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Crystals, Volume 11, Issue 8 (August 2021) – 168 articles

Cover Story (view full-size image): Subjected to the spherical curvature and confinement without edges of shells—surrounded by water and also enclosing a droplet of water—the long-range-ordered self-organization in liquid crystals can give rise to many new phenomena. Here, we see the phase transition from nematic to smectic order in a shell where the outer boundary imposes tangential and the inner normal director orientation. The conflicting boundary conditions lead to a nematic phase with precisely two antipodal topological defects, which then seed a well-ordered arrangement of focal conic defects in the smectic phase. The reduced order at the defects produces local reductions in density, leading to unconventional shell orientation if the shell is near-density-matched to the water phases. View this paper
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12 pages, 4209 KiB  
Article
A Study of the Characteristics of Plasma Generated by Infrared Pulse Laser-Induced Fused Silica
by Lixue Wang, Xudong Sun, Congrui Geng, Zequn Zhang and Jixing Cai
Crystals 2021, 11(8), 1009; https://doi.org/10.3390/cryst11081009 - 23 Aug 2021
Cited by 1 | Viewed by 1701
Abstract
When high energy infrared laser pulses are incident on fused silica, the surface of the fused silica is damaged and a laser-induced plasma is produced. Based on the theory of fluid mechanics and gas dynamics, a two-dimensional axisymmetric gas dynamic model was established [...] Read more.
When high energy infrared laser pulses are incident on fused silica, the surface of the fused silica is damaged and a laser-induced plasma is produced. Based on the theory of fluid mechanics and gas dynamics, a two-dimensional axisymmetric gas dynamic model was established to simulate the plasma generation process of fused silica induced by a millisecond pulse laser. The results show that the temperature of the central region irradiated by the laser is the highest, and the plasma is first produced in this region. When the laser energy density is 1.0 × 104 J/cm2 and the pulse width is 0.2 ms, the maximum expansion velocity of the laser-induced plasma is 17.7 m/s. Under the same experimental conditions, the results of the simulation and experiment are in good agreement. With an increase in pulse width, the plasma expansion rate gradually decreases. Full article
(This article belongs to the Special Issue Advances in Middle Infrared Laser Crystals and Its Applications)
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15 pages, 2830 KiB  
Review
Ionic Conductors: Effect of Temperature on Conductivity and Mechanical Properties and Their Interrelations
by Masaru Aniya, Haruhito Sadakuni and Eita Hirano
Crystals 2021, 11(8), 1008; https://doi.org/10.3390/cryst11081008 - 23 Aug 2021
Cited by 6 | Viewed by 3232
Abstract
The ionic transport and the mechanical properties in solids are intimately related. However, few studies have been done to elucidate the background of that relation. With the objective to fill this gap and gain further understanding on the fundamental properties of ion conducting [...] Read more.
The ionic transport and the mechanical properties in solids are intimately related. However, few studies have been done to elucidate the background of that relation. With the objective to fill this gap and gain further understanding on the fundamental properties of ion conducting materials, we are studying systematically the mechanical properties of different materials. In the present study, after showing briefly our previous results obtained in crystalline materials, results regarding the relation between ionic conduction and mechanical properties in superionic glasses is presented. All these results indicate the intimate relation between the mechanical and ionic conduction. The results also indicate that the Grüneisen parameter and the Anderson–Grüneisen parameter of ionic conductors exhibit large temperature dependence and increase with temperature. Full article
(This article belongs to the Special Issue All-Solid-State Batteries)
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5 pages, 2904 KiB  
Communication
Crystallization Behavior in Bi2O3-B2O3-ZnO Glass Braze and Its Application for Joining Ferrite Ceramics at a Relatively Low Temperature
by Wei Guo, Li Fu and Peng He
Crystals 2021, 11(8), 1007; https://doi.org/10.3390/cryst11081007 - 23 Aug 2021
Cited by 2 | Viewed by 1718
Abstract
50Bi2O3-30B2O3-20ZnO (mol.%) glass was designed and prepared in our previous work. On the basis of preliminary work on DSC analysis, the crystallization behavior of the glass was further investigated in the present work. The results [...] Read more.
50Bi2O3-30B2O3-20ZnO (mol.%) glass was designed and prepared in our previous work. On the basis of preliminary work on DSC analysis, the crystallization behavior of the glass was further investigated in the present work. The results showed that Bi38ZnO58 and Bi45BO69 crystals were formed in the glass during the heating process. Subsequently, ferrite ceramics were then brazed at one of the peak temperatures, 551 °C. The results showed that Bi38ZnO58 and Bi45BO69 crystals were formed in the joint domain, and the joint possessed a shear strength value of 76.6 MPa. Full article
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12 pages, 2352 KiB  
Article
Highly Conductive n-Al0.65Ga0.35N Grown by MOCVD Using Low V/III Ratio
by Christian J. Zollner, Yifan Yao, Michael Wang, Feng Wu, Michael Iza, James S. Speck, Steven P. DenBaars and Shuji Nakamura
Crystals 2021, 11(8), 1006; https://doi.org/10.3390/cryst11081006 - 23 Aug 2021
Cited by 13 | Viewed by 2562
Abstract
Highly conductive silicon-doped AlGaN and ohmic contacts are needed for deep-UV LEDs and ultrawide bandgap electronics. We demonstrate improved n-Al0.65Ga0.35N films grown by metal–organic chemical vapor deposition (MOCVD) on sapphire substrates using a low V/III ratio (V/III = 10). [...] Read more.
Highly conductive silicon-doped AlGaN and ohmic contacts are needed for deep-UV LEDs and ultrawide bandgap electronics. We demonstrate improved n-Al0.65Ga0.35N films grown by metal–organic chemical vapor deposition (MOCVD) on sapphire substrates using a low V/III ratio (V/III = 10). A reduced V/III ratio improves repeatability and uniformity by allowing a wider range of silicon precursor flow conditions. AlxGa1−xN:Si with x > 0.5 typically has an electron concentration vs. silicon concentration trend that peaks at a particular “knee” value before dropping sharply as [Si] continues to increase (self-compensation). The Al0.65Ga0.35N:Si grown under the lowest V/III conditions in this study does not show the typical knee behavior, and instead, it has a flat electron concentration trend for [Si] > 3 × 1019 cm−3. Resistivities as low as 4 mΩ-cm were achieved, with corresponding electron mobility of 40 cm2/Vs. AFM and TEM confirm that surface morphology and dislocation density are not degraded by these growth conditions. Furthermore, we report vanadium-based ohmic contacts with a resistivity of 7 × 10−5 Ω-cm2 to AlGaN films grown using a low V/III ratio. Lastly, we use these highly conductive silicon-doped layers to demonstrate a 284 nm UV LED with an operating voltage of 7.99 V at 20 A/cm2, with peak EQE and WPE of 3.5% and 2.7%, respectively. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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16 pages, 771 KiB  
Review
Properties of Barium Cerate-Zirconate Thin Films
by Piotr Winiarz, Monica Susana Campos Covarrubias, Mantas Sriubas, Kristina Bockute, Tadeusz Miruszewski, Wojciech Skubida, Daniel Jaworski, Giedrius Laukaitis and Maria Gazda
Crystals 2021, 11(8), 1005; https://doi.org/10.3390/cryst11081005 - 23 Aug 2021
Cited by 4 | Viewed by 2426
Abstract
In this work, we review several experimental results showing the electrical properties of barium cerate-zirconate thin films and discuss them in view of the possible influence of various factors on their properties. Most of the presented Ba(Ce, Zr, Y)O3 thin films were [...] Read more.
