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Crystals, Volume 11, Issue 3 (March 2021) – 100 articles

Cover Story (view full-size image): Electrons interact strongly with matter, which makes it possible to obtain high-resolution electron diffraction data from nano- and submicron-sized crystals. Using electron beam as a radiation source in a transmission electron microscope (TEM), ab initio structure determination can be conducted from crystals that are 6–7 orders of magnitude smaller than using X-rays. The rapid development of three-dimensional electron diffraction (3DED) techniques has attracted increasing interests in the field of metal-organic frameworks (MOFs), where it is often difficult to obtain large and high-quality crystals for single-crystal X-ray diffraction. View this paper
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17 pages, 4764 KiB  
Article
Processability and Optimization of Laser Parameters for Densification of Hypereutectic Al–Fe Binary Alloy Manufactured by Laser Powder Bed Fusion
by Wenyuan Wang, Naoki Takata, Asuka Suzuki, Makoto Kobashi and Masaki Kato
Crystals 2021, 11(3), 320; https://doi.org/10.3390/cryst11030320 - 23 Mar 2021
Cited by 9 | Viewed by 2839
Abstract
Centimeter-sized samples of hypereutectic Al–15 mass% Fe alloy were manufactured by a laser powder bed fusion (L-PBF) process while systematically varying laser power (P) and scan speed (v). The effects on relative density and melt pool depth of L-PBF-manufactured [...] Read more.
Centimeter-sized samples of hypereutectic Al–15 mass% Fe alloy were manufactured by a laser powder bed fusion (L-PBF) process while systematically varying laser power (P) and scan speed (v). The effects on relative density and melt pool depth of L-PBF-manufactured samples were investigated. In comparison with other Al alloys, a small laser process window of P = 77–128 W and v = 0.4–0.8 ms−1 was found for manufacturing macroscopically crack-free samples. A higher v and P led to the creation of macroscopic cracks propagating parallel to the powder-bed plane. These cracks preferentially propagated along the melt pool boundaries decorated with brittle θ-Al13Fe4 phase, resulting in low L-PBF processability of Al–15%Fe alloy. The deposited energy density model (using P·v−1/2) would be useful for identifying the optimum L-PBF process conditions towards densification of Al–15%Fe alloy samples, in comparison with the volumetric energy density (using P·v−1), however, the validity of the model was reduced for this alloy in comparison with other alloys with high thermal conductivities. This is likely due to inhomogeneous microstructures having numerous coarsened θ–Al13Fe4 phases localized at melt pool boundaries. These results provide insights into achieving sufficient L-PBF processability for manufacturing dense Al–Fe binary alloy samples. Full article
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22 pages, 7394 KiB  
Article
Synthesis and Characterization of Potent and Safe Ciprofloxacin-Loaded Ag/TiO2/CS Nanohybrid against Mastitis Causing E. coli
by Naheed Zafar, Bushra Uzair, Muhammad Bilal Khan Niazi, Ghufrana Samin, Asma Bano, Nazia Jamil, Waqar-Un-Nisa, Shamaila Sajjad and Farid Menaa
Crystals 2021, 11(3), 319; https://doi.org/10.3390/cryst11030319 - 23 Mar 2021
Cited by 10 | Viewed by 3426
Abstract
To improve the efficacy of existing classes of antibiotics (ciprofloxacin), allow dose reduction, and minimize related toxicity, this study was executed because new target-oriented livestock antimicrobials are greatly needed to battle infections caused by multidrug-resistant (MDR) strains. The present study aims to green [...] Read more.
To improve the efficacy of existing classes of antibiotics (ciprofloxacin), allow dose reduction, and minimize related toxicity, this study was executed because new target-oriented livestock antimicrobials are greatly needed to battle infections caused by multidrug-resistant (MDR) strains. The present study aims to green synthesize a biocompatible nanohybrid of ciprofloxacin (CIP)-Ag/TiO2/chitosan (CS). Silver and titanium nanoparticles were green synthesized using Moringa concanensis leaves extract. The incorporation of silver (Ag) nanoparticles onto the surface of titanium oxide nanoparticles (TiO2NPs) was done by the wet chemical impregnation method, while the encapsulation of chitosan (CS) around Ag/TiO2 conjugated with ciprofloxacin (CIP) was done by the ionic gelation method. The synthesized nanohybrid (CIP-Ag/TiO2/CS) was characterized using standard techniques. The antibacterial potential, killing kinetics, cytotoxicity, drug release profile, and minimum inhibitory concentration (MIC) were determined. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) revealed spherical agglomerated nanoparticles (NPs) of Ag/TiO2 with particle sizes of 47–75 nm, and those of the CIP-Ag/TiO2/CS nanohybrid were in range of 20–80 nm. X-ray diffractometer (XRD) patterns of the hetero system transmitted diffraction peaks of anatase phase of TiO2 and centered cubic metallic Ag crystals. Fourier Transform Infrared spectroscopy (FTIR) confirmed the Ti-O-Ag linkage in the nanohybrid. The zeta potential of CIP-Ag/TiO2/CS nanohybrid was found (67.45 ± 1.8 mV), suggesting stable nanodispersion. The MIC of CIP-Ag/TiO2/CS was 0.0512 μg/mL, which is much lower than the reference value recorded by the global CLSI system (Clinical Laboratory Standards Institute). The CIP-Ag/TiO2/CS nanohybrid was found to be effective against mastitis causing MDR E. coli; killing kinetics showed an excellent reduction of E. coli cells at 6 h of treatment. Flow cytometry further confirmed antibacterial potential by computing 67.87% late apoptosis feature at 6 h of treatment; antibiotic release kinetic revealed a sustained release of CIP. FESEM and TEM confirmed the structural damages in MDR E. coli (multidrug-resistant Escherichia coli). The CIP-Ag/TiO2/CS nanohybrid was found to be biocompatible, as more than 93.08% of bovine mammary gland epithelial cells remained viable. The results provide the biological backing for the development of nanohybrid antibiotics at a lower MIC value to treat infectious diseases of cattle and improve the efficacy of existing classes of antibiotics by conjugation with nanoparticles. Full article
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12 pages, 2339 KiB  
Article
Microtubules as One-Dimensional Crystals: Is Crystal-Like Structure the Key to the Information Processing of Living Systems?
by Noemí Sanchez-Castro, Martha Alicia Palomino-Ovando, Pushpendra Singh, Satyajit Sahu, Miller Toledo-Solano, Jocelyn Faubert, J. Eduardo Lugo, Anirban Bandyopadhyay and Kanad Ray
Crystals 2021, 11(3), 318; https://doi.org/10.3390/cryst11030318 - 23 Mar 2021
Cited by 2 | Viewed by 3357
Abstract
Each tubulin protein molecule on the cylindrical surface of a microtubule, a fundamental element of the cytoskeleton, acts as a unit cell of a crystal sensor. Electromagnetic sensing enables the 2D surface of microtubule to act as a crystal or a collective electromagnetic [...] Read more.
