPa when using Cr₂O₃ oxide against MIG weld (532 MPa), and the resistance to sudden load in AMIG welds (189 J/cm²) is higher than that of MIG weld (149 J/cm²). The corrosion resistance of the weld made with Fe₂O₃ oxide flux is greater than that of the other AMIG and MIG welds, as well as the parent metal. The AMIG welding technique variant enhances productivity and decreases the cost and energy consumption of the welding material compared to the traditional MIG process. This allows for joining the same thickness without affecting mechanical properties and corrosion resistance, meeting the industry’s requirements. Full article

(This article belongs to the Special Issue Welding and Joining of Metallic Materials: Microstructure and Mechanical Properties, 2nd Edition)

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16 pages, 6194 KiB

Open AccessPerspective

Integrating and Exploiting Molecular, Supramolecular, and Time Crystal Synthons in Advanced Synthesis

by Indrajit Chakraborty, Tusar Kanti Dutta, Sudipta Ray, Deepak Kumar and Pathik Sahoo

Crystals 2024, 14(10), 901; https://doi.org/10.3390/cryst14100901 - 17 Oct 2024

Viewed by 836

Abstract

Molecular reactions occur through functional groups that drive covalent synthesis. These reactions often proceed via catalytic processes, leading to the formation of time crystals, which can be integrated into shared molecules or reactions—a concept referred to as the time crystal synthon. The concept [...] Read more.

Molecular reactions occur through functional groups that drive covalent synthesis. These reactions often proceed via catalytic processes, leading to the formation of time crystals, which can be integrated into shared molecules or reactions—a concept referred to as the time crystal synthon. The concept of time crystal synthons, introduced by Sahoo, pushes these ideas into the temporal realm, where molecular assemblies exhibit periodic behavior over time. This temporal aspect allows the creation of materials with unique functionalities, such as enhanced stability and responsiveness to external stimuli. A molecular synthon generates a specifically designed molecule within a catalytic reaction cycle or a time crystal. If this molecule or any associated reaction steps can be transferred or shared with a neighboring time crystal to facilitate their integration, it can be identified as a time crystal synthon. Supramolecular synthons, in contrast, enable the assembly of complex structures through non-covalent interactions among the molecules, playing a crucial role in crystal engineering. This paper further explores the applications of these synthons in various domains, including supramolecular architecture design, the integration of time crystal cycles, and the development of advanced materials. By mastering these interconnected synthons, scientists can gain greater control over molecular and material properties, driving advances in nanotechnology, materials science, and beyond. This paper explores the interconnected paradigms of molecular, supramolecular, and time crystal synthons within their respective engineering fields. Molecular synthons are foundational units within molecules, essential for designing and synthesizing new compounds with targeted properties. Full article

(This article belongs to the Section Crystal Engineering)

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11 pages, 7259 KiB

Open AccessArticle

Effect of Solution Annealing on Microstructure, Tensile and Corrosion Properties of SDSS Deposited by Directed Energy Deposition

by Pavel Salvetr, Šárka Msallamová and Michal Brázda

Crystals 2024, 14(10), 900; https://doi.org/10.3390/cryst14100900 - 17 Oct 2024

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Abstract

The super duplex stainless steel (SDSS) powder SAF2507 was deposited using directed energy deposition. In the as-built state, the microstructure consists of a nearly balanced ferrite–austenite ratio, with an austenite content of 47 vol.%, in contrast to the SDSS processed by the powder [...] Read more.

The super duplex stainless steel (SDSS) powder SAF2507 was deposited using directed energy deposition. In the as-built state, the microstructure consists of a nearly balanced ferrite–austenite ratio, with an austenite content of 47 vol.%, in contrast to the SDSS processed by the powder bed method, which produces a very low austenite content. This work investigated the differences in the microstructure, mechanical and corrosion properties of the “high-austenite” as-built state and the solution-annealed (SA) state (at 1100 °C for 60 min, followed by quenching in water). In the SA state, an increase in austenite content to 55 vol.% was observed. In addition, the partitioning of alloying elements into austenite and ferrite also occurred, the austenite grains coarsened and a ferrite grain size reduction was found. Microstructural changes were evident in the development of the mechanical properties. The increase in austenite content was accompanied by an increase in the elongation, and conversely, both the yield strength and ultimate tensile strength decreased. No secondary phases, such as carbides or sigma phase, were observed in either state. Both the as-built and solution-annealed samples exhibited a passivation zone in model seawater at 70 °C, but at the same time, the corrosion current density (i_corr) of the as-built state was five times higher. Full article

(This article belongs to the Special Issue Modern Technologies in the Manufacturing of Metal Matrix Composites)

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15 pages, 2118 KiB

Open AccessReview

Tailoring the Synthesis Method of Metal Oxide Nanoparticles for Desired Properties

by Adriana-Gabriela Schiopu, Daniela Monica Iordache, Mihai Oproescu, Laura Mădălina Cursaru and Adriana-Miruna Ioța

Crystals 2024, 14(10), 899; https://doi.org/10.3390/cryst14100899 - 17 Oct 2024

Viewed by 986

Abstract

Metal oxide nanoparticles (MONs) are particles with at least one dimension in the nanoscale range (1–100 nm). Their unique properties, significantly different from their bulk counterparts, make them promising materials for a wide range of applications in fields such as medicine, electronics, catalysis, [...] Read more.