In this work, we review several experimental results showing the electrical properties of barium cerate-zirconate thin films and discuss them in view of the possible influence of various factors on their properties. Most of the presented Ba(Ce, Zr, Y)O3 thin films were formed by the pulsed laser deposition (PLD) technique, however thin films prepared using other methods, like RF magnetron sputtering, electron-beam deposition, powder aerosol deposition (PAD), atomic layer deposition (ALD) and spray deposition are also reported. The electrical properties of the thin films strongly depend on the film microstructure. The influence of the interface layers, space-charge layers, and strain-modified layers on the total conductivity is also essential but in many cases is weaker. Full article
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11 pages, 1208 KiB  
Article
Reuse of Sintered Sludge from Municipal Sewage Treatment Plants for the Production of Lightweight Aggregate Building Mortar
by Changyong Li, Xiaoyan Zhang, Bingxin Zhang, Yunfei Tan and Fenglan Li
Crystals 2021, 11(8), 999; https://doi.org/10.3390/cryst11080999 - 22 Aug 2021
Cited by 5 | Viewed by 1619
Abstract
In recent years, the sludge produced by municipal sewage treatment plants has become an important recyclable resource for producing green building materials. After the systematic processing of incineration and particle formation, the sintered sludge can be processed into fine lightweight aggregate to produce [...] Read more.
In recent years, the sludge produced by municipal sewage treatment plants has become an important recyclable resource for producing green building materials. After the systematic processing of incineration and particle formation, the sintered sludge can be processed into fine lightweight aggregate to produce building mortar with the controlled leaching of heavy metals and radioactivity. In this paper, to increase its economic and environmental benefits, mortar with sintered sludge aggregate was made by cement admixing of fly ash or limestone powder. The water-to-binder ratio was set at three levels—0.82, 0.68, and 0.62—and either flay ash or limestone powder was used to replace equal masses of cement at 10%, 20%, or 30%. Eighteen groups of mortar were studied to evaluate their workability, air content, compressive strength, tensile adhesive strength, dry density, and thermal conductivity. The results indicate that with a proper water-to-binder ratio, and the replacement ratio of fly ash or limestone powder, the mortar can be produced with good workability, consistency, water-retention rate, layering degree, and setting time. The mortar made with sintered sludge lightweight aggregate, designated by the mix-proportion method for conventional lightweight aggregate mortar, did not meet the target strength, although the compressive strength of mortar was no less than 3.0 MPa, which meets the strength grade M2.5. The tensile adhesive strength reached 0.18 MPa. The mortar was super lightweight with a dry density less than 400 kg/m3, and a thermal conductivity within 0.30~0.32 W/(m⋅K). The effects of water-to-binder ratio and replacement ratio of fly ash or limestone powder on the above properties are discussed with test results. The study provides a basis for using sintered sludge lightweight aggregate for building mortar. Full article
(This article belongs to the Special Issue Advances in Green Building Materials and Structural Performances)
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10 pages, 2408 KiB  
Article
Research on Shock Acceleration Limit of an Ultra-Stable Optical Cavity for Space Applications Based on the Finite Element Methodology
by Guanjun Xu, Dongdong Jiao, Long Chen, Linbo Zhang, Jun Liu, Ruifang Dong, Tao Liu and Junbiao Wang
Crystals 2021, 11(8), 998; https://doi.org/10.3390/cryst11080998 - 22 Aug 2021
Cited by 1 | Viewed by 1703
Abstract
Ultra-stable optical cavities (USOCs) as fragile precision instruments have many important applications in space. In order to protect them from being damaged during a rocket launch, we analyzed a USOC by means of finite element methodology. The shock acceleration limits that the USOC [...] Read more.
Ultra-stable optical cavities (USOCs) as fragile precision instruments have many important applications in space. In order to protect them from being damaged during a rocket launch, we analyzed a USOC by means of finite element methodology. The shock acceleration limits that the USOC can withstand in different directions and under various conditions are given. To increase the shock acceleration limit, the midplane thickness and the fixed hole diameter should be selected to be as high as possible. It is worth noting that the launch direction of the USOC should be selected as the horizontal direction, for which the shock acceleration limit that the USOC can withstand is approximately two times that of the vertical direction. In this paper, results provide guidance for the design of USOCs for space applications, especially the design to prevent the damage caused by a shock. The method could then be applied to other space optical cavities, providing a tool to improve the effect of shock at high accelerations. Full article
(This article belongs to the Special Issue Advanced Laser Technology and Applications)
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17 pages, 4123 KiB  
Article
The Polymorphism of 2-Benzoyl-N,N-diethylbenzamide
by Lygia S. de Moraes, Jie Liu, Elumalai Gopi, Ryusei Oketani, Alan R. Kennedy and Yves H. Geerts
Crystals 2021, 11(8), 1004; https://doi.org/10.3390/cryst11081004 - 22 Aug 2021
Cited by 1 | Viewed by 2524
Abstract
The crystal structures of two new polymorphs of 2-benzoyl-N,N-diethylbenzamide were obtained after recrystallization trials with different solvents. The new forms II and III were monoclinic and crystallized in the same space group with similar a, b and c lengths but [...] Read more.
The crystal structures of two new polymorphs of 2-benzoyl-N,N-diethylbenzamide were obtained after recrystallization trials with different solvents. The new forms II and III were monoclinic and crystallized in the same space group with similar a, b and c lengths but different β angles. The forms had no conformation differences within themselves; however, the long-range packing (>two unit cells) was not isostructural. In comparison with the previously published crystal structure, form I, different conformations and packing arrangements were observed. The new form II was thermally characterized and stable at room temperature, when heated up to its melting point and when cooled to −170 °C. Additionally, once form II was re-heated, a fourth form is observed after a phase transition from the monoclinic to the orthorhombic crystal systems, form IV. Full article
(This article belongs to the Special Issue Feature Papers in Organic Crystalline Materials)
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8 pages, 729 KiB  
Article
Effects of the Rare Earth Y on the Structural and Tensile Properties of Mg-based Alloy: A First-Principles Study
by Yan Gao, Chuang Wu, Wenjiang Feng, Yan He, Haisheng He, Jingyu Yang and Xiuyan Chen
Crystals 2021, 11(8), 1003; https://doi.org/10.3390/cryst11081003 - 22 Aug 2021
Cited by 23 | Viewed by 1910
Abstract
In order to investigate the effect of the rare earth element Y on the strengthening potency of magnesium alloys and its strengthening mechanism under tension. In this paper, the solid solution structures with Y atom content of 1.8 at.% and 3.7 at.% were [...] Read more.
