Crystals

13 pages, 51806 KiB

Open AccessReview

Ti:Sa Crystals in Ultra-High Peak and Average Power Laser Systems

by Vladimir Chvykov

Crystals 2021, 11(7), 841; https://doi.org/10.3390/cryst11070841 - 20 Jul 2021

Cited by 6 | Viewed by 3057

In this paper, Ti:Sa amplifiers with crystals of the different geometries are discussed. Benefits of using this active medium for a thin disk (TD) and slab amplifiers are evaluated numerically and tested experimentally. Thermal management for amplifiers with multi-kW average power and multi-J [...] Read more.

In this paper, Ti:Sa amplifiers with crystals of the different geometries are discussed. Benefits of using this active medium for a thin disk (TD) and slab amplifiers are evaluated numerically and tested experimentally. Thermal management for amplifiers with multi-kW average power and multi-J pulse energy has been demonstrated. The presented numerical simulations revealed the existing limitations for heat extraction in TD geometry in the sub-joule energy regime for higher repetition rate operation. Geometry conversion from TD to thin-slab (TS) and cross-thin-slab (XTS) configurations significantly increases the cooling efficiency with an acceptable crystal temperature for pump average power values up to few kW with room temperature cooling, and up to tens of kW with cryogenic cooling. The abilities to attain 0.3 J output energy and a greater than 50% extraction efficiency were demonstrated with a repetition rate exceeding 10 kHz with room temperature cooling and one order more of a repetition rate with cryogenic conditions with pulsed pumping. Direct diode pumping simulated for CW regimes demonstrated 1.4 kW output power with 34% extraction efficiency using room temperature cooling and more than 10 kW and ~40% efficiency with cryogenic cooling. Full article

(This article belongs to the Special Issue Ti:Sapphire (Ti:Sa) Crystal: Properties Study and Application)

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17 pages, 30796 KiB

Open AccessReview

Fluorescent Azobenzene-Containing Compounds: From Structure to Mechanism

by Lulu Xue, Ying Pan, Shaohai Zhang, Yinjie Chen, Haifeng Yu, Yonggang Yang, Lixin Mo, Zhicheng Sun, Luhai Li and Huai Yang

Crystals 2021, 11(7), 840; https://doi.org/10.3390/cryst11070840 - 20 Jul 2021

Cited by 19 | Viewed by 9193

Abstract

The reversible photoisomerization of azobenzenes has been extensively studied to construct systems with optical responsiveness; however, this process limits the luminescence of these compounds. Recently, there have been many efforts to design and synthesize fluorescent azobenzene compounds, such as inhibition of electron transfer, [...] Read more.

The reversible photoisomerization of azobenzenes has been extensively studied to construct systems with optical responsiveness; however, this process limits the luminescence of these compounds. Recently, there have been many efforts to design and synthesize fluorescent azobenzene compounds, such as inhibition of electron transfer, inducing aggregation, and metal-enhancement, which make the materials ideal for application in fluorescence probes, light-emitting devices, molecular detection, etc. Herein, we review the recently reported progress in the development of various fluorescent azobenzenes and summarize the possible mechanism of their fluorescence emission. The potential applications of these materials are also discussed. Finally, in order to guide research in this field, the existing problems and future development prospects are discussed. Full article

(This article belongs to the Special Issue Liquid Crystals in China)

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16 pages, 19541 KiB

Open AccessArticle

Petrographic-Mineralogical Characterization of Archaeological Materials from “Casa di Diana” Mithraeum Sited in the Open Museum of Ostia Antica

by Claudia Scatigno, Maria Preite Martinez, Nagore Prieto-Taboada, Juan Manual Madariaga and Aida Maria Conte

Crystals 2021, 11(7), 839; https://doi.org/10.3390/cryst11070839 - 20 Jul 2021

Cited by 2 | Viewed by 2801

Abstract

Mithraea, religious Roman buildings, are very common in Italian archeological sites. There are sixteen in Ostia Antica (Rome, Italy)The poor state of conservation, due to the intrinsic environmental conditions, characterized them: they consist of open-air museums and caves simultaneously. These places of [...] Read more.

Mithraea, religious Roman buildings, are very common in Italian archeological sites. There are sixteen in Ostia Antica (Rome, Italy)The poor state of conservation, due to the intrinsic environmental conditions, characterized them: they consist of open-air museums and caves simultaneously. These places of worship are characterized by the presence of heterogeneous materials, such as wall building materials (bricks and mortars) and others used for furnishings and fittings. This increases the risk of accelerated damage because the materials ‘rheology is different. Here, a full petrographic-mineralogical characterization with polarized light microscopy (PLM), X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray (SEM-EDS) and isotopic analysis (δ13C, δ18O) is carried out on materials like travertine, marble, pumice, ceramic, and wall-building materials in “Casa di Diana” Mithraeum (Ostia Antica). Their characterization gives provenance information as well as conservation and restoration purposes. The prevalence of siliciclastic or carbonate components discriminates between red and yellow bricks, as well as different textures and minerals in the aggregate of the red ones. The mortars are typically pozzolanic, and the aggregate is mostly made up of black and red pozzolanic clasts. In the altar, apse, and aedicule, which constitute the principal place of the Mithraeum, a variety of materials used for the ornamental purpose are represented by pumices, travertine, marble, and limestone. The altar material, catalogued as marble, resulted in being a limestone coated with a white pigment. Full article

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53 pages, 4735 KiB

Open AccessReview

Modern History of Organic Conductors: An Overview

by Toshio Naito

Crystals 2021, 11(7), 838; https://doi.org/10.3390/cryst11070838 - 20 Jul 2021

Cited by 27 | Viewed by 6671

Abstract

This short review article provides the reader with a summary of the history of organic conductors. To retain a neutral and objective point of view regarding the history, background, novelty, and details of each research subject within this field, a thousand references have [...] Read more.

This short review article provides the reader with a summary of the history of organic conductors. To retain a neutral and objective point of view regarding the history, background, novelty, and details of each research subject within this field, a thousand references have been cited with full titles and arranged in chronological order. Among the research conducted over ~70 years, topics from the last two decades are discussed in more detail than the rest. Unlike other papers in this issue, this review will help readers to understand the origin of each topic within the field of organic conductors and how they have evolved. Due to the advancements achieved over these 70 years, the field is nearing new horizons. As history is often a reflection of the future, this review is expected to show the future directions of this research field. Full article

(This article belongs to the Special Issue Organic Conductors)

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13 pages, 4705 KiB

Open AccessArticle

Preparation of Aligned Steel-Fiber-Reinforced Concrete Using a Magnetic Field Created by the Assembly of Magnetic Pieces

by Ru Mu, Ruixin Dong, Haoqi Liu, Haoyu Chen, Qingao Cheng and Chunhao Fan

Crystals 2021, 11(7), 837; https://doi.org/10.3390/cryst11070837 - 20 Jul 2021

Cited by 13 | Viewed by 3138

Abstract

In steel-fiber-reinforced composites, when the direction of a steel fiber is parallel to the direction of tensile stress, the capacity of the strengthening and toughening effect of the steel fiber can be fully applied to the composites. In this paper, a method to [...] Read more.