Metal oxide nanoparticles (MONs) are particles with at least one dimension in the nanoscale range (1–100 nm). Their unique properties, significantly different from their bulk counterparts, make them promising materials for a wide range of applications in fields such as medicine, electronics, catalysis, environmental remediation, and energy storage. The precise control of MONs’ properties, including size, shape, composition, crystallinity, and surface chemistry, is significant for optimizing their performance. This study aims to investigate the characteristics of synthesis methods of MONs. Correlation between synthesis parameters and properties highlights that creating nanomaterials with defined and controlled dimensions is a complex task that requires a deep understanding of various factors. Also, this study presents a model with adaptive parameters for synthesis conditions to acquire desired nanometric scale for particles size, which represents an essential task. Full article

(This article belongs to the Special Issue Synthesis and Characterization of Oxide Nanoparticles)

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11 pages, 5631 KiB

Open AccessArticle

A Study on Tooth Wear Mechanisms During the Bandsawing of Cr12MoV with a Bimetal Bandsaw Blade

by Yuzhen Jia, Jigang Wu, Yuqiang Chen, Bing Chen, Guoyue Liu and Zhiyong Ouyang

Crystals 2024, 14(10), 898; https://doi.org/10.3390/cryst14100898 - 17 Oct 2024

Viewed by 564

Abstract

Bandsaw blades are typical band-shaped cutting tools that are characterized by their low stiffness and micro-level cutting depth, resulting in distinct wear mechanisms compared to rigid cutting tools. In this study, the wear curve and wear mechanisms of the bandsaw tooth during the [...] Read more.

Bandsaw blades are typical band-shaped cutting tools that are characterized by their low stiffness and micro-level cutting depth, resulting in distinct wear mechanisms compared to rigid cutting tools. In this study, the wear curve and wear mechanisms of the bandsaw tooth during the bandsawing of Cr12MoV cold-working steel were investigated. The tool life was divided into two stages: a rapid wear stage (Stage I) and a homogeneous wear stage (Stage II). In Stage I, the wear was dominated by chipping, although multiple wear mechanisms were found due to their relatively low manufacturing accuracy compared to rigid cutting tools, which resulted in remarkable differences in the cutting depth of each tooth. In Stage II, abrasive and adhesive wear were the primary wear mechanisms instead of chipping, which was related to the microstructure of Cr12MoV. Furthermore, methods for increasing bandsaw performance were proposed, based on the tooth wear mechanisms. Full article

(This article belongs to the Special Issue Modern Technologies in the Manufacturing of Metal Matrix Composites)

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17 pages, 3240 KiB

Open AccessArticle

Comparative VUV Synchrotron Excitation Study of YAG: Eu and YAG: Cr Ceramics

by Amangeldy M. Zhunusbekov, Zhakyp T. Karipbayev, Akbota Tolegenova, Kuat K. Kumarbekov, Erik E. Nurmoldin, Muratbek M. Baizhumanov, Aleksei Kotlov and Anatoli I. Popov

Crystals 2024, 14(10), 897; https://doi.org/10.3390/cryst14100897 - 16 Oct 2024

Viewed by 1142

Abstract

Using synchrotron radiation, a comparative VUV excitation study of YAG ceramics doped with Eu³⁺ and Cr³⁺ ions under VUV excitation (10.5–3.7 eV) at 9 K was conducted in this work. Both ceramics exhibit distinct excitation peaks in the VUV region, indicating [...] Read more.