Each tubulin protein molecule on the cylindrical surface of a microtubule, a fundamental element of the cytoskeleton, acts as a unit cell of a crystal sensor. Electromagnetic sensing enables the 2D surface of microtubule to act as a crystal or a collective electromagnetic signal processing system. We propose a model in which each tubulin dimer acts as the period of a one-dimensional crystal with effective electrical impedance related to its molecular structure. Based on the mathematical crystal theory with one-dimensional translational symmetry, we simulated the electrical transport properties of the signal across the microtubule length and compared it to our single microtubule experimental results. The agreement between theory and experiment suggests that one of the most essential components of any Eukaryotic cell acts as a one-dimensional crystal. Full article
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12 pages, 1748 KiB  
Article
Formation of Interstitial Dislocation Loops by Irradiation in Alpha-Iron under Strain: A Molecular Dynamics Study
by Mohammad Bany Salman, Mehmet Emin Kilic and Mosab Jaser Banisalman
Crystals 2021, 11(3), 317; https://doi.org/10.3390/cryst11030317 - 23 Mar 2021
Cited by 4 | Viewed by 2377
Abstract
The present work reports the formation of an interstitial dislocation loop with a lower primary knock-on atom (PKA) energy in alpha-iron under strain conditions by the use of molecular dynamics simulation. The study was conducted using a PKA energy of 1~10 keV and [...] Read more.
The present work reports the formation of an interstitial dislocation loop with a lower primary knock-on atom (PKA) energy in alpha-iron under strain conditions by the use of molecular dynamics simulation. The study was conducted using a PKA energy of 1~10 keV and hydro-static strain from −1.4 to 1.6%. The application of 1.6% hydrostatic strain results in the formation of ½<111> dislocation loop with a low PKA of 3 keV. This result was associated with a threshold displacement energy decrement when moving from compression to tension strain, which resulted in more Frenkel pairs initiated at peak time. Furthermore, many of the initiated defects were energetically favorable by 2 eV in the form of the interstitial dislocation loop rather than a mono defect. Full article
(This article belongs to the Special Issue Strain Reversal in Metals and Alloys: Origins and Consequences)
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15 pages, 882 KiB  
Review
Molecular Simulation of Crystallisation in External Electric Fields: A Review
by Niall J. English
Crystals 2021, 11(3), 316; https://doi.org/10.3390/cryst11030316 - 22 Mar 2021
Cited by 3 | Viewed by 2811
Abstract
Elucidating the underlying mechanisms of molecular solidification in both homo- and hetero-geneous systems is of paramount importance for a large swathe of natural phenomena (whether on Earth or throughout the Universe), as well as a whole litany of industrial processes. One lesser-studied aspect [...] Read more.
Elucidating the underlying mechanisms of molecular solidification in both homo- and hetero-geneous systems is of paramount importance for a large swathe of natural phenomena (whether on Earth or throughout the Universe), as well as a whole litany of industrial processes. One lesser-studied aspect of these disorder-order transitions is the effect of external applied fields, shifting both thermodynamic driving forces and underlying kinetics, and, indeed, fundamental mechanisms themselves. Perhaps this is nowhere more apparent than in the case of externally-applied electric fields, where there has been a gradually increasing number of reports in recent years of electro-manipulated crystallisation imparted by such electric fields. Drawing motivations from both natural phenomena, state-of-the-art experiments and, indeed, industrial applications, this review focusses on how non-equilibrium molecular simulation has helped to elucidate crystallisation phenomena from a microscopic perspective, as well as offering an important, predictive molecular-design approach with which to further refine in-field-crystallisation operations. Full article
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12 pages, 2498 KiB  
Review
Real-Time Identification of Oxygen Vacancy Centers in LiNbO3 and SrTiO3 during Irradiation with High Energy Particles
by Miguel L. Crespillo, Joseph T. Graham, Fernando Agulló-López, Yanwen Zhang and William J. Weber
Crystals 2021, 11(3), 315; https://doi.org/10.3390/cryst11030315 - 22 Mar 2021
Cited by 11 | Viewed by 3754
Abstract
Oxygen vacancies are known to play a central role in the optoelectronic properties of oxide perovskites. A detailed description of the exact mechanisms by which oxygen vacancies govern such properties, however, is still quite incomplete. The unambiguous identification of oxygen vacancies has been [...] Read more.
Oxygen vacancies are known to play a central role in the optoelectronic properties of oxide perovskites. A detailed description of the exact mechanisms by which oxygen vacancies govern such properties, however, is still quite incomplete. The unambiguous identification of oxygen vacancies has been a subject of intense discussion. Interest in oxygen vacancies is not purely academic. Precise control of oxygen vacancies has potential technological benefits in optoelectronic devices. In this review paper, we focus our attention on the generation of oxygen vacancies by irradiation with high energy particles. Irradiation constitutes an efficient and reliable strategy to introduce, monitor, and characterize oxygen vacancies. Unfortunately, this technique has been underexploited despite its demonstrated advantages. This review revisits the main experimental results that have been obtained for oxygen vacancy centers (a) under high energy electron irradiation (100 keV–1 MeV) in LiNbO3, and (b) during irradiation with high-energy heavy (1–20 MeV) ions in SrTiO3. In both cases, the experiments have used real-time and in situ optical detection. Moreover, the present paper discusses the obtained results in relation to present knowledge from both the experimental and theoretical perspectives. Our view is that a consistent picture is now emerging on the structure and relevant optical features (absorption and emission spectra) of these centers. One key aspect of the topic pertains to the generation of self-trapped electrons as small polarons by irradiation of the crystal lattice and their stabilization by oxygen vacancies. What has been learned by observing the interplay between polarons and vacancies has inspired new models for color centers in dielectric crystals, models which represent an advancement from the early models of color centers in alkali halides and simple oxides. The topic discussed in this review is particularly useful to better understand the complex effects of different types of radiation on the defect structure of those materials, therefore providing relevant clues for nuclear engineering applications. Full article
(This article belongs to the Special Issue New Trends in Lithium Niobate: From Bulk to Nanocrystals)
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15 pages, 5890 KiB  
Article
Effect of Bi Content on the Microstructure and Mechanical Performance of Sn-1Ag-0.5Cu Solder Alloy
by Heba Y. Zahran, Ashraf S. Mahmoud and Alaa F. Abd El-Rehim
Crystals 2021, 11(3), 314; https://doi.org/10.3390/cryst11030314 - 22 Mar 2021
Cited by 6 | Viewed by 2583
Abstract
The purpose of this work is to explore the impact of 0.5, 1.5, 2.5 and 3.5 wt.% Bi additions on the microstructure and mechanical performance of Sn-1Ag-0.5Cu solder alloy. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were utilized to examine the microstructure [...] Read more.