In steel-fiber-reinforced composites, when the direction of a steel fiber is parallel to the direction of tensile stress, the capacity of the strengthening and toughening effect of the steel fiber can be fully applied to the composites. In this paper, a method to control the direction of steel fibers from one side surface of the mold full of a fresh mixture of steel-fiber-reinforced concrete using a magnet composed of small magnet squares is proposed, which has the advantage that the approach is suitable for specimens or elements with any size or shape. The influence of the method on the orientation effect of steel fiber is explored, and the flexural properties of the specimens prepared by different orientation methods are compared and analyzed through a three-point bending test. The test results show that the steel fibers in the mixture are successfully aligned by the magnetic treatment and the fiber orientation effective coefficient reaches 0.9 or more. The flexural properties of the aligned steel-fiber-reinforced cementitious composite (ASFRC) prepared by the magnetic device is significantly improved. The test results also show that the properties of the ASFRC prepared by the new method are comparable with that prepared by the previous electromagnetic field in terms of the fiber orientation effective coefficient and flexural strength. Full article

(This article belongs to the Special Issue Advances in Green Building Materials and Structural Performances)

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14 pages, 3313 KiB

Open AccessArticle

Carbonation of Sodium Aluminate/Sodium Carbonate Solutions for Precipitation of Alumina Hydrates—Avoiding Dawsonite Formation

by Danai Marinos, Dimitrios Kotsanis, Alexandra Alexandri, Efthymios Balomenos and Dimitrios Panias

Crystals 2021, 11(7), 836; https://doi.org/10.3390/cryst11070836 - 20 Jul 2021

Cited by 11 | Viewed by 5878

Abstract

Experimental work has been performed to investigate the precipitation mechanism of aluminum hydroxide phases from sodium aluminate/sodium carbonate pregnant solutions by carbon dioxide gas purging. Such solutions result from leaching calcium aluminate slags with sodium carbonate solutions, in accordance with the Pedersen process, [...] Read more.

Experimental work has been performed to investigate the precipitation mechanism of aluminum hydroxide phases from sodium aluminate/sodium carbonate pregnant solutions by carbon dioxide gas purging. Such solutions result from leaching calcium aluminate slags with sodium carbonate solutions, in accordance with the Pedersen process, which is an alternative process for alumina production. The concentration of carbonate ions in the pregnant solution is revealed as a key factor in controlling the nature of the precipitating phase. Synthetic aluminate solutions of varying sodium carbonate concentrations, ranging from 20 to 160 g/L, were carbonated, and the resulting precipitating phases were characterized by X-ray diffraction analysis. Based on the results of the previous carbonation tests, a series of experiments were performed in which the duration of carbonation and the aging period of the precipitates varied. For this work, a synthetic aluminate solution containing 20 g/L free Na₂CO₃ was used. The precipitates were characterized with X-ray diffraction analysis and Fourier-transform infrared spectroscopy. Full article

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10 pages, 4130 KiB

Open AccessArticle

Tetrabromoethane as σ-Hole Donor toward Bromide Ligands: Halogen Bonding between C₂H₂Br₄ and Bromide Dialkylcyanamide Platinum(II) Complexes

by Anna M. Cheranyova and Daniil M. Ivanov

Crystals 2021, 11(7), 835; https://doi.org/10.3390/cryst11070835 - 20 Jul 2021

Cited by 6 | Viewed by 2535

Abstract

The complexes trans-[PtBr₂(NCNR₂)₂] (R₂ = Me₂1, (CH₂)₅2) were cocrystallized with 1,1,2,2-tetrabromoethane (tbe) in CH₂Cl₂ forming solvates 1·tbe and 2·tbe, respectively. In [...] Read more.

The complexes trans-[PtBr₂(NCNR₂)₂] (R₂ = Me₂1, (CH₂)₅2) were cocrystallized with 1,1,2,2-tetrabromoethane (tbe) in CH₂Cl₂ forming solvates 1·tbe and 2·tbe, respectively. In both solvates, tbe involved halogen bonding, viz. the C–Br···Br–Pt interactions, were detected by single-crystal X-ray diffractions experiments. Appropriate density functional theory calculations (M06/def2-TZVP) performed for isolated molecules and complex-tbe clusters, where the existence of the interactions and their noncovalent nature were confirmed by electrostatic potential surfaces (ρ = 0.001 a.u.) for isolated molecules, topology analysis of electron density, electron localization function and HOMO-LUMO overlap projections for clusters. Full article

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11 pages, 6843 KiB

Open AccessArticle

Self-Assembly of an Equimolar Mixture of Liquid Crystals and Magnetic Nanoparticles

by Gaurav P. Shrivastav

Crystals 2021, 11(7), 834; https://doi.org/10.3390/cryst11070834 - 19 Jul 2021

Cited by 3 | Viewed by 2766

Abstract

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found [...] Read more.

We studied the equilibrium self-assembly of an equimolar mixture of uniaxial liquid crystals (LCs) and magnetic nanoparticles (MNPs) using molecular dynamics simulations. The LCs are modeled by ellipsoids interacting via Gay–Berne potential, and MNPs are represented by dipolar soft spheres (DSS). We found that the LCs show isotropic, nematic, and smectic phases when the mixture is compressed at a fixed temperature. The DSS form chain-like structures, which remain randomly oriented at low densities where the LCs are in the isotropic phase. At intermediate and high densities, the DSS chains align along the nematic and smectic directors of LCs. We found that the DSS inside a chain follow a ferromagnetic ordering. However, the mixture does not show a significant macroscopic magnetization. The extent of nematic order in the DSS remains very similar to the LCs in intermediate densities. At high densities, the DSS have a lower extent of nematic order than the LCs. The structure of the LC–DSS mixture was further analyzed via projected pair correlation functions for distances parallel and perpendicular to directors in the nematic and smectic phases. Full article

(This article belongs to the Special Issue Patterned-Liquid-Crystal for Novel Displays)

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11 pages, 3335 KiB

Open AccessArticle

Microstructures and Mechanical Properties of Al-Ti-Zr-Nb-Ta-Mo-V Refractory High-Entropy Alloys with Coherent B2 Nanoprecipitation

by Zhenhua Wang, Dongming Jin, Jincan Han, Qing Wang, Zhongwei Zhang and Chuang Dong

Crystals 2021, 11(7), 833; https://doi.org/10.3390/cryst11070833 - 19 Jul 2021

Cited by 8 | Viewed by 4227

Abstract

In this work, the microstructural evolution and mechanical properties of new body-centered cubic (BCC)-based Al-Ti-Zr-Nb-Ta-Mo-V refractory high-entropy alloys (RHEAs) with coherent B2 precipitation are investigated. These designed alloy ingots were solid-solutionized at 1573 K for 2 h and then aged at 873 K [...] Read more.