Using synchrotron radiation, a comparative VUV excitation study of YAG ceramics doped with Eu³⁺ and Cr³⁺ ions under VUV excitation (10.5–3.7 eV) at 9 K was conducted in this work. Both ceramics exhibit distinct excitation peaks in the VUV region, indicating high-energy transitions related to the internal electronic levels of the dopants and interband transitions within the YAG matrix. For YAG:Eu, the main excitation peaks at 6–7 eV correspond to transitions within the 4f-shell of Eu³⁺ and Eu³⁺-O²⁻ charge transfer states, showing weak dependence on the crystal field and high energy conversion efficiency. In contrast, YAG:Cr shows broad excitation bands due to transitions between levels influenced by strong crystal field interactions, resulting in lower luminescence efficiency. The study highlights the importance of crystal structure and dopant interactions in determining the spectral characteristics of YAG-based ceramics, offering potential for their application in advanced optoelectronic devices. Full article

(This article belongs to the Special Issue Structure and Properties of Ceramic Materials)

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12 pages, 5565 KiB

Open AccessArticle

The Effects of Montmorillonite–Humic Acid Composite Particles on the Photolysis of Tetracycline in Water

by Wenfang Zhou, Zirui Wang, Qingfeng Wu, Qinping Nie and Yi Wang

Crystals 2024, 14(10), 896; https://doi.org/10.3390/cryst14100896 - 16 Oct 2024

Viewed by 677

Abstract

Suspended particulate matter (SPM) is an important component of natural water bodies and can significantly influence the photolytic behavior of water pollutants. A comprehensive understanding of the photochemical behavior of water pollutants in natural waters requires consideration of the presence of SPM. In [...] Read more.

Suspended particulate matter (SPM) is an important component of natural water bodies and can significantly influence the photolytic behavior of water pollutants. A comprehensive understanding of the photochemical behavior of water pollutants in natural waters requires consideration of the presence of SPM. In this study, montmorillonite–humic acid (MMT-HA) composite particles were synthesized to simulate SPM in natural waters and their effects on the photolysis of tetracycline (TC) were investigated. The results demonstrated that the presence of MMT-HA composite particles in water significantly enhanced the photolysis of TC, with the photolytic kinetics following a pseudo-first-order model. Electron spin resonance spectra and free radical quenching experiments indicated that the photoactive components (MMT and humic acids) in the composite particles induced the generation of reactive oxygen species under light exposure, further contributing to the enhanced photolysis of TC. Comparative analysis of the free radical signals and adsorption experiments revealed that the accelerated photolysis of TC was also related to the interfacial interaction between the MMT in the composite particles and the TC molecules. The formation of surface complexes between TC molecules and the negatively charged sites on the MMT surface facilitated light absorption and electron transfer, thereby accelerating the photolysis of TC. Photoproduct analysis indicated that the primary degradation pathways of TC in the composite particle systems included the addition of hydroxyl radicals to the aromatic ring, as well as demethylation, deamination and dehydration in the side chains. This study shows that SPM in water bodies can affect the photochemical behavior of pollutants and should be taken into account when assessing the phototransformation of pollutants in natural waters. Full article

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

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13 pages, 7830 KiB

Open AccessArticle

Electrolytic Plasma Nitriding of Medium-Carbon Steel 45 for Performance Enhancement

by Zarina Satbayeva, Almasbek Maulit, Nurlybek Ispulov, Daryn Baizhan, Bauyrzhan Rakhadilov and Rinat Kusainov

Crystals 2024, 14(10), 895; https://doi.org/10.3390/cryst14100895 - 15 Oct 2024

Viewed by 683

Abstract

This article analyzes the effect of electrolytic plasma nitriding on the performance of medium-carbon steel 45 under increased mechanical loads and in aggressive environments. Nitrided samples in carbamide electrolytes, both with and without the addition of ammonium nitrate, were compared to the initial [...] Read more.

This article analyzes the effect of electrolytic plasma nitriding on the performance of medium-carbon steel 45 under increased mechanical loads and in aggressive environments. Nitrided samples in carbamide electrolytes, both with and without the addition of ammonium nitrate, were compared to the initial material. SEM with EDX and XRD analysis was used to examine the microstructure and phase composition of nitrided samples. Wear resistance was studied using the ‘ball-on-disk’ method and Vickers microhardness testing, while corrosion resistance was studied using potentiodynamic polarization curves. The study results show that the sample without ammonium nitrate demonstrated better mechanical and corrosion properties due to a more homogeneous and denser nitride layer, approximately 10 µm thick, containing phases FeN and Fe₄N. Its wear resistance doubled compared to that of the initial sample. The sample treated in an electrolyte with the addition of ammonium nitrate demonstrated a higher current density (2.8672 × 10⁻⁵ A/cm²) and a lower corrosion potential (−0.565 V) compared to the initial sample (i_corr = 1.8971 × 10⁻⁵ A/cm², E_corr = −0.480 V) and the sample without ammonium nitrate (i_corr = 1.7315 × 10⁻⁵ A/cm², E_corr = −0.376 V). This is due to the formation of an uneven nitride layer and the presence of microcracks on the surface. Full article

(This article belongs to the Topic Microstructure and Properties in Metals and Alloys, 3rd Volume)