The purpose of this work is to explore the impact of 0.5, 1.5, 2.5 and 3.5 wt.% Bi additions on the microstructure and mechanical performance of Sn-1Ag-0.5Cu solder alloy. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were utilized to examine the microstructure of the present solders. Creep measurements have been used for the preliminary assessment of mechanical properties. The steady-state creep rate, έst, diminished as the Bi’s concentration increased and reached 2.5 wt.%, with this trend altering above this point. Furthermore, increasing the aging or testing temperature caused the έst values to increment for all the investigated solders. έst variations with different Bi content and aging temperature were observed by examining the Sn-Ag-Cu solders’ structural evolutions. The mean value of the activation energy of all investigated solder alloys was found to be ∼52 kJ/mol. This value is appropriate to that quoted for the dislocation climb through the core diffusion as the dominant operating mechanism. The XRD findings supported the microstructure and lattice parameters variations with both aging temperatures and bismuth concentrations. Full article
(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)
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11 pages, 4855 KiB  
Article
Transport and Dielectric Properties of Mechanosynthesized La2/3Cu3Ti4O12 Ceramics
by Mohamad M. Ahmad, Hicham Mahfoz Kotb, Celin Joseph, Shalendra Kumar and Adil Alshoaibi
Crystals 2021, 11(3), 313; https://doi.org/10.3390/cryst11030313 - 22 Mar 2021
Cited by 14 | Viewed by 1748
Abstract
La2/3Cu3Ti4O12 (LCTO) powder has been synthesized by the mechanochemical milling technique. The pelletized powder was conventionally sintered for 10 h at a temperature range of 975–1025 °C, which is a lower temperature process compared to the [...] Read more.
La2/3Cu3Ti4O12 (LCTO) powder has been synthesized by the mechanochemical milling technique. The pelletized powder was conventionally sintered for 10 h at a temperature range of 975–1025 °C, which is a lower temperature process compared to the standard solid-state reaction. X-ray diffraction analysis revealed a cubic phase for the current LCTO ceramics. The grain size of the sintered ceramics was found to increase from 1.5 ± 0.5 to 2.3 ± 0.5 μm with an increase in sintering temperature from 975 to 1025 °C. The impedance results show that the grain conductivity is more than three orders of magnitude larger than the grain boundary conductivity for LCTO ceramics. All the samples showed a giant dielectric constant (1.7 × 103–3.4 × 103) and dielectric loss (0.09–0.17) at 300 K and 10 kHz. The giant dielectric constant of the current samples was attributed to the effect of internal barrier layer capacitances due to their electrically inhomogeneous structure. Full article
(This article belongs to the Special Issue Advanced Functional Oxide Ceramics)
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10 pages, 2282 KiB  
Article
Simultaneous Multi-Bragg Peak Coherent X-ray Diffraction Imaging
by Florian Lauraux, Stéphane Labat, Sarah Yehya, Marie-Ingrid Richard, Steven J. Leake, Tao Zhou, Jean-Sébastien Micha, Odile Robach, Oleg Kovalenko, Eugen Rabkin, Tobias U. Schülli, Olivier Thomas and Thomas W. Cornelius
Crystals 2021, 11(3), 312; https://doi.org/10.3390/cryst11030312 - 22 Mar 2021
Cited by 7 | Viewed by 2779
Abstract
The simultaneous measurement of two Bragg reflections by Bragg coherent X-ray diffraction is demonstrated on a twinned Au crystal, which was prepared by the solid-state dewetting of a 30 nm thin gold film on a sapphire substrate. The crystal was oriented on a [...] Read more.
The simultaneous measurement of two Bragg reflections by Bragg coherent X-ray diffraction is demonstrated on a twinned Au crystal, which was prepared by the solid-state dewetting of a 30 nm thin gold film on a sapphire substrate. The crystal was oriented on a goniometer so that two lattice planes fulfill the Bragg condition at the same time. The Au 111 and Au 200 Bragg peaks were measured simultaneously by scanning the energy of the incident X-ray beam and recording the diffraction patterns with two two-dimensional detectors. While the former Bragg reflection is not sensitive to the twin boundary, which is oriented parallel to the crystal–substrate interface, the latter reflection is only sensitive to one part of the crystal. The volume ratio between the two parts of the twinned crystal is about 1:9, which is also confirmed by Laue microdiffraction of the same crystal. The parallel measurement of multiple Bragg reflections is essential for future in situ and operando studies, which are so far limited to either a single Bragg reflection or several in series, to facilitate the precise monitoring of both the strain field and defects during the application of external stimuli. Full article
(This article belongs to the Special Issue Coherent X-ray Scattering)
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11 pages, 4399 KiB  
Article
Comparison of Mode Shapes of Carbon-Fiber-Reinforced Plastic Material Considering Carbon Fiber Direction
by Chan-Jung Kim
Crystals 2021, 11(3), 311; https://doi.org/10.3390/cryst11030311 - 22 Mar 2021
Cited by 10 | Viewed by 2294
Abstract
Previous studies have demonstrated the sensitivity of the dynamic behavior of carbon-fiber-reinforced plastic (CFRP) material over the carbon fiber direction by performing uniaxial excitation tests on a simple specimen. However, the variations in modal parameters (damping coefficient and resonance frequency) over the direction [...] Read more.
Previous studies have demonstrated the sensitivity of the dynamic behavior of carbon-fiber-reinforced plastic (CFRP) material over the carbon fiber direction by performing uniaxial excitation tests on a simple specimen. However, the variations in modal parameters (damping coefficient and resonance frequency) over the direction of carbon fiber have been partially explained in previous studies because all modal parameters have only been calculated using the representative summed frequency response function without modal analysis. In this study, the dynamic behavior of CFRP specimens was identified from experimental modal analysis and compared five CFRP specimens (carbon fiber direction: 0°, 30°, 45°, 60°, and 90°) and an isotropic SCS13A specimen using the modal assurance criterion. The first four modes were derived from the SCS13A specimen; they were used as reference modes after verifying with the analysis results from a finite element model. Most of the four mode shapes were found in all CFRP specimens, and the similarity increased when the carbon fiber direction was more than 45°. The anisotropic nature was dominant in three cases of carbon fiber, from 0° to 45°, and the most sensitive case was found in Specimen #3. Full article
(This article belongs to the Special Issue Dynamic Behavior of Carbon Fiber Related Materials)
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25 pages, 962 KiB  
Review
Application of Fundamental Techniques for Physicochemical Characterizations to Understand Post-Formulation Performance of Pharmaceutical Nanocrystalline Materials
by Bwalya A. Witika, Marique Aucamp, Larry L. Mweetwa and Pedzisai A. Makoni
Crystals 2021, 11(3), 310; https://doi.org/10.3390/cryst11030310 - 21 Mar 2021
Cited by 4 | Viewed by 2998
Abstract
Nanocrystalline materials (NCM, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from drug delivery and electronics to optics. Drug nanocrystals (NC) and nano co-crystals (NCC) are examples of NCM with fascinating physicochemical properties and have [...] Read more.