In this work, the microstructural evolution and mechanical properties of new body-centered cubic (BCC)-based Al-Ti-Zr-Nb-Ta-Mo-V refractory high-entropy alloys (RHEAs) with coherent B2 precipitation are investigated. These designed alloy ingots were solid-solutionized at 1573 K for 2 h and then aged at 873 K for 24 h, in which each treatment was followed by water quenching. It was found that there exists phase separation of BCC matrix, Ti/Zr-rich BCC1 and Nb/Ta-rich BCC2 in these alloys. Moreover, ultra-fine spherical B2 nanoparticles with a size of 3~5 nm were dispersed in BCC2 matrix. These B2 nanoparticles could be coarsened up to 25~50 nm after aging and the particle morphology also changes to a cuboidal shape due to a moderate lattice misfit (ε = 0.7~2.0%). Also, Zr₅Al₃ phase could coexist with the B2 phase, where the difference between them is that the Ti element is enriched in B2 phase, rather than in Zr₅Al₃. Among them, the solutionized Al₂Ti₅Zr₄Nb_2.5Ta_2.5 RHEAs exhibit good compressive mechanical property with a high yield strength of 1240 MPa and a large plasticity, which is mainly attributed to the coherent precipitation in the BCC matrix. Full article

(This article belongs to the Special Issue High-Entropy Materials)

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14 pages, 3454 KiB

Open AccessArticle

Photoluminescent Properties of Hydroxyapatite and Hydroxyapatite/Multi-Walled Carbon Nanotube Composites

by Edna X. Figueroa-Rosales, Javier Martínez-Juárez, Esmeralda García-Díaz, Daniel Hernández-Cruz, Sergio A. Sabinas-Hernández and Maria J. Robles-Águila

Crystals 2021, 11(7), 832; https://doi.org/10.3390/cryst11070832 - 17 Jul 2021

Cited by 25 | Viewed by 4171

Abstract

Hydroxyapatite (HAp) and hydroxyapatite/multi-walled carbon nanotube (MWCNT) composites were obtained by the co-precipitation method, followed by ultrasound-assisted and microwave radiation and thermal treatment at 250 °C. X-ray diffraction (XRD) confirmed the presence of a hexagonal phase in all the samples, while Fourier-transform infrared [...] Read more.

Hydroxyapatite (HAp) and hydroxyapatite/multi-walled carbon nanotube (MWCNT) composites were obtained by the co-precipitation method, followed by ultrasound-assisted and microwave radiation and thermal treatment at 250 °C. X-ray diffraction (XRD) confirmed the presence of a hexagonal phase in all the samples, while Fourier-transform infrared (FTIR) spectroscopy elucidated the interaction between HAp and MWCNTs. The photoluminescent technique revealed that HAp and the composite with non-functionalized MWCNTs present a blue luminescence, while the composite with functionalized MWCNTs, under UV-vis radiation shows an intense white emission. These findings allowed presentation of a proposal for the use of HAp and HAp with functionalized MWCNTs as potential materials for optoelectronic and medical applications. Full article

(This article belongs to the Special Issue Hydroxyapatite Base Nanocomposites (Volume II))

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15 pages, 2112 KiB

Open AccessArticle

From Bend to Splay Dominated Elasticity in Nematics

by Davide Revignas and Alberta Ferrarini

Crystals 2021, 11(7), 831; https://doi.org/10.3390/cryst11070831 - 17 Jul 2021

Cited by 6 | Viewed by 3657

Abstract

In the past decade, much evidence has been provided for an unusually low cost for bend deformations in the nematic phase of bent-core mesogens and bimesogens (liquid crystal dimers) having a bent shape on average. Recently, an analogous effect was observed for the [...] Read more.

In the past decade, much evidence has been provided for an unusually low cost for bend deformations in the nematic phase of bent-core mesogens and bimesogens (liquid crystal dimers) having a bent shape on average. Recently, an analogous effect was observed for the splay mode of bent-core mesogens with an acute apical angle. Here, we present a systematic computational investigation of the Frank elastic constants of nematics made of V-shaped particles, with bend angles ranging from acute to obtuse. We show that by tuning this angle, the elastic behavior switches from bend dominated (

K_{33} > K_{11}

) to splay dominated (

K_{11} > K_{33}

), with anomalously low values of the splay and the bend constant, respectively. This is related to a change in the shape polarity of particles, which is associated with the emergence of polar order, longitudinal for splay and transversal for bend deformations. Crucial to this study is the use of a recently developed microscopic elastic theory, able to account for the interplay of mesogen morphology and director deformations. Full article

(This article belongs to the Special Issue In Celebration of Noel A. Clark’s 80th Birthday)

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17 pages, 2377 KiB

Open AccessArticle

On Modeling Concrete Compressive Strength Data Using Laplace Birnbaum-Saunders Distribution Assuming Contaminated Information

by Farouq Mohammad A. Alam and Mazen Nassar

Crystals 2021, 11(7), 830; https://doi.org/10.3390/cryst11070830 - 17 Jul 2021

Cited by 6 | Viewed by 2353

Abstract

Compressive strength is a well-known measurement to evaluate the endurance of a given concrete mixture to stress factors, such as compressive loads. A suggested approach to assess compressive strength of concrete is to assume that it follows a probability model from which its [...] Read more.

Compressive strength is a well-known measurement to evaluate the endurance of a given concrete mixture to stress factors, such as compressive loads. A suggested approach to assess compressive strength of concrete is to assume that it follows a probability model from which its reliability is calculated. In reliability analysis, a probability distribution’s reliability function is used to calculate the probability of a specimen surviving to a certain threshold without damage. To approximate the reliability of a subject of interest, one must estimate the corresponding parameters of the probability model. Researchers typically formulate an optimization problem, which is often nonlinear, based on the maximum likelihood theory to obtain estimates for the targeted parameters and then estimate the reliability. Nevertheless, there are additional nonlinear optimization problems in practice from which different estimators for the model parameters are obtained once they are solved numerically. Under normal circumstances, these estimators may perform similarly. However, some might become more robust under irregular situations, such as in the case of data contamination. In this paper, nine frequentist estimators are derived for the parameters of the Laplace Birnbaum-Saunders distribution and then applied to a simulated data set and a real data set. Afterwards, they are compared numerically via Monte Carlo comparative simulation study. The resulting estimates for the reliability based on these estimators are also assessed in the latter study. Full article

(This article belongs to the Special Issue Performance Prediction, Durability and Modelling of Concrete Materials and Structures)

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14 pages, 2258 KiB

Open AccessArticle

Drying of a Colloidal Suspension Deposited on a Substrate: Experimental and Numerical Studies

by Nathalie Olivi-Tran, Laurent Bonnet and Pascal Etienne

Crystals 2021, 11(7), 829; https://doi.org/10.3390/cryst11070829 - 17 Jul 2021

Viewed by 2554

Abstract

We studied a colloidal suspension of polystyrene beads deposited on a glass substrate. The glass substrate contained either straight rough areas on the borders of an open channel or only straight rough areas. The drying of the suspension was observed with an optical [...] Read more.