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13 pages, 12477 KiB

Open AccessArticle

Influence of Al₂O₃ Nanoparticles on the Morphology and Growth Kinetics of Cu-Sn Intermetallic Compounds in Sn-Ag-Zn/Cu Solder Joints

by Lung-Chuan Tsao and Pei-Chun Lai

Crystals 2024, 14(10), 894; https://doi.org/10.3390/cryst14100894 - 14 Oct 2024

Viewed by 487

Abstract

Intermetallic compounds (IMCs) growth can simultaneously bring about low-resistance electrical pathways and drastically reduce joint lifetime. Recently, incorporated trace nanoparticles into the free-Pb solder were found to promote the performance of the solder joints. Sn3Ag0.9Zn (SAZ) nano-composite solders were developed by doping 0.5 [...] Read more.

Intermetallic compounds (IMCs) growth can simultaneously bring about low-resistance electrical pathways and drastically reduce joint lifetime. Recently, incorporated trace nanoparticles into the free-Pb solder were found to promote the performance of the solder joints. Sn3Ag0.9Zn (SAZ) nano-composite solders were developed by doping 0.5 wt.% Al₂O₃ nanoparticles into the SAZ solder. The IMCs formation and growth behavior at the interfacial reactions between the SAZ-0.5Al₂O₃ nano-composite solder and the Cu substrate during soldering at temperatures ranging from 250 to 325 °C for 30 min were investigated. The results showed that after the addition of Al₂O₃ nanoparticles into the SAZ solder, the elongated-type IMCs layer changed into a prism-type IMCs layer, and Ag₃Sn nanoparticles were absorbed on the grain surface of the interfacial Cu₆Sn₅ phase, effectively suppressing the growth of the IMCs layers. The activation energies (Q) for the IMCs layers (Cu₆Sn₅ + Cu₃Sn) were determined to be 36.4 and 39.1 kJ/mol for the SAZ/Cu and SAZ-Al₂O₃/Cu solders, respectively. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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17 pages, 1944 KiB

Open AccessArticle

Energies of an Electron in a One-Dimensional Lattice Using the Dirac Equation: The Coulomb Potential

by Raúl García-Llamas, Jesús D. Valenzuela-Sau, Jorge A. Gaspar-Armenta, Raúl Aceves and Rafael A. Méndez-Sánchez

Crystals 2024, 14(10), 893; https://doi.org/10.3390/cryst14100893 - 14 Oct 2024

Viewed by 570

Abstract

The energies of an electron in a one-dimensional crystal are studied with both the Schrödinger and Dirac equations using the plane wave expansion method. The crystalline potential sensed by the electron in a cell was calculated by accounting for the Coulombic (electrostatic) interaction [...] Read more.

The energies of an electron in a one-dimensional crystal are studied with both the Schrödinger and Dirac equations using the plane wave expansion method. The crystalline potential sensed by the electron in a cell was calculated by accounting for the Coulombic (electrostatic) interaction between the electron and the surrounding cores (immobile positive ions at the center of the crystal cells). The energies and wave functions of the electron were calculated as a function of four parameters: the period

a_{p}

of the lattice, the dimension

n_{d i m}

of the matrix in the momentum space, the partition number

l_{p a}

in which the unit cell is divided to calculate the potential and the number of cores

n_{c o}

that affect the electron. It was found that 8000 cores (surrounding the electron) were needed to reach our convergence criterion. An analytical equation that accurately describes the behavior of the energies in function of the cores that affect the electron was also found. As case studies, the energies for pseudo-lithium and pseudo-graphene were obtained as a first approximation for one-dimensional lattices. Subsequently, the energies of an isolated dimer nanoparticle were also calculated using the supercell method. Full article

(This article belongs to the Section Crystal Engineering)

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13 pages, 4255 KiB

Open AccessArticle

Hydrothermal Synthesis of ZnO Nanoflowers: Exploring the Relationship between Morphology, Defects, and Photocatalytic Activity

by Essam M. Abdel-Fattah, Salman M. Alshehri, Satam Alotibi, Mohammed Alyami and Doaa Abdelhameed

Crystals 2024, 14(10), 892; https://doi.org/10.3390/cryst14100892 - 14 Oct 2024

Viewed by 732

Abstract

Two forms of flower-like ZnO nanostructures were synthesized using hydrothermal methods at various growth times/temperatures and zinc precursors. The morphology, structure, chemical composition, and optical properties of these ZnO nanoflowers were studied using a scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), X-ray [...] Read more.