Nanocrystalline materials (NCM, i.e., crystalline nanoparticles) have become an important class of materials with great potential for applications ranging from drug delivery and electronics to optics. Drug nanocrystals (NC) and nano co-crystals (NCC) are examples of NCM with fascinating physicochemical properties and have attracted significant attention in drug delivery. NCM are categorized by advantageous properties, such as high drug-loading efficiency, good long-term physical stability, steady and predictable drug release, and long systemic circulation time. These properties make them excellent formulations for the efficient delivery of a variety of active pharmaceutical ingredients (API). In this review, we summarize the recent advances in drug NCM-based therapy options. Currently, there are three main methods to synthesize drug NCM, including top-down, bottom-up, and combination methods. The fundamental characterization methods of drug NCM are elaborated. Furthermore, the applications of these characterizations and their implications on the post-formulation performance of NCM are introduced. Full article
(This article belongs to the Special Issue Pharmaceutical Crystals (Volume II))
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19 pages, 5985 KiB  
Article
Numerical Simulation of Microstructure Evolution in Solidification Process of Ferritic Stainless Steel with Cellular Automaton
by Wenli Wang, Qin Shi, Xu Zhu and Yinhua Liu
Crystals 2021, 11(3), 309; https://doi.org/10.3390/cryst11030309 - 21 Mar 2021
Cited by 3 | Viewed by 2872
Abstract
In order to study the basic principles of vibration-excited liquid metal nucleation technology, a coupled model to connect the temperature field calculated by ANSYS Fluent and the dendritic growth simulated by cellular automaton (CA) algorithm was proposed. A two-dimensional CA model for dendrite [...] Read more.
In order to study the basic principles of vibration-excited liquid metal nucleation technology, a coupled model to connect the temperature field calculated by ANSYS Fluent and the dendritic growth simulated by cellular automaton (CA) algorithm was proposed. A two-dimensional CA model for dendrite growth controlled by solute diffusion and local curvature effects with random zigzag capture rule was developed. The proposed model was applied to simulate the temporal evolution of solidification microstructures under different degrees of surface undercooling and vibration frequency of the crystal nucleus generator conditions. The simulation results showed that the predicted columnar dendrites regions were more developed, the ratio of interior equiaxed dendrite reduced and the size of dendrites increased with the increase of the surface undercooling degrees on the crystal nucleus generator. It was caused by a large temperature gradient formed in the melt. The columnar-to-equiaxed transition (CET) was promoted, and the refined grains and homogenized microstructure were also achieved at the high vibration frequency of the crystal nucleus generator. The influences of the different process parameters on the temperature gradient and cooling rates in the mushy zone were investigated in detail. A lower cooling intensity and a uniform temperature gradient distribution could promote nucleation and refine grains. The present research has guiding significance for the process parameter selection in the actual experimental. Full article
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12 pages, 3607 KiB  
Article
The Effect of Threads Geometry on Insertion Torque (IT) and Periotest Implant Primary Stability: A High-Density Polyurethane Simulation for the Anterior Mandible
by Stefano Fanali, Margherita Tumedei, Pamela Pignatelli, Morena Petrini, Adriano Piattelli and Giovanna Iezzi
Crystals 2021, 11(3), 308; https://doi.org/10.3390/cryst11030308 - 20 Mar 2021
Cited by 6 | Viewed by 3148
Abstract
The implant geometry provides a key role in the osseointegration process and is able to improve the mechanical interaction and primary stability into the bone tissue. The aim of the present investigation was to compare different implant profiles to evaluate their influence on [...] Read more.
The implant geometry provides a key role in the osseointegration process and is able to improve the mechanical interaction and primary stability into the bone tissue. The aim of the present investigation was to compare different implant profiles to evaluate their influence on the primary stability on high-density polyurethane block. Methods: A total of 100 implants were used on 20 pcf polyurethane density in the present investigation, i.e., 20 implants for each of 5 groups (A, B, C, D, and E), characterized by different thread pitch and geometry. The insertion torque (IT), and Periotest mean values were recorded during the implant positioning. Results: Mean values for insertion torque values were higher for the group C and group E implant profiles when compared to all other groups (p < 0.01). No significant differences were detected between these two groups (p < 0.05). Lower IT (<20 Ncm2) were presented by groups A, B, and D (p < 0.05). All groups showed negative Periotest values. Group C implants showed the lowest level of Periotest values (p < 0.05). No significant Periotest differences were found between group B and group D and between group A and group E (p > 0.05). Conclusions: Implants with a wider and V-thread profile and a round apex showed a higher stability in a standardized polyurethane foam. Their use could be suggested in high-density bone in clinical practice. Full article
(This article belongs to the Special Issue Biomaterials Surface Integrity)
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9 pages, 1225 KiB  
Article
Isotropic Nature of the Metallic Kagome Ferromagnet Fe3Sn2 at High Temperatures
by Rebecca L. Dally, Daniel Phelan, Nicholas Bishop, Nirmal J. Ghimire and Jeffrey W. Lynn
Crystals 2021, 11(3), 307; https://doi.org/10.3390/cryst11030307 - 20 Mar 2021
Cited by 7 | Viewed by 3953
Abstract
Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic [...] Read more.
Anisotropy and competing exchange interactions have emerged as two central ingredients needed for centrosymmetric materials to exhibit topological spin textures. Fe3Sn2 is thought to have these ingredients as well, as it has recently been discovered to host room temperature skyrmionic bubbles with an accompanying topological Hall effect. We present small-angle inelastic neutron scattering measurements that unambiguously show that Fe3Sn2 is an isotropic ferromagnet below TC660 K to at least 480 K—the lower temperature threshold of our experimental configuration. Fe3Sn2 is known to have competing magnetic exchange interactions, correlated electron behavior, weak magnetocrystalline anisotropy, and lattice (spatial) anisotropy; all of these features are thought to play a role in stabilizing skyrmions in centrosymmetric systems. Our results reveal that at the elevated temperatures measured, there is an absence of significant magnetocrystalline anisotropy and that the system behaves as a nearly ideal isotropic exchange interaction ferromagnet, with a spin stiffness D(T=480 K)=168 meV Å2, which extrapolates to a ground state spin stiffness D(T=0 K)=231 meV Å2. Full article
(This article belongs to the Special Issue Advances in Topological Materials)
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11 pages, 1453 KiB  
Article
Coordination Ability of 10-EtC(NHPr)=HN-7,8-C2B9H11 in the Reactions with Nickel(II) Phosphine Complexes
by Marina Yu. Stogniy, Svetlana A. Erokhina, Kyrill Yu. Suponitsky, Igor B. Sivaev and Vladimir I. Bregadze
Crystals 2021, 11(3), 306; https://doi.org/10.3390/cryst11030306 - 19 Mar 2021
Cited by 9 | Viewed by 2154
Abstract
The complexation reactions of nido-carboranyl amidine 10-PrNHC(Et)=HN-7,8-C2B9H11 with different nickel(II) phosphine complexes such as [(PR2R’)2NiCl2] (R = R’ = Ph, Bu; R = Me, R’ = Ph) were investigated. As a [...] Read more.