We studied a colloidal suspension of polystyrene beads deposited on a glass substrate. The glass substrate contained either straight rough areas on the borders of an open channel or only straight rough areas. The drying of the suspension was observed with an optical microscope, the light bulb of which acted as an energy source to evaporate the suspension. Moreover, the light bulb of the microscope provided optical pressure due to light. We observed that the colloidal particles were trapped on the rough areas of the substrate and not in the open channel at the end of the drying process. In order to understand the experimental results, we modeled numerically the drying of the suspension using a Molecular Dynamics program. The forces imposed on the substrate by the particles are their weight, the optical pressure due to the light bulb of the optical microscope, the attractive Van der Waals force and the repulsive diffuse layer force. The forces acting between two particles are the attractive Van der Waals forces, the repulsive diffuse layer force and the capillary force. The Gaussian random force (linked to Brownian motion) and the particle liquid viscous drag force (also linked to Brownian motion) are horizontal and applied on one particle. The relation between the normal forces N (forces acting by the particles on the substrate) and the horizontal forces F is Amontons’ third law of friction

F \leq μ_{k} N

; in rough areas of the substrate,

μ_{k}

is larger than in smooth areas. This explains that particles are trapped in the areas with high roughness. Full article

(This article belongs to the Special Issue Feature Papers on "Hybrid and Composite Crystalline Materials" 2021-2022)

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13 pages, 5155 KiB

Open AccessArticle

Tunable Low Frequency Band Gap and Waveguide of Phononic Crystal Plates with Different Filling Ratio

by Shaobo Zhang, Jiang Liu, Hongbo Zhang and Shuliang Wang

Crystals 2021, 11(7), 828; https://doi.org/10.3390/cryst11070828 - 16 Jul 2021

Cited by 4 | Viewed by 2664

Abstract

Aiming at solving the NVH problem in vehicles, a novel composite structure is proposed. The new structure uses a hollow-stub phononic-crystal with filled cylinders (HPFC) plate. Any unit in the plate consists of a lead head, a silicon rubber body, an aluminum base [...] Read more.

Aiming at solving the NVH problem in vehicles, a novel composite structure is proposed. The new structure uses a hollow-stub phononic-crystal with filled cylinders (HPFC) plate. Any unit in the plate consists of a lead head, a silicon rubber body, an aluminum base as outer column and an opposite arranged inner pole. The dispersion curves are investigated by numerical simulations and the influences of structural parameters are discussed, including traditional hollow radius, thickness, height ratio, and the new proposed filling ratio. Three new arrays are created and their spectrum maps are calculated. In the dispersion simulation results, new branches are observed. The new branches would move towards lower frequency zone and the band gap width enlarges as the filling ratio decreases. The transmission spectrum results show that the new design can realize three different multiplexing arrays for waveguides and also extend the locally resonant sonic band gap. In summary, the proposed HPFC structure could meet the requirement for noise guiding and filtering. Compared to a traditional phononic crystal plate, this new composite structure may be more suitable for noise reduction in rail or road vehicles. Full article

(This article belongs to the Special Issue Applications of Phononic Crystals & Acoustic Metamaterials)

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22 pages, 6561 KiB

Open AccessReview

Quaternary Semiconductor Cd_1−xZn_xTe_1−ySe_y for High-Resolution, Room-Temperature Gamma-Ray Detection

by Sandeep K. Chaudhuri, Joshua W. Kleppinger, OmerFaruk Karadavut, Ritwik Nag and Krishna C. Mandal

Crystals 2021, 11(7), 827; https://doi.org/10.3390/cryst11070827 - 16 Jul 2021

Cited by 26 | Viewed by 3670

Abstract

The application of Cd_0.9Zn_0.1Te (CZT) single crystals, the primary choice for high-resolution, room-temperature compact gamma-ray detectors in the field of medical imaging and homeland security for the past three decades, is limited by the high cost of production and [...] Read more.

The application of Cd_0.9Zn_0.1Te (CZT) single crystals, the primary choice for high-resolution, room-temperature compact gamma-ray detectors in the field of medical imaging and homeland security for the past three decades, is limited by the high cost of production and maintenance due to low detector grade crystal growth yield. The recent advent of its quaternary successor, Cd_0.9Zn_0.1Te_1−ySe_y (CZTS), has exhibited remarkable crystal growth yield above 90% compared to that of ~33% for CZT. The inclusion of Se in appropriate stoichiometry in the CZT matrix is responsible for reducing the concentration of sub-grain boundary (SGB) networks which greatly enhances the compositional homogeneity and growth yield. SGB networks also host defect centers responsible for charge trapping, hence their reduced concentration ensures minimized charge trapping. Indeed, CZTS single crystals have shown remarkable improvement in electron charge transport properties and energy resolution over CZT detectors. However, our studies have found that the overall charge transport in CZTS is still limited by the hole trapping. In this article, we systematically review the advances in the CZTS growth techniques, its performance as room-temperature radiation detector, and the role of defects and their passivation studies needed to improve the performance of CZTS detectors further. Full article

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16 pages, 14455 KiB

Open AccessArticle

Preparation of Organic Crystal Seed and Its Application in Improving the Functional Period of Biodegradable Agricultural Film

by Runmeng Qiao, Xin Wang, Guangjiong Qin, Qi Liu, Jialei Liu and Wenqing He

Crystals 2021, 11(7), 826; https://doi.org/10.3390/cryst11070826 - 16 Jul 2021

Cited by 9 | Viewed by 2820

Abstract

White pollution caused by agricultural films has recently attracted great attention. In some areas, the content of micro plastic in the soil has reached 30 kg/ha. The most effective way to solve this problem is to replace traditional polyethylene agricultural films with degradable [...] Read more.

White pollution caused by agricultural films has recently attracted great attention. In some areas, the content of micro plastic in the soil has reached 30 kg/ha. The most effective way to solve this problem is to replace traditional polyethylene agricultural films with degradable agricultural films. The consistency between the degradation rate and the crop growth period has become the biggest obstacle for the wide application of such novel agricultural films. In this paper, crystallinity regulation is used to adjust the functional period of degradable agricultural films. In addition, an organic nucleating agent of polyethylenimine (PEI) is selected by doping it to poly(butylene adipate-co-terephthalate) (PBAT) polymers using a double-screw extruder. The PBAT doped with 1 wt% PEI films revealed a significant increase in mechanical properties, water holding capacity, and crystallinity compared with the pure PBAT film. There was a 31.9% increase in tensile strength, a 30.5% increase in elongation at break, a 29.6% increase in tear resistance, a 30.9% decrease in water vapor permeability, and a 3.1% increase in crystallinity. Furthermore, the induction period of PBAT doped with 1 wt% PEI under photoaging (without soil) was about 160 h longer than PBAT film, and the experienced biodegradation in soil (without light) was 1 week longer than PBAT film. Experimental results exhibited that the change of degradation degree was linearly proportional to the degree of crystallinity. This study proposes a convenient, low-cost, and effective method to adjust the crystallinity and change the degradation rate. Full article

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12 pages, 2242 KiB

Open AccessArticle

Synthesis, Optical, Magnetic and Thermodynamic Properties of Rocksalt Li_1.3Nb_0.3Mn_0.4O₂ Cathode Material for Li-Ion Batteries

by Mohamed Kamel, Abanoub R. N. Hanna, Cornelius Krellner, Rüdiger Klingeler, Mohamed Abdellah, Mahmoud Abdel-Hafiez, Arafa Hassen, Ahmed S. G. Khalil, Tarob Abdel-Baset and Abdelwahab Hassan

Crystals 2021, 11(7), 825; https://doi.org/10.3390/cryst11070825 - 16 Jul 2021

Cited by 3 | Viewed by 3873

Abstract

Since the discovery of the reversible intercalation of lithium-ion materials associated with promising electrochemical properties, lithium-containing materials have attracted attention in the research and development of effective cathode materials for lithium-ion batteries. Despite various studies on synthesis, and electrochemical properties of lithium-based materials, [...] Read more.