Two forms of flower-like ZnO nanostructures were synthesized using hydrothermal methods at various growth times/temperatures and zinc precursors. The morphology, structure, chemical composition, and optical properties of these ZnO nanoflowers were studied using a scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy, and UV–Vis spectroscopy. The SEM images revealed two forms of flower-like nanostructures, namely lotus- and tulip-like flower ZnO nanostructures. The XPS analysis revealed the oxidation state of the Zn and O elements, as well as the presence of OH groups on the surface of the lotus-like flower ZnO nanostructure. The XRD results revealed less crystallinity of the lotus-like ZnO nanoflowers (NFs) compared with the tulip-like ZnO NFs. The XRD results revealed the presence of Zn (OH)₂ in the ZnO NFs. The Raman results confirmed less crystallinity of the lotus-like ZnO NFs. The estimated optical bandgap was 2.92 and 3.0 eV for the tulip- and lotus-like ZnO NFs, respectively. The tulip-like ZnO NFs showed superior photocatalytic degradation of methylene blue dye, verified via UV–Vis radiation, compared with the lotus-like ZnO NFs, which show the impact of the structure defects and OH- impurities on the photocatalytic performance of ZnO nanoflowers. Full article

(This article belongs to the Special Issue Sustainable Heterogeneous Catalyst: From Structure to Application)

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15 pages, 3009 KiB

Open AccessArticle

Local Orientation Transitions to a Lying Helix State in Negative Dielectric Anisotropy Cholesteric Liquid Crystal

by Ivan V. Simdyankin, Artur R. Geivandov, Irina V. Kasyanova and Serguei P. Palto

Crystals 2024, 14(10), 891; https://doi.org/10.3390/cryst14100891 - 13 Oct 2024

Viewed by 741

Abstract

Orientation transitions in a cholesteric liquid crystal (CLC) layer with negative dielectric anisotropy, under the influence of a non-uniform spatially periodic electric field created using a planar system of interdigitated electrodes, were studied experimentally and numerically. In the interelectrode space, transitions are observed [...] Read more.

Orientation transitions in a cholesteric liquid crystal (CLC) layer with negative dielectric anisotropy, under the influence of a non-uniform spatially periodic electric field created using a planar system of interdigitated electrodes, were studied experimentally and numerically. In the interelectrode space, transitions are observed from a planar Grandjean texture, with the helix axis perpendicular to the layer plane, to states with a lying helix, when the helix axis is parallel to the layer plane and perpendicular to the electrode stripes. It was found that the relaxation time of the induced state in the Grandjean zones, corresponding to two or more half-turns of the helix, significantly exceeded the relaxation time for the first Grandjean zone with one half-turn. An analysis of experimentally observed and numerically simulated textures shows that slow relaxation to the initial state in the second Grandjean zone, as well as in higher-order zones, is associated with the formation of local topologically equivalent states. In these states, the helix has a reduced integer number of helix half-turns throughout the layer thickness or unwound into the planar alignment state. Full article

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

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13 pages, 4995 KiB

Open AccessArticle

Plasmonic ZnO-Au Nanocomposites: A Synergistic Approach to Enhanced Photocatalytic Activity through Nonthermal Plasma-Assisted Synthesis

by Essam M. Abdel-Fattah

Crystals 2024, 14(10), 890; https://doi.org/10.3390/cryst14100890 - 13 Oct 2024

Viewed by 757

Abstract

A novel and efficient method for synthesizing Au-decorated ZnO nanoparticles (NPs) with enhanced photocatalytic activity is presented. The synthesis involves a two-step process: hydrothermal preparation of ZnO NPs followed by nonthermal plasma-assisted deposition of Au nanoparticles on their surface. Comprehensive characterization of the [...] Read more.

A novel and efficient method for synthesizing Au-decorated ZnO nanoparticles (NPs) with enhanced photocatalytic activity is presented. The synthesis involves a two-step process: hydrothermal preparation of ZnO NPs followed by nonthermal plasma-assisted deposition of Au nanoparticles on their surface. Comprehensive characterization of the ZnO and ZnO–Au NPs was carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Optical properties were evaluated via UV-Vis absorption and fluorescence measurements. The synthesized ZnO NPs displayed a hexagonal wurtzite structure, and the successful deposition of Au NPs was confirmed by TEM and XPS analysis, along with Raman and fluorescence data showing the quenching effect caused by Au. The incorporation of Au nanoparticles led to the appearance of localized surface plasmon resonance (LSPR) at 540 nm, enhancing visible light absorption and improving photocatalytic performance. Notably, the methylene blue (MB) degradation efficiency increased from 78% with pure ZnO NPs to 91.6% with ZnO–Au NPs under UV-Vis irradiation, demonstrating superior photocatalytic activity. This study introduces a simple and scalable method for synthesizing plasmonic ZnO-Au hybrid nanomaterials using plasma technology and highlights the critical role of Au NPs in enhancing photocatalytic performance by reducing electron–hole recombination. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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11 pages, 4779 KiB