In order to investigate the effect of the rare earth element Y on the strengthening potency of magnesium alloys and its strengthening mechanism under tension. In this paper, the solid solution structures with Y atom content of 1.8 at.% and 3.7 at.% were built, respectively, and their cohesive energies and stress-strain curve were calculated in the strain range of 0–20%. The calculation results of the cohesive energies showed that the structure of element Y is more stable with the increase of strains. The calculation results of stress and strain showed that Y element can improve the yield strength and tensile strength of the Mg-based alloy, and the strengthening effect is better when the Y content is 3.7 at.%. Full article
(This article belongs to the Special Issue Crystal Plasticity (Volume II))
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21 pages, 7998 KiB  
Article
Effect of Ultrafine Additives on the Morphology of Cement Hydration Products
by Grigory Yakovlev, Rostislav Drochytka, Gintautas Skripkiūnas, Larisa Urkhanova, Irina Polyanskikh, Igor Pudov, Ekaterina Karpova, Zarina Saidova and Ali E. M. M. Elrefai
Crystals 2021, 11(8), 1002; https://doi.org/10.3390/cryst11081002 - 22 Aug 2021
Cited by 5 | Viewed by 2579
Abstract
The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of [...] Read more.
The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of the research, the modification of ordinary Portland cement was performed by the suspension of multi-walled carbon nanotubes (MWCNTs), carbon black (CB) paste, and silica fume (SF). Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, thermal analysis, and Fourier-transform infrared (FTIR) spectroscopy were used to study cement hydration products. The morphology of hardened cement paste depends on the chemical reactivity of additives, their geometry, and their genesis. The action mechanism of the inert carbon-based additives and pozzolanic silica fume were considered. The cement hydration products formed in the process of modification by both types of ultrafine additives are described. In the case of the modification of cement paste by inert MWCNTs and CB paste, the formation of cement hydration products on their surface without strong adhesion was observed, whereas in the case of the addition of SF separately and together with MWCNTs, the strong adhesion of additives and cement hydration products was noted. Full article
(This article belongs to the Special Issue Advances in Cement-Based Composites and Novel Construction Products)
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22 pages, 6610 KiB  
Article
Development of a Sulfate Resistance Performance Test for Concrete by Tensile Strength Measurements: Determination of Test Conditions
by Johannes Haufe, Anya Vollpracht and Thomas Matschei
Crystals 2021, 11(8), 1001; https://doi.org/10.3390/cryst11081001 - 22 Aug 2021
Cited by 5 | Viewed by 2179
Abstract
Assessing the sulfate resistance of concrete is essential for the use of concrete in sulfate rich environments. A multitude of test methods exists worldwide, showing the relevance of the problem and the difficulty to find a suitable test setup. Testing the relative tensile [...] Read more.
Assessing the sulfate resistance of concrete is essential for the use of concrete in sulfate rich environments. A multitude of test methods exists worldwide, showing the relevance of the problem and the difficulty to find a suitable test setup. Testing the relative tensile strength of ASTM C307 concrete briquette specimens after exposure to a sulfate solution is a new direct method to assess the degree of deterioration. The aim of this study is to develop a new performance test, which considers both the chemical and physical resistance of a specific concrete mix against sulfate attack. In the experimental investigations, the binder type, storage temperature, type and concentration of sulfate solution, and concrete composition were varied, and the remaining tensile strength evaluated to define the test parameters. To gain significantly distinguishable data within nine months of storage, the use of sodium sulfate solution with 6000 mg SO42−/L at 5 °C is proposed. Full article
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16 pages, 3345 KiB  
Article
Microwave Absorption Performance of Single-Layer and Multi-Layer Structures Prepared by CNTs/Fe3O4 Nonwoven Materials
by Rong Zhan, Jiaqiao Zhang, Qiang Gao, Qi Jia, Zhixiang Zhang, Guangyu Zhang and Wenyan Gu
Crystals 2021, 11(8), 1000; https://doi.org/10.3390/cryst11081000 - 22 Aug 2021
Cited by 9 | Viewed by 2491
Abstract
Electromagnetic radiation can cause serious harm to the human body, such as the rise in body temperature and the decrease in immune function. In this study, the carbon nanotubes (CNTs)/Fe3O4 nonwovens were used to prepare wearable flexible absorbing materials. First, [...] Read more.
Electromagnetic radiation can cause serious harm to the human body, such as the rise in body temperature and the decrease in immune function. In this study, the carbon nanotubes (CNTs)/Fe3O4 nonwovens were used to prepare wearable flexible absorbing materials. First, the single-layer absorbing structures were prepared by hot rolling, dipping, and film fabrication, respectively. Then, the single-layer structures were combined to form the multi-layer absorbing structures. By testing and analyzing the absorbing performance of various structures in the X-band frequency range, the optimum combination scheme was found, together with a good reflection loss value of CNTs/Fe3O4 nonwoven material. The experiment results displayed that the single-layer hot-rolled nonwovens modified by CNTs have the best wave absorbing performance. Its minimum reflection loss of −18.59 dB occurred at 10.55 GHz, and the efficient frequency occurred at 8.86–12.40 GHz. The modified film can significantly improve the absorbing performance of multi-layer structures. In addition, the absorbing performance was closely related to both the place where the absorbing film was introduced and the type of absorbing fillers. When the film-forming CNTs (FC) film was located at the bottom layer of the multi-layer structure, the hot rolled CNTs hot rolled mixed reagent film forming CNTs (HC-HM-FC) structure constructed exhibited the best absorbing effects. Its minimum reflection loss can reach −33 dB, and the effective absorbing frequency range covered half of the X-band. Full article
(This article belongs to the Special Issue Synthesis, Properties, and Applications of Functional Nanocomposites)
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10 pages, 1863 KiB  
Article
Binding Strength and Hydrogen Bond Numbers between COVID-19 RBD and HVR of Antibody
by Ryan Taoran Wang, Alex Fan Xu, Qi Zhou, Tinglu Song, Kelvin J. Xu and Gu Xu
Crystals 2021, 11(8), 997; https://doi.org/10.3390/cryst11080997 - 21 Aug 2021
Cited by 4 | Viewed by 2019
Abstract
The global battle against the COVID-19 pandemic relies strongly on the human defense of antibody, which is assumed to bind the antigen’s receptor binding domain (RBD) with its hypervariable region (HVR). Due to the similarity to other viruses such as SARS, however, our [...] Read more.