Since the discovery of the reversible intercalation of lithium-ion materials associated with promising electrochemical properties, lithium-containing materials have attracted attention in the research and development of effective cathode materials for lithium-ion batteries. Despite various studies on synthesis, and electrochemical properties of lithium-based materials, fairly little fundamental optical and thermodynamic studies are available in the literature. Here, we report on the structure, optical, magnetic, and thermodynamic properties of Li-excess disordered rocksalt, Li_1.3Nb_0.3Mn_0.4O₂ (LNMO) which was comprehensively studied using powder X-ray diffraction, transient absorption spectroscopy, magnetic susceptibility, and low-temperature heat capacity measurements. Charge carrier dynamics and electron–phonon coupling in LNMO were studied using ultra-fast laser spectroscopy. Magnetic susceptibility and specific heat data are consistent with the onset of long-range antiferromagnetic order at the Néel temperatures of 6.5 (1.5) K. The effective magnetic moment of LNMO is found to be 3.60

μ_{B}

. The temperature dependence of the inverse magnetic susceptibility follows the Curie–Weiss law in the high-temperature region and shows negative values of the Weiss temperature 52 K (3), confirming the strong AFM interactions. Full article

(This article belongs to the Special Issue Progress in Advanced Battery Materials)

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8 pages, 3113 KiB

Open AccessArticle

High-Order Resonant Peaks and Polarization Dependence of Microphotoluminescence in Whispering-Gallery Mode ZnO Microrod Cavity

by Jiatian Guo, Huihui Wei, Jingyi Song, Yunhui Guo and Xiaobo Yuan

Crystals 2021, 11(7), 824; https://doi.org/10.3390/cryst11070824 - 15 Jul 2021

Viewed by 2434

Abstract

High order phenomena in the visible range and with polarization dependence in the ultraviolet (UV) region of the microphotoluminescence (micro-PL) spectrum in whispering-gallery mode (WGM) ZnO microrod cavity have been thoroughly studied at room temperature. WGM ZnO microrod cavity with good crystallinity is [...] Read more.

High order phenomena in the visible range and with polarization dependence in the ultraviolet (UV) region of the microphotoluminescence (micro-PL) spectrum in whispering-gallery mode (WGM) ZnO microrod cavity have been thoroughly studied at room temperature. WGM ZnO microrod cavity with good crystallinity is produced by the CVD growth method, and the ZnO microrod structures are characterized by structural and optical methods. Through the micro-PL spectrum measurement of the ZnO microrod, it is found that high-order resonance peaks appeared in the visible region. The different polarization conditions can be adjusted by rotating the angles of the polarizer, and it is proved that the micro-PL spectrum has strong polarization-dependent behavior in the UV region. Our results imply broad application potentials in the study of ZnO microrod-based photonic cavity devices. Full article

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22 pages, 6469 KiB

Open AccessArticle

Molecular and Supramolecular Structures of Cd(II) Complexes with Hydralazine-Based Ligands; A New Example for Cyclization of Hydrazonophthalazine to Triazolophthalazine

by Saied M. Soliman, Raghdaa A. Massoud, Hessa H. Al-Rasheed and Ayman El-Faham

Crystals 2021, 11(7), 823; https://doi.org/10.3390/cryst11070823 - 15 Jul 2021

Cited by 5 | Viewed by 2457

Abstract

Molecular and supramolecular structures of two polymeric and one trinuclear Cd(II) complex with hydralazine-type ligands were presented. Self-assembly of E-1-(2-(thiophen-2-ylmethylene)hydrazinyl)phthalazine (HL) and CdCl₂ gave the 1D coordination polymer [Cd(H₂L)Cl₃]_n*H₂O, 1, in which [...] Read more.

Molecular and supramolecular structures of two polymeric and one trinuclear Cd(II) complex with hydralazine-type ligands were presented. Self-assembly of E-1-(2-(thiophen-2-ylmethylene)hydrazinyl)phthalazine (HL) and CdCl₂ gave the 1D coordination polymer [Cd(H₂L)Cl₃]_n*H₂O, 1, in which the Cd(II) ion is hexa-coordinated with one cationic monodentate ligand (H₂L⁺) and five chloride ions, two of them acting as connectors between Cd(II) centers, leading to the formation of a 1D coordination polymer along the a-direction. Using DFT calculations, the cationic ligand (H₂L⁺) could be described as a protonated HL with an extra proton at the hydrazone moiety. Repeating the same reaction by heating under reflux conditions in the presence of 1 mL saturated aqueous KSCN solution, the ligand HL underwent cyclization to the corresponding [1,2,4]triazolo[3,4-a]phthalazine-3(2H)-thione (TPT) followed by the formation of [Cd(TPT)(SCN)₂]_n*H₂O, 2, a 1D coordination polymer. In this complex, the Cd(II) is coordinated with one NS-donor TPT bidentate chelate and two bridged μ(1,3)-thiocyanate ions connecting the Cd(II) centers forming the 1D polymer array along the b-direction. Heating E-2-(1-(2-(phthalazin-1-yl)hydrazono)ethyl)phenol HL^OH with CdCl₂ under reflux condition gave the trinuclear complex [Cd₃(Hydralazine)₂(H₂O)₂Cl₆], 3, indicating the hydrolysis of the hydrazonophthalazine ligand HL^OH during the course of the reaction. Due to symmetry considerations, there are only two different Cd(II) centers having CdN₂Cl₃O and CdN₂Cl₄ coordination environments. Hirshfeld topology analysis was used to analyze the solid-state supramolecular structure of the studied complexes. Full article

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15 pages, 22306 KiB

Open AccessArticle

Influence of LiCl and AgNO₃ Doping on the Electrical Conductivity of PVA Flexible Electrolyte Polymer Film

by Abdullah F. Al Naim

Crystals 2021, 11(7), 822; https://doi.org/10.3390/cryst11070822 - 15 Jul 2021

Cited by 4 | Viewed by 2898

Abstract

Recently, the electrical conductive electrolyte based on flexible polymeric films have been attracted much attentions, due to their applications in batteries, thermoelectrics, temperature sensors and others. In this regard, two polymeric electrolytes (PVA/LiCl) and (PVA/AgNO₃) films have been engineered and the [...] Read more.