The complexation reactions of nido-carboranyl amidine 10-PrNHC(Et)=HN-7,8-C2B9H11 with different nickel(II) phosphine complexes such as [(PR2R’)2NiCl2] (R = R’ = Ph, Bu; R = Me, R’ = Ph) were investigated. As a result, a series of novel half-sandwich nickel(II) π,σ-complexes [3-R’R2P-3-(8-PrN=C(Et)NH)-closo-3,1,2-NiC2B9H10] with the coordination of the carborane and amidine components was prepared. The acidification of obtained complexes with HCl led to the breaking of the Ni-N bond with formation of nickel(II) π-complexes [3-Cl-3-R’R2P-8-PrNH=C(Et)NH-closo-3,1,2-NiC2B9H10]. The crystal molecular structure of [3-Ph3P-3-(8-PrN=C(Et)NH)-closo-3,1,2-NiC2B9H10] was determined by single crystal X-ray diffraction. Full article
(This article belongs to the Special Issue Carborane: Dedicated to the Work of Professor Alan Welch)
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11 pages, 3012 KiB  
Article
Understanding Nonlinear Pulse Propagation in Liquid Strand-Based Photonic Bandgap Fibers
by Xue Qi, Kay Schaarschmidt, Guangrui Li, Saher Junaid, Ramona Scheibinger, Tilman Lühder and Markus A. Schmidt
Crystals 2021, 11(3), 305; https://doi.org/10.3390/cryst11030305 - 19 Mar 2021
Cited by 2 | Viewed by 2075
Abstract
Ultrafast supercontinuum generation crucially depends on the dispersive properties of the underlying waveguide. This strong dependency allows for tailoring nonlinear frequency conversion and is particularly relevant in the context of waveguides that include geometry-induced resonances. Here, we experimentally uncovered the impact of the [...] Read more.
Ultrafast supercontinuum generation crucially depends on the dispersive properties of the underlying waveguide. This strong dependency allows for tailoring nonlinear frequency conversion and is particularly relevant in the context of waveguides that include geometry-induced resonances. Here, we experimentally uncovered the impact of the relative spectral distance between the pump and the bandgap edge on the supercontinuum generation and in particular on the dispersive wave formation on the example of a liquid strand-based photonic bandgap fiber. In contrast to its air-hole-based counterpart, a bandgap fiber shows a dispersion landscape that varies greatly with wavelength. Particularly due to the strong dispersion variation close to the bandgap edges, nanometer adjustments of the pump wavelength result in a dramatic change of the dispersive wave generation (wavelength and threshold). Phase-matching considerations confirm these observations, additionally revealing the relevance of third order dispersion for interband energy transfer. The present study provides additional insights into the nonlinear frequency conversion of resonance-enhanced waveguide systems which will be relevant for both understanding nonlinear processes as well as for tailoring the spectral output of nonlinear fiber sources. Full article
(This article belongs to the Special Issue Specialty Photonic Crystal Fibres and Their Applications)
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19 pages, 2571 KiB  
Review
Concepts of Nucleation in Polymer Crystallization
by Jun Xu, Günter Reiter and Rufina G. Alamo
Crystals 2021, 11(3), 304; https://doi.org/10.3390/cryst11030304 - 19 Mar 2021
Cited by 43 | Viewed by 8853
Abstract
Nucleation plays a vital role in polymer crystallization, in which chain connectivity and thus the multiple length and time scales make crystal nucleation of polymer chains an interesting but complex subject. Though the topic has been intensively studied in the past decades, there [...] Read more.
Nucleation plays a vital role in polymer crystallization, in which chain connectivity and thus the multiple length and time scales make crystal nucleation of polymer chains an interesting but complex subject. Though the topic has been intensively studied in the past decades, there are still many open questions to answer. The final properties of semicrystalline polymer materials are affected by all of the following: the starting melt, paths of nucleation, organization of lamellar crystals and evolution of the final crystalline structures. In this viewpoint, we attempt to discuss some of the remaining open questions and corresponding concepts: non-equilibrated polymers, self-induced nucleation, microscopic kinetics of different processes, metastability of polymer lamellar crystals, hierarchical order and cooperativity involved in nucleation, etc. Addressing these open questions through a combination of novel concepts, new theories and advanced approaches provides a deeper understanding of the multifaceted process of crystal nucleation of polymers. Full article
(This article belongs to the Topic Polymer Crystallization)
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18 pages, 986 KiB  
Review
Solution Cocrystallization: A Scalable Approach for Cocrystal Production
by Nitin Pawar, Anindita Saha, Neelesh Nandan and Jose V. Parambil
Crystals 2021, 11(3), 303; https://doi.org/10.3390/cryst11030303 - 18 Mar 2021
Cited by 33 | Viewed by 9042
Abstract
With an increasing interest in cocrystals due to various advantages, demand for large-scale cocrystallization techniques is rising. Solution cocrystallization is a solvent-based approach that utilizes several single-component crystallization concepts as well as equipment for generating cocrystals. Solution-based techniques can produce cocrystals with reasonable [...] Read more.
With an increasing interest in cocrystals due to various advantages, demand for large-scale cocrystallization techniques is rising. Solution cocrystallization is a solvent-based approach that utilizes several single-component crystallization concepts as well as equipment for generating cocrystals. Solution-based techniques can produce cocrystals with reasonable control on purity, size distribution, morphology, and polymorphic form. Many of them also offer a scalable solution for the industrial production of cocrystals. However, the complexity of the thermodynamic landscape and the kinetics of cocrystallization offers fresh challenges which are not encountered in single component crystallization. This review focuses on the recent developments in different solution cocrystallization techniques for the production of pharmaceutically relevant cocrystals. The review consists of two sections. The first section describes the various solution cocrystallization methods, highlighting their benefits and limitations. The second section emphasizes the challenges in developing these techniques to an industrial scale and identifies the major thrust areas where further research is required. Full article
(This article belongs to the Special Issue Crystal Nucleation and Growth Kinetics)
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14 pages, 934 KiB  
Article
Polaron Trapping and Migration in Iron-Doped Lithium Niobate
by Laura Vittadello, Laurent Guilbert, Stanislav Fedorenko and Marco Bazzan
Crystals 2021, 11(3), 302; https://doi.org/10.3390/cryst11030302 - 17 Mar 2021
Cited by 6 | Viewed by 2152
Abstract
Photoinduced charge transport in lithium niobate for standard illumination, composition and temperature conditions occurs by means of small polaron hopping either on regular or defective lattice sites. Starting from Marcus-Holstein’s theory for polaron hopping frequency we draw a quantitative picture illustrating two underlying [...] Read more.