The global battle against the COVID-19 pandemic relies strongly on the human defense of antibody, which is assumed to bind the antigen’s receptor binding domain (RBD) with its hypervariable region (HVR). Due to the similarity to other viruses such as SARS, however, our understanding of the antibody-virus interaction has been largely limited to the genomic sequencing, which poses serious challenges to containment and rapid serum testing. Based on the physical/chemical nature of the interaction, infrared spectroscopy was employed to reveal the binding disparity, the real cause of the antibody-virus specificity at the molecular level, which is inconceivable to be investigated otherwise. Temperature dependence was discovered in the absorption value from the 1550 cm−1 absorption band, attributed to the hydrogen bonds by carboxyl/amino groups, binding the SARS-CoV-2 spike protein and closely resembled SARS-CoV-2 or SARS-CoV-1 antibodies. The infrared absorption intensity, associated with the number of hydrogen bonds, was found to increase sharply between 27 °C and 31 °C, with the relative absorbance matching the hydrogen bonding numbers of the two antibody types (19 vs. 12) at 37 °C. Meanwhile, the ratio of bonds at 27 °C, calculated by thermodynamic exponentials, produces at least 5% inaccuracy. Beyond genomic sequencing, the temperature dependence, as well as the bond number match at 37 °C between relative absorbance and the hydrogen bonding numbers of the two antibody types, is not only of clinical significance in particular but also as a sample for the physical/chemical understanding of vaccine–antibody interactions in general. Full article
(This article belongs to the Special Issue Biomolecular Crystals Characterization by Powder Diffraction)
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14 pages, 3039 KiB  
Article
High-Performance Flexible Transparent Electrodes Fabricated via Laser Nano-Welding of Silver Nanowires
by Tao Wang, Yinzhou Yan, Liye Zhu, Qian Li, Jing He, Xiaoxia Zhang, Xi Li, Xiaohua Zhang, Yongman Pan and Yue Wang
Crystals 2021, 11(8), 996; https://doi.org/10.3390/cryst11080996 - 21 Aug 2021
Cited by 2 | Viewed by 2431
Abstract
Silver nanowires (Ag-NWs), which possess a high aspect ratio with superior electrical conductivity and transmittance, show great promise as flexible transparent electrodes (FTEs) for future electronics. Unfortunately, the fabrication of Ag-NW conductive networks with low conductivity and high transmittance is a major challenge [...] Read more.
Silver nanowires (Ag-NWs), which possess a high aspect ratio with superior electrical conductivity and transmittance, show great promise as flexible transparent electrodes (FTEs) for future electronics. Unfortunately, the fabrication of Ag-NW conductive networks with low conductivity and high transmittance is a major challenge due to the ohmic contact resistance between Ag-NWs. Here we report a facile method of fabricating high-performance Ag-NW electrodes on flexible substrates. A 532 nm nanosecond pulsed laser is employed to nano-weld the Ag-NW junctions through the energy confinement caused by localized surface plasmon resonance, reducing the sheet resistance and connecting the junctions with the substrate. Additionally, the thermal effect of the pulsed laser on organic substrates can be ignored due to the low energy input and high transparency of the substrate. The fabricated FTEs demonstrate a high transmittance (up to 85.9%) in the visible band, a low sheet resistance of 11.3 Ω/sq, high flexibility and strong durability. The applications of FTEs to 2D materials and LEDs are also explored. The present work points toward a promising new method for fabricating high-performance FTEs for future wearable electronic and optoelectronic devices. Full article
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21 pages, 7954 KiB  
Article
Comparative Study of the Sensitivity of PLA, ABS, PEEK, and PETG’s Mechanical Properties to FDM Printing Process Parameters
by Mohammed Algarni and Sami Ghazali
Crystals 2021, 11(8), 995; https://doi.org/10.3390/cryst11080995 - 21 Aug 2021
Cited by 76 | Viewed by 7968
Abstract
Significant advances in fused deposition modeling (FDM), as well as its myriad applications, have led to its growing prominence among additive manufacturing (AM) technologies. When the technology was first developed, it was used for rapid prototyping to examine and analyze a product in [...] Read more.
Significant advances in fused deposition modeling (FDM), as well as its myriad applications, have led to its growing prominence among additive manufacturing (AM) technologies. When the technology was first developed, it was used for rapid prototyping to examine and analyze a product in the design stage. FDM facilitates rapid production, requires inexpensive tools, and can fabricate complex-shaped parts; it, therefore, became popular and its use widespread. However, various FDM processing parameters have proven to affect the printed part’s mechanical properties to different extents. The values for the printing process parameters are carefully selected based on the part’s application. This study investigates the effects of four process parameters (raster angle, layer thickness, infill percentage, and printing speed) on the mechanical behavior of printed parts that are based on available literature data. These process parameter’s influence on part’s mechanical properties varies depending on the FDM material. The study focuses on four FDM materials: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyether ether ketone (PEEK), and polyethylene terephthalate glycol (PETG). This paper summarizes the state-of-the-art literature to show how sensitive the material’s mechanical properties are to each process parameter. The effect of each parameter on each material was quantified and ranked using analysis of variance (ANOVA). The results show that infill percentage then layer thickness are the most influential process parameter on most of the material’s mechanical properties. In addition, this work identifies gaps in existing studies and highlights opportunities for future research. Full article
(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)
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12 pages, 3580 KiB  
Article
Crystal Plasticity with Micromorphic Regularization in Assessing Scale Dependent Deformation of Polycrystalline Doped Copper Alloys
by Matti Lindroos, Tom Andersson, Jarkko Metsäjoki and Anssi Laukkanen
Crystals 2021, 11(8), 994; https://doi.org/10.3390/cryst11080994 - 21 Aug 2021
Cited by 2 | Viewed by 1981
Abstract
It is planned that doped copper overpacks will be utilized in the spent nuclear fuel repositories in Finland and in Sweden. The assessment of long-term integrity of the material is a matter of importance. Grain structure variations, segregation and any possible manufacturing defects [...] Read more.