Open AccessArticle

Insights into Crystallization of Neuronal Nicotinic α4β2 Receptor in Polarized Lipid Matrices

by Juan C. Villalobos-Santos, Mallerie Carrasquillo-Rivera, Josué A. Rodríguez-Cordero, Orestes Quesada and José Antonio Lasalde-Dominicci

Crystals 2024, 14(10), 889; https://doi.org/10.3390/cryst14100889 - 12 Oct 2024

Viewed by 837

Abstract

Obtaining high-resolution 3D structures of membrane proteins through X-ray crystallography remains a longstanding bottleneck in the field of structural biology. This challenge has led to the optimization of purification methods to acquire high-yielding, pure proteins suitable for crystallization. In this study, we performed [...] Read more.

Obtaining high-resolution 3D structures of membrane proteins through X-ray crystallography remains a longstanding bottleneck in the field of structural biology. This challenge has led to the optimization of purification methods to acquire high-yielding, pure proteins suitable for crystallization. In this study, we performed crystallization screenings of purified human α4β2 nAChR using a polarized in meso method. After reconstituting the detergent-solubilized α4β2 nAChR into the LCP matrix, the samples were incubated in a polarized lipid matrix using the RMP@LMx device developed in our laboratory. The results showed that under these conditions, the α4β2-nAChR-LFC 16 complex gave a mobile fraction >0.8, suggesting that its diffusion in the polarized lipid matrix is favorable for crystal nucleation. Voltages above 70 mV restricted crystal formation due to sample dehydration. Furthermore, a lipid analysis using UPLC-ESI MS/MS revealed a profile necessary for preserving protein integrity and promoting diffusion across the LCP. We harvested a single crystal and subjected it to X-ray diffraction, resulting in reflections comparable to previous studies of the muscle-type nAChR from Torpedo californica. X-ray diffraction of a single crystal gave distinct low-resolution diffractions of protein nature. These findings lay the groundwork for further optimization of membrane protein crystallization in polarized in meso phases. Full article

(This article belongs to the Section Biomolecular Crystals)

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24 pages, 9620 KiB

Open AccessArticle

Evaluation of Processing Parameters in the Solvothermal Synthesis of Cu-Rich Tetrahedrites for Potential Application as Thermoelectric Materials

by Itzel J. Soní-Castro, Ana B. López-Oyama, Eugenio Rodríguez González, Deyanira Del Ángel-López, Miguel A. Aguilar-Frutis and Juan J. Reyes-Valdez

Crystals 2024, 14(10), 888; https://doi.org/10.3390/cryst14100888 - 12 Oct 2024

Viewed by 560

Abstract

The major issue associated with thermoelectric performance is the low efficiency of power conversion. The main challenge is achieving a combination of high Seebeck coefficient, high electrical conductivity, and low thermal conductivity for a significantly improved figure of merit (ZT). Developing strategies include [...] Read more.

The major issue associated with thermoelectric performance is the low efficiency of power conversion. The main challenge is achieving a combination of high Seebeck coefficient, high electrical conductivity, and low thermal conductivity for a significantly improved figure of merit (ZT). Developing strategies include the production of tetrahedrites with an intrinsically low thermal conductivity through the solvothermal method, using a low reaction time and processing temperature. Here, we report on the preparation of Cu-rich tetrahedrites through the solvothermal technique at low temperature, providing a promising strategy for the preparation of materials with potential applications in thermoelectricity. The influence of synthesis reaction time and temperature on the morphological, structural, and thermoelectrical properties of the samples was investigated through different characterization techniques. Tetrahedrite synthesized at 180 °C for 19 h yielded a favorable ZT value of >0.43 and a thermal conductivity of 0.2 Wm⁻¹ K⁻¹ (423 K), related to the Sb³⁺/Sb⁵⁺ and Cu⁺/Cu²⁺ ratio, as was observed by XPS. The cubic tetrahedrite phase attributed to the (222) plane was confirmed by XRD and TEM and the intense Raman mode observed at 351 cm⁻¹. SEM images revealed that nanotetrahedral Cu-rich tetrahedrites efficiently assemble into spherical structures, resulting in an improvement in the Seebeck coefficient (437 µVK⁻¹) and electrical conductivity. Full article

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

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16 pages, 6242 KiB

Open AccessArticle

Analysis of Low-Frequency Sound Absorption Performance and Optimization of Structural Parameters for Acoustic Metamaterials for Spatial Double Helix Resonators

by Yuanqing Luo, Tao Yu, Shuang Kang, Dacheng Zhang, Shiyue Liu, Xueyong Tian and Feng Sun

Crystals 2024, 14(10), 887; https://doi.org/10.3390/cryst14100887 - 12 Oct 2024

Viewed by 559

Abstract

Low-frequency noise absorbers often require large structural dimensions, constraining their development in practical applications. In order to improve space utilization, an acoustic metamaterial with a spatial double helix, called a spatial double helix resonator (SDHR), is proposed in this paper. An analytical model [...] Read more.