Photoinduced charge transport in lithium niobate for standard illumination, composition and temperature conditions occurs by means of small polaron hopping either on regular or defective lattice sites. Starting from Marcus-Holstein’s theory for polaron hopping frequency we draw a quantitative picture illustrating two underlying microscopic mechanisms besides experimental observations, namely direct trapping and migration-accelerated polaron trapping transport. Our observations will be referred to the typical outcomes of transient light induced absorption measurements, where the kinetics of a polaron population generated by a laser pulse then decaying towards deep trap sites is measured. Our results help to rationalize the observations beyond simple phenomenological models and may serve as a guide to design the material according to the desired specifications. Full article
(This article belongs to the Special Issue New Trends in Lithium Niobate: From Bulk to Nanocrystals)
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13 pages, 3338 KiB  
Article
Effects of Different Amounts of Nb Doping on Electrical, Optical and Structural Properties in Sputtered TiO2−x Films
by Daniel Dorow-Gerspach, Dieter Mergel and Matthias Wuttig
Crystals 2021, 11(3), 301; https://doi.org/10.3390/cryst11030301 - 17 Mar 2021
Cited by 7 | Viewed by 2115
Abstract
Highly conductive TiO2 films with different Nb doping levels (up to 5 at%) were prepared by reactive DC magnetron sputtering under precise control of the oxygen partial pressure. They were deposited on unheated substrates, covered with a protective Si3N4 [...] Read more.
Highly conductive TiO2 films with different Nb doping levels (up to 5 at%) were prepared by reactive DC magnetron sputtering under precise control of the oxygen partial pressure. They were deposited on unheated substrates, covered with a protective Si3N4 layer, and subsequently annealed at 300 °C. The doping efficiency of Nb is greater than 90%. Conductivity is a maximum for a partly oxidized target in the transition range. The best films exhibit a resistivity of 630 µΩ cm and a mobility of 7.6 cm2/Vs combined with a high transparency above 70%. Comparing the behavior of undoped and Nb-containing films, intrinsic limits of the conductivity in the TiO2−x:Nb system could be observed, and a consistent model explaining these findings is presented. The conductivity is limited—by decreasing electron density due to Nb oxidation—by increasing incorporation formation of Nb2O5 clusters as scattering centers with increasing oxygen partial pressure and Nb concentration, by a transition from the crystalline to the amorphous state of the films below a critical oxygen partial pressure. Full article
(This article belongs to the Special Issue Transparent Conducting and Semiconducting Oxides)
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17 pages, 3283 KiB  
Article
Synthesis, Spectroscopic Characterization, and Biological Activities of New Binuclear Co(II), Ni(II), Cu(II), and Zn(II) Diimine Complexes
by Ahmed Gaber, Arafa A. M. Belal, Ibrahim M. El-Deen, Nader Hassan, Rozan Zakaria, Walaa F. Alsanie, Ahmed M. Naglah and Moamen S. Refat
Crystals 2021, 11(3), 300; https://doi.org/10.3390/cryst11030300 - 17 Mar 2021
Cited by 4 | Viewed by 2184
Abstract
Metal-ligand complexes have attracted major interest due to their potential medical applications as anticancer agents. The work described in the current article aimed to synthesize, spectroscopic, thermal, and biological studies of some metal-diimine complexes. A diimine ligand, namely 2-{[2-(4-chlorophenyl)-2-hydroxyvinyl]-hydrazonomethyl}phenol (diim) was prepared via [...] Read more.
Metal-ligand complexes have attracted major interest due to their potential medical applications as anticancer agents. The work described in the current article aimed to synthesize, spectroscopic, thermal, and biological studies of some metal-diimine complexes. A diimine ligand, namely 2-{[2-(4-chlorophenyl)-2-hydroxyvinyl]-hydrazonomethyl}phenol (diim) was prepared via the reaction of p-chlorophenacyl bromide with hydrazine hydrate in ethanol, then condensation was completed with 2-hydroxybenzaldehyde in acetic acid. The Co(II), Ni(II), Cu(II), and Zn(II) complexes were prepared with a metal:ligand stoichiometric ratio of (2:1). 1H-NMR, UV-Vis, FTIR spectroscopic data, molar conductivity measurements, and microanalytical data (carbon, hydrogen, nitrogen, and halogen) were used for characterization of the formed ligand and its metal complexes. It was found that the diimine ligand act as tetradentate fashion. The non-electrolytic character for all the complexes was proved by molar conductivity. The first metal atom of the synthesized binuclear diimine complexes coordinates with the nitrogen of hydrazine group and oxygen of OH group. While, the second metal atom coordinates with the other nitrogen atom of the hydrazine group and oxygen of phenolic group. All the synthesized metal complexes have a six-coordinated except for Zn(II) has four-coordinated. Thermogravimetric analysis and its differential analysis were done to discuss the thermal degradation of the free ligand and its metal complexes. Molecular docking calculation showed that the diimine ligand is a good inhibitor for breast cancer 3hb5 and 4o1v kidney cancer proteins. Additionally, these compounds were evaluated as antibacterial and antifungal agents. Full article
(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)
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3 pages, 158 KiB  
Editorial
Biominerals: Formation, Function, Properties
by Helmut Cölfen, Erika Griesshaber and Wolfgang W. Schmahl
Crystals 2021, 11(3), 299; https://doi.org/10.3390/cryst11030299 - 17 Mar 2021
Cited by 3 | Viewed by 1653
Abstract
Triggered by geochemical cycles, large-scale terrestrial processes and evolution, a tremendous biodiversity evolved over the geological record and produced proto- and metazoa with biomineralized hard tissue, characterized by unique structural designs and exquisite performance [...] Full article
(This article belongs to the Special Issue Biominerals: Formation, Function, Properties)
10 pages, 4426 KiB  
Article
Electro-Optic Control of Lithium Niobate Bulk Whispering Gallery Resonators: Analysis of the Distribution of Externally Applied Electric Fields
by Yannick Minet, Hans Zappe, Ingo Breunig and Karsten Buse
Crystals 2021, 11(3), 298; https://doi.org/10.3390/cryst11030298 - 17 Mar 2021
Cited by 8 | Viewed by 3127
Abstract
Whispering gallery resonators made out of lithium niobate allow for optical parametric oscillation and frequency comb generation employing the outstanding second-order nonlinear-optical properties of this material. An important knob to tune and control these processes is, e.g., the linear electro-optic effect, the Pockels [...] Read more.