It is planned that doped copper overpacks will be utilized in the spent nuclear fuel repositories in Finland and in Sweden. The assessment of long-term integrity of the material is a matter of importance. Grain structure variations, segregation and any possible manufacturing defects in microstructure are relevant in terms of susceptibility to creep and damage from the loading evolution imposed by its operating environment. This work focuses on studying the microstructure level length-scale dependent deformation behavior of the material, of particular significance with respect to accumulation of plasticity over the extensive operational period of the overpacks. The reduced micromorphic crystal plasticity model, which is similar to strain gradient models, is used in this investigation. Firstly, the model’s size dependent plasticity effects are evaluated. Secondly, different microstructural aggregates presenting overpack sections are analyzed. Grain size dependent hardening responses, i.e., Hall-Petch like behavior, can be achieved with the enhanced hardening associated with the micromorphic model at polycrystalline level. It was found that the nominally large grain size in the base material of the overpack shows lower strain hardening potential than the fine grained region of the welded microstructure with stronger strain gradient related hardening effects. Size dependent regularization of strain localization networks is indicated as a desired characteristic of the model. The findings can be utilized to provide an improved basis for modeling the viscoplastic deformation behavior of the studied copper alloy and to assess the microstructural origins of any integrity concerns explicitly by way of full field modeling. Full article
(This article belongs to the Special Issue Micromechanical Modelling and Its Applications to Polycrystals)
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18 pages, 7377 KiB  
Article
An Experimental Study of the Road Performance of Cement Stabilized Coal Gangue
by Junfeng Guan, Meng Lu, Xianhua Yao, Qing Wang, Decai Wang, Biao Yang and Huaizhong Liu
Crystals 2021, 11(8), 993; https://doi.org/10.3390/cryst11080993 - 20 Aug 2021
Cited by 12 | Viewed by 2554
Abstract
The research into the road performance of coal gangue is of great significance for the consumption of coal gangue and reducing pollution. In this paper, the coal gangues were prepared by separation and crushing processes, and their gradations were also optimized. Aiming to [...] Read more.
The research into the road performance of coal gangue is of great significance for the consumption of coal gangue and reducing pollution. In this paper, the coal gangues were prepared by separation and crushing processes, and their gradations were also optimized. Aiming to identify the possible problems of coal gangue as a pavement base, an unconfined compressive strength test, a splitting test, a freeze–thaw test, and a drying shrinkage test of cement stabilized gangue with varying cement amounts were carried out, and the test results were compared and analyzed. The test results showed that the maximum dry density and optimum moisture content (OMC) of the optimized cement stabilized gangue and cement stabilized macadam increased with cement content. The maximum dry density and OMC of cement stabilized macadam were larger than that of cement stabilized gangue with the same cement content. The optimized 7-day unconfined compressive strength of cement stabilized gangue can meet the requirements for a secondary and lower highway base and subbase. The OMC and cement content are the critical factors affecting the compressive strength loss rate of cement stabilized gangue after freeze–thaw cycles. The smaller the OMC of cement stabilized gangue and the larger the cement content, the lower the compressive strength loss rate. With an increase in cement content, the drying shrinkage strain of cement stabilized gangue increased. The results show that a cement content of 4% is optimal for the cement stabilized coal gangue, which can be used for the light traffic base and heavy traffic subbase of class II and below highways. It provides a basis, guide, and reference for the application of coal gangue materials in a high-grade highway base. Full article
(This article belongs to the Special Issue Advances in Sustainable Concrete System)
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8 pages, 2131 KiB  
Article
Heat-Induced Transformation of Luminescent, Size Tuneable, Anisotropic Eu:Lu(OH)2Cl Microparticles to Micro-Structurally Controlled Eu:Lu2O3 Microplatelets
by Madeleine Fellner, Alberto Soppelsa and Alessandro Lauria
Crystals 2021, 11(8), 992; https://doi.org/10.3390/cryst11080992 - 20 Aug 2021
Viewed by 1635
Abstract
Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare [...] Read more.
Synthetic procedures to obtain size and shape-controlled microparticles hold great promise to achieve structural control on the microscale of macroscopic ceramic- or composite-materials. Lutetium oxide is a material relevant for scintillation due to its high density and the possibility to dope with rare earth emitter ions. However, rare earth sesquioxides are challenging to synthesise using bottom-up methods. Therefore, calcination represents an interesting approach to transform lutetium-based particles to corresponding sesquioxides. Here, the controlled solvothermal synthesis of size-tuneable europium doped Lu(OH)2Cl microplatelets and their heat-induced transformation to Eu:Lu2O3 above 800 °C are described. The particles obtained in microwave solvothermal conditions, and their thermal evolution were studied using powder X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical microscopy, thermogravimetric analysis (TGA), luminescence spectroscopy (PL/PLE) and infrared spectroscopy (ATR-IR). The successful transformation of Eu:Lu(OH)2Cl particles into polycrystalline Eu:Lu2O3 microparticles is reported, together with the detailed analysis of their initial and final morphology. Full article
(This article belongs to the Special Issue Optical and Spectroscopic Properties of Rare-Earth-Doped Crystals)
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11 pages, 3984 KiB  
Article
Grain Rotation Accommodated GBS Mechanism for the Ti-6Al-4V Alloy during Superplastic Deformation
by Junzhou Yang and Jianjun Wu
Crystals 2021, 11(8), 991; https://doi.org/10.3390/cryst11080991 - 20 Aug 2021
Cited by 7 | Viewed by 2023
Abstract
An investigation of flow behavior and the deformation mechanism for Ti-6Al-4V alloy during the superplastic deformation process is presented in this paper. Constant strain rate tensile tests were performed at 890–950 °C and strain rates of 10−2, 10−3, and [...] Read more.
An investigation of flow behavior and the deformation mechanism for Ti-6Al-4V alloy during the superplastic deformation process is presented in this paper. Constant strain rate tensile tests were performed at 890–950 °C and strain rates of 10−2, 10−3, and 10−4/s. Then, surface observation by Optical Microscope (OM), Scanning Electron Microscopy (SEM), and Electron Back-scattered Diffraction (EBSD) was applied to obtain the microstructure mechanism. With pole figure maps (PF) for α-phase, obvious texture gradually changed in the main deformation direction. For the titanium alloy, the evolution of texture in deformed samples was attributed to grain rotation (GR). Significant grain rearrangement occurred between grains after deformation. A complete grain rotation accommodated grain boundary sliding (GBS) deformation mechanism is proposed, which can explain texture evolution without grain deformation. Full article
(This article belongs to the Topic Superplastic Forming)
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13 pages, 3144 KiB  
Article
The Natural Breakup Length of a Steady Capillary Jet: Application to Serial Femtosecond Crystallography
by Alfonso M. Gañán-Calvo, Henry N. Chapman, Michael Heymann, Max O. Wiedorn, Juraj Knoska, Braulio Gañán-Riesco, José M. López-Herrera, Francisco Cruz-Mazo, Miguel A. Herrada, José M. Montanero and Saša Bajt
Crystals 2021, 11(8), 990; https://doi.org/10.3390/cryst11080990 - 20 Aug 2021
Cited by 6 | Viewed by 3286
Abstract
One of the most successful ways to introduce samples in Serial Femtosecond Crystallography has been the use of microscopic capillary liquid jets produced by gas flow focusing, whose length-to-diameter ratio and velocity are essential to fulfill the requirements of the high pulse rates [...] Read more.