Recently, the electrical conductive electrolyte based on flexible polymeric films have been attracted much attentions, due to their applications in batteries, thermoelectrics, temperature sensors and others. In this regard, two polymeric electrolytes (PVA/LiCl) and (PVA/AgNO₃) films have been engineered and the influence of the dopants and the annealing temperature on the structural, morphology and ac and dc conductivities is extensively studied. It was found that the films crystallinity has the order PVA/AgNO₃ (49.44%) > PVA (38.64%) > PVA/LiCl (26.82%). Additionally, the dc conductivity of the films is increased with embedding the dopants into the PVA as the order PVA/AgNO₃ (13.7 × 10⁻⁴ S/cm) > PVA/LiCl (1.63 × 10⁻⁵ S/cm) > PVA (1.71 × 10⁻⁶ S/cm) at 110 °C. It is also found that there is a sharp increase for σ_ac as the frequency increases up to 10⁷ Hz and also as the temperature increases to 110 °C. However, the order of increasing the σ_ac is PVA/LiCl (155 × 10⁻³ S/cm) > PVA/AgNO₃ (2.5 × 10⁻⁵ S/cm) > PVA (2 × 10⁻⁶ S/cm) at f = 10⁷ Hz and 110 °C. The values of exponent are 0.870, 0.405 and 0.750 for PVA, PVA/AgNO₃ and PVA/LiCl, respectively, and it is increased as the temperature increases for PVA and PVA/LiCl, but it is decreased for PVA/AgNO₃. The activation energies E_a are 0.84, 0.51 and 0.62 eV for PVA, PVA/AgNO₃ and PVA/LiCl, respectively. Moreover, the values of activation energy for charge carrier migration E_m are 0.60, 0.34 and 0.4 eV for PVA, PVA/AgNO₃ and PVA/LiCl, respectively. By using a simple approximation, the carrier concentration, carrier mobility and carrier diffusivity are calculated, and their values are increased as the temperature increases for all samples, but they are higher for PVA/LiCl than that of PVA/AgNO₃. These results are discussed in terms of some obtained parameters such as hopping frequency, free volume and chain mobility. Interestingly, the conduction mechanism was found to be the electronic charge hopping for PVA and PVA/LiCl films, however it was found to be the ionic charge diffusion (n < 0.5) for PVA/AgNO₃ film. It has been predicted that these electrolytic films have a prospective applications in batteries design, temperature sensors, electronic and wearable apparatuses at an affordable cost. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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6 pages, 841 KiB

Open AccessArticle

Pelletizing Analysis on MgO-Fluxed Pellets by DEM

by Fang Long, Fengman Shen, Xin Jiang, Fu Yang, Yulu Zhou and Haiwei An

Crystals 2021, 11(7), 821; https://doi.org/10.3390/cryst11070821 - 15 Jul 2021

Cited by 1 | Viewed by 2232

Abstract

The Discrete Element Method (DEM) was used to analyze the pelletization process of MgO-fluxed pellets. The effects of the charge ratio and rotational speed of the disc pelletizer on the behavior of MgO-fluxed pellets were investigated by using a simulation. The simulation results [...] Read more.

The Discrete Element Method (DEM) was used to analyze the pelletization process of MgO-fluxed pellets. The effects of the charge ratio and rotational speed of the disc pelletizer on the behavior of MgO-fluxed pellets were investigated by using a simulation. The simulation results show that under the condition of a certain tilt angle of the disc pelletizer (the tilt angle is 49°), the suitable parameters of the disc pelletizer are that the charge ratio is 20% and the rotational speedis 0.7 N/NC. This simulation model proposed will be useful to research pellets behavior and for the design of disc pelletizers. Full article

(This article belongs to the Topic Iron Concentrate Particles)

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14 pages, 2361 KiB

Open AccessArticle

Molecular Characterization of the Native (Non-Linked) CD160–HVEM Protein Complex Revealed by Initial Crystallographic Analysis

by Simona Lenhartová, Marek Nemčovič, Radka Šebová, Mário Benko, Dirk M. Zajonc and Ivana Nemčovičová

Crystals 2021, 11(7), 820; https://doi.org/10.3390/cryst11070820 - 15 Jul 2021

Viewed by 3497

Abstract

An increasing number of surface-exposed ligands and receptors acting on immune cells are being considered as a starting point in drug development applications. As they are dedicated to manipulating a wide range of immune responses, accurately predicting their molecular interactions will be necessary [...] Read more.

An increasing number of surface-exposed ligands and receptors acting on immune cells are being considered as a starting point in drug development applications. As they are dedicated to manipulating a wide range of immune responses, accurately predicting their molecular interactions will be necessary for the development of safe and effective therapeutics to enhance immune responses and vaccination. Here, we focused on the characterization of human CD160 and HVEM immune receptors, whose mutual engagement leads to bidirectional signaling (e.g., T cell inhibition, natural killer cell activation or mucosal immunity). In particular, our study reports on the molecule preparation, characterization and initial crystallographic analysis of the CD160–HVEM complex and both HVEM and CD160 in the absence of their binding partner. Despite the importance of the CD160–HVEM immune signaling and its therapeutic relevance, the structural and mechanistic basis underlying CD160–HVEM engagement has some controversial evidence. On one hand, there are studies reporting on the CD160 molecule in monomeric form that was produced by refolding from bacterial cells, or as a covalently linked single-chain complex with its ligand HVEM in insect cells. On the other hand, there are older reports providing evidence on the multimeric form of CD160 that acts directly on immune cells. In our study, the native non-linked CD160–HVEM complex was co-expressed in the baculovirus insect host, purified to homogeneity by anion-exchange chromatography to provide missing evidence of the trimeric form in solution. Its trimeric existence was also confirmed by the initial crystallographic analysis. The native CD160–HVEM complex crystallized in the orthorhombic space group with unit cell parameters that could accommodate one trimeric complex (3:3) in an asymmetric unit, thus providing ample space for the multimeric form. Crystals of the CD160–HVEM complex, CD160 trimer and HVEM monomer (reported in two space groups) diffracted to a minimum Bragg spacing of 2.8, 3.1 and 1.9/2.1 Å resolution, respectively. The obtained data will lead to elucidating the native structure of the complex. Full article

(This article belongs to the Special Issue Advances in Protein Crystallization and Crystallography)

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10 pages, 2675 KiB

Open AccessArticle

Formation Laws of Direction of Fano Line-Shape in a Ring MIM Plasmonic Waveguide Side-Coupled with a Rectangular Resonator and Nano-Sensing Analysis of Multiple Fano Resonances

by Dayong Zhang, Li Cheng and Zuochun Shen

Crystals 2021, 11(7), 819; https://doi.org/10.3390/cryst11070819 - 14 Jul 2021

Cited by 8 | Viewed by 2599

Abstract

Plasmonic MIM (metal-insulator-metal) waveguides based on Fano resonance have been widely researched. However, the regulation of the direction of the line shape of Fano resonance is rarely mentioned. In order to study the regulation of the direction of the Fano line-shape, a Fano [...] Read more.