Whispering gallery resonators made out of lithium niobate allow for optical parametric oscillation and frequency comb generation employing the outstanding second-order nonlinear-optical properties of this material. An important knob to tune and control these processes is, e.g., the linear electro-optic effect, the Pockels effect via externally applied electric fields. Due to the shape of the resonators a precise prediction of the electric field strength that affects the optical mode is non-trivial. Here, we study the average strength of the electric field in z-direction in the region of the optical mode for different configurations and geometries of lithium niobate whispering gallery resonators with the help of the finite element method. We find that in some configurations almost 100% is present in the cavity compared to the ideal case of a cylindrical resonator. Even in the case of a few-mode resonator with a very thin rim we find a strength of 90%. Our results give useful design considerations for future arrangements that may benefit from the strong electro-optic effect in bulk whispering gallery resonators made out of lithium niobate. Full article
(This article belongs to the Special Issue New Trends in Lithium Niobate: From Bulk to Nanocrystals)
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21 pages, 4677 KiB  
Article
Correlation between Structural and Transport Properties of Ca-Doped La Nickelates and Their Electrochemical Performance
by Elena Pikalova, Vladislav Sadykov, Ekaterina Sadovskaya, Nikita Yeremeev, Alexander Kolchugin, Alexander Shmakov, Zakhar Vinokurov, Denis Mishchenko, Elena Filonova and Vladimir Belyaev
Crystals 2021, 11(3), 297; https://doi.org/10.3390/cryst11030297 - 17 Mar 2021
Cited by 12 | Viewed by 2687
Abstract
This work presents the results from a study of the structure and transport properties of Ca-doped La2NiO4+δ. La2−xCaxNiO4+δ (x = 0–0.4) materials that were synthesized via combustion of organic-nitrate precursors and characterized by [...] Read more.
This work presents the results from a study of the structure and transport properties of Ca-doped La2NiO4+δ. La2−xCaxNiO4+δ (x = 0–0.4) materials that were synthesized via combustion of organic-nitrate precursors and characterized by X-ray diffraction (XRD), in situ XRD using synchrotron radiation, thermogravimetric analysis (TGA) and isotope exchange of oxygen with C18O2. The structure was defined as orthorhombic (Fmmm) for x = 0 and tetragonal (I4/mmm) for x = 0.1–0.4. Changes that occurred in the unit cell parameters and volume as the temperature changed during heating were shown to be caused by the excess oxygen loss. Typical for Ruddlesden–Popper phases, oxygen mobility and surface reactivity decreased as the Ca content was increased due to a reduction in the over-stoichiometric oxygen content with the exception of x = 0.1. This composition demonstrated its superior oxygen transport properties compared to La2NiO4+δ due to the enhanced oxygen mobility caused by structural features. Electrochemical data obtained showed relatively low polarization resistance for the electrodes with a low Ca content, which correlates well with oxygen transport properties. Full article
(This article belongs to the Special Issue Diffusion and Degradation Phenomena in Solid Oxide Materials)
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9 pages, 3401 KiB  
Article
Microstructure and Optical Characterization of Mid-Wave HgCdTe Grown by MBE under Different Conditions
by Xiao-Fang Qiu, Sheng-Xi Zhang, Jian Zhang, Yi-Cheng Zhu, Cheng Dou, San-Can Han, Yan Wu and Ping-Ping Chen
Crystals 2021, 11(3), 296; https://doi.org/10.3390/cryst11030296 - 16 Mar 2021
Cited by 4 | Viewed by 2409
Abstract
The mid-wave single-crystal HgCdTe (211) films were successfully grown on GaAs (211) B substrates by molecular beam epitaxy (MBE). Microstructure and optical properties of the MBE growth HgCdTe films grown at different temperatures were characterized by X-ray diffraction, scanning transmission electron microscopy, Raman [...] Read more.
The mid-wave single-crystal HgCdTe (211) films were successfully grown on GaAs (211) B substrates by molecular beam epitaxy (MBE). Microstructure and optical properties of the MBE growth HgCdTe films grown at different temperatures were characterized by X-ray diffraction, scanning transmission electron microscopy, Raman and photoluminescence. The effects of growth temperature on the crystal quality of HgCdTe/CdTe have been studied in detail. The HgCdTe film grown at the lower temperature of 151 °C has high crystal quality, the interface is flat and there are no micro twins. While the crystal quality of the HgCdTe grown at higher temperature of 155 °C is poor, and there are defects and micro twins at the HgCdTe/CdTe interface. The research results demonstrate that the growth temperature significantly affects the crystal quality and optical properties of HgCdTe films. Full article
(This article belongs to the Special Issue Low-Dimensional Materials for Electronic Device Applications)
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17 pages, 2803 KiB  
Article
Strategies for High-Performance Large-Area Perovskite Solar Cells toward Commercialization
by Tianzhao Dai, Qiaojun Cao, Lifeng Yang, Mahmoud H. Aldamasy, Meng Li, Qifeng Liang, Hongliang Lu, Yiming Dong and Yingguo Yang
Crystals 2021, 11(3), 295; https://doi.org/10.3390/cryst11030295 - 16 Mar 2021
Cited by 26 | Viewed by 7092
Abstract
Perovskite solar cells (PSCs) have received a great deal of attention in the science and technology field due to their outstanding power conversion efficiency (PCE), which increased rapidly from 3.9% to 25.5% in less than a decade, comparable to single crystal silicon solar [...] Read more.
Perovskite solar cells (PSCs) have received a great deal of attention in the science and technology field due to their outstanding power conversion efficiency (PCE), which increased rapidly from 3.9% to 25.5% in less than a decade, comparable to single crystal silicon solar cells. In the past ten years, much progress has been made, e.g. impressive ideas and advanced technologies have been proposed to enlarge PSC efficiency and stability. However, this outstanding progress has always been referred to as small-area (<0.1 cm2) PSCs. Little attention has been paid to the preparation processes and their micro-mechanisms for large-area (>1 cm2) PSCs. Meanwhile, scaling up is an inevitable way for large-scale application of PSCs. Therefore, we firstly summarize the current achievements for high efficiency and stability large-area perovskite solar cells, including precursor composition, deposition, growth control, interface engineering, packaging technology, etc. Then we include a brief discussion and outlook for the future development of large-area PSCs in commercialization. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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19 pages, 22203 KiB  
Article
Experimental Analysis and Mathematical Model of FSW Parameter Effects on the Corrosion Rate of Al 6061-T6-Cu C11000 Joints
by Félix Alan Montes-González, Nelly Abigaíl Rodríguez-Rosales, Juan Carlos Ortiz-Cuellar, Carlos Rodrigo Muñiz-Valdez, Josué Gómez-Casas, Jesús Salvador Galindo-Valdés and Oziel Gómez-Casas
Crystals 2021, 11(3), 294; https://doi.org/10.3390/cryst11030294 - 16 Mar 2021
Cited by 5 | Viewed by 2484
Abstract
Friction stir welding is characterized as an ecological and low-cost process in comparison to traditional welding techniques, and due to its application in the solid state, it is a feasible option for joining similar and/or dissimilar materials. The present investigation seeks to determine [...] Read more.