One of the most successful ways to introduce samples in Serial Femtosecond Crystallography has been the use of microscopic capillary liquid jets produced by gas flow focusing, whose length-to-diameter ratio and velocity are essential to fulfill the requirements of the high pulse rates of current XFELs. In this work, we demonstrate the validity of a classical scaling law with two universal constants to calculate that length as a function of the liquid properties and operating conditions. These constants are determined by fitting the scaling law to a large set of experimental and numerical measurements, including previously published data. Both the experimental and numerical jet lengths conform remarkably well to the proposed scaling law. We show that, while a capillary jet is a globally unstable system to linear perturbations above a critical length, its actual and shorter long-term average intact length is determined by the nonlinear perturbations coming from the jet breakup itself. Therefore, this length is determined solely by the properties of the liquid, the average velocity of the liquid and the flow rate expelled. This confirms the very early observations from Smith and Moss 1917, Proc R Soc Lond A Math Phys Eng, 93, 373, to McCarthy and Molloy 1974, Chem Eng J, 7, 1, among others, while it contrasts with the classical conception of temporal stability that attributes the natural breakup length to the jet birth conditions in the ejector or small interactions with the environment. Full article
(This article belongs to the Special Issue Time Resolved Crystallography)
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12 pages, 2196 KiB  
Article
Complexes of 1,3-Diisobutyl Thiourea with Copper(I), Zinc(II) and Mercury(II): Their Antioxidant and Antibacterial Evaluation
by Adnan Shahzad, Ezzat Khan, Muhammad Said, Gul Shazada Khan, Mian Gul Syed, Awal Noor, Muhammad Zahoor, Riaz Ullah and Ahmed Bari
Crystals 2021, 11(8), 989; https://doi.org/10.3390/cryst11080989 - 20 Aug 2021
Cited by 7 | Viewed by 2323
Abstract
The reaction of 1,3-Diisobutyl thiourea (Tu) with metal salts, {[CuX (X = Cl, I)], [ZnCl2] and [HgI2] in an appropriate stoichiometric ratio afforded the corresponding metal complexes [Tu2CuCl] (1), [Tu3CuI] (2), [Tu2ZnCl2 [...] Read more.
The reaction of 1,3-Diisobutyl thiourea (Tu) with metal salts, {[CuX (X = Cl, I)], [ZnCl2] and [HgI2] in an appropriate stoichiometric ratio afforded the corresponding metal complexes [Tu2CuCl] (1), [Tu3CuI] (2), [Tu2ZnCl2] (3) and [Tu2HgI2] (4) in good yields. The FT-IR data show typically broad signals (3278–3288 cm−1) attributed to the involvement of NH bonds in extensive hydrogen bonding. The structures of complexes were proposed based on a spectroscopic data set. Compounds 1 and 2 were additionally characterized by single-crystal X-ray analysis. Complexes 1–4 were tested for their free radical scavenging efficiency using 2,2-diphenyl-1-picrylhydrazyl free radical (hereafter abbreviated as DPPH). The free radical scavenging activity was a function of decrease in the resultant absorption of DPPH solution after the mixing of an appropriate concentration of the respective complex. The activity of complexes was determined to be dose dependent and increased concentration of the complex resulted in improved antioxidant activity. Compound 1 was found to be the most efficient, with 79.9% free radical scavenging activity. Complexes were also tested for their efficiency against selected strains of bacteria (E. coli, S. flexneri, S. typhi, and P. aeruginosa) and the activities were compared to commercially available standard drug cephradine. Compound 1 was more active against P.aeruginosa (ZI 13.25), while compound 4 was found to be more active against E. coli (ZI 11.0), S. flexneri (ZI 11.2), and S. typhi (ZI 10.5). Full article
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20 pages, 4540 KiB  
Article
Experimental Analysis of Changes in Cement Mortar Containing Oil Palm Boiler Clinker Waste at Elevated Temperatures in Different Cooling Conditions
by Muhammad Firdaus Anuar, Payam Shafigh, Azman Ma’amor, Sumra Yousuf and Farid Wajdi Akashah
Crystals 2021, 11(8), 988; https://doi.org/10.3390/cryst11080988 - 20 Aug 2021
Cited by 4 | Viewed by 1880
Abstract
Changes in cement-based materials containing waste after exposure to elevated temperatures are an important aspect that should be studied in developing sustainable construction materials. Modified cement-based materials obtained using the industrial waste present robust engineering properties can lead to sustainable development. This work [...] Read more.
Changes in cement-based materials containing waste after exposure to elevated temperatures are an important aspect that should be studied in developing sustainable construction materials. Modified cement-based materials obtained using the industrial waste present robust engineering properties can lead to sustainable development. This work evaluated the capacity of oil palm boiler clinker (OPBC) waste that had been produced during the palm oil extraction process as partial and full substitutions for natural sand to produce cement mortar. The mortar materials were cured under three different curing conditions and were then tested at a room temperature of approximately 27 °C and elevated temperatures of 200 °C to 1000 °C using an electric furnace. The specimens were maintained in the electric furnace under maximum temperatures for 2 h and were then cooled down with water or under ambient temperature. The changes in the forms of colour, weight, compressive strength, microstructure, mineralogical composition, and thermal conductivity were investigated. Test results showed that the compressive strength of OPBC mortars was generally higher than the strength of the control mortar after heat exposure. Water cooling exerted less damage to samples compared to air cooling. The results from field emission scanning electron microscopy–energy-dispersive X-ray spectroscopy demonstrated that the mineral composition varied at different temperatures. In conclusion, this work provides an extensive report and can be used as a guide in utilising OPBC as cementitious materials for future cement-based applications. Full article
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13 pages, 17495 KiB  
Article
Growth of SrB4O7 Crystal Fibers along the c-Axis by Micro-Pulling-Down Method
by Ryouta Ishibashi, Harutoshi Asakawa and Ryuichi Komatsu
Crystals 2021, 11(8), 987; https://doi.org/10.3390/cryst11080987 - 20 Aug 2021
Cited by 1 | Viewed by 2463
Abstract
SrB4O7 (SBO) receives much attention as solid-state ultraviolet lasers for micro-machining, photochemical synthesis, and laser spectroscopy. For the application of SBO, the SBO crystals require the control of twinning to amplify the conversion light. We also expected that the inhibitation [...] Read more.