Plasmonic MIM (metal-insulator-metal) waveguides based on Fano resonance have been widely researched. However, the regulation of the direction of the line shape of Fano resonance is rarely mentioned. In order to study the regulation of the direction of the Fano line-shape, a Fano resonant plasmonic system, which consists of a MIM waveguide coupled with a ring resonator and a rectangle resonator, is proposed and investigated numerically via FEM (finite element method). We find the influencing factors and formation laws of the ‘direction’ of the Fano line-shape, and the optimal condition for the generation of multiple Fano resonances; and the application in refractive index sensing is also well studied. The conclusions can provide a clear theoretical reference for the regulation of the direction of the line shape of Fano resonance and the generation of multi Fano resonances in the designs of plasmonic nanodevices. Full article

(This article belongs to the Special Issue Advances in Middle Infrared Laser Crystals and Its Applications)

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15 pages, 2210 KiB

Open AccessArticle

Predicting Perovskite Performance with Multiple Machine-Learning Algorithms

by Ruoyu Li, Qin Deng, Dong Tian, Daoye Zhu and Bin Lin

Crystals 2021, 11(7), 818; https://doi.org/10.3390/cryst11070818 - 14 Jul 2021

Cited by 19 | Viewed by 4257

Abstract

Perovskites have attracted increasing attention because of their excellent physical and chemical properties in various fields, exhibiting a universal formula of ABO₃ with matching compatible sizes of A-site and B-site cations. In this work, four different prediction models of machine learning algorithms, [...] Read more.

Perovskites have attracted increasing attention because of their excellent physical and chemical properties in various fields, exhibiting a universal formula of ABO₃ with matching compatible sizes of A-site and B-site cations. In this work, four different prediction models of machine learning algorithms, including support vector regression based on radial basis kernel function (SVM-RBF), ridge regression (RR), random forest (RF), and back propagation neural network (BPNN), are established to predict the formation energy, thermodynamic stability, crystal volume, and oxygen vacancy formation energy of perovskite materials. Combined with the fitting diagrams of the predicted values and DFT calculated values, the results show that SVM-RBF has a smaller bias in predicting the crystal volume. RR has a smaller bias in predicting the thermodynamic stability. RF has a smaller bias in predicting the formation energy, crystal volume, and thermodynamic stability. BPNN has a smaller bias in predicting the formation energy, thermodynamic stability, crystal volume, and oxygen vacancy formation energy. Obviously, different machine learning algorithms exhibit different sensitivity to data sample distribution, indicating that we should select different algorithms to predict different performance parameters of perovskite materials. Full article

(This article belongs to the Special Issue Applications of Machine Learning to the Study of Crystalline Materials)

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10 pages, 1773 KiB

Open AccessArticle

Pressure-Tuned Superconducting Dome in Chemically-Substituted κ-(BEDT-TTF)₂Cu₂(CN)₃

by Yohei Saito, Anja Löhle, Atsushi Kawamoto, Andrej Pustogow and Martin Dressel

Crystals 2021, 11(7), 817; https://doi.org/10.3390/cryst11070817 - 14 Jul 2021

Cited by 5 | Viewed by 3356

Abstract

The quantum spin liquid candidate

κ

-(BEDT-TTF)

_{2}

Cu

_{2}

(CN)

_{3}

has been established as the prime example of a genuine Mott insulator that can be tuned across the first-order insulator–metal transition either by chemical substitution or by physical pressure. Here, we [...] Read more.

The quantum spin liquid candidate

κ

-(BEDT-TTF)

_{2}

Cu

_{2}

(CN)

_{3}

has been established as the prime example of a genuine Mott insulator that can be tuned across the first-order insulator–metal transition either by chemical substitution or by physical pressure. Here, we explore the superconducting state that occurs at low temperatures, when both methods are combined, i.e., when

κ

-[(BEDT-TTF)

_{1 - x}

(BEDT-STF)

_{x}

]

_{2}

Cu

_{2}

(CN)

_{3}

is pressurized. We discovered superconductivity for partial BEDT-STF substitution with x = 0.10–0.12 even at ambient pressure, i.e., a superconducting state is realized in the range between a metal and a Mott insulator without magnetic order. Furthermore, we observed the formation of a superconducting dome by pressurizing the substituted crystals; we assigned this novel behavior to disorder emanating from chemical tuning. Full article

(This article belongs to the Special Issue Feature Papers in Organic Crystalline Materials)

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11 pages, 1967 KiB

Open AccessArticle

Effects of Expansive Additives on the Shrinkage Behavior of Coal Gangue Based Alkali Activated Materials

by Xu Gao, Chao Liu, Zhonghe Shui and Rui Yu

Crystals 2021, 11(7), 816; https://doi.org/10.3390/cryst11070816 - 14 Jul 2021

Cited by 13 | Viewed by 3130

Abstract

The suitability of applying shrinkage reducing additives in alkali activated coal gangue-slag composites is discussed in this study. The effect of sulphoaluminate cement (SAC), high performance concrete expansion agent (HCSA) and U-type expansion agent (UEA) on the reaction process, shrinkage behavior, phase composition, [...] Read more.

The suitability of applying shrinkage reducing additives in alkali activated coal gangue-slag composites is discussed in this study. The effect of sulphoaluminate cement (SAC), high performance concrete expansion agent (HCSA) and U-type expansion agent (UEA) on the reaction process, shrinkage behavior, phase composition, microstructure and mechanical properties are evaluated. The results show that the addition of SAC slightly mitigates the early stage reaction process, while HCSA and UEA can either accelerate or inhibit the reaction depending on their dosage. The addition of SAC presents an ideal balance between drying shrinkage reduction and strength increment. As for HCSA and UEA, the shrinkage and mechanical properties are sensitive to their replacement level; excessive dosage would result in remarkable strength reduction and expansion. The specific surface area and average pore size of the hardened matrix are found to be closely related with shrinkage behavior. SAC addition introduces additional hydrotalcite phases within the reaction products, while HCSA and UEA mainly result in the formation of CaCO₃ and Ca(OH)₂. It is concluded that applying expansive additives can be an effective approach in reducing the drying shrinkage of alkali activated coal gangue-slag mixtures, while their type and dosage must be carefully handled. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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20 pages, 3812 KiB

Open AccessArticle

Numerical Simulation of the Effect of Wall-Equiaxed Crystal Density on the Number of Columnar Crystals and the Thickness of an Equiaxed Crystal Layer for Al-4.7%Cu Alloy Ingot Based on 3D LBM-CA Method

by Qi Wang, Yingming Wang, Yan Li, Shijie Zhang and Ri Li

Crystals 2021, 11(7), 815; https://doi.org/10.3390/cryst11070815 - 14 Jul 2021

Cited by 2 | Viewed by 2252

Abstract

In this paper, the lattice Boltzmann–cellular automata (LBM-CA) model with dynamic and static grids was used to study the growth of three-dimensional (3D) multidendrites under directional solidification with random preferred angles. In the static grid, the temperature field, flow field, and solute field [...] Read more.