Friction stir welding is characterized as an ecological and low-cost process in comparison to traditional welding techniques, and due to its application in the solid state, it is a feasible option for joining similar and/or dissimilar materials. The present investigation seeks to determine the effect of friction stir welding’s parameters on the corrosion resistance of an Al 6061-T6–Cu C11000 dissimilar joint, with mathematical analysis to validate the results. After the welding process, the samples were exposed to a NaCl solution in an electrochemical cell to determine the corrosion rate via potentiodynamic tests. Microstructural characterization revealed a laminar structure, composed of aluminum and copper, as well as copper particles and the formation of intermetallic compounds distributed in the weld zone. The potentiodynamic tests showed that the corrosion rate increased with the rotational and traverse speeds. The mathematical model quantifies the relationship between corrosion rate and rotational and traverse speeds. Full article
(This article belongs to the Section Inorganic Crystalline Materials)
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13 pages, 3590 KiB  
Article
Sodium, Silver and Lithium-Ion Conducting β″-Alumina + YSZ Composites, Ionic Conductivity and Stability
by Liangzhu Zhu and Anil V. Virkar
Crystals 2021, 11(3), 293; https://doi.org/10.3390/cryst11030293 - 16 Mar 2021
Cited by 6 | Viewed by 2552
Abstract
Na-β″-alumina (Na2O.~6Al2O3) is known to be an excellent sodium ion conductor in battery and sensor applications. In this study we report fabrication of Na- β″-alumina + YSZ dual phase composite to mitigate moisture and CO2 corrosion [...] Read more.
Na-β″-alumina (Na2O.~6Al2O3) is known to be an excellent sodium ion conductor in battery and sensor applications. In this study we report fabrication of Na- β″-alumina + YSZ dual phase composite to mitigate moisture and CO2 corrosion that otherwise can lead to degradation in pure Na-β″-alumina conductor. Subsequently, we heat-treated the samples in molten AgNO3 and LiNO3 to respectively form Ag-β″-alumina + YSZ and Li-β″-alumina + YSZ to investigate their potential applications in silver- and lithium-ion solid state batteries. Ion exchange fronts were captured via SEM and EDS techniques. Their ionic conductivities were measured using electrochemical impedance spectroscopy. Both ion exchange rates and ionic conductivities of these composite ionic conductors were firstly reported here and measured as a function of ion exchange time and temperature. Full article
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23 pages, 6756 KiB  
Article
Thermal Properties, Isothermal Decomposition by Direct Analysis in Real-Time-of-Flight Mass Spectrometry and Non Isothermal Crystallization Kinetics of Poly(Ethylene-co-Vinyl Alcohol)/Poly(ε-Caprolactone) Blend
by Abdulaziz Ali Alghamdi, Hussain Alattas, Waseem Sharaf Saeed, Abdel-Basit Al-Odayni, Ahmed Yacine Badjah Hadj Ahmed, Ahmad Abdulaziz Al-Owais and Taieb Aouak
Crystals 2021, 11(3), 292; https://doi.org/10.3390/cryst11030292 - 16 Mar 2021
Cited by 8 | Viewed by 2079
Abstract
A series of poly(ethylene-co-vinyl alcohol)/poly(ε-caprolactone) blends with different compositions were prepared using solvent casting. The miscibility of this pair of polymers was investigated using differential scanning calorimetry (DSC), and proved by a negative Flory interaction parameter value calculated from the Nishi–Wang equation. The [...] Read more.
A series of poly(ethylene-co-vinyl alcohol)/poly(ε-caprolactone) blends with different compositions were prepared using solvent casting. The miscibility of this pair of polymers was investigated using differential scanning calorimetry (DSC), and proved by a negative Flory interaction parameter value calculated from the Nishi–Wang equation. The miscibility of this blend was also confirmed by scanning electronic microscopy (SEM). The thermal behaviors of the obtained materials were investigated by DSC, thermogravimetric analysis, and direct analysis in real-time–time-of-flight mass spectrometry and the results obtained were very relevant. Furthermore, the crystalline properties of the obtained materials were studied by DSC and X-ray diffraction where the Ozawa approach was adopted to investigate the non-isothermal crystallization kinetics. The results obtained revealed that this approach described the crystallization process well. Full article
(This article belongs to the Special Issue New Trends in Crystals at Saudi Arabia)
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14 pages, 3302 KiB  
Article
Improving Compactness of 3D Metallic Microstructures Printed by Laser-Induced Forward Transfer
by Niv Gorodesky, Sharona Sedghani-Cohen, Ofer Fogel, Amir Silber, Maria Tkachev, Zvi Kotler and Zeev Zalevsky
Crystals 2021, 11(3), 291; https://doi.org/10.3390/cryst11030291 - 16 Mar 2021
Cited by 14 | Viewed by 2831
Abstract
Laser-induced forward transfer (LIFT) has been shown to be a useful technique for the manufacturing of micron-scale metal structures. LIFT is a high-resolution, non-contact digital printing method that can support the fabrication of complex shapes and multi-material structures in a single step under [...] Read more.
Laser-induced forward transfer (LIFT) has been shown to be a useful technique for the manufacturing of micron-scale metal structures. LIFT is a high-resolution, non-contact digital printing method that can support the fabrication of complex shapes and multi-material structures in a single step under ambient conditions. However, LIFT printed metal structures often suffer from inferior mechanical, electrical, and thermal properties when compared to their bulk metal counterparts, and often are prone to enhanced chemical corrosion. This is due mostly to their non-compact structures, which have voids and inter-droplet delamination. In this paper, a theoretical framework together with experimental results of achievable compactness limits is presented for a variety of metals. It is demonstrated that compactness limits depend on material properties and jetting conditions. It is also shown how a specific choice of materials can yield compact structures, for example, when special alloys are chosen along with a suitable donor construct. The example of printed amorphous ZrPd is detailed. This study contributes to a better understanding of the limits of implementing LIFT for the fabrication of metal structures, and how to possibly overcome some of these limitations. Full article
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