SrB4O7 (SBO) receives much attention as solid-state ultraviolet lasers for micro-machining, photochemical synthesis, and laser spectroscopy. For the application of SBO, the SBO crystals require the control of twinning to amplify the conversion light. We also expected that the inhibitation of the SrB2O4 appearance was essential. Here, we show the growth of SBO crystals along the c-axis through the micro-pulling-down method while alternating the application of electric fields (E). Without the application, single crystals were grown. At E ≧ 400 V/cm no needle domains of SrB2O4 inside SBO crystals existed; however, composition planes were formed and twin boundaries did not appear. In contrast, the inversion of surface morphology emerged, and the convex size was especially large at 1000 V/cm. These results demonstrate that convection is generated perpendicular to the growth front by alternating the application of electric fields. This surface morphological change contradicts the conventional concept of growth through the micro-pulling-down method. The distance from seed crystals vs. grain density plot also showed that the density did not decrease with a sufficient slope. Consequently, we concluded that the selection of the c-axis as growth faces is not fruitful to fabricate twins, and the selection of the growth condition, under which geometrical selection strongly affects, is the key. Full article
(This article belongs to the Special Issue New Trends in Growth Technique of Micro-Pulling-Down Method)
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27 pages, 8630 KiB  
Article
Synthesis, Single Crystal Structural Investigation, Hirshfeld Surface Analysis, Thermoanalysis and Spectroscopic Study of Two New Cu(II) and Co(II) Transition-Metal Complexes
by Rim Boubakri, Mirosław Szybowicz, Mariola Sadej, Sarra Soudani, Frédéric Lefebvre, Valeria Ferretti, Cherif Ben Nasr and Kamel Kaabi
Crystals 2021, 11(8), 986; https://doi.org/10.3390/cryst11080986 - 19 Aug 2021
Cited by 6 | Viewed by 2257
Abstract
Two new complexes, [Cu(dimpyr)2(H2O)2](NO3)2.2H2O (1) and (Hamdimpy)2[CoCl4].H2O (2), with the monodentate ligand 2-amino-6-methylpyrimidin-4-(1H)-one (dimpyr) and the countercation 4-amino-2,6-dimetylpyrimidium (Hamdimpy), [...] Read more.
Two new complexes, [Cu(dimpyr)2(H2O)2](NO3)2.2H2O (1) and (Hamdimpy)2[CoCl4].H2O (2), with the monodentate ligand 2-amino-6-methylpyrimidin-4-(1H)-one (dimpyr) and the countercation 4-amino-2,6-dimetylpyrimidium (Hamdimpy), respectively, were prepared and characterized by single crystal X-ray diffraction, elemental analysis and IR spectroscopy. In (1), the Cu(II) cation is tetracoordinated, in a square plan fashion, by two nitrogen atoms from the pyrimidine ring of the organic ligand and two oxygen atoms of two coordinated water molecules. In the atomic arrangement, the CuO2N2 square planes are interconnected via the formation of O-H…O hydrogen bonds involving both coordinated and free water molecules and NO3 nitrate anions to form inorganic layers parallel to the (a, b) plane at z = (2n + 1)/4. In (2), the central atom Co(II) is four-coordinated in a distorted tetrahedral fashion by four Cl ions. The [CoCl4]2− tetrahedra are arranged parallel to the plane (1¯10) at x = (2n + 1)/2 and the organic cations are grafted between them by establishing with them hydrogen bonds of CH…Cl and NH…Cl types. The vibrational absorption bands were identified by infrared and Raman spectroscopy. Intermolecular interactions were investigated via Hirshfeld surfaces and electronic properties such as HOMO and LUMO energies were derived. The two compounds were characterized by thermal analysis to determine their thermal behavior with respect to temperature. Full article
(This article belongs to the Special Issue Current Advances in Metal Complexes)
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13 pages, 22213 KiB  
Article
Wideband Reflector and Analogue Electromagnetically Induced Reflection in Metamaterials
by Wei Huang, Ningye He, Renxia Ning and Zhenhai Chen
Crystals 2021, 11(8), 985; https://doi.org/10.3390/cryst11080985 - 19 Aug 2021
Viewed by 1635
Abstract
Metamaterials are highly demanded for advanced applications in absorbers, sensors, and filters. However, metamaterial reflectors, especially broadband reflectors, remain challenging. In this paper, we theoretically investigate a wideband metamaterial reflector which consists of cross shaped graphene strips and a silica (SiO2) [...] Read more.
Metamaterials are highly demanded for advanced applications in absorbers, sensors, and filters. However, metamaterial reflectors, especially broadband reflectors, remain challenging. In this paper, we theoretically investigate a wideband metamaterial reflector which consists of cross shaped graphene strips and a silica (SiO2) substrate. The cross shaped graphene strips are coated on the top of the structure, and the cross shape rotated 45° graphene strips are spun on the bottom of it. The calculated reflection can be tuned through length and width of the graphene strips. By comparison, not only broadband reflection but also analogue electromagnetically induced reflection (EIR) can be realized. Moreover, the structure can generate a bi-directional broadband reflection of insensitive polarization. This kind of bi-directional reflector at microwave frequencies is obtained because the top and bottom graphene strip structures are similar. We employ the electric field distribution of the designed structure to elucidate the mechanism of the analogue EIR effect. We further discuss the influence of incident angle on the analogue EIR effect. Such a bi-directional reflector can be potentially applied to a wideband reflector, antenna, and sensor. Full article
(This article belongs to the Special Issue Advances in Metamaterials)
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13 pages, 38242 KiB  
Article
Magnesium Insertion and Related Structural Changes in Spinel-Type Manganese Oxides
by Ana Robba, Elena Tchernychova, Jan Bitenc, Anna Randon-Vitanova and Robert Dominko
Crystals 2021, 11(8), 984; https://doi.org/10.3390/cryst11080984 - 19 Aug 2021
Cited by 1 | Viewed by 1890
Abstract
Commercial LiMn2O4 powder was used as the base material for probing magnesiation, cycling behavior, and structural stability/changes in (MgxLi1-x)Mn2O4 spinel cathodes in aqueous Mg(NO3)2 and non-aqueous Mg(TFSI)2/diglyme and [...] Read more.