Low-frequency noise absorbers often require large structural dimensions, constraining their development in practical applications. In order to improve space utilization, an acoustic metamaterial with a spatial double helix, called a spatial double helix resonator (SDHR), is proposed in this paper. An analytical model of the spatial double-helix resonator is established and verified by numerical simulations and impedance tube experiments. By comparing the acoustic absorption coefficients of the spatial double-helix resonator, it is shown that the results of the analytical model, the numerical model, and the experiments are in good agreement, proving the accuracy of the theoretical model. The effects of different structural parameters on the peak sound absorption coefficient and resonance frequency are quantitatively revealed. The impedance variation law of the model is obtained, and the resistance and reactance distributions at the resonance frequency are analyzed. In the optimization model, the Back Propagation (BP) network is used to construct the mapping between the structural parameters and the resonance frequency and sound absorption coefficient, and this is used as the constraints of the equation, which is combined with Wild Horse Optimization (WHO) to establish the BP-WHO optimization model to minimize the volume of the spatial double helix resonator. The results show that, for a given noise frequency, the optimized structural parameters enhance the space utilization without affecting the performance of the space double helix resonator. Full article

(This article belongs to the Special Issue Metamaterials and Their Devices)

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18 pages, 6517 KiB

Open AccessArticle

Antibacterial Amorphous–Crystalline Coatings Based on Wollastonite and ZnO Particles

by Mariya B. Sedelnikova, Violetta V. Mayer, Olga V. Bakina, Alexander D. Kashin, Pavel V. Uvarkin, Margarita A. Khimich, Nikita A. Luginin, Ivan A. Glukhov, Tatiana V. Tolkacheva, Anna V. Ugodchikova and Yurii P. Sharkeev

Crystals 2024, 14(10), 886; https://doi.org/10.3390/cryst14100886 - 11 Oct 2024

Viewed by 557

Abstract

This study considers the regularities in the formation of amorphous–crystalline coatings with zinc oxide and wollastonite particles via micro-arc oxidation (MAO) on metal substrates made from a Mg-0.8 wt.% Ca alloy. The combination of components with increased antibacterial and osteogenic properties made it [...] Read more.

This study considers the regularities in the formation of amorphous–crystalline coatings with zinc oxide and wollastonite particles via micro-arc oxidation (MAO) on metal substrates made from a Mg-0.8 wt.% Ca alloy. The combination of components with increased antibacterial and osteogenic properties made it possible to obtain a unique bioactive and corrosion-resistant coating that slowed down the bioresorption of a magnesium implant and stimulated the processes of osteointegration. The coating was examined using various methods, including scanning and transmission electron microscopy, X-ray crystallography, scratch testing, energy-dispersive X-ray spectroscopy, and potentiodynamic polarization testing. As a result of plasma-chemical interactions between electrolyte components and the magnesium substrate, a porous amorphous–crystalline coating comprising wollastonite (CaSiO₃), zinc oxide (ZnO), forsterite (Mg₂SiO₄), and periclase (MgO) was formed at varying voltages (350–500 V) during the MAO process. The protective properties of the coating were exceptional, as evidenced by the mass loss values of the coated samples (1.4–2.3%) in 0.9% NaCl solution, which were significantly lower than the mass loss of the uncoated alloy (8.9%). The coating synthesized at a voltage of 500 V was characterized by a maximum zinc content of 8 at.%, which was responsible for the highest antibacterial activity against Staphylococcus aureus (99.1%). Full article

(This article belongs to the Special Issue Synthesis, Characterization and Properties of Crystalline Materials)

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16 pages, 2072 KiB

Open AccessReview

Chiral, Topological, and Knotted Colloids in Liquid Crystals

by Ye Yuan and Ivan I. Smalyukh

Crystals 2024, 14(10), 885; https://doi.org/10.3390/cryst14100885 - 11 Oct 2024

Viewed by 878

Abstract

The geometric shape, symmetry, and topology of colloidal particles often allow for controlling colloidal phase behavior and physical properties of these soft matter systems. In liquid crystalline dispersions, colloidal particles with low symmetry and nontrivial topology of surface confinement are of particular interest, [...] Read more.