In this paper, the lattice Boltzmann–cellular automata (LBM-CA) model with dynamic and static grids was used to study the growth of three-dimensional (3D) multidendrites under directional solidification with random preferred angles. In the static grid, the temperature field, flow field, and solute field during solidification were calculated by the LBM method, and in the dynamic grid, each dendrite evolution was calculated based on the CA method at its preferential crystallographic orientation. The coupling of LBM and CA was made by interpolation of the correlation quantities between the two sets of grids. The effects of wall-equiaxed crystal density on the number of columnar crystals and the thickness of the equiaxed crystal layer were studied by this model. The results showed that the density of the wall-equiaxed crystal has little effect on the number of columnar crystals and the thickness of the equiaxed crystal layer. When other conditions were the same, the lower the undercooling, the fewer the columnar crystals, and the thicker the equiaxed layer. In addition, the smaller the heat transfer coefficient, the lower the number of columnar grains, and the smaller the thickness of equiaxed grains. Full article

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56 pages, 5318 KiB

Open AccessReview

The Progress of Additive Engineering for CH₃NH₃PbI₃ Photo-Active Layer in the Context of Perovskite Solar Cells

by Mayuribala Mangrulkar and Keith J. Stevenson

Crystals 2021, 11(7), 814; https://doi.org/10.3390/cryst11070814 - 13 Jul 2021

Cited by 27 | Viewed by 7402

Abstract

Methylammonium lead triiodide (CH₃NH₃PbI₃/MAPbI₃) is the most intensively explored perovskite light-absorbing material for hybrid organic–inorganic perovskite photovoltaics due to its unique optoelectronic properties and advantages. This includes tunable bandgap, a higher absorption coefficient than conventional [...] Read more.

Methylammonium lead triiodide (CH₃NH₃PbI₃/MAPbI₃) is the most intensively explored perovskite light-absorbing material for hybrid organic–inorganic perovskite photovoltaics due to its unique optoelectronic properties and advantages. This includes tunable bandgap, a higher absorption coefficient than conventional materials used in photovoltaics, ease of manufacturing due to solution processability, and low fabrication costs. In addition, the MAPbI₃ absorber layer provides one of the highest open-circuit voltages (V_oc), low V_oc loss/deficit, and low exciton binding energy, resulting in better charge transport with decent charge carrier mobilities and long diffusion lengths of charge carriers, making it a suitable candidate for photovoltaic applications. Unfortunately, MAPbI₃ suffers from poor photochemical stability, which is the main problem to commercialize MAPbI₃-based perovskite solar cells (PSCs). However, researchers frequently adopt additive engineering to overcome the issue of poor stability. Therefore, in this review, we have classified additives as organic and inorganic additives. Organic additives are subclassified based on functional groups associated with N/O/S donor atoms; whereas, inorganic additives are subcategorized as metals and non-metal halide salts. Further, we discussed their role and mechanism in terms of improving the performance and stability of MAPbI₃-based PSCs. In addition, we scrutinized the additive influence on the morphology and optoelectronic properties to gain a deeper understanding of the crosslinking mechanism into the MAPbI₃ framework. Our review aims to help the research community, by providing a glance of the advancement in additive engineering for the MAPbI₃ light-absorbing layer, so that new additives can be designed and experimented with to overcome stability challenges. This, in turn, might pave the way for wide scale commercial use. Full article

(This article belongs to the Special Issue Progress in Advanced Battery Materials)

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13 pages, 6792 KiB

Open AccessArticle

Fabrication of Superhydrophobic Ni-Co-BN Nanocomposite Coatings by Two-Step Jet Electrodeposition

by Hengzheng Li, Yanjiang Li, Guangzhen Zhao, Binhui Zhang and Guang Zhu

Crystals 2021, 11(7), 813; https://doi.org/10.3390/cryst11070813 - 13 Jul 2021

Cited by 5 | Viewed by 2165

Abstract

The stability of hydrophobic surface has an important influence on the application of superhydrophobic function. The destruction of hydrophobic micro-nano structures on the material surface is the main factor leading to the loss of superhydrophobic property. In order to improve the corrosion resistance [...] Read more.

The stability of hydrophobic surface has an important influence on the application of superhydrophobic function. The destruction of hydrophobic micro-nano structures on the material surface is the main factor leading to the loss of superhydrophobic property. In order to improve the corrosion resistance of superhydrophobic surface, Ni-Co-BN nanocomposite coatings with superhydrophobic property were prepared on 45 steel by two-step jet electrodeposition. The surface morphology, water contact angle, and corrosion resistance of the samples were measured and characterized by scanning electron microscope, surface contact angle measuring instrument, and electrochemical workstation. The results of electrochemical analysis show that the superhydrophobic property improved the corrosion resistance of Ni-Co-BN nanocomposite coating. The enhanced corrosion resistance is of great significance to the integrity of the microstructure and the durability of the superhydrophobic function. Full article

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18 pages, 4002 KiB

Open AccessArticle

Co-Crystallization Kinetics of 2:1 Benzoic Acid–Sodium Benzoate Co-Crystal: The Effect of Templating Molecules in a Solution

by Freshsya Zata Lini, Dhanang Edy Pratama and Tu Lee

Crystals 2021, 11(7), 812; https://doi.org/10.3390/cryst11070812 - 12 Jul 2021

Cited by 3 | Viewed by 4590

Abstract

The addition of dissolved templating molecules in crystallization will create “supramolecular assemblies” within the solution, serving as “anchor points” for the solute molecules to nucleate and grow. In this work, nucleation and crystal growth kinetics of 2:1 benzoic acid (HBz)–sodium benzoate (NaBz) co-crystallization [...] Read more.

The addition of dissolved templating molecules in crystallization will create “supramolecular assemblies” within the solution, serving as “anchor points” for the solute molecules to nucleate and grow. In this work, nucleation and crystal growth kinetics of 2:1 benzoic acid (HBz)–sodium benzoate (NaBz) co-crystallization with or without templates in a solution were analyzed by monitoring the concentration of the mother liquor during cooling crystallization. The results showed that the addition of the dissolved 2:1 or 1:1 HBz–NaBz co-crystals as templating molecules could reduce the critical free energy barrier of 2:1 HBz–NaBz co-crystal during its nucleation, but did not significantly affect the order of crystal growth rate. On the other hand, the critical free energy barrier of the nucleation process was increased if dissolved NaBz was used as a templating molecule, while a significant rise in the order of crystal growth rate occurred. The crystal habit obtained from the NaBz-templated system was needle-like, suggesting that sodium–sodium coordination chains of NaBz supramolecular assemblies in the solution phase were responsible for creating elongated crystals. Conversely, a large prismatic crystal habit found in non-templated and 2:1 and 1:1 HBz–NaBz co-crystal-templated systems implied that those templating molecules formed sparsely interconnected supramolecular assemblies in the solution phase. Full article

(This article belongs to the Special Issue Pharmaceutical Crystallization)

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