Commercial LiMn2O4 powder was used as the base material for probing magnesiation, cycling behavior, and structural stability/changes in (MgxLi1-x)Mn2O4 spinel cathodes in aqueous Mg(NO3)2 and non-aqueous Mg(TFSI)2/diglyme and Mg(Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolytes. Each of the samples was delithiated and, then, magnesiated electrochemically in the corresponding electrolyte. The electrochemical activity of the cathode cycled in aqueous electrolyte showed high reversibility during the oxidation process; however, large polarization and a relatively fast capacity fading were the culprits of the system. Cycling in Mg(TFSI)2/diglyme electrolyte solution resulted in much lower initial specific capacity compared to an aqueous counterpart, as well as a much faster failure. On the other hand, cycling in Mg(HFIP)2 − 2Al(HFIP)3/diglyme electrolyte solution demonstrated excellent cycling performance with very low polarization in the first cycles. The observed voltages for this system were near theoretical values for the Mg insertion. Although the electrochemical measurements suggest reversible magnesiation, detailed structural and analytical STEM investigation revealed the differences in the atomic structure and Mn valence of all three cathode samples upon cycling. The electrolytes’ influence on the structural rearrangement during Mg insertion is discussed for each of the three systems. Full article
(This article belongs to the Special Issue Lithium Transition Metal Oxides)
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11 pages, 1580 KiB  
Article
New Metakaolin-Based Geopolymers with the Addition of Different Types of Waste Stone Powder
by Ivana Perná, Martina Novotná, Daniela Řimnáčová and Monika Šupová
Crystals 2021, 11(8), 983; https://doi.org/10.3390/cryst11080983 - 19 Aug 2021
Cited by 11 | Viewed by 1912
Abstract
The search for new alternative raw materials and their subsequent use supports the sustainability of natural resources. This article describes the use of waste stone powder (WSP) in geopolymer synthesis. Five different types of WSP (feldspar, limestone, marlstone, dolomite, marble) were comprehensively characterized [...] Read more.
The search for new alternative raw materials and their subsequent use supports the sustainability of natural resources. This article describes the use of waste stone powder (WSP) in geopolymer synthesis. Five different types of WSP (feldspar, limestone, marlstone, dolomite, marble) were comprehensively characterized and their influence on the resulting properties (especially mechanical and textural properties, setting time and structure) of metakaolin-based geopolymer composites was investigated. Their comparison with a geopolymer composite containing only quartz sand has revealed that WSP additions have a small but positive effect on the mechanical or textural properties of geopolymers. Moreover, setting time measurements have shown that waste stone powders can be used as an accelerator of geopolymer reaction solidification. The results demonstrated that the mentioned types of WSP, previously landfilled, can be used for the preparation of geopolymers. This can help reduce the environmental burden. Full article
(This article belongs to the Special Issue Geopolymer Composites)
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12 pages, 3630 KiB  
Article
An N4-Tetradentate Hydrazone Ligand That Binds in a Neutral, Mono- and Bisdeprotonated Form to Iron(II) and Zinc(II) Metal Ions
by Devaraj Pandiarajan, Thomas Fox and Bernhard Spingler
Crystals 2021, 11(8), 982; https://doi.org/10.3390/cryst11080982 - 19 Aug 2021
Cited by 2 | Viewed by 2102
Abstract
The coordination chemistry of butane-2,3-dione bis (2′-pyridylhydrazone) towards the divalent first-row transition metals zinc and iron has been explored. Depending upon the conditions, the ligand in the six complexes was found to be either neutral, mono, or doubly deprotonated. The zinc(II) and iron(II) [...] Read more.
The coordination chemistry of butane-2,3-dione bis (2′-pyridylhydrazone) towards the divalent first-row transition metals zinc and iron has been explored. Depending upon the conditions, the ligand in the six complexes was found to be either neutral, mono, or doubly deprotonated. The zinc(II) and iron(II) complexes were fully characterized by elemental analysis, mass spectrometry, and X-ray diffraction methods. Full article
(This article belongs to the Special Issue New Bioinorganic Compounds)
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12 pages, 5579 KiB  
Article
Synthesis of Ag Loaded ZnO/BiOCl with High Photocatalytic Performance for the Removal of Antibiotic Pollutants
by Zhihao Zhang, Amir Zada, Nan Cui, Naiwen Liu, Minghui Liu, Yuzhuo Yang, Delong Jiang, Jianhui Jiang and Shuyuan Liu
Crystals 2021, 11(8), 981; https://doi.org/10.3390/cryst11080981 - 18 Aug 2021
Cited by 27 | Viewed by 2531
Abstract
Ag@ZnO/BiOCl composites were successfully prepared by in situ precipitation and hydrothermal synthesis and used for the photocatalytic degradation of tetracycline hydrochloride antibiotics. An enhanced photodegradation efficiency was detected after loading Ag nanoparticles, which is attributed to the surface plasmon resonance effect. The optimized [...] Read more.
Ag@ZnO/BiOCl composites were successfully prepared by in situ precipitation and hydrothermal synthesis and used for the photocatalytic degradation of tetracycline hydrochloride antibiotics. An enhanced photodegradation efficiency was detected after loading Ag nanoparticles, which is attributed to the surface plasmon resonance effect. The optimized sample containing 4% Ag showed 80.4% degradation efficiency in 80 min, which is 2.1 and 1.9 times higher than those of ZnO and ZnO/BiOCl, respectively. The major degrading species involved in the photocatalytic process were detected to be super oxide anions and holes. Based on the obtained results, a possible charge transfer and degradation mechanism has been proposed. This study shows that Ag@ZnO/BiOCl catalyst has a good potential for photodegradation of organic pollutants in water. Full article
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9 pages, 2955 KiB  
Article
RF-Characterization of HZO Thin Film Varactors
by Sukhrob Abdulazhanov, Quang Huy Le, Dang Khoa Huynh, Defu Wang, Maximilian Lederer, Ricardo Olivo, Konstantin Mertens, Jennifer Emara, Thomas Kämpfe and Gerald Gerlach
Crystals 2021, 11(8), 980; https://doi.org/10.3390/cryst11080980 - 18 Aug 2021
Cited by 5 | Viewed by 2546
Abstract
A microwave characterization at UHF band of a ferroelectric hafnium zirconium oxide metal-ferroelectric-metal (MFM) capacitors for varactor applications has been performed. By using an impedance reflectivity method, a complex dielectric permittivity was obtained at frequencies up to 500 MHz. Ferroelectric Hf0.5Zr [...] Read more.
A microwave characterization at UHF band of a ferroelectric hafnium zirconium oxide metal-ferroelectric-metal (MFM) capacitors for varactor applications has been performed. By using an impedance reflectivity method, a complex dielectric permittivity was obtained at frequencies up to 500 MHz. Ferroelectric Hf0.5Zr0.5O2 of 10 nm thickness has demonstrated a stable permittivity switching in the whole frequency range. A constant increase of the calculated dielectric loss is observed, which is shown to be an effect of electric field distribution on highly resistive titanium nitride (TiN) thin film electrodes. The C-V characteristics of a “butterfly” shape was also extracted, where the varactors exhibited a reduction of capacitance tunability from 18.6% at 10 MHz to 15.4% at 500 MHz. Full article
(This article belongs to the Special Issue Ferroelectrics Materials for Microwave Devices)
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