The geometric shape, symmetry, and topology of colloidal particles often allow for controlling colloidal phase behavior and physical properties of these soft matter systems. In liquid crystalline dispersions, colloidal particles with low symmetry and nontrivial topology of surface confinement are of particular interest, including surfaces shaped as handlebodies, spirals, knots, multi-component links, and so on. These types of colloidal surfaces induce topologically nontrivial three-dimensional director field configurations and topological defects. Director switching by electric fields, laser tweezing of defects, and local photo-thermal melting of the liquid crystal host medium promote transformations among many stable and metastable particle-induced director configurations that can be revealed by means of direct label-free three-dimensional nonlinear optical imaging. The interplay between topologies of colloidal surfaces, director fields, and defects is found to show a number of unexpected features, such as knotting and linking of line defects, often uniquely arising from the nonpolar nature of the nematic director field. This review article highlights fascinating examples of new physical behavior arising from the interplay of nematic molecular order and both chiral symmetry and topology of colloidal inclusions within the nematic host. Furthermore, the article concludes with a brief discussion of how these findings may lay the groundwork for new types of topology-dictated self-assembly in soft condensed matter leading to novel mesostructured composite materials, as well as for experimental insights into the pure-math aspects of low-dimensional topology. Full article

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

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14 pages, 6223 KiB

Open AccessArticle

X-ray Structure of Eleven New N,N′-Substituted Guanidines: Effect of Substituents on Tautomer Structure in the Solid State

by Vijayaragavan Elumalai, Vaclav Eigner, Nicholas Alexander Janjua, Per-Olof Åstrand, Torkild Visnes, Eirik Sundby and Bård Helge Hoff

Crystals 2024, 14(10), 884; https://doi.org/10.3390/cryst14100884 - 11 Oct 2024

Viewed by 815

Abstract

Guanidine-containing molecules are an interesting class of compounds within both medicinal and material sciences. Having knowledge of their tautomerism is key in designing guanidines that interact with biological and chemical receptors. However, there are limited data on the solid-phase structure of N,N′-substituted [...] Read more.

Guanidine-containing molecules are an interesting class of compounds within both medicinal and material sciences. Having knowledge of their tautomerism is key in designing guanidines that interact with biological and chemical receptors. However, there are limited data on the solid-phase structure of N,N′-substituted guanidines. Thus, eleven guanidines bearing a 4,6-dimethylpyrimidyl at one end and substituents of varying sizes and electronic properties at the other side, were synthesised, crystallised, and analysed by X-ray crystallography. Calculations of isolated molecules of tautomer energies and bond lengths were performed for comparison. One class of guanidines crystallised as a cis–trans tautomer with the shorter bond directed towards the pyrimidyl unit. When more electron-deficient aniline substituents were inserted, the crystallised tautomer changed to a cis–cis form where the shorter bond was directed towards the aniline. The switch in the tautomer structure is concluded to be due to both the electronic properties of the substituents and the intermolecular hydrogen bonding in the crystal lattice. Full article

(This article belongs to the Section Organic Crystalline Materials)

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26 pages, 1433 KiB

Open AccessReview

Advancements in and Applications of Crystal Plasticity Modelling of Metallic Materials

by Vasilis Loukadakis and Spyros Papaefthymiou

Crystals 2024, 14(10), 883; https://doi.org/10.3390/cryst14100883 - 10 Oct 2024

Viewed by 1556

Abstract

Integrated Computational Materials Engineering (ICME) is a set of methodologies utilized by researchers and engineers assisting the study of material behaviour during production processes and/or service. ICME aligns with societal efforts for the twin green and digital transitions while improving the sustainability and [...] Read more.

Integrated Computational Materials Engineering (ICME) is a set of methodologies utilized by researchers and engineers assisting the study of material behaviour during production processes and/or service. ICME aligns with societal efforts for the twin green and digital transitions while improving the sustainability and cost efficiency of relevant products/processes. A significant link of the ICME chain, especially for metallic materials, is the crystal plasticity (CP) formulation. This review examines firstly the progress CP has made since its conceptualization and secondly the relevant thematic areas of its utilization and portraits them in a concise and condensed manner. CP is a proven tool able to capture complex phenomena and to provide realistic results, while elucidating on the material behaviour under complex loading conditions. To this end, a significant number of formulations falling under CP, each with their unique strengths and weaknesses, is offered. It is a developing field and there are still efforts to improve the models in various terms. One of the biggest struggles in setting up a CP simulation, especially a physics-based one, is the definition of the proper values for the relevant parameters. This review provides valuable data tables with indicative values. Full article

(This article belongs to the Special Issue Crystallization of High Performance Metallic Materials (2nd Edition))

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9 pages, 2324 KiB

Open AccessArticle

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

Viewed by 553

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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